A sea surface temperature anomaly in the tropical Pacific Ocean during the peak of the 2009-10 El Niño.

A sea surface temperature anomaly in the tropical Pacific Ocean during the peak of the 2009-10 El Niño.


NASA/Jet Propulsion Laboratory

Drought in Australia; an end to drought in Brazil; poor crops across Asia; record global temperatures. If you start hearing about these in the next year, remember this news from the week:

El Niño is back.

That's the word from scientists who have been watching the tropical Pacific. Surface temperatures there are going up, winds are shifting and that could mean big weather-related changes around the world over the next year or so.

El Niño is part of a climate cycle in the tropical Pacific known as the El Niño Southern Oscillation; it flips back and forth every few years between the cool La Niña and the warm El Niño phases. In the El Niño phase, ocean surface temperatures rise, easterly trade winds along the equator slow or even reverse and the planet in general tends to warm up.

Scientists expected El Niño last year, but it was a no-show. But this year, American researchers reported in March that a weak El Niño had finally set in. Now Japanese and Australian scientists say it's definitely here, and likely to be much bigger than the American predictions — with global implications.

Maps of typical jet stream locations and patterns during La Niña (left) and El Niño (right) winters. Patterns are similar in spring, but are often weaker. Based on original graphics from NOAA’s Climate Prediction Center.



In parts of Brazil, it could mean a lot more rain — which could be a good thing, with other parts of the country in the midst of a wrenching drought. In Australia, the effect may well be the opposite: drier and hotter weather in many areas, possibly exacerbating existing water shortages.

That heating and drying out could stretch from Australia all the way around to eastern Africa and southern Asia, possibly cutting into harvests of key crops like rice, soybeans, corn and palm oil from India to China to Indonesia.

In the United States, El Niño often brings rain to California and the South, raising hopes that a return this year would bring drought relief to the parched West Coast. That seemed unlikely when scientists identified the weak El Niño in March, figuring it would be too small to have much of an impact. But the prospects for substantial rain could be improved with the revised forecast.

Meanwhile, the global forecast is for higher overall temperatures, quite possibly even a record.

Until last year, the hottest year on record was 1998, which saw a big El Niño. After that, the next warmest was 2010, another El Niño year. Last year broke both of those records by a hair, which was a bit of a surprise — and a concern to many, because it wasn't an El Niño year.

But with the overall temperature trend sharply up — the 10 hottest years on record have all come since 1998 — scientists are anticipating that the warmth contributed by El Niño may well bring another new global record, and perhaps put to rest the contention by climate change deniers that global temperatures have plateaued.

UPDATED: A previous version of this story incorrectly stated that São Paulo was the capital of Brazil. Brasília is the capital of Brazil.

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