Climate warming could weaken aerosol-cloud interactions in subtropical marine stratocumulus

Abstract Radiative effects of aerosol-cloud interactions constitute the most uncertain climate forcing of the Earth system. To understand how these interactions may change with climate, we conduct 3-day-long large-eddy simulations of a stratocumulus-to-cumulus transition along an airmass-following trajectory over the Northeast Pacific Ocean. By perturbing boundary-layer aerosol concentrations, aerosol-cloud interactions are simulated in present-day and warmed climate with increased CO 2 . Aerosol-induced cloud changes, including the Twomey effect and adjustments of cloud fraction and liquid water path, are inhibited in a doubled-CO 2 climate. Decomposing the aerosol-induced cloud radiative effect change (ΔCRE) reveals that aerosol-induced cloud fraction changes dominate ΔCRE. Doubling CO 2 attenuates the aerosol-induced ΔCRE (i.e., cooling) by >30% in our simulations. Our results also show that low cloud feedbacks are sensitive to the background aerosol concentration, highlighting the interplay between climate forcings and feedbacks. These results may aid in predicting the cooling potential of marine cloud brightening in a changing climate.