Saturday, 3 March 2012

Why CAGW theory is not “settled science” - Watts Up With That?

This guest post, elevated from a comment on Watts Up With That? is worthy of being reproduced in its entirety. Selected quotations would do both it and its author a disservice. I could not possibly improve on the reflections and analysis contained therein:

Guest post by Dr. Robert Brown, Duke University Physics Department

For the general public that does not have an objective scientific bent, how do you tell virtual reality from the real thing?

That’s a serious problem, actually. Hell, I have an objective scientific bent and I have plenty of trouble with it.

Ultimately, the stock answer is: We should believe the most what we can doubt the least, when we try to doubt very hard, using a mix of experience and consistent reason based on a network of experience-supported best (so far) beliefs.

That’s not very hopeful, but it is accurate. We believe Classical Non-Relativistic Mechanics after Newton invents it, not because it is true but because it works fairly consistently to describe Kepler’s purely observational laws, and (as it is tested) works damn well to describe a lot of quotidian experience as well on a scale less grand than planetary orbits. We encounter trouble with classical mechanics a few hundred years later when it fails to consistently describe blackbody radiation, the photoelectric effect (the one thing Einstein actually got the Nobel Prize for), the spectra of atoms, given Maxwell’s enormously successful addition to the equations of electricity and magnetism and the realization that light is an electromagnetic wave.

Planck, Lorentz, Einstein, Bohr, de Broglie, Schrodinger, Heisenberg and many others successively invent modifications that make space-time far more complex and interesting on the one hand — relativity theory — and mechanics itself far, far more complex than Newton could ever have dreamed. The changes were motivated, not by trying to be cool or win prizes, but by failures of the classical Euclidean theory to explain the data! Basically, Classical flat-space mechanics was doomed the day Maxwell first wrote out the correct-er equations of electrodynamics for the first time. We suddenly had the most amazing unified field theory, one that checked out empirically to phenomenal accuracy, and yet when we applied to cases where it almost had to work certain of its predictions failed spectacularly.

In fact, if Maxwell’s Equations and Newton’s Law were both true, the Universe itself should have existed for something far, far less than a second before collapsing in a massive heat death as stable atoms based on any sort of orbital model were impossible. Also, if Maxwell’s equations and flat spacetime with time an independent variable was correct, the laws of nature would not have had the invariance with respect to reference frame that Newtonian physics had up to that time enjoyed. In particular, moving a charged particle into a different inertial reference frame caused magnetic fields to appear, making it clear that the electric and magnetic fields were not actually vector forms! The entire geometry and tensor nature of space and time in Newtonian physics was all wrong.

This process continues today. Astronomer’s observe the rotational properties of distant galaxies to very high precision using the red shift and blue shift of the stars as they orbit the galactic center. The results don’t seem to agree with Newton’s Law of Gravitation (or for that matter, with Einstein’s equivalent theory of general relativity that views gravitation as curvature of spacetime. Careful studies of neutrinos lead to anomalies, places where theory isn’t consistent with observation. Precise measurements of the rates at which the Universe is expanding at very large length scales (and hence very long times ago, in succession as one looks farther away and back in time at distant galaxies) don’t quite add up to what the simplest theories predict and we expect. Quantum theory and general relativity are fundamentally inconsistent, but nobody knows quite how to make a theory that is “both” in the appropriate limits.

People then try to come up with bigger better theories, ones that explain everything that is well-explained with the old theories but that embrace the new observations and explain them as well. Ideally, the new theories predict new phenomena entirely and a careful search reveals it there where the theory predicts. And all along there are experiments — some of them fabulous and amazing — discovering high temperature superconductors, inventing lasers and masers, determining the properties of neutrinos (so elusive they are almost impossible to measure at all, yet a rather huge fraction of what is going on in the Universe). Some experiments yield results that are verified; others yield results — such as the several times that magnetic monopoles have been “observed” in experiments — that have not been reproducible and are probably spurious and incorrect. Neutrinos that might — even now — have gone faster than light, but again — probably not. A Higgs particle that seems to appear for a moment as a promising bump in an experimental curve and then fades away again, too elusive to be pinned down — so far. Dark matter and dark energy that might explain some of the unusual cosmological observations but a) are only one of several competing explanations; and b) that have yet to be directly observed. The “dark” bit basically means that they don’t interact at all with the electromagnetic field, making them nearly impossible to see — so far.

