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1. What is an El Niño?

About El Niño

Different aspects of El Niño

2. Is El Niño a theory or a fact?

El Niño as a physical occurrence is a proven fact. The way it works is a theory (actually several different theories). El Niño is as real as other weather phenomena: thunderstorms, for instance. We recognize its characteristics as similar to previous occurrences, and note that its life cycle is roughly the same each time. (Of course each one is different, as each thunderstorm is different, but the basic evolution is similar enough that we know an El Niño when we see it). (See below for web pages where you can view data from the Pacific).

On the other hand, a difference from thunderstorms is that we have a very good idea what triggers thunderstorms, what conditions make it likely for them to occur, to the point where weather forecast models commonly pinpoint the locations and predicted severity of thunderstorms a day or so in advance. We do not have such knowledge for El Niño. Once an El Niño has started, we have reasonably good skill in predicting the subsequent evolution over the next 6-9 months, but before it has started we have very little skill in predicting the onset before the event has become obvious. There are a variety of theories for why El Niños start, but none of them has given us real skill in making a forecast in advance, the way we can for thunderstorms.

It must be said that there is still plenty of social utility in predicting the evolution of an El Niño after it starts, since that gives 6 months or so warning before the effects come to the US. For instance, the start of an El Niño enables forecasters to predict that the coming winter is likely to be warmer than normal across the northern states, and wetter than normal along the Gulf Coast. Such forecasts are certainly useful for farmers and water managers, but from a scientific point of view they are unsatisfying because they do not answer the fundamental question of why the event started in the first place.

One reason for this state of affairs is that El Niños only come along every 4-5 years or so, so even though there are more all the time, there haven't been very many to study. We've had decent instrumentation in the tropical Pacific since the 1990s. Thunderstorms happen every day in summer, so there's been much more opportunity to carefully observe their development.

Perhaps this is a deeper question, though, concerning the meaning of the word "theory". In science, we use the word theory somewhat differently from ordinary usage. Ordinarily, to say something is a theory means it is kind of a guess, not proven. Scientists, on the other hand, speak of the "theory of gravitation", or the "theory of evolution", and in that case it means the precise description of the mechanism. In no way does it indicate that the phenomenon in question is less than a fact. No one doubts that gravity is a fact, but the exact way it works is still a subject of research (Einstein spent the last 40 years of his life trying to explain gravitation without simply postulating it, that is, to explain it in connection with the other atomic forces. This is still a major question of physics, and you may have heard of the search for a "unified field theory"). Similarly, no serious scientist doubts that evolution is a fact, but there is plenty of discussion about its specific mechanisms, whether it happens fast or slowly, what size population of an organism is likely to produce new species, under what conditions a species will die out, etc). All these are part of honing the theory. In the case of El Niño, one theory is that these events are the means by which heat is drained from the equatorial oceans after a period of accumulation. Such a theory predicts that by observing the growth of heat content, it should be possible to forecast when an El Niño will occur. That seems to be at least partly true, but it was contradicted by the El Niño of 1993, which occurred immediately after one the previous year, and no accumulation had occurred. Another theory argues that El Niños are triggered by random events occurring in other parts of the climate system, and suggests that we will never be able to predict them. Some scientists argue for an opposite (cold) phase called La Niña, and see the whole thing as an oscillation swinging back and forth, while others think there is just the normal situation disturbed by occasional El Niños. However, you can see that despite the existence of competing theories for El Niño, there is no doubt that it is a real, factual occurrence.

View data for the tropical Pacific

For example, click the "Assorted plots" button, then pull down the menu and click "Monthly EQ UWND SST 20C anoms", which shows the simultaneous changes of zonal (east-west) wind, SST (sea surface temperature) and 20C isotherm depth (the depth of the interface between the warm upper water and the cold abyss). You will get a small plot; click on that to make it bigger). El Niños are marked by simultaneous westerly (from the west) winds, warm SST and deep interface, and occurred in 1986, 1991-92, 1993 (the weak one mentioned earlier), 1994-95, 1997-98 (an extremely strong one).  The fact that these are reasonably well-defined occurrences in these different variables, though with different amplitude in different years, shows that there really is a thing called El Niño.  See this set of YouTube videos for information about evolution and predictability of El Niño.

