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The Pacific Ocean hot streak known as El Niño appears to be fading, but will keep whipping up weird weather and driving up global temperatures for several more months, UN forecasters announced Thursday.
The current El Niño appears to have topped out in December after pushing Pacific sea surface temperatures up by about 2 degrees Celsius (3.6 Fahrenheit). That figure has dropped by about half a degree since then, the World Meteorological Organization reported.
"In meteorological terms, this El Niño is now in decline," WMO Secretary-General Petteri Taalas said in a written statement on the findings. "But we cannot lower our guard as it is still quite strong and in humanitarian and economic terms, its impacts will continue for many months to come."
The announcement came a day after the UN children's aid agency UNICEF warned that "unprecedented" El Niño-related crop losses in Africa have left millions in need of food aid. Leila Gharagozloo-Pakkala, UNICEF's regional director for eastern and southern Africa, said the effects could ripple through the continent for years. The World Food Program estimates up to 14 million people in southern and eastern Africa face hunger amid the driest season the region has experienced in more than 30 years.
El Niño turned what scientists said was already likely to be a second straight global temperature record in 2015 into a blowout, boosting average annual temperatures to nearly an entire degree C over the 20th century average. It may not have been the strongest on record — the jury's still out on that — but it's in the top three, along with the 1982-83 and 1997-98 periods, Taalas said.
Mike Halpert, deputy director of the Climate Prediction Center at the National Oceanic and Atmospheric Administration in the United States, said the current phenomenon isn't likely to go quietly.
"The El Niño remains strong, so impacts are still anticipated," Halpert said. It's likely to take two more months to fade, "during which we can reasonably expect to see significant rainfall in southern California."
That was supposed to be one of the few bright spots about this year's phenomenon — a break in the epic drought that has gripped California and large chunks of the western United States for several years. And it has helped a bit, but not as much as hoped.
"There has been quite a bit that is unusual about this El Niño," Pennsylvania State University climatologist Michael Mann said. "It has actually been somewhat disappointing from the standpoint of California rainfall and snowfall totals."
Rain and snow have been "nowhere close" to what fell during the major El Niño period of 1982-83, and most of the state is now expected to remain in drought through the end of the winter rainy season, Mann said. While mountain snowpacks that store water for the dry season have rebounded from record lows, it's still not enough to offset the arid years.
Mann said pre-El Niño Pacific warming associated with human-induced climate change may be changing how the atmosphere responds to an El Niño.
"We can't rely on the impact of a large El Niño now being the same as it was in 1982-83," he said. "That is a sobering reality that we have to acknowledge."
An El Niño forms every two to seven years, when the trade winds of the equatorial Pacific Ocean slow down. That warms the waters of the tropics, usually bringing more temperature winters to the Northern Hemisphere but aggravating natural hazards worldwide.
December saw spring-like Christmas temperatures in the eastern United States and Canada, while Hurricane Patricia, which slammed into Mexico's West Coast in October, was the strongest storm on record in the Western Hemisphere.
Scientists are questioning whether El Niño helped boost the spread of the mosquito-borne Zika virus into South America, where record-breaking temperatures and drought created conditions that made it easier for the bugs to breed.
In India, El Niño also fueled a heat wave that authorities blamed for more than 2,000 deaths, followed by autumn flooding that killed hundreds more in the southern industrial hub of Chennai. In Southeast Asia, it drove an intense summer drought that aggravated Indonesia's forest fire crisis, leaving much of that country and some of its neighbors wreathed in choking haze.
And as it fades, scientists are now looking at whether the Pacific swings into a La Niña phase — El Niño's cooler twin. That pattern typically means drier weather across the southern United States and tropical South America, while bringing more moisture to places like Southeast Asia, Australia, and India. Mann said the odds are good that La Niña will follow in late 2016.
"El Niño is like a spring," he said. "Once you set it going in one direction, it doesn't just return to the starting point. It tends to overshoot back in the other direction."
Follow Matt Smith on Twitter: @mattsmithatl