Olympus, where they say, the gods' eternal mansion stands unmoved, never rocked by galewinds, never drenched by rains, nor do the drifting snows assail it, no, the clear air stretches away without a cloud, and a great radiance plays across that world where the blithe gods live all their days in bliss.
--Homer, Odyssey VI
This planet's different climatic zones are all related by the winds. These invisible threads of the climate tapestry weave the deserts and jungles, the steppes and tundra, into a cohesive whole.
--George S. Philander, Is the Temperature Rising?
Come late February, the Indian sun becomes hotter with the advent of spring. First, garden flowers wither. Then wild flowering trees burst forth in scarlet and orange, the silk cotton and the coral and flame trees. Brilliantly flowering flamboyants line the sides of dirt roads, defying the ever hotter sun. By late March, the hardiest species have shed their flowers and leaves, even the golden yellow-flowered laburnum that adorns so many Punjab gardens. The sun heats and scorches as the days grow longer, drying the dew before it settles. Tinder-dry brush and woodland burst into flame, filling the dusty air with thick wood ash. The dry earth cracks and fissures as shimmering heat creates quicksilver mirages on the parched fields.
Everyone waits and waits for rain. Menacing banks of dark clouds form every May afternoon on the southern horizon as the temperature falls slightly. Solid masses of locusts cover the sun. Fine dust falls from heaven. The clouds dissipate in violent winds that fell trees and blow off roofs. The winds die down as rapidly as they came, and the heat builds relentlessly. The poet Rudyard Kipling wrote in "Two Months":
Fall off, the Thunder bellows her despair
To echoing earth, thrice parched. The lightnings fly
In vain. No help the heaped-up clouds afford,
But wearier weight of burdened, burning air.
What truce with Dawn? Look, from the aching sky,
Day stalks, a tyrant with a flaming sword!
The aching sky--Kipling's description is an apt one. The still heat is furnacelike, bringing prickly heat and a lifeless, hazy sky of leachedout blue. Then suddenly, in May or June, the black-and-white bulbuls appear, pied crested cuckoos with long tails (Clamator jacobinus), newly arrived from Africa on the vanguard of the monsoon. Black clouds build again on the horizon, flashes of lightning in their midst. Thunderclaps sound. Large raindrops spatter the waiting earth, drying as they hit the ground. Then a giant thundering erupts as torrential rain cascades onto people's upturned faces. They run around wildly in the open, waving their hands, welcoming the cool and the rain.
Monsoon rains are no ordinary storms, over in a few hours. Instead, it rains and rains. Dark clouds pass over the plains and mountains, bringing shower after shower through August and September as the monsoon spends its last force against the distant Himalayas before retreating southward in autumn. The earth turns from a desert into a sea of muddy puddles. Wells and lakes fill up. Rivers overflow their banks. Mud-hut walls melt as houses collapse. The land comes alive. Almost overnight the landscape turns green as grass sprouts, crops grow, and trees acquire new foliage. Frogs croak day and night, animals breed, farmers plant their crops, and life begins anew.
The summer monsoon is the epitome of Indian life, an experience both intensely personal and deeply spiritual, the source of human existence itself. Each year the monsoon not only brings the fullness of harvest but creates life from desolation, hope from despair. The monsoon is the smell of freshly watered earth, the sound of thunder, the season when peacocks strut their magnificent plumage, the time for merriment and lovemaking. The dark clouds of the southwest monsoon are symbols of hope, their coming commemorated by Indian writers for centuries. In the late sixth century A.D., the writer Subandhu wrote: "Peacocks danced at eventide. The rain quelled the expanse of dust as a great ascetic quells the tide of passion." Eight centuries later, the poet Vidyapati wrote:
Roaring the clouds break
And rain falls
The earth becomes a sea.
