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Our Affair with El Niño
How We Transformed an Enchanting Peruvian Current into a Global Climate Hazard Chapter One
A MERCURIAL CHARACTER
There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
-William Shakespeare,
Hamlet Stockbrokers on Wall Street mutter "El Niño" when the market is erratic. Commuters in London do the same when the traffic is exceptionally bad. Humorists everywhere depict El Niño as a little devil responsible for everything that goes wrong. The rascal is so remarkably versatile and ubiquitous-the strange weather he causes globally includes floods and droughts, mild and severe winters-that his name has become part of our vocabulary; it designates a mischievous gremlin. El Niño joins a host of meteorological phenomena that serve as metaphors in our daily speech: the president is under a cloud; the test was a breeze; the economy is in the doldrums. The meanings of these statements are perfectly clear because everyone has intimate familiarity with clouds and breezes, and is aware of the depressing, perennially overcast doldrums near the equator. El Niño, however, remains a mystery to most people, despite all the publicity he currently receives. Who is El Niño?
El Niño is Spanish for "the boy" and can also be translated as "the small one." This is an odd name for a global phenomenon that adversely affects millions of people worldwide. Is irony intended? The name becomes even more intriguing when we investigate why the first letters in El Niño are capitalized. Apparently the people of Ecuador and Peru, who first used the name, had in mind, not any boy, but specifically the Child Jesus. Why that name for a phenomenon that amounts to a disaster? Were some of the early South American converts to Christianity cynical? Not at all. Originally the term El Niño referred to a warm coastal current that appears along the shores of Ecuador and Peru around Christmastime, when it brings welcome relief from the cold waters that otherwise bathe those shores.1 The transformation of a regional curiosity, which we used to welcome as a blessing, into a global climate hazard happened recently, during the second half of the twentieth century.
We first "encountered" him, more than a century ago, along the shores of Ecuador and Peru. We assumed that he was an angel and named him El Niño. We eventually identified his relatives-La Niña, Southern Oscillation, ENSO-and proceeded to devote learned tomes to descriptions and exegesis of this remarkable family. These scriptures provide such a rich spectrum of historical, cultural, and scientific perspectives on El Niño that we are now having difficulties interpreting our own texts. We have become confused about issues as fundamental as the identity of El Niño. A member of our clergy, a scientist, summarizes the cur- rent, bewildering state of affairs as follows:2
The atmospheric component tied to El Niño is termed the "South-ern Oscillation." Scientists often call the phenomenon where the atmosphere and ocean collaborate ENSO, short for El Niño -Southern Oscillation. El Niño then corresponds to the warm phase of ENSO. The opposite "La Niña " ("the girl" in Spanish) phase consists of a basinwide cooling of the tropical Pacific and thus the cold phase of ENSO. However, for the public, the term for the whole phenomenon is "El Niño. "
The clerics are confused. They have been grappling with the question Who is El Niño? for some time, and they find the answer to be frustratingly elusive. In the early 1980s they appointed an august committee to define El Niño quantitatively,3 but shortly after that committee promulgated a definition, based on the "typical" behavior of El Niño up to that time, El Niño visited and behaved in a manner entirely inconsistent with the definition. His visits used to start along the shores of Peru, whereafter he proceeded westward across the Pacific, but in 1982 he reversed his itinerary: he first appeared in the far western equatorial Pacific and then moved eastward, arriving in Peru in a season different from the "usual" one. His personality proved too complex to be captured with a simple definition involving a handful of numbers. Clergymen who insist on narrow, rigid definitions of El Niño are at risk of becoming Mr. Gradgrind:
"Bitzer," said Thomas Gradgrind, "your definition of a horse."
"Quadruped. Gramnivorous. Forty teeth, namely twenty-four grinders, four eye-teeth, and twelve incisive. Sheds coat in the spring; in marshy countries sheds hoofs too. Hoofs hard, but requiring to be shod with iron. Age known by marks in mouth." Thus (and much more) Bitzer.
