Arnold Kling  

McKitrick on Global Warming

Economists for Self-Improvemen... School Choice Pessimism...

Ross McKitrick writes,

In a greenhouse, movement of air is diminished, so the radiative portion of the energy drain must intensify. Physics can predict with certainty that in order to increase outbound radiation from a greenhouse, temperature inside the greenhouse must increase. A greenhouse must warm up.

But the story in the atmosphere is different. We are adding small amounts of infrared-absorbing gases (like carbon dioxide) to the atmosphere. This does not “trap heat” as the saying goes, instead it diminishes the efficiency of the radiation drain. So the fluid dynamics must adjust to maintain energy flow balance. In order to predict what will happen at the Earth’s surface, it is necessary to solve the equations governing fluid dynamics.

The problem is that no one knows how to do it.

McKitrick, like me, is someone with an economics background who is skeptical on global warming. He is much more conversant than I am on the scientific issues. Read the whole thing.

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COMMENTS (35 to date)
Ben Kalafut writes:

Is he, too, both skeptical and hobbled?

What I mean to ask is: Is he discussing his concerns with working climatologists, as you should be doing? Signs point to McKitrick doing more spitting than anything, especially on the "hockey stick" issue. He certainly hasn't been listening.

I'm reading what he has to say about the Navier-Stokes equations, and I believe you're the victim of a clever act of misdirection. You've been had, once again. (To be fair, it could just be that McKitrick is extremely unfamiliar with the science. If so, nonetheless, an honest man would not offer an opinion in that case.)

A good physics student knows that solutions to the Navier-Stokes equations exist in the colloquial sense, as he has solved them. (See e.g. Batchelor's textbook on fluids.) Having read the description of the problem for which the Clay Institute is offering a prize, I have found nothing that could be construed by a mathematically literate reader (and I presume that McKitrick is mathematically literate, if nothing else) to mean that the Navier-Stokes equations cannot be solved. The Clay Institute is offering a prize for showing either
(A) Solutions exist for all smooth boundary conditions.
(B) Solutions exist for all smooth periodic boundary conditions.
(C) A's negation
(D) B's negation.

This mathematician's general case has no bearing on whether or not climatologists understand convection, and most certainly not on the time-scales of the climate simulations.

If you had chatted up your local atmospheric scientists, you'd have known this already. Why post a manifestation of ignorance and wait for a biophysicist 3000 miles away to set you straight?

david writes:

I also have to say that this is bordering on the silly. There are (although few) scientists that have the training to evaluate these things and that are sceptical of global warming. None of those, as far as I know, is of the opinion, that the problem is that fluid dynamics cannot be handled.

If someone came to you, clearly without any knowledge of even undergraduate textbook economics, and claimed that all of economics is utterly wrong, you would call that person silly, right? But at this point, that is what you are doing. Sorry. Move on.

Arnold Kling writes:

Actually, if someone had come along in 1970 and said, "All of macroeconomics is wrong," they would have been more right than the typical macroeconomist at the time.

It is one thing to say that it is silly to question settled science. It is less silly to question science that is settled only at a political level.

Ben Kalafut writes:

"Science only settled at the political level" is an interesting hypothetical, but it doesn't apply here.

Here we have science only not settled at the political level, its dual. That isn't to say that climatologists all agree on the ins and outs of AGW, but rather that the question of whether AGW is happening is no longer itself scientifically current. You can demonstrate this to yourself by scanning the geophysics/climatology literature.


Consider objecting to AGW due to a belief that scientists can't handle fluids akin to a student coming to you in 1970 and saying "all of economics is wrong because none of these seminal papers are taking into account how the 'surplus value' is stolen by The Capitalist". "No" isn't even a good enough answer; the Japanese/Zen 'Mu' may suffice.

David writes:

If someone in the 70s came along, had no understanding of what macroeconomists at that time did, and claimed it was all wrong, he might have been right, but it would have been pure luck. Now, you can hope that you are the lucky one in this case, but you cannot seriously expect anyone to take you serious with such a line of argument.

ed writes:

Umm, I don't get his criticism at all. He says half the energy from the son is removed by radiation back into space, and the other half is "removed by the fluid dynamics of the atmosphere: convection, turbulence, wind, evaporation, and so forth."

