Climate Change in Japanese History and Prehistory:
A Comparative Overview

Bruce L. Batten, Ph.D.

Professor of Japanese History, J. F. Oberlin University
3758 Tokiwa-machi, Machida-shi, Tokyo 194-0294, Japanbruce@obirin.ac.jp

Harvard University
Edwin O. Reischauer Institute of Japanese Studies
Occasional Papers in Japanese Studies
Number 2009-01
January 2009©2009 Bruce L. Batten1This paper is the revised and updated version of a presentation given at the Fifth Annual
Michael P. Malone Memorial Conference, “Japan’s Natural Legacies: Bodies andLandscapes Realized, Idealized, and Poisoned,” at Big Sky, Montana on October 1-5, 2008.
The conference was hosted by the Department of History and Philosophy, Montana State
University, and sponsored by the College of Letters and Science, Montana State University;
University of Notre Dame; Harvard University Center for the Environment; and Edwin O.
Reischauer Institute of Japanese Studies, Harvard University.

2

I. Introduction

It is difficult to think of a contemporary issue as important or widely discussed as global
warming. Scarcely a day goes by without another story about melting glaciers, shrinking
icecaps, torrential storms, or devastating droughts. Debate has shifted from whether or notglobal warming is real, or whether or not we are to blame; most observers now agree that itis, and we are. The question is no longer what is happening or why; it is what we can
expect if present trends continue and what, if anything, we can do to slow or halt them.
Although popular accounts sometimes give the impression that climate wasrelatively stable before people began burning fossil fuels, that is far from the case: itchanged frequently, and for largely natural reasons. Global temperatures fluctuate on scalesof 20,000-100,000 years as the result of changes in the earth’s orbit (the so-called
Milankovich cycles). Climate is also affected by natural changes in the atmosphericconcentration of greenhouse gases and aerosols, in solar radiation, in volcanic activity, and1

in oceanic and atmospheric circulation.1 Some of these variations, such as those inatmospheric composition, operate at truly geological scales2; others, such as those caused
by volcanic eruptions, are measured at most in years.
During the lifetime of our species, perhaps the most striking example of climatechange was the long, bumpy transition from the Last Glacial Maximum or LGM(23,000-18,000 BP3) to the warm, stable conditions of the Holocene or recent period(roughly the last 10,000 years).4 This early instance of global warming was what madeagriculture – and civilization as we know it – possible.5 As this example suggests, in

1Committee on Surface Temperature Reconstructions for the Last 2,000 Years, Board on
Atmospheric Sciences and Climate, Division on Earth and Life Studies, National ResearchCouncil of the National Academies, ed., Surface Temperature Reconstructions for the Last
2,000 Years (Washington, D.C.: The National Academies Press, 2006), 25-26, 99-105;
Robert B. Dunbar, “Climate Variability During the Holocene: An Update,” in The Way theWind Blows: Climate, History, and Human Action, ed. Roderick J. McIntosh, Joseph A.
Tainter and Susan Keech McIntosh (New York: Columbia University Press, 2000).
2Regarding extremely long-term changes in atmospheric composition and their effect on
the evolution of life on earth, see Peter Douglas Ward, Out of Thin Air: Dinosaurs, Birds,
and Earth’s Ancient Atmosphere (Washington, D.C.: J. Henry Press, 2006), and Under a
Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Mean for
Our Future (New York: Smithsonian Books / Collins, 2007).
3
Before Present; “present” customarily refers to 1950 CE.
4
On yet earlier climatic shifts of equal magnitude and the role they played in the human
exodus from Africa, see Stephen Oppenheimer, The Real Eve: Modern Man’s Journey outof Africa, revised paperback ed. (New York: Carroll & Graf Publishers, 2004).
5
According to William James Burroughs, Climate Change in Prehistory: The End of theReign of Chaos (Cambridge: Cambridge University Press, 2005), reduced climatic
variability, rather than increased temperature per se, was the key factor.
2premodern times climatic change could have an important, if not determining, influence onsociety – unlike today, when the influence tends to run the other way. (Another conclusion
to be drawn is that climatic change, even global warming, is not necessarily a bad thing: it
all depends.)
During the past few decades, historians and archaeologists in Europe and North
America have paid increasing attention to the role of climate change in human history.6
Ultimately, this trend reflects scholars’ concern about contemporary environmental andclimatic issues, but it has also been facilitated by spectacular new scientific data from ocean
sediments, ice cores, and other sources. (Needless to say, most of the research responsible
for the new data has also been spurred by current concerns over climate change.)
Detailed climatic reconstructions for Japan are also available, but so far have failed
to attract widespread attention from historians. True, Japanese archaeologists are quick to

6See, for example, McIntosh, Tainter and McIntosh, eds., The Way the Wind Blows;
Burroughs, Climate Change; Brian Fagan, The Little Ice Age: How Climate Made History
1300-1850 (New York: Basic Books, 2000); Fagan, The Long Summer: How Climate
Changed Civilization (New York: Basic Books, 2004); and Fagan, The Great Warming:
Climate Change and the Rise and Fall of Civilizations (New York: Bloomsbury Press,
2008).
3

acknowledge the importance of climate for prehistoric cultures in the archipelago. And forthe historic period, the crop failures and famines of the seventeenth through nineteenth
centuries are routinely blamed on Little Ice Age conditions. But there have been few
systematic attempts to examine the larger patterns in Japanese history from a climatic
perspective.7 This is unfortunate, not just because of the contemporary relevance of the
topic, but because (as we shall see) the Japanese case offers some interesting comparisonsand contrasts with what is known from other regions of the world.
The purpose of the present study is to summarize what is known about Japan’s
climatic history during the period of human occupation, and to offer some tentative
speculations about the role of climate in Japanese history and prehistory from an explicitly
comparative perspective. I begin with an overview of the various methodologies that have
7

Important exceptions include Yutaka Sakaguchi, “Warm and Cold Stages in the Past 7600
Years in Japan and Their Global Correlation — Especially on Climatic Impacts to the
Global Sea Level Changes and the Ancient Japanese History —,” Bulletin of the
Department of Geography, University of Tokyo 15 (1983): 1-31; Sakaguchi, “Kako 8000
nen no kikō henka to ningen no rekishi” (Climate Change and Human History during the
Past 8000 Years), Senshū jinbun ronshū (Senshū University Essays in the Humanities) 51(1993): 79-113; William S. Atwell, “Volcanism and Short-Term Climatic Change in East
Asian and World History, ca. 1200-1699,” Journal of World History 12, no. 1 (2001):
29-98; and William Wayne Farris, “Famine, Climate, and Farming in Japan, 670-1100,” inHeian Japan, Centers and Peripheries, ed. Mikael S. Adolphson, Edward Kamens, andStacie Matsumoto (Honolulu: University of Hawai‘i Press, 2007), 275-304.
4

been used to reconstruct past climates in Japan. This is followed by a new, eight-stage
periodization of the Japanese past based on climatic criteria. For each era, I provide a brief
description of major climatic trends and discuss some of the important historical questions
they suggest when viewed from a comparative, global perspective.

II. Methodologies

How can we reconstruct past climates? The most reliable information, of course, comesfrom instrumental data, but this is generally unavailable for premodern times. In theabsence of instrumental data, past temperatures or climatic trends can be reconstructedusing proxies. These fall into two major types: information gleaned from historical sources(historical proxies), and that based on measurements of various physical quantities (natural
proxies).

5

1. Instrumental Data
Until recently, it was believed that instrument-based meteorological observations in Japanbegan as part of the Meiji government’s modernization program, specifically with theestablishment of a meteorological station in Hakodate, Hokkaido, in 1872. (Observations inTokyo began three years later, in 1875.) However as Demarée and others have recently
shown, Dutch observers in Nagasaki were making instrument-based observations as earlyas 1819, over half a century before the Hakodate station was established.8 That said, it

8

Gastone Demarée, “Some XVII-th and XVIII-th Centuries Dutch MeteorologicalObservations at Deshima, Nagasaki (Japan), Seen as a Complement to Japanese
Climatological Historical Documents,” in Proceedings of the International Conference on
Climate Change and Variability – Past, Present and Future –, ed. Takehiko Mikami(Hachioji-shi, Tokyo: International Geographical Union Commission on Climatology /Department of Geography, Tokyo Metropolitan University, 2000), 107-13; T. Mikami, M.
Zaiki, G.P. Können, and P.D. Jones, “Winter Temperature Reconstruction at Dejima,
Nagasaki Based on Historical Meteorological Documents During the Last 300 Years,” inProceedings of the International Conference on Climate Change and Variability, 103-6;
G.P. Können, M. Zaiki, A.P.M. Baede, T. Mikami, P.D. Jones, and T. Tsukahara,“Pre-1872 Extension of the Japanese Instrumental Meteorological Observations Series
Back to 1819,” Journal of Climate 16 (2003): 118-31; Tsukahara Tōgo, Zaiki Masumi,
Matsumoto Keiko, and Mikami Takehiko, “Nihon no kiki kansoku no hajimari: Dare ga,
dono yō na jōkyō de hajimeta no ka / Beginning of Instrumental MeteorologicalObservation in Japan: By Whom, in What Context, and Its Transitional Nature,” Gekkan
chikyū (Earth Monthly) 27, no. 9 (2005): 713-20; Zaiki Masumi, Tsukahara Tōgo, Mikami
Takehiko, and Matsumoto Keiko, “Nihon ni okeru 19 seiki ikō no kokishō kiroku to sonokikōgaku teki igi / Old Instrumental Records in Japan since 19th Century and Its
Climatological Significance,” Gekkan chikyū 27, no. 9 (2005): 706-12; and M. Zaiki, G.P.
Können, T. Tsukahara, P.D. Jones, T. Mikami, and K. Matsumoto, “Recovery of
Nineteenth-Century Tokyo/Osaka Meteorological Data in Japan,” International Journal of
Climatology 26 (2006): 399-423.
6

remains true that prior to the nineteenth century we are entirely without instrumental dataon Japanese weather and must rely on proxies such as those discussed below.

