Low European methyl chloroform emissions inferred from long-term atmospheric measurements

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From: Nature(Vol. 433, Issue 7025)
Publisher: Nature Publishing Group
Document Type: Article
Length: 3,607 words
Lexile Measure: 1550L

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Author(s): Stefan Reimann (corresponding author) [1]; Alistair J. Manning [2]; Peter G. Simmonds [3]; Derek M. Cunnold [4]; Ray H. J. Wang [4]; Jinlong Li [4]; Archie McCulloch [3]; Ronald G. Prinn [5]; Jin Huang [5]; Ray F. Weiss [6]; Paul J. Fraser [7]; Simon O'Doherty [3]; Brian R. Greally [3]; Konrad Stemmler [1]; Matthias Hill [1]; Doris Folini [1]

Methyl chloroform (CH3 CCl3 , 1,1,1,-trichloroethane) was used widely as a solvent before it was recognized to be an ozone-depleting substance and its phase-out was introduced under the Montreal Protocol [1]. Subsequently, its atmospheric concentration has declined steadily [2, 3, 4] and recent European methyl chloroform consumption and emissions were estimated to be less than 0.1 gigagrams per year [1, 5]. However, data from a short-term tropospheric measurement campaign (EXPORT) indicated that European methyl chloroform emissions could have been over 20 gigagrams in 2000 (ref. 6), almost doubling previously estimated global emissions [1, 4]. Such enhanced emissions would significantly affect results from the CH3 CC13 method of deriving global abundances of hydroxyl radicals (OH) (refs 7-12)--the dominant reactive atmospheric chemical for removing trace gases related to air pollution, ozone depletion and the greenhouse effect. Here we use long-term, high-frequency data from Mace Head, Ireland and Jungfraujoch, Switzerland, to infer European methyl chloroform emissions. We find that European emission estimates declined from about 60 gigagrams per year in the mid-1990s to 0.3-1.4 and 1.9-3.4 gigagrams per year in 2000-03, based on Mace Head and Jungfraujoch data, respectively. Our European methyl chloroform emission estimates are therefore higher than calculated from consumption data [1, 5], but are considerably lower than those derived from the EXPORT campaign in 2000 (ref. 6).

Consumption of CH3 CCl3 is to be phased out by 2015. Consequently, global emissions of CH3 CCl3 decreased from about 720 to 20 Gg (1990-2000; ref. 1) and atmospheric background concentrations have declined from 140-150 parts per trillion (p.p.t) in the 1990s [2, 3, 7, 8] to 25 p.p.t in 2003. However, in modelling measurements of four flights in a campaign in 2000 (EXPORT), European CH 3 CCl3 emissions were estimated to be >20 Gg yr-1 (ref. 6). This was supported by high concentrations of CH3 CCl3 measured in a three-week campaign (MINOS) in Crete in 2001 (ref. 13). These large European emissions would more than double the reported global CH 3 CCl3 emissions of about 20 Gg in 2000 (ref. 4) and would significantly impact on estimations of global OH-radical abundances, using global emissions of CH 3 CCl3 (refs 8, 11, 12).

Our study investigates this inconsistency using long-term CH3 CCl3 measurements at Mace Head (Ireland, 1994-2003) and Jungfraujoch (Switzerland, 2000-2003). Compared to earlier estimates from Mace Head alone [14, 15], the Jungfraujoch data extend the spatial coverage towards central and southern Europe. European emission estimates (EU-15 and Switzerland) are derived from inter-species correlations with carbon monoxide (CO) at Mace Head and Jungfraujoch, or from a meteorological transport model (for...

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Gale Document Number: GALE|A185472019