## 4 Conclusions and Discussions
### The Risks of Sensitive or Vulnerable Region to Additional 0.5 \({}^{\circ}\)C Warming  
Although 2 \({}^{\circ}\)C warming will not bring more risks of warming on NPP and NEP of Chinese terrestrial ecosystems on the national scale compared with that at 1.5 \({}^{\circ}\)C, we should also notice the decrease of NPP increase rate and carbon sequestration in some regions, especially in northern China. The tipping points of ecosystem security or food production in these regions may occur during the global warming process. IPCC AR5 mentioned that although regional scale or sub-regional scale ecosystem tipping points have not occurred in the recent past, they could occur soon in the future [15]. Furthermore, climate extremes would bring extra risks, which should be taken into consideration in assessing future carbon dynamics. The additional 0.5 \({}^{\circ}\)C increase in global mean temperature reveals the substantial differences for heat-related or precipitation-related extremes on both global and regional scales [72]. Northwestern China, northeastern China, and the Tibetan Plateau would be more sensitive to extreme climate events with the additional 0.5 \({}^{\circ}\)C [73]. On the other hand, the mean temperature of China increased significantly higher than the global mean [19]. So, under 2 \({}^{\circ}\)C global warming scenario, the mean temperature of China would be higher than the warming threshold, which is likely to bring a high risk of extremes in some regions. In this case, appropriate strategies should be taken to enhance climate resilience of terrestrial ecosystems and mitigate the potential risks of warming on productivity and carbon sequestration. Besides, extreme climate events, even under a lower emission scenario, should be considered for ensuring that ecosystems in sensitive areas can deal with the potential risks of 2 \({}^{\circ}\)C of global warming.  
Conceptualization, L.Y., F.G. and M.H. ([PERSON]); methodology, L.Y.; software, M.H. ([PERSON]); validation, Z.W., and M.H. ([PERSON]); formal analysis, L.Y.; investigation, M.H. ([PERSON]); resources, Z.W.; data curation, M.H. ([PERSON]); writing--original draft preparation, L.Y. and F.G.; writing--review and editing, B.T.; visualization, L.Y.; supervision, M.H. ([PERSON]); project administration, M.H. ([PERSON]); funding acquisition, M.H. ([PERSON]); L.Y. and F.G. contributed equally to this work. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Key R&D Program of China, grant number 2017 YFC0503905, National Natural Science Foundation of China, grant number 41991285 and Central Public-interest Scientific Institution Basal Research Fund, grant number BSRF201708.  
This work has been conducted under the framework of the Inter-Sectoral Impact Model Intercomparison Project (ISMIP). Our thanks go to the modelers who submitted results to this project. Weacknowledge the climate change projection team and [PERSON], who provided projected climate data of RCPs scenarios in China. The same thanks to [PERSON] and Dr. [PERSON] at the National Climate Center for very useful advice to the manuscript.