Within this well-defined area, the intense heat causes the seawater to evaporate and the warm air above it to rise—so gigantic banks of cloud form and billow skyward. As they do so, they lower the air pressure in the void they leave behind them. Cooler and heavier air then pours into the low-pressure zone, from the north and the south. Thanks to the west-to-east spinning of the earth, this air tracks in a more or less westerly direction as it cascades inward: the air from the north heading toward the southwest, the air from the south tracking to the northwest. Since it is the custom to name winds for the direction from which they are coming (whereas currents, confusingly, are named according to where they are traveling to), these inrushings of cool air become the famous trade winds: the northeast trades in the Northern Hemisphere, the southeast trades below the equator.
A great deal goes on within this specific area, where the world’s climatic business begins. It is where the trade winds blow. It is the site of the so-called Intertropical Convergence Zone, where the hot, humid, and (infuriatingly, for those traders who used sailing vessels) windless doldrums lie. It is where all the cyclones, hurricanes, and typhoons are born. It is where the monsoons begin their lives.
In the Pacific portion of this tropical area (which is by far the world’s largest portion, since the Pacific is the sea of greatest extent), a series of curious atmospheric and oceanic events occurs, and which now seems to be most crucial of all to both the marking and the making of cycles of the world’s weather. These events, long known, were once reasonably predictable, and were gathered under the general rubric name of El Niño. Now, though, such occurrences seem to be becoming both more frequent and increasingly irregular. Their timing these days is perhaps somehow linked to the undeniable warming of the ocean, as the global climate (for whatever reason, man-made or not) continues to alter.
These oceanic events have long been marked initially by sudden strange changes in the business of fishing. They have been long recorded, and scrupulously so. As far back as the late sixteenth century, Peruvian fishermen working out of ports in the north of the country (from Tumbes, on the Ecuadorian border, to Chimbote, close to Lima) would make careful note of the changes in the local fish population, since their livelihoods depended on what was taking place.
Chimbote was once known as the World Anchovy Capital, because of the small, silvery, and memorably pungent anchoveta fish that were to be found in staggering abundance in the cold waters just twenty miles offshore. Few fish have ever known such a boom as the Peruvian anchoveta: from the early settlement of the country, fisheries would spring up in every possible harbor along the coast, and thousands of men would work the waters, eventually making the anchoveta the most exploited wild fish in the world. Thirteen million tons of it were hauled into nets in 1971. Most of it was ground into fishmeal and sent off to fertilize fields and feed livestock all across the world.
The abundance of the fish was a fitful thing, though, as the Chimbote fishermen came to know all too well. Once every five or six years, with some ragged regularity, and most usually in November or December, the anchoveta would all but vanish. One day there would be darts of quicksilver shoals all around; the next, nothing but the blue silence of the deep. And there was another thing: the cold waters offshore, which would bring in the evening fogs so welcome in seaside desert towns such as Chimbote, would at the same time become mysteriously warmer. The fogs would vanish, too, and the skies would magically clear.
The want of catch would frustrate the fishermen, to be sure, and they would curse their empty nets. The absence of fish had an effect that then spread insidiously all the way up the food chain. The gannets, cormorants, and pelicans that fed on the anchovies died, or else they flew long distances in search of food, abandoning their nests and leaving their waiting chicks to die in their stead. Squid, turtles, even small sea mammals would pass away also, either because of their intolerance of the warmer water or because of the sudden strange voids in the food chain, spawned by the lack of anchovies. Then, compounding the misery, large numbers of these dead creatures would float to the surface and create small islands of decay, the foul gases they emitted so acidic as to blister the hulls of the fishermen’s boats.
The loss of anchovies was an economic disaster; the smorgasbord of other deaths and absences made the event curious and more sinister. Because the happenings invariably arrived around the anniversary of Christ’s birth, the fishermen would name it, with a bitter and sardonic humor, El Niño de Navidad, the “Christmas Child.”
The term El Niño first appeared in the English language at the end of the nineteenth century—and not so much because of the fishermen’s melancholia, but as a name for the change in the current in the waters below. What happened was that the cold waters of the Humboldt Current, part of the normal pattern of Pacific circulation that powerfully sweeps Antarctic waters northward up along the South American coast before the waters head west along the equator, become on occasion mysteriously disrupted. Instead they are replaced, or nudged farther out to sea, by an irruption of warm water that bullies its way down from the equator—and in the case of the anchoveta, this warm water smothered the upwelling of nutrients on which the little fish fed. The fish then went elsewhere, well beyond the ken of the Peruvian fishermen. They simply vanished from Peru.
Early on it was nothing more than the change of current, this unusual warming of the sea, that came to be named El Niño—and it remained so until oceanographers and climatologists in the mid-twentieth century realized that the change of currents off Peru was just one of many features of a much larger and more important phenomenon, one that had its impact across the entire breadth of the ocean.
Many names are associated with the research that confirmed this. One in particular belongs to a civil servant in British India, Gilbert Walker, who had a meteorological epiphany in 1924 that helped secure what would become the Pacific’s reputation as weather maker for the world.
