Mr. Alan W. WilliamsTo ask the Secretary of State for the Environment what is the latest estimate of the average depletion of the ozone layer on an annualised basis(a) at British latitudes and (b) at all latitudes; and what are the projections of the extent of depletion over the period 2000 to 2050.
§ Mr. MacleanThe latest estimates of ozone layer depletion remain substantially the same as published in the 1991 report of the Department's stratospheric ozone review group, copies of which are in the Library. Ozone depletion at British latitudes is at a maximum in the early spring, averaging 0.8 per cent. per year. Ozone levels recover substantially during the summer. The annual558W average depletion taken over all latitudes is about 0.3 per cent. per year—we do not have an equivalent figure for British latitudes. The extent of ozone depletion in future years will depend on how the Montreal protocol controls are tightened, but the review group estimate that under the present controls the potential for ozone depletion will increase until at least 1997, and then decline slowly over the next century.