Seasonal and regional changes in terrestrial carbon uptake under an overshoot scenario

Abstract

Carbon dioxide removal (CDR) could change terrestrial carbon uptake due to biosphere responses. Here we examine the seasonal and regional responses of net biome productivity (NBP) and its components to carbon emissions reduction under the SSP5–3.4 overshoot scenario simulated by eight CMIP6 Earth system models. Globally averaged NBP is lower under SSP5–3.4 than under SSP5–8.5, with 102±7 Pg C (51%) less accumulated during 2041 to 2100. About 59% of accumulated change in NBP is from reduction in net ecosystem productivity in the boreal growing season, associated with the reduction in atmospheric CO2 concentrations and the resulting climate change. The rest of the accumulated reduction in NBP is due to greater disturbances from bioenergy crop expansion and land use change. These results imply that improved land management, more aggressive carbon emissions reduction and CDR will be needed to reach time flagged carbon neutrality targets after considering the adjustment in the terrestrial carbon sink.