An Ocean of Air (14 page)

This is one reason that global warming researchers have always had an image problem. It's not too hard to jolt people into action if you can point to a massive oil spill, or a forest that's been devastated by acid rain. But where the effects of carbon dioxide are concerned, the long view is the only one that matters. Nobody will
ever
be able to say "this particular heat wave was caused by global warming" or finger it as the culprit for that individual flood. Instead, the potentially nefarious effects of carbon dioxide are all about something that's much harder to pin down:
trends.

And yet the world was now stirring to this new threat. Records seemed to suggest that temperatures had risen by a fraction of a degree in the past century, and though it wasn't by much, it was the first real sign of change. Then, in 1995, an international group of climate scientists announced for the first time that the balance of evidence, in their opinion, had slipped over a threshold. Global warming, they declared, is upon us. Hot on the heels of that announcement came news that 1995 was the warmest year since records began. The year 1997 was even warmer, and 1998 warmer still.

And then, a scientific paper published in 1999 struck what many consider to be the killer blow against global warming skeptics. The paper came from decades of work in what is, officially, the coldest place on Earth. Vostok station, a Russian base in the frigid heart of the Antarctic Ice Sheet, reaches winter temperatures cold enough to shatter steel. Even in summer it's a forbidding place. The temperature scarcely ever rises above
-10 degrees Fahrenheit and the air is almost as dry as the Sahara. Its handful of occupants live in a station that is perpetually starved of funds and seems to cling to the ice through sheer Russian tenacity.

But the ice at Vostok is miraculous. More than two miles thick, it holds a frozen archive of past climate stretching back hundreds of thousands of years. For decades Russian scientists, aided by some French and then American researchers, had been drilling a hole into this storehouse, and the deeper they went, the farther back in time they penetrated. They had already announced a record of temperatures for the past 400,000 years and discovered a series of four successive ice ages, each with a warmer period in between. But what they produced in 1999 caused a sensation. They had managed to recover not only temperatures, but minuscule amounts of Earth's ancient atmosphere.

How could something as insubstantial as air be preserved? Well, whenever snow falls at Vostok, it traps a small amount of air among its flakes. Gradually, over the years, the flakes become buried by yet more snow. They are squeezed and compressed until finally they turn into ice. At this point, the trapped air can no longer wriggle its way to the surface. It remains in cold storage, tiny bubbles that provide time capsules of the planet's ancient atmosphere. The researchers at Vostok had not only managed to recover these tiny bubbles. They had carefully broken into them and released air last breathed when the human species, Homo sapiens, had only just appeared on the evolutionary scene.

And then they had measured it. With extreme patience, the scientists managed to extract these tiny quantities of carbon dioxide and feed them through their measuring devices. They produced a record of carbon dioxide levels stretching back 400,000 years, to match the one they had already created for temperatures.

Plotted side by side, these two records revealed something remarkable. Whenever the temperature was lower, so were the carbon dioxide levels. Whenever the temperature was higher, the carbon dioxide was higher, too. Climate and carbon dioxide clearly marched in lockstep. Tyndall and Arrhenius had been absolutely right. We still don't know the exact connection between carbon dioxide and temperature, or all the complex inter
relations of Earth's atmosphere. But history shows us that carbon dioxide is clearly a hugely important driver for our planet's temperature.

And there was something else, something even more striking. Carbon dioxide levels seemed to vary quite naturally, along with natural changes in temperature. But when the researchers studied their record more carefully, they discovered that at no point in the last 400,000 years had carbon dioxide levels been anything near what they are today.

A newer ice core, drilled a few hundred miles from Vostok at Dome C by a consortium of European researchers known as EPICA, has now gone even farther back in time, almost 800,000 years. They found exactly the same story. Carbon dioxide changes mirrored temperatures with astonishing fidelity. And as far as they could reach with their ingenious frozen time machine, levels in our atmosphere have never been as high as they are today. The highest level Earth managed naturally during that time, which includes all of human history, was about 280 parts per million, or 0.0028 percent. But today we have more than 380 parts per million—and it is rising.

