Climate Scenarios for the Fourth National Climate Assessment and the Sustained Assessments Process

An overview of scenarios development for the Fourth National Climate Assessment (NCA4) will be presented.  A decision was made early on that the CMIP5 suite of climate model simulations would form the foundation for climate scenarios for the NCA4.  Scenarios are also being developed using the latest version of the Localized Constructed Analogs (LOCA) statistically downscaled CMIP5 climate projections for North America.  Examples being derived from the LOCA data sets include counts of days exceeding various threshold temperatures (e.g. 90F, 99^th percentile) and precipitation amounts (e.g. 2 inches), annual maximum and minimum temperature and precipitation, growing season length, degree days (heating, cooling, and growing), and number of consecutive wet and dry days.  In addition, a model weighting scheme is being considered that will weight the CMIP5 model simulations according how well they reproduce the current climate, and how independent each model is from the others in the CMIP5 suite.