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Cooling The Past In Illinois

April 21, 2014

By Paul Homewood





Steve Goddard has been regularly reporting how NOAA temperature adjustments have been making this winter appear less cold than it really has been.

For instance, in this post, he reports that NWS have declared December to March as the coldest 4-month period on record in Chicago. Yet, according to NOAA it is only the 4th coldest.

The State Climatological Reports have now been published for December, so we can now check individual stations in detail, and see how they stack up against NOAA’s claims.


According to NOAA, December 2013 was the 28th coldest since 1895 in Illinois.




We can drill this down into individual divisions, and the chart below is for Division 2, the Northeast Division which includes Chicago.




In this division, December 2013 ranks 21st coldest, and ties with December 1977 at 21.8F.

But how do the individual stations listed in the State Climatological Reports compare with 1977?

The Illinois Report for 1977 lists 16 stations, of which 9 are still currently reporting. The table below compares the December mean temperatures in fahrenheit for both years. I also show the airport stations and population (based on GISS).


  Airport? Population
x 1000
1977 2013 Difference
Chicago O’Hare Y 6216 24.2 23.3 -0.9
Chicago Aurora   6216 23.1 22.1 -1.0
Chicago Midway Y 6216 24.7 24.6 -0.1
De Kalb   43 21.5 19.6 -1.9
Elgin   109 20.8 21.1 +0.3
Marengo   7 21.7 19.0 -2.7
Ottawa   18 25.2 22.8 -2.4
Park Forest   22 22.5 23.3 +0.8
Peru   10 23.3 21.6 -1.7
DIVISIONAL AVERAGE     23.0 21.9 -1.1



Even including the three Chicago sites in the average, December 2013 works out as 1.1F colder than 1977, contrasting with NOAA’s claim that the two years are the same. There is also clearly a UHI effect in Chicago, where the average difference is 0.7F, as against 1.3F for the other six stations.

One would also suspect that Elgin, with a population of over 100,000 is also heavily affected by UHI. Indeed, at the two sites with 10,000 population or less, Marengo and Peru, the difference between the two years goes up to 2.2F.

(GISS use the Brightness Index to determine whether a station is rural or not. The Index ranges from 0 to 256, and they count anything of 10 or below as rural. The only site above that fits this category is Ottawa).



So where does this all leaves us? We can safely say that NOAA’s claimed temperature record for this Division is showing 2013 as at least 1.1F hotter than the individual station records justify.

Furthermore, when UHI is factored in, the true figure could be over 2F.

At this stage, someone usually waves their arms and shouts “TOBS” , or Time of Observation Bias. This can creep in when the times, that temperature readings are taken, change. NOAA adjust for this, though many meteorologists insist it is, statistically, a non issue.

But let’s test whether the TOBS adjustment can account for the difference we have identified.


Marengo is one station where the time of observation changed, from 6pm in 1977 to 7am currently, and we can use the USHCN database to find out how much allowance has been made for TOBS.

The answer is 0.8F, i.e the temperature for 1977 has been artificially adjusted down by 0.8F. So, even assuming this adjustment is justified, and that no compensating adjustment needs to be made for UHI, Marengo was still 1.9F colder last December than it was in 1977.


These discrepancies keep cropping up across the USA, as I have regularly pointed out, and it is clear that there is a fundamental flaw in NOAA’s system.

Interestingly, Steve Goddard’s calculations show that 1970’s temperatures in Illinois have been adjusted down by something like 1.5 to 2.0F, a very similar picture to the one I have found.

It is clear that NOAA’s temperature record for the US is rapidly becoming worthless.




1) State Climatological Reports are available here.

  1. William Abbott permalink
    April 21, 2014 4:54 pm

    NOAA bias is disturbing. The adjustments to summer 1936 in Nebraska accomplished the the same thing. Cooler than the archive’s historical record. The TOBS adjustments don’t account for the amount of downward adjustment. If you wanted to alter the record to make it look warmer now – this is exactly how you might do it.

    NOAA doesn’t explain how they get their new, cooler, numbers. That is the most disturbing part. No real explanation, just a new set of cooler numbers. They really owe us an explanation.

  2. April 21, 2014 6:14 pm

    Reblogged this on CraigM350.

  3. Chuck L permalink
    April 21, 2014 6:44 pm

    It is not a “fundamental flaw.” IMO, it is intentional with the goal of extending the manmade global warming/CO2 narrative as long as possible before even “adjusted” temperatures can no longer be used to deny level or falling temperatures.

  4. Mikky permalink
    April 21, 2014 9:01 pm

    In science you explain what you did to raw data and then present the results.
    In business and politics you hide what you did to get the results.

    Go figure.

  5. John F. Hultquist permalink
    April 21, 2014 9:21 pm

    Back before there was “climate science” I took a chemistry class with many laboratory hours. The Prof. required each of us to have a bound notebook. What we did and the results we got had to be written in the notebook. If we realized we did something wrong or if the instructor pointed out a problem – we did the experiment over. The pages detailing the “wrong” procedure had to be labeled as “incorrect” (if there were several pages they could be paper-clipped together) but those pages could not be removed from the notebook. We were not allowed to use a 3-ring binder (or other such thing). As scientists, we were bound to report our work – all of it.

    • William Abbott permalink
      April 21, 2014 9:44 pm

      Exactly right. Its a legal requirement too. Lab Notebooks are required for any work you do documenting pesticides during the registration process with EPA. Its the law.

  6. John F. Hultquist permalink
    April 21, 2014 9:31 pm

    Oh, see the comment under “Secret Science” by the Science and Environmental Policy Project here:

    Click to access TWTW%204-19-14%20-%20Final.pdf

    “. . . the EPA cannot produce all of the original data from . . .”

    [Now cross posted on WUWT.]

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