From: NELL GREENFIELDBOYCE, NPR
Published July 12, 2016 09:00 AM

Climate change is apparently shifting clouds towards the poles

The way clouds cover the Earth may be changing because of global warming, according to a study published Monday that used satellite data to track cloud patterns across about two decades, starting in the 1980s.

Clouds in the mid-latitudes shifted toward the poles during that period, as the subtropical dry zones expanded and the highest cloud-tops got higher.

These changes are predicted by most climate models of global warming, even though those models disagree on a lot of other things related to clouds, says Joel Norris, a climate scientist at the University of California, San Diego.

"I guess what was surprising is that a lot of times we think of climate change as something that's going to occur in the future," says Norris. "This is happening right now. It's happened during my lifetime — it was a bit startling."

About 70 percent of our planet is covered by clouds, at any given moment. These constantly moving shape-shifters aren't exactly easy for scientists to study.

Clouds aren't as simple as their fluffy nature might suggest. To understand them, scientists have to track the behavior of tiny water droplets, as well as huge masses of clouds that might be hundreds of miles wide.

And climate modelers also have to take into account the fact that clouds can have two different effects on temperatures.

"During daytime, if there are a lot of clouds present, thick clouds, then that will keep the temperature cooler," says Norris, because clouds reflect incoming sunlight back to space.

But thick clouds can also act like a blanket that keeps the Earth's warmth in, he says, "which is the reason why a cloudy night won't be as cold at the surface as a clear night."

About 70 percent of Earth is covered by clouds at any given moment. Their interaction with climate isn't easy to study, scientists say; these shape-shifters move quickly. Image credit: NOAA/Flickr

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