What version of the GHCN-M analysis is currently being used?
Effective May 2, 2011, the GHCN-M version 3 dataset of monthly mean temperature replaced GHCN-M version 2 monthly mean temperature dataset. Beginning with the April 2011 State of the Climate Report, GHCN-M version 3 will be used for NCDC climate monitoring activities, including calculation of global land surface temperature anomalies and trends. It will also be merged with the Extended Reconstruction Sea Surface Temperature (ERSST) version 3b dataset to form the merged land and ocean surface temperature dataset, which is used to calculate the global average temperature from 1880 to present. For more detailed information, please see: Summary of Recent Changes in the GHCN-M Temperature Dataset and Merged Land-Ocean Surface Temperature Analysis.