Scientists have a new explanation for the last two years of record heat

But even those factors, scientists say, are not sufficient to explain the world’s recent record heat.

Earth’s overall energy imbalance — the amount of heat the planet is taking in minus the amount of heat it is releasing — also continues to rise, worrying scientists. The energy imbalance drives global warming. If it rises, scientists expect global temperatures to follow.

Two new studies offer a potential explanation: fewer clouds. And the decline in cloud cover, researchers say, could signal the start of a feedback loop that leads to more warming.

“We have added a new piece to the puzzle of where we are headed,” Helge Goessling, a climate physicist at the Alfred Wegener Institute in Germany and the author of one of the studies, said in a video interview.

For years, scientists have struggled to incorporate clouds’ influence into the large-scale climate models that help them predict the planet’s future. Clouds can affect the climate system in two ways: First, their white surfaces reflect the sun’s light, cooling the planet. But clouds also act as a kind of blanket, reflecting infrared radiation back to the surface of the planet, just like greenhouse gases.

Which factor wins out depends on the type of cloud and its altitude. High, thin cirrus clouds tend to have more of a warming effect on the planet. Low, fluffy cumulus clouds have more of a cooling effect.

“Clouds are a huge lever on the climate system,” said Andrew Gettelman, an affiliate scientist at the University of Colorado at Boulder. “A small change in clouds could be a large change in how we warm the planet.”

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