小冰期气候的研究

本文总结分析了近年来国内外对小冰期气候的研究，对亚洲、欧洲、北美、南美、非洲、北极地区及南极洲的各种重建气温序列进行了整理。所有序列均取１０００－１９８９年每５０年的平均值(最后一个仅有４０年)，并统一对近千年平均求距平。发现１７世纪及１９世纪的冷期有很大普遍性。平均比２０世纪后半低１．０℃左右。火山活动与太阳活动(¹⁴Ｃ)指数及平均气温序列的相关系数分别为－０．４９及－０．７３，说明这两个因素可能是小冰期形成的原因。

STUDIES ON CLIMATE OF THE LITTLE ICE AGE

Studies on the climate of the Little Ice Age were reviewed. The temperature series reconstructed by proxy data were reanalyzed from Asia, Europe, North America, South America, South Africa and the Arctic and Antarctic regions. The Proxy data used in this paper can be grouped in to four groups:δ¹⁸O in ice cores, treering, documentary data and others.δ¹⁸O is a good indicator of climatic changes for its close relationship to the temperature of snow and for its high time resolution, at least in the last millennium. A lot of ice core data are available especially in the Arctic and Antarctic regions.Tree-ring can also offer high-qualified information of temperature. Recently,not only the width of tree-ring but also its density have been used in studies of climatic changes. In addition, tree-ring has a high and homogeneous time resolution, favourable for the reconstruction of the past climate.Documentary data related to climatic changes are very abundant, especially in China. However, two problems should be solved in use of the documentary data:discontinuity and ambiguity.The fourth source involves glacier, pollen and others. Most of them characterize only long-term climatic changes, and have lower time resolutions.Five cold stages were identified in the world. The 17th century and the 19th century were two cold stages common to the globe. The first half of the 12th century, the second half of the 13th century and the second half of the 15th century were relatively weak cold stages, and they appeared only in some parts of the earth surface. The cold stages identified from proxy data sources can be outlined as follows:East Asia1100-1149, 1250-1349, 1425-1474, 1600-1699, 1800-1899Europe1100-1149, 1300-1399, 1550-1699, 1800-1899Former USSR1200-1299, 1400-1499, 1650-1749, 1850-1949North America1100-1149, 1200-1249, 1300-1349, 1450-1499, 1600-1699, 1800-1849Polar Regions1100-1149, 1250-1299, 1450-1499, 1600-1699, 1800-1899Southern Hemisphere1100-1149, 1250-1299, 1450-1499, 1550-1699, 1775-1824, 1875-1924The average temperatures of the 17th and 19th centuries are about 0.5-1.0℃lower than the last millennium average. But the average temperature of the 20th century is 0.5℃ higher than the last millennium average. Therefore, the average temperature of the Little Ice Age is about 1.0-1.5℃ lower than the present average.The average temperature of the Medieval Warm Period is 1.0℃ higher than th elast millennium average and 0.5℃ higher than the present average. The average temperature of ten regions in the world shows that a warm peak occurred in the second half of the century and that a prolonged cold period was from 1600 to 1900AD. The so called Little Ice Age refers just to the period of 1600 to 1900 AD.The acidity and ¹⁴C abundance in Greenland ice cores were used to study volcanism and solar activity.. The correlation of these two indices with the average temperat-ure anomalies are-0.49 and -0.73, respectively. The cold stages of the 13th, the 15th and the 17th century are more or less in line with the periods with minimum solar activities, i.e., well-known Wolf minimum, Spokane minima and Maunder minimum. Two maxima of volcanism seem also to contribute to the occurrence of the 15th and the 17th cold century. However,the weak cold stage of the later 12th century and the strong cold of the 19th century are difficult to be attributed directly to changes of solar activity or volcanism. Therefore, the variations of volcanic aerosol and solar irradiance are probably responsible for the formation of the Little Ice Age, but other factors may also contribute to the climatic changes during the last millennium