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FIGURE I I.I I Ten-year mean annual temperature departures (from 1880— 1979 means) based on historical documents from East China (above) and North China (below). East China comprises five provinces: Shanghai, Jiangsu, Jiangxi, Anhui, and Zhejiang. North China covers Beijing, Hebei, Henan, Shandong, and Shanxi provinces (Wang, 1991 b).

synoptic information provided by the network of early observers (Yoshimura, 1996). All of the information has been coded and digitized for computer-based analysis (Yoshimura, 1992). These historical records have provided a wealth of information about the climate of Japan during the last 250 yr (Murata, 1992; Mizukoshi, 1992; Tagami and Fukaishi, 1992). For example, Fukaishi and Tagami (1992) classified the observations into those patterns that are typical of characteristic "winter-like" pressure patterns, with high pressure in the west and low pressure in the east. Figure 11.13 shows the number of days with this pattern during the November-March period of each year, from 1720-1869. Unusually cold conditions with heavy snow were common in the years when this pressure pattern prevailed (e.g., 1726-1733, 1777-1785, 1808-1819, and 1826-1836).

11.3.2 Europe

Evidence for significant changes in the climate of Europe over the last few centuries is abundant. In particular, there are many wonderful paintings of alpine glaciers (far in advance of their current positions) that vividly illustrate the environmental consequences of recent climatic changes in the Alps (Zumbiihl, 1980; Grove, 1988). These pictorial images make it easy to accept the notion of a "Little Ice Age" (LIA) gripping Europe over the last few hundred yr. In fact, there is enough similar glacial evidence from virtually all mountainous parts of the world to indicate that some large-scale forcing was involved in bringing the Little Ice Age about. Unfortunately, the term is often used without clarity; some authors consider the LIA began in the fourteenth or fifteenth centuries, others date it as starting in the 1600s.

In reality, this deterioration was one of several late Holocene cool episodes (neoglacials) that led Matthes (1940) to introduce the term. He wrote: "We are living in an epoch of renewed but moderate glaciation — a "little ice age" that already has lasted about 4,000 years . . . glacier oscillations of the last few centuries have been among the greatest that have occurred during the 4,000 year period . . . the greatest since the end of the Pleistocene ice age."

It is this latest and most dramatic episode of neoglaciation to which the term "Little Ice Age" is now generally applied; there were a series of post-Medieval cool events, varying in intensity from one region to another, but there seems to have

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FIGURE 11.12 An example of coded weather data for January 15-25, 1754, derived from diaries kept by feudal clans in 14 different locations throughout Japan (Fukaishi andTagami, 1992).

® cold and heavy snow t : Tohoku k> Kanto s : San'in

• warm and little snow h : Hokuriko ki Kinki Ky Kyushu

FIGURE 11.13 Annual number of days with a "winter-like" pressure pattern across Japan (high pressure in the west, low pressure in the east) for the period November I -March 31 each year from 1720-1869, based on an interpretation of mapped weather information obtained from diaries (Fukaishi andTagami, 1992).

® cold and heavy snow t : Tohoku k> Kanto s : San'in

• warm and little snow h : Hokuriko ki Kinki Ky Kyushu

FIGURE 11.13 Annual number of days with a "winter-like" pressure pattern across Japan (high pressure in the west, low pressure in the east) for the period November I -March 31 each year from 1720-1869, based on an interpretation of mapped weather information obtained from diaries (Fukaishi andTagami, 1992).

been more widespread climatic deterioration after -1510 ± 50 (Bradley and Jones, 1992b). There is general agreement that the LIA came to an abrupt end in the mid-nineteenth century (-1850). If we therefore consider the overall "Little Ice Age" as having lasted from -1510-1850, we find that conditions were not continuously cold, nor was it uniformly cold in all regions. Even within Europe there were temporal and geographical differences in temperature variations (Brâzdil, 1996). At some times, in some areas, decadal mean temperatures were comparable to twentieth century values (particularly during the eighteenth century). Particular insight into European climate during this period has been obtained from the comprehensive paleoclimatic reconstructions produced by Pfister for Switzerland (Pfister, 1984, 1985, 1992). Pfister used phenological data, lake freeze/thaw dates, snow cover duration, and tithe auction dates (related to the time of maturation of rye) with other information, to construct monthly indices of temperature for the last 470 yr (Table 11.7). The data were calibrated with instrumentally recorded temperature data from Basel, enabling estimates of seasonal temperature anomalies to be made. Data on floods and low-water levels also enabled estimates of precipitation anomalies to be made (Fig. 11.14). These studies (like those reported by Brâzdil) indicate that the record of past anomalies varied between seasons. Winters

TABLE 11.7 Indicators Used by Pfister to Determine the Thermal Character of Individual Months

Month

Cold

Warm

Dec-Jan

March

April

June

July

April-July August

September

October

November

Uninterrupted snow cover Freezing of lakes

Long snow cover High snow frequency

Snow cover and snow frequency

Beech tree leaf emergence

Snow cover Snow frequency

Long snow cover High snow frequency Freezing of lakes

Scarcity of snow cover Signs of vegetation

Beech tree leaf emergence

Tithe auction date

Barley first beginning

Tithe auction dates [± 0.6 °C] Vine full flower [± 1.2 °C] Vine last flower Coloration of first grapes

Coloration/maturity of first grapes Wine harvest dates [± 0.6 °C]

Wine yields [± 0.6 °C] Tree ring density [± 0.8 °C]

Reappearance of spring vegetation (cherry flowering etc.)

No snowfall Cattle in pastures

Pfister (1992).

Figures in brackets give the standard error of the estimates.

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FIGURE 11.14 Estimates of seasonal and annual temperature (heavy line) and precipitation (lighter line) for Switzerland (I l-yr moving averages) expressed as departures from the mean for 1901-1960 (Pfister, 1992).

March April May

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historical evidence of weather conditions across the region (Wanner et al., 1994).

were especially cold in the late seventeenth century and throughout most of the nineteenth century, whereas the coldest summers were in the early 1800s and the late 1800s/early 1900s. Indeed summer temperatures from -1600-1800 appear to have been quite similar to the twentieth century average. It is also of interest that for much of the last few hundred years conditions were drier than in the twentieth century. Pfister's studies in Switzerland indicate that overall, the coldest conditions of the last 500 yr were in the late seventeenth and nineteenth centuries, especially the early nineteenth century, which can be considered as the "Climatic Pessimum" of the last 1000 yr. Since most of our longest instrumental temperature records began during this time, perhaps the coldest period of the last millennium, much of the "global warming" registered since then represents a recovery from that low point in the early to mid-nineteenth century.

Historical climatology in Europe has greatly benefited from the activities of the EURO-CLIMHIST project led by C. Pfister (see the volumes edited by Frenzel et al., 1992b, 1994). In order to be able to compare diverse historical observations in many different European languages, uniform procedures for coding information have been developed (Schiile and Pfister, 1992; Schwarz-Zanetti et al., 1992). The EURO-CLIMHIST project has helped to coordinate historical clima-tological studies across Europe, so that daily iconographie maps of weather conditions over Europe can now be constructed, for extended periods of time, as has been carried out in Japan. These have been interpreted by meteorologists familiar with the atmospheric circulation of Europe to produce estimates of the prevailing pressure regimes over the region, consistent with the recorded historical observations (Fig. 11.15). Such maps provide scenarios that can be updated and revised as additional historical data become available. Eventually, it should be possible to establish in great detail how atmospheric circulation in Europe during the Little Ice Age differed from that in the twentieth century, providing clues about the factors causing these changes.

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