The comparison showed that the use of stratospheric sulfate aerosols can be the most effective. It is emphasized that all geo-engineering
The authors found that while all three solar radiation management techniques led to similar global mean temperature increases compared to the
This study investigates traditional and modern geoengineering techniques through a systematic literature review.
Pertinent to stratospheric sulfate aerosol geoengineering, this perspective takes into account that the climate effects of solar geoengineering will depend on the magnitude (e.g., Niemeier & Timmreck, 2015), latitude (Tilmes et al., 2017; Dai et al., 2018), altitude (Tilmes et al., 2018), and time of year of injection (Kravitz & Robock, 2011). The results may also depend on how the sulfate aerosols are formed, for example, SO2 injection, as is done when large volcanic eruptions occur (Robock, 2000) versus direct condensation of H2SO4 droplets to overcome rapid particle growth and thus reduced geoengineering efficacy and increased stratospheric RESEARCH ARTICLE 10.1029/2019JD030329 Key Points: • Tropospheric and stratospheric side effects of equatorial solar geoengineering are reduced if nonequatorial injections are applied • Some residual temperature effects from equatorial injection can be offset with multiple injection locations • There are still residuals in surface climate and the stratosphere that cannot be offset with four injection locations Supporting Information: • Supporting Information S1 Correspondence to: B.
Geoengineering methods are intended to reduce climate change, which is already having demonstrable effects on ecosystem structure and functioning in some
Our paper, *Impact of solar geoengineering on temperature-attributable mortality*, is a first effort to provide a quantitative risk-risk comparison for any solar geoengineering method. David was part of prior collaboration with Gabe Vecchi which produced an important estimate of solar geoengineering’s potential to reduce regional climate hazards. * Many groups have called for risk-risk analysis of solar geoengineering including the National Academy, NASEM 2021, The Carnegie Climate Governance Initiative, C2G and the call-for-balanceletter with Peter Singer, James Hansen, and Bjorn Stevens, as signatories, see paper. * The air pollution mortality estimate by Eastham combines the direct impacts of injected aerosol that makes it to the surface with climate-mediate changes in the amount of surface ozone and particulate air pollution produced from given industrial emissions. While not comprehensive, these are important risk pathways: temperature-attributable mortality may account for more than half of the monetized harms of climate change, and air pollution and ozone loss are among the most salient impacts of stratospheric sulfate geoengineering.
Solar geoengineering (SG) refers to a set of methods aimed at cooling the Earth in order to counteract the warming effects of increases in greenhouse gases (
2 These studies include the Royal Society report mentioned in (1) and two reports from the US Na-tional Research Council: Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration (2015), and Climate Intervention: Reflecting Sunlight to Cool Earth (2015), The National Acadamies Press, Washington, D.C. 182 8 Geoengineering Counteracting approached a tipping point—a threshold beyond which the Earth would enter a vastly different climate state—then emergency measures would likely garner more serious attention. 1.1 Types of Climate Intervention Geoengineering methods fall under two classes: 1) Carbon dioxide removal (CDR), which removes CO2 from the atmosphere, and 2) solar radiation management (SRM), which reflects sunlight back into space. Box 8.1: Exercise to examine the mass scales involved in one type of enhanced chemical weathering6 185 Geoengineering 8 CO2 Removal 2.2 Ocean Fertilization Another of Nature’s ways of removing CO2 from the atmosphere is through photosynthesis by phytoplankton at the surface of the ocean (Figure 8.2).