Climate and environment in historyof study. For example, Sweda (Sueda) Tatsuo and Takeda Shin’ichi used disks and cores from
about 200 medieval and early modern cypress logs from the Kiso Mountains to estimate winter
temperatures going back to 1177 ce.^12 Finally, many recent studies are based on lake varves, that
is, annual sediment layers. Cores of 430,000 years and more than 150,000 years, respectively,
have been recovered from Lake Biwa in Shiga prefecture and Lake Suigetsu in Fukui prefec-
ture.^13 The cores were originally used to calibrate radiocarbon curves, a topic that need not
concern us here. But they have also proved gold mines for paleoclimatologists, who have made
extensive use of their sedimentary and geochemical features and the fossil pollen and diatoms
they contain to reconstruct past temperatures and extreme events such as floods and tsunami.^14
Whether based on historical or scientific evidence, all of these studies show that climatic trends
in Japan were generally similar to those in other temperate parts of the Northern Hemisphere.^15
To summarize, the Paleolithic period, which encompassed the Last Glacial Maximum (very
roughly 24,000 bce), was cold. The following Jōmon period was generally warm. A dramatic
cooling occurred around 1000 bce. After a brief return to warm, wet conditions in the late cen-
turies bce, cooling recommenced. Sakaguchi refers to the ensuing period, c. 250–700 ce, as the
“Kofun Cold Stage,” which was not only cold but also wet.^16 This was followed by Japan’s
version of the Medieval Warm Period, sometimes called the Little Hypsithermal Period.^17
Summer temperatures increased dramatically after 700, with frequent droughts.^18 Winter tem-
peratures remained low until about 900, after which mild winters became the norm. The Medi-
eval Warm Period came to an end in Japan around 1300. Between 1300 and around 1600,
summers remained generally warm, but winters became harsher. Different authors report slightly
different results, but it is clear that particularly cold periods occurred in the mid- fourteenth
century (roughly 1330s–1360s) and again in the first half of the sixteenth (1520s–1550s). Around
1600, Japan entered the Little Ice Age. As in Europe, temperatures were generally, but not uni-
formly, cold. Again, authors differ in their conclusions, but the coldest conditions seem to have
occurred at the end of the seventeenth century and in the early nineteenth century (1820s–1830s).
During these phases, winters were severe with much snowfall, particularly on the Sea of Japan
side of Honshu. Summers were cool, particularly in the northern part of the country, and fre-
quently rainy. Interestingly, 1816, known elsewhere as the “year without a summer” because of
cooling caused by the massive 1815 eruption of Mt. Tambora in the Dutch East Indies, was
wholly unexceptional in Japan. On the other hand, an earlier “year without a summer” occurred
in 1783 following the eruptions of Mt. Asama in Japan and the Laki fissure in Iceland; the cold
weather significantly exacerbated the ongoing Tenmei Famine (named for the calendar era) in
northeastern Japan.^19
Mention of the Tenmei Famine provides a convenient segue. It is one thing to establish the
“facts” of Japan’s climate, or more broadly physical environment, and how they have changed
over time. It is quite another to say how such physical parameters relate to the course of Japanese
history. It is to this topic we now turn.
Environment as actor
It is fair to say that until recently, most discussions of human- natural relations in premodern
Japan were concerned primarily with the influence of natural conditions upon society—a way of
thinking nowadays decried as “environmental determinism.” An early example is the philo-
sopher Watsuji Tetsurō’s book Fūdo (Climate and Culture), published in 1935.^20 Watsuji classi-
fied human cultures on the basis of their physical environment as pastoral, desert, or monsoon.
Some of Watsuji’s ideas were later adopted and expanded by environmental archaeologist Yasuda
Yoshinori. In Yasuda’s view, the monsoons and forests of Asia, including Japan, fostered the