Atlantic

by Simon Winchester

  And then, of course, there was Hurricane Katrina. The devastation caused by this Category Five storm, which was born in the Atlantic Ocean off the Bahamas on August 23, 2005, and struck the south coast of Louisiana and Mississippi six days later, was appalling. Though it did not hit New Orleans and was only a Category Three storm when it made landfall, nearly two thousand people died in and around the devastated river city, and damage to property was in the scores of billions of dollars, making it the costliest natural disaster in American history.

  The government was severely criticized for its inept handling of the storm’s aftermath—but that overshadowed the stellar achievement of the one government agency charged with predicting the storm in the first place. Katrina was so classic in its development and construction that the National Weather Service, with uncanny precision, predicted just about everything about it. The NWS bulletin issued by the Baton Rouge, Louisiana, office just a few hours before Katrina made landfall remains a textbook instance of when official language can be far more chilling than the purplest of literary prose:

  URGENT—WEATHER MESSAGE

  NATIONAL WEATHER SERVICE NEW ORLEANS LA

  1011 AM CDT SUN AUG 28, 2005

  DEVASTATING DAMAGE EXPECTED

  HURRICANE KATRINA: A MOST POWERFUL HURRICANE WITH UNPRECEDENTED STRENGTH, RIVALING THE INTENSITY OF HURRICANE CAMILLE OF 1969.

  MOST OF THE AREA WILL BE UNINHABITABLE FOR WEEKS, PERHAPS LONGER. AT LEAST ONE HALF OF WELL CONSTRUCTED HOMES WILL HAVE ROOF AND WALL FAILURE. ALL GABLED ROOFS WILL FAIL, LEAVING THOSE HOMES SEVERELY DAMAGED OR DESTROYED.

  THE MAJORITY OF INDUSTRIAL BUILDINGS WILL BECOME NON FUNCTIONAL. PARTIAL TO COMPLETE WALL AND ROOF FAILURE IS EXPECTED. ALL WOOD FRAMED LOW RISING APARTMENT BUILDINGS WILL BE DESTROYED. CONCRETE BLOCK LOW RISE APARTMENTS WILL SUSTAIN MAJOR DAMAGE, INCLUDING SOME WALL AND ROOF FAILURE.

  HIGH RISE OFFICE AND APARTMENT BUILDINGS WILL SWAY DANGEROUSLY. A FEW TO THE POINT OF TOTAL COLLAPSE. ALL WINDOWS WILL BLOW OUT.

  AIRBORNE DEBRIS WILL BE WIDESPREAD . . . AND MAY INCLUDE HEAVY ITEMS SUCH AS HOUSEHOLD APPLIANCES AND EVEN LIGHT VEHICLES. SPORT UTILITY VEHICLES AND LIGHT TRUCKS WILL BE MOVED. THE BLOWN DEBRIS WILL CREATE ADDITIONAL DESTRUCTION. PERSONS, PETS AND LIVESTOCK EXPOSED TO THE WINDS WILL FACE CERTAIN DEATH IF STRUCK.

  POWER OUTAGES WILL LAST FOR WEEKS . . . AS MOST POWER POLES WILL BE DOWN AND TRANSFORMERS DESTROYED. WATER SHORTAGES WILL MAKE HUMAN SUFFERING INCREDIBLE BY MODERN STANDARDS.

  THE VAST MAJORITY OF NATIVE TREES WILL BE SNAPPED OR UPROOTED. ONLY THE HEARTIEST WILL REMAIN STANDING . . . BUT BE TOTALLY DEFOLIATED. FEW CROPS WILL REMAIN. LIVESTOCK LEFT EXPOSED TO THE WINDS WILL BE KILLED.

  AN INLAND HURRICANE WIND WARNING IS ISSUED WHEN SUSTAINED WINDS NEAR HURRICANE FORCE OR FREQUENT GUSTS AT OR ABOVE HURRICANE FORCE ARE CERTAIN WITHIN THE NEXT 12 TO 24 HOURS.

  ONCE TROPICAL STORM AND HURRICANE FORCE WINDS ONSET, DO NOT VENTURE OUTSIDE!

