The Public and Climate Change
Since antiquity, people believed that human activity might alter a local climate, but could scarcely affect the grand balances that governed the planet overall. Gradually scientists, aided by science journalists, informed the minority of educated people that modern civilization might cause global warming, sometime far in the future. In the early 1970s, the question began to concern a wider public. By then most people had come to fear planet-wide harm from technology in general. Now an onslaught of droughts suggested we were already damaging the climate. The issue was confused, however, when experts debated whether pollution would bring global warming or, instead, an appalling new ice age. By the end of the 1970s, scientific opinion had settled on warming as most likely, probably becoming evident around the year 2000 — that is, in a remote and uncertain future. (In continuation page:) By the end of the 1970s, scientific opinion had settled on warming as most likely, probably becoming evident around the year 2000 — which at that point lay in a remote and uncertain future. Some scientists nevertheless went directly to the public to demand action to avert the warming, and a few politicians took up the issue. During the hot summer of 1988, a few outspoken scientists, convinced by new evidence that rapid climate change might be imminent, made the public fully aware of the problem. Scientific discussions now became entangled with fierce political debates over the costs of regulating greenhouse gases. Corporations and conservatives spent large sums to sow uncertainty and denial of any danger from global warming. It was not until around 2005 that American media reported clearly that scientists had resolved the controversy, while films and ominous weather events gave citizens a better idea of what global warming might mean. The majority of Americans had moved gradually to a vague feeling that some kind of action should be taken. But the issue became increasingly politicized; on the right, doubt and denial increased. Stronger worries meanwhile grew among people in most other countries. (This essay deals mainly with the United States, but until the late 1990s opinions were generally similar in other industrialized nations. The response of American policy-makers is covered in an essay on Government: the View from Washington.)
From ancient times, people suspected thats human activity could change the climate of a territory over the course of centurie. For example, Theophrastus, a pupil of Aristotle, told how the draining of marshes had made a particular locality more susceptible to freezing, and he speculated that lands became warmer when the clearing of forests exposed them to sunlight. Renaissance and later scholars who pored over ancient manuscripts saw that deforestation, irrigation, and grazing had altered the lands around the Mediterranean. Surely these human interventions had affected the local weather? The scholars thought it plausible, and common people adopted the notion.(1) Human and Planetary Forces (1800s-1930s)
The most striking change, obvious within a single lifetime, was the conversion of Eastern North America from forest to croplands. By the early 19th century many believed the transformation was altering the region’s climate — probably for the better. Count C.-F. Volney, traveling in the United States around 1800, was told by settlers everywhere from Kentucky to upstate New York that the local climate had grown warmer and milder promptly after the forests were cleared. When sodbusters took over the Great Plains they were told that “rain follows the plough.”
Not everyone agreed, and the topic could always raise a lively discussion. Some experts reported that where forests were cut down, the flow of water in rivers did not rise but actually fell. Deforestation not only caused rainwater to run off rapidly in useless floods, they said, but reduced rainfall itself. European professors, alert to any proof that their nations were wiser than others, explained that the Orientals of the Ancient Near East had heedlessly converted their once lush lands into impoverished deserts.
In the latter 19th century, official commissions in several European countries studied the question of whether reforestation should be encouraged — probably the first government concern for human effects on climate, a century ahead of its time. These inquiries could not lead to action, when scientists disagreed on whether a given change in land use brought more rain or less. “It seems almost a psychological puzzle,” an expert complained in 1890, “that for one and the same country serious scientists have at every step insisted on climate changes which are mutually exclusive…. We have to admit that even today we are still far from a definite answer…”The farmers and other concerned people who paid attention to these debates could readily see that science had nothing reliable to say about climate change.(2)
Meanwhile, national weather agencies had begun to compile masses of reliable observations of temperature, rainfall, and the like. When the figures were analyzed they showed many rises and dips, but no steady long-term change. By the end of the century, scientific opinion had turned decisively against any belief in a human influence on climate. No plausible theory had been developed for how it could happen, and the evidence was against it. The idea lingered in the public mind, among the countless scientific speculations about matters of possible interest to future generations but of no immediate concern.
Whatever the local effects, few had imagined humans could affect the climate of the planet as a whole. Today, in the 21st century, “wilderness” is something we imagine as a preserve of trees and animals surrounded by the fuming machinery of civilization. Earlier people saw the world the other way around, themselves living in a village surrounded by endless expanses of wild nature. At the start of the 20th century, civilization still seemed like an enclave, a patch of hopeful technology amid wastelands only partly explored. There were barely a billion and a half humans scattered across the planet, mostly peasants relying on no energy sources but wood, wind, water, and brute muscle power. If people converted a forest to plowland or rice paddies, those were local improvements, which nobody imagined could affect the planet as a whole. The atmosphere in particular was controlled by geochemical forces that were surely indifferent to any human activity.
These planetary forces, however, could bring devastating changes. Everyone had seen illustrations of the old ice ages, with cavemen hunting wooly mammoths through the snow. Looking farther back, scientists described a tropical age of dinosaurs basking in balmy swamps, even in regions that were now arctic. A popular theory held that the dinosaurs had perished because gradually, over millions of years, the world had become too cold for them. Or geological forces, such as a long series of volcanic eruptions, might impose a world desert like the one where the last dinosaurs lay down to die in the 1940 Disney movie Fantasia. Even Bible fundamentalists accepted climate change, arguing that our sorrowful world of storms and snows had replaced an originally temperate, Edenic climate. Consider, they said, how mammoths had been found frozen intact with grass in their stomachs, apparently felled when the climate changed in a single night.(3*) Turning to historical times, scientists and popular writers proposed theories about how gradual natural shifts between rainy times and dry times had caused the rise or fall of ancient civilizations.
All these theories were chiefly a matter for geologists and historians of antiquity. In the foreseeable future of human society, the next few hundred years, people expected the climate to stay near its “normal” state — the state congenial to human civilization. Of course there could be deviations from the normal. From Noah’s Flood to the Dust Bowl drought of the 1930s, ideas about climate included a dose of catastrophe. But a catastrophe was by definition transient, passing away after a few years. As for long-term climate shifts of the sort that some believed had laid low Near Eastern civilizations, if such shifts existed at all they had been too gradual to be noticeable except over several generations. Anyway the climate changes that people thought about affected only this or that local region. People scarcely imagined that their own doings, so puny among the vast natural powers, could upset the “Balance of Nature” that governed the planet as a whole.
This view of Nature as supra human and inherently stable lay deep in most human cultures. In Western thinking this belief was traditionally tied up with religious faith: the God-given order of the universe would stand in flawless and imperturbable harmony until the Last Days. Indeed clerics might point to examples of natural regulatory mechanisms as proofs of Divine Providence. Darwin’s theory of evolution shook this faith only a little. Even those who acknowledged evolution believed that changes in the planet’s inventory of living creatures must be so gradual and progressive that harmony would prevail at every stage.
Scientists too believed in the Balance of Nature. By the end of the 19th century, geologists had become convinced that nature operates through steady and uniform processes. They held that view all the more strongly because of vehement opposition from people who tried to explain geological features by abrupt, supernatural catastrophes like Noah’s Flood. Modern geology declared that many millions of years of Earth’s geological history showed that biological and geophysical systems had maintained an overall equilibrium.
This was a serious obstacle for G.S. Callendar when, in 1938, he presented sketchy evidence that humanity’s use of fossil fuels could be causing global warming through the greenhouse effect of carbon dioxide gas (CO2). Callendar recalled how nearly every expert on climate rejected his arguments. “The idea that man’s actions could influence so vast a complex,” he wrote, “is very repugnant to some.”(4) What scientists did find plausible were simple hand-waving arguments that seemed to prove that emissions of CO2, or any other human intervention, could not possibly change global climate. Since this was the answer they expected, few tried to probe deeper. When journalists reported what scientists said, the confidence in natural self-regulation not only echoed but reinforced the public’s beliefs.
