Climate Change May Be Abrupt— and Unstoppable

A woman in a down coat crouches on a field of snow atop a frozen lake, her bare hand clutching a lit match. Next to her, another bundled figure stabs the icy ground with a metal spike. There’s a loud hissing, then a whoosh as the woman brings the match close to the puncture and the air bursts into flames. A roaring jet of blue and yellow fire a foot high spews from the spot on the snowy ground, until a third figure jabs the ice with a long metal pry bar. A huge red fireball instantly pulses through the frame of the YouTube video. The people jump away, giggling and gasping.

In his small office high in the Berkeley hills, Lawrence Berkeley National Lab biogeochemist William Riley laughs too. On his office computer we’ve just witnessed the drama of thermokarst lakes—shallow ponds that form when Arctic permafrost melts and slumps, creating depressions that fill with water. In the winter, those lakes, found in Arctic regions like Alaska and Siberia, freeze over, creating a blanket of ice that traps methane gas bubbling up from decomposing soil on the bottom. Poke a hole in the ice to release the methane, strike a match, and you’ve got tundra pyrotechnics.

But flashy videos aren’t why Riley and colleagues embarked in late 2008 on a five-year quest to model what’s happening up in those Arctic ponds. The fun has dark implications: the methane these lakes release may foreshadow climate change scarier than anything you’ll find in current predictions. That chance is what earned the thermokarst lakes a spot under the (metaphorical) microscope, as part of a US Department of Energy project to measure and simulate natural systems that could have a huge influence on our planet’s climate. Riley and his colleagues at Berkeley, who are translating data about how the methane in the lakes behaves into numbers and equations, represent just one node in a big network of scientists trying to tease out new clues about climate change from the messy chaos of the world.

The $15 million project, called Investigation of the Magnitudes and Probabilities of Abrupt Climate Transitions
(IMPACTS), involves researchers from six national laboratories and collaborators from more than a dozen universities. It should take some of the mystery out of the under-studied but essential field of predicting abrupt climate
change. That’s what researchers call a set of runaway shifts that could happen if the global climate crosses a point of no return, or a point where reducing greenhouse gas emissions (climate change’s cause) would no longer have the power to reduce global warming (its effect). Some experts, including NASA’s top climate scientist James Hansen, fear we may be about to cross the line, though no one can say for sure. Understanding where that threshold is and what might push us past it could mean the difference between slow climate shifts that Earth’s inhabitants might be able to adapt to over the course of the next few centuries, or dramatic, chaotic changes that would transform our world by the time today’s toddlers hit middle age.

If the past is any clue, we could be in for a wild ride. If the past is any clue, we could be in for a wild ride. As far back in the fossil and geologic records as we can see, Earth’s climate has been hopping all over the place; our planet has alternately been an icy snowball, a sweltering sauna, and everything in between. Evidence collected over the past twenty years, ranging from glacial ice cores to sea floor samples to ancient pollens to stalagmites, has convinced scientists that the transitions from one state to another have sometimes been unfathomably quick. Traditional theories assumed that it took thousands of years for large ice sheets to build up during cold phases; newer evidence shows the planet’s climate can drive major changes within just decades. Humanity’s experience of a steady climate is nothing but an historical anomaly. “We don’t have direct human experience of [abrupt climate change],” says William Collins, another Lawrence Berkeley National Lab scientist who leads the IMPACTS project. “That’s biased our thinking about climate change as being something that happens gradually.” In fact, sometimes climate change doesn’t creep up on the planet; it changes the world within a human generation.

One example of abrupt climate shift was a prehistoric doozy of a cold snap known as the Younger Dryas. This “big freeze” started about 12,800 years ago, as the frozen planet was slowly thawing and moving toward conditions much like today’s temperate ones. Suddenly the warming reversed, and within a few decades cold, dry, and windy conditions became the norm for another millennium. Then the cold snap broke, even more rapidly than it began. Greenland’s average temperature
rose by as much as eighteen degrees Fahrenheit in ten years, about the difference between today’s average annual temperatures in Los Angeles and Buffalo, NY.

Scientists are still debating what caused the Younger Dryas’ dramatic swings in climate, which happened under
a very different set of conditions than those we face today. A leading explanation is that a giant lake in central
Canada sent a rush of melting glacial water into the North Atlantic, shutting down the major ocean current that had carried heat north from the tropics. Alternatively, a few researchers posit that the freshwater influx was the product of a comet that exploded above the Earth, melting glaciers. Whatever its cause, the Younger Dryas shows that climate is fickle. The Earth’s climate history features dozens of other known incidents—saddled with abstruse names like the Bolling-Allerod interval and Dansgaard-Oeschger events—of major, lasting, widespread changes that happened within decades.

To understand how the system could change so quickly, imagine the climate as a marble resting in the bottom of a large bowl. Push it a little in one direction with a finger, and it will roll around for a while before it settles on the bottom again. Keep pushing it little by little up the side of the bowl (“forcing” it in a certain direction, in climate terms), and it will climb higher and higher. Let go, and it will eventually settle back where it started. But force it high enough, and the next little nudge could send it over the bowl’s lip and into uncharted territory. That’s an abrupt change. Even if you take the forcing mechanism (your finger) away, the marble won’t roll back to where it started.