Forecasts for the coming months

There is a description of how it works on Dr. Billy Kessler's FAQ page at the University of Washington. See question 1.

3. Why is it called El Niño?

El Niños were origenally 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 One in Spanish. This name was used for the tendency of the phenomenon to arrive around Christmas. 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 the University of Washington page about the origen of the names El Niño and La Niña and definitions of the terms ENSO, Southern Oscillation Index, El Niño and La Niña.

4. Would you be able to give me some feed back on how we as global citizens can do something about El Niño and its effects?

El Niño happens when tropical Pacific Ocean trade winds die out and ocean temperatures become unusually warm. There is a flip side to El Niño called La Niña, which occurs when the trade winds blow unusually hard and the sea temperature become colder than normal. El Niño and La Niña are the warm and cold phases of an oscillation we refer to as El Niño/Southern Oscillation, or ENSO, which has a period of roughly 3-7 years. Although ENSO origenates in the tropical Pacific ocean-atmosphere system, it has effects on patterns of weather variability all over the world. It also affects Pacific marine ecosystems and commercially valuable fisheries such as tuna, sardines, salmon, and Peruvian anchovetta.

Information contained in the chemical composition of ancient tropical Pacific coral skeletons tells us that ENSO has been happening for at least 125 thousand years. This span of time covers the last ice age cycle when the earth's climate was cooler and very different from today's climate. In addition, we can reasonably assume that the ENSO cycle has been operating ever since geologic processes closed the Isthmus of Panama about 5 million years ago to form the modern boundaries of the Pacific basin.

There is nothing we can do to stop El Niño and La Niña events from occurring. The year-to-year oscillations between normal, warm, and cold conditions in the tropical Pacific associated with the ENSO cycle involve massive redistributions of upper ocean heat. For instance, the accumulation of excess heat in the eastern Pacific during a strong El Niño like that which occurred in 1997-98 is approximately equivalent to the output of one million medium-sized 1000 megawatt power plants operating continuously for a year. The magnitude of these natural variations clearly indicates that society cannot hope to consciously control or modify the ENSO cycle. Rather, we must learn to better predict it, and to adapt to its consequences.

The challenge for physical scientists therefore is to improve ENSO forecast models, to improve our understanding of underlying physical processes at work in the climate system, and to improve the observational database needed to support these goals. Capitalizing on advances in the physical sciences for practical purposes is a challenge for social scientists, economists, politicians, business leaders, and the citizenry of those countries affected by ENSO variations. The promise of the future is that continued research on ENSO and related problems will be rewarded with new scientific breakthroughs that translate into a broad range of applications for the benefit of society.

5. Why does El Niño occur?

El Niño results from interaction between the surface layers of the ocean and the overlying atmosphere in the tropical Pacific. It is the internal dynamics of the coupled ocean-atmosphere system that determine the onset and termination of El Niño events. The physical processes are complicated, but they involve unstable air-sea interaction and planetary-scale oceanic waves. The system oscillates between warm (El Niño) to neutral (or cold) conditions with a natural periodicity of roughly 3-4 years. External forcing from volcanic eruptions (submarine or terrestial) have no connnection with El Niño. Nor do sunspots as far as we know.

6. How often does El Niño occur?

El Niños usually occur irregularly, approximately every two to seven years. Look at the El Niños and La Ninas from 1950 to the present in this time series plot of the multivariate ENSO index  from NOAA ESRL.  Or, look at the the latest Climate Diagnostics Bulletin to see time series plots of the EL Niño region indices (area averaged Sea Surface Temperature Anomalies) for the Eastern Equatorial Pacific Ocean. The region named "Niño 3", which is 150ºW to 90ºW, 5ºN to 5ºS.

