Climatic impacts of cloud whitening geoengineering simulated by GFDL CM2G

Projected increase in greenhouse gases have prompted serious discussion on geoengineering the climate system to counteract global climate change. Cloud albedo enhancement is an economically and technologically feasible geoengineering approach, but previous research suggests undesirable consequences of globally uniform cloud whitening. The present study uses GFDL's CM2G global coupled model to simulate cloud albedo enhancement via increases in cloud condensation nuclei (CCN) targeted at the marine stratus deck of the Pacific Ocean, where persistent low clouds offer a regional approach to cloud whitening with hitherto unexplored impacts. We investigate the impact of this regional geoengineering on global circulation and climate. Preliminary results indicate surface temperatures returned to near Pre-Industrial over much of the globe; significant cooling over the Equatorial Pacific; continued Arctic warming; large precipitation changes over the western Pacific; and an eastward compression and intensification of the Walker Circulation. Increases in low- and mid-level cloud amounts, resulting from increases in CCN, are well correlated with the simulated changes in the top-of-atmosphere energy balance. Future investigation will determine long-term impacts of cloud whitening and the dynamical processes driving these changes.