The Montreal Protocol of 1987 is a landmark achievement in global environmental policy, and represents widespread, science-backed cooperation with industry. This international treaty phased out the production and use of ozone-depleting compounds, of which the most well-known were chlorofluorocarbons (CFCs) used in refrigeration, as spray can propellants, and in insulating foams. Substitutes for the CFCs were found in all of these applications, and as a result of this stringent regulation, the ozone layer is now recovering. This reversal also has positive effects for human health: by the end of this century, the Montreal Protocol will have averted approximately 250 million cases of skin cancer and 50 million cases of cataracts. And in limiting emissions of ozone-depleting substances that double as potent greenhouse gases, the Montreal Protocol also protects against global warming. By 2010, it had averted about 15 gigatons of equivalent CO2 emissions per year.
But the Montreal Protocol isn’t watertight. In an invited Nature Communications article, MIT Lee and Geraldine Martin Professor of Environmental Studies Susan Solomon and her colleagues explain the gaps. Solomon is one of the atmospheric chemists who determined the cause of the Antarctic ozone hole, and whose work helped push through the Montreal Protocol. Solomon is both heartened by the Montreal Protocol’s achievements, and keenly aware that global policy must now evolve to stave off further ozone depletion and the damaging consequences of a global temperature increase of 1.5°C.
This month marks the 35th anniversary of the Montreal Protocol. As Solomon describes, the policy has been effective — but there are gaps in it that cause unnecessary damage to the ozone and the climate, and it’s time to address them.