High‐Latitude Stratospheric Aerosol Geoengineering Can Be More Effective if Injection Is Limited to Spring

Lee, Walker; MacMartin, Douglas G.; Visioni, Daniele; Kravitz, Ben

doi:10.1029/2021gl092696

Cited by 47 publications

(92 citation statements)

References 68 publications

(115 reference statements)

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“…Visioni et al ( 2020) found that regional climate response would be significantly different with injection at the same location and height but different season. Lee et al (2021) find that spring injections of stratospheric aerosol are most efficient in restoring sea ice as the injected particles stay in the stratosphere throughout the summer. The exploration of climate response to different seasonal patterns of aerosol addition, together with different latitudinal and altitudinal distributions of aerosol addition, merits further investigation.…”

Section: Discussionmentioning

confidence: 87%

“…Many studies have investigated the climate response to SAI, and a subset of them have investigated the injection of SO 2 into the tropical lower stratosphere (Berdahl et al, 2014;Jones et al, 2010;Kravitz et al, 2011;Rasch, Tilmes, et al, 2008;Robock et al, 2008). Climate effect of injecting SO 2 into the high-latitude stratosphere, such as over the Arctic, has been also examined (Jackson et al, 2015;Lee et al, 2021;Robock et al, 2008). More recent studies examine climate response to SO 2 injections at multiple latitudes.…”

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confidence: 99%

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Climate Response to Latitudinal and Altitudinal Distribution of Stratospheric Sulfate Aerosols

et al. 2021

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Despite the effort to reduce anthropogenic carbon emissions, continued increase in atmospheric CO 2 indicates that current emission reductions may be insufficient to avoid risks from anthropogenic climate change (Clarke et al., 2014; NAS, 2021;Rogelj et al., 2018). Solar radiation modification (SRM) (also sometimes termed as solar geoengineering), which aims to intentionally reduce the amount of sunlight reaching the surface, has been proposed as a backup option to alleviate some detrimental effects of anthropogenic climate change (Muthyala

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Section: Discussionmentioning

confidence: 87%

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confidence: 99%

Climate Response to Latitudinal and Altitudinal Distribution of Stratospheric Sulfate Aerosols

et al. 2021

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“…In practice, an SAI implementation would be much more sophisticated than G4, for example, aiming to preserve existing hemispheric temperature balance, as well as equator-to-pole temperature gradients (Kravitz et al, 2016), and with seasonally varying injection rates. These types of implementations might be expected to for example, well preserve Arctic sea ice (Lee et al, 2021), along with and AMOC and Greenland ice sheet mass balance (Tilmes et al, 2020). Although detailed analyses of differences between this kind of SAI deployment and the simple version applied here have not been done, they appear to be second order compared with the impacts introduced by temperature rises due to greenhouse gas scenarios.…”

Section: Climate Forcingmentioning

confidence: 99%

Vatnajökull Mass Loss Under Solar Geoengineering Due to the North Atlantic Meridional Overturning Circulation

