In the Climate Casino: An Exchange

this article warms the cockles of my heart.  William Nordhaus, Economics Professor, Yale argues in favor of global warming

16 experts, among 300 distinguished professors emeritus of physics and related temperature fields refute his argument. 

joe, see below, more comments from Brophy later

april 26, 2012

Roger W. Cohen, William Happer, and Richard Lindzen, reply by William D. Nordhaus

In response to:

Why the Global Warming Skeptics Are Wrong from the March 22, 2012 issue                                                  

To the Editors:

In the March 22, 2012, issue of The New York Review, William Nordhaus presents his opinion on why global warming skeptics in general, and the sixteen scientists and engineers who wrote two Wall Street Journal Op Eds1 in particular, are “wrong.” We are three of those sixteen authors, and we respond here to Professor Nordhaus.

Professor Nordhaus’s essay contains six points.


Thomas Rowlandson: The Hazard Room, 1792

The first point contorts the obvious fact that there has been no statistically significant warming for about the past fifteen years into a claim that we did not make: that there has been no warming over the past two centuries. Professor Nordhaus proceeds to confuse this with the issue of attribution, i.e., the determination of what caused the warming. Attribution is a distinctly different matter. While there is much to contest in the published temperature records, there is general acceptance that there has been a net increase in global mean temperature similar to that shown in Professor Nordhaus’s first graph.

The prior two- to three-hundred-year period was much cooler and is known as the Little Ice Age, and, of course, a longer record would have shown still-earlier periods as warm or warmer than the present. The observation that the last few years include some of the warmest years on record no more implies future warming than record stock market highs imply a steadily rising future market. The fact that warming has greatly slowed does imply that, at the least, there are other processes that are currently competitive with the impact of steadily increasing greenhouse gases.

The second point concerns our observation that current computer climate models appear to exaggerate warming due to CO2. This bears on the critical issue of the climate sensitivity, the temperature rise for a doubling of atmospheric CO2. Professor Nordhaus presents two graphs from the IPCC 2007 report2 that purport to show that without anthropogenic emissions, models successfully simulate the global mean temperature until about 1970 but cannot do so thereafter. This is the basis for the IPCC’s claim that it is likely that most of the warming over the past fifty years is due to man’s emissions. Such a procedure absolutely requires that the model include correctly all other sources of variability. However, the failure of the models to predict the hiatus in warming over the past fifteen years is acknowledged to indicate that this condition has not been met.3 Furthermore there is the embarrassing fact that the models do not reproduce the 1910–1940 warming, which is nearly identical to the 1970–2000 warming but occurred before man’s emissions became large enough to be considered important.

With respect to climate sensitivity, it should be noted that the IPCC referred to all of man’s emissions rather than just CO2. The reason is that without the cooling effect of aerosols formed from certain emissions, the models significantly overpredict warming from greenhouse gases. However, each model needed a different value for the aerosol cancellation.4 This lack of consistency means that aerosols were merely an adjustment factor to bring the models into agreement with the historical record, while preserving a high climate sensitivity. Therefore, the claim that the models cannot account for post-1970 warming without including human emissions means nothing scientifically.

The third point concerns our statement that CO2 is not a pollutant, that we were perhaps using a commonsense, dictionary definition of pollutant. The Oxford English Dictionary defines pollutant as “a polluting agent; esp. a noxious or poisonous substance which pollutes the environment.” Professor Nordhaus says, “The contention that CO2 is not a pollutant is a rhetorical device.” Rather he takes a 5–4 Supreme Court decision to be definitive. In fact, the Supreme Court majority did not rule CO2 a pollutant; it merely found that the Clean Air Act’s definition is so broad that CO2 falls under the statute, regardless of the facts of the matter. The concurrence of an economist (Richard Tol) is then taken as confirmation of the existence of specific externalities associated with CO2. We consider such references to be the real “rhetorical devices” because they obscure the key scientific issue: whether this critical component of the earth’s biosphere will cause significant and destructive global warming.

In another rhetorical flourish, Professor Nordhaus’s fourth point misrepresents us as claiming that “skeptical climate sci-entists are living under a reign of terror about their professional and personal livelihoods.” This reductio ad absurdum is inappropriate, but we observe that individuals like climate scientist James Hansen, environmental activist Robert Kennedy Jr., and economist Paul Krugman have characterized critics of climate alarm as “traitors to the planet.” We noted the systematic dismissal of editors who publish peer-reviewed papers questioning climate alarm, as well as the legitimate fears of untenured faculty whose promotions depend on publications and grant support. We note here that editors like Donald Kennedy at the prestigious Science magazine have publically declared their opposition to the publication of papers finding results in opposition to climate dogma.5

The Climategate e-mails6 specifically describe these tactics, and numerous examples are given in Lindzen (2012.)7 While defense of existing paradigms is normal in science, the present situation is clearly pathological in its imposition of conformity. We cannot speak to the situation in economics, but the notion that dissident voices and new theories are encouraged in climate science is downright silly, though Professor Nordhaus is correct to view such encouragement as critical to a healthy science. Unfortunately, the current situation in climate science is far from healthy. Professor Nordhaus contributes to this when he succumbs to the introduction of the false analogy with tobacco, and his call for political leaders to “be extremely vigilant to prevent pollution [sic] of the scientific process by the merchants of doubt” is not atypical of the current situation.

Regarding Professor Nordhaus’s fifth point that there is no evidence that money is at issue, we simply note that funding for climate science has expanded by a factor of 15 since the early 1990s, and that most of this funding would disappear with the absence of alarm. Climate alarmism has expanded into a hundred-billion-dollar industry far broader than just research. Economists are usually sensitive to the incentive structure, so it is curious that the overwhelming incentives to promote climate alarm are not a consideration to Professor Nordhaus. There are no remotely comparable incentives to the contrary position provided by the industries that he claims would be harmed by the policies he advocates.

In his sixth point, Professor Nordhaus says that we did not properly represent his results when we said, “Nearly the highest benefit-to-cost ratio is achieved for a policy that allows 50 more years of economic growth unimpeded by greenhouse gas controls.” He objects to our reference to this ratio instead of net benefits as a metric for comparing policies: “Elementary cost- benefit and business economics teach that [benefit-to-cost ratio] is an incorrect criterion for selecting investments or policies.” Yet values of calculated benefit-to-cost ratios are highlighted in the key summary Table 5-3 of his book A Question of Balance.8 Indeed, this ratio is often used for guidance in the real world of business investment. One reason is that it can be relatively insensitive to the choice of discount rate and therefore may give more robust insights, whereas net benefits may be extremely sensitive to this choice (more on this below). Both benefit-to-cost and net benefits have their place.

