PNNL

Abstract

A frequently raised concern regarding solar geoengineering is that some regions will benefit from its use ("winners"), and some will be harmed ("losers"). These claims are often predicated on implicit assumptions about the amount of geoengineering, the relative weighting of different climatological fields in determining climate change impacts, and the baseline of comparison. We examine simulated departures of temperature and precipitation from preindustrial conditions in 12 participating models in the Geoengineering Model Intercomparison Project (GeoMIP) in geographic regions spanning most of Earth's continents. If normalized temperature and precipitation departures are equally weighted, all models show less climate change in all regions for up to 85% of the solar reduction that would return globally-averaged temperature to its preindustrial level. However, there are regions that do not show reduced climate changes (compared to high CO2) for any amount of solar reduction when solely considering precipitation. A substantial amount of geoengineering can offset modeled CO2-induced temperature and precipitation changes in all regions, but non-climatic assessments of regional geoengineering effects may favor no geoengineering. Arguments about the creation of "winners and losers" require specificity about how geoengineering is conducted and how to evaluate its effectiveness.