Nobody yet knows what effect this will have on our world, although most scientists think that it's now too late to avert at least some amount of change. We know, or at least suspect, that in its ancient history our planet experienced levels of carbon dioxide even higher than today's. But that was long before humans, or even our apelike ancestors, existed. In the past few hundred years, we've put a huge amount of effort into developing our society according to the present climate, the present pattern of floods and storms and rainfall, of crops and livestock. We are embedded in our present homes and places of work. And we can't just lift up our skirts and move if the warming sea begins to rise and encroach on our waterside cities, if storm surges begin to devastate our coastlines, and if the interiors of our continents begin to turn into dust bowls.

Meanwhile, yet more evidence has emerged from the ice, suggesting that our entire complex climate system, driven by the engine of Earth's atmosphere, can sometimes be delicately balanced between dramatically different states. One slight shift can send temperatures soaring or plummeting. In 1987, an ever-prescient climate researcher from New York, Wally
Broecker, commented that we had been treating the greenhouse effect as a "cocktail hour curiosity," and it was time to take it seriously. The climate system, he said, was a capricious beast, and we were poking it with a sharp stick.

After 35,000 people died during a fierce heat wave in Europe in 2003, the U.K. Government's chief science adviser declared that global warming was "an even worse threat than terrorism." But while politicians wrangle and scientists plead, we continue our lives more or less as normal. And every time any one of us drives a car, catches a plane, switches on an electric light, or does any one of a myriad of ordinary tasks, another whiff of carbon dioxide rises into the sky.

One final cautionary tale about the powers of carbon dioxide comes from our sister planet, Venus. Being a little closer to the sun than we are, you'd expect Venus to be slightly warmer, but in many other ways—size, for instance—it could be our twin. However, at some point in the past, carbon dioxide worked its wicked magic on Venus's air. For some reason, a little too much carbon dioxide trickled out from Venus's volcanoes into its atmosphere. The air grew warmer, which meant it sucked up water from the oceans. The extra water vapor acted as a greenhouse gas in its own right and reinforced the behavior of the carbon dioxide. Soon the atmosphere was filled with carbon dioxide and water molecules, all catching infrared heat as it tried to escape and flinging it back to the ground. The result: Venus's oceans are long gone. The rocks on its surface are now dry as a bone, and hot enough to melt lead.

Many researchers take comfort from Venus's greater proximity to the sun and say that such a greenhouse catastrophe could never happen here on Earth. But there is a chance they might be wrong. A recent project that used thousands of PC screen savers to run versions of a climate model and predict the possible future outcome of climate change suggested a doubling of carbon dioxide levels could produce a global temperature change of as much as 20 degrees Fahrenheit. That would trigger such droughts and wildfires that yet more carbon dioxide would flood into the atmosphere, leading to a catastrophic meltdown. The chance may be small, of the order of 1 percent, but it is still possible.

Carbon dioxide, then, is both a crucial and dangerous element of the air. We need it for food and warmth, but we abuse it only at our peril. Along with oxygen, nitrogen, and the sheer thickness of the air, it helps transform our lump of rock into a living, breathing world. The final part of this transformation involves not what the air contains, but how it moves. You encounter the motion of air every time you're struck by a gust of wind, and every time a door mysteriously slams in the house when windows are open on either side. But it is in the grand movements of vast bodies of air around the planet that wind truly comes into its own as an agency for life.

FOR ALMOST AS LONG AS AIR
has been in motion, living things have hitched a ride on the wind. The obvious animals to find in our ocean of air are the ones that can fly. But aside from the birds and the bees, there are plenty of other living things that simply float. The air is full of pollen grains seeking to fertilize plants and protect them from inadvertent incest; there are seeds hunting out new fertile soil, and tiny shelled sea creatures whipped up with the foam. Every breath you take contains dozens of microscopic fungi, not to mention the minuscule viruses and bacteria that are spreading their secret infections. (Even before anyone knew about microbes, there were those who suspected that air could bring disease—hence malaria ("bad air").) Every word you speak, especially those with explosive consonants like
p
and
t,
sprays bacteria out into the air around you, ready to be passed on by the wind. A cough produces two thousand and a sneeze, 400,000. Certain devious viruses have even evolved so that when we have bred them in our bodies, we spray them out with a sneeze so they can fan out on the wind.

