This is a guest post by Jerry Lundry
Two plots are presented for annual average temperature in the United States Historical Climate Network (USHCN). This data set is highly regarded by some in climate science and is sometimes used as a surrogate for world-wide temperatures. Among its attributes are its coverage of a large land mass (the forty-eight contiguous United States), dense coverage of that land mass (1218 stations), and records that are complete to 1912 and missing only about eighty stations back to 1895. Temperatures for all stations are also provided for 1908.
In 2012, the author downloaded and produced annual average temperatures for this data set. The first figure below provides average annual temperatures for 1908 and 1912-2011. The curve faired through the data is a standard Excel sixth-order polynomial. This curve shows minima in years 1914 and 1970, and maxima in years 1940 and 2004, give or take a year or two.