comments to the 11-page critique in
January 2002 Scientific American (SA), (in black)
Substantially finished December 31, 2001; latest update January 4, 2002, 12:06:44
Recently I have received – through informal channels – the final
proofs of an 11 page feature in Scientific American, all of it
devoted to a throughout trashing of my recent book The Skeptical
Environmentalist, Cambridge University Press 2001 (referred as
SE in references).
As I write these words Scientific American has as yet not given
me a chance to put my side of the argument before their readers.
The four critiques and accompanying editorial will be the only
statement that readers of SA will receive as the basis on which to
judge the cogency of my arguments.
I have had some half-promises that I might get to state my side
of the argument in Scientific American, but there is no firm
promises with respect to either format or date.
I shall now present a preliminary critique of the feature, article
for article, point for point. References to various works are, unless
otherwise noted, to the same sources as used in SE. The full
bibliography can be downloaded at]
Scientific American, p61-71, January 2002, (in red).
The text comes from the final draft and has been transferred from pdf into Word, meaning that occasionally italics
or words may have been dropped. Most of the layout has been retained in headings, subheadings and usage of
capital lettering. The first page (p61) is an editorial by editor-in-chief, John Rennie, the other ten pages flow in
three columns into each other, with a sentence on each page in very large font for interest. These sentences will be
pointed out below, but may come from an editorial decision. On the web, Scientific American describes the
collection of essays thus:
Misleading Math about the Earth
The book The Skeptical Environmentalist uses statistics to dismiss warnings about peril for the planet. But the
science suggests that it's the author who is out of touch with the facts.
Science defends itself against The Skeptical
This statement is potentially the most surprising of all – that the following critique should be science
defending itself against my book. In a sense this encapsulates the bias of the following critiques. My
book clearly makes a claim to science and to be factually based. I openly state the facts and my
sources, and thus anybody is free to point out where these are faulty or incorrect and of course, such
errors will then be posted on my web site.
Thus, there is no need to defend science from my book – any possible defeat of science was never
the issue. The discussion is whether the statements in my book are correct or not. The need to make it
sound like a battle of science against my book seems entirely to misplace and bias the focus. Rather,
the standpoint that might need to defend itself from my book would be the alarmist environmentalism,
and that is perhaps the headline that would make more sense: Alarmist environmentalism defends itself
against the Skeptical Environmentalist.
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 2/32
CRITICAL thinking and hard data are the cornerstones of all good science. Because
environmental sciences are so keenly important to both our biological and economic
survival—causes that are often seen to be in conflict—they deserve full scrutiny. With that
in mind, the book The Skeptical Environmentalist (Cambridge University Press), by Bjørn
Lomborg, a statistician and political scientist at the University of Aarhus in Denmark,
should be a welcome audit. And yet it isn’t.
As its subtitle—Measuring the Real State of the World— indicates, Lomborg’s intention
was to reanalyze environmental data so that the public might make policy decisions based
on the truest understanding of what science has determined. His conclusion, which he writes
surprised even him, was that contrary to the gloomy predictions of degradation he calls “the
litany,” everything is getting better. Not that all is rosy, but the future for the environment is
less dire than is supposed. Instead Lomborg accuses a pessimistic and dishonest cabal of
environmental groups, institutions and the media of distorting scientists’ actual findings. (A
copy of the book’s first chapter can be found at
The problem with Lomborg’s conclusion is that the scientists themselves disavow it.
Many spoke to us at SCIENTIFIC AMERICAN about their frustration at what they
described as Lomborg’s misrepresentation of their fields. His seemingly dispassionate
outsider’s view, they told us, is often marred by an incomplete use of the data or a
misunderstanding of the underlying science. Even where his statistical analyses are valid,
his interpretations are frequently off the mark—literally not seeing the state of the forests
for the number of the trees, for example. And it is hard not to be struck by Lomborg’s
presumption that he has seen into the heart of the science more faithfully than have
investigators who have devoted their lives to it; it is equally curious that he finds the same
contrarian good news lurking in every diverse area of environmental science.
Making it sound like all scientists disavow it is simply untrue. Many scientists, both in private and
publicly (e.g. statements on the book) have praised the book. Below, you will see that none of the
claims of “misrepresentation”, “incomplete use of data” and “misunderstanding of the underlying
science” are substantiated.
The only specific claim presented here by the editor is that I am “literally not seeing the state of the
forests for the number of the trees.” This can only refer to the one paragraph on forests by Lovejoy (the
only treatment of the matter in the following text) – and here the analysis is quite clear. I try to show
that environmental movements will tell us we are at risk of loosing “the last remaining forests on earth”
and that our time is “the eleventh hour for the world’s forests” (WWF, quoted in SE:110). Yet, the
longest data series actually tells us of very little change in the world forested area in the post-war
period (SE:111). Moreover, the longest future scenarios from the UN climate panel (IPCC) show that
in all likelihood the Earth will have even greater forest cover in 2100 than it has had since 1950 (IPCC
2000b, SE:283). Here, exactly looking coolly at the longest data series gives us much better
information than just going with the environmental myths and hype. Thus, in the editor’s only concrete
claim, he seems to be wide off the mark.
Pointing out that it seems questionable that I should know better than the people who’ve devoted
their lives to particular areas, though clearly circums tantial, nevertheless looks like a powerful point.
Yet, any person who has devoted his or her life to a single issue will naturally come to consider this
area one of the most crucial issues, and any problem inside the area will likely be seen as necessary to
And this is exactly my point – we should take the science of these people seriously, but we should
not uncritically adopt their evaluation of the problems. There are a multitude of problems in any area of
society – there are always things we would like to improve – but we only have a limited amount of
resources. Thus, as a society we need to ask, whether the problems are getting bigger or smaller (are we
going in the right direction), what can we do (much or marginal) and would this be the best use of our
resources (other areas where we could do even more good). Such an appraisal does not come
automatically from any single issue area. This is why we need to look, not only at the science of each
area, but also to ask: ‘so, all in all, how important a problem is your issue in the big scheme of things.’
This is what I have attempted to do with The Skeptical Environmentalist.
We asked four leading experts to critique Lomborg’s treatments of their areas—global
warming, energy, population and biodiversity—so readers could understand why the book
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 3/32
provokes so much disagreement. Lomborg’s assessment that conditions on earth are
generally improving for human welfare may hold some truth. The errors described here,
however, show that in its purpose of describing the real state of the world, the book is a
Notice that these four experts have certainly not been chosen randomly – two of the four reviewers
are actually directly criticized in my book. Lovejoy predicted back in 1980, that 15-20 percent of all
species on earth would have died by the year 2000 (1980:331, SE:252), a prediction which clearly did
not hold true and this is pointed out in the book. Holdren back in 1980 also clearly thought that many
resources were running out. Along with Ehrlich and Holdren, he bet on this belief with Julian Simon:
“Frustrated with the incessant claims that the Earth would run out of oil, food and raw
materials, the economist Julian Simon in 1980 challenged the established beliefs with a bet. He
offered to bet $10,000 that any given raw material – to be picked by his opponents – would have
dropped in price at least one year later. The environmentalists Ehrlich, Harte and Holdren, all of
Stanford University, accepted the challenge, stating that “the lure of easy money can be
irresistible.” The environmentalists staked their bets on chromium, copper, nickel, tin and
tungsten, and they picked a time frame of ten years. The bet was to be determined ten years
later, assessing whether the real (inflation-adjusted) prices had gone up or down. In September
1990 not only had the total basket of raw materials but also each individual raw material
dropped in price. Chromium had dropped 5 percent, tin a whopping 74 percent. The doomsayers
had lost.
Truth is they could not have won. Ehrlich and Co. would have lost no matter whether they had
staked their money on petroleum, foodstuffs, sugar, coffee, cotton, wool, minerals or
phosphates. They had all become cheaper.” (SE:137).
Since 1990 the price of raw materials has declined another third (Economist industrial price index,
The editor claims that the experts are chosen to show why the book is causing so much
“disagreement,” but given the choice of four experts who clearly feel the book is fundamentally wrong,
it is unclear how the reader should be able to understand that there might be any value to my argument,
and thus to the disagreement. The obvious lack of any concern for presenting a balanced review of my
work calls into question the real purpose of this Scientific American feature. However, one of its
contributors, Stephen Schneider, has on a former occasion made a suggestion that might throw some
light on the curious imbalance of the Feature under consideration.
Schneider considers the ”ethical double bind” that might occur to the scientist who is also concerned
to contribute to a better world. As a scientist he focuses on truth. As a concerned citizen he must take
an interest in political efficiency. Quite obviously, Schneider finds that this presents a delicate dilemma
and he expresses the hope that one might be both honest and effective. However, as Schneider agonizes
over this dilemma he does offer the following bit of unambiguous advice “So we have to offer up scary
scenarios, make simplified, dramatic statements, and make little mention of any doubts we might
have.”1 Could John Rennie have taken this as editorial advice? I don’t know, but I feel that it would
account for the tone and the lack of balance of the Feature considered as a whole. Unfortunately, this
tone and lack of balance also seem to represent a disappointing and painful abandonment of the long
proud tradition of enlightenment and rationality for which Scientific American has been respected in
the past.
Finally, John Rennie tells us that, yes – Lomborg’s fundamental assertion may hold “some truth,”
and yet, in the very next statement that the book is “a failure.” This could seem like somewhat of a
glaring contradiction and at least it relies heavily on the ability of the ensuing reviews to establish
fundamental and serious errors in the argument – something they never manage to do.
1 “On the one hand, as scientists we are ethically bound to the scientific method, in effect promising to tell the truth, the whole
truth, and nothing but - which means that we must include all the doubts, the caveats, the ifs, ands, and buts. On the other hand,
we are not just scientists but human beings as well. And like most people we’d like to see the world a better place, which in this
context translates into our working to reduce the risk of potentially disastrous climatic change. To do that we need to get some
broadbased support, to capture the public’s imagination. That, of course, entails getting loads of media coverage. So we have to
offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have. This
‘double ethical bind’ we frequently find ourselves in cannot be solved by any formula. Each of us has to decide what the right
balance is between being effective and being honest. I hope that means being both.” (Quoted in Discover, pp. 45-48, Oct. 1989,
see also American Physical Society, APS News August/September 1996,
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 4/32
Stephen Schneider
For three decades, I have been debating alternative solutions for sustainable development
with thousands of fellow scientists and policy analysts—exchanges carried out in myriad
articles and formal meetings. Despite all that, I readily confess a lingering frustration:
uncertainties so infuse the issue of climate change that it is still impossible to rule out either
mild or catastrophic outcomes, let alone provide confident probabilities for all the claims
and counterclaims made about environmental problems.
