SCIENCE PAPER
Inequal responses of drylands to radiative forcing geoengineering methods
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL084210
Abstract
Climate geoengineering has the potential to reduce global warming. However, the nonlinear responses of Earth's large‐scale circulation to climate geoengineering can exacerbate regional climate change, with potential inequality risks. We show noticeable inequality in the responses of drylands when three radiative forcing geoengineering (RFG) methodologies – cirrus cloud thinning (CCT), marine sky brightening (MSB), and stratospheric aerosol injection (SAI) – individually reduce the radiative forcing of the Representative Concentration Pathway 8.5 (RCP8.5) scenario using a set of the Norwegian Earth system model (NorESM1‐ME) experiments. In North America, CCT and SAI alleviate drylands expansion, whereas, drylands expand further under MSB. CCT induces significantly wetter conditions over the western Sahel. Wetting over Australia is enhanced and prevented by MSB and SAI, respectively. Our results suggest spatially inequal distributions of benefits and harms of individual RFGs on the projected distribution of drylands, which should be considered before any real‐world application of such RFGs.
Plain Language Summary
Climate geoengineering has the potential to reduce global warming levels significantly, according to modelling experiments. However, regional impacts of individual climate geoengineering methods are inequal, raising concerns about fairness of negative side effects of such methods. Here, impacts of climate geoengineering on the global distribution of drylands are projected using an Earth system model, NorESM1‐ME. Three geoengineering methods are adopted: cirrus cloud thinning (CCT), marine sky brightening (MSB), and stratospheric aerosol injection (SAI). All methods commonly reduce about 2 °C of global warming in the late 21st century relative to the high CO2 emission scenario, Representative Concentration Pathway 8.5. Drylands respond differently to individual methods, especially in North America, the western Sahel, and Australia. In North America, CCT and SAI alleviate drylands expansion, whereas, the expansion of drylands is intensified under MSB. CCT notably reduces drylands expansion over the western Sahel. The reduction of drylands in Australia is enhanced by MSB due to atmospheric circulation changes, but prevented by SAI. Our results suggest that climate geoengineering can exacerbate drylands expansion in some regions despite potential alleviation in other regions. Such inequalities should be considered if RFGs for real‐world applications to mitigate global warming were ever to be considered.
Summary … Geo-engineering is bad m'kay!