With Speed and Violence: Why Scientists Fear Tipping Points in Climate Change (5 page)

This is not the end of the story, however. While we can be fairly certain that more greenhouse gases in the air will push the atmosphere to further warming, big uncertainties remain about how the planet will respond. An assessment of the sensitivity of global temperatures to outside forcing -whether to changes in sunlight or the addition of greenhouse gasesmostly revolves around disentangling the main feedbacks: the things changed by an altered climate that influence the climate in turn. Positive feedbacks reinforce and amplify the change, and run the risk of producing a runaway change-the climatic equivalent of a squawk on a sound system. Negative feedbacks work in the other direction, moderating or even neutralizing change.

The current climate models concur with Arrhenius that the planet will amplify the warming. But skeptics believe that nature has strong stabilizing forces that will act as negative feedbacks and head off climate change. They don't by any means agree on how this will work. Some say a warmer world will be a cloudier world, providing us with more shade from the sun. Others, like the respected Massachusetts Institute of Technology meteorologist Richard Lindzen, have argued that the higher reaches of the troposphere might actually become drier, reducing the greenhouse effect of water vapor. Many of these arguments reflect legitimate uncertainty among climate scientists, though some of the negative feedbacks proposed by the skeptics, such as cloud processes, could equally turn into major positive feedbacks and make the IPCC projections too small.

Where does this leave us? Actually, with a surprising degree of scientific consensus about the basic science of global warming. When the science historian Naomi Oreskes, of the University of California in San Diego, reviewed almost a thousand peer-reviewed papers on climate change published between 1993 and 2003, she found the mainstream consensus to be real and near universal. "Politicians, economists, journalists and others may have the impression of confusion, disagreement or discord among climate scientists, but that impression is incorrect," she concluded. The disagreements were mainly about detail. The consensus, stretching from Tyndall through Arrhenius to the IPCC, lived on.

For hard-line skeptics, of course, any scientific consensus must, by definition, be wrong. As far as they are concerned, the thousands of scientists behind the IPCC models have either been seduced by their own doomladen narrative or are engaged in a gigantic conspiracy. For them, the greater the consensus, the worse the conspiracy. The maverick climatologist Pat Michaels, of the University of Virginia in Charlottesville, says we are faced with what the philosopher of science Thomas Kuhn called a "paradigm problem." Michaels, who is also the state meteorologist for Virginia, one of the United States' largest coal producers, and a consultant to numerous fossil fuel companies, says: "Most scientists spend their lives working to shore up the reigning world view-the dominant paradigmand those who disagree are always much fewer in number." The drive to conformity, he says, is accentuated by peer review, which ensures that only papers in support of the paradigm appear in the research literature, and by public funding of research into the prevailing "paradigm of doom."

Even if you accept this cynical view of how science is done, it doesn't mean that the orthodoxy is always wrong. The fact that scientists universally agree that the world is round does not make it flat. Many of the same claims that are now made against the global warming "paradigm" were once made about the "AIDS industry" by people who disputed that HIV caused AIDS. Some governments took their side for a long time, and their citizens are now living with the consequences. Where are those skeptics now? Some of them can be heard making the case against climate change.

But all that said, I do think the skeptics are important to the arguments about climate science. The desire for consensus is always likely to lead the mainstream scientific community to don blinkers. This has not only blotted out the arguments of skeptics but also sidelined results from the handful of "rogue" climate models that keep turning up tipping points that could tumble the world into much worse shape than what is currently predicted by the mainstream. One scientist told me in the corridors of a conference in early 2005: "By ignoring these outliers, IPCC has failed for ten years to investigate the possible effects of more extreme climate change."

So, despite their sometimes cynical motives, the skeptics have served a purpose in picking away at the IPCC orthodoxy. As in politics, every good government needs a good opposition. And though their arguments have often been opportunistic and personal, the skeptics have spotted the stifling impact of consensus-building. They are, if nothing else, helping to keep the good guys honest. The pity is that they have not done a better job, by engaging in more real science and less empty rhetoric. And in their enthusiasm to debunk climate change, they have failed to grasp one alarming possibility: that the IPCC could be underestimating, not overestimating, the threat that the world faces.

