Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air

Aydın, Murat; Verhulst, K. R.; Saltzman, E. S.; Battle, Mark; Montzka, S. A.; Blake, Donald R.; Tang, Qi; Prather, Michael J.

doi:10.1038/nature10352

Cited by 178 publications

(232 citation statements)

References 30 publications

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“…It is particularly difficult to reconcile the results here with the assertion of decreasing (10-30 Tg y −1 ) natural gas and oil fugitive emissions based on falling ethane mixing ratios (6,7). This scenario was selected as more likely than decreasing microbial emissions to explain the stabilization of CH 4 emissions in a recent review synthesis (3).…”

Section: Significancementioning

confidence: 98%

See 1 more Smart Citation

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

Rice

Butenhoff

Teama

et al. 2016

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

100

114

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Observations of atmospheric methane (CH 4 ) since the late 1970s and measurements of CH 4 trapped in ice and snow reveal a meteoric rise in concentration during much of the twentieth century. Since 1750, levels of atmospheric CH 4 have more than doubled to current globally averaged concentration near 1,800 ppb. During the late 1980s and 1990s, the CH 4 growth rate slowed substantially and was near or at zero between 1999 and 2006. There is no scientific consensus on the drivers of this slowdown. Here, we report measurements of the stable isotopic composition of atmospheric CH 4 ( 13 C/ 12 C and D/H) from a rare air archive dating from 1977 to 1998. Together with more modern records of isotopic atmospheric CH 4 , we performed a time-dependent retrieval of methane fluxes spanning 25 y (1984-2009) using a 3D chemical transport model. This inversion results in a 24 [18,27] Tg y −1 CH 4 increase in fugitive fossil fuel emissions since 1984 with most of this growth occurring after year 2000. This result is consistent with some bottom-up emissions inventories but not with recent estimates based on atmospheric ethane. In fact, when forced with decreasing emissions from fossil fuel sources our inversion estimates unreasonably high emissions in other sources. Further, the inversion estimates a decrease in biomass-burning emissions that could explain falling ethane abundance. A range of sensitivity tests suggests that these results are robust.atmospheric methane | greenhouse gas emissions | methane isotopic composition | methane trends | Bayesian inversion C onsiderable research since the 1970s has established the role of methane (CH 4 ) in climate, as an infrared active gas, and as a chemically reactive species affecting hydroxyl radical, ozone, and carbon monoxide in the troposphere and chlorine, ozone, and water vapor in the stratosphere. At a globally averaged mixing ratio of 1,800 ppb, the abundance of CH 4 in the atmosphere has more than doubled since the industrial revolution as a result of population growth, agricultural practices, and fossil fuel use (1). The rise in CH 4 concentration is considered to contribute 0.48 Wm −2 of the 2.83 Wm −2 radiative forcing by wellmixed greenhouse gases since 1750 (2). Including indirect effects from CH 4 emissions roughly doubles its effective radiative forcing. Its global warming potential (not including feedbacks) is 28 based on a 100-y time horizon, but 84 based on a 20-y timescale [global warming potential (GWP) is relative to CO 2 ], illustrating the potential of large changes in the burden of CH 4 to influence climate on short timescales (2).Both the decrease in the CH 4 growth rate and its interannual variability since 1984 are well documented by at least four global networks of atmospheric measurements; agreement between time series is excellent with some exceptions early on. Recently, a review and synthesis of the CH 4 budget (3) pointed to some consensus of measurement and modeling studies and their comparisons toward understanding temporal changes in the CH 4 budget....

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Section: Significancementioning

confidence: 98%

“…In particular, two recent studies using the tracer ethane have linked a sustained drop in ethane mixing ratios to a decrease in fugitive fossil fuel-based CH 4 emissions by 10-30 Tg y −1 since the 1980s (6,7). This top-down result differs with bottom-up emissions inventories that show increasing or flat fugitive fossil fuel CH 4 emissions (8).…”

mentioning

confidence: 99%

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

Rice

Butenhoff

Teama

et al. 2016

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

100

114

View full text Add to dashboard Cite

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“…For our Antarctic samples, the reproducibility for ethane obtained on B34, WAIS and TALDICE ranges between 21 ppt for WAIS and 156 ppt for B34. More critical is that the reconstructed absolute mixing ratios exceed the modern values for Antarctica and those reconstructed from Antarctic firn air samples (Aydin et al, 2011). Whole procedure blank measurements, "gas free ice as sample", indicate that a large fraction of the ethane and propane signal of the Antarctic cores B34, WAIS and TALDICE is generated during the melting process from the vessel surfaces (Table 2).…”

Section: Ice Core Samples and Replicatesmentioning

confidence: 99%

“…to these traditional trace gases at ppm (CO 2 ) or ppb levels (CH 4 and N 2 O), CO and atmospheric trace gases at ppt level, like ethane, propane or methyl chloride, are currently being studied in firn (Aydin et al, 2011;Worton et al, 2012) and ice core studies (Saltzman et al, 2009;Wang et al, 2010;Verhulst et al, 2013). Although these ppt-level gases do not significantly influence climate via the greenhouse effect, they act indirectly, e.g.…”

