Cross-post: Kesten Green – Is climate forecasting immune from Occam’s razor?

Several authors have argued that the hypothesis of dangerous man made global warming fails the test of Occam’s razor because the simple hypothesis of natural variation fits the data with fewer assumptions. As Harold Jeffreys noted, “simpler laws have the greater prior probability”. But are forecasts of dangerous warming immune from Occam’s razor?

It is on the basis of forecasts that the political leaders and government officials gathered in Paris are discussing agreements that would impose extraordinarily disruptive and expensive policies on the nations of the world. Those forecasts—called scenarios and projections by the U.N. Intergovernmental Panel on Climate Change (IPCC)—are the product of complex computer models involving multitudes of interacting assumptions.

The finding of Kesten Green and Scott Armstrong’s recent review that complexity increased forecast errors by 27% on average should give delegates at the Paris climate policy talks pause for thought. Occam’s razor would appear to apply to scientific forecasting, too.

At this year’s International Symposium on Forecasting, Kesten and Scott presented a review of the IPCC’s modeling procedures using a nine-item checklist on conformance with evidence-based guidance on simplicity in forecasting.

They found that the IPCC procedures have a “simplicity rating” of 19%. That figure contrasts with a simplicity rating of 93% for the Green, Armstrong and Soon no-change (no-trend) model of long-term global average temperatures.

Given the vast sums that have been spent on the IPCC process and how seriously the outputs are being taken by the Paris delegates, is it possible that alarm over dangerous manmade global warming is an exception to Occam’s razor in forecasting

Apparently not. The evidence presented by a notional bet between Scott Armstrong and Al Gore—represented by forecasts from the simple no-trend model and the IPCC model “business as usual” projected warming rate of 0.03C per annum, respectively—is that the IPCC’s preference for complexity has increased the size of forecast errors by as much as 45% over a seven year period.

Earlier evidence in Green, Armstrong, and Soon’s (2009) validation study found that the IPCC’s complex forecasting models increased the size of forecast errors by seven times relative to the simple no-change model for the period of exponentially increasing atmospheric CO2 from 1851 to 1975.

Kesten and Scott’s conference paper abstract and slides are available from ResearchGate, here.

Their paper, “Simple versus complex forecasting: The evidence” and their Simplicity Checklist are available from the Simple-Forecasting.com pages of theForecastingPrinciples.com (ForPrin.com) website. (You can do your own ratings of the IPCC procedures, to check if your ratings might lead to a different conclusion.) The original Green, Armstrong, and Soon validation study of IPCC forecasting is available here.

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22 Responses to Cross-post: Kesten Green – Is climate forecasting immune from Occam’s razor?

  1. Stackja

    “The science is settled” of course. Who can dispute it? /sarc

  2. Turtle of WA

    It’s immune from reason altogether.

  3. nerblnob

    I really don’t know why anybody wastes energy trying to prove these people wrong.
    They’re not interested in proof.

    Nor are they interested in physics, mathematics, chemistry or statistical analysis, ( let alone economics and history).

    They have something new called The Science.

  4. duncanm

    I’m with nerblob – there’s no point arguing reason and facts with these people. They’ve abandoned both long ago.

  5. John Constantine

    They saved the planet from the Y2K bug, they saved the planet from the ozone layer and now they will save the planet from history. Carbon is just the codeword for the right sort to recognise each other.

  6. JohnA

    John Constantine, please remove Y2K from the above.

    You have conflated a specific problem with a defined solution which WAS implemented, with two nebulous and poorly understood problems with no solution humanity is capable of achieving.

  7. rickw

    The Occam’s Razor approach climate says that the big hot thing that we are spinning around has something to do with it.

  8. rickw

    You have conflated a specific problem with a defined solution which WAS implemented, with two nebulous and poorly understood problems with no solution humanity is capable of achieving.

    In some cases yes, in a lot of cases no, the problem either didn’t exist or only had the potential to cause minor issues around the roll over. The whole issue was massively over-hyped which I think is pretty much Johns point.

    The IT industry shouldn’t get much thanks fixing an issue that it engineered to begin with.

  9. nerblnob

    At least the Y2k bug only had one future Point of No Return.
    Pretty amateur really.

