The Little Ice Age: How Climate Made History 1300-1850 (37 page)

Then there are the clouds. In a fascinatingly esoteric piece of research,
Hans Neuberger studied the clouds shown in 6,500 paintings completed
between 1400 and 1967 from forty-one art museums in the United
States and Europe.2 His statistical analysis revealed a slow increase in
cloudiness between the beginning of the fifteenth and the mid-sixteenth
centuries, followed by a sudden jump in cloud cover. Low clouds (as opposed to fair-weather high clouds) increase sharply after 1550 but fall again after 1850. Eighteenth- and early nineteenth-century summer
artists regularly painted 50 to 75 percent cloud cover into their summer
skies. The English landscape artist John Constable, born in Suffolk in
1776 and a highly successful painter of English country life, on average
depicted almost 75 percent cloud cover. His contemporary Joseph Mallord William Turner, who traveled widely painting cathedrals and English scenes, did roughly the same.

After 1850, cloudiness tapers off slightly in Neuberger's painting sample. But skies are never as blue as in earlier times, a phenomenon Neuberger attributes to both the "hazy" atmospheric effects caused by short
brush strokes favored by impressionists and to increased air pollution resulting from the Industrial Revolution, which diminished the blueness of
European skies.

The changes were not mere artistic fashion but probably accurate depictions of increased cloud cover. The closing decades of the Little Ice
Age brought the usual unpredictable climatic shifts. The 1820s and
1830s saw warmer springs and autumns, with 1826 bringing the warmest
summer between 1676 and 1976. In the exceptionally cold and wet August of 1829, by contrast, rain fell in the Scottish lowlands on twentyeight of the month's thirty-one days. Floods washed out bridges, ruined
crops and changed river courses. In the same year, Lake Constance in
Switzerland froze over for the first time since 1740; it would not do so
again until the exceptional cold of 1963. The winter of 1837/38 was so
harsh in Scandinavia that ice linked southern Norway with the port of
Skagen at the northern tip of Denmark, and extended far west out of
sight of land.

The 1840s perpetuated the same unpredictable swings, with several
cold winters and cool summers. Warmer summers such as 1846 saw long
periods of calm, humid weather as anticyclone after anticyclone built over
Europe. Heat waves extended from the west deep into Siberia, where the
skipper of a Russian survey vessel on the Lena River had difficulty finding
the main channel in the midst of a rapidly thawing, flooded landscape.
Tree trunks and huge lumps of peat cascaded alongside as he found his
way by listening to the roaring and rushing of the stream. Suddenly, the
flood waters carried alongside the boat a perfectly preserved mammoth head, released from the permafrost that had refrigerated it for thousands
of years since the Ice Age. The crew had just enough time to examine the
hairy cranium with stunned astonishment before it vanished into the
muddy torrent. After 1850, the climate warmed slowly and almost continually, as a new climatic player took the stage-humanity.

When an austere and humorless missionary named Samuel Marsden
landed at Oihi in New Zealand's Bay of Islands on Christmas Day, 1814,
he brought "horses, sheep, cattle, poultry, and the gospel." With a finely
developed sense of occasion, he preached to the curious Maori on the
text, "Behold I bring you glad tidings of great joy." Within half a century,
his tidings had changed Maori society and New Zealand's environment
beyond recognition.3

By 1839, Christianity had a strong foothold in the country and tribal
wars had virtually ceased. In that year, the missionaries claimed 8,760
Maori as regular churchgoers. A large part of their success came from
agriculture. In 1824, a missionary farmer named Davis had founded a
model farm at Waimate, where he introduced up-to-date English agriculture and stock-raising practices. His methods were already spreading
among the Maori when a flood of European settlers arrived, sponsored by
the New Zealand Colonization Company in London. By 1843, 11,500
Europeans lived in New Zealand, most of them in the heavily forested
North Island. The settlers pushed inland, cutting down trees and clearing
land for intensive European-style farming. The effects on Maori culture
were disastrous. Between 1860 and 1875, as more than 4 million hectares
of Maori land passed into settler ownership, thousands of hectares of forest and woodland fell before the farmer's axe.

New Zealand was not alone. Mid-nineteenth century immigration
brought tens of thousands of land-hungry farmers to Australia, North
America, South Africa, and elsewhere. The newcomers felled millions of
trees as they cleared their farmlands or provided firewood and lumber for
the growth of cities and the spreading Industrial Revolution. The longterm environmental effects for earth were profound.

A standing forest can contain as much as 30,000 metric tons of carbon
per square kilometer in its trees, and still more in its undergrowth.4
When the trees are felled, much of this carbon enters the atmosphere. Similarly, virgin grassland soils have an organic content of up to 5,000
metric tons per square kilometer, half of which may be lost within six
months when it is cultivated. One estimate has the twenty-year global
burst of pioneer agriculture and land modification between 1850 and
1870 raising the carbon dioxide level in the atmosphere by about 10 percent, even allowing for absorption by the world's oceans. Isotopic levels in
tree rings from long-living California bristlecone pines chronicle a rise in
carbon dioxide levels during these very years, at a time when the discharge from fossil fuel burning was still relatively small.