Even the most credible international assessment body, the Intergovernmental Panel on
Climate Change (IPCC), has refused to attempt subjective probabilistic estimates of future
temperatures. This has forced politicians to make their own guesses about the likelihood of
various degrees of global warming. Will temperatures in 2100 increase by 1.4 degrees
Celsius or by 5.8? The difference means relatively adaptable changes or very damaging
Against this background of frustration, I began increasingly to hear that a young Danish
statistician in a political science department, Bjørn Lomborg, had applied his skills in
statistics to better determine how serious environmental problems are. Of course, I was
anxious to see this highly publicized contribution— The Skeptical Environmentalist:
Measuring the Real State of the World. A “skeptical environmentalist” is certainly the best
kind, I mused, because uncertainties are so endemic in these complex problems that suffer
from missing data, incomplete theory and nonlinear interactions. But the “real state of the
world”—that is a high bar to set, given the large range of plausible outcomes.
And who is Lomborg, I wondered, and why haven’t I come across him at any of the
meetings where the usual suspects debate costs, benefits, extinction rates, carrying capacity
or cloud feedback? I couldn’t recall reading any scientific or policy contributions from him
either. But there was this massive 515 page tome with a whopping 2,930 endnotes to wade
through. On page xx of his preface, Lomborg admits, “I am not myself an expert as regards
environmental problems”—truer words are not found in the rest of the book, as I’ll soon
illustrate. I will report primarily on the thick global warming chapter and its 600plus
endnotes. That kind of deadweight of detail alone conjures at least the trappings of
comprehensive and careful scholarship. So how does the reality of the text hold up to the
pretense? I’m sure you can already guess, but let me give some examples to make clear
what I learned by reading.
These paragraphs do not really discuss my book but establish several important rhetorical points that
need to be mentioned. First is the John Rennie’s incantation of “investigators who have devoted their
lives” to the science: Schneider is the venerable scientist whereas I’m a nobody.
Second, he quotes my introduction where I state I’m not an expert as regards environmental
problems. True, but the quote in full actually places this point in context:
“I have let experts review the chapters of this book, but I am not myself an expert as regards
environmental problems. My aim has rather been to give a description of the approaches to the
problems, as the experts themselves have presented them in relevant books and journals, and
to examine the different subject-areas from such a perspective as allows us to evaluate their
importance in the overall social prioritization.
The key idea is that we ought not to let the environmental organizations, business lobbyists
or the media be alone in presenting truths and priorities. Rather, we should strive for a careful
democratic check on the environmental debate, by knowing the real state of the world –
having knowledge of the most important facts and connections in the essential areas of our
world. It is my hope that this book will contribute to such an understanding.” (pxx)
Of course, saying that truer words are not found in the rest of the book is clearly a rhetoric point, as
much of what I say is simply quotes of the best available statistics from the official entities like the UN,
OECD, World Bank, EU, US etc.Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 5/32
Third, Schneider lets us consider the argument that my many endnotes conjure at least trappings of
academic argument. This seems an unreasonable critique, since it really makes it a lot easier for my
critics to attempt to show exactly where I might be wrong. The argument also easily backfires, since
Schneider does not supply any endnotes or other trappings of academic argument himself. Of course,
Scientific American has limited space, but one could easily have imagined that SA would have put out
an annotated version of the papers on their website. (That Schneider considers his SA article his best
argument is evident from his other, shorter and fiercer article from
grist/books/schneider121201.asp, where he specifically refers to his SA piece and the Pimm & Harvey
Nature article for documentation. Incidentally, the Nature article is also almost devoid of
documentation, see download on my web-site,
The climate chapter makes four basic arguments:
Climate science is very uncertain, but nonetheless the real state of the science is that the
sensitivity of the climate to carbon dioxide will turn out to be at the low end of the IPCC
uncertainty range—which is for a warming of 1.5 to 4.5 degrees C if carbon dioxide were to
double and be held fixed over time.
Emissions scenarios, according to the IPCC, fall into six “equally sound” alternative
paths. These paths span a doubling in carbon dioxide concentrations in 2100 up to more
than tripling and well beyond tripling in the 22nd century. Lomborg, however, dismisses all
but the lowest of the scenarios: “Temperatures will increase much less than the maximum
estimates from IPCC—it is likely that the temperature will be at or below the B1 estimate
[the lowest emissions scenario] (less than 2° C in 2100) and the temperature will certainly
not increase even further into the twenty-second century.”
Cost-benefit calculations show that although the benefits of avoiding climate change
could be substantial ($5 trillion is the single figure Lomborg cites), this is not worth the cost
to the economy of trying to constrain fossil fuel emissions (a $3trillion to $33trillion range
he pulls from the economics literature). Asymmetrically, no range is given for the climate
The Kyoto Protocol, which caps industrialized countries’ output of greenhouse gases, is
too expensive. It would reduce warming in 2100 by only a few tenths of a degree—“putting
off the temperature increase just six years.” This number, though, is based on a straw-man
policy that nobody has seriously proposed: Lomborg extrapolates the Kyoto Protocol, which
is applicable only up to 2012, as the world’s sole climate policy for another nine decades.
Schneider deserves credit for making clear the main thrust of his criticism in these four points,
though he clearly cannot bear just to state them without pejorative statements like “asymmetrically, no
range…” and “straw-man policy”, both of which are incorrect and will be dealt with below.
Before providing specifics of why I believe each of assertions is fatally flawed, I should
say something about Lomborg’s methods. First, most of his nearly 3,000 citations are to
secondary literature and media articles. Moreover, even when cited, the peer-reviewed
articles come elliptically from those studies that support his rosy view that only the low end
of the uncertainty ranges will be plausible. IPCC authors, in contrast, were subjected to
three rounds of review by hundreds of outside experts. They didn’t have the luxury of
reporting primarily from the part of the community that agrees with their individual views.
There is an important distinction between secondary sources and media articles. When discussing the
entire state of the world, it would be incredibly inefficient not to use the vast collection of data and
theory offered by secondary sources – this is exactly the reason for secondary literature and in general
why it is possible to have specialization in science. However, almost all of these secondary sources are
exactly the ones used by almost all discussants of the state of the world – the reports of the UN, (FAO,
UNDP, UNEP, WHO etc.), IMF, the World Bank, OECD, WRI, Worldwatch Institute, EU, US
government agencies etc. In the climate chapter, which Schneider discusses, references to the IPCC
reports constitute about one-third of all 646 endnotes. Yet, the IPCC reports are clearly secondary
sources. Surely, most people – including myself – would consider these reports the best available
summary of our understanding of the climate science, which exactly was my argument for primarily
using them as references:
“In the following I shall – unless otherwise stated – use the figures and computer models
from the official reports of the UN climate panel, the IPCC. The IPCC’s reports are theLomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 6/32
foundation for most public policy on climate change and the basis for most of the arguments
put forth by the environmental organizations.” (SE:259).
When I use media articles this is almost always when analyzing media discussion and illustrating
what I believe to be a bias towards bad news or even incorrect information that permeates
environmental news reporting. When discussing the IPCC temperature interval for 2100 of 1.4-5.8°C, I
point out that:
“In the reporting from the major media, such as CNN, CBS, The Times, and Time, it was
found that all used the high estimate of 5.8°C warming, and yet none mentioned the low
estimate of 1.4°C.”
Naturally, this statement uses media articles as reference but is the use problematic? Should such a
bias not be pointed out?
Likewise, I debunk U.S. News & World Report for telling its readers in February 2001 of how global
warming would have lots of serious consequences. One of the most outrageous would be the US
prediction: “By midcentury, the chic Art Deco hotels that now line Miami's South Beach could stand
waterlogged and abandoned,” despite IPCC estimates of a water rise of just 16cm (6in) by 2050
(SE:289-91). Is this use of media sources unreasonable?
Then, the critique of my use of sources continues with the charge that when I use peer-reviewed
articles I do so primarily to support my rosy view of a low range but no further evidence of this is
Second, it is ironic that in a popular book by a statistician one can’t find a clear discussion
of the distinction among different types of probabilities, such as frequentist and Bayesian
(that is, “objective” and “subjective”). He uses the word “plausible” often, but, curiously for
a statistician, he never attaches any probability to what is “plausible.” The Third
Assessment Report of the IPCC, on the other hand, explicitly confronted the need to
quantify all confidence terms. Working Group I, for example, gave the term “likely” a 66 to
90 percent chance of occurring. Although the IPCC gives a wide range for most of its
projections, Lomborg generally dismisses these ranges, focusing on the least serious
outcomes. Not so much as one probability is offered for the chance of a dangerous outcome,
yet he makes a firm assertion that climate “will certainly” not go beyond 2 degrees C
warming in the 22nd century—a conclusion at variance with the IPCC, other national
climate assessments and most recent studies in the field of climate science.
It is correct that IPCC has quantified its ‘plausible’, but IPCC themselves quite rightly made it clear
what the limits were on the accuracy of their different types of probability: “the following words have
been used where appropriate to indicate judgmental estimates of confidence: virtually certain (greater
than 99% chance that a result is true); very likely (90-99% chance); likely (66-90% chance); medium
likelihood (33-66% chance); unlikely (10-33% chance); very unlikely (1-10% chance); exceptionally
unlikely (less than 1% chance),” (IPCC 2001d:2, italics added). Unless we are talking about events
with very well-established probability distributions (which is the case for almost none of the important
global warming issues) it really is just a judgement call whether something has a 89% or 91% chance
of occurring – thus, had I made a similar endnote, defining the words of confidence, it might have
appeared slightly more objective but not really made any addition to the facts at hand.
The second claim is much more serious: that I generally dismiss the IPCC ranges and focus on the
least serious outcomes. Neglecting such ranges generally or without reason would, of course, be
seriously misleading, which is why I don’t do it in the book and which may explain why my critic
offers no examples. Take two of the most important characteristics of global warming, sea level
increases and temperature impacts on agriculture. For sea level increase I clearly write out the ranges
from the main scenarios (SE:264) and for agriculture impact I clearly state the IPCC ranges (SE:288).
Next, it is claimed that I do not offer any probability of a dangerous outcome. This is plainly
incorrect. In a whole section entitled “Fear of catastrophe” (SE: 315-7) I discuss the two major worries
of dangerous outcomes, the sliding of the West Antarctic Ice Sheet (WAIS) and the shut-down of the
thermohaline circulation (THC) that drives the Gulf Stream. Here I quote the 2001 IPCC report that a
WAIS breakup is considered “very unlikely during the 21st century” (SE:315). Likewise, with respect
to the THC, I write out that the 2001 “IPCC conclude that ‘the current projections using climate models
do not exhibit a complete shut down of the thermohaline circulation by 2100’ but point out that it could
completely, and possibly irreversibly, shut down ‘if the change in radiative forcing is large enough and
applied long enough’” (SE:316). In the endnote it is discussed how likely it is that the radiative forcing
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 7/32
will be large enough and applied long enough for this shut-down to happen. Thus, for both the major
dangerous outcomes I discuss the probability in detail, contrary to Schneider’s claim.
