Climate responses to vegetation greening in China and India and their combined effects

Global vegetation greening is a prominent trend, with China and India as major contributors. However, the individual and combined climatic impacts of greening in these two regions remain insufficiently understood. Based on satellite data from 1982 to 2020, we selected regions with significant greening in China and India as sensitive areas, and used a coupled land-atmosphere model (CAM6.0-CLM5.0) to simulate the biophysical climate effects under three scenarios: individual China greening, individual India greening, synergistic vegetation greening in both regions. Results show that vegetation greening in China induces a local cooling effect, accompanied by regionally heterogeneous precipitation responses, with increased precipitation over southern and northeastern China and reduced precipitation over central eastern China. In contrast, greening in India leads to local warming and a widespread reduction in precipitation. When greening occurs simultaneously in both regions, more than half of the land area exhibits climate responses consistent with the sign-consistent superposition of the individual effects. Notably, the synergistic greening produces a robust cooling and wetting response over southern China and a consistent cooling over western Eurasia, while warming dominates over northern North America. Further analysis indicates that these climate responses are associated with changes in surface energy fluxes, cloud cover, diabatic heating, large-scale atmospheric circulation, including modifications to Rossby wave propagation and the upper-level jet. Our findings highlight the role of cross-regional vegetation-atmosphere interactions and reveal the influence of low- to mid-latitude vegetation change on climate variability in northern high-latitudes.