Guest Essay By Walter Dnes
There have been a number of posts on USHCN temperature adjustments, including 1, 2, 3, 4, 5 and 6. They have focused primarily on annual adjustments. Whilst looking into the USHCN adjustments, I noticed that each of the 12 months is adjusted differently. Here is a plot of average USHCN temperature adjustments, for each month plus the annual average, by year for 1970-2013:
Here is the full plot for 1872-2013.
The calculation of average monthly adjustment consists of:
- Calculating the total accumulated values of (final-temp – raw_temp) where the raw and final values of USHCN monthly temperatures were both non-missing
- Count the number of occurrences where the raw and final values of monthly temperatures were both non-missing
- Divide item 1 by item 2.
As you can see, there are marked differences in adjustments since 1970 for each month. To analyze in more detail, we need to look at some numbers. In the table below…
- The columns “2013″ and “2014″ list the average adjustment in Celsius degrees for the corresponding months in the years 2013 and 2014 (where available).
- “Slope” means the slope attributable to USHCN adjustments, in Celsius degrees per century, during the period from 1970 to 2013.
What are the implications of the USHCN adjustments?
- The talk about winters in the USA getting warmer may be an artifact of the adjustments. The adjustments for January/February/March are the highest of the 12 months. In 2013, they combined to average +0.1433 Celsius degree, while the overall annual adjustment for 2013 was -0.0126 Celsius degrees.
- This is a booby-trap for the unwary. When you see articles in February/March/April about HUGE upward adjustments by USHCN so far during the year, you’ll know why. By the following January, the adjustment will cover the entire calendar year and look more reasonable. Mind you, this is still over half a Celsius degree above the adjustments for the 1930s.
- Speaking of the 1930s, one wonders if this an attempt to disappear the heat waves and droughts of “The Dirty Thirties” in a manner similar to attempts to disappear the Medieval Warm Period. It’s hard to talk about “the hottest ever”, when there’s “inconvenient data” around, showing that the 1930s were hotter. The 2nd graph shows the adjustments from the 1870′s onwards. Compare 2013′s -0.0126 annual adjustment with annual adjustments for the 1930s…
- 1930 -0.5586
- 1931 -0.5628
- 1932 -0.5639
- 1933 -0.5770
- 1934 -0.5877
- 1935 -0.5851
- 1936 -0.5846
- 1937 -0.5907
- 1938 -0.5852
- 1939 -0.5810
USHCN monthly data is available on the web in the ftp directory ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/ The specific files used for my analysis were…
- readme file (data formats and basic instructions): ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/readme.txt
- station metadata: ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/ushcn-v2.5-stations.txt
- raw monthly mean temperature data: ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/ushcn.tavg.latest.raw.tar.gz
- final monthly mean temperature data: ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2.5/ushcn.tavg.latest.FLs.52i.tar.gz
Odds and Ends
Interesting stuff I stumbled across whilst working on this article…
- Station USH00381310, i.e. “CAMDEN 3 W”, South Carolina has raw data for August 1853. The next piece of raw data for that station is August 1906. The first piece of any final data for any station is 1866. I wonder if the date is a typo.
- There is some USHCN raw data for the years 1853, 1868, 1869, and 1871 onwards.
- There is USHCN final data from 1866 onwards
Wait a minute. Where does the USHCN final data for 1866, 1867, and 1870 come from, if there is no USHCN raw data for those years? A closer look shows that the small amount of data for those 3 years is all from station USH00303033 “FREDONIA”, New York. It’s located at 42.4497 -79.3120 which translates to 42° 26′ 59″ North 79° 18′ 43″ West. This is near the shore of Lake Erie, not that far from Canada. Let’s check what nearby Canadian data is available for that time span.
- Point your web browser to http://climate.weather.gc.ca/advanceSearch/searchHistoricData_e.html
- Select the “Search by Proximity” tab
- Select 200 in the “kilometres away from” menu
- Click on the “location coordinates:” radio button and enter latitude 42 26 59 and longitude 79 18 43
- Click on the “for years from” radio button, and select 1866 to 1870
- Click on the “Search” button.
The 2 closest sites are Simcoe at 90 km, and Hamilton at just over 100 km. There are another 6 sites within 165 km of Fredonia.
It sort of makes sense that the Fredonia data was created from these sites. I can’t think of any other semi-reasonable explanation. I’ll leave it to professional meteorologists like Anthony to comment on the validity of using data from sites located northwest of Lake Erie to generate estimated data for a site southeast of Lake Erie.
- “The Rise and Fall of USHCN Raw Data” is of interest, in that the less raw data available, the more estimation has to be done to fill out the data set. The theoretical full annual complement of data is 1218 stations with 12 months of data per year, meaning 1,218 * 12 = 14,616 station-months each year. The following graph shows the number of raw and final station-months in the USHCN data over the years. The graph ends at 2013.
- Plots of adjustments over period of record first alerted me to the fact that adjustments were 12 separate data sets, 1 for each month. I ran a script to crank out adjustment plots for all 1218 stations in USHCN, “to see what I could see”. The plot below is an example. Note the period from 1904 to 1911. The adjustments for all 8 of those years were…
- January -2.91 degrees each year
- February -2.94 or -2.95 degrees each year
- March -3.00 degrees each year
- April -3.03 degrees each year
- May -2.93 degrees each year
- June -2.84 degrees each year
- July -2.86 or -2.87 degrees each year
- August -2.87 or -2.88 degrees each year
- September -2.90 or -2.91 degrees each year
- October -2.88 or -2.89 degrees each year
- November -2.95 or -2.96 degrees each year
- December -2.94 or -2.95 degrees each year
Other portions of the data have their own stretches of the same adjustments 12 months apart.