Discrepant 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 temporal trends remains unknown. Here, we systematically analyzed the trend of the difference between satellite-based Ts and station-based Ta (Ts-Ta) over 2003-2022. We found the global land warming rate inffered from Ts was on average 42.6% slower than that from Ta (Ts-Ta trend: -0.011 degrees C yr(-1), p = 0.06) during daytime of summer. This slower Ts-based warming was attributed to recent Earth greening, which effectively cooled canopy surface through enhancing evapotranspiration and turbulent heat transfer. However, Ts showed faster warming than Ta during summer nighttime (0.015 degrees C yr(-1), p < 0.01), winter daytime (0.0069 degrees C yr(-1), p = 0.08) and winter nighttime (0.0042 degrees C yr(-1), p = 0.16), when vegetation activity is limited by temperature and solar radiation. Our results indicate potential biases in assessments of atmospheric warming and the vegetation-air temperature feedbacks using satellite-observed surface temperature proxies.