David Keith (@davidkeith.bsky.social)

Ken @kencaldeira.bsky.social, Bala Govindasamy, B. B. Cael, and me are running an effort to assess climate hazards that might be caused by stratospheric aerosol injection. We want your input: forms.gle/cN6aXgwBdB.... 1/2

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Solar geoengineering: What could go wrong? A natural science perspective We want your input on climate hazards that might be caused by stratospheric aerosol injection. Suggestions will be considered by a small group of scientists assessing solar geoengineering risks. Consider a scenario where sulfate aerosols are injected into the stratosphere. The injection rate is ramped up to achieve a peak cooling of ≤0.5°C at the time of peak radiative forcing by greenhouse gases. The injection rate is then ramped down about as fast as it was ramped up. During the ramp-up period, sulfate cooling increases by ≤0.1°C per decade. Injection is always adjusted to minimize hemispheric asymmetry. Here is a published example of one such scenario. Our questions are about the climate hazards that might arise from such a scenario. We are focusing on physical events that may harm humans or environmental systems on which humans depend, consistent with the IPCC’s definition of a climate hazard. We consider mechanisms or causal chains from the deployment of sulfate aerosols to climate hazards. Such mechanisms are limited to the natural sciences. Solar geoengineering may also cause harm mediated by sociopolitical pathways, such as the moral hazard of reduced attention to emissions cuts. These are important, perhaps more important than climate hazards, but beyond the scope of this survey. We are especially interested in any potential hazard or uncertainty that the broader literature or the scientific community has ignored so far, or is not aware of. The more of the following questions you answer, the more carefully we can evaluate your suggestion. https://forms.gle/cN6aXgwBdBUTo1KC8