Fire-climate interactions through the aerosol radiative effect in a global chemistry-climate-vegetation model

Abstract

Fire emissions influence radiation, climate, and ecosystems through aerosol radiative effects. These can drive rapid atmospheric and land surface adjustments which feed back to affect fire emissions. However, the magnitude of such feedback remains unclear on the global scale. Here, we quantify the impacts of fire aerosols on radiative forcing and the fast atmospheric response through direct, indirect, and albedo effects based on the two-way simulations using a well-established chemistry-climate-vegetation model. Globally, fire emissions cause a reduction of 0.565 ± 0.166 Wm-2 in net radiation at the top of the atmosphere with dominant contributions by the aerosol indirect effect (AIE). Consequently, terrestrial surface air temperature decreases by 0.061 ± 0.165 °C with coolings of >0.25 °C over the eastern Amazon, the western US, and boreal Asia. Both the aerosol direct effect (ADE) and AIE contribute to such cooling, while the aerosol albedo effect (AAE) exerts an offset warming, especially at high latitudes. Land precipitation decreases by 0.180 ± 0.966 mmpermonth (1.78 %± 9.56 %) mainly due to the inhibition in central Africa by AIE. Such a rainfall deficit further reduces regional leaf area index (LAI) and lightning ignitions, leading to changes in fire emissions. Globally, fire emissions reduce by 2 %-3 % because of the fire-induced fast responses in humidity, lightning, and LAI. The fire aerosol radiative effects may cause larger perturbations to climate systems with likely more fires under global warming.