This grant will support and enhance the Community Climate System Model (CCSM) by developing several anthropogenic impact scenarios. Scenarios will be developed to simulate large-scale impacts of urbanization and soil degradation, intended for use in CCSM. Specific goals of the project include the development of new urban landuse classes for use in the CCSM's Land Surface Model (LSM). Urban and suburban landuse class will be developed for LSM using parameters estimated from the urban climatology literature. To simulate urban areas extent over time, the PIs will develop a population density database from 1750 to 2050. A new 1 km resolution human population density database will be used along with past and future population estimates from UN and historical data sources. Urban extent will then be estimated from population density maps. In addition, the population density database will be used along with the UNEP/GRID soils degradation database to develop a time series of human impacts on soils from 1750-2050. This database will be used to alter soil water holding capacities over time in LSM and will be used to simulate the impacts of soil degradation on global scales.