The final quote of “will certainly” only works because it has been taken out of context:
“This more realistic model holds several key points. First, it shows that global warming is
not an ever worsening problem. In fact, under any reasonable scenario of technological change
and without policy intervention, carbon emissions will not reach the levels of A1FI and they
will decline towards the end of the century, as we move towards ever cheaper renewable
energy sources. Second, temperatures will increase much less than the maximum estimates
from IPCC – it is likely that the temperature will be at or below the B1 estimate (less than 2°C
in 2100) and the temperature will certainly not increase even further into the twenty-second
century. Third, …” (SE:286, italics added).
The quote “will certainly” comes from a model which is deemed “more realistic,” but it is naturally
only within this model that I can say that the temperature will be below 2°C and not keep increasing
into the 22 nd century. To make me say otherwise (that I should make “a firm assertion”) is simply
called misquoting.
Now let us look in more detail at the four major arguments he makes in this chapter.
Climate science. A typical example of Lomborg’s method is his paraphrase of a
secondary source in reporting a 1989 Hadley Center paper in the journal Nature in which
the researchers make modifications to their climate model: “The programmers then
improved the cloud parameterizations in two places, and the model reacted by reducing its
temperature estimate from 5.2° C to 1.9° C.” Had this been first-rate scholarship, Lomborg
would have consulted the original article, in which the concluding sentence of the first
paragraph presents the authors’ caveat: “Note that although the revised cloud scheme is
more detailed it is not necessarily more accurate than the less sophisticated scheme.” In a
similar vein, he cites Richard S. Lindzen’s controversial stabilizing feedback, or “iris
effect,” as evidence that the IPCC climate sensitivity range should be reduced by a factor of
almost three. He fails either to understand this mechanism or to tell us that it is based on
only a few years of data in a small part of one ocean. Extrapolating this small sample of data
to the entire globe is like extrapolating the strong destabilizing feedback over
midcontinental landmasses as snow melts during the spring—such an inappropriate
projection would likely increase estimates of climate sensitivity by a factor of several.
I am glad to have pointed out the typical way I refer to secondary sources – namely quote them
accurately. The quote comes from Science magazine in 1997:
“A few years ago, a leading climate model – developed at the British Meteorological
Office's Hadley Center for Climate Prediction and Research, in Bracknell – predicted that an
Earth with twice the preindustrial level of carbon dioxide would warm by a devastating 5.2
Degrees Celsius. Then Hadley Center modelers, led by John Mitchell, made two
improvements to the model's clouds--how fast precipitation fell out of different cloud types
and how sunlight and radiant heat interacted with clouds. The model's response to a carbon
dioxide doubling dropped from 5.2 Celsius to a more modest 1.9 Celsius.” (Kerr 1997a:1040).
However, the claim that I should have gone back to the original article seems suspect on several
grounds. First, why would a major Science overview article not be a trustworthy source in general (and
why not mention that the source is Science, rather than merely “a secondary source”)? Second, it is of
course possible that there are errors in secondary sources, though the risk is probably very small when
using reputable sources like Science. The necessary question, though, is whether this is an important
error? And if so, why has nobody (including my critic) corrected the article when it appeared in
Science? Finally, is it really correct that the only relevant article to go back to is an article from 1989
(eight years earlier), where they point out the more detailed cloud scheme is “not necessarily more
accurate”? Naturally, much research has been done since 1989 to establish which cloud scheme is the
more accurate; in a 1993 article Michell points out (together with C. A. Senior):
“The importance of the representation of cloud in a general circulation model is investigated
by utilizing four different parameterization schemes for layer cloud in a low-resolution
version of the general circulation model at the Hadley Centre for Climate Prediction and
Research at the United Kingdom Meteorological Office. The performance of each version of
the model in terms of cloud and radiation is assessed in relation to satellite data from the Earth
Radiation Budget Experiment (ERBE). Schemes that include a prognostic cloud water
variable show some improvement on those with relative humidity-dependent cloud, but all still
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 8/32
show marked differences from the ERBE data. The sensitivity of each of the versions of the
model to a doubling of atmospheric C02 is investigated. Midlevel and lower-level clouds
decrease when cloud is dependent on relative humidity, and this constitutes a strong positive
feedback. When interactive cloud water is included, however, this effect is almost entirely
compensated for by a negative feedback from the change of phase of cloud water from ice to
water. Additional negative feedbacks are found when interactive radiative properties of cloud
are included and these lead to an overall negative cloud feedback. The global warming
produced with the four models then ranges from 5.4° with a relative humidity scheme to 1.9°C
with interactive cloud water and radiative properties. Improving the treatment of ice cloud
based on observations increases the model's sensitivity slightly to 2.1°C. Using an energy
balance model, it is estimated that the climate sensitivity using the relative humidity scheme
along with the negative feedback from cloud radiative properties would be 2.8°C. Thus, 2.8°–
2.1°C appears to be a better estimate of the range of equilibrium response to a doubling of
C02.” (Senior & Mitchell 1993,
issn=1520-0442&volume=006&issue=03&page=0393, italics added).
Here, they basically tell us that the model which produced the 1.9°C is better though not necessarily
by a lot (“some improvement”) and that the low-end estimates are “better estimates.”
Thus, the example of secondary source quotation seems curious at best or deliberately misleading at
The claim against Lindzen seems unreasonable as pointed out in Lindzen’s own letter to Scientific
American, available at my web-site. Here Lindzen writes:
“One small point of personal interest to me illustrates the rather bizarre nature of these
attacks. Schneider claims that Lomborg cites a paper by me and colleagues (Lindzen, Chou
and Hou, Does the Earth Have an Adaptive Infrared Iris?, Bulletin of the American
Meteorological Society, 82, 2001) on what we refer to as the ‘iris effect’ in order to reduce the
IPCC claimed sensitivities by a factor of 3. What Lomborg does, is devote a quarter of a page
to our paper in order to point out that it ‘might pose a challenge’ to the IPCC range. Schneider
goes on to chide Lomborg for failing to present an allegedly fatal flaw in our argument: that it
is simply the extrapolation of data from “a few years of data from a small part of one ocean.”
He also presents an absurdly incomprehensible ‘analogy’ to positive feedbacks from
midcontinental ice melts in spring. What Schneider really illustrates is that he completely
misunderstands what we have done, which is to assess the effect of temperature on the
behavior of cumulonimbus convection and its impact on large scale upper level cirrus clouds
in the tropics. The primary requirement of such a study is that it deal with a period and a
region which contain a large enough number of cumulonimbus towers; the results (which are
normalized by a measure of cumulus activity) are then scalable to the entire tropics – a far cry
from naive extrapolation . The period we dealt with (20 months in the paper, but now
extended to 4 years) and the area looked at (30 o S-30 o N, and 130 o E-170 o W) amply
satisfied this criterion. As a logical test of this, we showed that the dependence of the ratio of
cirrus area to convective activity remained robust even when we restricted ourselves to
arbitrary small subsets in time and space of our full data set. We have also ascertained that
existing climate GCMs fail to replicate the observations. As our paper amply stresses (and as
Lomborg acknowledges), there remain uncertainties in our work, but Schneider’s concern
over ‘extrapolation’ is not one of them.
Thus, at one fell swoop, Schneider misrepresents both the book he is attacking and the
science that he is allegedly representing.”
As a final example, he quotes a controversial hypothesis from Danish cloud physicists
that solar magnetic events modulate cosmic rays and produce “a clear connection between
global low-level cloud cover and incoming cosmic radiation.” The Danish researchers use
this hypothesis to support an alternative to carbon dioxide for explaining recent climate
change. Lomborg fails to discuss— and I haven’t seen it treated by the authors of that
speculative theory either— what such purported changes to this cloud cover have done to
the radiative balance of the earth. Increasing clouds, it has been well known since papers by
Syukuro Manabe and Richard T. Wetherald in 1967 and myself in 1972, can warm or cool
the atmosphere depending on the height of the cloud tops, the reflectivity of the underlying
surface, the season and the latitude. The reason the IPCC discounts this theory is that its
advocates have not demonstrated any radiative forcing sufficient to match that of much
more parsimonious theories, such as anthropogenic forcing.
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 9/32
Schneider calls this theory “an alternative to carbon dioxide for explaining recent climate change.”
However, neither the Danish cloud physicists nor I say that they are an alternative, but a supplementary
explanation: “the sun as another important factor in the explication of increasing global temperatures”
(SE:276, italics added). Moreover, I do point out both its still unsolved scientific problems but also its
force and an attempt to show the relative importance of the two:
“A number of unanswered questions and unsolved scientific problems still remain in these
theoretical relationships. But the point is that the sunspot theory has created a possible
correlation in that a shorter sunspot cycle duration, such as the one we are experiencing now,
means more intense solar activity, less cosmic radiation, fewer low-level clouds, and therefore
higher temperatures. This theory also has the tremendous advantage, compared to the
greenhouse theory, that it can explain the temperature changes from 1860 to 1950, which the
rest of the climate scientists with a shrug of the shoulders have accredited to “natural
Notice that the connection between temperature and the sunspot cycle seems to have
deteriorated during the last 10-30 years, with temperatures outpacing sunspot activity in
Figure 165. Most likely we are instead seeing an increasing signal, probably from greenhouse
gases like CO2. Such a find exactly underscores that neither solar variation nor greenhouse
gases can alone explain the entire temperature record. Rather, the fact that the emerging
greenhouse gas signal only appears now seems to indicate once again that the estimated CO2
warming effect needs to be lowered. One such critical study finds that the solar hypothesis
explains about 57 percent of the temperature deviations and that the data suggest a climate
sensitivity of 1.7°C, a 33 percent reduction of the IPPC best estimate” (SE:277-8, italics
In conclusion, I do not accept the charge of having misconstrued climate science. If I am so wrong,
one would expect that my critic should have had an easy time showing it, not having to rely on
nitpicking, quoting out of context, and misrepresenting.
