Introduction
Grammar teaching has often been regarded as a structure based, formal activity. After the integration of several sources and techniques, which are mainly based on communicative activities, the teaching of grammar gained a new insight. In the teaching of grammar, technique-resource combinations are often modified to structure-discourse match and if well developed, they can be used effectively for all phases of a grammar lesson. In order to make a grammar lesson effective, beneficial, and interesting a teacher should use some well-developed and fascinating techniques in the classroom. In the present paper, the examples of such integrated sources and techniques -the use of songs, verse, games, and problem solving activities- will be clarified and several examples will be provided.
Using Songs and Verse
Songs
Since the meaning is an important device in teaching grammar, it is important to contextualize any grammar point. Songs are one of the most enchanting and culturally rich resources that can easily be used in language classrooms. Songs offer a change from routine classroom activities. They are precious resources to develop students abilities in listening, speaking, reading, and writing. They can also be used to teach a variety of language items such as sentence patterns, vocabulary, pronunciation, rhythm, adjectives, and adverbs. As stated by Lo and Fai Li (1998:8), learning English through songs also provides a non-threatening atmosphere for students, who usually are tense when speaking English in a formal classroom setting.
Songs also give new insights into the target culture. They are the means through which cultural themes are presented effectively. Since they provide authentic texts, they are motivating. Prosodic features of the language such as stress, rhythm, intonation are presented through songs, thus through using them the language which is cut up into a series of structural points becomes a whole again.
There are many advantages of using songs in the classroom. Through using contemporary popular songs, which are already familiar to teenagers, the teacher can meet the challenges of the teenage needs in the classroom. Since songs are highly memorable and motivating, in many forms they may constitute a powerful subculture with their own rituals. Furthermore, through using traditional folk songs the base of the learners knowledge of the target culture can be broadened. Correctly chosen, traditional folk songs have the dual motivating attack of pretty tunes and interesting stories, plus for many students- the added ingredient of novelty (Hill, 1999:29). Most songs, especially folk songs, follow a regularly repeated verse form, with rhyme, and have a series of other discourse features, which make them easy to follow.
In consequence, if selected properly and adopted carefully, a teacher should benefit from songs in all phases of teaching grammar. Songs may both be used for the presentation or the practice phase of the grammar lesson. They may encourage extensive and intensive listening, and inspire creativity and use of imagination in a relaxed classroom atmosphere. While selecting a song the teacher should take the age, interests of the learners and the language being used in the song into consideration. To enhance learner commitment, it is also beneficial to allow learners to take part in the selection of the songs.
Teaching Procedure
There are various ways of using songs in the classroom. The level of the students, the interests and the age of the learners, the grammar point to be studied, and the song itself have determinant roles on the procedure. Apart from them, it mainly depends on the creativity of the teacher.
For primary students, the best songs would be those that are either familiar to the children or those, though maybe not familiar, which have an international nature, such as Old MacDonald. Since there is not a strict teaching procedure, the teacher can mainly concentrate on what to teach rather than on how to teach. For instance, while teaching them individual letter sounds or spelling the words, the traditional camp song 'Bingo', or while teaching them counting 'Johnny Works with One Hammer' will be useful. In order to make the songs more meaningful and more enjoyable, motions can be added to the song which parallel the words of the song. Since most children enjoy singing fun and nonsensical lyrics, using easy children songs will be useful. Furthermore, choosing lively action songs through which they can dance or act while singing will ensure a lively atmosphere.
For teenagers or adults in the intermediate or advanced level, it is better to use more meaningful or popular songs, which not only review or introduce grammar points but also reflect cultural aspects. At the primary level of singing the song, the prosodic features of the language is emphasized. At the higher levels, where the practice of grammar points is at the foreground, songs can be used with several techniques. Some examples of these techniques are:
Gap fills or close texts
Focus questions
True-false statements
Put these lines into the correct sequence
Dictation
Add a final verse
Circle the antonyms/synonyms of the given words
Discuss
A teacher's selection of a technique or a set of techniques should be based on his or her objectives for the classroom. After deciding the grammar point to be studied, and the song and the techniques to be used, the teacher should prepare an effective lesson plan. Since songs are listening activities, it is advisable to present them as a listening lesson, but of course it is necessary to integrate all the skills in the process in order to achieve successful teaching.
When regarding a lesson plan, as a pre-listening activity, the theme, the title, or the history of the song can be discussed. By directing the students toward specific areas, problem vocabulary items can be picked up in advance. Before listening to the song, it is also beneficial to let the students know which grammar points should be studied. At this stage, pictures may also be used to introduce the theme of the song. In the listening stage, some of the techniques listed above can be used, but among them gap filling is the most widely used technique. Through such gaps, the vocabulary, grammar, or pronunciation are highlighted. This stage can be developed by the teacher according to the needs of the students and the grammar point to be studied.
In the follow-up, integrated skills can be used to complete the overall course structure. Since many songs are on themes for which it is easy to find related reading texts, it may lead the learner to read a text about the singer or the theme. Besides, many songs give a chance for a written reaction of some kind. Opinion questions may lead the learner to write about his own thoughts or reflections. Some songs deal with a theme that can be re-exploited through role plays. Acting may add enthusiasm to the learning process. Finally, some songs deal with themes, which can lead to guided discussion. By leading the students into a discussion, the grammar point could be practiced orally and, in a way, naturally.
Exploitation of songs for grammatical structures can be illustrated through several examples. For present tense 'Let It Be' by the Beatles, for past tense 'Yesterday' by the Beatles, for present progressive 'Sailing' by Rod Stewart, for present perfect 'Nothing Compares to You' by Sinead Occonor, for past perfect 'Last Night I Had...' by Simon and Garfunkel, for modals 'Blowing in the Wind' by Bob Dylan, and for conditionals 'El Condor Pasa' by Simon and Garfunkel can be used. However, it should be kept in mind that songs, which provide frequent repetitions, or tell a story, or provide comments about life, or introduce cultural themes are the effective ones, since they provide authentic and meaningful material.
As a consequence, the use of songs in language classrooms provides many advantages. They entertain and relax the learners while they are learning or practicing a structure, and they often eliminate the students negative attitude towards learning. Through providing authenticity and context they make the grammar points more understandable and easy. As language teachers, we can benefit from using songs, since our concern is to motivate the students and draw their utmost attention on the subject during teaching.
Poems
Poems, like songs, contextualize a grammar lesson effectively. Since poetry is often spoken, repeated, dealt with, and considered, it acts as an effective tool for practicing a specific grammatical structure. Through repeating and considering the poem, the grammatical structures become more deeply internalized. Thus, poetry not only provides a rewarding resource for structured practice of grammar, but also a proper basis for review. If a poem that exemplifies a particular structure is also a good poem, it engages the eye, the ear and the tongue simultaneously while also stimulating and moving us; this polymorphic effect makes poetry easier to memorize than other things for many students (Celce-Murcia and Hills, 1988:123).
Like songs, poems exaggerate the rhythmic nature of the language. Thus it is an important aspect to be taught, since English is a syllable timed language with stressed syllables being spoken at roughly equal time pauses, even in everyday speech. Similar to songs, poems have an enormous linguistic value as they provide authenticity and cultural views. A poem's capacity to comfort the reader or the listener also increases its effectiveness as a teaching resource. Once a poem or song has been learned, they stay in the minds of the students for the rest of their lives, with all the rhythms, grammatical features and vocabulary.
Poems may bring the use of creativity and the rhythm into the language classroom, though they may also bring some difficulties. Poems are not constructed in a simple way and syntactically they are at a higher level than prose, thus it might be very difficult for a foreign language learner to comprehend them completely. As stated by Povey (cited in Celce-Murcia and Hills, 1988) there are three main barriers for literature including poetry. They are linguistic, cultural, and intellectual barriers. Linguistic difficulties are the problems caused by the syntax or the lexicon of the poem. Cultural difficulties include imagery, tone, and allusion. At the intellectual level, the students should be intellectual and mature enough to understand the theme of the poem. These difficulties could be easily removed if the teacher provides a poem which is syntactically and thematically appropriate to the level, age and the interests of the students. Thus, by removing or minimizing the potential problems, poetry can provide an enormously rich, enjoyable and authentic context for foreign language learners.
In the selection of a poem, the teacher should first consider the grammatical structure to be presented, practiced, or reviewed, then the level and the age of the students, next the theme and the length of the poem and its appropriateness to the classroom objectives. It is advisable to select a poem from 20th century poets. As older poems often provide a more difficult lexicon and syntax, and as they reflect some old-fashioned ideas, it is more convenient to use contemporary poems than older ones. Poems, which reflect cultural themes, universal features, humanistic values, or emotional aspects, will be more relevant to the foreign language learners. Finally, through taking the classroom objectives into consideration, a teacher should effectively benefit from poems as teaching aids.
Teaching Procedure
At the teaching stage of a poem, it is not advisable to talk about the meaning of the poem in advance. Since they offer a reading and listening activity, poems could be presented through a reading plan. At the pre-reading stage, students might be motivated through some enthusiastic talks about poetry or the poet. Some necessary vocabulary can also be handled at this stage. At the reading stage, in order to create images and stress the prosodic features, the teacher may want the students to close their eyes while he/she is reading the poem. After the poem has been read at least twice, it is better to elicit the primary responses of the students about the poem. Next, after distributing the poem to students, students may be asked to read it either loudly or silently. In order to practice the determined grammar point, students may be asked to paraphrase the poem. Through transforming the verse into prose students get acquainted with the structure.
After easing the grammar and understanding the vocabulary, students get an idea about the theme of the poem. Reading the paraphrased poem reinforces the grammatical structure under consideration. Asking questions about context may follow the reading. Through asking Wh- questions, providing additional information about the culture, and asking students to share their experience with the subject matter, the cultural content of the poem becomes more real and vivid. Words, pictures, and shared experiences can eliminate the gap that is created by different cultures, as no one can deny that poems cannot always evoke the same sounds, sights, smells, and associations for both native speakers and foreign language learners. After discussing the surface content of the poem, students may again asked to close their eyes and visualize the poem while listening to it.
As a follow-up activity a discussion may be held. After reviewing the plot of the poem and providing adequate artful questions, the students will eventually discover the deeper meaning of the poem. As being a facilitator, a teacher should always avoid telling the meaning. After each student grasps his or her own meaning, it is proper to discuss the depth of the poem. In this procedure, the teacher's aim is to support the students in their attempts to understand the poem and make it relevant to their lives. Once they have understood it and perceived its relevance, they will have no objection to practicing the poem or even memorizing it, for it will have become special for them (Celce-Murcia and Hills, 1988:126). At the follow-up stage, providing the determined structure, students may also be asked to write a poem about anything they want. In such a procedure the four skills are effectively integrated to practice or present any grammar point.
Since every class is different, teachers should creativity determine the teaching procedure. It is not advisable to apply one procedure too strictly. A teacher should adopt the activities according to the needs of the learners. However, it might not be very useful to use poems for young students or for beginners. Instead of poems, using nursery rhymes or songs would be more helpful since they provide more joyful and easier contexts. From pre-intermediate to advanced levels, it is really beneficial to use either songs or poems. Several poems can be adopted from contemporary poem books. The poems of the W.H. Auden, Robert Frost, Stanley Kunitz, Delmore Schwartz, W.D. Snodgrass, Theodore Roethke, Gary Snyder, Richard Wilbur, and Robert Lowell, etc. are suggested for the language teachers who want to use poems in their grammar lessons.
Using Games and Problem-Solving Activities
The latest concern of the foreign language teachers is to make the students use the language communicatively. After the realization of communicative competence , activities or techniques that are task-oriented and that lead students to use the language creatively have gained importance. Games and problem-solving activities, which are task-based and have a purpose beyond the production of correct speech, are the examples of the most preferable communicative activities. Such activities highlight not only the competence but also the performance of the learner. Yet they are the indispensable parts of a grammar lesson, since they reinforce a form-discourse match. In such activities the attention is on the discourse context.
Both games and problem-solving activities have a goal. Games are organized according to rules, and they are enjoyable. Most games require choral responses or group works, whereas problem-solving activities (though they are structured) require individual response and creative solutions. Games and problem-solving activities are generally used after the presentation, in the practice part, because such communicative tasks can only be handled after mastering sufficient grammar and lexical points.
Through well-planned games, learners can practice and internalize vocabulary, grammar and structures extensively. Play and competition that are provided by games enhance the motivation of the students. They also reduce the stress in the classroom. While playing games, the learners attention is on the message, not on the language. In a way, students acquire language unconsciously since their whole attention is engaged by the activity. By providing personal, social, and cross-cultural issues to define, they sometimes simulate real life situations. Many grammar games can be found in teaching grammar or course books.
There is a great overlap between games and problem solving activities. Though games generally place an emphasis on competition and wining, they also require some type of problem-solving activity. Like games, problem-solving activities have communicative purposes. Questions which require students to use available evidence to reach a conclusion and the logic problems which assist language learning by challenging students to demonstrate their understanding of English in an interesting way are the types of problem-solving activities. In problem solving activities, the problems are either based on real or imaginary situations. In the activities students are given a real or an imagery situation, and they are expected to find solutions for the problems.
Games and problem solving activities can be used for all levels. By regarding the proficiency, age and experience of the learners, appropriate activities might be applied successfully. It is also important to design clear and easy directions for the games or the activities.
Through problem solving activities students utmost attention is to the detail and to the meaning. The solution part of the problem can be used to generate any specific grammar point. In such activities a teacher should act as a facilitator rather than a director. It is also possible to integrate all skills in such activities. Reading or listening to a situation, a problem, or a question; responding or commenting either through speaking or writing. It is also advisable to keep in mind that such activities provide entertaining opportunities to practice thinking clearly while focusing on the form unconsciously.
In sum, games and problem solving activities provide favorable usages for extended communicative practice of grammar. They are both motivating and challenging. They encourage students to interact and communicate. Through such activities students match the discourse with the context of the game or the problem solving activity. So these activities create a meaningful context for language use. The use of such activities both increases the cooperation and competition in the classroom. Thus, potential classroom ideas come into being, and a successful, joyful and enthusiastic learning is provided.
Conclusion
So far, the usage of songs, poems, games, and problem solving activities are clarified. The advantages and some key points are explained. It is now more apparent that the teaching of grammar can be supported effectively by using such resources. According to the needs analysis of a classroom, several techniques can be integrated with such resources. Since teaching is a developing art, which requires innovative and creative ideas to enrich its effectiveness, we must not hesitate to use such resources in our classrooms. These resources can assist our teaching of grammar while providing a relaxed atmosphere and motivated students. Such activities are student centered, hence, by using them we give a chance to our students to express themselves, enjoy themselves during learning, and use the reserves of their minds. As, it should be born in mind that all these resources require the activation of both left and right hemispheres. Thus, we let our students use their long-term memory and learn effectively during such activities. So there is an undeniable fact that if our concern is to provide a successful and beneficial teaching, we must not hesitate to use songs, poems, games, and problem solving activities, which bring the structural, pragmatic, prosodic and communicative aspects of language together, in our language classrooms.
Bibliography
Celce-Murcia, M. & Hilles, S. (1988). Techniques and resources in teaching grammar. Oxford: Oxford University Press.
Cross, D. (1992). A practical handbook of language teaching. G.B.: Prentice Hall.
Eken, D.K. (1996). Ideas for using songs in the English language classroom. English Teaching FORUM, 34/1:46-47
Graham, C. (1993). Grammar chants. Oxford: Oxford University Press
Hill, D.A. (1999). Traditional folk songs in class. MET, 8/2:28-33
Horner, D. (1993). Classroom ideas: songs and music. MET, 2/3:33-39
Hutchinson, T. (1997). Lifelines: elementary- teachers book. Oxford: Oxford University Press.
Hutchinson, T. (1999). Lifelines: pre-intermediate-teachers book. Oxford: Oxford University Press.
Kim, L.S. (1995). Creative games for the language class. English Teaching FORUM, 33/1: 35-36
Lo, R. & Fai Li,H.C. (1998). Songs enhance learner involvement. English Teaching FORUM, 36/3:8-11
McKay, S.L. (1987). Teaching grammar. G.B.: Prentice Hall.
Murphey, T. (1992). Music and song. Oxford: Oxford University Press.
Rinvolucri, M. & Davis,P. (1995). More grammar games. Cambridge: Cambridge University Press.
Towndrow, P. (1999). Logic problems and English language learning. MET, 8/1:34-37
Saturday, May 3, 2008
Oxfam
Oxfam International is a confederation of 13 organizations working with over 3,000 partners in more than 100 countries to find lasting solutions to poverty and injustice.
The Oxfam International Secretariat leads, facilitates and supports collaboration between the Oxfam affiliates to increase Oxfam International’s impact on poverty and injustice through advocacy campaigns, development programs and emergency response.
Oxfam Great Britain is based in Oxford, UK. It was founded in England in 1942 as the Oxford Committee for Famine Relief by a group of Quakers, social activists, and Oxford academics. It was one of a number of local committees formed in support of the National Famine Relief Committee. Their mission was to persuade the UK government to allow food relief through the Allied blockade for the starving citizens of Nazi-occupied Greece. The first overseas Oxfam was founded in Canada in 1963. The committee changed its name to its telegraph address, OXFAM, in 1965.
Contents
1 History and beginnings
2 Oxfam's work
3 Shops
4 Funding
5 Fundraising
6 Criticism
7 References
8 See also
9 External links
9.1 National Oxfam websites
9.2 Campaigns
9.3 Resources and Materials
10 Further Reading
History and beginnings
The original Oxford Committee for Famine Relief, from which Oxfam takes its name, was a group of concerned citizens such as Canon Theodore Richard Milford (1896–1987), Professor Gilbert Murray and his wife Lady Mary, Cecil Jackson-Cole and Sir Alan Pim.
