Retrieval of ethane from ground-based FTIR solar spectra using improved spectroscopy: Recent burden increase above Jungfraujoch

Franco, Bruno; Bader, Whitney; Toon, G. C.; Bray, Cédric; Perrin, A.; Fischer, Emily V.; Sudo, Kengo; Boone, C. D.; Bovy, Benoît; Lejeune, Bernard; Servais, Christian; Mahieu, Emmanuel

doi:10.1016/j.jqsrt.2015.03.017

Cited by 41 publications

(89 citation statements)

References 62 publications

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“…Negative ethane trends for 1996-2006 are also reported by Angelbratt et al (2011) from FTIR observations at four European NDACC stations. The recent ethane trend reversal identified at the Zugspitze observatory is also observed at the high-altitude NDACC station of Jungfraujoch, Swiss Alps (Franco et al, 2015). Furthermore, longterm in situ measurements in the US show increasing ethane concentrations over the past years linked with increasing natural gas production (Vinciguerra et al, 2015).…”

Section: Results Of Long-term Trend Analysismentioning

confidence: 70%

“…Mid-infrared NDACC-type methane retrievals are in good agreement with near-infrared FTIR measurements from the Total Carbon Column Observing Network (TCCON; Sussmann et al, 2013;Ostler et al, 2014). For the retrieval of column-averaged ethane we follow the strategy applied in Vigouroux et al (2012Vigouroux et al ( ) using two microwindows (2976Vigouroux et al ( .66-2976Vigouroux et al ( .95, 2983Vigouroux et al ( .20-2983.55 cm −1 ), an ethane pseudo-line list (Franco et al, 2015), and first-order Tikhonov regularization. In agreement with the NDACC Infrared Working Group retrieval recommendations (IRWG, 2014), we consider three interfering species (water vapor, ozone, and methane) and choose an a priori volume mixing ratio profile derived from WACCM (Whole Atmosphere Chemistry Model, version 6; Garcia et al, 2007).…”

Section: P Hausmann Et Almentioning

confidence: 69%

“…An increase of this strength does not seem to be reasonable and is not evident from the literature. Consequently, we do not consider geologic ethane emissions in our box model as done in several previous ethane studies (Pozzer et al, 2010;Aydin et al, 2011;Franco et al, 2015 …”

Section: Appendix B: Atmospheric Two-box Modelmentioning

confidence: 99%

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Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007–2014): top–down estimate from ethane and methane column observations

2016

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Abstract. 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 (47 • N, 11 • E; 2964 m a.s.l.) and at Lauder (45 • S, 170 • 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. 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 columnaveraged ethane provide a valuable constraint on the source attribution of methane emission changes and provide basic knowledge for developing effective climate change mitigation strategies.

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Section: Results Of Long-term Trend Analysismentioning

confidence: 70%

Section: P Hausmann Et Almentioning

confidence: 69%

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Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007–2014): top–down estimate from ethane and methane column observations

2016

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“…It should be noted that our modeling Y. Huang et al: Surface ozone and its precursors at Summit, Greenland period reflects a time when there was a reversal of the atmospheric C 2 H 6 trend, most likely reflecting emission changes during that time. Atmospheric C 2 H 6 had a decreasing trend from 1980 to 2009 (Simpson et al, 2012;Helmig et al, 2014a) but then began to increase around 2009 (Franco et al, 2015Hausmann et al, 2016;Helmig et al, 2016) in the Northern Hemisphere at a rate of increase that is approximately 4-6 times higher than its earlier rate of decline. It has been argued that the most likely cause for this trend and emission reversal is increasing emissions from oil and gas production, mostly from North America (Franco et al, 2015Hausmann et al, 2016;Helmig et al, 2016).…”

Section: Nmhcmentioning

confidence: 89%

Surface ozone and its precursors at Summit, Greenland: comparison between observations and model simulations

Huang¹,

Wu²,

Kramer³

et al. 2017

Atmos. Chem. Phys.

