The international treaty to protect the ozone layer may have the inadvertent benefit of preventing up to a further 1掳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鈥檚 atmosphere and threatening the health of humans and ecosystems. The ozone 鈥渉ole鈥� has since begun to recover and . The protocol has previously been described as 鈥�perhaps the single most successful international environmental agreement鈥� by Kofi Annan, former secretary general of the UN.
杏吧原创s have now revealed a new way it may have helped us slow climate change, too. Past research has looked at the treaty鈥檚 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聽global effects聽on plants聽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鈥檚 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掳C by 2100.
鈥淭he Montreal protocol, as well as protecting the ozone layer, is an extremely successful climate treaty. And it鈥檚 not just because CFCs are greenhouse gases, but it鈥檚 actually stopped additional CO2 going into the atmosphere,鈥� says Young.
However, at the University of Leeds, UK, says the research does use some 鈥渆xtreme鈥� hypothetical simulations and numbers. 鈥淭hey 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,鈥� he says.
Young concedes the precise amount of carbon expected to be stored by plants may be slightly different from the team鈥檚 estimate because we don鈥檛 know how every plant species would respond to the extra UV, but says the figures are a 鈥渄efensible鈥� order of magnitude. 鈥淲e鈥檙e definitely confident it鈥檚 a negative effect,鈥� he says.
Despite the protocol protecting plants and probably helping to slow warming, Young doesn鈥檛 think we can take its victory as a reason to think the Paris Agreement on climate change 鈥� the subject of a major summit in Glasgow this November 鈥� will succeed. 鈥淭he greenhouse gas problem is so much more enmeshed in everything we do. So there aren鈥檛 many lessons that are transferable,鈥� he says.
Nature
