The state-owned atmospheric and water research institute has taken the unusual step of publishing a graph of raw climate data on its website to answer critics who accused it of fiddling the figures.

With just days to go before the Copenhagen climate conference, Niwa published data from 11 climate stations around the country showing New Zealand has warmed close to 1C since the 1930s.

The data was published on Niwa's website in its raw form to rebut allegations that scientists were "adjusting" the figures to make the country look warmer.

The analysis featured a guest appearance by former employee Jim Salinger, who has been in an employment dispute with the institute since he was dismissed over breaches of media protocol.

He worked on the statement with Niwa principal climate scientist James Renwick.

The pair were responding to accusations by the New Zealand Climate Science Coalition, an organisation that questions man-made global warming, that Niwa had lowered early figures from several climate stations to make the newer readings look warmer.

The allegations stemmed from a Niwa practice of adjusting the record for climate stations if they are moved to a different spot.

Niwa said last week that when scientists needed to put old and new records together to see a long-term trend, it adjusted the data.

For example, Wellington's climate station was moved in 1928 from Thorndon to Kelburn - where it is higher and on average 0.8C cooler - so the Thorndon record was adjusted in long-term graphs.

The graph published yesterday was from climate stations that had not moved since the 1940s, to prove they showed the same 1C warming trend as all the climate stations put together. Dr Renwick said that any selection of "reasonably representative" sites would show roughly the same trend.

He said Niwa had explained why it adjusted the data to members of the Climate Science Coalition in 2006, only to have it raised again two weeks before a major climate conference.

"It does seem a coincidence," he said.

Doubters of man-made global warming have gone into overdrive in recent weeks as world leaders prepared to agree to new cuts to greenhouse gases.

An email hack at a respected British climate research centre, at the University of East Anglia, led to the centre's leader stepping aside after questions were raised about his working methods.

NZ negotiators said this week the scandal would make no difference to the conference.

Meanwhile, the Government's pledge of about $90 million to a US$10 billion global climate fund for developing countries has been criticised by the charity Oxfam.

Prime Minister John Key has said NZ's contribution to the fund will be $10 million to $50 million a year for three years, and probably a mid-point between the two.

Oxfam said $30 million a year was about 4 per cent of the $700 million NZ should give to help developing countries, including low-lying islands, to reduce their emissions and protect themselves from climate change.

A spokesman said a total of about US$150 billion a year was needed, and this estimate was likely to go up. NZ's share was worked out based on its wealth weighted equally against its greenhouse gas emissions to 2005.

By the same index, NZ should cut greenhouse gas emissions by 52 per cent from 1990 levels by 2020, in order to reach a world total of 40 per cent. The UN's climate panel says emission cuts of 25-40 per cent by 2020 should keep world warming within 2C.

The so-called "adaptation fund" is to help convince developing countries to lower their greenhouse gas emissions and join in a climate treaty.

Developed countries have said their contributions to the fund will rise over time.

Eloise Gibson will be reporting from the Copenhagen climate conference.