For thousands of years Indian farmers sweated through spring and early summer, watching for that climatic moment when the monsoon rains broke. An enormous folk literature surrounds the unpredictable monsoon, doggerel and proverbs about the formation of nimbus clouds, the arrival of migrant birds, and subtle changes in vegetation. The pied crested cuckoo is said to arrive on the west coast a day or two before the rains, fly inland at a leisurely pace, and then appear in Delhi about two weeks after the monsoon breaks over the Western Ghat Mountains inshore from the coast.
Proverbs from one end of the monsoon belt to the other offer folk signs of impending rain and hope of bounty. According to Ghagh, a seventeenth-century Brahmin poet: "When clouds appear like partridge feathers and are spread across the sky, they will not go without shedding rain." He also tells us, "If clouds appear on Friday and stay till Saturday, be sure it will bring rain." The proverbs disguise the agony of the long wait through searing heat, the hopeful search for the building nimbus clouds, the ecstasy of the first rains. The anguish and anticipation were based in harsh reality. Until the twentieth century, much of India was but a monsoon away from disaster.
I dimly remember my father and grandfather talking about the summer monsoon. Tall, slender, the epitome of a discreet imperial bureaucrat, my grandfather had served as financial secretary of the Punjab in the early years of the twentieth century. He was high in the intricate hierarchy of India's British Raj, a member of the governor-general's Legislative Council with awesome responsibilities if the monsoon failed. For much of the year he administered the routine of tax collection and assigned precious funds for major capital expenditures like railroads and irrigation schemes. But the summer monsoon dominated his life, and the specter of famine always overshadowed his work. Every year he awaited the monsoon with eager anticipation mingled with profound apprehension. With the monsoon came a different country, which my father once described to me by quoting E. M. Forster's The Hill of Devi: "Now there is a new India--damp and grey, and but for the unusual animals I might think myself in England."
Even in his old age, my grandfather remembered the tense weeks of waiting, the crushing heat, the shrill cries of cuckoos, the massing clouds on the far horizon. Like the village farmers in the countryside, he watched for the coming of the monsoon and waited--for abundance or hunger. He administered the lives of thousands of villagers, but he could not control or predict the natural engine of their existence.
The word monsoon comes from the Arabic word mausem (season). The monsoon is a season of rains borne on the dark nimbus clouds of summer that blow in from the southwest. A huge circulation of air determines the intensity of the monsoon. As the earth's tilt varies with summer and winter, so the monsoon circulation moves--farther north in summer, southward in winter. In summer the northern edge of the monsoon borders on the Himalayas. Winds blow across the Arabian Sea and the Bay of Bengal, bringing moisture-laden air to Sri Lanka in May, and to the southernmost parts of peninsular India by the first week of June. The rains move steadily northward to Bombay. By mid-June they normally cover all of Gujerat, with heavy rain along the west coast and the shores of the Bay of Bengal. In a good monsoon year, rain showers continue throughout western India and Pakistan through September, and, less certainly, from the southward-retreating monsoon into November. The agricultural lives of millions of village farmers depend on this pattern of circulation from south to north and back again. If the pattern fails, less moisture, sometimes almost none, reaches the Punjab or Rajasthan. Farther south, the usually strong southwestern monsoon winds blow with less force and drop scanty rainfall inland. Even in good years, irregular rainfall patterns can play havoc with crops of all kinds.
What happened when the unpredictable dark clouds never massed on the horizon and the monsoon failed? With almost mind-numbing regularity, Indian farmers died by the tens of thousands, sometimes millions. The story of the scientific understanding of El Nino and other global weather phenomena begins with famine and the Indian monsoon.