Emissions scenarios. Lomborg asserts that over the next several decades new, improved
solar machines and other renewable technologies will crowd fossil fuels off the market. This
will be done so efficiently that the IPCC scenarios vastly overestimate the chance for major
increases in carbon dioxide. How I wish this would turn out to be true! But wishes aren’t
analysis. One study is cited; ignored is the huge body of economics work he later accepts to
estimate a range of costs if we were to implement emissions controls. In fact, most of these
economists strongly believe high emissions are quite likely: they usually project carbon
dioxide doubling to tripling (or more) as “optimal” economic policy. I have attacked this
literature for failing to point out that climate policies that raise the price of conventional
fuels spur investments in alternative energy systems. But such incentives need policies
first—and Lomborg opposes those very policies. No credible analyst can just assert that a
fossil fuel intensive scenario is not plausible—and, typically, he gives no probability that it
might occur.
This is perhaps the most curious and weak argument of Schneider. He does nothing to confront my
critique of the new IPCC scenarios, which in the words of one of the modeling teams are “an attempt at
‘computer-aided storytelling.’” Here, IPCC has abandoned any attempt to predict the future and instead
only talk about different possible futures. However, if the stories generating the worst outcomes are
consistently unlikely, then clearly there is a great risk that we might end up spending vast amount of
resources to combat threats that only occur in very unlikely storytelling.
I point out how the price of renewables such as solar power have been dropping by more than 50%
per decade over the past 30 years. Then I present a peer-reviewed model (Chakravorty et al. 1997),
which shows that if this trend continues it will mean the beginning of renewables as a substantial
source of energy by 2025 and the end of fossil fuels by 2065. Even if a much lower price decrease of
30% per decade is assumed for the future, it means phasing in renewables by 2035 and the end of fossil
fuels by 2105 (SE:284ff). Schneider merely counters this by pointing to the many models of the cost
and benefits of global warming (the integrated models), which do not show this decline in carbon
emissions. This is correct but entirely irrelevant – these models deal with different issues of costs and
benefits (primarily with the timing of costs from early phasing out of carbon emissions), and the
Chakravorty paper was exactly written to counter this problem.
Thus, my critic does not really have a counter-argument – he only seems to dismiss the analysis as
wishful thinking and stating that “no credible analyst” can say this. These are arguments of authority,
not science. If Schneider is aware of any other study that has looked at the relative costs of renewables
and fossil fuels over time, taking into account the remarkable increase in efficiency of the renewables
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 10/32
over the past decades, but which shows that renewables will not take over – we should be given these
references and more details.
Cost-benefit calculations. Lomborg’s most egregious distortions and poorest analyses
are his citations of cost-benefit calculations. First, he chides the governments that modified
the penultimate draft of the report from IPCC’s Working Group II. These modifications
downgraded the significance of economic studies that aggregate climate change damages.
Lomborg says: “A political decision stopped IPCC from looking at the total cost-benefit of
global warming.” (As an aside, I should mention that it is strange he chose to cite the
penultimate and pre-approval draft report in this case but didn’t mention the very first item
in the approved summary—that recent temperature trends have caused a discernible effect
on plants and animals. Even more puzzling is his failure to discuss ecological impacts in
general, focusing instead on health and agriculture, sectors he thinks won’t be much harmed
by climate change of the minuscule amount he predicts.)
Here, two different arguments are being confused. Yes, I chide governments for editing the WGII
technical summary, which stated the controversial but fairly well established point: Moderate global
warming will have grave, negative net impact on the developing world but zero or maybe even a
positive net impact for the developed world. In the more technical language of the WGII summary, this
“Published estimates indicate that increases in global mean temperature would produce net
economic losses in many developing countries for all magnitudes of warming studied, and that
the losses would be greater in magnitude the higher the level of warming. In many developed
countries, net economic gains are projected for global mean temperature increases up to
roughly 2°C. Mixed or neutral net effects are projected in developed countries for temperature
increases in the approximate range of 2 to 3°C, and net losses for larger temperature increases.
The projected distribution of economic impacts is such that it would increase the disparity in
well being between developed countries and developing countries, with the disparity growing
with higher temperatures. The more damaging impacts estimated for developing countries
reflects, in part, their lesser adaptive capacity.” (IPCC 2001b:Summary for Policymakers,
original government draft, 2.6., SE:301)
In the final version, this clear message disappeared without any additional scientific information being
supplied. It certainly seems reasonable to criticize such a move. Schneider suggests that this should be
due to a downgrading of economic studies, and he then mentions my following quote “a political
decision…”. However, this is about WGIII – a totally different issue. (That this is not just an accidental
typo is seen in Schneider’s Grist article, where he also talks about WG2).
Thus, Schneider makes no argument against the fact that governments changed the unpleasant
Instead he makes the almost incomprehensible aside that it is strange that I mention one thing from
the penultimate report but not a completely different thing from the finished report. Such argument just
does not make sense – I mention the one thing because it is important in the context of the issues
discussed; Schneider may find that I should have talked about others, and in a book dealing with so
many and such varied issues, such a critique if of course always possible. However, dealing with the
impact of global warming on agriculture and health rather than ecology seems entirely justified given
the much greater attention, both scientifically and media-wise, to the first two issues, and also the
human-centered evaluation presented openly in the beginning of my book (SE:11-2).
The government representatives downgraded aggregate cost-benefit studies for a reason:
these studies fail to consider so many categories of damages held to be important by
political leaders as to render them just a guideline on market sector transactions, not the
“total cost-benefit” analysis Lomborg wants. A total analysis would have to include the
value of species lost, crucial ecosystem services degraded, inequity created by the poor
being hurt more than the rich (which Lomborg does acknowledge), quality of life reduced
(for example, a rise in sea level driving small-island inhabitants from traditional
homelands), and likely changes to climatic extremes and variability. Then again, Lomborg
cites only one value for climate damages—$ 5 trillion—even though the same economics
papers he refers to for costs of climate policy generally acknowledge that climate damages
can vary from benefits up to catastrophic losses.
Here it is claimed without any reference that the government representatives should have stopped
cost-benefit analysis because it did not include all categories, but honestly, it seems highly unlikely that
it would have been stopped for such a reason – it would have been a much more obvious choice to
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 11/32
make the cost-benefit analysis more inclusive. Moreover, it is scientifically unreasonable to argue that
since we don’t have all the data, we shouldn’t even try to get them but just – stop! Then what do we
Finally, it is claimed that the $5 trillion (total, discounted cost) is unreasonable, since one economist
(Nordhaus) has shown that the cost could be much less and with a catastrophe it could be more. I
merely write out the mean estimated cost of Nordhaus’ latest model. The cost is also comparable to the
one estimated by IPCC in its 1996 report (which due to the end of cost-benefit analysis is not replicated
in 2001), finding an annual cost of about 1.5-2% of global GDP. This is not unreasonable, when the
global warming costs are compared to the same mean estimates of mitigation (see discussion below).
It is precisely because the responsible scientific community cannot rule out such
catastrophic outcomes at a high level of confidence that climate mitigation polices are
seriously proposed. And to give one number—rather than a broad range—for avoided
climate damages defies explanation, especially when he does give a range for climate policy
costs. This range, however, is based on the economics literature but ignores the findings of
engineers. Engineers dispute the economists’ typical estimates because the economists fail
to take into account preexisting market imperfections such as energy-inefficient machines,
houses and processes. These engineering studies, including a famous one by five U.S.
Department of Energy laboratories— hardly environmental radicals —suggest that climate
policies that provide incentives to replace inefficient equipment with more efficient state-of-the-
art products could actually reduce some emissions at below-zero costs.
Of course the higher the probability of catastrophic outcomes the more urgent climate mitigation
policies appear. However, it is surprising that my critic can now tell us unequivocally that the reason
the responsible scientific community cannot rule out catastrophic outcomes that we should cut back
carbon emissions. On his interpretation this means that almost the entire three IPCC 2001 reports are
worthless in the discussion on what to do about global warming, because almost all of the models and
results discussed are based on non-catastrophic outcomes. Indeed, the only two major catastrophes
discussed (WAIS slipping and THC shutting down), the current models are exactly showing very small
risks of these happening (as discussed above). Moreover, almost all of the public discussion has
focused on what will happen with rising sea levels, higher mean temperatures, possibly more malaria
etc. – all of which are dependent on the non-catastrophic models of the IPCC. (Notice also, that these
are the issues brought forth by Schneider himself above: “value of species lost, crucial ecosystem
services degraded, inequity created by the poor being hurt more than the rich (which Lomborg does
acknowledge), quality of life reduced (for example, a rise in sea level driving small-island inhabitants
from traditional homelands), and likely changes to climatic extremes and variability.”)
I do agree with Schneider that we need to focus more of our attention to possible catastrophic
outcomes (“we ought to spend more effort looking into the likelihood of such [catastrophic]
occurrences than on improving our mean prognosis, since it is the extreme occurrences that are truly
costly” SE:316). However, this has clearly not been the mainstay of the global warming argument and
to suddenly claim so seems both incorrect and disingenuous.
Then Schneider goes on to say, as he did in the summary above, that I give one figure for the cost of
global warming ($5T) but a range for “climate policy costs” ($3-33T), and that this “asymmetry” is
unreasonable. (In Grist, Schneider puts it less diplomatically: “this putative statistician quotes a range
of costs when convenient but not a range of benefits when inconvenient”)
The problem is that Schneider is clearly comparing two different kinds of numbers and two different
kinds of ranges. The $5T is indeed the central cost estimate of global warming from Nordhaus and
Boyer (and it is broadly consistent with the IPCC estimate as discussed above). This is simply the cost
of global warming when comparing a Business-as-usual (BAU) world with the hypothetical BAU
world, where there was no man-made global warming. In essence, this is the price we’ll have to pay if
we don’t do anything.
The other figures ($3-33T) come from the extra costs of choosing different emission cut policies. For
instance, the Nordhaus/Boyer estimate for a global stabilization policy (a kind of global Kyoto) would
be about $8.5T (SE:310). However, had we done nothing the cost would still have been $5T, so the
extra cost of choosing global stabilization is about $3.5T. If we instead choose a policy to limit the
temperature increase to 1.5°C, the Nordhaus/Boyer estimate is a cost of $37.5T or an extra cost of
$32.5T. These strategies are some of the limit points in the range of $3-33T, which I mention and
which Schneider quotes (SE:318).
Now, clearly you cannot compare the $5T with the range $3-33T, because the $5T includes the cost
of global warming, the range denotes the extra cost. Thus, Schneider is plainly wrong in comparing the
two (or claiming that the one should be the cost, and the other the benefits, as he does in Grist).
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 12/32
This also shows why the complaint of range vs. single number is entirely misplaced. The $5T is the
cost of global warming under BAU. You can only ‘do nothing’ in exactly one way. Therefore there is
just one number. The $3-33T is a range of net costs under a wide variety of policy choices. Now, we
can make lots of different policies, ranging from very light to very invasive – the light policies
incurring only a smaller net cost ($3T) and the invasive ones incurring very high net costs (e.g. $33T).
