How the Updated Earth System Models Project Terrestrial Gross Primary Productivity in China under 1.5 and 2 °C Global Warming

Three Earth system models (ESMs) from the Coupled Model Intercomparison Project phase 6 (CMIP6) were chosen to project ecosystem changes under 1.5 and 2 degrees C global warming targets in the Shared Socioeconomic Pathway 4.5 W m(-2) (SSP245) scenario. Annual terrestrial gross primary productivity (GPP) was taken as the representative ecological indicator of the ecosystem. Under 1.5 degrees C global warming, GPP in four climate zones-i.e., temperate continental; temperate monsoonal; subtropical-tropical monsoonal; high-cold Tibetan Plateau-showed a marked increase, the smallest magnitude of which was around 12.3%. The increase was greater under 2 degrees C of global warming, which suggests that from the perspective of ecosystem productivity, global warming poses no ecological risk in China. Specifically, in comparison with historical GPP (1986-2005), under 1.5 degrees C global warming GPP was projected to increase by 16.1-23.8% in the temperate continental zone, 12.3-16.1% in the temperate monsoonal zone, 12.5-14.7% in the subtropical-tropical monsoonal zone, and 20.0-37.0% on the Tibetan Plateau. Under 2 degrees C global warming, the projected GPP increase was 23.0-34.3% in the temperate continental zone, 21.2-24.4% in the temperate monsoonal zone, 16.1-28.4% in the subtropical-tropical monsoonal zone, and 28.4-63.0% on the Tibetan Plateau. The GPP increase contributed by climate change was further quantified and attributed. The ESM prediction from the Max Planck Institute suggested that the climate contribution could range from -12.8% in the temperate continental zone up to 61.1% on the Tibetan Plateau; however, the ESMs differed markedly regarding their climate contribution to GPP change. Although precipitation has a higher sensitivity coefficient, temperature generally plays a more important role in GPP change, primarily because of the larger relative change in temperature in comparison with that of precipitation.