"Famine is India's specialty. Everywhere famines are inconsequential incidents; in India they are devastating cataclysms," wrote a Victorian traveler who witnessed the horrors of the 1896 famine in southern India. Famine was endemic in India for thousands of years, until railroads and improved communications made the shipment of grain and other food supplies to hungry villages a practical relief strategy. In 1344-1345 such a severe famine affected India that even royalty starved. The famine of 1631, following the failure of the monsoon rains in 1629 and again in 1630, devastated all of monsoon Asia. Entire rural districts were depopulated as people moved elsewhere to escape hunger and died by the roadside. Millions of cattle perished. Cholera epidemics carried away entire villages. Many areas did not recover for half a century. Another major drought came in 1685-1688. A century later the famine of 1770 caused a third of Bengal to lie "waste and silent" for two decades. An Indian army official, Colonel Baird Smith, described how food prices rose inexorably as the rains faltered in two previous years. By January 1770, fifty people a day were dying of starvation in northern Bengal. Smith saw the dead "left uninterred; dogs, jackals, and vultures were the sole scavengers." The historian Thomas Babington Macaulay described how "tender and delicate women, whose veils had never been lifted before the public gaze ... threw themselves on the earth before the passer-by, and with loud wailings implored a handful of rice for their children." The streets of Calcutta were blocked by the dead and dying.
The South Asian monsoon failed again in 1789. A year later droughts also descended on Australia, Mexico, the island of Saint Helena in the south Atlantic, and southern Africa. The Nile River fell to record lows. The Indian drought endured until 1792, interspersed with destructive rainstorms. In three days in late October 1791, 650 millimeters of rain fell on Madras. A year later at least 600,000 people in the northern Madras region starved to death as the drought returned. No one connected the famines in India and southern Africa and the summer crop failures in distant Europe to a global weather event. They lacked the observation tools to do so.
The British administration in India had to take famine and famine relief very seriously. Official commissions studied the phenomenon and collected statistics diligently. They found that major famines had occurred about every twelve years, killing fifteen million people over a forty-year period of Queen Victoria's reign. During the 1896-1897 famine, when government relief efforts were somewhat better organized (thanks in part to improved railroads), no less than four and a half million people were on some form of temporary government assistance. Hundreds of thousands more perished of hunger and epidemic disease. As every commission and every concerned humanitarian and missionary body knew, the ever fickle monsoon rains were behind these periodic famines. The monsoon was India's salvation and scourge, and it was completely beyond human control.
The famine of 1899-1900, breaking out only two years after the previous catastrophic drought, was the worst on record. Rainfall was at least 27 percent below the norm of over 1,000 millimeters a year. The dead littered villages and roadsides. The bones of famine victims lay bleached-white in the sun. Vaughan Nash, the Manchester Guardian's India correspondent, wrote on May 4, 1900, of "skeleton mothers ... trying to keep the life in their babies--anatomies rather than living creatures; rows of emaciated children sat in silence, some of them clasping their heads in their hands and with eyes tight shut, others asleep in the dust."
Over one million square kilometers of central, western, and southern India were affected. A Reuters news agency telegram to London described the fertile farmlands of the Punjab as a "vast, bare, brown, lonely desert." Of the 62 million people who were severely affected by total crop failure, 41.7 million lived not in native states but under British rule. A critical fodder famine killed millions of head of cattle, especially in Gujerat, where more than 70 percent perished. By March of the following year, the viceroy of India reported that the farmlands of the Deccan plains in the south were fast becoming a wilderness of "dismal, sun-cracked, desert-charred earth ... sent flying in clouds of pungent dust. No water in the wells; no water in the rivers." Vaughan Nash met scores of families migrating toward government-sponsored work camps, where they would carry out manual labor in exchange for basic rations. The refugees walked in "the burning dust, with lips and throats too parched for speech, their garments often in shreds and their eyes hollow with hunger." At one village in Gujerat, the fierce heat dried up the river so fast that hundreds of fish flapped in the shallows. Starving people from kilometers around gathered up the fish by hand and ate them. Someone in the crowd introduced cholera. Two hundred people died the first day. The villagers panicked and fled, abandoning the dead and dying. "The air became laden with the stench of putrifying bodies.... People suddenly sat down in the midst of conversation and rapidly sank.... Whichever way we turn we discover these ghastly corpses, twisted and bloated, in almost every position that agony can produce."
