New research provides evidence that an international policy first enacted more than three decades ago is buffering Earth from a severe climate change path that would have sent global temperatures soaring. 

According to a new study published in the journal Nature, the global ban of chlorofluorocarbons and other ozone-depleting substances prescribed by the 1987 Montreal Protocol and its subsequent amendments has prevented the eventual collapse of the ozone layer, thereby shielding vegetation from harmful ultraviolet radiation. This has preserved the planet’s ability to absorb and store carbon from the atmosphere as plant biomass and prevented a substantial increase in global temperatures by the end of the century.

Scientists already understood that ozone-depleting substances were also potent greenhouse gases that trap heat in the atmosphere, and this study confirmed that the Montreal Protocol has reduced warming caused by the greenhouse effect. But this study, led by Lancaster University, is the first to show that the preservation of plants prevents substantial additional warming, something that had not been considered before. 

The new study used a novel modeling framework that combines data about ozone depletion, climate change, plant damage, and the carbon cycle. Two scientists from the National Center for Atmospheric Research (NCAR), Sasha Madronich and Rolando Garcia, contributed to the study by helping quantify how much plant damage would have been caused by increased UV radiation if not for the ban.

Key findings from the study are:

• Continued growth in CFCs would have led to a worldwide collapse in the ozone layer by the 2040s.
• Without the Montreal Protocol, the scientists estimate there would have been 325-690 billion tons less carbon held in plants and soil at the end of this century.
• The preservation of plant biomass will prevent an additional 0.85°C of warming by the end of this century. This is an addition to the prevention of 1.7°C of warming that would be caused by the greenhouse effect of the ozone-depleting substances.
• By 2100 there would have been 60% less ozone above the tropics. This level of depletion would have been worse than was ever observed in the Antarctic ozone hole.
• By 2050 the intensity of solar UV radiation reaching the ground in the mid-latitudes, which includes most of Europe, the United States, and central Asia, would be higher than it is today in the tropics.

Read the full press release from Lancaster University.

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