  10. Bruce of Newcastle

    The day after the climapalooza wraps up we get this:
    Saudi snow
    Obviously they stopped global warming by sheer will, or something.

  11. Dr Faustus

    Obviously they stopped global warming by sheer will, or something.

    Their Sunni dispositions?

  12. cohenite

    Alarmism is delivered wisdom; it transcends science and mundane proof standards. Just try it; quote the IPCC (their reports have enough contrary evidence to refute AGW) to any hysteric and like the truly religious they will ignore their own source of proof if it contradicts their belief.

  13. Baldrick

    You cannot argue reason with an industry that calls carbon dioxide, ‘carbon pollution’.

    Until reason is introduced into the debate, which will be never, the luvvies will always get their way.

  14. Dr Faustus

    The IPCC is well aware that it is practicing scoundrel science. It is at great pains to insist that it produces ‘projections’ rather than ‘forecasts’ – although, if politicians and bureaucrats somehow assume projections are forecasts, well, what can we do?

    Specifically, the IPCC AR5 assessment report notes:

    Skilful multi-annual to decadal climate predictions (in the technical sense of ‘skilful’ as outlined in 11.2.3.2 and FAQ 11.1) are being pro- duced although technical challenges remain that need to be overcome in order to improve skill. These challenges are now being addressed by the scientific community.

    Shorter: We can’t get the farkn models to match reality – and we need more funding, or the World gets it

  15. Fat Tony

    Catastrophic Anthropogenic Global Warming (CAGW) has never been about the science – it never has and never will be. That’s why it is immune to physics, chemistry, engineering, logic etc.

    CAGW has always been about the power and/or money. It’s that simple.

  16. egg_

    Is climate forecasting immune from Occam’s razor?

    Were they engaged in a professional service, they’d be cleaned up in court, just like Al Gore’s mockumentary film.

  17. Diogenes

    At least the Y2k bug only had one future Point of No Return.

    The Y2K bug was a well understood problem, and was in, most cases being taken care of. Buuuuutttt when the shysters and scaremongers got involved a lot wasted so that in the event of a lawsuit they could prove due diligence. It never had the potential to be as bad as was predicted & Ed Yourdan , one of the greats of IT , lost much of his reputation as a result.

    The shysters are why I sat in “war room” with strangers running tests until 3am to prove what we knew would happen, instead of being tucked up in my little bed or celebrating with family.

  18. Elizabeth (Lizzie) B.

    Projections?

    Garbage in, garbage out. Ever t’was thus.
    Models are only as good as their premises and assumptions and what is considered in them.

    Not that the IPCC cares. The issue is now liturgical.

  19. Elizabeth (Lizzie) B.

    At least the Y2k bug only had one future Point of No Return.

    Yes, and a simple fix.

    The Religion of Climate Doom has no point of demonstration. Climate is Forever.

  20. Elizabeth (Lizzie) B.

    technical challenges remain that need to be overcome in order to improve skill.

    Nothing a bit of ‘scientific’ tinkering won’t fix.

    And they’ve been working in Paris lately on some new Psalms: provisionally called ‘Agreements’.

  21. Senile Old Guy

    In some cases yes, in a lot of cases no, the problem either didn’t exist or only had the potential to cause minor issues around the roll over. The whole issue was massively over-hyped which I think is pretty much Johns point.

    The Y2K nonsense was symptomatic of the new era of “scientific” catastrophic delusion. To anyone with a functioning brain it was obvious that Y2K, like climate change, would be a minor problem. The “media” told me that many of my devices would malfunction, even though I knew these devices did not have chips which could be affected. This included computers.

    Climate change is a similar non-problem. The Paris conference has finished with the aim of keeping the temperature change to less than 2 C, despite the fact that the average global temperature has not changed in 20 years, that “global average” temperature is an idiotic concept, as is the idea that we can control the climate.

  22. Andrew M

    Simpler climate models certainly have their appeal.
    http://imgur.com/jOLMXcP
    Getting all the main phenomena right at a gross level of detail is much more important than mashing together a biased subset of factors simulated at 10km resolution and 15 minute time scales.

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