The horrors of the 1899 famine echo down the years. The Presbyterian missionary James Inglis toured Ajmer and saw dogs fighting over the body of a child by the roadside. "I counted in one evening's journey forty dead bodies on the road, and the next day thirty-two, and the following day twenty-five." In 1897 one government physician called half of India "a great charnel-house, in which countless thousands have already perished of cholera, plague, dysentery, and starvation.... Twenty thousand cases of cholera weekly, with a seventy-five per cent mortality, representing 15,000 deaths every seven days." The situation was even worse in 1899.
The "great famine" of 1899 was documented as no Indian famine before it, thanks to photography and a sustained controversy over government and missionary relief efforts. Lord Curzon, the viceroy and governor-general, led the public appeals for humanitarian aid, but his own administration tried to spend as little money as possible on relief operations. Curzon said: "If any man is in any doubt as to whether he should subscribe, I would gladly give him a railway-ticket to a famine district.... He might go with a hard heart, but he would come back with a broken one." The initiatives from his government, however, were grossly inadequate, especially since the authorities refused to intervene in the open market and control grain prices, which soared as crops failed. Eventually, the Indian Famine Relief Commission received millions of pounds and gifts of grain from private sources as far away as Kansas, but much of the effort was too late.
Government relief policy was, in general, devoid of any humanitarian consideration at a time when the people were weakened both physically and economically by the 1896 famine. Relief efforts began in October, long after the famine began; crop failure had become apparent in June. Curzon was stringent in his economies because of the enormous debt India owed its colonial master. About one-quarter of the Indian government's total expenditure went to pay for Britain's India Office, British officials' pensions, and interest on a rapidly increasing national debt. The excessive overhead charges levied on the Indian government by home authorities and, in turn, on village communities consumed most of India's grain surpluses in the years immediately preceding the monsoon failures of 1896-1897 and 1899-1900. Many grain shipments arrived too late and were little more than a salve for British consciences. No one knows exactly how many perished in the great famine, but it could have been as many as four and a half million people. Between 1895 and 1905, India's total population declined for ten years as a result of economic depression, repeated famines, and plague.
Missionaries called the 1899 famine "the great visitation." They preached that humanity's lot was misery and suffering. The lesson, they said, was that "natural law in its normal movement" was irrevocable and implacable; humans were helpless in the face of such emergencies as a monsoon failure. Dogma aside, many government officials, like my grandfather, worried about the constant specter of famine. How could India plan ahead to meet and mitigate such awful visitations?
The British Raj left rural India well alone, except when rapidly expanding commercial agriculture ventures aimed at overseas markets needed cheap labor. The colonial authorities were content to collect taxes and exercise administrative control while investing little in village development. Over many decades, late-nineteenth-century administrators favored a cautious policy of preventing famine rather than mitigating it. To this end, they diverted considerable resources to the building of railroads (which also helped boost India's food exports) and to the improvement of irrigation works, on the grounds that onetime capital expenditures would pay long-term dividends and could also produce revenue from tickets, freight charges, and taxes, as well as stimulate exports. In 1869, eight thousand kilometers of railroad linked Indian cities. By the end of the century, there were forty thousand kilometers of track, some of it heavily subsidized for strategic--and sometimes famine relief--purposes. For example, the government guaranteed a return on investment to a private company that built the Southern Maratha Railway in the 1880s specifically to carry grain into famine-prone areas. The strategy paid off when the collection and transport of food was better organized after 1900, for the government was able to move grain surpluses from unaffected areas into famine zones with considerable efficiency, a task that authorities called "working" a famine.
Thanks to carefully orchestrated relief policies and a slowly expanding economy, famines became a bureaucratic euphemism: "food crises." Since the early twentieth century, there has been only one famine with major loss of life--that of 1943-1944, which resulted directly from the wartime disruption of the transport infrastructure and of the economic opportunities and government relief that usually turned famine into food crisis.