But it matters little which metric one uses. The difference between Professor Nordhaus’s optimal carbon tax policy and a fifty-year delay policy is insignificant economically or climatologically in view of major uncertainties in (1) future economic growth (including reductions in carbon emissions intensity); (2) the physical science (e.g., the climate sensitivity); (3) future positive and negative environmental impacts (e.g., the economic “damage function”); (4) the evaluation of long-term economic costs and benefits (e.g., the discount rate); and (5) the international political process (e.g., the impact of less than full participation).

Professor Nordhaus computes a $0.94 trillion difference between the net benefits of the two policies, just 4 percent of the computed maximum $22.55 trillion in supposed environmental damage. Results are given to three or four numerical significant figures. Yet we do not know the underlying driver for all of this, the climate sensitivity, to even one significant figure.

This relatively small difference, indeed whether it is positive or negative, depends critically on factors such as the five listed above, in particular the value of the climate sensitivity. Professor Nordhaus chooses 3.0 degrees C for doubling of CO2,9 a value that empirical evidence suggests is greatly exaggerated.10 To illustrate the point, for a climate sensitivity of 1.0 degree, a value suggested by a number of empirical studies, Professor Nordhaus’s “DICE” model calculates that the optimum policy’s net benefits drop from about $3 trillion to a net cost of about $1 trillion, and the benefit-to-cost ratio plunges from 2.4 to 0.5. The fifty-year-delay policy is then greatly preferred.

We are asked to take the computed difference between the two policies seriously despite Professor Nordhaus’s finding11 that the optimal policy ultimately “saves” only about 0.1 degree C in global warming relative to the fifty-year delay. Putting this in perspective, 0.1 degree is only about 10 percent of the observed warming since 1850 and is a typical year-to-year fluctuation. This tiny difference is predicted by the DICE model to occur fifty years to two centuries in the future, and yet climate models have failed the test of prediction over twenty years. Furthermore, as outlined in our Op Eds, the strong negative environmental impacts assumed in the DICE model’s economic damage function are acknowledged to be extremely uncertain. There exist potential net benefits of increased atmospheric CO2, especially for a small climate sensitivity (e.g., in agricultural and timber productivity).12

We are not the first to note that Professor Nordhaus’s optimal carbon tax is hardly distinguishable from a policy of delay. For example, economist Clive Hamilton said in an essay entitled “Nordhaus’ Carbon Tax: An Excuse to Do Nothing?”13 written shortly after publication of Professor Nordhaus’s book, “For some of those who want no action, arguing for a carbon tax has become the tactic du jour.” Advocates such as Dr. Hamilton and Sir Nicholas Stern favor a discount rate far below anything familiar in a market economy, for to do otherwise means that (per Hamilton) “the interests of future generations disappear from the analysis.” This, along with wildly exaggerated climate damage scenarios, is needed to justify aggressive short-term interventions such as the Al Gore or Stern proposals.14 Since calculated net benefit results for a two-hundred-year horizon are extremely sensitive to the choice of a discount rate, the debate over the discount rate is far more than technical.

Thus, when one considers the nature and magnitude of uncertainties in the climate sensitivity, the economic damage function, and the discount rate, Professor Nordhaus’s defense of a difference in policies that is tiny compared to these uncertainties is difficult to understand.

The larger point here is that uncertainties in the physical science and the economic science need to be properly considered. As suggested above, a key uncertainty in the economic analysis can be treated by examining the economic impact of realistic values of the climate sensitivity. We have seen that a likely small climate sensitivity turns the optimum policy economic values sharply negative. Mother Nature continues to tell us that the climate sensitivity is likely to be below the range considered by Professor Nordhaus.15 This is not surprising because his choices of its most likely value and its statistical “spread” were strongly influenced by a suite of climate models that have exaggerated past warming and that share common problems. These considerations make Professor Nordhaus’s option of a fifty-year delay the wisest policy choice.

Roger W. Cohen
Fellow, American Physical Society.
He receives no funding and declares no conflict of interest.

William Happer
Professor of Physics, Princeton University.
His research is supported by the United States Air Force Office of Scientific Research.
He declares no conflict of interest.

Richard Lindzen
Professor of Atmospheric Sciences, MIT.
His research has been supported by grants from the NSF, NASA, and the DOE.
He currently has no research funding and declares no conflict of interest.

William Nordhaus replies:

In reading the letter from Roger Cohen, William Happer, and Richard Lindzen (CHL), I have the sense of walking into a barroom brawl. They defend the article by sixteen scientists in The Wall Street Journal by firing a fusillade of complaints at everyone in sight, including Science editor Donald Kennedy, climate scientists with hacked e-mails, columnist Paul Krugman, biologist Paul Ehrlich, activist Robert Kennedy Jr., economist Nicholas Stern, and even former Vice President Al Gore.

However, when all the shooting has stopped and you look up from behind the table, what you see can be summarized in one central point. They argue that global warming is full of uncertainties, but its dangers are being systematically exaggerated by climate scientists. I will review the key issues in this response.

CHL begin by agreeing that global temperatures have in fact risen over the last century. So we have cleared at least one of the hurdles raised by climate-change skeptics.

They asserted in their original article that temperatures have declined over the last decade. In my article I pointed out that, because the year-to-year movements in temperature are so volatile, declines over a decade contain little information. Here is a useful way to see this point: we have a reading of average global temperature from 1880 to 2011 (shown in the figure of my article). Take the ten-year change in temperature for each of the 122 years for which we can make that calculation. Of those, forty-one show declines. In other words, if we were to pick a year at random, the chance is one in three that the ten-year change would be negative. Short-term movements in such volatile series do not provide information about long-term trends.a

As a final comment on their discussion, it has a stale quality of people repeating ancient arguments that do not reflect the current state of climate science. Climate scientists have moved way beyond global mean temperature in looking for evidence of human-caused climate change. Scientists have found several indicators that point to human-caused warming, including melting of glaciers and ice sheets, ocean heat content, rainfall patterns, atmospheric moisture, river runoff, stratospheric cooling, and the extent of Arctic sea ice. Those who look only at global temperature trends are like investigators using only eyewitness reports and ignoring fingerprints and DNA-based evidence.

The second point in CHL’s response involves climate modeling. I noted that the climate models reviewed by the UN’s Intergovernmental Panel on Climate Change (IPCC) showed that temperature trends in the last century could not be explained on the basis of natural forces (such as volcanic eruptions) alone. The IPCC indicated that the long-term rise in global temperatures over the last century could be explained when the influence of CO2 and other human factors were introduced into the models.

CHL do not dispute the point that model simulations excluding human influences cannot capture global temperature trends. Rather, they contend that the models overstate the sensitivity of climate to atmospheric CO2 concentration.b This subject has been intensively studied over more than three decades. Different climate models show different climate sensitivities, and the differences among them have not been resolved. The actual number might be smaller than the consensus, or it might be larger, but CHL have no special insight or results to demonstrate that they are right and others are wrong. I return to the issue of the uncertainties in the last point below.c

The next three points are argumentative and have little scientific significance. Surprisingly, the statement by the sixteen scientists that “CO2 is not a pollutant” is defended by reference to a common dictionary rather than to a scientific source.d But in the end they agree that the real issue is whether this “component” will “cause significant and destructive global warming.” This simply returns the discussion back to the major question under discussion.

