Temperature and methane changes over the past 1000 years recorded in Dasuopu glacier (central Himalaya) ice core

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Abstract
In 1997, three ice cores were recovered from Dasuopu glacier on the northern slope of the central Himalaya. the first core, 159.9 m long, was drilled at 7000ma.s.l. down the flowline from the top of the col. the second core, 149.2m long, was drilled on the col at 7200ma.s.l. the third core, 167.7 m long, was also drilled on the col at 7200ma.s.l., 100 maway from the second core. the present paper discusses the δ18O and methane results reconstructed for the past 1000 years based on the second core. the δ18O can be interpreted as an air-temperature signal. the methane concentration is mainly representative of atmospheric methane concentration. Both δ18O and methane records show an obvious increasing trend in the past 1000 years. Methane concentration in the record is similar to the fluctuations of δ18O, decreasing during cold periods and increasing during warm periods. the Little Ice Age was well recorded in the core by both δ18O and methane. the coldest period appeared in the late 18th century, accompanied by a decrease in methane concentration. the abrupt methane-concentration increase starting after the 18th century is no doubt due to anthropogenic input. the observed methane-concentration decrease during World Wars I and II clearly demonstrates the importance of the anthropogenic input to atmospheric methane concentration if further measurements prove that it is a true atmospheric signal.