While government officials grappled with famine relief strategies, British Raj scientists turned their attention to the cause of all the suffering--the monsoon that provides nearly all of India's annum rainfall. They drew on centuries of indigenous knowledge and scientific inquiry.
Merchant seaman have sailed the Indian Ocean for five thousand years. As early as 2300 B.C., King Sargon of Agade in Mesopotamia, "the land between the rivers" that is now Iraq, boasted that ships from as far afield as Dilmun (Bahrein) and Meluhha (the Indus Valley, seat of the ancient Harappan civilization) tied up at Agade's quays. Sailors in this long-distance trade down the Persian Gulf and across to South Asia must have observed the seasonal changes in ocean winds and scheduled their voyages accordingly. Mesopotamian clay tablets give tantalizing clues that seasonal departures for India in the month se-KIN-kud (February to March), when favorable winds allow easy passage to the southeastward, were underway by 2000 B.C. One thousand years later, lateen-rigged South Arabian ships traveled regularly between the Red Sea and India, coasting for days along the Arabian shoreline against the northeast monsoon. Once well to windward, the skipper would head offshore and ride the northeast monsoon to Indian shores, returning with the southwestern winds of summer. Carefully guarded knowledge of the monsoon winds passed for hundreds of years from father to son.
The secret of the monsoon cycle remained unknown to the Mediterranean countries until an Indian ship was wrecked and the skipper brought to Alexandria in Egypt. With his help, a Greek adventurer named Eudoxus of Cyzicus made two journeys from the Red Sea to India and back around 115 B.C. It was either on these expeditions or soon afterward that a Greek skipper named Hippalus worked out a strategy for much faster, direct voyaging, using the boisterous August monsoon wind to sail directly from Socotra Island at the mouth of the Red Sea to India and back within the same twelve-month period instead of a much longer coasting journey. The Western discovery linked India with Rome, and the East African coast with Hindus and Buddhists, Sri Lanka, even distant China. The cycles of the monsoon winds became the Silk Road of the southern latitudes, a catalyst for the development of the world economic system that ultimately brought the Portuguese, British, and French to India.
"The basadra [summer monsoon wind] gives life to the people of the land, for the rain makes it fertile, because, if it didn't rain, they would die of hunger," wrote the Arab geographer Abu Zayd in A.D. 916. Arab scholars were well aware of the rhythms of the monsoon winds. However, Arabic physics was at a loss to explain the seasonal variations in wind and rainfall, dependent as it was on a mixture of Aristotelian natural philosophy, Islamic religious belief, astrology, and folklore. Even the great tenth-century geographer al-Mas'udi was moved to remark that "the angel to whose care the seas are confided immerses the heel of his foot into the sea at the extremity of China, and, as the sea is swelled, the flow takes place."
Seven centuries later, new requirements for long-distance navigation by Western nations put the study of monsoon circulation on a firmer scientific basis and prompted the first tentative studies of global climatic patterns. In 1666 the Royal Society of London prepared Directions for Sea-Men, Bound for Far Voyages, which contained precise instructions for the collection of data on winds and currents. The great astronomer Edmund Halley (1656-1742) used observations by dozens of seamen to prepare the first meteorological flowchart of the tropical oceans of the world. His map depicted the trade wind zones and monsoon circulations, but only in the most general terms. In 1686 he first advanced the idea that global winds follow a consistent pattern, as part of a general circulation of air over the earth. Halley argued that differential heating of land and sea produces trade winds and monsoon circulations. He theorized that the Indian monsoons result from such heating effects and are a regional modification of the trade wind circulation. He wrote: "In April when the sun begins to warm those Countries to the North, the S.W. Monsoon begins, and blows through the Heats till October."
Halley argued for a physical relationship between atmospheric pressure, temperature, and wind. But neither Halley nor other scientists of his day examined the ways in which atmospheric pressure and pressure variations affect wind circulation. In 1746 the Berlin Academy of Sciences went so far as to offer a prize for the best research on the laws governing air in motion, but the resulting equations were not applied to general circulations of the air around the rotating earth until the mid-nineteenth century.