But those things don't actually "remove" any energy from the earth, as far as I can tell, they just change it into different forms, which probably eventually get converted into heat (unless is is somehow stored as chemical energy or something, but I don't see how that would happen and he doesn't say.) Can anyone make sense of this?

Matthew writes:

I find it quite ludicrous to say that AGW is a settled scientific issue, given that we don't understand the causes of natural climate cycles such as the ice ages.

Given that we don't understand natural climate variation, what hope do we have of understanding natural + anthropogenic climate variation?

MANUELG writes:

I enjoy this blog. Ben Kalafut worded his reply very strongly and rudely. But I confess I agree with the substance.

I am very interested in the views of the people (scientists, but also laymen and other climate science non-professionals) who deny human causality in global warming, or at least deny causality by humans burning burning fossil.

I am very interested in the views of people who say global warming is not a net negative. I am very interested in the views of people who research if the costs of regulating fossil fuel use would outweigh the benefits.

But how can I have any patience for people who perpetrate or condone the art of controversy?

* Scientific consensus on global warming - What is consensus _really_? Hire a pollster! (Talking about climate change, all of a sudden the concept of consensus becomes fraught with difficulty? How much patience for skeptics who attack every word with more than two syllables?)

* Ocean levels rising, ice caps melting - Mass hysteria! Mass hypnosis!

* Temperatures are not rising, and if they are, it is from natural causes! (If I tell my wife that I am not having an affair, _but_ if I _was_ having an affair, my mistress really doesn't mean anything to me... my argument is _not_ strengthened by joining the two lines of argumentation, obviously. Pick the horse you think will win, and stick with it.

* Convection in a greenhouse - Navier-Stokes hasn't been solved! (mathematicians have known that Fermat's last theorem was true since Fermat first wrote it down in 1637. The interest in the proof completed in 1995 wasn't that there was doubt of the theorem, the interest was in the analytical tools that had to be created to put the statement into the realm of mathematical certainty. The The Clay Mathematics Institute prize is for the mathematician who handles the Navier-Stokes equation similarly. Physicists are not barred from using the equation and trusting the results, today. Mathematicians hold themselves to a much more rigorous standard, or else research on Fermat's theorem would have closed in 1637.)

* Once there is scientific consensus, for social and economic reasons it is impossible to change dominant theories! (ignoring the contradiction with the assertion that consensus doesn't exist... if you marshal the facts on your side, and the facts match your hypothesis, there is very little you _can not_ do. That is why we don't study bodily humours in medicine, and we don't study the vibration of cosmic ether, and why we don't consider heat to be a substance. In each case, the truth overcame almost universal opposing consensus. Each case, the truth allowed for better predictions to experiments, or better summary of disparate data, and the universal opposing consensus evaporated. If the truth of climate skepticism is like a small schoolboy that runs away from a bully, it is then a very _peculiar_ type of scientific truth.)

(I remind myself: I compose this note for my own benefit, and to no one else's benefit. I will keep a copy on my thumbdrive. If you delete this and any other push-back on your climate skepticism, I trust I will continue to read and enjoy your blog, because I appreciate your viewpoint and writing. Cheers.)

dearieme writes:

"mathematicians have known that Fermat's last theorem was true since Fermat first wrote it down in 1637": shouldn't that be that mathematicians (what, all of them?) were confident that...? To "know" in maths needs proof, surely?

Anyway, Navier-Stokes. You can certainly solve the equations for all sorts of special cases, in the classical sense of "solve" - getting closed form solutions. But to solve them for many other cases is to change the meaning of "solve": it might be proper to admit to that.

Fly Fisher writes:

A while back, Arnold provided a post to a chapter from Freeman Dyson's book "A Many-Colored Glass":

A quote from Professor Dyson that appears to be relevant is:

My first heresy says that all the fuss about global warming is grossly exaggerated. Here I am opposing the holy brotherhood of climate model experts and the crowd of deluded citizens who believe the numbers predicted by the computer models. Of course, they say, I have no degree in meteorology and I am therefore not qualified to speak. But I have studied the climate models and I know what they can do. The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world that we live in. The real world is muddy and messy and full of things that we do not yet understand. It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds. That is why the climate model experts end up believing their own models.