"Now girl number twenty," said Mr. Gradgrind, "you know what a horse is."
Charles Dickens,
Hard Times To methodical scientists, who cope best with an idealized, consistent world, El Niño is frustratingly whimsical. He was brief and intense in 1997, mild and languorous in 1992. He can be regular and energetic during some decades (the 1960s) but practically absent during other decades (the 1920s and 1930s). Laymen, who are more tolerant of caprice and impulse than scientists are, find him fascinating and beguiling, as is evident from the humorous ways in which they now use the term El Niño as a metaphor in their daily speech. The clerics should applaud this development because it offers a solution to their quandary.
The use of words cannot be legislated. Today everyone associates El Niño with the appearance of warm waters in the eastern tropical Pacific and believes him to be capable of interfering with weather patterns worldwide. This means that the term El Niño, as used at present, refers to a phenomenon with both atmospheric and oceanic aspects. Those who insist that El Niño is a strictly oceanic phenomenon, who recall that it originally referred to a seasonal current along the coast of Peru, can take pride in their erudition, but they should realize that their use of the term is becoming archaic. Unless they wish to be an elite culture with its own unintelligible argot, they should follow those who accept that El Niño has both atmospheric and oceanic aspects.
Until 1957, a lack of measurements led us to believe that El Niño was a regional phenomenon, confined to the shores of Peru and Ecuador. When he visited that year, many scientists happened to be engaged in a program to collect atmospheric and oceanic data on a global scale over an extended period.4 The data revealed that we had been completely mistaken about the true dimensions of El Niño. We discovered that he is associated with the appearance of unusually warm waters, not only along the western coast of South America, but right across the vast tropical Pacific. It was natural to conclude that such an exceptional state of affairs amounts to a major departure from "normal" conditions. We therefore analyzed El Niño 's subsequent appearances in order to identify the "triggers" that initiate the development of such unusual conditions. At first some scientists proposed that a collapse of the trade winds precedes the appearance of El Niño. 5 Today many believe that the "triggers" are bursts of westerly winds along the equator in the vicinity of the date line; critical subsequent developments include oceanic Kelvin waves that propagate eastward along the equator. (The detection of these waves in satellite photographs of the Pacific is sometimes regarded as an annunciation, to be celebrated with a press conference.)
A very different perspective on El Niño became available in the 1980s once we had records sufficiently long to cover many consecutive episodes. To share this perspective, inspect surface temperature fluctuations in the eastern tropical Pacific over the past century. (The occasional warming of the surface waters in that region amounts to El Niño 's signature.) Figure 1.1 calls into question the earlier view that El Niño is a departure from "normal" conditions. Such conditions, which correspond to the horizontal line, are seen to prevail very seldom. Temperatures are either above the horizontal line, during El Niño episodes, or they are below that line. We are dealing with an unending oscillation that has a distinctive timescale of approximately four years. It is as if we are listening to a continuous melody that has a distinctive beat. El Niño is only part of this ever present tune, so it makes little sense to listen to his notes in isolation. To appreciate his high, shrill notes we should also pay attention to the deep, resonant notes of the complementary periods when the waters are cold. La Niña is an apposite name for those cold periods.6 The continual Southern Oscillation between El Niño and La Niña seems to have no beginning or end.
Are El Niño and La Niña the complementary phases of a cycle with no beginning or end? Or is each one of them an independent event, a departure from "normal" conditions "triggered" by certain disturbances, some of which lead to the appearance of warm water, some to the appearance of cold water. These different points of view reflect different perceptions of time itself. Those who believe that "triggers" initiate El Niño regard time as an arrow that moves in a definite direction as El Niño progresses from a beginning to an end, from birth to death. A more reassuring perception of time, one that gives us a continual sense of renewal, is in terms of natural cycles. El Niño can then be regarded as part of an endless cycle, similar to those mentioned in Ecclesiastes:
The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose. The wind goeth toward the south, and returneth about unto the north; it whirlith about continually, and the wind returneth again according to his circuits. All the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come, thither they return again . . . The things that hath been, it is that which shall be; and that which is done is that which shall be done.