Other bacteria hitch a ride on clouds, and may even choose their own drop-off point by making ice crystals that induce the clouds to form rain. As the water droplets fall back to the ground, the bacteria simply fall with them. Orb and crab spiders spin invisible gossamer threads and then use them like sails to catch the wind. The slightest updraft, the thinnest shaft of sunlight to warm a patch of air, and the spiders will launch themselves into the air to begin their travels. Nobody yet knows exactly how they arrange their journeys. They may simply continually land and relaunch themselves until they find the ideal resting spot, though some scientists
think they might regulate their flight, reeling in threads to raise or lower their sail, or perhaps even steer.

And of course, the wind carries people. Even before the days of balloons and planes, wind was the only way to cross the seas. In fourteenth-century Europe, after centuries of dark ages, blighted by the battles of the Middle Eastern crusades, the Renaissance had dawned, and with it a new urge to look outward. This was the age of the great ocean explorers, and their fortunes rested on the wind. Some seventy years before the birth of Galileo Galilei, another Italian, a former weaver from Genoa, knew how important currents of air would be for his mission. What he didn't know is that he was about to stumble across two of the biggest wind systems in the world, the trade winds and the mighty westerlies, great globe-girdling torrents that form part of the final crucial ingredient for life on Earth.

AUGUST
3, 1492

Half an hour before sunrise, a small fleet slipped out of the Spanish port of Palos. Two of the ships, the
Pinta
and
Niña,
were caravels, with small triangular sails. But the flagship, the
Santa María,
was magnificent, square-rigged with castles fore and aft. She was gaily painted above the waterline, her sails plastered with crosses and heraldic devices. The royal flag of Spain hung from her main mast, while the foremast bore the expedition's own banner, a green cross set on a white background, bearing four gold crowns.

The commander of the
Santa María
had already had several names in his forty-one years, and would be given more in the centuries to follow. His Genoese parents had known him as Cristoforo Columbo, but he had shaken off his Italian roots and language along with his father's profession of wool combing. Now, he was a seaman, a captain general on a mission for Spain. He had embraced his adopted country with typical fervor. He wrote in Spanish, even in his most private journal, and the name he used was a Spanish one: Cristobál Colón.

The man we now know as Christopher Columbus looked nothing like his Iberian crew. His hair had once been tawny, but it had turned snow white ten years ago, when he was barely thirty. His face was pale and freckled, his nose Roman, and his blue-gray eyes often burned with passion, and with temper.

His mission, of course, was to sail west in order to reach the East. Fifteenth-century Europe was full of tales of the fabulous riches of the Orient. In the previous century the Venetian voyager Marco Polo had written a graphic (though embellished) account of his travels in these lands of spices, silks, gems, and unimaginable quantities of gold. The newly invented printing press had spread his stories throughout Europe; merchants and monarchs read Marco Polo's book and felt their fingers itch. There had to be a way to reach those cargoes.

But the countries that Marco Polo had called Cathay and Cipangu, and that we now know as China and Japan, remained stubbornly out of reach. The land journey was far too long and perilous for transporting costly merchandise, and the entire continent of Africa was in the way of the eastern sailing route. Thus the whisper began. What about the west? If you could slip across the ocean and approach the Orient from its backside, all the wealth and glory waiting in those distant lands would be yours.

Now at last, after years of fundraising and pestering, Columbus had his chance. His backers, King Fernando and Queen Isabella of Spain, had provided him with this handsome fleet and promised him the rank of Admiral of the Seas if he should be successful. There was only one thing more he needed: a wind to blow him westward.