Remember when the biggest concern about our planet was that there was a growing hole in ozone layer? After warnings that the atmospheric layer—which protects us from ultraviolet rays that can cause skin cancer and cataracts, along with harm to crops and marine life—was failing, the world rallied, finalizing the Montreal Protocol in 1987. The protocol called for countries to end the production and consumption of chlorofluorocarbon, or CFCs, an ozone-depleting substance, which at the time were found in everything from refrigerators to aerosol cans.
The Montreal Protocol was the first worldwide environmental treaty, and it worked: the 0zone is expected to recover to early 1970 levels between 2040 and 2070.But the global agreement had an even broader effect: it slowed the rate of global warming—the first such global agreement to do so, new research notes—and serves as a reminder that global consensus can help solve global problems.
The global warming data was noted by researchers from the University of New South Whales, in a paper published in Environmental Research Letters. They found that the Earth is already cooler than it would be without that global agreement and will be significantly cooler in the future than if we had never adopted it.
While ozone depletion and climate change are often thought of as two distinct problems, they’re connected. CFCs are also greenhouse gases, and with their decrease, we’ve been able to avoid nearly 1 degree Celsius of warming over large areas of Earth, and will avoid a total of 3 to 4 degrees C over most regions of the Arctic by 2050. That means we’ve avoided more ice melt, as well; summer sea ice around the Arctic is around 25% greater today than it would be without that reduction in CFC emissions.
The Montreal Protocol has actually been more effective when it comes to curbing global warming than other worldwide treaties specifically focused on that issue, lead author Rishav Goyal and the other researchers argue. Take the Kyoto Protocol for example: signed in 1997, that international treaty was the first to target greenhouse gas emissions, and yet it will only reduce global temperatures by 0.12°C by 2050. One reason why, Goyal explains, is that it was the first-ever UN treaty to be ratified by all 197 UN member states, whereas Kyoto majorly involved developed nations.
For their findings, the researchers created a climate model and ran it through two atmospheric chemistry scenarios; one with the enactment of the Montreal Protocol and one without. Those models then simulated the climate from 1974 to 2065, looking at how CFC emissions and ozone depletion would have continued without the Montreal Protocol and how the ozone recovers and CFC emissions decrease under the agreement. The global warming benefits have previously been overlooked, researchers say, because the focus of other Montreal Protocol experiments has been the (“incredibly important,” Goyal notes) health impacts, as well as climate impacts like ozone recovery and polar vortex.
Though the Montreal Protocol’s main aim wasn’t mitigating global warming, it still worked to take a first important step in that direction, and that shows that these global emission treaties do work. “Montreal Protocol became a huge success because the whole world came together and believed in science,” Goyal says in an email. “We need a similar action to reduce carbon emissions—every country in the world has to understand their responsibility and play their respective role in solving this problem and to save the planet from the dangers of global warming. We need to make Paris ‘the Montreal equivalent for carbon.'”