Sir Gilbert Walker, described in the closing paragraph of his 1958 obituary as “modest, kindly, liberal-minded, wide of interest and a very perfect gentleman,” was a classic of his breed, a polymath of the old school. He was first and foremost a Cambridge mathematician—no less than the 1889 Senior Wrangler, meaning that he had achieved his country’s greatest intellectual achievement of the year. But he was many other things besides: a designer of flutes, a keen student of the boomerang and of the flight paths of ancient Celtic spears, an authority on the aerodynamics of birds’ wings, a passionate advocate of the sports of skating and gliding, a wizard in the more arcane uses of statistics, and a recognized expert on the formation of clouds.
He loved India and the Himalayas, and when he was appointed director-general of observatories in India, he spent twenty years trying (in vain, as it happened) to figure out a mathematical means of predicting monsoons. He had been led to this obsession by a monsoon failure in 1890 that caused a terrible famine. His frustrated quest might well have caused him to leave India somewhat deflated—except that, as it happened, Walker’s work on the monsoon prompted him, during his retirement years, to come up with quite another and rather more globally significant discovery.
He was a habitual collector of what turned out to be colossal tonnages of meteorological statistics. His exhaustive analysis of these, of decades of weather records from all across the British Empire, allowed him to demonstrate incontrovertibly that the El Niño events occurring off the Peruvian coast—the fishermen’s phenomenon was by now well known to scientists around the world—were part of an enormous and all-encompassing transpacific set of weather patterns. These patterns turned out to be mirror-image combinations, in which precisely opposite meteorological manifestations were occurring on one side of the ocean or the other, in one season or another, for one extended period or another.
Periods of warming here led to episodes of cooling there. The Peruvian sea starvation during a locally warm-sea El Niño event would in time be followed by a local sea cooling and return to abundance, an
d that would be called (keeping to the Christmas-themed naming practice) a La Niña time. Floods on one side of the ocean led to droughts on the other. There were periodic swings in weather and in the human response to it. There were times when there were more cyclones and times when there were fewer. Some years when the Indian monsoon never happened, the fields were parched and crops failed. Other years were marked by luxuriant summertime drenchings. There were years of famine and years of abundance, of dust bowl summers and harvest-rich autumns, years of concomitant prosperity and ruin, periods of consequent peace and turmoil—within the Pacific, around the Pacific’s coasts, and even, perhaps, beyond them and around the globe.
Sir Gilbert Walker, a British meteorologist based for decades in India, is memorialized by one of his discoveries, the Walker Circulation, a main driving atmospheric force behind the making and unmaking of the cyclical El Niño phenomenon.*
And all of it—Sir Gilbert Thomas “Boomerang” Walker realized through all his Renaissance man amusements of flutes and bird flight and skating techniques—was due to a hitherto unseen natural phenomenon. Walker declared that what drove the regular and dramatic changes in the Pacific weather must be some kind of repeating mechanism high up in the atmosphere. Whatever it was, this pattern of invisible winds and movements seemed to him to operate as a kind of unseen atmospheric seesaw, a beam engine balance around a central pivot lying somewhere smack dab in the center of the ocean.
The axis seemed to hover where the International Date Line crossed the equator, in the middle of that sprawl of limestone specks then known as the Gilbert Islands and the Phoenix Islands, now the Republic of Kiribati. Up on one side of this fulcrum meant down on the other; high pressure here meant low pressure there; hot here, cool across the other side; cruelly wet in this place, bone dry in that. It had a beautiful logic to it; and measurements taken over the years that followed have proved that Walker was exactly right.
This transpacific atmospheric wind pattern he discovered was in time to be named, and in his honor, the Walker circulation. This was the engine, the mechanism, that then produced what Sir Gilbert himself went on to name, for the back-and-forth, hot-and-cold, wet-and-dry, stormy-and-serene periods that appeared to dominate the tropical Pacific’s weather: the Southern Oscillation.
ENSO—the acronym is formed from the combined initials of the El Niño and the Southern Oscillation—denotes what today is recognized as undeniably the planet’s most important climatic phenomenon. If the Pacific is truly the generator of the world’s weather, then ENSO represents the turbines that give it the power to do so. And the Walker circulation is the force that sets the turbines spinning in the first place.
The Walker circulation’s basic structure is made up of long-lasting cells of pressure in certain places around the ocean. The eastern Pacific generally has high atmospheric pressure. Correspondingly, the western Pacific generally has a large low-pressure area, most notably around the sea-spattered islands of Indonesia and the Philippines, the area that oceanographers and meteorologists like to call, if oxymoronically, the Maritime Continent. The air above the ocean then moves, as physics demands, from the high-pressure area to the low—in other words, from east to west. The trade winds at the surface, which blow nearly constantly in this direction, are of course this movement’s very visible and familiar manifestation.