Of course, the real climate is much more complicated
than a marble in a bowl, and it’s hard to know what factors might send the system past a point of no return. The IMPACTS tasks represent researchers’ best guesses about mechanisms that might start a runaway forcing process very soon, within twenty to thirty years. The lakes are part of the IMPACTS project because they could contribute to a cycle that pushes the climate past its tipping point. Here’s how it could work: First, rising temperatures cause permafrost to melt. In some places, the ground subsides and water pools to form the shallow thermokarst lakes. At the bottom of the lakes, microbes munch on the defrosted soil, producing methane gas. Some of the gas bubbles up through the water into the atmosphere. The process happens year-round, because the layers of water and ice insulate the microbes from the frigid Arctic winter. Methane, which is over twenty times as effective as carbon dioxide at trapping heat in the atmosphere over a hundred-year period, helps warm the climate. Higher temperatures melt still more permafrost, more lakes release more methane, and a nasty feedback loop emerges. It doesn’t help that the Arctic is warming more rapidly than anywhere else.

Collins calls the handful of phenomena that IMPACTS is studying “The Four Horsemen of the Apocalypse.” The project’s scientists are trying to understand how Arctic sources of greenhouse gases, including thawed permafrost and Riley’s thermokarst lakes, might speed up warming worldwide. The surprising dynamics of the Antarctic ice sheet, which is breaking up faster than anyone predicted and could lead to major sea-level rises, and the extent and behavior of frozen methane pellets deep on the sea floor, which could melt, release big stores of the gas, and start a vicious cycle accelerating change. They’re also exploring how factors like dust storms, fires, and plant biology could cause or accelerate mega-droughts in America’s Southwest.

Flammable gas bubbling through frigid, distant lakes doesn’t seem like a big deal in isolation, but then again, neither does driving a car, burning coal, or other human activities that have spewed enough greenhouse gases into the atmosphere to start changing the climate. Yet within the context of our elaborate climate system, which acts in nonlinear, only partly predictable ways, the thermokarst lakes and their methane, or any of the other phenomena that make up the IMPACTS portfolio, could turn out to be the push that puts the marble over the edge of the bowl. “We don’t know what the risks of abrupt climate change are,” Collins explains. “It’s a lot like building an actuarial table. If you smoke, what’s your risk of dying? If you emit carbon dioxide, what’s your risk of breaking up Antarctica?”

And while the scientists are rushing to calculate the risks these factors pose, the driving forces behind climate change aren’t letting up. “There’s this pressure to get an answer,” Riley says. “We’re running as fast as we can, but it’s possible the system is going to get ahead of us.”

The scariest part about the possibility of abrupt climate change is that it could happen faster than many of the planet’s life forms, including us, could adapt. Sudden, long-lasting drops in precipitation, for example, probably contributed to the collapse of the Akkadian empire in Mesopotamia 4,200 years ago and to the disappearance of the Anasazi from the American Southwest in the 13th century. “Mankind has predicated its existence on the stability of climate zones,” says Collins. “That’s where we plant our crops, that’s where we grow our wine, that’s where we base our cities.” Some anthropologists even correlate the beginnings of agriculture with the pause in drastic climate swings we’ve enjoyed for the past ten thousand years.

If an abrupt change in climate occurs again soon, our surroundings could shift faster than even modern societies could handle. Rising sea level could inundate coastal areas, changes in weather patterns could devastate crops, energy and transportation infrastructure, and leave millions of people cut off from reliable drinking water. One only has to think of California’s current drought, or the 1930s dustbowl, or the disruption caused by natural disasters like Hurricane Katrina or the 2004 Indian Ocean tsunami, to realize the stress that weather and climate can put on a region’s food supplies and livelihoods. Climate shifts that come on more slowly would allow time for people to adapt: planting crops that use more or less water, shoring up or moving flood-prone roads and buildings, finding substitutes for dried-up hydroelectric power. Real adaptation would require both foresight and resources.

But even the most progressive governments are only beginning to consider what changes may need to happen, and the planet’s poorest regions may be especially vulnerable to sudden change. “What if Phoenix was no longer viable as a city?” Riley asks. “Even under pretty extreme conditions, Americans will be able to adapt. We have the money. But what are you going to do if you’re in Bangladesh, and you’ve got nothing?” Developed nations wouldn’t be off the hook, though, in the event of a global crisis. If, for example, sea level were to rise twenty feet in a century because Antarctica’s ice sheet collapsed, America’s troubles could extend beyond relocating its coastal population. Major climate change could prompt international conflicts over increasingly scarce natural resources, including food and water. “We have no clue what might happen if something shifts worldwide,” says Susanne Moser, a research associate at the Institute of Marine Sciences at UC Santa Cruz, who studies climate vulnerability. “What if there’s turmoil in seventeen places at the same time?”

