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Happy Birthday, Charles Darwin!

Filed under: — raypierre @ 16 February 2006

Charles Darwin was born on February 12, 1809. The events commemorating Darwin’s birthday anniversary last Sunday, together with the recent conclusion of an important court case concerning the teaching of Intelligent Design (ID) in public schools prompts me to some musing concerning the relation of the Evolution/ID dialog to similar issues arising in connection with anthropogenic global warming. The age of the two theories is similar as well: Darwin introduced his theory in 1859, whereas Fourier initiated the study of the effect of atmospheres on climate with his 1821 treatise, stimulating the chain of developments leading to Arrhenius’ enunciation in 1896 of the theory that human influences on the atmosphere’s CO2 content could change the climate.

I don’t propose to wade into questions of religion, or the question of whether or in what form ID could be taught in public schools. However, the discussion surrounding ID is significant because it has focused a lot of public attention on the question of : "What is science?" A Nov. 5, 2005 letter to the Chicago Tribune by one Mr. Ross Williams makes the connection explicit: In his letter, Mr Williams implies that the Theory of Global Warming is more like ID than it is like Evolution. Referring to global warming, he states: "It is no more than an idea, a notion." and goes on to say:

  • " The scientists pursuing this hypothesis are struggling to test it and make predictions using their ideas. Thus far, they have had extremely limited success in testing, and virtually no luck in predicting–resulting in continually modified (and, consequently, less severe) forecasts. Despite this, they are spawning a whole cadre of non-scientific worry warts who are declaring that, well, really, the science doesn’t matter."

In Mr. Williams lexicon, a hypothesis is just "a notion," presumably not much better than ID. In this article, I will attempt to explain why the bleak picture painted by Mr. Williams and people of like mind is unwarranted.

Another relation between the two issues is that Evolution skeptics are motivated by ideology to deny a well-established scientific theory. In the case of Evolution, the ideological motivation is a perceived conflict between the picture of the operation of the natural world presented by the Theory of Evolution, and the tenets of certain faiths (a perceived conflict that, I am happy to see, is not shared by all people of faith, as witness the extensive "Evolution Sunday " activities ). Similarly, most Global Warming denialists are for the most part motivated not by abstract curiosity about the behavior of climate systems, but by a perceived conflict between the actions that would need to be taken to avert unacceptable climate change, and their beliefs about the extent to which economic growth and material prosperity based on fossil-fuel energy use should be unfettered. (Again, not all economists or members of the business community perceive a conflict here). In both cases, the skeptics prosecute not just an attack on the policy implications of science, but on the scientific method itself, often using similar rhetorical devices. In fact, sometimes skepticism about global warming and about evolution are combined in one and the same person, as is the case for Roy Spencer, for example (see his article on evolution here.)

Just what is the theory here?

First, we need to get straight on just what we might be talking about when referring to "The Theory of Global Warming." There’s a natural tendency to identify such a theory with the statement that "The Earth is Warming." That’s wrong because it confuses a theory with observations that might be used to test a theory. It’s also wrong because it would imply that the only reason we think that the Earth will continue warming in response to increased CO2 is that we already see it warming today; it loses the chain of physical causation. Somewhat better would be the statement, "The Earth is warming, and the warming is largely due to increases in atmospheric CO2 and other long lived greenhouse gases." This is defensible as a hypothesis, but I think it would be far better to consider this statement, too, as more properly in the domain of one of the tests we might apply to the Theory of Global Warming.

My own preferred statement of The Theory of Global Warming is this:

  • An increase in the atmospheric concentration of CO2 and other long lived greenhouse gases requires the surface temperature to ultimately increase so as to maintain a balance with the absorbed solar radiation. The increase is amplified by water vapor (also a greenhouse gas), which increases with temperature in such a way as to keep relative humidity approximately constant. Melting of ice will further amplify the warming, particularly in high latitudes. The resulting widespread warming corresponding to a doubling of CO2 will be large enough and rapid enough to be well outside the range of past experience of the human species, by an amount comparable to the difference between a glacial and interglacial climate. Changes in atmospheric cloud properties may somewhat reduce or increase the sensitivity, but do not substantially alter the conclusion.

The last part of the statement of the theory is, of course, the hard part, and the most uncertain.

I have deliberately left the matter of the severity of the impacts of such a climate change out of the hypothesis. Theories regarding the impact are nascent and in many regards still rather ill-formed, in comparison to the theory dealing with the physical dimensions of climate change. Also, insofar as there are uncertainties about the severity of the impacts of climate change, it is a matter for the political apparatus to decide how to deal with the uncertainties, and the extent to which one should pay attention to the worst case vs. the most likely case. The question of how to factor in the uneven distribution of harms (and possibly benefits) across the peoples of the Earth, and between human societies and natural ecosystems, is also at heart a matter of ethics and values. These are questions that can be informed by science, but they are not themselves scientific questions.

Finally, one must be careful not to be confused by the usage of the word "theory" in common everyday English. Statements like, "Oh, that’s just a theory, not a fact" have little to do with the scientific understanding of the word "theory." Linguistic confusion goes the other direction as well: Scientists often talk about "believing" in a theory, but this expresses a judgement of whether the balance of tests of a theory against observations lends sufficient support to the theory to rely on it in drawing further inferences. It does not declare that subscribing to the theory or not is an article of faith, to be left to one’s conscience. If I say that I "believe in" quantum theory, that is expressing a different kind of judgement than if I say I "believe in" the tenets of Buddhism.

Judge Jones on "What is Science"

Judge Jones (a George W. Bush appointee, by the way) of the Middle District Court of Pennsylvania, presided over the case Kitzmiller v. Dover Area School District, which dealt with the constitutionality of an attempt to introduce some limited teaching of Intelligent Design into science classes. His decision that teaching ID in public school science classes would be an unconstitutional establishment of religion, is a masterpiece of wit, scholarship and clear thinking. Most of the decision deals with application of tests (such as the "Lemon Test") of whether a government action constitutes an establishment of religion. These make fascinating reading, and show Judge Jones’ wide ranging intellect, but they are not of concern to me here. What’s relevant to the point at hand is the rather extensive part of the decision devoted to the question "How do we know whether something is science?" This question wasn’t entirely central to the basis of the Judge’s decision, but he devoted a lot of attention to it because, in his words,

  • "Having so concluded, we find it incumbent upon the Court to further address an additional issue raised by Plaintiffs, which is whether ID is science. To be sure, our answer to this question can likely be predicted based upon the foregoing analysis. While answering this question compels us to revisit evidence that is entirely complex, if not obtuse, after a six week trial that spanned twenty-one days and included countless hours of detailed expert witness presentations, the Court is confident that no other tribunal in the United States is in a better position than are we to traipse into this controversial area. Finally, we will offer our conclusion on whether ID is science not just because it is essential to our holding that an Establishment Clause violation has occurred in this case, but also in the hope that it may prevent the obvious waste of judicial and other resources which would be occasioned by a subsequent trial involving the precise question which is before us."

In other words, Judge Jones had already seen enough irreducible complexity, bacterial flagella, fossil record interpretations and panda’s thumbs to last a lifetime (maybe two), and didn’t want any of his colleagues to have to go through the same business all over again.

For the most part, the good judge takes a positivist approach to the definition of science, following Karl Popper. This approach emphasizes that a scientific theory should be falsifiable. The centrality of this notion has been challenged by Thomas Kuhn and a few other philosophers of science , but as a description of the way most of us in the trenches actually see our enterprise, Popper does pretty well, as long as we allow a little flexibility in the matter of what counts as falsifiability. The important thing is that a scientific theory should be productive. It should make predictions that can be tested against observation and experiment, the more the better. Thus, Ptolemy’s epicycle theory of planetary motion is not bad as a scientific theory: it does make predictions about where planets will be, that can be tested against data. Newton’s theory is far better, though, because it makes far more predictions over a vastly wider range of circumstances, while requiring far fewer assumptions. It’s not just that it’s more economical than epicycles. It’s far more productive of testable predictions — all of which prove true, so long as one steers clear of speeds close to that of light and very strong gravitational fields. Einstein’s General Theory of Relativity is even more productive, covering the extreme cases while reducing to Newton’s theory in the low speed and weak gravity limit.

