## 4 Discussion
### Changes in NDVI in China Under a High-Emission Scenario  
Under a high-emission scenario (such as SSP585), although global warming is projected to lead to a series of negative environmental effects, the NDVI in China's region is forecasted to increase. This phenomenon may appear counterintuitive at first glance since higher greenhouse gas emissions are typically associated with more severe ecological challenges. However, through quantifying changes in various meteorological factors and NDVI from 2023 to 2100 under different SSP scenarios, this phenomenon can be understood more profoundly. Quantification results for changes in different meteorological factors and NDVI in China's region under the SSP585 scenario during this period are shown in Figure 8, while results under SSP126, SSP245, and SSP370 scenarios are presented in Supplementary Material (Figures S8-S10). Within this timeframe, SWVL1 changes predominantly manifest as significant reductions, with nearly all (96.11%) regions showing decreased SWVL1, and only a tiny proportion (3.89%) showing an increase. TP changes are primarily positive, with the vast majority (89.74%) of regions experiencing increased TP, while about 10% saw decreases. SWR changes are also predominantly positive, accounting for about 85.9%, indicating that most regions received enhanced solar radiation, while approximately 14% experienced reduced SWR. T2m changes are almost entirely positive, with virtually all regions (99.35%) undergoing temperature increases, and only a negligible number showed slight decreases. This anomalous phenomenon likely stems from the combined effect of multiple factors. Firstly, rising temperatures could extend the growing season of plants, thereby favoring vegetation expansion and lushness [95]. Specifically, near-universal temperature increases (over 99% of regions) provide more favorable thermal conditions, prolonging the plant growth cycle. [PERSON] et al. 's study on vegetation temperature sensitivity under global warming highlights that under the SSP245 and SSP585 scenarios, vegetation temperature sensitivity shows an increasing trend, with a more significant rise under the SSP585 scenario, especially in the northern Eurasian continent and the Tibetan Plateau. In contrast, under the SSP126 scenario, vegetation temperature sensitivity increases before 2080 but starts to decline after 2080 [96]. This also confirms that under the SSP585 scenario, the rise in temperature is expected to lead to an increase in NDVI values. Secondly, elevated atmospheric CO\({}_{2}\) concentrations can enhance photosynthetic efficiency, thus boosting vegetation productivity [97]. Moreover, increased precipitation (nearly 90% of regions) might improve moisture conditions in some arid areas, supporting vegetation growth. Although RH and SWVL1 generally show decreasing trends, these adverse impacts may be compensated for or outweighed by other more favorable conditions. The enhancement of SWR (about 85.9% of regions) may also promote the photosynthesis process, further supporting vegetation growth. In summary, under the SSP585 scenario, despite facing adverse factors such as reductions in RH and SWVL1, the NDVI value in China's region is expected to rise due to the influence of increased temperatures, precipitation, and SWR. This suggests that certain aspects of climate change may temporarily promote an increase in vegetation cover under specific conditions. However, this study must consider the concept of ecosystem tipping points. Although current predictions show an overall upward trend in NDVI under the SSP585 scenario, this improvement may mask potential vulnerabilities. The response of vegetation to climate change is not a linear relationship; rather, it is constrained by resilience thresholds [98]. Once these thresholds are exceeded, the ecosystem's ability to recover from stress will significantly decline [99].