Effect of anthropogenic land-use and land cover changes on climate and land carbon storage in CMIP5 projections for the 21st century

This is the final version of the article. Available from the American Meteorological Society via the DOI in this record.The effects of land-use changes on climate are assessed using specified-concentration simulations complementary to the representative concentration pathway 2.6 (RCP2.6) and RCP8.5 scenarios performed for phase 5 of the Coupled Model Intercomparison Project (CMIP5). This analysis focuses on differences in climate and land–atmosphere fluxes between the ensemble averages of simulations with and without land-use changes by the end of the twenty-first century. Even though common land-use scenarios are used, the areas of crops and pastures are specific for each Earth system model (ESM). This is due to different interpretations of land-use classes. The analysis reveals that fossil fuel forcing dominates land-use forcing. In addition, the effects of land-use changes are globally not significant, whereas they are significant for regions with land-use changes exceeding 10%. For these regions, three out of six participating models—the Second Generation Canadian Earth System Model (CanESM2); Hadley Centre Global Environmental Model, version 2 (Earth System) (HadGEM2-ES); and Model for Interdisciplinary Research on Climate, Earth System Model (MIROC-ESM)—reveal statistically significant changes in mean annual surface air temperature. In addition, changes in land surface albedo, available energy, and latent heat fluxes are small but significant for most ESMs in regions affected by land-use changes. These climatic effects are relatively small, as land-use changes in the RCP2.6 and RCP8.5 scenarios are small in magnitude and mainly limited to tropical and subtropical regions. The relative importance of the climatic effects of land-use changes is higher for the RCP2.6 scenario, which considers an expansion of biofuel croplands as a climate mitigation option. The underlying similarity among all models is the loss in global land carbon storage due to land-use changes.We acknowledge the World Climate Research Programme Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups for producing and making available their model output. We thank Karl Taylor and Charles Doutriaux for help with setting up the CMOR tables for the LUCID–CMIP5 experiments. We appreciate a support by the staff of the German Climate Computing Center (DKRZ), in particular by Stephanie Legutke and Estanislao Gonzalez, in performing the LUCID–CMIP5 simulations and in making the model results available via DKRZ ESG gateway. We thank Andy Pitman and an anonymous reviewer for providing constructive and helpful comments on the manuscript. CDJ was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). EK was supported by the Environmental Research and Technology Development Fund (S-5, S-10) of the Ministry of the Environment, Japan. PF and FP were supported by the EU-FP7 COMBINE project (Grant 226520)