Oxfam's work
Though Oxfam's initial concern was the provision of food to relieve famine, over the years Oxfam has developed strategies to combat the causes of famine. In addition to food and medicine Oxfam also provides tools to enable people to become self-supporting and opens markets of international trade where crafts and produce from poorer regions of the world can be sold at a fair price to benefit the producer.
Oxfam's program has three main points of focus: development work, which tries to lift communities out of poverty with long-term, sustainable solutions based on their needs; humanitarian work, assisting those immediately affected by conflict and natural disasters (which often leads in to longer-term development work), especially in the field of water and sanitation; and lobbyist, advocacy and popular campaigning, trying to affect policy decisions on the causes of conflict at local, national, and international levels.
Oxfam works on trade justice, fair trade, education, debt and aid, livelihoods, health, HIV/AIDS, gender equality, conflict (campaigning for an international arms trade treaty) and natural disasters, democracy and human rights, and climate change.
Shops
The first permanent Oxfam gift shop opened in February 1948 on the ground floor of 17 Broad Street, Oxford, England, a lease on which building had been taken by the Oxford Committee for Famine Relief (later Oxfam) the previous November. Today Oxfam operates approximately 750 shops throughout Britain as well as a number in other countries. Over 70 of the organization's shops in the UK are specialist Oxfam bookshops, making them the largest retailer of second-hand books in the United Kingdom. Oxfam Canada sold off its Bridgehead fair trade business, which in 2000 became the Bridgehead Coffee chain which continues to promote fair trade coffee and related products.
Oxfam shops also sell fair trade products from developing communities around the world.
Funding
Oxfam has received funding from the Ford Foundation, the Bill and Melinda Gates Foundation, the John D. and Catherine T. MacArthur Foundation, the Minneapolis Foundation, the Public Welfare Foundation, the Rockefeller Brothers Fund, and the European Union. It has an annual operating budget of over $300 million USD.
Fundraising
Oxfam has a number of successful fundraising channels in addition to its shops. Over half a million people in the UK make a regular financial contribution towards its work, and vital funds are received from gifts left to the organization in people's wills. Many London Marathon competitors run to raise money for Oxfam, and Oxfam also receives funds in return for providing and organizing volunteer stewards at festivals such as Glastonbury. In conjunction with the Gurkha Welfare Trust, Oxfam also runs several Trailwalker events in Hong Kong, Australia, New Zealand, the United Kingdom and Japan.
Criticism
On 26 October 2006, Oxfam accused Starbucks of asking the National Coffee Association to block a trademark application from Ethiopia for two of the country's coffee beans, Sidamo and Harar. They claim this could result in denying Ethiopian coffee farmers potential annual earnings of up to £47m.
Robert Nelson, the head of the NCA, added that his organization initiated the opposition for economic reasons, "For the U.S. industry to exist, we must have an economically stable coffee industry in the producing world...This particular scheme is going to hurt the Ethiopian coffee farmers economically." The NCA claims the Ethiopian government was being badly advised and this move could price them out of the market.
Facing more than 90,000 letters of concern, Starbucks placed pamphlets in its stores accusing Oxfam of "misleading behavior" and insisting that its "campaign need[s] to stop." On 7 November, The Economist derided Oxfam's "simplistic" stance and Ethiopia's "economically illiterate" government, arguing that Starbucks' (and Illy's) standards-based approach would ultimately benefit farmers more.
Nonetheless, on 20 June 2007 representatives of the Government of Ethiopia and senior leaders from Starbucks Coffee Company announced that they had concluded an agreement regarding distribution, marketing and licensing that recognizes the importance and integrity of Ethiopia’s specialty coffee designations.
Oxfam Great Britain has been strongly criticised by other NGOs for becoming too close to Tony Blair's New Labour Government in the UK.
In 2005, the website "New Internationalist" described Oxfam as a "Big International Non-Government Organisation (BINGO)." The website criticises such organizations for being undemocratic whilst wielding enormous financial and economic clout.
On 28 April 2007 two academics in Melbourne, Australia representing a right-wing think tank lodged a complaint with the Australian Competition and Consumer Commission accusing Oxfam of misleading or deceptive conduct under the Trade Practices Act in its promotion of Fairtrade coffee. The academics claimed that high certification costs and low wages for workers undermine claims that Fairtrade helps to lift producers out of poverty. These claims were subsequently dismissed by the Commission.
In 2003, Oxfam Belgium produced a poster with a picture of a dripping blood orange. The poster read, "Israeli fruits have a bitter taste...reject the occupation of Palestine, don't buy Israeli fruits and vegetables." Oxfam was widely criticized because of the poster’s perceived anti-Israel political message and its allusion to traditional, antisemitic blood libel rhetoric. Following publicity and pressure the NGO Monitor, Oxfam removed the poster from their web site and Ian Anderson, the chairman of Oxfam International, issued a letter of apology. However, Oxfam maintained its support for a boycott of products grown in the West Bank and Gaza. Oxfam was criticized for its policy of what has been termed "selective morality."
The Oxfam International Secretariat leads, facilitates and supports collaboration between the Oxfam affiliates to increase Oxfam International’s impact on poverty and injustice through advocacy campaigns, development programs and emergency response.
Oxfam Great Britain is based in Oxford, UK. It was founded in England in 1942 as the Oxford Committee for Famine Relief by a group of Quakers, social activists, and Oxford academics. It was one of a number of local committees formed in support of the National Famine Relief Committee. Their mission was to persuade the UK government to allow food relief through the Allied blockade for the starving citizens of Nazi-occupied Greece. The first overseas Oxfam was founded in Canada in 1963. The committee changed its name to its telegraph address, OXFAM, in 1965.
Contents
1 History and beginnings
2 Oxfam's work
3 Shops
4 Funding
5 Fundraising
6 Criticism
7 References
8 See also
9 External links
9.1 National Oxfam websites
9.2 Campaigns
9.3 Resources and Materials
10 Further Reading
History and beginnings
The original Oxford Committee for Famine Relief, from which Oxfam takes its name, was a group of concerned citizens such as Canon Theodore Richard Milford (1896–1987), Professor Gilbert Murray and his wife Lady Mary, Cecil Jackson-Cole and Sir Alan Pim.
Oxfam's work
Though Oxfam's initial concern was the provision of food to relieve famine, over the years Oxfam has developed strategies to combat the causes of famine. In addition to food and medicine Oxfam also provides tools to enable people to become self-supporting and opens markets of international trade where crafts and produce from poorer regions of the world can be sold at a fair price to benefit the producer.
Oxfam's program has three main points of focus: development work, which tries to lift communities out of poverty with long-term, sustainable solutions based on their needs; humanitarian work, assisting those immediately affected by conflict and natural disasters (which often leads in to longer-term development work), especially in the field of water and sanitation; and lobbyist, advocacy and popular campaigning, trying to affect policy decisions on the causes of conflict at local, national, and international levels.
Oxfam works on trade justice, fair trade, education, debt and aid, livelihoods, health, HIV/AIDS, gender equality, conflict (campaigning for an international arms trade treaty) and natural disasters, democracy and human rights, and climate change.
Shops
The first permanent Oxfam gift shop opened in February 1948 on the ground floor of 17 Broad Street, Oxford, England, a lease on which building had been taken by the Oxford Committee for Famine Relief (later Oxfam) the previous November. Today Oxfam operates approximately 750 shops throughout Britain as well as a number in other countries. Over 70 of the organization's shops in the UK are specialist Oxfam bookshops, making them the largest retailer of second-hand books in the United Kingdom. Oxfam Canada sold off its Bridgehead fair trade business, which in 2000 became the Bridgehead Coffee chain which continues to promote fair trade coffee and related products.
Oxfam shops also sell fair trade products from developing communities around the world.
Funding
Oxfam has received funding from the Ford Foundation, the Bill and Melinda Gates Foundation, the John D. and Catherine T. MacArthur Foundation, the Minneapolis Foundation, the Public Welfare Foundation, the Rockefeller Brothers Fund, and the European Union. It has an annual operating budget of over $300 million USD.
Fundraising
Oxfam has a number of successful fundraising channels in addition to its shops. Over half a million people in the UK make a regular financial contribution towards its work, and vital funds are received from gifts left to the organization in people's wills. Many London Marathon competitors run to raise money for Oxfam, and Oxfam also receives funds in return for providing and organizing volunteer stewards at festivals such as Glastonbury. In conjunction with the Gurkha Welfare Trust, Oxfam also runs several Trailwalker events in Hong Kong, Australia, New Zealand, the United Kingdom and Japan.
Criticism
On 26 October 2006, Oxfam accused Starbucks of asking the National Coffee Association to block a trademark application from Ethiopia for two of the country's coffee beans, Sidamo and Harar. They claim this could result in denying Ethiopian coffee farmers potential annual earnings of up to £47m.
Robert Nelson, the head of the NCA, added that his organization initiated the opposition for economic reasons, "For the U.S. industry to exist, we must have an economically stable coffee industry in the producing world...This particular scheme is going to hurt the Ethiopian coffee farmers economically." The NCA claims the Ethiopian government was being badly advised and this move could price them out of the market.
Facing more than 90,000 letters of concern, Starbucks placed pamphlets in its stores accusing Oxfam of "misleading behavior" and insisting that its "campaign need[s] to stop." On 7 November, The Economist derided Oxfam's "simplistic" stance and Ethiopia's "economically illiterate" government, arguing that Starbucks' (and Illy's) standards-based approach would ultimately benefit farmers more.
Nonetheless, on 20 June 2007 representatives of the Government of Ethiopia and senior leaders from Starbucks Coffee Company announced that they had concluded an agreement regarding distribution, marketing and licensing that recognizes the importance and integrity of Ethiopia’s specialty coffee designations.
Oxfam Great Britain has been strongly criticised by other NGOs for becoming too close to Tony Blair's New Labour Government in the UK.
In 2005, the website "New Internationalist" described Oxfam as a "Big International Non-Government Organisation (BINGO)." The website criticises such organizations for being undemocratic whilst wielding enormous financial and economic clout.
On 28 April 2007 two academics in Melbourne, Australia representing a right-wing think tank lodged a complaint with the Australian Competition and Consumer Commission accusing Oxfam of misleading or deceptive conduct under the Trade Practices Act in its promotion of Fairtrade coffee. The academics claimed that high certification costs and low wages for workers undermine claims that Fairtrade helps to lift producers out of poverty. These claims were subsequently dismissed by the Commission.
In 2003, Oxfam Belgium produced a poster with a picture of a dripping blood orange. The poster read, "Israeli fruits have a bitter taste...reject the occupation of Palestine, don't buy Israeli fruits and vegetables." Oxfam was widely criticized because of the poster’s perceived anti-Israel political message and its allusion to traditional, antisemitic blood libel rhetoric. Following publicity and pressure the NGO Monitor, Oxfam removed the poster from their web site and Ian Anderson, the chairman of Oxfam International, issued a letter of apology. However, Oxfam maintained its support for a boycott of products grown in the West Bank and Gaza. Oxfam was criticized for its policy of what has been termed "selective morality."
Who We Are
CARE is a leading humanitarian organization fighting global poverty. Non-political and non-sectarian, we operate each year in more than 65 countries in Africa, Asia, Latin America, the Middle East and Eastern Europe, reaching more than 50 million people in poor communities.
CARE helps tackle underlying causes of poverty so that people can become self-sufficient. CARE is often one of the first to deliver emergency aid to survivors of natural disasters and war and, once the immediate crisis is over, we help people rebuild their lives. While CARE is a large international organisation with more than 14,500 employees worldwide, we have a strong local presence: more than 90 % of our staff are nationals of the countries where our programmes are run.
Our Vision
All of CARE International’s member organizations share a common vision to fight against worldwide poverty and to protect and enhance human dignity:
"We seek a world of hope, tolerance and social justice, where poverty has been overcome and people live in dignity and security. CARE will be a global force and partner of choice within a worldwide movement dedicated to ending poverty. We will be known everywhere for our unshakeable commitment to the dignity of people."
In this context, emergency relief is an important part of CARE’s mandate since natural and manmade disasters can drive otherwise self-sustaining populations into poverty and can often eradicate years of development work. CARE pays particular attention to the marginalized members of society and those least able to defend themselves, especially women and children.
Our Mission
CARE’s mission is to serve individuals and families in the poorest communities in the world. Drawing strength from our global diversity, resources and experience, we promote innovative solutions and are advocates for global responsibility. We promote lasting change by:
Strengthening capacity for self-help
Providing economic opportunity
Delivering relief in emergencies
Influencing policy decisions at all levels
Addressing discrimination in all its forms
Guided by the aspirations of local communities, we pursue our mission with both excellence and compassion because the people whom we serve deserve nothing less.
Our Core Values
Respect We affirm the dignity, potential and contribution of participants, donors, partners and staff.
Integrity We act consistently with CARE's mission, being honest and transparent in what we do and say, and accept responsibility for our collective and individual actions.
Commitment We work together effectively to serve the larger community.
Excellence We constantly challenge ourselves to the highest levels of learning and performance to achieve greater impact.
We hold ourselves accountable for being consistent with these principles, and ask others to help us do so, not only in our programming, but in all that we do.
CARE helps tackle underlying causes of poverty so that people can become self-sufficient. CARE is often one of the first to deliver emergency aid to survivors of natural disasters and war and, once the immediate crisis is over, we help people rebuild their lives. While CARE is a large international organisation with more than 14,500 employees worldwide, we have a strong local presence: more than 90 % of our staff are nationals of the countries where our programmes are run.
Our Vision
All of CARE International’s member organizations share a common vision to fight against worldwide poverty and to protect and enhance human dignity:
"We seek a world of hope, tolerance and social justice, where poverty has been overcome and people live in dignity and security. CARE will be a global force and partner of choice within a worldwide movement dedicated to ending poverty. We will be known everywhere for our unshakeable commitment to the dignity of people."
In this context, emergency relief is an important part of CARE’s mandate since natural and manmade disasters can drive otherwise self-sustaining populations into poverty and can often eradicate years of development work. CARE pays particular attention to the marginalized members of society and those least able to defend themselves, especially women and children.
Our Mission
CARE’s mission is to serve individuals and families in the poorest communities in the world. Drawing strength from our global diversity, resources and experience, we promote innovative solutions and are advocates for global responsibility. We promote lasting change by:
Strengthening capacity for self-help
Providing economic opportunity
Delivering relief in emergencies
Influencing policy decisions at all levels
Addressing discrimination in all its forms
Guided by the aspirations of local communities, we pursue our mission with both excellence and compassion because the people whom we serve deserve nothing less.
Our Core Values
Respect We affirm the dignity, potential and contribution of participants, donors, partners and staff.
Integrity We act consistently with CARE's mission, being honest and transparent in what we do and say, and accept responsibility for our collective and individual actions.
Commitment We work together effectively to serve the larger community.
Excellence We constantly challenge ourselves to the highest levels of learning and performance to achieve greater impact.
We hold ourselves accountable for being consistent with these principles, and ask others to help us do so, not only in our programming, but in all that we do.
Structure of CARE
CARE International (CI) is a confederation composed of twelve national Members, each being an autonomous non-governmental organization in its own right. CI Members in North America, Europe, Asia and Australia carry out a range of project-related, advocacy, fundraising, and communications activities in support of CARE’s relief and development programmes in over 65 countries worldwide.
Robert Glasser
CI Secretary General
CARE International Secretariat
The CI Secretariat is based in Geneva, Switzerland, with representation offices in New York and in Brussels to liaise with the United Nations and the European institutions respectively. To know more about CARE’s advocacy work, please click here.
The CI Secretariat is an international foundation, registered under Swiss law, and governed by the CARE International Board of Directors. Under the leadership of CI Secretary General, Robert Glasser, it coordinates and supports the work of the CARE national Members and Country Offices, carrying out the following activities:
providing support to the CI Board of Directors
implementing policy decisions made by the Board of Directors
promulgating and ensuring Member and Country Office compliance with the CI Code, a document that comprises policies and guidelines by which Members agree to conduct their domestic and overseas activities, and to interact with one another
ensuring effective representation on behalf of the Members and Country Offices with multilateral institutions and other international bodies
co-ordinating CI's response to humanitarian disasters
co-ordinating CI's policy and advocacy response to humanitarian and development issues prioritised by the membership
supporting the organisational development of CI's Members
establishing and overseeing standards and criteria that pertain to membership of CI
overseeing CI's organisational evolution
The CI Secretariat is the home of the CARE Emergency Group, which provides a quick-reaction capability in situations in which an emergency is likely to overwhelm normal CARE programmes or when a disaster strike in a place where CARE has no presence.
CARE International Members
Each CARE Member is registered as a non-profit charitable organization according to the laws of its own country, and is regulated by these laws and its statutes. Governance oversight is provided by a board of directors, who serve as trustees. The management of each CARE Member is conducted under the leadership of the National Director, who is the chief executive, and his/her senior management team.
CARE International's twelve Members are as follows:
CARE Australia
CARE Canada
CARE Danmark
CARE International Deutschland
CARE France
CARE International Japan
CARE Nederland
CARE Norge
CARE Österreich
Raks Thai Foundation (CARE Thailand)
CARE International UK
CARE USA
CARE International's Country Offices
Health Education in Bangladesh. © CARE.
For every country in which CARE operates, all programmes and projects are implemented through a single integrated operational presence, termed the Country Office, under the leadership of the CARE Country Director.
CARE Members participate in country programmes by becoming involved in project identification and design, and through their subsequent provision of technical assistance, financing, human resources or other kinds of support to the Country Office. In all cases, participation occurs within the context of the Country Office strategic plan and its programme and programme support structures.
Robert Glasser
CI Secretary General
CARE International Secretariat
The CI Secretariat is based in Geneva, Switzerland, with representation offices in New York and in Brussels to liaise with the United Nations and the European institutions respectively. To know more about CARE’s advocacy work, please click here.