This change may have been one of the mechanisms that gradually
raised global temperatures during the late nineteenth century, ending
the Little Ice Age by about 1850. The pioneer agricultural explosion,
fueled by large-scale emigration, railroads, and ocean steamships, was
the first human activity that genuinely altered the global environment.
The second came from coal, already a significant air polluter in large
cities.

"In the third week of November, in the year 1895, a dense yellow fog settled down upon London. From the Monday to the Thursday I doubt if it
were ever possible from our windows in Baker Street to see the loom of
the opposite houses." Thus Arthur Conan Doyle keeps Sherlock Holmes
pacing restlessly at home, impatient for action, watching "the greasy,
heavy brown swirl still drifting past us and condensing to oily drops on
the window panes."5 The choking "pea soupers" of the great detective's
London came from factory chimneys and millions of coal fires pouring
smoke into still, cold air. I remember a day in the early 1960s when you
could not see your hand in front of your face, and everyone wore masks
to protect their lungs. The advent of smokeless fuels has mercifully consigned the pea souper to historical oblivion.

By the sixteenth century, England's forests had shrunk drastically in
the face of rising rural populations and an insatiable demand for construction lumber and firewood. Londoners turned to coal instead and
choked in clouds of coal smoke hovering over streets and crowded roofs. During a cold spell in January 1684, diarist John Evelyn complained of
the "fuliginous steame of the Sea Coal," which filled Londoners' lungs
with "grosse particles." King Charles II contemplated ways of abating
London's smog, which was later made worse by the Industrial Revolution
with its coal-powered steam engines, railroads, and factories.6 You can see
the nineteenth century's air pollution in the work of London artists. Sailing ships, tugs, and freighters work their way against the Thames tides in
a yellowy or pink-gray light; sunsets over Saint Paul's Cathedral glow with
a hazy red that was unknown in earlier centuries.?

Global temperature anomalies since 1860. Note the pronounced warming trend,
which accelerates after the I970s.

Industrial and domestic coal burning not only choked passers by, it released enormous concentrations of atmospheric carbon dioxide. In the
early twentieth century, the mass-produced automobile and a shift from
coal to oil and gas poured even more carbon dioxide into the atmosphere.
Antarctic and Greenland ice cores have trapped air bubbles that date back
long before the Industrial Revolution and show that carbon dioxide levels
in the atmosphere have risen sharply since 1850. Other greenhouse gases,
such as methane, have increased at the same time, as global human populations rise and engage in ever more intense rice paddy agriculture and cattle herding. It is surely no coincidence that global temperatures have
gradually and inexorably risen over the past 150 years.

The first half of the twentieth century was not unusual by Little Ice Age
standards. At first, the warming matched that between the late 1600s and
the 1730s, when full twentieth-century warmth was attained for a
decade. The eighteenth-century warm spell ended with the harsh winter
of 1739/40. Unpredictable climatic shifts continued for the next century
and three-quarters, with no significant longer term trends except for cycles of cold caused by volcanic activity. Europe also enjoyed twenty years
of warmth in the 1820s and 1830s, but again nothing like the sustained
warming that began between 1890 and 1900 and continues, with one
short interruption, to this day.

The period 1900 to 1939 saw a high incidence of westerly winds and
mild winters, characteristic of a high North Atlantic Oscillation condition. The strong pressure gradient between the Azores high and the Icelandic low helped maintain the westerlies. Air temperatures over the
globe reached a peak in the early 1940s, after decades of strong atmospheric circulation. Locations near the edge of the Arctic like Iceland and
Spitzbergen experienced warming even more extreme than that in Europe. The area of the north covered by pack ice shrank between 10 and
20 percent. Snow levels rose on northern mountains. Ships could now
visit Spitzbergen for over seven months a year, compared with three
months before 1920. The distribution and variability of rainfall altered
over much of the world as well. Northern and western Europe experienced more rainfall, as mud-bound troops on the Western Front in 1916
found to their cost. My father, who fought on the Western Front, complained in his diary of "constant rain, grey skies, and mud everywhere.
We sink into it up to our knees, sloppy dreadful stuff that rots our feet.
No one fights in either side, we just suffer silently in the wet."s

The additional precipitation continued into the 1920s and 1930s as
subpolar cyclones became larger and spread their wind circulation further into the Arctic. The warming increased the length of the growing season
in western Europe by as much as two weeks compared with the mid-nineteenth century, as the last spring frost came earlier and the first autumn
freeze later. After 1925, Alpine glaciers disappeared from valley floors up
into the mountains. Equivalent stronger westerlies over the Pacific extended the arid wind shadow of the Rocky Mountains far eastward,
bringing the disastrous droughts of the Oklahoma Dust Bowl era in the
1930s. Changes in atmospheric circulation brought much more reliable
monsoon winds to India. There were only two partial monsoon failures
in the thirty-six years between 1925 and 1960, a dramatic contrast to the
catastrophic failures of the late nineteenth century, when millions of Indian villagers perished in terrible famines.9