Next winter could be radically different for Americans. The U.S. Climate Prediction Center has issued an El Niño watch, forecasting the possible arrival of the periodic phenomenon in which warming of the Pacific Ocean triggers dramatic weather changes for Australia and the Americas.
Past El Niño events have brought heavy rain and flooding to California and made winter far warmer—with less snow—in the Midwest and Northeast. Based on Pacific Ocean temperature readings, the center predicts a 52 percent chance of an El Niño occurring this summer. “There are still dominoes that have to fall here,” Michelle L’Heureux, a climate scientist at the center, told Bloomberg News. “This is not a guarantee, but certainly we’re issuing this watch so folks have a heads-up.”
The impact of an El Niño depends on how intense the water-warming effect becomes. (The opposite effect, called La Niña, involves a cooling of the eastern Pacific.) The last El Niño occurred in late 2009 through early 2010; the most dramatic in recent history was in 1982-83, when the eastern Pacific warmed by 3.5C (6F) and caused more than $8 billion in damage. That El Niño included heavy flooding in California and Southern states and a lack of snow that crippled U.S. ski resorts.
The heavy rains can also wreak havoc for agriculture. In South America, areas of Ecuador and Peru received as much as 100 inches of rain in six months, “transforming the coastal desert into a grassland dotted with lakes,” according to a report by the Department of Atmospheric Sciences at the University of Washington. The rains and new vegetation produced swarms of grasshoppers, record shrimp production, and heavy bouts of malaria infection due to an abundance of mosquitoes.
“Predicting the life cycle and strength of a Pacific warm or cold episode is critical in helping water, energy and transportation managers, and farmers plan for, avoid or mitigate potential losses,” the climate center says on its website. The effect is caused by a natural “oscillation” in which the westerly trade winds calm, the typical warmer waters in the western Pacific begin to shift east under the surface, and the central and eastern Pacific begins to warm.