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If the world had adopted the proposal widely endorsed at the end of the ’80s — a freezing of carbon emissions, with a reduction of 20 percent by 2005 — warming could have been held to less than 1.5 degrees.

Action had to be taken, and the United States would need to lead. It didn’t.

There can be no understanding of our current and future predicament without understanding why we failed to solve this problem when we had the chance.

The first suggestion to Rafe Pomerance that humankind was destroying the conditions necessary for its own survival came on Page 66 of the government publication EPA-600/7-78-019. It was a technical report about coal

‘This Is the Whole Banana’ Spring 1979

here was an urgent problem that demanded their attention, MacDonald believed, because human civilization faced an existential crisis. In “How to Wreck the Environment,” a 1968 essay published while he was a science adviser to Lyndon Johnson, MacDonald predicted a near future in which “nuclear weapons were effectively banned and the weapons of mass destruction were those of environmental catastrophe.” One of the most potentially devastating such weapons, he believed, was the gas that we exhaled with every breath: carbon dioxide. By vastly increasing carbon emissions, the world’s most advanced militaries could alter weather patterns and wreak famine, drought and economic collapse.

the Jasons. They were like one of those teams of superheroes with complementary powers that join forces in times of galactic crisis. They had been brought together by federal agencies, including the C.I.A, to devise scientific solutions to national-security problems: how to detect an incoming missile; how to predict fallout from a nuclear bomb; how to develop unconventional weapons, like plague-infested rats.

Agle pointed to an article about a prominent geophysicist named Gordon MacDonald, who was conducting a study on climate change with the Jasons, the mysterious coterie of elite scientists to which he belonged

During the spring of 1977 and the summer of 1978, the Jasons met to determine what would happen once the concentration of carbon dioxide in the atmosphere doubled from pre-Industrial Revolution levels. It was an arbitrary milestone, the doubling, but a useful one, as its inevitability was not in question; the threshold would most likely be breached by 2035.

The Jasons’ report to the Department of Energy, “The Long-Term Impact of Atmospheric Carbon Dioxide on Climate,” was written in an understated tone that only enhanced its nightmarish findings: Global temperatures would increase by an average of two to three degrees Celsius; Dust Bowl conditions would “threaten large areas of North America, Asia and Africa”; access to drinking water and agricultural production would fall, triggering mass migration on an unprecedented scale. “Perhaps the most ominous feature,” however, was the effect of a changing climate on the poles. Even a minimal warming “could lead to rapid melting” of the West Antarctic ice sheet. The ice sheet contained enough water to raise the level of the oceans 16 feet.

MacDonald explained that he first studied the carbon-dioxide issue when he was about Pomerance’s age — in 1961, when he served as an adviser to John F. Kennedy. Pomerance pieced together that MacDonald, in his youth, had been something of a prodigy: In his 20s, he advised Dwight D. Eisenhower on space exploration; at 32, he became a member of the National Academy of Sciences; at 40, he was appointed to the inaugural Council on Environmental Quality, where he advised Richard Nixon on the environmental dangers of burning coal. He monitored the carbon-dioxide problem the whole time, with increasing alarm.

They were surprised to learn how few senior officials were familiar with the Jasons’ findings, let alone understood the ramifications of global warming. At last, having worked their way up the federal hierarchy, the two went to see the president’s top scientist, Frank Press.

Thus began the Gordon and Rafe carbon-dioxide roadshow. Beginning in the spring of 1979, Pomerance arranged informal briefings with the E.P.A., the National Security Council, The New York Times, the Council on Environmental Quality and the Energy Department, which, Pomerance learned, had established an Office of Carbon Dioxide Effects two years earlier at MacDonald’s urging

. Out of respect for MacDonald, Press had summoned to their meeting what seemed to be the entire senior staff of the president’s Office of Science and Technology Policy — the officials consulted on every critical matter of energy and national security. What Pomerance had expected to be yet another casual briefing assumed the character of a high-level national-security meeting.

MacDonald would begin his presentation by going back more than a century to John Tyndall — an Irish physicist who was an early champion of Charles Darwin’s work and died after being accidentally poisoned by his wife. In 1859, Tyndall found that carbon dioxide absorbed heat and that variations in the composition of the atmosphere could create changes in climate. These findings inspired Svante Arrhenius, a Swedish chemist and future Nobel laureate, to deduce in 1896 that the combustion of coal and petroleum could raise global temperatures. This warming would become noticeable in a few centuries, Arrhenius calculated, or sooner if consumption of fossil fuels continued to increase.

Four decades later, a British steam engineer named Guy Stewart Callendar discovered that, at the weather stations he observed, the previous five years were the hottest in recorded history. Humankind, he wrote in a paper, had become “able to speed up the processes of Nature.” That was in 1939.

MacDonald’s history concluded with Roger Revelle, perhaps the most distinguished of the priestly caste of government scientists who, since the Manhattan Project, advised every president on major policy; he had been a close colleague of MacDonald and Press since they served together under Kennedy. In a 1957 paper written with Hans Suess, Revelle concluded that “human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.” Revelle helped the Weather Bureau establish a continuous measurement of atmospheric carbon dioxide at a site perched near the summit of Mauna Loa on the Big Island of Hawaii, 11,500 feet above the sea — a rare pristine natural laboratory on a planet blanketed by fossil-fuel emissions.

After nearly a decade of observation, Revelle had shared his concerns with Lyndon Johnson, who included them in a special message to Congress two weeks after his inauguration. Johnson explained that his generation had “altered the composition of the atmosphere on a global scale” through the burning of fossil fuels, and his administration commissioned a study of the subject by his Science Advisory Committee. Revelle was its chairman, and its 1965 executive report on carbon dioxide warned of the rapid melting of Antarctica, rising seas, increased acidity of fresh waters — changes that would require no less than a coordinated global effort to forestall.Yet emissions continued to rise, and at this rate, MacDonald warned, they could see a snowless New England, the swamping of major coastal cities, as much as a 40 percent decline in national wheat production, the forced migration of about one-quarter of the world’s population. Not within centuries — within their own lifetimes.

On May 22, Press wrote a letter to the president of the National Academy of Sciences requesting a full assessment of the carbon-dioxide issue. Jule Charney, the father of modern meteorology, would gather the nation’s top oceanographers, atmospheric scientists and climate modelers to judge whether MacDonald’s alarm was justified — whether the world was, in fact, headed to cataclysm.

If Charney’s group confirmed that the world was careering toward an existential crisis, the president would be forced to act.

Hansen turned from the moon to Venus. Why, he tried to determine, was its surface so hot? In 1967, a Soviet satellite beamed back the answer: The planet’s atmosphere was mainly carbon dioxide. Though once it may have had habitable temperatures, it was believed to have succumbed to a runaway greenhouse effect: As the sun grew brighter, Venus’s ocean began to evaporate, thickening the atmosphere, which forced yet greater evaporation — a self-perpetuating cycle that finally boiled off the ocean entirely and heated the planet’s surface to more than 800 degrees Fahrenheit

At the other extreme, Mars’s thin atmosphere had insufficient carbon dioxide to trap much heat at all, leaving it about 900 degrees colder. Earth lay in the middle, its Goldilocks greenhouse effect just strong enough to support life.

We want to learn more about Earth’s climate, Jim told Anniek — and how humanity can influence it. He would use giant new supercomputers to map the planet’s atmosphere. They would create Mirror Worlds: parallel realities that mimicked our own. These digital simulacra, technically called “general circulation models,” combined the mathematical formulas that governed the behavior of the sea, land and sky into a single computer model. Unlike the real world, they could be sped forward to reveal the future.

The government officials, many of them scientists themselves, tried to suppress their awe of the legends in their presence: Henry Stommel, the world’s leading oceanographer; his protégé, Carl Wunsch, a Jason; the Manhattan Project alumnus Cecil Leith; the Harvard planetary physicist Richard Goody. These were the men who, in the last three decades, had discovered foundational principles underlying the relationships among sun, atmosphere, land and ocean — which is to say, the climate.

When, at Charney’s request, Hansen programmed his model to consider a future of doubled carbon dioxide, it predicted a temperature increase of four degrees Celsius. That was twice as much warming as the prediction made by the most prominent climate modeler, Syukuro Manabe, whose government lab at Princeton was the first to model the greenhouse effect. The difference between the two predictions — between warming of two degrees Celsius and four degrees Celsius — was the difference between damaged coral reefs and no reefs whatsoever, between thinning forests and forests enveloped by desert, between catastrophe and chaos.

The discrepancy between the models, Arakawa concluded, came down to ice and snow. The whiteness of the world’s snowfields reflected light; if snow melted in a warmer climate, less radiation would escape the atmosphere, leading to even greater warming. Shortly before dawn, Arakawa concluded that Manabe had given too little weight to the influence of melting sea ice, while Hansen had overemphasized it. The best estimate lay in between. Which meant that the Jasons’ calculation was too optimistic. When carbon dioxide doubled in 2035 or thereabouts, global temperatures would increase between 1.5 and 4.5 degrees Celsius, with the most likely outcome a warming of three degrees.

within the highest levels of the federal government, the scientific community and the oil-and-gas industry — within the commonwealth of people who had begun to concern themselves with the future habitability of the planet — the Charney report would come to have the authority of settled fact. It was the summation of all the predictions that had come before, and it would withstand the scrutiny of the decades that followed it. Charney’s group had considered everything known about ocean, sun, sea, air and fossil fuels and had distilled it to a single number: three. When the doubling threshold was broached, as appeared inevitable, the world would warm three degrees Celsius

The last time the world was three degrees warmer was during the Pliocene, three million years ago, when beech trees grew in Antarctica, the seas were 80 feet higher and horses galloped across the Canadian coast of the Arctic Ocean.

After the publication of the Charney report, Exxon decided to create its own dedicated carbon-dioxide research program, with an annual budget of $600,000. Only Exxon was asking a slightly different question than Jule Charney. Exxon didn’t concern itself primarily with how much the world would warm. It wanted to know how much of the warming Exxon could be blamed for.

“It behooves us to start a very aggressive defensive program,” Shaw wrote in a memo to a manager, “because there is a good probability that legislation affecting our business will be passed.”

Shaw turned to Wallace Broecker, a Columbia University oceanographer who was the second author of Roger Revelle’s 1965 carbon-dioxide report for Lyndon Johnson. In 1977, in a presentation at the American Geophysical Union, Broecker predicted that fossil fuels would have to be restricted, whether by taxation or fiat. More recently, he had testified before Congress, calling carbon dioxide “the No.1 long-term environmental problem.” If presidents and senators trusted Broecker to tell them the bad news, he was good enough for Exxon.

The company had been studying the carbon-dioxide problem for decades, since before it changed its name to Exxon. In 1957, scientists from Humble Oil published a study tracking “the enormous quantity of carbon dioxide” contributed to the atmosphere since the Industrial Revolution “from the combustion of fossil fuels.” Even then, the observation that burning fossil fuels had increased the concentration of carbon in the atmosphere was well understood and accepted by Humble’s scientists.

The American Petroleum Institute, the industry’s largest trade association, asked the same question in 1958 through its air-pollution study group and replicated the findings made by Humble Oil. So did another A.P.I. study conducted by the Stanford Research Institute a decade later, in 1968, which concluded that the burning of fossil fuels would bring “significant temperature changes” by the year 2000 and ultimately “serious worldwide environmental changes,” including the melting of the Antarctic ice cap and rising seas.

The ritual repeated itself every few years. Industry scientists, at the behest of their corporate bosses, reviewed the problem and found good reasons for alarm and better excuses to do nothing. Why should they act when almost nobody within the United States government — nor, for that matter, within the environmental movement — seemed worried?

Why take on an intractable problem that would not be detected until this generation of employees was safely retired? Worse, the solutions seemed more punitive than the problem itself. Historically, energy use had correlated to economic growth — the more fossil fuels we burned, the better our lives became. Why mess with that?

