Observational evidence that cloud feedback amplifies global warming

Global warming drives changes in Earth's cloud cover, which, in turn, may amplify or dampen climate change. This cloud feedback is the single most important cause of uncertainty in Equilibrium Climate Sensitivity (ECS)-the equilibrium global warming following a doubling of atmospheric carbon dioxide. Using data from Earth observations and climate model simulations, we here develop a statistical learning analysis of how clouds respond to changes in the environment. We show that global cloud feedback is dominated by the sensitivity of clouds to surface temperature and tropospheric stability. Considering changes in just these two factors, we are able to constrain global cloud feedback to 0.43 +/- 0.35 W center dot m-2 center dot K-1 (90% confidence), implying a robustly amplifying effect of clouds on global warming and only a 0.5% chance of ECS below 2 K. We thus anticipate that our approach will enable tighter constraints on climate change projections, including its manifold socioeconomic and ecological impacts.

Automated summary

Global warming influences Earth's cloud cover, which plays a crucial role in the uncertainty of Equilibrium Climate Sensitivity (ECS). Through analyzing how clouds respond to environmental changes, global cloud feedback is constrained to 0.43 +/- 0.35 W·m-2·K-1, indicating a robust amplifying effect of clouds on global warming. This approach is expected to provide tighter constraints on climate change projections and its various socioeconomic and ecological impacts.