Clouds Aren't Where They Used to Be

The clouds are shifting, and a new study suggests that's a worrisome thing for the planet. Satellite images collected between 1983 and 2009 show two trends: Clouds have been migrating away from the Equator toward the Earth's poles, and the tops of those clouds are reaching higher into the atmosphere, say the scientists behind the study in Nature. Add it up and it amounts to what the Washington Post calls "one of the most profound planetary changes yet to be caused by a warming climate." Clouds moving toward the poles means that dry zones in mid-latitude areas are expanding; clouds reaching higher means that a thicker cloud barrier has formed, one that traps heat radiation instead of letting it escape into space. The upshot is that both changes suggest clouds will worsen climate change instead of relieving it, reports the Christian Science Monitor.

"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," one of the researchers tells NPR. "This is happening right now. It's happened during my lifetime—it was a bit startling." Climate change models had predicted this kind of thing would happen, but clouds are notoriously difficult to study and predict, and this study seems to be the first confirmation of it. One gray area is how much of the shift is attributable to us humans and how much to two large volcanic eruptions that occurred during the time studied. "This is a very good attempt to try and get a handle on this, but I don't think it's the final answer," says a scientist at the National Center for Atmospheric Research in Colorado. (See how clouds are hurting Greenland's ice sheet.)