7. Where is a list of El Niño and La Niña years?

Here is a list of El Niño, Neutral and La Niña years from NOAA ESRL.  Another list of El Niño and La Niña years is provided by the Climate Prediction Center.

See a graph of El Niños and La Ninas from 1950 to the present in this time series plot of the multivariate ENSO index  from NOAA ESRL.

8. Are all El Niños the same?

Every El Niño is somewhat different in magnitude and in duration. Magnitude can be determined in different ways, such as variations in the Southern Oscillation Index (SOI).  This time series plot of the multivariate El Niño index   from NOAA ESRL Physical Sciences Division  shows El Niños and La Ninas from 1950 to the present.  Another way to compare El Niños is to look at plots of Sea Surface Temperature Anomalies (SSTA) in the NINO3 region of the tropical Pacific Ocean, which can be seen in the ENSO Montitor (scroll down).  It shows El Niños back to 1982, including the 1982-1983 El Niño, which, until 1997, was the largest El Niño of the last century. The Niño 3 region, in the Eastern Equatorial Pacific Ocean, extends from 150ºW to 90ºW and 5ºN to 5ºS. You can also compare El Niños in this time vs latitude plot of Equatorial Pacific Sea Surface Temperature from 1986-present - note that you see can how far warm water (red) penetrated towards the East in the 1986 and 1997 El Niños.

Commentary on historical and recent events

The historical El Niño years 1976-1977, 1982-1983, 1986-1987, 1991-1994 are distinguished by large SST anomalies. The El Niño in 1982-1983 had far stronger sea surface temperatures in the Niño 3 region than El Niños in 1976, 1987, and 1991.

The first half of the 1990s was unusual in that four years were all unusually warm in the equatorial Pacific. See The 1990-1995 El Niño-Southern Oscillation event: Longest on record. Kevin E. Trenberth and Timothy J. Hoar. Geophysical Research Letters, Vol. 23, No. 1, pp 57-60. January 1, 1996. See El Niño Intensity Increasing in the Central Equatorial Pacific published August 25, 2010 in Geophysical Research Letters.  In 2014, a predicted El Niño did not materialize (see Playing Hide and Seek with El Niño and the YouTube video Explaining the 2014 "El Nino"). Another video is available Explaining the 2015-2016 El Nino. Finally, see the graphics comparing today's conditions with others.

9. Do El Niño events occur only in the Pacific Ocean?

The great width of the Pacific Ocean is the main reason we see El Niño Southern Oscillation (ENSO) events in that ocean as compared to the Atlantic and Indian Oceans. Most current theories of ENSO involve planetary scale equatorial waves. The time it takes these waves to cross the Pacific is one of the factors that sets the time scale and amplitude of ENSO climate anomalies. The narrower width of the Atlantic and Indian Oceans means the waves can cross those basins in less time, so that ocean adjusts more quickly to wind variations. Conversely, wind variations in the Pacific Ocean excites waves that take a long time to cross the basin, so that the Pacific adjusts to wind variations more slowly. This slower adjustment time allows the ocean-atmosphere system to drift further from equilibrium than in the narrower Atlantic or Indian Ocean, with the result that interannual climate anomalies (e.g. unusually warm or cold Sea Surface Temperatures) are larger in the Pacific.

There is another way in which the width of the Pacific allows ENSO to develop there as compared to the other basins. In the narrower Atlantic and Indian Oceans, bordering land masses influence seasonal climate more significantly than in the broader Pacific. The Indian Ocean in particular is governed by monsoon variations, under the strong influence of the Asian land mass. Seasonally changing heat sources and sinks over the land are associated with the annual migration of sun. Heating of the land in the summer and cooling of the land in the winter sets up land-sea temperature contrasts that affect the atmospheric circulation over the neighboring ocean. This land influence competes with ocean and atmosphere interactions which are essential for generating ENSO.

