Chronology Of Climate Change

5 billion years ago Birth of planet Earth

600 million years ago Last occurrence of "Snowball Earth," followed by warm era

400 million years ago Start of long-term cooling

65 million years ago Short-term climate conflagration after meteorite hit

55 million years ago Methane "megafart" from ocean depths causes another short-term conflagration

50 million years ago Cooling continues as greenhouse-gas levels in air start to diminish

25 million years ago First modern ice sheet starts to form on Antarctica

3 million years ago First ice-sheet formation in the Arctic ushers in era of regular ice ages

100,000 years ago Start of most recent ice age

16,000 years ago Most recent ice age begins stuttering retreat

14,500 years ago Sudden warming causes sea levels to rise 65 feet in 400

years

12,800 years ago Last great "cold snap" of the ice age, known as the Younger

Dryas era, is triggered by emptying glacial lake in North America and continues for around 1,300 years before ending very abruptly

8,200 years ago Abrupt and mysterious return to ice-age conditions for several hundred years, followed by warm and stable Holocene era

8,000 years ago Storegga landslip in North Sea, probably triggered by methane clathrate releases that also bolster the warm era

5,500 years ago Sudden aridification of the Sahara

4,200 years ago Another bout of aridification, concentrated in the Middle East, causes widespread collapse of civilizations

1,200 to 900 years ago Medieval warm period in the Northern Hemisphere;

megadroughts in North America

700 to 150 years ago Little ice age in the Northern Hemisphere, peaking in the

1690s

1896 Svante Arrhenius calculates how rising carbon dioxide levels will raise global temperatures

1938 Guy Callendar provides first evidence of rising carbon dioxide levels in the atmosphere, but findings ignored

1958 Charles Keeling begins continuous monitoring program that reveals rapidly rising carbon dioxide levels in the atmosphere

1970s Beginning of strong global warming that has persisted ever since, almost certainly attributable to fast-rising carbon dioxide emissions, accompanied by shift in state of key climate oscillations such as El Nino and the Arctic Oscillation, and increased melting of the Greenland ice sheet

Early 1980s Shocking discovery of Antarctic ozone hole brings new fears of human influence on global atmosphere

1988 Global warming becomes a front-page issue after Jim Hansen's presentations in Washington, D.C., during U.S. heat wave 1992 Governments of the world attending Earth Summit promise to prevent "dangerous climate change" but fail to act decisively

1999 Warmest year on record, and probably for thousands of years, accompanied by strong El Nino and exceptionally "wild weather," especially in the tropics; major carbon releases from burning peat swamps in Borneo

2001 Government of Tuvalu, in the South Pacific, signs deal for New

Zealand to take refugees as its islands disappear beneath rising sea levels

2003 European heat wave—later described as the first extreme- weather event attributable to man-made global warming—kills more than 30,000; a third of the world is reported as being at risk of drought: twice as much as in the 1970s

2005 Evidence of potential "positive feedbacks" accumulates with exceptional hurricane season in the Atlantic, reports of melting Siberian permafrost, possible slowing of ocean conveyor, escalating loss of Arctic sea ice, and faster glacial flow on Greenland the cast

Richard Alley, Perm State University, Pennsylvania. A glaciologist and leading analyst of Greenland ice cores, Alley is one of the most articulate interpreters of climate science. He has revealed that huge global climate changes have occurred over less than a decade in the past.

Svante Arrhenius, a Swedish chemist. In the 1890s, he was the first to calculate the likely climatic impact of rising concentrations of carbon dioxide in the atmosphere, and thus invented the notion of "global warming." Modern supercomputers have barely improved on his original calculation.

Gerard Bond, formerly of Lamont-Doherty Earth Observatory, Columbia University, New York. A geologist, Bond was one of the first analysts of deep-sea cores; until his death, in 2005, he was an advocate of the case that regular pulses in solar activity drive cycles of climate change on Earth, such as the little ice age and the medieval warm period.

Wally Broecker, Lamont-Doherty Earth Observatory, Columbia University. An oceanographer and one of the most influential and controversial U.S. climate scientists for half a century, Broecker discovered the ocean conveyor, a thousand-year global circulation system that begins off Greenland and ends in the Gulf Stream, which keeps Europe warm.

Peter Cox, UK Centre for Hydrology and Ecology, Wareham. Cox is an innovative young climate modeler of aerosols' likely role in keeping the planet cool — and of the risks that land plants will turn from a "sink" for to a "source" of carbon dioxide later in this century.

