## 3 Results
### Dominant Meteorological Factors Driving the Projected Terrestrial GPP Variations  
The main meteorological factors governing the variations in GPP influenced by global climate change were determined through sensitivity analyses, as depicted in Figure 4. In January, Tmin and Srad dominate 66% (43%) and 34% (57%) of the study area under the SSP126 (SSP585) scenario, respectively. The regions dominated by Srad are predominantly located in southerly areas, such as the Yunnan, Guangxi, and Guangdong provinces. Notably, a transition from Tmin-dominated to Srad-dominated influence occurs primarily within the SCB, Hubei, and Hunan provinces with the exacerbation of climate change. In April, approximately two-thirds of the study area exhibited variations in GPP driven by Srad, while one-fifth was influenced by Tmin across all SSP scenarios. Regions characterized by Tmin dominance were mainly situated in westerly areas with higher altitudes. It is worth mentioning that GPP variations in Yunnan Province are primarily influenced by VPD [47]. This finding can be attributed to increased VPD reducing stomatal conductance and impeding vegetation growth under the influence of climate change [46]. Moving on to July, around 80% of the study area was governed by Srad dominance, while VPD exerted control over approximately 20%. Notably, the NCP emerged as a prominent region dominated by VPD effects aligning with previous studies, highlighting significant correlations between ecosystem productivity and air moisture levels within this region [48; 49]. Overall spatial patterns observed during April persisted in October; however, proportions of regions exhibiting Srad or VPD dominance decreased or increased correspondingly. The PER induces variations in pollutant concentrations, such as PM\({}_{2.5}\) and O\({}_{3}\), which subsequently alter the meteorological parameters influencing GPP, including Srad, Tmin, and VPD [50]. As presented in Table 3, due to a significant decrease in anthropogenic emissions, PM\({}_{2.5}\) concentrations exhibit substantial reductions across all seasons, particularly in January (\(-\)49.22 ug/m\({}^{3}\)) and October (\(-\)18.31 ug/m\({}^{3}\)). These changes are mainly concentrated in heavily polluted regions [19], such as the NCP and SCB (see Figure S3). Declines  
Figure 4: (**a–p**) Main factors cause GPP variations influenced by global climate change scenario. Pie charts indicate the proportions of the region occupied by the dominant factors. are also observed in O\({}_{3}\) concentrations but to a lesser extent ranging between \(-9.36\) ppbv and \(-2.04\) ppbv. The radiative effects of aerosol particles influence shortwave radiation reaching the surface [51; 52] and modulate air temperature and VPD [53; 54]. Increases of Srad ranging from 0.27 MJ/m\({}^{2}\) to 1.18 MJ/m\({}^{2}\) are observed among different seasons. Tmin exhibits more pronounced increases in January and October (0.15 \({}^{\circ}\)C and 0.19 \({}^{\circ}\)C) compared to April and July (only 0.06 \({}^{\circ}\)C and 0.03 \({}^{\circ}\)C). Correspondingly, more noticeable increases of VPD occur both in January and October either (22.77 Pa and 28.19 Pa), with an additional increase observed in July (16.80 Pa). Sensitivity analyses reveal that Srad is the primary driver governing variations in GPP throughout the year, with the exception of January when Tmin takes precedence. In Figure 5, it can be observed that areas dominated by Tmin account for 54% of the study area, primarily concentrated in Yunnan Province and central China in January. Conversely, Srad dominates approximately 45% of the study area, mainly encompassing the Yunnan border, SCB, and southern China. The dominance of Srad expands to cover 65%, 79%, and 54% of the study area in April, July, and October, respectively. On the other hand, proportions of areas dominated by Tmin are found to be around 19% and 25% in April and October, respectively, but negligible in July.