Low Head and the Gnomes of Norwich

Low Head is not a manouevre at a Hollywood party or a physical description of the gnomes of Norwich (the location of CRU), but a lighthouse in Tasmania, which John Daly photographed and brought to the attention of Neil Plummer, who had used it in Jones et al 1990. Plummer wrote back to Daly that the inhomogeneity had been taken into consideration in their revised data in Torok and Nichols. Well, was it?

Actually, yes, or at least a qualified yes and the adjustments are pretty interesting. The version from Jones et al 1990 (recently archived) is shown in red. There is a pronounced increase in maximum temperatures, which John Daly had reported to the Australiean BoM as being attributable to changing landscape at the lighthouse. Plummer replied that this had been allowed for in their High Quality network and, as shown in black, they made substantial adjustments to the series. In some years, the adjustment to the maximum temperature is as high as 1.8 degrees C.
lowhea11.gif
Low Head annual averages from Jones et al 1990 (red) and Torok and Nicholls archive (black, blue). The blue is the calculated annual average. Black is the 13th column which appears to be the adjusted annual average.

Let’s go back to Jones et al 1990. Their argument capping 20th century UHI at 0.05 deg C was based on the supposed small difference between the rather urban-based CRU gridded data and the supposedly “rural” comparandum in China, Russia and Austrlian comparisons – each of which has hair on it. In a spot check of an Australian site in Jones et al 1990 (and this is the only site that I’ve checked), there was a substantial bias in the rural comparandum which was known at least by 1996. Are there similar problems in other series? I don’t know. When Plummer and Coughlan discovered that they needed to re-state the Low Head series so substantially in their High Quality series, they should have published a Corrigendum or some other notice to the community relying on Jones et al 1990 – which continues to be cited, most recently in AR4.


13 Comments

  1. Bill F
    Posted Apr 27, 2007 at 5:17 PM | Permalink

    Steve,

    I am trying to wrap my hands around the meaning of the various plotted lines and how they relate to the adjustments. It appears that there was a clear rise in the Jones max series (can’t tell when, as there is no date scale visible). Am i reading it correctly to see that the adjustment applied by Plummer was to increase all the earlier temperatures to match the later data? If the adjustment is intended to remove a warm bias that occurred due to development around the site, why wouldn’t they apply a negative correction to the later data instead of a positive correction to the earlier data? Or am I simply reading what was done incorrectly?

  2. Steve McIntyre
    Posted Apr 27, 2007 at 7:30 PM | Permalink

    Fixed the scale. They probably use later part of series as normal and adjust the earlier portion, but nothing turns on which portion is adjusted. The John Daly description is here showing inhomogeneiry due to bushes growing around the thermometer, not urban development as conventionally understood.

  3. Follow the Money
    Posted Apr 27, 2007 at 8:43 PM | Permalink

    Low Head is not a manouevre at a Hollywood party

    Is that an allusion to Shampoo?

  4. Gary
    Posted Apr 27, 2007 at 9:20 PM | Permalink

    Google Earth provides a nice satellite view of the narrow Low Head Light peninsula (41 deg,03′,22″S and 146deg,47′,25″E). Although I can’t quite identify the meteorological station’s location, given that the point extends about a mile from the main land, I’m wondering just how much shielding the vegetation actually is causing. It seems a simple thing to take a few measurement at a nearby unshielded spots and determine the difference. This is science fair project stuff: “The Shrubbery Heat Island Effect in Tasmania” that would inform what seems to be only speculation.

  5. David Charlton
    Posted Apr 27, 2007 at 9:58 PM | Permalink

    I can’t resist this; “Low Head and the Gnomes of Norwich” would be a great name for a rock band.

  6. Steve McIntyre
    Posted Apr 27, 2007 at 10:04 PM | Permalink

    Gary, I’m doing something different than John Daly. I’m not trying to decide whether there’s a shrubbery effect or not – it is, as you say, science fair stuff. I’m presuming that Torok and Nicholls have already decided that Low Head adjustment was appropriate. If so, then the adjustment should be carried through to the Jones et al 1990 network, which requires amendment at least for this one series. They haven’t done Mannian principal components so the result isn’t going to be dominated by one series – so the question is: given that Jones et al 1990 missed a 1.8 deg C inhomogeneity at Low Head, what other inhomogeneity problems affect the network?

  7. Ed Snack
    Posted Apr 27, 2007 at 10:57 PM | Permalink

    Gary, John Daly’s original analysis bears reading, I believe it is still on his old website.

    The Low Head record is interesting because when you examine the detailed records, not just the average, it seems that the day temperatures are essentially entirely responsible for the change, and the night temperatures have remained more or less steady. Thus the warming was, to JD anyway, contrary to the theoretical explanation of AGW which would predict that the diurnal anomaly would decrease not increase. He therefore hypothesized that the growth of the shrubbery around the site protected the measurement instruments from the wind, and hence the measurements are not a good measure of the local temperature as the environment has changed significantly. It is worth noting that Plummer appears to agree that the record is not representative.

    This is interesting in another way, the Low Head record (presumably unadjusted) was used as a local temperature record in the Huon Pine tree ring data that was used in MBH98 & 99. Yet another potential source of distortion in that paper.

  8. DaleC
    Posted Apr 28, 2007 at 5:42 AM | Permalink

    See here for a chart of just the Jones1990 TMAX and TMIN series.

  9. John Lang
    Posted Apr 28, 2007 at 5:55 AM | Permalink

    This is just one site. I’m assuming Jones did not adjust one series at a time but applied systematic adjustments to whole ranges of locations. Does the whole series show this increased variance between Min and Max?

  10. Posted Apr 28, 2007 at 11:37 AM | Permalink

    Re: #9

    John, could you explain why you think the adjustment should be independent of location?

    Sinan

  11. JerryB
    Posted Apr 28, 2007 at 2:21 PM | Permalink

    John Lang,

    The discussion at http://www.ncdc.noaa.gov/oa/climate/research/ushcn/ushcn.html#QUAL
    suggests that such adjustments are usually done on a station by station basis, even
    if they are calculated by some form of analysis of “nearby” stations.

  12. Posted Apr 29, 2007 at 12:53 PM | Permalink

    As an aside, I have to admit to some guilt regarding this expression, “Gnomes of Norwich”. There was a TV comedy from ? the Thatcher years, The Gnomes of Dulwich (was Dulwich MT’s electorate ?), which I thought had some v good passages but anyway the show flopped in Oz. In a phone chat with JD one day we were sharing a few choice moments from The G of D, which of course he appreciated as a Pom and somehow the expression, G of N emerged. JD had a good laugh and after that he used it whenever.

  13. Paul Linsay
    Posted Apr 29, 2007 at 7:14 PM | Permalink

    #12

    The original gnomes

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