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Clouds May Speed Up Global Warming

Clouds May Speed Up Global Warming

They may make both the best and worst-case scenarios for climate change less likely

One of the most fundamental questions about climate change is also one of the thorniest: How much, exactly, will the Earth warm in response to future greenhouse gas emissions?

The answer, scientists say, lies in the sky above our heads. Clouds are the fluffy, unlikely gatekeepers of climate change—they play a critical role in how quickly the world warms.

A series of recent studies have shed new light on that role. As the world warms, cloud cover will change across the globe. And these changing clouds will probably speed up global warming.

That means the Earth may be slightly more sensitive to greenhouse gases than some older estimates might have suggested.

“Clouds are a big uncertainty,” said Paulo Ceppi, a climate scientist at Imperial College London and a co-author of one of the new studies. “And so that was the main motivation. We want to understand how clouds will change and how this cloud feedback will affect global warming.”

Cloud research is a tricky business. Clouds sometimes have a warming effect on the local climate and sometimes a cooling effect—it all depends on the type of cloud, the local climate and a variety of other conditions.

Climate change only complicates the matter. Global warming is expected to increase certain types of clouds in certain places and decrease them in others. All in all, it’s a big, complex patchwork of effects all over the globe.

For years, scientists have struggled to determine exactly how clouds would change with future warming—and whether they’ll make climate change worse, or whether they might dampen some of its effects. It’s been a difficult question to answer. Scientists typically use computer models to make predictions about future climate change. But clouds are famously difficult to simulate, especially on a global scale.