2. Historical Proxies
Japan has a voluminous historical record going back to about 700 CE (and containingreferences, not always reliable, to still earlier times). Descriptions of weather conditions arefound in sources ranging from poetry collections (e.g., Man’yōshū; Collection of Ten
Thousand Leaves) to official chronicles (e.g., Nihon shoki; Chronicles of Japan). However,by far the best information comes from diaries. For the old capital of Kyoto, we havearistocratic diaries going back to the ninth century. For the rest of the country, diary
coverage is relatively limited until the Edo period (1600-1867), when literacy became
widespread and warriors, clerics, and even commoners throughout the country began totake note of their daily activities.9 Japanese diary entries, whether written by Heian

9

For a more or less comprehensive index of fifteenth-century and later diaries and travelaccounts useful for purposes of climatic reconstruction, see Yamamoto Takeo, Fukaishi
Kazuo, Maejima Ikuo, Mizukoshi Mitsuharu, Yoshimura Minoru, Shitara Hiroshi,
Urushibara Kazuko, Hayashi Yōsei, and Kurosaka Hiroyuki, “Kokikō fukugen ni riyō
7aristocrats or nineteenth-century schoolchildren, routinely begin with a laconic comment
about the weather, so taken in sum, these sources constitute a very precious resource for the
climate historian.
Since about 1970, Japanese researchers have used a variety of techniques toreconstruct past climate from historical proxies, particularly for the well-documented Edo
period. The following discussion, which is by no means exhaustive, introduces some of theprincipal methodologies employed.

a. Phenological data from dates of cherry-viewing
Anyone who has lived in Japan will be familiar with the custom of “cherry-blossom
viewing.” This custom is an ancient one and many old diaries, particularly from Kyoto,note the dates of the flower viewing parties held each spring on the day or days when the

dekiru nikki, ryokōki nado no chiiki betsu mokuroku (I)” (Regionally-Organized Catalogueof Diaries, Travelogues, Etc., That Can Be Used to Reconstruct Past Climates, Part 1),
Kikōgaku, kishōgaku kenkyū hōkoku (Climatological and Meteorological Research Reports)
5 (1982): 60-82; and Yamamoto, Fukaishi, Maejima, Mizukoshi, Yoshimura, Shitara,
Urushibara, Hayashi, and Kurosaka, “Kokikō fukugen ni riyō dekiru nikki, ryokōki nado nochiiki betsu mokuroku (II)” (Regionally-Organized Catalogue of Diaries, Travelogues, Etc.,
That Can Be Used to Reconstruct Past Climates, Part 2), Kikōgaku, kishōgaku kenkyūhōkoku 8 (1983): 54-59.
8

cherries were in full bloom. As we all know from experience, warm weather in early springcauses flowers to bloom early, while cool weather tends to delay their appearance. Annual
variations in the date of blossom viewing parties at a given location, then, presumablyreflect differences in mean spring temperatures. Arakawa, Yamamoto, and most recently
Aono and Omoto have used this approach to reconstruct climatic trends in Kyoto.10 Aono’s
work, in particular, is noteworthy for its use of comparative modern data to calculate mean

10

H. Arakawa, “Climatic Changes as Revealed by the Blooming Dates of the Cherry
Blossoms at Kyoto,” Journal of Meteorology 13 (1956): 599-600; Yamamoto Takeo,“Rekishi no nagare ni sou Nihon to sono shūhen no kishō no hensen” (Meteorological
Change in Japan and Vicinity over the Course of History), Chigaku zasshi / Journal of
Geography 76 (1967): 115-41; Yamamoto, “On the Climate Change in XV and XVICenturies in Japan,” Geophysical Magazine 35, no. 2 (1971): 187-206; Yamamoto, “On the
Nature of the Climatic Change in Japan since the ‘Little Ice Age’ Around 1800 A.D.,”
Journal of the Meteorological Society of Japan 49 (1971): 789-812; Yamamoto, “On the
Nature of the Japanese Climate in So-Called ‘Little Ice Age’ Between 1750 and 1850,”
Geophysical Magazine 35, no. 2 (1971): 165-85; Yamamoto, Kikō no kataru Nihon norekishi (Japanese History as Told by Climate), Soshiete bunko (Society Library), (Tokyo:
Soshiete, 1976); Y. Aono and Y. Omoto, “Variation in the March Mean Temperature
Deduced from Cherry Blossoms in Kyoto since the 14th Century,” Journal of Agricultural
Meteorology 48, no. 5 (1993): 635-38; Aono and Omoto, “Sakura no kaika shiryō ni yoru
11 seiki ikō no Kyōto no kion no suitei” (Temperature Trends in Kyoto since the EleventhCentury Based on Records of Cherry Blooms), Nōgyō kishō (Agricultural Meteorology) 49,
no. 4 (1994): 263-72; Aono, “Sakura no kaika no kisetsu suii” (Seasonal Trends of Cherry
Blooms), Kikō eikyō, riyō kenkyūkai kaihō (Bulletin of Research Group on Climate
Influence and Use) 19 (2001): 15-20; and Aono, “Kyōto no kokiroku o mochiita sakura no
kaikabi no fukugen to kion e no yomikae” (Reconstruction of Cherry Bloom Dates Using
Old Records from Kyoto and Their Conversion into Temperatures), in Kikōgaku torekishigaku no sōgū (Higashi Ajia kankyōshi, kikō hendō kokusai shinpojiumu hōkokusho)(The Encounter of Climatology and History [Proceedings of the International Symposium
on East Asian Environmental History and Climate Change]), ed. Tsukahara Tōgo, Mikami
Takehiko, and Naitō Tomoko (Kobe: Tsukahara Tōgo, 2003), 27-41.
9

March temperatures for Kyoto going back more than 1200 years to 801 CE. Climaticreconstruction based on the dates of cherry blooms has also been attempted for Kanazawa(by Kawamura) and Tokyo (by Aono) but only since the early nineteenth century,
presumably for lack of suitable earlier data.11

b. Snow ratio and snow cover
Diaries also contain useful information on precipitation, including snowfall. Yamamoto,
Maejima, and others have computed the “snow days ratio” (the ratio of snowy days to totaldays with precipitation during the winter months) for various sequences of years (again,mainly for Kyoto).12 The basic idea is that higher snow ratios reflect colder winter11

Aono, “Climatic Change in March Temperature Deduced from Phenological Record for
Flowering of Cherry Tree in Tokyo since the Late 18th Century,” Bulletin of Osaka
Prefectural University, Series B 50 (1998): 11-19; Takeshi Kawamura, “Estimation of
Climate in the Little Ice Age Using Phenological Data in Japan,” in Proceedings of theInternational Symposium on the Little Ice Age Climate, ed. T. Mikami (Tokyo: Editorial
Committee of LIAC Proceedings, Department of Geography, Tokyo Metropolitan
University, 1992), 52-57.
12
Yamamoto, “Rekishi no nagare ni sou Nihon to sono shūhen no kishō no hensen”;
Yamamoto, “On the Climate Change”; Yamamoto, “On the Nature of the Climatic
Change”; Yamamoto, “On the Nature of the Japanese Climate”; Yamamoto, Kikō nokataru; Yamamoto, “Kikō to rekishi” (Climate and History), in Kikō to bunmei, kikō torekishi (Climate and Civilization, Climate and History), ed. Suzuki Hideo and Yamamoto
Takeo (Tokyo: Asakura shoten, 1978), 71-144; Yamamoto, “A.D. 1-1600 nen no Nihon
10temperatures. Another rough guide to mean winter temperatures is the date of first or lastappearance of snow cover on selected hills or mountains. This approach was used by
Yamamoto for Mt. Kurakake in Yamanashi, northern Honshu, and by Yaji and Misawa for
Mt. Iwaki in Aomori, also northern Honshu.13

c. Freezing of lakes and rivers
Also indicative of winter temperatures are the dates of freezing or thawing of rivers or lakes.
Yamamoto used records of freezing of the Yodo and Saho Rivers in the Kansai area toargue for the existence of cold winters in the early eighth century.14 However, by far thebest source of information on winter freezes comes from Lake Suwa in Nagano, for which a(seinan Nihon Kyōto-shi) no kikō henka” (Climate Change in Japan [Kyoto City,
Southwest Japan], A.D. 1-1600), Kishō kenkyū nōto (Meteorological Research Notes) 147(1983): 627-39; Ikuo Maejima, “Some Remarks on the Climatic Conditions of Kyoto
During the Period from 1474 to 1533 A.D,” Geographical Reports of Tokyo Metropolitan
University 1 (1966): 103-11; and Ikuo Maejima and Yoshio Tagami, “Climatic Change
During Historical Time in Japan — Reconstruction from Climatic Hazard Records,”
Geographical Reports of Tokyo Metropolitan University 21 (1986): 157-71.
13
Yamamoto, “On the Nature of the Climatic Change” and “On the Nature of the Japanese
Climate”; Yaji Masataka and Misawa Meiko, “Tenpō kikin zengo no kikō ni kansuru
ichikōsatsu / Some Notes on the Japanese Climates before and after the Tempo Lean Years,
1828-1844,” Science Reports of the Yokohama National University: Section II, Biologicaland Geological Sciences 28 (1981): 91-108.
14
Yamamoto, “On the Climate Change,” “On the Nature of the Climatic Change,” “On the
Nature of the Japanese Climate,” and “A.D. 1-1600 nen no Nihon.”11

near-continuous historical record (kept by officials at the lakeside Suwa Shrine) exists fromthe fifteenth century. Dates of freezing and “omiwatari” (literally, “divine crossing”), an
unusual buckling of surface ice caused by geothermal circulation in the lake, have beenused by Yamamoto and others to estimate mean winter temperatures for the region.15 Most
recently, Mikami and coworkers used statistical comparisons with modern data to produce
an absolute curve of mean winter temperatures going back to 1444 (Figure 1).16

15

Arakawa Hidetoshi, “5 seiki ni wataru Suwako omiwatari no kenkyū / On Five
Centuries of Freezing Dates of Lake Suwa (36º N, 138º E) in the Central Japan,” Chigaku
zasshi / Journal of Geography 63, no. 4 (1954): 1-8; Arakawa, “Fujiwara Sakuhei hakaseikō ‘Suwako keppyō kijitsu narabi ni omiwatari kijitsu nippyō’ ni tsuite / Fujiwhara on Five
Centuries of Freezing Dates of Lake Suwa (36º N, 138º E) in the Central Japan,” Chūō
kishōdai kenkyū jihō / Journal of Meteorological Research 6, no. 5 (1954): 138-46;
Yamamoto, “On the Climate Change” and “A.D. 1-1600 nen no Nihon”; Minoru Tanaka
and Masatoshi M. Yoshino, “Re-Examination of the Climatic Change in Central Japan
Based on Freezing Dates of Lake Suwa,” Weather 37 (1982): 252-59.
16
T. Mikami and Y. Tsukamura, “The Climate of Japan in 1816 as Compared with an
Extremely Cool Summer Climate in 1783,” in The Year without a Summer? World Climate
in 1816, ed. C.R. Harrington (Ottawa: Canadian Museum of Nature, 1992), 462-75;
Mikami Takehiko and Ishiguro Naoko, “Suwako ketsuei kiroku kara mita kako 550 nenkanno kikō hendō” (Climate Change during the Past 550 Years as Seen from Records ofFreezing of Lake Suwa), Kishō kenkyū nōto (Meteorological Research Notes) 191 (1998):
73-83; Mikami, “Quantitative Climatic Reconstruction in Japan Based on Historical
Documents,” Kokuritsu rekishi minzoku hakubutsukan kenkyū hōkoku / Bulletin of the
National Museum of Japanese History 81 (1999): 41-50; Mikami, “Summer and WinterTemperature Reconstructions in Japan,” PAGES News 10, no. 3 (2002): 17-18; Mikami,“Kako 1000 nenkan no kikō hendō to 21 seiki no kikō yosoku / Global Climatic Variations
for the Last 1000 Years and Their Prospects in Future,” Chiri zasshi / Journal of
Geography 114, no. 1 (2005): 91-96.
12Figure 1. December-January Temperatures at Lake Suwa,
1444-1870 (Reconstructed) and 1891-1995 (Observed)
Source: Takehiko Mikami, “Quantitative Climatic Reconstruction in Japan Based on Historical Documents,”
Kokuritsu rekishi minzoku hakubutsukan kenkyū hōkoku / Bulletin of the National Museum of Japanese
History 81 (1999): 47. Used with permission.

d. Precipitation frequency
Summer temperatures have also been estimated on the basis of comparisons with modern
data. The earliest work in this area was, again, by Yamamoto17, but the best recent research

