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Cooling The Past In New Zealand

February 9, 2015

By Paul Homewood



In case you thought widespread temperature adjustments were confined to the Arctic and South America, consider again. Apparently, New Zealand has caught Paraguayan fever!


There are five stations currently operational under GHCN in New Zealand and surrounding islands. It will come as no great surprise now to learn that GHCN warming adjustments have been added to every single one. (Full set of graphs below).


In all cases, other than Hokitika, the adjustment has been made in the mid 1970’s.


This adjustment has been triggered by a drop in temperatures in 1976, as we can see with Gisborne, below. (The algorithm did not spot that temperatures recovered to previous levels two years later!)



Raw Data



Was this temperature drop due to some local, non-climatic factor at Gisborne. Apparently not, because the same drop occurred at all eleven of the other NZ stations operating at that time.

Below is a comparison of the unadjusted annual temperatures for 1975 and 1976.


1975 1976 Change
Gisborne 14.37 13.37 -1.00
Napier 14.65 13.69 -0.96
New Plymouth 14.22 13.07 -1.15
Auckland 15.59 14.66 -0.93
Wellington 12.84 11.53 -1.31
Nelson 12.87 11.72 -1.15
Kaitaia 15.87 15.00 -0.87
Christchurch 11.86 10.52 -1.34
Hokitika 12.17 11.09 -1.08
Chatham I 11.58 10.36 -1.22
Invercargill 10.34 9.17 -1.17
Raoul I 19.57 19.04 -0.53


As a result of the adjustment, Gisborne’s temperatures for 1974 and earlier have been lowered by 0.7C. Similar sized adjustments seem to have been made at the other stations.

As the algorithm cannot have arrived at the adjustment by comparing NZ stations with each other, it must have used stations further away, presumably in Australia.

But can we really compare the two? Once again, the evidence points strongly to the adjustments being incorrect, and reacting to a genuine drop in temperature.


It is often claimed that, overall, temperature adjustments up and down largely cancel each other out. But, while we keep coming across warming adjustments that are questionable, I don’t see cooling ones similarly criticised. Maybe most of these are justifiable.

If this is the case, and many of the warming ones are not, then the overall effect would be much greater than suggested.

On the other hand, if many cooling adjustments are also incorrect, it does not inspire much confidence in the process.

















  1. A C Osborn permalink
    February 9, 2015 6:20 pm

    As Nick Stokes and Mosher say “but it hardly affects the Global Trend”.

  2. February 9, 2015 6:35 pm

    NIWA did the same to its version of NZ. See essay When Data Isnt in ebook Blowing Smoke. Strong evidence that the regional expectations assumption in all homogenization algorithms, no matter whose, is flawed. Best single example is BEST 166900, were the algorithm QC’d away 26 months of lows. 166900 is Amundsen Scott research base at the South Pole, arguably the best station on the planet. The nearest station from which to derive the regional expectation is McMurdo, 1300 km away and 2700 meters lower on Antarctic’s coast!

  3. February 9, 2015 6:42 pm

    Roger Andrews has a post on Energy Matters today that summarises the data from 800 stations – Roger seems to have worked on this for over a decade 🙂

    The main messages;

    N Hemisphere adjustments don’t appear to bias data
    S Hemisphere adjustments do – systematically add cooling to the distant past or warming to the recent past
    On GISS the global impact is muted because it is a land based measure, most land in the N

    But its enough to bias global data to provide impression of continued warming.

  4. February 9, 2015 6:44 pm

    One of the interesting charts

  5. February 9, 2015 6:59 pm

    The adjustments at Hokitika are discussed in great detail here. In particular, the main adjustment at 1910 starts with an observation made at the time, on file, that the readings were believed to be 3°F too high. They didn’t say why, but presumably a calibration issue.

  6. ghostwhowalksnz permalink
    February 9, 2015 10:01 pm

    NIWA has updated its ‘seven stations’ long term temperature series. They said they would publish a peer reviewed paper to show it was all legit. This hasnt happened and the explanation is the paper is stuck in peer review, which doesnt sound good

  7. richardcfromnz permalink
    February 9, 2015 10:06 pm

    >”As a result of the adjustment, Gisborne’s temperatures for 1974 and earlier have been lowered by 0.7C. Similar sized adjustments seem to have been made at the other stations.”

    This is not an adjustment that NIWA make in the NZ 7SS compilation used by HadCRUT4. Which in turn has triple the trend of the alternative 7SS using Rhoades & Salinger (1993) methodology:

    A Reanalysis of Long-Term Surface Air Temperature Trends in New Zealand – by C. R. de Freitas & M. O. Dedekind & B. E. Brill.

    Neither does BEST make the adjustment for NZ stations e.g.:

    Breakpoint Adjusted Annual Average Comparison

    BTW, posts such as yours above Paul and similar from Real Science and elsewhere are referenced in the ‘Temperature records’ thread at Climate Conversation Group (NZ) e.g. the above post here:

    Similarly the CCG ‘Climate models’ thread e.g. the Remote Sensing Systems Climate Analysis article:

    RSS – “The troposphere has not warmed as fast as almost all climate models predict.”