Well put.

Ben Kalafut writes:


Significant progress has been made in the understanding of natural, long-term, quasi-cyclic phenomena like ice ages. To say "we don't understand" is equivocal. We do understand. Our understanding is limited and could be better.

Nonetheless that has little bearing on whether or not scientists understand the underlying physics enough to say something meaningful about a relatively short-timescale phenomenon like anthropogenic climate forcing.

Ross McKitrick writes:

Ben Kalafut, in answer to your first question, Yes of course I have discussed this issue at length with a mathematician who has spent many years studying fluid dynamics problems. I wrote a book with him in fact, and much of the first section is taken up with the problem. I don't claim any knowledge of the subject beyond what resulted from writing that book, but it is enough for me to be justified in saying that this is important for users of model outputs to be aware of.

I don't know what it means to say "solutions exist in a colloquial sense." Perhaps you mean solutions exist in special cases. If exact, general solutions existed for describing the fluid dynamics of the atmosphere (including turbulence), then all the models would use the same equations and predictions would be identical. But modelers use parameterizations rather than exact theory, and models differ from one to the other both in structure and predictions. There has to be a reason for this. My understanding is that the theory does not exist to support exact computations.

As for your suggestion that I am "spitting" on the hockey stick issue etc., I take exception to this. We published our papers in journals, we presented our arguments to the National Academy panel, and our work was thoroughly investigated by the Wegman committee. We won those arguments fair and square.

David, I have said nothing analogous to "all economics is utterly wrong" or even "all modeling is wrong". I am arguing that models are useful within their limits, and to understand those limits you need to understand where the theory does and does not provide guidance. I can't see why that is controversial. Yes, the fluid dynamics can be "handled" in the sense that models do something. The questions is how good that "something" is.

ManuelG: I suggested taking a poll because so many other commentators have placed weight on understanding the extent of consensus, yet never cite poll numbers to support their beliefs. I am confident a poll would reveal more disagreement than the common perception.

For those deeply convinced of GHG-induced global warming, I would be interested in your responses to the following:
- what about the tropical troposphere record?
- what about the evidence that the surface data are contaminated with a warming bias?

Dan Pangburn writes:

Climate obviously has changed and will continue to change. The observation that ice is melting does not show that human activity is the cause. The assertion that humans are or ever can have a significant influence on climate by limiting the use of fossil fuel (a.k.a. limiting human production of carbon dioxide) is not supported by any historical record. Avoid the group-think and de facto censorship by Climate Scientists. Directly interrogate official government data that taxpayers have paid for from ORNL and NOAA as follows: If the carbon dioxide level from Lawdome, Antarctica is graphed on the same time scale as fossil fuel usage from it is discovered that the current carbon dioxide level increase started about 1750, a century before any significant fossil fuel use. If average earth temperature since 1880 from is graphed on the same time scale as fossil fuel use it is discovered that there is no correlation between rising fossil fuel use and average global temperature to 1976. The asserted hypothesis that, since 1976, increasing carbon dioxide level has caused the temperature to rise is refuted by the carbon dioxide level from and earth temperature from determined from the Vostok, Antarctica ice cores. If these are graphed on a higher resolution time scale it is discovered that the change in atmospheric carbon dioxide level lags earth temperature change by hundreds of years. If Lawdome and recent carbon dioxide data and Vostok and recent temperature are plotted on the same graph since 1000 AD (or before) it is observed that temperature oscillates up to plus or minus 1.5 degrees Celsius (half pitch about 100 yr) while carbon dioxide level remains essentially unchanged (between 9000BC and 1750AD). This will also show that the average global temperature 200 years ago was about the same as now, 400 years ago was significantly higher than now and current rate of temperature change is fairly typical. Recent measurements show that average earth temperatures in 2006 and 2007 were actually lower than in 1998. As shown at ,for most of the history of earth carbon dioxide level has been several times higher than the present. The conclusion from all this is that carbon dioxide change does not cause significant climate change. Actions based on the human-caused global warming mistake put American freedom and prosperity at risk.