17

Yamamoto, “On the Climate Change,” “On the Nature of the Climatic Change,” and“On the Nature of the Japanese Climate.”
13

Figure 2. July Temperatures in Tokyo, 1721-1995
Source: Takehiko Mikami, “Quantitative Climatic Reconstruction in Japan Based on Historical Documents,”
Kokuritsu rekishi minzoku hakubutsukan kenkyū hōkoku / Bulletin of the National Museum of Japanese
History 81 (1999): 45. Used with permission.

is by Mikami. Modern instrumental data show a negative correlation between frequency ofsummer precipitation and mean summer temperature in Tokyo; Mikami combined this datawith information on rainfall from Edo-period sources to produce an absolute curve ofsummer temperatures going back to 1721 (Figure 2).18

18

Mikami, “Climate Variations in Japan During the Little Ice Age – Summer Temperature
Reconstructions since 1771 –,” In Proceedings of the International Symposium on the Little
Ice Age Climate, ed. Mikami, 176-81; Mikami, “Nikki tenkō kiroku kara suitei shita
14

3. Natural Proxies
As interesting as these techniques may be, they retain the limitations of the sources on
which they are based. Historical data are subjective and increasingly fragmentary thefarther we go back in time, disappearing for all practical purposes around 700 CE. For moreobjective, complete data on historical periods, and for any data at all on earlier periods, wemust turn to physical evidence, that is, to natural proxies. Some of the more importantnatural proxies that have been used by to reconstruct Japanese climate are described below.

a. Pollen
As in many other countries, the first scientific studies of past climates in Japan made use offossil pollen. Although various researchers have contributed, by far the most importantbody of work is by Sakaguchi, who (like Mikami) worked at Tokyo Metropolitan

shōhyōki kōhan no kaki onhendō / Summer Temperature Variabilities in Japan
Reconstructed from Diary Weather Records During the Little Ice Age,” Chiri zasshi /Journal of Geography 102, no. 2 (1993): 144-51; Mikami, “Long Term Variations ofSummer Temperatures in Tokyo since 1721,” Geographical Reports of Tokyo Metropolitan
University 31 (1996): 157-65; Mikami, “Quantitative Climatic Reconstruction”; Mikami,“Summer and Winter”; and Mikami, “Kako 1000 nenkan.”
15

Figure 3. Temperature Reconstruction
Based on Pine Pollen from Ozegahara (Full Sequence)
Source: Redrawn from Sakaguchi Yutaka, “Kako 8000 nen no kikō henka to ningen no rekishi” (Climate
Change and Human History during the Past 8000 Years), Senshū jinbun ronshū (Senshū University Essays in
the Humanities) 51 (1993): 86.

University for most of his career. In an important series of papers, Sakaguchi analyzed
pollen from a 450 cm peat column collected from a pit dug at Ozegahara Moor in 1973.19

19

Except as otherwise noted, information in this and the following paragraph come from
Yutaka Sakaguchi, “Warm and Cold Stages in the Past 7600 Years in Japan and Their
Global Correlation — Especially on Climatic Impacts to the Global Sea Level Changes andthe Ancient Japanese History —,” Bulletin of the Department of Geography, University ofTokyo 15 (1983): 1-31. Other important works by the same author are: “Climatic
Variability During the Holocene Epoch in Japan and Its Causes,” Bulletin of the
Department of Geography, University of Tokyo 14 (1982): 1-27; “Nihon no senshi, rekishi
jidai no kikō: Ozegahara ni kako 7600 nen no kikō henka no rekishi o saguru” (Climate inJapanese Prehistory and History: Searching at Ozegahara for the History of Climate Change
during the Past 7,600 Years), Shizen (Nature) 39, no. 5 (1984): 18-36; Ozegahara no
shizenshi (Natural History of Ozegahara), Chūkō shinsho (New Books from Chūō Kōron),No. 928 (Tokyo: Chūō kōronsha, 1989); and “Kako 8000 nen no kikō henka to ningen no
rekishi” (Climate Change and Human History during the Past 8000 Years), Senshū jinbun
16

(Ozegahara, the largest raised bog in Japan, is located approximately 150 km north ofTokyo in the mountains of Gunma.)
For his analysis, Sakaguchi sliced the column in sections of 2 cm in thickness
before extracting and identifying the enclosed pollen grains. He obtained 14C dates atintervals of 50 cm and calibrated them using the known dates of four intercalated layers oftephra (volcanic ash). The total record extended back about 8000 years. Sakaguchi based
his analysis on pine pollen, which fell into two types, spherical (Diploxylon) andhemispherical (Haploxylon). The Haploxylon pollen were ascribed to Pinus pumila and P.
parviflora, two cold-adapted species currently found on the slopes of nearby Mt. Shibutsu.
The average proportion of Haploxylon pollen among total pine pollen across the entire
interval was 8%. Samples containing more than 8% were interpreted by Sakaguchi as
representing cooler intervals, and those with less as representing warmer ones (Figures 3, 4).
The general validity of this approach was confirmed by the tendency of Haploxylon pollen
frequencies to fluctuate in parallel with those of pollen from cold-loving conifer genera

ronshū (Senshū University Essays in the Humanities) 51 (1993): 79-113.
17

such as Abies (fir), Picea (spruce), and Tsuga (hemlock). According to Sakaguchi, averageannual temperatures at Ozegahara varied on the order of ±3 ºC over the period inquestion.20 To this day, Sakaguchi’s work on the Ozegahara peat column remains unique inJapan for its chronological depth and completeness.

Figure 4. Temperature Reconstruction
Based on Pine Pollen from Ozegahara (Last Two Millennia)
Source: Redrawn from Sakaguchi Yutaka, “Kako 8000 nen no kikō henka to ningen no rekishi” (Climate
Change and Human History during the Past 8000 Years), Senshū jinbun ronshū (Senshū University Essays in
the Humanities) 51 (1993): 86.

20

Sakaguchi, “Kako 8000 nen,” 80.
18

b. Tree rings
Important information about past climates can also be obtained from tree rings.
Dendroclimatological studies in Japan have been based on physical characteristics such as
width and density of tree rings, as well as chemical characteristics such as the ratio of stablecarbon isotopes. All of these are affected in complex ways by climate and other variables.
Let us begin with isotope ratios.

Figure 5. Temperature Reconstruction
Based on δ13C from Yaku Island Cedar
Source: Redrawn from Kitagawa Hiroyuki, “Yakusugi ni kizamareta rekishi jidai no kikō hendō” (Climate
Change during the Historical Period as Inscribed in Yaku Cedars), in Rekishi to kikō (History and Climate), ed.
Yoshino Masatoshi and Yasuda Yoshinori, vol. 6 of Kōza: Bunmei to kankyō (Lectures on Civilization andEnvironment) (Tokyo: Asakura shoten, 1995), 50.

19

Probably the best-known dendroclimatological study in Japan is that by Kitagawa
and Matsumoto, who examined carbon isotopes in giant Japanese cedars (sugi;
Cryptomeria japonica) on Yaku Island to the south of Kyushu. These authors measured
δ13C, that is, the ratio of 13C to 14C expressed in parts per thousand (‰), from tree cellulose
in modern cedars on the island. They found that δ13C was highly dependent on elevation,and hence average annual temperature. (Specifically, δ13C increased as temperatures went
down and decreased as they went up.) Although other factors, including precipitation,
physiology, and light intensity, also affect δ13C values, these were fairly uniform across thearea of study and could safely be ignored. Kitagawa and Matsumoto then applied theobserved relationship between δ13C and temperature to a core taken from a giant ancientcedar growing on the same island, measuring δ13C for every tenth successive tree-ring tocreate a reconstruction of temperatures fluctuations in Yaku over the past two millennia(Figure 5).21 Although the time depth in this study is significantly less than in Sakaguchi’s

21

Kitagawa Hiroyuki, “Yakusugi ni kizamareta rekishi jidai no kikō hendō” (Climate
Change during the Historical Period as Inscribed in Yaku Cedars), in Rekishi to kikō, ed.
Yoshino and Yasuda, vol. 6 of Kōza: Bunmei to kankyō (Lectures on Civilization andEnvironment) (Tokyo: Asakura shoten, 1995), 47-55; H. Kitagawa and E. Matsumoto,20

palynological work, the resolution is much better because tree rings are annual and can becounted with minimal risk of error.

Figure 6. Temperature Reconstruction
Based on Kiso Cypress Tree-Ring Widths
Source: Tatsuo Sweda, “Dendroclimatological Reconstruction for the Last Sub-Millennium in Central Japan,”
Terrestrial, Atmospheric and Oceanic Sciences 5, no. 3 (1994): 440. Use authorized by publisher.

“Carbon-Isotope Variation within Trunks of Japanese Cedars from Yakushima Islands,
Southern Japan,” Geochemical Journal 29, no. 2 (1995): 149-53; Kitagawa and Matsumoto,“Climatic Implications of δ13C Variations in a Japanese Cedar (Cryptomeria japonica)
during the Last Two Millennia,” Geophysical Research Letters 22, no. 16 (1995): 2155–58;
and Kitagawa and Matsumoto, “Yakusugi nenrin no tanso dōitaihi hendō kara suitei sareru
kako 2000 nenkan no kikō hendō” (Climate Change during the Past 2000 Years as Inferredfrom Carbon Isotope Variations in Tree Rings of Yaku Cedars), Kishō kenkyū nōto
(Meteorological Research Notes) 191 (1998): 1-13.
21

There is also some Japanese research based on physical characteristics of tree rings
such as width and density. Of particular note are several papers by Sweda, who studied
Japanese cypress (hinoki; Chamaechyparis obtusa) trees from Kiso in the mountains ofcentral Honshu. Sweda first established an empirical correlation between wintertemperature and width of tree-rings in modern cypress. Then he went on to apply theseresults to disks and cores from about 200 medieval and early modern logs lying in the sameforest. The result was a detailed temperature curve going back to 1177 CE (Figure 6).22
Similar studies, with somewhat less impressive results, have been published by Kobayashi
and coworkers for fir (Abies) and by D’Arrigo and coworkers for oak (Quercus).23 Another22

Sweda, Tatsuo. “Dendroclimatological Reconstruction for the Last Sub-Millennium inCentral Japan,” Terrestrial, Atmospheric and Oceanic Sciences 5, no. 3 (1994): 431-42.
Also see Sweda, “Little Ice Age Climate of Central Japan as Revealed by
Dendroclimatological Reconstruction,” in Proceedings of the International Symposium on
the Little Ice Age Climate, ed. Mikami, 34-39; and Tatsuo Sweda and Shinichi Takeda,“Construction of an 800-Year-Long Chamaecyparis Dendrochronology for Central Japan,”
Dendrochronologia 11 (1994): 79-86. Sweda refers to the trees in his sample as “Japanesecedar,” but here I use the more standard English translation to avoid confusion with sugi or
Cryptomeria.
23
O. Kobayashi, Y. Abe, and T. Sweda, “Construction of a Tree-Ring-Width Chronology
for the Ishizuchi Range, Japan,” in Proceedings of the International Conference on Climate
Change and Variability, ed. Mikami, 127-32; R.D. D’Arrigo, D.K. Yamaguchi, G.C. Wiles,
G.C. Jacoby, A. Osawa, and D.M. Lawrence, “A Kashiwa Oak (Quercus dentata)
Tree-Ring Width Chronology from Northern Coastal Hokkaido, Japan,” Canadian Journalof Forestry Research 27 (1997): 613-17.
22

approach is represented by the research of Yasue and coworkers, who found that thedensity of spruce (Picea) tree-rings correlated positively with summer temperatures andused this result to calculate temperatures in northern Japan going back to 1750.24

c. Borehole temperatures
To the layman, possibly the most bizarre scientific approach to climatic reconstruction
involves the measurement of actual temperatures at different depths in boreholes.25 The
basic idea is that temperature at a given depth is a function of surface temperature, thermal
conductivity distribution, and heat flow from below. If measured temperatures differ fromwhat would be predicted based on these factors, it is argued, the deviation reflects
variations in past surface temperatures, whose effects have propagated downward in
proportion to elapsed time. As even its practitioners admit, borehole temperature analysis
24