I also criticized their suggestion that climate-change skeptics are suffering under a reign of terror similar to that of Soviet geneticists in the Lysenko era; they dismiss my criticism as a “rhetorical flourish.” If they did not mean to imply a parallel of the situations of Soviet geneticists and Western climate skeptics, why did they use the example? Their approach is like the campaigner who smiles benignly and says, “I would never call my opponent a Communist.”

As a fifth point, they defend their argument that standard climate science is corrupted by the need to exaggerate warming to obtain research funds. They elaborate this argument by stating, “There are no remotely comparable incentives to the contrary position provided by the industries that he claims would be harmed by the policies he advocates.”

This is a ludicrous comparison. To get some facts on the ground, I will compare two specific cases: that of my university and that of Dr. Cohen’s former employer, ExxonMobil. Federal climate-related research grants to Yale University, for which I work, averaged $1.4 million per year over the last decade. This represents 0.5 percent of last year’s total revenues.

By contrast, the sales of ExxonMobil, for which Dr. Cohen worked as manager of strategic planning and programs, were $467 billion last year. ExxonMobil produces and sells primarily fossil fuels, which lead to large quantities of CO2 emissions. A substantial charge for emitting CO2 would raise the prices and reduce the sales of its oil, gas, and coal products. ExxonMobil has, according to several reports, pursued its economic self-interest by working to undermine mainstream climate science. A report of the Union of Concerned Scientists stated that ExxonMobil “has funneled about $16 million between 1998 and 2005 to a network of ideological and advocacy organizations that manufacture uncertainty” on global warming.e So ExxonMobil has spent more covertly undermining climate-change science than all of Yale University’s federal climate-related grants in this area.

The final part of the response of CHL comes back to the economics of climate change and public policy. They make two major points: that the difference between acting now and doing nothing for fifty years is “insignificant economically or climatologically,” and that the policy questions are dominated by major uncertainties.

Is the difference between acting now and waiting fifty years indeed “insignificant economically”? Given the importance attached to this question, I recalculated this figure using the latest published model. When put in 2012 prices, the loss is calculated as $3.5 trillion, and the spreadsheet is available on the Web for those who would like to check the calculations themselves.f If, indeed, the climate skeptics think this is an insignificant number, they should not object to spending much smaller sums for slowing climate change starting now.

But the larger point is that climate-change economics and policies are haunted by vast uncertainties. They mention five: economic growth, physical science, the impacts of climate change, politics, and discounting.

Economists have made major efforts to include these uncertainties in their models. However, other uncertainties have proven much more resistant. The first is a set of threats from climate change to the “world’s cultural and natural treasures” (to cite the words of the UNESCO World Heritage Convention), among them major glaciers, marine and terrestrial biodiversity, archaeological sites, and historical cities and settlements. For example, with respect to sea-level rise, there are major threats to the cities of London and Venice and to several low-lying coastal ecosystems.g Ecologists and economists have been unable to find reliable ways of incorporating these threats into economic models.

A second and even more dangerous uncertainty is caused by “tipping points” in the earth system. Among the global-scale tipping points identified by earth scientists are the collapse of large ice sheets in Greenland and Antarctica, changes in ocean circulation, feedback processes by which warming triggers more warming, and the acidification of the ocean.h

The thrust of CHL’s argument is that the uncertainties are likely to resolve in favor of inaction rather than strong action to slow climate change policies, and in any case, they argue, policies are unimportant given the size of the uncertainties.

Are the uncertainties likely to be resolved in favor of inaction? Of course, if we knew the answer, we would not be uncertain. However, the economic models have attempted to reflect the state of scientific knowledge and uncertainty as it is reflected in the best unbiased assessments. In the one area that has been around long enough to judge—the impact on climate of rising concentrations of CO2—the interesting finding is that assessments of the uncertainties have changed little since the first major review in 1979.

However, the major problem with the conclusions of CHL is that they ignore the perils of the climate-change uncertainties. To illustrate, think of the issues as if we are playing roulette in a Climate Casino. Each time the roulette wheel stops, we resolve one of the uncertainties. Our best guess is that CO2 doubling will increase temperatures by 3°C, but if the ball lands on black it will be 2°C while a ball on red will produce 4°C. Similarly, a ball in a black pocket will lead to minimal damages from a certain amount of warming, while a ball in a red pocket will lead to much larger warming than we anticipate. On the next spin, a ball in the black will produce low growth and slow growth in emissions, while a ball in the red will produce rapid growth in CO2 emissions. And so forth.

But, in the Climate Casino, the ball also might land on zero or double-zero. If it lands on zero, we find significant loss of species, ecosystems, and cultural landmarks like Venice. If it lands on double-zero, we find an unanticipated shift in the earth’s climate system, such as a rapid disintegration of the West Antarctic Ice Sheet.

CHL suggest in effect that the ball will always land in the black pocket. We might hope that all the balls land to our advantage on black, but the odds of that outcome on five spins of the wheel are only 1 in 50.i Moreover, when the different uncertainties interact, the outcomes are likely to be even more costly because of nonlinearities in the physical system. For example, assume that the climate uncertainties are larger than we thought and that the impacts were much more damaging than we projected. This would lead to disproportionately larger damages than in the “best-guess” case.

The point is that CHL have the impact of uncertainty exactly backward. A sensible policy would pay a premium to avoid the roulette wheel in a Climate Casino. This means that the economic model estimates of the cost of doing nothing for fifty years are understated because they cannot incorporate all the uncertainties—not just the obvious ones such as climate sensitivity but also the zero and double-zero uncertainties such as tipping points, including ones that are yet undiscovered.

The arguments of the sixteen scientists in The Wall Street Journal, their response here, and others who continue to attack climate science and economics are sometimes serious and sometimes foolish. We sometimes hear that we cannot act because scientists are not really 100 percent sure that global warming will occur. But a good scientist is never 100 percent sure of any empirical phenomenon. This point was captured by the following comment on scientific uncertainty by the distinguished physicist Richard Feynman:

Some years ago I had a conversation with a layman about flying saucers…. I said, “I don’t think there are flying saucers.” So my antagonist said, “Is it impossible that there are flying saucers? Can you prove that it’s impossible?”

“No,” I said, “I can’t prove it’s impossible. It’s just very unlikely.” At that he said, “You are very unscientific. If you can’t prove it impossible, then how can you say that it’s unlikely?” But that is the way that is scientific. It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible.j

This story is a reminder about how good science proceeds. It is possible that the world will not warm over the coming years. It is possible that the impacts will be small. It is possible that a miraculous technology will be invented that can suck CO2 out of the atmosphere at low cost. But in view of the evidence we now have, it would be foolish to bet on these outcomes just because they are possible.