Further, the notion of prediction has to be broadly construed. The fact that we can’t predict the exact weather a year out is no refutation of the basic theory of climate, any more than the fact that we can’t predict the position of Pluto in its chaotic orbit is a refutation of Newtonian mechanics. In the context of testing scientific theories, a prediction need not refer to something that happens in the future; this is important in observational sciences such as Earth science or cosmology, where one’s "predictions" often deal with things that happen in the past. A prediction in this context is any inference drawn on the basis of a theory, that can be objectively tested against observations. For that matter, a prediction need not even come in advance of an observation. Obviously, it is a more convincing test of a theory if the inference is made before the observation, since this provides some protection against the accusation of tuning unknown parameters; however, there are other ways to check whether a match succeeds only because of unwarranted tuning.

Judge Jones’ considers three basic arguments in his consideration of whether ID is science. The detailed application of each argument to ID is buttressed by numerous citations to theological, scientific and ID-advocacy writings, which are not reproduced in detail below.

The first argument is against ID as science is that science does not rely on untestable supernatural causes. Supernatural explanations are "science stoppers" which preclude further inquiry. This is, in essence, a restatement of the falsifiability (positivist) criterion. Among the many documents Judge Jones cites is a National Academy of Sciences statement that notes that the publications arguing for ID "do not offer hypotheses subject to change in light of new data, new interpretations, or demonstration of error. This contrasts with science, where any hypothesis or theory always remains subject to the possibility of rejection or modification in the light of new knowledge." The Judge declares, on the basis of the evidence, that "ID fails to meet the essential ground rules that limit science to testable, natural explanations."

The Judge notes that the preceding alone is sufficient to disqualify ID as science, but given a surfeit of evidence, he does not want to stop halfway. The next argument he produces is quite different from the positivism criterion, namely that the arguments for ID rest on a contrived dualism. "ID is at bottom premised upon a false dichotomy, namely, that to the extent evolutionary theory is discredited, ID is confirmed, " he writes. He then points out that arguments for ID based on this contrived dualism are, from a scientific standpoints, not arguments for ID at all, but merely tests of the Theory of Evolution — and hence only serve to further establish that Evolution is science. Judge Jones, in this connection, disassembles some of the arguments against Evolution made by ID proponents, but this is a matter of evaluating tests of Evolution as a scientific theory, not a matter of deciding whether ID is science. The notion of "irreducible complexity," for example, is a refutable and testable negative argument against evolution, but that does not make it a testable argument for ID. The discussion of the merit of ID proponents’ arguments against Evolution does, however turn up a point that has some relevence also to the argument brought to bear against the Theory of Global Warming. Discussing testimony on the ID case against Evolution, the judge writes: "We find that such evidence demonstrates that the ID argument is dependent upon setting a scientifically unreasonable burden of proof for the theory of evolution." (My emphasis added). The judge finds that Evolution skeptics argue by "pointing to real gaps in scientific knowledge, which indisputably exist in all scientific theories, but also by misrepresenting well-established scientific propositions." This description applies word-for-word to many skeptics’ arguments against global warming, for example to most of Richard Lindzen’s testimony to the House of Lords (discussed here)

Judge Jones’ third argument is a pragmatic one: it assumes that there is such a thing as a recognized scientific community, and that it knows science when it sees it even if it may be hard to rigorously and unambiguously define the criteria. He specifically looks to the peer-reviewed publication process as an indicator: "A final indicator of how ID has failed to demonstrate scientific warrant is the complete absence of peer-reviewed publications supporting the theory." After some further discussion of the publication record of ID, he concludes "ID is not science and cannot be adjudged a valid, accepted scientific theory as it has failed to publish in peer-reviewed journals, engage in research and testing, and gain acceptance in the scientific community."

Does "Global Warming Theory" pass Judge Jones’ science test?

In one sense, the Theory of Global Warming is clearly a falsifiable scientific theory: all we need to do is wait around a while until industrial activities have doubled CO2, and observe what has happened to atmospheric temperature, water vapor and clouds. This indeed seems to be the experiment that most of the world seems intent on carrying out.

However, when we talk about "verifying" the Theory of Global Warming, what most of us have in mind is doing something to test the theory right now, so that (to the extent that it is correct) necessary policy decisions can be informed by the predictions of the theory.

Earth science shares the full range of difficulties generic to observational sciences, in that we can carry out laboratory experiments testing individual basic physical principles making up our theories, but have only limited opportunities to conduct experiments on the collective behavior of the whole system. For the latter, we must do the best we can with those ready-made examples that Nature provides. In this regard, the situation of the Theory of Global Warming is rather similar to that of the Theory of Evolution.

There are indeed a great many aspects of the Theory of Global Warming that are falsifiable without waiting for the next century’s climate to come upon us. There are, to start, all the laboratory tests of basic physics, such as the infrared absorption properties of CO2 and water vapor. There are also field tests of the predictions of these basic physical theories, as is done when one measure water vapor and temperature in the atmosphere, and compares the predictions of radiative transfer theory with observed infrared radiation measured at the top of the atmosphere by satellite, or at the surface by radiation sensors. One can check the evaporation formulae used in climate models against the measured evaporation at buoys in the ocean, or the predictions of cloud models against observed cloud reflectivity. Going up the scale in complexity, one can compare the predictions of the theory against observations of recent climates, and of climates of the more distant past. General circulation models encapsulate the assumptions of the theory, and provide the tool necessary for testing hypotheses in such a complex system.

A further point regarding the positivist criterion is the the Theory of Global Warming is productive. The implied influence of CO2 (or methane) on climate can be, and has been, applied to the understanding of the Last Glacial Maximum, to Snowball Earth, to the Faint Young Sun, and to Cretaceous warmth. Variants apply also to Venus, Mars (present and past) and Titan. It is fair to say that this theory plays as central a role in the theory of planetary climate as the Theory of Evolution plays in biology. A relatied point is that the theory can be and has been challenged by data, and forced to adapt accordingly. This was the case in the precursor to the theory, when Tyndall discovered that minor constituents (CO2 and water vapor) dominated the greenhouse effect; the resulting adaptation of Fourier’s theory opened the way for Arrhenius to conclude that human influences on the atmosphere could change the climate. A more recent adaptation was the incorporation of aerosol effects in the late 1980′s which was forced upon the theory by the inability to explain the pattern of 20th century climate change with greenhouse gas increases alone. Contrary to the assertion in Mr. Williams’ letter to the Chicago Tribune, revisions to the theory have not led to any systematic downward revision of the appraisal of the magnitude of the thread caused by doubling CO2. Indeed, some discoveries, notably the prevalance of abrupt climate change in the past record, have raised concerns that the current understanding may underpredict the magnitude of the response.

What of Judge Jones’ other two criteria applied in the Kitzmiller case? The false duality issue does not arise in the judgement of Global Warming Theory itself, since the theory has never been argued for on the basis of such a stipulated duality ("The world is warming, and if it’s not the Sun, then it must be CO2!"). On the other hand, a false duality has often been invoked in arguing against the Global Warming Theory. This typically takes the form of pointing out some aspect of the observations that Global Warming Theory doesn’t explain, and then jumping to the conclusion that the observed warming must be due to the local skeptic’s favorite cause: maybe solar variability, maybe some unspecified sort of "natural variability." Often such arguments involve holding Global Warming up to unreasonable standards of proof ("If we don’t understand everything about climate, then we understand nothing about climate."), and often, like ID proponents arguing against Evolution, the arguments offered against Global Warming are at best distortions of scientific truth. In this regard, Global Warming plays the role of the Theory of Evolution, with the Global Warming Skeptics playing the role of ID advocates.

