Paleoclimate informed simulations for constraining aerosol radiative effects

Aerosol radiative effects are still one of the major sources of uncertainty in terms of a quantitative understanding of climate changes across time scales, despite many advances in the field. Yet, paleodata databases offer the opportunity to constrain to some extent past natural aerosol emissions, allowing to account for aerosol radiative effects in a more realistic way in simulations with Earth System Models, at least from the point of view of amounts and spatial distributions of different aerosol species.

Here we first present the results of simulations conducted with CESM1.0 using paleodust constrained emissions for different equilibrium climate states, then broaden our discussion on the importance of historical and paleoclimate aerosol radiative effects, considering the published literature. We estimated that preindustrial to present-day aerosol radiative effects are affected by emission uncertainties that are just as large as model spread uncertainties (2.8 W m−2). We advocate that more efforts are put into improving and expanding existing paleodata collections and that those available should be taken into account when assessing uncertainties related to aerosol radiative effects. In particular we propose a new intercomparison project (AERO-HISTMIP) that compares outcomes when using multiple emission pathways in CMIP historical simulations.