Lord writes:

The conclusion from all this is that carbon dioxide change does not cause significant climate change.

Talk about ill founded arguments. Did it ever occur to you that fossil fuels are not the only means of modifying carbon dioxide? That most of the early modification would have come from deforestation and increased cultivation that produced the need for fossil fuels in the first place?

Matthew writes:

We do understand. Our understanding is limited and could be better.

OK, what causes the cycles of glacial / interglacial periods?

Ben Kalafut writes:
If exact, general solutions existed for describing the fluid dynamics of the atmosphere (including turbulence), then all the models would use the same equations and predictions would be identical. But modelers use parameterizations rather than exact theory, and models differ from one to the other both in structure and predictions. There has to be a reason for this. My understanding is that the theory does not exist to support exact computations If exact, general solutions existed for describing the fluid dynamics of the atmosphere (including turbulence), then all the models would use the same equations and predictions would be identical. But modelers use parameterizations rather than exact theory, and models differ from one to the other both in structure and predictions. There has to be a reason for this. My understanding is that the theory does not exist to support exact computations

Not entirely true. There are many cases in the hard sciences where exact, general solutions are known--and knowing them is a different matter than existence proofs!--but go unused, and for good reason. Consider for example the old BCS theory of low-temp. superconductivity.

There is no general solution to the Navier-Stokes equation, and as you point out in the letter Kling cited, there is not even a proof that a smooth solution exists for every smooth boundary condition!. What of it? Citing that mathematicians' problem does not constitute a valid argument that physicists do not understand fluids well enough to model the climate.

Regarding spitting, you may wish to step back for a moment and ask yourself just what was vindicated at the Wegman hearing and what you mean by "won", let alone "fair and square". Ask yourself why Michael Mann is not convinced. Ask yourself why Wahl and Amman are not convinced. Ask yourself why climatologists in general are not convinced. Ask yourself whether it is ever proper to demagogue a scientific question. Ask youself whether your conduct has been that of a responsible scientist, in spreading the notion that the theory of AGW hinges on a particular paleoclimatic reconstruction whose methodology you find lacking.

Regarding supposed contamination of the global temperature estimate, consider for example that the NASA's GISS data reveal no correlation between temperature anomaly and urbanization, or that the rural-only estimate closely matches the rural plus urban method. Have a look at and references therein regarding how this is dealt with. Peterson et al, Journal of Climate 16 (2003) also makes good reading

You may have had sound if not damning concerns about paleoclimatic reconstuction methodologies, ones which have subsequently been addressed by climate scientists, but these innuendoes about contamination of the temperature record in this context (as if such contamination is damning for AGW) are without merit.

While you're at it, ask yourself why you're still trying to sell a schematic curve (that baloney with the MWP and LIA) from Chapter 7 of the 1990 IPCC report as though it's the technical equivalent of modern paleoclimatic reconstructions. Note the caveat about this curve present in the 1990 IPCC report. Note moreover that even if the MWP/LIA curve were to be correct, it does not automatically follow that 20th/21st century warming is not of anthropogenic origin. Worth noting, too, is that the statement that the MWP/LIA pattern was the consensus view until Mann et al is totally without base. Not only does the caveat of the 1990 IPCC report show that the consensus view was "we don't really know", by 1992 the supplement was citing the Wang and Wang study (Wang, S. and Wang, R. 1991: Reconstruction of temperature series of North China from 1380s to 1980s . Science in China (Series B) 6, 751–759 .), whose (limited) reconstruction had no MWP or LIA.

Your willingness to pitch both possibly-sound arguments (like the criticism of Mann et al, who have been vindicated by subsequent statistical work and newer reconstructions), and the blatantly bogus (the 1990 Little Ice Age/Medieval Warm Period), rather than sticking to the former, together with your apparent unwillingness to address the scientific merit of attribution studies (instead prefering to impress ignorant folk by noting a Clay Institute prize for an existence proof!) causes one to greatly doubt your sincerity and your claim to genuine skepticism, Mr McKitrick.

