First Simulations of Feedback Algorithm-Regulated Marine Cloud Brightening

Feedback control algorithms are important tools in climate intervention simulation design because they facilitate “top-down” design, in which climate goals (often temperatures) are prescribed and a strategy chosen to meet the target. This approach is commonly used in simulations of stratospheric aerosol injection (SAI) interventions, but have never been used with marine cloud brightening (MCB) interventions. Using data from previously published MCB simulations, we use the Community Earth System Model (CESM2) to simulate MCB deployments over regions which expand with time to limit global warming to 1.5°C in the SSP2-4.5 scenario, and we design a feedback control algorithm to determine the scope of intervention each year. Our methodology is able to control global mean temperature in this way, but controlling global mean temperature does not by itself mitigate regional impacts common to tropical MCB; additionally, the algorithm takes longer than intended to converge, indicating room for future improvement.