The radiative effect and climate responses of present-day wildfire emissions

Abstract. Aerosols exert spatially inhomogeneous radiative effects (REs) that can drastically perturb global and regional climate. While studies have investigated the impacts of regional anthropogenic aerosol emissions on climate, there is no past work systematically exploring the impacts of regional wildfire emissions. This study investigates the interconnection between wildfires and the atmosphere, focusing on the global RE and climate responses from wildfire emissions. We examine the effects of carbonaceous aerosols and O₃ precursors via atmosphere-only and ocean-atmosphere coupled simulations using EC-Earth3, driven by the CMIP6 wildfire emissions. Additional atmosphere-only perturbation simulations with wildfire emissions removed from selected regions, i.e., Boreal North America, South America, Africa, Boreal & Central Asia, and Equatorial Asia, were also performed to determine their local and remote effects. We identify which regions experience stronger RE and separate direct influences of emissions on radiation from secondary mechanisms. Our simulations indicate that the global RE of short-lived wildfire emissions is negative (cooling), dominated by aerosol-cloud interactions, with aerosol-radiation interactions and side effects via O₃, water vapor and surface albedo being particularly important in specific regions. The slow, ocean-mediated response dominates the total climate response to wildfire emissions, showing substantial global cooling, and pronounced regional effects on precipitation especially in the tropics. Wildfire emissions affect regions both locally and remotely to the emissions, as they alter circulation, land-atmosphere coupling, convection, and energy transport across the globe, producing a highly interconnected climate response. Overall, this study demonstrates that short-lived wildfire emissions can be a substantial modifier of the global climate system.