With less carbon in plants and soils, more of it remains in the atmosphere as CO 2. Ozone depleting substances, such as CFCs, are also potent greenhouse gases and previous research has shown that their ban prevented their contribution to global warming through their greenhouse effect.
By the end of this century, their greenhouse effect alone would have contributed an additional 1. This is in addition to the newly quantified 0. Dr Paul Young, lead author from Lancaster University, said: "Our new modelling tools have allowed us to investigate the scorched Earth that could have resulted without the Montreal Protocol's ban on ozone depleting substances.
The increased UV would have massively stunted the ability of plants to soak up carbon from the atmosphere, meaning higher CO 2 levels and more global warming. Although we can hope that we never would have reached the catastrophic world as we simulated, it does remind us of the importance of continuing to protect the ozone layer.
Entirely conceivable threats to it still exist, such as from unregulated use of CFCs. Even if we had somehow managed to get to net zero CO 2 emissions, the additional 2. This is far in excess of the 1. The ozone layer is an essential barrier that protects us by filtering the sun's harmful UV -- when a hole in the layer was discovered above Antarctica in the s, it caused great alarm because of the damage UV can cause to human health through conditions such as skin cancers. The Montreal Protocol, which was signed in , is championed as an exemplar in environmental diplomacy.
Without the treaty, Earth and its flora would have been exposed to far more of the Sun's ultraviolet UV radiation. Continued and increased use of chlorofluorocarbons CFCs would have contributed to global air temperatures rising by an additional 2.
Part of that would have been caused directly by CFCs, which are also potent greenhouse gases. But the damage they cause the ozone layer would also have released additional planet-heating carbon dioxide - currently locked up in vegetation - into the atmosphere. In May , researchers documented a mysterious spike in atmospheric concentrations of trichlorofluoromethane 1 , or CFC, that had begun in around Production of the chemical had been banned since under the Montreal Protocol, a legally binding treaty that has been remarkably successful in curbing the use of ozone-depleting substances, so scientists surmised that the sudden increase was probably the result of a new source of illegal emissions.
By May , scientists had traced the bulk of the emissions to eastern China 2. In response to significant international pressure , the country committed to rectifying the problem. In a pair of studies published in Nature on 10 February, scientists report that atmospheric concentrations of CFC have dropped precipitously since 3 , 4.
Assuming the current trend continues, the damage to the ozone layer from several years of illegal emissions will be negligible, says Stephen Montzka, an atmospheric chemist at the National Oceanic and Atmospheric Administration in Boulder, Colorado, who led one of the studies.
But the actual rate is slower, owing to continued emissions of the chemical from old refrigeration systems and from insulating foam when buildings are demolished. Between and , CFC emissions fell by around 0. But that rate halved — to about 0. The most likely culprit was the manufacture and use of foam insulation. The analysis published this week, using data from two independent global air-monitoring networks, indicates that concentrations of CFC began to decline more rapidly in In a second paper, Montzka and colleagues used measurements from air-monitoring stations in South Korea and Japan, as well as detailed atmospheric-transport modelling, to show that the largest source of the rogue emissions — in eastern China — has been shut down.
The study incorporated independent analyses from four different research groups and two models, all of which showed consistent results, says Luke Western, an atmospheric scientist at the University of Bristol, UK, and a co-author on the paper.
The scientists used computer modeling to see how unabated CFC use would have affected the ozone layer -- which sits between nine and 22 miles above the Earth -- and what impacts that would have had on the planet.
They concluded the CFC ban had avoided a "scorched Earth," in which the ozone layer breaks down by the late s, putting humans at greater risk of health problems, like skin cancer, and degrading the ability of plants and trees to absorb carbon from the atmosphere. Read More. That already means extreme weather like heatwaves, which can contribute to wildfires, and heavy rainfall and storms, which can cause flooding, will become more frequent and intense.
But the more the Earth warms, the worse these weather events are likely to become. A simulated image of the ozone over the Antarctic pole. The purple and blue show where there is the least ozone, and the yellows and reds are where there is more.
Paul Young, an atmospheric and climate scientist from Lancaster University and the study's lead author, told CNN that there would have been "drastic consequences" in areas like agriculture and human health. But as you can imagine, the consequences would have been absolutely dire," he said. I think it would have been quite apocalyptic really, and it would have been a problem all over the world.
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