Thickness of the ozone layer, 1980-2002
In the last 22 years, the ozone layer has got approximately 3% thinner. It has not got any thinner in recent years.
Thickness of the ozone layer, globally and above the Netherlands
Since 1980, the ozone layer has got thinner, both globally and above the Netherlands (KNMI and KMI). This is a result of the increased concentration of ozone-depleting substances in the atmosphere. This phenomenon was particularly evident in the period 1980-1990. Since the early nineties, the thickness of the layer has remained more or less constant at this reduced level.
From 1997-2002, the ozone layer was approximately 3% thinner globally and in temperate zones such as the Netherlands than it was prior to 1980. The reduction in the thickness of the ozone layer varies with the seasons: approximately 4% in winter and spring and approximately 2% in summer and autumn.
Thickness of the ozone layer above the polar regions
The depletion of the ozone layer since 1980 has been particularly evident above the polar regions (WMO, 2002). Over the South Pole, depletion has stabilised since the mid-nineties. In September and October, the ozone layer is on average 40-50% thinner than before 1980.
In 2002, the pattern in the ozone layer over the South Pole was unusual; the thinning was less pronounced than usual in September and October and the 'hole' disappeared faster. This was probably a result of natural variations in wind flows in the atmosphere. The fall in the concentrations of ozone-depleting substances is still too small to explain the small hole in 2002.
In a few recent years with cold winters in the North Pole, the ozone layer was also approximately 30% thinner there. As a rule, the thinning of the layer above the North Pole varies more widely from year to year than above the South Pole, and the ozone layer above the North Pole is thicker than above the South Pole.
Initial recovery of ozone layer expected after 2010
It is probable that the peak concentration of ozone-depleting substances in the stratosphere has now been almost reached. As a result, the ozone layer may recover in time. However, this recovery is not expected to become apparent before 2010. Complete recovery will take more than 50 years.
The increase in greenhouse gases in the atmosphere cools down the stratosphere and may have an effect on the recovery of the ozone layer. It is expected that ozone will therefore be broken down less quickly in the higher stratosphere. But as a result of uncertainty about the effect of reduced temperatures on ozone in the lower stratosphere, the effect on the ozone layer as a whole is not yet properly understood. The effect may be either positive or negative (WMO, 2002).
Impact on people and the environment
The fall in the amount of ozone in the stratosphere has led to an increase in UV radiation. This increase has numerous harmful effects on health and the environment, including additional cases of skin cancer.
The Montreal Protocol for substances that deplete the ozone layer
International policy aims to restrict or stop the production and use of ozone-depleting substances. This objective was set out in 1987 in the Montreal Protocol (UNEP, 1987-2000). The countries that signed the protocol agreed to use no more chlorinated fluorocarbons (CFCs) from 1996 onwards. For developing countries, this obligation will apply from 2010 onwards. The protocol permits the use of HCFCs for a number of years to come.