On Judge Jones’ final criterion (presence in the peer-reviewed literature) the Theory of Global Warming gets an easy and obvious pass. Here, the Global Warming skeptics are in a somewhat better position than the ID advocates, in that a very few of the skeptics arguments have appeared in the peer reviewed literature. This doesn’t make them right, but it does mean that to some extent, some of them are playing by the rules of science. Still, the relative paucity of skeptics arguments being played out in the peer reviewed literature suggests that they may not be as wrong as the ID advocates, but that they are not as right as the vastly greater number of researchers who have published in support of the Global Warming Theory.

To what extent is "Global Warming Theory" verified?

The basic physical principles upon which the Theory of Global Warming is based include the notion of interconvertibility amongst forms of energy (introduced by Fourier in his formulation of planetary energy balance), thermodynamics (air cools when it rises), thermodynamics of phase change (cold air holds less water), quantum theory (absorption and emission of infrared by CO2 and other greenhouse gases), blackbody radiation, and Newton’s laws of motion. Each of these components has passed literally thousands of tests in the laboratory. There is essentially zero uncertainty in the validity of such things, which form the basic physical underpinning of the Theory of Global Warming. If any of these parts of the theory didn’t work, neither would microwave ovens, computers, steam engines, infrared remote controls, and any number of other everyday devices.

Tests of the collective behavior of the Earth’s climate system are somewhat harder to come by, but there has been substantial progress here as well. I would highlight the following, which is far from an exhaustive list:

  • Reproduction of the temporal and spatial pattern of 20th and 21st century warming. To be sure, models with varying assumptions about clouds and aerosols can fit the observed warming equally well, indicating that the job is not complete. However, no quantitative model based on physical principles can match the 20th century warming without incorporation of a substantial warming component from greenhouse gas increases.
  • The rapid increase in atmospheric greenhouse gases should throw the Earth’s radiation budget out of balance, because the ocean has not yet had time to warm up to restore balance. The expected imbalance has been observed. (Hansen et al. 2005)
  • The planet’s energy imbalance has implications for the pattern of subsurface ocean warming. The predicted pattern has been observed. (Discussed here.)
  • Satellite observations indicate that mid-tropospheric water vapor is indeed increasing with temperature, as the theory requires and as models predict (Discussed here).. Note that the water vapor assumption I included as part of the statement of the Theory of Global Warming is not itself built into the general circulation models used to predict climate change. It is an emergent property that is deduced from more basic assumptions made in the models. In this regard, the statement regarding the presumed behavior of water vapor amounts to a statement that the models capture the same processes governing water vapor in the real atmosphere. There is now a wealth of evidence (in the "large scale control" literature) supporting this viewpoint.
  • Melt-back of Northern Hemisphere sea ice
  • Nearly worldwide melting of mountain glaciers, many of which survived previous naturally occurring warm periods
  • The theory predicts that the stratosphere should be cooling at the same time the surface is warming. This pattern is observed.
  • The degree of cooling of the Tropics and Southern Hemisphere during the Last Glacial Maximum, for which there would be no explanation if we were to assume that current models substantially overestimate sensitivity to CO2. An interesting bit of history concerning this point is that in the 1980′s the tropical behavior in glacial times was considered an indication that models were wrong: CLIMAP data indicated little surface cooling in the tropics, while mountain snowlined data did show cooling. This led to all sorts of theories spun about exotic thermostat mechanisms and strange lapse rate behavior. In the end, it turned out that the models were right and that the CLIMAP data was wrong. Thus, in this instance, the models (based on theory) made a true prediction, which was verified after the fact.

The scientific community is still searching for a really good way to evaluate the nature of cloud effects, though comparisons with past and recent climates provide some reassurance that we are not too far off base with cloud effects. More importantly, there is not yet a physically based hypothesis on the table which is compatible with data and which reduces climate insensitivity to inconsequential levels. Lindzen’s "Iris" hypothesis comes closest, but it has been evaluated in the scientific literature and most of the community remains unconvinced.

Besides the ongoing problem with clouds, the general theory of Earth’s climate, like any good scientific theory, continues to be confronted by phenomena it cannot yet fully explain, and to evolve in response. Some notable problems include the tendency of many coupled general circulation models to produce double Intertropical Convergence Zones in the Tropics, inconsistencies in the prediction of the regional distribution of climate change, inability to make firm inferences concerning the effect of global warming on El Nino, and the inability of general circulation models to reproduce recurrent abrupt climate change events like D-O events or even the full magnitude of response to the Younger-Dryas event. An especially notable unresolved challenge is the inability of models to reproduce the low North-South gradient in warm climates such as the Cretaceous. In this case as well as in others (such as the problem of vertical structure of tropical tropospheric warming) the problem may lie as much in the data sets being used to test the theories as in the theories themselves.

A theory can never be definitively proved; there is always the possibility that some new observation will overturn it, and most theories are imperfect and fail in one way or another to account for some of the data. The question thus emerges as to the extent to which global warming skeptics are holding the theory up to an "unreasonable standard of proof," much as ID proponents do in the case of Evolution. Given that the intensity of interest in the Theory of Global Warming stems largely from its policy implications, it is fair to ask how the standards of proof to which global warming has been held stack up against other theories that have been used to make policy decisions of enormous consequence. "Supply Side Economics" (the theory that tax cuts pay for themselves by stimulating economic growth) is a telling example that comes to mind (to say nothing of the "theory" that Iraq had WMD).

Afterword

And speaking of intelligent design, I feel compelled to remark that the CO2 molecule seems rather admirably designed from the standpoint of regulating climate. It’s a good infrared absorber even in small quantities so you don’t need to much of it, yet the radiative effect is logarithmic in concentration, so you don’t have to tune its concentration too terribly precisely to get a habitable climate. There’s plenty of it in the form of carbonates in the Earth’s crust, so you can always get more if you need some to keep the climate warm enough. Most importantly, it plays well with liquid water, so that if the planet gets too warm or too cold the rate of removal tends to adjust to reset the atmospheric carbon dioxide at a point where the climate will stay relatively equable. It has thermodynamic properties that keep it from condensing out of the atmosphere (in contrast to water vapor), resulting in it having a long enough lifetime to even out the vicissitudes of climate forcing fluctuations. How strange it is, then, that the Earth should have an abundant supply of so attractive and convenient fuel as coal. A fuel which, unfortunately, messes up the system by releasing CO2 when it is burned.

Bad design? Or just forbidden fruit?

References

Hansen, J., et al. 2005. Earth’s energy imbalance: Confirmation and implications. Science 308, 1431-1435, doi:10.1126/science.1110252.


255 Responses to “Happy Birthday, Charles Darwin!”

  1. 51
    Brian Forbes says:

    Armagh observatory has kept a record of temperatures for the last 200 years and has published a paper relating the temperature readings to the sun spot cycle showing that that it gets cooler when the Sun’s cycle is longer and that it is warmer when the cycle is shorter.Admittedly this is only for one place on earth but it is more effected by the sun than CO2
    The sun shines on all the earth just as CO2 pervades the atmosphere what is true for Armagh appears to be true for all the truly rural sites in the GISS data however most of those were closed during the 1960s.

  2. 52
    George Balella MD says:

    Re # 40

    The current warming IS unusual in the context of the instramental record. It also appears to me to be unusual in the context of the paleoclimate record. Kilmanjaro is about to loose its 7,000 year old ice cap, Glacier National Park is about to loose ALL of its glaciers…many which formed thousands of years ago, plants buried under glaciers in South America 5,000 years ago are now being exposed, a 3,000 year old Arctic ice dam has collapsed, oxygen isotopic records from the Himalaya show the current period warmer then any of the last 2,000 years…..this appears to me to be something new under the sun and its static output. Something never before seen by civilization….What would convince you?

  3. 53
    nanny_govt_sucks says:

    #50 That’s all well and good as long as you ignore the work of Solanki et. al that shows a good correlation between solar irradience and global temperature for the supposed “aersol cooling” 35 year period:

    see Fig 5.
    http://www.mps.mpg.de/projects/sun-climate/resu_body.html

    You’d also need a pretty good explanation of why increased regional aerosol production in China/SE Asia has led to exceptional warming there over the last 20 years or so. The aerosols should have a pretty powerful cooling effect if they are a regional phenomenon and are supposed to have been the dominant global cooling forcing for 35 years. Where do we see that powerful cooling effect today?