So there is no sinister, ‘putative statistician’ presenting ranges only when it fits him – the single
number is a single cost – the range is net costs of a range of policy choices. Both comparing these, and
complaining about their asymmetry is simply incorrect.
Then it is claimed that I base the cost estimates on the economics literature, “but ignores the findings
of engineers.” This is incomprehensible and again incorrect. I spend almost two pages discussing these
alternative engineer (or bottom-up) cost estimates (see SE:312-3). The problem with most of these
engineer estimates is that they only count direct costs and benefits but neglect the (typically much
bigger) indirect costs and benefits on economic production. A clear example of this is given in the
book, where UNEP (the UN Environmental Programme) evaluates the CO2 reduction potential in
Denmark: “The main question is: How much of this [CO2 reduction] potential can be realised without
substantial increases in costs associated with finding and implementing these options, and without
serious welfare losses? None of these costs are included in the following calculations, which are based
on the concept of direct costs” (UNEP 1994:II, 21, SE:426). Thus, I conclude – along with most
economists – that these engineer estimates are likely to be huge overestimates of the actual
opportunities, because they systematically neglect the costs down the line. Schneider may disagree and
have new data to convince us, but he should present such data instead of incorrectly claiming that I
have not dealt with the issue.
Finally, Schneider writes that researchers have found that it is possible to provide incentives, which
in some cases will cut carbon emissions with net benefits. He also writes this as if it was astounding
and somehow in opposition to my arguments. However, the statement that some emissions may
actually be cut at below-zero costs is entirely standard, and also replicated in my book. The argument is
not whether there are below-zero cost ways to cut emissions (the so-called ‘no regret’ options) but how
“Most economists are therefore extremely skeptical towards assertions of such
improvements in efficiency which can be implemented at no cost or even produce a profit,
among other things because these calculations, as we have seen above, often omit important
items of expenditure. For this reason, economists also argue that if it really is possible to
implement profitable restructuring then it would be reasonable to expect that the possibility
would already have been exploited.
One typical economist’s expression is that “there is no such thing as a free lunch” – that
costs are bound to occur somewhere along the line. Nordhaus expresses the problem of the
possible, profitable carbon dioxide emissions reductions thus: “In the colloquialism of
economics, this analysis suggests not only that there are free lunches, but that in some
restaurants you can get paid to eat!”
A new study also seems to suggest that these “no regret” possibilities are mu ch more limited
than normally assumed; it turns out that they can probably only reduce consumption by a
couple of percent and could possibly be pushed to providing 5 percent. Equally, a study of
monthly electricity bills showed that the engineers’ estimates of huge savings from attic
insulation fell far short of real payoffs, which were closer to what economists would have
expected.” (SE:313).
Again, Schneider does not add to our information but he manages to make it seem as if he has
countered an argument of mine, though I clearly write that there could 2-5% cuts that could be made at
below-zero cost.
The Kyoto Protocol. Lomborg’s creation of a 100-year regime for a decade-long
protocol is a distortion of the climate policy process. Every IPCC report has noted that
carbon dioxide emissions need to be cut by more than 50 percent below most baseline
projections to avoid large increases in concentration in the late 21st and 22nd centuries.
Most analysts know “Kyoto extended” can’t make such large cuts and that both developed
and developing nations will have to fashion cooperative and cost-effective solutions over
time. This will take a great deal of learning-by-doing: international cooperation is not a
common experience. Kyoto is a starting point. And yet Lomborg, with his creation of a
straw-man 100-year projection, would squash even this first step.
The book clearly shows that Kyoto-in-itself will have very little effect on global warming, and it is
good to see that Schneider concurs. However, he then claims that Kyoto-in-itself is a straw-man,
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 13/32
because we should be doing much more. Now, this entails both an analytic and a democratic problem.
To take the democratic first: almost all democratic discussion is about choosing or not choosing Kyoto.
Since this is the deal offered, would it not be reasonable to discuss what is the actual outcome of the
deal that we are talking about? Likewise, if Schneider contends that the real issue is not Kyoto but
something much more restrictive, would it not be democratically more honest to say that the decision is
not Kyoto but something much more stringent? Moreover, it is somewhat of a rhetorical misnomer to
talk about “Lomborg’s creation of a 100-year regime for a decade-long protocol is a distortion of the
climate policy process.” This extension I refer to actually comes from an article written by one of the
lead-authors of the 1996 IPCC report, Wigley. He does in fact extend the Kyoto protocol to ascertain
what its effect might be. In doing this, is professor Wigley really creating a distortion of the climate
policy process?
The other, analytic problem is that Schneider only talks about my analysis of Kyoto and actually
neglects that I deal with a range of much more stringent policies (which was why we got the $3-33T
range, mentioned above). This seems odd, to say the least. Of course, if Schneider wants to advocate a
policy of much-more-than-Kyoto, that is fine, but the cost-benefit analyses are very clear on the issue.
Kyoto is almost irrespective of how it is implemented a bad deal, and going even further is a much
worse deal.
This is the absolutely central issue of the book, which Schneider ignores: That all cost-benefit
analyses show that high carbon reductions are not justified (SE:318): “A central conclusion from a
meeting of all economic modelers was: ‘Current assessments determine that the ‘optimal’ policy calls
for a relatively modest level of control of CO2.’”
The last sentence, which claims that I want to “squash” the Kyoto protocol, is language from policy,
not science. I try to point out the costs and benefits of our different policy choices, and yes, I point out
that for the benefit of Kyoto will be to postpone global warming in 2100 by six years, whereas the cost
of Kyoto each year will be as great as the one-off cost of giving clean drinking water and sanitation to
every single human being, forever.
So what then is “the real state of the world”? Clearly, it isn’t knowable in traditional
statistical terms, even though subjective estimates can be responsibly offered. The ranges
presented by the IPCC in its peer-reviewed reports give the best snapshot of the real state of
climate change: we could be lucky and see a mild effect or unlucky and get the catastrophic
outcomes. The IPCC frames the issue as a risk-management decision about hedging. It is
not the everything-will-turn-out-fine affair that Lomborg would have us believe.
It ought not to be necessary to point out, but IPCC offers us insight into the science of global
warming, but they (exactly because of the political decision to stop pursuing cost-benefit analysis) do
not give us the answer to whether our limited resources are better spent on averting more global
warming or on e.g. supplying clean drinking water and sanitation to the world.
Saying that my book is an everything-will-turn-out-fine statement is a rhetorical and entirely
misleading treatment of my book. I point out that we should deal with environmental problems, work
to decrease air pollution even further, invest in renewable energy research and development etc., as
well as tackle the many other, important global problems such as poverty and starvation. The point I
make, however, is that we should continuously be aware of the necessary prioritization – that we
should strive to make the decisions, which actually do good and not just the ones that sound good. This
requires straight and honest analysis that is willing to challenge any however well established myth.
For such an interdisciplinary topic, the publisher would have been wise to ask natural
scientists as well as social scientists to review the manuscript, which was published by the
social science side of the house. It’s not surprising that the reviewers failed to spot
Lomborg’s unbalanced presentation of the natural science, given the complexity of the
many intertwining fields. But that the natural scientists weren’t asked is a serious omission
for a respectable publisher such as Cambridge University Press.
The claim of “unbalanced presentation of the natural science” clearly cannot be upheld, given my
critic’s lack of ability to provide such examples. This also suggests that his stated regret that
Cambridge University Press has chosen to publish my book really amounts to a desire to see critical
arguments suppressed.
Unfortunately, angry reviews such as this one will be the result. Worse still, many
laypeople and policymakers won’t see the reviews and could well be tricked into thinking
thousands of citations and hundreds of pages constitute balanced scholarship. A better rule
of thumb is to see who talks in ranges and subjective probabilities and to beware of the
myth busters and “truth tellers.”
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 14/32
This, of course, is a surprising ending. The entire Scientific American piece is sold as a truth-telling
story. My own understanding of science is that we should exactly try to bust myths and be truth tellers.
Questioning truth saying and myth busting seems to undercut the entire endeavor that Scientific
American is trying to achieve, but perhaps and unfortunately it is a very accurate description of the
state of the critique.
Stephen Schneider, professor in the department of biological sciences and senior fellow
at the Institute for International Studies at Stanford University, is editor of Climatic Change
and the Encyclopedia of Climate and Weather and lead author of several IPCC chapters
and the IPCC guidance paper on uncertainties.
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 15/32
John P. Holdren
Lomborg’s chapter on energy covers a scant 19 pages. It is devoted almost entirely to
attacking the belief that the world is running out of energy, a belief that Lomborg appears to
regard as part of the “environmental litany” but that few if any environmentalists actually
hold. What environmentalists mainly say on this topic is not that we are running out of
energy but that we are running out of environment—that is, running out of the capacity of
air, water, soil and biota to absorb, without intolerable consequences for human well-being,
the effects of energy extraction, transport, transformation and use. They also argue that we
are running out of the ability to manage other risks of energy supply, such as the political
and economic dangers of overdependence on Middle East oil and the risk that nuclear
energy systems will leak weapons materials and expertise into the hands of proliferation
prone nations or terrorists.
It is good to see that Holdren is actually saying it is correct, we’re not running out of energy, and that
I am right. Somewhat contradictorily is the pejorative “scant” 19 pages – if I’m right and the issue is
easily settled, presumably there is no need to use many more?
However, Holdren then goes on to say that environmentalists are worrying about running out of
environment (the statement singled out in SA) and running out of the ability to manage political,
economic and military dangers. This is exactly the kind of exposition which I try to counter in my book
– without any references Holdren manages to describe everything as going ever worse and even
include into the environmental agenda concepts that are far removed from its core, such as nuclear
proliferation, terrorism and economic recession from oil price hikes. Let us just point out one issue-area,
air pollution (estimated by the US EPA to be the by far most important area, SE:163). Here we
are plainly not running out of environment or running out of the air’s capacity to absorb without
intolerable consequences for human well-being – all criteria pollutants in the US have diminished in
concentration over the past few decades, as I demonstrate EPA references for in the book (SE:ch.15).
Here, Holdren simply choose a sound-good quote (running out of environment), presumably in the
quest to defend science, but without references and plainly incorrect, even as demonstrated in my book.
