Tipping point in North American Arctic-Boreal carbon sink persists in new generation Earth system models despite reduced uncertainty

Abstract Estimating the impacts of climate change on global carbon cycle relies projections from Earth system models (ESMs). While ESMs currently project large warming in high northern latitudes, magnitude and sign future balance Arctic-Boreal ecosystems are highly uncertain. The new generation increased complexity Intergovernmental Panel Climate Change Sixth Assessment Report (IPCC AR6) is intended to improve projections. Here, we benchmark Coupled Model Intercomparison Project (CMIP) 5 6 (8 CMIP5 members 12 CMIP6 members) with International Land Benchmarking (ILAMB) tool over region NASA’s vulnerability experiment (ABoVE) North America. We show that projected average net biome production (NBP) 2100 higher than ABoVE domain, despite model spread being slightly narrower. Overall, shows better agreement contemporary observed variables (photosynthesis, respiration, biomass) CMIP5, except for soil turnover time. Although both CMIP ensemble domain will remain a sink by end 21st century, strength increases CO 2 emissions. ensembles indicate tipping point defined here as negative inflection NBP curve 2050–2080 independently shared socioeconomic pathway (SSP) or representative concentration (RCP) CMIP5. therefore suggest that, if keeps declining throughout America may become source next century.