Regional Climate Impacts of Stabilizing Global Warming at 1.5 K Using Solar Geoengineering

Jones, Anthony C.; Hawcroft, Matt; Haywood, Jim M.; Jones, Andy; Guo, Xiaoyi; Moore, John C.

doi:10.1002/2017ef000720

Cited by 72 publications

(102 citation statements)

References 104 publications

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“…Geoengineering has been proposed as a way to limit global warming by deliberately altering the climate to both alleviate some of the consequences of anthropogenic greenhouse gas emissions (Irvine et al, ) and as part of strategic approach to keep temperatures below thresholds such as 1.5 °C above pre‐industrial (Jones et al, ; MacMartin & Kravitz, ). Climate models simulating the Atlantic Meridional Over‐turning Circulation (AMOC) show that it decreases in intensity as atmospheric greenhouse gas concentrations and temperatures rise.…”

Section: Introductionmentioning

confidence: 99%

Greenland Ice Sheet Response to Stratospheric Aerosol Injection Geoengineering

et al. 2019

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The Greenland ice sheet is expected lose at least 90% of its current volume if ice sheet summer temperatures warm by around 1.8°C above pre-industrial. Geoengineering by stratospheric sulfate aerosol injection might slow Greenland ice sheet melting and sea level rise by reducing summer temperature and insolation; however, such schemes could also reduce precipitation and affect large-scale climate drivers such as the Atlantic Meridional Over-turning Circulation (AMOC). Earlier work found that AMOC increased under geoengineering and that might lead to greater mass loss from Greenland than under greenhouse gas forcing alone. We simulated Greenland ice sheet climates using four Earth system models running the stratospheric sulfate aerosol injection experiment GeoMIP G4 and the CMIP RCP4.5 and RCP8.5 greenhouse gas scenarios that were then used to drive the surface energy and mass balance model, SEMIC. Simulated runoff is 20% lower under G4 than RCP4.5, while under RCP8.5 it is 17% higher. The mechanism is through increased Arctic sea ice concentration and reduced humidity leading to surface cooling of the ablation zone. Reduced absorption of outgoing longwave radiation caused by hydrological cycle weakening dominates associated decreases in precipitation under geoengineering and stronger AMOC than under RCP4.5. An ice dynamics model simulates 15% lower ice losses under G4 than RCP4.5. Thus, total sea level rise by 2070 from the Greenland ice sheet under G4 geoengineering is about 15-20% lower than under the RCP4.5 scenario. Plain Language SummaryMass loss from the Greenland ice sheet is expected to raise sea levels by tens of centimeters this century and far more in the further future. Rising seas are one of the most damaging aspects of the warming climate, affecting hundreds of millions, and costing $ trillions by 2100, and geoengineering might be one approach that could be used against this threat. But the North Atlantic climate is a complex region where the flux of warm tropical waters is being reduced by greenhouse warming, which geoengineering would reverse. Hence, how Greenland would likely respond is a key factor in deciding the potential utility of doing geoengineering. We examine the impact of stratospheric aerosol geoengineering on both the surface ice sheet water runoff (which accounts for half of present-day ice loss) and the dynamic loss of ice from fast-flowing glaciers that are being accelerated by warming ocean currents (accounting for the other half). We find that aerosol injection equivalent to about ¼ Pinatubo volcanic eruption per year can slow mass loss from Greenland by 15-20% compared with greenhouse gas forcing alone, mainly due to reduced surface melting.

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Section: Introductionmentioning

confidence: 99%

Greenland Ice Sheet Response to Stratospheric Aerosol Injection Geoengineering

et al. 2019

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“…Stratospheric aerosol geoengineering could be considered as part of a portfolio of options for managing future climate change (Crutzen, 2006;Keith & MacMartin, 2015;Long & Shepherd, 2014;MacMartin et al, 2018;Wigley, 2006) and could reduce many impacts relative to the warmer world without geoengineering (e.g., Keith & Irvine, 2016). However, while geoengineering could be used to maintain some particular target for global mean temperature, such as a 1.5 or 2 • C rise above preindustrial levels, the resulting climate would not be the same as one in which these targets were achieved solely through limiting atmospheric greenhouse gas (GHG) concentrations (e.g., Jones et al, 2018;MacMartin et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Timescale for Detecting the Climate Response to Stratospheric Aerosol Geoengineering

