THE LITTLE (VOLCANIC) ICE AGE - Tambora: The Eruption that Changed the World - page 18

given up his impressions of English landscapes for experimental canvases filled entirely with
clouds and their subtle peregrinations across a muted sky. 18 The 1810s also marks Charles
Dickens's first decade of life. His deep body memory of a volcanic childhood infuses his fic-
tion: think of the “cold, biting weather: foggy withal” of A Christmas Carol . Though his adult
life and writing career date from a sunnier, warmer England (everything's relative!), his grim
weatherscapes of the 1810s have entered the popular imagination as definitive representa-
tions of the ever-cloudy, bone-chilling atmosphere of Victorian London.
For the Tamboran decade of the 1810s to warrant the title of “longest sustained cold
period” since the Middle Ages is no small thing, since the period 1250-1850 itself has long
been referred to as the “Little Ice Age.” Before 1250—during the so-called Medieval Warm-
ing Period—Englishmen produced their own wine, while the Danes set up farming colonies
on Greenland. From the late thirteenth century onward, however, such luxuries were denied
by frequent spikes of brutally cold conditions. The English pulled up their vineyards and
took to skating on the Thames. No universal glaciation occurred, of course, and bursts of
warmth, sometimes decades long, interrupted the general cooling trend. Not an “Ice Age” at
all, then—but more like an intermittent six-century cold snap.
Climate models have shown that the cool conditions of the Little Ice Age lie outside the
range of natural variability, so climatologists have been compelled to seek out its anomalous
causes. One long-popular school of thought has focused on the irregularity of solar radiation,
traceable in the historical record through accounts of sunspot activity. Although recent NASA
studies support a minor link between solar minima and cooler winters, there have long been
skeptics of a solar trigger for the Little Ice Age. 19 The renowned climatologist Alan Robock,
among others, has shown that fluctuations in sunspot activity have little impact on global
climate on decadal, let alone centennial, scales. 20 According to Robock, as well as a 2012 pa-
leoclimatological study in the Canadian Arctic and Iceland, responsibility for launching the
Little Ice Age lies instead with a spasm of major volcanic eruptions in the late thirteenth cen-
tury, possibly beginning with a massive tropical eruption in 1258 (precise location again “un-
known”). This concentrated sequence of volcanic blasts in the late 1200s altered the baseline
conditions of global climate by a degree or more, beyond the threshold at which colder tem-
peratures became self-reinforcing through expansion of the Arctic ice pack: a classic climate
change feedback loop.
Individually, volcanoes of the magnitude that sustained the Little Ice Age have the capa-
city to influence climate for two to three years, until their aerosol cloud washes from the at-
mosphere. Volcanoes erupting in clusters, however—as they did in the thirteenth century and
in the Tambora period of the early nineteenth century—achieve a cumulative chilling power
over global climate by virtue of the slow thermal recovery of the world's oceans, which con-
tinue to depress temperatures for a decade or more after the volcanic dust of any one eruption
has vanished from the atmosphere. 21 Thus regular eruptions during the 1250-1850 period
reinforced the initial cooling events. Six centuries after the 1258 Great Unknown, with glob-
al volcanic activity on the wane and temperatures on the upswing, the celebrated Krakatau
eruption, which grabbed world attention in 1883, thus stands as a last hurrah, or encore, of
the Little “Volcanic” Ice Age.
In the chilling case of the volcanic 1810s, the global ocean-atmospheric system had not
yet recovered from the cooling effect of the 1809 Unknown event when the colossal eruption
of Tambora occurred. The aftermath of that eruption, spanning the second half of the decade,