The Population Bomb, Nuclear Winter and the Role of Science in Public Advocacy

In 1996 Cornell astrophysicist and science popularizer Carl Sagan posed the question, "What are conservatives conserving?" It was not something he asked lightly. The question appeared in his final book following a prolonged battle with bone marrow disease. Faced with his own mortality, he wanted to understand the individuals whose actions, whether consciously or not, threatened the lives of so many others. Sagan was a passionate advocate for science but, first and foremost, he was an advocate for humanity itself.

A kindred spirit, someone representing the same passion for science and his fellow man, is found in the Stanford biologist Paul Ehrlich who was both a colleague and a friend of the late astronomer. Both scientists have been attacked by the political right with as much venom as their scientific results have produced admiration from their colleagues. Ehrlich has published hundreds of peer-reviewed studies as well as dozens of books in his long career and is now featured in a profile by Steve Olson at

Ironically, at this time last year Ehrlich was under attack. Hoover Institute Fellow Mary Eberstadt, writing in the conservative Catholic journal First Things, pilloried Ehrlich's 1968 book The Population Bomb as an "apocalyptic thesis" that amounted to little more than "doom-mongering." The passage that Eberstadt objected to was the following:

The battle to feed all of humanity is over. In the 1970s and 1980s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now.

Eberstadt held that such a shocking claim was an example of a scientist trying to gain publicity by publishing his "direst thoughts about humanity" and that it was part of a general trend that hoped to undermine support for the Catholic ban on contraception (coincidentally decreed by the Pope just two months before The Population Bomb's release). One problem with Eberstadt's condemnation is that the claim she objects to is actually true. An estimated 100 to 200 million people, mostly children, died of hunger in those two decades alone (and the trend hasn't slowed down).

Nevertheless, for Eberstadt and many conservative pundits like her, the general feeling is that scientists should stick to assembling the facts and leave the commentary to people like them. Whether the issue is environmental degradation, global warming, stem cells, nuclear technology or concerns about genetically modified foods and chemical additives the resounding call from conservatives is that scientists should butt out of the debate centering on . . . science.

The most cited example of "inappropriate" scientific meddling in political issues was the nuclear winter debate from the early 1980s championed by none other than Carl Sagan and Paul Ehrlich. Today it is most frequently used as a justification to cast doubt on the scientific consensus for global climate change. Michael Crichton, author of Jurassic Park and The Andromeda Strain, made headlines a few years ago when he gave a speech before the California Institute of Technology stating:

[N]uclear winter was a meaningless formula, tricked out with bad science, for policy ends. It was political from the beginning, promoted in a well-orchestrated media campaign that had to be planned weeks or months in advance. . . . I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you're being had.

For nearly two decades prior to his death in 1996 Carl Sagan had been the focus of repeated attacks by conservative critics who objected to his public advocacy of environmental concerns and his opposition to nuclear war. Most people today remember Sagan as he was presented in his PBS series Cosmos; as a frail waif of a man, permanently attired in a turtle-neck sweater and who had a funny way of pronouncing billions. But few remember him for his outspoken advocacy for the issues he believed in, issues that wouldn't become mainstream until their champion left the shores of our cosmic ocean.

In 1983 Sagan penned an article entitled "The Nuclear Winter" for Parade magazine, a Sunday supplement that reached an audience of an estimated twenty million readers. This was the height of Reagan's America, a place where rhetoric about "the evil Empire" was as pervasive as the idea that a nuclear war could be won (the fact that a policy known as MAD, or Mutual Assured Destruction, actually existed and wasn't immediately ridiculed is just one example illustrating the tenor of the time). After summarizing the evidence that would be published in the journal Science the following month, Sagan wrote to the American public that:

It is now almost 40 years since the invention of nuclear weapons. We have not yet experienced a global thermonuclear war -- although on more than one occasion we have come tremulously close. I do not think our luck can hold forever. Men and machines are fallible, as recent events remind us. Fools and madmen do exist, and sometimes rise to power. Concentrating always on the near future, we have ignored the long-term consequences of our actions. We have placed our civilization and our species in jeopardy.

The next day, October 31st, Carl Sagan attended a conference in Washington, D.C. entitled "The Long-Term Worldwide Biological Consequences of Nuclear War" headed by himself and Paul Ehrlich. Right on the heels of Sagan's paper on nuclear winter, popularly known as TTAPS after the first letter of each authors' last name, Paul Ehrlich also published a study that looked at the biological threat posed by nuclear winter. As reported by Time magazine:

Sagan and Ehrlich picked as their "baseline case" a 5,000 megaton war. . . The results of such a war: a cloud of dust and smoke weighing 1.2 billion tons rapidly envelops the Northern Hemisphere and swiftly swirls into the Southern Hemisphere as well, blocking out 90% or more of the sun's light. Surface temperatures plunge to an average of --13° F and remain below freezing for three months, even if the war is fought in the Northern Hemisphere summer. Nothing can grow; those humans who survive the blast and radiation of the explosions freeze or starve to death. At best, Ehrlich figures, small bands of hunters and gatherers would be left in the Southern Hemisphere.

Both scientists also appeared together on ABC Nightly News to advocate their findings and both wrote numerous articles and gave public lectures. The condemnations came pouring in. Conservative heavyweights such as Henry Kissinger, Richard Perle and Edward Teller denied their science in writing and on television. Conservative newspapers and magazines attacked their work even before their studies had been released and the accusations of political bias continued coming. Political scientist Leon Gouré, an analyst at the military think tank known as the RAND Corporation, maligned them in The Washington Times as scientists "who engage in 'doomsday' predictions." Televangelist Jerry Falwell claimed they were promoting an "Armageddon ideology," while conservative commentator William F. Buckley, Jr., editor of the National Review, condemned such advocacy as "politically inspired lying."

Nevertheless, their work fundamentally changed the debate on nuclear weapons. In a February 12, 1985 interview with the New York Times President Ronald Reagan detailed nuclear winter as a reason why the US and Russia should reduce their stockpiles:

A great many reputable scientists are telling us that such a [nuclear] war could just end up in no victory for anyone because we could wipe out the Earth as we know it.

And, according to Andrei A. Kokoshin, former First Deputy Minister of Defense in Russia in his 1998 historical study of Soviet Strategic Thought (p. 136):

In the first half of the 1980s, the findings of U.S. and Soviet physicians on the aftermath of nuclear war and the 'nuclear winter' theory noticeably influenced the Soviet leadership.

Furthermore, to the chagrin of those who announced that the threats from nuclear winter had been exaggerated, a follow up study in 2007 published in the Journal of Geophysical Research (pdf here) corroborated the bulk of their findings:

A global average surface cooling of -7°C to -8°C persists for years, and after a decade the cooling is still -4°C. Considering that the global average cooling at the depth of the last ice age 18,000 yr ago was about -5°C, this would be a climate change unprecedented in speed and amplitude in the history of the human race. The temperature changes are largest over land ... Cooling of more than -20°C occurs over large areas of North America and of more than -30°C over much of Eurasia, including all agricultural regions.

While disagreements over the specifics remain (afterall, computer models are based on many uncertainties) the evidence is consistent that even a low-level nuclear war would be devastating to human civilization, a view even shared by those critics who favor the term "nuclear autumn." What is most revealing about the political firestorm that erupted over the nuclear winter controversy is that the fiercest critics objected based primarily on politics not science. It was a turf war and scientists were fundamentally challenging powerful elements in both military and foreign policy circles, and they were winning. In the free market of ideas a scientific argument had trounced military drum beating. Should Sagan and Ehrlich have instead published their papers and then sat idly by to wait for political action? Supposing that their science was fatally flawed, would there have been any harm (other than to their reputations) by presenting their ideas to the public? When important issues that affect millions of people are at stake doesn't the harm of inaction outweigh the harm of caution?

Science, through it's careful reasoning and slow, plodding rate of change, is an inherently conservative doctrine. This is what gives scientific findings such weight and why scientific consensus, while not foolproof, is a powerful and persuasive source of knowledge. Political conservatives would do well to understand this conservative nature of the scientific enterprise. Scientists are trained to be devoted to finding patterns in evidence and to mercilessly critique the conclusions of their colleagues. Unlike in politics, scientists rise more through merit than personality. They represent a culture that is badly missing in our political discourse: skepticism and honest debate.

So what is the harm in having more scientific voices, of all stripes, present in the public sphere? Economic analysts are everywhere in the mainstream news offering their prescription for a litany of social ills. Doctors and health professionals appear nightly to discuss the latest medical scares. Political scientists give their estimates on what Sarah Palin's resignation speech means for the 2012 elections (not a lot is the general conclusion). Why shouldn't scientists offer their skills to important questions of public policy? Leaving the data in the hands of political pundits and partisans is abdicating a responsibility that should be viewed as a public trust.

