First, apropos of some of the discussion below but more urgent than any of that, the council of the American Physical Society is considering revising its 2007 statement on climate change. If you are an APS member with an opinion on the issue, write immediately to one of the councillors; they need your input before the November 8th council meeting.
So... let me start by saying I love physics. I think I decided to be a physicist by age 13 or 14. My best friend in high school also got a physics PhD. I married a physicist. I published a couple of dozen physics research papers. I've met Nobel Prize winners in physics, talked with some of the most prominent names in the field. I work with dozens of physicists every day. I've had a wide variety of physicist friends and colleages for decades.
I hate to stereotype people, and the physicists I know span a huge variety of personality types. But training and experience in physics gives you a very powerful toolbox of techniques, intuitions and approaches to solving problems that molds your outlook and attitude toward the rest of the world. Other fields of science or engineering are limited in their scope. Mathematics is powerful and immense in logical scope, but in the end it is all tautology, as I tease my mathematician friends, with no implied or even desired connection to the real world. Physics is the application of mathematics to reality and the 20th century proved its remarkable effectiveness in understanding that world, from the behavior of the tiniest particles to the limits of the entire cosmos. Chemistry generally confines itself to the world of atoms and molecules, biology to life, wonderful in itself, but confined so far as we know to just this planet. The social sciences limit themselves still further, mainly to the behavior of us human beings - certainly a complex and highly interesting subject, but difficult to generalize from. Engineering also has a powerful collection of intuitions and formulas to apply to the real world, but those tend to be more specific individual rules, rather than the general and universal laws that physicists have found.
Computer scientists and their practical real-world programming cousins are perhaps closest to physicists in justified confidence in the generality of their toolbox. Everything real can be viewed as computational, and there are some very general rules about information and logic that seep into the intuition of any good programmer. As physics is the application of mathematics to the real world of physical things, so programming is the application of mathematics to the world of information about things, and sometimes those two worlds even seem to be merging.
But physics is older and has a lot more experience. Confidence in the tools of physics has proven itself in the weaponry of war from Archimedes to the nuclear era. The industrial revolution arose from application of physical understanding to energy - the steam engine and engines that followed, electricity. The basis of our modern information technology - semiconductors, magnetic devices, lasers, fiber optics as just recognized by the Nobel committee - all derive from the work of physicists. Many tools of advanced medicine - X-rays, MRI's, various radiation-based cancer therapies - derive from physical understanding. The need for basic understanding of the laws of physics are exemplified perhaps most in recent debates over energy policy - politicians who talk about being able to drive hydrogen cars by filling up the tank with water, for instance. Physics gives direct power over the world, but also imposes limits on what is physically possible, and understanding both is essential. In recent years physicists flocked to Wall Street to prove the worth of their skills in the world of finance - quantitative analysis, and several of my friends heard that siren song. But money is a fickle thing, much different from the solid world we're accustomed to thinking about, and I'm not sure my colleagues' toolbox is quite big enough yet to fully understand what they're dealing with in that realm.
In general though, physicists have good reason to be arrogant. Each of us in the intellectual world is like an armed policeman. A certain swagger is justified, we feel confident we have the tools to handle any situation. A problem asserts itself, and we walk in with the self-assurance of those who have tackled thousands of similar cases in the past. For a really challenging problem we know how to put out a call for reinforcements. One all-purpose tool is reductionism - breaking a problem into smaller more comprehensible pieces, and then tackling those one by one. Modeling, a topic I've written about before , is what reduces a problem of reality to a mathematical problem. Every model is an approximation, but a wide variety of intuitions guide the physicist in isolating the essential characteristics of a problem into an appropriate model. Consideration of energy scales, expected magnitude of perturbations, symmetries and the like provide ways to separate effects that are important from those that are likely irrelevant to the problem in question. Systems that exhibit seemingly universal behavior, for example the ubiquity of oscillations, or the prevalance of power laws in complex systems, give the physicist a diverse collection of analogues to compare with the model developed for any given problem.
