Evaporative cooling exceeded albedo-induced warming in greening areas of global drylands

Greening plays a key role in surface-atmosphere energy exchanges, exerting feedback on the climate. While several studies have examined greening feedback in forested regions, the effect on temperature feedbacks in global drylands remain poorly understood. In this study, we used a combination of satellite and reanalysis data to examine the global dryland greening trends over the past two decades and assessed the changes in the biophysical properties. Results show that the greening-induced changes in surface albedo affected net shortwave radiation; however, evapotranspiration linked to changes in soil moisture dominated the temperature feedback, accounting for approximately 54-83% of the feedback signal. This dominance was most pronounced for daytime surface temperature, where the evapotranspiration effect was up 66% more than that of surface albedo. Significant greening was associated with a decrease in daytime surface temperature of 0.53 and 0.8 °C/decade, while significant browning was associated with an increase of 0.86 and 1.32 °C/ decade. Although greening was significant over the global drylands, soil moisture availability strongly controlled evapotranspiration and its contribution to temperature feedback. As dryland continues to warm, moisture availability is important for plant functioning, which impacts the regional climate through surface and atmosphere feedback and, therefore, the sustainability of drylands.