In the end, this barroom brawl is just an entertaining diversion from the main issue. Scientists, economists, and politicians have serious challenges beyond dodging distractions. We must continue to improve our scientific understanding, particularly of the impacts of climate change; we must implement policies such as raising the market price of carbon to provide incentives to households to alter their consumption so that they will have a low- carbon diet; we must also raise carbon prices to send a signal to firms like ExxonMobil that their future lies in research, development, and production of low-carbon fuels; and we must devise mechanisms so that countries will join in a global effort rather than one limited to northwest Europe. All these efforts need to start now, not in fifty years.

  1. 1

    Claude Allegre et al., “ No Need to Panic About Global Warming,” The Wall Street Journal , January 27, 2012; Claude Allegre et al., “ Concerned Scientists Reply on Global Warming ,” The Wall Street Journal online, February 21, 2012. 

  2. 2

    Climate Change 2007: The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , edited by S. Solomon and others (Cambridge University Press, 2007), p. 687. 

  3. 3

    D.M. Smith, S. Cusack, A.W. Colman, C.K. Folland, G.R. Harris, J.M. Murphy, “ Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model,” Science , Vol. 317 (2007); N.S. Keenlyside, M. Latif, J. Jungclaus, L. Kornblueh, and E. Roeckner, “ Advancing Decadal-Scale Climate Prediction in the North Atlantic Sector,” Nature , Vol. 453 (2008). 

  4. 4

    J.T. Kiehl, “Twentieth-Century Climate Model Response and Climate Sensitivity,” Geophysical Research Letters. , Vol. 34 (2007). 

  5. 5

    D. Kennedy, “Science, Policy, and the Media,” Bulletin of the American Academy of Arts & Sciences , Vol. 61 (2008). 

  6. 6

    The complete Climategate documents can readily be found on the Web. A short summary is available at http://www.climateau 

  7. 7

    R.S. Lindzen, “ Climate Science: Is It Currently Designed to Answer Questions?” Euresis Journal (in press). An earlier version is available online at 

  8. 8

    William D. Nordhaus, A Question of Balance: Weighing the Options on Global Warming Policies (Yale University Press, 2008). 

  9. 9

    Nordhaus, A Question of Balance , p. 45. 

  10. 10

    Evidence for a small climate sensitivity can be found in the peer-reviewed literature, as well as online sources. It includes results from a variety of different empirical approaches, including (1) time series analyses of the published temperature record; (2) examination of the response of the earth’s outgoing radiation response to transient climate events; (3) calorimetric studies of the ocean-atmosphere system; (4) mechanisms for secular climate change arising from ocean circulation systems and astronomical influences; and (4) radiative and convective heat transfer in the oceans and atmosphere. 

  11. 11

    Nordhaus, A Question of Balance , Table 5–8. 

  12. 12

    The Impact of Climate Change on the United States Economy, edited by Robert Mendelsohn and James Neumann (Cambridge University Press, 1999); Robert Mendelsohn, The Greening of Global Warming (AEI Press, 1999). 

  13. 13

    Clive Hamilton, “Nordhaus’ Carbon Tax: An Excuse to Do Nothing?,” May 4, 2009, available at .au/cms/media/critique_of_nordhaus.pdf. 

  14. 14

    Nordhaus, A Question of Balance , p. 18. 

  15. 15

    Nordhaus, A Question of Balance , p.127. 

  16. a

    This can be seen more generally as follows. Assume, based on the historical data, that temperature is following an upward trend with an average increase of 0.006°C per year and a random variability (standard deviation for a normal error) of 0.133°C per year. Elementary statistics will show that this process will have decadal declines in temperature in 44 percent of the years. 

  17. b

    More precisely, CHL argue that the standard estimates of the sensitivity of climate to increases in CO2 and other greenhouse gases are overstated. The technical term for this is the “equilibrium climate sensitivity,” which is the equilibrium or long-run global average surface warming following a doubling of atmospheric CO2 concentration. 

  18. c

    CHL further argue that the inputs into the models for the simulations of historical climate models are reverse-engineered to produce the results, that is, that modelers have selected the inputs of radiative forcings for their models to match historical temperature changes. “Radiative forcing” is a technical term denoting the impact of the different gases and climate-affecting factors on the earth’ s energy balance. Forcings are measured as watts per meter squared in the lower atmosphere, but I simply call these “warming units.” Some impacts, such as those caused by CO2 concentrations in the atmosphere, are well determined. However, others are very difficult to measure. CHL correctly point to the large uncertainties here. The largest uncertainty is the forcing due to “aerosols,” which are basically particles caused by sources such as power plants, agriculture, and clearing of forests. (For this discussion, I rely on the authoritative discussion in the IPCC Fourth Assessment Report, Climate Change 2007: The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon and others (Cambridge University Press, 2007.)
    To give a sense of the magnitudes here, the IPCC estimated the change in forcings from 1750 to 2005 from CO2 alone to be 1.7 units of warming, while the total including all other factors was estimated to be 1.6 units. However, there is great uncertainty about the impact of the other forcings, particularly aerosols. The IPCC estimates that the uncertainty range for total warming was between 0.6 and 2.4 units of warming (p. 4). This range is the (5, 95) percentile confidence interval and reflects the authors’ expert judgment that there is at least a 9 in 10 chance that the actual number is within the cited range.
    Climate scientists have recognized this uncertainty for many years and are working to reduce it, but model-building is not simply a curve-fitting exercise. A recent model comparison shows clearly the importance of aerosols for simulating historical climates. The model ensemble with aerosols alone is estimated to reduce global mean temperature by about 0.5°C over the last century. Simulations that include all forcings except aerosols lead to an overprediction of approximately the same amount (see Olivier Boucher et al., “Climate Response to Aerosol Forcings in CMIP5,” CLIVAR Exchanges , No. 56, Vol. 16, No. 2, May 2011). The ultimate answer to the uncertainty is not to dismiss our climate models but to improve our measurements, particularly of the effects of aerosols. 

  19. d

    For example, a leading textbook on air pollution cites the following definition from the US Environmental Protection Agency as a good place to start thinking: “Air pollution: The presence of contaminants or pollutant substances in the air that interfere with human health or welfare, or produce other harmful environmental effects.” Daniel A. Vallero, Fundamentals of Air Pollution , fourth edition (Academic Press, 2008), p. 3. 

  20. e

    “Smoke, Mirrors, and Hot Air,” available at documents/global_warming/exxon_report.pdf. 

  21. f

    For those who would like to see the Excel spreadsheet model on which these calculations were made to check them, or try other experiments, it is available at Download the Excel program, go to the sheet named “50yeardelay” and follow the instructions there. You will be able to verify the number in the text and do other experiments as well. 

  22. g

    The case studies can be found in Augustin Colette et al., Case Studies on Climate Change and World Heritage (Paris: UNESCO World Heritage Centre, 2007), available at e.pdf. 