et al. 2019

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Stratospheric aerosol geoengineering could be used to maintain global mean temperature despite increased atmospheric greenhouse gas (GHG) concentrations, for example, to meet a 1.5 or 2 °C target. While this might reduce many climate change impacts, the resulting climate would not be the same as one with the same global mean temperature due to lower GHG concentrations. The primary question we consider is how long it would take to detect these differences in a hypothetical deployment. We use a 20‐member ensemble of stratospheric sulfate aerosol geoengineering simulations in which SO2 is injected at four different latitudes to maintain not just the global mean temperature, but also the interhemispheric and equator‐to‐pole gradients. This multiple‐latitude strategy better matches the climate changes from increased GHG, while the ensemble allows us both to estimate residual differences even when they are small compared to natural variability and to estimate the statistics of variability. We first construct a linear emulator to predict the model responses for different scenarios. Under an RCP4.5 scenario in which geoengineering maintains a 1.5 °C target (providing end‐of‐century cooling of 1.7 °C), the projected changes in temperature, precipitation, and precipitation minus evaporation (P − E) at a grid‐scale are typically small enough that in many regions the signal‐to‐noise ratio is still less than one at the end of this century; for example, for P − E, only 30% of the land area reaches a signal‐to‐noise ratio of one. These results provide some context for the projected magnitude of climate changes associated with a limited deployment of stratospheric aerosol cooling.

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“…Deploying it with a radiative forcing large enough to offset all temperature changes is simulated to, for example, weaken the global hydrological cycle, more-than-offsetting the strengthening expected under climate change (Govindasamy andCaldeira 2000, Tilmes et al 2013). However, modeling studies have found that if deployed to offset all warming it would nevertheless reduce many aspects of change to mean climate and climate extremes relative to a case without solar geoengineering (Boucher et al 2013, Kravitz et al 2013, Curry et al 2014, Jones et al 2018. In addition, there are sideeffects of stratospheric aerosol geoengineering such as ozone loss and air pollution that are expected to grow as the scale of deployment grows (Crutzen 2006, Eastham et al 2018.…”

Section: Introductionmentioning

confidence: 99%

Halving warming with stratospheric aerosol geoengineering moderates policy-relevant climate hazards

Irvine

Keith

2020

Environ. Res. Lett.

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Stratospheric aerosol geoengineering is a proposal to artificially thicken the layer of reflective aerosols in the stratosphere and it is hoped that this may offer a means of reducing average climate changes. However, previous work has shown that it could not perfectly offset the effects of climate change and there is a concern that it may worsen climate impacts in some regions. One approach to evaluating this concern is to test whether the absolute magnitude of climate change at each location is significantly increased (exacerbated) or decreased (moderated) relative to the period just preceding deployment. In prior work it was found that halving warming with an idealized solar constant reduction would substantially reduce climate change overall, exacerbating change in a small fraction of places. Here, we test if this result holds for a more realistic representation of stratospheric aerosol geoengineering using the data from the geoengineering large ensemble (GLENS). Using a linearized scaling of GLENS we find that halving warming with stratospheric aerosols moderates important climate hazards in almost all regions. Only 1.3% of land area sees exacerbation of change in water availability, and regions that are exacerbated see wetting not drying contradicting the common assumption that solar geoengineering leads to drying in general. These results suggest that halving warming with stratospheric aerosol geoengineering could potentially reduce key climate hazards substantially while avoiding some problems associated with fully offsetting warming. OPEN ACCESS RECEIVED

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Regional Climate Impacts of Stabilizing Global Warming at 1.5 K Using Solar Geoengineering

Cited by 72 publications

References 104 publications

Greenland Ice Sheet Response to Stratospheric Aerosol Injection Geoengineering

Greenland Ice Sheet Response to Stratospheric Aerosol Injection Geoengineering

Timescale for Detecting the Climate Response to Stratospheric Aerosol Geoengineering

Halving warming with stratospheric aerosol geoengineering moderates policy-relevant climate hazards

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