by Brian Fagan
The great Indian famines of the late nineteenth century were a direct result of a series of monsoon failures now known to be linked to major El Niño events. Such failures were nothing new. A thousand years ago, millions of people in South and Southeast Asia and along the shores of the Indian Ocean, from the Nile to China, lived at the mercy of the monsoon and its complex relationships with El Niño and La Niña.
As we have seen, there were prolonged La Niña conditions across much of the Pacific during the Medieval Warm Period, which had an effect as far away as northeast Africa, on the western shores of the Indian Ocean. Monsoon rains falling on the Ethiopian highlands provide about 90 percent of all the water flowing downriver during the river’s annual rise. Contrary to popular belief, the summer Nile inundation is unpredictable and varies from year to year, as drought or plentiful rain affect Ethiopia. In the days before the Aswan Dam, Egyptian farmers went hungry when too little floodwater spilled across the floodplain. A flood that was 6 feet (2 meters) below average could leave up to three quarters of some provinces in upper Egypt without irrigation water. At the other extreme, an exceptionally high flood would rise precipitously and sweep everything, even entire villages, before it. With good reason, generations of ancient Egyptian pharaohs fretted about the flood levels and tried to predict them with carefully calibrated measuring devices, today called Nilometers.5 So did their successors.
Locations mentioned in this chapter; also, general monsoon wind routes.
In A.D. 715, an Umayyad caliph, Sulayman Abd al-Malek, exercised about low river levels and the social disorder that ensued, ordered the construction of a Nilometer at the south end of Rhoda (Rawda) Island near Cairo.6 A century and a half later, an Abbasid caliph, al-Mutawakkil, commissioned a major reconstruction under the direction of the Turkestan-born astronomer Abu’l ‘Abbas Ahmad ibn Mohammad ibn Kathir al-Farghani, known in the west as Alfraganus. The great astronomer built an octagonal column within a stone-lined pit connected to the Nile by three tunnels. A scale of 19 Egyptian cubits (a cubit is 1.77 feet or 0.54 meters) carved on the column recorded the maximum and minimum levels of the river, making it capable of measuring a flood of 30 feet (9.2 meters). The walls of the Nilometer bear texts from the Quran referring to water, vegetation, and prosperity. An ideal inundation reached 16 cubits. Less meant drought and famine. A measurement over 19 cubits (33.6 feet [10.2 meters]) foretold catastrophic flooding.
The Rhoda column may seem like an unlikely source of climatological information, but its record extends back over fifteen hundred years. The archaeologist and demographer Fekri Hassan has calibrated flood data from Rhoda to reflect silting and other factors. He records a major episode of low flood levels between A.D. 930 and 1070, followed by a high from 1070 to 1180, after which the Nile plunged again, with low inundations for 170 years. With poor floods came meager harvests, famine, and inflated grain prices. The caliphs had ample cause for concern and good reason to invest in their Nilometer. Between A.D. 622 and 999, there were 102 years with poor floods—that is, the floods were poor in just under 28 percent of years.7 In A.D. 967, 600,000 people died of starvation and famine-related diseases, a quarter of Egypt’s population. During another famine, in A.D. 1220–21, between 100 and 500 people a day perished in Cairo alone.
The prolonged tenth- and thirteenth-century droughts known from the Rhoda Nilometer also affected East Africa. Lake Naivasha in central Kenya experienced a long period of intense aridity from about A.D. 1000 to 1270, with only one brief period of higher rainfall, from about 1200 to 1240. In contrast, the period from 1770 to 1850, the apogee of the Little Ice Age, was generally wetter.8 The Naivasha record is far from unique. Lakes Victoria, Tanganyika, and Malawi all experienced prolonged droughts and low water levels after 1040. Mount Kilimanjaro experienced unusual aridity during the same century. The lakes lie outside the East African highlands, where cattle people had flourished for at least two thousand years. We know nothing of these groups, who had few possessions and were constantly on the move, but when lengthy droughts arrived, the people would have stayed within easy reach of permanent water supplies. Judging from historic droughts, they probably lost thousands of head of cattle as grazing grass withered year after year. However, like other pastoralists, they would increase the size of their herds during well-watered years to cushion themselves against future potential losses. As with the herders of the Saharan Sahel, the fate of their herds depended on climatic forces generated on the other side of the world.
