The international treaty to protect the ozone layer may have the inadvertent benefit of preventing up to a further 1°C of warming this century, through the protection it gives to plants.
The Montreal protocol of 1987 banned ozone-destroying CFCs to stop an increase in ultraviolet radiation breaching Earth’s atmosphere and threatening the health of humans and ecosystems. The ozone “hole” has since begun to recover and . The protocol has previously been described as “perhaps the single most successful international environmental agreement” by Kofi Annan, former secretary general of the UN.
żěè¶ĚĘÓƵs have now revealed a new way it may have helped us slow climate change, too. Past research has looked at the treaty’s impact on avoided cases of skin cancer, and also on reduced warming due to the fact that CFCs are potent greenhouse gases. Now, at Lancaster University in the UK and colleagues are the first researchers to explore the global effects on plants of this lack of CFCs and the resulting change in UV radiation.
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They modelled future ozone, climate, UV and vegetation with and without the Montreal protocol, factoring in past experiments on how UV affects plants. They found that, if there had been no treaty, the extra UV that would have reached Earth’s surface would have disrupted plant growth so much that there would have been between 325 and 690 billion tonnes less carbon locked up in plants and soil by the end of the century. Without that carbon storage, the world would have warmed by a further 0.5 to 1°C by 2100.
“The Montreal protocol, as well as protecting the ozone layer, is an extremely successful climate treaty. And it’s not just because CFCs are greenhouse gases, but it’s actually stopped additional CO2 going into the atmosphere,” says Young.
However, at the University of Leeds, UK, says the research does use some “extreme” hypothetical simulations and numbers. “They assume that through uncontrolled use of CFCs we would have a thinner ozone layer globally, and year-round, than in the deepest actual Antarctic ozone hole,” he says.
Young concedes the precise amount of carbon expected to be stored by plants may be slightly different from the team’s estimate because we don’t know how every plant species would respond to the extra UV, but says the figures are a “defensible” order of magnitude. “We’re definitely confident it’s a negative effect,” he says.
Despite the protocol protecting plants and probably helping to slow warming, Young doesn’t think we can take its victory as a reason to think the Paris Agreement on climate change – the subject of a major summit in Glasgow this November – will succeed. “The greenhouse gas problem is so much more enmeshed in everything we do. So there aren’t many lessons that are transferable,” he says.
Nature
