Tambora: The Eruption That Changed the World, page 9
The sum of these effects was a hotter stratosphere but a net cooling of surface temperatures, initiating a three-year depression of the thermal cycle of the South Asian continent, and ultimately the globe. This depression of summer minima and maxima—at the height of the growing season—proved devastating to farmers in the temperate zones of the North Atlantic in 1816 and 1817. But in the tropical latitudes of South and East Asia, raw surface temperature decline was less important than the impact of a disrupted thermal synchrony between land, sea, and sky on the life-giving monsoon.
The ecology of the Bengali river delta is inseparable from its monsoonal climate. From their first encounter with the South Asian continent, European travelers identified the monsoon as its defining cultural and economic driver. Dry through much of the year, the land would be uninhabitable but for the awesome three-month deluge that replenished aquifers and generated crops. In addition, monsoonal winds brought trade. For centuries before the British arrival in the 1700s, Arab merchants—and later the Portuguese and Dutch—had sailed the monsoonal courses to India and Africa, where they bought spices and slaves to sell on the Mediterranean market.
In the dry, cooler months from November to March, the prevailing winds in India come from the north. Then in May, the geophysical mechanisms of the Indian wet monsoon begin to stir.12 As the Earth’s summer tilt draws the sun’s maximum heat to the latitudes just north of the equator, the land responds more quickly to the increased solar input than does the vast thermal sink of the Indian Ocean. The temperature gradient between land and ocean steepens, awakening the cloud-bearing monsoonal winds from the south, which rush en masse into the depressurized atmosphere over the Indian continent. The winds abruptly swerve northeast, according to the rotation of the Earth, and head directly for the Bengal delta, bearing storm clouds that brood and toil over the Indo-Gangetic plain for weeks on end, powered by an atmosphere crackling with energy. Cooling as it rises over the heated earth, the moisture condenses, depositing wave after wave of torrential rains onto the parched earth in the form of cataclysmic storms. At the height of this annual meteorological drama, the Ganges River takes to imitation of its ocean neighbor: gale winds from the south turn the river current against itself, propelling storm surges over the stone ghauts, bringing down houses built too daringly near the banks, while river traders moor their craft to the shore, hoping to survive long enough to enjoy the blessings of the sharif, the monsoon crop.
Figure 4.3. A synoptic map showing the major weather systems associated with monsoonal fluctuations across South Asia. In summer, a low-pressure system over land results in the influx of moist air from the Bay of Bengal, while in the winter dry season the reverse occurs: a high-pressure system drives moisture away from the landmass. (Bin Wang, ed., The Asian Monsoon [Berlin: Springer, 2006], 145.)
But in the Tambora year 1816, these rains wouldn’t come.13 As long as the volcano’s sulfate veil cooled the Earth, inhibiting evaporation from the ocean and deflating the temperature differentiation of land and sea, the Indian monsoon lacked its vital motive fuel. In a recent climate modeling study that examined the impact of tropical volcanoes on the Asian monsoons, scientists from the National Center for Atmospheric Research found “significant” alteration in the hydrological cycle of the monsoon in the aftermath of a high-impact eruption, with the strong likelihood of “large reductions” in summer rainfall in South Asia.14
Across the breadth of the Indian Ocean, the trade winds faded, stalling thousands of ships on their westward course. Farmers on the Ganges plains waited in vain for the expected shift of winds to the south bearing ocean-fed storm clouds. For the vital sharif, timing was everything. But when to plant? No chorus of birds gave the familiar sign, levitating above the trees like flags before the arriving wind. In the absence of the seasonal rains, essential ecosystem services for the human population of the Ganges delta deteriorated rapidly. Because of the inwelling tides from the bay, the river waters were considered poor for drinking. Ordinary people relied on rainwater ponds, called “tanks,” while the affluent drew upon sweetwater artesian wells. In the absence of monsoonal replenishment, tanks and wells alike grew fetid. For desperate Bengali villagers, the failure of the monsoon represented a divine judgment. They reflected now on what terrible sins had been committed in their communities for the monsoon to forsake them so completely. Through the middle months of 1816, prayers and pujah ceremonies rang through Hindu temples all along the Ganges. The holy men consulted the stars or divined the intent of the winds from the smoke of coconut oil burned in its shell.