The CI Secretariat is an international foundation, registered under Swiss law, and governed by the CARE International Board of Directors. Under the leadership of CI Secretary General, Robert Glasser, it coordinates and supports the work of the CARE national Members and Country Offices, carrying out the following activities:
providing support to the CI Board of Directors
implementing policy decisions made by the Board of Directors
promulgating and ensuring Member and Country Office compliance with the CI Code, a document that comprises policies and guidelines by which Members agree to conduct their domestic and overseas activities, and to interact with one another
ensuring effective representation on behalf of the Members and Country Offices with multilateral institutions and other international bodies
co-ordinating CI's response to humanitarian disasters
co-ordinating CI's policy and advocacy response to humanitarian and development issues prioritised by the membership
supporting the organisational development of CI's Members
establishing and overseeing standards and criteria that pertain to membership of CI
overseeing CI's organisational evolution
The CI Secretariat is the home of the CARE Emergency Group, which provides a quick-reaction capability in situations in which an emergency is likely to overwhelm normal CARE programmes or when a disaster strike in a place where CARE has no presence.
CARE International Members
Each CARE Member is registered as a non-profit charitable organization according to the laws of its own country, and is regulated by these laws and its statutes. Governance oversight is provided by a board of directors, who serve as trustees. The management of each CARE Member is conducted under the leadership of the National Director, who is the chief executive, and his/her senior management team.
CARE International's twelve Members are as follows:
CARE Australia
CARE Canada
CARE Danmark
CARE International Deutschland
CARE France
CARE International Japan
CARE Nederland
CARE Norge
CARE Österreich
Raks Thai Foundation (CARE Thailand)
CARE International UK
CARE USA
CARE International's Country Offices
Health Education in Bangladesh. © CARE.
For every country in which CARE operates, all programmes and projects are implemented through a single integrated operational presence, termed the Country Office, under the leadership of the CARE Country Director.
CARE Members participate in country programmes by becoming involved in project identification and design, and through their subsequent provision of technical assistance, financing, human resources or other kinds of support to the Country Office. In all cases, participation occurs within the context of the Country Office strategic plan and its programme and programme support structures.
Greenhouse effect
A schematic representation of the exchanges of energy between outer space, the Earth's atmosphere, and the Earth surface. The ability of the atmosphere to capture and recycle energy emitted by the Earth surface is the defining characteristic of the greenhouse effect.
The greenhouse effect is the process in which the emission of infrared radiation by the atmosphere warms a planet's surface. The name comes from an incorrect analogy with the warming of air inside a greenhouse compared to the air outside the greenhouse. The greenhouse effect was discovered by Joseph Fourier in 1824 and first investigated quantitatively by Svante Arrhenius in 1896.[1]
The Earth's average surface temperature of 14 °C (57 °F) would otherwise be about -19 °C (-2.2 °F) in the absence of the greenhouse effect.[2] Global warming, a recent warming of the Earth's lower atmosphere, is believed to be the result of an enhanced greenhouse effect due to increased concentrations of greenhouse gases in the atmosphere. In addition to the Earth, Mars and Venus have greenhouse effects.
Contents
1 Basic mechanism
2 Greenhouse gases
3 Positive feedback , runaway greenhouse effect and tipping point
4 Anthropogenic greenhouse effect
5 Real greenhouses
6 See also
7 References
Basic mechanism
See also: Radiative forcing
Solar radiation at top of atmosphere and at Earth's surface.
Pattern of absorption bands generated by various greenhouse gases and their impact on both solar radiation and upgoing thermal radiation from the Earth's surface. Note that a greater quantity of upgoing radiation is absorbed, which contributes to the greenhouse effect.
The Earth receives energy from the Sun in the form of radiation. Most of the energy is in visible wavelengths and in infrared wavelengths that are near the visible range (often called "near infrared"). The Earth reflects about 30% of the incoming solar radiation. The remaining 70% is absorbed, warming the land, atmosphere and oceans.
For the Earth's temperature to be in steady state so that the Earth does not rapidly heat or cool, this absorbed solar radiation must be very closely balanced by energy radiated back to space in the infrared wavelengths. Since the intensity of infrared radiation increases with increasing temperature, one can think of the Earth's temperature as being determined by the infrared flux needed to balance the absorbed solar flux. The visible solar radiation mostly heats the surface, not the atmosphere, whereas most of the infrared radiation escaping to space is emitted from the upper atmosphere, not the surface. The infrared photons emitted by the surface are mostly absorbed in the atmosphere by greenhouse gases and clouds and do not escape directly to space.
The reason this warms the surface is most easily understood by starting with a simplified model of a purely radiative greenhouse effect that ignores energy transfer in the atmosphere by convection (sensible heat transport) and by the evaporation and condensation of water vapor (latent heat transport). In this purely radiative case, one can think of the atmosphere as emitting infrared radiation both upwards and downwards. The upward infrared flux emitted by the surface must balance not only the absorbed solar flux but also this downward infrared flux emitted by the atmosphere. The surface temperature will rise until it generates thermal radiation equivalent to the sum of the incoming solar and infrared radiation.
A more realistic picture taking into account the convective and latent heat fluxes is somewhat more complex. But the following simple model captures the essence. The starting point is to note that the opacity of the atmosphere to infrared radiation determines the height in the atmosphere from which most of the photons are emitted into space. If the atmosphere is more opaque, the typical photon escaping to space will be emitted from higher in the atmosphere, because one then has to go to higher altitudes to see out to space in the infrared. Since the emission of infrared radiation is a function of temperature, it is the temperature of the atmosphere at this emission level that is effectively determined by the requirement that the emitted flux balance the absorbed solar flux.
But the temperature of the atmosphere generally decreases with height above the surface, at a rate of roughly 6.5 °C per kilometer on average, until one reaches the stratosphere 10-15 km above the surface. (Most infrared photons escaping to space are emitted by the troposphere, the region bounded by the surface and the stratosphere, so we can ignore the stratosphere in this simple picture.) A very simple model, but one that proves to be remarkably useful, involves the assumption that this temperature profile is simply fixed, by the non-radiative energy fluxes. Given the temperature at the emission level of the infrared flux escaping to space, one then computes the surface temperature by increasing temperature at the rate of 6.5 °C per kilometer, the environmental lapse rate, until one reaches the surface. The more opaque the atmosphere, and the higher the emission level of the escaping infrared radiation, the warmer the surface, since one then needs to follow this lapse rate over a larger distance in the vertical. While less intuitive than the purely radiative greenhouse effect, this less familiar radiative-convective picture is the starting point for most discussions of the greenhouse effect in the climate modeling literature.
The term "greenhouse effect" is a source of confusion in that actual greenhouses do not warm by this mechanism (see section Real greenhouses). Popular discussions often imply incorrectly that they do; this error is sometimes made even in materials from scientific or governmental agencies (e.g., the U.S. Environmental Protection Agency).
Greenhouse gases
Main article: Greenhouse gas
Quantum mechanics provides the basis for computing the interactions between molecules and radiation. Most of this interaction occurs when the frequency of the radiation closely matches that of the spectral lines of the molecule, determined by the quantization of the modes of vibration and rotation of the molecule. (The electronic excitations are generally not relevant for infrared radiation, as they require energy larger than that in an infrared photon.)
The width of a spectral line is an important element in understanding its importance for the absorption of radiation. In the Earth’s atmosphere these spectral widths are primarily determined by “pressure broadening”, which is the distortion of the spectrum due to the collision with another molecule. Most of the infrared absorption in the atmosphere can be thought of as occurring while two molecules are colliding. The absorption due to a photon interacting with a lone molecule is relatively small. This three-body aspect of the problem, one photon and two molecules, makes direct quantum mechanical computation for molecules of interest more challenging. Careful laboratory spectroscopic measurements, rather than ab initio quantum mechanical computations, provide the basis for most of the radiative transfer calculations used in studies of the atmosphere.
The molecules/atoms that constitute the bulk of the atmosphere: oxygen (O2), nitrogen (N2) and argon (Ar); do not interact with infrared radiation significantly. While the oxygen and nitrogen molecules can vibrate, because of their symmetry these vibrations do not create any transient charge separation. Without such a transient dipole moment, they can neither absorb nor emit infrared radiation. In the Earth’s atmosphere, the dominant infrared absorbing gases are water vapor, carbon dioxide, and ozone (O3). The same molecules are also the dominant infrared emitting molecules. CO2 and O3 have "floppy" vibration motions whose quantum states can be excited by collisions at energies encountered in the atmosphere. For example, carbon dioxide is a linear molecule, but it has an important vibrational mode in which the molecule bends with the carbon in the middle moving one way and the oxygens on the ends moving the other way, creating some charge separation, a dipole moment, thus carbon dioxide molecules can absorb IR radiation. Collisions will immediately transfer this energy to heating the surrounding gas. On the other hand, other CO2 molecules will be vibrationally excited by collisions. Roughly 5% of CO2 molecules are vibrationally excited at room temperature and it is this 5% that radiates. A substantial part of the greenhouse effect due to carbon dioxide exists because this vibration is easily excited by infrared radiation. CO2 has two other vibrational modes. The symmetric stretch does not radiate, and the asymmetric stretch is at too high a frequency to be effectively excited by atmospheric temperature collisions, although it does contribute to absorption of IR radiation. The vibrational modes of water are at too high energies to effectively radiate, but do absorb higher frequency IR radiation. Water vapor has a bent shape. It has a permanent dipole moment (the O atom end is electron rich, and the H atoms electron poor) which means that IR light can be emitted and absorbed during rotational transitions, and these transitions can also be produced by collisional energy transfer. Clouds are also very important infrared absorbers. Therefore, water has multiple effects on infrared radiation, through its vapor phase and through its condensed phases. Other absorbers of significance include methane, nitrous oxide and the chlorofluorocarbons.
Discussion of the relative importance of different infrared absorbers is confused by the overlap between the spectral lines due to different gases, widened by pressure broadening. As a result, the absorption due to one gas cannot be thought of as independent of the presence of other gases. One convenient approach is to remove the chosen constituent, leaving all other absorbers, and the temperatures, untouched, and monitoring the infrared radiation escaping to space. The reduction in infrared absorption is then a measure of the importance of that constituent. More precisely, define the greenhouse effect (GE) to be the difference between the infrared radiation that the surface would radiate to space if there were no atmosphere and the actual infrared radiation escaping to space. Then compute the percentage reduction in GE when a constituent is removed. The table below is computed by this method, using a particular 1-dimensional model of the atmosphere. More recent 3D computations lead to similar results.
Gas removed percent reduction in GE
H2O 36%
CO2 9%
O3 3%
(Source: GISS-GCM ModelE simulation)
By this particular measure, water vapor can be thought of as providing 36% of the greenhouse effect, and carbon dioxide 9%, but the effect of removal of both of these constituents will be greater than the total that each reduces the effect, in this case more than 45%. An additional proviso is that these numbers are computed holding the cloud distribution fixed. But removing water vapor from the atmosphere while holding clouds fixed is not likely to be physically relevant. In addition, the effects of a given gas are typically nonlinear in the amount of that gas, since the absorption by the gas at one level in the atmosphere can remove photons that would otherwise interact with the gas at another altitude. The kinds of estimates presented in the table, while often encountered in the controversies surrounding global warming, must be treated with caution. Different estimates found in different sources typically result from different definitions and do not reflect uncertainties in the underlying radiative transfer.
Positive feedback , runaway greenhouse effect and tipping point
The Tipping point in global warming is the point at which change due to human activity brings about sufficient new processes in nature to make any human reversal of the change impossible. Some climate scientists believe this will be reached in about 2017 , while others , notably James Hansen, NASA's top climate scientist, believe it has already been reached.
When there is a loop of effects such as the concentration of a greenhouse gas itself being a function of temperature, there is a feedback. If the effect is to act in the same direction on temperature it is a positive feedback; and if in the opposite direction it is a negative feedback. Sometimes feedback effects can be on the same cause as the forcing but it can also be via another greenhouse gas or on other effects such as change in ice cover affecting the planet's albedo.
Positive feedbacks do not have to lead to a runaway effect. With radiation from the Earth increasing in proportion to the fourth power of temperature, the feedback effect has to be very strong to cause a runaway effect. An increase in temperature from greenhouse gases leading to increased water vapour which is a greenhouse gas causing further warming is a positive feedback. This cannot be a runaway effect or the runaway effect would have occurred long ago. Positive feedback effects are common and can always exist while runaway effects are much rarer and cannot be operating at all times.
If the effects from the second iteration of the loop of effects is larger than the effects of the first iteration of the loop this will lead to a self perpetuating effect. If this occurs and the feedback only ends after producing a major temperature increase, it is called a runaway greenhouse effect. A runaway feedback could also occur in the opposite direction leading to an ice age. Runaway feedbacks are bound to stop, since infinite temperatures are not observed. They are allowed to stop due to things like a reducing supply of a greenhouse gas or a phase change of the gas or ice cover reducing towards zero or increasing toward a large size that is difficult to increase.
According to the clathrate gun hypothesis a runaway greenhouse effect could be caused by liberation of methane gas from hydrates by global warming if there are sufficient hydrates close to unstable conditions. It has been speculated that the Permian-Triassic extinction event was caused by such a runaway effect. It is also thought that large quantities of methane could be released from the Siberian tundra as it begins to thaw, methane being 21-times more potent a greenhouse gas than carbon dioxide.
A runaway greenhouse effect involving CO2 and water vapor may have occurred on Venus due to its closer proximity to the sun. On Venus today there is little water vapor in the atmosphere. If water vapor did contribute to the warmth of Venus at one time, this water is thought to have escaped to space. Venus is sufficiently strongly heated by the Sun that water vapor can rise much higher in the atmosphere and is split into hydrogen and oxygen by ultraviolet light. The hydrogen can then escape from the atmosphere and the oxygen recombines. Carbon dioxide, the dominant greenhouse gas in the current Venusian atmosphere, likely owes its larger concentration to the weakness of carbon recycling as compared to Earth, where the carbon dioxide emitted from volcanoes is efficiently subducted into the Earth by plate tectonics on geologic time scales..
Even so, the high temperatures on Venus are only partially caused by carbon dioxide; a major contributor is the thick bank of clouds containing sulphuric acid. Although these clouds give Venus a high reflectivity in the visible region, the Galileo probe showed that the clouds appear black at infrared wavelengths of 2.3 microns due to strong infrared absorption .
Anthropogenic greenhouse effect
Main article: Global warming
CO2 production from increased industrial activity (fossil fuel burning) and other human activities such as cement production and tropical deforestation has increased the CO2 concentrations in the atmosphere. Measurements of carbon dioxide amounts from Mauna Loa observatory show that CO2 has increased from about 313 ppm (parts per million) in 1960 to about 375 ppm in 2005. The current observed amount of CO2 exceeds the geological record of CO2 maxima (~300 ppm) from ice core data.
Because it is a greenhouse gas, elevated CO2 levels will increase global mean temperature; based on an extensive review of the scientific literature, the Intergovernmental Panel on Climate Change concludes that "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations".
Over the past 800,000 years, ice core data shows unambiguously that carbon dioxide has varied from values as low as 180 parts per million (ppm) to the pre-industrial level of 270ppm. Certain paleoclimatologists consider variations in carbon dioxide to be a fundamental factor in controlling climate variations over this time scale.
Real greenhouses
A modern Greenhouse in RHS Wisley
The term 'greenhouse effect' originally came from the greenhouses used for gardening, but it is a misnomer since greenhouses operate differently. A greenhouse is built of glass. It heats up mainly because the sun warms the ground inside it and this warms the air in the greenhouse. The air continues to heat because it is confined within the greenhouse, unlike the environment outside the greenhouse where warm air near the surface rises and mixes with cooler air aloft. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature will drop considerably. It has also been demonstrated experimentally (Wood, 1909): a "greenhouse" built of rock salt (which is transparent to infrared radiation) heats up just as one built of glass does. Greenhouses thus work primarily by preventing convection; the atmospheric greenhouse effect however reduces radiation loss, not convection. It is quite common, however, to find sources that make the erroneous "greenhouse" analogy. Although the primary mechanism for warming greenhouses is the prevention of mixing with the free atmosphere, the radiative properties of the glazing can still be important to commercial growers. With the modern development of new plastic surfaces and glazings for greenhouses, this has permitted construction of greenhouses which selectively control radiation transmittance in order to better control the growing environment.
The greenhouse effect is the process in which the emission of infrared radiation by the atmosphere warms a planet's surface. The name comes from an incorrect analogy with the warming of air inside a greenhouse compared to the air outside the greenhouse. The greenhouse effect was discovered by Joseph Fourier in 1824 and first investigated quantitatively by Svante Arrhenius in 1896.[1]
The Earth's average surface temperature of 14 °C (57 °F) would otherwise be about -19 °C (-2.2 °F) in the absence of the greenhouse effect.[2] Global warming, a recent warming of the Earth's lower atmosphere, is believed to be the result of an enhanced greenhouse effect due to increased concentrations of greenhouse gases in the atmosphere. In addition to the Earth, Mars and Venus have greenhouse effects.
Contents
1 Basic mechanism
2 Greenhouse gases
3 Positive feedback , runaway greenhouse effect and tipping point
4 Anthropogenic greenhouse effect
5 Real greenhouses
6 See also
7 References
Basic mechanism
See also: Radiative forcing
Solar radiation at top of atmosphere and at Earth's surface.
Pattern of absorption bands generated by various greenhouse gases and their impact on both solar radiation and upgoing thermal radiation from the Earth's surface. Note that a greater quantity of upgoing radiation is absorbed, which contributes to the greenhouse effect.
The Earth receives energy from the Sun in the form of radiation. Most of the energy is in visible wavelengths and in infrared wavelengths that are near the visible range (often called "near infrared"). The Earth reflects about 30% of the incoming solar radiation. The remaining 70% is absorbed, warming the land, atmosphere and oceans.
