In Europe the increase in ultra-violet radiation (UV) is estimated to be larger over the western parts because of large depletion in the total ozone column. UV global trends are estimated to increase by 3-4% per decade in northern hemisphere midlatitudes and 3-9% in southern hemisphere midlatitudes. The ozone layer can start recovering, but full recovery will take another 50 years if emissions of ozone depleting substances (ODS) were zero in 1999, the earliest recovery year physically possible would be 2033. Global production and emissions of ozone depleting substances have fallen sharply since the end of the 1980s as a direct result of international measures. In the EU, production of halons stopped in 1994, while production of chlorofluorocarbons (CFCs) was phased out in 1995. Consumption of hydroclorofluorocarbons (HCFCs) and methyl bromides are to be phased out by 2020 and 2005 respectively, although the European Commission is drafting proposals to bring these dates forward to 2015 and 2001, and also limit the production of HCFCs and ban the production of methyl bromide. The potential “chlorine plus bromine” concentration, a measure for the total potential depletion of the ozone layer, peaked in 1994 and is now decreasing. Effective stratospheric chlorine peaked in about 1997 and is now expected to fall (assuming full compliance of the latest Amendments of the Montreal Protocol).
The atmospheric concentration of halons is still increasing, contrary to earlier expectations. There exists a relatively large potential for eliminating global halon emissions by stopping production and destroying halons used in existing equipment.
Assuming that measures currently in force are fully implemented, additional cases of skin cancer caused by ozone depletion should peak at 78 per million per year around 2055. Total additional cases from now until the end of the 21 st century are estimated at 5 000 per million.
Production of CFCs is still permitted (until 2010) in developing countries and in developed countries for use by developing countries. A more rapid phasing out would speed the recovery of the ozone layer. There are indications that around 10% of developing country production is imported illegally into developed countries; and continued smuggling on this scale would delay recovery.
International regulations have led to significant reductions in production, usage and emissions of ozone-depleting substances (ODSs), despite smuggling and illegal production, although large amounts of CFCs and halons are still in use; there is now a challenge to assist developing countries in meeting their commitments to phase out ODSs.
The total potential chlorine concentration in the lower atmosphere has decreased since its maximum in 1994, mainly due to the rapid phase-out of methyl chloroform, although the atmospheric concentration of halons is still increasing contrary to earlier expectations.
Increased levels of UV radiation will continue, with damaging effects for humans and ecosystems; full recovery of the ozone layer is unlikely before 2050.
There is some limited scope for additional measures to speed up ozone-layer recovery, mainly by eliminating global halon emissions.