Climate change can affect agricultural production and soil and water conservation. The potential for global climate changes to increase the risk of soil erosion is clear, but the actual damage is not. The objectives of this study were to develop a method for downscaling monthly climate forecasts to daily weather series using a climate generator (CLIGEN), and to determine the potential impacts of projected mean and variance changes in precipitation and temperature on soil erosion and wheat (Triticum Aestivum L.) yield. Monthly forecasts for the periods of 1950-1999 and 2056-2085 for the Oklahoma region, projected by a general circulation model (HadCM3), were used. Projected mean and variance changes in precipitation and temperatures between the two periods were satisfactorily incorporated into CLIGEN input parameters derived for the El Reno station, Oklahoma, and future transitional probabilities of precipitation occurrence were estimated as a linear function of historical monthly precipitation. Five climate change scenarios were constructed, and the Water Erosion Prediction Project (WEPP) model was run for each combination of five climate scenarios and three tillage systems. A 50% increase in CO2 resulted in some 26% increase in wheat yield. At that elevated CO2 level, projected decrease in total precipitation decreased surface runoff, soil loss, and wheat yield. However, predicted changes in precipitation variance increased runoff by 15 to 17%, and increased soil loss by 110 and 19% under conservation and conventional tillage, respectively. Predicted increase in mean temperature reduced wheat yield by 31%, and increased soil loss by 40 and 19% under conservation and conventional tillage, respectively. Under the assumed climate change, predicted average soil loss under conventional tillage was about 2.6 times that under conservation tillage and 29 times that under no-till. With all changes considered, predicted average wheat yield during 2056-2085, compared with the present climate at the present CO2 level, would decrease by 12%; runoff would increase by <7%; and soil loss would increase by <8% in all tillage systems. Overall results indicate that adoption of conservation tillage and no-till will be effective in controlling soil erosion under projected climate change used in this study.
