Preprints
https://doi.org/10.5194/acp-2021-285
https://doi.org/10.5194/acp-2021-285

  09 Apr 2021

09 Apr 2021

Review status: this preprint is currently under review for the journal ACP.

Temporary pause in the growth of atmospheric ethane and propane in 2015–2018

Hélène Angot1,2, Connor Davel1, Christine Wiedinmyer3, Gabrielle Pétron3,4, Jashan Chopra1, Jacques Hueber1,5, Brendan Blanchard1, Ilann Bourgeois3,6, Isaac Vimont3, Stephen A. Montzka4, Ben R. Miller3,4, James W. Elkins4, and Detlev Helmig1,5 Hélène Angot et al.
  • 1Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA
  • 2School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Sion, Switzerland
  • 3Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
  • 4NOAA, Global Monitoring Laboratory (GML), Earth System Research Laboratories, Boulder, CO, USA
  • 5Boulder A.I.R. LLC, Boulder, CO, USA
  • 6NOAA, Chemical Sciences Laboratory (CSL), Earth System Research Laboratories, Boulder, CO, USA

Abstract. Atmospheric non-methane hydrocarbons (NMHCs) play an important role in the formation of secondary organic aerosols and ozone. After a multidecade global decline in atmospheric mole fractions of ethane and propane – the most abundant atmospheric NMHCs – previous work has shown a reversal of this trend with increasing atmospheric abundances from 2009 to 2015 in the Northern Hemisphere. These concentration increases were attributed to the unprecedented growth in oil and natural gas (O&NG) production in North America. Here, we supplement this trend analysis building on the long-term (2008–2010; 2012–2020) high-resolution (~3-hour) record of ambient air C2-C7 NMHCs from in-situ measurements at the Greenland Environmental Observatory at Summit station (GEOSummit, 72.58° N, 38.48° W, 3210 m above sea level). We confirm previous findings that the ethane mole fraction significantly increased by +69.0 [+47.4, +73.2; 95 % confidence interval] ppt per year from January 2010 to December 2014. Subsequent measurements, however, reveal a significant decrease by −58.4 [−64.1, −48.9] ppt per year from January 2015 to December 2018. A similar reversal is found for propane. The upturn observed after 2019 suggests, however, that the pause in the growth of atmospheric ethane and propane might only have been temporary. The analysis of 2012–2019 air mass back-trajectories shows that this pause in mole fraction increases can neither be attributed to changes in atmospheric transport nor to changes in regional emissions. Discrete samples collected at other northern-hemisphere baseline sites under the umbrella of the NOAA cooperative global air sampling network show a similar decrease in 2015–2018 and suggest a hemispheric pattern. Here, we further discuss the potential contribution of biomass burning and O&NG emissions, the main sources of ethane and propane, and we conclude that O&NG activities likely played a role in these recent changes. This study, however, highlights the crucial need for better constrained emission inventories.

Hélène Angot et al.

Status: open (until 04 Jun 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Hélène Angot et al.

Hélène Angot et al.

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Short summary
After a multi-decade global decline in atmospheric concentrations of ethane and propane (precursors to tropospheric ozone and aerosols), previous work showed a reversal of this trend in 2009–2015 in the Northern Hemisphere due to the growth in oil and natural gas production in North America. Here we show a temporary pause in the growth of atmospheric ethane and propane in 2015–2018 and highlight the critical need for additional top-down studies to further constrain ethane and propane emissions.
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