Guest Essay By Walter Dnes

There is much interest in the latest temperature anomaly adjustments by NOAA/NCEI (formerly known as NOAA/NCDC). This author has been downloading NOAA monthly temperature anomaly data since 2010. The May 2015 adjustment is not the only one. There appear to have been 8 adjustments between November 2010 and May 2015. Assuming that these changes are legitimate adjustments, one has to wonder, if they got it wrong the last 7 tries, what confidence can we have that they got it right THIS TIME, or will they change it again if Earth doesn’t cooperate? To paraphrase Darth Vader…

Credit and a special thanks to Josh for his incredible artistry and humor!

The NOAA/NCEI monthly raw datasets from January 2010 to May 2015 have been uploaded on WUWT to here for those of you who might wish to do your own analysis. I’ve also included some data documentation in the readme.txt file included in the download. Current NOAA/NCEI data can be downloaded here, click on “Anomalies and Index Data”.

There are 65 months from January 2010 to May 2015. Eight of those months saw significant changes in the anomaly data. There were only very minor changes from January 2010 to October 2010. Note also that the data was originally available to both 2 and 4 significant digits. It is now available to only 2 significant digits. The 2-digit values appear to be rounded-off versions of the 4-digit data.

The first notable change occurred in November 2010, with most anomalies adjusted upwards over the period of record. Mid 1939 to mid 1946 was not raised. Keeping it unchanged while everything else is bumped up is effectively equivalent to lowering it. Of interest is that for the period 1880-to-1909, anomalies for the two months April and November received the most significant boosts.

The next change occurs in April 2011. The period 1912-to-1946 appears to be depressed relative to the rest of the record. Here is the delta between March 2011 and April 2011. And here is the accumulated change from October 2010 to April 2011.

The next change occurs in October 2011. The periods 1880-to-1885 and 1918-to-1950 appear to be depressed relative to the rest of the record. Here is the delta between September 2011 and October 2011. And here is the accumulated change from October 2010 to October 2011.

The next change occurs in January 2012. The period 1905-to-1943 appears to be depressed relative to the rest of the record. 1974-onwards is raised relative to the rest of the record. Here is the delta between December 2011 and January 2012. And here is the accumulated change from October 2010 to January 2012.

The next change occurs in February 2012. The period 1898-to-1930 is raised relative to the rest of the record. Here is the delta between January 2012 and February 2012. And here is the accumulated change from October 2010 to February 2012.

The next change occurs in August 2012. The period 1880-to-1947 is lower relative to 1948-to-2010. Here is the delta between July 2012 and August 2012. And here is the accumulated change from October 2010 to August 2012.

The next graph is not an adjustment. It’s a sanity check. February 2014 was the last available month of 4-significant-digit data. Starting March 2014, 2-significant-digit data is being used. The comparison between February 2014 and March 2014 confirms that the 2-digit data is a rounded-off version of the 4-digit data. The “jitter” is within +/- 0.01, i.e. roundoff error.

The next change occurs in April 2015. The 2-digit data results in a more jagged, sawtooth graph. The period 1880-to-1905 is slightly raised, and the period 1931-to-1958 is slightly lowered relative to the rest of the record. Here is the delta between March 2015 and April 2015. And here is the accumulated change from October 2010 to April 2015.

Some of the changes from April 2015 data (downloaded mid-May) to May 2015 (downloaded mid-June) look rather wild. A drop of as much as 0.14 C degree in 1939 anomalies and a rise of as much as 0.15 C degree in 1945 anomalies made me do a double-take, and inspect the data manually to insure there was no error in my graph. The raw data confirms what the spreadsheet graph shows…

Data for April 2015 versus May 2015 Data month April 2015 May 2015 Change 1938/11 0.11 0.01 -0.10 1948/12 -0.13 -0.25 -0.12 1939/01 -0.02 -0.16 -0.14 1939/02 0.01 -0.11 -0.12 1944/12 -0.02 0.10 0.12 1945/01 0.01 0.16 0.15 1945/02 -0.13 0.02 0.15

And now for the “pause-buster” adjustment. Here is the delta between April 2015 and May 2015. This adjustment is a roller-coaster ride.

The period 1880-to-1925 is up-and-down

1926-to-1937 is relatively stable, down approximately 0.03 to 0.04 degree from April.

1938-to-1939 crashes down to 0.10 degree below April.

The adjustment spikes sharply up to +0.15 by the end of 1944

It drops down sharply to 1948.

Slides gradually down to 1963.

Stable 1963-to-1973

Rises 1973-to-1980

Stable 1980-to-1992

Falls 1992-to-1998

Rises 1999 to November 2010 (end of comparison)

And here is the accumulated change from October 2010 to May 2015. Because the May 2015 change is the largest, the accumulated change from October 2010 to May 2015 is similar to the May 2015 monthly change. One thing that stands out… because 5 or 6 of the 8 adjustments pushed down part or all of the years between WWI and WWII, there is a marked drop from 1920 to 1939 in adjusted temperatures. This has the effect of doing to “The Dirty Thirties” what Michael Mann tried to do the Medieval Optimum warm period; i.e. erasing it from the temperature records. So as our friend Daft Bladder says, “I am altering the data. Pray I don’t alter it any further”.

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