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HADCRUT Update August 2012

October 8, 2012


By Paul Homewood


Just a quick update of the August Global Temperature figures. HADCRUT3V numbers finally came in for the month last week while I was away, so the chart looks like this.


August 2012 anomaly 0.26 0.34 0.51 0.56
Inc/Dec from last month -0.03 +0.06 +0.06 +0.09
12 month running average 0.16 0.18 0.36 0.50
Average 2002-11 0.26 0.18 0.42 0.55



The 12 month average for HADCRUT remains at 0.36C, the same as in July. A look at the long term shows a similar picture to the other three datasets, with current temperatures running below those from 2002-2007. Remember that the detail on the other datasets is already posted here.




With the HADCRUT figures in, as promised, I can now show how temperatures trends have diverged since satellite monitoring began in 1979. Each of the four datasets uses a different baseline for calculation of anomalies (detail here), so naturally the numbers are all different. In order to compare them directly, I have re-centred GISS, HADCRUT and UAH to the anomalies that RSS show for 1979. For example:-


RSS – 1979 : -0.09C

GISS – 1979: +0.10C

GISS Re-centred 1979: +0.10 – 0.19C = –0.09

Therefore all GISS anomalies are reduced by 0.19C. Note that this does not affect the GISS trend at all, but simply shifts the scale on the graph. When all the datasets are re-centred in this way, the trends since 1979 look like this.




Based on 12 month running averages and with all four sets starting at the same point, GISS clearly come up with a significantly greater warming trend than the other sets. Furthermore, this divergence has really only taken off since around 2001. Until then there were occasional fluctuations, but the GISS figures tended to fit into the overall pattern of things. The actual numbers illustrate just how big the divergence has been.


12-Month Running Average Increase 1979-2012
RSS 0.25C
UAH 0.34C
GISS 0.40C


In other words, more than a third of the warming that GISS claim is not shown by RSS. It is also worth pointing out here that UAH are in the middle of introducing their new Version 5.5. More on this next month, but in simple terms they have been picking up spurious warming because of problems with the Aqua system. The new Version, which I will be using in my next update, effectively reduces temperatures for the last year by about 0.05C. This will bring UAH closely into line with RSS and HADCRUT, and emphatically leaves GISS as an outlier.

Something else worth pointing out is that RSS have less coverage of the Antarctic than UAH. RSS can only monitor down to 70oS, whereas UAH go to 85oS. Why is this significant? It is generally accepted that the Antarctic has been getting colder in recent years. It seems unlikely that RSS are picking up the full effect of this in their global numbers, which, if that were the case, would be over estimated.

More on this and a closer look at the trends over the last decade in the September update. Hopefully the HADCRUT figures will be on time for this!

  1. Ray permalink
    October 8, 2012 7:24 pm

    Paul, just out of interest, why do you use the variance adjusted version of HadCRUT3?
    The non-variance adjusted version is the one quoted by the MO and is usually available sooner on the MO Hadley Centre website than the figures on the CRU site. Having said that, the data files are a bit harder to find on the MO site.
    Here is a link to the global data:
    The August non-variance adjusted figure was 0.508c and the rolling annual figure is 0.36c.
    Also, are you aware that the UAH anomaly for August has been reduced to 0.208c, along with most of the figures for the last 2 years, as a result of spurious warming in the AQUA AMSU CH5 temperature figures?

    • October 8, 2012 10:03 pm

      I understand that CRU regard the Variance Adj version as their “official” one. I’ll run a comparison of the two next time. It certainly can be a pain updating this one, as older numbers can change from month to month.

      • Ray permalink
        October 9, 2012 8:57 am

        I think that the non-variance adjusted figures might change just as much.
        I don’t think there is much difference in the figures, but as far as I am aware, the figure usually quoted in not variance adjusted.
        I am fairly certain that this informtion sheet, authored by Phil Jones, refers to HadCRUT3, not HadCRUT3v, well that’s what the graph says.
        Also please note that the RSS figure for September has just been published.

      • October 9, 2012 9:23 am



  2. Ray permalink
    October 8, 2012 7:27 pm

    Sorry, I now see from your comments that you are aware of the situation with UAH, I didn’t read that far!

  3. Paul Matthews permalink
    October 9, 2012 3:00 pm

    To add to the confusion, HADCRUT have produced a new version called HADCRUT4. Originally this only went up to 2010, but in the last few days it has been extended to Aug 2012.
    No prizes for guessing whether the new version HADCRUT4 shows more or less warming than HADCRUT3.
    It’s not clear which is the ‘official’ version but I think the new IPCC report will use HADCRUT4.

  4. Ray permalink
    October 9, 2012 4:33 pm

    Thanks Paul, that’s where I get mine from.
    A slightly different layout to the HadCRUT3 data.
    I notice that in the case of HadCrut4, there don’t seem to be monthly/annual data files for NH & SH extratropics or tropics & mid-latitudes, as there are for HadCRUT3.

  5. Paul Matthews permalink
    October 10, 2012 3:14 pm

    David Whitehouse has written some comments on HADCRUT4 at

    • October 10, 2012 4:10 pm

      Yes, David takes the view that the changes are relatively small and that HADCRUT4 still shows flat, or a cooling trend. I have taken a slightly different tack though, on my latest post.

  6. January 1, 2013 11:30 pm

    Reblogged this on Climate Ponderings.

  7. January 5, 2013 8:47 am

    I’m gone to inform my little brother, that he should also pay a quick visit this web site on regular basis to take updated from most recent information.

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