## 3 Results  
### Responses of NPP to 1.5 \({}^{\circ}\)C and 2 \({}^{\circ}\)C Warming  
Our results indicate the annual NPP averaged over China's terrestrial ecosystem is about 518.8 \(\pm\) 29.0 g C m\({}^{-2}\) yr\({}^{-1}\) of the two scenarios during the reference period. The annual NPP is projected to be increased to 585.9 \(\pm\) 16.7 g C m\({}^{-2}\) yr\({}^{-1}\) for 1.5 \({}^{\circ}\)C warming and 622.4 \(\pm\) 21.8 g C m\({}^{-2}\) yr\({}^{-1}\) for 2 \({}^{\circ}\)C warming. The increment of NPP is approximately 13% for 1.5 \({}^{\circ}\)C warming and 19% for 2 \({}^{\circ}\)C warming, compared with the reference period. The annual NPP of Chinese terrestrial ecosystems increases significantly (\(p<0.01\)) during the 1.5 \({}^{\circ}\)C and 2 \({}^{\circ}\)C warming periods for both RCP4.5 and RCP8.5 scenarios, but with different slopes in respect to different warming periods and different warming scenarios (Figure 1). On the national scale, the increase of NPP is greater in the 2 \({}^{\circ}\)C warming period than that in the 1.5 \({}^{\circ}\)C warming period, and the overall relative increase of NPP is about 6% with the additional 0.5 \({}^{\circ}\)C warming. Under the RCP4.5 scenario, the growth rate of NPP for the 1.5 \({}^{\circ}\)C warming period is the highest among other warming periods, and it slows down obviously in the 2 \({}^{\circ}\)C warming period. Conversely, under the RCP8.5 scenario, the increasing rate of NPP is higher in the 2 \({}^{\circ}\)C warming period than that in the 1.5 \({}^{\circ}\)C warming period. Meanwhile, the fluctuation of annual NPP in the 2 \({}^{\circ}\)C warming period is greater under the RCP4.5 scenario than that under the RCP8.5 scenario, and the standard deviation of the former is 1.5 times higher than that of the latter. The results suggest that warming increased to 2 \({}^{\circ}\)C under a lower emission scenario would not only decrease the growth rate of terrestrial NPP but also increase the annual fluctuation of NPP. Both the annual NPP averaged over the 1.5 \({}^{\circ}\)C and 2 \({}^{\circ}\)C warming periods show clear spatial patterns with obvious gradients decreasing from south to north and from east to west. The annual NPP shows an increase for the extra 0.5 \({}^{\circ}\)C warming under both scenarios; the increment of NPP is about 35.6 \(\pm\) 13.4 g C m\({}^{-2}\) yr\({}^{-1}\) under RCP4.5 and 41.1 \(\pm\) 12.4 g C m\({}^{-2}\) yr\({}^{-1}\) under RCP8.5. The increment of NPP is less in North China under RCP4.5 but higher under RCP8.5. Meanwhile, the increment of NPP is higher under RCP4.5 but less under RCP8.5 in southwest China. The spatial patterns of NPP under different future scenarios are similar to those in the reference period, and also agree with the other model simulations [8]. As shown in Figure 2, overwhelming majority areas in terrestrial ecosystems of China have an increasing trend of NPP responding to temperature rising for both the RCP4.5 and RCP8.5 scenarios under 1.5 \({}^{\circ}\)C and 2 \({}^{\circ}\)C warming, and only less than 1% of the grids show a decreasing trend of NPP. The relative increase of NPP shows the same spatial patterns under different warming targets or different scenarios, and it is greater in northwestern China than that in southeastern China. The highest increase of NPP occurred in Qinghai-Tibet Plateau and the northwestern arid regions. Comparing to southeastern China, northwestern China and Qinghai-Tibet Plateau have a lower mean annual temperature and are more sensitive to global warming. Moreover, northwestern China has a higher increase in precipitation in the future under the two scenarios. The plant growth is limited by water shortage in northwestern China and will be stimulated by increasing precipitation [45]. Figure 1: Linear fitting of annual NPP during the period of the 1.5 \({}^{\circ}\)C and 2 \({}^{\circ}\)C global warming for representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios.