2. Sunspot cycles, volcanic anomalies, and summer temperature variations in the seventeenth century.
The number of sunspots observed and recorded by European astronomers (top) shows the Maunder Minimum (1643–1715), in which fewer sunspots appeared in seventy years than appear in a single year now. Measurements of volcanic deposits in the polar icecap (the ‘Ice-Volcanic Index’) reveal a peak in the 1640s. Both phenomena show a striking correlation with lower summer temperatures in the northern hemisphere.
The changed weather conditions in the Pacific Ocean during this period emerge starkly from two anomalies recorded in historical sources. On the one hand, the coastal province of Guangdong in southern China suffered more typhoon landfalls between 1660 and 1680 than at any other time in recorded history.43 On the other hand, the voyages of galleons sailing from Acapulco in Mexico to Manila in the Philippines took longer than in any other period. In the first and last decades of the seventeenth century the crossing took an average of 80 days (a few took only 50 days), but between 1640 and 1670 the average duration rose to over 120 days (and three took over 160). Some ships never arrived: of the 11 galleons known to have sunk or run aground before reaching Manila during the seventeenth century, nine did so between 1639 and 1671. The return voyage from Manila to Acapulco also took much longer: the average duration rose from 160 to well over 200 days, and the longest voyages ever recorded (240 days, or eight months) took place in the 1660s. Nothing except a major shift in wind pattern could explain such a dramatic change. Diego de Villatoro, a crown official who had made the voyage twice, saw the connection clearly. In a memorial written in 1676 he noted sadly that ‘now we consider a voyage from the Philippines to Acapulco that takes less than seven months to be good’, and he perceptively ascribed the longer duration ‘to a change in the monsoons’.44
Villatoro, of course, lacked the expertise either to blame this change on the increased frequency of El Niño activity or to associate El Niño with reduced solar activity, weaker Asian monsoons and increased volcanic activity. But we now know that in ‘normal’ years, when easterly winds prevail, the Pacific stands some 24 inches higher off the Asian than off the American coast, whereas in El Niño years, when westerly winds prevail, those levels reverse. The movement of such a huge volume of water places enormous pressure on the edges of the earth's tectonic plates around the Pacific periphery, where the most violent and most active volcanoes in the world are located, and this may trigger a spate of eruptions.45 If this hypothesis is true, it creates a deadly cycle:
• Reduced solar energy received on earth lowers temperatures, which increases the risk of more, and more severe, El Niño events.
• El Niño events may trigger volcanic eruptions around the Pacific that throw sulphur dioxide into the stratosphere, which further reduces the solar energy received on earth.
• El Niño activity becomes twice as likely after a major volcanic eruption.
Whatever the exact connections between these natural phenomena (and not all scientists agree), the mid-seventeenth century certainly experienced both an unusual spate of earthquakes, fireball fluxes, volcanic eruptions and El Niño episodes, and a drastic reduction in sunspot activity, the weakest monsoons and some of the lowest global temperatures recorded in the past few centuries.
Climate and Crops
So what? To a sceptic, ‘global cooling’ that amounts to a fall of only one or two degrees Celsius in mean summer temperatures, and a modest glacier advance, may seem insignificant; but that is to think in linear terms. On the one hand, the mean global temperature has shown remarkable stability over the last six millennia: the difference at the equator between the ‘Medieval Optimum’ (the hottest temperatures recorded until the late twentieth century) and the Little Ice Age was probably less than 3°C. A change of even one degree is thus highly significant. On the other hand, in the northern hemisphere, home to the majority of humankind and site of most of the wars and revolutions of the seventeenth century, solar cooling reduces temperatures far more than at the equator, in part because increased snow cover and sea-ice reflect more of the sun's rays back into space. The extension of the polar icecaps and glaciers in the mid-seventeenth century would thus have reduced mean temperatures in northerly latitudes dramatically.
