The Montreal Protocol was characterized by Kofi Annan as "one of the great success stories of international cooperation." As a recently released simulation of Earth without the Montreal Protocol shows, there would have been grim consequences for a business as usual approach. (See Figure 1.) Among other things, this simulation predicts an Earth with a dangerously insufficient ozone layer by 2050.
As the preparations for the Copenhagen Climate Change summit continue this week, this is an opportune moment to review the encouraging results of this Protocol, arguably the most successfully implemented international environmental treaty to date. A newly negotiated climate change treaty will need to scale many of the same hurdles that the Montreal Protocol did in 1987: regulate a globally dispersed pollutant with non-trivial residence times, determine differentiated target schedules between developing and developed countries, fund a mechanism for developing country adoption, and remain flexible in light of new findings.
Figure 1. What Would have Happened to the Ozone Layer if Chlorofluorocarbons (CFCs) had not been Regulated?
The colors in the video signify total ozone in Dobson Units. Red, orange, yellow and green are adequate levels of total ozone. The average ozone layer around the Earth is about 300 Dobson Units which is represented by green-blue. As the color changes to darker shades of blue and into purple the phenomenon known as an ozone hole occurs. (Videos and images of the Antarctic ozone hole can be viewed here.)
Source: NASA, 2009
History of the Protocol
Ozone depletion linked to the production of chlorofluorocarbons (CFCs) was first noticed in the mid-1970s, prompting some isolated policy measures in individual countries. When the Antarctic ozone hole was discovered in 1985, public awareness prompted the need for international action beyond these isolated regulations. Two years later, representatives from 43 countries signed the Montreal Protocol to reduce the production and consumption of ozone-depleting substances, initially CFCs and some halons. (Here is a complete list of controlled ozone-depleting substances.) The Protocol was designed to be amended regularly on the basis of periodic scientific and technological assessments. However, some recent amendments have had less successful rates of adoption than the original protocol.
Between 1989 and 2007, global consumption of ozone-depleting substances declined dramatically (see Figure 2). The data for production of these substances has a correspondingly similar profile.
Figure 2. Consumption of Ozone-Depleting Substances
Note: The figure may suffer from some inaccuracy in the early 1990s due to non-reporting by some countries; still the trend remains obvious and drastic.
By the mid-1990s, the atmospheric concentrations of all major ozone-depleting substances began to decline in response to the decreased production and consumption shown above. While the concentrations of less destructive HCFCs continues to increase, CFCs reached their peak around 2000, and have decreased by about 4 percent since. (Carlowicz, 2009) (See Figure 3.) The sum of these international efforts has made the non-polar region free of any continued ozone layer deterioration. On the present course, it is estimated that ozone levels outside the polar region will achieve complete recovery (pre-1980 levels) around 2050. (UNEP, 2008)
Figure 3. Trends in Observed Tropospheric Concentration of Ozone-Depleting Substances
Despite our collective success in reducing the use of ozone-depleting substances and subsequent reduction in atmospheric concentrations, ending the threat of the ozone hole over Antarctica will not be achieved in the near future. Figure 4 shows the average ozone hole area during its annual peak, as well as minimum ozone levels. Recent years have seen large ozone holes and relatively low concentrations of ozone. The most common CFCs have residence times between 45 and 100 years, with some as much as 1700 years. Due to these long lifetimes in the atmosphere, a certain amount of delayed gratification must be maintained. However, the forecast remains positive with Arctic ozone levels expected to return to pre-1980 levels before 2050 and the Antarctic ozone expected to recover between 2060 and 2075. (UNEP, 2008)
Figure 4. Average Antarctic Ozone Hole Conditions
Lessons for the Future
The success of the Montreal Protocol was in large part due to adopting legally binding phase-out schedules which gave strong signals to develop and commercialize alternatives to ozone-depleting substances. This ended the use of CFCs faster, and with less cost, than was originally anticipated. (UNEP, 2008) Greenhouse gases, however, are intensely integrated into our daily lives and the changes needed may be more than just technological in nature. Even with these challenges, the successful lessons of the Montreal Protocol should validate continued international action on climate change.
"Let us hope that our successful efforts on this front will inspire sustained and resolute multilateral action on the world’s many other environmental problems."
-Kofi Annan on International Ozone Day, 2007
EarthTrends
Global Gas Concentrations: CFC-11
Global Gas Concentrations: CFC-113
Global Gas Concentrations: CFC-12
Global Gas Concentrations: Carbon tetrachloride
Global Gas Concentrations: Methyl chloroform
Related Links
United Nations Environment Program Ozone Secretariat
NASA Ozone Hole Watch
NASA New Simulation Shows Consequences of a World Without Earth's Natural Sunscreen
Atmospheric Chemistry and Physics. What would have happened to the ozone layer if chlorofluorocarbons (CFCs) had not been regulated?
Advanced Global Atmospheric Gases Experiment (AGAGE)
Large loses of total ozone in Antarctica reveal seasonal ClOx/NOx Interaction
