This data set is distributed through the Conservation Biology Institute's Data Basin site: http://app.databasin.org/app/pages/datasetPage.jsp?id=5a1a66e950534fd095dee1a68a8c6f61
From the metadata: "This dataset shows the predicted change in average precipitation between historical (1961-1990) and future (2070-2099) time periods, simulated by the dynamic global vegetation model MC1 under the Hadley climate change projection and the anthropogenic emissions scenario A2. Change in precipitation (per ~ 8 km pixel) is depicted as a ratio of the average precipitation for 2070-2099 / the average for 1961-1990. Data values above 1 represent a projected increase in precipitation and values less than 1 represent a projected decrese in precipitation.
Background: The dynamic global vegetation model MC1 was run for the North American continent at using historical and future climate projections to simulate vegetation shifts, carbon gains and losses, hydrological flows, and wildfires. This work has not been published yet and should be considered as not peer reviewed.
Data Source Acknowledgements: PNW Research Station, Canadian Forest Service, Climate Source LLC, Oregon Climate Service, HadCM3."