>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.


It is based on the John Daly archived data:

and the current Contiguous U.S. surface temperature anomaly data from GISS:

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:

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:



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



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




About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
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