## 4 Results
### Spatial Variations in GPP
However, it can also be observed that the GPP during 2041-2060 closely aligns with that of 2021-2040, suggesting a gradual increase in the impact of the temperature and CO\({}_{2}\) on the GPP. Besides the 3000-4500 m range, changes are also noticeable in the 1000-1500 m elevation band. Under the ssp585 scenario, the range of elevation bands showing significant differences across the periods is broader. In addition to the 3000-4500 m elevation band, significant changes could be observed in the 1000-1500 m range. Although the GPP during 2041-2060 closely aligns with that of 2021-2040, under this scenario, the differences between 2061-2080 and 2041-2060 are substantially greater than those under the other three scenarios. This indicates a stronger GPP response under high-emission scenarios. However, high-emission scenarios may also have negative impacts. The differences between 2081-2100 and 2061-2080 under this scenario are smaller than those under the ssp370 scenario, suggesting that high-emission scenarios do not always favor vegetation growth. Furthermore, [PERSON]'s slope for the annual GPP during the period of 1982-2018 has been computed and is presented in Figure 9 to illustrate the spatial distribution of the GPP trends on the Tibetan Plateau. [PERSON]'s slope is used to determine the change rate for time series data [46]. The results reveal substantial spatial heterogeneity in the GPP trends across the region, which is largely attributed to variations in the climatic conditions. Over the past four decades, regions where the GPP changes passed the significance tests are predominantly located in the southeastern part of the plateau. The number of significant grid points gradually decreases from the southeast to the northwest. Notably, areas exhibiting an increasing GPP trend with statistical significance are mainly found in the Yellow River Basin and the Eastern Oilian Mountains. Conversely, regions showing a decreasing GPP trend with statistical significance are primarily located in the middle and upper reaches of the Yarlung Zangbo River, the upper Nu River, and the Qiangtang region. Overall, the Northeastern Tibetan Plateau shows an increasing GPP trend in the next few decades, whereas the GPP is decreasing along the Himalayas from the southeast to the northwest. When considered alongside Figure 7, it becomes apparent that the significant trends coincide with the spatial distribution of the GPP. Specifically, areas with higher GPP also exhibit pronounced and positive trends, indicating that productive vegetation on the Tibetan Plateau has been more responsive to climate change over the past forty years. Statistically, 43.59% of the area experienced an increasing GPP trend, while 22.31% showed a decreasing  
Figure 7: Spatial patterns of annual GPP averaged from 1982 to 2018 on the Tibetan Plateau. trend. The remaining regions exhibited no significant change. Among these, areas with a significant increasing trend account for 16.02% of the total area of the Tibetan Plateau, whereas those with a significant decreasing trend make up 3.71%. This suggests that the overall trend on the Tibetan Plateau over the last four decades has been predominantly an increase in GPP, aligning with the conclusions drawn in Section 4.2. Figure 10 illustrates the GPP trends over the 80 years from 2021 to 2100. Similar to Figure 9, only grid points where the changes passed the statistical significance tests are displayed. Under the ssp126 scenario, the majority of the Tibetan Plateau shows no statistically significant trend in the GPP. The statistical analysis reveals that only 55.39% of the grid points show significant changes, with 49.52% exhibiting an increasing trend and 5.87% showing a decreasing trend. This finding is consistent with the conclusions of Section 4.2,  
Figure 8: Average of the predicted future GPP per two decades, varying with elevation, on the Tibetan Plateau during 2021-2100 under the (**a**) ssp126, (**b**) ssp245, (**c**) ssp370, and (**d**) ssp585 scenarios.