  23. h

    A major source here is Timothy M. Lenton et al., “Tipping Elements in the Earth’s Climate System,” Nature , Vol. 105, No. 6 ( February 12, 2008). 

  24. i

    More exactly, it is (16/38) 5 = 0.0238. Moreover, on five rolls of the wheel, there is a 24 percent chance that a zero or double-zero catastrophic event will occur. These probabilities are only illustrative to show how multiple uncertainties interact. 

  25. j

    Richard Feynman, The Character of Physical Law (MIT Press, 1970). 





Why the Global Warming Skeptics Are Wrong

March 22, 2012

William D. Nordhaus



Icebergs in Iceland’s Jökulsárlón lagoon, which is constantly growing as the Vatnajökull glacier—Europe’s largest—melts; photograph by Olaf Otto Becker from his book Under the Nordic Light: A Journey Through Time, Iceland, 1999–2011, which has just been published by Hatje Cantz

The threat of climate change is an increasingly important environmental issue for the globe. Because the economic questions involved have received relatively little attention, I have been writing a nontechnical book for people who would like to see how market-based approaches could be used to formulate policy on climate change. When I showed an early draft to colleagues, their response was that I had left out the arguments of skeptics about climate change, and I accordingly addressed this at length.

But one of the difficulties I found in examining the views of climate skeptics is that they are scattered widely in blogs, talks, and pamphlets. Then, I saw an opinion piece in The Wall Street Journal of January 27, 2012, by a group of sixteen scientists, entitled “No Need to Panic About Global Warming.” This is useful because it contains many of the standard criticisms in a succinct statement. The basic message of the article is that the globe is not warming, that dissident voices are being suppressed, and that delaying policies to slow climate change for fifty years will have no serious economic or environment consequences.

My response is primarily designed to correct their misleading description of my own research; but it also is directed more broadly at their attempt to discredit scientists and scientific research on climate change.1 I have identified six key issues that are raised in the article, and I provide commentary about their substance and accuracy. They are:

• Is the planet in fact warming?

• Are human influences an important contributor to warming?

• Is carbon dioxide a pollutant?

• Are we seeing a regime of fear for skeptical climate scientists?

• Are the views of mainstream climate scientists driven primarily by the desire for financial gain?

• Is it true that more carbon dioxide and additional warming will be beneficial?

As I will indicate below, on each of these questions, the sixteen scientists provide incorrect or misleading answers. At a time when we need to clarify public confusions about the science and economics of climate change, they have muddied the waters. I will describe their mistakes and explain the findings of current climate science and economics.


The first claim is that the planet is not warming. More precisely, “Perhaps the most inconvenient fact is the lack of global warming for well over 10 years now.”

It is easy to get lost in the tiniest details here. Most people will benefit from stepping back and looking at the record of actual temperature measurements. The figure below shows data from 1880 to 2011 on global mean temperature averaged from three different sources.2 We do not need any complicated statistical analysis to see that temperatures are rising, and furthermore that they are higher in the last decade than they were in earlier decades.3


One of the reasons that drawing conclusions on temperature trends is tricky is that the historical temperature series is highly volatile, as can be seen in the figure. The presence of short-term volatility requires looking at long-term trends. A useful analogy is the stock market. Suppose an analyst says that because real stock prices have declined over the last decade (which is true), it follows that there is no upward trend. Here again, an examination of the long-term data would quickly show this to be incorrect. The last decade of temperature and stock market data is not representative of the longer-term trends.

The finding that global temperatures are rising over the last century-plus is one of the most robust findings of climate science and statistics.


A second argument is that warming is smaller than predicted by the models:

The lack of warming for more than a decade—indeed, the smaller-than-predicted warming over the 22 years since the UN’s Intergovernmental Panel on Climate Change (IPCC) began issuing projections—suggests that computer models have greatly exaggerated how much warming additional CO2 can cause.

What is the evidence on the performance of climate models? Do they predict the historical trend accurately? Statisticians routinely address this kind of question. The standard approach is to perform an experiment in which (case 1) modelers put the changes in CO2 concentrations and other climate influences in a climate model and estimate the resulting temperature path, and then (case 2) modelers calculate what would happen in the counterfactual situation where the only changes were due to natural sources, for example, the sun and volcanoes, with no human-induced changes. They then compare the actual temperature increases of the model predictions for all sources (case 1) with the predictions for natural sources alone (case 2).

This experiment has been performed many times using climate models. A good example is the analysis described in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (for the actual figure, see the accompanying online material4). Several modelers ran both cases 1 and 2 described above—one including human-induced changes and one with only natural sources. This experiment showed that the projections of climate models are consistent with recorded temperature trends over recent decades only if human impacts are included. The divergent trend is especially pronounced after 1980. By 2005, calculations using natural sources alone underpredict the actual temperature increases by about 0.7 degrees Centigrade, while the calculations including human sources track the actual temperature trend very closely.

In reviewing the results, the IPCC report concluded: “No climate model using natural forcings [i.e., natural warming factors] alone has reproduced the observed global warming trend in the second half of the twentieth century.”5


The sixteen scientists next attack the idea of CO2 as a pollutant. They write: “The fact is that CO2 is not a pollutant.” By this they presumably mean that CO2 is not by itself toxic to humans or other organisms within the range of concentrations that we are likely to encounter, and indeed higher CO2 concentrations may be beneficial.

However, this is not the meaning of pollution under US law or in standard economics. The US Clean Air Act defined an air pollutant as “any air pollution agent or combination of such agents, including any physical, chemical, biological, radioactive…substance or matter which is emitted into or otherwise enters the ambient air.” In a 2007 decision on this question, the Supreme Court ruled clearly on the question: “Carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons are without a doubt ‘physical [and] chemical…substance[s] which [are] emitted into…the ambient air.’ …Greenhouse gases fit well within the Clean Air Act’s capacious definition of ‘air pollutant.’”6

In economics, a pollutant is a form of negative externality—that is, a byproduct of economic activity that causes damages to innocent bystanders. The question here is whether emissions of CO2 and other greenhouse gases will cause net damages, now and in the future. This question has been studied extensively. The most recent thorough survey by the leading scholar in this field, Richard Tol, finds a wide range of damages, particularly if warming is greater than 2 degrees Centigrade.7 Major areas of concern are sea-level rise, more intense hurricanes, losses of species and ecosystems, acidification of the oceans, as well as threats to the natural and cultural heritage of the planet.

In short, the contention that CO2 is not a pollutant is a rhetorical device and is not supported by US law or by economic theory or studies.


The fourth contention by the sixteen scientists is that skeptical climate scientists are living under a reign of terror about their professional and personal livelihoods. They write:

Although the number of publicly dissenting scientists is growing, many young scientists furtively say that while they also have serious doubts about the global-warming message, they are afraid to speak up for fear of not being promoted—or worse….

