The mystery of how clouds affect the climate is finally solved

Central Park Reservoir is one of the few places in New York City to get a good view of the clouds. Looking north from the reservoir’s edge, there’s a large gap between the buildings that lets you see the clouds rolling in from the harbor. Meteorologist Kara Lamb suggested we try our hand at cloud watching here.

At the time, the sky is full of fluffy cumulus clouds beneath a ceiling of altostratus. One of them looks a lot like a whale. But Lam, who studies clouds at Columbia University in New York, doesn’t think they’re so strange. “Clouds are fascinating because they’re cool to look at,” he says. “But I think about clouds in terms of climate” – understanding how the sunlight they reflect and the heat they trap beneath them affect the Earth’s temperature.

What the casual cloud watcher may not know is that clouds are the biggest unknown in predicting future climate change to determine how this balance will change in a warming world. If carbon dioxide doubles from pre-industrial levels, will the world get a manageable 1.5°C warming or a hellish 4.5°C warming? The biggest source of this uncertainty is our lack of understanding of clouds.

But researchers are making progress. Lamb is looking at ice crystals in the clouds, which play a surprisingly large role in influencing climate. Some researchers are using cloud chambers, and are planning to set up cloud chambers…