The Montreal Protocol: 30 Years Later

Amidst the recent, heated debate over the Paris Accord, it’s worthwhile to consider that some international agreements on environmental measures have proven to be both necessary and highly effective. This is particularly true regarding the Montreal Protocol adopted in 1987 to address stratospheric ozone depletion.

In 1974, UC Irvine chemists Frank Rowland and Mario Molina published an article in Nature Magazine suggesting that chlorofluorocarbons (CFCs) used in aerosol sprays and “Freon” refrigerants were gradually ascending to the stratosphere and interrupting high-altitude ozone formation. Previously, CFCs had been viewed as particularly benign due to their essentially inert chemical composition.

Rowland and Molina theorized that, under high-altitude bombardment from ultraviolet radiation, CFCs could split into their individual components. Chlorine atoms liberated from these CFCs would then interrupt the process by which oxygen atoms normally bond to form ozone molecules.

The pair’s research raised awareness of the issue and led to a Congressional hearing in December 1974. Federal funds were subsequently allocated for further research. In 1976, the National Academy of Sciences issued a report confirming the validity of their theory.

While a seemingly obscure issue, stratospheric ozone depletion actually posed troubling consequences for life on the planet. Ozone content in the stratosphere provides an important buffer against incoming solar radiation, blocking much of the intense shortwave ultraviolet radiation that would otherwise reach the earth’s surface. An increase in ultraviolet penetration could mean an increase in skin cancer rates along with potential damage to plant growth.

The alarming implications of such ozone depletion galvanized public opinion. But the overall theory wasn’t without detractors. Several major chemical companies argued that the relevant science was incomplete and that little evidence existed to justify the elimination of CFC products.

In 1985, a British survey team in the Antarctic documented abnormally low ozone concentrations over the South Pole. Subsequent research confirmed these findings, leading to the ‘Montreal Protocol’ signed in 1987. The agreement established a timetable for the complete elimination of ozone-depleting chemicals (ODCs). Eventually, the Protocol led to a complete phase-out of CFCs and other ozone-depleting gases by 1996.

During the past 20 years, the Montreal Protocol has been updated to include more recently identified ODC gases, including methyl bromide—which was eliminated in 2005—and hydrofluorocarbons (HCFCs), which are scheduled for phase-out by 2030.

Thankfully, chlorine levels are now slowly declining in the stratosphere. And ozone levels are gradually returning to previous levels. Unfortunately, the overall restoration of ozone content has been slow, and a full recovery could take many decades.

Notably, the Montreal Protocol has demonstrated the importance of international agreement and action when a global threat is identified and completely documented through extensive research. And the agreement’s success suggests that signatory nations should continue to cooperate in identifying chemicals that can pose a threat to stratospheric ozone content and environmental safety.

Comments (4)

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    General P. Malaise


    there seems to be a lot of conclusions being stated and without evidence. many of the conclusions stated here have been challenged and many of the past observations about the ozone layer have been proven false.

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    Spurwing Plover


    They have used Junk Science and phonie or tampred data to ban certian stuff like DDT,CFC, or regulate them like it is with this Climate Change/Global Warming lies its all about Control under the Useless Nations and Trumps rejection of the junk science Paris Accord is a great leap foward

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      Charles Higley


      The major scientist, who claimed evidence that CFCs hurt ozone, admitted, 20 years later, that he was paid to do so by Dupont Chemical and that the science was bogus; note, this was only admitted after Dupont’s patent on the replacement refrigerant had expired.

      We know now that it is solar radiation and nitrogen gas in the atmosphere that breaks down ozone at very low temperatures. As we know that the EPA makes up evidence out of thin air and then lies (the PM-2.5 debacle), it is easy to guess that any of the ODCs they have banned have been convicted based on association and extrapolation and no real scientific evidence. The trick is to ask, regarding each banned chemical, who benefits from the ban.

      • Avatar

        R. Johnson


        A very accurate description of what actually occurred. The EPA bureaucrats continue to punish AC manufacturers, consumers and American industry by selectively phasing out refrigerants and the refrigerant systems–with made up data on ozone depletion. My last R22 system lasted 26 years; true it was down on efficiency by design but it was a working paid for system. Today sellers cannot ship a high efficiency R22 condenser to my area of the country!

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