This is not the way science is supposed to work, but we have seen it before—for example, in the frightening period when Trofim Lysenko hijacked biology in the Soviet Union. Soviet biologists who revealed that they believed in genes, which Lysenko maintained were a bourgeois fiction, were fired from their jobs. Many were sent to the gulag and some were condemned to death.

While we must always be attentive to a herd instinct, this lurid tale is misleading in the extreme. Some background on Lysenko will be useful. He was the leader of a group that rejected standard genetics and held that the acquired characteristics of an organism could be inherited by that organism’s descendants. He exploited the Soviet ideology about heredity, the need for agricultural production, and the favor of a powerful dictator—Stalin—to attract adherents to his theories. Under his influence, genetics was officially condemned as unscientific. Once he gained control of Russian biology, genetics research was prohibited, and thousands of geneticists were fired. Many leading geneticists were exiled to labor camps in Siberia, poisoned, or shot. His influence began to wane after Stalin’s death, but it took many years for Soviet biology to overcome the disastrous consequences of the Lysenko affair.8

The idea that skeptical climate scientists are being treated like Soviet geneticists in the Stalinist period has no basis in fact. There are no political or scientific dictators in the US. No climate scientist has been expelled from the US National Academy of Sciences. No skeptics have been arrested or banished to gulags or the modern equivalents of Siberia. Indeed, the dissenting authors are at the world’s greatest universities, including Princeton, MIT, Rockefeller, the University of Cambridge, and the University of Paris.

I can speak personally for the lively debate about climate change policy. There are controversies about many details of climate science and economics. While some claim that skeptics cannot get their papers published, working papers and the Internet are open to all. I believe the opposite of what the sixteen claim to be true: dissident voices and new theories are encouraged because they are critical to sharpening our analysis. The idea that climate science and economics are being suppressed by a modern Lysenkoism is pure fiction.


A fifth argument is that mainstream climate scientists are benefiting from the clamor about climate change:

Why is there so much passion about global warming…? There are several reasons, but a good place to start is the old question “cui bono?” Or the modern update, “Follow the money.”

Alarmism over climate is of great benefit to many, providing government funding for academic research and a reason for government bureaucracies to grow. Alarmism also offers an excuse for governments to raise taxes, taxpayer-funded subsidies for businesses that understand how to work the political system, and a lure for big donations to charitable foundations promising to save the planet.

This argument is inaccurate as scientific history and unsupported by any evidence. There is a suggestion that standard theories about global warming have been put together by the scientific equivalent of Madison Avenue to raise funds from government agencies like the National Science Foundation (NSF). The fact is that the first precise calculations about the impact of increased CO2 concentrations on the earth’s surface temperature were made by Svante Arrhenius in 1896, more than five decades before the NSF was founded.

The skeptics’ account also misunderstands the incentives in academic research. IPCC authors are not paid. Scientists who serve on panels of the National Academy of Science do so without monetary compensation for their time and are subject to close scrutiny for conflicts of interest. Academic advancement occurs primarily from publication of original research and contributions to the advancement of knowledge, not from supporting “popular” views. Indeed, academics have often been subject to harsh political attacks when their views clashed with current political or religious teachings. This is the case in economics today, where Keynesian economists are attacked for their advocacy of “fiscal stimulus” to promote recovery from a deep recession; and in biology, where evolutionary biologists are attacked as atheists because they are steadfast in their findings that the earth is billions rather than thousands of years old.

In fact, the argument about the venality of the academy is largely a diversion. The big money in climate change involves firms, industries, and individuals who worry that their economic interests will be harmed by policies to slow climate change. The attacks on the science of global warming are reminiscent of the well-documented resistance by cigarette companies to scientific findings on the dangers of smoking. Beginning in 1953, the largest tobacco companies launched a public relations campaign to convince the public and the government that there was no sound scientific basis for the claim that cigarette smoking was dangerous. The most devious part of the campaign was the underwriting of researchers who would support the industry’s claim. The approach was aptly described by one tobacco company executive: “Doubt is our product since it is the best means of competing with the ‘body of fact’ that exists in the mind of the general public. It is also the means of establishing a controversy.”9

One of the worrisome features of the distortion of climate science is that the stakes are huge here—even larger than the economic stakes for keeping the cigarette industry alive. Tobacco sales in the United States today are under $100 billion. By contrast, expenditures on all energy goods and services are close to $1,000 billion. Restrictions on CO2 emissions large enough to bend downward the temperature curve from its current trajectory to a maximum of 2 or 3 degrees Centigrade would have large economic effects on many businesses. Scientists, citizens, and our leaders will need to be extremely vigilant to prevent pollution of the scientific process by the merchants of doubt.


A final point concerns economic analysis. The sixteen scientists argue, citing my research, that economics does not support policies to slow climate change in the next half-century:

A recent study of a wide variety of policy options by Yale economist William Nordhaus showed that nearly the highest benefit-to-cost ratio is achieved for a policy that allows 50 more years of economic growth unimpeded by greenhouse gas controls. This would be especially beneficial to the less-developed parts of the world that would like to share some of the same advantages of material well-being, health and life expectancy that the fully developed parts of the world enjoy now. Many other policy responses would have a negative return on investment. And it is likely that more CO2 and the modest warming that may come with it will be an overall benefit to the planet.

On this point, I do not need to reconstruct how climate scientists made their projections, or review the persecution of Soviet geneticists. I did the research and wrote the book on which they base their statement. The skeptics’ summary is based on poor analysis and on an incorrect reading of the results.

The first problem is an elementary mistake in economic analysis. The authors cite the “benefit-to-cost ratio” to support their argument. Elementary cost-benefit and business economics teach that this is an incorrect criterion for selecting investments or policies. The appropriate criterion for decisions in this context is net benefits (that is, the difference between, and not the ratio of, benefits and costs).

This point can be seen in a simple example, which would apply in the case of investments to slow climate change. Suppose we were thinking about two policies. Policy A has a small investment in abatement of CO2 emissions. It costs relatively little (say $1 billion) but has substantial benefits (say $10 billion), for a net benefit of $9 billion. Now compare this with a very effective and larger investment, Policy B. This second investment costs more (say $10 billion) but has substantial benefits (say $50 billion), for a net benefit of $40 billion. B is preferable because it has higher net benefits ($40 billion for B as compared with $9 for A), but A has a higher benefit-cost ratio (a ratio of 10 for A as compared with 5 for B). This example shows why we should, in designing the most effective policies, look at benefits minus costs, not benefits divided by costs.

