Global Warming

Cool Pacific Ocean Slowed Global Warming

The Pacific Ocean has been a planetary air conditioner for the past two decades, but the relief may soon end, a new study finds.

The Pacific and Atlantic oceans undergo decades-long natural oscillations that alter their sea surface temperatures. These natural cycles flip-flop between cooler and warmer phases. Over the past 130 years, the tempo of global warming has revved up or slowed down in tune with changing ocean temperatures, researchers reported today (Feb. 26) in the journal Science.

"The Pacific Ocean appears to be driving the slowdown in warming over the past 15 years," said lead study author Byron Steinman, a climate scientist at the University of Minnesota-Duluth.

The period since 1998 is often called a global warming pause or global warming hiatus, because the planet's thermometer slowed its steady climb. However, it's more accurate to call the intervening years a global warming slowdown. Temperatures never stopped rising, and the 10 hottest years ever recorded have all happened since 1998. And though global surface temperatures have plateaued, the oceans are still warming — studies have found the "missing" heat is going into deeper layers of the sea.

"We are in a turning point right now, and the slowdown will presumably reverse in the decades ahead," Mann said. "When we do, we may see warming even faster than what the models are predicting."