The National Institute of Water and Atmospheric Research is standing by its prediction that global warming will cause more floods of the type that devastated Northland.
Niwa climate scientist Dr Jim Salinger rejects Climate Science Coalition criticism describing Niwa's observations as simplistic and unscientific, especially as summer hadbrought below-average temperatures.
Coalition spokesman Augie Auer claimed Dr Salinger's argument on global warming was not credible.
Dr Auer said Niwa's own figures showed New Zealand had been cooling since the El Nino weather pattern in 1998, and asked why Niwa would not admit this.
But Dr Salinger said yesterday that long-term records showed New Zealand and the world were warmer than they were 100 years ago.
Nineteen of the world's 20 warmest years had occurred since 1980. Eleven of the past 12 years ranked among the warmest years recorded since 1850.
"You have to look at long term records, not just those since 1998," Dr Salinger said.
"During the 20th century, New Zealand temperatures went up by 0.9 C."
Dr Auer also claimed there was no proof that carbon dioxide caused the minimal warming that occurred from time to time in the atmosphere.
There was no need for the Kyoto protocol, carbon taxes and "other costly red herrings currently being spun in political circles."
Dr Salinger said there was plenty of evidence about carbon dioxide in the fourth assessment from the Inter-Government Panel on Climate Change report issued in February.
Concentrations of carbon dioxide in greenhouse gases had increased markedly since 1750 and now exceeded industrial revolution levels, Dr Salinger said.
The assessment report considered there was now a nine out of 10 chance that carbon dioxide was the cause, reflecting the effect of human activity on global warming.
