New Zealand may not have warmed at all in the past 100 years, according to a peer-reviewed paper published in the international science journal, Environmental Modeling & Assessment.
The paper, “A Reanalysis of Long-Term Surface Air Temperature Trends in New Zealand,” by New Zealand authors, Chris De Freitas, Bob Dedekind and Barry Brill, covered the period 1909-2009. It shows an increase of 0.28 degrees C, +/- 0.29 degrees/century, compared with the current official NIWA 7-station (7SS) series showing an increase of nearly 1 degree C.
The government must take this new finding into account in future climate policy development, says Prof Robert M. Carter, a graduate of Otago University and Honorary Fellow of the Royal Society of New Zealand.
Professor Carter explains:
“To place a rate of warming of 0.28 deg. C in context, extensive geological data sets show that rates of temperature change have varied naturally by up to plus and minus 2.5 deg. C/century during the last 10,000 years (i.e., through the interglacial warm period that we currently live in). In other words, pre-historic rates of natural change exceeded the warming in New Zealand over the last century by as much as 10 times.
“Furthermore, the margin for error associated with de Freitas et al.’s warming estimate is plus or minus 0.29 deg. C/century. In other words, statistically, this is indistinguishable from no warming at all in New Zealand over the last 100 years.
In 1980, Dr M.J. Salinger applied a new statistical technique of homogenisation to the period of New Zealand record between 1853 and 1975, using data from seven geographically spread observing stations. This seven-station series (7SS) showed a rate of warming of about 1 deg. C/century, a figure that has been widely factored into climate policy determinations in New Zealand.
In this new paper, the authors have undertaken an updated reanalysis of the 7SS record. They say they have followed strictly the statistical technique pioneered by Salinger (as published in a paper by Rhoades & Salinger in 1993), though incorporating subsequent data corrections identified in the scientific literature, and provide a detailed schedule of the adjustments that were made in their analysis.
The full paper can be read here.