During this driest of Indian Mays, wild fluctuations between excessive cold and record heat saw Bengalis and Europeans alike “drop down dead in the streets.”15 This regional South Asian heat wave, in an era of general volcanic cooling, may be explained by an enhanced meridional circulation. In the northern hemisphere, Tambora’s stratospheric impact prompted an outflow of Arctic air to the temperate zones of Europe and New England, cooling the landmasses. Meanwhile, on the subcontinent of India, a counterbalancing circulation, possibly allied with a cyclical El Niño system, produced a northerly poleward flow of tropical air through Bengal, spawning localized heat spikes and drought. For the suffering Bengalis, the June rains were inexplicably scanty. Vital tributary streams across the delta dried up, threatening the rice crop. This crippling monsoonal break, lasting until late August at least, is the longest in the historical record of the Asian subcontinent. A tree-ring study of Himalayan cedars from 2007 shows an “extreme low growth” in trees all across the river basins of northern India in 1816, an indication of severe moisture stress.16
When, too late, the volcanic retardants in the atmosphere were overcome and the depressed monsoonal machine returned to furious life, the now unseasonal rains it carried were ruinously extreme. The drought of 1816 subsequently gave way to hundred-year floods, bringing a second season of failed crops, famine, and misery to Bengal. In September, typically a month of monsoonal decline, monster storms inundated the delta on a scale remarkable even in a region accustomed to seventy inches of seasonal rain. Various local disease outbreaks—designated “Bilious Fever” or simply “Malignant Sore Throat” by perplexed British doctors—took hundreds of victims. In the 59th Regiment stationed in Jessore, north of Calcutta, as many as a dozen soldiers perished daily, while the banks of the rivers across the Ganges delta were “covered at all times with the dead and the dying” from the local villages.17 All this, however, was but an overture to the main act of the Tambora climate emergency in India.
DEATH ON THE GHAUTS
As bad as 1816 had been, 1817 in Bengal began like no other year. January and February were looked forward to as months of serene weather: cold, clear nights and morning fogs rising like a curtain onto sunny days freshened by breezes from the great mountains to the north. But Tambora’s second year announced itself instead with clouds and heavy rain. The winds veered crazily from the north to the east, then to the south, bringing drenching downpours. On March 21, an unprecedented hailstorm destroyed the spring grain crop and tore up orchards of dates, bananas, and papaya all across the fragile alluvial plain.
The disease cholera had been seasonally endemic to Lower Bengal since time immemorial. Traveling the narrow coastal roads of the Sunderbans in the Bay of Bengal today, one still comes across shrines dedicated to Ola Bibi, the goddess of cholera.18 But in May 1817, when the monsoon arrived three weeks early and delivered further calamitous quantities of rain to the delta region, the perennial Bengal cholera suddenly appeared out of season, showing unusual strength and breadth. By August an unprecedented “epidemic” of the disease had spread among the Indian population. A short month later an official report declared cholera to be “raging with extreme violence” through both the Indian and European populations of Bengal but also embarking on an unprecedented outward course to the north and west, following the river.19
For the early nineteenth-century European tourist, the uncultivated riverbanks of the Ganges offered the gratifying sight of monkeys, buffalo, and occasional elephants wallowing in the mud. On the river itself water-loving lotus flowers and lilies brushed along the boat’s hull, signs of the nutrient-rich ecology of the delta. “A paradise of flowers,” was one Englishwoman’s commentary on her pleasure trip from Calcutta to Benares.20 At a bend in the river, the source of these botanical offerings might hove into view. The local ghaut—broad stone steps leading directly to the river—served as a kind of Indian town square and impressed foreigners as a grand forum of daily village life. From first light, people could be seen washing clothes and bathing, while women bore jars of water on their heads back up the steps. At the summit of the ghaut invariably stood a temple, where dedications were made to the sacred river on which all these essential activities depended.