For the Earth's temperature to be in steady state so that the Earth does not rapidly heat or cool, this absorbed solar radiation must be very closely balanced by energy radiated back to space in the infrared wavelengths. Since the intensity of infrared radiation increases with increasing temperature, one can think of the Earth's temperature as being determined by the infrared flux needed to balance the absorbed solar flux. The visible solar radiation mostly heats the surface, not the atmosphere, whereas most of the infrared radiation escaping to space is emitted from the upper atmosphere, not the surface. The infrared photons emitted by the surface are mostly absorbed in the atmosphere by greenhouse gases and clouds and do not escape directly to space.
The reason this warms the surface is most easily understood by starting with a simplified model of a purely radiative greenhouse effect that ignores energy transfer in the atmosphere by convection (sensible heat transport) and by the evaporation and condensation of water vapor (latent heat transport). In this purely radiative case, one can think of the atmosphere as emitting infrared radiation both upwards and downwards. The upward infrared flux emitted by the surface must balance not only the absorbed solar flux but also this downward infrared flux emitted by the atmosphere. The surface temperature will rise until it generates thermal radiation equivalent to the sum of the incoming solar and infrared radiation.
A more realistic picture taking into account the convective and latent heat fluxes is somewhat more complex. But the following simple model captures the essence. The starting point is to note that the opacity of the atmosphere to infrared radiation determines the height in the atmosphere from which most of the photons are emitted into space. If the atmosphere is more opaque, the typical photon escaping to space will be emitted from higher in the atmosphere, because one then has to go to higher altitudes to see out to space in the infrared. Since the emission of infrared radiation is a function of temperature, it is the temperature of the atmosphere at this emission level that is effectively determined by the requirement that the emitted flux balance the absorbed solar flux.
But the temperature of the atmosphere generally decreases with height above the surface, at a rate of roughly 6.5 °C per kilometer on average, until one reaches the stratosphere 10-15 km above the surface. (Most infrared photons escaping to space are emitted by the troposphere, the region bounded by the surface and the stratosphere, so we can ignore the stratosphere in this simple picture.) A very simple model, but one that proves to be remarkably useful, involves the assumption that this temperature profile is simply fixed, by the non-radiative energy fluxes. Given the temperature at the emission level of the infrared flux escaping to space, one then computes the surface temperature by increasing temperature at the rate of 6.5 °C per kilometer, the environmental lapse rate, until one reaches the surface. The more opaque the atmosphere, and the higher the emission level of the escaping infrared radiation, the warmer the surface, since one then needs to follow this lapse rate over a larger distance in the vertical. While less intuitive than the purely radiative greenhouse effect, this less familiar radiative-convective picture is the starting point for most discussions of the greenhouse effect in the climate modeling literature.
The term "greenhouse effect" is a source of confusion in that actual greenhouses do not warm by this mechanism (see section Real greenhouses). Popular discussions often imply incorrectly that they do; this error is sometimes made even in materials from scientific or governmental agencies (e.g., the U.S. Environmental Protection Agency).
Greenhouse gases
Main article: Greenhouse gas
Quantum mechanics provides the basis for computing the interactions between molecules and radiation. Most of this interaction occurs when the frequency of the radiation closely matches that of the spectral lines of the molecule, determined by the quantization of the modes of vibration and rotation of the molecule. (The electronic excitations are generally not relevant for infrared radiation, as they require energy larger than that in an infrared photon.)
The width of a spectral line is an important element in understanding its importance for the absorption of radiation. In the Earth’s atmosphere these spectral widths are primarily determined by “pressure broadening”, which is the distortion of the spectrum due to the collision with another molecule. Most of the infrared absorption in the atmosphere can be thought of as occurring while two molecules are colliding. The absorption due to a photon interacting with a lone molecule is relatively small. This three-body aspect of the problem, one photon and two molecules, makes direct quantum mechanical computation for molecules of interest more challenging. Careful laboratory spectroscopic measurements, rather than ab initio quantum mechanical computations, provide the basis for most of the radiative transfer calculations used in studies of the atmosphere.
The molecules/atoms that constitute the bulk of the atmosphere: oxygen (O2), nitrogen (N2) and argon (Ar); do not interact with infrared radiation significantly. While the oxygen and nitrogen molecules can vibrate, because of their symmetry these vibrations do not create any transient charge separation. Without such a transient dipole moment, they can neither absorb nor emit infrared radiation. In the Earth’s atmosphere, the dominant infrared absorbing gases are water vapor, carbon dioxide, and ozone (O3). The same molecules are also the dominant infrared emitting molecules. CO2 and O3 have "floppy" vibration motions whose quantum states can be excited by collisions at energies encountered in the atmosphere. For example, carbon dioxide is a linear molecule, but it has an important vibrational mode in which the molecule bends with the carbon in the middle moving one way and the oxygens on the ends moving the other way, creating some charge separation, a dipole moment, thus carbon dioxide molecules can absorb IR radiation. Collisions will immediately transfer this energy to heating the surrounding gas. On the other hand, other CO2 molecules will be vibrationally excited by collisions. Roughly 5% of CO2 molecules are vibrationally excited at room temperature and it is this 5% that radiates. A substantial part of the greenhouse effect due to carbon dioxide exists because this vibration is easily excited by infrared radiation. CO2 has two other vibrational modes. The symmetric stretch does not radiate, and the asymmetric stretch is at too high a frequency to be effectively excited by atmospheric temperature collisions, although it does contribute to absorption of IR radiation. The vibrational modes of water are at too high energies to effectively radiate, but do absorb higher frequency IR radiation. Water vapor has a bent shape. It has a permanent dipole moment (the O atom end is electron rich, and the H atoms electron poor) which means that IR light can be emitted and absorbed during rotational transitions, and these transitions can also be produced by collisional energy transfer. Clouds are also very important infrared absorbers. Therefore, water has multiple effects on infrared radiation, through its vapor phase and through its condensed phases. Other absorbers of significance include methane, nitrous oxide and the chlorofluorocarbons.
Discussion of the relative importance of different infrared absorbers is confused by the overlap between the spectral lines due to different gases, widened by pressure broadening. As a result, the absorption due to one gas cannot be thought of as independent of the presence of other gases. One convenient approach is to remove the chosen constituent, leaving all other absorbers, and the temperatures, untouched, and monitoring the infrared radiation escaping to space. The reduction in infrared absorption is then a measure of the importance of that constituent. More precisely, define the greenhouse effect (GE) to be the difference between the infrared radiation that the surface would radiate to space if there were no atmosphere and the actual infrared radiation escaping to space. Then compute the percentage reduction in GE when a constituent is removed. The table below is computed by this method, using a particular 1-dimensional model of the atmosphere. More recent 3D computations lead to similar results.
Gas removed percent reduction in GE
H2O 36%
CO2 9%
O3 3%
(Source: GISS-GCM ModelE simulation)
By this particular measure, water vapor can be thought of as providing 36% of the greenhouse effect, and carbon dioxide 9%, but the effect of removal of both of these constituents will be greater than the total that each reduces the effect, in this case more than 45%. An additional proviso is that these numbers are computed holding the cloud distribution fixed. But removing water vapor from the atmosphere while holding clouds fixed is not likely to be physically relevant. In addition, the effects of a given gas are typically nonlinear in the amount of that gas, since the absorption by the gas at one level in the atmosphere can remove photons that would otherwise interact with the gas at another altitude. The kinds of estimates presented in the table, while often encountered in the controversies surrounding global warming, must be treated with caution. Different estimates found in different sources typically result from different definitions and do not reflect uncertainties in the underlying radiative transfer.
Positive feedback , runaway greenhouse effect and tipping point
The Tipping point in global warming is the point at which change due to human activity brings about sufficient new processes in nature to make any human reversal of the change impossible. Some climate scientists believe this will be reached in about 2017 , while others , notably James Hansen, NASA's top climate scientist, believe it has already been reached.
When there is a loop of effects such as the concentration of a greenhouse gas itself being a function of temperature, there is a feedback. If the effect is to act in the same direction on temperature it is a positive feedback; and if in the opposite direction it is a negative feedback. Sometimes feedback effects can be on the same cause as the forcing but it can also be via another greenhouse gas or on other effects such as change in ice cover affecting the planet's albedo.
Positive feedbacks do not have to lead to a runaway effect. With radiation from the Earth increasing in proportion to the fourth power of temperature, the feedback effect has to be very strong to cause a runaway effect. An increase in temperature from greenhouse gases leading to increased water vapour which is a greenhouse gas causing further warming is a positive feedback. This cannot be a runaway effect or the runaway effect would have occurred long ago. Positive feedback effects are common and can always exist while runaway effects are much rarer and cannot be operating at all times.
If the effects from the second iteration of the loop of effects is larger than the effects of the first iteration of the loop this will lead to a self perpetuating effect. If this occurs and the feedback only ends after producing a major temperature increase, it is called a runaway greenhouse effect. A runaway feedback could also occur in the opposite direction leading to an ice age. Runaway feedbacks are bound to stop, since infinite temperatures are not observed. They are allowed to stop due to things like a reducing supply of a greenhouse gas or a phase change of the gas or ice cover reducing towards zero or increasing toward a large size that is difficult to increase.
According to the clathrate gun hypothesis a runaway greenhouse effect could be caused by liberation of methane gas from hydrates by global warming if there are sufficient hydrates close to unstable conditions. It has been speculated that the Permian-Triassic extinction event was caused by such a runaway effect. It is also thought that large quantities of methane could be released from the Siberian tundra as it begins to thaw, methane being 21-times more potent a greenhouse gas than carbon dioxide.
A runaway greenhouse effect involving CO2 and water vapor may have occurred on Venus due to its closer proximity to the sun. On Venus today there is little water vapor in the atmosphere. If water vapor did contribute to the warmth of Venus at one time, this water is thought to have escaped to space. Venus is sufficiently strongly heated by the Sun that water vapor can rise much higher in the atmosphere and is split into hydrogen and oxygen by ultraviolet light. The hydrogen can then escape from the atmosphere and the oxygen recombines. Carbon dioxide, the dominant greenhouse gas in the current Venusian atmosphere, likely owes its larger concentration to the weakness of carbon recycling as compared to Earth, where the carbon dioxide emitted from volcanoes is efficiently subducted into the Earth by plate tectonics on geologic time scales..
Even so, the high temperatures on Venus are only partially caused by carbon dioxide; a major contributor is the thick bank of clouds containing sulphuric acid. Although these clouds give Venus a high reflectivity in the visible region, the Galileo probe showed that the clouds appear black at infrared wavelengths of 2.3 microns due to strong infrared absorption .
Anthropogenic greenhouse effect
Main article: Global warming
CO2 production from increased industrial activity (fossil fuel burning) and other human activities such as cement production and tropical deforestation has increased the CO2 concentrations in the atmosphere. Measurements of carbon dioxide amounts from Mauna Loa observatory show that CO2 has increased from about 313 ppm (parts per million) in 1960 to about 375 ppm in 2005. The current observed amount of CO2 exceeds the geological record of CO2 maxima (~300 ppm) from ice core data.
Because it is a greenhouse gas, elevated CO2 levels will increase global mean temperature; based on an extensive review of the scientific literature, the Intergovernmental Panel on Climate Change concludes that "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations".
Over the past 800,000 years, ice core data shows unambiguously that carbon dioxide has varied from values as low as 180 parts per million (ppm) to the pre-industrial level of 270ppm. Certain paleoclimatologists consider variations in carbon dioxide to be a fundamental factor in controlling climate variations over this time scale.
Real greenhouses
A modern Greenhouse in RHS Wisley
The term 'greenhouse effect' originally came from the greenhouses used for gardening, but it is a misnomer since greenhouses operate differently. A greenhouse is built of glass. It heats up mainly because the sun warms the ground inside it and this warms the air in the greenhouse. The air continues to heat because it is confined within the greenhouse, unlike the environment outside the greenhouse where warm air near the surface rises and mixes with cooler air aloft. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature will drop considerably. It has also been demonstrated experimentally (Wood, 1909): a "greenhouse" built of rock salt (which is transparent to infrared radiation) heats up just as one built of glass does. Greenhouses thus work primarily by preventing convection; the atmospheric greenhouse effect however reduces radiation loss, not convection. It is quite common, however, to find sources that make the erroneous "greenhouse" analogy. Although the primary mechanism for warming greenhouses is the prevention of mixing with the free atmosphere, the radiative properties of the glazing can still be important to commercial growers. With the modern development of new plastic surfaces and glazings for greenhouses, this has permitted construction of greenhouses which selectively control radiation transmittance in order to better control the growing environment.
Seahorse
Seahorses are a genus (Hippocampus) of fish belonging to the family Syngnathidae, which also includes pipefish and leafy sea dragons. There are over 32 species of seahorse, mainly found in tropical and subtropical coastal and reef waters all over Pacific, Atlantic and Indian oceans. Colonies have also been found in European waters such as the Thames Estuary. From North America down to South America there are approximately four species, ranging from very small in size (dwarf seahorses are only about an inch long) to those much larger, found off the Pacific Coast of Central America (which get to be about a foot long, called the Hippocampus ingens). Found in the Caribbean’s coral reefs are Hippocampus reidi, which are large slender seahorses that turn fluorescent neon colors when they dance. The Hippocampus erectus are bigger and fatter seahorses found anywhere from Nova Scotia down to around Uruguay. These fish stick to narrow zones, with males staying in about one square meter of their habitat while females range about one hundred times that area. They bob around in sea grass meadows, mangrove stands, and coral reefs where they are camouflaged by murky brown and grey patterns that blend into the sea grass backgrounds. During social moments or in unusual surroundings, seahorses turn bright colors. According to co-founder of Project Seahorse, Amanda J. Vincent, mates can blush a shade of creamy yellow when meeting each other in the morning. She even encountered one male who took the shade of the orange tape she used to mark the grid in the study area.
Contents
1 Physical Description
2 Courtship
3 Birth
4 Costs
5 Adaptations
6 Pets
7 Use in Chinese medicine
8 Philippine luminous seahorse sanctuary
9 Species
10 Cultural references
11 Gallery
12 Notes
13 Further reading
14 External links
Physical Description
Seahorses range in adult head-to-genital sizes from 13.3mm (0.52 inches) in the recently discovered Hippocampus denise to 35cm (13.78 inches). Seahorses and pipefishes are notable for being the only species in which males become "pregnant".
The seahorse has a dorsal fin located on the lower body and pectoral fins located on the head near their gills. A seahorse has highly mobile eyes to watch for predators and prey without moving its body. Like the leafy sea dragon, it also has a long snout with which it sucks up its prey. Its fins are small because it must move through thick water vegetation. The seahorse has a long, prehensile tail which it will curl around any support such as seaweed to prevent being swept away by currents.
Courtship
When two parties discover a mutual interest at the beginning of breeding season, they court for several days, even while others try to interfere. During this time they have been known to change color, swim side by side holding tails or grip the same strand of sea grass with their tails and wheel around in unison in what is known as their “pre-dawn dance”. They eventually engage in their “true courtship dance” lasting about 8 hours, during which the male pumps water through the egg pouch on his trunk which expands and cleaves open to display an appealing emptiness. When the female’s eggs reach maturity, she and her mate let go of any anchors and snout-to-snout, drift upward out of the seagrass, often spiraling as they rise. "The female inserts her ovipositor into the male’s brood pouch, where she deposits her eggs, which the male fertilizes. The fertilized eggs then embed in the pouch wall and become enveloped with tissues." New research indicates the male releases sperm into the surrounding sea water during fertilization, and not directly into the pouch as was previously thought. Most seahorse species' pregnancies lasts approximately two to three weeks.
As the female squirts anywhere from dozens to thousands of eggs from a chamber in her trunk into his pouch, her body slims while his swells. Both seahorses then sink back to the bottom and she swims off. Scientists believe the courtship behavior serves to synchronize the movements of the two animals so that the male can receive the eggs when the female is ready to deposit them. The eggs are then fertilized in the father’s pouch which is coursed with prolactin, the same hormone responsible for milk production in pregnant women. He doesn’t supply milk, but his pouch provides oxygen as well as a controlled environment incubator. The eggs then hatch in the pouch where the salinity of the water is regulated. This prepares the babies for life in the sea. Throughout the male’s pregnancy, his mate visits him daily for “morning greetings”. The female seahorse swims over for about 6 minutes of interaction reminiscent of courtship. “They change color, wheel around sea grass fronds, and finally promenade, holding each other’s tails. Then, the female swims away until the next morning, and the male goes back to vacuuming up food through his snout.”
Birth
The male seahorse can give birth to as many as 2,000 babies at a time and pregnancies last anywhere from 10 to 25 days, depending on the species. When the babies are ready to be born, the male undergoes muscular contractions to expel the “fry” from his pouch. He typically gives birth at night and is ready for the next batch of eggs by morning when his mate returns. Like almost all other fish species, seahorses do not care for their young once they are born. Infants are susceptible to death from predators or being swept into ocean currents, where they drift away from rich feeding grounds or into temperatures too extreme for their delicate bodies. Fewer than five infants of every 1,000 born survive to adulthood, helping to explain why litters are so large. The survival rates of these infants are actually fairly high compared to fish standards, because they are initially sheltered in their father’s pouch during the earliest stages of development, while the eggs of most other fish are abandoned immediately after fertilization. This makes the process worth the great cost to the father of incubating his offspring.
