Temperature adjustments science or art?

a beautiful iced-up waterfall

Barry Brill rips into NIWA’s showcase paper on the Hokitika weather adjustments — the one intended to demonstrate that data adjustment is science rather than art.    – Richard Treadgold

— by Barry Brill, Chairman of the New Zealand Climate Science Coalition

In February 2010, NIWA published a showcase paper titled Creating a Composite Temperature Record for Hokitika, offering details of adjustments it made to the NZ Climate Database for the Hokitika Airport weather station — one of the “Seven-station Series” (7SS) which makes up the official New Zealand temperature record.

The NZ MetService measurements for Hokitika cover the 20th century and display no significant linear trend up or down. The temperature recorded here in 1900 was 11.8°C, while 2008 was 11.93°C, and the 30-year average from 1971–2000 was 11.74°C.

The NIWA-adjusted version, on the other hand, shows a linear warming trend of 1.3°C, largely brought about by downward adjustments in the Hokitika temperatures in the first half of the century. The justification for those adjustments has been cited repeatedly as being an Appendix to a university thesis submitted in 1981 (see “The Salinger Thesis”).

NIWA temp adjustments with scales of justice

The Hokitika details were made public as a worked example of the adjustments that NIWA has made to all seven weather stations in the 7SS, in consequence of the Salinger thesis. Accordingly, the credibility of the entire project stands or falls on the strength of reasoning advanced for the Hokitika alterations.

But that reasoning is not sound. Continue Reading →