Hybrid Delta Ensembles

Because downscaled climate data provides 234 climate projections that vary from one another it is necessary to provide a statistically reliable means of sorting them and determining average change factors that can be used for climate prediction. To do this the Climate Analysis Toolkit analyzes two ranges of climate data for each of the 234 projections (one from the past years and one from future years) and calculates averages changes between them. Once these changes have been recorded the toolkit creates 5 groups of projections or ensembles that are statistically relevant. Each ensemble contains 10 projections and correlates to an intersecting range of temperature and precipitation change.  Each projection within an ensemble is a nearest neighbor to this statistical intersection.  An average change factor is then calculated from each ensemble to provide 5 climate scenarios which are Wamer/Drier, Wamer/Wetter, Hotter/Drier, Hotter/Wetter and Median. The Table below shows these scenarios and their corresponding percentiles. 

 

 

The projections are plotted on graph showing average change in temperature between the two time periods versus average percentage change in precipitation between the two time periods.  The intersections of the specified percentile ranges represent the point from which nearest neighbor ensembles are calculated. A visual representation of the plotted projections is shown below.