Discrepant decadal trends in global land-surface and air temperatures controlled by vegetation biophysical feedbacks

Satellite-based land surface temperature (Ts) with continuous global coverage is increasingly used as a complementary measure for air temperature (Ta), yet whether they observe similar decadal trends remains unknown. Here, we systematically analyzed the trend of the difference between satellite-based Ts and station-based Ta (Ts–Ta) over 2003–2018. We found the global land warming rate based on Ts was on average 56.7% slower than that on Ta (Ts–Ta trend: -0.0166℃ yr^-1, p<0.01) during daytime of boreal summer. This slower Ts-based warming was attributed to recent Earth greening, which effectively cooled canopy surface through higher evapotranspiration and turbulent heat transfer. However, Ts showed faster warming than Ta during boreal summer nighttime (0.0159℃ yr^-1, p<0.01) and boreal winter daytime (0.011℃ yr^-1, p=0.14), when vegetation activity is limited by temperature and radiation. Our results indicate potential biases when using Ts in assessments of atmospheric warming and the vegetation-air temperature feedbacks.