James Croll, a nineteenth-century Scottish artisan and self-taught academic. After many years of study, he uncovered the astronomical causes of the ice ages, a discovery that was later attributed to the Serbian mathematician Milutin Milankovitch.

Paul Crutzen, Max Planck Institute for Chemistry, Mainz, Germany. An atmospheric chemist who won the Nobel Prize in 1995 for his work predicting the destruction of the ozone layer, Crutzen pioneered thinking about stratospheric chemistry, the role of man-made aerosols in shading the planet, and "nuclear winter," and coined the term "Anthropocene."

Joe Farman, formerly of the British Antarctic Survey, Cambridge. Farman's dogged collection of seemingly useless data was rewarded by discovery of the ozone hole over Antarctica.

Jim Hansen, director of NASA's Goddard Institute for Space Studies, New York. Hansen's unimpeachable scientific credentials have preserved his position as President George W. Bush's top climate modeler (as this book goes to press), despite his outspoken warnings that the world is close to dangerous climate change, which have clearly irked the Bush administration.

Charles David Keeling, formerly of Scripps Institution of Oceanography, La Jolla, California. Until his death, in 2005, Keeling had made continuous measurements of atmospheric carbon dioxide on top of Mauna Loa, in Hawaii, since 1958. The resulting "Keeling curve," the most famous graph in climate science, shows a steady annual rise superimposed on a seasonal cycle as Earth breathes."

Sergei Kirpotin, Tomsk State University, Russia. Kirpotin is the ecologist who told the world about the "meltdown" of permafrost in the West Siberian peat lands, raising fears that massive amounts of methane would be released into the atmosphere.

Michael Mann, director of the Earth System Science Center, Penn State University, Pennsylvania. A climate modeler and the creator of the "hockey stick" graph, a reconstruction of past temperatures showing that recent warming is unique to the past two millennia, Mann is the butt of criticism from climate skeptics, but gives as good as he gets. He is the co founder of the RealClimate Web site.

Peter deMenocal, Lamont-Doherty Earth Observatory, Columbia University, New York. A climate historian, deMenocal has charted megadroughts, the sudden drying of the Sahara, and other major climate shifts of the past 10,000 years, and their role in the collapse of ancient cultures.

John Mercer, formerly of Ohio State University, Columbus. The glaciologist who first proposed that the West Antarctic ice sheet has an Achilles heel, and that a "major disaster" there may be imminent, Mercer also pioneered research on tropical glaciers.

Drew Shindell, NASA's Goddard Institute for Space Studies, New York. An ozone-layer expert and climate modeler, Shindell is doing groundbreaking research on unexpected links between the upper and the lower atmosphere, revealing how the stratosphere can amplify small changes in surface temperature.

Lonnie Thompson, Byrd Polar Research Institute, Ohio State University, Columbus. A geologist, Thompson has probably spent more time above 20,000 feet than any lowlander alive, all in the pursuit of ice cores from tropical glaciers that are rewriting the planet's climate history.

Peter Wadhams, head of polar ocean physics at the University of Cambridge. He rode in British military submarines to provide the first data on thinning Arctic sea ice and discovered the mysterious "chimneys" off Greenland where the global ocean conveyor starts.

preface: the chimney

The Greenland Sea occupies a basin between Greenland, Norway, Iceland, and the Arctic islands of Svalbard. It is like an antechamber between the Atlantic and the Arctic Ocean: the place where Arctic ice flowing south meets the warm tropical waters of the Gulf Stream heading north. Two hundred years ago, the sea was a magnet for sailors intent on making their fortunes by harpooning its great schools of bowhead whales. For a few decades, men such as the Yorkshire whaling captain and amateur Arctic scientist William Scoresby sailed north each spring as the ice broke up and dodged the ice floes to hunt the whales that had congregated to devour the spring burst of plankton. Scoresby was the star of the ice floes, landing a world-record thirty-six whales at Whitby Harbour after one trip in 1798. He was the nimblest navigator around a great ice spur in the sea known as the Odden tongue, where the whales gathered.

Scoresby was too clever for his own good, and boom turned to bust when all the whales had been killed. What was once the world's most prolific and profitable whaling ground is still empty of bowheads. But just as the unique mix of warm tropical waters and Arctic ice was the key to the Greenland Sea's whaling bonanza, so it is the key to another hidden secret of these distant waters.

