The coalition said the New Zealand Temperature Records (NZTR) were the historical base of NIWA’s advice to the Government on issues relating to climate change.
Coalition spokesman Bryan Leyland said many scientists believed although the earth had been warming for 150 years, it had not heated as much as Government archives 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.
The warming figure was high and almost 50 per cent above the global average, said Mr Leyland.
The coalition said the 1degC warming during the 20th century was based on adjustments taken by Niwa from a 1981 student thesis by then student Jim Salinger, a Niwa employee who was later sacked after talking to the media without permission.
The Salinger thesis was subjective and untested and meteorologists more senior to Dr Salinger did not consider the temperature data should be adjusted, it said.
COMMENTS: Would a scientist bend the data to promote their own cause, na that wouldnt happen, or would it ! Fellow NZders your govt is using shoddy data just to TAX you some more !