A regular assessment of the effects of the Montreal Protocol has given an indication of just how bleak the world's fate would have been if action had not been taken to prevent ozone depletion. Even with all the work that was done, people have died from the extra ultraviolet light flooding the planet. However, their numbers pale in comparison to the disaster swift action averted.
The possibility that certain gases, primarily chlorofluorocarbons (CFCs), could damage the ozone layer that protects the world from excessive ultraviolet radiation was first raised in the early 1970s. Industries dismissed the work as “theoretical”, and observational data to confirm the risks was lacking. Nevertheless, where easy substitutes existed the Carter administration ordered CFCs be replaced, and ramped up research into alternatives elsewhere.
By the time experimental evidence emerged in the mid-80s, replacements were available, or at least on the horizon, leading the world to sign the 1987 Montreal Protocol, setting timelines to replace all the gases that posed a danger.
A review of what we have learned since has been published in Nature Sustainability. It reveals that more than 40 years after the problem was identified, we know a lot about the direction of the effects ozone depletion has and could have had than the size of the impact.
Nevertheless, it's clear some serious threats were dodged. Skin cancers are rising, and while only a small portion of this is considered to be attributable to ozone depletion, without the Protocol we would have been facing an estimated 2 million more cases by 2030, many of them fatal.
“Without the Montreal Protocol, UV radiation levels in the near future... would have changed the whole way we live our lives – even a few minutes outdoors would have caused sunburn,” author Professor Robyn Lucas of the Australian National University said in a statement.
Depletion is thought to be responsible for a small fraction of the 60,000 annual deaths from melanoma, but Lucas told IFLScience most of the damage occurs in childhood, so cancers caused by more intense UV won't peak until the 2030s.
CFCs don't just destroy stratospheric ozone, they are also powerful warming gases. “Modelling studies indicate that in the absence of the Montreal Protocol, global mean temperatures would have risen more than 2°C (3.6°F) by 2070 owing to the warming effects from ozone-depleting substances alone,” the review notes.
The few benefits from lack of action, such as increased vitamin D, would be minor compared to the likely damage.
The report is vague on how much of a part ozone depletion has played in possibly the biggest problem of all, the loss of biological productivity in the Southern Ocean, which Lucas told IFLScience is “another area where we need more field research.”