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Continuing emissions of methyl chloroform from Europe


The consumption of methyl chloroform (1,1,1-trichloroethane), an industrial solvent, has been banned by the 1987 Montreal Protocol because of its ozone-depleting potential. During the 1990s, global emissions have decreased substantially and, since 1999, near-zero emissions have been estimated for Europe and the United States. Here we present measurements of methyl chloroform that are inconsistent with the assumption of small emissions. Using a tracer transport model, we estimate that European emissions were greater than 20 Gg in 2000. Although these emissions are not significant for stratospheric ozone depletion, they have important implications for estimates of global tropospheric hydroxyl radical (OH) concentrations, deduced from measurements of methyl chloroform. Ongoing emissions therefore cast doubt upon recent reports of a strong and unexpected negative trend in OH during the 1990s and a previously calculated higher OH abundance in the Southern Hemisphere compared to the Northern Hemisphere.

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Figure 1: Flight tracks of the British C-130 aircraft.
Figure 2: Analysis of the EXPORT flights as a function of height.
Figure 3: MCF and CO simulations compared to Mace Head observations.
Figure 4: Methyl chloroform measurements performed in the MINOS and CARIBIC projects, showing substantial variability up to 2001.

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Assistance from E. Atlas and S. Montzka in instrumental design and calibrations is gratefully acknowledged. R.G. Prinn and colleagues provided the AGAGE MCF and CO data at Mace Head. We thank F. J. Dentener for comments and help with the implementation of the EDGAR 3.2 CO emissions, which were provided by J. Olivier. We also thank C. v.d. Veen and R. Hofmann for experimental assistance. EXPORT CO data were provided by H. Barjat and J. Kent of the UK Met Office using an instrument on loan from the Institut für Chemie und Dynamik der Geosphaere Forschungszentrum Jülich. EXPORT was funded by the UK Natural Environment Research Council (NERC) with additional funds from the UK Department of Environment, Food and Rural Affairs (DEFRA) and the UK Met Office. M.K. is supported by the Space Research Organisation Netherlands (SRON). V.G. is supported by a scientific cooperation between MPG and CNRS.

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Krol, M., Lelieveld, J., Oram, D. et al. Continuing emissions of methyl chloroform from Europe. Nature 421, 131–135 (2003).

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