18 Politically relevant solar geoengineering scenarios

Abstract

Solar geoengineering, also known as Solar Radiation Modification (SRM), has been proposed to alter Earth’s radiative balance to reduce the effects of anthropogenic climate change. SRM has been identified as a research priority, as it has been shown to effectively reduce surface temperatures, while substantial uncertainties remain around side effects and impacts. Global modeling studies of SRM have often relied on idealized scenarios to understand the physical processes of interventions and their widespread impacts. These extreme or idealized scenarios are not directly policy-relevant and are often physically implausible (such as imposing global solar reduction to counter the warming of an instantaneous quadrupling of CO2). The climatic and ecological impacts of politically relevant and potentially plausible SRM approaches have rarely been modeled and assessed. Nevertheless, commentators and policymakers often falsely assume that idealized or extreme scenarios are proposed solutions to climate change. This paper proposes 18 scenarios that appear to be broadly plausible from political and Earth System perspectives and encompass futures that could be both warnings or perhaps desirable. We place these scenarios into four groups following broader strategic contexts: (1) Global Management; (2) Regional Emergencies; (3) Coordinated Regional Interventions; and (4) Reactive Global Interventions. For each scenario, relevant model experiments are proposed. Some may be performed with existing setups of global climate models, while others require further specification. Developing and performing these model experiments – and assessing likely resulting impacts on society and ecosystems – would be essential to inform public debate and policymakers on the real-world issues surrounding SRM.

Flawed Emergency Intervention: Slow Ocean Response to Abrupt Stratospheric Aerosol Injection

“…In this study, we examine as SRM as an emergency intervention instead, to be deployed only after prolonged heating. This notion, adapted from Lockley et al (2022), naturally arises when SRM deployments are restricted to particularly extreme situations such as rapid climate tipping. To what extent can later deployments reverse the impacts of heating?…”

“…This notion, adapted from Lockley et al. (2022), naturally arises when SRM deployments are restricted to particularly extreme situations such as rapid climate tipping. To what extent can later deployments reverse the impacts of heating?…”

Interactive effects of changes in UV radiation and climate on terrestrial ecosystems, biogeochemical cycles, and feedbacks to the climate system

“…There are many uncertainties associated with this intervention, including risks to the stratospheric ozone layer that could increase ground-level UV irradiance [ 23 – 25 ]. In addition to the risks associated with the initiation of SAI, once adopted, any subsequent termination of this climate intervention would lead to a rapid increase in temperature and extreme deleterious effects on ecosystems [ 26 , 27 ]. This, and other SRM interventions, would likely expose the Earth’s ecosystems to new and potentially rapidly changing combinations of UV radiation and other biotic and abiotic environmental factors [ 28 ].…”

Assessing the Impact of Stratospheric Aerosol Injection on US Convective Weather Environments

“…Several Earth‐system models have been used to simulate a future climate with SAI under different climate change scenarios (Kravitz et al., 2011; Richter et al., 2022; Tilmes et al., 2018; Visioni et al., 2023). Research to date has included examining changes in global and regional temperature and precipitation (Hueholt et al., 2023; Richter et al., 2022; Tilmes et al., 2018), atmospheric circulation patterns (Bednarz et al., 2022), extreme temperature and precipitation events (Barnes et al., 2022; Ji et al., 2018), and ecological responses (Zarnetske et al., 2021), in addition to potential deployment technologies (Lockley et al., 2022; Smith & Wagner, 2018). Such studies have demonstrated that SAI could potentially be deployed to stabilize or reduce global mean temperature to a specific temperature target (Richter et al., 2022; Tilmes et al., 2018; Visioni et al., 2021); however, research has also indicated that regional impacts of SAI could be both positive and negative compared to the impacts and risks of anthropogenic climate change.…”