Human industry was in fact too small in the first half of the 20th century to noticeably affect the global climate. Hardly anyone expected much greater impact during the next century or two. People did not grasp the prodigious fact that both population and industrialization were exploding in a pattern of exponential growth.Between the start of the 20th century and its end the world’s population would triple, and the use of fossil-fuel energy by an average person would quadruple, making a twelve-fold increase in the rate of emission of CO2 from fossil fuels. Yet the First World War and Great Depression led industrialized nations to worry about a possible decline in their populations. Their industries seemed to be plodding ahead in linear growth, that is, expanding no faster in the current decade than last decade. As for “backward” regions like China or Brazil, industrialization scarcely entered anyone’s calculations except as a possibility for the remote future.(5*)
Even if human activity could have global effects some day, was that a problem? Nearly everyone saw technology as benign. People believed that in the centuries to come, scientists and engineers would turn deserts into gardens, poverty and ignorance would decline, and everyone would become steadily happier. Typical was the attitude of Svante Arrhenius, the first scientist to suggest that sometime (thousands of years from now) we might have produced enough CO2 by burning fossil fuels to warm the atmosphere. In a popularizing book of 1908 he wrote, “we may hope to enjoy ages with more equable and better climates, especially as regards the colder regions of the Earth, ages when the Earth will bring forth much more abundant crops than at present, for the benefit of rapidly propagating mankind.”(6) Callendar, when he presented his evidence that greenhouse effect warming was already underway, likewise looked forward to it. Not only would the warmth and extra carbon help crops to grow more abundantly, he said, but “the return of the deadly glaciers [of the ice ages] should be delayed indefinitely.”(7) A Swedish meteorologist and friend of Arrhenius, Nils Ekholm, was still more sanguine. Writing in 1901 in the heyday of optimism for technology and progress, he exclaimed that “it seems possible that Man will be able efficaciously to regulate the future climate of the Earth.” Man could release natural gas, Ekholm explained, or if desired absorb CO2 by “ruling the growth of plants according to his wants and purposes.”(8)
The public heard little of this. Only an educated minority of a few millions were attentive to science at all. These people might notice a rare mention of greenhouse warming buried as a paragraph or two in some popularizing article about climate. To them, as to most scientists, that was just one of the many barely plausible stories about a distant, science-fiction future, a subject for crackpot speculations and outright fantasy. One example was a popular Japanese children’s tale of 1932 in which the hero set off a volcanic eruption to warm the Earth with carbon dioxide emissions.(8a) The vast majority of the world’s people, even educated people, suspected that rain-makers might manipulate local weather, but never imagined that we had already begun to alter the entire planet’s climate.
From Grandfathers’ Tales to Nuclear Fears (1930s-1950s)
The first hint of actual global warming came from public memory. In the 1930s, grandfathers were heard to say that when it came to weather, the younger generation had it easy. Gone were the early frosts and daunting blizzards of their own youth. The popular press began to publish articles, pointing out that in fact rivers were not freezing over as formerly and so forth. Science reporters found experts who confirmed that crops and codfish were now harvested in northern zones where they had not been seen for centuries. When meteorologists scrutinized the records, they confirmed that a warming trend was underway. As Time magazine put it in 1939, “gaffers who claim that winters were harder when they were boys are quite right… weather men have no doubt that the world at least for the time being is growing warmer.”(9)
Nobody was much concerned. The meteorologists thought it likely that temperatures rose and fell modestly in centuries-long cycles. The grander and slower cycle of ice ages might also be on a warming upswing (“But you can work up a cycle for anything,” as one expert told a reporter).(10) If the 20th century happened to be a time of warming, so much the better. A typical popular article of 1950 promised that “vast new food-producing areas will be put under cultivation.” It was reminiscent of old familiar theories about how ancient civilizations had risen and fallen in obedience to gradual shifts of rainfall and other regional climate changes.
Some reports were more sensational. If warming continued, new deserts might appear, and the oceans might rise to flood coastal cities — “another deluge, such as the catastrophe recorded in the Bible.”(11) People recalled also the old Euro-centric belief, repeated by some scientists, that heat is enervating. Many Europeans thought it was a scientific fact that the temperate zones inhabited by the “Caucasian race” were naturally superior for the spread of civilization. Life magazine warned that a warmed-up climate might make everyone as lazy as the natives of the tropics were supposed to be. And then there was the fact that sex crimes rose at the start of summer!(12)
As prediction, all this was plainly nothing but colorful speculation about the remote future. Time magazine explained that “Meteorologists do not know whether the present warm trend is likely to last 20 years or 20,000 years.” Many professional meteorologists doubted that there was in fact any world-wide warming trend. They saw only normal, temporary, regional fluctuations. In 1952 the New York Times remarked that thirty years ahead, people might look back fondly on the mild winters of the 1950s.(13)
The future was all the more obscure since the cause of the supposed warming trend was unknown. Some articles mentioned the possibility of a CO2 greenhouse effect, but they only listed it along with more widely accepted theories of climate change — erratic volcanoes, solar variations, and so forth.(14) (Much later, scientists concluded that it was indeed such forces that had caused the warming of the early 20th century; greenhouse gas emissions were not yet large enough to dominate.) At times even good journalists would report some half-baked theory of climate change advocated by someone with a Ph.D. Further speculations came from amateur meteorologists, who were not yet easy to distinguish from professionals. As one writer put it, “Everyone has his own theory — and each sounds good — until the next lad comes along with his theory and knocks the others into smithereens.”(15) In short, the science-attentive public was well informed that climate theory was in a dismal state. That scarcely seemed to matter, if nothing we could do would change the climate anyway.
It took barely a decade for public attitudes to reverse. The reversal was not because of any changes in what scientists knew about global warming. The public’s rising concern for human impacts came from far more visible connections between technology and the atmosphere.
One of these was a growing awareness of the dangers of atmospheric pollution. In the 1930s, citizens had been happy to see smoke rising from factories: dirty skies meant jobs. But in the 1950s, as the economy soared and life expectancy lengthened, in industrialized countries a historic shift began from worries about poverty to worries about chronic health conditions. Doctors were learning that air pollution was mortally dangerous for some people. Meanwhile, on top of smoke from coal-burning factories came exhaust from the rapidly proliferating automobiles. A “killer smog” that smothered London in 1953 demonstrated that the stuff we put into the air could actually slay several thousand people in a few days. Effects on health also became evident in Los Angeles during the 1950s. Many Americans did not take the problem seriously, however, until a deadly smog assaulted New York City in 1966. Events in New York always had a disproportionate influence on the media headquartered there.(16)
Another thing that drew the public’s attention to the air was exciting news about manipulating weather. During the 1950s, the press prominently reported attempts to make rain by “seeding” clouds with silver iodide smoke. Scientists openly speculated about other technical tricks, such as spreading a cloud of particles at a selected level in the atmosphere to interfere with solar radiation. Journalists and science-fiction authors explained that in a not distant future we might alter climates over entire nations to their benefit. Or perhaps to their harm. Scientists publicly warned about the approach of “climatological warfare.” Might the Russians someday inflict deadly blizzards on the United States in a truly Cold War?
It had become plausible that by putting materials into the air, humans could alter climate on the largest scale. The frequent and colorful press coverage of cloud seeding and so forth helped convince the public of that possibility. Even decades later, when poll-takers asked people about causes of climate change, many thought first not of industrial emissions but of technical feats such as spaceship launches and nuclear explosions.(17)
The astonishing advent of nuclear energy was central to the change in thinking. Suddenly nothing seemed beyond human power. To many people the news of a limitless energy source was hopeful, even utopian. For example, experts speculated that we would soon be able to use salvoes of atomic bombs to control weather patterns, bringing rain exactly where it was needed. At the same time, scientists warned that a nuclear war could destroy civilization. Science-fiction stories, like the widely seen 1959 movie On the Beach, pictured the extinction of all life by radioactive fallout, carried around the world on the winds after a nuclear war. Many among the public suspected that dust from atomic bomb tests was already affecting the weather. From about 1953 until open-air testing ceased in the mid 1960s, as opponents of nuclear armaments pointed with horror to the invisible dangers of fallout, some people blamed the faraway tests for almost any unseasonable heat or cold, drought or flood. In a magazine article laying out the evidence that global temperatures were rising, the authors remarked that “Large numbers of people wonder whether the atomic bomb is responsible for it all.”(18)
The new threats awoke images and feelings that most people had scarcely experienced outside their dreams and nightmares. Humans were introducing unnatural technologies, meddling with the very winds and rain, spreading pollution everywhere. Would we provoke retribution? Would “Mother Nature” pay us back for our attacks upon “her”? At the deepest level, horror movies about radioactive monsters hinted at infantile fantasies of filth and incest, attack and punishment.(19) Such veiled anxieties were not detectable in the sober discussions of subjects like climate change. But the public did develop a vague feeling that natural disasters followed not only scientific law but moral law — a punishment for unhallowed human assaults.
Of course, this was nothing new. Many tribal peoples attributed climate disasters, such as an unusually severe winter, to human misdeeds. Somebody’s “polluting” transgression of rules was to blame. The community was being punished because someone had carelessly bungled a ceremony, violated an incest taboo, or the like. Just so was the Flood of Noah called down upon humanity by our sins. It was not only primitive tribes, but sophisticated civilizations too, that saw the natural order as so intrinsically benign and harmonious that any severe disruption must be due to human misdeeds. Chinese dynasties were shaken when people held the corruption of the Emperor and his mandarins to blame for devastating floods; European and American communities into modern times declared days of public penance as an answer to droughts.