But sometimes that arrogance and self-assurance and collection of intuitions lead us, or at least a few of us, astray. We forget that there are other smart people in the world, who have been thinking about their limited problem for a lot longer and perhaps have a deeper understanding than we give them credit for. We jump in with our simplified models and ideas and then wonder why they don't find them helpful. Or we too deeply trust the intuition of a colleague who has been often right before or who we trust for other reasons, but in a particular instance has not put in the effort to properly understand the problem, and ends up only embarrassing themselves, and us by association.
I experienced a bit of this myself when I first started working at my current job. I now work in scientific publishing, and back in late 1995, when the web was young, I knew deep down that the scientific publishing business model had to change, and I came in with many ideas for reform. There was a definite lack of respect in my attitude for the experience and background of the many others in my office. I was right about some of the things that needed to be done, but naive about how to initiate those changes. My approach was unhelpful - to the extent that my boss decided, after about a year of this, to have a big sit-down talk with me and send me off to a Dale Carnegie course. I learned a bit of humility then - but I am still regularly accused of arrogance in my communications elsewhere, so perhaps there's a bit of room for further improvement. On the other hand, when you have a proven track record of being right, it's hard not to be assertive about it.
I also find myself occasionally making what I later recognize as slightly embarrassing assertions, when I extrapolate from some simple model I've made of a situation or circumstance, and find my prediction turns out to be wrong. Life is endlessly complex and fascinating. And that includes the physical world that we typically take such pride in understanding.
Unfortunately there are a few cases I've witnessed recently when, instead of recognizing the embarrassment they are causing themselves, a group of physicists digs in, asserting that their naive assertions and understanding are the truth, and that everybody else has got it wrong. This sort of thing isn't too unusual in the normal course of science. As Thomas Kuhn (himself a physics PhD) pointed out in The Structure of Scientific Revolutions, there often seems to be a generation gap between those of the old understanding (or paradigm, in his usage) and those of the new one of greater explanatory power, and at least some of the individuals holding the old paradigm go to their graves without recognizing the value of the new.
Worse though, in the examples I'll show here, are cases where there is a clear objective truth and a well-reasoned collection of logical deductions from observations and theory, and yet an "old guard" insists on embarrassing itself by denying that reality using what are clearly bizarre, inconsistent and fundamentally unscientific arguments. Science relies on the assumption that there is a real underlying objective reality that manifests itself in ways we can come to agreement on through repeatable measurements. Is it just the typical arrogance of the physicist that sustains these strange denials of reality?
Gerlich and Tscheuschner
The subject in question is, as usual, human causation of climate change and the world's responsibility to fix the problem. Many well-respected and traditional climate scientists have training in physics. Jim Hansen, perhaps the most prominent advocate among scientists in the US for strong action to limit our CO2 emissions, has a PhD in physics. Sir Robert May, at the top of Tim Prall's most-cited climate authors list, also received a PhD in physics, as did many of the most prominent scientists on Prall's list.
There are also a number of climate "skeptics" who have a physics background. I'll talk a bit more about Freeman Dyson and Will Happer later in this note. Among blogger and blog-comment "skeptics" there are several who prominently tout their physics background - Lubos Motl for instance - asserting that their physics expertise in some way makes their commentary on the subject more relevant. Of course I have used much the same stance myself - arrogance isn't confined to those who are wrong... Most recently Nathan Myhrvold, with a triple dose of arrogance in his physics PhD, his information technology background and his long tenure at Microsoft has come out as a climate skeptic - or at least a skeptic on the merits of solar energy. Though perhaps he was misquoted, as others have been.
But the first example I want to look at in detail, because the violations of the standards of science are so egregious, is the case of two German physicists and some of their colleagues who have come to their defense. In July 2007, Gerhard Gerlich and Ralf D. Tscheuschner posted this article (a version of which has, even more remarkably, actually appeared in a scientific journal) that claims to "falsify" the "atmospheric CO2 greenhouse effects" - i.e. the entire premise of a greenhouse effect in the first place.
