New surface temperature analyses for climate monitoring

Global surface temperature is a critical measure of climate variation. Here the averages of a new surface-temperature analysis are compared to an estimate of the global average which has been used for monitoring surface-temperature variations at NOAA's National Climatic Data Center (NCDC) since 1998. As a replacement to the existing method, this new analysis uses improved methods that provide error estimates as well as the ability to perform analyses on finer spatial scales. Comparisons show only minor global-average differences, and the two estimates indicate essentially the same trend over the historical record, beginning in 1880. The two are most similar after about 1970, a period with a large change in the global-average temperature. The uncertainty estimates computed here account for changes in sampling and for systematic bias uncertainties. The means of the different analyses generally fall within the uncertainty estimates. The uncertainty computed here indicates that anomalies in the 19th century may not be significant, but the 20th century trends are significant.