Odp For Ch 3 Br example essay topic

Methyl Bromide The Crop Protection Coalition (CPC) suggests that the scientific foundation for the phase out of methyl bromide (CH 3 Br) may not be justified. The implication of the CPC is that the effects of CH 3 Br on stratospheric ozone is likely to continue to decrease because there was a decreasing effect noted as the science progressed through the 1990's. However, the science community completed a major new assessment of stratospheric ozone (Scientific Assessment of Ozone Depletion: 2002; available through the World Meteorological Organization in Geneva) where little difference was found relative to the findings of the 1998 assessment determination of the Ozone Depletion Potential (ODP) for methyl bromide. This finding was not surprising.

CH 3 Br still accounts for roughly 50% of the organic bromine reaching the stratosphere. Determination of the ODP for methyl bromide primarily depends on the understanding of its total lifetime in the atmosphere, which in turn depends on the understanding of its removal processes from the atmosphere. During the 1990's, it was discovered that ocean and soil sinks for methyl bromide need to be considered in determining the lifetime of methyl bromide. Those sinks are now considered in our analyses (a recent reevaluation of the ocean sink gave results very similar to the analyses used in the 1998 assessment). While there remains some uncertainty in the soil sink, this is unlikely to further change the ODP for methyl bromide in any significant manner. With ocean and soil removal processes now included in the analyses of its ODP, it is unlikely that there will be major changes in the ODP for methyl bromide unless there are significant changes to the understanding of its removal processes.

The current evaluated global lifetime for CH 3 Br is 0.7 years, resulting in an ODP of 0.38. If all of the uncertainties in the soil sinks were to go the maximum amount towards increasing the sink, the ODP for CH 3 Br could decrease a little more. However, this is extremely unlikely, as it would produce a huge inconsistency between the sources and sinks, exacerbating the difference already existing in the 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 currently not decreasing means that bromine will become more and more important in its effects on ozone. The analyses done in the assessments on future emissions of methyl bromide assume that the Protocol has been followed faithfully up the point where a sensitivity analysis is done (such as continuing use of CH 3 Br or stopping its use entirely in 2004). One has to be careful therefore in interpreting these sensitivity studies if the Protocol is not being fully followed. While I would agree that effects from methyl bromide can be corrected quickly through further controls because of its relatively short atmospheric lifetime, one does need to be careful that near term effects on ozone are not exacerbated through use of methyl bromide that does not follow the Protocol. Ozone levels should be at their minimum now, so any increase in use of compounds that otherwise would be controlled under the Montreal Protocol needs to be carefully evaluated so as to not result in a further decline in ozone amounts.