A global assessment of the carbon cycle and temperature responses to major changes in future fire regime

Changes in the current fire regime would directly affect carbon cycling, land-atmosphere exchanges, and atmospheric composition, and could therefore modulate the ongoing climate warming. We used a coupled climate-carbon model to quantify the effect of major changes in non-deforestation fires on the global carbon cycle and temperature, from 2015 to 2300. When considering only CO2 fire emissions, the impacts from changes in fire frequency were limited for the global carbon cycle, and almost negligible for the global atmospheric surface temperature. The net fire emissions were only a fraction of the CO2 directly emitted during combustion due to vegetation regrowth and climate-CO2 feedbacks, and the albedo increases caused by changes in vegetation cover countered the effect of increased atmospheric CO2 on global temperature. When employing a simplified approach based on global-mean radiative forcings in order to estimate the impact of non-CO2 fire emissions, the effect of increased fire frequency on global temperature depended critically on the uncertain net aerosol forcing. Despite this major uncertainty, our results overall do not support the hypothesis of a strong positive climate-fire feedback for the coming centuries.