This isn't merely old-guard reactionism, in this case. Gerlich and Tscheuschner are claiming that the greenhouse effect discovered by some of the founders of thermodynamics itself over 100 years ago (Fourier and Tyndall) violates those same laws of thermodynamics. That is a stunningly bold and arrogant assertion. If they were actually right, it would be of monumental importance. Surely, to avoid embarrassing themselves, they must have been very careful to understand their subject before diving in? But the arrogance of physicists, in some cases at least, knows no bounds.
There are dozens of ways to show that the greenhouse effect indeed involves no violation of the second law of thermodynamics, that net heat flows in the system are always from the hot sun to the surface of the Earth and up through the atmosphere; the colder atmosphere does not "heat" the surface in the second-law violating sense that Gerlich and Tscheuschner assert. Figuring out why they think it does anyway is a problem of psychology, not physics.
But they also assert (essentially 4 of the six claims in their original abstract) that the whole framework describing the natural greenhouse effect is fundamentally wrong. That framework uses balance of energy flux (the first law of thermodynamics) and a variety of averages over Earth's surface to show the natural greenhouse effect has warmed our planet's surface by at least 33 degrees Celsius, above what it would be without infrared-trapping gases in the atmosphere. In February 2008 I posted a response using the most straightforward-possible mathematical reasoning in a Proof of the Atmospheric Greenhouse Effect. This was of course no new scientific result - Fourier and Tyndall had it right in the 19th century. Nevertheless my posting received several interesting responses. First from some very prominent global warming "skeptics" who thanked me for my clear refutation of the nonsense of Gerlich and Tscheuschner, an article that they found personally embarrassing to be in any way associated with. But second, I was vehemently attacked on a variety of grounds, including apparently my ignorance of basic mathematics, by one Gerhard Kramm, who seems to have allied himself with Gerlich and Tscheuschner and comes to their defense at every opportunity. Arrogance amplified - interestingly half of Kramm's arguments also logically contradict Gerlich and Tscheushcner's paper, but it doesn't seem to embarrass any of them.
To briefly summarize the Gerlich and Tscheuschner argument on the 33 K issue and my refutation (and to pause in wonder that such logic could have been approved by the editor of a scientific journal) first let's make note of the essential, agreed-upon observations of the system:
(1) Earth's surface absorbs a certain pretty steady amount of total incoming energy from the Sun (some is reflected by the atmosphere or surface, so leave that part out)
(2) Earth's surface radiates essentially as a black body everywhere, which by the Stefan-Boltzmann law means the rate of radiated energy flow varies as the fourth power of the local surface temperature
(3) If Earth had no atmosphere, (1) and (2) would be the only heat transfers touching Earth's surface, so they have to balance in the long run. Using the standard equations you find an effective radiating temperature for the Earth of 255 K (-18 degrees C).
(4) There is a mathematical relationship between first-power averages and fourth-power averages that ensures that the average temperature must always be less than the effective radiating temperature (3).
(5) But the real Earth does have an atmosphere, and it also has an observed average temperature that is much warmer than 255 K - satellite and surface measurements agree on close to 288 K (+15 degrees C), for a difference of 33 K.
So the question is, what explains the difference between these two numbers, the 255 K effective radiating temperature of (3), and the observed 288 K average temperature of (5)?
The standard answer, as explained in my "proof" paper, is that the atmosphere's blocking of infrared radiation presents a barrier to the flow from Earth's surface, so to get the same energy flow rate out to space to balance incoming sunlight, the surface needs to warm up. The greenhouse effect. The conflict between observations (5) and (3) given the mathematical relationship (4) is proof that the atmosphere is having this real effect on our planet.