About a thousand years ago, just as the African droughts were at their height, Muslim traders established themselves in small communities along what is now the Kenyan and Tanzanian coast. They had come in search of ivory, timber, and tropical products for many centuries, but now they settled permanently on the East African shore. The attraction must have been purely commercial, for the coastal environment is hot and dry. An arid and inhospitable hinterland separated these towns from the herders of the far interior, but the small, polyglot “stone towns” (so named after their coral houses), partly African, partly Islamic, prospered off a trade in African gold, iron, ivory, and timber. They were the outposts of the vast commercial world of a thousand years ago that depended on the monsoon and on a classic sailing vessel, the lateen-sailed dhow.9
THE NORTHERN INDIAN Ocean is, on the whole, the kindest of the world’s great seas to the mariner. Ancient Arabic songs called it the Flying Fish Ocean. Much smaller than the Pacific and with more reliable winds, the Indian is an embayed ocean, checked by Asia and divided in the north by India into the Arabian Gulf and the Bay of Bengal, the latter linking with the eastern seas off Southeast Asia. Asia confines the ocean and upsets the normal passage of ocean winds. North of the equator, the mariner sails in the monsoon belt. On the western side of the Indian Ocean, from the Mozambique Channel between Africa and Madagascar, north and east through the Gulf of Arabia and into the Bay of Bengal and adjacent waters, the rhythms of the northeast and southwest monsoons have governed ocean voyaging for thousands of years.
During the first century A.D., an anonymous Greek-Alexandrine merchant or sailor compiled the Periplus Maris Erythraei, “The Periplus of the Erythraean Sea.” The Greek word periplus means “a going about,” which is just what the unknown writer recorded, almost certainly from firsthand knowledge of an ocean that many skippers sailed in all weathers and at all times of year. He had sailed from port to port from Africa to India, and also direct far offshore, on the wings of the monsoon winds: “This whole voyage as above described, from Cana and Eudaemon Arabia, they used to make in small vessels, sailing close around the shores of the gulfs; and Hippalus was the pilot who by observing the location of the ports and the conditions of the sea, first discovered how to lay his course straight across the ocean.”10 The Book of Revelation describes a Red Sea and monsoon trade in lyrical terms: “Gold, and silver, and precious stones, and pearls, and fine linen, and purple, and silk, and all sweet wood, and all manner of vessels of ivory.”11 This was the trade that led to the founding of strategic commercial towns on the East African coast as far south as Kilwa in southern Tanzania.
The extent of monsoons.
Each monsoon wind blows for about half the year, but the changeover is never abrupt. The southwest monsoon brings rain to the west coast of India by the end of May, reaches its full and boisterous strength during July, and lessens until October, when it disperses. Heavy rainfall and strong winds effectively close exposed ports on the Indian coast even for large sailing vessels during strong monsoon years, often associated with La Niña–like conditions in the Pacific. The rains can fall for forty or fifty days with only short periods of fair weather. These are not gracious conditions for the ocean sailor, especially not for coasting vessels with open cargo holds.
The northeast monsoon is benign and dependable, never reaches great strength, and blows day and night with a predictable routine that is balm to a skipper’s soul. Between November and May, this remarkable breeze carried dhows from the Persian Gulf to Ind
ia, and vessels from Indian ports to Mesopotamia and far westward along the shores of southern Arabia to the distant, spice-rich island of Socotra at the mouth of the second great arm of the Indian Ocean, the Red Sea. Meanwhile, as merchant ships reached India from the east, Chinese junks and other ships bound for the Malay Peninsula and points east had already left port on the southwest monsoon that blew across the Bay of Bengal from April to July. The same winds could carry sailing vessels as far as the coast of Vietnam and into the South China Sea until September, when the weakening southerlies gave way to the northeasterly monsoon. This, in turn, lasted until April, when the cycle renewed itself. The monsoon winds allowed India and China to establish contact with the Roman and Islamic worlds by sea.
