Protecting the ozone layer saved the world over 2C of warming – study

In the paper published in the prestigious journal Nature, researchers – including Niwa scientist Olaf Morgenstern – connected five different computer models to create this alternative world.

As scientists uncovered the ozone layer damage during the 1970s and 80s, the use of ozone-depleting substances was on the rise. Some soft drinks were made using non-toxic gas, Morgenstern said. “The fizz that came out was CFCs.”

So in the alternative reality, the research team projected that ozone-depleting gases continued to increase by 3 per cent every year. “It’s a business-as-usual scenario.”

As well as destroying ozone, these chemicals are powerful greenhouse gases, Morgenstern said. “On a per-molecule basis, they trap tens of thousands of times more heat than carbon dioxide. But then they are much less abundant.”

Some of these gases may hang around in the atmosphere for decades, while others last for centuries. Although every country agreed to get rid of CFCs, monitoring stations are still recording small amounts of new gas.

The Montreal Protocol – created in 1987 to phase out these gases and ratified by every UN member country – was more concerned about the ozone destruction than the greenhouse effect, Morgenstern added. “We didn’t know we were fighting climate change, or at least climate change was not the motivating factor.”

As well as helping to make our planet habitable, ozone is a greenhouse gas – so the repairing ozone layer balances out some cooling from large drops in CFCs.

However, the regulation of ozone-depleting gases had a major, unintended bonus, the research quantified: the reduction in UV protected land plants across the globe, which suck up huge amounts of the greenhouse gas carbon dioxide.

“The UV causes damage to the tissue and the photosynthesis of that plant,” Morgenstern said.

If CFC use had continued to grow, these gases would still be devastating the world’s ozone – particularly in temperate regions such as New Zealand. In this reality, the layer would be headed for collapse in the 2040s.

“It would affect food production,” he added. “Skin cancer is bit more complicated, because it has an incubation period… It takes time to be reflected in the skin cancer statistics.”

In protecting the globe’s flora from UV, society ensured plant species and soils will absorb 325–690 billion more tonnes of carbon dioxide by the end of the century, the modelling found. This equates to between 0.5C and 1C of warming.

This is in addition to the 1.7C of warming that the CFCs would have directly contributed to global temperatures by 2100, he added.

Under the Paris Agreement, the world is aiming to limit global warming to 1.5C, though the planet has heated by nearly 1.1C already, according to the Intergovernmental Panel on Climate Change.

Although the Montreal Convention turned out to be a win for a stable climate, the fight against climate change remains “ahead of us”, Morgenstern said.

Source: Stuff

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