Mike M. writes:

Some more thoughts to ponder. The hysteria behind AGW is based largely on expected positive feedbacks, none of which appear to be happening. Climate sensitivity to just co2 itself is about 1.3c. about .7c having occurred already. It's a much better bet that negative feedbacks, primarily precipitation and ocean currents, will mitigate Co2 warming.
There is no way we will see warming with the next two solar cycles, either. We are about to experience minimal sunspot activity not seen for two hundred years. Top that off with the Pacific Decadel Oscillation and the North Atlantic Oscillation finally flipping back negative after 30 years of havoc and AGW will be a thing of the past.
Am I right, Ross, or what? Nice smackdown by the way. Not sure how anyone can take the Hockey Stick seriously anymore. Not even the IPCC really pays attention to it.

Ben Kalafut writes:

What causes ice to begin or end? Astronomical forcings, biological events, changes in ocean currents, volcanism.

To understand a problem is not the same as being able to produce a wind-up clock or analytic formula that exactly duplicates it. (If so, we'd say that economists don't understand anything!)

Why did I just answer for "Matthew" something he could have looked up himself? I don't know. Toss that to Bryan C as an example of irrationality.

Rolf writes:

I'm afraid Kitrick has got his basic physics wrong, in any case: A greenhouse does not work in the manner he suggests, and neither does the Earth's energy balance. In particular, he says:

"About half the energy at the surface leaves through infrared radiation, and the other half is removed by the fluid dynamics of the atmosphere."

This is wrong. The only way fluid dynamics can remove energy from the Earth is to actually kick particularly hot molecules into space; this does not happen, to a really excellent approximation. It is possible that he means to say that the energy is moved from the dirt that makes up the surface in the proportions he suggests; that could well be accurate but it has nothing to do with the energy balance. As long as the energy is not leaving the Earth's atmosphere, it's going to be doing something. In particular, it's going to heat up some part of the Earth. To the extent that this involves those fluid dynamics, it will mean more-energetic weather. We generally do not like this.

Mike M. writes:

Vindicated my ass. You haven't seen Craig Loehle's paper which uses 18 different peer reviewed reconstructions to prove that not only DID the MWP exists but that it was warmer then than it is today? Maybe you need more evidence ?
Get a grip, man. You obviously believe that everything you need to know is found at Realclimate, a place of circled wagons and groupthink. Try Climate Audit for a week if you have any intellectual principles left.

Matt writes:

"About half the energy at the surface leaves through infrared radiation, and the other half is removed by the fluid dynamics of the atmosphere: convection, turbulence, wind, evaporation, and so forth."

That statement by Mr. McKitrick is misleading and not relevant. We are talking about the total globe, and it can only lose energy by radiation or particle emission.

His point about fluid dynamics is relevant, and many of the alternative theories propose changes in cloud flow, or rain flow that moves more heat, more often to the upper atmosphere (for radiation).

But, McKitrick, in his critique does admit to the basic issue, the globe dynamics must change to accomodate less radiation drain, to restore balance. So, leave it there.

We can calculate the change in radiative drain because we can measure GH in most points of the globe, and that is not fluid dynamics. So, we can calculate with McKitrick certainty the quantity of change required in new fluid dynamics, or heat retention that must be accommodated. And, if I interpret the data, we are gonna get hot or we need a lot of storms to move heat upward. Either way, we have an economic liability, time for the jury.

Ben Kalafut writes:

This is what I mean about false skepticism. McKitrick makes a big deal--and competently--about pitfalls of Mann et al, but feels just fine citing the Loehle study from Energy and Environment.

It really ought be clear who needs to "get a grip". One of us confounds a mathematical nicety (the existence proof) with the ability to do fluid dynamics itself--or deliberately leads others to do so. One of us hawks a schmatic fudge from the 1990 IPCC report as evidence of some wrongdoing on the part of climatologists.

Climate Audit is cute, but there's too much FUD and and alarmism. It's almost as bad as getting science news from the mainstream media; little to no differentiation is made between motes and beams, and the soi-disant "skeptics" get a pass.