Koh Yasue, Ryo Funada, and Yoshihiro Nobori, “Tree-Ring Data Obtained by
Densitrometric Analysis as Indicators for Past Climate Reconstruction in Northern Japan,”in Proceedings of the International Conference on Climate Change and Variability, ed.
Mikami, 121-26.
25
Note that this technique differs from the others discussed here in that “temperature itself
is being measured, not a proxy for temperature”: Committee on Surface Temperature
Reconstructions for the Last 2,000 Years, Surface Temperature Reconstructions for theLast 2,000 Years, 78.
23

has rather poor resolution – centuries, as opposed to decades or years. Nonetheless, it canbe useful in confirming long-scale climatic trends.
In Japan, borehole temperatures have been the subject of several studies. Perhaps
the most ambitious was by Gotō and coworkers, who recorded temperatures within a 920 m
borehole at Karasuma on the southeastern coast of Lake Biwa, central Honshu, and thenused the data to reconstruct surface temperature trends for the past 3000 years (Figure 7).
Although the analysis produced credible results (showing, among other things, effects dueto the Medieval Warm Period and the Little Ice Age), the researchers found somewhat
greater temperature disparities than they expected. They attributed this to tectonic
movement, specifically earthquakes that had alternately drowned and exposed the locationof the borehole relative to the surface of the lake.26 In addition to the work by Gotō andcoworkers, a number of rather crude reconstructions going back to 1500 have been

26

Shusaku Goto, Hideki Hamamoto, and Makoto Yamano, “Climatic and Environmental
Changes at Southeastern Coast of Lake Biwa over Past 3000 Years, Inferred from Borehole
Temperature Data,” Physics of the Earth and Planetary Interiors 152, no. 4 (2005): 314-25.
The invocation of tectonic movement seems somewhat strained to me.
24published online by Taniguchi.27

Figure 7. Temperature Reconstruction Based on
Borehole Temperatures at Lake Biwa (Last Two Millennia)
Source: Redrawn and modified from Shusaku Goto, Hideki Hamamoto, and Makoto Yamano, “Climatic andEnvironmental Changes at Southeastern Coast of Lake Biwa over Past 3000 Years, Inferred from Borehole
Temperature Data,” Physics of the Earth and Planetary Interiors 152, no. 4 (2005): 321.

d. Lake sediments
Other data related to paleoclimates comes from sediment cores from lakes, which can bedated by counting annual varves or, more typically, by AMS (accelerator mass

27

Available in the Borehole Temperatures and Climate Reconstruction Databasemaintained by Shaopeng Huang at the University of Michigan:
http://www.geo.lsa.umich.edu/climate/ASI.html
25spectrometry) radiocarbon. Researchers record geochemical or sedimentological features ofthe sample at various depths, and then attempt to relate observed variations to climaticfluctuations, such as temperature, in the past. In Japan, some of the more illuminating
studies using lake cores were by Fukusawa for Lake Suigetsu (Fukui) and Lake
Mikurigaike (Toyama), both on the Sea of Japan coast of Honshu, and by Adhikari andKumon for Lake Nakatsuna (Nagano) in the mountains of central Honshu.28

e. Other
Other proxies abound, for example variations in annual bands in coral, which were used by

28

Fukusawa Hitoshi and Yasuda Yoshinori, “Suigetsuko no sairyū taisekibutsu dekenshutsu sareta kako 2000 nenkan no kikō hendō” (Climate Change during the Past 2000
Years as Recovered from Fine-Grained Sediments from Lake Suigetsu), Rekishi to kikō, ed.
Yoshino and Yasuda, 26-46; Fukusawa, “Koshō nenkō taisekibutsu ni yoru chūsei ondanki
no kikō hendō to tozan katsudō no kaishi / Onset of Mountain Climbing Caused by Climate
Warming since the Medieval Warm Period: Investigation from Varved Lacustrine
Sediments,” Gekkan chikyū 27, no. 9 (2005): 665-72; and D.P. Adhikari and F. Kumon,“Climatic Changes During the Past 1300 Years as Deduced from the Sediments of Lake
Nakatsuna, Central Japan,” Limnology 2, no. 3 (2001): 157-68. Also see Megumi Kato,
Osamu Fujiwara, and Yoshinori Yasuda, “Non-Glacial Varved Sediments in Lake
Tougou-Ike, Western Japan and High Resolution Relationships between Global Climate
and Sea-Level Changes During the Holocene,” in Proceedings of the International
Conference on Climate Change and Variability, ed. Mikami, 267-70; and Fujio Kumon,
Rie Ohno, Toshikazu Sakai, Sanae Sakami, and Jun’ichi Sakai, “Climatic Records During
the Last 40,000 Years in Lake Nojiri, Central Japan,” in Proceedings of the International
Conference on Climate Change and Variability, ed. Mikami, 41-44.
26

Morimoto and coworkers to calculate ancient sea surface temperatures for the waters
around Kikai Island, south of Kyushu.29 But enough on methodology; it is now time to turnto the results of the various studies described above and what they imply for human history
in Japan.

III. Climate in Japanese History and Prehistory

After such a lengthy buildup, it is perhaps anticlimactic to report that most studies
conducted in Japan, whether using historical or natural proxies, simply confirm what isalready known about global climatic trends.30 Of course, there are many short-term

29

Maki Morimoto, Hajime Kayanne, Nobuyuki Yonekura, Osamu Abe, Ching-Hsin Chiu,
and Eiji Matsumoto, “Sea Surface Temperature around 6000 Years Ago: Reconstructed by
Coral Annual Bands from Kikai Island in the Subtropical Northwestern Pacific,” inProceedings of the International Conference on Climate Change and Variability, ed.
Mikami, 29-33.
30
On which, see: Richard Alley, The Two-Mile Time Machine: Ice Cores, Abrupt Climate
Change, and Our Future (Princeton, N.J.: Princeton University Press, 2003); Burroughs,
Climate Change in Prehistory; Dunbar, “Climate Variability”; Committee on Surface
Temperature Reconstructions for the Last 2,000 Years, Surface Temperature
Reconstructions for the Last 2,000 Years; William F. Ruddiman, Plows, Plagues &Petroleum: How Humans Took Control of Climate (Princeton: Princeton University Press,
2005); and Ruddiman, Earth's Climate: Past and Future, 2d ed. (New York, NY: W.H.
Freeman and Co., 2008).
27

discrepancies. But what concern us here are the long-term trends, and for these, theJapanese results are similar to those from other temperate regions of the northernhemisphere. This is reassuring, because otherwise one would either have to doubt thevalidity of the Japanese studies, or look for an explanation of why Japan should be
climatically unique.
What, then, are these broad, long-term features? At the crudest level, the northernhemisphere experienced rapid warming after about 14,500 BP, followed by a brief return tonear-glacial conditions between roughly 12,900 and 11,600 BP (the so-called Younger
Dryas), followed in turn by a long period of relative climatic stability (the Holocene)
lasting until the present. The term “relative” is important, because the Holocene has also
been punctuated by several climatic fluctuations, minor in absolute terms, but important to
the people living through them. Among the more recent events were periods of marked
cooling during the first millennium BCE and the first millennium CE; the so-called Medieval
Warm Period; the Little Ice Age; and the recent period of anthropogenic warming.
Sakaguchi, based on his observations of these and other trends in the pollen samples

28

from Ozegahara, proposed a climatic periodization of Japanese prehistory and history.31
Although his scheme has much to recommend it, some modifications are called for in orderto highlight the complex interaction between climate and human society.
For purposes of the following discussion, I have divided the period of humanhabitation in Japan into eight stages. These stages are based primarily on climatologicaltrends, which are not unique to Japan. However since the purpose of the discussion is tohighlight the interplay between climate and society in the Japanese islands, I have taken
Japanese archeological and historical developments into account when that seemed
appropriate. For each stage, I give a brief description of climatic conditions and then offersome speculations on how these may or may not relate to important social or historical
trends. In the end, as shall be seen, we are left with many questions and few definite
answers.

31

See works cited in note 19, above.
29

1. 35,000–14,500 BCE
The first human occupation of the Japanese islands took place during the last Ice Age.
Local temperatures were considerably lower than today, as attested by pollen and otherfossil evidence. (Another potential, although largely unexploited, source of information is
the 40,000-year sequence of varves from Lake Suigetsu on the Sea of Japan coast.32)
Although popular works often convey the impression that the Japanese islands wereconnected to the Asian continent by “land bridges” during the Ice Age, this idea appears to
be false except for the case of Hokkaido.33 An important corollary is that the first people toarrive in the other Japanese islands must have done so by boat, as was the case in Australia,
which was settled as early as 60,000 BP.
The date of initial human occupation of Japan has been the object of much scholarly

32

H. Kitagawa J. van der Plicht, “A 40,000 Year Varve Chronology from Lake Suigetsu,
Japan: Extension of the Radiocarbon Calibration Curve,” Radiocarbon 40 (1998): 505-16.
33
S.-C. Park, D.-G. Yoo, C.-W. Lee, and E.-I. Lee, “Last Glacial Sea-Level Changes andPaleogeography of the Korea (Tsushima) Strait,” Geo-Marine Letters 20, no. 2 (2000):
64-71; Kawada Shin’ichirō, “Nihon rettō no ho’nyūrui” (Mammals of the JapaneseArchipelago), in Nihon rettō no shizenshi (Natural History of the Japanese Archipelago), ed.
Kokuritsu hakubutsukan (National Museum) (Tokyo: Tōkai daigaku shuppankai [Tōkai
University Press], 2006), 94-97.

30

confusion, thanks to a series of spectacular frauds perpetrated in the late twentieth century
by Fujimura Shin’ichi, a rogue amateur archaeologist. At present, the oldest actual humanremains are the femur and humerus of a child of 6 or 7 that were discovered at
Yamashita-chō Cave in Okinawa in 1986.34 These have been radiometrically dated to
32,000 BP, which in terms of actual calendar years probably works out to a few thousand
years earlier. (Currently, calibration for 14C dates extends back only to 26,000 BP.) A date inthis general range makes very good sense in the context of what is known about the spreadof anatomically modern humans in other parts of Asia and Oceania.35 Note that this wasconsiderably before the LGM, meaning that humans first came to the islands before sea
levels reached their minimum.