That June, Jimmy Carter signed the Energy Security Act of 1980, which directed the National Academy of Sciences to start a multiyear, comprehensive study, to be called “Changing Climate,” that would analyze social and economic effects of climate change. More urgent, the National Commission on Air Quality, at the request of Congress, invited two dozen experts, including Henry Shaw himself, to a meeting in Florida to propose climate policy.

On April 3, 1980, Senator Paul Tsongas, a Massachusetts Democrat, held the first congressional hearing on carbon-dioxide buildup in the atmosphere. Gordon MacDonald testified that the United States should “take the initiative” and develop, through the United Nations, a way to coordinate every nation’s energy policies to address the problem.

During the expansion of the Clean Air Act, he pushed for the creation of the National Commission on Air Quality, charged with ensuring that the goals of the act were being met. One such goal was a stable global climate. The Charney report had made clear that goal was not being met, and now the commission wanted to hear proposals for legislation. It was a profound responsibility, and the two dozen experts invited to the Pink Palace — policy gurus, deep thinkers, an industry scientist and an environmental activist — had only three days to achieve it, but the utopian setting made everything seem possible

We have less time than we realize, said an M.I.T. nuclear engineer named David Rose, who studied how civilizations responded to large technological crises. “People leave their problems until the 11th hour, the 59th minute,” he said. “And then: ‘Eloi, Eloi, Lama Sabachthani?’ ” — “My God, my God, why hast thou forsaken me?”

The attendees seemed to share a sincere interest in finding solutions. They agreed that some kind of international treaty would ultimately be needed to keep atmospheric carbon dioxide at a safe level. But nobody could agree on what that level was.

William Elliott, a NOAA scientist, introduced some hard facts: If the United States stopped burning carbon that year, it would delay the arrival of the doubling threshold by only five years. If Western nations somehow managed to stabilize emissions, it would forestall the inevitable by only eight years. The only way to avoid the worst was to stop burning coal. Yet China, the Soviet Union and the United States, by far the world’s three largest coal producers, were frantically accelerating extraction.

“Do we have a problem?” asked Anthony Scoville, a congressional science consultant. “We do, but it is not the atmospheric problem. It is the political problem.” He doubted that any scientific report, no matter how ominous its predictions, would persuade politicians to act.

The talk of ending oil production stirred for the first time the gentleman from Exxon. “I think there is a transition period,” Henry Shaw said. “We are not going to stop burning fossil fuels and start looking toward solar or nuclear fusion and so on. We are going to have a very orderly transition from fossil fuels to renewable energy sources.”

What if the problem was that they were thinking of it as a problem? “What I am saying,” Scoville continued, “is that in a sense we are making a transition not only in energy but the economy as a whole.” Even if the coal and oil industries collapsed, renewable technologies like solar energy would take their place. Jimmy Carter was planning to invest $80 billion in synthetic fuel. “My God,” Scoville said, “with $80 billion, you could have a photovoltaics industry going that would obviate the need for synfuels forever!”

nobody could agree what to do. John Perry, a meteorologist who had worked as a staff member on the Charney report, suggested that American energy policy merely “take into account” the risks of global warming, though he acknowledged that a nonbinding measure might seem “intolerably stodgy.” “It is so weak,” Pomerance said, the air seeping out of him, “as to not get us anywhere.”

Scoville pointed out that the United States was responsible for the largest share of global carbon emissions. But not for long. “If we’re going to exercise leadership,” he said, “the opportunity is now.

One way to lead, he proposed, would be to classify carbon dioxide as a pollutant under the Clean Air Act and regulate it as such. This was received by the room like a belch. By Scoville’s logic, every sigh was an act of pollution. Did the science really support such an extreme measure? The Charney report did exactly that, Pomerance said.

Slade, the director of the Energy Department’s carbon-dioxide program, considered the lag a saving grace. If changes did not occur for a decade or more, he said, those in the room couldn’t be blamed for failing to prevent them. So what was the problem?

“Call it whatever.” Besides, Pomerance added, they didn’t have to ban coal tomorrow. A pair of modest steps could be taken immediately to show the world that the United States was serious: the implementation of a carbon tax and increased investment in renewable energy. Then the United States could organize an international summit meeting to address climate change

these two dozen experts, who agreed on the major points and had made a commitment to Congress, could not draft a single paragraph. Hours passed in a hell of fruitless negotiation, self-defeating proposals and impulsive speechifying. Pomerance and Scoville pushed to include a statement calling for the United States to “sharply accelerate international dialogue,” but they were sunk by objections and caveats.

They never got to policy proposals. They never got to the second paragraph. The final statement was signed by only the moderator, who phrased it more weakly than the declaration calling for the workshop in the first place. “The guide I would suggest,” Jorling wrote, “is whether we know enough not to recommend changes in existing policy.”

Pomerance had seen enough. A consensus-based strategy would not work — could not work — without American leadership. And the United States wouldn’t act unless a strong leader persuaded it to do so — someone who would speak with authority about the science, demand action from those in power and risk everything in pursuit of justice.

The meeting ended Friday morning. On Tuesday, four days later, Ronald Reagan was elected president.

‘Otherwise, They’ll Gurgle’ November 1980-September 1981

In the midst of this carnage, the Council on Environmental Quality submitted a report to the White House warning that fossil fuels could “permanently and disastrously” alter Earth’s atmosphere, leading to “a warming of the Earth, possibly with very serious effects.” Reagan did not act on the council’s advice. Instead, his administration considered eliminating the council.

After the election, Reagan considered plans to close the Energy Department, increase coal production on federal land and deregulate surface coal mining. Once in office, he appointed James Watt, the president of a legal firm that fought to open public lands to mining and drilling, to run the Interior Department. “We’re deliriously happy,” the president of the National Coal Association was reported to have said. Reagan preserved the E.P.A. but named as its administrator Anne Gorsuch, an anti-regulation zealot who proceeded to cut the agency’s staff and budget by about a quarter

Reagan “has declared open war on solar energy,” the director of the nation’s lead solar-energy research agency said, after he was asked to resign). Reagan appeared determined to reverse the environmental achievements of Jimmy Carter, before undoing those of Richard Nixon, Lyndon Johnson, John F. Kennedy and, if he could get away with it, Theodore Roosevelt.

When Reagan considered closing the Council on Environmental Quality, its acting chairman, Malcolm Forbes Baldwin, wrote to the vice president and the White House chief of staff begging them to reconsider; in a major speech the same week, “A Conservative’s Program for the Environment,” Baldwin argued that it was “time for today’s conservatives explicitly to embrace environmentalism.” Environmental protection was not only good sense. It was good business. What could be more conservative than an efficient use of resources that led to fewer federal subsidies?

Meanwhile the Charney report continued to vibrate at the periphery of public consciousness. Its conclusions were confirmed by major studies from the Aspen Institute, the International Institute for Applied Systems Analysis near Vienna and the American Association for the Advancement of Science. Every month or so, nationally syndicated articles appeared summoning apocalypse: “Another Warning on ‘Greenhouse Effect,’ ” “Global Warming Trend ‘Beyond Human Experience,’ ” “Warming Trend Could ‘Pit Nation Against Nation.’

Pomerance read on the front page of The New York Times on Aug. 22, 1981, about a forthcoming paper in Science by a team of seven NASA scientists. They had found that the world had already warmed in the past century. Temperatures hadn’t increased beyond the range of historical averages, but the scientists predicted that the warming signal would emerge from the noise of routine weather fluctuations much sooner than previously expected. Most unusual of all, the paper ended with a policy recommendation: In the coming decades, the authors wrote, humankind should develop alternative sources of energy and use fossil fuels only “as necessary.” The lead author was James Hansen.

Pomerance listened and watched. He understood Hansen’s basic findings well enough: Earth had been warming since 1880, and the warming would reach “almost unprecedented magnitude” in the next century, leading to the familiar suite of terrors, including the flooding of a 10th of New Jersey and a quarter of Louisiana and Florida. But Pomerance was excited to find that Hansen could translate the complexities of atmospheric science into plain English.

7. ‘We’re All Going to Be the Victims’ March 1982

Gore had learned about climate change a dozen years earlier as an undergraduate at Harvard, when he took a class taught by Roger Revelle. Humankind was on the brink of radically transforming the global atmosphere, Revelle explained, drawing Keeling’s rising zigzag on the blackboard, and risked bringing about the collapse of civilization. Gore was stunned: Why wasn’t anyone talking about this?

Most in Congress considered the science committee a legislative backwater, if they considered it at all; this made Gore’s subcommittee, which had no legislative authority, an afterthought to an afterthought. That, Gore vowed, would change. Environmental and health stories had all the elements of narrative drama: villains, victims and heroes. In a hearing, you could summon all three, with the chairman serving as narrator, chorus and moral authority. He told his staff director that he wanted to hold a hearing every week.

The Revelle hearing went as Grumbly had predicted. The urgency of the issue was lost on Gore’s older colleagues, who drifted in and out while the witnesses testified. There were few people left by the time the Brookings Institution economist Lester Lave warned that humankind’s profligate exploitation of fossil fuels posed an existential test to human nature. “Carbon dioxide stands as a symbol now of our willingness to confront the future,” he said. “It will be a sad day when we decide that we just don’t have the time or thoughtfulness to address those issues.”

That night, the news programs featured the resolution of the baseball strike, the ongoing budgetary debate and the national surplus of butter.

There emerged, despite the general comity, a partisan divide. Unlike the Democrats, the Republicans demanded action. “Today I have a sense of déjà vu,” said Robert Walker, a Republican from Pennsylvania. In each of the last five years, he said, “we have been told and told and told that there is a problem with the increasing carbon dioxide in the atmosphere. We all accept that fact, and we realize that the potential consequences are certainly major in their impact on mankind.” Yet they had failed to propose a single law. “Now is the time,” he said. “The research is clear. It is up to us now to summon the political will.”

Hansen flew to Washington to testify on March 25, 1982, performing before a gallery even more thinly populated than at Gore’s first hearing on the greenhouse effect. Gore began by attacking the Reagan administration for cutting funding for carbon-dioxide research despite the “broad consensus in the scientific community that the greenhouse effect is a reality.” William Carney, a Republican from New York, bemoaned the burning of fossil fuels and argued passionately that science should serve as the basis for legislative policy

the experts invited by Gore agreed with the Republicans: The science was certain enough. Melvin Calvin, a Berkeley chemist who won the Nobel Prize for his work on the carbon cycle, said that it was useless to wait for stronger evidence of warming. “You cannot do a thing about it when the signals are so big that they come out of the noise,” he said. “You have to look for early warning signs.”

Hansen’s job was to share the warning signs, to translate the data into plain English. He explained a few discoveries that his team had made — not with computer models but in libraries. By analyzing records from hundreds of weather stations, he found that the surface temperature of the planet had already increased four-tenths of a degree Celsius in the previous century. Data from several hundred tide-gauge stations showed that the oceans had risen four inches since the 1880s

It occurred to Hansen that this was the only political question that mattered: How long until the worst began? It was not a question on which geophysicists expended much effort; the difference between five years and 50 years in the future was meaningless in geologic time. Politicians were capable of thinking only in terms of electoral time: six years, four years, two years. But when it came to the carbon problem, the two time schemes were converging.

“Within 10 or 20 years,” Hansen said, “we will see climate changes which are clearly larger than the natural variability.” James Scheuer wanted to make sure he understood this correctly. No one else had predicted that the signal would emerge that quickly. “If it were one or two degrees per century,” he said, “that would be within the range of human adaptability. But we are pushing beyond the range of human adaptability.” “Yes,” Hansen said.