Physicists therefore usually know better than to believe the very stuff that they peddle. When I teach students introductory physics, I tell them up front — “Everything I’m going to teach you over the next two semesters is basically wrong — but it works, and works amazingly well, right up to where it doesn’t work and we have to find a better, broader explanation.” I also tell them not to believe anything I tell them because I’m telling them, and I’m the professor and therefore I know and its up to them to parrot me and believe it or else. I tell them quite the opposite. Believe me because what I teach you makes sense (is consistent), corresponds at least roughly with your own everyday experience, and because when you check it in the labs and by doing computations that can be compared to e.g. planetary observations, they seem to work. And believe me only with a grain of salt then — because further experiments and observations will eventually prove it all wrong.

That isn’t to say that we don’t believe some things very strongly. I’m a pretty firm believer in gravity, for example. Sure, it isn’t exactly right, or consistent with quantum theory at the smallest and perhaps largest of scales, but it works so very, very well in between and it is almost certainly at least approximately true, true enough in the right milieu. I’m very fond of Maxwell’s Equations and both classical and, in context, quantum theory, as they lead to this amazing description of things like atoms and molecules that is consistent and that works — up to a point — to describe nearly everything we see every day. And so on.

But if somebody were to argue that gravitation isn’t really a perfect force, and deviations at very long length scales are responsible for the observed anomalies in galactic rotation, I’d certainly listen. If the new theory still predicts the old results, explains the anomaly, I’d judge it to be quite possibly true. If it predicted something new and startling, something that was then observed (variations in near-Earth gravitation in the vicinity of Uranium mines, anomalies in the orbits of planets near black holes, unique dynamics in the galactic cores) then I might even promote it to more probably true than Newton’s Law of Gravitation, no matter how successful, simple, and appealing it is. In the end, it isn’t esthetics, it isn’t theoretic consistency, it isn’t empirical support, it is a sort of a blend of all three, something that relies heavily on common sense and human judgement and not so much on a formal rule that tells us truth.

Where does that leave one in the Great Climate Debate? Well, it damn well should leave you skeptical as all hell. I believe in the theory of relativity. Let me explain that — I really, really believe in the theory of relativity. I believe because it works; it explains all sorts of experimental stuff. I can run down a list of experimental observations that are explained by relativity that could scarcely be explained by anything else — factors of two in spin-orbit coupling constants, the tensor forms and invariants of electromagnetism, the observation of -mesons produced from cosmic ray collisions in the upper atmosphere far down near the surface of the Earth where they have no business being found given a lifetime of microseconds — and observation I personally have made — and of course all the particle accelerators in the known Universe would fail miserably in their engineering if relativity weren’t at least approximately correct. Once you believe in relativity (because it works) it makes some very profound statements about causality, time ordering, and so on — things that might well make all the physics I think that I know inconsistent if it were found to be untrue.

Yet I was — and continue to be — at least willing to entertain the possibility that I might have to chuck the whole damn thing, wrong from top to bottom — all because a silly neutrino in Europe seems to be moving faster than it should ever be aver to move. Violations of causality, messages from the future, who knows what carnage such an observation (verified) might wreak! I’m properly skeptical because what we have observed — so far — works so very consistently, and the result itself seems to be solidly excluded by supernova data already in hand, but you know, my beliefs don’t dictate reality — it is rather the other way around.

The sad thing about the Great Climate Debate is that so far, there hasn’t really been a debate. The result is presented, but no one ever takes questions from the podium and is capable of defending their answers against a knowledgeable and skeptical questioner.

I can do that for all of my beliefs in physics — or at least, most of them — explain particular experiments that seem to verify my beliefs (as I do above). I’m quite capable of demonstrating their consistency both theoretically (with other physical laws and beliefs) and with experiment. I’m up front about where those beliefs fail, where they break down, where we do not know how things really work. Good science admits its limits, and never claims to be “settled” even as it does lead to defensible practice and engineering where it seems to work — for now.

Good science accepts limits on experimental precision. Hell, in physics we have to accept a completely non-classical limitation on experimental precision, one so profound that it sounds like a violation of simple logic to the uninitiated when they first try to understand it. But quite aside from Heisenberg, all experimental apparatus and all measurements are of limited precision, and the most honest answer for many things we might try to measure is “damfino” (damned if I know).