34

Baba, “Nihon rettō no kyūsekki jin,” in Nihon rettō no shizenshi, ed. Kokuritsu
hakubutsukan, 263-75; Mark J. Hudson, “Japanese Beginnings,” in A Companion to
Japanese History, ed. William M. Tsutsui (Malden, MA: Blackwell Publishing, 2007),
15-17.
35
Research on this topic continues to expand exponentially; for a good recent overview(based largely on genetic research) see Oppenheimer, The Real Eve.
31

2. 14,500-1000 BCE
As noted above, the LGM came to an end around 18,000 BP. Temperatures oscillated andthen warmed very dramatically around 14,500 BP (the “Bølling warming”). Then, between
12,900 and 11,600 BP, there was a return to near-glacial conditions (the “Younger Dryas”)
when a massive burst of freshwater from Lake Agassiz temporarily shut down the Gulf
Stream. (Lake Agassiz, in what is now eastern Canada, had formed from the melting of theLaurentide Ice Sheet.) Following the resumption of thermohaline circulation in the Atlantic,
temperatures rose again until around a second pulse of meltwater from Lake Agassiz caused
them to plummet between 8200 and 8000 BP. This so-called “8.2 ka event” was followed by
the Holocene “climatic optimum” or “hypsithermal” of around 6000 BP, when averagetemperatures in the Northern hemisphere were several degrees above contemporary
levels.36 In Japan, according to Sakaguchi’s pollen data, the hottest period was between

36

On these changes, see Fagan, The Long Summer; and Burroughs, Climate Change in
Prehistory. Quite recently, a team of scientists has argued that the onset of the Younger
Dryas resulted from extraterrestrial impacts in North America. This does not necessarily
negate the “meltwater” hypothesis, as the impacts are said to have destabilized theLaurentide Glacier. See R.D. Firestone, A. West, J.P. Kennett, L. Becker, T.E. Bunch, Z. S.
Revay, P. H. Schultz, T. Belgya, D.J. Kennett, J.M. Erlandson, O.J. Dickenson, A.C.
Goodyear, R.S. Harris, G.A. Howard, J.B. Kloosterman, P. Lechler, P.A. Mayewski, J.
32

5871 and 4360 BCE.37 (Sea levels also rose as the result of global warming and isostatic
effects, culminating in the so-called “Jōmon Transgression” of c. 6500-5000 BCE.38) In
general, the climate remained warm until about 1000 BCE, although the pollen data forJapan show another brief cold spell between 2587 and 2409 BCE.39
This period under discussion corresponds archaeologically to the Jōmon culture,
distinguished from the Paleolithic culture that preceded it by the appearance of fixed
settlements and what is apparently the world’s oldest pottery. The origins of the pottery area mystery, but that aside, most studies of the Jōmon culture link its emergence to climaticchanges, specifically to early Holocene warming. Many older works give the impressionthat the Jōmon culture appeared around 10,000 BCE, but that is not correct; the first pottery

Montgomery, R. Poreda, T. Darrah, S.S. Que Hee, A.R. Smith, A. Stich, W. Topping, J.H.
Wittke, and W. S. Wolbach, “Evidence for an Extraterrestrial Impact 12,900 Years Ago
That Contributed to the Megafaunal Extinctions and the Younger Dryas Cooling,”
Proceedings of the National Academy of Sciences 104, no. 41 (2008): 16016-21; and D.J.
Kennett, J.P. Kennett, A. West, C. Mercer, S.S. Que Hee, L. Bement, T.E. Bunch, M.
Sellers, and W.S. Wolbach, “Nanodiamonds in the Younger Dryas Boundary SedimentLayer,” Science 323, no. 5910 (2009): 94.
37
Sakaguchi, “Warm and Cold Stages,” 11-16; Sakaguchi, “Kako 8000 nen,” 87-89. Notethat these dates give an impression of greater accuracy than exists: Sakaguchi’s data by nomeans have an annual resolution.
38
Junko Habu, Ancient Jomon of Japan, Case Studies in Early Societies (Cambridge:
Cambridge University Press, 2004), 45-46.
39
Sakaguchi, “Warm and Cold Stages,” 11-16; Sakaguchi, “Kako 8000 nen,” 87-89.
33

actually dates from around 14,500 BCE. Habu, in her discussion of this problem, notes that
this date places the emergence of the Jōmon culture before the end of the last Ice Age,nullifying any explanation based on climatic warming per se. Habu herself thinks thatclimatic oscillation was the deciding factor.40 Presumably, rapid oscillations in climate
would have placed unusual demands on human society.
For comparative purposes, it is perhaps worthwhile to note that the transition fromthe Ice Age to the Holocene is associated with the “Neolithic Revolution” in the core areasof Eurasia. In the Near East, which is best known, the initial warming after the LGM wasfollowed by the emergence of fixed settlements and early experiments with thedomestication of animals and plants. Then, during the Younger Dryas, arid conditions
forced a subsistence crisis that could only be solved by a full-scale conversion toagriculture.41
The Jōmon people in Japan must also have faced difficult times during the Younger40

Habu, Ancient Jomon, 26-42.
See Fagan, The Long Summer; Burroughs, Climate Change in Prehistory; and Peter
Bellwood, First Farmers: The Origins of Agricultural Societies (Malden, MA: Blackwell
Pub., 2005).
41

34

Dryas, but they did not turn to agriculture, possibly because the natural environment was sorich, or possibly for lack of suitable cultigens. Rice and other cereals (with the possible
exception of barnyard millet) are not native to Japan, and while remains of these and othercultigens have been found at various Jōmon sites42, it is not clear (at least to me) whether
any of these finds go back as far as the Younger Dryas. Their presence later in the periodshows that the Jōmon people had at least some contacts with the Asian mainland and werefamiliar with the idea of agriculture. That they never went further than limited horticulture
is perhaps further evidence for the basic richness of their environment, making the Jōmon
the ultimate “affluent foragers.”43

3. 1000 BCE-250 CE
Like the previous stage, this one too contains some dramatic fluctuations. On the whole,
42

Gary W. Crawford, “East Asian Plant Domestication,” in Archaeology of Asia, ed.
Miriam T. Stark (Malden, MA: Blackwell Publishing, 2006), 77-95. Also see Habu,
Ancient Jomon, 70-72; and Keiji Imamura, Prehistoric Japan: New Perspectives on Insular
East Asia (Honolulu: University of Hawai‘i Press, 1996), 106-9. Imamura believes thatbuckwheat may be indigenous, although the consensus would seem to favor an origin insouthern China.
43
Shuzo Koyama and David H. Thomas, Affluent Foragers, Senri Ethnological Studies,No. 9 (Osaka: National Museum of Ethnology, 1981).
35

though, it represents a transition between the warm conditions of the post-glacial Jōmon era
and the extremely cold conditions of the succeeding stage. According to Fagan, a reduction
in solar activity led to widespread cooling in the first millennium BCE.44 For Japan, thestory is best told by the pollen record at Ozegahara.45 First, there was a sudden, dramatic
cooling around 1000 BCE, described by Sakaguchi as “the most important climatic turning
point of the past 8000 years.”46 Next, there was a return to warm, wet conditions fromaround 580 to 100 BCE. Finally, between 100 BCE and 250 CE there was a gradual
deterioration of climate forming a prelude to the very cold conditions that prevailed after
250 CE.
In terms of human society, this stage corresponds to the Yayoi period, which was
initiated by the arrival of agricultural colonists from the Asian continent.47 Food
production fueled rapid population growth among the immigrants, who replaced or

44

Fagan, The Long Summer, 197-98.
Sakaguchi, “Warm and Cold Stages,” 16-17; Sakaguchi, “Kako 8000 nen,” 87-89.
46
Sakaguchi, “Kako 8000 nen,” 88.
47
The literature on this topic is, of course, immense, but one essential reading in English isMark J. Hudson, Ruins of Identity: Ethnogenesis in the Japanese Islands (Honolulu:
University of Hawai‘i Press, 1999).
45

36

absorbed the indigenous Jōmon foragers throughout much of the archipelago. Agriculture
also facilitated surplus accumulation, social stratification, and the concentration of politicalpower in regional chiefdoms.
The beginning of the Yayoi period is traditionally dated to 300 or 400 BCE, whichappears to make sense climatologically – after all, would not the warm, wet conditions
prevailing at that time be conducive to the adoption of agriculture? However, AMS dating
now shows that the Yayoi period began much earlier than previously believed, specifically,around 900 or 1000 BCE.48 This is just after the beginning of a very cold phase, suggesting
a possible causal relationship between climatic deterioration and the appearance of the newculture. Were the Yayoi immigrants fleeing from harsher conditions in the continent? We
may never know. In any case, it seems likely that colder conditions in Japan were inimical
to the Jōmon way of life, making food production an attractive and indeed necessary
alternative for immigrants and perhaps indigenes alike. Although the situation in Japan is48

Harunari Hideji and Imamura Mineo, eds., Yayoi jidai no jitsunendai: tanso 14 nendai omegutte (Absolute Age of the Yayoi Period: Regarding Carbon 14 Dates) (Tokyo:
Gakuseisha, 2004).
37

complicated by the factor of immigration, the notion of human populations being forced
into agriculture by climatic deterioration is congruent with what is known about conditionsin the Middle East during the Younger Dryas. Once agricultural society was firmly
established, the later temporary warming of the climate may have had little effect, except tofacilitate the spread of wet-rice farming into the colder regions of northern Honshu.

4. 250-700 CE
The next stage, referred to by Sakaguchi as the “Kofun Cold Stage,” was one of profoundand sustained cooling.49 According to the same author, this was the longest cold stage ofthe past 7600 years, and its intensity exceeded that of the more famous Little Ice Age.50
The period was not only cold but also wet, at least judging from the flood deposits seen atvarious archaeological sites.51
Like the other stages discussed in this paper, the “Kofun Cold Stage” was not

49

Sakaguchi, “Warm and Cold Stages,” 17-22; Sakaguchi, “Kako 8000 nen,” 89-91.
Sakaguchi, “Warm and Cold Stages,” 19.
51
Sakaguchi, “Kako 8000 nen,” 90-91.
50

38

localized to Japan; temperate zones everywhere experienced dramatic cooling. The initialcooling may have resulted from volcanism, which was rampant during the third century.52
Another factor seems to have been lower concentrations of atmospheric CO2, which arereported from ice cores between around 200 and 600. Ruddiman, an eminent climatologist,
ascribes the reduction in atmospheric CO2 to heavy mortality in Eurasia from plague andother epidemic diseases. Specifically, he claims that large-scale population loss was
accompanied by the reversion of cropland to forests, resulting in lower atmosphericconcentrations of CO2 and CH4 (methane).53 It remains to be seen whether this argument
will stand the scrutiny of other climatologists and historians.
Whatever the initial cause of cooling, conditions were considerably worsened in 536
CE by a mysterious “dry fog” recorded in historical sources from the Mediterranean to

China. Tree ring studies confirm that solar irradiation was reduced for an incredible fifteen

