Canada's National Environmental Indicator Series 2003

Average annual protective ozone levels (Dobson units)

Headline Indicators | Technical supplements | Data (in HTML)

Meter Calculation

Trend in Canadian values from 1990 to 2000.

Indicator content	Supporting indicators
• Context • Indicators • Actions • Linkages • Challenges • Home	• Atmospheric concentrations of chlorofluorocarbons • New supplies of ozone depleting substances (ODSs) • Global chlorofluorocarbon (CFC) production

Context

Stratospheric ozone protects life on Earth by filtering out biologically harmful wavelengths of ultraviolet (UV) radiation emanating from the sun. The depletion of ozone in the upper atmosphere, commonly referred to as the thinning of the ozone layer, has resulted in increased mid-range UV-B radiation at the Earth's surface, a rise of 10% from 1986 to 1996 when globally averaged. Excessive exposure of humans to UV-B causes sunburn and DNA damage, which can lead to skin cancer, depression of the immune system, and an increased risk of cataracts. It is believed that a sustained 1% decrease in stratospheric ozone will result in a 2% increase in cases of non-melanoma skin cancer. The incidence of melanoma in Canada has doubled during the last 20 years.

The single largest factor in ozone depletion is the release of halocarbons, which include chlorofluorocarbons (CFCs), bromofluorocarbons, methyl chloroform, carbon tetrachloride, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These ozone-depleting substances have been used in air conditioning and refrigeration equipment, foams, aerosols, and fire extinguishers and as solvents and pesticides. If atmospheric concentrations of these gases can be sufficiently reduced, it is hoped that natural processes will return ozone concentrations to pre-industrial-era levels.

Indicators

Since 1979, the annual average amount of stratospheric ozone has dropped globally by 3-6% per decade at midlatitudes, 12% at high northern latitudes such as northern Canada, and 10-18% at far southern latitudes, such as Antarctica. There has been a similar trend in the depletion of Canadian stratospheric ozone levels since 1980. While the extreme meteorological conditions of the Antarctic are unlikely to occur in the Canadian Arctic, the late-winter/spring ozone levels in the Arctic have been unusually low in six of the last nine years. Due to the long atmospheric lifetimes of ozone-depleting chemicals in the upper atmosphere, ozone levels are not expected to show signs of recovery until at least 2030 - a recovery that could be further slowed by climate change.

Global CFC production fell by 88% between 1988 and 1999. The global abundance of CFC-11 in the lower atmosphere peaked around 1994 and is now slowly declining, while the level of CFC-12 is still increasing very gradually. New supplies of ozone-depleting substances in Canada fell from a high of 27.8 kilotonnes in 1987 to about 1 kilotonne (composed mostly of HCFCs) in 2000. Annual new supplies of HCFCs are currently frozen at 1996 levels, and production will cease by 2022, except for small quantities used for servicing equipment and as laboratory standards.

Atmospheric concentrations of chlorofluorocarbons (CFCs) 11 and 12 (parts per trillion)

Chlorofluorocarbons (CFCs)
CFCs are a group of organic chemicals consisting of carbon, chlorine, and fluorine. They are hydrocarbon derivatives where chlorine and fluorine partially or fully replace the hydrogen. CFC-11 and CFC-12 are the most abundant CFCs.

Technical supplements | Data (in HTML)

New supplies of ozone depleting substances (ODSs) in Canada (kilotonnes, expressed as CFC-11 equivalent)

Technical supplements | Data (in HTML)

Global chlorofluorocarbon production (kilotonnes, expressed as CFC-11 equivalent)

Technical supplements | Data (in HTML)

Top

Actions

During the late 1980s, nations from around the world met to discuss the urgent need to protect the stratospheric ozone layer by reducing emissions of ozonedepleting substances. In 1989, the Montreal Protocol of the Vienna Convention for the Protection of the Ozone Layer was ratified, and today 183 countries have joined this agreement. Under the Montreal Protocol, all new supplies of ozone-depleting ubstances, except HCFCs and methyl bromide, were phased out by developed countries, including Canada, by January 1996. Methyl bromide will be phased out by 2005, and HCFCs by 2030.

Linkages

Ozone is a greenhouse gas as well as a UV filter. Thus, a loss of stratospheric ozone leads to cooling of the stratosphere. CFCs and HCFCs act as potent greenhouse gases. These gases trap heat within the lower atmosphere before it can reach the stratosphere. Both of these processes cause a cooling of the stratosphere, further contributing to the conditions that are conducive to ozone depletion.

Increased UV-B levels also affect human health, reduce crop yields, and disrupt marine food chains. Some species may be so sensitive to UV-B (e.g., amphibians) that the additional stress on their populations could increase their risk of extinction.

Challenges

Although the lack of reporting by some countries and smuggling of ozonedepleting substances create uncertainties, significant progress has been made. Nonetheless, the ozone layer is still seriously damaged and has not yet begun to recover, and signs of recovery are not expected before 2030. Furthermore, recent findings are suggesting that by the 2030s, climate change may surpass CFCs as the main driver of overall ozone loss. Scientists continue to search for effective alternatives that do not deplete the ozone layer or act as greenhouse gases.

Websites of interest

Environmental Signals: National Indicator Series 2003 Home

Introduction

Highlights

Meter description

Ecological life-support systems

Human health and well-being

Natural resources sustainability

Human activities

Conclusions

Technical supplements

PDF (2867kb)

View in print format

View in print format	Previous Top Next Indicator Home
	\| What's New \| About Us \| Your Environment \| Information/Publications \| Weather \| Home \|
	Français \| Contact Us \| Help \| Search \| Canada Site \|
	The Green Lane^TM, Environment Canada's World Wide Web site
	Last updated: 2005-04-11	Important Notices and Disclaimers