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Global Temperature Update–September 2012

October 31, 2012

By Paul Homewood


The HADCRUT data has now been released for September, so we can have a look at the latest figures for the four main global temperature datasets. I have now switched to HADCRUT4, although the Hadley Centre are still producing numbers for HADCRUT3.


September 2012 anomaly 0.38 0.52 0.34 0.60
Increase/Decrease From Last Month +0.12 -0.01 +0.14 +0.03
12 Month Running Average 0.16 0.42 0.11 0.50
Average 2002-11 0.26 0.47 0.19 0.55

                                   Global Temperature Anomalies – Degree Centigrade           


The pattern is similar across all datasets, with September temperatures above both long term and 12 month averages, although, interestingly, both satellite sets have picked up a bigger spike than the other two. We are currently seeing the lagged effect on temperature from the mild El Nino, which began in April and has now pretty much fizzled out, as can be seen below. Purely thinking aloud, but is this an indication that atmospheric warming is slower to dissipate than surface warming?




My guess is that temperatures will settle back slightly by the end of the year. If ENSO conditions remain fairly neutral in the next few months, we should get a good indication of underlying temperatures, for the first time for a while.

The following graphs show 12-month running averages for each set. As I mentioned before, we often get fixated with calendar year figures, which obviously change a good deal from year to year. It therefore seems much more sensible to look at 12 month averages on a monthly basis, rather than wait till December.







In all cases, the 12 month averages are lower than they were at the start of the year.


Finally, I mentioned last month that UAH had just brought out a new Version 5.5, which corrected for spurious warming from the Aqua satellite. (Roy Spencer has the full technical stuff here). The new version is now incorporated and backdated in my analysis above. I have also plotted the difference between the old and new versions below.




As can be seen, the divergence really started to be noticeable towards the end of last year, and has steadily grown wider over the last few months.


Remember that all monthly updates can be accessed on the “Global Temperature Updates” page.




  1. Ray permalink
    October 31, 2012 4:07 pm

    I agree entirely about the fixation with calendar year figures.
    As a result of this according to the UKMO, the “highest annual mean CET figure ever recorded, was 10.82c”, for calendar year 2006, but it was actually 11.6c for the 12 months ending May 2007.
    This is important, because if 10.82 is ever exceeded, they will be saying it is a record, when it isn’t.

    • Michael Hart permalink
      October 31, 2012 10:04 pm

      …and also a fixation with “records” in general.

      As most sports fans know [especially Baseball or Cricket] there is effectively no end of new ways to calculate a new “record” of one sort or another. Whether it is seen as good or bad usually depends on which team you support.

      In this case, most of us already know which “team’s” perspective almost invariably gets the support of the the UKMO and the MSM.

  2. Michael Hart permalink
    October 31, 2012 10:25 pm

    “Purely thinking aloud, but is this an indication that atmospheric warming is slower to dissipate than surface warming?”

    I started wondering something similar just as I was finishing your previous sentence. Do the satellites show any historical tendency to do the same thing at “significant” points in the ENSO cycles? [notwithstanding that ENSO is an index, rather than a measurement as I understand it].

    • October 31, 2012 10:40 pm

      I have noticed previously that HADCRUT never seems to change as much as the others when there is NINO extremes.

  3. November 2, 2012 3:37 am

    Paul, talking about temps, i have been trying to get the BOM to use the 1980 – 2010 baseline, because the anomaly maps are a joke using the old baseline, much like GISS. The closest i can get is to use the new baseline on the GISS site. Is there any other way to check OZ temps?

    • November 2, 2012 10:44 am

      Not that I know of.

      I gather it is the policy (or at least recommendation) of the WMO to use 1981-2010, as the most recent three decades. The UK have just switched over for that reason. You might try asking the BOM why they are not following the rules.

  4. Ray permalink
    November 2, 2012 12:00 pm

    An interesting fact I have discovered is that the mean HadCRUT3 anomaly for 1961-90 is -0.0277c when it should theoretically be zero. Otherwise, for some reason, HadCRUT3 is no longer relative to 1961-90, but actually Dec. 1964 to Nov. 1994. This in effect means you have to add 0.0277c to HadCRUT3 in order to correct it to itself. This problem seems to have been eliminated in HadCRUT4
    The above is the average figure. If you use the monthly discrepancies and use them to adjust the 2012 monthly HadCRUT3 figures, the average differences between HadCRUT3 and HadCRUT4 are much lower.

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