During the 1950s, human-caused disruptions of nature all the way up to global destruction took on a veneer of scientific plausibility. As the nuclear arsenals grew, Bible fundamentalists got a wider hearing than ever for their prophecies of rivers of blood, rains of fire, and the like. Told that our depravity would bring apocalyptic wars and the end of all things, the listener might be uncertain whether the warning came from a moralizing preacher or a concerned atomic scientist.
In this mental environment, people increasingly saw the natural world itself as unreliable, quite aside from human sin or divine punishment. Immanuel Velikovsky and several other would-be scientists were writing popular books that declared that the Earth had suffered extremely swift and cataclysmic changes not long ago. The poles had shifted thousands of miles in only a few years, bringing sudden floods and ice ages — with instantly frozen mammoths as evidence. These theories deserved scarcely a moment’s attention as science. Yet with titles like Earth in Upheaval, Earth’s Shifting Crust, and Popular Awakening Concerning the Impending Flood, the catastrophist writings resonated with apocalyptic fears and excited widespread popular interest.(20)
The widespread forebodings about the planet’s fate made it easier for scientists to conceive theories of climate catastrophe and get a hearing. By far the best-publicized theory was offered in 1956 by two respected scientists, Maurice Ewing and William Donn. They argued that a warm spell could melt the Arctic Ocean’s ice pack and trigger processes that would bring an ice age. Popularizations, such as a widely read article on “The Coming Ice Age” by freelance journalist Betty Friedan, speculated that flooded coasts and other calamities might soon arrive.(21) The publicity brought Ewing dozens of letters over the next several years from amateur enthusiasts of climate studies, as well as from cranks with elaborate ice-age theories of their own.(22) Careful science journalists warned that scientists saw no more in the Ewing-Donn theory than an interesting unproved speculation. But most writers agreed that significant climate change was possible.(23*)
Ewing and Donn’s theory sounded like a rational version of ancient myths of climate catastrophe. There had always been something deeply buried in human consciousness that resonated with the Nordic myth of Fimbulwinter — the future time when three years without a summer would herald the doom of men and gods. And something resonated with the annihilating world-flood described not only in the Bible but in the folklore of many peoples. Images of an end of the world in ice, in flood or in (nuclear) fire were no longer confined to the spheres of fable and religion. Underwritten by scientists, the images were leaking into sensible everyday conversations.
Suspicions of a Human-Caused Greenhouse (1956-1969)
Now that it seemed plausible that human technology could alter the planet as a whole, journalists found it easier to suggest that the greenhouse effect of CO2 from fossil fuels was a possible cause of global warming. Evidence that the world had been growing a bit warmer had become strong enough to convince most meteorologists. In a 1955 news conference, the head of the U.S. Weather Bureau said that a significant rise in average global temperature (3.6°F, that is, 2°C) had been seen in the previous fifty years.(24) During the 1950s, newspaper readers could repeatedly run across small items with anecdotes of warming, such as crops and codfish flourishing hundreds of miles north of their former ranges. Easier to visualize were stories of mountain glaciers retreating. (That turned out to be confusing, however, since mountain glaciers advance and retreat erratically, depending less on global temperature than on purely local variations in snowfall.) On a larger scale, in 1959 the New York Times reported that the ice in the Arctic Ocean was only half as thick as it had been in the previous century. Still, the report concluded, “the warming trend is not considered either alarming or steep.” Nor was the trend clearly caused by human activity; to many of the scientists who reported the warming, it was just another phase of mysterious natural cycles.(25)
The respected oceanographer Roger Revelle took the lead in suggesting that trouble might lie ahead. When he calculated that a rise in the level of CO2 was likely, Revelle took pains to talk about global warming with science journalists and government officials. He said that humanity was inadvertently undertaking a huge “experiment” on the atmosphere, and the phrase was quickly picked up by others. Revelle meant “experiment” in the traditional scientific sense — a useful logical exercise, with the rise of CO2 offering a fascinating opportunity for the study of geophysical processes. But the word “experiment” increasingly reminded ordinary people of nuclear bomb tests, or even Frankenstein at work on his monster.
Revelle himself at times warned that the experiment might bring serious problems. Testifying to Congress in 1957, he was one of the first to use another new and potent metaphor: “The Earth itself is a space ship,” he said. The ventures into space that began with the Soviet launching of Sputnik in 1957 were pushing many people toward seeing the planet as if from outside, as a whole. For Revelle, it meant we had better keep an eye on the spaceship’s air control system. Noting that climate had changed “quite abruptly” in the past, perhaps bringing the downfall of entire civilizations in the ancient world, he warned that the rise of CO2 might turn Southern California and Texas into “real deserts.”(26) A few newspapers carried accounts with headlines like, “Fumes Seen Warming Arctic Seas,” and reported Revelle’s prediction that the Soviet Union could become a “great maritime nation” within as little as fifty years. It was in a newspaper account of Revelle’s scientific work that the phrase “global warming” was published for the first time and “climate change” for almost the first time, although neither phrase would become common until the late 1970s.(27)
Another scientist the media noticed was the physicist Gilbert Plass, whose own work had convinced him that CO2 would warm the planet. In a 1959 Scientific American article he boldly predicted that global temperatures would rise something like 3°F (1.7°C) by the end of the century. Plass, thinking as a scientist, only remarked that this would allow a conclusive test of the CO2 theory of climate change. But the magazine’s editorial staff connected his ideas with the public’s growing concern about pollution, printing a photograph of coal smoke belching from factories. The caption read, “Man upsets the balance of natural processes by adding billions of tons of carbon dioxide to the atmosphere each year.” The New York Times veteran science reporter Waldemar Kaempffert, likewise looking at warming centuries ahead, opined that since “coal and oil are still plentiful and cheap,” despite pollution “both will be consumed by industry so long as it pays to do so.”(28*)
Most people did not see anything ominous. “There would seem to be every reason for producing as much carbon dioxide as we can manage,” one popularization had concluded back in 1957. “It is helping us towards a warmer and drier world.” In any case none of it would happen until the 21st century, which seemed very distant indeed from the 1950s. The subject was scarcely noticed by anyone outside the science-minded minority who happened upon the reports, which were mostly buried in the back pages of newspapers or dropped into a news magazine as a brief paragraph.(30*)
After all, nothing here was certain, not even the recent warming trend. In 1961, a Weather Bureau expert announced that since about 1940 the world had in fact been cooling. Just around the time scientists had started to become convinced that there was a long-term warming trend, it had reversed, although the random fluctuations were so great that it had taken two decades for the reversal to become plain. (It didn’t help that in the world’s media capital, New York City, unusual warm spells happened to continue through the 1950s and 1960s.) For most of the 1960s and 1970s, science popularizations were dismally confused. A magazine might one year predict a tropical world with cities drowned by rising oceans, and the following year warn of cities overwhelmed by gigantic glaciers. It was uncomfortably obvious that experts could not agree about the actual trend of climate change, let alone its possible causes. “Man may be changing his weather…,” an environmental study group warned; “through his inadvertent action he may be driving the atmosphere either to a disastrous ice age — or as bad — to a catastrophic melting of the ice caps… Despite firm predictions by some ecologists, we do not know the answers.”(30a)
The one unchallenged fact was Keeling’s measurement of the amount of CO2 in the atmosphere. His curve rose year by year through the 1960s.The rise impressed scientists who reviewed climate issues on behalf of various committees. A pioneer was the private Conservation Foundation, which sponsored a 1963 conference on climate. The scientists issued a report warning of “potentially dangerous atmospheric increases of carbon dioxide.”(31) In 1965, the issue rose to a high level of government, when a panel of the U.S. President’s Science Advisory Committee decided that the potential for global warming was a matter of serious national concern. But their report mentioned it only as one brief item among many other, more troubling environmental problems.(32)
While some knowledgeable people were beginning to worry about how humans might be altering the atmosphere, their anxiety was only partly provoked by developments in climate science. Equally important was the historic shift of attitudes about how technology might affect the natural world. Utopian hopes dissolved as the nuclear arms race hurtled onward. The vague, almost mythological anxieties of the1950s were reinforced by specific and immediate fears, voiced in shrill public debates and mass demonstrations against nuclear weapons tests. Exquisitely sensitive instruments detected radioactive fallout from the explosions half a world away — the first recognized form of global atmospheric pollution. It was easy to imagine a post-nuclear war world like what a science-fiction story portrayed later in the decade: the atmosphere so wrecked that horrible and uncanny storms perpetually swept the discolored skies.(33)
The lesson of fallout was that the world’s air was no longer pristine, not anywhere. Science writer Rachel Carson recalled that she used to think “the clouds and the rain and the wind were God’s,” but now she knew otherwise. In her 1962 book Silent Spring she warned that agricultural pesticides such as DDT and other chemical pollution, drifting around the world like fallout, could endanger living creatures not just in the neighborhood of the polluter, but everywhere.(34) Meanwhile scientists reported that the increasingly despised urban smogs could no longer be attacked as just a local problem, for the pollution measurably dimmed the skies a thousand miles downwind.
These influences and many others brought a new generation of social critics onto the public stage. The “conservationists” of an earlier generation had fought against local harms, the toxic river, the razed forest or stinking air in their own vicinity. That was the immorality of fouling one’s own neighborhood. Now the moral lesson was still more severe. As poor farming practices had apparently aggravated the Dust Bowl, as ancient civilizations had destroyed their lands through overgrazing, so now human carelessness and greed seemed to endanger the entire global environment. Rejecting the traditional admiration for technology, the new “environmentalists” exclaimed that human activities threatened all life on Earth.
These influences and many others brought a new generation of social critics onto the public stage. The “conservationists” of an earlier generation had fought against local harms, the toxic river, the razed forest or stinking air in their own vicinity. That was the immorality of fouling one’s own neighborhood. Now the moral lesson was still more severe. As poor farming practices had apparently aggravated the Dust Bowl, as ancient civilizations had destroyed their lands through overgrazing, so now human carelessness and greed seemed to endanger the entire global environment. Rejecting the traditional admiration for technology, the new “environmentalists” exclaimed that human activities threatened all life on Earth.
A new view was growing of the planet Earth as a system, an interlocking and fragile whole. Presumably this view was somehow connected with improved intellectual understandings. dDiscussion of the “population explosion” was teaching people the fierce power of exponential increase. Experts and public alike began to foresee trouble as the rise in the number of humans not only multiplied on itself, but was multiplied again by advances in technology. Meanwhile, beyond nuclear weapons a general Cold War mobilization of environmental sciences was seeking ways to control nature in order to inflict widespread harm on an enemy.(35) People were coming to think in global terms not only about population growth but also about its intricate relationship with the planet’s stock of chemicals and other resources, including the atmosphere itself.
Analyzing such a tangle seemed impossible.. Nevertheless a few people at the Massachusetts Institute of Technology, the world center of enthusiasm for computer modeling, attempted to construct global resource models. Environmental issues like greenhouse warming were in the back of their minds (we will see that one of the instigators, Carroll Wilson, was meanwhile organizing landmark conferences on climate change). Their trail blazing 1972 book on The Limits to Growth proclaimed that the limits were strict. The computer said that exploding population would use up all available food and minerals, and if somehow we avoided that, we would eventually choke in our own polluting exhaust. The book sold millions of copies worldwide, deeply impressing thoughtful people with its calculation of “the predicament of mankind.” For most of the public, and policymaking elites too, it was not only the first time they had faced up to the finite capacity of the planet, but also the first time they had seen a numerical analysis of the global physical and economic system.(36)
Meanwhile scientists showed how widespread harm might be wreaked by modest quantities of materials, and not only radioactive fallout or DDT. Meteorologists calculated, and explained to science reporters, that a modest addition of ordinary dust or gases to the atmosphere might trigger serious and unpredictable changes. It was just now, in the mid 1960s, that climate science — one of the few fields that tried to model an entire planetary system — became acutely aware of feedbacks and the mathematics of chaos. New models of the atmosphere interacting with oceans and ice raised the possibility of huge and sudden upheavals. It is not clear how far these intellectual developments affected public opinion, since most people scarcely heard of them. There may have been as much influence in the other direction. While models of an unstable climate had scientific roots stretching back into the 1950s, scientists may have been encouraged to develop the models when their thinking expanded along with the shift of public opinion toward seeing global disruptions as plausible.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
Scientific ideas of any sort meant less to the public than technological coups, and not just the bomb tests. Most impressive of all was a photograph that an astronaut took from lunar orbit in 1968. Here was our small blue sphere, decorated with lacy whirls of cloud, floating like an oasis in endless black space. Astronauts declared with an almost mystical insistence that from their high viewpoint, national boundaries became invisible as a global perspective opened up.(37) The photographs, compared with even the most scientifically informed earlier paintings, showed weather systems that were far more elaborately organized, more delicate and more ravishingly beautiful — a planet to cherish.
The first Earth Day, held in 1970, marked the emergence of environmentalism into powerful political action. New public attitudes supported bitter attacks on authorities, especially in government and industry. They were the villains held responsible for pollution and many other problems. To the new breed of environmentalists, almost any novel technology looked dangerous. As one example, the press revealed that the U.S. military in Vietnam had engaged in a massive cloud-seeding program, trying to bog down the Communist army with rains. The military was now widely despised, and in the eyes of many around the world, this attempt at climate modification was malignant. Where once people had held utopian hopes for the ways humanity would modify the environment, either deliberately or as a side-effect of “progress,” now such “interference” seemed ignorant, reckless, and perhaps wicked. In every democratic industrial nation, citizens pressed their government to enact environmental protection laws. Governments gave way, taking steps to reduce smog, clean up water supplies, and the like. Meanwhile bureaucracies improved the organization (and in some cases the funding) of research on the atmosphere, along with every other element of the environment.
The new attitudes affected scientists along with everyone else. Some experts were getting worried about climate change, and made deliberate efforts to stir up other scientists and the public. Especially important was a “Study of Critical Environmental Problems” organized in 1970 at the Massachusetts Institute of Technology. The organizer was Carroll Wilson, a dynamic science policy entrepreneur who had earlier managed the U.S. Atomic Energy Commission. Under his expert leadership, some 40 scientists deliberated for a month over desertification, pollution of the air and oceans, and other harms. In their concluding conference report, as the first item in a big list of potential problems, the scientists pointed to the global rise of CO2. The risk of global warming, they declared, was “so serious that much more must be learned about future trends of climate change.”(38) The media paid some attention, although they mostly overlooked global warming among more immediate pollution threats.
Wilson followed up the MIT study by organizing a meeting of experts in Stockholm. This “Study of Man’s Impact on Climate,” focused tightly on climate change, was a landmark in the development of awareness. The group concluded with a ringing call for attention to the dangers of humanity’s emissions of greenhouse gases and particle pollutants. Their widely read report gave as its epigraph a Sanskrit prayer: “Oh, Mother Earth… pardon me for trampling on you.”(39) Another example of the new tone was a deliberately provocative 1971 book titled Impingement of Man on the Oceans. “The shocking reality,” said the author, “is that the hour is fast approaching when the people of the Earth will have exhausted nature’s ability to adjust to the complexities of human attack.”(40)
Contemplating the relationship between science and society, some people would say that the judgment of scientists bent under the pressure of the mass prejudices of the day. Others would say that public opinion responded intelligently to new scientific facts. Both views go too far in separating scientific from popular thought. In regions like North America and Europe, where the public was relatively well educated and informed, the views of scientists and public tended to evolve together.
Not everyone adopted such thinking. Many still felt, as the veteran meteorologist Joseph Smagorinsky had declared in 1969, that “our physical environment must be considered an enemy to humanity until we master it.”(41) But the rhetoric and attitudes of the environmental movement spread rapidly, not only among the general public but also among climate researchers. Smagorinsky himself worried in 1972 that we were standing “at the threshold of a possible crisis which could have as much of an impact on man as his invention of war.”(42)
Climate was now seen as one of the planet’s vulnerable spots, and many people expected that whatever we did to it would be for the worse. For example, in 1969 (Feb. 20) the New York Times reported that greenhouse warming of the Arctic Ocean might make the pole ice-free within a decade or two. The resulting climate change would turn much of the United States and Europe from breadbaskets to deserts. On the other hand, the Times article continued, some scientists held there was a cooling trend. That too could be blamed on humanity. Increased dust and other aerosols, stirred up by agriculture and industry, might bring destructive cold spells.