That “the energy problem” is not primarily a matter of depletion of resources in any
global sense but rather of environmental impacts and sociopolitical risks—and, potentially,
of rising monetary costs for energy when its environmental and sociopolitical hazards are
adequately internalized and insured against—has in fact been the mainstream
environmentalist position for decades. It was, for example, the position I elucidated in the
1971 Sierra Club “Battlebook” Energy (coauthored with Philip Herrera, then the
environment editor for Time). It was also the position elaborated on by the Energy Policy
Project of the Ford Foundation in the pioneering 1974 report A Time to Choose; by Amory
Lovins in his influential 1976 Foreign Affairs article “Energy Strategy: The Road Not
Taken”; by Paul R. and Anne H. Ehrlich and me in our 1977 college textbook Ecoscience;
and so on. So whom is Lomborg so resoundingly refuting with his treatise on the abundance
of world energy resources? It would seem that his targets are pundits (such as the
correspondents for E magazine and CNN cited at the opening of this chapter) and
professional analysts (although only a few of these are cited, and those very selectively)
who have argued not that the world is running out of energy altogether but only that it might
be running out of cheap oil. Lomborg’s dismissive rhetoric notwithstanding, this is not a
silly question, nor one with an easy answer.
Holdren acknowledges that my targets are pundits and analysts, who have been arguing that we
would be running out of cheap oil. Are these not reasonable people to challenge? He also tries to point
out that many even in the 70s did not worry about running out of oil, but it is curious how he neglects
the most important and influential environmental influence from the 70s, the Limits to Growth
argument that clearly predicted oil to run out before 1992 (Meadows et al. 1972:58). Likewise, Ehrlich
worried in 1987 that the oil crisis would return in the 1990s (Ehrlich and Ehrlich 1987:222). Finally, he
tries to say that the pundits and analysts say something else than do I, because they just worry about
running out of cheap oil. But of course, this is the same thing, as is also pointed out in the book: “Even
if we were to run out of oil, this would not mean that oil was unavailable, only that it would be very,
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 16/32
very expensive. If we want to examine whether oil is getting more and more scarce we have to look at
whether oil is getting more and more expensive” (SE:122).
Oil is the most versatile and currently the most valuable of the conventional fossil fuels
that have long provided the bulk of civilization’s energy, and it remains today the largest
contributor to world energy supply (accounting for nearly the whole of energy used for
transport, besides other roles). But the recoverable conventional resources of oil are
believed (on substantial evidence) to be far smaller than those of coal and probably also
smaller than those of natural gas; the bulk of these resources appears to lie in the politically
volatile Middle East; much of the rest lies offshore and in other difficult or environmentally
fragile locations; and it is likely that the most abundant potential replacements for
conventional oil will be more expensive than oil has been. For all these reasons, concerns
about declining availability and rising prices have long been more salient for oil than for the
other fossil fuels. There is, accordingly, a serious technical literature (produced mainly by
geologists and economists) exploring the questions of when world oil production will peak
of oil might be in 2010, 2030 or 2050, with considerable disagreement among informed
professionals on the answers.
This paragraph does not really criticize, but contains the statement “it is likely that the most abundant
potential replacements for conventional oil will be more expensive than oil has been.” This statement is
supplied without references and on faith, but I actually give reference to the US Energy Information
Agency (EIA 1997c:37) that today it is “possible to produce about 550 billion barrels of oil from tar
sands and shale oil at a price below $30, i.e. that it is possible to increase the present global oil reserves
by 50 percent. And it is estimated that within 25 years we can commercially exploit twice as much in
oil reserves as the world’s present oil reserves” (SE:128). Thus, Holdren’s statement seems wrong.
Lomborg gets right the basic point that the dominance of oil in the world energy market
will end not because no oil is left in the ground but because other energy sources have
become more attractive relative to oil. But he seems not to recognize that the transition from
oil to other sources will not necessarily be smooth or occur at prices as low as those enjoyed
by oil consumers today. Indeed, while ridiculing the position that the world’s heavy oil
dependence may again prove problematic in our lifetimes, he shows no sign of
understanding (or no interest in communicating) why there is real debate among serious
people about this.
Holdren then agrees with me again, but accuses me of neglecting that the transition may not
necessarily be smooth or cheap. It is of course true that this could happen (nobody can predict anything
100%) but the basic argument in the book is exactly that the crisis, Holdren sees may happen is indeed
very unlikely – we have had this kind of fear of running out many times, and each time it has proven
incorrect, and moreover, we have good reason to believe that the many different energy sources can
give us sufficient energy also for future use at competitive prices.
Lomborg does not so much as offer his readers a clear explanation of the distinction—
crucial to understanding arguments about depletion—between “proved reserves” (referring
to material that has already been found and is exploitable at a profit at today’s prices, using
today’s technologies) and “remaining ultimately recoverable resources” (which incorporate
estimates of additional material exploitable with today’s technology at today’s prices but
still to be found, as well as material both al will be exploitable with future technologies at
potentially higher future prices). And, while noting that most of the world’s oil reserves lie
in the Middle East (and failing to note, having not even introduced the concept, that a still
larger share of remaining ultimately recoverable resources is thought to lie there), he
placidly informs us that it is “imperative for our future energy supply that this region
remains reasonably peaceful,” as if that observation did not undermine any basis for
complacency. (At this juncture, one of his 2,930 footnotes helpfully adds that this peace
imperative for the Middle East was “one of the background reasons for the Gulf War”!)
Holdren spends half this paragraph complaining that I do not explain all distinctions, while above
arguing that I make an obvious point (so that I presumably should not spend vast amounts of space
explaining everything). Even on a kind reading, this critique seems excessively compulsive.
Accepting that I do point out that most of the world’s oil reserves lie in the Middle East, Holdren
nevertheless criticizes me for not spending enough paper on digressing into other areas like
International Relations (the relative peacefulness of the Middle East and its consequences for
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 17/32
commodity trade). Again, it is unclear what standard this critique sets up, wanting the energy
discussion to take much more space or much less?
The final parenthetical comment entirely leaves out that I actually refer to a congressional research
paper for this statement.
Lomborg’s treatment of energy resources other than oil is not much better. He is correct
in his basic proposition that resources of coal, oil shale, nuclear fuels and renewable energy
are immense (which few environmentalists—and no well-informed ones—dispute). But his
handling of the technical, economic and environmental factors that will govern the
circumstances and quantities in which these resources might actually be used is superficial,
muddled and often plain wrong. His mistakes include apparent misreadings or
misunderstandings of statistical data—in other words, just the kinds of errors he claims are
pervasive in the writings of environmentalists— as well as other elementary blunders of
quantitative manipulation and presentation that no self-respecting statistician ought to
This is the paragraph in which Holdren gets tough. Here he says that the rest is not much better than
the treatment of oil (where Holdren agreed with much and found no concrete errors). Here he also says
Lomborg “is correct in his basic proposition,” but then that I make loads of misreadings or
misunderstandings as well as elementary blunders. These are harsh words Holdren should be able to
back up below.
He tells us correctly, for example, that the world has huge resources of coal, but in
observing that “it is presumed that there is sufficient coal for well beyond the next 1,500
years” he says nothing about the rate of coal use for which this conclusion might obtain.
Concerning the environmental questions that increased reliance on coal would raise, he
writes the following: “Typically, coal pollutes quite a lot, but in developed economies
switches to low-sulfur coal, scrubbers and other air-pollution control devices have today
removed the vast part of sulfur dioxide and nitrogen dioxide emissions.” To the contrary,
data readily available on the Web in the Environmental Protection Agency report National
Air Pollutant Emission Trends 1900–1998 reveal that U.S. emissions of nitrogen oxides
from coal-burning electric power plants were 6.1 million short tons in 1980 and 5.4 million
short tons in 1998. Emissions of sulfur dioxide from U.S. coal-burning power plants were
16.1 million short tons in 1980 and 12.4 million short tons 1998. These are moderate
reductions, welcome but hardly the “vast part” of the emissions.
The first main example of how I misread or misunderstand environmental data (“just the kinds of
errors [Lomborg] claims are pervasive in the writings of environmentalists”) clearly suggests a casual
reading of what I have written. Holdren claims that I’m correct in saying that the world has huge coal
resources, but when stating that the world has 1,500 years of coal, that I should say nothing about the
rate of coal use for which this conclusion might obtain. This is curious, because I use the same metric
throughout: that the years-of-consumption are measured from the year discussed (SE:127):
“As with oil and gas, coal reserves have increased with time. Since 1975 the total coal
reserves have grown by 38 percent. In 1975 we had sufficient coal to cover the next 218 years
at 1975 levels, but despite a 31 percent increase in consumption since then, we had in 1999
coal reserves sufficient for the next 230 years. The main reason why years-of-consumption
have not been increasing is due to reduced prices. The total coal resources are estimated to be
much larger – it is presumed that there is sufficient coal for well beyond the next 1,500 years.”
And if readers are curious about the 1,500 years, they (as almost everything else in the book) have a
reference, which can be consulted. Why not get hold of this reference before attacking me for
misreading or misunderstanding? And even if there was a problem, why would it be important, when
Holdren accepts that the main point (huge coal resources) is correct?
Holdren’s other claim is that my statement on diminished pollution from coal is incorrect. It is
unclear whether he believes that I am misreading or misleading, since he does not seem to have
checked my source, from which I take this statement. Anyway, Holdren claims that US emissions for
SO2 have only declined 23 percent since 1980 (0.23=1-12.4/16.1), rendering my statement incorrect.
However, Holdren seems to neglect that the US use of coal for coal-burning power plants has increased
dramatically over the past decades – since 1980 it has increased from 569.3 million short tons to 951.6
million short tons in 1999 ( Thus, the SO2 pollution
per quantity of coal burned has declined not just 23 percent but 56 percent. Moreover, why did Holdren
pick 1980 as the starting point, when clearly environmental improvements have been taking place since
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 18/32
at least 1970? And from 1970, the SO2 pollution per quantity of coal has dropped by 75 percent,
underscoring that the statement of vastly diminished pollution from coal burning is correct.
Moreover, I clearly state the very significant contribution to air pollution that is still being made by
coal but this goes unrecognized in the SA critique. For the benefit of those who do not have access to
my text I repeat below the unequivocal statement I make about the environmental hazard of coal
“Typically, coal pollutes quite a lot, but in developed economies switches to low-sulfur
coal, scrubbers and other air-pollution control devices have today removed the vast part of
sulfur dioxide and nitrogen dioxide emissions. Coal, however, is still a cause of considerable
pollution globally, and it is estimated that many more than 10,000 people die each year
because of coal, partly from pollution and partly because coal extraction even today is quite
Concerning nuclear energy, Lomborg tells us that it “constitutes 6 percent of global
energy production and 20 percent in the countries that have nuclear power.” The first figure
is right, the second seriously wrong. Nuclear energy provides a bit less than 10 percent of
the primary energy supply in the countries that use this energy source. (It appears that
Lomborg has confused contributions to the electricity sector with contributions to primary
energy supply.) After a muddled discussion of the relation between uranium-resource
estimates and breeding (which omits altogether the potentially decisive issue of the usability
of uranium from seawater), he then barely notes in passing that breeder reactors “produce
large amounts of plutonium that can be used for nuclear weapons production, thus adding to
the security concerns.” He should have added that this problem is so significant that it may
preclude use of the breeding approach altogether, unless we develop technologies that make
breeding much less susceptible to diversion of the plutonium while not making this
approach even more uneconomic than it is today.
