Biophysical Impact of Land Use and Land Cover Change on Subgrid Temperature in CMIP6 Models

In this study, we investigate the air temperature response to land use and land cover change (LULCC; cropland expansion and deforestation) using subgrid model output generated by a set of CMIP6 model simulations. Our study is motivated by the fact that ongoing land use activities are occurring at local scales, typically significantly smaller than the resolvable scale of a gridcell in earth system models. It aims to explore the potential for a multi-model approach to better characterize LULCC local climatic effects. On annual scale, the CMIP6 models are in general agreement that croplands are warmer than primary and secondary land (psl; mainly forests, grasslands and bare ground) in the tropics and cooler in the mid- to high latitudes, except for one model. The transition from warming to cooling occurs at approximately 40°N. Although the surface heating potential, which combines albedo and latent heat flux effects, can explain reasonably well subgrid temperature variations between crop and psl tiles in the historical simulations, it does not provide a good prediction on subgrid temperature for other land tile configurations (crop versus forest; grass versus forest) under SSP5-8.5 forcing scenarios. A subsect of simulations with the CESM2 model reveals that subgrid temperature variation is positively related with variation in net surface shortwave radiation and negatively related with variation in the surface energy redistribution factor, with a dominant role from the latter south of 30°N. We suggest that this emergent relationship can be used to benchmark the performance of land surface parameterizations and for prediction of local temperature response to LULCC.