Science reporters were especially impressed by a 1972 warning from the oceanographer Cesare Emiliani. His ground-breaking research on past climate cycles had persuaded him that in the natural course of events the present “amiable climate” could give way, within the next few thousand years, to a new ice age. But the prediction, Emiliani explained, might be confounded by human interference such as deforestation and pollution, for the climate was extremely unstable. “We may soon be confronted with a runaway glaciation,” Time magazine quoted him as saying — or perhaps instead a greenhouse “runaway deglaciation” that would flood our coastal cities.(43) The most common scientific viewpoint was summed up by a scientist who explained that the rise in dust pollution worked in the opposite direction from the rise in CO2, so nobody could say whether there would be cooling or warming. But in any case, “We are entering an era when man’s effects on his climate will become dominant.”(44)
Such climate pronouncements were no longer always hidden in the back pages. In the early 1970s, the public learned that climate change could be an urgent problem. What aroused them was a spectacular series of disasters. In 1972, drought ravaged crops in the Soviet Union and several other regions; this caught attention around the world when the Soviet government made massive grain purchases and prices rose sharply. Also in 1972 the Peruvian fisheries collapsed because of an El Niño event, while the Indian monsoon failed (and again in 1974). Meanwhile droughts struck the Midwestern United States too, severely enough to show up repeatedly on the front pages of newspapers and in television news programs. In 1974 world prices of food soared to a level never seen before. Most dramatic of all, years of drought struck the African Sahel and reached an appalling peak in 1972, threatening millions with starvation, bringing on mass migrations and hundreds of thousands of actual deaths. Television and magazine pictures of sun-scorched fields and emaciated refugees brought home just what climate change could signify. Worries about humanity’s relationship to the planet’s resources were further sharpened by the much-discussed 1972 Limits to Growth report and by a 1973 crisis when an Arab oil embargo made for long lines at gas stations.
Climate scientists did not know what caused any of the weather disasters, but some publicly suggested that humans were partly responsible. Looking at the disaster in Africa in particular, they speculated that our pollution of the atmosphere was changing global weather patterns. Or perhaps overgrazing of the semi-arid Sahel had started a vicious cycle, where the barren ground reflected more sunlight, altering the winds so as to cause further desertification. Whatever the cause of the disasters, they undercut the public’s traditional belief that weather conditions would never get far from their old accustomed pattern. Climate scientists had already been moving away from that during the past decade. People increasingly understood that there existed no such a thing as a “normal” climate, and many began to worry that permanent shifts were underway.(45)
The rise in attention can be seen in the popular articles in American magazines listed in the Readers’ Guide to Periodical Literature under the rubric “Global temperature change.” The articles put interviews of climate scientists alongside the recurring news of droughts and other weather disasters. In the mid 1970s, the number exploded from roughly three articles per year to more than twenty.(46) That was still a low level compared with many other issues that agitated the public. But it was enough so that well-read people would be generally aware of climate change as a public issue.
As usual, news media drew attention to the worst dangers. Various journalists reported that scientists suspected the weather fluctuations could be the harbinger of another ice age. To be sure, most articles made it clear that the top scientists frankly admitted uncertainty. Many scientists believed that cooling was less likely than global warming, or than no particular change at all. Newsweek explained, in a direct quote from a National Academy of Sciences report, that “Not only are the basic scientific questions largely unanswered, but in many cases we do not yet know enough to pose the key questions.” Yet there was one thing that nearly all experts agreed on, news reports explained. As Time put it, “the world’s prolonged streak of exceptionally good climate has probably come to an end — meaning that mankind will find it harder to grow food.”(47) When rising population crashed against the increasingly erratic weather, the world might face widespread famine, even warfare over the dwindling food supply.
A leader in stirring public anxiety was the respected climate expert Reid Bryson. Scarcely any popular article on climate in the 1970s lacked a Bryson quote or at least a mention of his ideas. His big worry was the increase in smoke and dust, not only from industry but also from lands laid waste by deforestation and slash-and-burn agriculture. Already in the late 1960s, he had gone to the public to warn that such pollution was probably bringing on global cooling.(49) He explained that like the smoke from a huge volcanic eruption, the “human volcano” could cause disastrous shifts in weather patterns. His claims were forcefully stated and unequivocal, backed up by an argument that the droughts in Africa and India already showed how air pollution was halting the rain-bringing monsoons. (Three decades later scientists were still unsure about that, although they suspected that pollution had in fact contributed to the deadly African drought.) Journalists quoted Bryson’s warnings that the effects of human interference “are already showing up in rather drastic ways,” as Fortune magazine reported in 1974. We faced unprecedented dangers, the magazine declared, perhaps “a billion people starving.”(50)
Most climate experts thought Bryson went too far, at least as reported in the media. “There has been much hand-waving of late,” the respected climatologist William Kellogg complained in 1971, “and the ‘prophets of doom’ have taken the spotlight of public attention. Virtually none of these people who speak of the ‘doom’ of our earthly environment are scientists…” He insisted that our planet had “a remarkably stable life-support system” and that “the natural sources of contamination… still far outweigh all of man’s contributions, taken on a global scale.”
Yet the majority of climate experts were beginning to worry. Kellogg himself confessed to a “haunting realization that man may be able to change the climate of the planet Earth.” A 1974 study by leading figures, convened by the National Academy of Sciences, concluded that “there is a finite probability that a serious worldwide cooling could befall the Earth within the next 100 years.” The shift, moreover, could be “rather sudden.”(51) Another official (or official-sounding) endorsement came in 1976 with the publication of a secret 1974 report by the Central Intelligence Agency. The report’s authors, relying on Bryson’s theory, gave dire warnings that impending cooling could bring economic dislocation and perhaps even wars. “There would be increasingly desperate attempts on the part of powerful but hungry nations to get grain any way they could. Massive migrations, sometimes backed by force, would become a live issue…” Climate scientists publicly attacked the CIA report as “sloppy” and full of “patent nonsense” (Bryson himself had to spend a good part of the next year explaining to people that he wasn’t responsible for what it said). However, news accounts went on to say that nearly all scientists did admit that severe climate variations were possible.(52)
News of such reports and studies was still usually relegated to a few paragraphs on the inside pages of the better newspapers or in the science-and-culture section of news magazines, reaching only the more alert citizens. This limited but important audience, if they happened to open to the right page on the right day, might notice a significant discovery. Strong new evidence showed that the coming and going of ice ages followed a rhythm set by predictable astronomical variations of the Earth’s orbit around the Sun. Projecting these orbital variations forward, several experts calculated that we were now in the descending part of the natural cycle, with the onset of the next ice age probably scheduled to come within the next few thousand years. (It would be a couple of decades before more accurate calculations showed that the next scheduled ice age was not due for tens of thousands of years.) A few scientists argued that it would be prudent to make preparations for the possibility that the supposed cooling cycle would begin to get serious within the next century or two. After all, journalists pointed out, weather records revealed widespread temperature declines since the 1950s. (Later studies would find the cooling had come only in the Northern Hemisphere, and particularly in the much-watched North Atlantic region. It didn’t help that the 1970s brought especially cold weather to the world’s media capital, New York City.)
The startling images of a sudden ice age in popular media scarcely resembled the scientific literature, where articles were published only after review by other experts. In those journals, during the 1970s only a few papers projected that the world might freeze within a century or two. Many more authors foresaw not global cooling but global warming, and still more weighed the pros and cons but insisted that it would be impossible to make any prediction until much more work was done. This understanding was reflected in the few more-or-less “official” pronouncements by bodies that presumed to speak for a consensus of scientists. The World Meteorological Organization in 1976 addressed the “controversial statements on climatic change… issued in recent years by various bodies and individuals…” Their own statement acknowledged the possibility of rapid climate changes caused by human activities, including aerosol pollution, but the only possibility they noted specifically was “a long-term warming” from CO2. And a lengthy study by the U.S. National Academy of Sciences that concluded in 1977 scarcely bothered with worries about cooling. The report focussed on global warming from CO2 emissions, warning of a future risk of rising seas, failures of agricultural and marine production, and so forth — while admitting that much more research was needed before anything could be said for certain. (54)
The ideas seemed plausible to Nigel Calder, a respected British science journalist, who featured them in a two-hour television feature about weather that was broadcast in 1974. One short but memorable segment warned of a possible “snowblitz” set off by an Antarctic ice surge, or directly by global warming or pollution, or just by pure chance. Entire countries could be obliterated under layers of snow, said Calder, and billions would starve. The new ice age “could in principle start next summer, or at any rate during the next hundred years.” This was the first time the threat of abrupt climate change appeared as the subject of a major television presentation.(57) But it was an isolated case, and it did not reach beyond the minority who watched educational shows on public television. Climate change was not yet a topic of widespread public discussion.
