Designing a radiative antidote to CO2

Seeley, Jacob T., Nicholas J. Lutsko, and David W. Keith. “Designing a radiative antidote to CO2.” Geophysical Research Letters (Submitted). Publisher's Version Abstract

Solar Radiation Modification (SRM) reduces the CO₂‐induced change to the mean global hydrological cycle disproportionately more than it reduces the CO₂‐induced increase in mean surface temperature. Thus if SRM were used to offset all CO₂‐induced mean warming, global‐mean precipitation would be less than in an unperturbed climate. Here we show that the mismatch between the mean hydrological effects of CO₂ and SRM may partly be alleviated by spectrally tuning the SRM intervention (reducing insolation at some wavelengths more than others). By concentrating solar dimming at near‐infrared wavelengths, where H₂O has strong absorption bands, the direct effect of CO₂ on the tropospheric energy budget can be offset, which minimizes perturbations to the mean hydrological cycle. Idealized cloud‐resolving simulations of radiative‐convective equilibrium confirm that spectrally‐tuned SRM can simultaneously maintain mean surface temperature and precipitation at their unperturbed values even as large quantities of CO₂ are added to the atmosphere.

An earth system governance perspective on solar geoengineering

Reynolds, Jesse, and Joshua Horton. “An earth system governance perspective on solar geoengineering.” Earth System Governance 3 (2020). Publisher's Version Abstract

An earth system governance perspective on solar geoengineering

Solar geoengineering appears capable of reducing climate change and the associated risks. In part because it would be global in effect, the governance of solar geoengineering is a central concern. The Earth System Governance (ESG) Project includes many researchers who, to varying degrees, utilize a common vocabulary and research framework. Despite the clear mutual relevance of solar geoengineering and ESG, few ESG researchers have considered the topic in substantial depth. To stimulate its sustained uptake as a subject within the ESG research program, we identify significant contributions thus far by ESG scholars on the subject of solar geoengineering governance and survey the wider solar geoengineering governance literature from the perspective of the new ESG research framework. Based on this analysis, we also suggest specific potential lines of inquiry that we believe are ripe for research by ESG scholars: nonstate actors’ roles, polycentricity, public engagement and participation, and the Anthropocene.

Experimental reaction rates constrain estimates of ozone response to calcium carbonate geoengineering

Dai, Zhen, Debra K. Weisenstein, Frank N. Keutsch, and David W. Keith. “Experimental reaction rates constrain estimates of ozone response to calcium carbonate geoengineering.” Communications Earth & Environment 1, no. 63 (2020). Publisher's Version Abstract

Experimental reaction rates O3 CaCO3

Stratospheric solar geoengineering (SG) would impact ozone by heterogeneous chemistry. Evaluating these risks and methods to reduce them will require both laboratory and modeling work. Prior model-only work showed that CaCO₃ particles would reduce, or even reverse ozone depletion. We reduce uncertainties in ozone response to CaCO₃ via experimental determination of uptake coefficients and model evaluation. Specifically, we measure uptake coefficients of HCl and HNO₃ on CaCO₃ as well as HNO₃ and ClONO₂ on CaCl₂ at stratospheric temperatures using a flow tube setup and a flask experiment that determines cumulative long-term uptake of HCl on CaCO₃. We find that particle ageing causes significant decreases in uptake coefficients on CaCO₃. We model ozone response incorporating the experimental uptake coefficients in the AER-2D model. With our new empirical reaction model, the global mean ozone column is reduced by up to 3%, whereas the previous work predicted up to 27% increase for the same SG scenario. This result is robust under our experimental uncertainty and many other assumptions. We outline systematic uncertainties that remain and provide three examples of experiments that might further reduce uncertainties of CaCO₃ SG. Finally, we highlight the importance of the link between experiments and models in studies of SG.

An earth system governance perspective on solar geoengineering

Reynolds, Jesse, and Joshua Horton. “An earth system governance perspective on solar geoengineering.” Earth System Governance 3 (2020). Publisher's Version Abstract

Reynolds_Horton_2020.pdf

An earth system governance perspective on solar geoengineering

Reynolds, Jesse L., and Joshua B. Horton. “An earth system governance perspective on solar geoengineering.” Earth System Governance 3 (2020).Abstract

an_earth_system_governance_perspective_on_solar_geoengineering.pdf

Steering and Influence in Transnational Climate Governance: Nonstate Engagement in Solar Geoengineering Research

Horton, Joshua B., and Barbara Koromenos. “Steering and Influence in Transnational Climate Governance: Nonstate Engagement in Solar Geoengineering Research.” Global Environmental Politics 20, no. 3 (2020): 93-111. Publisher's Version Abstract

transnational_climate_gov_horton_and_koromenos.pdf

Theorists of transnational climate governance (TCG) seek to account for the increasing involvement of nonstate and substate actors in global climate policy. While transnational actors have been present in the emerging field of solar geoengineering—a novel technology intended to reflect a fraction of sunlight back to space to reduce climate impacts— many of their most significant activities, including knowledge dissemination, scientific capacity building, and conventional lobbying, are not captured by the TCG framework. Insofar as TCG is identified with transnational governance and transnational governance is important to reducing climate risks, an incomplete TCG framework is problematic for effective policy making. We attribute this shortcoming on the part of TCG to its exclusive focus on steering and corollary exclusion of influence as a critical component of governance. Exercising influence, for example, through inside and outside lobbying, is an important part of transnational governance—it complements direct governing with indirect efforts to inform, persuade, pressure, or otherwise influence both governor and governed. Based on an empirical analysis of solar geoengineering research governance and a theoretical consideration of alternative literatures, including research on interest groups and nonstate advocacy, we call for a broader theory of transnational governance that integrates steering and influence in a way that accounts for the full array of nonstate and substate engagements beyond the state.

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What is Geoengineering?

Geoengineering refers to a set of emerging technologies that could manipulate the environment and partially offset some of the impacts of climate change.

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Frank Keutsch — Heterogeneous Chemistry and Ageing of Designer Aerosol Particles to Assess the Risk of Solar Geoengineering

Robert Stavins — Governance of Solar Geoengineering: Advancing Understanding and Action

Designing a radiative antidote to CO2

An earth system governance perspective on solar geoengineering

Experimental reaction rates constrain estimates of ozone response to calcium carbonate geoengineering

An earth system governance perspective on solar geoengineering

An earth system governance perspective on solar geoengineering

Steering and Influence in Transnational Climate Governance: Nonstate Engagement in Solar Geoengineering Research

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