During the early nineteenth century, the German explorer and scientist Alexander von Humboldt approached the monsoon problem from a different perspective. Von Humboldt was an innovative thinker, one of the first scholars to think about environmental questions on a world scale. He examined temperatures at various locations in Europe and North America and found significant differences along the same circles of latitude. Unlike earlier scientists, he argued that land-sea distributions played a vital role in modifying global wind circulations, which he regarded as the major agent of the world's climates. In 1817 von Humboldt started recording widely separated temperature distributions by using isotherms, lines that join points with similar temperatures. He adapted this recording method from the common use of isoclines to mark magnetic declination on nautical charts. Humboldt's chart showed that "the foremost effect on the climate of a place stems from the configuration of the continents surrounding it. These general causes are modified by mountains, state of the surface, etc.... which are merely local causes."
In 1830 the German meteorologist Ludwig Kamtz constructed a global temperature chart. Using more complete observations than Humboldt, he proposed that the monsoon was controlled by differential heating and cooling of the land and sea and, just as important, by the deflecting force of the earth's rotation.
The pace of observations and research accelerated as investigators realized that latent heat in convective currents of moist air could release torrential rainfall. The American meteorologist Matthew Fontaine Maury (1806-1873) devoted his life to preparing wind and sailing charts for the world's oceans. His Explanations and Sailing Directions to Accompany the Wind and Current Charts of 1854 incorporated hundreds of ship observations to demonstrate the circulation pattern of the Indian monsoon and was a major advance on Halley's pioneering research of nearly two centuries earlier. As a result of Maury's work, several seafaring nations developed sailing handbooks designed to shorten the length of voyages to India and back. Maury, also used 11,697 observations along the coast of the Bay of Bengal to conclude that the southwest monsoon moved southward in summer at a speed of about twenty-four to thirty-two kilometers a day.
Maury and his contemporaries realized that the study of the monsoon depended on accurate observations from many locations over long periods of time. Yet, until 1875, observations of Indian weather conditions were unsystematic and unreliable, despite the dedicated efforts of a few scientists and military officers. Rightly concerned about the safety of its merchant ships, the East India Company directed most of its research from the late eighteenth century toward studying the tropical cyclones that ravaged the Bay of Bengal every summer. The monsoon was ignored until a disastrous famine in 1866 led to the founding of the Indian Meteorological Service nine years later. Its first director, Henry Blanford, organized throughout the continent an efficient observation network that coincided to a great extent with the area of the southwest monsoon. Working with a skeleton staff, he and his successors tried to establish the causes of the southwest monsoon and the factors that triggered its torrential rainfall. From the beginning the Meteorological Department strove to develop seasonal forecasts of monsoon rainfall as a means of preparing for famines. Blanford organized a system of daily weather reports, sent by telegram to headquarters from all parts of India. By 1888 the department was furnishing daily weather forecasts.
The early forecasters were preoccupied with the dramatic onset of the summer monsoon, a memorable experience for everyone who had suffered through weeks of torrid heat. Wrote Colonel Edward Tennant of the East India Company in 1886: "The sky, instead of its brilliant blue, assumes the sullen tint of lead ... the days become overcast and hot, banks of cloud rise over the ocean to the west.... At last the sudden lightnings flash among the hills, and shoot through the clouds that overhang the sea, and with a crash of thunder the monsoon bursts over the thirsty land."