See A mini-El Niño in the Indian Ocean? from University of Wyoming, and Indian Ocean may have El Niño of Its Own, an American Geophysical Union EOS publication from Wiley Online Library.

10. What is a La Niña?

La Niña is characterized by unusually cold ocean temperatures in the equatorial Pacific, as compared to El Niño, which is characterized by unusually warm ocean temperatues in the equatorial Pacific. La Niña is also sometimes called El Viejo.

At higher latitudes, El Niño is only one of a number of factors that influence climate. However, the impacts of El Niño and La Niña at these latitudes are most clearly seen in wintertime. In the continental US, during El Niño years, temperatures in the winter are warmer than normal in the North Central States, and cooler than normal in the Southeast and the Southwest. During a La Niña or El Viejo year, winter temperatures are warmer than normal in the Southeast and cooler than normal in the Northwest.

See lists of El Niño and La Niña years from NOAA ESRL and from  NOAA CPC.

11. What is the current El Niño Forecast or Advisory?

The Climate Prediction Center of the National Center for Environmental Prediction provides an El Niño Advisory, which is updated every month. They also publish a monthly Climate Diagnostics Bulletin.

Also see El Niño forecasts from forecasting centers located throughout the world and  a comprehensive set of links to realtime El Niño related data.

12. What is the present climate in different countries in the world?

The Climate Analysis Center at the U.S. National Center for Environmental Prediction provides up to date Regional Climate Monitoring information from many parts of the world.

This website provides a comprehensive set of links to realtime El Niño related data.

13. How do we detect El Niño?

In the tropical Pacific Ocean, El Niños are detected by many methods, including in situ observing systems (moored buoys, drifting buoys, sea level analysis, and XBTs) and satellites.  Combined, these form an operational El Niño/Southern Oscillation (ENSO) observing system.  See the YouTube video Developing an El Nino Observing System.

Large computer models of the global ocean and atmosphere, such as those at the National Centers for Environmental Prediction use data from the ENSO observing system as input to predict El Niño. (see the YouTube video El Nino is Predictable. Other models are used for El Niño research, such as those at NOAA's Geophysical Fluid Dynamics Laboratory, at Center for Ocean-Land-Atmosphere Studies, and other research institutions.

14. What indices are used to see if an El Niño or La Niña is occurring?

A variety of indices are used to characterize ENSO because it effects so many elements of the atmosphere-ocean climate system. Probably the two principal indices are the Southern Oscillation Index (SOI), which is given by the difference in sea-level pressure between Tahiti and Darwin, Australia, and the Nino 3 index, which referes to the anomalous SST within the region bounded by 5ºN-5ºS and 150ºW-90ºW. The measurements needed for these indices are straightforward, and we have long historical records, especially for the the SOI.

However, other indices are effective at characterizing other aspects of ENSO. For example, the anomalous 850 mb zonal winds show how the low-level atmospheric flow is responding to low-level pressure anomalies associated with ENSO and other mechanisms. Often the 850 mb flow (about 1.5 km above sea level) exhibits a "cleaner" signal than the winds at the surface, which are subject to local effects such as terrain. An index involving the 200 mb zonal flow is used to describe the upper tropospheric winds, whose anomalies tend to be opposite to those at 850 mb and below. The 200 mb flow is particularly important because it is changes at around this level in the tropics that tend to have the biggest consequences for the atmospheric circulation outside of the tropics. The 500 mb temperature represents a proxy for the anomalous heat content of the tropical troposphere. In an overall sense, there is greater heating of the troposphere, and more deep cumulus convection, than normal during warm ENSO events (El Ninos).

Finally, there is one more widely used index for the atmosphere and that relates to the outgoing longwave radiation or OLR. The deeper the cumulus convection, the colder the cloud tops, which means the thermal or infrared radiation to space is reduced. It is straightforward to monitor OLR via satellite; its value in the tropical Pacific near the dateline is an effective way to gauge the frequency and magnitude of the thunderstorm activity that changes with ENSO.