Just like those of the Pacific Ocean trades, the patterns of the monsoon winds were far from constant. An irregular and still little-understood cycle shifted monsoon winds north and south over the Indian Ocean. When the winds were to the south, the Ethiopian highlands received ample rainfall, but when they moved northward, rainfall diminished, culminating in severe droughts lasting a decade or more. The droughts of the warm centuries were especially prolonged, apparently during still little-documented periods of La Niña conditions in the Pacific. During the tenth- and thirteenth-century arid cycles, the monsoon winds were to the north. As we have seen, Ethiopia and the East African lakes region experienced diminished rainfall. So, while India received heavy rain and the southwest monsoon blew strongly, Africa suffered under drought. According to the historian Ian Blanchard, the north–south cycle had a periodicity of about 100 to 120 years, operating like a slow-moving pendulum.12
Sailing conditions in the Indian Ocean were challenging during the warm centuries, when strong southwesterly monsoons, associated with persistent La Niña conditions farther east in the Pacific and blowing onshore, made the approach to India’s western coast a dangerous proposition. The polyglot skippers who plied the Red Sea, Persian Gulf, and Indian Ocean adjusted their sea routes as the prevailing winds changed. So did the merchants, who could save days by traveling overland from ports of the Red Sea to the Nile instead of battling strong headwinds. Travel by land or sea was never easy. “By day . . . many [ships] are lost because the straits are stormy because of land winds,” wrote the Portuguese traveler Thomé Pires in 1513.13 The strong southwesterly monsoons of the Medieval Warm Period made for fast ocean passages eastward, which may have made the East African coast, with its rich stocks of elephant ivory, especially attractive to long-distance sailors. Permanent settlement by merchants with connections elsewhere may have resulted. (The ivory of the African elephant is softer and more easily carved than that of its Indian relative, a fact that created an insatiable demand for African ivory in India, where it was prized for, among other things, bridal ornaments.) Sailing conditions during much of the year may have been more hazardous, but, from the dhow skipper’s perspective, the situation in the Indian Ocean during the warm centuries was somewhat like that faced by camel caravans in the Sahara. When rainfall increased slightly in the desert, the caravans used routes in the heart of the Sahara where water could now be found. During dry times, they moved westward, closer to the Atlantic. Camels allowed their owners to adapt effortlessly to climatic shifts. So did the dhow, which sailed well downwind in the hands of sailors who waited patiently for wind shifts and listened carefully to intelligence about the north–south movement of the best sailing routes. Their ability to adapt quickly to different wind conditions meant that the Indian Ocean trade never ceased through the warm centuries. In the days before automobiles, railroads, and steamships, the tentacles of long-distance trade on land and ocean were infinitely adaptable and constantly shifting. On the shores of the Indian Ocean, the ports where ships called might silt up; pirates might infest a once safe estuary; the pattern of the monsoon winds might falter. Visiting ships would now trade elsewhere.
LOW NILE FLOODS, drought in East Africa, strong southwesterly monsoon winds, and changing sailing routes across the Indian Ocean: all these phenomena stemmed ultimately from climatic shifts across an enormous sweep of the globe and from an area of the southwestern Pacific known as the Hot Pool.
We’ve examined many of the rainfall and temperature changes in earlier chapters. Far from the Indian Ocean, a deep-sea core in California’s Santa Barbara Channel chronicles a long period of cooler sea surface temperatures and strong upwelling from about A.D. 500 to 1300 that is typical of La Niña, the counterpoint of El Niño (as described in chapter 7). The ancient corals from Palmyra Island in the central Pacific also hint at relatively cool and dry, perhaps sometimes La Niña conditions, during the twelfth century (see chapter 10). A deep-sea core off coastal Peru documents a long period of La Niña–like climate between A.D. 800 and 1250. Lakes in the Ecuadorian Andes and the central Chilean lowlands also record a low incidence of the floods and torrential rainfall typical of strong El Niños between A.D. 900 and 1200 (as we saw in chapter 9).