A recent ‘model’ of the probable global climate in the later seventeenth century shows significantly colder weather in Siberia, North Africa, North America and northwest India; colder and drier weather in central China and Mongolia; and cooler and less stable conditions in the Iberian Peninsula, France, the British Isles and Germany. As already noted, these same areas – the Russian and Ottoman empires in Eurasia; the Ming and Qing states in East Asia; and the dominions of Philip IV, Charles I, Louis XIV and Ferdinand II in Europe – reported not only cooler weather in the 1640s and 1650s but also a significant number of extreme weather events and serious political upheavals. The former should cause no surprise: an overall decline in mean temperatures is normally associated with a greater frequency of severe weather events – such as flash floods, freak storms, prolonged droughts and abnormal (as well as abnormally long) cold spells. All of these climatic anomalies can critically affect the crops that feed the people.
In the ‘temperate zone’, which stretches roughly from 30 to 50 degrees of latitude, crop yields suffer disproportionately from a cold spell during germination, a drought in the early growing season and a major storm just before harvest. To take a single example, a Gazetteer from Zhejiang in eastern China reported that ‘When on the 13th day of the 5th moon in 1640 the fields were inundated, those who had planted out on the 12th or earlier had no disaster once the flood had subsided, but those who planted on or after the 13th’ lost everything.46 An unseasonable frost could prove equally disastrous. In areas of wet rice cultivation, a fall of 0.5°C in the average spring temperature prolongs the risk of the last frost by 10 days, while a similar fall in the average autumn temperature advances the risk of the first frost by the same amount. Either event suffices to kill the entire crop. Even without frosts, a fall of 2°C during the growing season – precisely the scale of global cooling in the 1640s – reduces rice harvest yields by between 30 and 50 per cent, and also lowers the altitude suitable for wet-rice cultivation by about 1,300 feet. Likewise, in cereal-growing regions, a fall of 2°C shortens the growing season by three weeks or more, diminishes crop yields by up to 15 per cent, and lowers the maximum altitude at which crops will ripen by about 300 feet. Drought, too, destroys harvests by depriving crops of the precipitation they required. As a Chinese manual of agriculture, published in 1637, warned: ‘All rice plants die if water is lacking for ten [consecutive] days.‘47
Extreme weather could also destroy crops indirectly. Excessive rain might allow rodents to multiply. In Moldavia in 1670 ‘myriads of mice’ not only ate ‘all they found in the vegetable gardens’ but also, ‘climbing up the trees, ate all the fruit, finishing them up; and to end the job’ they ‘finished the wheat in the field’.48 Drought favoured locusts. In 1647 the Moldavian nobleman Miron Costin reported that ‘about the time of the year when people pick up their sickles to harvest the wheat’, he and some companions were on the road and ‘suddenly noticed a cloud towards the south’:
We thought it was a rainstorm until we were suddenly hit by the locust swarm, coming at us like a flying army. The sun disappeared immediately, veiled by the blackness of these insects. Some of them flew high, at three or four metres, while others flew at our level, or even right above the ground … They flew around us without fearing anything … It took an hour for a swarm to pass, and then after an hour and a half there came another, and then another, and so on. It lasted from noon till dusk. No leaf, no blade of grass, no hay, no crop, nothing remained.49
In latitudes north of the ‘temperate zone’, where the growing season is shorter, the impact of climate change on crop cultivation increases. First, it radically reduces yields. In Manchuria, with a total of only 150 frost-free days in even ‘good’ years, a
fall of 2°C in mean summer temperature reduces harvest yields by a stunning 80 per cent. In Finland, the growing season even in ‘normal’ years is the shortest compatible with an adequate harvest so that even a single summer night's frost can kill an entire crop. Seventeenth-century Finland saw 11 crop failures (compared with only one in the eighteenth century).50 Second, global cooling increases the frequency of harvest failure in northerly latitudes.
• In the ‘temperate zone’, if early winters or summer droughts occur with a frequency of P = 0.1, the harvest will fail once every 10 years, and two consecutive harvests will fail once every 100 years. If, however, early winters or summer droughts occur with a frequency of P = 0.2, the harvest will fail once every 5 years (double the risk) while two consecutive harvests will fail every 25 years (quadruple the risk).
