b'14 Carnegie Science|Fall 2019StratosphereTroposphereOcean LandGeoengineeringTheoretically, solar geoengineering would curb the effects of climate change by seeding the atmosphere with aerosol particles that create a layer, which would reflect some of the Suns Versus a Volcano radiation back into space to cool the planet (left) much like major volcanic eruptions that spew ash particles into the atmosphere (right). Images courtesy Chemical and Engineering News adapted,and Paul Byrne Carnegie Institution for Sciencetheir results demonstrate that volcanic eruptionsare imperfect analogs for geoengineeringMajor volcanic eruptions spew ashHowever, the volcanic eruption created a particles into the atmosphere, whichgreater temperature difference between the reflect some of the Suns radiation backland and sea than did the geoengineering into space and cool the planet. Could thissimulation. This resulted in different effect be intentionally re-created to fightprecipitation patterns between the two climate change? A new paper inscenarios. In both situations, precipitation Geophysical Research Letters decreases over landmeaning less water forinvestigates. Solar geoengineering is a theoreticalmany people living therebut the decrease approach to curbing the effects of climatewas more significant in the aftermath of a change by seeding the atmosphere with avolcanic eruption than it was in the regularly replenished layer of intentionallygeoengineering case. released aerosol particles. ProponentsWhen a volcano goes off, the land cools sometimes describe it as being like asubstantially quicker than the ocean. This human-made volcano.Senior staff scientist Ken Caldeira and team useddisrupts rainfall patterns in ways that you Nobody likes the idea of intentionallysophisticated models to investigate the effects of a single,wouldnt expect to happen with a sustained tinkering with our climate system atvolcano-like eruption releasing particulates that remain indeployment of a geoengineering system, the atmosphere for a few years, versus a long-term global scale, said Carnegies Ken Caldeira.geoengineering particle release to cool the planet.said lead author Duan. Even if we hope these approaches wontImage courtesy Carnegie Institution for Science Overall, the authors say that their results ever have to be used, it is really importantdemonstrate that volcanic eruptions are that we understand them becausesingle volcano-like event, which releasesimperfect analogs for geoengineering and someday they might be needed to helpparticulates that linger in the atmospherethat scientists should be cautious about alleviate suffering.for just a few years, and of a long-termextrapolating too much from them. He, along with Carnegies Lei Duan (ageoengineering deployment, whichWhile its important to evaluate former student from Zhejiang University),requires maintaining an aerosol layer ingeoengineering proposals from an informed Long Cao of Zhejiang University, andthe atmosphere.position, the best way to reduce climate risk is Govindasamy Bala of the Indian InstituteThey found that regardless of how itto reduce emissions, Caldeira concluded.of Science, compared the effects on thegot there, when the particulate material is climate of a volcanic eruption and of solarinjected into the atmosphere there is aSUPPORT:geoengineering. They used sophisticatedrapid decrease in surface temperature, withThe National Key Basic Research Program of China, the National Natural Science Foundation of China, and the Carnegie models to investigate the impact of athe land cooling faster than the ocean.Department of Global Ecology supported this work.'