How soon, Scheuer asked, would they have to change the national model of energy production? Hansen hesitated — it wasn’t a scientific question. But he couldn’t help himself. He had been irritated, during the hearing, by all the ludicrous talk about the possibility of growing more trees to offset emissions. False hopes were worse than no hope at all: They undermined the prospect of developing real solutions. “That time is very soon,” Hansen said finally. “My opinion is that it is past,” Calvin said, but he was not heard because he spoke from his seat. He was told to speak into the microphone. “It is already later,” Calvin said, “than you think.”

From Gore’s perspective, the hearing was an unequivocal success. That night Dan Rather devoted three minutes of “CBS Evening News” to the greenhouse effect. A correspondent explained that temperatures had increased over the previous century, great sheets of pack ice in Antarctica were rapidly melting, the seas were rising; Calvin said that “the trend is all in the direction of an impending catastrophe”; and Gore mocked Reagan for his shortsightedness. Later, Gore could take credit for protecting the Energy Department’s carbon-dioxide program, which in the end was largely preserved.

8. ‘The Direction of an Impending Catastrophe’ 1982

Following Henry Shaw’s recommendation to establish credibility ahead of any future legislative battles, Exxon had begun to spend conspicuously on global-warming research. It donated tens of thousands of dollars to some of the most prominent research efforts, including one at Woods Hole led by the ecologist George Woodwell, who had been calling for major climate policy as early as the mid-1970s, and an international effort coordinated by the United Nations. Now Shaw offered to fund the October 1982 symposium on climate change at Columbia’s Lamont-Doherty campus.

David boasted that Exxon would usher in a new global energy system to save the planet from the ravages of climate change. He went so far as to argue that capitalism’s blind faith in the wisdom of the free market was “less than satisfying” when it came to the greenhouse effect. Ethical considerations were necessary, too. He pledged that Exxon would revise its corporate strategy to account for climate change, even if it were not “fashionable” to do so. As Exxon had already made heavy investments in nuclear and solar technology, he was “generally upbeat” that Exxon would “invent” a future of renewable energy.

Hansen had reason to feel upbeat himself. If the world’s largest oil-and-gas company supported a new national energy model, the White House would not stand in its way. The Reagan administration was hostile to change from within its ranks. But it couldn’t be hostile to Exxon.

The carbon-dioxide issue was beginning to receive major national attention — Hansen’s own findings had become front-page news, after all. What started as a scientific story was turning into a political story.

The political realm was itself a kind of Mirror World, a parallel reality that crudely mimicked our own. It shared many of our most fundamental laws, like the laws of gravity and inertia and publicity. And if you applied enough pressure, the Mirror World of politics could be sped forward to reveal a new future. Hansen was beginning to understand that too.

1. ‘Caution, Not Panic’ 1983-1984

in the fall of 1983, the climate issue entered an especially long, dark winter. And all because of a single report that had done nothing to change the state of climate science but transformed the state of climate politics.

After the publication of the Charney report in 1979, Jimmy Carter had directed the National Academy of Sciences to prepare a comprehensive, $1 million analysis of the carbon-dioxide problem: a Warren Commission for the greenhouse effect. A team of scientist-dignitaries — among them Revelle, the Princeton modeler Syukuro Manabe and the Harvard political economist Thomas Schelling, one of the intellectual architects of Cold War game theory — would review the literature, evaluate the consequences of global warming for the world order and propose remedies

Then Reagan won the White House.

the incipient report served as the Reagan administration’s answer to every question on the subject. There could be no climate policy, Fred Koomanoff and his associates said, until the academy ruled. In the Mirror World of the Reagan administration, the warming problem hadn’t been abandoned at all. A careful, comprehensive solution was being devised. Everyone just had to wait for the academy’s elders to explain what it was.

The committee’s chairman, William Nierenberg — a Jason, presidential adviser and director of Scripps, the nation’s pre-eminent oceanographic institution — argued that action had to be taken immediately, before all the details could be known with certainty, or else it would be too late.

Better to bet on American ingenuity to save the day. Major interventions in national energy policy, taken immediately, might end up being more expensive, and less effective, than actions taken decades in the future, after more was understood about the economic and social consequences of a warmer planet. Yes, the climate would change, mostly for the worst, but future generations would be better equipped to change with it.

Government officials who knew Nierenberg were not surprised by his conclusions: He was an optimist by training and experience, a devout believer in the doctrine of American exceptionalism, one of the elite class of scientists who had helped the nation win a global war, invent the most deadly weapon conceivable and create the booming aerospace and computer industries. America had solved every existential problem it had confronted over the previous generation; it would not be daunted by an excess of carbon dioxide. Nierenberg had also served on Reagan’s transition team. Nobody believed that he had been directly influenced by his political connections, but his views — optimistic about the saving graces of market forces, pessimistic about the value of government regulation — reflected all the ardor of his party.

That’s what Nierenberg wrote in “Changing Climate.” But it’s not what he said in the press interviews that followed. He argued the opposite: There was no urgent need for action. The public should not entertain the most “extreme negative speculations” about climate change (despite the fact that many of those speculations appeared in his report). Though “Changing Climate” urged an accelerated transition to renewable fuels, noting that it would take thousands of years for the atmosphere to recover from the damage of the last century, Nierenberg recommended “caution, not panic.” Better to wait and see

The damage of “Changing Climate” was squared by the amount of attention it received. Nierenberg’s speech in the Great Hall, being one-500th the length of the actual assessment, received 500 times the press coverage. As The Wall Street Journal put it, in a line echoed by trade journals across the nation: “A panel of top scientists has some advice for people worried about the much-publicized warming of the Earth’s climate: You can cope.”

On “CBS Evening News,” Dan Rather said the academy had given “a cold shoulder” to a grim, 200-page E.P.A. assessment published earlier that week (titled “Can We Delay a Greenhouse Warming?”; the E.P.A.’s answer, reduced to a word, was no). The Washington Post described the two reports, taken together, as “clarion calls to inaction.

George Keyworth II, Reagan’s science adviser. Keyworth used Nierenberg’s optimism as reason to discount the E.P.A.’s “unwarranted and unnecessarily alarmist” report and warned against taking any “near-term corrective action” on global warming. Just in case it wasn’t clear, Keyworth added, “there are no actions recommended other than continued research.”

Edward David Jr., two years removed from boasting of Exxon’s commitment to transforming global energy policy, told Science that the corporation had reconsidered. “Exxon has reverted to being mainly a supplier of conventional hydrocarbon fuels — petroleum products, natural gas and steam coal,” David said. The American Petroleum Institute canceled its own carbon-dioxide research program, too.

Exxon soon revised its position on climate-change research. In a presentation at an industry conference, Henry Shaw cited “Changing Climate” as evidence that “the general consensus is that society has sufficient time to technologically adapt to a CO₂ greenhouse effect.” If the academy had concluded that regulations were not a serious option, why should Exxon protest

2. ‘You Scientists Win’ 1985

3. The Size of The Human Imagination Spring-Summer 1986

Curtis Moore’s proposal: Use ozone to revive climate. The ozone hole had a solution — an international treaty, already in negotiation. Why not hitch the milk wagon to the bullet train? Pomerance was skeptical. The problems were related, sure: Without a reduction in CFC emissions, you didn’t have a chance of averting cataclysmic global warming. But it had been difficult enough to explain the carbon issue to politicians and journalists; why complicate the sales pitch? Then again, he didn’t see what choice he had. The Republicans controlled the Senate, and Moore was his connection to the Senate’s environmental committee.

Pomerance met with Senator John Chafee, a Republican from Rhode Island, and helped persuade him to hold a double-barreled hearing on the twin problems of ozone and carbon dioxide on June 10 and 11, 1986

F.Sherwood Rowland, Robert Watson, a NASA scientist, and Richard Benedick, the administration’s lead representative in international ozone negotiations, would discuss ozone; James Hansen, Al Gore, the ecologist George Woodwell and Carl Wunsch, a veteran of the Charney group, would testify about climate change.

As Pomerance had hoped, fear about the ozone layer ensured a bounty of press coverage for the climate-change testimony. But as he had feared, it caused many people to conflate the two crises. One was Peter Jennings, who aired the video on ABC’s “World News Tonight,” warning that the ozone hole “could lead to flooding all over the world, also to drought and to famine.”

The confusion helped: For the first time since the “Changing Climate” report, global-warming headlines appeared by the dozen. William Nierenberg’s “caution, not panic” line was inverted. It was all panic without a hint of caution: “A Dire Forecast for ‘Greenhouse’ Earth” (the front page of The Washington Post); “Scientists Predict Catastrophes in Growing Global Heat Wave” (Chicago Tribune); “Swifter Warming of Globe Foreseen” (The New York Times).

After three years of backsliding and silence, Pomerance was exhilarated to see interest in the issue spike overnight. Not only that: A solution materialized, and a moral argument was passionately articulated — by Rhode Island’s Republican senator no less. “Ozone depletion and the greenhouse effect can no longer be treated solely as important scientific questions,” Chafee said. “They must be seen as critical problems facing the nations of the world, and they are problems that demand solutions.”

The old canard about the need for more research was roundly mocked — by Woodwell, by a W.R.I. colleague named Andrew Maguire, by Senator George Mitchell, a Democrat from Maine. “Scientists are never 100 percent certain,” the Princeton historian Theodore Rabb testified. “That notion of total certainty is something too elusive ever to be sought.” As Pomerance had been saying since 1979, it was past time to act. Only now the argument was so broadly accepted that nobody dared object.

The ozone hole, Pomerance realized, had moved the public because, though it was no more visible than global warming, people could be made to see it. They could watch it grow on video. Its metaphors were emotionally wrought: Instead of summoning a glass building that sheltered plants from chilly weather (“Everything seems to flourish in there”), the hole evoked a violent rending of the firmament, inviting deathly radiation. Americans felt that their lives were in danger. An abstract, atmospheric problem had been reduced to the size of the human imagination. It had been made just small enough, and just large enough, to break through.

Four years after “Changing Climate,” two years after a hole had torn open the firmament and a month after the United States and more than three dozen other nations signed a treaty to limit use of CFCs, the climate-change corps was ready to celebrate. It had become conventional wisdom that climate change would follow ozone’s trajectory. Reagan’s E.P.A. administrator, Lee M. Thomas, said as much the day he signed the Montreal Protocol on Substances That Deplete the Ozone Layer (the successor to the Vienna Convention), telling reporters that global warming was likely to be the subject of a future international agreement

Congress had already begun to consider policy — in 1987 alone, there were eight days of climate hearings, in three committees, across both chambers of Congress; Senator Joe Biden, a Delaware Democrat, had introduced legislation to establish a national climate-change strategy. And so it was that Jim Hansen found himself on Oct. 27 in the not especially distinguished ballroom of the Quality Inn on New Jersey Avenue, a block from the Capitol, at “Preparing for Climate Change,” which was technically a conference but felt more like a wedding.

John Topping was an old-line Rockefeller Republican, a Commerce Department lawyer under Nixon and an E.P.A. official under Reagan. He first heard about the climate problem in the halls of the E.P.A. in 1982 and sought out Hansen, who gave him a personal tutorial. Topping was amazed to discover that out of the E.P.A.’s 13,000-person staff, only seven people, by his count, were assigned to work on climate, though he figured it was more important to the long-term security of the nation than every other environmental issue combined.

Glancing around the room, Jim Hansen could chart, like an arborist counting rings on a stump, the growth of the climate issue over the decade. Veterans like Gordon MacDonald, George Woodwell and the environmental biologist Stephen Schneider stood at the center of things. Former and current staff members from the congressional science committees (Tom Grumbly, Curtis Moore, Anthony Scoville) made introductions to the congressmen they advised. Hansen’s owlish nemesis Fred Koomanoff was present, as were his counterparts from the Soviet Union and Western Europe. Rafe Pomerance’s cranium could be seen above the crowd, but unusually he was surrounded by colleagues from other environmental organizations that until now had shown little interest in a diffuse problem with no proven fund-raising record. The party’s most conspicuous newcomers, however, the outermost ring, were the oil-and-gas executives.

