Premium
Climate More Responsive to Marine Cloud Brightening Than Ocean Albedo Modification: A Model Study
Author(s) -
Zhao Mengying,
Cao Long,
Duan Lei,
Bala Govindasamy,
Caldeira Ken
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033256
Subject(s) - cloud forcing , shortwave , environmental science , albedo (alchemy) , radiative forcing , forcing (mathematics) , atmospheric sciences , climatology , climate model , shortwave radiation , sunlight , climate change , atmosphere (unit) , earth's energy budget , cloud albedo , sea surface temperature , cloud feedback , cloud cover , climate sensitivity , meteorology , radiative transfer , cloud computing , geology , geography , radiation , physics , oceanography , art , computer science , operating system , quantum mechanics , art history , astronomy , performance art
Abstract Solar radiation modification has been suggested as a backup option to reduce anthropogenic warming. Marine cloud brightening (MCB) and ocean albedo modification (OAM) are two proposed approaches to intentionally reflect sunlight back to space over oceanic regions. Using the NCAR Community Earth System Model, we compare climate response to MCB and OAM under the framework of fast adjustment and slow feedback. We implement MCB and OAM uniformly over the global ocean to offset CO 2 ‐induced warming. We find that to offset 3.3 K global mean warming from a doubling of CO 2 , diagnosed effective radiative forcing is −4.8 and −3.6 W m −2 for OAM and MCB, respectively. Correspondingly, radiative forcing efficacy of OAM is about 70% of MCB. Fast climate adjustment differs in response to MCB and OAM forcing. MCB cools the lower atmosphere by reflecting sunlight from cloud, causing a reduction in sunlight absorption in the atmosphere. In contrast, OAM, by reflecting more sunlight from surface, increases shortwave heating of the lower atmosphere, leading to a decrease in low marine clouds and hence a positive cloudy‐sky shortwave forcing that partly compensates the negative clear‐sky shortwave forcing. The slow climate response and pattern of equilibrium climate change are similar between MCB and OAM. As for hydrological cycle, relative to the climate under a doubling of CO 2 , both MCB and OAM produce an increase in precipitation and runoff over tropical land.