In Gerlich and Tscheuschner's paper, while acknowledging (and using) each of the above assertions, they also throw confusion on every one of them at the same time, and it is hard to follow the logic. In section 3.7.4 of their paper they present calculations for a planet in instantaneous balance with local incoming radiation, so that on the dark side of the planet (where no radiation comes in) the temperature is absolute zero, and corresponding temperatures on the warm side are inordinately hot. Computing the average temperature for their model planet, they find it a very cold 140 K (-133 C). This clearly satisfies the inequality in question (4 above) - in fact the two averages are expected to become all the more unequal the greater the divergence in individual measured temperatures that go into the averages.
To illustrate this, rather than going through the Gerlich and Tscheuschner case in full, look at a slightly simpler model with our planet uniformly at 0 K on one half, and 304 K on the other. Then the average temperature of the planet is (0 + 304)/2 = 152 K, not much warmer than the 140 K they found. The effective radiating temperature is ((0 + 304^4)/2)^(1/4) = 256 K, a full 104 degrees warmer. So it's easy to find a model of a planet where the average temperature is much lower than the effective radiating temperature, satisfying the inequality (4).
But this says nothing about how to get a planet with a higher average temperature than the effective radiating temperature. If the fourth power average is kept fixed, as it must be on a planet with no atmosphere, then the highest possible average surface temperature is when the temperature is completely uniform, all at the same temperature (255 K in Earth's case). Without an atmosphere there is no way to maintain a higher average.
All this Gerlich and Tscheuschner appear to agree with. Their eq. 89 is the same as my assertion (4) above. But they conclude from their mathematical model that the greenhouse effect increase in temperature is not 33 K, but a much larger number (their calculation shows that the "difference temperature that defines the natural greenhouse effect [can] explode"). And therefore "something must be fundamentally wrong here". And go on to make essentially hand-waving arguments about the invalidity of energy balance and how local temperatures are so variable you can't really average them. How they believe that any such measurement errors could mean Earth's actual average temperature is well below freezing, with a mostly liquid water surface, is still beyond me.
They have found no logical contradiction, only a contradiction to their (poor) intuitions. Let 'G' stand for the assertion that Earth's average temperature without an atmosphere would be less than or equal to 255 K (combining (3) and (4) above). If some model could be found that showed 'G' to be false, showing a temperature distribution on the surface that gave a higher average than the effective radiating temperature, then we might have an explanation of Earth's observed average temperature of 288 K that didn't involve the greenhouse effect. That would be a stunning achievement, deserving of their paper's title. But in fact every one of their examples shows 'G' to be true, and they even essentially prove it to be true. They assert it in their eq. 89. There is no logical disproof of 'G' anywhere in Gerlich and Tscheuschner's paper. And therefore no logical counter to the simple truth that the presence of Earth's infrared-absorbing atmosphere does indeed raise our planet's surface temperature by at least 33 degrees C from what it would be otherwise.
Any ordinary person would surely be embarrassed by such illogic, once the error was pointed out. Understanding how they got there and still apparently claim they are right to this day (after well over a year of people pointing out how they're wrong) is definitely a matter for psychology, and not physics.
The APS Statement
My second example is less egregiously wrong, but a little more disturbing to me because it involves people I have met and have some respect for. The issue starts with the American Physical Society official Statement on Climate Change, adopted by the APS Council in 2007:
Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth's climate. Greenhouse gases include carbon dioxide as well as methane, nitrous oxide and other gases. They are emitted from fossil fuel combustion and a range of industrial and agricultural processes.
The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.
Because the complexity of the climate makes accurate prediction difficult, the APS urges an enhanced effort to understand the effects of human activity on the Earth’s climate, and to provide the technological options for meeting the climate challenge in the near and longer terms. The APS also urges governments, universities, national laboratories and its membership to support policies and actions that will reduce the emission of greenhouse gases.
This statement was adopted after the release of the 4th assessment report from the Intergovernmental Panel on Climate Change (IPCC), and the three simple paragraphs of the APS statement echo the three major sections of that report: working group 1's assessment of the physical science basis, working group 2's assessment of the impacts of climate change that has already occurred and projections of the disruptive effects of future impacts, and working group 3's analysis of the steps needed to avoid these dire consequences. As such the APS statement as it stands is founded on the work of the thousands of scientists involved in the IPCC reports, and the thousands of peer-reviewed publications those reports are in turn based on, and every portion of the statement can be strongly supported by reference to the peer-reviewed literature and the scientific understanding that has developed in recent decades around the subject.
