A reconstruction of daily weather back to 1806 puts current climate trends into historical perspective.

Historical weather reconstructions, or reanalyses, combine weather model output and observations from many sources to estimate the state of the atmosphere at a particular instant in time, over the entire globe. Reanalyses provide the context for understanding how weather and climate events and trends are changing over time and support improved prediction of future changes.

An interagency partnership between NOAA and DOE supported an updated version of the 20th Century Reanalysis Project (20CRv3), a unique high-resolution reconstruction of the global climate that uses surface observations to estimate daily weather back to 1806 on a 75-km grid. The 20CRv3 is able to accurately reconstruct individual weather events, variability in precipitation from year to year, and recent long-term trends in atmospheric temperature. The extension of 20CRv3 back to 1806 means that individual weather events and trends can now be placed into a consistent 210-year context—allowing scientists to understand, for example, how the frequency and intensity of severe winter storms are varying and changing over time.

20CRv3 is led by NOAA and the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, supported by DOE.