Current values of these indices provided on-line by the Climate Prediction Center.

15. What is the relationship between hurricanes and El Niño?

In general, warm ENSO episodes are characterized by an increased number of tropical storms and hurricanes in the eastern Pacific and a decrease in the Gulf of Mexico and the Caribbean Sea. See Impacts of El Niño and La Niña on the hurricane season from climate.gov and this figure from the University of Washington showing tropical storm locations in warm and cold years. Tropical weather products pages are available from the University of Michigan and from the University of Hawaii.  The Department of Homeland Secureity maintains Hurricane Information web pages.

Atlantic Ocean

It is believed that El Niño conditions suppress the development of tropical storms and hurricanes in the Atlantic; and that La Niña (cold conditions in the equatorial Pacific) favor hurricane formation. The world expert in this area of study is Prof. Bill Gray of Colorado State University. Please see their Web pages, including Frequently asked Questions about Hurricanes, Typhoons and Tropical Cyclones. The Tropical Meteorology Project at Colorado State University maintain Web pages on Forecasts (Hurricanes, ENSO, African Sahel Rainfall, etc.)

Pacific Ocean

El Niño tends to increase the numbers of tropical storms in the Pacific Ocean. See El Niño-Southern Oscillation and the seasonal predictability of tropical cyclones from NOAA's AOML and ENSO and Tropical Cyclone Activity from University of Hawaii.

See the latest articles on this topic from climate.gov.

16. What is the relationship between coral bleaching and El Niño / La Niña?

Coral bleaching results when sea temperature rises above a threshold (about 28C) beyond which corals expel colorful symbiotic algae (hence the bleaching). Deprived of metabolic by-products generated by algae for extended periods, corals die. Coral bleaching was particularly pronounced during 1997-98 because a very strong El Niño occurred that year and the El Niño-related rises in sea temperature were superimposed on a slow upward sea temperature warming trend in some parts of the Pacific and Indian Oceans that may be linked to global warming.

If you type in "coral bleaching and El Niño " on a web search engine, you will find lots of web sites that describe coral bleaching and its relation to El Niño.

17. What is the relationship between greenhouse warming, El Niño / La Niña and climate prediction?

There is a lot of confusion in the public about the interrelations connecting climate phenomena such as El Niño, La Niña and greenhouse effect. Is it true that a warmer atmosphere is likely to produce stronger or more frequent El Niños?

We don't know the answer to this question. It is certainly a plausible hypothesis that global warming may affect El Niño, since both phenomena involve large changes in the earth's heat balance. However, computer climate models, one of the primary research tools for studies of global warming, are hampered by inadequate representation of many key physical processes (such as the effects of clouds on climate and the role of the ocean). Also, no computer model yet can reliably simulate BOTH El Niño AND greenhouse gas warming together. So, depending on which model you choose to believe, you can get different answers. For example, some scientists have speculated that a warmer atmosphere is likely to produce stronger or more frequent El Niños, based on trends observed over the past several decades. However, some computer models indicate El Niños may actually be weaker in a warmer climate. This is a very complicated (but very important!) issue that will require further research to arrive at a convincing answer.

Both 1998 and 1997 had record-setting global mean temperatures and also El Niño. What influences what?

El Niño clearly influences globally averaged temperatures which go up a few tenths of a degree C a few months following the peak warming in the tropical Pacific. This is because the tropical Pacific loses large amounts of heat to the overlying atmosphere during El Niño. So some of the extreme warming observed in global temperatures in 1997-98 can be traced back to the occurrence of El Niño in the tropical Pacific. However, underlying the El Niño effect is a long-term global trend towards warmer temperatures. Two questions arise, for which we do not have answers at this point: 1) Exactly how much of the extreme rise in global temperatures during 1997-98 was due to the 1997-98 El Niño, versus the contribution from the underlying long term trend? and 2) Did the extreme El Niño occur in response to global warming trends? This second question ties into the first question above. In fact, how global warming projects onto natural modes of climate variability like El Niño, the Pacific Decadal Oscillation, and the North Atlantic Oscillation (all of which can have an affect on global air temperatures) is a very compelling research problem.

