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Ozone in a Changing Atmosphere - the Canadian Contribution
|By: Angus Fergusson and S&T Liaison|
Swept up into the stratosphere, ozone-depleting substances can destroy the ozone layer, increasing UV radiation at the Earth’s surface. Increased UV radiation heightens the risk of skin cancers and cataracts and weakens the immune system.
As well as increased risks to health, depletion of the ozone layer has led to changes in the chemistry and dynamics of the atmosphere with effects on weather and climate. Measurements indicate that the ozone layer over southern Canada remains depleted during the spring and summertime affecting the amount of ultraviolet radiation received at the Earth’s surface. Severe depletion is still possible in the Arctic during very cold winters and this can affect the ozone layer over the rest of Canada.
Ozone depletion is a global issue that affects society, the economy and the environment, and requires global action.
Seeking Solutions through S&T
Since the late 1970s, Canadian research has been at the forefront of efforts to protect the ozone layer. Environment Canada scientists developed the world’s most accurate ozone-measuring instrument--the Brewer Ozone Spectrophotometer--which is now used worldwide for measuring the thickness of the ozone layer. Brewer Ozone Spectrophotometer networks and ozonesonde networks in Canada and other countries are critical to our ability to understand the evolution of the ozone layer and its eventual recovery.
In recent years, Canada has led the way in studying the ozone layer from space. Environment Canada scientists have worked with academia and government scientists, nationally and internationally, to design instruments on rockets, satellites and high-altitude balloons and aircraft. As a result, satellite technology has become increasingly efficient in providing space-based observations of the ozone layer and ultraviolet radiation with global coverage.
Canada played a leadership role in the formation of the Vienna Convention and the Montreal Protocol on Substances that Deplete the Ozone Layer. Canada hosted the tenth and twentieth anniversaries of the Montreal Protocol, producing two ozone assessments with the unique Canadian science perspective to support national policy development. Through full compliance with the Montreal Protocol, Canada has reduced its ozone-depleting substance (ODS) consumption and use by 98%--an amount greater than required by the Protocol.
The problem of ozone depletion has not been solved yet but clearly we are addressing the issue under the Montreal Protocol. Scientific research has shown that the abundance of ozone-depleting substances is leveling off or decreasing in the atmosphere, and stratospheric chlorine loading has begun to decrease. There are signs that the ozone layer is responding to the changes in chlorine, and that ozone depletion has stabilized. However, future ozone levels will also depend on the linkages with climate change.
Atmospheric models of the interaction between ozone depletion and climate change indicate that if the controls under the Montreal Protocol are followed and there are no significant gaps in our understanding, the ozone layer should return to pre-1980 levels (the beginning of discernible global ozone depletion) by the middle of this century, with the Antarctic ozone hole disappearing between 2060 and 2070. However, considerable uncertainty about regional aspects of these projections still remains because of our incomplete understanding of the effects of climate change on ozone recovery.
Figure shows the near-global total ozone as projected by the Canadian Middle Atmosphere Models (grey), projected changes in organic chlorine (green) and the observed changes in ozone from 1964 to the present (red).
Transforming Knowledge into Action
To achieve the goal of ozone recovery, our growing understanding of ozone depletion must continue to inform effective policies, decision making and action. It is clear our knowledge is not complete, particularly with regard to the Arctic, where severe depletions can still occur. These depletions can affect springtime and summertime ozone levels over southern Canada. It is important that Canada maintains a strong monitoring program to track these changes and determine their impact on Canadians, as well as contribute to the global effort to monitor the long-term evolution of the ozone layer.
First, Canada should maintain its ground-based ozone network and the ozonesonde network. Second, Canada should promote development of computer models to continue to improve their ability to simulate ozone depletion chemistry, dynamics and radiative processes and thereby address policy-related questions. Finally, Canada should continue to invest in its highly successful science satellite program.
Benefits to Canadians
Canada’s work through the Montreal Protocol on Substances that Deplete the Ozone Layer, and in concert with the other 191 countries has set us on a path that could see the ozone layer approach its former state by the latter half of the 21st century. This will require the sustained commitment of all nations to the Protocol and to the Vienna Convention, its science foundation.
The United Nations’ Environment Programme estimates that as a result of the Montreal Protocol and amendments, the atmospheric loading of ozone-depleting substances will be tenfold reduced by 2050, leading to up to 20 million fewer cases of skin cancer and 130 million fewer cases of eye cataracts. As citizens of the world, Canadians will benefit from global action made possible, in large part, by the contribution of Canadian government science.
Canadian scientists produced the first Canadian assessment on the ozone layer, Ozone Science: A Canadian Perspective on the Changing Ozone Layer, which was distributed to delegates at the Montreal Protocol meeting in September 1997.
For the twentieth anniversary in September 2007, a brochure was produced containing articles on the history of the ozone story, a review of ozone science in Canada, and the findings of the 2007 Canadian Ozone Science Assessment. The assessment, which is made up of a series of papers by leading Canadian scientists in ozone and ultraviolet radiation science, was published in a special issue of the journal Atmosphere-Ocean in March 2008 and an Executive Summary was also published at that time.
For more information:
S&T Liaison | Tel 905 315 5228 | Fax 905 336 4420
© Her Majesty the Queen in Right of Canada, represented by the Minister of Environment, 2008.
Catalogue No. En164-15/10-2008E; ISBN 978-1-100-11126-1
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