Temperature Records in Illinois

The CRU team used a station called Chicago/O'Hare for that windy city that has grown rapidly over the last century.  This no doubt  means that the recording was first in the city and then moved to O'Hare Airport.  CRU made two adjustments to Chicago.

Check the Satellite UHI Images from the main page to see the very large UHI signature for Chicago.  How much does this signature mean in degrees?  To find out, we compare the record with three nearby rural stations from the GHCN dataset.  The graphic below displays the differences between Chicago and Brodhead, Galva and Hooperstown.

All three lines show the Chicago record warming up compared to its rural neighbours from 1910 to ~1970.  Early in the 1970's comes a cooling step in Chicago, possibly due to a move to O'Hare.

Since all four stations are near neighbours sharing the same general climate, the differences should be a "zig zag" horizontal line.  The zig zags happen because even in close stations the annual temperature numbers are never perfectly in step.  But creeping non-climatic warming or cooling in the central station will result in the differences taking on a slope - as we see clearly here from 1910-1970.

The next graph down shows how Peoria is subject to the same sort of warming creep as Chicago.  Peoria,  a much smaller center south of Chicago, was also adjusted by the CRU team to be slightly cooler up to 1943.  The graph compares it with four rural stations in the same area, taken from the GHCN database.  Note how the heavy red trace for Peoria starts off low down in the skein of temperature traces, but gradually works its way through the pack until it finishes near the top.

Looking below at the differences produced by subtracting the four rurals in turn from Peoria,  we see a steady warming in Peoria, of roughly the alleged magnitude of “global warming”.  If you just eyeball the scale in Celsius you can estimate the warming indicated in Peoria for yourself.  Close inspection also suggests a cooling step down in Peoria around 1960 and a warming step up around 1980.

And Peoria is just a little place.  Check the Satellite UHI Images from the main page to see its small UHI signature.  But even a small heat island like that of Peoria still produces data contamination comparable with the claimed rate of “global warming”.

Originally posted mid 2000
Re-written 9, June, 2001

© Warwick Hughes, 2000

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