小规模平流层注入气溶胶实验有助于地球工程研究

Small scale stratospheric aerosol injection experiments benefits solar geoengineering research

2018年12月12日,国际著名学术期刊Nature刊登了'2018年度十大科学长篇专题报道:这一年最难忘的科学故事'(https://www.nature.com/articles/d41586-018-07748-5).Nature评选出2018年度最受欢迎的十大科学长篇专题报道:从首个遮挡太阳的实验,到传统中医的兴起,再到拯救消失的野生动物.

Solar geoengineering,also termed as solar radiation management or albedo modification,has been proposed as a potential means to mitigate anthropogenic global warming.Proposed solar geoengineering schemes include deployment of mirrors in space,increase of low-level cloud albedo,and enhancement of land or ocean surface albedo.One of the most widely discussed solar geoengineering methods is to inject sulfate aerosol or its gaseous precursors into the stratosphere to scatter more sunlight to space,and thus cool the Earth.To date,all studies on stratospheric aerosol injection have been climate modeling,engineering assessments,and social science research(including study of economic impacts,ethical/philosophical implications,governance issues,public perceptions).As an attempt to study fundamental processes related to stratospheric aerosol geoengineering,a team of scientists from Harvard University plans to release about 100 to 1000 grams of calcium carbonate particles into the stratosphere at an approximate height of 20 km above the Southwest United States as early as 2019.This experiment,named Stratospheric Controlled Perturbation Experiment(SCoPEx),would be the first field study intended to be relevant to solar geoengineering.Nature selected ten favorite feature stories in 2018:One of them is'First Sun-dimming experiment will test a way to cool Earth',which refers to SCoPEx.Calcium carbonate aerosols,instead of sulfate particles,will be used in this experiment because past research showed negative effect of sulfate aerosols on stratospheric ozone.In my view,the SCoPEx experiment is useful in several aspects.First,the direct observation of the fate of injected particles into the stratosphere would help to deepen our understanding of the microphysics(such as aerosol dispersion and aerosol size distribution and evolution)of injected aerosols and the effect on ambient stratospheric dynamics and chemistry.This observation is important for understanding fundamental sciences relevant to climate response to stratospheric aerosol injection.Second,observational results from SCoPEx can be used to bridge the gap between plume-scale and GCM(General Circulation Model)-scale aerosol processes.These results can be used to test GCM-simulated physical and chemical processes of injected stratospheric aerosols,and help improve model’s ability in predicting climate response to stratospheric aerosol injection.Third,the insight gained from SCoPEx will not only be useful for solar geoengineering research,but in general provide new insights into our understanding of aerosol microphysics and its climate implication as well.Many useful insights into the climate response to solar geoengineering have been gained from climate modelling studies.However,model representation of climate physics and chemistry,in particular small-scale processes,rely on real world observations.Field experiments like SCoPEx will provide new opportunities for understanding climate response to stratospheric aerosol injection.