With their attention turned to the heavens by this awesome spectacle, the forecasters used two approaches to predict monsoon rains--the correlation between rainfall variations and sunspot cycles, and atmospheric circulation. At first, sunspot research in India appeared to show a direct relationship between monsoon rainfall and the sunspot cycle. Blanford himself analyzed sixty-four years' worth of rainfall readings from six Indian stations and found that minimum rainfall readings "somewhat anticipated" cycles of low sunspot activity, and vice versa. The British Astronomer Royal Sir Norman Lockyer, famous for his eccentric research on the Egyptian pyramids, was so impressed by this initial research that he wrote: "Surely in meteorology, as in astronomy, the thing to hunt down is a cycle." Many researchers agreed that variations in solar activity affected the intensity of the monsoon as a whole. They felt, however, that the same activity had no effect on the geographic distribution of rainfall, a key factor in the extent of monsoon-caused droughts.
Like other sciences, meteorology can easily become preoccupied with local observations, what the nineteenth-century Austrian meteorologist Julius Hann called the "church tower politics" of observation--the distance one can see from atop a church tower. However, the invention of the telegraph in 1843 allowed observers to send temperature, rainfall, and pressure readings to one another in a few hours and to track severe storms as they moved over Europe. Many countries began to set up networks of observation stations after a savage gale destroyed a French fleet in the Black Sea in 1854. The tragedy could have been avoided had the telegraph alerted fleet commanders to a storm that had already caused destruction farther west.
By the 1880s and 1890s, as more scientists realized that church tower observations had a much wider context, they became interested in global patterns of atmospheric circulation. During these two decades, European meteorologists studied the seasonal movements of the Atlantic Ocean's major pressure centers, giving them names like the Icelandic Low and the Azores High. Norwegian scientists, tracking the movements of air masses, invented the term "front" to define the lines where warm and cold air clash. On the other side of the world, Henry Blanford also extended his interests to atmospheric circulation. In 1880 he showed that there was compensation of mean barometric pressure over India and Russia in winter. Blanford then took this hypothesis still further, arguing that "unusually heavy and especially late falls of snow in the North-Western Himalaya" were followed by "deficient summer rainfall on the plains." The lower snow line in the mountains, he speculated, condensed the lower levels of the atmosphere and cooled the land, thereby weakening the monsoon.
Forecasts based on this hypothesis proved to be reasonably accurate in 1883, so research continued in the hands of Blanford's successor, Sir John Eliot. Eliot studied the relationship between Indian monsoon rainfall and changing barometric pressure over the southern Indian Ocean. He argued that the "burst" of the monsoon came from the advance of humid current from the equatorial zone of the southeast trade winds south of the equator. "The monsoon rains are due to the invasion of this current," he wrote. Despite page after page of detailed justification for their forecasts, Eliot and his colleagues met with little success after 1883. Matters came to a head when they failed to forecast the terrible drought of 1899. As a result of an outcry in the press, their predictions were no longer published in the media.
John Eliot's successor was Sir Gilbert Walker, the greatest of all directors of observatories in India. Unlike his predecessors, Walker was not a meteorologist. From 1895 to 1902, he was a senior wrangler in mathematical physics at Cambridge University, where his specialty was electrodynamics. His interests and publications ranged over electromagnetism, games and sports, even the flight of birds. He had such a passion for boomerangs and other primitive hunting devices that he earned the nickname "Boomerang Walker" from his Cambridge friends. This modest and liberal man was the epitome of the English gentleman.
Walker was appointed to the Foreign Service in 1903, served for six months as Eliot's meteorological assistant, and then assumed charge of the grossly understaffed weather service late in that year, at a time when accurate forecasts of monsoon rainfall were the director's most important concern.
Walker's lack of meteorological experience turned out to be a godsend. He was an expert statistician who believed that "what is wanted in life is ability to apply principles to the actual cases that arise." For twenty years in India, and during an additional three decades after his retirement, this remarkable scientist used statistical methods and thousands of local observations to establish the relationships between the complex atmospheric and other conditions that affect monsoon rainfall. A brilliant administrator and organizer, Walker soon expanded his work far beyond India. He established that monsoon droughts do not result from human environmental modification, such as deforestation. In a memorable paper published in 1910, he examined rainfall data from India and the Nile Valley and concluded there was no evidence that India's disastrous droughts had been caused by permanent climate change. In the same year he wrote in the Memoirs of the Indian Meteorological Service: "The variations of monsoon rainfall ... occur on so large a scale [that we can assume they are] preceded and followed by abnormal conditions at some distance." With these words, he turned his attention to the complex interrelationships between the monsoon and global atmospheric circulation. Three years later he was able to show that increased sunspot activity could intensify existing monsoon conditions but did not play a major role in monsoon failure.