3

THE YEAR

How the wild weather of x998 broke all records

Lidia Rosa Paz was at a loss. She caught my arm and pointed despairingly into the raging river. Out there, about 50 yards into the water, was the spot where, until days before, she had lived. On the night of October 28, 1998, her shantytown of Pedro Dias, in the town of Choluteca, in Honduras, had been washed away, taking more than a hundred people to their deaths. Lidia had survived, but every one of her possessions was gone. "What will I do now?" she asked. I didn't have an answer.

Hers was one story from a night when floods and landslides ripped apart the small Central American country's geography, leaving more than 10,000 Hondurans dead and 2 million homeless. It was the night that Hurricane Mitch, the most vicious hurricane to hit the Americas in 200 years, came calling, and dumped a year's rain in just a few hours. Choluteca is in southern Honduras, on the Pacific coast, far from the normal track of Caribbean hurricanes. When the radio issued storm warnings that night, neither Lidia nor any of her neighbors took much notice. "Hurricanes never come here," she told me. Or at least they never had.

I was in Honduras a couple of weeks after the hurricane had struck. The devastation was appalling. Huge floods had rushed down rivers and into the capital, Tegucigalpa, in the mountainous heart of the country, ripping away whole communities. A thousand people lost their lives beneath a single slide that landed on the suburb of Miramesi. Another stopped just short of the American embassy in the capital. Rivers changed their paths right across the country, obliterating towns. And flash floods on steep hillsides buried whole communities under mud. Sixty percent of the country's bridges were destroyed, along with a quarter of its schools and half its agricultural productivity, including nearly all its banana plantations. The first visitors to the southern town of Mordica reported, "All you can see is the top of the church." Ministers said the country's economic development had been put back twenty years.

For tens of millions of people across the world, the violence of Mitch is an omen. Many climatologists believe that Mitch, a ferocious hurricane made worse by the warm seas that allowed it to absorb huge amounts of water from the ocean, was a product of global warming-and a sign of things to come for the hundreds of millions of inhabitants of flood-prone river valleys and coastal plains across the world; for those living on deforested hillsides prone to landslips; and for many millions more who do not yet know that they are vulnerable in a new era of hyperweather. People like Lidia before Mitch hit.

Those who do not believe that global warming is a real and dangerous threat should visit places like Choluteca and talk to people like Lidia. It may not convince them that climate change is making superhurricanes and megafloods. But it will show them the forces of nature untamed and the human havoc caused when weather breaks its normal shackles. For hundreds of millions of people, these issues are no longer a matter for computer modeling or debate in the corridors of Congress or future forecasts. They are about real lives and deaths. The question is not: Can we prove that events like Mitch are caused by climate change? It is: Can we afford to take the chance that they are?

The year 1998 was the warmest of the twentieth century, perhaps of the millennium. It was also a year of exceptionally wild weather, and few doubt that the two were connected. That year, besides the storms, the rainforests got no rain. Forest fires of unprecedented ferocity ripped through the tinder-dry jungles of Borneo and Brazil, Peru and Tanzania, Florida and Sardinia. New Guinea had the worst drought in a century; thousands starved to death. East Africa saw the worst floods in half a century-during the dry season. Uganda was cut off for several days, and much of the desert north of the region flooded. Mongol tribesmen froze to death as Tibet had its worst snows in fifty years. Mudslides washed houses off the cliffs of the desert state of California. In Peru, a million were made homeless by floods along a coastline that often has no rain for years at a time. The water level in the Panama Canal was so low that large ships couldn't make it through. Ice storms disabled power lines throughout New England and Quebec, leaving thousands without power or electric light for weeks. The coffee crop failed in Indonesia, cotton died in Uganda, and fish catches collapsed in the Pacific off Peru. Unprecedented warm seas caused billions of the tiny algae that give coral their color to quit reefs across the Indian and Pacific Oceans, leaving behind the pale skeletons of dead coral.

