KLUM@LPJ: Integrating dynamic land-use decisions into a dynamic global vegetation and crop growth model to assess the impacts of a changing climate. A feasibility study for Europe

We test the hypothesis that models should be coupled to accurately project the impacts of climate change on the agro-economic and agro-environmental system. We couple the LPJ-C global dynamic vegetation model for crops to the global agricultural land-use model KLUM. Potential crop yields, from LPJ-C, and crop prices drive the land-use decisions; cropland allocation from KLUM scale the carbon entering the soil litter pool in LPJ-C. Through the crop prices, economic effects are projected directly on the carbon cycle. Global change impacts are projected on the agricultural sector and can be economically assessed. The coupled model performs reasonably well for the observed climate and prices for 6 crops in Europe on a 0.5x0.5 longitude-latitude grid. We estimate the impact of climate change on agriculture in Europe for A1 and B2 scenarios of the IPCC. The coupled model reproduces the essential processes and interactions of the modeled system. Simulations with the uncoupled models are used to estimate the accuracy added by the model coupling. Sign and size of the biases from ignoring the feedbacks are substantial for some parameters, and particularly their spatial pattern, while for other parameters (e.g., the European total of soil organic carbon) biases are negligible. The answer to the question “Should models be coupled?” is “It depends on what you’re interested in”.