Come back when your "side" of the issue has put out a scientifically sound counter-argument, preferably an attribution study, in a climatology or general interest (e.g. Nature, Science, PNAS, Phys Rev) journal. Having to convince experts in the field may just restore your intellectual integrity.

Matt writes:

The other problem that must be admitted by "restore the balance" critics is why, if the globe can restore balance, did we miss the last glacial cycle some 12,000 years ago?

This cyclic trend, measured with more than 5% accuracy, tells us that we run almost precisely timed glacial cycles. There was no geological change, so unless we theorize an asteroid, something in the biology changed, something the AGW critics are loathe to admit is possible.

Ben Kalafut writes:

Mea culpa: Mike M is not Ross McKitrick.

Ross McKitrick writes:

Ben, if Mike Mann, or Wahl and Ammann, still believe the MBH98 PC method is valid, or that a reconstruction can be considered robust whose ranking of the 20th century against the medieval era reverses upon the inclusion of the Graybill bristlecone pines, then they do so against the conclusions of both the Wegman report and the NRC report. And more to the point, if they still hold those views (which I doubt), they are simply wrong, regardless of how many people they count as supporters. Wahl and Ammann ended up conceding our arguments on the insignificance of the MBH98 reconstruction--see Table S1 in their Climatic Change article, and they also concur that removal of the bristlecones removes the hockey stick shape. Their position is that bristlecones ought to be included, but the NRC panel recommended they should be avoided, which I would say is a point of general agreement.

The argument for AGW does not rest solely on the hockey stick, but it was central to the AGW arguments circa 2000-2003. This is not my invention. It's there in the IPCC and other reports, on government web sites, in comments by government officials, etc. If it was so unimportant then 2 outsiders calling it into question would never have attracted attention. I am not trying to "sell" the IPCC 1990 diagram, my point is that, despite being a schematic, it summarizes what people thought at the time. Had MBH98 not appeared it is unlikely that the IPCC report in 2001 would have dared assert the relative warmth of the modern era so strongly. And if the IPCC had such a wide range of non-MBH evidence as of 2001 for eliminating the MWP/LIA, they should have shared it with their readers.

The subsequent "vindication" of the MBH work consists largely of studies that re-use the bristlecones, or even in some cases reuse the same PC methodology. Look at the Wegman Report's analysis of how these "independent" studies re-use the same core data series over and over. Take out those studies and you are left with little basis for trying to rank the 20th century and the medieval era.

I have already shown that NASA GISS data correlate with measures of surface economic activity, in a 2004 paper in Climate Research. My new JGR paper discusses Peterson and the other articles on which the IPCC has based its defence, including Jones 1990. My findings are not "innuendoes" they are published statistical papers. Note that in the AR4 (Ch 3, p 244) the IPCC cites our 2004 paper, and the deLaat/Maurellis results, and offers no citations in support of their dismissal of the problem. They claim that climate oscillations explain away our results and make them insignificant. This statement is sheer invention, and provably false.

Rolf/Matt: you are referring to radiation to space from the top of the atmosphere. I am talking about change at the surface, where convective cooling takes place.

max writes:

Well, McKitrick is wrong and right. If he assesses that a perfect solution for Navier-Stokes equations is not obtainable, but this is not how engineers and natural scientists work.
Actually there are solution methods for specific fluid dynamic problems and there are generalisations and simplifications that can aid (F.e. you can reduce the differential equations to a point where a solution is obtainable by educated assumptions (though you should prove your assumptions), or you can try to use Finite discretisations, which leave a margin of error that is, however, in most cases insubstantial).

However, to assert that fluid motion as compared to the static environment of a greenhouse(only true for long periods of time and in respect to the hall house!) are totally uncontrolled for in climate models lacks a certain understanding.
I am critical of many conceptions in climate models and many of the assumptions should be checked, but fluid motion and its description most likely is not the problem.

However, it is also untrue that McKitrick and McIntyre are not conversing with scientists, it is however mostly the other side that doesn't want to discuss issues they believe are settled.
The sternest and most interesting critique on climate models by M&M (imo) is about climate modeling per se. Here econometricians and statisticians have a better understanding of the issue than most natural scientists and thus there criticism is valid.