That evening, as a storm spat and coughed outside, Rafe Pomerance gave one of his exhortative speeches urging cooperation among the various factions, and John Chafee and Roger Revelle received awards; introductions were made and business cards earnestly exchanged. Not even a presentation by Hansen of his research could sour the mood. The next night, on Oct. 28, at a high-spirited dinner party in Topping’s townhouse on Capitol Hill, the oil-and-gas men joked with the environmentalists, the trade-group representatives chatted up the regulators and the academics got merrily drunk. Mikhail Budyko, the don of the Soviet climatologists, settled into an extended conversation about global warming with Topping’s 10-year-old son. It all seemed like the start of a grand bargain, a uniting of factions — a solution.

Hansen was accustomed to the bureaucratic nuisances that attended testifying before Congress; before a hearing, he had to send his formal statement to NASA headquarters, which forwarded it to the White House’s Office of Management and Budget for approval. “Major greenhouse climate changes are a certainty,” he had written. “By the 2010s [in every scenario], essentially the entire globe has very substantial warming.”

By all appearances, plans for major policy continued to advance rapidly. After the Johnston hearing, Timothy Wirth, a freshman Democratic senator from Colorado on the energy committee, began to plan a comprehensive package of climate-change legislation — a New Deal for global warming. Wirth asked a legislative assistant, David Harwood, to consult with experts on the issue, beginning with Rafe Pomerance, in the hope of converting the science of climate change into a new national energy policy.

In March 1988, Wirth joined 41 other senators, nearly half of them Republicans, to demand that Reagan call for an international treaty modeled after the ozone agreement. Because the United States and the Soviet Union were the world’s two largest contributors of carbon emissions, responsible for about one-third of the world total, they should lead the negotiations. Reagan agreed. In May, he signed a joint statement with Mikhail Gorbachev that included a pledge to cooperate on global warming.

Al Gore himself had, for the moment, withdrawn his political claim to the issue. In 1987, at the age of 39, Gore announced that he was running for president, in part to bring attention to global warming, but he stopped emphasizing it after the subject failed to captivate New Hampshire primary voters.

5. ‘You Will See Things That You Shall Believe’ Summer 1988

It was the hottest and driest summer in history. Everywhere you looked, something was bursting into flames. Two million acres in Alaska incinerated, and dozens of major fires scored the West. Yellowstone National Park lost nearly one million acres. Smoke was visible from Chicago, 1,600 miles away.

In Nebraska, suffering its worst drought since the Dust Bowl, there were days when every weather station registered temperatures above 100 degrees. The director of the Kansas Department of Health and Environment warned that the drought might be the dawning of a climatic change that within a half century could turn the state into a desert.

On June 22 in Washington, where it hit 100 degrees, Rafe Pomerance received a call from Jim Hansen, who was scheduled to testify the following morning at a Senate hearing called by Timothy Wirth. “I hope we have good media coverage tomorrow,” Hansen said.

Hansen had just received the most recent global temperature data. Just over halfway into the year, 1988 was setting records. Already it had nearly clinched the hottest year in history. Ahead of schedule, the signal was emerging from the noise. “I’m going to make a pretty strong statement,” Hansen said.

Hansen returned to his testimony. He wrote: “The global warming is now large enough that we can ascribe with a high degree of confidence a cause-and-effect relationship to the greenhouse effect.” He wrote: “1988 so far is so much warmer than 1987, that barring a remarkable and improbable cooling, 1988 will be the warmest year on record.” He wrote: “The greenhouse effect has been detected, and it is changing our climate now.”

“We have only one planet,” Senator Bennett Johnston intoned. “If we screw it up, we have no place to go.” Senator Max Baucus, a Democrat from Montana, called for the United Nations Environment Program to begin preparing a global remedy to the carbon-dioxide problem. Senator Dale Bumpers, a Democrat of Arkansas, previewed Hansen’s testimony, saying that it “ought to be cause for headlines in every newspaper in America tomorrow morning.” The coverage, Bumpers emphasized, was a necessary precursor to policy. “Nobody wants to take on any of the industries that produce the things that we throw up into the atmosphere,” he said. “But what you have are all these competing interests pitted against our very survival.”

Hansen, wiping his brow, spoke without affect, his eyes rarely rising from his notes. The warming trend could be detected “with 99 percent confidence,” he said. “It is changing our climate now.” But he saved his strongest comment for after the hearing, when he was encircled in the hallway by reporters. “It is time to stop waffling so much,” he said, “and say that the evidence is pretty strong that the greenhouse effect is here.”

The press followed Bumpers’s advice. Hansen’s testimony prompted headlines in dozens of newspapers across the country, including The New York Times, which announced, across the top of its front page: “Global Warming Has Begun, Expert Tells Senate.”

Rafe Pomerance called his allies on Capitol Hill, the young staff members who advised politicians, organized hearings, wrote legislation. We need to finalize a number, he told them, a specific target, in order to move the issue — to turn all this publicity into policy. The Montreal Protocol had called for a 50 percent reduction in CFC emissions by 1998. What was the right target for carbon emissions? It wasn’t enough to exhort nations to do better. That kind of talk might sound noble, but it didn’t change investments or laws. They needed a hard goal — something ambitious but reasonable. And they needed it soon: Just four days after Hansen’s star turn, politicians from 46 nations and more than 300 scientists would convene in Toronto at the World Conference on the Changing Atmosphere, an event described by Philip Shabecoff of The New York Times as “Woodstock for climate change.”

Pomerance had a proposal: a 20 percent reduction in carbon emissions by 2000. Ambitious, Harwood said. In all his work planning climate policy, he had seen no assurance that such a steep drop in emissions was possible. Then again, 2000 was more than a decade off, so it allowed for some flexibility.

Mintzer pointed out that a 20 percent reduction was consistent with the academic literature on energy efficiency. Various studies over the years had shown that you could improve efficiency in most energy systems by roughly 20 percent if you adopted best practices.

Of course, with any target, you had to take into account the fact that the developing world would inevitably consume much larger quantities of fossil fuels by 2000. But those gains could be offset by a wider propagation of the renewable technologies already at hand — solar, wind, geothermal. It was not a rigorous scientific analysis, Mintzer granted, but 20 percent sounded plausible. We wouldn’t need to solve cold fusion or ask Congress to repeal the law of gravity. We could manage it with the knowledge and technology we already had.

Besides, Pomerance said, 20 by 2000 sounds good.

The conference’s final statement, signed by all 400 scientists and politicians in attendance, repeated the demand with a slight variation: a 20 percent reduction in carbon emissions by 2005. Just like that, Pomerance’s best guess became global diplomatic policy.

Hansen, emerging from Anniek’s successful cancer surgery, took it upon himself to start a one-man public information campaign. He gave news conferences and was quoted in seemingly every article about the issue; he even appeared on television with homemade props. Like an entrant at an elementary-school science fair, he made “loaded dice” out of sections of cardboard and colored paper to illustrate the increased likelihood of hotter weather in a warmer climate. Public awareness of the greenhouse effect reached a new high of 68 percent

global warming became a major subject of the presidential campaign. While Michael Dukakis proposed tax incentives to encourage domestic oil production and boasted that coal could satisfy the nation’s energy needs for the next three centuries, George Bush took advantage. “I am an environmentalist,” he declared on the shore of Lake Erie, the first stop on a five-state environmental tour that would take him to Boston Harbor, Dukakis’s home turf. “Those who think we are powerless to do anything about the greenhouse effect,” he said, “are forgetting about the White House effect.”

His running mate emphasized the ticket’s commitment to the issue at the vice-presidential debate. “The greenhouse effect is an important environmental issue,” Dan Quayle said. “We need to get on with it. And in a George Bush administration, you can bet that we will.”

This kind of talk roused the oil-and-gas men. “A lot of people on the Hill see the greenhouse effect as the issue of the 1990s,” a gas lobbyist told Oil & Gas Journal. Before a meeting of oil executives shortly after the “environmentalist” candidate won the election, Representative Dick Cheney, a Wyoming Republican, warned, “It’s going to be very difficult to fend off some kind of gasoline tax.” The coal industry, which had the most to lose from restrictions on carbon emissions, had moved beyond denial to resignation. A spokesman for the National Coal Association acknowledged that the greenhouse effect was no longer “an emerging issue. It is here already, and we’ll be hearing more and more about it.”

By the end of the year, 32 climate bills had been introduced in Congress, led by Wirth’s omnibus National Energy Policy Act of 1988. Co-sponsored by 13 Democrats and five Republicans, it established as a national goal an “International Global Agreement on the Atmosphere by 1992,” ordered the Energy Department to submit to Congress a plan to reduce energy use by at least 2 percent a year through 2005 and directed the Congressional Budget Office to calculate the feasibility of a carbon tax. A lawyer for the Senate energy committee told an industry journal that lawmakers were “frightened” by the issue and predicted that Congress would eventually pass significant legislation after Bush took office

The other great powers refused to wait. The German Parliament created a special commission on climate change, which concluded that action had to be taken immediately, “irrespective of any need for further research,” and that the Toronto goal was inadequate; it recommended a 30 percent reduction of carbon emissions

Margaret Thatcher, who had studied chemistry at Oxford, warned in a speech to the Royal Society that global warming could “greatly exceed the capacity of our natural habitat to cope” and that “the health of the economy and the health of our environment are totally dependent upon each other.”

The prime ministers of Canada and Norway called for a binding international treaty on the atmosphere; Sweden’s Parliament went further, announcing a national strategy to stabilize emissions at the 1988 level and eventually imposing a carbon tax

the United Nations unanimously endorsed the establishment, by the World Meteorological Organization and the United Nations Environment Program, of an Intergovernmental Panel on Climate Change, composed of scientists and policymakers, to conduct scientific assessments and develop global climate policy.

One of the I.P.C.C.’s first sessions to plan an international treaty was hosted by the State Department, 10 days after Bush’s inauguration. James Baker chose the occasion to make his first speech as secretary of state. “We can probably not afford to wait until all of the uncertainties about global climate change have been resolved,” he said. “Time will not make the problem go away.”

: On April 14, 1989, a bipartisan group of 24 senators, led by the majority leader, George Mitchell, requested that Bush cut emissions in the United States even before the I.P.C.C.’s working group made its recommendation. “We cannot afford the long lead times associated with a comprehensive global agreement,” the senators wrote. Bush had promised to combat the greenhouse effect with the White House effect. The self-proclaimed environmentalist was now seated in the Oval Office. It was time.

8. ‘You Never Beat The White House’ April 1989

After Jim Baker gave his boisterous address to the I.P.C.C. working group at the State Department, he received a visit from John Sununu, Bush’s chief of staff. Leave the science to the scientists, Sununu told Baker. Stay clear of this greenhouse-effect nonsense. You don’t know what you’re talking about. Baker, who had served as Reagan’s chief of staff, didn’t speak about the subject again.

despite his reputation as a political wolf, he still thought of himself as a scientist — an “old engineer,” as he was fond of putting it, having earned a Ph.D. in mechanical engineering from M.I.T. decades earlier. He lacked the reflexive deference that so many of his political generation reserved for the class of elite government scientists.

Since World War II, he believed, conspiratorial forces had used the imprimatur of scientific knowledge to advance an “anti-growth” doctrine. He reserved particular disdain for Paul Ehrlich’s “The Population Bomb,” which prophesied that hundreds of millions of people would starve to death if the world took no step to curb population growth; the Club of Rome, an organization of European scientists, heads of state and economists, which similarly warned that the world would run out of natural resources; and as recently as the mid-’70s, the hypothesis advanced by some of the nation’s most celebrated scientists — including Carl Sagan, Stephen Schneider and Ichtiaque Rasool — that a new ice age was dawning, thanks to the proliferation of man-made aerosols. All were theories of questionable scientific merit, portending vast, authoritarian remedies to halt economic progress.

