This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: As an El Niño of historic proportions is taking shape in the tropical Pacific, a University of Michigan study has found that El Niño events have become nearly 40% stronger in the last 40 years than they were in the preindustrial era. In fact, the study, which examined modern and ancient corals in the Galápagos Islands, found that El Niño events in the last four decades were stronger than any in the 1,000 years before about 1850, when humans began affecting the climate with greenhouse gases.
"We don't see a time in the past where El Niños have been as strong as today, and we show that the strength of El Niño changes in parallel with warming global temperatures," said lead author Julia Cole, professor and chair of the U-M Department of Earth and Environmental Sciences. "Our findings tell us that the big El Niño events of the last 40 years are not normal in the context of the last thousand years." El Niño is a natural phenomenon that, every few years, causes the tropical Pacific to become warmer than usual. Under normal conditions, trade winds blow along the equator from east to west.
This pushes warm water from South America toward Australia. But when the trade winds weaken, warm water spreads eastward, back toward South America, kicking off an El Niño event. The atmospheric circulation responds as heavy rainfall shifts from Indonesia into the central Pacific, leaving the western Pacific in drought.
This weakens the trade winds further, locking in El Niño conditions that can persist for one to two years. These temperature and precipitation fluctuations originate in the tropical Pacific, but they affect weather all over the world. Storm tracks over the U.S. shift southward, bringing more rain to the desert Southwest and less to the Northwest.
Similar shifts around the world lead to droughts and flooding that bring disease, crop failure, wildfires and other crises that affect people's health and well-being. "The question is not whether the current El Niño will happen, but how bad it is going to be, and how bad the impacts will be?" Cole said. "This event is superimposed on global warming, and it's likely to supercharge the temperature increase that we would normally see from greenhouse gases.
There are forecasts that we might get as hot as 1.7 or 1.8 degrees Celsius above preindustrial temperatures, which is quite a bit higher than the current record." To examine historic El Niño patterns, Cole and fellow researchers sampled cores from 13 corals, including living colonies and boulders of ancient coral, from the Galápagos Islands. Corals grow 1 to 2 centimeters (0.4 to 0.8 inches) per year by secreting layers of calcium carbonate. The chemistry of these layers provides a record of the seawater temperature in which the corals grew.
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