Thermal buffering of forest greening across spatiotemporal scales in China

Pronounced forest greening is observed in China due to national ecological restoration. However, the biophysical effects of forest greening on local thermal environment in China across different spatiotemporal scales have not yet been assessed. By integrating multiple satellite datasets with land surface model simulations, we show that in the past two decades (2001-2020), approximately 97% of forested areas in China exhibited an overall greening trend of 0.352m²m^-2decade^-1. Forest greening in China exerted a daily cooling effect of 0.146°C/decade on more than 98% of forested areas through biophysical processes, which intensified with decreasing latitude. The competition among changes in shortwave radiation (SW), latent heat (LE), and sensible heat (H) induced by forest greening is the primary biophysical processes influencing surface temperature. On an annual scale, the contributions of LAI-induced changes in SW, LE, and H to LST variations averaged 6.31%, 47.87%, and 43.42%, respectively. The LAI changes dominated the annual mean surface temperature change of needle forests through H change, and the LAI changes dominated the annual mean surface temperature change of deciduous broadleaf forests through LE change. The dominant process of LAI changes in evergreen broadleaf forests affecting annual mean surface temperature depended on the difference in effect intensity of H changes in autumn and winter and LE changes in spring and summer. We highlight the need for sustainable forest restoration for thermal buffering against climate change.