Volcanism and Short-Term Climatic Change in East Asian and World History, c. 1200-1699

There is . . . a tendency for the North Atlantic zone of main cyclonic activity to be shifted somewhat south in the summers after great [volcanic] eruptions, this accounting for many, perhaps most, of the coldest, wettest summers of the last three hundred years in western Europe and eastern North America. The same probably applies to the North Pacific (Lamb 1982: 59).

[A] cold summer with excessive prolonged rains is the commonest cause of a failure in the harvest [in the Tohoku region of northern Japan]. . . . 1782-1787, 1833-1839, and 1866-69 are famous in Japanese historical writings as the worst famines in the last half of the Tokugawa period. . . . During [these] three great famines, . . . there were remarkably low temperatures in the summer months (Arakawa 1957b: 212).

Summer climates in Japan and China . . . are characterized by simultaneous variations of dry and wet areas. . . . In 1978, when it was extremely dry and hot in Japan and middle China, the axis of [the North Pacific High] was located northward, while in 1980, when it was exceedingly wet and cool in Japan and middle China, the axis was shifted far to the south (Mikami 1987: 69).

To those whose noon sunshine has been replaced by cimmerian darkness, the volcanic origin of their misery may be suffocatingly obvious if falling ash is sifting down around them. But it may be difficult for someone observing a small anomaly in his daily circumstances to relate that anomaly to events taking place on a volcano thousands of miles away, of whose very existence he may be unaware (Francis 1993: 368).

Part One: Some Recent Approaches to the Study of Volcanism and Short-Term Climatic Change

Introduction: The "Dust Veil" and "Volcanic Explosivity" Indexes

Although there has been serious discussion of the possible connection between volcanic activity and short-term climatic change for at least two centuries, research in this field has advanced greatly since the 1960s (see, for example, the summaries in Lamb 1988: 301-328; Rampino, Self, and Stothers 1988; American Geophysical Union 1992; Chester 1993: 158-185; Bradley and Jones 1995b; Robock 2000). ¹ One reason for this advance is that after more than four decades of relative quiet following two massive eruptions in Alaska in 1912, there has been a substantial increase in both the frequency and magnitude of global volcanism since the mid-1950s. Especially noteworthy in this increase were the July 1953 eruption of Alaska's Mt. Spurr, the March 1956 eruption of Mt. Bezymianny in Kamchatka, and the March 1963 eruption of Mt. Agung on the Indonesian island of Bali. This last eruption was particularly important because the large quantities of volcanic matter it injected high into the stratosphere helped to cause brilliant sunsets, hazy skies, and other optical effects that attracted the attention of observers from around the world for the next several years (Lamb 1970: 525; Newell 1981).

One of those observers was the pioneer meteorological historian H. H. Lamb, who was inspired to take up the complex question of volcanism and its possible impact on global climate. This resulted in a path-breaking article (Lamb 1970) that contained both a chronology of major eruptions over the previous 450 years and a preliminary assessment of their climatic impact. Particularly important for subsequent research was Lamb's compilation of a "Dust Veil Index" (DVI), an ingenious attempt to estimate both the quantities of fine ash and other matter injected into the atmosphere by major eruptions and how long they remained there. Using the relatively well-studied 1883 eruption of Indonesia's Mt. Krakatau (Krakatoa) as a benchmark, Lamb compiled this index by reviewing the records of more than 200 notable eruptions since 1500, taking into account both the qualitative comments of observers at the time and whatever quantitative information he could find on the volume...