All a coincidence? Not according to the IPCC. Some of the damage was caused by an intense outbreak of a natural climate cycle in the Pacific known as El Nino. Every few years, this causes a reversal of winds and ocean currents across the equatorial Pacific, for a few months taking rains to drought regions and droughts to normally wet areas. But as we shall see in Chapter 30, there is growing evidence that El Ninos are becoming stronger and more frequent under the influence of global warming. This is probably part of a pattern identified by the IPCC, in which, all around the world, the weather is becoming more extreme and more unpredictable as the world warms. And 1998, the warmest year yet, was the epitome of the trend.

The heat is intensifying the hydrological cycle. Globally, average annual rainfall increased by up to io percent during the twentieth century, because warming has increased evaporation. Locally, the trends are even stronger. The floods that inundated Mozambique in 2000 occurred because maximum daily rainfall there had risen by 50 percent. In the eastern U.S., the proportion of rain falling in heavy downpours has increased by a quarter. In Britain, winter rain falls in intense downpours twice as often as it did in the 196os. There are similar patterns in Australia, South Africa, Japan, and Scandinavia. Even the Asian monsoon has become more intense but less predictable. At the same time, dry areas in continental interiors have become drier, causing deserts to spread. The year 1998 was the first in a run of years of intense drought that stretched from the American West through the Mediterranean to Central Asia.

At the time of this writing, no other year has been as hot as 1998-and no other year so climatically violent. Unless, that is, you were caught in one of the record number of tropical storms in the North Atlantic in 2005. But if you want to know what the first stage of climate change is shaping up to be like, look no further than 1998.

4

THE ANTHROPOCENE

A new name for a new geological era

Welcome to the Anthropocene. It's a new geological era, so take a good look around. A single species is in charge of the planet, altering its features almost at will. And what more natural than to name this new era after that top-of-the-heap anthropoid, ourselves? The term was coined in 2000 by the Nobel Prize-winning Dutch atmospheric scientist Paul Crutzen to describe the past two centuries of our planet's evolution. "I was at a conference where someone said something about the Holocene, the long period of relatively stable climate since the end of the last ice age," he told me later. "I suddenly thought that this was wrong. The world has changed too much. So I said: 'No, we are in the Anthropocene.' I just made up the word on the spur of the moment. Everyone was shocked. But it seems to have stuck."

The word is catching on among a new breed of scientists who study Earth systems-how our planet functions. Not just climate systems, but also related features, such as the carbon cycle on land and at sea, the stratosphere and its ozone layer, ocean circulation, and the ice of the cryosphere. And those scientists are coming to believe that some of these systems are close to breakdown, because of human interference. If that is true, then the gradual global warming predicted by most climate models for the next centuries will be the least of our worries.

The big new discovery is that planet Earth does not generally engage in gradual change. It is far cruder and nastier, says Will Steffen, an Australian expert on climate and carbon cycles who from 1998 to 2004 was director of the International Geosphere Biosphere Programme, a research agency dedicated to investigating Earth systems. A mild-mannered man not given to hyperbole, Steffen nonetheless takes a hard-nosed approach to climate change. "Abrupt change seems to be the norm, not the exception," he says. We have been lured into a false sense of security by the relatively quiet climatic era during which our modern complex civilizations have grown and flourished. It may also have left us unexpectedly vulnerable as we stumble into a new era of abrupt change.

We have also been blind, he says, to the extent of the damage we are doing to our planetary home. We often see our impact as limited to individual parts of the system: to trashed rainforests, polluted oceans, and even raised air temperatures. We rarely notice that by doing all these things at once, we are undermining the basic planetary systems. Something, Steffen says, is going to give: "The planet may have an Achilles heel. And if it does, we badly need to know about it." Without that knowledge and the will to act, he says, the Anthropocene may well end in tears.