Impacts of 1.5 °C and 2 °C Global Warming on Net Primary Productivity and Carbon Balance in China's Terrestrial Ecosystems

Assessing potential impacts of 1.5 degrees C and 2 degrees C global warming and identifying the risks of further 0.5 degrees C warming are crucial for climate adaptation and disaster risk management. Four earth system models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and a process-based ecosystem model are used in this study to assess the impacts and potential risks of the two warming targets on the carbon cycle of China's terrestrial ecosystems. Results show that warming generally stimulates the increase of net primary productivity (NPP) and net ecosystem productivity (NEP) under both representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios. The projected increments of NPP are higher at 2 degrees C warming than that at 1.5 degrees C warming for both RCP4.5 and RCP8.5 scenarios; approximately 13% and 19% under RCP4.5, and 12.5% and 20% under RCP8.5 at 1.5 degrees C and 2 degrees C warming, respectively. However, the increasing rate of NPP was projected to decline at 2 degrees C warming under the RCP4.5 scenario, and the further 0.5 degrees C temperature rising induces the decreased NPP linear slopes in more than 81% areas of China's ecosystems. The total NEP is projected to be increased by 53% at 1.5 degrees C, and by 81% at 2 degrees C warming. NEP was projected to increase approximately by 28% with the additional 0.5 degrees C warming. Furthermore, the increasing rate of NEP weakens at 2 degrees C warming, especially under the RCP8.5 scenario. In summary, China's total NPP and NEP were projected to increase under both 1.5 degrees C and 2 degrees C warming scenarios, although adverse effects (i.e., the drop of NPP growth and the reduction of carbon sequestration capacity) would occur in some regions such as northern China in the process of global warming.