Monitoring climate change requires timely access to observations and reanalyses.
An important requirement for reanalysis is that it uses a single model version and data assimilation method, in order to produce a consistent data set for the full reanalysis period. If, in addition, the reanalysis can be continued close to real time, then it can be used to monitor changes in the climate and its variability on long time scales.
ERA-Interim is ECMWF's current atmospheric reanalysis, based on a 2006 version of the Integrated Forecast Model. ERA-Interim data are available for dates from 1979 and continues to be extended forward in time.
ERA5, produced by C3S at ECMWF, which will replace ERA-Interim, is based on a 2016 version of the Integrated Forecast Model. Eventually, ERA5 will be available for dates from 1950 and will be extended forward in time.