Such a brief, assertive (even arrogant?) summary of the major science results was bound to come under attack from those who feel they somehow know better than the thousands of deeply committed scientists who have spent decades working in the field. The first volley of opposition became public with the July 2008 issue of an APS unit newsletter, "Physics and Society", where the editors, apparently at the urging of physicist Gerald Marsh, published a highly erroneous article on climate sensitivity by a non-scientist with a reputation for misrepresenting climate science.
Said non-scientist and his associates, upon publication of their screed, immediately pounced with a press release that made its way around the blogosphere and into the Drudge Report where it was announced that the American Physical Society has "reversed its stance on climate change". APS was forced to post a clear statement on the organization's home page asserting that in fact no such reversal had taken place, that this was merely the work of an unsupervised editor and the article and associated editorial commentary did not represent in any way official position or policy of the organization.
While disturbing, that incident gave some insight into the potential importance of such statements from scientific societies who have almost unanimously now signed on to the main consensus. And so the APS statement has now drawn the attention of a handful of "skeptic" members within the organization (almost uniformly among the very oldest members of the society - so perhaps it is in part a Kuhnian generational paradigm shift problem).
Robert Austin, the APS Council member who urged the society to "reconsider" the statement and seems to have been behind this open letter on the subject, is a person I have met a number of times and have had interesting discussions with in the past. When I heard he was behind this I contacted him and we've exchanged a few letters; from that I've become convinced his understanding of the issues is relatively shallow and that he's relying on his trust in a few other physicists on the subject - trust that they may deserve on many other issues, but not this one. In particular, since Austin is at Princeton, he has some associations with Freeman Dyson and Will Happer, well-known and highly respected physicists in their own fields. But no person can be right about everything, and the recent NY Times Magazine profile of Dyson gives some perspective on where Dyson has gone astray on this issue - he is shaky on many details of the underlying science, and merely repeats assertions without providing detailed reasoning or justification.
Which is characteristic of the open letter as well. This is the sort of scientific claim without foundation that would never pass normal peer-review (unless of the sort that Gerlich and Tscheuschner seem to have been favored with). Let's look at this display of arrogance (their proposed revision of the APS statement) in a little more detail:
Greenhouse gas emissions, such as carbon dioxide, methane, and nitrous oxide, accompany human industrial and agricultural activity.
This slightly restates the second and third sentences of the first paragraph in the current APS statement, but omits the first sentence that clearly states these gases have an effect on climate. Do the authors of this proposed statement actually believe, like Gerlich and Tscheuschner, that the effect of greenhouse gases on climate is zero?
While substantial concern has been expressed that emissions may cause significant climate change, measured or reconstructed temperature records indicate that 20th 21st century changes are neither exceptional nor persistent, and the historical and geological records show many periods warmer than today.
Today's temperatures are not "exceptional" in the historical or geological record, as the IPCC report describes (in particular section 6 of the working-group 1 report of IPCC's 4th assessment report - AR4 WG1 sec. 6 - discusses the paleo-climate record: 3 million years ago it was 2-3 C warmer than now). But how can it be claimed they are "not persistent"? Every year from 2001 through 2008 the measured average global temperature has been warmer than all but 1 to 4 years of the entire 20th century (depending on which analysis you look at). What scientific justification is there to claim that the 20th century warming is not persisting?
Moreover, this statement is clearly intended to imply that there should be no expectation of continued increases in temperatures, but a huge weight of evidence points to at least a 2 degrees C transient response for a doubling of CO2, as stated in the IPCC report. Given continued greenhouse emissions (which the first sentence of the proposed statement admits), that certainly brings us into temperature territory that the Earth has not seen since well before human civilization began. "Exceptional" is hardly a precise term, but I think to any ordinary person, higher temperatures than human civilization has ever seen should qualify, and by that definition exceptional temperatures are surely coming unless we cut back on CO2 emissions significantly.
