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There is still much to learn about the thinning ozone layer. Scientists know that ozone-destroying industrial chemicals are the major cause of ozone loss. However, only about half of the observed ozone loss in the upper atmosphere can be definitely attributed to these chemicals. Other factors, such as climate change, could also be involved.
Due to these uncertainties, changes in the ozone layer must be carefully tracked to determine the effectiveness of the actions we have taken to reduce ozone-depleting chemicals. Canadian scientists use a variety of techniques to keep tabs on the ozone layer, including high-altitude research balloons, satellite measurements and ground-based instruments.
Environment Canada operates a cross-country network of monitoring stations which has kept continuous watch on Canada's ozone layer for nearly four decades. The early records, which were taken before there was any major human influence on the ozone layer, are vital to understanding the changes that are occurring today. These observations are stored with records from other countries at the World Ozone and Ultraviolet Data Centre, an international archive which has been maintained by Environment Canada since 1961, on behalf of the United Nations' World Meteorological Organization.
Canada has also made a major contribution to global ozone science. Canadian research on the ozone layer began in the 1930s when it was believed that ozone observations might assist in weather forecasting. Our efforts were strengthened in the 1980s, when decreases in ozone levels were first observed. In 1993, Environment Canada scientists gained international recognition by completing the first long-term study conclusively showing that the thinning of the ozone layer has led to an increase in UV levels at the earth's surface.
The Arctic is a major focus for Canadian ozone studies, where research must be carried out in 24-hour darkness and in temperatures which regularly dip to -40°C. To assist scientists working in this harsh northern climate, Environment Canada built an ozone laboratory at Eureka, a remote weather station less than 1,000 km from the North Pole, on Ellesmere Island. Opened in 1993, the observatory has enabled researchers to carry out intensive studies of the Arctic ozone layer and has become a centre for international research.
Environment Canada scientists have also made significant contributions to ozone science by developing two highly sophisticated ozone-measuring instruments - the Sunphotospectrometer and the Brewer Ozone Spectrophotometer. The Sunphotospectrometer, a small portable instrument, was used by Canadian astronaut Marc Garneau to measure the ozone layer during his historic flight in the space shuttle in 1984. An updated version was used by astronaut Steve MacLean on his flight in 1992. The Brewer Ozone Spectrophotometer is recognized as the world's most accurate ozone-measuring instrument, and is now used to take ground-based measurements in more than 35 countries.
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