Unintended consequences of atmospheric injection of sulphate aerosols.

Abstract

Most climate scientists believe that climate geoengineering is best considered as a potential complement to the mitigation of CO 2 emissions, rather than as an alternative to it. Strong mitigation could achieve the equivalent of up to −4Wm −2 radiative forcing on the century timescale, relative to a worst case scenario for rising CO 2 . However, to tackle the remaining 3Wm −2 , which are likely even in a best case scenario of strongly mitigated CO 2 releases, a number of geoengineering options show promise. Injecting stratospheric aerosols is one of the least expensive and, potentially, most effective approaches and for that reason an examination of the possible unintended consequences of the implementation of atmospheric injections of sulphate aerosols was made. Chief among these are: reductions in rainfall, slowing of atmospheric ozone rebound, and differential changes in weather patterns. At the same time, there will be an increase in plant productivity. Lastly, because atmospheric sulphate injection would not mitigate ocean acidification, another side effect of fossil fuel burning, it would provide only a partial solution.Future research should aim at ameliorating the possible negative unintended consequences of atmospheric injections of sulphate injection. This might include modeling the optimum rate and particle type and size of aerosol injection, as well as the latitudinal, longitudinal and altitude of injection sites, to balance radiative forcing to decrease negative regional impacts. Similarly, future research might include modeling the optimum rate of decrease and location of injection sites to be closed to reduce or slow rapid warming upon aerosol injection cessation. A fruitful area for future research might be system modeling to enhance the possible positive increases in agricultural productivity. All such modeling must be supported by data collection and laboratory and field testing to enable iterative modeling to increase the accuracy and precision of the models, while reducing epistemic uncertainties. 6 CONTENTS

Considering stratospheric aerosol injections beyond an environmental frame: The intelligible ‘emergency’ techno-fix and preemptive security

“…26 Depending on the aerosol used for SAI, it may, in fact, exacerbate the problem of ocean acidification and contribute to increased pollution, which will in turn increase pollution related deaths and the hole in the ozone layer. 27 There are also concerns that without reduction in carbon in the atmosphere the nutritional content and quality of food will be lowered and agricultural yields will be affected, 28 rainfall patterns will be disrupted, 29 and new research indicates it may substantially increase the incidence of malaria in regions that do not currently experience high case rates. 30 In addition to these biophysical risks, if extensive SAI is undertaken without a corresponding reduction of carbon in the atmosphere through mitigation strategies, then it can never be safely stopped because of the possibility of termination shock -shooting sulfates or other compounds into the atmosphere would have to continue without interruption unless and until atmospheric carbon and other greenhouse gases were reduced.…”

Performance assessment for climate intervention (PACI): preliminary application to a stratospheric aerosol injection scenario

“…Radiative efficacy declines as deployed mass increases beyond some value (Smith, 2020). Covert deployment (rogue actor attempting to geoengineer the world) may be unlikely (Smith and Henly, 2021) Uncertainty in warming scenarios Assumptions about Representative Concentration Pathway (RCP; e.g., 4.5, 6.0, 8.5) as deployment modeling is performed to estimated capability of SAI (Smith, 2020) Change in aerosol candidates Due to negative environmental impacts and negative health impacts, an aerosol other than sulfates may be necessary (Goldstein et al, 2010) Interruption of deployment Deployment would need to be continuous or cooling effect would cease (Parker and Irvine, 2018 , 2002). SPI values are classified as: extremely dry (≤−2.…”