Uncertainty in Future Scenarios of N2O Emission Simulations in Agro-ecosystems in Kansas

Regional climate models (GCMs) are tools, which use climate simulations from global climate models (GCM) to simulate climatic conditions at a regional scale for several decades into the future. Ecosystem models have been useful tools for examination of possible impacts of management strategies and their impact in different climate change scenarios. This study assesses the relative uncertainties from GCMs, RCMs in modeling climate change impact on Nitrous Oxide (N₂O) emissions across Kansas, USA. Simulations of precipitation and maximum and minimum temperatures from a number of GCM/RCM combinations are obtained from North American Regional Climate Change Assessment Program (NARCCAP). These were input to Denitrification DeComposition (DNDC), an ecosystem model to obtain future simulations of N₂O. For regional modeling, the USGS level 14 hydrologic unit code boundaries (HUC14 watersheds) were used as the mapping unit. Change factors (CF) were calculated from baseline (20C3M, 1968-2000) and future (A2, 2038-2070) simulations of meteorological variables. The CFs was then applied to the historical dataset of 23 weather stations across Kansas and then applied to DNDC for a regional simulation of N2O emissions under different agricultural management practices. The uncertainties were estimated using probability distribution functions. Preliminary results indicated an increase in temperatures across the state and the rate of increase varied among the stations. In the case of precipitation, there was variability in the rate and direction of change across the state. As a result of changes in climate, N2O emissions predicted from the DNDC model was highly variable due to changes in climate and agricultural management practices.