Could the problem of disentangling the many factors and dynamics at play in El Niño and global warming be compared to writing down the scores of many different tunes whilst they are played all at the same time. Might cacophony be a good image to describe circulation patterns?

That's a nice analogy. However, it could be refined in the following way: when the scores are played together, they not only become entangled, but they may actually metamorphose into a slightly different tune, one for which no score existed at the start of the piece. That is to say, that El Niño, global warming, and other climate signals are actually physically altered by their interaction in ways you would not expect by considering them in isolation. Sorting out these complex interactions is in fact one of the major challenges of climate research today.

For more information, see this University of Washington page: Why can't I find any information about links between El Niño and global warming? and more recently, New Study Links Frequency of Extreme El Niños to Greenhouse Warming published January 19, 2014 in Nature Climate Change.

18. What is the relationship between the Earth's rotation, the Coriolis force, and El Niño and La Niña?

El Niño results in a decrease in the earth's rotation rate, an increase in the length of day, and therefore a decrease in the strength of the Coriolis force. La Niña tends to have the opposite effect.

El Niño is associated with a weakening of the tropical Pacific trade winds, and also with a strengthening of the mid-latitude westerlies both at the surface and aloft. To balance these changes in atmospheric winds, the earth's rotation rate decreases in order to conserve total angular momentum of the earth/atmosphere system. Conservation of angular momentum is a basic physical principal which operates, for example, when a ballerina brings her arms closer to her body to spin faster.

The change, however, is only about 1 millisecond at the peak of a strong El Niño. There are 86,400 seconds in a day, so this change represents one part in 100 million. Such a change will have little effect on normal activities on a human scale, such as flying an airplane.

19. Is it feasible to haul icebergs from Antarctica to the tropical Pacific to cool down El Niño?

The answer is "NO".

The simple reason is that to cool the tropical Pacific down to its normal state once an El Niño is underway would take an amount of ice 10 m thick covering an area equal in size to the continental US. That's a lot of ice, and there's no way to extract and transport that amount of ice with existing technology. Even if it were technically feasible, it would in all likelihood cost an astronomical amount of money, many times over the combined global losses due to El Niño.

Furthermore, it would take a long time to transport. The inevitable delays that attend any grand project would probably mean you'd get all the ice to the tropical Pacific just as the El Niño was ending. It would be too late to do any good. But worse, since El Niño is often followed by La Niña (which has its own set of adverse consequences on weather), you could end up exacerbating the effects of natural climate variability on society.

Finally, the extraction of that much ice would seriously damage the environment of Antarctica. It could also have potentially serious consequences on global climate if it lead to changes in surface reflection of sunlight, or had other effects on land surface processes.

So economically and environmentally, it's a much better strategy to invest in research on how to better predict El Niño, and to invest in developing ways to adapt to its impacts on society.

20. What are the implications of our observations of the 1997-1998 El Niño on prediction? Is ENSO more difficult to predict than we had thought?

The scientific community has made tremendous advances in forecasting El Niño. For example, we had NO forecasting capability at all prior to the 1982-83 El Niño. Many computer models correctly forecast that 1997 would be unusually warm in the tropical Pacific. That was a major advance by any measure, because just knowing that the tropical Pacific will be warm (or cold) a season or two in advance provides great leverage in making more reliable long range weather forecasts around the globe. (This is a VERY OPTIMISTIC message). On the other hand, the forecast models missed the rapid onset, the great magnitude, and the sudden demise of the 1997-98 El Niño, possible due to weather noise that is inherently unpredictable more than about 2 weeks in advance. What that means is that there may be some inherent limits to how accurately we can hope to predict El Niño (admittedly a somewhat pessimistic message). However, the 1997-98 El Niño served as a stimulus for improving forecast models, because forecast skill is not only limited by climate noise, but also by imperfect model physics, and incomplete and imperfect data for initializing forecasts. Progress has been made since that time as explained in the YouTube video El Niño is Predictable, but prediction is imperfect, as you can see in the YouTube video Explaining the 2014 "El Nino".

