Welcome to the 'Double El Niño' — and more extreme weather

We’re about to experience a “double El Niño” — a rare weather phenomenon that climatologists had warned about several months ago.

That means two consecutive years of the concentration of warm water in the Pacific Ocean that brings West Coast storms, quiet hurricane seasons in the Atlantic and busy ones in the Pacific. The danger is that this could mean more than a few months of odd weather, but instead usher in a new phase of climate change. Last year was the warmest year on record; 2015 looks set to be even warmer.

What kind of temperature increase are we talking about? Trenberth says it could mean a rise of two- or three-tenths-of-a-degree Celsius, or up to half a degree Fahrenheit. The change could occur “relatively abruptly,” but then stick around for five or 10 years.

“With that kind of an increase, there is about 2 percent increase in the moisture in the atmosphere, which feeds into all the weather systems that occur, and it gets concentrated and magnified by all of the storms, so you can get double or quadruple the effects,” Trenberth says.