52

Joel D. Gunn, “A.D. 536 and Its 300-Year Aftermath,” in The Years without Summer:
Tracing A.D. 536 and Its Aftermath, ed. Joel D. Gunn (Oxford: Archaeopress, 2000), 11-12.
Note, however, that Committee on Surface Temperature Reconstructions for the Last 2,000
Years, Surface Temperature Reconstructions for the Last 2,000 Years, 104, Figure 10-3,
does not seem to support this claim.
53
Ruddiman, Plows, Plagues & Petroleum.
39years. There is no scientific consensus on the nature of the 536 event, although the leading
contenders are comet debris and the eruption of a supervolcano. In any case, the disaster led
to widespread crop failures and social disruption in Eurasia, Africa, and the Americas.54
Although clearly important, the 536 event has been the subject of exaggerated
claims by some authors. A book-length study by Keys, for example, argues that “in a matterof decades, the old order died and a new world – essentially the modern world as we know
it today – began to emerge.”55 Regarding Japan, Keys states that the event of 536 caused
famines that paved the way for the introduction of Buddhism, the Sinicization of Japan, and“ultimately the emergence of the Japanese nation.”56 Needless to say, this claim is so broadas to be virtually devoid of meaning. That said, there is some indirect evidence of famine,
specifically a reference in Nihon shoki to the establishment of public granaries in 536 as
54

Joel D. Gunn, ed., The Years without Summer: Tracing A.D. 536 and Its Aftermath, BarInternational Series, No. 872 (Oxford: Archaeopress, 2000). Also see Antti Arjava, “TheMystery Cloud of 536 CE in the Mediterranean Sources,” Dumbarton Oaks Papers 59(2005): 73-94; M.G.L. Baillie, “Dendrochronology Raises Questions About the Nature of
the A.D. 536 Dust-Veil Event,” Holocene 3 (1994): 212-17; Emma Rigby, Melissa
Symonds, and Derek Ward-Thompson, “A Comet Impact in AD 536?,” Astronomy &Geophysics 45, no. 1 (2004): 23-26; and R.B. Stothers, “Mystery Cloud of A.D. 536,”
Nature 307 (1984): 344-45.
55
David Keys, Catastrophe: An Investigation into the Origins of the Modern World (NewYork: Ballantine Books, 1999), blurb on front cover flap.
56
Keys, Catastrophe, 172-180; quotation from flow chart, 178.
40

(among other uses) a “preparation for evil years.”57
Although it is difficult to make a case for the long-term effects of the 536 event per
se on Japanese society, the “Kofun Cold Stage” as a whole is another matter. In terms ofsocial development, the single most important feature of the four and a half centuries
beginning in 250 CE was state formation, manifested archaeologically by the appearance ofthe huge tumuli or kofun for which the period is named.58 I suggest, following earlier
speculation by Sakaguchi59, that state formation in the Japanese islands was at least in parta response to the cold, wet conditions prevailing at the time. The emergence of the Yamato
polity is generally understood as the natural result of the growth in population and social
complexity that accompanied the spread of agriculture in the preceding Yayoi period. Theremay be an element of truth to that, but just as the adoption of agriculture was probably“forced” by cold climate after 1000 BCE, so the emergence of a new level of social
57

W.G. Aston, tr., Nihongi: Chronicles of Japan from the Earliest Times to A.D. 697, twovolumes in one (Rutland, Vermont: Tuttle, 1972), vol. II, 34.
58
On state formation in Japan see Hiroshi Tsude, “The Kofun Period and State
Formation,” Acta Asiatica 63 (1992): 64-86; Joan R. Piggott, The Emergence of JapaneseKingship (Stanford: Stanford University Press, 1997); and Gina L. Barnes, State Formationin Japan: Emergence of a 4th-Century Ruling Elite, Durham East Asian Series (London:
Routledge, 2007).
59
Sakaguchi, “Warm and Cold Stages,” 20-21; Sakaguchi, “Kako 8000 nen,” 105-108.
41

organization – the state – may have occurred as a response to the challenges posed byincreasingly cold, wet conditions. Among other things, I would argue, crop failures andfloods required countermeasures such as public granaries and hydraulic works, which inturn required better organization and central direction. Japan’s first state may have been the
result.60

5. 700-1300 CE
The notion of a Medieval Warm Period originates with Hubert Lamb, the pioneer ofhistorical climatology. Working from such evidence as was available in the 1950s and1960s, Lamb argued that there had been four centuries of relatively warm weather
beginning around 800. As he also showed, the onset and end of warming varied

60

This hypothesis differs somewhat from the one offered by Sakaguchi, who placesemphasis on competition between regional powers over increasingly scarce agricultural
resources and on the role of rulers in introducing and improving agricultural techniques. On
state formation in general, see the parsimonious discussion in David Christian, Maps of
Time: An Introduction to Big History, The California World History Library, No. 2(Berkeley and Los Angeles: University of California Press, 2004), 245-52. Christian
distinguishes between “top-down” and “bottom-up” theories of state formation, concluding
reasonably that most states probably resulted from a combination of top-down direction andbottom-up needs.
42significantly by region. Today’s scholars have access to much better data than did Lamb.
Some have used the accumulating evidence of regional variation to discredit the idea of aMedieval Warm Period, but as a general rule Lamb’s notion has held up surprisingly well.61
The causes of the Medieval Warm Period are not entirely clear, although one factor
may have been reduced levels of volcanic activity.62 Also at work, according to Ruddiman,
were increased levels of atmospheric CO2 and methane, which he ascribes to population
recovery (and thus renewed conversion of forests into agricultural land) after the “DarkAges.”63
The Medieval Warm Period is generally defined as beginning around 800 or 900,
but here I am using a chronology that seems to better fit the Japanese case. Although forearlier periods proxy evidence is mostly limited to pollen, tree rings, and borehole

61

See Fagan, The Great Warming, 12-18, for background. For a contrary view see Tim F.
Flannery, The Weather Makers: How Man Is Changing the Climate and What It Means forLife on Earth (New York: Atlantic Monthly Press, 2005), 44, which states that “the idea ofa global Medieval Warm Period is bunk.” Flannery’s point is that the period was notuniversally warmer than the present day, which may be true, but he ignores the important
fact that in most regions it was considerably warmer than the immediately preceding or
succeeding periods. (This lapse aside, Flannery’s book has much to recommend it.)62
Committee on Surface Temperature Reconstructions for the Last 2,000 Years, Surface
Temperature Reconstructions for the Last 2,000 Years, 21.
63
Ruddiman, Plows, Plagues & Petroleum.
43temperatures, after 700 we also have historical records, making it possible to paint a rather
detailed portrait of climate in Japan. Sakaguchi, based on his study of pollen at Ozegahara,argued that temperatures became warm after 732 and stayed that way through the thirteenth
century.64 Maejima, Tagami, and others have refined this picture using historical records.
To summarize, summers between 700 and 1300 were generally hot, with frequent droughts,
except for a temporary cool spell in the ninth century. Winter temperatures, however, did
not warm up until about 900. Winters from 900 to 1300 were generally mild, with the
exception of a cold spell in the late twelfth century.65 (Note that here we are speaking hereof average conditions; there was considerable variation from year to year.)
From a world historical standpoint, not just the timing, but also the effects of theMedieval Warm Period varied considerably by region. Some areas, for example Europe andChina, experienced significant agricultural and demographic growth, although drought was

64

Sakaguchi, “Warm and Cold Stages,” 22-23; Sakaguchi, “Kako 8000 nen,” 91-92.
Ikuo Maejima and Yoshio Tagami, “Climatic Change During Historical Time,” 164-67.
Also see Adhikari and Kumon, “Climatic Changes During the Past 1300 Years”; Aono andOmoto, “Sakura no kaika shiryō”; Aono, “Sakura no kaika no kisetsu suii”; and Aono,“Kyōto no kokiroku.” On droughts in particular, see Farris, “Famine, Climate, andFarming”; and Farris, Japan’s Medieval Population: Famine, Fertility, and Warfare in a
Transformative Age (Honolulu: University of Hawai‘i Press, 2006).
65

44

sometimes a problem. Good weather is said to have allowed the Norse to colonize Icelandand Greenland, while conversely a drying out of the steppes is often cited as a factor in theeruption of the Mongols from their traditional homeland. In the Americas, recurrent, severe
droughts associated with the Medieval Warm Period have been implicated in the collapse of
the Classic Maya in Mesoamerica and of the Chaco Canyon culture and other societies in
the American Southwest.66
What about Japan? In terms of traditional historiography, the period from 700 to
1300 encompasses the Nara and Heian eras, as well as most of the Kamakura epoch. This
half millennium witnessed the consolidation of imperial authority and the flourishing ofaristocratic culture in the capital, followed by a slow drift toward decentralization and themilitarization of local society. It is difficult to see what, if any, relationship such trends

66

On the effects of the Medieval Warm Period, the best overview is Fagan, The Great
Warming. On the Maya, see Richardson B. Gill, The Great Maya Droughts: Water, Life,and Death (Albuquerque: University of New Mexico Press, 2000); and Jared Diamond,
Collapse: How Societies Choose to Fail or Succeed (New York: Viking, 2005), 157-77. On
Chaco Canyon, see Diamond, Collapse, 136-56. Diamond presents a well-organizedargument to the effect that social collapse typically results from some combination of fivecontributing factors: (1) damage that people inadvertently inflict on their environment; (2)climate change; (3) hostile neighbors; (4) decreased support by friendly neighbors; and (5)society’s responses to its problems: Diamond, Collapse, 10-15.
45

might bear to climate.67 More relevant for our purposes is the fact, recently established by
Farris, that Japanese society experienced little or no demographic or economic growthduring these five centuries.68 At first glance this seems odd, especially given the apparently
robust nature of the Nara and early Heian states. Farris places the blame on recurrent
epidemics of smallpox, measles, and influenza, coupled with recurrent drought. Although
the epidemics had nothing to do with climate, the droughts most certainly did. So it seems
fair to say that the Medieval Warm Period was not particularly kind to Japan, although theconsequences were far less severe than in the case of, say, the Classic Maya.

6. 1300-1600 CE
This brings us to the next period, here defined as lasting from about 1300 to 1600. Some
researchers consider these centuries to be part of the Little Ice Age, while others prefer toreserve that term for the period after the late sixteenth or even late seventeenth century.

