Simulated climate and terrestrial biosphere response to three radiation geoengineering schemes
Abstract
Geoengineering refers to the large-scale intervention of the climate system to counteract some undesired aspects of anthropogenic climate change. We compare the response of global climate and the terrestrial biosphere to three proposed geoengineering schemes that aim to offset global warming by altering the Earth's radiation balance: 1) increasing the burden of sulfate aerosols in the stratosphere (stratospheric aerosol increase); 2) increasing the reflectivity of low-level clouds over ocean (marine cloud brightening); 3) decreasing the amount of high-level cirrus clouds (cirrus cloud thinning). The first two schemes aim to reduce global warming by deflecting more solar radiation back to space, and the last one by allowing more terrestrial radiation to escape to space.
Using the NCAR CESM model, we perform idealized simulations of these radiation geoengineering schemes to offset global warming in response to an abrupt doubling of atmospheric CO2. Our simulations show that different amount of radiative forcings are needed for these three schemes to compensate CO2-induced global mean warming, which is associated with different climate feedback parameters for these different forcing agents. Apparent hydrological sensitivity, i.e., change in equilibrium global mean precipitation per degree of equilibrium temperature change, differs substantially between these geoengineering schemes, which is found to be mainly a result of different fast adjustment processes. By analyzing land carbon cycle response such as gross and net primary production, plant and soil respiration, we show that these three geoengineering schemes also have different effects on the terrestrial biosphere as a result of different changes in direct/diffuse sunlight and climate fields.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC31H1351C
- Keywords:
-
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3359 Radiative processes;
- ATMOSPHERIC PROCESSESDE: 1622 Earth system modeling;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGE