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.