Holdren is correct here that the 20 percent is an error – I should have written 20 percent of the
electricity generation from nuclear power (this will naturally be put up on the error page of my web
site). Naturally, one would like such errors not to occur, but to claim that it is a “serious error,” when
the figure is given as general information and not used in any arguments seems out of proportion.
The other critique, that Lomborg “barely notes in passing” the added security concerns seems again
out of proportion – the entire nuclear fission discussion takes up three paragraphs of 272 words, where
the security concern is mentioned twice. This is hardly “barely notes in passing.” For reference, here
are the three paragraphs (SE:129):
“Ordinary nuclear power exploits the energy of fission by cleaving the molecules of
uranium-235 and reaping the heat energy. The energy of one gram of uranium-235 is
equivalent to almost three tons of coal. Nuclear power is also a very clean energy source
which, during normal operation, almost does not pollute. It produces no carbon dioxide and
radioactive emissions are actually lower than the radioactivity caused by coal-fueled power
At the same time nuclear power also produces waste materials that remain radioactive for
many years to come (some beyond 100,000 years). This has given rise to great political
debates on waste deposit placement and the reasonableness of leaving future generations such
an inheritance. Additionally, waste from civilian nuclear reactors can be used to produce
plutonium for nuclear weapons. Consequently, the use of nuclear power in many countries
also poses a potential security problem.
For the moment there is enough uranium-235 for about 100 years. However, a special type
of reactor – the so-called fast-breeder reactor – can use the much more common uranium-238
which constitutes over 99 percent of all uranium. The idea is that while uranium-238 cannot
be used directly in energy production it can be placed in the same reactor core with uranium-235.
The uranium-235 produces energy as in ordinary reactors, while the radiation transforms
uranium-238 to plutonium-239 which can then be used as new fuel for the reactor. It sounds a
bit like magic, but fast-breeder reactors can actually produce more fuel than they consume.
Thus it is estimated that with these reactors there will be sufficient uranium for up to 14,000
years. Unfortunately these reactors are more technologically vulnerable and they produce
large amounts of plutonium that can be used for nuclear weapons production, thus adding to
the security concerns.”
Lomborg has some generally sensible things to say about the large contributions that are
possible from increased energy end-use efficiency and from renewable energy—on these
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 19/32
topics he seems, to his credit, to be more a contributor to the “environmental litany” than a
critic of it. But on these subjects as on the others, his treatment is superficial, uneven and
marred by numerous errors and infelicities. For example, he persistently presents numbers
to two- and three-figure precision for quantities that cannot be known to such accuracy: “43
percent of American energy use is wasted”; “the costs of carbon dioxide” emissions are
“0.64 cents per kWh”; plant photosynthesis is “1,260 EJ” annually. He makes claims, based
on single citations and without elaboration, that are far from representative of the literature:
“We know today that it is possible to produce safe cars getting more than 50-100 km per
liter (120–240 mpg).” (How big would these cars be, and powered how?) He bungles
terminology: “Energy can be stored in hydrogen by catalyzing water.” (He must mean “by
electrolyzing water” or “by catalytic thermochemical decomposition of water.”) And he
propagates a variety of conceptual confusions, such as the idea that grid-connected wind
power requires “a sizeable excess capacity” in the windmills because these alone “need to
be able to meet peak demand.”
Again, Holdren says I am right about many things, but still the treatment is criticized thoroughly.
Most incredibly, I am criticized for being too precise. Of course, there are a lot of numbers that we do
not know well, but the general idea in statistics is that if these numbers have been generated by a
process described by evenly distributed errors, the more precise number is still the best predictor of the
real number – or to put it more clearly: If studies have shown that 43 percent of all American energy
use is wasted, then the real number may very well be 38-48 percent, but had I rounded this figure down
to 40 or up to 45, it would have been worth less – and Holdren could then have criticized me for
conveying muddled results. Moreover, the 43 percent is actually described right off one of the best-selling
college environment books by professor Miller – is Holdren also claiming that he is wrong?
Holdren claims that I make claims that are far from representative of the literature, gives us one
example, but does not give us other references that show this statement to be incorrect or even an
indication of why this statement would be far from representing the literature.
I am accused of bungling terminology – it is true that ‘catalyzing’ was translated from the Danish
version, and should have been electrolyzing. But again, how important is this?
The conceptual confusion seems to stem from Holdren not reading the two paragraphs. If the wind-mills
were connected to a coal-fired power grid, then clearly they would not need to be able to meet
peak demand, but this clearly would not be a long-term renewable strategy. Rather, I discuss the
interaction of dams and windmills (SE:134):
“If the power grid is hooked to dams, these can be used for storage. Essentially, we use
wind power when the wind blows, and store water power by letting water accumulate behind
the dams. When there’s no wind, water power can produce the necessary electricity.
However, this implies that both wind power and water power require a sizeable excess
capacity, since both need to be able to meet peak demand. The solution also depends on
relatively easy access to large amounts of hydroelectric power.”
Of course, much of what is most problematic in the global energy picture is covered by
Lomborg not in his energy chapter but in those that deal with air pollution, acid rain, water
pollution and global warming. The last is devastatingly critiqued by Stephen Schneider on
page 62. There is no space to deal with the other energy-related chapters; suffice it to say
that I found their level of superficiality, selectivity and misunderstanding roughly consistent
with that of the energy chapter reviewed here. This is a shame. Lomborg is giving
skepticism— and statisticians—a bad name.
Given that Holdren could find little but a badly translated word and a necessary specification for
nuclear energy production in this chapter, I find comfort that he finds the other chapters of equal value.
However, I do find the tone of the entire critique surprisingly rough, indicating that Holdren found it
necessary to substitute good analysis with plain negative words.
John P. Holdren is the Teresa and John Heinz Professor of Environmental Policy at the
John F. Kennedy School of Government, as well as professor of environmental science and
public policy in the department of earth and planetary sciences, at Harvard University.
From 1973 to 1996 he coled the interdisciplinary graduate program in energy and
resources at the University of California, Berkeley. He is a member of the National
Academy of Sciences and the National Academy of Engineering.
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 20/32
John Bongaarts
Around the world, countries are experiencing unprecedented demographic change. The
best-known example is an enormous expansion in human numbers, but other important
demographic trends also affect human welfare. People are living longer and healthier lives,
women are bearing fewer children, increasing numbers of migrants are moving to cities and
to other countries in search of a better life, and populations are aging. Lomborg’s
unbalanced presentation of some of these trends and their influences emphasizes the good
news and neglects the bad. Environmentalists who predicted widespread famine and blamed
rapid population growth for many of the world’s environmental, economic and social
problems overstated their cases. But Lomborg’s view that “the number of people is not the
problem” is simply wrong.
First, Bongaarts write that things are going better and that the environmentalists’ predictions of
widespread famines were wrong. Okay. So, not much of ‘Science defending itself against Lomborg’
here. But then he sets the high standard of saying that I am wrong in saying that the number of people
is not the problem. We will see below that Bongaarts does not even try to lift the burden of proving this
statement and rather abandon it at the end. But, of course, its inclusion here makes the piece appear
Curiously, Bongaarts also neglects to write why I say the number of people is not the problem and
instead identify poverty (SE:48):
“We often hear about overpopulation of the Earth. We most often see overpopulation
illustrated by large glossy color pictures of tightly packed masses or overcrowded
underground stations.
The famous population biologist Paul Ehrlich in his best-seller on the population explosion
wrote: “Psychologically, the population explosion first sunk in on a stinking hot night in
Delhi. The streets were alive with people. People eating, people washing themselves, people
sleeping, people working, arguing and screaming. People reaching their hands in through taxi
windows to beg. People shitting, people pissing. People hanging off buses. People driving
animals through the streets. People, people, people.”
The point is, however, that the number of people is not the problem. Many of the most
densely populated countries are in Europe. The most densely populated region, Southeast
Asia, has the same number of people per square km as the United Kingdom. The Netherlands,
Belgium and Japan are far more densely populated than India, and Ohio and Denmark are
more densely populated than Indonesia.
Today, Ehrlich and others also agree on this. Instead, two other interpretations of
overpopulation have come into the fore. One of them conjures up images of starving families;
wretched, cramped conditions and premature death. Such images are real enough but are
actually the result of poverty rather than population density. We shall discuss poverty below.”
His selective use of statistics gives the reader the impression that the population problem
is largely behind us. The global population growth rate has indeed declined slowly, but
absolute growth remains close to the very high levels observed in recent decades, because
the population base keeps expanding. World population today stands at six billion, three
billion more than in 1960. According to U.N. projections, another three billion will likely be
added by 2050, and population size will eventually reach about 10 billion.
Here, Bongaarts accuses me of fudging the statistics. However, the ensuing documentation seems to
point its accusing finger the other way. Bongaarts says that the global population growth rate has
indeed declined slowly, but the absolute growth remains close to the top. First, he makes it sound like I
don’t say that, but I do, as can be seen here in the relevant paragraph from the book (SE:47):
“As demonstrated in Figure 13 [graph of the rate and absolute number of growth], the
growth of the global population peaked in the early 1960s at just over 2 percent a year. It has
since fallen to 1.26 percent and is expected to fall further, to 0.46 percent, by 2050. Even so,
the absolute growth of the population did not peak until 1990, when almost 87 million people
were added to world population. Today growth is around 76 million per year and will have
fallen to approximately 43 million by 2050.”
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 21/32
Second, when Bongaarts say that the rate has only declined “slowly”, though it has actually declined
from 2.17% in 1964 down to 1.26% today (more than a 40% decline). Bongaards claim that the
absolute growth remains close to the very high levels of the recent decades – yet today’s 76 million is
the lowest number in the last two decades.
I also show the UN graph of population development from 1750-2200 (SE:46), with the latest 2000
UN estimates, where I point out that the expectation is actually 9.3 billion in 2050, and the stable
population estimated at almost 11 billion (not 10, as Bongaarts claim):
“The UN continuously calculates how many of us live on Earth now and will in the future.
