Streetwise Professor

February 17, 2007

Models vs. Data

Filed under: Climate Change — The Professor @ 11:11 am

File this under “looking for the cloud surrounding the silver lining.” Un-freaking-believable. A sad commentary on the state of climate science and its dominance by the modeling priesthood.

On 15 February, David Bromwich of Ohio State University released results of an important study showing that “[a] new report on climate over the world’s southernmost continent shows that temperatures during the late 20th century did not climb as had been predicted by many global climate models. . . . It also follows a similar finding from last summer by the same research group that showed no increase in precipitation over Antarctica in the last 50 years. Most models predict that both precipitation and temperature will increase over Antarctica with a warming of the planet.” Bromwich states: “What we see now is that the temperature regime is broadly similar to what we saw before with snowfall. In the last decade or so, both have gone down.”

So far, so good. Solid empirical research on a crucial geographic region. Indeed, inasmuch as the most alarming (and probably most alarmist) prediction regarding global warming is that heating in the polar regions will result in a massive release of water that will raise sea levels by catastrophic amounts, these findings represent very good news. Or at least, you’d think they would. But you’d be wrong. And that’s where the real interest in this story lies.

These results regarding snowfall and temperature are starkly at odds with the predictions of global climate models. These models predict that warming should be greatest at polar latitudes. Hence, these empirical results represent a major challenge to these models—and hence to the entire edifice of climate change theorizing and policy that rests on the models.

But rather than point this out in the emphatic way it deserves, Dr. Bromwich does everything he can to minimize the importance of his own research! (What’s up with that? The usual academic sin is to over-hype one’s own results.) Bromwich says “It isn’t surprising that these models are not doing as well in these remote parts of the world. These are global models and shouldn’t be expected to be equally exact for all locations.” [Query: Why should remoteness from civilization matter a rat’s rump in determining the implications of a region’s climate for global climate change? Isn’t the global climate a collection of largely remote regional climates? Or if it does matter, shouldn’t this cut the other way? That is, if economic development corrupts the surface temperature record, as has been plausibly argued and reasonably documented, wouldn’t you want to look at remote regions less affected by such development and place more emphasis on the results derived therefrom? Is Dr. Bromwich a reverse Bayesian who wants to put less weight on less biased observations and more weight on more biased ones? For that matter, if remote regions don’t matter, why is Dr. Bromwich wasting his time—and presumably freezing his tukkus—studying them? Masochism?]

In some ways the best response to Bromwich’s denigration of the poor regional performance of these models is “Duh”: it is well known that the skill of models in predicting the regional climate is pitiful. But the problem is much deeper than that. If the models are right, the regional impact of greenhouse gases should be greatest in the polar regions because the models predict that these regions are most sensitive to CO2 emissions. That is, if the models are right, they should do best in the Arctic and Antarctic, rather than failing miserably.

Dr. Bromwich attempts mightily to spin away from this obvious conclusion. He avers that “[i]t’s hard to see a global warming signal from the mainland of Antarctica right now. It’s very hard in these polar latitudes to demonstrate a global warming signal. . . . Part of the reason is that there is a lot of variability there.” However, the models predict that the climate change signal should be STRONGEST in the polar regions! If we can’t find it there, where the models predict it should be strongest, how can we have any confidence that we can detect it anywhere else? That is, if natural variability makes it “very hard in these polar latitudes to demonstrate a global warming signal” where the signal should be strongest how in God’s name can we detect it where the models predict it should be weaker? [Further my last aside: shouldn’t this enhance suspicion that the purported detection of a global climate signal from the instrumental record reflects in part—and perhaps in large part—biases in that record?]

There are other interesting tidbits. For instance, the research documents increasing strength in westerly winds in Antarctica. Well, an increase in the temperature gradient between polar and temperate regions is the most likely cause of an increase in winds. Standard models predict that GHG induced global warming should reduce the gradient (i.e., the poles should warm relative to temperate regions) and hence the winds should decrease in intensity.

Strike Three!: temperature predictions (wrong); snowfall predictions (wrong); wind predictions (wrong). Not even a foul ball in the whole at bat. Three cuts, three bad whiffs.

Bromwich notes that the increase in westerlies may be contributing to the warming of, and the consequent breakup of ice on, the Antarctic Peninsula—another iconic image in the Church of Global Warming. But if the winds result from an increase in the temperature gradient, this warming of the Peninsula is not a signal of global warming. Indeed, it could actually be a signal of global cooling—or at least polar cooling, which is flatly inconsistent with the anthropogenic global warming hypothesis which unambiguously predicts that the warming should occur disproportionately at the poles.

Like the recent research on the decline of heat content in the ocean in recent years, this study presents a major challenge to the model-driven “consensus.” (Ugh—how can self-respecting scientists worship consensus?) Rather than shout this from the rooftops, Dr. Bromwich cringingly attempts to shield the models from criticism. It’s not quite an auto da fe, but I suspect that Dr. Bromwich is striking such an attitude precisely because he wants to avoid offending the modeling establishment, thereby deflecting criticism and funding problems, or the necessity of walking through the public square recounting and recanting his heresy.

This is an inversion of the scientific method. Models are wrong. Always. Good modelers know they are wrong when they create them, but at the outset we don’t know how or why they are wrong. They are fleeting matches we light in a dark cave, not the Eternal Light of Truth. We are ignorant of the particular ways in which they are wrong, and learn by discovering their failures and adjusting our models and our understanding accordingly. Models push empirical work, and when empirical work documents failings in models the appropriate response is to revisit and revise—and sometimes junk—the received models. Scientific progress should be built on the rubble of discarded models.

Acting like the sycophants in “The Emperor’s New Clothes” is exactly the wrong way to respond to anomalous empirical results. The models are disposable, rapidly depreciating assets. The empirical evidence is not. The latter should take precedence. Spinning the empirical results so as not to discredit the models is antithetical to the advancement of our understanding of complex processes.

This episode and the ocean heat content one that preceded it (explained away as a “speed bump” as described in an earlier post) are symptomatic of a divergence between how science should work and how it works in practice. This should not be surprising. Kuhn pointed out years ago that there was a gulf between how science really works and the ideal scientific method. In practice, the tendency is to suppress empirical anomalies that challenge the conventional wisdom, rather than to pursue them doggedly in order to improve on—and perhaps jettison—the conventional wisdom.

So, there is little new under the sun. However, given the immense stakes in the climate change debate, these methodological deficiencies are much more costly than when the dispute involved phlogiston theory or the theory of the ether.

So please, Dr. Bromwich: revel in your results. Point out with relish how they conflict with the predictions of the models. Relentlessly needle the modelers into improving their products. Exult if your research consigns current models to Ozymandias-like oblivion. Go out and collect more data, and let the empirical chips fall where they may. Wear apostasy like a badge. Disdain consensus. In other words, be a scientist.

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