KEY POINTS:
New Zealand's climate forecasts are as reliable as the toss of a coin, research by climate scientists shows.
The Climate Science Coalition claims its study of seasonal weather predictions by the National Institute of Water and Atmospheric Research shows they are only right about half the time.
Niwa scientists hit back last night saying their predictions stacked up against any other forecasting service round the world.
The Herald yesterday reported Niwa's prediction that the country's indian summer was not completely gone, with much of the country likely to enjoy average or above average temperatures over the next two months.
But the coalition's Malcolm Taylor says his analysis of five years of Niwa forecasts from May 2002 to April 2007 - shows Niwa were correct in only about half of their predictions.
Over the 60 periods studied, Niwa scored a better than 67 per cent accurate prediction on 25 occasions and were worse than 33 per cent accurate 26 times.
Niwa's overall accuracy was 48 per cent.
Coalition spokesman Augie Auer said it raised the question as to "whether taxpayers should be funding Niwa forecasters who have no better odds of success than flipping a coin".
"This has serious consequences for our rural community. Farmers in South Canterbury in June last year were hit with a very severe snow dump with minimum warning."
But Dr Jim Renwick, climate scientist at Niwa, said the organisation was doing as well as any other weather forecaster around the world.
He had not read Mr Taylor's findings but "like pretty much every country around the world who do this we are doing about as well as anybody else".
"Climate prediction is hard, half of the variability in the climate system is not predictable so we don't expect to do terrifically well," Dr Renwick said.
"We have a level of skill that is better than guessing for sure; it's all about probability and making maximum use of those observations.
"What he is saying doesn't sound too shocking; it's what we've said ourselves in our own publication."
Every month in its climate update, Dr Renwick said Niwa released a summary of how the forecast went for the previous month or season.
"Getting 50 per cent accuracy on seasonal forecasts is about what you would expect."