Hollywood loves doomsday “bad weather” scenarios (see, for instance, the 2004 disaster flick The Day After Tomorrow in which an ice age sets in over just a few days), but do we really need to worry about a violent climate swing anytime soon? Nobody knows. “People didn’t even know this was happening until recently,” says Riley after we watch the fireball video. He’s talking about the bubbling methane, but he could just as easily be referring to other processes that IMPACTS projects are examining, such as the accelerating breakup of Antarctica’s ice sheet. “It’s complicated because the system’s so complicated. There are so many things that we’re still learning about,” Riley continues.

The forecast for our climate is already pretty grim. The United Nations’ Intergovernmental Panel on Climate Change (IPCC), the leading body for compiling climate change science, predicts that continuing greenhouse gas emissions will cause global temperatures to warm by as much as seven degrees Fahrenheit by the year 2099, and that sea level will rise over the next century, with harmful effects on human health, economies, and ecosystems worldwide. Closer to home, a report released earlier this year by the state of California, based on the IPCC’s data, warns that “extreme events from heat waves, floods, droughts, wildfires, and bad air quality are likely to become more frequent in the future and pose serious challenges to Californians.”

The magnitude of the changes we’ll face will likely depend on how much and how quickly we cut our greenhouse
gas emissions. The IPCC bases its scenarios on variables like population growth and fossil fuel use, using them to predict how the climate will react under different conditions. Yet the natural processes the IMPACTS team is studying—like the methane escaping from the thermokarst lakes—are missing from the climate models currently produced by research and government agencies worldwide. These previously unstudied factors could substantially alter the climate outlook even under the same emissions scenarios—though nobody knows exactly to what extent. The science just hasn’t been done. “Representing this type of change in models that can project the future of the climate has been really challenging,” Collins says. “It’s only recently become possible from a scientific and a computational perspective. We’re poised to do this now in kind of a unified framework
that’s unprecedented.

For Riley and his colleagues to include the lakes in future models, the team must attach numbers and formulas to a complicated combination of factors, everything from the geology of how permafrost slumps to the physics of how methane bubbles and the biology of how microbe populations act. Their model has to capture the behaviors of millions of lakes ranging in size from a few yards to a few miles across. To make things harder, because the methane spewing from thermokarst lakes was discovered so recently, the researchers are building models without the benefit of a long history of field data.

The team starts by trying to model an individual site. They test their computer program by comparing what it would predict in past conditions to actual observations. Next they do similar tests at many other sites, trying to refine their lake model to match what happens in the real world. Once the team feels confident that their model works well—Riley expects to have it ready by February, 2010—they will plug it into a general circulation climate model, which takes into account hundreds of other systems and processes, like those included in the IPCC report, to mimic the global climate as a whole. With the models coupled, the IMPACTS researchers can start to predict how likely and how sudden abrupt changes might be under different emissions scenarios, and create projections that could guide policymakers in preventing or reacting to climate change.

What if the models show we’re likely to get a dramatic shift in temperature, sea level, or rainfall over a short period of time? “I can tell you that we are in no way prepared,” says Moser, who has worked with the state of California on its adaptation strategies. “We are barely prepared for our ‘normal’ disasters, as New Orleans showed very well. There’s simply a horrific picture you get in scientists’ eyes, how bad it would be to go to that place, but no one has data on what that would mean. Certainly not for the state of California.”

Despite the scarcity of data-based predictions, there have been a few attempts from the policy side to think seriously about the possibility of abrupt climate change. In 2003, two consultants for the San Francisco-based Global Business Network, which specializes in scenario planning, prepared a report for the Pentagon on its national security implications. “Because of the potentially dire consequences,” the report warned, “the risk of abrupt climate change, although uncertain and quite possibly small, should be elevated beyond a scientific debate to a US national security concern.” The report drew media attention in 2004, but the federal government didn’t react in any visible way. Federal and local policymakers rarely discuss or acknowledge abrupt climate change. “We’re driving with a heavy foot on the accelerator and basically closing our eyes,” Moser says.

Admittedly, it can be hard to distinguish whether a change like a regional decrease in rainfall is a short-term blip or part of a large-scale shift. One hope for the IMPACTS models is that they might help us tell if we’re already in the midst of an abrupt change. “Things are changing so fast, it’s possible that we already are,” Riley muses. Collins is more cautious. “The last thing we want to be is alarmist,” he says. “That said, we want to be realistic and we’ll go where the science leads us.”

Riley is optimistic about the progress his team is making, but it may beyond anyone’s capability to figure out what’s really happening in a system as complex and rapidly changing as Earth’s climate, and assign meaningful numbers to nebulous climate-change factors, many of which we may not even have discovered yet. Like the actuaries they’re emulating, the IMPACTS scientists will do their best to figure out the likelihood these small changes will add up to a big shift, and how soon that shift may happen. The rest will be up to policymakers. Even when this project is complete, we won’t be entirely able to predict our future. “There’s only one real experiment,” Riley says, “and we’re living in it.”


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