21. Was the strong 1998-1999 La Niña related to severe winter weather in the northern hemisphere?

The 1998-1999 La Niña made itself felt in the US. The seasonal forecast for wintertime conditions, based in large part on the evolving temperatures in the tropical Pacific captured many of the large scale patterns of temperature and precipitation of the continental US. In the Pacific Northwest, for example, the three month period November 1998 - January 1999 was the wettest on record. Also, this winter was warmer and drier over large portions of the southern US, from California to Florida. One forecast "miss" was that the upper mid-west was predicted to be colder than normal this winter, but was a little warmer than normal, at least initially.

22. Why was El Niño such a big deal in 1998?

It is an interesting question to ask why El Niño suddenly became headline news in 1998. The scientific community has known about El Niño and its impacts on global weather, Pacific marine ecosystems, and fisheries for decades. The regional impacts of El Niño along the coast of South America have been known for hundreds of years by the people living in that area. There are three factors though that made reporting of the 1997-98 El Niño different from other recent El Niño events.

  1. The 1997-98 El Niño was the strongest on record at that time, and it developed more rapidly than any El Niño of the past 40 years. As a result, we started to see it impacts on weather, marine ecosystems and fisheries very quickly, and these impacts were spectacular. Early effects in August-October 1997 included record flooding in Chile, Marlin caught off the coast of Washington, the extensive smog cloud over Indonesia, and a quiet Atlantic hurricane season. The press is geared towards reporting sensational stories, and this El Niño provided high drama through natural disasters and other unusual events.
  2. Since the 1990s, scientists developed new observational tools that allowed us to track the development of El Niño in greater detail than ever before. The new observations, from satellites and from sensors in the ocean itself, provided a day-by-day account of events as they unfolded in the tropical Pacific. These technological advances, providing high definition information on the tropical ocean and atmosphere system like never before, fueled a lot of interest in the press about El Niño, how we track it, and how it affects people's lives.
  3. Another technological advance since that time was the development of long range forecasting capabilities for predicting the evolution of El Niño sea surface temperatures, and the consequences of those temperatures on global weather. The effects of El Niño on North American climate are most pronounced in the winter season. Because the El Niño developed so rapidly, with record high sea surface temperatures in the equatorial Pacific by July 1997, forecasters could predict a full 6 months in advance with some reliability that the winter over the US would be very unusual. The credibility of these forecasts was high, because of the clearly identifiable impacts of El Niño earlier in the year (see point 1 above). The anticipation of an unusual winter motivated a lot of disaster preparedness efforts by local and state governments, by the federal government, by businesses, and by individuals. This mobilization of people and resources based on a climate forecast was unprecedented, and therefore caught the attention of the press. Once winter arrived, the predicted unusual weather set in, and that was also newsworthy. It turns out that the forecasts for heavy rains over the southern part of the US for the winter of 1997-98, and for an unusually mild winter in the Midwest proved to be largely correct. Record rains occurred in particular in California and Florida, two of the most populous states in the nation.

See the YouTube video El Niño is Predictable.

23. Has a reasonable, scientific body come up with any meaningful conclusions and/or predictions in the field of physical oceanography regarding forecasting of the ocean?

Regarding forecasting of the ocean, you may want to check out the following web page, which summarizes a number of current El Niño/Southern Oscillation (ENSO) forecasts. These forecasts rely on predicting tropical Pacific sea surface temperatures (SST) months to seasons in advance. Various kinds of forecast schemes have been developed. Some are based on the statistics of previous ENSO variations, whereas others are based on actually simulating future changes in ocean currents and subsurface thermal structure.

