Methyl bromideThe Crop Protection Coalition (CPC) suggests that the scientific basis for phasing out methyl bromide (CH3Br) may not be justified. The implication of the CPC is that the effects of CH3Br on stratospheric ozone will likely continue to decline because a decreasing effect was noted as the science progressed throughout the 1990s. However, the scientific community completed a major new assessment of stratospheric ozone (Scientific Assessment of Ozone Depletion: 2002; available through the World Meteorological Organization in Geneva) in which little difference was found from the assessment determination results of 1998 ozone depletion potential. (ODP) for methyl bromide. This finding was not surprising. CH3Br still accounts for about 50% of the organic bromine reaching the stratosphere. Determining the ODP for methyl bromide depends primarily on understanding its total lifetime in the atmosphere, which in turn depends on understanding its removal processes from the atmosphere. During the 1990s, it was discovered that methyl bromide sinks in oceans and soil need to be considered when determining the lifetime of methyl bromide. These wells are now factored into our analyzes (a recent reassessment of the ocean basin yielded very similar results to the analyzes used in the 1998 assessment). While there remains some uncertainty regarding soil sorption, it is unlikely that this will further change the ODP for methyl bromide significantly. With ocean and land removal processes now included in analyzes of its ODP, large changes in the ODP for methyl bromide are unlikely to occur unless there are significant changes in the understanding of its removal processes. The currently evaluated global shelf life for CH3Br is 0.7 years, resulting in an ODP of 0.38. If all soil sink uncertainties were to be maximally directed toward sink augmentation, the ODP for CH3Br could decrease a bit more. However, this is extremely unlikely, as it would produce a huge inconsistency between sources and sinks, exacerbating the already existing difference between known sources and sinks. The bottom line is that the ODP for methyl bromide is unlikely to change further. As chlorine in the stratosphere decreases under the effects of the Montreal Protocol, the fact that stratospheric bromine is not currently decreasing means that bromine will become increasingly important in its production. effects on ozone.