  4. 54

    Re #42 and “Alright the global temprature has gone but I doubt that you can prove CO2 is the cause.”

    If not, what is the cause? We know more CO2 in the air creates a hotter surface temperature if all else is held constant, and checks on “all else” don’t show any feedback strong enough to prevent it. What’s to prove?

  5. 55
    Matt says:

    The law of theromdynamics that says entropy always increases tells me that any closed carbon cycle will leak energized cartbon, and that in the limit we can do no better than the microbes. To be as benign as the microbes we would be further limited to using the first meter of soil carbon.

    The other alternative would be to collect some portion of the sun fix carbon for the long term, or find some other energy source to fix carbon. Once we open the carbon cycle, then we have a free variable.

    So, we have an operational test of ID. Let man do what he does currently, then, according to ID theory, man (or some new microbe) should, in the next few years have a breakthrough in long term carbon fixing.

  6. 56

    I believe, and evidently the New Horizons team believes, that we can predict the position of Pluto in its chaotic orbit … well actually, its nonchaotic orbit.

    — Graham Cowan, former hydrogen fan
    Boron: internal combustion, nuclear cachet

    [Response: The New Horizons team only has to predict the position of Pluto over a relatively short time. Every chaotic system has a predictability decay time, and so can be predicted over sufficiently short time scales with the use of initial conditions having an achievable accuracy. For the evidence that Pluto's orbit is chaotic, I'm relying on ``Numerical evidence that the motion of Pluto is chaotic,'' Gerald Jay Sussman and Jack Wisdom, in Science, 241, 22 July 1988; I don't know if this is the last word on the subject. There's no question, though, that asteroids are in chaotic orbits, and rather little question that the obliquity of Mars is chaotic. Either one serves equally well for the purposes of my example of the problems with taking too restricted a notion of "prediction" in testing a theory. ]

  7. 57
    Coby says:

    Re #54,

    nanny_govt_sucks, thanks for the link but your response indicates you did not read vaery carefully the comment you are replying to. Solar forcing was listed among the various factors that control climate. Yes, there is good correlation for solar and early to mid 20th century temperatures. You bring up other factors as well, which is fine, but you seem to assume they are all ignored, or they somehow contradict AGW theory. They are not ignored, they are all factored in and all play their part in a system whose current changes are currently dominated overall by CO2. These other factors need to be understood and incorporated into the models also, as they are.

    But the fact remains that there is no consistent explanation for the observed 20th century trends that does not include a dominant role for CO2 concentraion changes. That other factors ameliorate, amplify or temporarily dominate does not in any way contradict the science behind greenhouse theory of climate.

  8. 58
    Tom Fiddaman says:

    Re 48, 54

    You seem to be engaged in a search for univariate causality, picking bits and pieces of data even when it would seem to contradict your conclusion (Solanki: “It is highly likely, however, that after 1980 the Sun has not contributed in any significant way to global warming.”) If you’re serious, put all your favorite forcings in a simple energy balance model and show how you can replicate historic temperatures without anthropogenic GHGs.

  9. 59
    Tom Fiddaman says:

    Re 48, 54

    You seem to be engaged in a search for univariate causality, picking bits and pieces of data even when it would seem to contradict your conclusion (Solanki: “It is highly likely, however, that after 1980 the Sun has not contributed in any significant way to global warming.”) If you’re serious, put all your favorite forcings in a simple energy balance model and show how you can replicate historic temperatures without anthropogenic GHGs.

  10. 60
    Brian Forbes says:

    25 years of nonconformity of the temperature with observation does not invalidate 185 years of conformity with the Solar cycle.
    How sure are you that the temperatures derived by GISS are error free?

    [Response: Brian, take a step back and think about what it is you are asking for here. You are implying that a) if CO2 is a factor now, no other forcing can have been important in the past, and b) that temperature data be 'error-free' for the last 25 years before you attribute anything, but temperatures for the last 185 years are good enough to show solar forcing? No data source is error free and the existence (and detectability) of solar forcing does not preclude CO2 having a radiative impact. -gavin]

  11. 61
  12. 62

    Re #58, 59, 60:

    If we accept the latest estimates of increase in solar radiation in the past two solar cycles (see Scafetta and West), then solar may have contributed 10-30% to the increase in surface temperature of the last decades. But even if the sun didn’t increase in radiation in the past decades, it takes several decades (and longer for deep sea temperatures) for the oceans to come into equilibrium with the increased insolation since 1900.

    And while current models all (need to) “predict” the past temperatures, there is a lot of room for equally validated variants, where solar sensitivity (with cloud feedbacks) is enhanced and/or sensitivity for aerosols (uncertain) and CO2 is reduced…

  13. 63
    Timothy says:

    nanny [54]: Apologies for writing my reply “on-the-fly” and not going into exhaustive detail. I wrote that aerosols were “dominant” for the cooling period. This certainly appears to be the case as changes in solar and volcanic forcing are not large enough to counteract the growing forcing from CO2 over this time period. It doesn’t mean that there were no changes in other forcings over this period, just that the aerosols were the most important.

    I also find it strange that you don’t notice the most obvious feature of the figure 5 that you link to: the massive divergence between recorded temperatures and solar irradiance in the later part of the 20th century.

    The situation is that “GW Theory” encompasses many different bits of information [including solar forcing], and it can account for the last century of climate change by considering how the evolution of these different forcings evolves in time and what their respective balance is.

    Alternative explanations tend to ignore this wealth of evidence and try to ‘prove’ the importance of one factor [e.g. solar] over CO2. To do this they normally have to posit an unproven mechanism whereby the forcing from their chosen factor is magnified by feedbacks of the climate system [to account for 20th century variation] and, simultaneously, the forcing from CO2 is supressed by feedbacks of the climate system. Needless to say such explanations are considerably less ‘fit’ than the current state of play in “GW Theory”.

    You can hide from the evidence for only so long, but when even the evidence you bring forward in your defence contradicts you…surely then you must admit defeat.

    A brief word on Asian aerosols. Apparently emissions of Chinese aerosols have already begun to peak, much earlier than had been predicted. They keep on having to revise the aerosol preditions downward. Thus growth of aerosol production in Asia is not keeping pace with growth of CO2 production. I don’t know enough about regional trends in temperature to comment definitively, but I think that the global trend in temperature has been so strong that it would swamp local effects.

  14. 64

    Re #36 (comment):

    Which one, water or CO2 is the best ID molecule can be discussed… CO2 is not very effective in keeping the greenhouse warm, as can be seen in the diurnal temperature difference of the dry Sahara (~40 K), vs. moderate (wetter) countries (~10 K on clear days, a few K on cloudy days)… And even to get out of the “snowball earth”, one needed CO2 levels a few hundred times current (according to some models)…

    But the best ID molecule aside, I do understand the “cold” side of the extremes, but I don’t see the “warm” side, the (water -vapour- induced) runaway process. In the more extreme cases, like the Cretaceous, all polar ice was melted and the temperature gradient between tropics and poles was less than today. Although the higher global temperatures certainly would have increased water vapour, the heat loss at the poles still would have been high (and normally higher than with lower polar sea surface temperatures)…

    Further CH4 helping at the high end? Please explain a little further. Organic haze indeed may be plausible…

    [Response: The problem on the warm side is the following. If you have a large ocean which can supply moisture to the atmosphere to keep it at some proportion of saturation, then at sufficiently high surface temperatures the atmosphere becomes so optically thick in the infrared that the outgoing longwave radiation becomes independent of surface temperature. If you increase the surface temperature, you just elevate the radiating level, keeping the OLR constant. This only happens at temperatures considerably above the Cretaceous range. It's the basis of the "runaway greenhouse" model of how Venus got the way it is. If the absorbed solar radiation exceeds the limiting OLR described above, then the surface temperature will keep increasing until the entire ocean has evaporated into the atmosphere. As for the methane regulation idea, that is due to Kasting and Pavlov, and draws its inspiration from atmospheric chemistry that is known to happen on Titan. Basically, if you have a methane dominated atmosphere, then methane combines to form complex organic hazes, which blocks sunlight and hence cools the surface. The methane thermostat posits that on the early Earth, the biosphere was dominated by methanogens, who keep warming up the planet by pumping out methane. If the methane concentration gets so high that it substantially exceeds the CO2, then chemistry says you form hazes, which will cool things down again. There's lots of this theory that remains to be worked out, but it certainly is an interesting new wrinkle, which is worth thinking about.]