When Mead talked about “far-reaching” decisions and “long-term consequences,” Sununu heard the marching of jackboots.

Sununu had suspected that the greenhouse effect belonged to this nefarious cabal since 1975, when the anthropologist Margaret Mead convened a symposium on the subject at the National Institute of Environmental Health Sciences.

While Sununu and Darman reviewed Hansen’s statements, the E.P.A. administrator, William K. Reilly, took a new proposal to the White House. The next meeting of the I.P.C.C.’s working group was scheduled for Geneva the following month, in May; it was the perfect occasion, Reilly argued, to take a stronger stand on climate change. Bush should demand a global treaty to reduce carbon emissions.

Sununu wouldn’t budge. He ordered the American delegates not to make any commitment in Geneva. Very soon after that, someone leaked the exchange to the press.

A deputy of Jim Baker pulled Reilly aside. He said he had a message from Baker, who had observed Reilly’s infighting with Sununu. “In the long run,” the deputy warned Reilly, “you never beat the White House.”

9. ‘A Form of Science Fraud’ May 1989

The cameras followed Hansen and Gore into the marbled hallway. Hansen insisted that he wanted to focus on the science. Gore focused on the politics. “I think they’re scared of the truth,” he said. “They’re scared that Hansen and the other scientists are right and that some dramatic policy changes are going to be needed, and they don’t want to face up to it.”

The censorship did more to publicize Hansen’s testimony and the dangers of global warming than anything he could have possibly said. At the White House briefing later that morning, Press Secretary Marlin Fitzwater admitted that Hansen’s statement had been changed. He blamed an official “five levels down from the top” and promised that there would be no retaliation. Hansen, he added, was “an outstanding and distinguished scientist” and was “doing a great job.”

10. The White House Effect Fall 1989

The Los Angeles Times called the censorship “an outrageous assault.” The Chicago Tribune said it was the beginning of “a cold war on global warming,” and The New York Times warned that the White House’s “heavy-handed intervention sends the signal that Washington wants to go slow on addressing the greenhouse problem.”

Darman went to see Sununu. He didn’t like being accused of censoring scientists. They needed to issue some kind of response. Sununu called Reilly to ask if he had any ideas. We could start, Reilly said, by recommitting to a global climate treaty. The United States was the only Western nation on record as opposing negotiations.

Sununu sent a telegram to Geneva endorsing a plan “to develop full international consensus on necessary steps to prepare for a formal treaty-negotiating process. The scope and importance of this issue are so great that it is essential for the U.S. to exercise leadership.”

Sununu seethed at any mention of the subject. He had taken it upon himself to study more deeply the greenhouse effect; he would have a rudimentary, one-dimensional general circulation model installed on his personal desktop computer. He decided that the models promoted by Jim Hansen were a lot of bunk. They were horribly imprecise in scale and underestimated the ocean’s ability to mitigate warming. Sununu complained about Hansen to D. Allan Bromley, a nuclear physicist from Yale who, at Sununu’s recommendation, was named Bush’s science adviser. Hansen’s findings were “technical poppycock” that didn’t begin to justify such wild-eyed pronouncements that “the greenhouse effect is here” or that the 1988 heat waves could be attributed to global warming, let alone serve as the basis for national economic policy.

When a junior staff member in the Energy Department, in a meeting at the White House with Sununu and Reilly, mentioned an initiative to reduce fossil-fuel use, Sununu interrupted her. “Why in the world would you need to reduce fossil-fuel use?” he asked. “Because of climate change,” the young woman replied. “I don’t want anyone in this administration without a scientific background using ‘climate change’ or ‘global warming’ ever again,” he said. “If you don’t have a technical basis for policy, don’t run around making decisions on the basis of newspaper headlines.” After the meeting, Reilly caught up to the staff member in the hallway. She was shaken. Don’t take it personally, Reilly told her. Sununu might have been looking at you, but that was directed at me.

Reilly, for his part, didn’t entirely blame Sununu for Bush’s indecision on the prospect of a climate treaty. The president had never taken a vigorous interest in global warming and was mainly briefed about it by nonscientists. Bush had brought up the subject on the campaign trail, in his speech about the White House effect, after leafing through a briefing booklet for a new issue that might generate some positive press. When Reilly tried in person to persuade him to take action, Bush deferred to Sununu and Baker. Why don’t the three of you work it out, he said. Let me know when you decide

Relations between Sununu and Reilly became openly adversarial. Reilly, Sununu thought, was a creature of the environmental lobby. He was trying to impress his friends at the E.P.A. without having a basic grasp of the science himself.

Pomerance had the sinking feeling that the momentum of the previous year was beginning to flag. The censoring of Hansen’s testimony and the inexplicably strident opposition from John Sununu were ominous signs. So were the findings of a report Pomerance had commissioned, published in September by the World Resources Institute, tracking global greenhouse-gas emissions. The United States was the largest contributor by far, producing nearly a quarter of the world’s carbon emissions, and its contribution was growing faster than that of every other country. Bush’s indecision, or perhaps inattention, had already managed to delay the negotiation of a global climate treaty until 1990 at the earliest, perhaps even 1991. By then, Pomerance worried, it would be too late.

Pomerance tried to be more diplomatic. “The president made a commitment to the American people to deal with global warming,” he told The Washington Post, “and he hasn’t followed it up.” He didn’t want to sound defeated. “There are some good building blocks here,” Pomerance said, and he meant it. The Montreal Protocol on CFCs wasn’t perfect at first, either — it had huge loopholes and weak restrictions. Once in place, however, the restrictions could be tightened. Perhaps the same could happen with climate change. Perhaps. Pomerance was not one for pessimism. As William Reilly told reporters, dutifully defending the official position forced upon him, it was the first time that the United States had formally endorsed the concept of an emissions limit. Pomerance wanted to believe that this was progress.

All week in Noordwijk, Becker couldn’t stop talking about what he had seen in Zeeland. After a flood in 1953, when the sea swallowed much of the region, killing more than 2,000 people, the Dutch began to build the Delta Works, a vast concrete-and-steel fortress of movable barriers, dams and sluice gates — a masterpiece of human engineering. The whole system could be locked into place within 90 minutes, defending the land against storm surge. It reduced the country’s exposure to the sea by 700 kilometers, Becker explained. The United States coastline was about 153,000 kilometers long. How long, he asked, was the entire terrestrial coastline? Because the whole world was going to need this. In Zeeland, he said, he had seen the future.

Ken Caldeira, a climate scientist at the Carnegie Institution for Science in Stanford, Calif., has a habit of asking new graduate students to name the largest fundamental breakthrough in climate physics since 1979. It’s a trick question. There has been no breakthrough. As with any mature scientific discipline, there is only refinement. The computer models grow more precise; the regional analyses sharpen; estimates solidify into observational data. Where there have been inaccuracies, they have tended to be in the direction of understatement.

More carbon has been released into the atmosphere since the final day of the Noordwijk conference, Nov. 7, 1989, than in the entire history of civilization preceding it

Despite every action taken since the Charney report — the billions of dollars invested in research, the nonbinding treaties, the investments in renewable energy — the only number that counts, the total quantity of global greenhouse gas emitted per year, has continued its inexorable rise.

When it comes to our own nation, which has failed to make any binding commitments whatsoever, the dominant narrative for the last quarter century has concerned the efforts of the fossil-fuel industries to suppress science, confuse public knowledge and bribe politicians.

The mustache-twirling depravity of these campaigns has left the impression that the oil-and-gas industry always operated thus; while the Exxon scientists and American Petroleum Institute clerics of the ’70s and ’80s were hardly good Samaritans, they did not start multimillion-dollar disinformation campaigns, pay scientists to distort the truth or try to brainwash children in elementary schools, as their successors would.

It was James Hansen’s testimony before Congress in 1988 that, for the first time since the “Changing Climate” report, made oil-and-gas executives begin to consider the issue’s potential to hurt their profits. Exxon, as ever, led the field. Six weeks after Hansen’s testimony, Exxon’s manager of science and strategy development, Duane LeVine, prepared an internal strategy paper urging the company to “emphasize the uncertainty in scientific conclusions.” This shortly became the default position of the entire sector. LeVine, it so happened, served as chairman of the global petroleum industry’s Working Group on Global Climate Change, created the same year, which adopted Exxon’s position as its own

The American Petroleum Institute, after holding a series of internal briefings on the subject in the fall and winter of 1988, including one for the chief executives of the dozen or so largest oil companies, took a similar, if slightly more diplomatic, line. It set aside money for carbon-dioxide policy — about $100,000, a fraction of the millions it was spending on the health effects of benzene, but enough to establish a lobbying organization called, in an admirable flourish of newspeak, the Global Climate Coalition.

The G.C.C. was conceived as a reactive body, to share news of any proposed regulations, but on a whim, it added a press campaign, to be coordinated mainly by the A.P.I. It gave briefings to politicians known to be friendly to the industry and approached scientists who professed skepticism about global warming. The A.P.I.’s payment for an original op-ed was $2,000.

It was joined by the U.S. Chamber of Commerce and 14 other trade associations, including those representing the coal, electric-grid and automobile industries

In October 1989, scientists allied with the G.C.C. began to be quoted in national publications, giving an issue that lacked controversy a convenient fulcrum. “Many respected scientists say the available evidence doesn’t warrant the doomsday warnings,” was the caveat that began to appear in articles on climate change.

The following year, when President Bill Clinton proposed an energy tax in the hope of meeting the goals of the Rio treaty, the A.P.I. invested $1.8 million in a G.C.C. disinformation campaign. Senate Democrats from oil-and-coal states joined Republicans to defeat the tax proposal, which later contributed to the Republicans’ rout of Democrats in the midterm congressional elections in 1994 — the first time the Republican Party had won control of both houses in 40 years

The G.C.C. spent $13 million on a single ad campaign intended to weaken support for the 1997 Kyoto Protocol, which committed its parties to reducing greenhouse-gas emissions by 5 percent relative to 1990 levels. The Senate, which would have had to ratify the agreement, took a pre-emptive vote declaring its opposition; the resolution passed 95-0. There has never been another serious effort to negotiate a binding global climate treaty.

. This has made the corporation an especially vulnerable target for the wave of compensatory litigation that began in earnest in the last three years and may last a generation. Tort lawsuits have become possible only in recent years, as scientists have begun more precisely to attribute regional effects to global emission levels. This is one subfield of climate science that has advanced significantly sin

Pomerance had not been among the 400 delegates invited to Noordwijk. But together with three young activists — Daniel Becker of the Sierra Club, Alden Meyer of the Union of Concerned Scientists and Stewart Boyle from Friends of the Earth — he had formed his own impromptu delegation. Their constituency, they liked to say, was the climate itself. Their mission was to pressure the delegates to include in the final conference statement, which would be used as the basis for a global treaty, the target proposed in Toronto: a 20 percent reduction of greenhouse-gas combustion by 2005. It was the only measure that mattered, the amount of emissions reductions, and the Toronto number was the strongest global target yet proposed.

The delegations would review the progress made by the I.P.C.C. and decide whether to endorse a framework for a global treaty. There was a general sense among the delegates that they would, at minimum, agree to the target proposed by the host, the Dutch environmental minister, more modest than the Toronto number: a freezing of greenhouse-gas emissions at 1990 levels by 2000. Some believed that if the meeting was a success, it would encourage the I.P.C.C. to accelerate its negotiations and reach a decision about a treaty sooner. But at the very least, the world’s environmental ministers should sign a statement endorsing a hard, binding target of emissions reductions. The mood among the delegates was electric, nearly giddy — after more than a decade of fruitless international meetings, they could finally sign an agreement that meant something.