• In latitudes north of the ‘temperate zone’, each fall of 0.5°C in mean summer temperatures decreases the number of days on which crops ripen by 10 per cent, doubles the risk of a single harvest failure, and increases the risk of a double failure six-fold.
• For those farming 1,000 feet or more above sea level, a fall of 0.5°C in mean summer temperatures increases the chance of two consecutive failures 100-fold.
Climate and Calories
In densely populated parts of the early modern world, whether sub-boreal, temperate or tropical, most people relied on a single crop, high in bulk and in carbohydrates, known as a ‘staple’. Cereals (wheat, rye, barley and oats) formed the principal staple in Europe, northern India and northern China. Rice occupied the same role in Monsoon Asia, maize in the Americas, and millet in upland India and Sub-Saharan Africa. The economic allure of staple crops is almost irresistible to farmers. An acre under cereals feeds between ten and twenty times as many people as an acre devoted to animal husbandry; furthermore, the same amount of money usually bought 10 pounds of bread but only 1 pound of meat. An acre planted with wet-rice yields up to 6 tons of food – three times as much as an acre of wheat or maize and sixty times as much as an acre devoted to animal husbandry. Not surprisingly, therefore, according to a Chinese textbook printed in 1637, ‘70 per cent of the people's staple food is rice’, while in Europe, cereals likewise provided up to three-quarters of the total calorie intake of every family (not only in the form of bread but also as a ‘filler’ for soups and as the basic ingredient for beer and ale).51
Steven Kaplan has rightly insisted on the ‘tyranny’ of popular dependence on staple crops – cereals, rice, maize or millet, depending on the region – in the pre-industrial world. In Europe,
Cereal-dependence conditioned every phase of social life. Grain was the pilot sector of the economy; beyond its determinant role in agriculture, directly and indirectly grain shaped the development of commerce and industry, regulated employment, and provided a major source of revenue for the state, the church, the nobility, and large segments of the Third Estate … Because most of the people were poor, the quest for subsistence preoccupied them relentlessly. No issue was more urgent, more pervasively felt, and more difficult to resolve than the matter of grain provisioning. The dread of shortage and hunger haunted this society.52
‘Shortage and hunger’ could arise in three distinct ways. First, throughout the early modern world, food accounted for up to half the total expenditure of most families, and so any increase in staple prices caused hardship because most families had little spare cash and soon faced the risk that they could not feed themselves. Second, spending more on food left little or nothing with which to purchase other goods, leading to a fall in demand: this meant that many non-agricultural workers lost their jobs and reduced the wages received by the rest – that is, their income fell just as their expenditure rose. Third, since the impact of harvest failure on the price of cereals is non-linear, any shortfall in the harvest reduced the food supply geometrically and not arithmetically. Suppose that
• In a normal year a European farmer sowed 50 acres with grain and harvested 10 bushels an acre, a total of 500 bushels. Of this, he needed 175 bushels for animal fodder and seed corn and 75 bushels to feed himself and his family – a total of 250 bushels – leaving 250 for the market.
• If bad weather reduced his crop by 30 per cent, the harvest would produce only 350 bushels yet the farmer still needed 250 of them for his immediate use. The share available for the market therefore dropped to 100 bushels – a fall of 60 per cent.
• But if bad weather reduced crops by 50 per cent, the harvest would produce only 250 bushels, all of them needed by the farmer, leaving virtually nothing for the market.
This non-linear correlation explains why a 30 per cent reduction in the grain harvest often doubled the price of bread, whereas a 50 per cent reduction quintupled it. It also explains why, if the harvest failed for two or more consecutive years, starvation almost always followed.
