## 4 Results
### Temporal Variation in GPP  
Figure 5 illustrates the historical changes in the annual GPP and the projected future changes under four SSP scenarios on the Tibetan Plateau. It indicates a significant increasing trend in the annual GPP during the historical period, which continues, albeit at a more gradual pace. Moreover, the rate of increase is projected to escalate as the forcing levels intensify in future scenarios. Statistical analysis (Table 3) reveals that, between 1982 and 2018, the average annual GPP on the Tibetan Plateau was 363.80 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), with a growth rate of 1.033 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\). In the period from 2021 to 2060, the projected average annual GPP under the ssp126, ssp245, ssp370, and ssp585 scenarios is 384.908 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), 385.319 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), 385.493 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), and 386.368 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), respectively. Compared to the baseline period of 1982-2018, the growth rates are 5.74%, 5.85%, 5.90%, and 6.15%. By the period from 2061 to 2100, these average values are expected to increase to 388.321 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), 394.338 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), 398.535 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), and 401.293 g C\(\cdot\)m\({}^{-2}\cdot\)year\({}^{-1}\), resulting in growth rates of 6.68%, 8.33%, 9.48%,  
ssp370 scenario, the annual GPP growth rate is 0.355 g C-m\({}^{-2}\)-year\({}^{-1}\) before 2060, rising to 0.375 g C-m\({}^{-2}\)-year\({}^{-1}\) from 2061 to 2100. These findings highlight the varying impacts of different socioeconomic pathways on the GPP, with more aggressive scenarios resulting in greater changes in GPP over time. In the ssp585 scenario, characterized by fossil-fuel-driven development, the GPP growth rate is projected to be 0.401 g C-m\({}^{-2}\).year\({}^{-1}\) from 2021 to 2060, followed by a significant decline to 0.325 g C-m\({}^{-2}\).year\({}^{-1}\) after 2060. These findings suggest that scenarios with lower forcing levels, such as ssp126 and ssp245, exhibit lower GPP growth rates after 2060 compared to the preceding period. Conversely, scenarios with higher forcing levels, such as ssp370, indicate an increase in the GPP growth rates after 2060, with the exception of ssp585. This phenomenon suggests that higher temperatures and levels of CO\({}_{2}\) emissions, coupled with more frequent extreme weather events such as droughts, could have adverse effects on plant growth [28]. Although ssp370 also involves elevated CO\({}_{2}\) emissions, the temperatures in high-altitude regions may not yet reach the critical thresholds that inhibit plant growth. In contrast, under ssp585, higher temperatures are likely to negatively impact plant growth. In short, the annual GPP is expected to significantly increase throughout the 21 st century under all future climate scenarios. The statistical analysis reveals that, between 2021 and 2100, the average uncertainty interval for the annual GPP on the Tibetan Plateau is 21.301 g C-m\({}^{-2}\).year\({}^{-1}\), 30.428 g C-m\({}^{-2}\).year\({}^{-1}\), 22.326 g C-m\({}^{-2}\).year\({}^{-1}\), and 24.684 g C-m\({}^{-2}\).year\({}^{-1}\) under the ssp126, ssp245, ssp370, and ssp585 scenarios, respectively. Overall, the uncertainty interval will increase with the increase in CO\({}_{2}\) emissions, and the uncertainty interval in the ssp245 scenario is significantly larger. Figure 6 illustrates both the historical seasonal GPP from 1982 to 2018 and the projected seasonal GPP from 2021 to 2100 under the four SSP scenarios. The data reveal pronounced seasonal patterns in the GPP. The GPP shows the most significant increase in summer, while there is essentially no change in winter, and it even gradually decreases.