  15. 65
    Matt says:

    Buying time.

    If we could develop a process that takes biomass in and produces carbon based, long lasting construction blocks, plus CO2 plus entropy; then we might be able to buy ourselves an extra 50-100 years. Over time we might expect the process to get more efficient, we would farm ourselves out of trouble in the short term.

    Eventually, this high energy process will cause us to worry the entropy term, but if we are efficient we can do this until we find alternative fuel. We still push fossil fuel conservation.

    The process would become an extension of the processed woods industry.

  16. 66
    Hank Roberts says:

    As I understand it, we might have farmed ourselves out of trouble if we’d started working on that back when the global population was under one billion — because we didn’t need to consume more than Earth could produce in any given year, back then.

    We’ve overshot that point. The text here — nine paragraphs — sums it up, with reference to the graphs.
    http://greatchange.org/footnotes-overshoot-graphs.html

    I think total energy use by people each year now is quite a bit more than the total possible biological material growing on Earth per year, right now.

    We’re running on fossil not because it’s easier — but because there’s more of it. There isn’t enough wood, corn, switchgrass and everything else added up total, available to burn, for our use of energy — each year.

  17. 67
    nanny_govt_sucks says:

    #64: “I wrote that aerosols were “dominant” for the cooling period. This certainly appears to be the case”

    Based on what science?

    Anyone can clearly see in the charts below that the places on the planet that have warmed the most in the last 20 years or so are the places that produce the MOST aerosols.

    See fig (a) for Anthropogenic Sulfate Production Rate
    http://www.grida.no/climate/ipcc_tar/wg1/fig5-2.htm

    See fig (d) for Annual Temperature Trends 1976 to 2000
    http://www.grida.no/climate/ipcc_tar/wg1/fig2-9.htm

    Where is this so-called cooling effect from sulfate aerosols?

    “I also find it strange that you don’t notice the most obvious feature of the figure 5 that you link to: the massive divergence between recorded temperatures and solar irradiance in the later part of the 20th century.”

    I presented the graphic in response to the fallacious claim that aerosols had something to do with global cooling during the period 1940 to 1975. Do you accept Solanki’s study? If so, then will you agree that aerosols were NOT involved significantly in global cooling from 1940-1975?

    “The situation is that “GW Theory” encompasses many different bits of information …”

    Moving the goalposts, are we? The subject from #46, #48, #50 was “CO2 Theory”. Let’s not change the subject.

    “You can hide from the evidence for only so long, but when even the evidence you bring forward in your defence contradicts you…surely then you must admit defeat.”

    Again, a subject change. My point was about the global cooling period from 1940-1975. Solanki’s study says it was due to solar changes, you say aerosol effects. Who’s right?

  18. 68
    Tom Fiddaman says:

    Re 68

    I presented the graphic in response to the fallacious claim that aerosols had something to do with global cooling during the period 1940 to 1975. Do you accept Solanki’s study? If so, then will you agree that aerosols were NOT involved significantly in global cooling from 1940-1975?

    The Solanki page you linked proves nothing of the sort; it’s not even a detection & attribution study. Eyeballing the two curves and concluding that aerosols can’t be involved is even more superstitious than eyeballing temperature and CO2 graphs and concluding that AGW must be real.

    Similarly, aerosols don’t necessarily cause cooling; they just cause less warming than would otherwise occur. Also, the spatial pattern of aerosol forcing differs from the spatial pattern of aerosol production you cited. Again, this is a case where eyeball correlations that work for simple systems fail with complex dynamic systems.

  19. 69
    Coby says:

    Hi nanny..

    Can you provide a quote from Solanki’s study where he says what you say he says? I don’t think so.

    You are making such shallow and naive arguments, I am wondering if you believe any of them? The simple fact of a reasonable correlation on a graph that is scaled for the best match hardly means that solar must be the one and only driver of temperature changes. Similarily, looking for cooling regions to correlate with less warming means you must have never heard of wind, which is not likely.

    Why is it so hard for you to accept that there are many factors at play and your search for the one and only cause (as long as it isn’t CO2) is misguided to say the least.

  20. 70
    Brian Forbes says:

    Re 60 & 61
    Temperatures from truly rural stations (with no warming effect from concrete & no cooling effect from fountains or trees) follow the activity of the sun very closely up to about 1980 virtually precluding any other cause.
    I have always theorised that aircraft vapour trails would have some effect on climate.
    http://www.agu.org/sci_soc/prrl/prrl9919.html
    especially since most flghts are in the N Hemisphere which is warming and hardly any over Antarctica which is cooling.
    Seems to me to be a better explanation of GW than CO2

    [Response:That's a testable theory... and has already been tested: Minnis et al, 2003, Hansen et al, 2005 - and found not to be as important as CO2, other greenhouse gases, volcanoes, aerosols, ozone etc.... - gavin]

  21. 71
    C. W. Magee says:

    Explaining the recent evolution course case is all well and good, but I was wondering… Have any global warming-related cases gone through the US court system yet?

    I would not be surprised if the litigation-friendly US environmental movement decided to buy an Arizona or North Carolina ski resort, and then sue the combined oil and coal industries for the cost of a week’s extra snowmaking.

    [Response: The proposed listing of polar bears as endangered species may require that some aspects of global warming theory be brought into the courtroom. A big part of the threat cited in the listing proposal is due to the loss of habitat associated with loss of sea ice. If that's attributable to anthropogenic global warming, it would seem that the US would have a legal obligation to reduce GHG emissions. But would we then have a legal obligation to somehow force China and India to also do so? How do you preserve habitat if the habitat is being destroyed by collective action of most of the world's population? The implications are mind boggling.--raypierre]

  22. 72

    “For the most part, the good judge takes a positivist approach to the definition of science, following Karl Popper. This approach emphasizes that a scientific theory should be falsifiable.”

    I think you are mixing the terms a bit here; Popper was a critic of positivism. While positivists demanded that propositions were verifiable, Popper suggested that they instead should be falsifiable. Also, Popper was less harsh on non-falsifiable propositions, admitting that his own philosophy (as well as the positivist’s) was non-verifiable and non-falsifiable — the positivists were infamous for deriding non-verifiable statements as “meaningless”.

    As least as I recall. (I also did a bit checking in wikipedia)

    But that doesn’t matter to your argument, of course.

    [Response: You're quite right. Thanks for the correction. The distinction between verifiability and falsifiability is a significant one.--raypierre]

  23. 73
    raypierre says:

    Regarding #27 again…

    I hope I didn’t appear to be laughing at Mr. Pollard, or to be disrespectful of his post. The very idea that anybody might agree to become an IPCC panelist for the sake of the material perks involved would give anybody who had been through the process an involuntary chuckle.

    It’s absolutely true that scientists are people, subject to the usual human shortcomings. To understand the scientific enterprise, though, it would be helpful to understand that the main temptations are not money and material wealth, but fame and a place in history. Scientists just want to be loved. This is especially true in climate science, where there isn’t much money to be made in the private sector or through government contracts (as compared to, say, biomedical, computer science and engineering, or defense contracting), but even where there are more material temptations, it’s fair to say that it’s the fame rather than the fortune that rules. Fortunately, the best way to achieve fame in science is to be RIGHT. Attempts to short-circuit the one true path to fame, as in the sad case of the recent Korean cloning debacle, are almost always rooted out quickly, and invariably lead to catastrophe for the scientists involved.

  24. 74
    Pat Neuman says:

    In 67, nanny_govt_sucks wrote: Again, a subject change. My point was about the global cooling period from 1940-1975. Solanki’s study says it was due to solar changes, you say aerosol effects.
    Who’s right?

