Assessing climatic impacts of future land use and land cover change projected with the CanESM2 model

To demonstrate the importance of land use and land cover change (LUCC) on future climate projections, the CanESM2 model experiments recommended by the LUCID project were used. Four fully coupled simulations were performed: with and without LUCC for two scenarios (RCP2.6 and RCP8.5). Model results show that the global LUCC effects are very small because of offsetting regional signals. Future global land-use emissions due to LUCC in the two scenarios are estimated to be 35.7 and 32.1 Pg C, respectively. The largest regional responses are directly associated with the land cover conversion in the tropics and subtropics. As the albedo effect dominates in mid- and high-latitudes, LUCC produces a small cooling or little effect in the western United States and Eurasia as a result of the reduction in needleleaf evergreen trees. LUCC increases temperature by 0.05-0.1 degrees C in the tropics due to the reduction in evapotranspiration because of the conversion from rainforests to croplands. When compared with greenhouse gases (GHGs) and aerosol influences, LUCC has a second-order effect on the temperature change at the global scale. However, for the CO2 fluxes, the LUCC and GHG/aerosol effects are equally important and the former is much stronger than the latter over some regions such as Africa and South and North America. The land-atmosphere CO2 flux can be regionally modulated by LUCC when compared with the effects of GHG/aerosol forcings. Although there is no significant land cover change in higher latitudes, climate responses to LUCC occur over boreal and arctic regions, indicating that atmospheric teleconnection can modify regional climate far away from the areas with LUCC. These results highlight the need to understand the responses of carbon cycle and remote climate to LUCC over longer time scales.