An Update of U.S. Temperature Trends

This note updates the temperature trend study of the contiguous 48 United States by Lund et al. for data observed during the 4-yr period 1997–2000. A parsimonious changepoint parameterization is now used, and the methods for handling missing data are improved. The number of stations with useable data has now increased from 359 to 969, thereby improving the accuracy of the reported spatial patterns in the trends. The average record length of the 969 stations is now 103 yr, with the longest record starting in 1812 and the shortest in 1926. The methodological improvements and additional 4 yr of data produce slightly smaller trend estimate standard errors. Warming is found in the Northeast, West, and northern Midwest, with slight cooling in the Southeast; overall, the trends here suggest more warming than those of the Lund et al. study.