In the final analysis, scientific advocacy is only as good as the science it's based upon. As a world-renowned scientist, Paul Ehrlich has been championing the public's right to know for more than forty years. Like his colleague who dared to dream that science could help build a better world, our society can only benefit from his questions, his search for answers and his willingness to put his conclusions into action.


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"Scientists are trained to be devoted to finding patterns in evidence and to mercilessly critique the conclusions of their colleagues."

They may be trained to do that at school, but in reality, scientists work for big business and the military. The military, with its bloated budget and limited oversight, can afford to buy up scientific work that might someday hold military value without regard to peer review. Bad work is often kept alive for political reasons as well. In big business, science is done for profit, and anything that challenges the profitability of a scientific breakthrough, like honest peer review, can be crushed with political might. I'm sorry science, but gone are the days of driven scientists working in a lone lab, testing things out on themselves, working toward a better understanding of the truth, for the sake of truth alone.

So, even though he's a self-righteous asshole, I have to agree with Crichton on this. Scientific consensus is not necessarily a sign of anything other than political scheming.

By John Gathly (not verified) on 04 Aug 2009 #permalink

Those who say that scientists should shut up and just produce data are often the same people who jeer at Hollywood types who speak out on social issues. The dismissal of 'mere actors' or 'pointy-headed scientists' is used selectively to marginalize people who disagree with them. They have no problem citing and lauding scientists and actors who agree with them, having a conservative outlook apparently counteracts the effects of being an entertainer or scientist.

I am overwhelmed with the urge to feed this troll.

1: Most scientists do not work for industry. They work for government funded research institutions or universities. And of those that work in industry, as in any human occupation, there will be a few willing to compromise their principles for money, but only a few. As for the rest, coercing research results to fit some a priori presumption is a definite no-no, and is usually exposed and rejected, because that is just the way science works. Peer review and experiment replication and all that.

2: Nuclear Winter, as an ideology, holds zero benefit for industry. In fact quite the opposite - it proposes they cease development in nuclear armaments. Not good for them. They have no incentive whatsoever to support it. But they do have an incentive to get trolls like you on their side against it (you may not think so, but your diatribe supports them by dismissing the consensus).

3: Scientific consensus is not the same kind of consensus as a political or managerial consensus. Just as a scientific theory is not just a guess, scientific consensus is not just bowing to political pressure and saying you agree with an ideology. Scientific consensus is the weighted result of the research, and is arrived at independently of the human component, in just the same manner as scientific theories are strengthened. Indeed this use of the word 'Consensus' is very close in meaning to the scientific use of the word 'Theory'.

4: While appeal to authority is poor reasoning, when the authority maintains some position and there are no authoritative valid criticisms, I tend to go with the authority. Unless I am one of those who know and work in the field and am myself one of the authorities, in which case I would trust myself to know better. But I never accept the criticisms from those who have not done the work themselves, I go to the sources. Crichton has not done the work. Sagan and Ehrlich have. You know which I pick to listen to.

I have much the same answers for the Climate Change denialists.

By Gray Gaffer (not verified) on 04 Aug 2009 #permalink

Perhaps it was not intended, but there are several false binary oppositions that have been set up in this post and they bug me.

For instance :

Having lived through the 1970s and 1980s, I don't remember anyone advocating nuclear war. I do remember the nuclear freeze and the nuclear disarmament movements. But I don't remember anyone being "pro nuclear war".

Yet here is your text

"For nearly two decades prior to his death in 1996 Carl Sagan had been the focus of repeated attacks by conservative critics who objected to his public advocacy of environmental concerns and his opposition to nuclear war. "

So conservative critics objected to his opposition to nuclear war and attacked him for it? For simply being opposed to nuclear war?

I know - you didn't mean it that way, but when one is trying to assemble a polemic which pits the rational against the irrational, the rational lose points when they make sweeping statements that basically dehumanize those they oppose. Conservatives may be irrationally motivated by things like religion and false suppositions, but one doesn't have to paint them as somehow seeking the deaths of all in one glorious holocaust, nor as such troglodytes that they'd abuse a man for saying "Nuclear War is bad."

Carl Sagan had specific prescriptions for the Nuclear Arms race. Those policies where what he was attacked for and, as it turned out, the evil conservatives that sought to confront the Soviets (somnething I fully opposed at the time) actually ended the arms race.