  So what exactly was Katrina? Was it merely the name given to the storm by the Weather Service—as names have been given since 1953—while in fact its real name should have been “global warming”? Or is such a claim, which was first made by a well-known columnist of the Boston Globe as the storm first hit, simply another example of the “unadulterated garbage,” as an Australian climatologist put it, that afflicts a debate that has now become both very public and very political?

  The questions that have loomed large ever since the end of the 2005 Atlantic hurricane season—which was especially ferocious, with two more storms after Katrina that were indeed much stronger, and record-breakingly so—is whether ocean warming is making hurricanes more numerous, whether it is making them individually stronger and more lethal, and whether perhaps it is making them both. And if ocean warming is the fault of humankind—then are we making hurricanes more deadly and more commonplace? Is it all, in other words, our fault?

  In 2005 sharp battle lines were drawn over this issue—in a battle that happened to coincide with the extraordinary ferocity of both Katrina itself and that year’s hurricane season generally. The 2004 season had been formidable, too: four titanic storms had hit Florida that summer, causing some $45 billion in damage. Now another season had brought death and destruction to an even greater degree. Something seemed to be going awry—to some a trend seemed to be developing.

  Starting with a ripple of wind in the African savannah, monstrous and enduring hurricanes occasionally form over the Cape Verde Islands in the eastern Atlantic. Those few that make landfall in the Caribbean or the Americas—such as Andrew in 1992, or Bonnie, illustrated here, in 1998—can be dramatic and lethal.

  Not surprisingly, press interest in the possible link between storms and man-made global warming grew wildly as the extent of the mayhem was fully realized: indeed, the climatologists’ famous “hockey stick” graph, which had long been touted as showing a recent near-exponential rise in atmospheric warming, was itself almost duplicated in appearance by a graph drawn by the author Chris Mooney in 2007 that showed the number of articles in the reputable American press discussing the possibility of the link: it appeared to rise exponentially, too.

  An Atlantic hurricane—a counterclockwise rotating windstorm, more accurately called an Atlantic tropical cyclone—is a surprisingly fragile creature. The place and manner in which it is conceived and born, the uncertain progress it takes toward its maturity, the direction and speed at which it then moves across the ocean, the ways in which it grows and then achieves its greatest strength, the mechanics of its decline and its subsequent staggering progress to extinction, are all the result of the tiniest and most subtle fluctuations in the condition of the ocean and the winds that feed, direct, and sustain it.

  Very basically, hurricanes—the word is originally Carib; a hurricane is specifically an Atlantic phenomenon only89—are created in the northern summertime, usually between June and November. For them to form, very warm subtropical seas must be overlain by relatively cold air, such that any moist air that rises from the sea is cooled rather quickly. Many hurricanes are first spawned in the shallow waters off the eastern Caribbean; a number of often very serious hurricanes are born much farther away, in the shallow waters of the eastern Atlantic, around the Cape Verde Islands. The conditions in what are known as these cyclogenetic regions are essentially the same: plenty of warm water below, nicely cool air above, and the rising up of water vapor and its subsequent unusually fast refrigeration.

  This rapid cooling—which causes clouds, and rainfall, and the release of latent heat by the mass of air—can under certain (and still not fully understood) circumstances result in the creation of great and powerful disturbances in the vertical columns of air—the making of invisible phenomena that a glider pilot or a weather balloon would readily recognize as very strong eddies and thermals.

  Beyond this column of air, the pressure gradients in the cyclogenetic latitudes, where these columns of fretful air are born, happen to generate winds, most usually trade winds, that blow from the northeast. These winds contrive to nudge or tickle any unstable column of air into movement—and this movement, under the effect of the Coriolis force, on some infrequent occasions causes the column to start rotating, turning always counterclockwise in the Northern Hemisphere. The prevailing trade winds then steer this fragile and vaguely rotating column westward across the sea—and providing that the water below is warm enough, so that the air ascending into the column is adequately moist, and providing that the upper atmosphere is sufficiently cool to condense it into cloud and rain, so more disturbance will be funneled into the rotating column and it will become supercharged with thermal energy that, when translated into kinetic energy, will cause the winds caused by its rotation to go around faster and faster. Once in a while, fifteen times or so each season, this whirling mass of air and cloud will develop into a proper storm. Depending on the speed of its maximum sustained winds, the storm can become classified as a hurricane, and if there is enough warm water to fuel it, it will spiral up through the five officia
l categories of vigor and potential danger until it becomes a thing of awesome proportion and power.

