Spurious Late Historical‐Era Warming in CESM2 Driven by Prescribed Biomass Burning Emissions
Historical era warming has been used as a constraint on the sensitivity of climate models to increased carbon dioxide concentrations. Here we show in CESM2 that such warming is also strongly influenced by the variability of prescribed biomass emissions from 40°-70°N in CMIP6, which undergo an abrupt and spurious transition during the satellite era.
This work highlights the unforeseen impact of a marked and spurious transition in the variability of biomass emissions from 40°-70°N in CMIP6 arising from combining disparate sources of emissions. In demonstrating the emissions’ impacts on clouds and climate in CESM2, this work also calls into question a growing body of work seeking to winnow the broad range of climate sensitivities across models in CMIP6 and underscores the importance of accurately simulating aerosol-cloud interactions.
Spurious variability in CMIP6 biomass emissions from 40°-70°N roughly double the rate of northern hemisphere warming in CESM2 from 1997 to 2014 due to nonlinear interactions between aerosols and clouds. While the existence of a similar response in other CMIP6 models is not known, indirect evidence indicates a potentially pervasive influence in some models, including E3SMv1, that undermines our ability to infer climate sensitivity from historical simulations.