Dynamics of Nonlinear Forcing and Cloud Cover Responses to Tropical and Midlatitude Marine Cloud Brightening in CESM2

Climate intervention via marine cloud brightening (MCB) could cool the planet, but the different impacts of MCB in different regions are still under investigation. The stratocumulus clouds in the tropical Pacific are most susceptible to brightening, but concentrating this forcing in a relatively small area could strongly overcool some areas, cause others to warm, and disrupt tropical precipitation. Brightening midlatitude clouds could distribute the forcing over a wider area, leading to a much more even cooling pattern. However, our MCB simulations with the Community Earth System Model (CESM2) demonstrate a slower cooling response for midlatitude MCB than for tropical MCB - midlatitude MCB requires a much longer period, on the order of 30 to 40 years, for the cooling effect to reach its maximum potential, which our investigation links to slower changes in cloud cover and sea surface temperature. This has implications for MCB strategy design, as well as for the construction of feedback control algorithms which regulate climate interventions in model simulations to maintain constant global mean surface temperature.