Nailing down climate uncertainty hints at greater future warming

Denis Fox

Although the basic outlines of climate change are well understood—the first science on the greenhouse effect was done back in the 1800s—there are a number of details where our understanding remains incomplete. One of the big ones is the effect of clouds. Depending on their altitude, clouds can either reflect sunlight (cooling the planet) or act as an insulator, warming it. Figuring out the exact balance between these effects has been a challenge.

A new paper, released by Nature, attempts to look at the details of cloud formation and find a specific aspect that's not well handled in climate models. That aspect alone accounts for roughly half the differences in their estimates of the climate's sensitivity to carbon dioxide. Based on real-world data, the authors conclude that the models with higher climate sensitivities—meaning those that predict greater warming—are handling clouds better.

Climate sensitivity is a convenient way to estimate the impact of CO₂ on future temperature increases. It's simply the expected increase in temperature for a doubling of carbon dioxide in the atmosphere. So, if the planet has a high climate sensitivity, it will warm more in response to added greenhouse gasses.