Three of the big meteorological agencies on the Pacific Rim now agree: El Nino has come.

The Australian Bureau of Meteorology joined the U.S. Climate Prediction Center and Japan Meteorological Agency recently in declaring that sea-surface temperatures in the equatorial Pacific are high enough — and the atmosphere above the ocean has reacted strongly enough — to mean an El Nino has begun.

If this seems like old news, that’s because people have been talking about this El Nino since 2013, when predictions began popping up among researchers and the media that the Pacific would warm and global weather patterns were going to be altered.

The obsession can be forgiven when you consider that El Ninos cause trouble. In 1982-83, an El Nino was blamed for setting off a series of droughts, wildfires and flooding from South America to Australia that cost $8 billion and killed almost 2,000 people, according to the National Oceanic and Atmospheric Administration.

The agency estimated the U.S. economic cost of the 1997-98 El Nino at $10 billion, with crops wilting or drowning in the fields and consumers spending $2.2 billion less on heating fuels. El Ninos also increase the risk of Eastern Pacific hurricanes while hindering the development of Atlantic storms.

Forecast models have been struggling to make sense of, well, uncharted waters. Large parts of the Pacific Ocean were warmer than normal last year, even while the atmosphere above the seas failed to react.

The models based on statistical analysis of the Pacific’s past performance have been “bamboozled,” said Kevin Trenberth, a distinguished senior scientist in the Climate Analysis Section at the National Center for Atmospheric Research in Boulder, Colorado. “What we are seeing is unprecedented, a sort of double El Nino.”

Even though Australia, the U.S. and Japan agree an El Nino has started, there hasn’t been a lot of unity in the chorus.

While Australia was saying the event was in its initial stages, Japan said it started last summer, weakened during the winter of 2015 and is now “likely to be redeveloping,” according to a statement by its Climate Prediction Division, which added it will probably persist until into the Northern Hemisphere’s fall.

In March, the U.S. Climate Prediction Center said the El Nino began in February.

The three agencies have their own criteria for the phenomena, which explains some of the differences, and commercial forecasters have weighed in with their own opinions. Given the lack of unity, no one should be surprised that there is no consensus about how strong it will be or how long it will last.

“It’s come on quickly and all of our model guidance predicts it’s going to continue to strengthen,” said David Jones, manager of Australia’s climate monitoring and prediction. “A significant or substantial event is likely.”

U.S. Climate Prediction Center Deputy Director Mike Halpert recently said he wasn’t ready to make a prediction on strength yet.

Commercial forecasters’ opinions also diverge.

It is possible that “this will be a strong event, perhaps on the magnitude of the last really strong event in 1997-98,” said Todd Crawford, chief meteorologist at WSI in Andover, Massachusetts.

“A lot of these climate models have a warm bias, so like last year, it’s best to fade them,” said Matt Rogers, president of the Commodity Weather Group in Bethesda, Maryland. He said because the models call for a strong El Nino, he is favoring a weak one through the summer at least.

No two El Ninos are exactly the same, Trenberth said.

Researchers tend to talk about “different flavors of El Ninos,” he said. “Mother Nature always seems to throw us a curve ball.”

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