According to the National Climatic Data Center (NCDC),, covered here, a new Beta version of the U.S. Historical Climatology Network will be released next year. They say that the new data set uses

“recent scientific advances that better address uncertainties in the instrumental record. Because different algorithms were used in making adjustments to the station data which comprise both data sets, there are small differences in annual average temperatures between the two data sets. These small differences in average temperatures result in minor changes in annual rankings for some years”.

One of these “minor changes” reverses the order of 1934 and 1999, with the relative change amounting to 0.45 deg F. And, in fact, the new changes are on top of some other puzzling changes which had already moved 1999 well up the league table.

Here’s the top part of the table comparing the top series in the two versions:

USHCN V1 USHCN Version 2 undergoing

beta testing 1. 2006 55.01 1998 55.09 2. 1998 54.94 2006 54.95 3. 1934 54.91 1999 54.61 4. 1999 54.53 1934 54.54 5. 1921 54.49 1921 54.37 6. 1931 54.34 1990 54.37 7. 1990 54.24 2001 54.35 8. 2001 54.23 2005 54.28 9. 1953 54.18 1931 54.20 10. 1954 54.13 1953 54.10

Contemporary Reporting

But even the USHCN V1 data shown here has already been adjusted substantially from contemporary reports. First here is a report from August 1999 on the 1998 annual results. Hansen stated:

The U.S. has warmed during the past century, but the warming hardly exceeds year-to-year variability. Indeed, in the U.S. the warmest decade was the 1930s and the warmest year was 1934.

Here is a graphic from the news release – I’ve been unable to locate a digital version of this dataset. In this image, the 1934 temperature is almost half a degree C (C not F) warmer than 1998, which was not even in second place.



From Hansen 1999 News Release.

Next, a contemporary account of 1999 said that it was the approximately the 10th warmest year:

The temperature in the United States was also warm, about 0.7°C above the 1951-1980 average (Figure 3). 1999 was approximately the 10th warmest year of the century. The warmest years in the United States occurred during the dust bowl era, with 1934 being the warmest year.

However, in the table shown above, 1999 had moved into 3rd place (in the 20th century standings) in USHCN V1 and then continued its retrospective advance up the league table by vaulting into 2nd place in USHCN V2 Beta. And to think that only 7 years, it ranked in 10th place.



