Update on the Ozone Layer over Canada

Environment Canada scientists, working in close co-operation with researchers in Canadian universities, are keeping close watch on the ozone layer over Canada. The following is an update on their most recent finding:

• Ozone thinning is continuing over Canada. It is most severe in the high Arctic during the early spring, where unexpected losses of up to 45% have occurred in recent years. Over the rest of Canada, ozone values have decreased by an average of about 6% since the late 1970s, with greater losses of about 8 to 10% in the springtime.
• Ozone depletion is not fully understood. About half of the observed ozone loss in the atmosphere can be definitely attributed to known ozone-depleting industrial chemicals; whether the remaining half is caused by these chemicals or other factors, such as climate change, is not yet known.
• Due to uncertainties in the science, changes in the ozone layer must be carefully tracked to determine the effectiveness of actions taken to reduce ozone-depleting substances.
• As a result of the thinning ozone layer, sunburning UV has increased by an average of about 7% in Canada, with levels increasing to 10 to 12% in the springtime. These increased UV levels, which are expected to remain higher than normal for the next 30-40 years, will affect human health, crops, forests and marine and freshwater ecosystems.
• Skin cancer rates will likely increase - the National Cancer Institute of Canada estimates that there will be about 67,000 new cases of skin cancer in 1998 in Canada alone. Most of these were likely caused by sun exposure in the 1970s and '80s, before depletion of the ozone layer. (In recent years, skin cancer rates have risen most probably because of our increased exposure to the sun, caused by sunbathing and briefer clothing.)
• In 1998, unusually warm conditions in the upper atmosphere led to less ozone thinning than in recent years. The ozone layer over Southern Canada this summer was near normal. In the high Arctic, where springtime depletion have been particularly severe in recent years, ozone losses of only 10% were recorded. Scientists feel that this does not represent a recovery of the ozone layer, but is rather a reflection of the unusual world-wide weather conditions caused by El Nino, this year. However, the link between ozone values and El Nino is not well understood.

What is happening in the Arctic?

In the high Arctic, dramatic ozone loss occurred in the spring of 1997, when ozone values were 45% below normal, and in 1996, when ozone was reduced by 30%. These are the lowest springtime values ever recorded in the Arctic. In both years, conditions in the upper atmosphere were unusual for the Arctic, and similar to those found in the Antarctic. It is not clear whether the unusual Arctic conditions are connected with climate change or natural events occurring only in 1996 and 1997. For comparison, in the Antarctic, ozone loss of up to 70% has been recorded.

Are ozone-depleting substances declining?

Under the Montreal Protocol, an international agreement to protect the ozone layer, action has been taken to reduce ozone-depleting substances. Measurements, including observations from Environment Canada's ozone Observatory in up the Canadian Arctic, show that the build up of the most significant CFCs in the lower atmosphere has been slowed, or even reversed. One of the key chemicals (CFC-11) is now decreasing. The ozone layer could return to near-normal by the year 2050. Compliance with the Montreal Protocol by all countries is essential for that recovery to occur.

For further information:
Environment Canada
Enquiry Centre
Ottawa, Ontario K1A 0H3

Enviro Fax Line:
1-819-953-0966

Visit Environment Canada's Ozone web site at :
http://www.ec.gc.ca/ozone

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