An Ocean of Air

by Gabrielle Walker

  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.

  CHAPTER 4

  BLOWING IN T
HE WIND

  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.

  Apart from the islands of the Azores, discovered a few decades earlier by Portuguese sailing ships, the Iberian peninsula marked the western edge of the world. Beyond was the stuff of legend: Some spoke of a fabled island called Antilla, supposedly discovered by the Carthaginians; others of fragments of Atlantis, which had somehow escaped inundation, or of a gigantic and beautiful island bearing seven great cities, each more splendid than the last. Many had tried to explore these lands, but until now all had been beaten back by a fierce headwind that whipped up the seas to a fury. The wind blew from exactly the wrong direction: the west, and no sailing ship could pass.

  But Columbus had a plan. In years past, when he was earning his sailing spurs, he had made several voyages down the African coast. And whenever he passed the Canary Islands, especially in winter, his ship had been buffeted gently but steadily from the east.

  This was the wind that Columbus had resolved to try to catch, the one that he hoped would carry him at least some of the way over the western ocean. When his three ships left Palos they headed not west, but south.

  ***

  The journey to the Canaries was difficult, the wind fitful and contrary. Life on board settled down into its routines. Crew and captain both were deeply religious. Each turning of the hourglass was accompanied by a boy singing out a blessing. The days began with hymns to Mary, and finished with evening prayers. Only the captain had a tiny wooden cabin. Since hammocks had not yet been discovered (they were waiting in the Caribbean), the rest of the crew had to find berthing where they could on deck, tying themselves in against a sudden rolling of the ship.

  Columbus was fretful. He wondered constantly if the easterly winds that he sought would even exist, and if so, how far west they would take him. (By exasperating convention, meteorologists label a wind by where it's coming from, not where it's going to. So an "easterly" blows from the east toward the west, and was just what Columbus needed.) The small fleet reached the Canaries three weeks after the start of their voyage. They reprovisioned, and then, on September 6, the ships weighed anchor and turned full west.

  For the whole of the next day, the ocean held its breath. And then, on Saturday, September 8, up rose a wind from the east and Columbus found himself where he had always wanted to be: in uncharted waters.

  The new easterly wind was beyond anything Columbus had dared to hope for. Over the next two weeks, it blew the fleet steadily farther and farther westward toward their goal. The sailing was magnificent. The weather, Columbus noted in his journal, was like Andalusia in spring. "The mornings are most delightful, wanting nothing but the melody of nightingales," he wrote, and a few days later: "The sea is smooth as a river, and [there is] the finest air in the world." The speed of the small fleet was astounding. On their best day's run they covered 182 miles, at an average speed of eight full knots. And the wind never stopped coming.

  Columbus had no idea what he had found, but this ultra-reliable easterly would prove to be every bit as impor
tant a discovery as the New World to which it carried him. For it was one of two giant belts of winds that stretch around the globe in the tropics, one north and one south of the equator. They are so steady and diligent that they would come to be known as the "trades," for the safe trading routes that they made possible. (They may even have been used by humans before Columbus. Norwegian archeologist Thor Heyerdahl has shown that the trade winds could blow a simple sailing vessel made of reeds from Europe all the way to the Caribbean, and suggested that the idea of building pyramids could have reached Central America by ancient Egyptians who took this route. Though if the ancient Egyptians did reach the Americas with tales of their pyramidal technologies, you'd think that they would also have mentioned the wheel.)

  For Columbus, though, the trades were beginning to become too much of a good thing. They were so steady, and so unabating, that his crew began to grow nervous. He'd had enough difficulty finding sailors willing to make their way into the unknown, to equip their ships with a year's provisions at a time when even the most daring voyage lasted only a few weeks. Now, as the fleet sped its way west, murmurs of unease started to spread. This wind that was blowing them with such speed and efficiency never seemed to die down. Columbus noted grimly in his diary that his crew had "grown much alarmed, dreading that they never should meet in these seas with a fair wind to return to Spain."

  Columbus did his best to distract his crew from their fears. He pointed out any scrap of evidence, however dubious, that made them seem close to land, and recorded each one in his journal. The "signs" could be almost anything: "It drizzled without wind," or "a great mass of dark, heavy clouds appeared in the north," or "saw a whale, an indication of land, as they always keep near the coast." He even announced false distances when announcing the day's progress, on the dubious principle that this might help. ("Sailed this day nineteen leagues, and determined to count less than the true number, that the crew might not be dismayed," he wrote on Sunday, September ninth; and again on the tenth: "This day and night sailed sixty leagues ... reckoned only forty-eight leagues, that the men might not be terrified.")