Arnold Kling writes:

Note: Mike M's earlier comment ("vindicated my ass") went outside of classroom etiquette. The editor took steps to address this.

burger flipper writes:

"Scientists are totally aware of the shortcomings of their models and up here in the Arctic they are gathering data with unprecedented energy."

This from the rebuttal to Dyson, which also appeared on EDGE:

burger flipper writes:

And a quick quote from the miraculous Cowen:

"Like Arnold Kling, I do not much trust climate models. Perhaps I have spent too much time doing macro, and the experience carries over. Nonetheless uncertainty about final effects gives us more to worry about, not less."

Chuck writes:

When engineers need to use an equation that they can not solve analytically, they simply use numerical analysis to solve it instead. We're talking about computer's with massive number crunching capability here.

Ben Kalafut writes:


The sternest and most interesting critique on climate models by M&M (imo) is about climate modeling per se. Here econometricians and statisticians have a better understanding of the issue than most natural scientists and thus there criticism is valid.

You're really going to have to justify this; AFAIK neither econometricians nor statisticians do computational fluid dynamics, finite element analysis, or anything similar.

Most natural scientists don't, either. But quite a few applied mathematicians, and more than a handful of physicists and engineers do.

Matthew writes:


I have a degree in geology, so I am perfectly aware of Milankovitch cycles and more irregular factors contributing to paleoclimate. The fact is, we have no good postdiction models for paleoclimate, so the idea that prediction models for future climate are somehow any better is simply not tenable.

It seems clear that at this point AGW science is all about politics and funding and "sending the right message". So I am quite skeptical of all the certitude displayed by AGW proponents.

Barkley Rosser writes:

Ross McKitrick,

So, while I am an economist, I am someone who has been working off and on with climatologists since the early 1970s, including with your coauthor, Pat Michaels' major professor. It was from him that I first learned about chaotic dynamics in the Lorenz model, which was before the term "chaos" was even being applied to the phenomenon. So, sure, climate is a complex system (and I have published papers on this matter), which means that the nonlinearities and complexities can cut either way: things might be better or they could be worse than the standard models say. Your argument is for fatter tails in both directions, not for a "Wow,everyting is cool, everybody can just ignore all this stuff."

I would also note that Pat Michaels these days does accept that global warming is happening. He is the one arguing that roughly the exponential increase in CO2 concentrations is about balancing off the roughly logarithmic relation between that concentration and global average temperature, leading to a roughly linear temperature increase, which is what he says we have seen since the mid-1970s, and which he thinks is the best bet for the near term future.

Ben Kalafut writes:


You would seem to be saying that difficulty in doing long time-scale modeling with ambiguous inputs somehow implies that we can't do medium time-scale modeling with better-known inputs.

I've gathered so far that the challenges involved are not the same; paleoclimate modeling of the sort used to study long-timescale phenomena like ice ages isn't merely a matter of running the models used to predict AGW longer and with different inputs.

It sounds a lot like a rehash of the old-codger criticism, a la Bill Gray: "They can't even predict the weather two weeks out". You and I should both know why that's not a sound criticism of AGW. Why is yours different? Could you point me to a reference or a few which would set me straight on that matter, or otherwise state directly whatever beef you have with the models commonly taken to imply that Man is warming the climate? It must be a big one if you deny that hypothesis outright.

Matthew writes:


I am very skeptical that we know and understand all the relevant inputs.

I think it is quite likely that CO2 levels are a minor impact on climate, and that the temperature rise since the 1970s has natural causes. I find it quite likely that the little ice age and medieval warm period represented similar temperature swings with natural causes, and the evidence I have seen that todays climate is "unprecedented" is questionable. I also suspect it is quite likely that temperatures will be heading down over the next couple of decades, falsifying the AGW hypothesis. However I am not at all certain about this, unlike the AGW crowd, who are all quite certain that they are correct.

One thing I would like to hear from AGW certitude proponents is what evidence would falsify their beliefs. For example, if global stratospheric temperatures do not continue to rise over the next 10 or 20 years, would you admit that AGW is falsified?

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