Deciphering Aerosol Effects on Climate from the Global to Regional Scales (Invited Presentation)

Anthropogenic emissions of greenhouse gases and aerosols, including precursors, have constituted two principal radiative drivers of climate change over the 20^th Century and into the 21^st Century. Their differing manner of perturbing the radiative fluxes at the top-of-the-atmosphere and surface influences the response of the climate system differently. In the case of aerosols, the complexity of the forcing and response is sensitive to the optical scattering and absorbing properties, the spatial distribution of aerosols, and the interaction of aerosols with clouds. In this presentation, we investigate the mechanisms that come into play in the response of the global and regional climate system to anthropogenic emissions, focusing on the contrasts between greenhouse gases and aerosols, and when the two forcings are taken together to represent the actual situation. We employ simulations conduced with 3 generations of NOAA/GFDL climate models (CM2.1, developed ~2005; CM3, developed ~2011; CM4, developed ~2018) to investigate the response in key climate parameters e.g., temperature, circulation, poleward transport of heat, and precipitation, and examine the adjustments taking place in the radiative, sensible, and latent heat fluxes to analyze the role of aerosols. We will discuss the significant uncertainties that remain concerning aerosols which affect quantitative inferences about the net anthropogenic forcing and detection-attribution of climate change over the 20^th Century, and climate projections for the 21^st Century.