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How ENSO leads to a cascade of global impacts

ENSO arises from changes across the tropical Pacific Ocean. So why does ENSO affect the climate over sizable portions of the globe, including some regions far removed from the tropical Pacific Ocean?  Does the strength of ENSO matter for global impacts? 

ENSO affects the sea surface temperature (SST) in regions where fishing is a major industry to some countries. A prominent example is the anchovy fishing routinely done off the northwest coast of Peru. When El Niño occurs, the warmed waters become unfavorable for the fish, which flee for cooler waters, resulting in poor harvests that are detrimental to the Peruvian economy.

But the abnormal tropical Pacfic SSTs are only the beginning of the story of ENSO’s impacts. When El Niño occurs, the central and eastern tropical Pacific Ocean becomes warmer than average. With the elevated SST, there is more thunderstorm activity, or convection, than usual over the waters in the central and eastern tropical Pacific. This convection is caused by the increased temperature and moisture in the air right above the warmed water.

This warm, moist air rises to form thunderstorm clouds. The process causes latent heating in the upper atmosphere: heat from the warmed surface of the ocean is released when water vapor condenses into clouds and rainfall. With more storminess than usual, the upper atmosphere becomes warmer than usual, and this extra heat sets in motion yet another series of important effects.

The Hadley Circulation

The rising air in the tropical Pacific can branch away from the equator toward the higher latitudes, both northward and southward, contributing to the complex circulation patterns that help establish the average worldwide climate features. This poleward movement of air in the upper atmosphere, sinking motion over the subtropics, and the return flow at lower levels of the atmosphere toward the lower pressure at the equator, is called the Hadley circulation (see figure).

When an El Niño causes excess heating in the tropical Pacific upper atmosphere, the air flow toward the poles becomes more vigorous. The change in the strength of the Hadley circulation leads to modifications in the circulation patterns worldwide, including, for example, the position of the jet stream that flows from west to east over the North Pacific in winter months. El Niño tends to lead to an elongated jet stream that can extend all the way to North America and bring an above-average supply of storms across the southern part of the United States.


By strengthening the Hadley circulation, El Niño can trigger a cascade of noticeable departures from the normal rainfall patterns around the globe. The changes in the atmospheric circulation, and subsequent ground-level climate impacts, that stretch across the globe are called El Niño teleconnections (see figure). Teleconnection patterns emerge in climate simulations, and they show up in historical observations.

Global map of typical El Niño and La Niña impacts worldwide

Typical rainfall patterns during El Niño events. Such teleconnections are likely during El Niño events, but not certain. Map by IRI.

Observations since 1950 indicate that impacts during El Niño depend on the season. The figure shows what changes, and during which seasons, El Niño is expected to bring about across the globe. It must be emphasized that while these impacts are likely during El Niño, they are not certain to occur. The stronger the El Niño, however, the more likely the teleconnection side effects become. There is also some correlation between the strength of the El Niño and the severity of the effects (Lyon and Barnston, 2005), but, again, it must be stressed that there are no guarantees here either.

The most reliable effects of El Niño are deficient rainfall over Indonesia and northern South America, and excess rainfall in southeastern South America, eastern equatorial Africa, and the southern US.


Lyon, B., and A. G. Barnston, 2005: ENSO and the spatial extent of interannual precipitation extremes in tropical land areas. J. Climate, 18, 5095-5109.


The Indian met department has cited El Nino as a factor in forecasting deficient monsoon this year over the Indian subcontinent. Any thoughts? I do see that the map here agrees in general with the forecast.

i live in Lebanon, in the middle east region. befor i learned about El nino/ La nina, since i was young i noticed severe changes in our local weather. the 1997 i was still in the university , and most of the days i had to return home " swimming", because of the heavy rainfall, a storm after a storm were heading toward us. in 2002 , i was pregnant , and people kept skiing until july ( night ski ).the last two and half years were like a permanent spring, in the map above nothing mentioned our area. so , if this year is going to be a nino year , and the weather is going to dramatically change, i will inform you.

You are confusing weather with climate. Weather is the condition of the atmosphere at any given time. It is tangib;e, measurabe and undeniable. Climate is a man made construct that describes the changes in weather patters over a period of not less than 30 years. Climate is a synthesis of the past, it cannoyt and does not predict the future. The main drivers of climate are. (1) The eliptical orbit of Earth aound the sun in approx. 365.25 days. (2) The passage of Earth through the Solar wind of the Sun's magnetosphere. (3) The precession cycle (wobble) of the earth's spin, of about 26,000 years. (4) The 11 degree tilt of the Earth's geograthic poles vs the Orbit around the Sun. (5) Continuous volcanic activity above and below the sea, there are about 600 active ones above the sea and there has been over 1,500 known eruptions over the past 10,000 years. (6) The elliptical orbit of the Moon around Earth (about 27.323 days), its mean inclination of the lunar orbit to the ecliptic plane, about 5.145degrees, Moon's Apsidial precession and its obliquity. (7) The Moon is getting further from Eath (a few cm per year). None of these factors can be influenced by any man, including movie makers and fiction writers and would-be presidents.

This person drank the Kool aid. He probably has a tinfoil hat and unvaccinated children. Watch out for chemtrails sparky, they are part of a vast deep state conspiracy to rob men of their precious bodily fluids. 97 percent of environmental scientists, the Pentagon, insurance actuaries, and basic chemistry and physics are wrong! Trust me, I saw a YouTube video.

Lyon, Bradfield, and Anthony G. Barnston. "ENSO and the spatial extent of interannual precipitation extremes in tropical land areas." Journal of Climate 18.23 (2005). Any AMS Journal older than two years is Open Access. Many journals have similar policies. For example, the Proceedings of the National Academy of Sciences makes articles older than six months open to all. Enjoy!

Dear NOAA, I want to ask about the impact of El Nino in my hometown, Pontianak, Indonesia in South east Asian Region. In this year, in first seven days of January, it was dry and inconsistent hot and cool temperature, while it should have been raining. However, the rest of January to Spring Equinox (March 21), it was consistently dry and cool. Since March 23, it consistently wet and hot with frequent rains in various intensity, from shower to thunderstorm. In May, there was a strong gust with severe rainfall. is it the sign of El Nino? I will inform you the weather in my hometown. Thank you.

I have lived in Southern California all my life. When we see sea temperatures as high as 76 degrees fahrenheit (Hermosa Beach) we are headed for a pretty strong El Niño.

I've been searching already a long time for a answer to this question. Are there any direct effects or forecast models which say how the NE trade winds are developing during a El Nino winter?

I'm pleased that I seen this website, precisely the proper information that I was trying to find! ddkegdefagkf

I've been looking for an article explaining this, and thought you could add some more tags so other people can find it. I had to search a lot deeper to find it. Add tags like effects of ENSO, oscillation results.

I live in Morocco, in the north west of africa. I can say that my country is directly and severly impacted by el nino/nina. after 3 years of observing this impact i can confirme that: el nino = Warm and very dry la nina = Cold and Wet this season exactly when Nino3.4 SST index become positive in january the weather had changed from wet in December (whene there was la nina) to a very dry weather in January. The CFSv2 SST forecast anomalies indicates a positive value this fist half of 2017. So i predict drought this year I HATE EL NINO

Hallow i live in edmonton i dont like the el ninio becuase it makes it rain during the colc cold months and i get reallly wettttt

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