摘要：Solar radiation management (SRM) geoengineering has been proposed as one means of
helping avoid the occurrence of dangerous climate change and undesirable state transitions
('tipping points') in the Earth system. The irreversible melting of the Greenland
Ice Sheet is a case in point—a state transition that could occur as a result of
CO2-driven elevated global temperatures, and one leading to potentially catastrophic sea-level
rise. SRM schemes such as the creation of a 'sunshade' or injection of sulfate aerosols into
the stratosphere could reduce incoming solar radiation, and in theory balance, in a
global mean, the greenhouse warming resulting from elevated concentrations of
CO2 in the atmosphere. Previous work has highlighted that a geoengineered world would have:
warming towards the poles, cooling in the tropics, and a reduction in the global
hydrological cycle, which may have important implications for the Greenland Ice
Sheet. Using a fully coupled global climate model in conjunction with an ice
sheet model, we assess the consequences for the mass balance of the Greenland
Ice Sheet of the reorganization of climate patterns by the combination of high
CO2 and geoengineering. We find that Greenland surface temperature and precipitation anomalies,
compared to the pre-industrial situation, decrease almost linearly with increasing levels of SRM
geoengineering, but that these combine to create a highly non-linear response of the ice sheet.
The substantial melting of the Greenland Ice Sheet predicted for four times pre-industrial
CO2 levels is prevented in our model with only a partial application of SRM, and hence without
having to fully restore the global average temperature back to pre-industrial levels. This
suggests that the degree of SRM geoengineering required to mitigate the worst impacts of
greenhouse warming, such as sea-level rise, need not be as extensive as generally assumed.