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Abstract. Recent studies have shown significant challenges for atmospheric models to simulate tropospheric ozone (O 3 ) and its precursors in the Arctic. In this study, ground-based data were combined with a global 3-D chemical transport model (GEOS-Chem) to examine the abundance and seasonal variations of O 3 and its precursors at Summit, Greenland (72.34 • N, 38.29 • W; 3212 m a.s.l.). Model simulations for atmospheric nitrogen oxides (NO x ), peroxyacetyl nitrate (PAN), ethane (C 2 H 6 ), propane (C 3 H 8 ), carbon monoxide (CO), and O 3 for the period July 2008-June 2010 were compared with observations. The model performed well in simulating certain species (such as CO and C 3 H 8 ), but some significant discrepancies were identified for other species and further investigated. The model generally underestimated NO x and PAN (by ∼ 50 and 30 %, respectively) for MarchJune. Likely contributing factors to the low bias include missing NO x and PAN emissions from snowpack chemistry in the model. At the same time, the model overestimated NO x mixing ratios by more than a factor of 2 in wintertime, with episodic NO x mixing ratios up to 15 times higher than the typical NO x levels at Summit. Further investigation showed that these simulated episodic NO x spikes were always associated with transport events from Europe, but the exact cause remained unclear. The model systematically overestimated C 2 H 6 mixing ratios by approximately 20 % relative to observations. This discrepancy can be resolved by decreasing anthropogenic C 2 H 6 emissions over Asia and the US by ∼ 20 %, from 5.4 to 4.4 Tg year −1 . GEOS-Chem was able to reproduce the seasonal variability of O 3 and its spring maximum. However, compared with observations, it underestimated surface O 3 by approximately 13 % (6.5 ppbv) from April to July. This low bias appeared to be driven by several factors including missing snowpack emissions of NO x and nitrous acid in the model, the weak simulated stratosphereto-troposphere exchange flux of O 3 over the summit, and the coarse model resolution.

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“…Some recent studies have pointed to an "upturn" in global concentrations of ethane (C2H6), coincident with the recent rise in CH4 (5,30,31), which may imply an increase in CH4 emissions caused by an increase in oil and gas extraction. Column-averaged measurements in the background atmosphere reveal trends in C2H6 between 2007 and 2014 of 23 (95% confidence interval = 18, 28) and −4 (95% confidence interval = −6, −1) pmol mol −1 y −1 in the northern and southern hemispheres, respectively (5).…”

Section: Discussionmentioning

confidence: 99%

Role of atmospheric oxidation in recent methane growth

Rigby

Montzka

Prinn

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

300

349

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The growth in global methane (CH 4 ) concentration, which had been ongoing since the industrial revolution, stalled around the year 2000 before resuming globally in 2007. We evaluate the role of the hydroxyl radical (OH), the major CH 4 sink, in the recent CH 4 growth. We also examine the influence of systematic uncertainties in OH concentrations on CH 4 emissions inferred from atmospheric observations. We use observations of 1,1,1-trichloroethane (CH 3 CCl 3 ), which is lost primarily through reaction with OH, to estimate OH levels as well as CH 3 CCl 3 emissions, which have uncertainty that previously limited the accuracy of OH estimates. We find a 64-70% probability that a decline in OH has contributed to the post-2007 methane rise. Our median solution suggests that CH 4 emissions increased relatively steadily during the late 1990s and early 2000s, after which growth was more modest. This solution obviates the need for a sudden statistically significant change in total CH 4 emissions around the year 2007 to explain the atmospheric observations and can explain some of the decline in the atmospheric 13 CH 4 / 12 CH 4 ratio and the recent growth in C 2 H 6 . Our approach indicates that significant OH-related uncertainties in the CH 4 budget remain, and we find that it is not possible to implicate, with a high degree of confidence, rapid global CH 4 emissions changes as the primary driver of recent trends when our inferred OH trends and these uncertainties are considered., the second most important partially anthropogenic greenhouse gas, is observed to vary markedly in its year to year growth rate (Fig. 1). The causes of these variations have been the subject of much controversy and uncertainty, primarily because there is a wide range of poorly quantified sources and because its sinks are ill-constrained (1). Of particular recent interest are the cause of the "pause" in CH4 growth between 1999 and 2007 and the renewed growth from 2007 onward (2-7). It is important that we understand these changes if we are to better project future CH4 changes and effectively mitigate enhanced radiative forcing caused by anthropogenic methane emissions.The major sources of CH4 include wetlands (natural and agricultural), fossil fuel extraction and distribution, enteric fermentation in ruminant animals, and solid and liquid waste. Our understanding of the sources of CH4 comes from two approaches: "bottom up," in which inventories or process models are used to predict fluxes, or "top down," in which fluxes are inferred from observations assimilated into atmospheric chemical transport models. Bottom-up methods suffer from uncertainties and potential biases in the available activity data or emissions factors or the extrapolation to large scales of a relatively small number of observations. Furthermore, there is no constraint on the global total emissions from bottom-up techniques. The topdown approach is limited by incomplete or imperfect observations and our understanding of atmospheric transport and chemical sinks. For CH4, these di...

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Retrieval of ethane from ground-based FTIR solar spectra using improved spectroscopy: Recent burden increase above Jungfraujoch

Cited by 41 publications

References 62 publications

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

Surface ozone and its precursors at Summit, Greenland: comparison between observations and model simulations

Role of atmospheric oxidation in recent methane growth

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