As the winds blow in this manner, they help push the warm waters of the tropical seas below them in the same direction. Incredible though this may sound, the sea then piles up very slowly and deliberately as a huge wave of water passes steadily across and into the western reaches of the ocean. The western Pacific can sometimes be a full two feet higher than the waters in the east. Some of this warm water evaporates as the huge cyclonic storms and typhoons, such as Tracy and Haiyan, form over the western seas. Some of it dives deep back into the ocean, cools, and is returned to the east by the work of deep ocean currents. In a normal series of years, this pattern is repeated again and again: the Walker circulation of the air above, the migration of the seawater below, the explosive growth of storms in the far western Pacific, the return of the cool and dry air and upwelling cool water (and with them the anchovies) to the Pacific east. As a result, calm and stability reign.
But sometimes, and for some still unexplained reason, the Walker circulation changes. The trade winds weaken or falter or even reverse their direction, and then an El Niño period occurs, and the system changes with it, and dramatically. It can sometimes strengthen in the opposite manner and with equal drama—and then the reverse, the phenomenon of La Niña, dominates the weather picture instead. Tracking and measuring the arrival of the two phenomena, El Niño and La Niña, have lately become major elements in worldwide weather forecasting and climate modeling. It is safe and reasonable to say that in the computation of the planet’s weather, all eyes are on the happenings in the Pacific and the behavior of the Southern Oscillations. For as the Pacific oscillates, so oscillates the world.
These days the Southern Oscillation that Gilbert Walker defined is measured by the careful tracking of the atmospheric pressures and the sea temperatures in the region. Pressure is measured at two key points: one in Tahiti, the other down in Darwin. If the pressure in Tahiti falls significantly below what is normal, and at the same time the pressure in Darwin rises above what is normal, then an El Niño period is declared to be under way. The American and the British weather services also like to measure sea temperature along the narrow equatorial zone that is (in more ways than one) central to the development of an El Niño. If the water temperature in the eastern part of this region (that closest to the South American coastline) rises by half a degree Celsius, and if, in accordance with the British weather researchers’ rules, it then holds that temperature for nine full months, then an El Niño is declared to be under way.
Map of the Pacific—Political* [Nick Springer/Springer Cartographics LLC.]
The El Niño Southern Oscillation, ENSO, is a still unpredictable and irregularly cyclical movement of waters and winds in the Pacific Ocean south of the equator, and a factor that determines much of the world’s major weather patterns.* [National Oceanic and Atmospheric Administration (NOAA).]
The Japanese government in particular is investing millions in its own studies of El Niño, and for good reason. Japan has historically been a magnet for highly destructive Pacific typhoons, storms that, along with the earthquakes, tsunamis, and volcanic eruptions that bring regular ruin, have helped forge the national character traits of stoicism and mutual philanthropy. Forecasting such traumatic occurrences would of course be a fine thing, for the national economy, for the nation’s morale. The recent accelerating ability to forecast the eruptions of volcanoes may still not have been matched by an ability to predict earthquakes. But to balance that, a major effort is now being made in Japan to fine-tune global long-term weather forecasting, and in particular to investigate the possibilities of predicting when an El Niño—with its clustering of typhoons—is most likely to occur.
This task is being handled by what has been claimed variously to be one of the world’s largest, most powerful, fastest, and most efficient supercomputers. It is grandly known as the Earth Simulator 2, and it is sited in a suburb of Yokohama, west of Tokyo, in the offices of JAMSTEC, the Japan Agency for Marine-Earth Science and Technology.
As a record breaker, the Simulator has recently been knocked off its perch by a new superfast machine in China, but it is still a remarkable and home-built device, which keeps being improved and upgraded: currently it can calculate at the rate of 122 teraFLOPS (122 trillion floating-point operations per second). A recent live test—which was conducted in its building with no more than the usual electrical hummings and air-conditioning whirs and the flashing of thousands of light-emitting diodes, and with only the operators squinting rather tensely at their terminals hinting at any anxiety—showed that the contraption can produce global weather analyses of witheringly complex detail: several times a day it can produce a three-dimen
sional map of the world’s atmosphere, showing the climatic details every three miles horizontally and through more than one hundred slices of the atmosphere vertically.
It is so costly a creation, and Japan is so seismically unstable an island chain, that its guardians protect it as if it were the Mona Lisa or the Hope Diamond. It has its own building mounted on gimbals and rubber feet; metal-mesh ceiling nets to diffuse lightning strikes; and special metal shields to keep stray magnetic fields at bay.
Swaddled in care, Japan’s Earth Simulator quietly crunches away at the numbers of what it sees. Its operators continue to try to divine, as do many others in similar laboratories around the world, whether the onset of an El Niño or a La Niña can be declared not merely under way but about to happen. Can it be predicted, in other words, just like any other weather forecast?
Most recently the Japanese team working on El Niño has been able to show that the onset of an ENSO warm phase is often preceded by a machine-gun-like series of small and intense storms north of Australia, in the waters off Papua New Guinea. The storms are small enough to be known as westerly wind bursts; and though for a while they were dismissed as random events, unconnected to the happenings on the far side of the ocean, nowadays scientists believe they may be linked. But as to whether they indicate the onset of an El Niño, or whether they are the result of the onset of an El Niño, is a matter of much debate in the meteorological community.
No one yet has come up with a way to forecast the onset of ENSO—which is a major concern at a time when the worldwide weather has become such a worldwide obsession. For El Niños wreak havoc everywhere.
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