Atmospheric chemistry enhances the climate mitigation potential of tree restoration

Abstract

Although tree restoration, including reforestation and afforestation, can enhance carbon sequestration and help mitigate climate change, this negative forcing can be strengthened or weakened through non-carbon cycle biogeophysical factors, including atmospheric chemistry. Here, we conduct climate modeling experiments with and without atmospheric chemistry driven by a high-end tree restoration scenario. Under both frameworks, the biogeophysical effects drive global mean warming due to surface darkening. This warming is muted in the Southern Hemisphere due to enhanced evapotranspiration. Furthermore, there is less warming—especially in the Southern Hemisphere—under interactive atmospheric chemistry, largely due to enhanced organic aerosol and cloud effects. Biogeophysical effects mute 45% of the biogeochemical cooling associated with enhanced land carbon storage, which decreases to 24% with atmospheric chemistry (including methane). Thus, higher climate change mitigation potential of tree restoration results from atmospheric chemistry effects, which are not usually considered.