The Great Climate Debate, however, is predicated from the beginning on one things. We know what the global average temperature has been like for the past N years, where N is nearly anything you like. A century. A thousand years. A hundred thousand years. A hundred million years. Four billion years.

We don’t, of course. Not even close. Thermometers have only been around in even moderately reliable form for a bit over 300 years — 250 would be a fairer number — and records of global temperatures measured with even the first, highly inaccurate devices are sparse indeed until maybe 200 years ago. Most of the records from over sixty or seventy years ago are accurate to no more than a degree or two F (a degree C), and some of them are far less accurate than that. As Anthony has explicitly demonstrated, one can confound even a digital electronic automatic recording weather station thermometer capable of at least 0.01 degree resolution by the simple act of setting it up in a stupid place, such as the southwest side of a house right above a concrete driveway where the afternoon sun turns its location into a large reflector oven. Or in the case of early sea temperatures, by virtue of measuring pails of water pulled up from over the side with crude instruments in a driving wind cooling the still wet bulb pulled out of the pail.

In truth, we have moderately accurate thermal records that aren’t really global, but are at least sample a lot of the globe’s surface exclusive of the bulk of the ocean for less than one century. We have accurate records — really accurate records — of the Earth’s surface temperatures on a truly global basis for less than forty years. We have accurate records that include for the first time a glimpse of the thermal profile, in depth, of the ocean, that is less than a decade old and counting, and is (as Willis is pointing out) still highly uncertain no matter what silly precision is being claimed by the early analysts of the data. Even the satellite data — precise as it is, global as it is — is far from free from controversy, as the instrumentation itself in the several satellites that are making the measurements do not agree on the measured temperatures terribly precisely.

In the end, nobody really knows the global average temperature of the Earth’s surface in 2011 within less than around 1K. If anybody claims to, they are full of shit. Perhaps — and a big perhaps it is — they know it more precisely than this relative to a scheme that is used to compute it from global data that is at least consistent and not crazy — but it isn’t even clear that we can define the global average temperature in a way that really makes sense and that different instruments will measure the same way. It is also absolutely incredibly unlikely that our current measurements would in any meaningful way correspond to what the instrumentation of the 18th and 19th century measured and that is turned into global average temperatures, not within more than a degree or two.

This complicates things, given that a degree or two (K) appears to be very close to the natural range of variation of the global average temperature when one does one’s best to compute it from proxy records. Things get more complicated still when all of the best proxy reconstructions in the world get turned over and turned out in favor of “tree ring reconstructions” based upon — if not biased by — a few species of tree from a tiny handful of sites around the world.

The argument there is that tree rings are accurate thermometers. Of course they aren’t — even people in the business have confessed (in climategate letters, IIRC) that if they go into their own back yards and cut down trees and try to reconstruct the temperature of their own back yard based on the rings, it doesn’t work. Trees grow one year because your dog fertilizes them, fail to grow another not because it is cold but because it is dry, grow poorly in a perfect year because a fungus attacks the leaves. If one actually plots tree ring thicknesses over hundreds of years, although there is a very weak signal that might be thermal in nature, there is a hell of a lot of noise — and many, many parts of the world simply don’t have trees that survived to be sampled. Such as the 70% of the Earth’s surface that is covered by the ocean…

But the complication isn’t done yet — the twentieth century perhaps was a period of global warming — at least the period from roughly 1975 to the present where we have reasonably accurate records appears to have warmed a bit — but there were lots of things that made the 20th century, especially the latter half, unique. Two world wars, the invention and widespread use and testing of nuclear bombs that scattered radioactive aerosols throughout the stratosphere, unprecedented deforestation and last but far from least a stretch where the sun appeared to be far more active than it had been at any point in the direct observational record, and (via various radiometric proxies) quite possibly for over 10,000 years. It isn’t clear what normal conditions are for the climate — something that historically appears to be nearly perpetually in a state of at least slow change, warming gradually or cooling gradually, punctuated with periods where the heating or cooling is more abrupt (to the extent the various proxy reconstructions can be trusted as representative of truly global temperature averages) — but it is very clear indeed that the latter 19th through the 20th centuries were far from normal by the standards of the previous ten or twenty centuries.