A few scientists thought the prospects of a calamity were so serious that they must make a personal effort to address the public directly. Bryson wrote a book titled Climates of Hunger, published in 1977. Drawing on his group’s historical researches, he described how native American societies had been destroyed by the sudden onset of prolonged droughts, far worse than anything known in recent centuries. A better-documented historical case, noted by many writers, was the “Little Ice Age” that had chilled the North Atlantic region from the 15th through the 18th century. Starvation had loomed as crops failed in the dank summers, the Thames at London and the Baltic Sea had frozen solid in winter, while advancing glaciers had crushed entire villages in the Alps and Viking colonies in Greenland had collapsed.(58) Bryson warned that such disasters could hit our own civilization unpredictably and swiftly.(59)
Some scientists criticized Bryson, Schneider, and others who spoke directly to the public. The time spent writing a book and going about the country delivering public lectures was time away from doing “real” science. Worse, most scientists felt that any definite statement about climate change was premature. After all, nobody had in fact published a firm prediction of an imminent ice age or runaway global warming in a peer-reviewed scientific journal.(60a) The whole subject was so riddled with uncertainties that it seemed unfit for presentation to the scientifically naive public. Experts whose profession demanded accuracy were upset by the shortcuts some colleagues took when explaining things in lay language. They particularly disliked the blunt and colorful statements, inevitably imprecise, that were necessary to catch the public’s ear. Since debate over the likelihood of severe climate change had become a salient public issue, any statement might be dragged into the media arena. Reporters were quizzing experts at scientific meetings and telephoning them with urgent questions about one or another discovery that was about to be published. Climate science professionals, accustomed to life in a quiet academic backwater, found the change both gratifying and disturbing.
Many of the experts felt that the climate controversy was inflated by a few irresponsible scientists and sensation-seeking journalists, agitating for no good reason. As the Director-General of the United Kingdom Meteorological Office explained in a 1976 lecture, the official message was, “no need for panic induced by the prophets of doom.” With other meteorologists, perhaps the majority, he insisted that “the climatic system is so robust, and contains so much inherent stability through the presence of negative feedback mechanisms, that man has still a long way to go before his influence becomes great enough to cause serious disruption….”(61*) In fact the public showed no signs of panic nor even much anxiety. The traditional belief in a benign Balance of Nature was still widely held. Warnings of a future climate calamity sounded no different from the countless other future threats that newspapers had been trumpeting for a hundred years.
We don’t know the public’s response for sure, since nobody took a poll. But a largely indifferent attitude is suggested by the very lack of polling, or any other distinct reaction by the experts who kept their finger on the public pulse. Politicians, even better attuned to public feelings, did show some desultory reactions. A few bills dealing with climate were proposed in the U.S. Congress, and the administration undertook a mild reorganization of climate research. But most politicians showed little interest in the topic.
Yet climate change was becoming a political issue, if only in the narrow sense that policies were at stake. At professional meteorological conferences, debates over technical questions such as the rate of CO2 buildup became entangled with debates over how governments should respond. In some meetings scientists addressed the policy issues formally in papers and working groups, struggling with questions far beyond their professional expertise. How much should reliance on fossil fuels be reduced, if at all? Should the destruction of tropical forests be a main target for reform? How much money and effort should be spent on averting climate change, amid the struggle to feed the world’s poor? With demands for equity rising and centralized government threatening freedom, what policies were desirable? Or even politically feasible? Which was more dangerous — to exclaim about the worst possible harms, and give science a reputation for sensationalism, or to offer cautious scenarios, which might delay action until it was too late? Was it even proper for a scientist to speak, as a scientist, on social questions?(62)
The different approaches showed up in exchanges like the following, at a 1972 symposium where scientists argued over intractable calculations on how much CO2 was emitted during deforestation. “I guess I am rather conservative…,” one expert remarked. “I really would like to see a better integration of knowledge and better data before I would personally be willing to play a role in saying something political about this.” A colleague replied, “To do nothing when the situation is changing very rapidly is not a conservative thing to do.”(63)
Unable to agree even whether the world was likely to get warmer or colder, the scientists did unanimously agree that the first step must be to redouble the effort to understand how the climate system worked. Calls for research always came naturally to researchers, but from the early 1970s onward, climate scientists issued these calls with increased frequency and passion. Even in technical articles in professional journals, many authors now went out of their way to state that an increased research effort was urgently needed. Interviewed by journalists, most climate scientists said they required far more data and analysis. In other words, governments should put up more money. As one meteorologist put it, “public opinion is being alerted and thus politicians may be able to act.”(64)
Not only more funds, but better organization seemed necessary. Individual scientists were backed up by official committee reports pressing these issues. In particular, around 1974 American scientists made a concerted effort, both in public and behind the scenes among officials, to urge their government to found a National Climate Program. That would give them both unified direction and sharply increased funding. Gathering data and organizing research on climate change, one expert explained, “should be regarded as an important aspect of national defense, or, more accurately, of defense of the entire planet against a common threat.”(65) Scientists also pushed for heightened international efforts. In the absence of a truly global public opinion, this action tended to be mostly hidden within conferences and in the corridors of bureaucracies.
A few people began to look beyond research policy to publicly demand immediate changes on a broader scale. Environmental activists were already attacking the damage in their neighborhoods due to overgrazing, smog emissions, and so forth. Such bad practices might alter the global climate as well. But this only added one more item to the list of arguments against specific practices. During the 1970s, only a few people speculated that it might be wise to impose serious changes on industry and agriculture for the special purpose of reducing their impact on climate. That was a world away from practical politics, rarely suggested even as an abstract future goal.
An example of the auxiliary part played by climate worries came up during a controversy that gathered around itself much of the political attention that could be spared for the atmosphere. This was a public debate that began in 1970 over the U.S. government’s plans to subsidize a fleet of commercial supersonic transport airplanes (SSTs). The transports would inject large amounts of water vapor and chemical aerosol particles into the stratosphere, and some scientists warned that this could have damaging effects on global climate. The public’s main worries, however, were that the fleet would be intolerably noisy, damage the high ozone layer that protected them from skin cancer, and waste taxpayers’ money. Under pressure from the entire list of objections, in 1971 Congress cancelled the project, perhaps the first time in American history such a major technological initiative was defeated by public pressure invoking environmental arguments. The controversy also brought the first widespread suspicion that human technology could have a dangerous environmental impact on the atmosphere.(66)
Pursuing the new concern for the stratosphere, in 1974 two scientists noticed that certain obscure gases produced by industry (nicknamed “CFCs”) lingered in the atmosphere. Some would drift up to the stratosphere where, the scientists discovered, ultraviolet rays would activate them in a process that destroyed ozone. Removing the high, thin layer of ozone would cause an increase of skin cancers, and perhaps bring still worse dangers to people, plants, and animals. CFCs were the propellents in aerosol sprays: every day millions of people were adding to the global harm as they used cans of deodorant or paint. Science journalists alerted the public, and environmentalists jumped on the issue. Chemical industry groups fought back with public relations campaigns that indignantly denied there was any risk whatsoever. Unconvinced, citizens bombarded government representatives with letters and boycotted spray cans. A survey showed that nearly three-quarters of Americans had heard about the issue. In 1977, the U.S. Congress added restrictions on the spray can chemicals to the new Clean Air Act.(67)
Climate change was nowhere to be seen in the spray can controversy. But the threat to the ozone layer sent a stinging message about how fragile the atmosphere was, how easily human activity might damage it. And how unexpectedly. Except for the chance circumstances that had stimulated studies of high-altitude airplanes, the danger from spray can propellants might have gone unnoticed for quite a few more years.
The ozone story added to the shapeless fears that human activity was somehow endangering the entire planetary atmosphere. The majority of citizens found it hard to distinguish among the various materials, whether airplane and automobile emissions, agricultural chemicals, or industrial pollution from either traditional smokes or strange new substances. Many scarcely distinguished among climate change from greenhouse warming, ozone damage from CFCs, and health threats from automobile tailpipes and power plant smokestacks. It was enough to feel that an eerie toxic smog threatened the entire planetary environment.
Scientific results continued to trickle in. None of the new studies was especially striking or definitive, but there was a significant overall tendency. It seemed that climate could indeed be more delicately balanced, more subject to swift changes, than scientists had supposed. An example of the claims that briefly caught the public eye were studies that suggested that severe droughts in western America followed a cycle, driven by changes in the number of sunspots. It was a reminder that the climate might be sensitive to all sorts of small and unexpected influences. This instability was driven home to scientists by new data on ancient climates, observations of disturbingly large annual shifts in the amount of snow cover in the Arctic, and novel theoretical models that showed how such changes might make the climate system flip abruptly from one state to another. This idea of runaway climate became terribly vivid to both scientists and the public when space probes brought news of a hellish furnace atmosphere on Venus and a permanent ice age on Mars.