  8. richardcfromnz permalink
    February 10, 2015 3:38 am

    Gisborne Aero monthly plotted on this page (click graph to zoom in):

    There is no reason for a break between 1974 and 1979. But 1975/76 is only a 0.1 adjustment. There is a progressive cumulative adjustment in 0.1 increments adding to 0.7.

    GISS raw monthly data (as plotted):

    GISS adj monthly data:

    See metANN column at far right of the data sheets.

    At 1963 the cumulative adjustment is 0.7
    At 1968 the cumulative adjustment is 0.6
    At 1972 the cumulative adjustment is 0.5
    At 1975 the cumulative adjustment is 0.4
    At 1980 the cumulative adjustment is 0.3
    At 1982 the cumulative adjustment is 0.2
    At 1986 the cumulative adjustment is 0.1
    At 2001 the cumulative adjustment is 0.1
    At 2002 the cumulative adjustment is 0.0

    There is no valid reason for adjustments of this nature. And there is no resemblance to the BEST adjustments:

    • richardcfromnz permalink
      February 10, 2015 4:51 am

      For some reason the GISS Gisborne Aero data sheet URLs return “Not found” sorry. Deleting “http://” works for the adjusted data, but for the raw data start at this page:

      Select “after removing suspicious records” and then “Download monthly data as text”

      I would point out that over the GISS period of Gisborne Aero dataset adjustments of which there appear to be about 7 in total 1962 – 2002, BEST make no adjustments whatsoever over the same period.

      • richardcfromnz permalink
        February 10, 2015 8:51 am

        In case the above comment does not make sense, it follows from a February 10, 2015 3:38 am comment awaiting moderation at this time.

  9. richardcfromnz permalink
    February 10, 2015 6:44 am

    The GISS Gisborne Aero 1973 cumulative adjustment is 0.5

    1973 monthly raw (top) vs adjusted (bottom)
    19.4 18.5 16.2 14.6 12.7 10.0 8.6 10.5 12.3 14.2 17.2 17.2
    18.9 18.0 15.7 14.1 12.2 9.5 8.1 10.0 11.8 13.7 16.7 16.8
    0.5 difference for every month

    The 1974 – 1977 range of common cumulative adjustment is 0.4

    1974 monthly raw (top) vs adjusted (bottom)
    17.7 20.6 15.1 14.8 11.2 10.1 10.1 8.9 12.1 13.6 15.5 17.8
    17.3 20.2 14.7 14.4 10.8 9.7 9.7 8.5 11.7 13.2 15.1 17.4
    0.4 difference for every month

    1977 monthly raw (top) vs adjusted (bottom)
    18.4 18.9 17.8 14.5 10.9 10.1 9.4 10.4 10.2 13.4 14.9 17.5
    18.0 18.5 17.4 14.1 10.5 9.7 9.0 10.0 9.8 13.0 14.5 17.2
    0.4 difference for every month

    The 1978 cumulative adjustment is 0.3

    1978 monthly raw (top) vs adjusted (bottom)
    19.2 19.5 17.6 16.4 12.0 10.0 9.7 10.3 11.3 12.0 16.0 18.0
    18.9 19.2 17.3 16.1 11.7 9.7 9.4 10.0 11.0 11.7 15.7 17.7
    0.3 difference for every month

    Apparently, according to GISS (but not BEST), there were 2 distinct 0.1 steps from 1978 to 1977 and from 1974 to 1973. Similarly for the other ranges of common cumulative adjustments.

    There is no justification for these 2 steps (or the others) in view of the raw monthly data series (and no site moves):

    GISS has some explaining to do.

  10. February 10, 2015 8:44 am

    When did these adjustments of temperatures start?

    it is basic scientific practice to report the data that are measured and any alterations must be clear or the data should be excluded from the analysis. Even trying to allow for time of day for measurement alteration changes involves considerable error as diurnal changes vary widely.

    “Correcting because sites a considerable distance away give different values can only be a very coarse approximation of reality especially in islands or coastal regions; as we know well in the UK very real large temperature changes occur over distances of a few miles very commonly.

    This throws up the simple question what is the real accuracy of the calculated global mean temperature used in calculating the anomaly? It appears that this value’s error makes the small changes being compared meaningless.

    • Retired Dave permalink
      February 11, 2015 11:35 am

      Jack Broughton

      “Correcting because sites a considerable distance away give different values can only be a very coarse approximation of reality especially in islands or coastal regions; as we know well in the UK very real large temperature changes occur over distances of a few miles very commonly.

      I totally agree Jack. close to 10 deg C is possible with stations only 10 to 20 miles apart – one without cloud/wind for 16 hours on a winter night and the other with low cloud and a little wind all night. Add in dry air and a snow cover at the clear sky site and…………

      There are sometimes good reasons to make adjustments to meteorological data, but they are few and far apart. Calibration errors are usually spotted quickly – or should be. Too many people involved in these historical adjustments have a built-in bias towards warming and seem very non self-aware.

      The first of these “suspicious” adjustments I heard of a few years ago were the Iceland ones for the 1930’s – all cooled to remove the embarrassment of them being as warm as recent times plus the need to create a false trend (which was chicken and which was egg). The excellent Icelandic Met service does not agree that these adjustments are necessary – the idea that all mercury in glass thermometers in 1930’s Iceland were reading “too high” is laughable.


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