    In RC “Calculating the greenhouse effect”
    http://www.realclimate.org/index.php?p=220

    I wrote:

    The link at:
    http://www.grida.no/climate/ipcc_tar/wg1/figspm-3.htm

    shows very low level of scientific understanding on a small amount of solar forcing for 2000 compared to year 1750.

    The link at: http://www.giss.nasa.gov/data/simodel/

    on forcings over the past 150 years determined by GISS does not explain 1880-2005 globally averaged surface temperature plots by NOAA and NASA, nor 1888-2005 climate station plots for the U.S. at:
    http://pg.photos.yahoo.com/ph/patneuman2000/my_photos

    The explanation for the warm 1930s, cool 1960s and rapid global warming we see happening now is best explained by the case I made in #117. ie. “The late-1920s-1930s surge in solar radiation was temporary only. After the 1930s, solar radiation fell back to it’s pre-1920s levels, and have remained nearly constant for 1940s to present. The global warming being observed now is entirely a result of human activity, mostly from GHG emissions (and subsequent global warming feedbacks)”. … 29 Jan 2006, comment 141

    There were no subsequent posts in that thread or this threat that successfully disputed the points that I made earlier regarding this discussion.

  25. 75
    Brian Forbes says:

    Re your comment on my 70
    If you use a computer model and and the temperatures issued by GISS of course the test will fail.
    Using the temperatures as defined (free from urban effects) which should reflect the true extent of GW the my model fits perfectly making the effect of CO2 about 10% of that which you calculate.

    [Response: You appear to be confusing correlation with causation. Models do not assign the CO2 effect by correlating it to anything. And if you are trying to do a calculation of climate sensitivity from the last century of data, then you are severely hampered by the uncertainty in aerosol, ozone and even solar effects (see here). If it was this easy, we would have done it already.... - gavin]

  26. 76

    It is interesting to consider why opponents of carbon emissions restraint attack the whole chain of logic at its strongest point. We know that greenhouse gases warm planets. We know we are substantially changing greenhouse gas concentrations. We know that our planet is warming by about the amount anticipated by the theory. We have no alternative theory as to why greenhouse gases would fail to warm the planet and we have no alternative theory as to why the planet should be warming as much as it is, presuming the greenhouse gases somehow were ineffective.

    Whether it is warming too much is up to the impacts studies, and what to do about it is up to the economics and policy studies. These are far less rigorous and far more uncertain than the science. Why is it that the physics is attacked rather than the economics and politics? I think this is because people understand risk well enough to respond to it substantively, however messily.

    Most people don’t understand radiative transfer, and efforts to close the gap are typically not met with great enthusiasm either by the public or the scientists.

    Meanwhile the vast and largely successful efforts to confuse the general public about the risk of anthropogenic climate change have serious consequences outside the particular issue at hand. Essentially they subvert the decision making process not only in this particular area. They subvert the connection between information and democracy.

    A misinformed democracy is not paying the price of freedom, which is eternal vigilance. Knowing who the real experts are and who the snake oil salesman is not easy, especially as the accumulated technique of the snake oil folks is continually refined.

    This brings us back to the analogy that Ray is making. There are of course legitimate points of scientific contact between climatology and evolutionary biology, each having evidence the other needs about the deep past. That we have a more unsettling common cause against organized obfuscation is not our doing.

    The forces of ignorance may mean well, but they can only do well quite by accident. A democratic society that is not connected to science is very deeply at risk. If we manage to cope with climate change by adopting fundamentalist arguments and thereby continue to concede the advance of willful ignorance our future nevertheless looks very bleak.

    A society that puts preconceived beliefs ahead of evidence is a society that will make many serious mistakes and will not be competitive. Both history and current events say so.

    In an ideal circumstance, we scientists can direct our efforts entirely to amassing knowledge, but sometimes we have to have the courage to defend knowledge against dogma.

  27. 77
    Hank Roberts says:

    Scientists want to be right and are respected for it.

    Those making a living by attacking scientists, though … well, look at today’s WSJ:
    http://online.wsj.com/public/article/SB114047541194578433.html?mod=todays_free_feature

    “… She has parlayed her backstabbing into a television career and speaking engagements. “Who knew that being soo bad could be soo good$$!!,” the show’s Web site quotes her as saying.

    “I wouldn’t jump to the conclusion that this kind of behavior is naturally rewarded,” cautions Paul Argenti, professor of corporate communication at Dartmouth’s Tuck School of Business. “But it does lead to success in some realms.” And those realms can include the legal profession, sales teams, trading floors, entrepreneurial endeavors — in other words, the corners of the business world where unmitigated gall can be more marketable than galling….”

    “That’s because in the rough and tumble of business, bad behavior is sometimes admired, and good behavior isn’t necessarily rewarded…., Prof. Argenti says.”

  28. 78

    Re #64 comment,

    Thanks Raypierre for the interesting theories, although we still are far from Venusian or Titanian atmospheres. What I miss in the theories is what will happen to (water) clouds on earth… Nowadays they seem to work as negative feedback in the energy budget (at least in the tropics and the Arctic), but what is expected if the temperatures get higher?

  29. 79
    Eachran says:

    Wonderful post and many thanks to RayPierre. It is not often that non-specialists like me can understand clearly and without “pain in the brain” what the issue is. Perhaps you ought to link to the philosopher’s website too because I liked the Popper referral (I cant give you the link because I am not working from my own comp.)?

    Two points :

    1. Sometime ago I posted on this site on : models, the issue of data and how it was managed : I see the same problem with, for example Mr Forbes but also others. Maybe it ought to be repeated : climate models are physical models using well known and established physical principles which even “deniers” wouldn’t – if I may put it like that. OK, statistics come into it eventually for verification and testing but the idea is to try to physically verify how climate works. This is not Pavlov and his dogs which I think is one of the main problems which Mr Forbes has.

    2. All the people on RC are true communicators but maybe do not yet know how effective they are. The Economist weekly which for a number of years has been a denier, has repented, and even this week is alerting readers to the dangers of sea level rise. There are not many deniers left.

  30. 80
    Pat Neuman says:

    In 78 Ferdinand wrote: … what will happen to (water) clouds on earth… Nowadays they seem to work as negative feedback in the energy budget (at least in the tropics and the Arctic),” …

    There is nothing to back up what Ferdinand wrote on that. Then he asked .. “but what is expected if the temperatures get higher?”

    How much higher, warmer than a hot tub?

    Ocean Warmer Than A Hot Tub
    by Staff Writers
    St Louis MO (SPX) Feb 20, 2006
    Scientists have found evidence that tropical Atlantic Ocean
    temperatures may have once reached 107°F (42°C)â??about 25°F (14°C)
    higher than ocean temperatures today and warmer than a hot tub. …

    http://www.terradaily.com/reports/Atlantic_Ocean_Warmer_Than_A_Hot_Tub.html

  31. 81

    Re #74,

    Pat, I am sorry to see that you repeat you opinion regarding solar strength since 1940, which is repeatedly shown to be wrong.

    Every known proxy which can be linked to solar variability shows an increase until 1940, a reduction after 1945, and an increase after 1975.
    That is the case for measurements of the sun’s magnetic field (via changes in the earth’s magnetic fiend), and its related isotope 10Be (not measurable for 14C, as nuclear tests dwarfed sun-related 14C levels after 1945), sun spots counts and sun cycle length. They all show that post 1975 solar irradiation is higher than anywhere since the 1930-1940′s.

    If you have any proof (proxy) that the sun is not more active now than anywhere in the first halve of the past century (or millennium or millennia), I am very interested.

