## 3 Results and Discussion  
### GPP Distribution and Projected Changes  
The climatological GPP distribution produced by each of the three ESMs from 1986 to 2005 is shown in Figure 1. The ESMs all produce a similar spatial pattern of GPP, showing high (low) values in the southeast (northwest) of China. Regionally, the GPP in the subtropical-tropical monsoonal zone is largest, followed in descending order by the temperate monsoonal zone, Tibetan Plateau, and temperate continental zone. The three ESMs produced comparable estimates in the climate zones except in the monsoonal regions, where CMCC-CM2-SR5 produced larger estimates, especially in the subtropical-tropical monsoonal zone. Figure 1: Climatological GPP distribution (unit: gC m\({}^{-2}\) yr\({}^{-1}\)) from 1986 to 2005 from (**a**) BCC-CSM2-MR, (**b**) CMCC-CM2-SR5, and (**c**) MPI-ESM1-2-HR. The four delineated regions represent the climate zones temperate continental (TC), temperate monsoonal (TM), subtropical–tropical monsoonal (STM), and high-cold Tibetan Plateau (TP). (**d**) Regional GPP from the ESMs (PgC yr\({}^{-1}\): petagram of carbon per year) (BCC: BCC-CSM2-MR; CMCC: CMCC-CM2-SR5; MPI: MPI-ESM1-2-HR). The bars and lines represent the standard deviation during the 20 years. The GPP change under 1.5 \({}^{\circ}\)C of global warming is shown in Figure 2. Throughout China, the GPP of all three ESMs showed a positive anomaly except over certain individual grid points. In the subtropical-tropical monsoonal with MPI-ESM1-2-HR, the negatively changed grids tend to concentrate (Figure 2e). The areal GPP reduction may be related to reduced local precipitation. However, many factors could contribute to the GPP change in addition to precipitation and temperature, such as land-use change, soil moisture, wind speed, humidity, solar radiation, nitrogen deposition, etc. Thus, it is really hard to be conclusive. Moreover, the aggregated negative grids tend to dissipate under 2 \({}^{\circ}\)C global warming (Figure 3e). The GPP change patterns differ among the models (Figure 2). For example, the largest anomaly in the output of BCC-CSM2-MR appears over the southeastern Tibetan Plateau, whereas the largest anomalies in the output of CMCC-CM2-SR5 and MPI-ESM1-2-HR appear in the central and southern parts of the subtropical-tropical monsoonal zone, respectively. The absolute GPP change is largest in the subtropical-tropical monsoonal zone; however, the relative change is rather small and stable among the models (Figure 2 right). The absolute change is smallest in the temperate continental zone owing to its low base value in GPP. The relative change is large over the Tibetan Plateau, and there are strong differences in the magnitude of the GPP increments among the different models. The GPP anomaly under 2 \({}^{\circ}\)C of global warming shows a spatial pattern similar to that found under 1.5 \({}^{\circ}\)C global warming but with a stronger intensity (Figure 3). Regional statistics indicate that the regional GPP changes will be larger under 2 \({}^{\circ}\)C of global warming. The projected increment of GPP in China under the different warming targets is consistent with previous findings [5; 7; 29]. This suggests that from the perspective of GPP, there is no ecological crisis in the projected future climate within the studied domain [3]. As with 1.5 \({}^{\circ}\)C warming, the subtropical-tropical monsoonal zone with the highest GPP value contributed the most to the increment in China's GPP under 2 \({}^{\circ}\)C of warming. However, the increase rate does not show much difference in magnitude when compared with that of other regions. It is worth noting that the rate of increase in GPP is substantial on the Tibetan Plateau--i.e., the increase is nearly 63% with regard to BCC-CSM2-MR. Thus, the Tibetan Plateau would appear to be the region most susceptible to the effects of climate warming, although the influence could be considered positive and beneficial.