Today a paper on the New Zealand temperature record (NZTR) was accepted by the journal Environmental Modeling & Assessment. Submitted in 2013, we can only imagine the colossal peer-review hurdles that had to be overcome in gaining acceptance for a paper that refutes the national temperature record in a developed country. The mere fact of acceptance attests to a fundamental shift in scientific attitudes to climate change, but expect strident opposition to this paper.
The authors present first a concise observational history of the NZTR, remarking that the established national record was a product of early methodology, then reconstruct an homogenised dataset using the peer-reviewed adjustment standards of Rhoades & Salinger, 1993 (RS93).
A Reanalysis of Long-Term Surface Air Temperature Trends in New Zealand was produced by principal author C.R. de Freitas with M.O. Dedekind and B.E. Brill.
Detecting trends in climate is important in assessments of global change based on regional long-term data. Equally important is the reliability of the results that are widely used as a major input for a large number of societal design and planning purposes. New Zealand provides a rare long temperature time series in the Southern Hemisphere, and it is one of the longest continuous climate series available in the Southern Hemisphere Pacific. It is therefore important that this temperature dataset meets the highest quality control standards. New Zealand’s national record for the period 1909 to 2009 is analysed and the data homogenized. Current New Zealand century-long climatology based on 1981 methods produces a trend of 0.91 °C per century. Our analysis, which uses updated measurement techniques and corrects for shelter-contaminated data, produces a trend of 0.28 °C per century.
The authors describe their intention as: “… to derive a modernized New Zealand Temperature Record (NZTR) providing a 100-year time series of mean monthly land surface temperature anomalies.” They claim to apply the method set out in RS93 exactly as described, “without adjusting it in any way,” noting it has been the adjustment method of choice in New Zealand climatology for over two decades and “we are unaware of any serious criticism or dispute regarding it.”
In the introduction, they make the point that “on the face of it, New Zealand’s long-term mean temperature has remained relatively stable at 12.6 °C over the past 150 years.” Which means that any new conclusion of warming must have solid grounds.
NZCSC media release
The NZ Climate Science Coalition has released a statement under a striking headline:
New paper finds no significant 20th century warming for New Zealand
A research paper on the homogenisation of the temperature record in New Zealand, reducing the current official warming rate of 0.9°C per century to 0.3°C per century, has just been published in the international scientific journal Environmental Modeling & Assessment.
The paper addresses the values of the data adjustments required during 100 years of the Seven Station Series, which is recognised as being representative of New Zealand as a whole. It also considers corrections to station data contaminated by vegetation growth, urbanisation and other factors.
The New Zealand historical temperature trend has not been addressed in the scientific literature since the first Seven Station Series was published by M.J. Salinger in 1980. At about the same time, a paper by J.W.D. Hessell called into question the quality of the New Zealand historical weather data used in the series.
The new paper builds on both viewpoints by applying modern techniques to correct sub-optimal raw data and to recalculate the 1980 adjustments. The method used for recalculations was that described in the leading New Zealand paper by Rhoades & Salinger (1993).
Lead author Chris de Freitas commented: “Regional and national temperature trends are widely used for a large number of societal design and planning purposes and it is important that they should be as reliable as modern methods allow.”
He added: “New Zealand provides one of the longest continuous climate series in the Pacific Ocean as well as one of the longest in the Southern Hemisphere. This means our trends are of ongoing interest to a wide audience of scientists.”
The paper finds that New Zealand warmed over the 20th century by 0.3°C, which, allowing for accepted margins of error, means that there has been no significant warming.
CO2 Science review
Dr Craig Idso, Director of CO2 Science, has reviewed a pre-release copy of the paper. This is his report.
In introducing their recent study of the subject, de Freitas et al. (2014) write that “a homogenized New Zealand national temperature record has only once appeared in the literature,” citing the one produced by Salinger (1980). They report, however, that it was based on a measurement technique that was significantly improved by its author and a colleague (Rhoades and Salinger, 1993) over a decade later. And although they state that “applying that improvement could have a significant effect on trends,” they indicate that such an improved trend for New Zealand “has never previously been published.”
The three New Zealand researchers thus set out to fill this void by applying the measurement technique described by Rhoades and Salinger to data for the period 1909-2009. And they did it, in their words, “exactly as they [Rhoades and Salinger] describe, without adjusting it in any way,” although they say they corrected for “the contamination of raw data identified in the refereed literature (Hessell, 1980)” and for “shelter-contaminated data.” So what was the final result?
De Freitas et al. report that, whereas the previous analysis yielded a trend of 0.91 ± 0.30°C per century, their analysis—which used updated measurement techniques and corrects for shelter-contaminated data—produces a trend of only 0.28 ± 0.29°C per century, which is a heck of a lot less than what had previously been believed to have been the case.
The significance of de Freitas et al.’s work is two-fold. First, the authors report that the old, contaminated data with the inflated warming trend has been “widely used as inputs for societal design and planning purposes” all across New Zealand. Second, de Freitas et al. note these data are “extensively used in hindcast verifications for regional and local models.” However, as the saying goes, “garbage in equals garbage out.” Therefore, at best, the corrected New Zealand temperature trend, which is three times smaller than the uncorrected version, calls into question all results, findings, conclusions and policies built upon or derived from the old contaminated data record. And at worst, it invalidates them.
Given the great importance of starting with the proper baseline, one would hope that with so much at stake in terms of economics, personal freedoms and governance much greater care and scrutiny would be applied to ensuring the quality and reliability of near-surface air temperature records. But obviously, such has not been the case for New Zealand. And it begs the question as to where else temperature records might be less than par.
Dr Idso notes that the paper finds warming just one-third of the ‘official’ century warming of 0.9°C and claims it “calls into question all results, findings, conclusions and policies built upon or derived from the old contaminated data record. And at worst, it invalidates them.” (emphasis mine). But I’m really not sure this applies to policy.
Our national policy decisions have been guided by IPCC recommendations, which are formed from global average temperatures, not local temperatures. One very good reason for this is that nobody knows reliably how to translate a degree of warming into weather effects, so forecasts are based on generalisations and covered all over with ‘might,’ ‘perhaps’ and ‘could’. However, I’m advised by well-informed and shrewd people that NIWA does foretell the future on its own account based on magically matching its national databases to IPCC forecasts, so if local temperatures have been overstated by 300%, errors will occur. Then territorial authorities will make mistakes in over-estimating future risks.
Anyone familiar with local policy and its origination would be most welcome to provide elaboration of this point.
I spoke with the authors; they won’t want me to say this, but their humility strikes me mightily (though of course they make no show of it). They exhibit no hint of swagger in doing this work, simply telling me that they see it as “just one more paper for the open-minded to consider.”
That is admirable.