But the issue isn't gone - Iran and North Korea have made that clear. Is anyone up to lecturing them on Nuclear Weapons policy?

By Adam Sullivan (not verified) on 04 Aug 2009 #permalink

@Gray Gaffer

I understand why you characterize me as a troll, and make assumptions about me from that characterization. However, I don't view myself that way, and I'd like to clarify my position on a few things, just for the public record.

I have nothing against Carl Sagan or any of his theories. Sagan was the first to turn me onto scientific thinking, and I affectionately refer to him as Papa Sagan for that very reason. I believe fully in the dangers of climate change. I believe in the possibility of nuclear winter. All I don't believe in, is the fact that science is some kind of holy order that produces people only interested in teasing the truth out of nature for no other reason than the high holy act of doing so. There are politics in any organization of people, especially an organization of educated people, like a university. Politics, social climbing, success seeking, jealousy of other's accomplishment, greed and personal enrichment will often come before any need to "mercilessly critique" one's colleagues and get at the "truth." I think science should work the way you say it does, and people should be given tons of funding for nothing more than the pursuit of truth, but until that happens, it's big business and its shadow (i.e. government) that run the world. And that world includes these Universities that are either funded by private interests (big business) or public money which mostly comes out of the Pentagon.

By John Gathly (not verified) on 04 Aug 2009 #permalink

BTW - your text:

"Nevertheless, their work fundamentally changed the debate on nuclear weapons. In a February 12, 1985 interview with the New York Times President Ronald Reagan detailed nuclear winter as a reason why the US and Russia should reduce their stockpiles:"

Yet the articles citing the opposition of Conservatives to said work were published after February 12,1985.

For example, the Buckley quote is from National Review 12/19/1986, Vol. 38 Issue 24, p19-20, 2p.

Your text implies a time progression that is the inverse of reality.

Really - are you making a simplistic rendering of what was a complex, multi-faceted and difficult debate about what few options seemed to exist in keeping nuclear anhilation at bay in order to create a false comparison to contemporary debate on complex and multi faceted issues that folks on "both" sides seem hell bent on oversimplifying?

Remember - what Sagan advocated as policy (a policy I supported) turned out to be wrong. I have no problem admitting - I was wrong on on the nuclear arms race when it was happening. So was Carl Sagan, regardless of who then accepted nuclear winter or not at the time.

By Adam Sullivan (not verified) on 04 Aug 2009 #permalink

@Adam: Having lived through the 1970s and 1980s, I don't remember anyone advocating nuclear war. I do remember the nuclear freeze and the nuclear disarmament movements. But I don't remember anyone being "pro nuclear war".

You may want to look at the history of American nuclear strategy. That might jog your memory.

As for the historical progression, yes, I chose a later quote from Buckley to illustrate his true feelings about Sagan's advocacy. I could have chosen many others. How about this one cited from Davidson's biography Carl Sagan: A Life (p. 373). Just after the two debated on Nightline along with Henry Kissinger, Edward Teller and Holocaust survivor Elie Wiesel:

Ann Druyan angrily recalls that during a break, she, Sagan, and Wiesel were talking. Buckley "walked in, obviously drunk--very drunk--and said: 'Oh, who is this group, the Concerned Holocaust Survivors?' To Elie Wiesel!? It just took our breath away." Wiesel made a motion indicating that they should ignore the remark. "Carl was ready to take Buckley and just, like, nail him up against the wall."

Unfortunately, the phenomenon of scientific consensus can be seen as a "powerful and persuasive" force for the channeling of investigation into certain avenues and preventing others from appropriate investigation. I recently read Lee Smolin's book "What's Wrong with Physics" detailing the predominance of string theory among theoretical physicists resulting in the explicit stifling of research into quantum gravity. The existence of this phenomenon was reinforced by Seth Lloyd's anecdote in "Programming the Universe" about being pulled off a "crazy" quantum gravity project at Rockefeller University by the head of the university and a couple of professors (Lloyd did eventually come to like the man after all). And, of course, we know the consternation, upset and resistance from scientists at the turn of the 19th century when they lost the aether.

Pete #9 - except that this weeks' Science magazine contains a serious discussion of quantum gravity.

