Global Carbon Cycle and Temperature Impacts of Future Changes in Fire Regime

English Abstract:

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 fully coupled climate–carbon model to quantify the effect of different non-deforestation fire scenarios 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 account for non-CO₂ fire emissions, the effect of increased fire frequency on global temperature depended critically on the uncertain net aerosol forcing. Overall, our results do not support the hypothesis of a strong positive climate–fire feedback for the coming centuries, and suggest that more frequent non-deforestation fires may even represent a net negative feedback to ongoing global warming.