11. ‘The Skunks at The Garden Party’ November 1989

It was nearly freezing — Nov. 6, 1989, on the coast of the North Sea in the Dutch resort town of Noordwijk

Losing Earth: The Decade WeAlmost Stopped Climate Change We knew everything we needed to know, and nothing stood in our way. Nothing, that is, except ourselves. A tragedy in two acts. By Nathaniel RichPhotographs and Videos by George Steinmetz AUG. 1, 2018

U.S. natural gas is far less damaging to the environment than coal. It has become so cheap that it is displacing coal in electricity generation, driving down emissions. To others, Cove Point is an environmental catastrophe. Natural gas is still a fossil fuel, and burning it releases lots of greenhouse-gas emissions, which cause climate change. Both arguments are right.

society must eliminate its carbon dependency. It cannot burn vast amounts of any fossil fuel for “decades and decades,” as Mr. Farrell hopes, unless there is a revolution in emissions capture technology. Even in the short term, U.S. emissions are rising, despite the restraint that stepped-up natural-gas burning has provided. The government must demand more change, more quickly.

One objection is that carbon pricing is not powerful enough. The European Union’s carbon pricing program has not worked well. But that is a failure of design and political will. A carbon price equal to the challenge would start high and rise higher, sending a much stronger price signal.

carbon pricing is still the best first-line policy

A high-enough carbon price would shape millions of choices, small and large, about what to buy, how to invest and how to live that would result in substantial emissions cuts. People would prioritize the easiest changes, minimizing the costs of the energy transition. With a price that steadily rose, market forces would steadily wring carbon dioxide out of the economy — without the government trying to dictate exactly how, wasting money on special-interest boondoggles.

The Intergovernmental Panel on Climate Change found last year that an average carbon price between 2030 and the end of the century of $100, $200 or even $300 per ton of carbon dioxide would result in huge greenhouse-gas emissions cuts, could restrain warming to the lowest safety threshold of 1.5 degrees Celsius and would almost certainly prevent the world from breaching the traditional warming limit of 2 degrees Celsius

Republicans never embraced the market-based idea, even though conservative economists admit its appeal, because they never accepted the need to act at all. Some environmentalists, meanwhile, are increasingly wary of carbon pricing. The Democrats’ Green New Deal, which is noncommittal on the policy, reflects the accelerating drift from the obvious.

A third objection is that carbon pricing is politically impossible, because it reveals the cost of fighting global warming in the prices people pay

Another criticism is that carbon pricing hurts the poor, who would suffer most when prices rose. But the revenue from carbon pricing could be recycled back to Americans in a progressive way, and most people would end up whole or better off.

This is a leadership challenge, not a policy challenge. More than 40 governments globally, including several states, have found the political will to embrace carbon pricing programs, which is the only option that would plausibly be bipartisan.

One objection does have merit: Though carbon pricing would spur huge change in infrastructure and power generation, that alone would not be enough. It would not stimulate all the innovation the nation needs in the climate fight, nor would it change behaviors in circumstances where the desired price signal is muted or nonexistent

Foreign aid to prevent deforestation could be among the most cost-effective climate-preserving measures. Helping other countries to replace archaic cooking stoves that produce noxious fumes would help cut emissions and improve quality of life across the developing world.

, economists know that companies that invest in research and development do not get rewarded for the full social value of their work. Others benefit from their innovations without paying. Consequently, firms do not invest in research as much as society should want

It would take only a small fraction of the revenue a carbon pricing system would produce to fund a much more ambitious clean-energy research agenda. Basic scientific research and applied research programs such as ARPA-E should be scaled up dramatically

The government must also account for the fact that not all greenhouse-gas emissions come from burning the fuels that a carbon pricing program would reach — coal, oil and gas. How would the government charge farmers for the methane their cows emit or for the greenhouse gases released when they till their soil? How about emissions from cement, ammonia and steel production? The federal government would have to tailor programs to the agricultural and industrial sectors, which might include judicious use of incentives and mandates.

only government can ensure adequate mass transit options. Local governments could help with zoning laws to encourage people to live in denser, more walkable communities. The federal government should also press automakers to steadily improve fuel efficiency.

That starts with making sure that emissions-cutting efforts at home do not have unintended consequences. If the United States puts a price on greenhouse-gas emissions, other countries would lure U.S. manufacturers with the promise of lax environmental rules. Relocated manufacturers could then export their goods to the United States. The net effect would be no benefit for the planet but fewer U.S. manufacturing jobs.

One response is a kind of tariff on goods entering the country from places with weaker carbon-dioxide policies. That would both eliminate the incentive to offshore manufacturing and encourage countries to strengthen their own rules.

Participating in the agreement would give the United States a forum — and a basis — to press other nations to reduce emissions.

Start with carbon pricing. Then fill in the gaps.

There are a lot of bad ideas out there.

The Green New Deal that some Democrats have embraced is case in point. In its most aggressive form, the plan suggests the country could reach net-zero greenhouse-gas emissions by 2030, an impossible goal

that would be more spent every three years than the total amount the country spent on World War II.

At the same time, the Democratic plan would guarantee every American “high-quality health care” and “a job with a family-sustaining wage, adequate family and medical leave, paid vacations, and retirement security.” These expensive aspirations, no matter how laudable, would do nothing to arrest greenhouse-gas emissions.

Massive social reform will not protect the climate. Marshaling every dollar to its highest benefit is the strongest plan.

In the electricity sector, emissions plunged by 10.3 percent in 2020, driven by a sharp decline in coal burning. As electricity demand sagged nationwide, utilities ran their coal plants far less often because coal has become the most expensive fuel in many parts of the country. Instead, they used more natural gas — which produces less carbon dioxide than coal, but still generates significant heat-trapping methane — and drew more heavily on emissions-free wind and solar power.

Emissions from heavy industry, such as steel and cement, dropped 7 percent in 2020 as automakers and other manufacturers churned out fewer goods amid the economic slump. America’s buildings, which produce carbon dioxide when they burn oil or natural gas for heat, saw emissions fall 6.2 percent, driven by both lockdowns and warmer-than-average weather.

Transportation, the nation’s largest source of greenhouse gases, saw a 14.7 percent decline in emissions in 2020 as millions of people stopped driving to work and airlines canceled flights. While travel started picking up again in the latter half of the year as states relaxed their lockdowns, Americans drove 15 percent fewer miles over all last year than they did in 2019 and the demand for jet fuel fell by more than one-third.

Renewable energy surged in 2020, as energy companies overcame disruptions from the pandemic to build a record number of new wind turbines and solar panels ahead of a key deadline to claim a federal tax credit. The United States produced roughly as much electricity from renewable sources last year as it did from coal, a milestone that has never been reached before.

The other caveat is that America’s emissions could tick back up again once vaccines are widely distributed and the economy recovers. The Rhodium Group report noted that a similar rebound occurred after the financial crisis of 2008-9 caused emissions to fall sharply. And it noted that many sectors, like air travel and steel making, have already been rebounding in recent months.

“The vast majority of 2020’s emission reductions were due to decreased economic activity and not from any structural changes that would deliver lasting reductions in the carbon intensity of our economy.”

Scientists warn that even a big one-year drop in emissions is not enough to stop global warming. Until humanity’s emissions are essentially zeroed out and nations are no longer adding greenhouse gases to the atmosphere, the planet will continue to heat up. As if to underscore that warning, European researchers announced last week that 2020 was quite likely tied with 2016 as the hottest year on record.

Countries’ commitments should reflect “equity and the principle of common but differentiated responsibilities and respective capabilities in the light of different national circumstances and in the context of sustainable development and efforts to eradicate poverty.”

It’s indisputable that poor nations should be allowed to develop and to eradicate poverty. Countries, obviously, can contribute to the global effort only to the extent of their capabilities

equity brings up a different, more slippery matter. What’s the just allocation of responsibility? What’s fair?

Countries, it turns out, have rather different takes on this question, potentially complicating efforts to make progress against climate change.

Consider the intended “nationally determined contributions” to battle climate change that various countries announced after the climate summit in Paris in 2015

One interesting study examined the notions of justice underpinning each national proposal. They were all over the map.

Critically, none of those experts considered the consequences of applying their logic to all countries across the board.

The aggregate notions of fairness did not add up to a solution. The countries that claimed responsibility for a small share of global emissions actually accounted for about a quarter of the total. Countries with per capita emissions ranging from 0.5 tons of carbon dioxide to 25 tons of CO2, roughly five times the global average, used this variable to justify modest plans.

The idea of an equitable and just distribution of responsibility might seem essential to achieve the shared goal of preventing a climate catastrophe

I can’t put precise odds on members of Congress accepting that the United States must bear one-fourth of the worldwide burden to cut greenhouse gas emissions because of the actions of long-dead Americans who had no idea they were causing damage. But the probability is quite low.

It seems only fair that countries such as the United States, which accounts for about a quarter of the greenhouse gases emitted by humanity since before the Industrial Revolution, should bear a much bigger share of the burden than, say, Brazil, which accounts for only 1 percent of historical emissions.

The United States, moreover, is quite rich and was made that way largely thanks to abundant and cheap fossil fuel.

Yet parsing how equity is to be achieved can get complicated

Should the goal be to equalize emissions per person, which today tilt heavily toward rich countries? (The United States emits some 18 tons per person; for India, the number is less than 3.

Or should we first cut emissions associated with the production of luxury goods and services that are mostly consumed in rich countries? Shouldn’t the emissions from producing the made-in-China toy you bought on Amazon accrue to the United States, where it is being played with?

They are in tension with the strategies championed by most rich countries, which are more sympathetic to the idea that historical emissions should be grandfathered in — not counted against them — and that they should be reduced in the future wherever reducing them is cheapest, which happens to be mostly in the developing world.

Many countries cannot afford the necessary mitigation pathways, either because they don’t have the resources to finance the new technologies needed to abandon fossil fuels, or because the resources they have are best deployed toward, say, buying air conditioning units or otherwise raising the standard of living.

There are essential truths that the world must acknowledge:

These countries are likely to face the gravest risks from climate change — whether measured in devastated crops, destroyed communities or people’s lives. Rich nations owe it to the world to ensure that resources and technologies are available for sufficient mitigation, adaptation and disaster relief

— not because they emitted a lot of greenhouse gases in the past, but because the task of preventing climate change and limiting its damage cannot be avoided, and they can afford it.

Many defended the fairness of their offer by pointing out that they accounted for a “small share” of global greenhouse gas emissions; others referred to their low per capita emissions. Many based their arguments on their vulnerability to climate change.

Consider the political ramifications of some climate justice arguments.

And that’s even without pointing out that China, today, emits more than double the amount of greenhouse gases the United States does.

Or consider how one research paper apportioned the remaining emissions budget — the greenhouse gases that can still be emitted in the future without breaching the warming ceiling (which in this estimate was set at 2 degrees Celsius)

It calculated nations’ responsibility for emissions starting only in 1992, when the world became aware of climate change, and assumed that each citizen of the world is entitled to the same budget since then. On this basis, it concluded that the United States would be entitled to 4.4 percent of the remainder, less than a fifth of its historic share.

That is fair. But it is also only 50 billion tons, or roughly nine years’ worth of emissions, at the nation’s current rate. I can’t imagine an administration that agreed to this surviving for long

The argument from guilt — built on the assumption that rich nations’ past development and emissions have incurred a moral debt to the rest of the world — will likely short-circuit the best case for action.

Better to draw on a different moral principle: to expect results from nations according to their capabilities and to assist them according to their needs. That frame could allow the job to get done.

 The committee's model calculations, while exploratory and highly uncertain, indicate that the benefits of making the transition, i.e. energy cost savings, improved vehicle technologies, and reductions in petroleum use and greenhouse gas emissions, exceed the additional costs of the transition over and above what the market is willing to do voluntarily."

