 This work has often been used as a foundation for reconstructing past global temperatures, and was used in previous versions of two of the best-known reconstructions, that prepared by the National Climatic Data Center (NCDC), and that prepared by NASA as its Goddard Institute for Space Studies (GISS) temperature set.The average temperature record is 60 years long with ~1650 records greater than 100 years and ~220 greater than 150 years (based on GHCN v2 in 2006).The earliest data included in the database were collected in 1697.