Christopher Burt Can’t See The Elephant In The Room
By Paul Homewood
Watts Up With That ran the story “NOAA’s National Climatic Data Center caught cooling the past – modern processed records don’t match paper records” the other day. The story, originally posted at Jeff Masters’ Wunderground, picked up on some research by Ken Towe.
Ken had discovered that the average state temperature records used in the current trends analysis by the NCDC (National Climate Data Center) do not reflect the actual published records of such as they appeared in the Monthly Weather Reviews and Climatological Data Summaries of years past. In most cases the temperatures now used for the 1920’s and 1930’s were lower than the ones actually reported at the time. This, of course, was creating a warming trend.
Ken used the example of Arizona to illustrate.
The state-by-state climate summary for the U.S. in February 1934. It may be hard to read, but the average temperature for the state of Arizona is listed as 52.0°F From Monthly Weather Review.
However, if we look at the current NCDC temperature analysis (which runs from 1895-present) we see that for Arizona in February 1934 they have a state average of 48.9°F, not the 52.0°F that was originally published:
Christopher Burt, who is an accomplished weather historian, penned an informative explanation for what Ken had found. To quote
The basic reason for the difference is that the NCDC has begun to switch over from using what they call the ‘Traditional Climate Division Data Set’ (TCDD) to a new ‘Gridded Divisional Dataset’ (GrDD) that takes into account inconsistencies in the TCDD.
He gives a good example of why this is significant.
For instance in the example I used of Arizona in 1934: the USWB (U.S. Weather Bureau, Dept. of Agriculture) based their 52.0F state average on data from 78 sites that reported from around the state that particular month of February 1934. Of these 78 sites 3 were in the city of Phoenix (Airport, USWB site, and Indian School), 3 were in Yuma (Citrus Station, USWB, and Valley site), and 2 were in Tucson (Airport and Univ. of Arizona campus). So 8 (more than 10%) of the 78 sites for the entire state were located in three of the warmest cities in the state. Furthermore, 27 of the 78 sites were in Maricopa and Yuma counties, the two warmest counties in the state that comprise 12.6% of the state’s landmass yet account for 34.6% of the observation sites.
This, of course, is all perfectly sensible stuff, and no doubt explains most of huge discrepancy of over three degrees in Arizona. However, Burt is being, shall we say, slightly economical with the truth.
Tucked away in the technical explanation is the following
4. Finally, none of the TCDD’s station-based temperature records contain adjustments for historical changes in observation time, station location, or temperature instrumentation, inhomogeneities which further bias temporal trends (Peterson et al., 1998).”
In fact adjustments for Time of Observation (TOBS) make up the lion’s share of such adjustments, as the others tend to cancel themselves out. As WUWT makes clear, these adjustments add about a degree fahrenheit of warming between 1930 and 2010 to US temperatures.
Burt even says “The original raw data of specific weather stations has not been changed”, but this is exactly what has happened.
[Dictionary Definition of “Adjusted” – Arranged or Changed]
He then quotes Chris Fenimore’s report, which summarises the effect of the changes, “The average change in trend was about 0.06°F per century.”. This, however, is highly misleading as it averages together cooling and warming adjustments as this graph for Alabama makes clear.
The bottom graph shows the amounts by which raw temperatures have been adjusted down (blue) or up (red) during the changeover in datasets.
Temperatures from 1930-50 have been reduced by nearly a degree fahrenheit, while temperatures since 1970 have been adjusted up by up to a quarter of a degree. The total adjustment, with the pluses and minuses offsetting each other, is fairly small, but the change between 1930 and 2010 is significant.
Previous analysis has shown that the mix of stations in Alabama has had very little effect on the overall average, whereas the TOBS effect can be very clearly seen by comparing these two graphs for Valley Head, Alabama – the first being raw temperatures, the second after TOBS adjustment.
It is a pity Mr Burt did not think it important to mention this.