Steven Kaplan concluded his study of famines in eighteenth-century France by suggesting that this cruel calculus ‘produced a chronic sense of insecurity that caused contemporaries to view their world in terms that may strike us as grotesquely or lugubriously overdrawn’. However, a study by Alex de Waal of the Darfur famine of 1984–5 in East Africa rejected the notion of ‘overdrawn’ where harvest shortfalls are concerned because, even today, failures can ‘cross a threshold of awfulness and become an order of magnitude worse’. Not only do large numbers of people die, so does their entire way of life.53 De Waal identified three characteristics of these ‘landmark famines’:
• First, they force those affected to use up their assets, including investments, stores and goods. Although a family might choose to go hungry for a season in order to preserve its ability to function as a productive unit (for example by keeping back grain to feed its livestock or to use as seed corn instead of eating it all), it can rarely maintain that strategy for a second, let alone a third year. Two or three successive harvest failures therefore leave victims permanently destitute.
• Second, prolonged starvation also forces those affected to use up their social claims (‘entitlements’). A hungry family may refrain from begging for assistance from other individuals and institutions for a short period, but once again it can rarely maintain that strategy for long. If a large number of families suddenly becomes destitute, it may cripple and even destroy the communities in which they live.
• Third, as communities cease to be viable, some families migrate. Initially, migration may form a reasonable ‘coping strategy’ in a famine because, although the migrants necessarily abandon both their assets and their ‘entitlements’ by leaving their local community, those who survive can return to their homes and their previous way of life when conditions improve. Prolonged dearth, however, will sever the links with the world they have left and thus, according to De Waal, lead to the ‘mortality’ of their entire way of life.
Calories and Death
Each day, every human needs to consume at least 1,500 calories to maintain her or his basic metabolic functions and to resist infection. Pregnant women and those who earn their living by physical labour require at least 2,500 calories. Few people in the early modern period were so lucky: during the Italian plague of 1630–1, hospital records show that each patient received a daily ration of half a kilo of bread, a quarter of a kilo of meat (probably in a stew), and half a litre of wine – a daily intake of scarcely 1,500 calories (and one seriously deficient in vitamins). Even in the ‘normal’ years of the seventeenth century, the average Frenchman consumed barely 500 calories more than his basic metabolic requirement, and the average Englishman barely 700 calories more.54
Two short-term ‘safety mechanisms’ help humans to adjust to malnutrition. We may cut back on energy demands (working more slowly, resting longer); and, as body weight declines, we can get by with fewer calories to sustain the basic metabolism (and the reduced physical activity). Nevertheless, in the long term, even a small reduction in our daily calorific intake can have dramatic consequences. A decrease of one-fifth, from 2,500 to 2,000 calories, halves our
ability to work efficiently because the body's basic metabolism still requires 1,500 calories. In the case of a pregnant woman, a similar reduction imperils the health of both mother and child. Furthermore, a weight loss of 10 per cent reduces energy by about one-sixth, but a weight loss of 20 per cent reduces energy by about one-half, and if a woman or man loses 30 per cent of their normal body weight, blood pressure falls and the ability to absorb nutrients fails.
In this weakened condition, any additional stress on the body, such as disease, usually proves fatal – and, amid the social disruption normally associated with famine, infectious diseases often spread rapidly – while cold and damp further weaken those who are starving. According to a report on an Indian famine in the nineteenth century: ‘The most common termination of life in those debilitated by famine was diarrhoea or dysentery, aggravated by damp and exposure … Cold and damp had a most detrimental effect upon the starving poor, and those in a physically reduced condition from chronic insufficiency of food.‘55 Observers in the seventeenth century described the same fatal decline. According to Yang Dongming, a government official and philanthropist in central China:
All beings are physically the same, alike in their intolerance of cold. Those people with old, tattered clothes … go nearly naked in the dead of winter, their hair dishevelled and feet bare and their teeth chattering; crying out and terrified … Being solitary, they have no place to go … [and] falling snow covers their bodies. At this point, their organs freeze and their bodies stiffen like pieces of wood. At first they are still able to groan. Gradually they cough up phlegm. Then, their lives are extinguished.
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