Guest essay by Kesten Green
Several authors have argued that the hypothesis of dangerous manmade 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 the ForecastingPrinciples.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.
re rising sea levels, seems it is caused by global warming, nowhere have I read that there are tectonic plates around the world that are constantly moving, up down and sideways, could these we having an effect on rising sea levels, or maybe sinking or eroding land would be closer to the truth. I believe the land in Indonesia moved over a metre during the last big earthquake, DUHHHH, now if it had sunk, would the global warmists be claiming it was caused by global warming, I wonder.
Did you ever try Crabtree’s Bludgeon ? Invented it seems by Prof RV Jones.
>>>..
And then – and here whimsicality took over – he adumbrated Crabtree’s
Bludgeon, a fearful blunting of Occam’s Razor: “No set of mutually
inconsistent observations can exist for which some human intellect
cannot conceive a coherent explanation, however complicated.” In
which case, he observed, all the Intelligence Officers can do is to
stand by Occam. But Crabtree? Unmentioned by obituarists so far, he
was Jones’s greatest spoof, though his genesis was shared with a
number of contemporaries, including a distinguished Professor of
German and a subsequent Public Orator of London University.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>……….
http://www.independent.co.uk/news/obituaries/obituary-professor-r-v-
jones-1290472.html
It seems that it is still in use but without acknowledgement
The problem with using Occam’s razor is that all things are not equal. There is far more money to be had if the global warming is anthropogenic rather than due to natural variation. (This leaves aside the issue of whether there is indeed any global warming at present.)
Well, of course it is immune from Occam’s razor. (Likewise, AGW is unfalsifiable nonsense.) But, good luck convincing the public that that is not a good thing. BTW, the same is true for meteorology’s ‘storm theory’.
Willis,
Consider for example the path of a river in a relatively flat river valley bottom. The simplest assumption is that
the river would take the
shortest path from the highest ground to the lowest ground, basically a straight line.
____
a river takes the shortest line, the (projected) fall line down the hill, until it encounters a strong resistance. Then it takes the path through a softer resistance: meandering.
Occam’s razor.
Regards – Hans
johann wundersamer December 20, 2015 at 2:17 pm Edit
Thanks, Hans, but although that is simple, as Occam recommends, it is simply not true. Consider. A model river meanders on a sand table, where it’s all just sand and there is no “strong resistance”. Why do you think that is?
In fact, the meander is the result of the action of the Constructal Law, a non-simple subject which you might enjoy reading about … I append some links to both the work of others and my own posts on the matter.
w.
Explanation and links from Adrian Bejan. From that link:
Wikipedia article on Constructal Law, in particular the section on Constructal Thermodynamics which shows how the Constructal Law explains a host of empirical relationships a priori.
Bejan’s work on Constructal Climate Theory
My own work
the simplestpath from A to B may never get trodden, and the physics is rarely simple …
the physics basics are usually not that complicated, insists Occam, though every now and then we have to wait for the Newtons to clear the way.
Regards – Hans
johann wundersamer December 20, 2015 at 2:34 pm
I thought I might wander into Occamland, wherein to my surprise I found a much earlier quote from Aristotle saying the same thing:
The closest Occam came to clearly stating his Razor seems to be when he said Numquam ponenda est pluralitas sine necessitate [Plurality must never be posited without necessity]
There are a couple of critical clauses, one in each formulation. One is “ceteris paribus” and the other is “sine necessitate”.
The challenge, of course, is that the climate is unimaginably complex, and nothing is ever ceteris paribus. It has important phenomena going on at all spatial scales from the molecular to the solar system and beyond. It has important phenomena going on at all temporal scales from nanoseconds to millions of years and beyond. It has six major subsystems (atmosphere, lithosphere, cryosphere, biosphere, hydrosphere, electromagnetosphere), all of which interact with all the others in known and unknown ways. None of the subsystems could be said to be well understood, and all of them have external forcings and internal feedbacks and resonances.
Invoking either “simple physics” or Occam’s Razor in the study of such a chaotic complex system is … well … let me call it “unsupported by the evidence” and leave it at that.
w.
Occam’s razor is a rule for selection of each inference that will be made by a model from among the many possibilities. The need for a rule arises in the circumstance that information needed for deductive conclusion from one or more of these inferences is missing. If information is not missing there is not the need for a rule.
As Toto points out, Occam’s razor is an example of a heuristic. As there are many possible heuristics, the use of a particular heuristic fails to deliver a unique solution of selecting the inferences. In this way, Occam’s razor violates the law of non-contradiction (LNC). The LNC is among the classical laws of thought; to violate it is illogical.
The alternative to the use of a heuristic is the use an optimization that delivers a unique solution to the problem of selecting the inferences. The existence of this solution is a consequence of the fact that in the probabilistic logic every inference has a unique measure. This measure is the missing information in the inference for a deductive conclusion per event, the so-called “entropy.” The unique solution is produced by maximization or (dependent upon the type of inference) minimization of the entropy of each inference. Thus, this rule can be described as “entropy minimax.”
Entropy minimax yields, for example, thermodynamics and Claude Shannon’s theory of telecommunication. The second law of thermodynamics is an expression of entropy maximization. Details on theoretical aspects of entropy minimax are available in the book “Multivariate Statistical Modeling” by Ronald Christensen (ISBN 0-938-87614-7). Applications have been made in engineering, medicine, meteorology and other fields of study but not in climatology.
Ok. So how about this for a suggestion of an explanation which requires the least possible steps. I have no clue as to if this means anything. It could just be a pretty picture.
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An who knew that Mann may have been right all along, just possibly for the wrong reasons. Hockey stick anyone?
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The problem with relying on Occam’s razor is that there are many, many examples in science in which it has proved to be incorrect. Just one example is energy metabolism in mammalian cells. It is not simple. It is nowhere near the simplest way one could conceive for energy to obtained form carbon-based molecules. If there is an obvious theme in mammalian energy metabolism, it is that efficiency and simplicity have been sacrificed to retain control and adaptability. This type of thing is so common in biology, that I do not know any serious biologists who use Occam’s razor in thinking about their research. It seems to me that the earth’s climate system is similarly complex, and I would suggest that Occam’s razor is useless in trying to understand it. Just for the record, I am a strong skeptic with regard to CAGW, but not because of Occam’s razor.
Steve:
As you point out, Occam’s razor is capable of guiding us to the wrong theory. An alternative to Occam’s razor that guides us to the right theory is available but unused in global warming climatology.
It emerges from the probabilistic logic. This logic is the generalization of the classical logic that results from replacement of the truth-values of propositions by probabilities.
In the probabilistic logic each inference that is made by a model has a unique measure. This measure is the missing information in this inference for a deductive conclusion per event, the so-called “entropy.” In selecting the inferences that will be made by the model, the model builder executes an optimization that maximizes the entropy of each such inference under constraints expressing the available information. Alternatively and dependent upon the type of inference the model builder minimizes the conditional entropy.
This approach yields a theory that is at an optimal rather than minimal level of complexity. Thermodynamics is a well-known result. It maximizes the entropy of the inferred microstate under the constraint of energy conservation.