Improving the efficiency of conventional vehicles is, up to a point, the most economical and easiest-to-implement approach to saving fuel and lowering emissions, the report says.  This approach includes reducing work the engine must perform -- reducing vehicle weight, aerodynamic resistance, rolling resistance, and accessories -- plus improving the efficiency of the internal combustion engine powertrain.

Improved efficiency alone will not meet the 2050 goals, however.  The average fuel economy of vehicles on the road would have to exceed 180 mpg, which, the report says, is extremely unlikely with current technologies.  Therefore, the study committee also considered other alternatives for vehicles and fuels, including:

Although driving costs per mile will be lower, especially for vehicles powered by natural gas or electricity, the high initial purchase cost is likely to be a significant barrier to widespread consumer acceptance

Wide consumer acceptance is essential, however, and large numbers of alternative vehicles must be purchased long before 2050 if the on-road fleet is to meet desired performance goals.  Strong policies and technology advances are critical in overcoming this challenge.

While corn-grain ethanol and biodiesel are the only biofuels to have been produced in commercial quantities in the U.S. to date, the study committee found much greater potential in biofuels made from lignocellulosic biomass -- which includes crop residues like wheat straw, switchgrass, whole trees, and wood waste.  This "drop-in" fuel is designed to be a direct replacement for gasoline and could lead to large reductions in both petroleum use and greenhouse gas emissions; it can also be introduced without major changes in fuel delivery infrastructure or vehicles.  The report finds that sufficient lignocellulosic biomass could be produced by 2050 to meet the goal of an 80 percent reduction in petroleum use when combined with highly efficient vehicles

Climate change will make those threats even worse, as floods, drought, storms and other types of extreme weather threaten to disrupt, and over time shrink, the global food supply

food shortages could lead to an increase in cross-border migration.

A particular danger is that food crises could develop on several continents at once

“The potential risk of multi-breadbasket failure is increasing,” she said. “All of these things are happening at the same time.”

The report also offered a measure of hope, laying out pathways to addressing the looming food crisis, though they would require a major re-evaluation of land use and agriculture worldwide as well as consumer behavior

Proposals include increasing the productivity of land, wasting less food and persuading more people to shift their diets away from cattle and other types of meat.

“People’s lives will be affected by a massive pressure for migration,” said Pete Smith, a professor of plant and soil science at the University of Aberdeen and one of the report’s lead authors. “People don’t stay and die where they are. People migrate.”

activities such as draining wetlands — as has happened in Indonesia and Malaysia to create palm oil plantations, for example — is particularly damaging. When drained, peatlands, which store between 530 and 694 billion tons of carbon dioxide globally, release that carbon dioxide back into the atmosphere.

Between 2010 and 2015 the number of migrants from El Salvador, Guatemala and Honduras showing up at the United States’ border with Mexico increased fivefold, coinciding with a dry period that left many with not enough food and was so unusual that scientists suggested it bears the signal of climate change

As a warming atmosphere intensifies the world’s droughts, flooding, heat waves, wildfires and other weather patterns, it is speeding up the rate of soil loss and land degradation, the report concludes.

Higher concentrations of carbon dioxide in the atmosphere

will also reduce food’s nutritional quality, even as rising temperatures cut crop yields and harm livestock

In some cases, the report says, a changing climate is boosting food production because, for example, warmer temperatures will mean greater yields of some crops at higher latitudes. But on the whole, the report finds that climate change is already hurting the availability of food because of decreased yields and lost land from erosion, desertification and rising seas

Overall if emissions of greenhouse gases continue to rise, so will food costs, according to the report, affecting people around the world.

“You’re sort of reaching a breaking point with land itself and its ability to grow food and sustain us,”

agriculture itself is also exacerbating climate change.

the window to address the threat is closing rapidly

Every 2.5 acres of peatlands release the carbon dioxide equivalent of burning 6,000 gallons of gasoline

And the emissions of carbon dioxide continues long after the peatlands are drained. Of the five gigatons of greenhouse gas emissions that are released each year from deforestation and other land-use changes, “One gigaton comes from the ongoing degradation of peatlands that are already drained,”

(By comparison, the fossil fuel industry emitted about 37 gigatons of carbon dioxide last year, according to the institute.)

cattle are significant producers of methane, another powerful greenhouse gas, and an increase in global demand for beef and other meats has fueled their numbers and increased deforestation in critical forest systems like the Amazon

each year, the amount of forested land that is cleared — much of that propelled by demand for pasture land for cattle — releases the emissions equivalent of driving 600 million cars

The authors urge changes in how food is produced and distributed, including better soil management, crop diversification and fewer restrictions on trade

They also call for shifts in consumer behavior, noting that at least one-quarter of all food worldwide is wasted

But protecting the food supply and cutting greenhouse emissions can also come into conflict with each other, forcing hard choices. For instance, the widespread use of strategies such as bioenergy — like growing corn to produce ethanol — could lead to the creation of new deserts or other land degradation

The report also calls for institutional changes, including better access to credit for farmers in developing countries and stronger property rights

Planting as many trees as possible would reduce the amount of greenhouse gases in the atmosphere by about nine gigatons each year

But it would also increase food prices as much as 80 percent by 2050.

“We cannot plant trees to get ourselves out of the problem that we’re in,

“The trade-offs that would keep us below 1.5 degrees, we’re not talking about them. We’re not ready to confront them yet.”

Preventing global temperatures from rising more than 1.5 degrees Celsius is likely to require both the widespread planting of trees as well as “substantial” bioenergy to help reduce the use of fossil fuels

“Above 2 degrees of global warming there could be an increase of 100 million or more of the population at risk of hunger,” Edouard Davin, a researcher at ETH Zurich and an author of the report, said by email. “We need to act quickly

The same is true for planting large numbers of trees (something often cited as a powerful strategy to pull carbon dioxide out of the atmosphere), which can push crops and livestock onto less productive land

“Agricultural practices that include indigenous and local knowledge can contribute to overcoming the combined challenges of climate change, food security, biodiversity conservation, and combating desertification and land degradation,”

an average of three people were killed per week defending their land in 2018, with more than half of them killed in Latin America.

the longer policymakers wait, the harder it will be to prevent a global crisis. “Acting now may avert or reduce risks and losses, and generate benefits to society,” the authors wrote. Waiting to cut emissions, on the other hand, risks “irreversible loss in land ecosystem functions and services required for food, health, habitable settlements and production.”

To achieve this goal, countries that signed on to the agreement promised that they would focus on cultivating clean, renewable energy sources and shift from the use of fossil fuels. They will also be required to report on their progress in reducing greenhouse gas emissions every five years.

The deal also commits countries to deliver $100 billion a year in aid for developing countries by 2020, with a promise to increase financing in the future.

In a preamble, the deal doubles down on a pledge made six years ago, that richer, industrialized countries will contribute at least $100 billion of aid a year to poorer nations to help them battle the effects of climate change by 2020. It also promises that countries will consider increases to that amount in the future.

So there may be many vested parties with a stake in the climate change deal -- but there are also a few key winners and losers. We take a look at them here:

According to the Internal Displacement Monitoring Centre's (IDMC) 2015 Global Estimates report, "an average of 26.4 million people per year have been displaced from their homes by disasters brought on by natural hazards" since 2008. These threatened populations are largely found in developing countries, which tend to be more vulnerable to rises in sea level, droughts, and floods.

The climate accord in Paris, however, have many in the developing world cheering.

According to President Obama, the targets are bold, but they also empower "businesses, scientists, engineers, workers, and the private sector -- investors -- to work together."

Mohamed Adow, senior climate change adviser from the disaster relief agency Christian Aid, told CBS News that this is one of the most important aspects of the COP21 accord: the promise provides poorer nations with the "assurance that the international community will not leave developing countries to deal with climate impact."

Some nations were not entirely satisfied with the final language -- there is still, after all, no legally binding provision that holds industrialized countries to this pledge for "adaptation" funds -- but nonetheless, Adow said, it gives significant hope to those countries hit especially hard with the threat of displaced citizens.

In fact, the aid money already seems to be flowing in light of the Paris negotiations: early this week, the U.S. promised to double its own aid to affected countries to $861 million as part of last-ditch efforts to push the climate deal through.

The effects of climate change in poor and developing nations also pose an increasing terror threat to the United States -- a connection that President Obama has made in the past, when he called global warming "an economic and security imperative" just weeks after the Nov. 13 attacks in Paris.

As Democratic presidential candidate Bernie Sanders explained it on CBS' "Face the Nation" in November: "If we are going to see an increase in drought, in flood, and extreme weather disturbances as a result of climate change, what that means is that people all over the world are going to be fighting over limited natural resources... When people migrate into cities and they don't have jobs, there's going to be a lot more instability, a lot more unemployment, and people will be subject to the types of propaganda that al Qaeda and ISIS are using right now."

Military reports have also viewed climate change as a "catalyst for conflict," and the Pentagon's Quadrennial Defense Review last year dubbed its effects as "threat multipliers" that ultimately lead to "conditions that can enable terrorist activity and other forms of violence."

But the climate change deal seeks to mitigate these possible conflict catalysts so that "countries that don't have the resources to address these problems head on, now will," Jon Powers, who served the Federal Chief Sustainability Officer and Special Advisor on Energy to the U.S. Army in the Obama Administration, told CBS News.

One important target put forth by the deal was to ensure that parties would "undertake rapid reductions thereafter in accordance with best available science, so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century."

Here, the deal aims to strangle heavy carbon-emitting industries -- the "anthropogenic emissions" -- and cut down on total fossil fuels burned worldwide. Importantly, it's also a nod to investment in and development of new technologies that would remove carbon dioxide from the air.

U.S. Energy Secretary Ernest Moniz told CNBC in an interview, "We recognize fossil fuels will continue to be a part of the portfolio for quite a long time," but that the popularity of other power sources are on the rise.

"Wind energy has gone up by several fold just in the last five to six years," Moniz said, "and now (wind) provides about 4.5 percent of our electricity. You add that with solar, we're talking 5 percent."

Kathleen McLaughlin, the chief sustainability officer for Walmart, said in a statement that the company would "support the U.N.'s call for the U.S. corporate sector to commit to science-based targets to reduce emissions."

Ahead of the Paris summit, China -- the world's biggest coal consumer -- said it would aim to cut its greenhouse gas emissions by nearly two-thirds of its 2005 levels. In the past, international monitoring of those numbers would have been difficult to do, but the COP21 deal changes that.

The agreement holds nations accountable for reporting their progress on their climate goals in a global "stocktake" every five years starting in 2023. It also means countries will be monitoring, verifying and reporting their greenhouse gas emissions in a single accounting system.

According to one report released last month by the carbon investment think tank Carbon Tracker, fossil fuel companies could risk over $2 trillion dollars of current and future projects being left valueless as the market for fossil fuels narrows with recent global climate change action.

“We’re going to do it in a way that’s very deliberate,” White House domestic climate adviser Gina McCarthy told reporters Monday in a call organized by the World Resources Institute. The administration wants to transition to a cleaner economy with good-paying occupations in communities that have been hit hardest by unemployment and underinvestment, she said. “It’s intended to meet the moment we are in.”

“We are on the verge of the abyss,” U.N. Secretary General António Guterres said Monday

China, the largest greenhouse gas polluter, has said it plans to reach peak emissions by 2030 and effectively erase its carbon footprint by 2060, though the details remain uncertain

despite myriad diplomatic tensions between the two countries, the United States and China vowed Saturday to jointly combat climate change “with the seriousness and urgency that it demands.”

The world remains nowhere near meeting the central Paris aim of limiting Earth’s warming to “well below” 2 degrees Celsius (3.6 Fahrenheit) compared with preindustrial levels — or ideally, remaining closer to 1.5 Celsius. Failure to hit those targets, scientists have warned, will result in a cascade of costly and devastating effects.

“We are way off track,” Guterres said. “This must be the year for action — the make-it-or-break-it year.”