Costs
This entire process costs the male a great amount of energy. This brings into question why the sexual role reversal even takes place. In an environment where one partner incurs more energy costs than the other, you would expect the lesser of the two to be the aggressor. Within the seahorse species, males are shown to be the more aggressive sex and sometimes “fight” for female attention. According to Amanda Vincent of Project Seahorse, only males tail-wrestled and even snap their heads toward each other. This discovery prompted further study in finding out whether males actually are incurring more costs than their female counterparts. To estimate the female’s direct contribution, researcher Heather D. Masonjones of Amherst College performed a chemical analysis of the energy stored in each egg. Furthermore, to measure the toll that pregnancy takes on a male, Masonjones built a tiny respirator that records oxygen concentrations in water flowing into and out of a chamber. Before a male became pregnant, she checked his baseline need for oxygen. Then, she monitored the increase as pregnancy progressed. The male’s body had to work hard by the end of the pregnancy, consuming almost a third again as much oxygen as he did before mating. To correct for oxygen used by the growing brood, Masonjones managed to keep ¼ inch-high preemie seahorses alive outside the pouch so she could measure their oxygen needs. Although they undergo weeks of pregnancy, males directly contribute only half as much energy for offspring as females do. Therefore, they do in fact fit into the widespread pattern of the less-invested sex being the less-choosy.
Adaptations
The question of why it is the males who undergo pregnancy rather than the females is actually not entirely known, though some researchers believe male pregnancy allows for shorter birthing intervals, hence more offspring. When looking at which sex has the ability to produce more young if they had an unlimited number of ready and willing partners, males have the potential to produce 17 percent more in a breeding season. Also, females have “time-outs” from the reproductive cycle that are 1.2 times longer than those of males. This does not seem to be based on physiology, rather mate choice. When the female’s eggs are ready, she must lay them in a few hours or else she has to eject them onto the sea floor which is a huge cost to her physically, as her eggs amount to about a third of her body weight. To protect against unwillingly losing a clutch, the female demands a long courtship period. Furthermore, the daily greetings help to cement the bond between the pair. Another study conducted by Amanda Vincent of Project Seahorse shows the importance of this daily ritual. She kept a female in a tank with two males and when the female filled one male’s pouch with eggs he was then taken away, while she was left with the other male (the one not impregnated). During the weeks of her mate’s pregnancy, the female and her tankmate greeted each other daily, clinging to the same bit of grass and changing color, but according to Vincent did not display signs of serious courtship. When the original mate had given birth he was returned to the tank. The females then had a choice between him and the other tankmate. While both males expressed enthusiasm for her attention, even tail wrestling and whacking each other, in all six tests the female rejected her original mate and presented the next clutch of eggs to the tankmate that she had greeted each day. The importance of the daily meeting is extremely high in maintaining their monogamous relationship. Although monogamy within species is not common, it does appear to exist for some. In this case, the mate-guarding hypothesis may be an explanation. This hypothesis states that “males remain with a single female because of ecological factors that make male parental care and protection of offspring especially advantageous.” Because the rates of survival for newborn seahorses are so low, incubation is essential at the beginning stages of life. Though not proven, males could have taken on this role because of the time period in which it takes females to produce their eggs. If the males carry the offspring while the females gather the nutrients needed to produce new eggs (which is again, 1/3 of their body weight), then they can continually reproduce batch after batch together, depending on one another for efficiency in spreading both of their genes.
Pets
This section needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007)
Seahorses (Hippocampus erectus) at the New England Aquarium.
While many aquarium hobbyists will keep seahorses as pets, seahorses collected from the wild tend to fare poorly in a home aquarium. They will eat only live foods such as brine shrimp and are prone to stress in an aquarium, which lowers the efficiency of their immune systems and makes them susceptible to disease.
In recent years, however, captive breeding of seahorses has become increasingly widespread. These seahorses survive better in captivity, and they are less likely to carry diseases. These seahorses will eat mysid shrimp, and they do not experience the shock and stress of being taken out of the wild and placed in a small aquarium. Although captive-bred seahorses are more expensive, they survive better than wild seahorses, and take no toll on wild populations.
Seahorses should be kept in an aquarium to themselves, or with compatible tank-mates. Seahorses are slow feeders, and in an aquarium with fast, aggressive feeders, the seahorses will be edged out in the competition for food. Special care should be given to ensure that all individuals obtain enough food at feeding times.
Seahorses can co-exist with many species of shrimp and other bottom-feeding creatures. Fish from the goby family also make good tank-mates. Some species are especially dangerous to the slow-moving seahorses and should be avoided completely: eels, tangs, triggerfish, squid, octopus, and sea anemones.
Animals sold as "freshwater seahorses" are usually the closely related pipefish, of which a few species live in the lower reaches of rivers. The supposed true "freshwater seahorse" called Hippocampus aimei was not a real species, but a name sometimes used for individuals of Barbour's seahorse and Hedgehog seahorse. The latter is a species commonly found in brackish waters, but not actually a freshwater fish.
Use in Chinese medicine
Medicinal seahorse.
Seahorse populations have been endangered in recent years by overfishing. Therefore, seahorse fishing is strictly illegal. The seahorse is used in traditional Chinese herbology, and as many as 20 million seahorses may be caught each year and sold for this purpose. Medicinal seahorses are not readily bred in captivity as they are susceptible to disease and have somewhat different energetics than aquarium seahorses.
Import and export of seahorses has been controlled under CITES since May 15, 2004.
The problem may be exacerbated by the growth of pills and capsules as the preferred method of ingesting medication as they are cheaper and more available than traditional, individually tailored prescriptions of raw medicinals but the contents are harder to track. Seahorses once had to be of a certain size and quality before they were accepted by TCM practitioners and consumers. But declining availability of the preferred large, pale and smooth seahorses has been offset by the shift towards prepackaged medicines, which make it possible for TCM merchants to sell previously unused juvenile, spiny and dark-coloured animals. Today almost a third of the seahorses sold in China are prepackaged. This adds to the pressure on the species.
Philippine luminous seahorse sanctuary
Getafe, Jandayan Island off Bohol is a marine sanctuary, since 1995 to the luminous seahorses swimming among corals in the dark waters. On December 9, 2007, the sanctuary was awarded the most outstanding marine protected area (MPA) in the Philippines by the MPA Support Network (MSN), a multisectoral alliance of organizations seeking to protect the marine environment. The 50-hectare Handumon marine sanctuary is part of a large barrier reef in the waters of Bohol, teeming with fish, seashells and thick mangroves. The Haribon Foundation set up a Project Seahorse Foundation in Handumon to protect seahorses.
Species
'Fucus like seahorse' from Lydekker's The Royal Natural History
Genus Hippocampus
Big-belly seahorse, Hippocampus abdominalis Lesson, 1827 (New Zealand and south and east Australia)
Winged seahorse, Hippocampus alatus Kuiter, 2001
West African seahorse, Hippocampus algiricus Kaup, 1856
Narrow-bellied seahorse, Hippocampus angustus Günther, 1870
Barbour's seahorse, Hippocampus barbouri Jordan & Richardson, 1908
Pygmy seahorse, Hippocampus bargibanti Whitley, 1970 (West Pacific area (Indonesia, Philippines, Papua New Guinea, Solomon Islands, etc)
False-eyed seahorse, Hippocampus biocellatus Kuiter, 2001
Réunion seahorse, Hippocampus borboniensis Duméril, 1870
Short-head seahorse or knobby seahorse, Hippocampus breviceps Peters, 1869 (south and east Australia)
Giraffe seahorse, Hippocampus camelopardalis Bianconi, 1854
Knysna seahorse, Hippocampus capensis Boulenger, 1900
Hippocampus colemani Kuiter, 2003
Tiger tail seahorse, Hippocampus comes Cantor, 1850
Crowned seahorse, Hippocampus coronatus Temminck & Schlegel, 1850
Denise's pygmy seahorse, Hippocampus denise Lourie & Randall, 2003
Lined seahorse, Hippocampus erectus Perry, 1810 (east coast of the Americas, between Nova Scotia and Uruguay)
Fisher's seahorse, Hippocampus fisheri Jordan & Evermann, 1903
Sea pony, Hippocampus fuscus Rüppell, 1838 (Indian Ocean)
Big-head seahorse, Hippocampus grandiceps Kuiter, 2001
Long-snouted seahorse, Hippocampus guttulatus Cuvier, 1829
Eastern spiny seahorse, Hippocampus hendriki Kuiter, 2001
Short-snouted seahorse, Hippocampus hippocampus (Linnaeus, 1758) (Mediterranean Sea and Atlantic Ocean)
Thorny seahorse, Hippocampus histrix Kaup, 1856 (Indian Ocean, Persian Gulf, Red Sea, and the Far East)
Pacific seahorse, Hippocampus ingens Girard, 1858 (Pacific coast of North, Central and South America)
Jayakar's seahorse, Hippocampus jayakari Boulenger, 1900
Collared seahorse, Hippocampus jugumus Kuiter, 2001
Great seahorse, Hippocampus kelloggi Jordan & Snyder, 1901
Spotted seahorse, Hippocampus kuda Bleeker, 1852
Lichtenstein's seahorse, Hippocampus lichtensteinii Kaup, 1856
Bullneck seahorse, Hippocampus minotaur Gomon, 1997
Japanese seahorse, Hippocampus mohnikei Bleeker, 1854
Monte Bello seahorse, Hippocampus montebelloensis Kuiter, 2001
Northern spiny seahorse, Hippocampus multispinus Kuiter, 2001
High-crown seahorse, Hippocampus procerus Kuiter, 2001
Queensland seahorse, Hippocampus queenslandicus Horne, 2001
Longsnout seahorse, Hippocampus reidi Ginsburg, 1933 (Caribbean coral reefs)
Half-spined seahorse, Hippocampus semispinosus Kuiter, 2001
Dhiho's seahorse, Hippocampus sindonis Jordan & Snyder, 1901
Hedgehog seahorse, Hippocampus spinosissimus Weber, 1913
West Australian seahorse, Hippocampus subelongatus Castelnau, 1873
Longnose seahorse, Hippocampus trimaculatus Leach, 1814
White's seahorse, Hippocampus whitei Bleeker, 1855 (east Australia)
Zebra seahorse, Hippocampus zebra Whitley, 1964
Dwarf seahorse, Hippocampus zosterae Jordan & Gilbert, 1882 (Gulf of Mexico and the Caribbean)
Cultural references
A sculpture of a heraldic seahorse that adorned an 18th or 19th century French naval vessel
In heraldry, a seahorse is depicted as a creature with the foreparts of a horse and the hindparts of a fish. See, for example, the right supporter of the Isle of Wight Arms, the supporters on either side of the crest of the city of Newcastle upon Tyne, or the coincidental arms of the University of Newcastle, Australia.
The seahorse is prominent in the logo of Waterford Crystal and the logotype of illustrator W. W. Denslow.
In the Seri culture of northwestern Mexico, the legend is that the seahorse is a person who, to escape his pursuers, fled into the sea, placing his sandals in his waistbelt at his back.
The National Society for Epilepsy has a seahorse for its mascot named Cesar (after the Roman emperor, Julius Caesar, who was believed to have had epilepsy). The seahorse mascot was chosen because the hippocampus, a part of the brain that is resistant to damage from epileptic seizures, resembles a seahorse in shape.
Contents
1 Physical Description
2 Courtship
3 Birth
4 Costs
5 Adaptations
6 Pets
7 Use in Chinese medicine
8 Philippine luminous seahorse sanctuary
9 Species
10 Cultural references
11 Gallery
12 Notes
13 Further reading
14 External links
Physical Description
Seahorses range in adult head-to-genital sizes from 13.3mm (0.52 inches) in the recently discovered Hippocampus denise to 35cm (13.78 inches). Seahorses and pipefishes are notable for being the only species in which males become "pregnant".
The seahorse has a dorsal fin located on the lower body and pectoral fins located on the head near their gills. A seahorse has highly mobile eyes to watch for predators and prey without moving its body. Like the leafy sea dragon, it also has a long snout with which it sucks up its prey. Its fins are small because it must move through thick water vegetation. The seahorse has a long, prehensile tail which it will curl around any support such as seaweed to prevent being swept away by currents.
Courtship
When two parties discover a mutual interest at the beginning of breeding season, they court for several days, even while others try to interfere. During this time they have been known to change color, swim side by side holding tails or grip the same strand of sea grass with their tails and wheel around in unison in what is known as their “pre-dawn dance”. They eventually engage in their “true courtship dance” lasting about 8 hours, during which the male pumps water through the egg pouch on his trunk which expands and cleaves open to display an appealing emptiness. When the female’s eggs reach maturity, she and her mate let go of any anchors and snout-to-snout, drift upward out of the seagrass, often spiraling as they rise. "The female inserts her ovipositor into the male’s brood pouch, where she deposits her eggs, which the male fertilizes. The fertilized eggs then embed in the pouch wall and become enveloped with tissues." New research indicates the male releases sperm into the surrounding sea water during fertilization, and not directly into the pouch as was previously thought. Most seahorse species' pregnancies lasts approximately two to three weeks.
As the female squirts anywhere from dozens to thousands of eggs from a chamber in her trunk into his pouch, her body slims while his swells. Both seahorses then sink back to the bottom and she swims off. Scientists believe the courtship behavior serves to synchronize the movements of the two animals so that the male can receive the eggs when the female is ready to deposit them. The eggs are then fertilized in the father’s pouch which is coursed with prolactin, the same hormone responsible for milk production in pregnant women. He doesn’t supply milk, but his pouch provides oxygen as well as a controlled environment incubator. The eggs then hatch in the pouch where the salinity of the water is regulated. This prepares the babies for life in the sea. Throughout the male’s pregnancy, his mate visits him daily for “morning greetings”. The female seahorse swims over for about 6 minutes of interaction reminiscent of courtship. “They change color, wheel around sea grass fronds, and finally promenade, holding each other’s tails. Then, the female swims away until the next morning, and the male goes back to vacuuming up food through his snout.”
Birth
The male seahorse can give birth to as many as 2,000 babies at a time and pregnancies last anywhere from 10 to 25 days, depending on the species. When the babies are ready to be born, the male undergoes muscular contractions to expel the “fry” from his pouch. He typically gives birth at night and is ready for the next batch of eggs by morning when his mate returns. Like almost all other fish species, seahorses do not care for their young once they are born. Infants are susceptible to death from predators or being swept into ocean currents, where they drift away from rich feeding grounds or into temperatures too extreme for their delicate bodies. Fewer than five infants of every 1,000 born survive to adulthood, helping to explain why litters are so large. The survival rates of these infants are actually fairly high compared to fish standards, because they are initially sheltered in their father’s pouch during the earliest stages of development, while the eggs of most other fish are abandoned immediately after fertilization. This makes the process worth the great cost to the father of incubating his offspring.
Costs
This entire process costs the male a great amount of energy. This brings into question why the sexual role reversal even takes place. In an environment where one partner incurs more energy costs than the other, you would expect the lesser of the two to be the aggressor. Within the seahorse species, males are shown to be the more aggressive sex and sometimes “fight” for female attention. According to Amanda Vincent of Project Seahorse, only males tail-wrestled and even snap their heads toward each other. This discovery prompted further study in finding out whether males actually are incurring more costs than their female counterparts. To estimate the female’s direct contribution, researcher Heather D. Masonjones of Amherst College performed a chemical analysis of the energy stored in each egg. Furthermore, to measure the toll that pregnancy takes on a male, Masonjones built a tiny respirator that records oxygen concentrations in water flowing into and out of a chamber. Before a male became pregnant, she checked his baseline need for oxygen. Then, she monitored the increase as pregnancy progressed. The male’s body had to work hard by the end of the pregnancy, consuming almost a third again as much oxygen as he did before mating. To correct for oxygen used by the growing brood, Masonjones managed to keep ¼ inch-high preemie seahorses alive outside the pouch so she could measure their oxygen needs. Although they undergo weeks of pregnancy, males directly contribute only half as much energy for offspring as females do. Therefore, they do in fact fit into the widespread pattern of the less-invested sex being the less-choosy.
Adaptations
The question of why it is the males who undergo pregnancy rather than the females is actually not entirely known, though some researchers believe male pregnancy allows for shorter birthing intervals, hence more offspring. When looking at which sex has the ability to produce more young if they had an unlimited number of ready and willing partners, males have the potential to produce 17 percent more in a breeding season. Also, females have “time-outs” from the reproductive cycle that are 1.2 times longer than those of males. This does not seem to be based on physiology, rather mate choice. When the female’s eggs are ready, she must lay them in a few hours or else she has to eject them onto the sea floor which is a huge cost to her physically, as her eggs amount to about a third of her body weight. To protect against unwillingly losing a clutch, the female demands a long courtship period. Furthermore, the daily greetings help to cement the bond between the pair. Another study conducted by Amanda Vincent of Project Seahorse shows the importance of this daily ritual. She kept a female in a tank with two males and when the female filled one male’s pouch with eggs he was then taken away, while she was left with the other male (the one not impregnated). During the weeks of her mate’s pregnancy, the female and her tankmate greeted each other daily, clinging to the same bit of grass and changing color, but according to Vincent did not display signs of serious courtship. When the original mate had given birth he was returned to the tank. The females then had a choice between him and the other tankmate. While both males expressed enthusiasm for her attention, even tail wrestling and whacking each other, in all six tests the female rejected her original mate and presented the next clutch of eggs to the tankmate that she had greeted each day. The importance of the daily meeting is extremely high in maintaining their monogamous relationship. Although monogamy within species is not common, it does appear to exist for some. In this case, the mate-guarding hypothesis may be an explanation. This hypothesis states that “males remain with a single female because of ecological factors that make male parental care and protection of offspring especially advantageous.” Because the rates of survival for newborn seahorses are so low, incubation is essential at the beginning stages of life. Though not proven, males could have taken on this role because of the time period in which it takes females to produce their eggs. If the males carry the offspring while the females gather the nutrients needed to produce new eggs (which is again, 1/3 of their body weight), then they can continually reproduce batch after batch together, depending on one another for efficiency in spreading both of their genes.
Pets
This section needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007)
Seahorses (Hippocampus erectus) at the New England Aquarium.
