A move by a group of climate change sceptics to take Niwa to court to challenge the accuracy of its temperature data has caused a stir at each end of the political spectrum.
The New Zealand Climate Science Coalition said it had lodged papers with the High Court asking it to invalidate Niwa's official temperature records, which it claims are inaccurate and being used to paint a misleading picture of global warming.
Coalition spokesman Bryan Leyland said many scientists believed that although the earth had been warming for 150 years, it had not heated as much as claimed.
He said the New Zealand Meteorological Service had shown no warming during the past century but Niwa had adjusted its records to show a warming trend of 1degC.
A spokesman for Niwa, which is state-owned and advises the government, said it couldn't comment in detail while court action was pending but that its information was objective and authoritative and it had full confidence in its science.
"We are confident that, in the unlikely event that [a court case] proceeds, then our stance and our science will be fully vindicated."
A full court case will proceed only if it is established during a depositions hearing that there is a case to answer.
Act Party leader Rodney Hide, who along with colleague John Boscawen has been a vocal sceptic of the notion that climate change is man-made and has lobbied against the Emissions Trading Scheme (ETS), has also been a harsh Niwa critic.
He said today he agreed with the coalition's claims and was pleased Niwa would be forced to explain its data.
"I think it's great that the taxpayers are holding this state entity to account, because what I've seen of them is shocking and I have been appalled at the way they have manipulated the data to produce a warming result and have been unable to explain why they adjusted the temperature records upwards," he told NZPA.
The ETS was a "disaster" for New Zealand and a lot of it was based on Niwa's arguments, he said.
But Green Party co-leader Russel Norman said the court case was a "dangerous distraction from the reality on the ground.
"We need to cut emissions and respond sensibly to the climate change already under way," Dr Norman said.
He said science was showing the east coast of New Zealand was becoming increasingly vulnerable to extreme climate events and that events such as the latest floods in Whakatane would be seen more commonly in the near future.
Dr Norman also called for central government to provide greater leadership on adapting to climate change-induced weather events through a national policy statement (NPS) on climate change adaptation.
Mr Hide said he was confident councils already had adequate plans to deal with adverse weather events.
University of Otago pro-vice chancellor of sciences Keith Hunter has also backed Niwa, saying taking court action against it was "stupid," while the Environmental Defence Society (EDS) said it may join court action in support of Niwa.
"On the face of it, it's hard to see how the issue can properly be brought before the court," said EDS chairman Gary Taylor. "We have no doubts that the science behind global warming predictions is robust and reliable and would wish to support the institute in any way that we can."
He said it was one thing to have robust debate about the science= but "quite another to attempt to belittle and undermine the need for action, as the coalition has been doing now for years."