This leads to the second point, which is that the authors summarize my results incorrectly. My research shows that there are indeed substantial net benefits from acting now rather than waiting fifty years. A look at Table 5-1 in my study A Question of Balance (2008) shows that the cost of waiting fifty years to begin reducing CO2 emissions is $2.3 trillion in 2005 prices. If we bring that number to today’s economy and prices, the loss from waiting is $4.1 trillion. Wars have been started over smaller sums.10

My study is just one of many economic studies showing that economic efficiency would point to the need to reduce CO2 and other greenhouse gas emissions right now, and not to wait for a half-century. Waiting is not only economically costly, but will also make the transition much more costly when it eventually takes place. Current economic studies also suggest that the most efficient policy is to raise the cost of CO2 emissions substantially, either through cap-and-trade or carbon taxes, to provide appropriate incentives for businesses and households to move to low-carbon activities.

One might argue that there are many uncertainties here, and we should wait until the uncertainties are resolved. Yes, there are many uncertainties. That does not imply that action should be delayed. Indeed, my experience in studying this subject for many years is that we have discovered more puzzles and greater uncertainties as researchers dig deeper into the field. There are continuing major questions about the future of the great ice sheets of Greenland and West Antarctica; the thawing of vast deposits of frozen methane; changes in the circulation patterns of the North Atlantic; the potential for runaway warming; and the impacts of ocean carbonization and acidification. Moreover, our economic models have great difficulties incorporating these major geophysical changes and their impacts in a reliable manner. Policies implemented today serve as a hedge against unsuspected future dangers that suddenly emerge to threaten our economies or environment. So, if anything, the uncertainties would point to a more rather than less forceful policy—and one starting sooner rather than later—to slow climate change.

The group of sixteen scientists argues that we should avoid alarm about climate change. I am equally concerned by those who allege that we will incur economic catastrophes if we take steps to slow climate change. The claim that cap-and-trade legislation or carbon taxes would be ruinous or disastrous to our societies does not stand up to serious economic analysis. We need to approach the issues with a cool head and a warm heart. And with respect for sound logic and good science.

—February 22, 2012


In the Climate Casino: An Exchange April 26, 2012

  1. 1

    The author is Sterling Professor of Economics at Yale University. He has received support for research on the economics of climate change during the last decade from the National Science Foundation, the Department of Energy, and the Glaser Foundation. Other than research associated with these and any future grants, the author declares no conflict of interest. 

  2. 2

    The three series are produced by the UK Hadley Center, the US Goddard Institute for Space Studies ( GISS ), and the US National Climatic Data Center ( NCDC ). For those who question whether the series on global mean temperature are themselves products of a scientific conspiracy, here is yet a further check. Together with my colleague Xi Chen, I constructed yet another index of global mean temperature. We did this by getting grid-cell temperature data and aggregating these into a global average using land-area weights from our own research. To be even more conservative, we also did an audit of the grid-cell data by going back to station data selected quasi-randomly for selected grid cells around the world (such as Dakar, Albuquerque, Casablanca, Llasa, Yinchuan, and Yellowknife). The historical temperature series we constructed behaved very similarly to the ones constructed by the climate scientists. 

  3. 3

    For those who would like a sample of how statisticians approach the issue of rising temperatures, here is an example. Many climate scientists believe that CO 2-induced warming has become particularly rapid since 1980. So we can use a statistical analysis to test whether the trend in global mean temperature is steeper in the 1980–2011 period than during the 1880–1980 period.

    A regression analysis determines that the answer is yes, the rise in temperature is indeed faster. Such an analysis proceeds as follows: The series “ TAV t” is the average of the GISS , NCDC , and Hadley annual series. We estimate a regression of the form TAV t = α + β Yeart + γ (Year since 1980)t + εt. In this formulation, “Yeart” is simply the year, while (Year since 1980)t is 0 up to 1980 and then (Year-1980) for years after 1980. The Greek letters (α, β, and γ) are coefficients, while εt is a residual error. The estimated equation has a coefficient on Year of 0.0042 (t-statistic = 12.7) and a coefficient on (Year since 1980) of 0.0135 (t-statistic = 8.5). The interpretation is that temperatures in the 1880–1980 period were rising at 0.0042 °C per year, while in the later period they were rising at 0.0135 °C per year more rapidly. The t-statistic in parentheses indicates that the coefficient on (Year since 1980) was 8.5 times its standard error. Using standard tests for statistical significance, this large a t-coefficient would be obtained by chance less than one time in a million. We can use other years as break points, from 1930 to 2000, and the answer is the same: there has been a more rapid rise in global mean temperature in the most recent period than in earlier periods. 

  4. 4

    I use this example to illustrate one experiment that has been conducted to determine the consistency of climate models and temperature observations. The experiment started with fourteen different climate models. The climate modelers calculated the temperature trajectory over the 1900–2005 period both with and without CO 2 and other human-induced factors. In the below figure from the IPCC Fourth Assessment Report, the bottom part shows the calculations including only natural forces, such as volcanic eruptions and changes in solar activity. The heavy black line is the actual temperature record, while the heavy blue line is the models’ average calculated global temperature with only natural forcings (“Without GHG s”). The several thin blue lines are the results of the individual models, while the gray vertical lines represent major cooling events due to volcanic eruptions.


    The top part shows the calculations with both natural forces and with estimated greenhouse gas concentrations and forcings. Again, the heavy black line is the actual temperature record, while the heavy red line is the models’ average calculated global temperature with CO 2 and other greenhouse gases as well as natural forces (“With GHG s”). The cloud of thin yellow lines represents the results of the individual models

    This experiment shows that the climate models are consistent with temperature trends over recent years only if the estimated warming induced by accumulations of CO 2 and other greenhouse gases are included. The source is Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change edited by S. Solomon and others (Cambridge University Press, 2007), p. 685f. 

  5. 5

    S. Solomon and others, Climate Change 2007 , p. 687. 

  6. 6

    Opinion of the Court in Massachusetts v. Environmental Protection Agency , 549 U.S. 497 (2007). 

  7. 7

    Richard S. J. Tol, “The Economic Effects of Climate Change,” The Journal of Economic Perspectives , Vol. 23, No. 2 (Spring 2009). 

  8. 8

    A chilling account of the history is told in Valery N. Soyfer, “The Consequences of Political Dictatorship for Russian Science,” Nature Reviews Genetics , Vol. 2 (September 2001). 

  9. 9

    Brown & Williamson Tobacco Corporation, “Smoking and Health Proposal” 1969, available at Legacy Tobacco Documents Library ( There is an extensive literature on the tobacco industry’s strategy for distorting the scientific record and promoting views that were favorable to smoking. See Stanton Glantz et al., The Cigarette Papers (University of California Press, 1996); and Robert Proctor, Cancer Wars: How Politics Shapes What We Know and Don’t Know about Cancer (Basic Books, 1995). The history is updated to the modern era and industry attacks on environmental science in Naomi Oreskes and Erik Conway, Merchants of Doubt (Bloomsbury, 2010). 

  10. 10

    The estimate is from A Question of Balance: Weighing the Options on Global Warming Policies (Yale University Press, 2008), p. 82. The updated number is calculated as follows. We update from 2005 to 2012 prices using the US GDP price index, which is estimated to be 15.6 percent higher in 2012 than in 2005. Then the number is put in 2012 economics by using a real discount rate of 6 percent per year. 



