Investigating the biogeophysical impacts of land cover change on future climate
Monday, 15 December 2014
Land use plays an important role in determining terrestrial–atmosphere mass and energy exchange, which in turn influences local to global climate. The CMIP5 project used “land use harmonization” to provide land use input for Earth System Model (ESM) simulations, but did not address numerous climate and carbon-cycle inconsistencies between Integrated Assessment Models (IAMs) and ESMs. Our new approach to reducing such inconsistencies is to integrate an IAM (Global Change Assessment Model) and an ESM (Community Earth System Model) into the first fully coupled model that directly simulates human–environment feedbacks. The resulting Integrated Earth System Model (iESM) is used to investigate the biogeophysical impacts of land cover change (LCC) at regional and global scales under RCP4.5 scenario. Regions with significant LCC differences between the coupled (predicted LCC with climate feedback) and control (prescribed LUC without climate feedback, CMIP5 style) runs include large portions of Europe, United States, eastern China, India, Indonesia and Brail at the end of 21st century. The model results suggest that the LCCs have little impact on globally averaged climatic variables (e.g., 2m temperature is -0.004 K cooler in the coupled simulation compared to control simulation with prescribed LCC). Within some of the regions with significant LCCs, there are relatively large changes o f selected climatic variables, but most are not statistically significant in the local annual mean (e.g., the reduction of precipitation is large as -0.115 mm/day over Southeast China, but not significant). Conversely, within some regions with small LCCs, there are relatively large and significant model changes (e.g., significant changes for precipitation, ET, LH, and net radiation appear over Tigris Euphrates). On the basis of our model experiments, it is important to consider the two-way feedbacks between the climate and LCC for projecting future climate, particularly at regional scales.