While many aquarium hobbyists will keep seahorses as pets, seahorses collected from the wild tend to fare poorly in a home aquarium. They will eat only live foods such as brine shrimp and are prone to stress in an aquarium, which lowers the efficiency of their immune systems and makes them susceptible to disease.
In recent years, however, captive breeding of seahorses has become increasingly widespread. These seahorses survive better in captivity, and they are less likely to carry diseases. These seahorses will eat mysid shrimp, and they do not experience the shock and stress of being taken out of the wild and placed in a small aquarium. Although captive-bred seahorses are more expensive, they survive better than wild seahorses, and take no toll on wild populations.
Seahorses should be kept in an aquarium to themselves, or with compatible tank-mates. Seahorses are slow feeders, and in an aquarium with fast, aggressive feeders, the seahorses will be edged out in the competition for food. Special care should be given to ensure that all individuals obtain enough food at feeding times.
Seahorses can co-exist with many species of shrimp and other bottom-feeding creatures. Fish from the goby family also make good tank-mates. Some species are especially dangerous to the slow-moving seahorses and should be avoided completely: eels, tangs, triggerfish, squid, octopus, and sea anemones.
Animals sold as "freshwater seahorses" are usually the closely related pipefish, of which a few species live in the lower reaches of rivers. The supposed true "freshwater seahorse" called Hippocampus aimei was not a real species, but a name sometimes used for individuals of Barbour's seahorse and Hedgehog seahorse. The latter is a species commonly found in brackish waters, but not actually a freshwater fish.
Use in Chinese medicine
Medicinal seahorse.
Seahorse populations have been endangered in recent years by overfishing. Therefore, seahorse fishing is strictly illegal. The seahorse is used in traditional Chinese herbology, and as many as 20 million seahorses may be caught each year and sold for this purpose. Medicinal seahorses are not readily bred in captivity as they are susceptible to disease and have somewhat different energetics than aquarium seahorses.
Import and export of seahorses has been controlled under CITES since May 15, 2004.
The problem may be exacerbated by the growth of pills and capsules as the preferred method of ingesting medication as they are cheaper and more available than traditional, individually tailored prescriptions of raw medicinals but the contents are harder to track. Seahorses once had to be of a certain size and quality before they were accepted by TCM practitioners and consumers. But declining availability of the preferred large, pale and smooth seahorses has been offset by the shift towards prepackaged medicines, which make it possible for TCM merchants to sell previously unused juvenile, spiny and dark-coloured animals. Today almost a third of the seahorses sold in China are prepackaged. This adds to the pressure on the species.
Philippine luminous seahorse sanctuary
Getafe, Jandayan Island off Bohol is a marine sanctuary, since 1995 to the luminous seahorses swimming among corals in the dark waters. On December 9, 2007, the sanctuary was awarded the most outstanding marine protected area (MPA) in the Philippines by the MPA Support Network (MSN), a multisectoral alliance of organizations seeking to protect the marine environment. The 50-hectare Handumon marine sanctuary is part of a large barrier reef in the waters of Bohol, teeming with fish, seashells and thick mangroves. The Haribon Foundation set up a Project Seahorse Foundation in Handumon to protect seahorses.
Species
'Fucus like seahorse' from Lydekker's The Royal Natural History
Genus Hippocampus
Big-belly seahorse, Hippocampus abdominalis Lesson, 1827 (New Zealand and south and east Australia)
Winged seahorse, Hippocampus alatus Kuiter, 2001
West African seahorse, Hippocampus algiricus Kaup, 1856
Narrow-bellied seahorse, Hippocampus angustus Günther, 1870
Barbour's seahorse, Hippocampus barbouri Jordan & Richardson, 1908
Pygmy seahorse, Hippocampus bargibanti Whitley, 1970 (West Pacific area (Indonesia, Philippines, Papua New Guinea, Solomon Islands, etc)
False-eyed seahorse, Hippocampus biocellatus Kuiter, 2001
Réunion seahorse, Hippocampus borboniensis Duméril, 1870
Short-head seahorse or knobby seahorse, Hippocampus breviceps Peters, 1869 (south and east Australia)
Giraffe seahorse, Hippocampus camelopardalis Bianconi, 1854
Knysna seahorse, Hippocampus capensis Boulenger, 1900
Hippocampus colemani Kuiter, 2003
Tiger tail seahorse, Hippocampus comes Cantor, 1850
Crowned seahorse, Hippocampus coronatus Temminck & Schlegel, 1850
Denise's pygmy seahorse, Hippocampus denise Lourie & Randall, 2003
Lined seahorse, Hippocampus erectus Perry, 1810 (east coast of the Americas, between Nova Scotia and Uruguay)
Fisher's seahorse, Hippocampus fisheri Jordan & Evermann, 1903
Sea pony, Hippocampus fuscus Rüppell, 1838 (Indian Ocean)
Big-head seahorse, Hippocampus grandiceps Kuiter, 2001
Long-snouted seahorse, Hippocampus guttulatus Cuvier, 1829
Eastern spiny seahorse, Hippocampus hendriki Kuiter, 2001
Short-snouted seahorse, Hippocampus hippocampus (Linnaeus, 1758) (Mediterranean Sea and Atlantic Ocean)
Thorny seahorse, Hippocampus histrix Kaup, 1856 (Indian Ocean, Persian Gulf, Red Sea, and the Far East)
Pacific seahorse, Hippocampus ingens Girard, 1858 (Pacific coast of North, Central and South America)
Jayakar's seahorse, Hippocampus jayakari Boulenger, 1900
Collared seahorse, Hippocampus jugumus Kuiter, 2001
Great seahorse, Hippocampus kelloggi Jordan & Snyder, 1901
Spotted seahorse, Hippocampus kuda Bleeker, 1852
Lichtenstein's seahorse, Hippocampus lichtensteinii Kaup, 1856
Bullneck seahorse, Hippocampus minotaur Gomon, 1997
Japanese seahorse, Hippocampus mohnikei Bleeker, 1854
Monte Bello seahorse, Hippocampus montebelloensis Kuiter, 2001
Northern spiny seahorse, Hippocampus multispinus Kuiter, 2001
High-crown seahorse, Hippocampus procerus Kuiter, 2001
Queensland seahorse, Hippocampus queenslandicus Horne, 2001
Longsnout seahorse, Hippocampus reidi Ginsburg, 1933 (Caribbean coral reefs)
Half-spined seahorse, Hippocampus semispinosus Kuiter, 2001
Dhiho's seahorse, Hippocampus sindonis Jordan & Snyder, 1901
Hedgehog seahorse, Hippocampus spinosissimus Weber, 1913
West Australian seahorse, Hippocampus subelongatus Castelnau, 1873
Longnose seahorse, Hippocampus trimaculatus Leach, 1814
White's seahorse, Hippocampus whitei Bleeker, 1855 (east Australia)
Zebra seahorse, Hippocampus zebra Whitley, 1964
Dwarf seahorse, Hippocampus zosterae Jordan & Gilbert, 1882 (Gulf of Mexico and the Caribbean)
Cultural references
A sculpture of a heraldic seahorse that adorned an 18th or 19th century French naval vessel
In heraldry, a seahorse is depicted as a creature with the foreparts of a horse and the hindparts of a fish. See, for example, the right supporter of the Isle of Wight Arms, the supporters on either side of the crest of the city of Newcastle upon Tyne, or the coincidental arms of the University of Newcastle, Australia.
The seahorse is prominent in the logo of Waterford Crystal and the logotype of illustrator W. W. Denslow.
In the Seri culture of northwestern Mexico, the legend is that the seahorse is a person who, to escape his pursuers, fled into the sea, placing his sandals in his waistbelt at his back.
The National Society for Epilepsy has a seahorse for its mascot named Cesar (after the Roman emperor, Julius Caesar, who was believed to have had epilepsy). The seahorse mascot was chosen because the hippocampus, a part of the brain that is resistant to damage from epileptic seizures, resembles a seahorse in shape.
El Niño-Southern Oscillation
Average circulation in the south Pacific Ocean
El Niño-Southern Oscillation (ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon. The Pacific ocean signatures, El Niño and La Niña are important temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. The name El Niño, from the Spanish for "the little boy", refers to the Christ child, because the phenomenon is usually noticed around Christmas time in the Pacific Ocean off the west coast of South America. La Niña, similarly, means "the little girl". Their effect on climate in the southern hemisphere is profound. These effects were first described in 1923 by Sir Gilbert Thomas Walker from whom the Walker circulation, an important aspect of the Pacific ENSO phenomenon, takes its name. The atmospheric signature, the Southern Oscillation (SO) reflects the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin, Australia. The most recent occurrence of El Niño started in September 2006 and lasted until early 2007. . From June 2007 on, data indicated a weak La Niña event, strengthening in early 2008.
ENSO is a set of specific interacting parts of a single global system of coupled ocean-atmosphere climate fluctuations that come about as a consequence of oceanic and atmospheric circulation. The irregularity of ENSO makes predicting it of high interest, as it is demonstrably connected to seasonal, even yearly, regional climatic effects on large areas. ENSO is the most prominent known source of inter-annual variability in weather and climate around the world (about 3 to 8 years), though not all areas are affected. ENSO has signatures in the Pacific, Atlantic and Indian Oceans. El Niño changes the distribution of rainfall, causing floods in some areas and drought in others.
During major warm events, El Niño warming extends over much of the tropical Pacific and becomes clearly linked to the intensity of the Southern Oscillation. While ENSO effects are basically in phase between the Pacific and Indian Oceans, ENSO effects in the Atlantic Ocean lag behind those in the Pacific by 12 to 18 months. Many of the countries most affected by ENSO are developing countries that are largely dependent upon their agricultural and fishery sectors for food supply, employment, and foreign exchange.
New capabilities to predict the onset of ENSO events can have global socio-economic impacts. While ENSO is a natural part of the Earth's climate, an important concern is whether its intensity or frequency may change as a result of global warming. Low-frequency variability has been evidenced; inter-decadal modulation of ENSO (from PDO or IPO) might exist. This could explain the so-called protracted ENSO of the early 1990s.
Contents
[hide]
1 El Niño and La Niña
2 Wider effects of El Niño conditions
2.1 Western Hemisphere Warm Pool
2.2 Atlantic effect
3 Non-climate effects
4 La Niña
4.1 Effects of La Niña
4.2 Recent occurrences
5 ENSO and global warming
6 Causes of El Niño
6.1 Major theories
7 History of the theory
8 History of the phenomenon
9 Southern Oscillation
10 Related images
11 References
12 Data sources
13 Further reading
14 Footnotes
15 See also
16 External links
El Niño and La Niña
Normal Pacific pattern. Equatorial winds gather warm water pool toward west. Cold water upwells along South American coast. (NOAA / PMEL / TAO)
El Niño Conditions. Warm water pool approaches South American coast. Absence of cold upwelling increases warming.
La Niña Conditions. Warm water is further west than usual.
El Niño and La Niña are officially defined as sustained sea surface temperature anomalies of magnitude greater than 0.5°C across the central tropical Pacific Ocean. When the condition is met for a period of less than five months, it is classified as El Niño or La Niña conditions; if the anomaly persists for five months or longer, it is classified as an El Niño or La Niña episode. Historically, it has occurred at irregular intervals of 2-7 years and has usually lasted one or two years.
The first signs of an El Niño are:
Rise in air pressure over the Indian Ocean, Indonesia, and Australia
Fall in air pressure over Tahiti and the rest of the central and eastern Pacific Ocean
Trade winds in the south Pacific weaken or head east
Warm air rises near Peru, causing rain in the northern Peruvian deserts
Warm water spreads from the west Pacific and the Indian Ocean to the east Pacific. It takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific.
El Niño's warm current of nutrient-poor tropical water, heated by its eastward passage in the Equatorial Current, replaces the cold, nutrient-rich surface water of the Humboldt Current, also known as the Peru Current, which support great populations of food fish. In most years the warming lasts only a few weeks or a month, after which the weather patterns return to normal and fishing improves. However, when El Niño conditions last for many months, more extensive ocean warming occurs and its economic impact to local fishing for an international market can be serious.
During non-El Niño conditions, the Walker circulation is seen at the surface as easterly trade winds which move water and air warmed by the sun towards the west. This also creates ocean upwelling off the coasts of Peru and Ecuador and brings nutrient-rich cold water to the surface, increasing fishing stocks. The western side of the equatorial Pacific is characterized by warm, wet low pressure weather as the collected moisture is dumped in the form of typhoons and thunderstorms. The ocean is some 60 cm higher in the western Pacific as the result of this motion.
In the Pacific, La Niña is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific, compared to El Niño, which is characterized by unusually warm ocean temperatures in the same area. Atlantic tropical cyclone activity is generally enhanced during La Niña. The La Niña condition often follows the El Niño, especially when the latter is strong.
Regional impacts of warm ENSO episodes (El Niño).
Regional impacts of cold ENSO episodes. (La Niña)
Wider effects of El Niño conditions
See also: Effects of the El Niño-Southern Oscillation in the United States
Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean.
The effects of El Niño in South America are direct and stronger than in North America. An El Niño is associated with warm and very wet summers (December-February) along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme. The effects during the months of February, March and April may become critical. Southern Brazil and northern Argentina also experience wetter than normal conditions but mainly during the spring and early summer. Central Chile receives a mild winter with large rainfall, and the Peruvian-Bolivian Altiplano is sometimes exposed to unusual winter snowfall events. Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia and Central America.
Direct effects of El Niño resulting in drier conditions occur in parts of Southeast Asia and Northern Australia, increasing bush fires and worsening haze and decreasing air quality dramatically. Drier than normal conditions are also generally observed in Queensland, inland Victoria, inland New South Wales and eastern Tasmania from June to August.
West of the Antarctic Peninsula, the Ross, Bellingshausen, and Amundsen Sea sectors have more sea ice during El Niño. The latter two and the Weddell Sea also become warmer and have higher atmospheric pressure.
In North America, typically, winters are warmer than normal in the upper Midwest states, the Northeast, and Canada, while central and southern California, northwest Mexico and the southwestern U.S., are wetter and cooler than normal. Summer is wetter in the intermountain regions of the U.S. The Pacific Northwest states, on the other hand, tend to experience dry but foggy winters and warm, sunny and precocious springs during an El Niño. During a La Niña, by contrast, the Midwestern U.S. tends to be drier than normal. El Niño is associated with increased wave caused coastal erosion along the US Pacific Coast and decreased hurricane activity in the Atlantic, especially south of 25º N; this reduction is largely due to stronger wind sheartropics.
Finally, East Africa, including Kenya, Tanzania and the White Nile basin experiences, in the long rains from March to May, wetter than normal conditions. There also are drier than normal conditions from December to February in south-central Africa, mainly in Zambia, Zimbabwe, Mozambique and Botswana.
Western Hemisphere Warm Pool
Study of climate records has found that about half of the summers after an El Niño have unusual warming in the Western Hemisphere Warm Pool (WHWP). This affects weather in the area and seems to be related to the North Atlantic Oscillation.
Atlantic effect
An effect similar to El Niño sometimes takes place in the Atlantic Ocean, where water along equatorial Africa's Gulf of Guinea becomes warmer and eastern Brazil becomes cooler and drier. This may be related to El Niño Walker circulation changes over South America.
Cases of double El Niño events have been linked to severe famines related to the extended failure of monsoon rains, as in the book Late Victorian Holocausts.
Non-climate effects
Along the west coast of South America, El Niño reduces the upwelling of cold, nutrient-rich water that sustains large fish populations, which in turn sustain abundant sea birds, whose droppings support the fertilizer industry.
East Pacific fishing
The local fishing industry along the affected coastline can suffer during long-lasting El Niño events. The world's largest fishery collapsed due to overfishing during the 1972 El Niño Peruvian anchoveta reduction. During the 1982-83 event, jack mackerel and anchoveta populations were reduced, scallops increased in warmer water, but hake followed cooler water down the continental slope, while shrimp and sardines moved southward so some catches decreased while others increased. Horse mackerel have increased in the region during warm events.
Shifting locations and types of fish due to changing conditions provide challenges for fishing industries. Peruvian sardines have moved during El Niño events to Chilean areas. Other conditions provide further complications, such as the government of Chile in 1991 creating restrictions on the fishing areas for self-employed fishermen and industrial fleets.
The ENSO variability may contribute to the great success of small fast-growing species along the Peruvian coast, as periods of low population removes predators in the area. Similar effects benefit migratory birds which travel each spring from predator-rich tropical areas to distant winter-stressed nesting areas. There is some evidence that El Niño activity is correlated with incidence of red tides off of the Pacific coast of California.
It has been postulated that a strong El Niño led to the demise of the Moche and other pre-Columbian Peruvian cultures.
A recent study of El Niño patterns suggests that the French Revolution was caused in part by the poor crop yields of 1788-89 in Europe, resulting from an unusually strong El-Niño effect between 1789-93.
La Niña
Sea surface skin temperature anomalies in November 2007 showing La Niña conditions
La Niña is the name for the cold phase of the Southern Oscillation, during which the cold pool in the eastern Pacific intensifies and the trade winds strengthen. The name La Niña originates from Spanish, meaning "the little girl", analogous to El Niño meaning "the little boy". It has also in the past been called anti-El Niño.
Effects of La Niña
Regional impacts of La Niña.
La Niña causes mostly the opposite effects of El Niño, for example, El Niño would cause a wet period in the Midwestern U.S., while La Niña would typically cause a dry period in this area.
