Clouds, radiation, and atmospheric circulation in the present-day climate and under climate change

We review the impact of cloud-radiation interactions for the atmospheric circulation in the present-day climate, its internal variability and its response to climate change. After summarizing cloud-controlling factors and cloud-radiative effects, we clarify the scope and limits of the Clouds On-Off Klimate Model Intercomparison Experiment (COOKIE) and cloud-locking modeling methods.

COOKIE showed that the presence of cloud-radiative effects shapes the circulation in the present-day climate in many important ways, including the width of the tropical rain belts and the position of the extratropical storm tracks. Cloud locking, in contrast, identified how clouds affect internal variability and the circulation response to global warming. This includes strong, but model-dependent, shortwave and longwave cloud impacts on the El-Nino Southern Oscillation, and the finding that most of the poleward circulation expansion in response to global warming can be attributed to radiative changes in clouds.