67

Although it has been argued that rise of warrior society in eastern Honshu was madepossible by warmer temperatures, which made the Kanto Plain more attractive for
agriculture than in earlier centuries: Toyama Shūichi, Shizen to ningen no kankeishi(History of the Nature-Human Relationship) (Tokyo: Kokon shoin, 2008), 140.
68
Farris, Japan’s Medieval Population, and “Famine, Climate, and Farming.”
46

This is mainly a matter of definition or taste, since all authors seem to agree that the climate
began to deteriorate around 1300 but that the most severe conditions came later.
Accordingly, I have chosen to split the period in two, which makes sense not only
climatologically but also in terms of historical developments in Japan. For reasons ofconvenience, the causes of the Little Ice Age will be discussed in the following section. In
the present section we will stick to the climatic facts and their effects on human society inJapan.
First, regarding Japanese climate, we are on increasingly solid ground thanks to themany available natural and historical proxies. To make a long story short, summer in Japanremained generally warm throughout this period. The real difference from the preceding
Medieval Warm Period came in winter, which was generally cold. The very coldest periods
were in the 1340s through 1360s; around the beginning of the fifteenth century; around1490; and then from the 1500s through the 1540s. Mild winters, by contrast, were the norm
for a time after 1470 and during the second half of the sixteenth century.69

69

This is based mainly on Maejima and Tagami, “Climatic Change During Historical
Time,” 164-67, with additional information from Adhikari and Kumon, “Climatic Changes
47

Next, regarding the historical implications of these trends, the record defies easyinterpretation. Outside of Japan, famines in early fourteenth century Europe can be
confidently ascribed to the deteriorating climate (specifically to cold and rain).70 But froma world historical viewpoint, the most important events of the fourteenth through sixteenth
centuries were the spread of the Black Death; the European “discovery” of the New World;
and the resulting “Columbian Exchange,” in which (among other things) the native
American population was decimated by exposure to Eurasian disease pools.71 It seems safe
to say that none of these developments had much to do with climate.72
What about Japan? As is well known, these centuries, roughly corresponding to the

During the Past 1300 Years”; Arakawa, “Climatic Changes as Revealed by the Blooming
Dates”; Aono and Omoto, “Sakura no kaika shiryō”; Aono, “Sakura no kaika no kisetsusuii”; Ikuo Maejima, “Some Remarks”; Mikami and Ishiguro, “Suwako ketsuei kiroku”;
Sakaguchi, “Warm and Cool Stages,” 23-24; Sakaguchi, “Kako 8000 nen,” 92-95;
Yamamoto, “On the Climate Change”; Yamamoto, Kikō no kataru; and Yamamoto, “A.D.
1-1600 nen no Nihon.” See Atwell, “Volcanism and Short-Term Climatic Change,” fordetailed discussion of some of the colder episodes and their causes.
70
Fagan, The Little Ice Age.
71
The term “Columbian Exchange” originates with Alfred W. Crosby, The Columbian
Exchange: Biological and Cultural Consequences of 1492 (Westport, CT: Greenwood
Press, 1972).
72
Unless for some reason cold weather brought humans into closer contact with rats,
increasing the likelihood of plague transmission. For a fascinating ecological study of ratsand plague in an earlier period, see Michael McCormick, “Rats, Communications, andPlague: Toward an Ecological History,” Journal of Interdisciplinary History 34, no. 1(2003): 1-25.
48

Muromachi and Sengoku (Warring States) periods, were characterized by political andsocial turmoil. Many specific uprisings can be traced to crop failures resulting from badweather.73 One is therefore tempted to generalize and blame all of the sociopoliticalproblems of this period on the cooler climate. However that would be a mistake. Althoughtemperatures were on average lower than during the Medieval Warm Period, overall thatwas probably a plus, as we shall see below. Further arguing against any simple link between
climate and social conditions is the example of the subsequent stage, which saw a return topolitical stability despite profound climatic deterioration.
There is another aspect of this period that merits consideration, and that relates toagricultural production and demography. In stark contrast to the bleak political situation,
Japan’s economy and population grew by leaps and bounds during these three centuries. (Intraditional agrarian societies, of course, economic and demographic growth are often moreor less the same thing.) According to Farris, Japan’s population “expanded on the order of
300 percent, from about 5.5-6.3 million in 1150 to 15-17 million in 1600, with almost all

73

See the many cases discussed by Atwell, “Volcanism and Short-Term Climate Change.”49the growth coming after 1280.”74 Absent immigration (not a significant factor in medieval
Japan), population growth can only result from increased life expectancy, or increased
fertility, or both. Although Farris couches his argument is slightly different terms, bothfactors seem to have been present in this case. Longevity was promoted by decreased
mortality from epidemic disease and famine, both of which had been rampant in theprevious period. Longer life also resulted from a general increase in physical well-being,
which Farris ascribes to agricultural improvements and a host of other indirect factors.
Better health also presumably led to increased fecundity, although as Farris readily admits,
the direct evidence for this is weak.
Looking at all of this from a climatological perspective, I would point out that thedecreased number of famines probably relates to the return of temperatures to a more
“normal” range following the extremes of the Medieval Warm Period. The obverse of thispoint is that climatic conditions in the Muromachi period were probably better suited to rice

74

Farris, Japan’s Medieval Population, 5. Note that Kitō, the leading Japanese authority,finds only a doubling, from 6.8 million to 12.3 million, over the same period: Kitō Hiroshi,
Jinkō kara yomu Nihon no rekishi (Japanese History as Read from Population), Kōdansha
gakujutsu bunko (Kōdansha Academic Library), No. 1430 (Tokyo: Kōdansha, 2000),
16-17.
50

agriculture than those in the preceding stage. It is usually a mistake to discount humanagency, and I have no doubt that the technological and social improvements cited by Farris
were important. But it would equally be a mistake to ignore the probable positive effects ofclimate change on agricultural productivity – and thus, indirectly on human longevity andfecundity – during the Muromachi and Sengoku periods.75

7. 1600-1850 CE
This brings us to the (narrowly defined) Little Ice Age, which has been of particular interestto scholars because of its relatively dramatic consequences and its proximity to our own
time.76 Japanese climatologists, like their colleagues elsewhere, have actively pursued

75

Farris, Japan’s Medieval Population, 94-127, seems to recognize the role of climate
when he describes the period from 1370 to 1450 as the “Muromachi Optimum,” butunfortunately there are problems with this concept. First, among climatologists the term
“optimum” is reserved for periods that are hotter than normal (otherwise known as“hypsithermals”). So while the Medieval Warm Period was a climatic optimum (and isoften referred to as such in the literature), the Muromachi period was not. It is possible, ofcourse, that the years from 1370 to 1450, while not an optimum in the technical sense, weresomehow optimal for agriculture in Japan. Perhaps this is Farris’s point. But if that is thecase, there seems little need to single out this particular 80-year interval. Except for a few,
relatively brief, periods of intense winter cold, similar climatic conditions prevailed
throughout the fourteenth through sixteenth centuries in Japan.
76
The classic study is Jean M. Grove, Little Ice Ages: Ancient and Modern, 2d ed.,Routledge Studies in Physical Geography and Environment (London: Routledge, 2004).
51

research on this period. Most significantly, in 1991 Tokyo Metropolitan University hosted
an “International Symposium on the Little Ice Age Climate,” whose proceedings containmore than a dozen important papers on this topic as it relates to Japan.77
In contrast to the Medieval Warm Period, which varied in timing and intensity
according to region, the Little Ice Age was relatively uniform in its effects, at least in
For a more popular account, see Fagan, The Little Ice Age.
77
Mikami, ed., Proceedings of the International Symposium on the Little Ice Age Climate.
Other important studies of the Little Ice Age in Japan are Maejima Ikuo, “Shōhyōki nai nokikō hendō: Nihon to Yōroppa no kenkyū seika no hikaku no tame ni” (Climate Change
within the Little Ice Age: For the Sake of a Comparison of Japanese and European
Research), Chiri shisō (Geographic Journal) 35, no. 2 (1994): 1-71; Maejima and Tagami,“Climate of Little Ice Age in Japan,” Geographical Reports of Tokyo Metropolitan
University 18 (1983): 91-111; Maejima and Tagami, “Nihon no shōhyōki no kikō ni tsuite:
Toku ni 1661 nen - 1867 nen no Hirosaki no tenkō shiryō o chūshin ni” (Regarding Climate
during Japan’s Little Ice Age: Based Chiefly on Weather Records from Hirosaki,
1661-1867), Kishō kenkyū nōto (Meteorological Research Notes) 147 (1983): 207-15;
Mikami, “Shōhyōki: kikō no sūhyakunen hendō” (The Little Ice Age: Climate Change over
Several Centuries), Kagaku (Science) 61, no. 10 (1991): 681-88; Mikami, “Shōhyōki nokikōzō” (Portrait of Climate in the Little Ice Age), Chiri (Geography) 37, no. 2 (1992):
25-30; Mikami, “Nikki tenkō kiroku”; Mizukoshi Mitsuharu, “Kinsei shōhyōki no kikō
kankyō fukugen” (Reconstruction of the Climatic Environment of the Early Modern Little
Ice Age), Kōgakukan daigaku shakai fukushi gakubu kiyō (Transactions of the School ofSocial Welfare, Kōgakukan University) 1 (1998): 137-42; Shuji Yamakawa, “Climate
Variations and Natural Disasters in Little Ice Age,” Kokuritsu rekishi minzoku
hakubutsukan kenkyū hōkoku / Bulletin of the National Museum of Japanese History 81(1999): 51-56; Yamamoto, “On the Nature of the Climatic Change”; Yamamoto, “On the
Nature of the Japanese Climate”; Minoru Yoshimura, “Climate in the Little Ice Age overJapan,” in Nature and Humankind in the Age of Environmental Crisis, ed. Ito Shuntaro and
Yasuda Yoshinori (Kyoto: International Research Center for Japanese Studies, 1995),
153-59; Yoshimura, “Shōhyōki no kikō” (Climate of the Little Ice Age), in Rekishi to kikō(History and Climate), ed. Yoshino and Yasuda, 183-99; and Yoshimura, “Konikki kara
Nihon no kikō o yomu: Shōhyōki to kikin no kankei” (Reading Japan’s Climate from Old
Diaries: The Relationship between the Little Ice Age and Famine), Kankyō kaigi(Environmental Conference) 22 (2004): 86-89.
52

temperate regions of the northern hemisphere. The causes of the Little Ice Age seem tohave been multifarious. Many scholars have blamed decreased solar activity, particularly
during the so-called “Maunder Minimum” of c. 1645-1710. Volcanic eruptions also
certainly played a role, especially in the late eighteenth and early nineteenth centuries. For
example, the so-called “Year Without a Summer” in 1816 was caused by volcanic dust in
the atmosphere from the 1815 eruption of Tambora, in what is now Indonesia. The Tambora
eruption is said to have been the most violent of the entire Holocene.78 Finally, as during
the “Kofun Cold Stage,” ice cores show reduced levels of atmospheric CO2, first between
1300 and 1400, and then again, more dramatically, from 1500 to 1750.79 By now, readers
will be unsurprised to learn that Ruddiman ascribes these drops in CO2 levels to population
loss following pandemics. Specifically, he attributes the fourteenth century drop to theeffects of the Black Death in Eurasia, and that between 1500 and 1750 to the loss of native

78

R.S. Bradley and P.D. Jones, “Records of Explosive Volcanic Eruptions over the Last
500 Years,” in Climate since A.D. 1500, ed. Raymond S. Bradley and Philip D. Jones(London: Routledge, 1992). Again, on volcanism as it pertains to East Asian history, thebest source is Atwell, “Volcanism and Short-Term Climate Change.”
79
Ruddiman, Plows, Plagues & Petroleum, 119.
53

populations in the Americas following the “Columbian Exchange.”80
Moving on to Japan, climatic conditions during this period have been reconstructedin great detail using data from diaries and other historical records, tree-rings, and otherproxies. The conclusions of various previous studies are summarized in Table 1, below. As
was the case in Europe and elsewhere, temperatures were generally, but not uniformly, cold.
The coldest conditions occurred from approximately 1611 to 1650, 1691 to 1740, and 1781
to 1880.81 During these three phases, winters were severe with much snowfall, particularlyon the Sea of Japan side of Honshu. Summers were cool, particularly in the northern part ofthe country, and frequently rainy.82 Interestingly, the “Year Without a Summer” was wholly
unexceptional in Japan, although an earlier “Year Without a Summer” occurred in 1783
following the eruptions of Mt. Asama in Japan and the Laki fissure in Iceland.83

