Sunday, December 6, 2009

On Warren Meyer and feedback

Elsewhere, FOTB Martel Firing asks for my take on a bit of 'blog science: (would-be) "Climate Skeptic" Warren Meyer's thoughts regarding feedback. The request is as follows:

I must admit that I'd find the papers beyond my knowledge as I remember nearly nothing from HS Chemistry decades ago. But thanks for the offer.
My point was simply that I think you were a bit harsh on Meyer, who although he has a good scientific/engineering education admits to being an amateur -- kind of like Benjamin Franklin and thousands of other amateurs who kept meticulous climate records before there was a single climatologist. For example, the world-wide effects when Krakatoa blew up in 1883 were chronicled in great detail mostly by amateurs. (See: Krakatoa by Simon Winchester)
If you want to refute Meyer's argument about AGW, I'd really like you to respond succinctly to his questioning of positive feedbacks needed to justify the catastrophic AGW climate models, e.g. what is the source of the positive feedbacks assumed by the models and what physical phenomenon and measurement thereof justifies a theory or run-away temperatures? (Less than 200 words, please, and no math. Thanks.) (...) See and be sure to review the links therein, including the video.

The "no math" request is a plea for a reason for the claimed positive feedback which seems rare in nature.

200 words is a bit short for such a big lump of errors, and to address feedback without math is a bit like trying to make a baby without using testicles, but I'll give it a go, anyway, with the caveat that I don't usually have patience for video, especially for video from people who can't get things right in the appropriate medium, which is writing, so the following addresses only the text. Here goes:

Naming positive feedbacks is easy. In paleoclimate, consider the effect of albedo changes at the beginning of an ice age or the "lagging CO2" at the end. In the modern climate, consider water vapor as a greenhouse gas, or albedo changes as ice melts. In everyday experience, consider convection's role in sustaining a fire. Consider the nucleation of raindrops or snowflakes or bubbles in a pot of boiling water. At the cellular level, consider the voltage-gated behavior of the sodium channels in a nerve axon or the "negative damping" of hair cells in the cochlea.

On to the meat of Meyer's argument: he seizes on one word ("feedback") and runs madly, from metaphor to mental model. Metaphor: "like in an ideal amplifier". Model: The climate experiences linear feedback as in an amplifier--see the math in his linked post or in the Lindzen slides from which he gets the idea. And then he makes the even worse leap, to claiming that climate models (GCMs) "use" something called "feedback fractions". They do not--they take no such parameters as inputs but rather attempt to simulate the effects of the various feedback phenomena directly. This error alone renders Meyer's take worthless--it's as though he enquires about what sort of oats and hay one feeds a Ford Mustang. Feedback in climate are also nonlinear and time-dependent--consider why the water vapor feedback doesn't continue until the oceans evaporate--so the ideal amplifier model cannot even be "forced" to apply.

Meyer draws heavily from a set of slides from a talk by Richard Lindzen before a noncritical audience. These slides are full of invective and conspiracy talk, and their scientific content is lousy. Specifically, Lindzen supposedly estimates effective linear feedbacks for various GCMs and finds some greater than one. The mathematics presented by Lindzen in his slides does not allow that, and he doesn't provide details of how such things even could be inferred. An effective linear feedback greater than one implies a runaway process, yet GCMs are always run for finite time, so there cannot be divergence to infinity. Moreover, as far as I know, all of the GCMs are known to converge once CO2 is stabilized.

In short, Meyer has the wrong idea about models (they don't take an amplifier-like feedback as a parameter), the wrong mental model of feedback (feedback in climate is nonlinear and time dependent) and he relies on a situationally unreliable source for numbers.