People outside of science believe that science works the same way that Hollywood or Politics does - with the discussion controlled by a tight elite. But in fact in the world of science, a young graduate student with the right idea can topple a major theory. In practice, this doesn't happen much because theories don't get to be theories until they've stood the test of data. Scientists dropped the aether very quickly as soon as they (1) had data against it [Mickelson and Morley] and (2) had a theory explaining why it wasn't necessary [Einstein]. A better example is quantum mechanics where scientists were wary of it for a long time, but scientists were working hard to disprove it as soon as it appeared.

String theory is still the best guess as to what is actually going on. But every string theorist will tell you that string theory might well be wrong. The reason quantum gravity has been losing (note not lost!) to string theory is that to the best approximation, quantum gravity is filled with infinities. It may be that the symmetries work out so QG is plausible but at this point, the likelihood of that happening is small.

Scientists tend to complain about large factory labs run by senior professors getting money, but that should not be confused with some centralized conspiracy to prevent the study of other phenomena. The excitement scientists find when a new experiment overturns a theory or a new theory explains messy experiments with a simple summation is very clear. The reason scientists trust the theory of evolution, of continental drift, or of climate change is because the data support it and no other theory fits the data.

PS. Continental drift is a good example of the process by which science accepts a new theory. In the 1920s, Wegener didn't have a mechanism or data to explain it. Once the mechanism was discovered and the data appeared (in the 1950s), it was accepted very quickly (within a decade).

Not claiming a conspiracy! As I said, scientific consensus can be a channeling force (or belief) that, in the case of quantum gravity at least, has caused apparently many senior scientists, according to the writings of two involved and credible theoretical physicists, to force research in one direction and actively prevent research in another direction. As I remember, Lloyd's experiences were in the early 90's and Smolin's book is copyright 2006, so perhaps this is still an issue.

The background to my post is my graduate education in psychology (clinical) when academic psychology was defensively and effectively promoting training in the theoretical and methodological bases of science as fundamental to the field. From that time I have always been very interested in the role of belief within the scientific community, from Thomas Kuhn through my recent reading of Smolin, Richard Dawkins, Francis Collins, etc. So, no surprise to read that support for string theory is sufficiently fervent to strongly bend the research direction. Seems like typical humans to me. But supporting conspiracy theories? Hardly.

Finally, as a non-physicist reader of Smolin, I recall that it is exactly the presence of many infinities that makes string theory problematic in his view. But I certainly can't argue one way or the other.

To comment on continental drift, in 1959 I took a required MS level geology course. Half of the course was devoted to debunking continental drift. By 1966 it was clear that the continents have moved. This is the best example I know of Kuhnian paradigm shift in science.

By Jim Thomerson (not verified) on 16 Aug 2009 #permalink

Thanks for this needed history lesson on Carl's role in ending the nuclear weapon escalation between the US & USSR. It's by no means a complete history, but goes a long way is fleshing things out.

I would recommend listening to the CFI free inquiry podcast which contains the essay "The Gifts of Carl Sagan" by Lauren Becker. It helps fill in more of the events of the 80's.

This was the height of Reagan's America, a place where rhetoric about "the evil Empire" was as pervasive as the idea that a nuclear war could be won (the fact that a policy known as MAD, or Mutual Assured Destruction, actually existed and wasn't immediately ridiculed is just one example illustrating the tenor of the time).

I'm not sure what you're trying to say, but Mutual Assured Destruction and the Reagan administration's seeming belief that nuclear war was "winnable" were largely at odds from each other; MAD relied on the belief that a nuclear power would not attack an enemy if they believed that the enemy's return strike would destroy them. MAD relied on creating the impression that nuclear war was unwinnable; more than that, that a nuclear war would be a disaster from which no participant could recover from. MAD proponents were actually somewhat pleased to see the Nuclear Winter hypothesis gain traction, because it made nuclear war more threatening, and therefor, made MAD more plausible. They used nuclear winter in their arguments. However - they disliked Carl Sagan, and often did not credit him with the genesis of the Nuclear Winter hypothesis, because Sagan was a proponent of nuclear arms reduction, which was antithetical to MAD.
Interpretation is complicated by the fact that while nearly all journalists, policiticans, and pundits tried to depict the controversy over nuclear weapons policy as having two sides, there were in fact at least three broad but mostly conflicting categories of nuclear weapons philosophy; the "prepare to win" crowd, exemplified by people Reagan and Teller, the disarmament crowd, exemplified by people like Sagan, and the MAD crowd, exemplified by people like Robert McNamara. Carter's "countervailing strategy" was something of a compromise between "prepare to win" and MAD.