80

Ruddiman, Plows, Plagues & Petroleum, 119.
Maejima and Tagami, “Climatic Change During Historical Time.” Also see Maejima
and Tagami, “Climate of Little Ice Age in Japan.”82
Yamamoto, “On the Nature of the Climatic Change,” and “On the Nature of theJapanese Climate.”
83
Mikami and Tsukamura, “The Climate of Japan in 1816”; Demarée and Mikami, “1783
nen no Raki (Aisurando), Asama (Nihon) kazan funka ni yoru kikō e no eikyō / Climatic
Impacts of Lakagígar (Iceland) and Asama (Japan) Volcanic Eruptions in the Year 1783,”
Gekkan chikyū 27, no. 9 (2005): 687-92. Also see R.B. Stothers, “The Great Dry Fog of1783,” Climatic Change 32 (1996): 79-89.
81

54

55

Notes to Table 1aTakeo Yamamoto, “On the Nature of the Climatic Change in Japan since the ‘Little Ice Age’ Around 1800

A.D.” Journal of the Meteorological Society of Japan 49 (1971): 789-812.
b

Yamamoto, “On the Nature of the Japanese Climate in So-Called ‘Little Ice Age’ Between 1750 and 1850,”

Geophysical Magazine 35, no. 2 (1971): 165-85.
cIkuo Maejima and Yoshio Tagami, “Climate of Little Ice Age in Japan,” Geographical Reports of Tokyo

Metropolitan University 18 (1983): 91-111.
dMaejima and Tagami, “Climatic Change During Historical Time in Japan — Reconstruction from Climatic

Hazard Records,” Geographical Reports of Tokyo Metropolitan University 21 (1986): 157-71.
e

Yoshio Tagami and Kazuo Fukaishi, “Winter and Summer Climatic Variation in Japan from the 17th

Century,” in Proceedings of the International Symposium on the Little Ice Age Climate, ed. T. Mikami(Tokyo: Editorial Committee of LIAC Proceedings, Department of Geography, Tokyo Metropolitan
University, 1992), 188-93.
f

Fukaishi and Tagami, “An Attempt of Reconstructing the Winter Weather Situations from 1720 to 1869 by

the Use of Historical Documents,” in Proceedings of the International Symposium on the Little Ice Age
Climate, ed. Mikami, 194-201.
g

Mikami Takehiko, “Nikki tenkō kiroku kara suitei shita shōhyōki kōhan no kaki onhendō / Summer

Temperature Variabilities in Japan Reconstructed from Diary Weather Records During the Little Ice Age,”
Chiri zasshi / Journal of Geography 102, no. 2 (1993): 144-51.
hMikami, “Long Term Variations of Summer Temperatures in Tokyo since 1721,” Geographical Reports ofTokyo Metropolitan University 31 (1996): 157-65.
iMikami, “Quantitative Climatic Reconstruction in Japan Based on Historical Documents,” Kokuritsu rekishi

minzoku hakubutsukan kenkyū hōkoku / Bulletin of the National Museum of Japanese History 81 (1999):
41-50.
jMikami, “Summer and Winter Temperature Reconstructions in Japan,” PAGES News 10, no. 3 (2002):

17-18.
k

Mikami, “Kako 1000 nenkan no kikō hendō to 21 seiki no kikō yosoku / Global Climatic Variations for theLast 1000 Years and Their Prospects in Future,” Chiri zasshi / Journal of Geography 114, no. 1 (2005):
91-96.

56

lMikami Takehiko and Ishiguro Naoko, “Suwako ketsuei kiroku kara mita kako 550 nenkan no kikō hendō”(Climate Change during the Past 550 Years as Seen from Records of Freezing of Lake Suwa), Kishō kenkyūnōto (Meteorological Research Notes) 191 (1998): 73-83.
m

Y. Aono and Y. Omoto, “Variation in the March Mean Temperature Deduced from Cherry Blossoms in

Kyoto since the 14th Century,” Journal of Agricultural Meteorology 48, no. 5 (1993): 635-38.
nAono and Omoto, “Sakura no kaika shiryō ni yoru 11 seiki ikō no Kyōto no kion no suitei” (Temperature

Trends in Kyoto since the Eleventh Century Based on Records of Cherry Blooms), Nōgyō kishō (Agricultural
Meteorology) 49, no. 4 (1994): 263-72.
oAono, “Sakura no kaika no kisetsu suii” (Seasonal Trends of Cherry Blooms), Kikō eikyō, riyō kenkyūkai

kaihō (Bulletin of Research Group on Climate Influence and Use) 19 (2001): 15-20.
pAono, “Kyōto no kokiroku o mochiita sakura no kaikabi no fukugen to kion e no yomikae” (Reconstructionof Cherry Bloom Dates Using Old Records from Kyoto and Their Conversion into Temperatures), in
Kikōgaku to rekishigaku no sōgū (Higashi Ajia kankyōshi, kikō hendō kokusai shinpojiumu hōkokusho) (The
Encounter of Climatology and History [Proceedings of the International Symposium on East Asian
Environmental History and Climate Change]), ed. Tsukahara Tōgo, Mikami Takehiko, and Naitō Tomoko(Kobe: Tsukahara Tōgo, 2003), 27-41.

What effects did the Little Ice Age have on human society? Discussions of this topic
by world historians typically center on crop failures and associated famines, particularly inEurope.84 As noted earlier, there is also a substantial literature on the Little Ice Age inJapan, and much of this also focuses on famines. Many authors, for example, have notedthat the Genroku Famine of 1695-1696, the Tenmei Famine of 1782-1787, and the Tenpō
Famine of 1833-1839 all occurred during particularly cold periods, and that all had their84

See discussion in Fagan, The Little Ice Age.
57

most severe effects in northern latitudes, where temperatures were lowest.85 Since theTenpō Famine was part of the background to the domestic unrest that contributed to the fallof the Tokugawa Shogunate, the enthusiastic climate historian might be forgiven for
claiming that the Little Ice Age put an end to Japan’s ancien régime, paving the way formodernization.
While it is true that cool temperatures frequently led to famine, this is not all there
was to the Little Ice Age, either in Japan or elsewhere. Another frequently-cited negative
effect involves the failure of the Norse settlements in Greenland, which had been
established during the preceding Medieval Warm Period.86 But what climate historians

85

Maejima and Tagami, “Climatic Change During Historical Time,” 169. Also see Mikami,“Kikin no kōzō: Tenmei no kikin o rei to shite” (The Structure of Famine: The Case of theTenmei Famine), Chiri (Geography) 27, no. 12 (1982): 51-57; Mikami and Tsukamura,“The Climate of Japan in 1816”; Yaji and Misawa, “Tenpō kikin zengo”; and Yamakawa,“Climate Variations and Natural Disasters.” Another major famine, the Kyōhō Famine of1732, was caused by a plague of locusts and was most severe in western Japan. There issome interesting evidence from upland regions in central Honshu that in times of poor
harvests peasants began to cultivate horse chestnuts as an alternate source of food: J.
Kitagawa, T. Nakagawa, T. Fujiki, K. Yamaguchi, and Y. Yasuda, “Human Activity andClimate Change During the Historical Period in Central Upland Japan with Reference toForest Dynamics and the Cultivation of Japanese Horse Chestnut (Aesculus turbinata),”
Vegetation History and Archaeobotany 13, no. 2 (2004): 105-13.
86
Neil Roberts, The Holocene: An Environmental History (Oxford: Blackwell Publishers,1998), 179-80; Diamond, Collapse, 248-76. Note that the Norse settlements met their end
around 1500 and thus somewhat before the Little Ice Age as defined here.
58

have inexplicably failed to note is that the Little Ice Age was not universally bad. Viewed
as a whole, the period saw dramatic demographic and economic growth, as well as stateand empire-building, throughout the core regions of Eurasia.87 This suggests either thatcolder temperatures had some sort of positive influence on society (by stimulating people
or states to greater efforts?), or alternatively, that the Little Ice Age was largely irrelevant to
the important historical trends of the era. In either case, historians may need to take off theirblinders and reexamine this topic from a broader perspective.
What can be said for world history can be said for Japanese history as well.
Although I concede that famines were important, and that many of them can be directly
blamed on the weather conditions of the Little Ice Age, I must also note that this period saw
some very positive developments, especially in the seventeenth century. As just one
example, Japan’s population continued to grow rapidly, doubling, according to Farris, from
15-17 million in 1600 to 31 million in 1721.88 Most of this increase took place during very87

See John F. Richards, The Unending Frontier: An Environmental History of the Early Modern
World, The California World History Library (Berkeley and Los Angeles: University of California
Press, 2003).
88
Farris, Japan’s Medieval Population, 263. Kitō believes that Japan’s population in 1600
59

cold conditions. While it is true that population growth ceased after 1721, this has nothing
to do with climate; it was simply that Japanese society had reached the demographic “limits
to growth” imposed by available resources and technologies. (Economic growth, however,did continue, albeit at a slower pace, throughout the period.) How are we to explain thesefacts if the Little Ice Age was such a terrible thing? Again, the question is begging to be
reopened.

8. 1850-2000 CE
The last phase in Japan’s climatic history is the contemporary period of anthropogenic
warming since around 1850. The facts are clear and well-known, and I see no need toreiterate them here. Moreover, unlike for all the earlier periods described above, there islittle point in trying to tie specific developments in human society to climate. Climate was,and is, not irrelevant; but it was no longer the primary engine of change – if, indeed, it ever

was only 12 million, but agrees with the figure of 31 million for 1721. Kitō, Jinkō, 16-17. If
this is correct, population growth during the early Edo period was even more rapid than
Farris’s figures suggest.
60

had been. Society in the nineteenth and twentieth centuries developed largely according to
its own logic.

IV. Conclusion

This survey of the role of climate in Japanese history and prehistory has been, at best,
sketchy and tentative. Much work remains to be done before we have a comprehensive
picture of how the weather and climatic change affected people and society in the Japanesearchipelago. The big picture seems relatively clear, but many of the details are missing.
Worse (or perhaps better, for those who like puzzles), even when we know what happened,
we do not usually know why.
Some of the results of this survey seem to fly in the face of common sense. For
temperate regions like Japan, it would seem natural to expect that warm conditions were“good” for agriculture and society while cold conditions were “bad.” My working
hypothesis when I began this study was that warm conditions would be associated with61

periods of growth and consolidation, while cold conditions would be associated withperiods of stagnation and disruption. That turns out not to be true; if anything, the reverse
was the case.
Cold conditions often produced good results for society in Japan. For example, theorigins of pottery (the Jōmon culture), of rice agriculture, and of the state all seem to becausally linked to unusually cold temperatures. The same is true of the explosive
demographic and economic growth of the seventeenth and early eighteenth centuries. The
full explanation for these apparent paradoxes must await the results of future research. Herelet me simply repeat my “hunch” that adverse climatic conditions brought out the best in
the residents of the Japanese islands, who collectively rose to the challenges presented themby nature.
Conversely, warm periods could produce bad results for society in Japan. True, thegenerally warm Jōmon period was one of exceptional prosperity for the hunter-gatherer
residents of the archipelago. But following the advent of full-blown agriculture, warm
conditions appear, if anything, to have been a liability. A case in point is the Medieval

62

Warm Period. Although the degree of political integration during the Nara and early Heianperiods was generally high, from a demographic or economic perspective these centuries
were characterized above all by stagnation. If this premodern example of global warming
had such dire consequences for Japanese society, one can only wonder where current trends
will lead. Yes, over time, the Japanese, like people elsewhere, have demonstrated increasing
control over their environment. But will technology save the day this time around? Only
time can tell.

63

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