These figures have been adjusted downward by 1.5 billion for 1994, 1996 and 1998 and
upwards again by half a billion for 2000, because of changes in the speed with which the
fertility falls in different countries. The latest long-term forecast from 2000 can be seen in
Figure 11. It shows that there will be almost 8 billion people on Earth by 2025 and about 9.3
billion by 2050. It is estimated that the world’s population will stabilize just short of 11 billion
in the year 2200.” (SE:47).
Apparently, Bongaarts’ paragraph was supposed to show that I fudged the statistics, but not only did
Bongaarts not show this, indeed his own argument seemed curiously fudged.
Any discussion of global trends is misleading without taking account of the enormous
contrasts among world regions. Today’s poorest nations in Africa, Asia and Latin America
have rapidly growing and young populations, whereas in the technologically advanced and
richer nations in Europe, North America and Japan, growth is near zero (or, in some cases,
even negative), and populations are aging quickly. As a consequence, nearly all future
global growth will be concentrated in the developing countries, where four fifths of the
world’s population lives. The
projected rise in population in the
developing world between 2000
and 2025 (from 4.87 to 6.72
billion) is actually just as large as
the recordbreaking increase in the
past quarter of a century. The
historically unprecedented
population expansion in the poorest
parts of the world continues largely
Again, Bongaarts seem to accuse me of not
taking into account the enormous differences
among world regions, though one of the most
consistent factors in the book is the
presentation of data for both developed and
developing countries. Yet, I did not present a
chart for population growth in the developing
world, so I will bring it here (Figure 1). Here,
again we see almost the same pattern as in Figure 13 from the book (SE:47), and indeed we also see
how questionable Bongaarts analysis is: He claims that the historically unprecedented population
expansion continues largely unabated, yet, the growth of 74 million in 2001 is the lowest since 1984,
and the rate has dropped from the maximal 2.6% to 1.5% today. The claim that the growth from 1975-2000
is almost the same as the growth 2000-2025 is technically true, but very misleading – the growth
in the early quarter century period came from ever increasing numbers of people being added, whereas
every year from 2000 onwards will see ever fewer numbers being added.
Past population growth has led to high population densities in many countries. Lomborg
dismisses concerns about this issue based on a simplistic and misleading calculation of
density as the ratio of people to all land. Clearly, a more useful and accurate indicator of
density would be based on the land that remains after excluding areas unsuited for human
habitation or agriculture, such as deserts and inaccessible mountains. For example,
according to his simple calculation, the population density of Egypt equals a manageable 68
persons per square kilometer, but if the unirrigated Egyptian deserts are excluded, density is
an extraordinary 2,000 per square kilometer. It is therefore not surprising that Egypt needs
to import a large proportion of its food supply. Measured properly, population densities
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 22/32
have reached ext remely high levels, particularly in large countries in Asia and the Middle
It is curious that Bongaarts, trying to show how wrong I am, is forced to use a hypothetical argument
(of Egypt) and does not even find it necessary to point out that I never make this argument. The real
challenge is in the text shown above, where I point out some of the most densely populated areas of the
world are in Europe. Is Bongaarts obvious point at all relevant to my examples of e.g. the Netherlands
being far more densely populated than India? We are never told.
Why does this matter? The effect of population trends on human welfare has been
debated for centuries. When the modern expansion of human numbers began in the late 18th
century, Thomas Robert Malthus argued that population growth would be limited by food
shortages. Lomborg and other technological optimists correctly note that world population
has expanded much more rapidly than Malthus envisioned, growing from one billion to six
billion over the past two centuries. And diets have improved. Moreover, the technological
optimists are probably correct in claiming that overall world food production can be
increased substantially over the next few decades. Average current crop yields are still
below the levels achieved in the most productive countries, and some countries still have
unused potential arable land (although much of this is forested).
Again, Bongaarts almost tell us that I am correct, though he does underplay the argument in two
rather conspicuous ways. He says diets have improved. That is true, though an understatement.
Actually, the global availability of calories has increased from 2257 calories in 1961 to 2792 in 1998,
an increase of 24%, and for the developing world an even greater increase of 38% from 1932 to 2663
calories (FAO 2001a).
Moreover, he says that food production is probably capable of being increased substantially because
of yield increases and “some countries still have unused potential arable land (although much of this is
forested).” This, again, is a serious understatement for arable land and an overstatement for forests. In
the latest FAO report on Agriculture towards 2030 (FAO 2000d), FAO explicitly discusses the use of
land in agricultural production and the extra availability of agricultural land.
FAO estimates that at present about 1.5Gha or 11% of the globe’s land surface is used for
agriculture, and an additional 2.9Gha has crop production potential (FAO 2000d:98). Of this area about
45% is forested (FAO 2000d:103). So there is ample room for bringing in new agricultural land and
none of it needs be forested. Actually, the FAO estimate for the developing countries (developed will
probably not increase their area at all) a much lower increase in land use till 2030 of about 0.12Gha, an
increase of 12%. This means that the agricultural land usage will go from 32% of the potential land use
to 36% in 2030. Globally, this probably means an increase in agricultural land use from 11% to 12% of
the land surface.
Agricultural expansion, however, will be costly, especially if global food production has
to rise twofold or even threefold to accommodate the demand for better diets from several
billion more people. The land now used for agriculture is generally of better quality than
unused, potentially cultivable land. Similarly, existing irrigation systems have been built on
the most favorable sites. And water is increasingly in short supply in many countries as the
competition for that resource among households, industry and agriculture intensifies.
Consequently, each new increase in food production is becoming more expensive to obtain.
This is especially true if one considers environmental costs not reflected in the price of
agricultural products.
This is one of the stunningly simplistic analyses from the environmental Litany: Since we have
already used the best land sites with the easiest irrigation etc., an expansion of the agricultural
production will lead to higher prices. However, this clearly neglects the historical trend towards ever
more efficient production and better crops which has given us steadily declining prices. However,
Bongaarts simply does not supply any evidence that his scenario of increasing prices should become
true – yet, both IFPRI, USDA and the World Bank predicts ever lower prices (IFPRI 1997, 1999; ERS
1997:4; USDA 2000b; Mitchell et al. 1997), which is a continuation of the almost constant decrease in
food prices since 1800 (data on wheat prices from 1316-2000 in SE:62).
Lomborg’s view that the production of more food is a non-issue rests heavily on the fact
that world food prices are low and have declined over time. But this evidence is flawed.
Massive governmental subsidies to farmers, particularly in the developed countries, keep
food prices artificially low. Although technological developments have reduced prices,
without these massive subsidies, world food prices would certainly be higher.
Lomborg’s reply to Scientific American January 2002 critique, 4-Jan-02 12:06 23/32
The last hypothetical sentence is true – without subsidies, prices would be higher, but the argument
lies with the trend of the price, which is downwards, and has been so since early 1800s. It is still
curious that Scientific American lets their critic ‘defend science’ by referring to such fickle speculation
instead of giving real references. Again, this could possibly be due to the fact that all major food
analysis institutions still predict decreasing food prices (as above, IFPRI 1997, 1999; ERS 1997:4;
USDA 2000b; Mitchell et al. 1997).
The environmental cost of what Paul R. and Anne H. Ehrlich describe as “turning the
earth into a giant human feedlot” could be severe. A large expansion of agriculture to
provide growing populations with improved diets is likely to lead to further deforestation,
loss of species, soil erosion, and pollution from pesticides and fertilizer runoff as farming
intensifies and new land is brought into production. Reducing this environmental impact is
possible but costly and would obviously be easier if population growth were slower.
Lomborg does not deny this environmental impact but asks unhelpfully, “What alternative
do we have, with more than 6 billion people on Earth?”
Surprisingly and without any statistical backing, Bongaarts invoke the doomsday metaphor of
“turning the earth into a giant human feedlot.” However, as we saw above, we are currently using about
11% of the global land surface area for agriculture, and in 2030, where we will be feeding more than 8
billion much better (3100 calories per person) we will be using 12% – hardly “turning the earth into a
giant human feedlot.” Moreover, had Bongaarts accessed the available statistics, he could have seen
that the increase in agricultural land use was actually bigger over the last 25 years than the coming 30
years (increasing land use by 0.173Gha, compared to the expected increase of 0.12Gha, FAO
Again, Bongaarts actually acknowledges that I do discuss the environmental impact, and yet only
says I ask the unhelpful question of what are the alternatives? Yet, this is misleading on at least three
counts. First, I do give an insight as to how to control population in the long run – this is a question of
poverty reduction and development (SE:46). This is why it was also problematic that Bongaarts cut off
the quote at the top of his article where I also point out poverty (SE:48).
Second, I do actually show some of the bad consequences of listening to parts of the environmental
movement in their advice as to abating some of the problems with food production. An often heard call
is to move to organic farming, because it would mean less fertilizer runoff. Yet, this would have other,
much more drastic consequences (SE:197):
“Today, it is estimated that 40 percent of all crop nitrogen comes from synthetic fertilizer, and
about one-third of human protein consumption depends on synthetic fertilizer. Moreover,
fertilizer allows us to produce more food on less farmland. This is one of the reasons why the
global population could double from 1960 to 2000 and get better fed, although farmland area
only increased 12 percent.
This should be compared with the quadrupling of farmland from 1700 to 1960 which of
course came from the conversion of large tracts of forests and grasslands. Essentially, the
extraordinary increase in fertilizer availability from 1960 onwards has made it possible to avoid
a dramatic increase in human pressure on other natural habitats. Had fertilizer use remained at
the 1960 level, we would need at least 50 percent more farmland than the present-day use – the
equivalent of converting almost a quarter of the global forests. Over the coming decades to
2070, were we to forsake fertilizer, the need for farmland to feed 10 billion people better would
place ever higher demands on the globe – one study puts the farmland requirement at an
impossible 210 percent of the land surface area. Thus, synthetic fertilizer has been and
especially will be crucially important in feeding the world while leaving sufficient space for
other species. However, the doubling of globally available nitrogen has also caused problems.”
[The text goes on to talk about the problems of fertilizer runoff problems.]
Third, it is amazing that Bongaarts criticizes me for not answering the question (which I do) and yet
does not himself come up with any answer. This becomes evident in the following paragraph.
Lomborg correctly notes that poverty is the main cause of hunger and malnutrition, but he
neglects the contribution of population growth to poverty. This effect operates through two
distinct mechanisms. First, rapid population growth leads to a young population, one in
which as much as half is below the age of entry into the labor force. These young people
have to be fed, housed, clothed and educated, but they are not productive, thus constraining
the economy. Second, rapid population growth creates a huge demand for new jobs. A large
number of applicants for a limited number of jobs exerts downward pressure on wages,