Section: Introductionmentioning

confidence: 99%

Online technique for isotope and mixing ratios of CH4, N2O, Xe and mixing ratios of organic trace gases on a single ice core sample

et al. 2014

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Abstract. Firn and polar ice cores enclosing trace gas species offer a unique archive to study changes in the past atmosphere and in terrestrial/marine source regions. Here we present a new online technique for ice core and air samples to measure a suite of isotope ratios and mixing ratios of trace gas species on a single sample. Isotope ratios are determined on methane, nitrous oxide and xenon with reproducibilities for ice core samples of 0.15 ‰ for δ 13 C-CH 4 , 0.22 ‰ for δ 15 N-N 2 O, 0.34 ‰ for δ 18 O-N 2 O, and 0.05 ‰ per mass difference for δ 136 Xe for typical concentrations of glacial ice. Mixing ratios are determined on methane, nitrous oxide, xenon, ethane, propane, methyl chloride and dichlorodifluoromethane with reproducibilities of 7 ppb for CH 4 , 3 ppb for N 2 O, 70 ppt for C 2 H 6 , 70 ppt for C 3 H 8 , 20 ppt for CH 3 Cl, and 2 ppt for CCl 2 F 2 . However, the blank contribution for C 2 H 6 and C 3 H 8 is large in view of the measured values for Antarctic ice samples. The system consists of a vacuum extraction device, a preconcentration unit and a gas chromatograph coupled to an isotope ratio mass spectrometer. CH 4 is combusted to CO 2 prior to detection while we bypass the oven for all other species. The highly automated system uses only ∼ 160 g of ice, equivalent to ∼ 16 mL air, which is less than previous methods. The measurement of this large suite of parameters on a single ice sample is new and key to understanding phase relationships of parameters which are usually not measured together. A multi-parameter data set is also key to understand in situ production processes of organic species in the ice, a critical issue observed in many organic trace gases. Novel is the determination of xenon isotope ratios using doubly charged Xe ions. The attained precision for δ 136 Xe is suitable to correct the isotopic ratios and mixing ratios for gravitational firn diffusion effects, with the benefit that this information is derived from the same sample. Lastly, anomalies in the Xe mixing ratio, δXe/air, can be used to detect melt layers.

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“…Based on these previous observations it was suggested that a steady state had been reached, but the latest observations suggest that since 2007 the trend has increased once again (Rigby et al, 2008;Dlugokencky et al, 2009). A number of possible explanations for both the long-term and year to year variations have been suggested including: changes in global OH concentration, the major atmospheric sink for CH 4 (Dentener et al, 2003;Wang et al, 2004;Fiore et al, 2006); and changes in emissions from sources including rice agriculture, wetlands, biomass burning and the use of fossil fuels (Dlugokencky et al, 2001;Langenfelds et al, 2002;Simpson et al, 2006Simpson et al, , 2012Bousquet et al, 2011;Kai et al, 2011;Aydin et al, 2011;Levin et al, 2012). However, these changes are not yet fully understood nor unequivocally linked to the global trend in CH 4 .…”

Section: Introductionmentioning

confidence: 99%

Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH4 and CO2

et al. 2013

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Abstract. High-resolution CH4 and CO2 measurements were made on board the FAAM BAe-146 UK (Facility for Airborne Atmospheric Measurements, British Aerospace-146) atmospheric research aircraft during a number of field campaigns. The system was based on an infrared spectrometer using the cavity-enhanced absorption spectroscopy technique. Correction functions to convert the mole fractions retrieved from the spectroscopy to dry-air mole fractions were derived using laboratory experiments and over a 3 month period showed good stability. Long-term performance of the system was monitored using WMO (World Meteorological Office) traceable calibration gases. During the first year of operation (29 flights) analysis of the system's in-flight calibrations suggest that its measurements are accurate to 1.28 ppb (1σ repeatability at 1 Hz = 2.48 ppb) for CH4 and 0.17 ppm (1σ repeatability at 1 Hz = 0.66 ppm) for CO2. The system was found to be robust, no major motion or altitude dependency could be detected in the measurements. An inter-comparison between whole-air samples that were analysed post-flight for CH4 and CO2 by cavity ring-down spectroscopy showed a mean difference between the two techniques of −2.4 ppb (1σ = 2.3 ppb) for CH4 and −0.22 ppm (1σ = 0.45 ppm) for CO2. In September 2012, the system was used to sample biomass-burning plumes in Brazil as part of the SAMBBA project (South AMerican Biomass Burning Analysis). From these and simultaneous CO measurements, emission factors for savannah fires were calculated. These were found to be 2.2 ± 0.2 g (kg dry matter)−1 for CH4 and 1710 ± 171 g (kg dry matter)−1 for CO2, which are in excellent agreement with previous estimates in the literature.

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Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air

Cited by 178 publications

References 30 publications

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

Online technique for isotope and mixing ratios of CH<sub>4</sub>, N<sub>2</sub>O, Xe and mixing ratios of organic trace gases on a single ice core sample

Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH<sub>4</sub> and CO<sub>2</sub>

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Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air

Cited by 178 publications

References 30 publications

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

Online technique for isotope and mixing ratios of CH&lt;sub&gt;4&lt;/sub&gt;, N&lt;sub&gt;2&lt;/sub&gt;O, Xe and mixing ratios of organic trace gases on a single ice core sample

Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH&lt;sub&gt;4&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt;

Contact Info

Product

Resources

About

Online technique for isotope and mixing ratios of CH<sub>4</sub>, N<sub>2</sub>O, Xe and mixing ratios of organic trace gases on a single ice core sample

Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH<sub>4</sub> and CO<sub>2</sub>