Contiguous U.S. GISTEMP Linear Trends: Before and After

Many of us have seen gif animations and blink comparators of the older version of Contiguous U.S. GISTEMP data versus the newer version, and here’s yet another one. The presentation is clearer than most.

http://i44.tinypic.com/29dwsj7.gif

It is based on the John Daly archived data:
http://www.john-daly.com/usatemps.006

and the current Contiguous U.S. surface temperature anomaly data from GISS:
http://data.giss.nasa.gov/gistemp/graphs/Fig.D.txt

In their presentations, most people have been concerned with which decade had the highest U.S. surface temperature anomaly: the 1940s or the 1990s. But I couldn’t recall having ever seen a trend comparison, so I snipped off the last 9 years from current data and let EXCEL plot the trends:
http://i44.tinypic.com/295sp37.gif

Before the post-1999 GISS adjustments to the Contiguous U.S. GISTEMP data, the linear trend for the period of 1880 to 1999 was 0.035 deg C/decade. After the adjustments, the linear trend rose to 0.044 deg C/decade.

Thanks to Anthony Watts who provided the link to the older GISTEMP data archived at John Daly's website in his post here:

http://wattsupwiththat.com/2009/06/28/an-australian-look-at-ushcn-20th-century-trend-is-largely-if-not-entirely-an-artefact-arising-from-the-%e2%80%9ccorrections%e2%80%9d/

CORRECTION

Anthony Watts has advised that the thanks should go to Michael Hammer who wrote the original post at Jennifer Marohasy's website:

http://jennifermarohasy.com/blog/2009/06/how-the-us-temperature-record-is-adjusted/

UPDATE

In the thread at WUWT, Steve McIntyre of ClimateAudit provided links to his posts from a couple of years ago:

http://www.climateaudit.org/?p=1142

http://www.climateaudit.org/?p=1139

http://www.climateaudit.org/?p=1891