It's called "the chimney." Only a handful of people have ever seen it. It is a giant whirlpool in the ocean, 6 miles in diameter, constantly circling counterclockwise and siphoning water from the surface to the seabed 2 miles below. That water will not return to the surface for a thousand years. The chimney, once one of a family, pursues its lonely task in the middle of one of the coldest and most remote seas on Earth. And its swirling waters may be the switch that can turn the heat engine of the world's climate system on and off. If anything could trigger the climatic conflagration shown in the Hollywood movie The Day After Tomorrow, it would be the chimney.

The existence of a series of these chimneys was discovered by a second British adventurer, Cambridge ocean physicist Peter Wadhams. In the 1990s, he began hitching rides in Royal Navy submarines beneath the Arctic ice. Like Scoresby, he was fascinated by his journeys to the Odden tongue—not for its long-departed whales, but because of the bizarre giant whirlpools he found there. He concluded that they were the final destination for the most northerly flow of the Gulf Stream. The waters of this great ocean current, which drives north through the tropical Atlantic bringing warmth to Europe, are chilled by the Arctic winds in the Greenland Sea and start to freeze around the Odden tongue. The water that is left becomes ever denser and heavier until it is entrained by the chimneys and plunges to the ocean floor.

This was a dramatic discovery. The chimneys were, Wadhams realized, the critical starting point of a global ocean circulation system that oceanographers had long hypothesized but had never seen in action. It traveled the world's oceans, passing south of Africa, around Antarctica, and through the Indian and Pacific Oceans, before gradually resurfacing and sniffing the air again as it returned to the Atlantic, joined the Gulf Stream, and moved north once again to complete a circulation dubbed by oceanographers the "ocean conveyor."

But even as he gazed on these dynamos of ocean circulation, Wadhams knew that they were in trouble. For the Arctic ice was disappearing. Sonar data he had collected from the naval submarines revealed that the entire ice sheet that once covered the Arctic was thinning and breaking up. By the end of the 1990s, the Odden tongue was gone. The Gulf Stream water still came north, but it never again got cold enough to form ice. The ice tongue has not returned.

"In 1997, the last year that the Odden tongue formed, we found four chimneys in a single season, and calculate there could have been as many as twelve," says Wadhams. Since then, they have been disappearing one by one—except for one particularly vigorous specimen. Wadhams first spot-ted it out in the open ocean, at 750 north and right on the Greenwich Mean Line, during a ship cruise in March 2001. By rights, it should not have been there without the ice, he says. But it was, hanging in there, propelled downward perhaps by the saltiness created by evaporation of the water in the wind.

He found the same chimney again later that summer, twice the following year, and a final time in spring 2003, before the British government cut off his research funds. Over the two years he tracked it, the last great chimney had moved only about 20 miles across the ocean, like an underwater tornado that refused to go away. Wadhams measured it and probed it. He sent submersible instruments down through it to measure its motion at depth. It rotated, he said, right to the ocean floor, and such was the force of the downward motion that it could push aside a column of water half a mile high. "It is amazing that it could last for more than a few days," Wadhams says. "The physics of how it did it is not understood at all."

The great chimney had in May 2003 one dying companion, 40 miles to the northwest. But that chimney no longer reached the surface and was, he says, almost certainly in its death throes. That left just one remaining chimney in the Greenland Sea. "It may be many decades old or just a transitory phenomenon," he says. "But either way, it, too, may be gone by now. We just don't know." Like Scoresby's bowheads, it may disappear unnoticed by the outside world. Or we may come to rue its passing.

introduction

Some environmental stories don't add up. I'm an environment journalist, and sometimes the harder you look at a new scare story, the less scary it looks. The science is flaky, or someone has recklessly extrapolated from a small local event to create a global catastrophe. Ask questions, or go and look for yourself, and the story dissolves before your eyes. I like to question everything. I am, I hope in the best sense, a skeptical environmentalist. Sometimes it is bad for business. I have made enemies by questioning theories about advancing deserts, by pointing out that Africa may have more trees than it did a century ago, and by condemning the politics of demographic doomsday merchants.

But climate change is different. I have been on this beat for eighteen years now. The more I learn, the more I go and see for myself, and the more I question scientists, the more scared I get. Because this story does add up, and its message is that we are interfering with the fundamental processes that make Earth habitable. It is our own survival that is now at stake, not that of a cuddly animal or a natural habitat.