Recent occurrences
There was a strong La Niña episode during 1988-1989. La Niña also formed in 1995, and in 1999-2000. The last La Niña was a minor one, and occurred 2000-2001. Currently, there is a moderate La Niña, which began developing in mid-2007. NOAA confirmed that a moderate La Niña developed in their November El Niño/Southern Oscillation Diagnostic Discussion, and that it will likely continue into 2008. According to NOAA, "Expected La Niña impacts during November – January include a continuation of above-average precipitation over Indonesia and below-average precipitation over the central equatorial Pacific. For the contiguous United States, potential impacts include above average precipitation in the Northern Rockies, Northern California, and in southern and eastern regions of the Pacific Northwest. Below-average precipitation is expected across the southern tier, particularly in the southwestern and southeastern states. " In March 2008, La Niña caused a drop in sea surface temperatures over Southeast Asia by an amount of 2°C. It also caused heavy rains over Malaysia, Singapore and Indonesia. "
ENSO and global warming
A few years ago, attribution of recent changes (if any) in ENSO or predictions of future changes were very weak. More recent results tend to suggest that the projected tropical warming may follow a somewhat El Niño-like spatial pattern, without necessarily altering the variability about this pattern, while the ENSO cycle may be minimally shortened .
Causes of El Niño
The mechanisms which might cause an El Niño event are still being investigated. It is difficult to find patterns which may show causes or allow forecasts. As the phenomenon is located near the equator, events in both hemispheres may have an effect. As the weather events are somewhat chaotic, the onsets of El Niño-events may also be. This is not to say predicting is totally impossible.
Major theories
Jacob Bjerknes in 1969 suggested that an anomalously warm spot in the eastern Pacific can weaken the east-west temperature difference, causing weakening in the Walker circulation and trade wind flows, which push warm water to the west. The result is increasingly warm water toward the east.
Wyrtki in 1975 proposed that increased trade winds could build up the western bulge of warm water, and any sudden weakening in the winds would allow that warm water to surge eastward. However, there was no such buildup preceding the 1982-83 event.
Recharge oscillator: Several mechanisms have been proposed where warmth builds up in the equatorial area, then is dispersed to higher latitudes by an El Niño event. The cooler area then has to "recharge" warmth for several years before another event can take place.
Western Pacific oscillator: In the western Pacific, several weather conditions can cause westerly wind anomalies. For example, cyclones north and south of the equator force west-to-east winds between. Such wind may counteract the typical easterly flows across the Pacific and create a tendency toward continuing the eastward motion. A weakening in the westward currents at such a time may be the final trigger needed to shift into an El Niño.
Equatorial Pacific Ocean may tend to be near El Niño conditions, with several random variations affecting behavior. Weather patterns from outside the area or volcanic events may be some such factors.
The Madden-Julian Oscillation (MJO) is an important source of variability that can contribute to a more rapid evolution toward El Niño conditions through related fluctuations in low-level winds and precipitation over the western and central equatorial Pacific. Eastward-propagating oceanic Kelvin waves can be produced by MJO activity. The MJO may in turn be influenced by a developing El Niño, leading to a positive feedback .
Adams, Mann and Ammann, using statistical analysis of paleoclimatic records, that a volcanic event in the tropics tilts the climate into a state where El Niño-like conditions are favored. (This is caused by the volcano's effect on solar radiation reaching the surface, not by the heat of the eruption itself.)
History of the theory
The first mention of the term "El Niño" to refer to climate occurs in 1892, when Captain Camilo Carrillo told the Geographical society congress in Lima that Peruvian sailors named the warm northerly current "El Niño" because it was most noticeable around Christmas. However even before then the phenomenon was of interest because of its effects on biological productivity, with its effects on the guano industry.
Normal conditions along the west Peruvian coast are a cold southerly current (the Humboldt Current) with upwelling water; the upwelling nutrients lead to great oceanic productivity; the cold currents leads to very dry conditions on land. Similar conditions exist elsewhere (California Current; Benguela Current off South Africa; West Australia Current). Thus the replacement of this with warmer northerly water leads to lower biological productivity in the ocean, and more rainfall - often flooding - on land; the connection with flooding was reported in 1895 by Pezet and Eguiguren.
Towards the end of the nineteenth century there was much interest in forecasting climate anomalies (for food production) in India and Australia. Charles Todd, in 1893, suggested that droughts in India and Australia tended to occur at the same time; Norman Lockyer noted the same in 1904. In 1924 Gilbert Walker (for whom the Walker circulation is named) first coined the term "Southern Oscillation".
For most of the twentieth century, El Niño was thought of as a largely local phenomenon.
The major 1982-3 El Niño lead to an upsurge of interest from the scientific community.
The 1998 El Niño event caused an estimated 16% of the world’s reef systems to die. Since then, mass coral bleaching has become common worldwide, with all regions having suffered ‘severe bleaching’.
History of the phenomenon
ENSO conditions seem to have occurred at every two to seven years for at least the past 300 years, but most of them have been weak.
Major ENSO events have occurred in the years 1790-93, 1828, 1876-78, 1891, 1925-26, 1982-83, and 1997-98.
Recent El Niños have occurred in 1986-1987, 1991-1992, 1993, 1994, 1997-1998, 2002-2003, 2004-2005 and 2006-2007.
The El Niño of 1997 - 1998 was particularly strong and brought the phenomenon to worldwide attention. The event temporarily warmed air temperature by 3°F, compared to the usual increase of 0.5°F associated with El Niño events . The period from 1990-1994 was unusual in that El Niños have rarely occurred in such rapid succession (but were generally weak). There is some debate as to whether global warming increases the intensity and/or frequency of El Niño episodes. (see also the ENSO and Global Warming section above).
Southern Oscillation
The Southern Oscillation is an oscillation in air pressure between the tropical eastern and western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is a record of the monthly or seasonal fluctuations in the normalized surface air pressure difference between Tahiti and Darwin, Australia. .
El Niño episodes, which are associated with negative values of the SOI, are usually accompanied by sustained warming of the central and eastern tropical Pacific Ocean, a decrease in the strength of the Pacific Trade Winds, and a reduction in rainfall over eastern and northern Australia. Conversely, La Niña episodes are associated with positive values of the SOI and are accompanied by stronger Pacific trade winds and warmer sea temperatures to the north of Australia. Waters in the central and eastern tropical Pacific Ocean become cooler during this time.
El Niño-Southern Oscillation (ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon. The Pacific ocean signatures, El Niño and La Niña are important temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. The name El Niño, from the Spanish for "the little boy", refers to the Christ child, because the phenomenon is usually noticed around Christmas time in the Pacific Ocean off the west coast of South America. La Niña, similarly, means "the little girl". Their effect on climate in the southern hemisphere is profound. These effects were first described in 1923 by Sir Gilbert Thomas Walker from whom the Walker circulation, an important aspect of the Pacific ENSO phenomenon, takes its name. The atmospheric signature, the Southern Oscillation (SO) reflects the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin, Australia. The most recent occurrence of El Niño started in September 2006 and lasted until early 2007. . From June 2007 on, data indicated a weak La Niña event, strengthening in early 2008.
ENSO is a set of specific interacting parts of a single global system of coupled ocean-atmosphere climate fluctuations that come about as a consequence of oceanic and atmospheric circulation. The irregularity of ENSO makes predicting it of high interest, as it is demonstrably connected to seasonal, even yearly, regional climatic effects on large areas. ENSO is the most prominent known source of inter-annual variability in weather and climate around the world (about 3 to 8 years), though not all areas are affected. ENSO has signatures in the Pacific, Atlantic and Indian Oceans. El Niño changes the distribution of rainfall, causing floods in some areas and drought in others.
During major warm events, El Niño warming extends over much of the tropical Pacific and becomes clearly linked to the intensity of the Southern Oscillation. While ENSO effects are basically in phase between the Pacific and Indian Oceans, ENSO effects in the Atlantic Ocean lag behind those in the Pacific by 12 to 18 months. Many of the countries most affected by ENSO are developing countries that are largely dependent upon their agricultural and fishery sectors for food supply, employment, and foreign exchange.
New capabilities to predict the onset of ENSO events can have global socio-economic impacts. While ENSO is a natural part of the Earth's climate, an important concern is whether its intensity or frequency may change as a result of global warming. Low-frequency variability has been evidenced; inter-decadal modulation of ENSO (from PDO or IPO) might exist. This could explain the so-called protracted ENSO of the early 1990s.
Contents
[hide]
1 El Niño and La Niña
2 Wider effects of El Niño conditions
2.1 Western Hemisphere Warm Pool
2.2 Atlantic effect
3 Non-climate effects
4 La Niña
4.1 Effects of La Niña
4.2 Recent occurrences
5 ENSO and global warming
6 Causes of El Niño
6.1 Major theories
7 History of the theory
8 History of the phenomenon
9 Southern Oscillation
10 Related images
11 References
12 Data sources
13 Further reading
14 Footnotes
15 See also
16 External links
El Niño and La Niña
Normal Pacific pattern. Equatorial winds gather warm water pool toward west. Cold water upwells along South American coast. (NOAA / PMEL / TAO)
El Niño Conditions. Warm water pool approaches South American coast. Absence of cold upwelling increases warming.
La Niña Conditions. Warm water is further west than usual.
El Niño and La Niña are officially defined as sustained sea surface temperature anomalies of magnitude greater than 0.5°C across the central tropical Pacific Ocean. When the condition is met for a period of less than five months, it is classified as El Niño or La Niña conditions; if the anomaly persists for five months or longer, it is classified as an El Niño or La Niña episode. Historically, it has occurred at irregular intervals of 2-7 years and has usually lasted one or two years.
The first signs of an El Niño are:
Rise in air pressure over the Indian Ocean, Indonesia, and Australia
Fall in air pressure over Tahiti and the rest of the central and eastern Pacific Ocean
Trade winds in the south Pacific weaken or head east
Warm air rises near Peru, causing rain in the northern Peruvian deserts
Warm water spreads from the west Pacific and the Indian Ocean to the east Pacific. It takes the rain with it, causing extensive drought in the western Pacific and rainfall in the normally dry eastern Pacific.
El Niño's warm current of nutrient-poor tropical water, heated by its eastward passage in the Equatorial Current, replaces the cold, nutrient-rich surface water of the Humboldt Current, also known as the Peru Current, which support great populations of food fish. In most years the warming lasts only a few weeks or a month, after which the weather patterns return to normal and fishing improves. However, when El Niño conditions last for many months, more extensive ocean warming occurs and its economic impact to local fishing for an international market can be serious.
During non-El Niño conditions, the Walker circulation is seen at the surface as easterly trade winds which move water and air warmed by the sun towards the west. This also creates ocean upwelling off the coasts of Peru and Ecuador and brings nutrient-rich cold water to the surface, increasing fishing stocks. The western side of the equatorial Pacific is characterized by warm, wet low pressure weather as the collected moisture is dumped in the form of typhoons and thunderstorms. The ocean is some 60 cm higher in the western Pacific as the result of this motion.
In the Pacific, La Niña is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific, compared to El Niño, which is characterized by unusually warm ocean temperatures in the same area. Atlantic tropical cyclone activity is generally enhanced during La Niña. The La Niña condition often follows the El Niño, especially when the latter is strong.
Regional impacts of warm ENSO episodes (El Niño).
Regional impacts of cold ENSO episodes. (La Niña)
Wider effects of El Niño conditions
See also: Effects of the El Niño-Southern Oscillation in the United States
Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean.
The effects of El Niño in South America are direct and stronger than in North America. An El Niño is associated with warm and very wet summers (December-February) along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme. The effects during the months of February, March and April may become critical. Southern Brazil and northern Argentina also experience wetter than normal conditions but mainly during the spring and early summer. Central Chile receives a mild winter with large rainfall, and the Peruvian-Bolivian Altiplano is sometimes exposed to unusual winter snowfall events. Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia and Central America.
Direct effects of El Niño resulting in drier conditions occur in parts of Southeast Asia and Northern Australia, increasing bush fires and worsening haze and decreasing air quality dramatically. Drier than normal conditions are also generally observed in Queensland, inland Victoria, inland New South Wales and eastern Tasmania from June to August.
West of the Antarctic Peninsula, the Ross, Bellingshausen, and Amundsen Sea sectors have more sea ice during El Niño. The latter two and the Weddell Sea also become warmer and have higher atmospheric pressure.
In North America, typically, winters are warmer than normal in the upper Midwest states, the Northeast, and Canada, while central and southern California, northwest Mexico and the southwestern U.S., are wetter and cooler than normal. Summer is wetter in the intermountain regions of the U.S. The Pacific Northwest states, on the other hand, tend to experience dry but foggy winters and warm, sunny and precocious springs during an El Niño. During a La Niña, by contrast, the Midwestern U.S. tends to be drier than normal. El Niño is associated with increased wave caused coastal erosion along the US Pacific Coast and decreased hurricane activity in the Atlantic, especially south of 25º N; this reduction is largely due to stronger wind sheartropics.
Finally, East Africa, including Kenya, Tanzania and the White Nile basin experiences, in the long rains from March to May, wetter than normal conditions. There also are drier than normal conditions from December to February in south-central Africa, mainly in Zambia, Zimbabwe, Mozambique and Botswana.
Western Hemisphere Warm Pool
Study of climate records has found that about half of the summers after an El Niño have unusual warming in the Western Hemisphere Warm Pool (WHWP). This affects weather in the area and seems to be related to the North Atlantic Oscillation.
Atlantic effect
An effect similar to El Niño sometimes takes place in the Atlantic Ocean, where water along equatorial Africa's Gulf of Guinea becomes warmer and eastern Brazil becomes cooler and drier. This may be related to El Niño Walker circulation changes over South America.
Cases of double El Niño events have been linked to severe famines related to the extended failure of monsoon rains, as in the book Late Victorian Holocausts.
Non-climate effects
Along the west coast of South America, El Niño reduces the upwelling of cold, nutrient-rich water that sustains large fish populations, which in turn sustain abundant sea birds, whose droppings support the fertilizer industry.
East Pacific fishing
The local fishing industry along the affected coastline can suffer during long-lasting El Niño events. The world's largest fishery collapsed due to overfishing during the 1972 El Niño Peruvian anchoveta reduction. During the 1982-83 event, jack mackerel and anchoveta populations were reduced, scallops increased in warmer water, but hake followed cooler water down the continental slope, while shrimp and sardines moved southward so some catches decreased while others increased. Horse mackerel have increased in the region during warm events.
Shifting locations and types of fish due to changing conditions provide challenges for fishing industries. Peruvian sardines have moved during El Niño events to Chilean areas. Other conditions provide further complications, such as the government of Chile in 1991 creating restrictions on the fishing areas for self-employed fishermen and industrial fleets.
The ENSO variability may contribute to the great success of small fast-growing species along the Peruvian coast, as periods of low population removes predators in the area. Similar effects benefit migratory birds which travel each spring from predator-rich tropical areas to distant winter-stressed nesting areas. There is some evidence that El Niño activity is correlated with incidence of red tides off of the Pacific coast of California.
It has been postulated that a strong El Niño led to the demise of the Moche and other pre-Columbian Peruvian cultures.
A recent study of El Niño patterns suggests that the French Revolution was caused in part by the poor crop yields of 1788-89 in Europe, resulting from an unusually strong El-Niño effect between 1789-93.
La Niña
Sea surface skin temperature anomalies in November 2007 showing La Niña conditions
La Niña is the name for the cold phase of the Southern Oscillation, during which the cold pool in the eastern Pacific intensifies and the trade winds strengthen. The name La Niña originates from Spanish, meaning "the little girl", analogous to El Niño meaning "the little boy". It has also in the past been called anti-El Niño.
Effects of La Niña
Regional impacts of La Niña.
La Niña causes mostly the opposite effects of El Niño, for example, El Niño would cause a wet period in the Midwestern U.S., while La Niña would typically cause a dry period in this area.
Recent occurrences
There was a strong La Niña episode during 1988-1989. La Niña also formed in 1995, and in 1999-2000. The last La Niña was a minor one, and occurred 2000-2001. Currently, there is a moderate La Niña, which began developing in mid-2007. NOAA confirmed that a moderate La Niña developed in their November El Niño/Southern Oscillation Diagnostic Discussion, and that it will likely continue into 2008. According to NOAA, "Expected La Niña impacts during November – January include a continuation of above-average precipitation over Indonesia and below-average precipitation over the central equatorial Pacific. For the contiguous United States, potential impacts include above average precipitation in the Northern Rockies, Northern California, and in southern and eastern regions of the Pacific Northwest. Below-average precipitation is expected across the southern tier, particularly in the southwestern and southeastern states. " In March 2008, La Niña caused a drop in sea surface temperatures over Southeast Asia by an amount of 2°C. It also caused heavy rains over Malaysia, Singapore and Indonesia. "
ENSO and global warming
A few years ago, attribution of recent changes (if any) in ENSO or predictions of future changes were very weak. More recent results tend to suggest that the projected tropical warming may follow a somewhat El Niño-like spatial pattern, without necessarily altering the variability about this pattern, while the ENSO cycle may be minimally shortened .
Causes of El Niño
The mechanisms which might cause an El Niño event are still being investigated. It is difficult to find patterns which may show causes or allow forecasts. As the phenomenon is located near the equator, events in both hemispheres may have an effect. As the weather events are somewhat chaotic, the onsets of El Niño-events may also be. This is not to say predicting is totally impossible.
Major theories
Jacob Bjerknes in 1969 suggested that an anomalously warm spot in the eastern Pacific can weaken the east-west temperature difference, causing weakening in the Walker circulation and trade wind flows, which push warm water to the west. The result is increasingly warm water toward the east.
Wyrtki in 1975 proposed that increased trade winds could build up the western bulge of warm water, and any sudden weakening in the winds would allow that warm water to surge eastward. However, there was no such buildup preceding the 1982-83 event.
Recharge oscillator: Several mechanisms have been proposed where warmth builds up in the equatorial area, then is dispersed to higher latitudes by an El Niño event. The cooler area then has to "recharge" warmth for several years before another event can take place.
