The Nonlocal Effects and Radiative Feedbacks of Sea Salt Aerosol Engineering in a GFDL Coupled Model

Geoengineering proposals, such as marine cloud brightening (MCB), have gained attention as a means to mitigate the effects of climate change. MCB involves increasing sea salt aerosols (SSA) emissions, which directly cools the atmosphere by scattering solar radiation and indirectly as cloud condensation nuclei which enhances cloud reflectivity. However, the complex interactions between aerosols and clouds make it challenging to predict the outcome of such interventions, and feedback from these interactions can either amplify or attenuate the desired cooling effects. We employ simulations of regionally enhanced SSA in the tropics using NOAA GFDL climate models to examine the radiative and cloud responses to MCB. Our results indicate that the implementation of MCB in the tropics leads to strong nonlocal changes spanning the whole globe, particularly in the Arctic and the Southern Ocean. The application of MCB leads to increased direct scattering of solar radiation by SSA emissions in the tropics, but SSA emissions decline in the Southern Ocean due to reduced wind. Furthermore, we study the climate feedback to investigate and compare the sensitivity of the GFDL model to changes in radiative forcing attributed to SSA and temperature pattern changes, thereby providing a more comprehensive assessment of the potential impact of MCB on the Earth's climate system. Ultimately, our results illustrate the need to develop new methodologies to analyze climate intervention proposals more rigorously.