Don't take my word for it. Often in environmental science it is the young, idealistic researchers who become the impassioned advocates. Here I find it is the people who have been in the field the longest—the researchers with the best reputations for doing good science, and the professors with the best CVs and longest lists of published papers—who are the most fearful, often talking in the most dramatic language. People like President George W. Bush's top climate modeler, Jim Hansen, the Nobel Prize-winner Paul Crutzen, and the late Charles Keeling, begetter of the Keeling curve of rising carbon dioxide levels in the atmosphere. They have seemed to me not so much old men in a hurry as old men desperate to impart their wisdom, and their sense that climate change is something special.

Nature is fragile, environmentalists often tell us. But the lesson of this book is that it is not so. The truth is far more worrying. Nature is strong and packs a serious counterpunch. Its revenge for man-made global warming will very probably unleash unstoppable planetary forces. And they will not be gradual. The history of our planet's climate shows that it does not do gradual change. Under pressure, whether from sunspots or orbital wobbles or the depredations of humans, it lurches—virtually overnight. We humans have spent 400 generations building our current civilization in an era of climatic stability—a long, generally balmy spring that has endured since the last ice age. But this tranquility looks like the exception rather than the rule in nature. And if its end is inevitable one day, we seem to be triggering its imminent and violent collapse. Our world may be blown away in the process.

The idea for this book came while I sat at a conference, organized by the British government in early 2005, on "dangerous climate change" and how to prevent it. The scientists began by adopting neutral language. They made a distinction between Type I climate change, which is gradual and follows the graphs developed by climate modelers for the UN's Intergovernmental Panel on Climate Change (IPCC), and Type II change, which is much more abrupt and results from the crossing of hidden "tipping points." It is not in the standard models. During discussions, this temperate language gave way.

Type II climate change became, in the words of Chris Rapley, director of the British Antarctic Survey, the work of climatic "monsters" that were even now being woken.

Later in the year, Jim Hansen spoke in even starker terms at a meeting of the American Geophysical Union, saying: "We are on the precipice of climate system tipping points beyond which there is no redemption." The purpose of this book is to introduce Rapley's monsters and Hansen's tipping points and to ask the question, How much time have we got?

The monsters are not hard to find. As I was starting work on this book, scientists beat a path to my door to tell me about them. I had an e-mail out of the blue from a Siberian scientist alerting me to drastic environmental change in Siberia that could release billions of tons of greenhouse gases from the melting permafrost in the world's biggest bog. Glaciologists, who are more used to seeing things happen slowly, told me of dramatic events in Greenland and Antarctica, where they are discovering huge river systems of meltwater beneath the ice sheets, and of events in Pine Island Bay, one of the most remote spots in Antarctica, that they discussed with a shudder. Soon, they said, we could be measuring sea level rise in feet rather than inches.

Along the way, I also learned about solar pulses, about the "ocean conveyor," about how Indian village fires may be melting the Arctic, about a rare molecule that runs virtually the entire clean-up system for the planet, and above all about the speed and violence of past natural climate change. Some of this, I admit, has the feel of science fiction. On one plane journey, I reread John Wyndham's sci-fi classic The Kraken Wakes, and was struck by the similarities between events he describes and predictions for the collapse of the ice sheets of Greenland and Antarctica. It is hard to escape the sense that primeval forces lurk deep in the ocean, in ice caps, in rainforest soils, and in Arctic tundra. Hansen says that we may have only one decade, and one degree of warming, before the monsters are fully awake. The worst may not happen, of course. Nobody can yet prove that it will. But, as one leading climate scientist put it when I questioned his pessimism, how lucky do we feel?

I hope I have retained my skepticism through this journey. One of the starting points, in fact, was a reexamination of whether the climate skeptics—those who question the whole notion of climate change as a threat—might be right. Much of what they say is political hyperbole, of more benefit to their paymasters in the fossil-fuel lobby than to science. Few of them are climate scientists at all. But in some corners of the debate, they have done good service. They have, for instance, provided a useful corrective to the common assumption that all climate change must be man-made. But my conclusion from this is the opposite of theirs. Far from allowing us to stop worrying about man-made climate change, the uncertainties they highlight underline how fickle climate can be and how vulnerable we may be to its capricious changes. As Wally Broecker, one of the high priests of abrupt planetary processes, says, "Climate is an angry beast, and we are poking it with sticks."

This book is a reality check about the state of our planet. That state scares me, just as it scares many of the scientists I have talked to—sober scientists, with careers and reputations to defend, but also with hopes for their own futures and those of their children, and fears that we are the last generation to live with any kind of climatic stability One told me quietly: "If we are right, there are really dire times ahead. Having a daughter who will be about my present age in 2050, and will be in the midst of it, makes the issue more poignant."

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