In 1817, this vivid, public life of the ghauts was transformed by cholera into a parade of horrors. All along the Ganges River, the busy tempo of village life gave way to mourning and public immolation of the dead. In the eyes of one English traveler, a clergyman named James Statham, the cholera epidemic transformed the vibrant and picturesque river life of the Ganges into a scene from Dante’s Hell:
None but those who have witnessed the distressing sight can form an adequate picture of human misery which the ghauts afford at the time when the cholera rages. The dead and dying are all huddled together in a confused mass, and several fires are blazing at the same time, consuming the bodies of the more rich and noble, who have just died, whilst the poor creatures who are expiring feel certain that in a few minutes their bodies must share the same fate, or be hurled into the flowing stream, to become the prey of waiting alligators, or, what is worse, to be left on the beach, a prey to jackals and vultures, which infest the spot. Fresh arrivals every hour multiply the misery, as groans and cries increase, while the stench proceeding from the burning bodies, and the lurid gleams of the blazing fires reflected by the water, and giving somewhat of an unearthly appearance to the features of the suffering victims around, furnish a scene of woe which completely baffles the power of description to portray.21
An almost hysterical fear of this new, insatiable cholera—inspired by its shocking symptoms and territorial expansion—seeps through the restrained bureaucratic prose of British colonial officials. The epidemical “cholera morbus” was an “evil,” “a horrid scourge,” “an awful and desolating calamity” that “threatened to sweep off a large portion of the Native population” if some means could not be found to counteract it. It was “a malady more destructive in its effects, and more extensive in its influence than any other recorded in the annals of the country.” As a consequence of this high mortality and general panic, the cholera threatened social order, the proper running of the Indian economy, and thus company profits. “Much mischief has arisen,” complained the Board of Revenue in Calcutta, “from the great alarm of the people, their quitting their habitations and their proper pursuits.”22 Death counts were hazy, perhaps inflated, and suspiciously round. Certainly thousands, perhaps tens of thousands, died in the first season. By the 1830s, at the beginning of the global cholera panic, European estimates of Indian fatalities since 1817 would run into the millions, numbers impossible to verify.23
Figure 4.4. William Hodges, The Ghauts at Benares (1787). (Royal Academy of Arts, London; Photo: John Hammond.)
CHOLERA AND CLIMATE CHANGE
Endemic cholera in Bengal had traditionally been associated with the “winter” months of November to January, with a smaller peak in the hot, dry months of April and May. The reach of the disease remained limited, in any given year, for the simple reason that it soon ran out of fresh victims. Explanations for the unprecedented epidemic outbreak in Bengal in 1817 depend upon the putative emergence of a new strain of cholera capable of bypassing the built-up immunity of its indigenous hosts, then spreading rapidly to successive populations in various directions.24
Energized by its passage through the human intestine, the cholera microbe achieves a temporary hyperinfective state. Density of human traffic is thus essential to its continued transmission. Carrying the fatal microbe with them in their bowels, soldiers, pilgrims, and traveling merchants in 1817 dispersed the infection to unsuspecting fresh host communities north and west across India. In the following years and decades, these same human vectors, following the webs of global trade, brought cholera southeast to the Dutch Indies and East Asia, and northwest across the great trading routes of Arabia to Russia, Europe, and finally the Americas. The eventual global death toll of nineteenth-century cholera stands in the tens of millions.
The “father of British medical writers on cholera,” Calcutta physician James Jameson, traced the cause of the 1817 cholera to abnormalities in the Bengal climate in the two-year period leading to the outbreak. His classic 1820 report to the Calcutta Medical Board includes a ninety-page prefatory description of the “distempered” state of the weather beginning in late 1815. By attributing the outbreak of cholera to meteorological causes, Jameson placed himself within an established tradition of environmentalist medical theories dating back to the Hippocratic revival of the late seventeenth century. The pathogens of disease, whether produced by the noxious exhalations of the Earth or the “vitiated” state of the atmosphere, were airborne. The Indian cholera, Jameson concluded, had been spread by the strangely humid atmosphere, drought, and unusual winds of 1816–17. With its detailed synoptic data—based on one hundred survey reports from physicians across British India—Jameson’s report is a landmark in medical and public health literature and was the most quoted text by English writers on cholera for decades.
