A cloudless future? The mystery at the heart of climate forecasts: New computational approaches help researchers include cloud physics in global models, addressing long-standing questions

We hear a lot about how climate change will change the land, sea, and ice. But how will it affect clouds?

“Low clouds could dry up and shrink like the ice sheets,” says Michael Pritchard, professor of Earth System science at UC Irvine. “Or they could thicken and become more reflective.”

These two scenarios would result in very different future climates. And that, Pritchard says, is part of the problem.

“If you ask two different climate models what the future will be like when we add a lot more CO2, you get two very different answers. And the key reason for this is the way clouds are included in climate models.”

No one denies that clouds and aerosols — bits of soot and dust that nucleate cloud droplets — are an important part of the climate equation. The problem is these phenomena occur on a length- and time-scale that today’s models can’t come close to reproducing. They are therefore included in models through a variety of approximations.

Analyses of global climate models consistently show that clouds constitute the biggest source of uncertainty and instability.

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