Finding the Right "Dose" for Solar Geoengineering

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Solar geoengineering could halve global temperature increases without making climate change worse, research shows.

One of the key misconceptions about solar geoengineering — putting aerosols into the atmosphere to reflect sunlight and reduce global warming — is that it could be used as a fix-all to reverse global warming trends and bring temperature back to pre-industrial levels.

It can’t. Applying huge doses of solar geoengineering to offset all warming from rising atmospheric C02 levels could worsen the climate problem — particularly rainfall patterns — in certain regions. But could smaller doses work in tandem with emission cuts to lower the risks of a changing climate?

New research from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with MIT and Princeton University, finds that if solar geoengineering is used to cut global temperature increases in half, there could be worldwide benefits without exacerbating change in any large geographic area.

“Some of the problems identified in earlier studies where solar geo-engineering offset all warming are examples of the old adage that the dose makes the poison,” said David Keith, the Gordon McKay Professor of Applied Physics at SEAS and senior author of the study. “This study takes a big step towards using climate variables most relevant for human impacts and finds that no IPCC-defined region is made worse off in any of the major climate impact indicators. Big uncertainties remain, but climate models suggest that geoengineering could enable surprisingly uniform benefits.”

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