Ecclesiastes 1:5-9
Much of literature is concerned with these two very different aspects of time, which are captured by the metaphors of time's arrow and time's cycle. The current debate about which of these metaphors best describes El Niño is reminiscent of the nineteenth-century debate about the interpretation of the geological record.7 Some early geologists, who subsequently became known as "catastrophists," described the history of the earth chronologically, in terms of a sequence of mostly biblical events and catastrophes that moved from a definite beginning to the present. (James Ussher, while he was bishop of Armagh in Ireland, determined that the creation started at precisely 9:00 A.M. on Monday, October 23, 4004 B.C.) In 1795 James Hutton put forward a radically different perspective when he proposed that the geological record extends back over an inconceivable length of time and should be interpreted in terms of repeated cycles with "no vestige of a beginning,-no prospect of an end."8 Hutton believed that unchanging geological processes such as erosion and the gradual uplifting of rocks, acting slowly and steadily over an immensity of time that is difficult to comprehend, shaped our landscape in the past and continue to do so today. His followers were therefore known as "uniformitarians." Although they developed convincing arguments that explain much of the geological record, it is difficult to deny that the fossil record tells a story of the sequential evolution of different species, a story that moves in a direction. After much debate, geologists reached an accommodation that has room for both time's arrow and time's cycle. Students of El Niño need to do the same.
Persuasive evidence that, in 1997, a burst of westerly winds contributed to the development of El Niño lends credence to the idea that El Niño has a definite beginning. However, similar wind bursts on other occasions have failed to produce El Niño. Appar- ently only bursts that appear at the "right" time are capable of inducing El Niño. What factors determine the "right" time? Consider a swinging pendulum subjected to modest blows at random times. A blow at the right time can increase the amplitude of the swing considerably. At the wrong time, it can cause the pendulum to come to a standstill. This argument suggests that we are dealing with an unending cycle, subject to random disturbances. This compromise between time's arrow and time's cycle explains why each El Niño is distinct. The phenomenon was particularly intense in 1997 because, as it was about to visit, a burst of westerly winds came along, causing a significant amplification and acceleration of developments. The absence of appropriate random disturbances is the reason why El Niño was weak and prolonged in 1992.
We have seen the signatures of El Niño and La Niña in figure 1.1, which tells us when each of them visited, but we still do not know what those phenomena look like. What are their distinctive features? Their pictures, in figure 1.2, are surprising and also sobering because they bring to mind Confucius' observation that "a common man marvels at uncommon things; a wise man marvels at the commonplace." We have been lavishing attention on uncommon El Niño, whom some of us regard as a departure from "normal" conditions, when in reality commonplace La Niña is the more interesting of the two! El Niño 's temperature patterns at the ocean surface are downright plain; uniformly warm surface waters are exactly what we expect in the tropics where sunshine is most intense. La Niña, by contrast, is intriguing and mysterious: she remains admirably cool under intense sunlight and expresses her coolness with flair. Her sea surface temperature patterns have fascinating asymmetries. Although the intensity of sunlight is independent of longitude and is perfectly symmetrical about the equator, she keeps the waters of the tropical Pacific colder in the east than the west and, in the east, warmest in a band to the north of the equator. La Niña transforms that renowned line, the equator, from a mere geographer's artifice into something very special-the location of a westward-stretching sliver of exceptionally cold waters, rich in nutrients and hence in marine life. So plentiful is nourishment along the Line that Moby Dick used to loiter there. That is where Captain Ahab went looking for the white whale.
La Niña expresses her alluring asymmetries not only in oceanic conditions but in atmospheric conditions too.
Continues...
Excerpted from Our Affair with El Niño by S. George Philander Excerpted by permission.
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