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Potential for perceived failure of stratospheric aerosol injection deployment - PubMed

  • ️Sat Jan 01 2022

Potential for perceived failure of stratospheric aerosol injection deployment

Patrick W Keys et al. Proc Natl Acad Sci U S A. 2022.

Abstract

As anthropogenic activities warm the Earth, the fundamental solution of reducing greenhouse gas emissions remains elusive. Given this mitigation gap, global warming may lead to intolerable climate changes as adaptive capacity is exceeded. Thus, there is emerging interest in solar radiation modification, which is the process of deliberately increasing Earth's albedo to cool the planet. Stratospheric aerosol injection (SAI)-the theoretical deployment of particles in the stratosphere to enhance reflection of incoming solar radiation-is one strategy to slow, pause, or reverse global warming. If SAI is ever pursued, it will likely be for a specific aim, such as affording time to implement mitigation strategies, lessening extremes, or reducing the odds of reaching a biogeophysical tipping point. Using an ensemble climate model experiment that simulates the deployment of SAI in the context of an intermediate greenhouse gas trajectory, we quantified the probability that internal climate variability masks the effectiveness of SAI deployment on regional temperatures. We found that while global temperature was stabilized, substantial land areas continued to experience warming. For example, in the SAI scenario we explored, up to 55% of the global population experienced rising temperatures over the decade following SAI deployment and large areas exhibited high probability of extremely hot years. These conditions could cause SAI to be perceived as a failure. Countries with the largest economies experienced some of the largest probabilities of this perceived failure. The potential for perceived failure could therefore have major implications for policy decisions in the years immediately following SAI deployment.

Keywords: climate change; internal climate variability; mitigation; perception; solar geoengineering.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.
Fig. 1.

Surface temperature trends. (A) Global mean surface temperature. Gray lines denote individual ensemble members, and the black line denotes the ensemble mean. (B and C) Ensemble-mean trends over years 2015 to 2034 under SSP2-4.5 (B) and 2035 to 2069 (C) with ARISE-SAI deployment. (D and E) Trends over the predeployment decade (D) and postdeployment decade (E) for ensemble member #9. (B–D) The percentage in the bottom of the maps denotes the percentage of land area that exhibited warming trends as defined in the text.

Fig. 2.
Fig. 2.

Predeployment and postdeployment surface temperature trends for Beijing, China. (A–D) Each panel highlights a different ensemble member denoted in each panel by the thick black line, with the other nine members shown as thin gray lines. SAI deployment was initiated in the year 2035 (teal shading). Ten-year linear best-fit lines are shown for 2025 to 2034 (orange) and 2035 to 2044 (teal).

Fig. 3.
Fig. 3.

Archetypal regional responses to ARISE-SAI. (A–D) The percentage of ensemble members that exhibited specific archetypal responses over the 10 y pre- and postdeployment: (A) Rebound Warming (not warming followed by warming), (B) Continued Warming (warming followed by warming), (C) Stabilization (not warming followed by not warming), and (D) Recovery (warming followed by not warming).

Fig. 4.
Fig. 4.

Perceived failure over the 10 y following SAI deployment under ARISE. (A) Probability of perceived failure over the postdeployment period, where the probability was computed as the fraction of ensemble members exhibiting warming trends. (B) Probability of a location exceeding its 2015 to 2034 (predeployment) maximum annual-mean temperature in the decade following SAI deployment (2035 to 2046). (C) Projected number of people at each location experiencing perceived failure of SAI over the postdeployment period in ensemble member #9 using projected populations for 2040. Gray denotes regions not experiencing perceived failure in that particular ensemble member. (D) Percentage of members with 10% or more of a country’s projected 2040 population (see

SI Appendix, Fig. S5

for alternative population thresholds) experiencing perceived failure following SAI deployment versus the country’s projected 2040 GDP in units of PPP. Circled area corresponds to the projected 2040 population experiencing perceived failure averaged across ensemble members.

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