When Will They Ever Learn? By Hendrik Tennekes

When Will They Ever Learn By Hendrik Tennekes

The current special issue of Climatic Change, the journal edited by Stanford University professor Stephen Schneider, is devoted to Learning and Climate Change. This appealed to me, so I started browsing. Let me quote a few highlights.


On p. 6, University of Maryland professor Andreas Lange writes:


“Considering limits in applying the expected utility framework to climate change problems, we consider a more recent framework with ambiguity aversion, which accounts for situations with imprecise or multiple probability distributions. We discuss both the impact of ambiguity  aversion on decisions and difficulties in applying such a non-expected utility framework to a dynamic context.”


On p. 67, MIT professor Mort Webster writes:


“We model endogenous learning by calculating posterior distributions of climate sensitivity from Bayesian updating, based on temperature changes that would be observed for a given true climate sensitivity and assumptions about errors, prior distributions, and the presence of additional uncertainties.”


On p. 139, University of California at Santa Barbara professor Charles Kolstad writes:


“Uncertainty with Complete Learning leads to higher expected membership but lower expected aggregate net benefits than No Learning, while Partial Learning almost certainly leads to lower membership and even lower expected aggregate net benefits.”


I am tempted to counter these exquisite examples of Bayesian scholarship with a few lines from my contributions to turbulence theory:


“The approximately log-normal probability distribution of the microstructure of turbulent flows has given rise to the concept of microstructural intermittency. The smallest scales of motion are active only in a small fraction of the space-time domain, requiring a revision of  the classic Kolmogorov theory of small-scale turbulence. The universal use of Fourier decompositions, however, is a complicating factor, because it causes spurious kinetic energy dispersion  in wave-number space.”


And what about an example of my hermetic jargon on the North Atlantic storm track?


“The meridional convergence of the zonal transient eddy momentum flux drives the momentum of the jet stream in a such a way that the suggestion is created that a negative eddy viscosity prevails. This concept, however, seems to contradict the Second Law of Thermodynamics, unless one is willing to make a thorough study of the energetics of the General Circulation.”


Obviously, it is not all that hard to poke fun with convoluted academic writing styles. I can do it too if I have to. But my mood changed when I came to the last paper in this issue of Climatic Science. It is a paper on Negative Learning by Michael Oppenheimer of Princeton University, Brian O’Neill of IIASA in Laxenburg, Austria, and Mort Webster. Negative Learning? The authors give a definition on p. 158:


“Negative Learning is a decrease or sustained divergence in the correspondence between the true outcome and the uncertainty characterization or belief over time.”


Their first alarm is sounded one page earlier:


“Our study suggests that twenty years of experience with large international assessments has failed to solve, and in some respects even aggregated the problem posed by negative learning for policy makers.”


I am capable of distinguishing between a bugle call on the battlefield and the incomprehensible jargon used by the Bayesian crowd, so I started reading this paper in earnest. On p. 156, I found:


“Overconfidence is one likely cause of negative learning, but it is by no means the only one. The use of expert elicitation to assess knowledge and uncertainty among limited groups of experts sometimes involves a  reflexive revision of judgments that is known to consolidate beliefs, revealing that some group interactions can lead to negative learning.”


Now, where did I hear such sounds before? Certainly not from James Hansen and Paul Crutzen, nor from Gavin Schmidt at RealClimate, nor from Susan Solomon, nor anyone of the recent 2007 Nobel Peace Prize winners at IPCC.  The message that Oppenheimer, O’Neill, and Webster want to convey is phrased in terms even a retired engineer like me can understand (p. 167-169):


“Given past experience, we recommend that the assessment process should be overhauled such that characterizing uncertainty becomes a co-equal partner with consensus building. Attention should be devoted to the implications of poorly understood or hypothetical but plausible processes and alternative model structures. Recommendations for improvements that would minimize the possibility of negative learning in the production and use of such assessments include avoiding uncertainty assessment based only on model intercomparison and explicit reporting of disagreements among assessment authors. In addition, research funding from mission-oriented agencies also bears the potential to reinforce existing assumptions. Funding could be explicitly allocated to research that explores alternative processes or assumptions not present in current models.”


“Almost no effort has been devoted to understanding why learning in the global change arena, whether in basic science or assessment, sometimes goes awry. It would be timely to perform critical reviews of particular assessment case histories, not just to compare predictions to outcomes, but to understand how specific judgments were made. Accordingly, IPCC working group discussions should become much more transparent, so that the basis for particular decisions might be understood by non-participants and participants alike. With more than three decades of experience in hand, the scientific community should apply the same strict standards of scholarship to examining how assessments perform and how they might be improved that it applies to its own research.”


These conclusions warm my heart. Is this paper in Climatic Change, certainly not a publication vessel for climate skeptics, perhaps a harbinger of things to come? Does the fact that worldwide temperatures have stopped climbing ten years ago finally penetrate even the stubborn and prejudiced minds that have been instrumental in forging the Consensus Doctrine? Is the tide finally shifting?


The message from Oppenheimer et al. to the IPCC crowd is evidently that IPCC should stop its addiction to Negative Learning. I want to add a message of my own. It is:


When will you ever learn?


In 1964, Bob Dylan wrote one of his most memorable lyrics:


“Come gather ‘round people

Wherever you roam

And admit that the waters

Around you have grown

And accept it that soon

You’ll be drenched to the bone.

If your time is to you

Worth savin’

Then you better start swimmin’

Or you’ll sink like a stone

For the times they are a-changin’.


The line it is drawn

The curse it is cast

The slow one now

Will later be fast

As the present now

Will later be past

The order is

Rapidly fadin’.

And the first one now

Will later be last

For the times they are a-changin’.”


I for one, hope that the times will yet change within my lifetime. 

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