On the interchangeability of skin and near-surface air temperature trends over land

Satellite land surface temperature (Ts) records have now reached 20+ year length, but their trends may differ from historical records built from in-situ measurements of near-surface air temperature (Tas). In the ERA5 reanalysis, 60°S—60°N land Ts and Tas trends can differ by up to ±0.06 °C decade-1 over 20 years, or more on smaller spatial scales. Here I use outputs from ACCESS1-0 simulations with prescribed land Ts to understand changes in Ts and Tas. CO2’s effective radiative forcing (ERF) causes adjustments that warm Tas relative to Ts. In ACCESS1-0, vegetation enhances the adjustments to CO2 over land, so conclusions could be affected by model land surface schemes. Over-land feedbacks in ACCESS1-0 oppose the adjustments, resulting in small long-term effects on global temperature estimates. In coupled simulations from other models, there is no agreement on which warms more and the most extreme case shows global long-term differences of just 5 % between land Ts or land Tas trends. The results contrast with over-ocean behaviour where adjustments and feedbacks drive larger long-term Tas warming relative to Ts across all models.