Gilbert Walker was a tireless scientist with a passion for detail and statistical calculation, but he maintained a wide grasp of much larger problems. Like his predecessor, Sir John Eliot, he looked far beyond India for global predictors--complex associations of widely separated atmospheric and weather events that could cause drought in India. By 1908 he had developed a forecasting formula in the form of a regression equation that drew on years of rainfall observations, and also on global phenomena observed by other scientists. The British astronomers Norman and William Lockyer had identified a complex pressure seesaw between South America and India in 1902. Walker was also aware of research by H. H. Hildebrandsson, who had observed an opposition of barometric pressure between Buenos Aires and Sydney, Australia, and of recent statistical studies of weather anomalies in the northern hemisphere. In a series of papers (his most important), "Correlations in Seasonal Variations of Weather," published in the Memoirs in 1923-1924, Walker identified what he called "strategic points of world weather." He wrote: "We can best summarize ... the situation by saying there is a swaying of press[ure] on a big scale backwards and forwards between the Pacific Ocean and the Indian Ocean, and there are swayings, on a much smaller scale, between the Azores and Iceland, and between the areas of high and low press[ure] in the N. Pacific."
Walker named the most important of these swayings the Southern Oscillation. "By the Southern Oscillation is implied the tendency of pressure at stations in the Pacific ..., and of rainfall in India and Java (presumably also in Australia and Abyssinia) to increase, while pressure in the region of the Indian Ocean ... decreases." By 1924, when he retired from the Indian Meteorological Service to become professor of meteorology at Imperial College in London, Walker was publishing charts of the Southern Oscillation in both summer and winter based on data from an enormous network of observation stations between Africa and South America. His charts clearly demonstrated relationships between pressure, temperature, and rainfall in the Pacific and Indian Oceans, between the intensity of monsoons and earlier, changing pressure conditions thousands of kilometers away. Still, Walker could not predict monsoon failure. As he himself admitted, such forecasts would be successful only in years of strong statistical relationships. Ever judicious, he preferred the term "foreshadowing" to "forecasting," what he called a "vaguer prediction." As his successor, Sir Charles Normand, observed prophetically in 1943, Walker's worldwide surveys offered more promise for weather prediction in other regions than for monsoon rainfall, where his research began.
Sir Gilbert Walker discovered the relationship between the Southern Oscillation and Indian monsoon rainfall, but his regression formulas, while considerably better than guesses, were only slightly better than those based on probability tables. Charles Normand verified eighteen years of monsoon forecasts (1931-1948) based on the formulas from Walker's research. For years of deficient rainfall alone, 66 percent of the forecasts were wrong. Normand questioned whether these particular predictions were any use at all. However, he favored their continuation "if only to keep the subject alive and in the hope that ideas for progress will emerge."
Walker's attempts to establish linkages between pressure anomalies, rainfall, and temperature in widely separated parts of the world were challenged or ignored by many of his contemporaries, despite their interest in such links. Unlike Walker, many of them relied on qualitative assessments or just plain guesses. His obituary in the Quarterly Journal of the Royal Meteorological Society for 1959 commented that "Walker's hope was presumably not only to unearth relations useful for forecasting, but to discover sufficient and sufficiently important relations to provide a productive starting point for a theory of world weather. It hardly seems to be working out like that."
Half a century later, Gilbert Walker is remembered as one of the great heroes of global climate and El Nino research. The Pacific atmospheric circulation that links the Southern Oscillation with sea surface temperatures now bears his name: the Walker Circulation.