  The ultimate key to the growth of a hurricane is the warmth of the water over which it passes. One of the reasons Katrina became so vicious was that when it passed westward from its birthplace above the Bahamas, it slid right over one of the feeder currents of the Gulf Stream, a narrow underwater river in the Gulf of Mexico known as the Loop Current—and in August 2005 the Loop Current was unusually warm. Its difference from normal may have been minimal—measured only in fraction of degrees—but for something as sensitive as a developing hurricane, it was enough to make an enormous difference. The additional fuel that this slightly warmer water provided powered the relatively modest Katrina storm right up to Category Five strength. This was the development that prompted the National Weather Service to issue its famously dramatic Sunday message, and the storm surge it created, and its eventual landing—though by then rather weaker—led to the dreadful catastrophe that followed the next day.

  If warm water is the key, and rising sea temperatures result in more warm water, then the correlation would seem obvious: warmer waters mean fiercer hurricanes, and possibly more of them. But the science is not that simple, and the correlation—at least in history—seems unconvincing. There is no certainty, for example, that any kind of trend has become truly apparent. In the short term the highly active hurricane seasons of 2004 and 2005 were followed by two years of below-average activity, then by a year, 2008, that with sixteen named hurricanes was only moderately severe, and then by 2009, which was about as violent as a vicarage tea party. In the medium term—in the years since 1995—there have been rather more hurricanes, and a very large number of stronger ones. But the very long-term statistics—and there is a project named HURDAT that seeks to find all available data on all Atlantic hurricanes since 1851—is tending to show less of a trend and instead a number of cyclical patterns.

  Many climatologists argue for the importance, in any discussion of sea temperature change, of what is known as thermohaline circulation: this involves the sinking into the cold depths of the saltier water that is formed by the evaporation of the sea at its warm surface, and the drawing into the ocean of warmer water to replace that which has been sunk. There appears to be a cycle—known as the Atlantic Multidecadal Oscillation—that is linked in some way to changes in thermohaline circulation. The years since 1995 have seen rather more intense thermohaline circulation than usual—though it is within the boundaries of its oscillations measured in the past—and so some believe that instead of witnessing a trend, we might be witnessing a normal cycle, with the oscillation today in one of its routine warm phases. This does not mean that warming is not happening: but the fact that it may be being superimposed on a cyclical phenomenon makes for more complication than is comfortable. (And of course the warming is happening, and it could be affecting the thermohaline circulation, rather than the other way around.)

  Moreover, even the most ardent believers in anthropogenic climate change acknowledge that superviolent storms like Katrina cannot in themselves be ascribable to global warming—only if there are a very large number of such catastrophes could such a correlation be certain, and there is still precious little data to support that. All that can be stated with certainty is a very obvious reality: that recent Atlantic storms have been lethal and costly not because there are more of them, but because more people have settled and more expensive buildings have been built in the places where the storms have happened to strike.

  So the best short-term solution to the regular destruction of so many Gulf and Atlantic coastal communities perhaps needs to be stated again: it requires not so much any need to cool the world, but to persuade people not to come to live in those places where, habitually, the world goes mad. There are many excellent reasons for wanting to limit carbon emissions, but preventing storm damage to American coastal communities is not one of them. The communities should never have been built. Strip the vulnerable coastlines of Florida, Louisiana, Alabama, Mississippi, and Texas of great mansions and sprawling oil refineries and strip malls and country clubs and casinos, and suggest to the inhabitants that they move inland and away from the hurricane corridors—then to a degree the human problem solves itself. The tropical Atlantic Ocean and its neighbor seas are capable of very great violence—perhaps greater today than ever before. Until they can be permitted or persuaded to calm down, the best immediate solution is simply to keep their waters and their winds at arm’s length. So long as the ocean is still going on, then down in hurricane land perhaps mankind should be thinking about going away.

  5. THE LITTLE-KNOWN SEA

  The warming of our oceans has its most visible effects on matters great and familiar—on Rotterdam, on hurricanes, on penguins or anchovies. But the rise in temperature, however caused, also seems to work its way into more unfamiliar worlds—and one of them illustrates the notion that it is probably best if we leave the seas alone, because we know much less about them than we think. For there is much currently expressed concern over whether global warming will have a particular effect—whether for good or ill we do not yet know—on a creature that turns out to be probably perhaps the most plentiful species on our planet, and yet one of whose very existence we were quite ignorant until 1986. That was the year when this creature was first discovered, and it was found in the Atlantic Ocean.

