NCDC Introduce More Temperature Adjustments–And Guess Which Way They Go!

By Paul Homewood

 

NCDC have introduced a new method this month of calculating state, (but not national) temperatures in the US.

 

This is what they say about the old system.

 

http://www.ncdc.noaa.gov/monitoring-references/maps/us-climate-divisions.php

 

And the new system.

 

http://www.ncdc.noaa.gov/monitoring-references/maps/us-climate-divisions.php

 

It will come as no surprise to anyone, that the new system makes the past cooler again. For instance, Alabama:

 

 

http://www.ncdc.noaa.gov/temp-and-precip/divisional-comparison/

 

 

Fortunately, I did an exercise a while ago, comparing NCDC temperatures for Alabama, with the original State Climatological Reports. Therefore we can directly compare the old and new systems.

The temperatures used in that exercise relate to November 1934 & 2011.

 

 

	Nov 1934	Nov 2011	Difference
NCDC Before	57.0F	55.5F	1.5F
NCDC After	55.8F	55.3F	0.5F
Difference	–1.2F	-0.2F	-1.0F

 

So the changeover has resulted in a reduction of 1934 temperatures, relative to 2011, of 1.0F. This is consistent with the above graph.

The old and new versions of Alabama temperatures can also be seen below, (the first being the old version taken from my post at the time). Notice how the trend has increased.

 

https://notalotofpeopleknowthat.wordpress.com/2012/06/08/ncdc-cooling-the-past-again/

 

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

 

My analysis of USHCN stations in Alabama, in the above mentioned exercise, suggested that the state temperature, under the old system, was already understating 1930’s temperatures, and consequently overstating warming trends. The latest tranche of adjustments have now added to that cooling of the past.

 

It needs to be restated that the national figures remain, to all intents and purposes, unaffected. This is because they were already calculated under the new system. This now explains why a weighted national average, calculated from NCDC’s own State figures, showed higher temperatures for 1934 than the national figure given by NCDC. When I looked at it last year, I reckoned that this extra set of adjustments added 0.4F to the warming since 1934.

 

NCDC, at least, provide a tool, which enables you to look at the changes made under the new system,which gives the graph which I showed above for Alabama. You can see just how much they are adjusting past temperatures downwards, by State or Region. It is accessible here . Go play!