et al. 2021

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Icelandic glaciers are rather sensitive to climate warming (e.g., Guðmundsson et al., 2011;Schmidt et al., 2018Schmidt et al., , 2020. This is because of their extreme maritime setting giving them high snowfall, and ice temperatures that are always close to the melting point, leading to both large accumulation rates in their upper reaches and rapid melt in their ablation zones. Iceland sits at the confluence of the warm Irminger and cold East Iceland ocean currents (e.g., Ólafsson et al., 2007) leading to a temperate maritime climate (Vilhjálmsson, 2002). Iceland is situated close to the overturning regions of the Atlantic Meridional Overturning Circulation (AMOC) that brings significant heat to the North Atlantic region. Atmospheric greenhouse gas concentration increases tend to reduce AMOC, albeit with heavily model-dependent results (Caesar Abstract The objective of solar geoengineering by stratospheric aerosol injection (SAI) is to lower global temperatures, but it may also have adverse side effects. Iceland is situated close to the overturning regions of the Atlantic Meridional Overturning Circulation (AMOC) that warms the North Atlantic area. Hence, this may be one region where reduced irradiance by SAI may not be successful in reducing impacts from greenhouse gas warming. We examine this proposition by estimating how the Icelandic Vatnajökull ice cap (VIC) surface mass balance (SMB) and surface runoff changes in response to greenhouse gas and solar geoengineering scenarios over the period 1982-2089. We use the surface energy and mass balance model SEMIC driven by Earth System Model output under the GeoMIP G4, and CMIP RCP4.5 and RCP8.5 greenhouse gas scenarios. Geoengineering significantly reduces VIC near-surface air temperature by 0.4°C, downward longwave radiation by 2.4 Wm −2 and increases snowfall by 4.9 mm yr −1 relative to RCP4.5. During the SAI period 2020-2069, modeled annual mean SMB under G4, RCP4.5 and RCP8.5 are −0.34 ± 0.18 m yr −1 , −0.56 ± 0.06 m yr −1 and −0.66 ± 0.04 m yr −1 , respectively; surface runoff reduction under G4 is 6 ± 6% and 7 ± 6% (95% confidence interval uncertainties) compared with that under RCP4.5 and RCP8.5, which is far smaller than the 20 ± 2% and 32 ± 2% reductions for the Greenland ice sheet. The differences may be attributed to the reinvigoration of AMOC under G4 relative to RCP4.5 which brings more heat to Iceland than Greenland, leading to around half the cooling and longwave radiation reductions than for Greenland. Plain Language SummaryThe unique location of Iceland, near the overturning regions of the Atlantic thermohaline overturning circulation, makes its response to climate change rather atypical. The overturning circulation supplies a lot of heat to Iceland, but this has been slowing, and is projected to reduce further as greenhouse warming continues over the century. Solar geoengineering has the potential to lower temperatures by artificially increasing planetary albedo and is predicted to reverse this decline in ocean circulation heat transport, but als...

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“…The most prominent of these proposed solutions has been planetary albedo modification schemes, where the amount of incoming solar radiation reflected back to space is artificially increased by some method. Such schemes have included introducing sulphate aerosols into the stratosphere globally (e.g., Irvine et al, 2016;McCusker et al, 2012;Rasch et al, 2008), as well as specifically in the Arctic (e.g., Jackson et al, 2015;Lee et al, 2021;Robock et al, 2008), marine cloud brightening (e.g., Kravitz et al, 2014;Latham, 1990), land albedo modification (e.g., Irvine et al, 2011) or sunshade geoengineering (e.g., Kravitz et al, 2013). There have also been geoengineering proposals focused on the Arctic.…”

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confidence: 99%

Arctic Sea Ice Response to Flooding of the Snow Layer in Future Warming Scenarios

Pauling

Bitz

2021

Earth's Future

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The projected decline in Arctic sea ice extent as the Earth warms in response to increased greenhouse gas concentrations will occur in conjunction with increased precipitation in the Arctic, and more of that precipitation is projected to fall as rain, especially in autumn and early winter. A recently proposed method of offsetting the decline in Arctic sea ice extent would pump seawater on the sea ice surface. Either way, we envision the liquid water first infiltrating the overlying snow layer creating slush. Winter conditions would then freeze the slush to directly thicken the ice. The net reduction in insulation would increase basal growth, adding an indirect thickening effect. Simulating the response to augmented snow layer flooding gives insights that are relevant in the future Arctic with or without the implementation of geoengineering. We use a hierarchy of models to show that flooding snow on sea ice is most effective at thickening Arctic sea ice when flooding begins early in the sea ice growth season. For the geoengineering scheme to be most effective, the pumps must be deployed almost immediately, while there is still a sufficient area of sea ice over which to flood, and must continue for decades. Sea ice loss would be best mitigated if flooding is combined with reducing greenhouse gas emissions. Furthermore, the increase in rainfall over the Arctic in the 21st century is unlikely to offset a substantial portion of the loss due to warming.

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High‐Latitude Stratospheric Aerosol Geoengineering Can Be More Effective if Injection Is Limited to Spring

Cited by 47 publications

References 68 publications

Climate Response to Latitudinal and Altitudinal Distribution of Stratospheric Sulfate Aerosols

Climate Response to Latitudinal and Altitudinal Distribution of Stratospheric Sulfate Aerosols

Vatnajökull Mass Loss Under Solar Geoengineering Due to the North Atlantic Meridional Overturning Circulation

Arctic Sea Ice Response to Flooding of the Snow Layer in Future Warming Scenarios

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