    Further, as repeatedly shown (and accepted by the IPCC), current models are as scientific uncertain about aerosol forcings as about climate forcing (and sensitivity) for solar, that means that several combinations of forcings and sensitivities (and feedbacks…), ranging from near 100% solar to near 100% GHGs/aerosols can fit the past century’s temperature trend, including the 1945-1975 cooling.
    The trillion(s) dollar question remains if it was more solar or more GHGs/aerosols, as that makes a huge difference for any model projection of what will happen with a CO2 doubling: benign, at the low side of the IPCC range or a catastrophe, at the high side of the range…

    [Response:This is not so. Sunspots peaked in 1957, neutron monitors show no trend in GCR, 10Be is flat in Antartica (though decreasing in Greenland) - they cannot both reflect global production. There may be some trend in the aa-index but it's small. -gavin]

  32. 82
  33. 83
    Pat Neuman says:

    Gary’s links end a couple or so years ago. The averaged temperature for the globe in 2005 was near or above the record warm temperature set in 1998. 1998 heat was enhanced by a powerful El Nino. El Nino and slight changes in solar radiation cannot explain the global heat of 2005. GHG accumulations do.

  34. 84
    Matt says:

    Pleistocene Man, Holocene Man and Carbocene Man have a conversation:

    Pleistocene man: Holocene man, we tried to forbid you from spreading seed around the hunting camp. Each season the foodstuffs increase and the people refuse to honor the hunting migration. They linger and forage for days, scaring away the game. You did not obey the snake taboo against taking gifts from the vegetation.

    Holocene Man: But Pleistocene Man, we worship the sun now, we bit the apple and your restrictions are ancient and worn.

    Carbocene Man: But Holocene man, are you not giving us that same argument that Pleistocene man gave you? Your experiment with agriculture halted Younger-Dryas and put us right in the middle of this mess.

    Holocene Man: Because we worship the sun, we are most intelligent, and our experiment with the Holocene period was something to learn by, now listen to us, we are even more wiser.

    Pleistocene man: But that is exactly what we told you, Holocene, you did not listen then, now you expect Carbocene Man to listen now.

    Carboocenen Man: OK, Pleistocene Man, what would you tell us to do?

    Pleistocene man: Kill the soil microbes.

  35. 85
    Hieronymous says:

    I enjoyed reading this post. It is a very nice exposition of how we do our science and of its results.

    I agree with the conclusions. However, I think the demarcation question (science vs pseudo-science) is more difficult than acknowledged.

    Popper has not only “been challenged by Thomas Kuhn and a few other philosophers of science,” but the simple form of his views often heard in the scientific community is almost completely discredited within the philosophy of science community. The reasons are numerous. One obvious reason is that science does not progress by falsification alone. The anomalous advance of Mercury’s perihelion, after accounting for the effects of the other planets, was known since 1859; it should have falsified Newton’s mechanics if science worked by falsification alone (more or less the view in Popper’s Logic of Scientific Discovery). But scientists hung on to Newton’s mechanics until Einstein came around. Later, responding to criticism, Popper amended his early version of falsificationism by adding that a theory is typically only rejected after unsuccessful attempts to amend auxiliary assumptions (if conflicting observations are more consistent with an available alternative theory that has greater empirical content than the first theory). With that modification, however, the answer to the demarcation question becomes more complicated: on the basis of this weak version of falsificationism, there is no simple test to decide which theories are scientific and which are not (falsifiability alone, even according to the later Popper, does not suffice). There are numerous critiques of Popper’s falsificationism, among them the writings by his student Imre Lakatos (e.g, The Methodology of Scientific Research Programs and “Science and Pseudoscience,” a brief summary of which is here). A summary of Lakatos’ criticism is here. A more sympathetic discussion of why falsificationism ultimately fails is here.

    As an aside, Popper was not a positivist in the sense in which the term is commonly understood and was understood by Popper himself — that is, an adherent of the logical positivism originating with Comte (who coined the term in his Cours de philosophie positive) and the Vienna Circle, which focused on the verifiability of theoretical propositions by empirical facts. Popper’s falsificationism was set against logical positivism and the problems of induction it faces. Popper wrote disparagingly about positivism (e.g., in Realism and the Aim of Science). In sociology, however, Adorno, Habermas, and others in the Frankfurt School called Popper a positivist, apparently because he shared with the logical positivists a belief in the unity of scientific method, which they rejected. A good discussion of the history and problems of positivism is in Ian Hacking’s book Representing and Intervening (which also includes an overview of more recent accounts of what a scientific theory is, many of them more satisfying and closer to how science actually works than Popper’s).

    Judge Jones’ decision on ID, rather than adopting a Popperian point of view, avoided a commitment to any school of what science is and focused on the common ground on what all agree is not science. However, the three criteria in the statement “ID is not science and cannot be adjudged a valid, accepted scientific theory as it has failed to [1.] publish in peer-reviewed journals, [2.] engage in research and testing, and [3.] gain acceptance in the scientific community” are not sufficient to demarcate science from pseudo-science. The first and third criterion are appeals to authority (science is what scientists say it is — a form of conventionalism which, at least in its naive form, we have rejected with the rejection of the scholastics). The second criterion echoes Hume (An Enquiry Concerning Human Understanding):

    If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but
    sophistry and illusion.

    The problem is that, according to these criteria, the 17th century literature on witchcraft is scientific literature. It was peer-reviewed (not in today’s sense, but it had to pass some level of scrutiny to be published), generally accepted by the ‘scientific’ community of the day, and plentiful in examples of research and empirical testing. Lakatos pointed out that “Glanvill, the house philosopher of the early Royal Society, regarded witchcraft as the paradigm of experimental reasoning.” One has to be more specific to find sufficient conditions to distinguish science from pseudo-science. Conversely, the criteria set out by the NAS and referred to in Jones’ decision may not be necessary conditions for what science is, since they do not seem to include parts of cosmology and string theory as science (a conclusion that some people may be willing to accept).

  36. 86
    David B. Benson says:

    Thank you for the fine summary. I especially enjoyed trying out the simulation available via the Hansen et al. paper you reference above.

  37. 87

    Re #81,

    Gavin, indeed I stand corrected, as I wrote “since” the 1930-1940′s, which isn’t correct. But current levels are anyway higher than in the 1920-1930′s of the previous century (which is what Pat denies).

    Re #80,

    Pat, for the change in clouds in the tropics, see: Wielicki ea. and Chen ea.
    For the Arctic, see: Wang and Key

    But thanks for the new link. It proves that the runaway GHG effect is not (yet) for tomorrow, despite the very high ocean temperature found (leading to much increased water vapour). But if that proves that CO2 has more effect on temperature than implemented in current models, remains to be seen. The opposite, that high temperatures have less effect on CO2 levels is as good possible. As you may know, the Cretaceous shows an abundant amount of CO2 binding species (coccoliths), which have build the enormous layers of chalk (the “White Cliffs of Dover”…) of the time period in question.

    But methane is different item, as IMHO that is a much more interesting greenhouse gas…

  38. 88
    Hank Roberts says:

    This may help:
    Peer Review: A Necessary But Not Sufficient Condition
    http://www.realclimate.org/index.php?p=109

  39. 89
    Steve Sadlov says:

    RE: Pleistocene man: Kill the soil microbes.

    How about this variation on that theme – let us manufacture petroleum. Let us do so in such abundance that we can throttle the climate (in both directions). We cannot control it. Maybe we can smooth the rough edges though. In any case, why let the detritus go to waste when it could be fueling our future.

  40. 90
    Pat Neuman says:

    Ferdinand,

    I you can get away with that (81,87), and many of your other posts, then I should be allowed to get this one through…

    Average temperatures at climate stations in the Upper Midwest broke 100
    year record warm averages in Jan. 2006. February has been running a
    degree or two F below normal, at this time.

    Professional meteorologists are misleading the public by talking about
    having two sides … i.e. because it was warm last month, it’s cold this month … it all evens out …

    It does NOT ALL EVEN OUT. Record warmth is not equal to a degree or two
    below normal!

    There are not two equal sides to climate and global warming. Rapid and
    uncontrollable global warming is happening. It’s being caused by CO2
    being dumped into the atmosphere, because of our addiction to energy.
    The CO2 is accumulating, changing the climate way to fast, and because
    of our actions, our home planet Earth, and everything we all love on it,
    is likely to pass. Have you got it yet? I do.

