Reversal of global atmospheric ethane and propane trends largely due to US oil and natural gas production

Helmig, Detlev; Rossabi, Samuel; Hueber, Jacques; Tans, Pieter P.; Montzka, S. A.; Masarie, K. A.; Thoning, K. W.; Plaß-Duelmer, C.; Claude, Anja; Carpenter, Lucy J.; Lewis, Alastair C.; Punjabi, Shalini; Reimann, Stefan; Vollmer, Martin K.; Steinbrecher, R.; Hannigan, James W.; Emmons, L. K.; Mahieu, Emmanuel; Franco, Bruno; Smale, Dan; Pozzer, Andrea

doi:10.1038/ngeo2721

Cited by 168 publications

(223 citation statements)

References 49 publications

(3 reference statements)

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“…For instance, the mean alkene level in 2016 was approximately 2.3 times higher than that in 2015. This phenomenon coincides with the findings of previous studies indicating that the levels of VOCs increased in the midhigh altitudes of the Northern Hemisphere (Herbin et al, 2009;González Abad et al, 2011;Simpson et al, 2012;Helmig et al, 2016). The same phenomenon was observed for CO and CH 4 in this study (Table 1).…”

Section: Cluster Analysis Of Backward Trajectoriessupporting

confidence: 82%

Characteristics of Summertime Volatile Organic Compounds in the Lower Free Troposphere: Background Measurements at Mt. Fuji

Ou-Yang

Chang

Wang

et al. 2017

Aerosol Air Qual. Res.

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Air samples were collected at Mt. Fuji Research Station (FRS) for the measurements of volatile organic compounds (VOCs) in the summers of 2015 and 2016. In this study, 24 compounds were analyzed, of which only 12 halocarbons were quantified in 2015. The average total concentrations of target VOCs were 2.62 ± 1.38 and 2.99 ± 0.95 ppb in 2015 and 2016, respectively. The concentrations of individual VOCs ranged from a few ppt to a few ppb, indicating a highly inhomogeneous feature at the FRS. A cluster analysis of 3-day backward trajectories was performed for the sampling time. Except for the aromatic compounds, the VOCs showed relatively low concentrations in association with air masses originating from the coastal region in the low latitudes (15°N-35°N) of East Asia in 2015. By contrast, the clusters with elevated VOC concentrations mainly came from the high latitudes (35°N-60°N) of the Asian continent in 2016. No particular diurnal pattern was found for VOCs and CO, which might have resulted from suppressed mountain-valley winds at the FRS. Halocarbons regulated by the Montreal Protocol showed low variability and were in favorable agreement with background values at the Gosan station (GSN) and those reported in the literature. Other partially halogenated compounds with higher variability, such as CH 3 Cl and CHCl 3 , showed discrepancies at the FRS and GSN. 1,2-dichloroethane (R-150), 1,1-dichloroethane (R-150a), and 1,4-dichlorobenzene (p-DCB) were also measured at the FRS with concentrations of 24 ± 14, 38 ± 13, and 13 ± 10 ppt, respectively, in 2015. A close relationship between n-pentane and i-pentane with R 2 more than 0.85 was found in both 2015 and 2016. Low ratios of n/i-pentane ranging from 0.25 to 0.67 were observed in the free troposphere at the FRS, comparable to most mountain stations.

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Section: Cluster Analysis Of Backward Trajectoriessupporting

confidence: 82%

Characteristics of Summertime Volatile Organic Compounds in the Lower Free Troposphere: Background Measurements at Mt. Fuji

Ou-Yang

Chang

Wang

et al. 2017

Aerosol Air Qual. Res.

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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.

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275

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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Reversal of global atmospheric ethane and propane trends largely due to US oil and natural gas production

Cited by 168 publications

References 49 publications

Characteristics of Summertime Volatile Organic Compounds in the Lower Free Troposphere: Background Measurements at Mt. Fuji

Characteristics of Summertime Volatile Organic Compounds in the Lower Free Troposphere: Background Measurements at Mt. Fuji

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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