In addition, there is an extensive scientific literature that examines beneficial effects of increased levels of carbon dioxide for both plants and animals.
This includes a radical assertion not backed up by any reference to the actual literature. I have, personally, never heard of a benefit of higher CO2 for animal life. According to this hazard sheet, CO2 leads to blood acidification, at 1% can be hazardous, and 5% is toxic. Granted, those levels are considerably higher than the 0.1% concentration that we might get in the next century under business-as-usual scenarios, but "beneficial"?
As for plant life - the question is whether the increase in CO2 compensates for higher temperatures and expected changes in precipitation, and that also depends on the type of plant (C3 or C4 respiration). This statement is extremely one-sided on the real issues here. Again, where is this "extensive scientific literature" that justifies such a statement of clear benefit? I've attended a lecture from folk at Brookhaven Lab who have been actually doing this research, and they're significantly less optimistic than this statement implies.
Studies of a variety of natural processes, including ocean cycles and solar variability, indicate that they can account for variations in the Earth’s climate on the time scale of decades and centuries.
On a time scale of 1 decade, certainly, variations in Earth's climate are determined by "natural processes" like the solar cycle, volcanoes, and ocean-atmosphere interactions. In fact, climate is not even well-defined for a single decade, since it represents the statistical distribution over all such short time-scale variations. Further in the past, orbital forcings (with ice-albedo and greenhouse-gas feedbacks) clearly account for the glacial-interglacial changes. But no known natural processes can account for the changes in Earth's climate observed in the 20th century. What scientific source could you possibly have for this statement that outweighs the very clear analyses the IPCC report is based on? The "can account for" in that context is a strong statement (implying anthropogenic GHG's have had no impact). We're back in the logic of Gerlich and Tscheuschner here, if this statement is to be believed at face value.
Current climate models appear insufficiently reliable to properly account for natural and anthropogenic contributions to past climate change, much less project future climate.
This statement doesn't even make logical sense. Climate models do not predict either natural or anthropogenic contributions to past climate change - they model the *response* to forcings, not the forcings themselves. Forcings are input (from other types of modeling). And in modeling responses they have been tremendously successful - one of the best examples of this is the response of the planet to the Pinatubo eruption's addition of stratospheric aerosols, which was predicted quite accurately by Jim Hansen at least 4 years before the eruption. And of course "climate models" ever since Arrhenius have predicted surface warming from increased CO2, as observed in the 20th century. What analysis of climate models is there in the literature that in any way justifies this statement?
Pure arrogance backed up by nothing.
The APS supports an objective scientific effort to understand the effects of all processes – natural and human --on the Earth’s climate and the biosphere’s response to climate change, and promotes technological options for meeting challenges of future climate changes, regardless of cause.
More research, always the call for more research. And "skeptics" complain that it's the climate scientists who are taking their positions in pursuit of more funding for themselves? To the contrary - most climate scientists recognize the problem and urge money to be spent not on themselves, but on solutions: clean energy, getting off coal. 350.org calls for action on October 24 - not to fund climate scientists, but to work to actually turn things around, and make the world a better place. Of course what this proposed revised statement omits is any call to action for governments or APS members to work to actually reduce greenhouse gas emissions.
Frankly I'm really disappointed in Austin, Dyson, and their colleagues. People like Gerlich and Tscheuschner, Kramm, Gerald Marsh, I never heard of them before this, and I have no expectation of their rationality. But I do expect better from people I've met and otherwise respected. What happened to clear scientific rational thinking, understanding problems, looking at the peer-reviewed literature and trying to really understand what's going on, what the previous work in the field shows?
I'll conclude with just one simple piece of advice: a little humility can save a lot of embarrassment. I urge all my physicist colleagues and friends to try it some time.