Yet on top of all of this confounding phenomena — with inaccurate and imprecise thermal records in the era of measurements, far less accurate extrapolations of the measurement era using proxies, with at most 30-40 years of actually accurate and somewhat reproducible global thermal measurements, most of it drawn from the period of a Grand Solar Maximum — climatologists have claimed to find a clear signal of anthropogenic global warming caused strictly by human-produced carbon dioxide. They are — it is claimed — certain that no other phenomena could be the proximate cause of the warming. They are certain when they predict that this warming will continue until a global catastrophe occurs that will kill billions of people unless we act in certain ways now to prevent it.

I’m not certain relativity is correct, but they are certain that catastrophic anthropogenic global warming is a true hypothesis with precise predictions and conclusions. I have learned to doubt numerical simulations that I myself have written that are doing simple, easily understandable things that directly capture certain parts of physics. They are doing far, far more complex numerical simulations — the correct theoretical answer, recall, is a solution to a set of coupled non-Markovian Navier-Stokes equation with a variable external driver and still unknown feedbacks in a chaotic regime with known important variability on multiple decadal or longer timescales — and yet they are certain that their results are correct, given the thirty plus years of accurate global thermal data (plus all of the longer timescale reconstructions or estimates they can produce from the common pool of old data, with all of its uncertainties).

Look, here’s how you can tell — to get back to your question. You compare the predictions of their “catastrophic” theory five, ten, twenty years back to the actual data. If there is good agreement, it is at least possible that they are correct. The greater the deviation between observed reality and their predictions, the more likely it is that their result is at least incorrect if not actual bullshit. That’s all. Accurately predicting the future isn’t proof that they are right, but failing to predict it is pretty strong evidence that they are wrong.

Such a comparison fails. It actually fails way back in the twentieth century, where it fails to predict or explain the cooling from 1945 to roughly 1965-1970. It fails to predict the little ice age. It fails to predict the medieval climate optimum, or the other periods in the last 10,000 years where the proxy record seems to indicate that the world was as warm or warmer than it is today. But even ignoring that — which we can, because those proxy reconstructions are just as doubtful in their own way as the tree-ring reconstructions, with or without a side-serving of confirmation bias to go with your fries — even ignoring that, it fails to explain the 33 or so years of the satellite record, the only arguably reliable measure of actual global temperatures humans have ever made. For the last third of that period, there has been no statistically significant increase in temperature, and it may even be that the temperature has decreased a bit from a 1998 peak. January of 2012 was nearly 0.1C below the 33 year baseline.

This behavior is explainable and understandable, but not in terms of their models, which predicted that the temperature would be considerably warmer, on average, than it appears to be, back when they were predicting the future we are now living. This is evidence that those models are probably wrong, that some of the variables that they have ignored in their theories are important, that some of the equations they have used have incorrect parameters, incorrect feedbacks. How wrong remains to be seen — if global temperatures actually decline for a few years (and stretch out the period with no increase still further in the process) — it could be that their entire model is fundamentally wrong, badly wrong. Or it could be that their models are partially right but had some of the parameters or physics wrong. Or it could even be that the models are completely correct, but neglected confounding things are temporarily masking the ongoing warming that will soon come roaring back with a catastrophic vengeance.

The latter is the story that is being widely told, to keep people from losing faith in a theory that isn’t working — so far — the way that it should. And I have only one objection to that. Keep your hands off of my money while the theory is still unproven and not in terribly good agreement with reality!

Well, I have other objections as well — open up the debate, acknowledge the uncertainties, welcome contradictory theories, stop believing in a set of theoretical results as if climate science is some sort of religion… but we can start with shit-canning the IPCC and the entire complex arrangement of “remedies” to a problem that may well be completely ignorable and utterly destined to take care of itself long before it ever becomes a real problem.

No matter what, we will be producing far less CO_2 in 30 years than we are today. Sheer economics and the advance of physics and technology and engineering will make fossil-fuel burning electrical generators as obsolete as steam trains. Long before we reach any sort of catastrophe — assuming that CAGW is correct — the supposed proximate cause of the catastrophe will be reversing itself without anyone doing anything special to bring it about but make sensible economic choices.

In the meantime, it would be so lovely if we could lose one single phrase in the “debate”. The CAGW theory is not “settled science”. I’m not even sure there is any such thing.

No comments:

Post a Comment