Abstract
Abstract. Previous climate modeling studies demonstrate the ability of feedback-regulated, stratospheric aerosol geoengineering with injection at multiple independent latitudes to meet multiple simultaneous temperature-based objectives in the presence of anthropogenic climate change. However, the impacts of climate change are not limited to rising temperatures but also include changes in precipitation, loss of sea ice, and many more; knowing how a given geoengineering strategy will affect each of these climate metrics is vital to understanding the limits and trade-offs of geoengineering. In this study, we first introduce a new method of visualizing the design space in which desired climate outcomes are represented by 2-D surfaces on a 3-D graph. Surface orientations represent how different injection choices influence that objective, and intersecting surfaces represent objectives which can be met simultaneously. Using this representation as a guide, we present simulations of two new strategies for feedback-regulated aerosol injection, using the Community Earth System Model with the Whole Atmosphere Community Climate Model – CESM1(WACCM). The first simultaneously manages global mean temperature, tropical precipitation centroid, and Arctic sea ice extent, while the second manages global mean precipitation, tropical precipitation centroid, and Arctic sea ice extent. Both simulations control the tropical precipitation centroid to within 5 % of the goal, and the latter controls global mean precipitation to within 1 % of the goal. Additionally, the first simulation overcompensates sea ice, while the second undercompensates sea ice; all of these results are consistent with the expectations of our design space model. In addition to showing that precipitation-based climate metrics can be managed using feedback alongside other goals, our simulations validate the utility of our design space visualization in predicting our climate model behavior under a given geoengineering strategy, and together they help illustrate the fundamental limits and trade-offs of stratospheric aerosol geoengineering.
Highlights
As a supplement to carbon emission reduction and negative emissions, the artificial addition of aerosols into the stratosphere could potentially reduce the effects of climate change by reflecting a small portion of the incoming solar radiation
A restoration value of less than 100 % indicates that a geoengineering strategy did not fully return that climate metric to its reference value, while a restoration value greater than 100 % indicates that a geoengineering strategy overcorrected that particular climate metric, bringing it beyond its reference value
While Kravitz et al (2016) showed that precipitation-based metrics can be controlled in a climate model by using solar reduction as a proxy for aerosol geoengineering, up until now, simulations of stratospheric aerosol injection controlled temperature gradients as proxies for non-temperature-based metrics, such as using T1 as a proxy for the Intertropical Convergence Zone (ITCZ) and T2 as a proxy for sea ice
Summary
As a supplement to carbon emission reduction and negative emissions, the artificial addition of aerosols into the stratosphere could potentially reduce the effects of climate change by reflecting a small portion of the incoming solar radiation. Climate modeling results agree that the addition of sulfate aerosols into the stratosphere will reduce global mean temperature (Robock et al, 2008; Aswathy et al, 2015; Jones et al, 2020); they show that this method of geoengineering will. Injections at different locations will affect each of these climate variables in different ways (Kravitz et al, 2019). Stratospheric aerosol geoengineering is not a “yes or no” problem but rather a design problem (Kravitz et al, 2016; MacMartin and Kravitz, 2019), and understanding the effects of injections at different locations on different climate variables is vital to mapping the design space
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