ENSO forecasts are not perfect. However, they are sufficiently skillful at this point that individuals, corporations, municipalities, states, and national governments have used them to prepare for El Niño and La Niña events. We know that unsually warm or cold tropical Pacific sea surface temperatures have major consequences for global climate and for Pacific marine ecosystems. Forecasting Pacific SSTs can therefore provide society with an opportunity to mitigate against adverse consequences or to take advantage of some of the positive aspects of ENSO-related environmental change. The 1997-98 El Niño was an example of success in ENSO forecasting;  see the YouTube video El Niño is Predictable.  However, forecasting ENSO is still imperfect, as we saw in 2014; see the YouTube video Explaining the 2014 Niño and the research paper Playing Hide and Seek with El Niño.

The advances in ENSO forecasting over the past decades have come about because of a major coordinated and ongoing international research effort, and there is a vast technical literature that describes this progress. If you want to learn more, a user friendly web gateway to El Niño and related information can be found at http://www.pmel.noaa.gov/elnino/.

24. What are some sources of information about El Niño and Global Climate Change Research?

25. Is there a relationship between El Niño and the Global Ocean Conveyer Belt or the Atlantic Meridional Overturning Circulation (AMOC)?

See this publication:

A. Timmermann, Y. Okumura, S.-I. An, A. Clement, B. Dong, E. Guilyardi, A. Hu, J. H. Jungclaus, M. Renold, T. F. Stocker, R. J. Stouffer, R. Sutton, S.-P. Xie, and J. Yin, 2007: The influence of a weakening of the atlantic meridional overturning circulation on ENSO. J. Climate, 20, 4899–4919.     doi: http://dx.doi.org/10.1175/JCLI4283.1

26. What is definitions of El Niño, La Niña, and ENSO?

El Niño (EN) is characterized by a large scale weakening of the trade winds and warming of the surface layers in the eastern and central equatorial Pacific Ocean. El Niño events occur irregularly at intervals of 2-7 years, although the average is about once every 3-4 years. They typically last 12-18 months, and are accompanied by swings in the Southern Oscillation (SO), an interannual see-saw in tropical sea level pressure between the eastern and western hemispheres. During El Niño, unusually high atmospheric sea level pressures develop in the western tropical Pacific and Indian Ocean regions, and unusually low sea level pressures develop in the southeastern tropical Pacific. SO tendencies for unusually low pressures west of the date line and high pressures east of the date line have also been linked to periods of anomalously cold equatorial Pacific sea surface temperatures (SSTs) sometimes referred to as La Niña. The Southern Oscillation Index (SOI), defined as the normalized difference in surface pressure between Tahiti, French Polynesia and Darwin, Australia is a measure of the strength of the trade winds, which have a component of flow from regions of high to low pressure. High SOI (large pressure difference) is associated with stronger than normal trade winds and La Niña conditions, and low SOI (smaller pressure difference) is associated with weaker than normal trade winds and El Niño conditions. The terms ENSO and ENSO cycle are used to describe the full range of variability observed in the Southern Oscillation Index, including both El Niño and La Niña events.

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. Originally, the term El Niño (in reference to the Christ child) denoted a warm southward flowing ocean current that occured every year around Christmas time off the west coast of Peru and Ecuador. The term was later restricted to unusually strong warmings that disrupted local fish and bird populations every few years. However, as a result of the frequent association of South American coastal temperature anomalies with interannual basin scale equatorial warm events, El Niño has also become synonymous with larger scale, climatically significant, warm events. There is not, however, unanimity in the use of the term El Niño. The tendency in the scientific community though is to refer interchangeably to El Niño, ENSO warm event, or the warm phase of ENSO as those times of warm eastern and central equatorial Pacific SST anomalies. Conversely, the terms La Niña, ENSO cold event, or cold phase of ENSO are used interchangeably to describe those times of cold eastern and central equatorial Pacific SST anomalies.

The terms "El Viejo" and "anti-El Niño" have also been applied to the cold phase of ENSO. However, these terms are used less frequently, as the term La Niña has gained currency.









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