Climate change sceptics have poured cold water on Niwa's claims an independent review has backed up the science used in its analysis that New Zealand temperatures have risen nearly 1degC in the last 100 years.
National Institute of Water and Atmospheric Research (Niwa) scientists last year used analysis of long-term measurements from seven weather stations showing warming -- backed up by other observations, including measurements from ships - to indicate climate change in New Zealand.
On Friday the state-owned science company issued a peer review by Australia's Bureau of Meteorology, which was carried out to ensure the ideas, methods, and conclusions stood up in terms of scientific accuracy, logic, and consistency.
Niwa chief executive John Morgan confirmed that the scientists from the bureau's National Climate Centre concluded that the results and underlying methodology used by his scientists were sound.
The series from the seven stations - Auckland, Wellington, Masterton, Nelson, Hokitika, Lincoln, and Dunedin - were reviewed in 1992, and then updated annually. They indicated a warming of about 0.9decC over the 100 years up to 2009.
But the Climate Science Coalition (CSC) dismissed the peer review, saying it did not go far enough and Niwa was overstating the Australian endorsement.
It was not a reanalysis of the seven station temperature record, said CSC spokesman Bryan Leyland.
"Such a task would require full access to the raw and modified temperature data and metadata, and would be a major scientific undertaking."
CSC had tried to get hold of the data but Niwa had told them it no longer had it on internal records, he said.
Trying to get meaningful data from seven widely separated weather stations for a meaningful national average temperature was not possible, Mr Leyland said.
He said Mr Morgan should resign for misleading people about the robustness of the review.
CSC would carry out its own review of the data in the New Year, Mr Leyland said.
Earlier this year Niwa said there were several reasons for adjusting the temperature record from specific sites, including introducing new thermometers or sensors to a weather site, and changes to its exposure caused by growing vegetation or urban sprawl.
Wellington figures had to be adjusted down when the official weather site moved up 120m in altitude in 1928 from the Thorndon waterfront to Kelburn, which is about 0.8degC cooler, on average.
Ignoring major changes in site location would produce wrong results, Niwa said.
"For the longer 'seven station' time series, adjustments to account for significant site changes are necessary in order to provide a meaningful estimate of New Zealand temperature trends," it said.
NZPA