No Need to Panic About Global Warming

There's no compelling scientific argument for drastic action to 'decarbonize' the world's economy.


Editor's Note: The following has been signed by the 16 scientists listed at the end of the article:

A candidate for public office in any contemporary democracy may have to consider what, if anything, to do about "global warming." Candidates should understand that the oft-repeated claim that nearly all scientists demand that something dramatic be done to stop global warming is not true. In fact, a large and growing number of distinguished scientists and engineers do not agree that drastic actions on global warming are needed.

In September, Nobel Prize-winning physicist Ivar Giaever, a supporter of President Obama in the last election, publicly resigned from the American Physical Society (APS) with a letter that begins: "I did not renew [my membership] because I cannot live with the [APS policy] statement: '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.' In the APS it is OK to discuss whether the mass of the proton changes over time and how a multi-universe behaves, but the evidence of global warming is incontrovertible?"

In spite of a multidecade international campaign to enforce the message that increasing amounts of the "pollutant" carbon dioxide will destroy civilization, large numbers of scientists, many very prominent, share the opinions of Dr. Giaever. And the number of scientific "heretics" is growing with each passing year. The reason is a collection of stubborn scientific facts.

Perhaps the most inconvenient fact is the lack of global warming for well over 10 years now. This is known to the warming establishment, as one can see from the 2009 "Climategate" email of climate scientist Kevin Trenberth: "The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't." But the warming is only missing if one believes computer models where so-called feedbacks involving water vapor and clouds greatly amplify the small effect of CO2.

The lack of warming for more than a decade—indeed, the smaller-than-predicted warming over the 22 years since the U.N.'s Intergovernmental Panel on Climate Change (IPCC) began issuing projections—suggests that computer models have greatly exaggerated how much warming additional CO2 can cause. Faced with this embarrassment, those promoting alarm have shifted their drumbeat from warming to weather extremes, to enable anything unusual that happens in our chaotic climate to be ascribed to CO2.

The fact is that CO2 is not a pollutant. CO2 is a colorless and odorless gas, exhaled at high concentrations by each of us, and a key component of the biosphere's life cycle. Plants do so much better with more CO2 that greenhouse operators often increase the CO2 concentrations by factors of three or four to get better growth. This is no surprise since plants and animals evolved when CO2 concentrations were about 10 times larger than they are today. Better plant varieties, chemical fertilizers and agricultural management contributed to the great increase in agricultural yields of the past century, but part of the increase almost certainly came from additional CO2 in the atmosphere.

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Although the number of publicly dissenting scientists is growing, many young scientists furtively say that while they also have serious doubts about the global-warming message, they are afraid to speak up for fear of not being promoted—or worse. They have good reason to worry. In 2003, Dr. Chris de Freitas, the editor of the journal Climate Research, dared to publish a peer-reviewed article with the politically incorrect (but factually correct) conclusion that the recent warming is not unusual in the context of climate changes over the past thousand years. The international warming establishment quickly mounted a determined campaign to have Dr. de Freitas removed from his editorial job and fired from his university position. Fortunately, Dr. de Freitas was able to keep his university job.

This is not the way science is supposed to work, but we have seen it before—for example, in the frightening period when Trofim Lysenko hijacked biology in the Soviet Union. Soviet biologists who revealed that they believed in genes, which Lysenko maintained were a bourgeois fiction, were fired from their jobs. Many were sent to the gulag and some were condemned to death.

Why is there so much passion about global warming, and why has the issue become so vexing that the American Physical Society, from which Dr. Giaever resigned a few months ago, refused the seemingly reasonable request by many of its members to remove the word "incontrovertible" from its description of a scientific issue? There are several reasons, but a good place to start is the old question "cui bono?" Or the modern update, "Follow the money."

Alarmism over climate is of great benefit to many, providing government funding for academic research and a reason for government bureaucracies to grow. Alarmism also offers an excuse for governments to raise taxes, taxpayer-funded subsidies for businesses that understand how to work the political system, and a lure for big donations to charitable foundations promising to save the planet. Lysenko and his team lived very well, and they fiercely defended their dogma and the privileges it brought them.

Speaking for many scientists and engineers who have looked carefully and independently at the science of climate, we have a message to any candidate for public office: There is no compelling scientific argument for drastic action to "decarbonize" the world's economy. Even if one accepts the inflated climate forecasts of the IPCC, aggressive greenhouse-gas control policies are not justified economically.

Related Video

Princeton physics professor William Happer on why a large number of scientists don't believe that carbon dioxide is causing global warming.

A recent study of a wide variety of policy options by Yale economist William Nordhaus showed that nearly the highest benefit-to-cost ratio is achieved for a policy that allows 50 more years of economic growth unimpeded by greenhouse gas controls. This would be especially beneficial to the less-developed parts of the world that would like to share some of the same advantages of material well-being, health and life expectancy that the fully developed parts of the world enjoy now. Many other policy responses would have a negative return on investment. And it is likely that more CO2 and the modest warming that may come with it will be an overall benefit to the planet.

If elected officials feel compelled to "do something" about climate, we recommend supporting the excellent scientists who are increasing our understanding of climate with well-designed instruments on satellites, in the oceans and on land, and in the analysis of observational data. The better we understand climate, the better we can cope with its ever-changing nature, which has complicated human life throughout history. However, much of the huge private and government investment in climate is badly in need of critical review.

Every candidate should support rational measures to protect and improve our environment, but it makes no sense at all to back expensive programs that divert resources from real needs and are based on alarming but untenable claims of "incontrovertible" evidence.

Claude Allegre, former director of the Institute for the Study of the Earth, University of Paris; J. Scott Armstrong, cofounder of the Journal of Forecasting and the International Journal of Forecasting; Jan Breslow, head of the Laboratory of Biochemical Genetics and Metabolism, Rockefeller University; Roger Cohen, fellow, American Physical Society; Edward David, member, National Academy of Engineering and National Academy of Sciences; William Happer, professor of physics, Princeton; Michael Kelly, professor of technology, University of Cambridge, U.K.; William Kininmonth, former head of climate research at the Australian Bureau of Meteorology; Richard Lindzen, professor of atmospheric sciences, MIT; James McGrath, professor of chemistry, Virginia Technical University; Rodney Nichols, former president and CEO of the New York Academy of Sciences; Burt Rutan, aerospace engineer, designer of Voyager and SpaceShipOne; Harrison H. Schmitt, Apollo 17 astronaut and former U.S. senator; Nir Shaviv, professor of astrophysics, Hebrew University, Jerusalem; Henk Tennekes, former director, Royal Dutch Meteorological Service; Antonio Zichichi, president of the World Federation of Scientists, Geneva.

A version of this article appeared January 27, 2012, on page A15 in some U.S. edi



Brophy Friday 06 April 2012 - 5:02 pm | | Global Warming

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