Data Sources

Global Climate Models

A Global Climate Model (GCM) is a type of General Circulation Model that focuses on projections of climate change by simulating how Earth’s physical processes respond to increasing greenhouse gas concentrations. Research groups worldwide develop GCMs for use in periodic climate assessment reports published by the United Nations Intergovernmental Panel on Climate Change (IPCC). GCM outputs help form the basis for many interpretations of future climate. The IPCC Fifth Assessment Report (AR5) was published in 2014.

For statistical and dynamical downscaling, SNAP uses:

  • CMIP3 model outputs from the IPCC’s Fourth Assessment Report (AR4). Outputs include the first ensemble model run under climate scenarios 20c3m, B1, A1B, and A2
  • CMIP5 model outputs from the IPCC Fifth Assessment Report (AR5). Outputs include the first ensemble model run under historical and RCP 4.5, 6.0, and 8.5 climate scenarios

Source: Lawrence Livermore National Laboratory Program for Climate Model Diagnosis and Intercomparison data portal.


Parameter elevation Regression on Independent Slopes Model (PRISM) data are some of the highest resolution spatial climate data currently available across large extents. SNAP uses PRISM temperature and precipitation data from the North and other regions as the baseline climatology in its delta downscaled products. For statistical downscaling, SNAP uses:

  • temperature and precipitation data from the 30-year (1961–1990) monthly climatology at 2-km spatial resolution covering Alaska and regions of Canada
  • 771-m spatial resolution data from 1971–2000 covering only Alaska
  • other PRISM datasets for specific projects

Climatic Research Unit (CRU)

The University of East Anglia’s Climatic Research Unit (CRU) provides monthly climate data from thousands of terrestrial and marine temperature stations. SNAP uses CRU TS data and CRU CL high resolution climatology data in our delta downscaled products.

European Reanalysis (ERA)

The European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis produces global numerical weather forecasts for users worldwide. SNAP uses ERA-40 for model selection methods and ERA-Interim for dynamical downscaling work.