Climate experts were quick to explain the new findings. A well-respected geochemist, Wallace Broecker, took the lead in 1975, warning in an influential Science magazine article that the world might be poised on the brink of a serious rise of temperature. “Complacency may not be warranted,” he said. “We may be in for a climatic surprise.”(68) In 1977, the National Academy of Sciences weighed in with a major study by a panel of experts who warned that temperatures might rise to nearly catastrophic levels during the next century or two. The report, announced at a press conference during the hottest July the nation had experienced since the 1930s, was widely noted in the press.(69)
Science journalists, by now closely attuned to the views of climate scientists, promptly reflected the shift of opinion. Media talk of a ruinous new ice age continued through the winter of 1976-1977, which was savagely cold in the Eastern half of the United States. But that was the end of it. From 1978 on, nearly all articles on climate in the New York Times were oriented toward greenhouse warming. In the Readers’ Guide listing of U.S. popular articles, warnings about climate were more or less evenly divided between heating and cooling up to 1977, but then articles about global warming took over almost completely.(70*)
As an example of the change, in 1976 the U.S. News & World Report described (with strong qualifications) the theories that the world would be getting cooler. The very next year the same magazine reported that “The world may be inching into a prolonged warming trend that is the direct result of burning more and more fossil fuels…” The ice-age theories, said the article, “are being convincingly opposed by growing evidence of human impact.”(71) Similarly, in 1976 Business Week had explained both sides of the debate but reported that “the dominant school maintains that the world is becoming cooler.” Just one year later, the magazine declared that CO2 “may be the world’s biggest environmental problem, threatening to raise the world’s temperature” with horrendous long-term consequences.(72*)
The change in press coverage was not due to any obvious change in the weather — the winter of 1978-79 was the coldest on record for the United States. Nor was there any single scientific revelation, for amid the complexities of geophysics, no individual finding could ever be decisive. But several research results published in the mid 1970s (perhaps especially from computer models) swayed the opinions of scientists. In early 1978 the New York Times reported that a poll of climate scientists found them evenly divided on whether there would be warming, cooling, or no particular change. But the balance among the handful of top experts had shifted strongly toward the likelihood of warming. In the scientific journals, where articles are published only after critical review by scientist peers, after the mid 1970s the papers predicting global warming predominated and became increasingly numerous.(72a)
The views represented in the scientific literature migrated, with the usual exaggeration and simplification, to science journalists. The journalists conveyed two important points to the public. One of these points would be obvious to anyone who read just the headlines and titles of the various articles: scientists remained uncertain and divided about what would really happen. The other point crept in on a deeper level. It was put explicitly in a 1977 Readers’ Digest article where the author, after emphasizing the disagreements among experts, stated his principal conclusion: “All scientists agree that a new factor has entered the game of climate change, a ‘wild card’ never there before — man himself.”(73)
Meanwhile new studies convinced an increasing number of scientists that, given a choice between warming and cooling, it was the greenhouse effect that would dominate sooner or later. Theoretical work on aerosols suggested that human smog and dust might not cool the atmosphere very much after all. At most, the increased pollution might bring a mild cooling that would only temporarily mask greenhouse warming. Other studies suggested that the greenhouse effect might already be changing the weather. Computer models, although still provisional, tended to agree that the rising level of CO2 would bring a degree or so of warming within decades.
Not only future weather, but weighty questions of present policies were at stake. The worries about climate change became entangled in debates about fuel supplies. The “oil crises” of 1973 and 1979, when gasoline became shockingly expensive or even unobtainable, aroused a keen public interest in energy policy. Environmentalists were mobilizing public opinion to block nuclear power. But their preferred technology of solar power was a long way from being cheap enough (or even environmentally friendly enough) to fuel the nation. The remaining alternative was a rapid boost in coal burning. Experts, including a minority of environmentalists, pointed out that coal might be worse than nuclear power because of its polluting emissions, including greenhouse gases. Some officials in the government energy establishment called for intensive study of global warming, in case the threat turned out to be severe. “If the CO2 problem looks big enough,” one of them promised, “we’ll make changes — and fast.”(74*)
These arguments only reached limited circles in government and industry, scarcely penetrating public consciousness. The sense of urgency about climate change was dwindling away. It had never been very strong, even during the droughts and famines of the early 1970s. By the end of the decade, the collapse of doom-filled claims about an imminent ice age, replaced by uncertain speculations about possible future warming, left little for the media to bite into. The widely reported debates over the speculations of a few scientists, added to confusion about whether even the observed temperatures were falling or rising, convinced many people that the science was too foggy to be worth much attention. Moreover, the basic climate concern of “food security” — the dread of famine that haunted everyone from grandmothers to policy makers — sank out of view for the first time in human history. In the 1970s, the biotechnology “green revolution” burst upon farmers. By the end of the century, world food prices would decline in real terms by some 70%. Neither famine nor anything else relating to climate change seemed immediately worrisome. The topic settled down as a mildly interesting public issue, far less urgent than many others.
Click here for continuation: The Public and Climate, since 1980
1. The classic discussion is Glacken (1967); see also Neumann (1985). BACK
2. Fleming (1990); Fleming (1998), ch.s 2-4; Stehr (1995); Stehr and von Storch (2000), introduction and chapter 4; the latter is a translation of Brückner (1890), chapter 1, including “psychological puzzle” on p. 115-16 of Stehr. BACK
3. Price (1995), pp. 59, 69. Actually every arctic hiker knows how swiftly a freeze can come and how a shifting riverbed can bury the careless in permafrost. BACK
4. Callendar, personal notes, Nov. 1960, Schove-Callendar Collection, Climatic Research Unit, University of East Anglia, Norwich, UK, quoted by Peter Brimblecombe and Ian Langford, “Guy Steward [sic] Callendar and the increase in global carbon dioxide,” paper presented at meeting of Air & Waste Management Association, San Antonio, Texas, June 1995 (paper 95-WA74A.02, available from AWMA). BACK
5. Thus Callendar in his landmark paper argued in 1938 that growing efficiency had stabilized the amount of gas production in the previous 20 years, ignoring the Depression’s effects, Callendar (1938), p. 231; Plass implicitly assumed linear growth in calculating that it would take a thousand years to use up known reserves of coal and oil, Plass (1956), p. 149; similarly in the crucial paper Revelle and Suess (1957). BACK
6. Arrhenius (1908), p. 63. BACK
7. Callendar (1938), p. 236. BACK
8. Ekholm (1901), p. 61. Revision of a paper first published in Sweden in 1895. See also Fleming (2010), pp. 4-5. BACK
8a. Miyazawa (1932). My thanks to Kooiti Masuda for this information. BACK
9. Time (1939); other examples: Kimble (1950); Abarbanel and McCluskey (1950); here and below, see also Fleming (1998), pp. 131-32. BACK
10. H.T. Kimble quoted Time (1951). BACK
11. “Deluge… new food-producing areas:” Abarbanel and McCluskey (1950), p. 63; a widely read book (first printing 100,000 copies) warning of floods and drought was Baxter (1953); Baxter was disparaged e.g. by Bello (1954). BACK
12. For racist-tinged concern that heat is enervating: e.g., Huntington (1916); Sears (1953), p. 43 (note also Shapley’s preface, p. vi); Coon (1953); discussion of Huntington in Fleming (1998), ch. 8; Coughlan (1950) (condensed in Readers’ Digest, Nov. 1950). BACK
13. “Do not know”: Time (1939). Thirty years hence: Editorial (probably by W. Kaempffert), New York Times, Aug. 10, 1952, section IV. BACK
14. For example, Engel (1953). BACK
15. Baxter (1953), p. 69. BACK
16. For the anti-smoke movement, Stradling (1999); on air pollution and pollution in general, McNeill (2000). BACK
17. Harrison (1982), p. 737. BACK
18. Weart (1988), p. 187 and passim; “large numbers:” This Week, condensed as Robbins (1956), p. 83; further references are in Hart and Victor (1993), pp. 647-48 and n22. BACK
19. Weart (1988), ch. 4, also pp. 296-99 and passim. BACK