Already by the Tambora period, however, debates over the etiology of cholera were shifting. In subsequent decades, a new legion of medical theorists of cholera would come to reject Jameson’s meteorological emphasis in favor of an emerging liberal paradigm that captured the imaginations of progressive physicians and public officials through the Victorian age. Infectious disease was not “natural” but rather the product of human-created filth, of the open sewers and fetid air of slums and industrial tenements. Cholera was a social disease, an index of failures by nation-states to regulate and sanitize their colonial ports of trade and booming industrialized cities. In the pulpits of Europe, the cholera would accordingly change shape from a divine punishment for wickedness to a progressive moral calling for social reform, to provide hygienic living conditions for the newly urbanized masses.
Thus the early climatological theories of cholera rapidly lost ground during the heroic age of nineteenth-century sanitarianism. For almost a century after the apparently definitive discovery of the comma-tailed cholera bacterium in a Calcutta pond by pioneer bacteriologist Robert Koch in 1883, both clinical theory and public health policy surrounding the disease endorsed the emerging contagionist consensus, focusing on its human-to-human transmission. The fecal matter of infected persons in waterways was simply the pathogen’s mode of transit from one human host to another, which might be denied by proper investment in sanitary engineering. This dominant model of twentieth-century cholera science relegated Jameson—and a host of other pre-Victorian writers in the medico-meteorological tradition—to the dustbin of history, as embarrassing examples of the puffed-up guesswork and shamanistic fantasies that passed for medical science before the discovery of bacterial infection. Jameson’s enlightenment medical geography, with its environmentalist perspective on disease transmission, had lost the battle of ideas, which resolved by century’s end into a narrower medical-scientific practice focused on the career of pathogens, to be charted by the new techniques of laboratory biology.
Now, however, at the beginning of the twenty-first century, the medico-meteorological worldview of James Jameson has experienced a second coming. The post-Victorian bacteriological consensus on cholera has been overtaken by a new, more complex etiological paradigm that restores credibility to the early nineteenth-century model of climatic disease dynamics. Beginning in the late 1960s, epidemiologists utilizing the tools of modern molecular biology discovered the vibrio cholerae thriving in nonendemic form among the zooplankton and protozoa of a wide range of aquatic environments—from the Chesapeake Bay to the lochs of Scotland—independent of human hosts. Not the “Asiatic” cholera after all! Nor are humans the end point or object of the cholera. We are merely accidental part-time hosts to a pathogen that enjoys ancient privileges in a range of aquasystems outside the human intestine. From its ancestral origins in the deep sea, the v. cholerae resides year-round in brackish reservoirs around the globe, while its pathogenic strains are favored only within dense human communities situated at low elevation along estuarine coasts, in tropical climates characterized by high temperatures, humidity, and heavy seasonal rain.25
To succeed in this global role, the cholera bacterium possesses an unusually flexible and adaptive genetic structure highly sensitive to changes in its aquatic environment. In the monsoonal waters into which the five major rivers of the Ganges delta flow, the vibrio cholerae prospers by attachment to benign organic hosts—plankton, algae, crustaceans, and even tiny insects—where they participate in the mineralization of matter vital for the replenishment of the aquatic food web. The circulation patterns and organic life cycles of the northern Indian Ocean are unique on account of the monsoonal climatic regime. Over the Bay of Bengal in June and July, the water vapor content of the atmosphere reaches its highest level anywhere in the world. The prevailing winds reverse twice annually, churning up the waters of the bay, while the summer rains create a vast freshwater runoff from the rivers. Mile-wide phytoplankton blooms, on which great colonies of v. cholerae depend, surface at the river mouths and glide along the coast by the East India coastal current according to a distinct but variable seasonal pattern that drives the bay’s dynamic interaction with the cholera microbe.
