Adjustments in the forcing-feedback framework for understanding climate change. Rapid adjustments of cloud and hydrological cycle to increasing CO 2: a review. Kamae, Y., Watanabe, M., Ogura, T., Yoshimori, M. A surface energy perspective on climate change. The equilibrium sensitivity of the Earth’s temperature to radiation changes. Constraints on future changes in climate and the hydrologic cycle. Our estimates, combined with an existing constraint to clear-sky shortwave absorption, suggest that hydrological sensitivity could be lower by 30% than raw estimates from global climate models. These compensating cloud effects are also robustly found in a multi-model ensemble, and further constrained using satellite observations. In contrast, hydrological sensitivity is suppressed through weakening of atmospheric longwave cooling, necessitating weakened condensational heating by precipitation. When the amount of low clouds decreases, ECS is enhanced through reductions in the reflection of shortwave radiation. Here, using a global climate model with a perturbed mean hydrological cycle, we show that ECS and hydrological sensitivity per unit warming are anti-correlated owing to the low-cloud response to surface warming. Despite their connection via the Earth’s energy budget, the physical linkage between these two metrics remains controversial. Equilibrium climate sensitivity (ECS) and hydrological sensitivity describe the global mean surface temperature and precipitation responses to a doubling of atmospheric CO 2.
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