Climate predictions “right only half the time”

From: Terry Dunleavy []

The New Zealand Climate Science Coalition

Media release (immediate) 7 June 2007

World climate predictors right only half the time

“The open admission by a climate scientist of the New Zealand National Institute of Water and Atmospheric Research (NIWA), Dr Jim Renwick, that his organisation achieves only 50 per cent accuracy in its climate forecasts, and that this is as good as any other forecaster around the world, should be a wake-up call for world political leaders,” said Rear Admiral Jack Welch, chairman of the New Zealand Climate Science Coalition.

Yesterday the coalition published an analysis of seasonal climate predictions by NIWA over the past five years which found that the overall accuracy of the predictions was just 48 per cent.

Defending the Niwa record, Dr Renwick said his organisation was doing as well as any other weather forecaster around the world. He was quoted by the country’s leading newspaper, the New Zealand Herald as saying: “Climate prediction is hard, half of the variability in the climate system is not predictable, so we don’t expect to do terrifically well.” Later on New Zealand radio, Dr Renwick said: “The weather is not predictable beyond a week or two.”

Admiral Welch said that these statements warrant immediate attention by governments around the world. “Dr Renwick is no lightweight. He was a lead author on Working Group I of the IPCC 4th Assessment Report, and serves on the World Meteorological Organisation Commission for Climatology Expert Team on Seasonal Forecasting. He is presumed to be au fait with the abilities of the official governmental climate prediction community round the world.

“All round the developed world, governments are being pressured by the United Nations Intergovernmental Panel on Climate Change (IPCC) to accept the integrity of scenarios of future climate behaviour agreed by their own climate bureaucrats, but these bureaucrats are the very people that Dr Renwick now tells us get it right only half the time. Worse, he tells us they are unable to predict weather beyond a week or two, yet in conjunction with the IPCC they presume to tell us what to expect over the next few decades.

“The link between climate and weather is well known: climate is determined by averaging weather variables over an extended period (usually 30 years) at one place or for a region. How can there be any faith in climate predictions by officials who admit they are unable to forecast the weather beyond a week or two?

“Perhaps now, governments will pay heed to those many independent climate scientists around the world who have been challenging the exaggerated projections by IPCC officials, and those political zealots such as Al Gore who use those predictions to mislead the ordinary public.

“In the light of these revelations and recent strong evidence that the sun not carbon dioxide controls the climate, the new Secretary General of the UN, Ban Ki Moon would do the world a great service by creating an opportunity for the world to hear from the independent scientists who disagree with the IPCC’s blaming mankind for climate variability that is natural and historic. There is no scientific justification for some of the extremist economic and social penalties that a minority of zealots are trying to impose on the people of the world.

“This is a matter of grave import and urgency for poorer nations who will suffer most from the proposed penal measures,” said Admiral Welch.

Contact: Rear Admiral (ret) Jack Welch CBE, tel 0064 9 4891237

7 thoughts on “Climate predictions “right only half the time””

  1. Interesting that NIWA is more frank in agreeing with the NZCSC about the shortcomings of their seasonal forecasts. In contrast to the Australian BoM who just keep on turning out their Outlooks that are “totally useless”, ref your 22 May post.

  2. Years ago I looked at seasonal forecasts and wrote up a paper on it (Hoyt, D. V., 1983. The probability of correct climate forecasts in the absence of any forecasting skill. Bull. Am. Met. Soc., 64, 1172-1173.) Going from memory, I compared NOAA forecast accuracy and the Old Farmer’s Almanac forecast accuracy for a few years. In both cases, the accuracy was hovering around 50% and the almanac actually did best with about a 51% accuracy. In 1983, the forecasts were not good enough to be useful and the same seems to be true today.

  3. Have coin, will travel ….. my fee is quite reasonable, and I require a lot less space and electrical current than a data centre …. LOL!

  4. In other words climate prediction is impossible – which is what we know from understanding it as a non-linear chaotic system.

    However if we have faith, then provided we spend money, lots of it, then we might improve our 50/50 chances?

  5. Warwick you wrote:

    Since the nighttime temperatures are rising three times as fast as the daytime temperatures (Karl et al., 1993), it implies a non-climatic signal in the nighttime data equal to about one half of the total warming. It implies the reported global warming of 0.6 C in the twentieth century should be reduced to about 0.3 C.

    Have you seen the analyses of Australia temperature data at,

    It shows that rising minimum temperatures are giving a false impression of rising nighttime temperatures, which are rising much less than the minimum, in a number cases there is no rise at all even though the minimum is rising.

    It is hard to avoid the conclusion that rising minimum temperatures reflect increased daytime warming and not increasing nighttime temperatures. As well as that increasing minimum and maximum temperatures are showing more heat gain to the system than there is.

  6. You had me searching for that quote Philip.
    It is on a page written by Dr Doug Hoyt,
    just above his references.
    I agree with his thrust there as I have thought for years now that IPCC supportive scientists have attributed DTR closure to a greenhouse signal when in fact it is exactly a UHI signal. Which they always manage to either ignore, trivialise or minimise in some way.
    In the early 1990’s I assembled data from various Southern Hemisphere remote locations and Islands and found no DTR closure.
    I have just posted a page listing reviews with links to comments of mine on some papers by the “great and good” of IPCC climate science,
    coincidentally the Karl et al 1993 paper in BAMS is on the list.

    Naturally I am very interested in Jonathon Lowe’s detailed analyses of Australian data and his finding that what we have thought of as warming minimums is in fact from increased warming in early morning sunshine.
    Hope I have not got that wrong.
    I have this on my list of things to do and need to clear my decks and devote at least half a day to going through what he has done step by step. Then seek out some long time series of T logging at frequent intervals through the day and examine some data myself.
    Here are just three links to some of Jonathon’s posts on the subject from last month.

    “Statistical Proof of sun caused global warming in South Australia Part II”
    May 04, 2007

    Statistical Proof of sun caused global warming in South Australia Part I, May 03, 2007

    “Maximums and Minimums”, May 2, 2007

    Thanks for your comment Philip.

  7. Global Temperature warming is explicitly that the global temperature background is increasing.

    As this number is the result of a summation of problematically positioned weather stations readings, however elegantly stated, means nothing more than tomorrow’s weather is unpredictable.

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