报告题目：

Abstract: This lecture discusses the sampling error variances of gridded monthly US Historical Climatology Network Version 2 (USHCN V2) time-of-observation bias (TOB) adjusted data. Our analysis of mean surface air temperature (SAT) assesses uncertainties, trends, and the rankings of the hottest and coldest years for the contiguous United States in the period of 1895-2008. Data from the USHCN network stations are aggregated onto a 2.5x3.5deg latitude-longitude grid by an arithmetic mean of the stations inside a grid box. The sampling error variances are smaller (mostly less than 0.2 (deg C)^2) over the eastern US where the station density is greater, and larger (with values of 1.3 (deg C)^2 for some grid boxes in the earlier period) over mountain and coastal areas. In the period of 1895-2008, every month from January to December has a positive linear trend. February has the largest trend of 0.162 deg C /decade, and September has the smallest at 0.020 deg C/decade. The three hottest (coldest) years measured by the mean SAT over the US were ranked as 1998, 2006, and 1934 (1917, 1895, and 1912).