01 Dec 2009


All Posts, Potpourri No Comments

* Gold broke $1,200.

* Larry Kudlow’s open letter to Tiger Woods. (Yes, he goes there.)

* Wesbury and Stein on anti-Obama-stimulus hypocrites.

* A fantastic Richard Lindzen op ed. Sometimes I think the climate change skeptics I respect the most don’t make their strongest points in a pop forum. But this one is out of the park. My favorite part, which needs some explanation:

The IPCC’s Scientific Assessments generally consist of about 1,000 pages of text. The Summary for Policymakers is 20 pages….However, it has been my experience that even the summary is hardly ever looked at. Rather, the whole report tends to be characterized by a single iconic claim.

The main statement publicized after the last IPCC Scientific Assessment two years ago was that it was likely that most of the warming since 1957 (a point of anomalous cold) was due to man. This claim was based on the weak argument that the current models used by the IPCC couldn’t reproduce the warming from about 1978 to 1998 without some forcing, and that the only forcing that they could think of was man. Even this argument assumes that these models adequately deal with natural internal variability—that is, such naturally occurring cycles as El Nino, the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation, etc.

Yet articles from major modeling centers acknowledged that the failure of these models to anticipate the absence of warming for the past dozen years was due to the failure of these models to account for this natural internal variability. Thus even the basis for the weak IPCC argument for anthropogenic climate change was shown to be false.

To understand Lindzen’s powerful argument, you need to know exactly what it means when leading climate scientists say that there is strong evidence of “anthropogenic [manmade] global warming.” Let me reproduce my earlier summary of their evidence:

Richard Lindzen…thinks that the cutting-edge models do not correctly model certain processes in the atmosphere at the “micro” level. Orthodox climatologists concede the point, but then challenge Lindzen to tweak their models in order to come up with a better simulated fit with historical observations (on temperatures, rainfall, etc.). Thus far Lindzen has been unable to do this, because the fastest computers would not be able to run a simulation of the entire world, at a scale small enough to capture the effects Lindzen points to, and obey all the laws of physics.[1] What has happened (it seems to me) is that even the latest generation of climate models necessarily make some heroic simplifying assumptions, in order to render the model tractable. Lindzen isn’t accusing the modelers of being lazy. Even so, he maintains that their models are still crude and give very misleading results. The connection between the work of Paul Samuelson and, say, Israel Kirzner should be obvious.

What is particularly worrisome to me is that the case for anthropogenic global warming runs basically like this (and see the Intergovernmental Panel on Climate Change Fourth Assessment Report [IPCC AR4] section here [pdf] in their own words, especially Frequently Asked Question 9.2 on page 702): When the modelers simulate the 20th century, they achieve a closer fit to the historical trends if they assume large, positive feedback effects from human greenhouse gas emissions. If the modelers adjust the dials (so to speak) and turn down the possible influence of human emissions, then, so long as we insist the models obey the laws of physics, the fit between the simulated temperatures and observed temperatures gets worse.

OK now with that background, you can understand the power of Lindzen’s WSJ argument. Global temperatures have undeniably risen quickly in the 20th century. Skeptics say that we can’t be sure human activities are driving this trend, because there is so much about natural variability that the computer models don’t take into account. But the IPCC standard bearers come back and say these models are good enough for the purpose, and from what we know of internal, natural variability, we can’t get the models to reproduce the warming of the 20th century. Only if we assume that human impacts on greenhouse gases (through emissions and cutting down forests etc.) have a large effect, can the latest computer models do a good job simulating the observed climate changes.

OK, so now Lindzen is bringing up a different point: It is well known that since 1998, global temperatures either have slightly fallen or have been flat (depending on whom you quote), even though greenhouse gas emissions grew faster than the models predicted they would. The models that the IPCC uses predicted that global temperatures would have risen from 1998 onward, of course subject to natural variability.

So what Lindzen is here claiming, is that the IPCC apologists are undercutting themselves. In order to explain away the lack of (modeled) warming in the last decade, they need to rely on a large variance in natural climate factors. But then this weakens their claim that natural variability alone is insufficient to explain the warming of the 20th century.

Before Climategate, I would have been much less likely to pay credence to Lindzen on this particular claim. I would have believed a Gavin Schmidt if he said, “We are correctly accounting for both ends of the issue, and we’re in the sweet spot middle. Our models have just enough natural variability to explain the recent flat temperatures, but not enough natural variability to explain the overall warming trend in the 20th century.”

Yet after seeing Michael Mann wonder aloud if he and his colleagues have actually checked that this explanation about post-1998 temperatures is consistent with their models, I am much more inclined to believe Lindzen’s take.

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