Western Pacific oscillator: In the western Pacific, several weather conditions can cause westerly wind anomalies. For example, cyclones north and south of the equator force west-to-east winds between. Such wind may counteract the typical easterly flows across the Pacific and create a tendency toward continuing the eastward motion. A weakening in the westward currents at such a time may be the final trigger needed to shift into an El Niño.
Equatorial Pacific Ocean may tend to be near El Niño conditions, with several random variations affecting behavior. Weather patterns from outside the area or volcanic events may be some such factors.
The Madden-Julian Oscillation (MJO) is an important source of variability that can contribute to a more rapid evolution toward El Niño conditions through related fluctuations in low-level winds and precipitation over the western and central equatorial Pacific. Eastward-propagating oceanic Kelvin waves can be produced by MJO activity. The MJO may in turn be influenced by a developing El Niño, leading to a positive feedback .
Adams, Mann and Ammann, using statistical analysis of paleoclimatic records, that a volcanic event in the tropics tilts the climate into a state where El Niño-like conditions are favored. (This is caused by the volcano's effect on solar radiation reaching the surface, not by the heat of the eruption itself.)
History of the theory
The first mention of the term "El Niño" to refer to climate occurs in 1892, when Captain Camilo Carrillo told the Geographical society congress in Lima that Peruvian sailors named the warm northerly current "El Niño" because it was most noticeable around Christmas. However even before then the phenomenon was of interest because of its effects on biological productivity, with its effects on the guano industry.
Normal conditions along the west Peruvian coast are a cold southerly current (the Humboldt Current) with upwelling water; the upwelling nutrients lead to great oceanic productivity; the cold currents leads to very dry conditions on land. Similar conditions exist elsewhere (California Current; Benguela Current off South Africa; West Australia Current). Thus the replacement of this with warmer northerly water leads to lower biological productivity in the ocean, and more rainfall - often flooding - on land; the connection with flooding was reported in 1895 by Pezet and Eguiguren.
Towards the end of the nineteenth century there was much interest in forecasting climate anomalies (for food production) in India and Australia. Charles Todd, in 1893, suggested that droughts in India and Australia tended to occur at the same time; Norman Lockyer noted the same in 1904. In 1924 Gilbert Walker (for whom the Walker circulation is named) first coined the term "Southern Oscillation".
For most of the twentieth century, El Niño was thought of as a largely local phenomenon.
The major 1982-3 El Niño lead to an upsurge of interest from the scientific community.
The 1998 El Niño event caused an estimated 16% of the world’s reef systems to die. Since then, mass coral bleaching has become common worldwide, with all regions having suffered ‘severe bleaching’.
History of the phenomenon
ENSO conditions seem to have occurred at every two to seven years for at least the past 300 years, but most of them have been weak.
Major ENSO events have occurred in the years 1790-93, 1828, 1876-78, 1891, 1925-26, 1982-83, and 1997-98.
Recent El Niños have occurred in 1986-1987, 1991-1992, 1993, 1994, 1997-1998, 2002-2003, 2004-2005 and 2006-2007.
The El Niño of 1997 - 1998 was particularly strong and brought the phenomenon to worldwide attention. The event temporarily warmed air temperature by 3°F, compared to the usual increase of 0.5°F associated with El Niño events . The period from 1990-1994 was unusual in that El Niños have rarely occurred in such rapid succession (but were generally weak). There is some debate as to whether global warming increases the intensity and/or frequency of El Niño episodes. (see also the ENSO and Global Warming section above).
Southern Oscillation
The Southern Oscillation is an oscillation in air pressure between the tropical eastern and western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is a record of the monthly or seasonal fluctuations in the normalized surface air pressure difference between Tahiti and Darwin, Australia. .
El Niño episodes, which are associated with negative values of the SOI, are usually accompanied by sustained warming of the central and eastern tropical Pacific Ocean, a decrease in the strength of the Pacific Trade Winds, and a reduction in rainfall over eastern and northern Australia. Conversely, La Niña episodes are associated with positive values of the SOI and are accompanied by stronger Pacific trade winds and warmer sea temperatures to the north of Australia. Waters in the central and eastern tropical Pacific Ocean become cooler during this time.
What is an El Niño?
El Niño is an oscillation of the ocean-atmosphere system in the tropical Pacific having important consequences for weather around the globe.
Among these consequences are increased rainfall across the southern tier of the US and in Peru, which has caused destructive flooding, and drought in the West Pacific, sometimes associated with devastating brush fires in Australia. Observations of conditions in the tropical Pacific are considered essential for the prediction of short term (a few months to 1 year) climate variations. To provide necessary data, NOAA operates a network of buoys which measure temperature, currents and winds in the equatorial band. These buoys daily transmit data which are available to researchers and forecasters around the world in real time.
In normal, non-El Niño conditions (top panel of schematic diagram), the trade winds blow towards the west across the tropical Pacific. These winds pile up warm surface water in the west Pacific, so that the sea surface is about 1/2 meter higher at Indonesia than at Ecuador.
The sea surface temperature is about 8 degrees C higher in the west, with cool temperatures off South America, due to an upwelling of cold water from deeper levels. This cold water is nutrient-rich, supporting high levels of primary productivity, diverse marine ecosystems, and major fisheries. Rainfall is found in rising air over the warmest water, and the east Pacific is relatively dry. The observations at 110 W (left diagram of 110 W conditions) show that the cool water (below about 17 degrees C, the black band in these plots) is within 50m of the surface.
During El Niño (bottom panel of the schematic diagram), the trade winds relax in the central and western Pacific leading to a depression of the thermocline in the eastern Pacific, and an elevation of the thermocline in the west. The observations at 110W show, for example, that during 1982-1983, the 17-degree isotherm dropped to about 150m depth. This reduced the efficiency of upwelling to cool the suface and cut off the supply of nutrient rich thermocline water to the euphotic zone. The result was a rise in sea surface temperature and a drastic decline in primary productivity, the latter of which adversely affected higher trophic levels of the food chain, including commercial fisheries in this region. The weakening of easterly tradewinds during El Niño is evident in this figure as well. Rainfall follows the warm water eastward, with associated flooding in Peru and drought in Indonesia and Australia. The eastward displacement of the atmospheric heat source overlaying the warmest water results in large changes in the global atmospheric circulation, which in turn force changes in weather in regions far removed from the tropical Pacific.
Recognizing El Niño
El Niño can be seen in Sea Surface Temperature in the Equatorial Pacific Ocean
Normal Conditions -
December 1993
El Niño (warm) Conditions -
December 1997
La Niña (cold) Conditions -
December 1998
Also see the entire Pacific Ocean
El Niño can be seen in measurements of the sea surface temperature, such as those shown above, which were made from the TAO Array of moored buoys. In December 1993, the sea surface temperatures and the winds were near normal, with warm water in the Western Pacfic Ocean (in red on the top panel of December 1993 plot), and cool water, called the "cold tongue" in the Eastern Pacific Ocean (in green on the top panel of the December 1993 plot). The winds in the Western Pacific are very weak (see the arrows pointing in the direction the wind is blowing towards), and the winds in the Eastern Pacific are blowing towards the west (towards Indonesia). The bottom panel of the December 1993 plot shows anomalies, the way the sea surface temperature and wind differs from a normal December. In this plot, the anomalies are very small (yellow/green), indicating a normal December. December 1997 was near the peak of a strong El Niño year. In December 1997, the warm water (red in the top panel of the December 1997 plot) has spread from the western Pacific Ocean towards the east (in the direction of South America), the "cold tongue" (green color in the top panel of the December 1997 plot) has weakened, and the winds in the western Pacific, usually weak, are blowing strongly towards the east, pushing the warm water eastward. The anomalies show clearly that the water in the center of Pacific Ocean is much warmer (red) than in a normal December.
December 1998 was a strong La Niña (cold) event. The cold tongue (blue) is cooler than usual by about 3° Centigrade. The cold La Niña events sometimes (but not always) follow El Niño events.
Animation of El Niño
Animation of physical processes allow scientists to better understand El Niño
If you have an MPEG animation viewer, and sufficient memory, you can view an animation of El Niño which shows the changes in monthly sea surface temperature in the tropical Pacific Ocean. The animation is about 1 Megabyte in size. As you view this animation, you will see the warm water spreading from the western Pacific to the eastern Pacific during 1997. The bottom panel in the animation, labeled anomalies, shows how much the sea surface temperature for each month is different from the long term average for that month. The red color in the anomalies plot indicates that the temperature of the water is much warmer than is normal for that month. Blue color indicates that the water is much cooler than is normal for that month
Recent El Niños
Several recent El Niños can be seen in Pacific Sea Surface Temperature representations
Mean and anomalies of sea surface temperature from 1986 to the present, showing El Niños in 1986-1987, 1991-1992, 1993, 1994 and 1997
In the left hand panel, you see the sea surface temperature at the Equator in the Pacific Ocean (Indonesia is towards the left, South America is towards the right). Time is increasing downwards from 1986 at the top of the plot, to the present, at the bottom of the plot. The first thing to note is the blue "scallops" on the right of the plot, in the eastern Pacific. These indicate the cool water typically observed in the Eastern Pacific (called the "cold tongue"). Cold tongue temperatures vary seasonally, being warmest in the northern hemisphere springtime and coolest in the northern hemisphere fall. The red color on the left is the warm pool of water typically observed in the western Pacific Ocean. El Niño is an exaggeration of the usual seasonal cycle. During the El Niño in 1986-1987, you can see the warm water (red) penetrating eastward in the Spring of 1987. There is another El Niño in 1991-1992, and you can see the warm water penetrating towards the east in the northern hemisphere spring of 1992. The El Niño in 1997-1998 is a very strong El Niño. El Niño years are easier to see in the anomalies on the right hand panel. The anomalies show how much the sea surface temperature is different from the usual value for each month. Water temperatures significantly warmer than the norm are shown in red, and water temperatures cooler than the norm are shown in blue.
Information on the names El Niño and La Niña
El Niño was originally recognized by fisherman off the coast of South America as the appearance of unusually warm water in the Pacific ocean, occurring near the beginning of the year. El Niño means The Little Boy or Christ child in Spanish. This name was used for the tendency of the phenomenon to arrive around Christmas.
La Niña means The Little Girl. La Niña is sometimes called El Viejo, anti-El Niño, or simply "a cold event" or "a cold episode". El Niño is often called "a warm event".
There has been a confusing range of uses for the terms El Niño, La Niña and ENSO by both the scientific community and the general public, which is clarified in this web page on definitions of the terms ENSO, Southern Oscillation Index, El Niño and La Niña. Also interesting is the Web page: Where did the name El Niño come from?
In the right-hand plot of sea surface temperature anomalies, it is very easy to see El Niños, with water warmer than usual (red) in the eastern Pacific, during in 1986-1987, 1991-1992, 1993, 1994 and 1997-1998. Notice the very cool water (blue), in the Eastern Pacific, in 1988-1989. This is a strong La Niña, which occurs after some (but not all) El Niño years. 1995-1996 was a weaker La Niña year. It is unusual for El Niños to occur in such rapid succession, as has been the case during 1990-1994.
Among these consequences are increased rainfall across the southern tier of the US and in Peru, which has caused destructive flooding, and drought in the West Pacific, sometimes associated with devastating brush fires in Australia. Observations of conditions in the tropical Pacific are considered essential for the prediction of short term (a few months to 1 year) climate variations. To provide necessary data, NOAA operates a network of buoys which measure temperature, currents and winds in the equatorial band. These buoys daily transmit data which are available to researchers and forecasters around the world in real time.
In normal, non-El Niño conditions (top panel of schematic diagram), the trade winds blow towards the west across the tropical Pacific. These winds pile up warm surface water in the west Pacific, so that the sea surface is about 1/2 meter higher at Indonesia than at Ecuador.
The sea surface temperature is about 8 degrees C higher in the west, with cool temperatures off South America, due to an upwelling of cold water from deeper levels. This cold water is nutrient-rich, supporting high levels of primary productivity, diverse marine ecosystems, and major fisheries. Rainfall is found in rising air over the warmest water, and the east Pacific is relatively dry. The observations at 110 W (left diagram of 110 W conditions) show that the cool water (below about 17 degrees C, the black band in these plots) is within 50m of the surface.
During El Niño (bottom panel of the schematic diagram), the trade winds relax in the central and western Pacific leading to a depression of the thermocline in the eastern Pacific, and an elevation of the thermocline in the west. The observations at 110W show, for example, that during 1982-1983, the 17-degree isotherm dropped to about 150m depth. This reduced the efficiency of upwelling to cool the suface and cut off the supply of nutrient rich thermocline water to the euphotic zone. The result was a rise in sea surface temperature and a drastic decline in primary productivity, the latter of which adversely affected higher trophic levels of the food chain, including commercial fisheries in this region. The weakening of easterly tradewinds during El Niño is evident in this figure as well. Rainfall follows the warm water eastward, with associated flooding in Peru and drought in Indonesia and Australia. The eastward displacement of the atmospheric heat source overlaying the warmest water results in large changes in the global atmospheric circulation, which in turn force changes in weather in regions far removed from the tropical Pacific.
Recognizing El Niño
El Niño can be seen in Sea Surface Temperature in the Equatorial Pacific Ocean
Normal Conditions -
December 1993
El Niño (warm) Conditions -
December 1997
La Niña (cold) Conditions -
December 1998
Also see the entire Pacific Ocean
El Niño can be seen in measurements of the sea surface temperature, such as those shown above, which were made from the TAO Array of moored buoys. In December 1993, the sea surface temperatures and the winds were near normal, with warm water in the Western Pacfic Ocean (in red on the top panel of December 1993 plot), and cool water, called the "cold tongue" in the Eastern Pacific Ocean (in green on the top panel of the December 1993 plot). The winds in the Western Pacific are very weak (see the arrows pointing in the direction the wind is blowing towards), and the winds in the Eastern Pacific are blowing towards the west (towards Indonesia). The bottom panel of the December 1993 plot shows anomalies, the way the sea surface temperature and wind differs from a normal December. In this plot, the anomalies are very small (yellow/green), indicating a normal December. December 1997 was near the peak of a strong El Niño year. In December 1997, the warm water (red in the top panel of the December 1997 plot) has spread from the western Pacific Ocean towards the east (in the direction of South America), the "cold tongue" (green color in the top panel of the December 1997 plot) has weakened, and the winds in the western Pacific, usually weak, are blowing strongly towards the east, pushing the warm water eastward. The anomalies show clearly that the water in the center of Pacific Ocean is much warmer (red) than in a normal December.
December 1998 was a strong La Niña (cold) event. The cold tongue (blue) is cooler than usual by about 3° Centigrade. The cold La Niña events sometimes (but not always) follow El Niño events.
Animation of El Niño
Animation of physical processes allow scientists to better understand El Niño
If you have an MPEG animation viewer, and sufficient memory, you can view an animation of El Niño which shows the changes in monthly sea surface temperature in the tropical Pacific Ocean. The animation is about 1 Megabyte in size. As you view this animation, you will see the warm water spreading from the western Pacific to the eastern Pacific during 1997. The bottom panel in the animation, labeled anomalies, shows how much the sea surface temperature for each month is different from the long term average for that month. The red color in the anomalies plot indicates that the temperature of the water is much warmer than is normal for that month. Blue color indicates that the water is much cooler than is normal for that month
Recent El Niños
Several recent El Niños can be seen in Pacific Sea Surface Temperature representations
Mean and anomalies of sea surface temperature from 1986 to the present, showing El Niños in 1986-1987, 1991-1992, 1993, 1994 and 1997
In the left hand panel, you see the sea surface temperature at the Equator in the Pacific Ocean (Indonesia is towards the left, South America is towards the right). Time is increasing downwards from 1986 at the top of the plot, to the present, at the bottom of the plot. The first thing to note is the blue "scallops" on the right of the plot, in the eastern Pacific. These indicate the cool water typically observed in the Eastern Pacific (called the "cold tongue"). Cold tongue temperatures vary seasonally, being warmest in the northern hemisphere springtime and coolest in the northern hemisphere fall. The red color on the left is the warm pool of water typically observed in the western Pacific Ocean. El Niño is an exaggeration of the usual seasonal cycle. During the El Niño in 1986-1987, you can see the warm water (red) penetrating eastward in the Spring of 1987. There is another El Niño in 1991-1992, and you can see the warm water penetrating towards the east in the northern hemisphere spring of 1992. The El Niño in 1997-1998 is a very strong El Niño. El Niño years are easier to see in the anomalies on the right hand panel. The anomalies show how much the sea surface temperature is different from the usual value for each month. Water temperatures significantly warmer than the norm are shown in red, and water temperatures cooler than the norm are shown in blue.
Information on the names El Niño and La Niña
El Niño was originally recognized by fisherman off the coast of South America as the appearance of unusually warm water in the Pacific ocean, occurring near the beginning of the year. El Niño means The Little Boy or Christ child in Spanish. This name was used for the tendency of the phenomenon to arrive around Christmas.
La Niña means The Little Girl. La Niña is sometimes called El Viejo, anti-El Niño, or simply "a cold event" or "a cold episode". El Niño is often called "a warm event".
There has been a confusing range of uses for the terms El Niño, La Niña and ENSO by both the scientific community and the general public, which is clarified in this web page on definitions of the terms ENSO, Southern Oscillation Index, El Niño and La Niña. Also interesting is the Web page: Where did the name El Niño come from?
In the right-hand plot of sea surface temperature anomalies, it is very easy to see El Niños, with water warmer than usual (red) in the eastern Pacific, during in 1986-1987, 1991-1992, 1993, 1994 and 1997-1998. Notice the very cool water (blue), in the Eastern Pacific, in 1988-1989. This is a strong La Niña, which occurs after some (but not all) El Niño years. 1995-1996 was a weaker La Niña year. It is unusual for El Niños to occur in such rapid succession, as has been the case during 1990-1994.
Subscribe to:
Posts (Atom)