The trajectory of tenth-to-thirteenth-century drought carried across a then cool and dry Pacific into the area of the Hot Pool, which is the crucible for the monsoon climates of Asia and the Indian Ocean. This reservoir of warm water sloshes over an area east to west along the equator for some 9,000 miles (14,500 kilometers) and about 1,500 miles (2,400 kilometers) north to south—an enormous bathtub, as it were, that covers an area four times that of the United States. The Hot Pool includes the waters of the western equatorial Pacific between New Guinea and Samoa, with a long tail extending through the Indonesian Archipelago and far into the Indian Ocean. These are the warmest waters on earth, warm enough to drive heat and moisture high into the atmosphere and to affect the climates of neighboring landmasses—China and India. The slow and cyclical fluctuations in the size and temperature of the Hot Pool may be closely linked to the intensity of El Niños, but no one yet knows what causes them.
When El Niños form, the Hot Pool moves eastward, closer to the international date line. A strong high-pressure system builds over Indonesia. The high-pressure center delays the monsoon, drought ensues, and forest fires rage over wide areas, as they did memorably during the great El Niño of 1997–98. Strong ENSOs reduce the amount of rainfall over much of Southeast Asia and as far south as Australia and New Zealand. During the intense El Niño cycles of 1870–1900, New South Wales and Victoria in Australia turned into dustbowls, with huge forest fires and dust storms lasting for days. Millions of sheep perished; crops failed over a wide area. But every El Niño is different, so the effects vary each time, modified also by still little-known decadal and longer shifts in such phenomena as Eurasian snow cover.
The climate of the Indian Ocean interacts with the Pacific’s ever shifting Southern Oscillation, but other, quite independent variables make a significant difference. One certainly cannot claim that there is a direct and invariable connection between a strong El Niño and monsoon failure over South and Southeast Asia. But the links between ENSOs and Indian droughts are real. Twenty out of twenty-two El Niño years between 1870 and 1991 saw drought or lower than average rainfall. There’s no reason to believe that such linkages weren’t operating in the past.
What, then, was the result of the persistent cooler conditions that flourished over the Pacific for much of the tenth to thirteenth centuries, not continuously, but certainly as the dominant climatic pattern? During cooler periods and La Niñas, the Hot Pool moves westward, away from the international date line. Unimpeded monsoons spread across Southeast and East Asia, bringing ample rainfall, sometimes too much.
We still know little about the workings of the Hot Pool, but it’s clear that even minor changes in sea surface temperatures can have a significant effect on climate in surrounding areas. In general terms, there seems little doubt that cool, arid La Niña–like conditions mean stronger summer monsoons and higher rainfall in South and Southeast Asia, even if the correlation is not exact or invariable. A few climatic proxies scattered over a vast area hint at a wetter period with stronger summer monsoons from A.D.
1000 to 1350. Among them are stalagmites in a shallow cave in Oman, a deep-sea core off Pakistan, and a fossil pollen sequence from Maili in northeast China.
These three and a half centuries were times of considerable turmoil in India, marked by Islamic incursions from northern nomads, the founding of a Muslim dynasty in Delhi, and the expulsion of Buddhism. But apparently, the generally prevalent La Niña–like conditions in the Pacific ensured good monsoon rains much of the time.
IN INDIA, the monsoon is much more than a matter of meteorology. Throughout the subcontinent, human existence, the very fabric of daily life, unfolds around two seasons, the wet and the dry. The wet season brings warm, moist conditions and heavy rain, carried by the monsoon winds blowing inland from the ocean. The other half of the year, the arid season, enjoys cool, dry air from the north. The coming of the summer monsoon is a highlight of the year to those who have suffered through the buildup after the pleasant winter months—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 hungry land.”14 The day when the monsoon broke was always memorable. The sixth-century writer Subandhu wrote: “Peacocks danced at eventide.”