Effect of regional marine cloud brightening on land climate

Abstract Marine cloud brightening (MCB) is one of the proposed climate intervention methods aiming to reduce anthropogenic warming. In this study, we use the CESM Earth system model to examine the land climate consequences of regional MCB. MCB is implemented from year 2031 by seeding sea salt aerosols into low-level clouds over 5% of the global area that is most susceptible to cloud brightening. Under the background scenario of SSP2-4.5, this MCB deployment stabilizes global mean temperature at approximately 1.5 °C above pre-industrial levels. MCB cools most land areas with heterogeneous regional responses in precipitation, soil moisture, and direct and diffuse solar radiation. By the middle of this century, relative to SSP2-4.5, MCB reduces drought stress over 55% of the land area, measured in terms of the standardized precipitation evapotranspiration index. By year 2100, compared to SSP2-4.5, MCB increases sunlit and shaded terrestrial gross primary production by 4% and 3%, respectively, as a result of MCB-induced land climate change. A sudden termination of MCB has far-reaching effects on the land climate. The decade following an abrupt termination of MCB experiences a mean land warming rate approximately four times greater than that under the SSP scenario without MCB, with many regions experiencing warming rates exceeding 1 °C per decade. Consequently, an MCB termination would subject more than 90% of global land area to a temperature velocity surpassing 2 km yr −1 , posing significant risks to many species’ ability to adapt to their habitats. Our findings demonstrate that regional implementation of MCB would have widespread climate effects over land—a critical consideration for designing and evaluating MCB as a proposed method to counteract human-caused climate change.