To craft the new pledge in the administration’s first 100 days, White House officials scrambled staffers at agencies across the government to look for funding, programs and policies that could help curb emissions in the years ahead. Agency by agency, sector by sector, federal officials tallied up the math in an effort to make Biden’s pledge credible.

The International Energy Agency this week projected that global carbon dioxide emissions are set to rise by 1.5 billion tons in 2021 — the second-largest increase in history — as the world comes out of the pandemic-induced downturn

“This is a dire warning that the economic recovery from the Covid crisis is currently anything but sustainable for our climate,”

In the United States, the power sector represents one of the best opportunities to cut greenhouse gas emissions. On Friday, a collection of 13 utilities, including Exelon, National Grid and PSEG, urged Biden to pursue a range of policies “to enable deep decarbonization of the power sector, including a clean electricity standard that ensures the power sector, as a whole, reduces its carbon emissions by 80 percent below 2005 levels by 2030.”

The Interior Department and the Environmental Protection Agency, meanwhile, are already laying the groundwork to curb methane emissions from oil and natural gas drilling, in part by reviving Obama administration standards reversed under Trump

the EPA is moving ahead to phase down the production and importation of hydrofluorocarbons — which are widely used as refrigerants and in air conditioning — by 85 percent over the next 15 years, as mandated by Congress.

Environmental activists, Democratic lawmakers, foreign leaders and hundreds of private companies, including Apple and Walmart, have implored the White House to make the boldest climate pledge possible.

Advocacy groups and academics have published detailed analyses, demonstrating ways they say the nation could cut at least half its emissions by the end of the decade.

But other major emitters, including China, India and Russia, have yet to spell out how exactly they intend to help put the world on a more sustainable trajectory.

to reach the 50 percent target, the administration will have to make some difficult-to-guarantee assumptions about the future. For instance, that new regulations aimed at curbing emissions won’t be reversed by a future administration or the courts — even though Trump furiously dismantled key Obama-era climate policies.

some Republicans have insisted that the far-reaching changes needed to cut greenhouse gas pollution so fast could harm an already struggling economy, particularly in communities that still depend on the fossil fuel industry.

Sen. Shelley Moore Capito (W.Va.), the top-ranking Republican on the Senate Environment and Public Works Committee, has argued that Biden’s aggressive climate actions could kill thousands of jobs in her state. On the Senate floor last month, she called the notion that new policies could quickly replace lost jobs in coal and other fossil fuels with ones in renewable energy “a fantasy world that does not exist.”

Persuading other key nations to bolster the promises they made in Paris remains critical if the world is to meet its collective goal of slowing Earth’s warming. The targets set by countries such as China, India, Russia and Brazil could dramatically affect whether the world can reach the goals set almost six years ago.

“The international community will have the opportunity to see that Biden is good for his word,” said Rachel Kyte, dean of the Fletcher School of Law and Diplomacy at Tufts University. “A lot of diplomacy is about momentum and building momentum.”

Biden has pledged to make the U.S. power sector 100% carbon-pollution free by 2035.

Thursday's summit did not detail how the White House plans to achieve the 50% reduction in emissions.

is nearly double the target set by Obama administration in 2015.

A second administration official said the White House expects other world leaders to follow Biden's announcement

But Biden's climate change agenda faces obstacles at home and abroad.

"The U.S. chose to come and go as it likes with regard to the Paris Agreement,"

"how it plans to make up for the lost four years."

The United States is the second-largest emitter of carbon dioxide (CO2), producing about 5.41 billion metric tons in 2018.

China emits nearly twice that amount.

Experts say the world's major economies need to dramatically scale back their carbon emissions to limit the rise of average global temperatures to 1.5 degrees Celsiu

Biden has pledged to be the most aggressive president on climate chang

"The Biden-Harris administration will do more than any in history to meet our climate crisis,"

But Biden's steps so far, and his promise to do more, have already unleashed a torrent of criticism from Republicans who argue that his climate policies will hurt American businesse

"It’s difficult to imagine the United States winning the long-term strategic competition with China if we cannot lead the renewable energy revolution

The Earth itself is our greatest ally in this effort. Ecosystems like California’s kelp forests absorb about half of the greenhouse gases humans emit, studies show. Without them, warming would be even worse. Nature shields us from the worst consequences of our own actions, forgiving the sins we refuse to repent.

If we hope to solve climate change, humanity must also address this biodiversity crisis — restoring ecosystems and the creatures that inhabit them.

One way to revitalize ecosystems: protect the ground they grow from.Think of the soft, spongy soil of an old-growth woodland. Here, a towering oak tree draws up water and nutrients via threadlike fungi attached to its roots. In exchange, the fungi take sugar from the oak, funneling carbon from the air into the ground.Now imagine a leaf from that oak drifting slowly to the forest floor. Perhaps it becomes food for an earthworm. Then microbes attack the earthworm’s droppings, breaking down the residue further still.Eventually, the carbon that was once a leaf can become trapped in clods of earth. Other atoms may form strong chemical bonds with minerals like iron, which prevents them from reacting with oxygen and returning to the air. Under the right conditions, carbon might stay locked away in dense, dark earth for centuries. Soils contain more carbon than the entire atmosphere and all the world’s plants combined.

This makes soil both a ticking time bomb and an overlooked climate solution

“And because soil is such an important reservoir,” Berhe said, “a small change in the release of that carbon can lead to a big change in the concentrations of greenhouse gases in the atmosphere.”

A 2020 analysis in the journal Nature Sustainability found that better soil stewardship could reduce emissions by at least 5.5 gigatons of carbon dioxide each year — about 15 percent of current annual emissions.

“Once that happens,” Berhe said, “it’s not just the carbon status of the soil that’s improved. The soil literally becomes softer. It holds more water and nutrients. It’s easier for plants to grow in … and serve as a home for the most abundant and diverse group of organisms that we know of.

Enhancing carbon in soils is just the beginning. In 2017, an international team of scientists set out to determine how much carbon the planet could pull out of the atmosphere, if humans would only give it a chance. In a study in the Proceedings of the National Academy of Sciences (PNAS), they concluded natural climate systems are capable of storing almost 24 gigatons of carbon dioxide per year — roughly two thirds of what people emit.

About half of that sequestration would be cost-effective, meaning enacting the necessary protections would cost less than the consequences of keeping that carbon in the air.

Of the climate solutions they studied, few delivered more carbon bang per buck than mangroves — lush systems of salt-tolerant shrubs and trees that thrive where freshwater rivers spill into the sea. Though these forests occupy just 0.5 percent of the Earth’s shorelines, they account for 10 percent of the coast’s carbon storage capacity.

But the unique ecosystems are too often dismissed as unproductive swamps, good for no one but the mosquitoes. In the past half-century, more than a quarter of the world’s mangroves have been destroyed — drained for development, converted for shrimp farms, poisoned by fertilizer and drowned by dammed-up streams.

Yet the Earth cannot compensate for all of humanity’s pollution, said William Schlesinger, former dean of Duke University’s School of the Environment and a co-author on the 2017 PNAS study. Unless people also reduce the amount of greenhouse gases we emit, no amount of ecological restoration will save us.

“The bottom line is we’ve got to get off of using fossil fuels in transportation and heating and lighting and everything else,”

In public talks, he puts it this way: “It’s easier to patch a hole in a bag than to pick up the marbles that fall out.”

Since the end of the last ice age, the frozen expanse at the top of the world has acted as a protective shield. During the summer, when the sun shines 24 hours a day, Arctic sea ice reflects about two-thirds of the light that hits it back into space. By contrast, the dark open ocean absorbs the majority of the sun’s heat.

If the Arctic loses its perpetual ice cover, it would add half a degree Celsius of warming to the global average temperature, studies suggest. The world is hurtling toward that milestone. Since 1979, the volume of ice left at the end of the summer has shrunk about 75 percent.

There is just one way to save it, she said: by stopping global warming. Only by ending the use of fossil fuels and eliminating greenhouse gas emissions can people prevent the Arctic from heating further and give the ice a chance to recover.

If we do nothing, models indicate, it will be a matter of decades before the summertime Arctic is ice-free for the first time in human history. Sea levels will surge, coastal communities will be deluged, and we will no longer have the planet’s air conditioning unit to help us cool our world down.

Our species evolved and our civilization was built under fairly stable climate conditions. When things changed, they changed slowly, giving us time to adapt.

The rapid transformation of our planet doesn’t just endanger ecosystems; humanity will suffer. People have never lived on a planet without mangroves, or peatlands, or summertime ice. We’ve never had to go without the benefits the Earth provides.

In the United States, the warming was most significant in the Northeast and Southwest.

With the 2020 results, the last seven years have been the warmest since the beginning of modern record-keeping nearly a century and a half ago, Dr. Schmidt said.

The planet has warmed more than 1 degree Celsius (about 2 degrees Fahrenheit) since the late 1800s, when the spread of industrialization led to rising emissions of carbon dioxide and other greenhouse gases, and the pace has accelerated in recent decades.

Dr. Schmidt said his team and others have been studying the effects of the coronavirus pandemic on 2020 temperatures. Lockdown orders and the economic slowdown reduced greenhouse gas emissions by about 10 percent in the United States alone, according to a recent report.

Dr. Schmidt said efforts were underway to quantify the effect over the past year. “The numbers aren’t large,” he said, but they may have played a role in making 2020 a record-tying year.

it turns out that the way we move largely determines the way we live.

gadgets cumulatively contribute only a fraction of what we save by living in a walkable neighborhood. It turns out that trading all of your incandescent lightbulbs for energy savers conserves as much carbon per year as living in a walkable neighborhood does each week.

“gizmo green”; the obsession with “sustainable” products that often have a statistically insignificant impact on the carbon footprint when compared to our location. And, as already suggested, our location’s greatest impact on our carbon footprint comes from how much it makes us drive.

study made it clear that, while every factor counts, none counts more than walkability. Specifically, it showed how, in drivable locations, transportation energy use consistently tops household energy use, in some cases by more than 2.4 to 1. As a result, the most green home (with Prius) in sprawl still loses out to the least green home in a walkable neighborhood.

because it’s better than nothing, LEED — like the Prius — is a get-out-of-jail-free card that allows us to avoid thinking more deeply about our larger footprint. For most organizations and agencies, it is enough. Unfortunately, as the transportation planner Dan Malouff puts it, “LEED architecture without good urban design is like cutting down the rainforest using hybrid-powered bulldozers.”

10 to 20 units per acre is the density at which drivable suburbanism transitions into walkable urbanism.

“We are a destructive species, and if you love nature, stay away from it. The best means of protecting the environment is to

The average New Yorker consumes roughly one-third the electricity of the average Dallas resident, and ultimately generates less than one-third the greenhouse gases of the average American.

the American anti-urban ethos remained intact as everything else changed. The desire to be isolated in nature, adopted en masse, led to the quantities and qualities we now call “sprawl,” which somehow mostly manages to combine the traffic congestion of the city with the intellectual culture of the countryside.

New York consumes half the gasoline of Atlanta (326 versus 782 gallons per person per year). But Toronto cuts that number in half, as does Sydney — and most European cities use only half as much as those places. Cut Europe’s number in half, and you end up with Hong Kong

Paris is one place that has determined that its future depends on reducing its auto dependence. The city has recently decided to create 25 miles of dedicated busways, introduced 20,000 shared city bikes in 1,450 locations, and committed to removing 55,000 parking spaces from the city every year for the next 20 years. These changes sound pretty radical, but they are supported by 80 percent of the population.

increasing density from two units per acre to 20 units per acre resulted in about the same savings as the increase from 20 to 200.

New York is our densest big city and, not coincidentally, the one with the best transit service. All the other subway stations in America put together would not outnumber the 468 stops of the MTA. In terms of resource efficiency, it’s the best we’ve got.