Atmospheric methane between 1000 AD and present: Evidence of anthropogenic emissions and climatic variability
Atmospheric methane between 1000 AD and present: Evidence of anthropogenic emissions and climatic variability
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DOI：
10.1029/98jd00923
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发表时间：
1998-07-20
影响因子：
4.4
通讯作者：
Langenfelds, RL
中科院分区：
文献类型：
--
作者：
Etheridge, DM;Steele, LP;Langenfelds, RL
在三个南极冰芯、两个格陵兰冰芯、南极冰层和澳大利亚塔斯马尼亚档案空气中测量了从公元 1000 年至今的大气甲烷混合比。通过对所有样本使用相同的测量程序和校准尺度，并确保冰芯和冰空气的高年龄分辨率和准确性，该记录是统一的。通过这种方式，可以准确确定甲烷混合比、增长率和极间差异。从公元 1000 年到 1800 年，全球平均甲烷混合比平均为 695 ppb，随气候变化而变化约 40 ppb。极间 (N-S) 差异在 24 到 58 ppb 之间变化。工业时期的特点是 1945 年至 1990 年甲烷增长率较高，在 1981 年达到峰值约 17 ppb yr(-1)，此后大幅下降。我们计算出公元 1000-1800 年平均总甲烷源为 250 Tg yr(-1)，在 1980 年代和 1990 年代接近稳定在 560 Tg yr(-1) 左右。在存档空气和冷空气中测量的同位素比 delta(13) CH4 自 1978 年以来有所增加，但增加速度在 20 世纪 80 年代中期放缓。 CH4 和 delta(13)CH(4) 的综合趋势支持 CH4 总来源的稳定。
Atmospheric methane mixing ratios from 1000 A.D. to present are measured in three Antarctic ice cores, two Greenland ice cores, the Antarctic firn layer, and archived air from Tasmania, Australia. The record is unified by using the same measurement procedure and calibration scale for all samples and by ensuring high age resolution and accuracy of the ice core and firn air. In this way, methane mixing ratios, growth rates, and interpolar differences are accurately determined. From 1000 to 1800 A.D. the global mean methane mixing ratio averaged 695 ppb and varied about 40 ppb, contemporaneous with climatic variations. Interpolar (N-S) differences varied between 24 and 58 ppb. The industrial period is marked by high methane growth rates from 1945 to 1990, peaking at about 17 ppb yr(-1) in 1981 and decreasing significantly since. We calculate an average total methane source of 250 Tg yr(-1) for 1000-1800 A.D:.,reaching near stabilization at about 560 Tg yr(-1) in the 1980s and 1990s. The isotopic ratio, delta(13) CH4, measured in the archived air and firn air, increased since 1978 but the rate of increase slowed in the mid-1980s. The combined CH4 and delta(13)CH(4) trends support the stabilization of the total CH4 source.