Basic physic predicts stronger high cloud radiative heating with warming

The interaction of cloud droplets and ice crystals with radiation, known as cloud radiative heating, alters temperature gradients in the atmosphere, affecting both cloud evolution as well as circulation and precipitation. Despite its climatic relevance, the response of cloud radiative heating to global warming remains largely unknown.

We study changes to cloud radiative heating profiles in a warmer climate, identify physical mechanisms responsible for these changes, and develop a theory based on well-understood physics to predict them. Our approach involves a stepwise procedure that starts with a simple hypothesis of an upward shift in cloud radiative heating at constant temperature, and gradually incorporates additional physical effects.

We find that cloud radiative heating intensifies as high clouds move upward, despite minimal changes in cloud properties and temperatures. We attribute this intensification to a decrease in air density, which often overcompensates for the decrease in high cloud fraction with warming in idealized multi-model simulations of radiative-convective equilibrium. Furthermore, the density-mediated changes in cloud radiative heating are also observed in satellite-derived retrievals of cloud radiative heating in the tropics.

The density-mediated increment in cloud radiative heating may increase the role of high clouds in controlling atmospheric flows in a warmer climate. Moreover, our results suggest that the uncertainty in model‐predicted changes in atmospheric circulations and hence regional climate could be reduced by narrowing the spread in model‐simulated cloud radiative heating in the present‐day climate.