## 3 Results
### Sensitivities of Vegetation Changes to Climate Factors Across Global Drylands  
#### 3.2.1 Sensitivities of Vegetation Growth to Changes in CO2, SW, and VPD  
Since the early 1980s, increased atmospheric and SW stress on ecosystem production has been occurring in drylands worldwide under global warming (Figure S3 in Supplementary Section S3.1). As a response, despite precipitation in global drylands showing a significant increasing trend with great interannual fluctuations (Figure S3d), SW content has gradually decreased at different depths of 0-7, 7-28, 28-100, and 100-289 cm over the past 37 years (Figure S3b). Atmospheric VPD has continuously increased during 1982-2018, and this upward trend has become more rapid since the early 2000s (Figure S3c). Undoubtedly, there are notable regional disparities in the patterns of the interannual trends of these climatic elements in worldwide drylands (Figure S4, Table S1 in Supplementary Section S3.2), where VPD is highly complementary with SW at varying depths, that is, an increase in VPD occurs when SW decreases at different depths and vice versa (Figure S4a,b). Not surprisingly, the patterns in the interannual trend of SW exhibited a spatial consistency among different soil  
Figure 2: Future trend in long-term series of LAI and GPP in global drylands from 2019 to 2100 derived by 22 ESMs from the CMIP6 projects across different SSP scenarios. (**a**) LAI, (**b**) GPP. depths during 1982-2018, as SW at four soil depths showed a decreasing trend in more than 65% of global drylands (Figure S5, Table S2 in Supplementary Section S3.2). Further, this study analyzed the sensitivities of annual LAI changes to CO\({}_{2}\), SW, and VPD in global drylands during 1982-2018, as shown in Figure 4. Results showed that vegetation growth was positively sensitive to CO\({}_{2}\) concentration and SW in most of the study areas, while negatively sensitive to VPD in most regions from 1982 to 2018. Specifically, vegetation growth was positively sensitive to increasing CO\({}_{2}\) concentration in global drylands from 1982 to 2018, with the positive sensitivity in 59.11% of grid cells reaching a statistical significance level (\(p<0.05\)) (Figure 4a). The high positive sensitivity of vegetation growth to CO\({}_{2}\) is mainly covered in the middle-latitude regions of the northern and southern hemispheres (Figure 4b). Additionally, this study found that vegetation growth tended to be positively sensitive to SW in most parts of global drylands, accounting for approximately 86.36% of the total study areas, with the positive sensitivity in 62.36% of regions reaching a 95% confidence interval (\(p<0.05\)). However, only 13.64% of grids showed the negative sensitivity of vegetation growth to SW, in which the negative sensitivity in 2.95% of the total areas passed the significance level (\(p<0.05\)) (Figure 4c). The regions with a high sensitivity occurred in middle-latitude regions, especially in the southern hemisphere (Figure 4d). In terms of VPD, most regions exhibited extensive negative sensitivity of vegetation growth to increasing VPD, mainly situated in most parts of Australia, the Sahel region, western Asia, and western North America, accounting for approximately 66.16% of the total study areas, and the sensitivity in 37.39% of regions reached up to the selected 95% significance level. Correspondingly, 33.84% of grid cells showed the positive sensitivity of LAI changes to VPD, distributed in the Sahel region and middle- and high-latitude  
Figure 3: Spatial distribution of interannual trend for vegetation greenness and productivity from different satellite-observed indexes during the period of 1982–2018 is separately presented in (**a**) averaged LAI trend from three LAI datasets, (**b**) latitude difference in LAI trend, (**c**) averaged GPP trend from three GPP datasets, (**d**) latitude difference in GPP trend, (**e**) GOSAT SIF trend from 2000 to 2018, and (**f**) latitude difference of SIF trend.