  The sea teems with tiny drifting beings, plankton, which are suspended, wafting, moving aimlessly among the placid similitude of the world beneath the surface. Where they are and what they do there depends much on the nature of the water on which they waft: on whether it is warm or cold—an attribute that depends on the one hand on latitude, and on the other hand on depth, for they drift inside a three-dimensional universe, whether it is very salty or less so, whether the pressure is high or not so high, whether the sea chemistry is benign or strange, whether it is light or dark—for no light at all finds its way below a thousand meters, and it is perpetually pitch-dark except for vague glimmers from the blooms of bioluminescent creatures and the tiny orange firefly glows from brave beasts that flourish beside the scalding thermal vents. Yet in every zone, from the oxygen-rich splashiness of the coastal waters to the near-freezing blackness and iron-crushing pressures of the deep abyssal trenches, there is almost invariably life, and most of it is microscopic, and most of it is still unknown.

  Many of the tiny creatures that inhabit the oceans’ well-lit upper waters emit gas or gaseous compounds. One hard-shelled algal beast, Emiliana huxleyi, emits dimethyl sulfide, which some believe contributes to the unique aroma we call the smell of the sea.90 But most, being photosynthesizing animals, suck in carbon dioxide, make carbohydrates, and in immense quantities turn out oxygen. Maybe 70 percent of the planet’s total oxygen comes from such seaborne organisms: one of these was discovered in 1986—a blue-green algae hitherto not known to exist, and which was given the name Prochlorococcus.

  Quite probably the most abundant living creature on the planet, the cyanobacterium Prochlorococcus was first discovered in the Atlantic’s Sargasso Sea in 1986. These minute creatures employ their chlorophyll-b to produce as much as one-fifth of the world’s atmospheric oxygen.

  A young researcher at the Massachusetts Institute of Technology, Penny Chisholm, first found the creature in the Sargasso Sea. She and Rob Olsen, her colleague from Woods Hole, were on a research vessel sailing from Cape Cod to Bermuda with, as an onboard trial, a machine normally used in hospitals to assay blood and known as a flow cytometer. The principle of this device is simple enough: a laser is shone across a tube through which a fluid flows at speed—blood in hospitals, seawater on Penny Chisholm’s boat—and detectors pick up the light scattered and deflected by any tiny particles, invisible to the naked eye, suspended in the flowing liquid. The two researchers had no idea the machine would even work on the boat; and if it did, they expected to find numerous examples of a particular blue-green algae they already knew existed.

  What the
y did not imagine was that the device would show the existence of millions and millions of even tinier creatures, tiny, oval-shaped living entities, around six microns in diameter, one two-hundredth of the width of a human hair. But these creatures were not simply tiny; once examined under electron microscopes, they were found to have incorporated into their minute workings a type of chlorophyll that permitted them to absorb carbon dioxide and to extract from the seawater a tiny amount of oxygen, which then escaped into the atmosphere.

  Taken individually the amount of free oxygen that any one of these algae might produce is microscopically insignificant; but Penny Chisholm calculated that Prochlorococcus existed in such unimaginably large numbers—one hundred thousand of them in a single cubic centimeter of water, perhaps a trillion trillion of them in total—that they were quite probably the most common creature in all the world, and would in total produce immense quantities of oxygen.

  They prefer to live in the warmer seas, essentially wafting about in the oceans between 40 degrees north and 40 degrees south, or south of a line connecting New York and Lisbon in the north, north of another drawn between Buenos Aires and Cape Town. There they lie, contentedly at the bottom of the food chain, waiting to be eaten by tiny shrimp that would then be consumed by small fish, and on and on, up until the hungriest predators of all, mankind. Or one perhaps should say they probably lie at the base of the food chain, for while it is difficult to imagine anything smaller existing in the sea, Dr. Chisholm felt that Prochlorococcus was an example of how nature had once again displayed its infinite capacity, as she put it, to humble the world of science, and could readily do so again. Before 1986 we did not know that such a creature existed; now it is recognized as perhaps the most common being on earth—or rather in the ocean—and it plays a central role in keeping land-based creatures alive.