  41. 91
    Lynn Vincentnathan says:

    Looks like my bit about Homo stupidus was deleted for being a bit too raucous…

    Another thought. Aside from many other factors, there are psychological factors that make many people reject evolution and GW theories. First they don’t like to think they “came from the apes” or share common ancestors with them…or with other more “lowly” creatures. And many might view GW as threatening their self-esteem as well, by implying they are responsible for something very bad; or they might feel GW threatens their life-world with predictions that things will radically change, unless they substantially change their habits.

    As for paradigms, the evolutionary paradigm of the 19th c. was carried out a bit too far. Evolution was everywhere — society, culture, language, religion, morality, with “primitive” peoples of today seen a “primitive” (first, early, unevolved) in all ways. This fed into racism & nazism. But are the “primitives” any worse than “civilized” man, who is really harming the earth through GW?

    As of yet the GW paradigm has not caught on enough to be excessive. When that time comes, I predict people will be blaming everything on GW, even toothaches, & cursing our generation for its evil ways.

    [Response: Another issue with regard to anthropogenic global warming is that people easily find reasons for denying things whose consequences are unpleasant or inconvenient (like making do with less fossil fuel burning). I don't think there are any completely painless ways to head off a dangerous degree of global warming, but I do try to point out to people ways in which the quality of life could be improved at the same time the burning of fossil fuels is reduced. --raypierre]

  42. 92
    Steve Sadlov says:

    RE: #90. Tell us more about this supposed addiction to energy. What are your proxies to demonstrate this? What are your units of measure? What are the projections for per capita energy use? What are the projections for population? Inquiring minds want to know.

  43. 93
    C. W. Magee says:

    Re 80, extreme atlantic water temperatures:

    The preprint is here:
    http://www.whoi.edu/science/GG/people/kbice/paleoceanography_Bice_etal_2006.pdf
    Given the age of the samples, I’m a bit concerned about the lack of attention given to the possibility of diagenesis, Mg/Ca exchange/ equilibration, or other possible post-depositional effects on the samples. I’m not saying that they are bodgey, and I don’t have the foram background to know what the most common foram problems are, but if you’re going to make extreme claims in a paper, you should cover yourself against such doubts by spending a few paragraphs and figures showing that there is no dolomite exsolution, recrystalization, clay-carbonate Mg or Al exchange, or other post depositional processes that can alter the mineral composition. All of the conclusions are based on data from 100 million year old carbonates, but the paper doesn’t even include a micrograph of the samples.

    The conclusions also fail to address other obvious potential problems with the conclusions, such as:
    -Would the postulated CO2 levels allow for carbonate deposition at the benthic paleotemperature of her deposition site?
    -Can 40 degree water even contain enough disolved O2 to keep her forams (and everything else in the fossil record) alive?

    In general, the paper seems to just accept the unusual dataset …. , and then launch off into model-land without really nailing down the analytical issues that underly the interpretations.

    [Response: We obviously aren't reading the same paper. They used two different ways to assess the temperatures and are quite clear about the uncertainties associated with them (for which there is a huge literature). -gavin]

  44. 94
    Urs Neu says:

    Re #81, #82, #87

    Some facts about solar influence:

    as Pat mentioned sunspots peaked in 1957, since the 1950ies there is no trend, since 1980 there is no trend, if ever it is negative.
    e.g. http://www.ngdc.noaa.gov/stp/SOLAR/COSMIC_RAYS/cosmic.html
    the same for other solar indices: http://www.brighton73.freeserve.co.uk/gw/solar/solar.htm

    From the papers cited in #82:
    “the Sun has never been as active as it has been during the past 60 years” and “Sunspots have been more common in the past seven decades than at any time in the last 8,000 years”
    It is clearly stated, that the sun has been extraordinarily active “during” the last 60 years, i.e. all the last 60 years, not the last 10, 20 or whatever years, no mention of any trend since 1940/50.

    Solar activity is higher than 1920/30, o.k., but that’s not what we are talking about. There might be a solar heating until 1940/50. However, we are talking about the warming since 1950. And since then there is no apparent trend in solar activity. There is a slight decrease until the 1970ies and maybe a slight increase of the same amount afterwards. However, the temperature increase after 1975 is about 5 times stronger than the decrease from 1945-1975.

    Ferdinand, any delayed climate reaction on the solar activity increase until 1940/50 (to get equilibrium and allow feedbacks), as you have suggested several times, would most likely be strongest just after the forcing has stopped and then decrease with time. It is very unlikely that there is no reaction for two decades and then an strong acceleration. Can you present any process who would explain such a pattern?

    The solar irradiance time series of Willson (paper in #82) is one of two existing time series, the other one is by Frohlich:
    http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant
    Willson finds a slight increase of solar irradiance, Frohlich finds no trend. The only fact which could favor one of the two composites is, that there is no trend (or negative) since 1980 in solar activity (sunspots), which is closely linked to solar irradiance. Frohlichs composite fits better to this observations.

    Ferdinand, Scafetta and West, whom you like citing over and over, just consider the Willson composite in their calculation (for no given reason), and find a solar influence of 10 to 30% on the warming since 1980. If you also consider the Frohlich composite (there is no reason for not doing it) the solar influence is -10 to 30%.

  45. 95
    Brian Forbes says:

    [Response: You appear to be confusing correlation with causation. Models do not assign the CO2 effect by correlating it to anything. And if you are trying to do a calculation of climate sensitivity from the last century of data, then you are severely hampered by the uncertainty in aerosol, ozone and even solar effects (see here). If it was this easy, we would have done it already.... - gavin]

    I worked for 20 years in thr chemical industry where finding a good correlation always led to a cause.
    The trouble with CO2 is that it does not have a good correlation with temperature.In order to improve this other varibles are introduced, one of which for example is sulphate cooling the only evidence for which is that the “global ttemperature” fell as SO2 rose.A good example of sulphate affected atmosphere is that of Venus.

  46. 96
    Thomas Bolger says:

    I see Lynn is at it again.If I called climate alarmists mad athiests, which I hasten to add they are not, you would censor me.

  47. 97
    Florifulgurator says:

    Re 92: See e.g. Fig 4 at http://dieoff.org/page224.htm

  48. 98
    Matt says:

    re: 89

    In order to oxidize ditritus, we need to get back some more of the carbon budget from nature. Our problem is that our carbon based economy (lumber, agriculture, manufacturing, housing, and the chemisty industry) use so much of the carbon cycle that the biosphere is running hot.

    I am looking for three solutions. Oil conservation, exothermic long term fixing of the biomass, and partial shut down of soil respiration. This gets us a few years.

    Shutting down soil respiration would be an emergency step we keep in our tool chest, you know, just in case we developed a little fever. We may have to crop dust the Northern tundra, seal it, just to save ourselves in the short term.

  49. 99
    Tom Fiddaman says:

    Re 95

    The observation that good correlation often leads to a cause is not proof that cause can’t exist without obvious correlation. If one’s standard of proof requires a clear pattern in a scatter plot of y against x, one will be forever mystified by noisy, nonlinear dynamic systems.

    I haven’t seen any claims that aerosols led to falling temperatures; rather that temperatures rose less than they would have otherwise. Unless you refer to volcanic aerosols, in which case the evidence seems pretty clear. Global temperature is not the only line of evidence on aerosol forcing; there are also optical and regional temperature measurements.

    The atmosphere of Venus is also affected by 92x the density of Earth’s, and is 96% CO2. The presence of aerosols doesn’t say much about aerosol forcing on earth, except to the extent that GCMs also work for Venus-like conditions.

  50. 100
    Steve Sadlov says:

    RE: #93. I have always suspected that at least some of the “climate science” community either elect to ignore, or, honestly lack the knowledge regarding, some of the basic issues regarding the geochemistry of natural waters, which you have raised in the referenced post. In fact, I can recommend a text by that very name (“The Geochemistry of Natural Waters” – sorry, can’t remember the author, Google for that …) for any who want to refresh their knowledge or for those who never have had the opportunity to gain this area of knowledge previously.

    [Response:And on what do you base this opinion? That a cloud specialist is not aware of the literature in deep sea chemistry is probably not a surprise, but to think that people working on ocean sediments aren't is ridiculous. - gavin]


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