ERA-20C is a climate reanalysis dataset covering the period 1900 to 2010.
ERA-20C assimilates observations of surface pressure and surface marine winds only. It is an outcome of the ERA-CLIM project.
For further details please see the ECMWF product page.
Also of interest: ERA-20C: ECMWF's atmospheric reanalysis of the 20th century (and comparisons with NOAA's 20CR)
Currently there are no known issues with ERA-20C.
Data is archived at ECMWF and available for download from ECMWF data services.
Poli, P., H. Hersbach, D.P. Dee, P. Berrisford, A.J. Simmons, F. Vitart, P. Laloyaux, D.G. Tan, C. Peubey, J. Thépaut, Y. Trémolet, E.V. Hólm, M. Bonavita, L. Isaksen, and M. Fisher. ERA-20C: An Atmospheric Reanalysis of the Twentieth Century, Journal of Climate, 2016, 29:11, 4083-4097, Doi: 10.1175/JCLI-D-15-0556.1
Some ERA-20C references available from the ECMWF E-Library.