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


Methyl chloroform (CH3CCl3, 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 Protocol1. Subsequently, its atmospheric concentration has declined steadily2,3,4 and recent European methyl chloroform consumption and emissions were estimated to be less than 0.1 gigagrams per year1,5. 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 emissions1,4. Such enhanced emissions would significantly affect results from the CH3CC13 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 data1,5, but are considerably lower than those derived from the EXPORT campaign in 2000 (ref. 6).

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Figure 1: CH3CCl3 at Mace Head and Jungfraujoch in 2000–03.
Figure 2: CH3CCl3 deviations from the baseline at Mace Head in 2000.


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We thank C. Harth and P. Salameh for calibration and data processing, G. Spain and D. Brown for instrument operation and maintenance at Mace Head and the Physics Department of NUI Galway for access to Mace Head facilities. Measurements and modelling at Mace Head are supported by NASA (USA) and DEFRA (UK). We thank SAEFL/BUWAL and BBW for financial support, HFSJG for access to Jungfraujoch facilities and P. Kaufmann (MeteoSwiss) for meteorological data. Both sites receive financial support from the EU 5th Framework Program (project SOGE).

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Correspondence to Stefan Reimann.

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Supplementary information

Supplementary Figure 1

This figure shows the comparison of measured CO time series at Mace Head in 2000 with modelled time series using NAME inversely estimated European emissions and EMEP emission estimates. (DOC 156 kb)

Supplementary Table 1

In this table best-fit estimated emissions of CH3CCl3 (three-year averages) from different European regions (Gg yr-1) by the NAME model are shown. (DOC 49 kb)

Supplementary Table 2

This table shows the decline of the world-wide regional emissions of CH3CCl3 between 1990 and 2000; calculated from consumption data. (DOC 37 kb)

Supplementary Table 3

In this table the comparison of regionalised European CH3CCl3 emission estimates, derived from the EXPORT campaign in 2000 and by the NAME inversion method from Mace Head (1999-2001) are shown. (DOC 35 kb)

Supplementary Table 4

This table shows excess concentrations of CO and CH3CCl3, which were used (together with the CO-emission estimates) for the calculation of the annual European emissions of CH3CCl3. (DOC 90 kb)

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Reimann, S., Manning, A., Simmonds, P. et al. Low European methyl chloroform emissions inferred from long-term atmospheric measurements. Nature 433, 506–508 (2005).

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