Cooling The Past In Illinois

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.

 

http://www.ncdc.noaa.gov/cag/

 

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

 

http://www.ncdc.noaa.gov/cag/

 

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).

 

Conclusions

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.

 

 

Sources

1) State Climatological Reports are available here.

http://www.ncdc.noaa.gov/IPS/cd/cd.html