20. Velikovsky (1955), mammoths p. 4; Hapgood (1958), mammoths ch. 8; Brown (1948) (an example of a crank pamphlet), mammoths p. 9; for further references, see Huggett (1990), pp. 119-21. BACK
21. Friedan (1958), also published condensed in Reader’s Digest, DATE??. BACK
22. Folder “Ice Age Fan Mail,” preliminary box 52, Maurice Ewing Collection, Center for American History, University of Texas at Austin. BACK
23. “Unproved speculation:” Cowen (1960), pp. 186-89, who also put any ice age centuries in the future. Another example: “the beginning of the next glacial era might still be breathing down our necks,” but “Much time and study and additional evidence will be necessary before even an informed guess can be made:” Andrist (1960). BACK
24. F.W. Reichelderfer at WMO Congress, New York Times, May 18, 1955. BACK
25. Helmut Landsberg reported in the New York Times, Feb. 15, 1959. For Hans Ahlmann, a main publicist of non-anthropogenic “polar warming,” see Sörlin (2011). BACK
26. United States Congress (85:2) (1957), pp. 104, 105, 106; one popular writer who took up the “experiment” term (quoting the Woods Hole oceanographer Columbus Iselin), was Robert C. Cowen, “Are men changing the Earth’s weather?” Christian Science Monitor, Dec. 4, 1957, see Cowen (1960), pp. 181-82; the “spaceship earth” trope was popularized a decade later by Buckminster Fuller, see Jasanoff (2001), p. 319. BACK
27. “Fumes Seen,” Lloyd Norman for Chicago Tribune Press Service, as seen in Washington Post, March 19, 1956. Phrases first published (“a large scale global warming, with radical climate changes may result” in The Hammond Times (Indiana), Nov. 6, 1957, from the Global Warming Newspaper Archive. Only one earlier relevant use of “climate change” is found there, from 1952. The archive shows only scattered uses of “global warming” (and little more for “climate change”) into the 1970s, with a significant rise for “global warming” after 1975. The publication that brought the phrase into widespread use was probably Broecker (1975) (titled, “Climatic Change: Are We on the Brink of a Pronounced Global Warming?”), although a Sept. 1976 statement by M.I. Budyko that “a global warming up has started,” as quoted by the Soviet news agency TASS, was more widely reported. BACK
28. Plass (1959); Plass’s 1953 calculation of a somewhat more gradual rise was carried earlier in the media in small notes, e.g., the climate may be “getting about 1-1/2 degrees hotter per century,” Newsweek (1953). Kaempffert considered but dismissed nuclear energy as a solution.Waldemar Kaempffert, “Warmer Climate on the Earth May Be Due To More Carbon Dioxide in the Air,” New York Times, Oct. 28, 1956. The Times also reported (Sept. 11, 1961) C.D. Keeling’s discovery that the CO2 level in the atmosphere was rising. BACK
30. Cook (1957), p. 121. An exceptional early response to Callendar’s and Plass’s work was Putnam (1953). Putnam, a wind-power engineer, noted that the exponential rise of fossil fuel consumption might eventually change the climate and raise sea level. His conclusion (p. 170): “If there exists a possibility that the maximum plausible expansion of demands for energy… may inadvertently affect the weather, we should investigate until doubt is removed.” BACK
30a. Council on Environmental Quality (1970), pp. 1043, 1046. BACK
31. Conservation Foundation, Annual Report for 1963, pp. 19-20, see Conservation Foundation (1963). BACK
32. President’s Science Advisory Committee (1965). BACK
33. Zelazny (1969). Later made into a B movie (1977, directed by Jack Smight). Based on a novelette that I read in 1967 in Galaxy magazine — I remember some of the scenes vividly even now. BACK
34. Carson quoted in Graham (1970), p. 14; on all this, see Weart (1988), pp. 323-25. BACK
35. E.g., Ehrlich and Holdren (1971). For “environmental catastrophism” see Hamblin (2013). See also Masco (2010). BACK
36. Meadows et al. (1972); Edwards (2000a). BACK
37. The influence of the Apollo pictures of Dec.1968 (Earthrise over the Moon, by William Anders) and Dec.1972 (the Whole Earth) cannot be proven but many have testified to it. Like all great symbols the Whole Earth was exploited for diverse purposes, see Garb (1985); Jasanoff (2001), pp. 316-17; Maher (2005); for astronauts, White (1987). BACK
38. SCEP (1970), p. 12; see also Matthews et al. (1971); Kellogg (1987), pp. 120-22. BACK
39. Wilson and Matthews (1971), p. v. BACK
40. Hood (1971), p. v, “provocative” p. vi. BACK
41. Smagorinsky (1970), p. 25, from a talk at an August 1969 conference. BACK
42. McIntyre (1972), p. 37. BACK
43. New York Times, Jan. 27, 1972. Quote: Time (1972). BACK
44. G.S. Benton, chair of Johns Hopkins Dept. of Earth & Planetary Sciences, to 1970 National Academy of Sciences symposium, New York Times, April 30, 1970. BACK
45. Henderson-Sellers and Robinson (1986), pp. 10-11. BACK
46. My counts. A sharp increase in coverage in magazines and newspapers in the mid 1970s is also reported by a qualitative survey, Harrison (1982), p. 737. BACK
47. harbinger: Time (1974a); Academy report: Newsweek (1975); Time (1974b), p. 83. BACK
48. Ponte (1976), pp. 234-35. BACK
49. Bryson (1967). BACK
50. Alexander (1974), quote p. 92; current thinking on the drought: Rotstayn and Lohmann (2002). BACK
51. Kellogg (1971), pp. 123, 131; GARP (1975), p. 189, from App. A (pp. 186-90) by J. Imbrie, W.S. Broecker, J.M. Mitchell, Jr., J.E. Kutzbach. New York Times, Jan. 19, 1975, p. 31. BACK
52. Central Intelligence Agency, “Potential implications of trends in world population, food production, and climate,” OPR-401, Aug. 1974, published as Appendix II to Impact Team (1977), quote p. 200. News of the report was first published in the New York Times, May 1, 1976, p. 2; scientists quoted: U.S. News & World Report (1976); Bryson, personal communication, 2002. BACK
53. Hays (1973), quotes p. 29, 32. Ponte (1976), p. xiv. BACK
54. Peterson et al. (2008) discuss all this in detail. World Meteorological Organization, Press Release and WMO Statement on Climatic Change, WMO/No.319 (June 18, 1976), copy kindly provided by John Mabb. National Academy of Sciences (1977). BACK
55. “Within our lifetime,” Wolkomir (1976), p. 50. “I am a little touchy about this point,” Bryson added. Bryson testimony, May 26, 1976, United States Congress (94:2) (1976), p. 211. BACK
56. Mammoths frozen “swiftly in their tracks,” Impact Team (1977), p. 19; trigger ice age: Rasool and Schneider (1971), see comment here on their paper; for lake sediments Wolkomir, op. cit., quotes David W. Folger, and for ice cores C. Langway, p. 78. BACK
57. “The Weather Machine,” BBC-television (a co-production with the U.S. Corporation for Public Broadcasting and WNET), first aired 20 Nov. 1974, expanded in a book: Calder (1975), quote p. 134; he based the “snowblitz” idea on Lamb and Woodroffe (1970); see also Brooks (1925), pp. 90-91. BACK
58. Fagan (2000). BACK
59. Bryson and Murray (1977). BACK
60. Schneider and Mesirow. (1976), esp. chap. 3; Kellogg and Schneider (1974); Hammond (1976); Glantz (1977). BACK
60a. In addition to Peterson et al. (2008) (as noted above), see Howe (2014), pp. 100-103, and discussion and references by RealClimate and W. Connolley. BACK
61. B.J. Mason, speaking mainly about aerosols and ozone. He admitted that greenhouse warming could become significant in 50-100 years. Gribbin (1976); Mason (1977). BACK
62. Stumm (1977), articles by A.M. Weinberg and R. M. Rotty, pp. 225-39, by H. Brooks, pp. 241-52, report by A. Nir et al., pp. 312-22, and passim. BACK
63. Reiners and Olson at 1972 Brookhaven Symposium in Biology, Reiners (1973), p. 327. BACK
64. Bert Bolin in McIntyre (1972), p. 253. BACK
65. Barrett and Landsberg (1975), p. 79. BACK
66. Horwitch (1982), pp. 318-20; Howe (2014), ch. 2. BACK
67. Gribbin (1988); also Dotto and Schiff (1978); Roan (1989), see p. 58. BACK
68. Broecker (1975), reported in New York Times, Aug. 14, 1975, p. 24. Influence of Broecker on a member of the President’s Council of Economic Advisers is reported in New York Times, June 3, 1977, IV p. 13. BACK
69. National Academy of Sciences (1977); reported: e.g., New York Times, July 25, 1977, p. 1, and Business Week (1977). BACK
70. My counts based on titles (for a given article the titles are all that most of the public reads). A compilation of cooling scare quotes includes items from 1971 and especially from 1975 to 1977 and none later, Bray (1991). BACK
71. U.S. News & World Report (1976); U.S. News & World Report (1977). BACK
72. Business Week (1976); Business Week (1977). BACK
72a. Poll: New York Times, Feb. 18, 1978, p. 9. Journals: Peterson et al (2008). BACK
73. Matthews (1977), p. 92. BACK
74. P.C. White of ERDA, quoted Business Week (1977). My own serious awareness of the greenhouse effect began ca.1980 when I began to study pro- and anti-nuclear power arguments; see the brief mention at Weart (1988), p. 338. BACK
copyright © 2003-2017 Spencer Weart & American Institute of Physics
The really interesting difference concerns hydro, solar and wind power. BP’s higher figure isn’t because it is more bullish on these. Rather, in order to make the renewables figures comparable with the ones for fossil fuels and nuclear power, BP grosses them up as if they also produced waste energy. The IEA doesn’t do this, so its figure represents just the energy derived from a solar panel, wind turbine, or hydro plant. The IEA figure is 36 percent of the BP one, similar to the 38 percent conversion factor BP uses to adjust the data.
