火山噴火と気候変動

Abstract

Major volcanic eruptions have often been followed by global cooling. The year 1816, often called the “year without a summer”, is well known for its extremely cool summer temperatures, extending over western Europe and eastern North America. This unusually cool weather was attributed to the eruption of Mt. Tambora in Indonesia, in 1815. This paper reviews the relationship between major volcanic eruptions and global climatic changes, based on recent articles in the field of climatology.The global mean temperature tends to decrease for 2 to 3 years after major volcanic eruptions (ANGELL and KORSHOVER, 1985). The degree of cooling and its regional extent depend upon various factors, such as, the latitude of the volcanoes, the eruption season, and the type of gases ejected. In general, the quantity of sulfur is probably the most important factor when we consider the impact of volcanic eruptions on global climate variation. It should be noted that temperature variations after major eruptions often show regional differences. This is connected with the modified global circulation patterns caused by changes in terrestrial radiation budgets after such eruptions.The Little Ice Age of the 16th to 19th centuries is known for its world wide cool climates. Time series of acidities in Greenland ice cores indicate frequent volcanic activities during the Little Ice Age (HAMMER et al., 1980). Over time intervals of 10 to 100 years, volcanic eruptions produce the greatest impact on global climatic change.