Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007-2014): top-down estimate from ethane and methane column observations
Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007-2014): top-down estimate from ethane and methane column observations
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DOI：
10.5194/acp-16-3227-2016
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发表时间：
2016-01-01
影响因子：
6.3
通讯作者：
Smale, Dan
中科院分区：
文献类型：
--
作者：
Hausmann, Petra;Sussmann, Ralf;Smale, Dan
1999-2014年期间大气甲烷和乙烷的柱平均摩尔分数的协调时间序列来自楚格峰峰会（47 A度aEuro-N，11 A度aEuro-E; 2964 m a.s.l.）的太阳傅里叶变换红外（FTIR）测量。和Lauder（45 A度aEuro-S，170 A度aEuro-E; 370米a.s.l.）。长期趋势分析显示，自2007年以来，楚格峰的甲烷持续增加6.2 [5.6，6.9] ppb/年（-1）（每年十亿分之一），兰黛的甲烷持续增加6.0 [5.3，6.7] ppb/年（-1）（95%置信区间）。最近的几项研究提供了证据，表明甲烷重新增加最有可能是由两个主要因素驱动的：（一）热带湿地甲烷排放量增加，其次是（二）由于石油和天然气生产的增加，产热甲烷排放量增加。在这里，我们量化的第二类来源的大小，使用长期测量的大气乙烷作为示踪剂的产热甲烷排放。2007年，在经历了多年的微弱下降之后，楚格峰乙烷时间序列突然出现了显著的正趋势（2007-2014年为2.3 [1.8，2.8]x -10（-2）ppb yr（-1）），而2007年之后，兰黛的负趋势持续存在（-0.4 [-0.6，-0.1]x -10（-2）ppb yr（-1））。楚格峰甲烷和乙烷时间序列在2007-2014年期间显著相关，并且可以被分配到乙烷与甲烷比率（EMR）为12- 19%的产热甲烷排放。我们提出了优化的排放情景，2007-2014年来自大气两箱模型。根据我们的趋势观察，我们推断2007-2014年期间石油和天然气来源的乙烷总排放量增加了1-11 Tg yr（-1）沿着，甲烷总排放量增加了24-45 Tg yr（-1）。基于这些结果，石油和天然气的排放贡献（C）的更新的甲烷增加推导出使用三种不同的排放情景与专用EMR范围。参考情景1假设石油和天然气排放组合的EMR= -7.0-16.2%，这导致最小贡献C >-39%（作为95%置信区间的下限给出）。除了这个最合理的情景1之外，我们还考虑了纯石油相关排放（情景2，EMR= -16.2-31.4%）和纯天然气来源（情景3，EMR= -4.4-7.0- %）的两种不太现实的限制情况，分别导致C >-18%和C >-73%。我们的研究结果表明，长期观测柱平均乙烷提供了一个有价值的限制甲烷排放变化的源属性，并提供了基础知识，制定有效的气候变化减缓战略。
Harmonized time series of column-averaged mole fractions of atmospheric methane and ethane over the period 1999-2014 are derived from solar Fourier transform infrared (FTIR) measurements at the Zugspitze summit (47A degrees aEuro-N, 11A degrees aEuro-E; 2964 m a.s.l.) and at Lauder (45A degrees aEuro-S, 170A degrees aEuro-E; 370 m a.s.l.). Long-term trend analysis reveals a consistent renewed methane increase since 2007 of 6.2 [5.6, 6.9] ppb yr(-1) (parts-per-billion per year) at the Zugspitze and 6.0 [5.3, 6.7] ppb yr(-1) at Lauder (95 % confidence intervals). Several recent studies provide pieces of evidence that the renewed methane increase is most likely driven by two main factors: (i) increased methane emissions from tropical wetlands, followed by (ii) increased thermogenic methane emissions due to growing oil and natural gas production. Here, we quantify the magnitude of the second class of sources, using long-term measurements of atmospheric ethane as a tracer for thermogenic methane emissions. In 2007, after years of weak decline, the Zugspitze ethane time series shows the sudden onset of a significant positive trend (2.3 [1.8, 2.8]x -10(-2) ppb yr(-1) for 2007-2014), while a negative trend persists at Lauder after 2007 (-0.4 [-0.6, -0.1]x -10(-2) ppb yr(-1)). Zugspitze methane and ethane time series are significantly correlated for the period 2007-2014 and can be assigned to thermogenic methane emissions with an ethane-to-methane ratio (EMR) of 12-19 %. We present optimized emission scenarios for 2007-2014 derived from an atmospheric two-box model. From our trend observations we infer a total ethane emission increase over the period 2007-2014 from oil and natural gas sources of 1-11 Tg yr(-1) along with an overall methane emission increase of 24-45 Tg yr(-1). Based on these results, the oil and natural gas emission contribution (C) to the renewed methane increase is deduced using three different emission scenarios with dedicated EMR ranges. Reference scenario 1 assumes an oil and gas emission combination with EMR= -7.0-16.2 %, which results in a minimum contribution C > -39 % (given as lower bound of 95 % confidence interval). Beside this most plausible scenario 1, we consider two less realistic limiting cases of pure oil-related emissions (scenario 2 with EMR= -16.2-31.4 %) and pure natural gas sources (scenario 3 with EMR= -4.4-7.0- %), which result in C > -18 % and C > -73 %, respectively. Our results suggest that long-term observations of column-averaged ethane provide a valuable constraint on the source attribution of methane emission changes and provide basic knowledge for developing effective climate change mitigation strategies.