A ‘significant milestone’ has been reached in the recovery of the ozone layer

A ‘significant milestone’ has been reached in the recovery of the ozone layer

The Earth’s ozone layer is vital for protecting all forms of life – from crops to people – from the sun’s harmful radiation. This shield in Earth’s stratosphere has been depleted for decades, endangering life on the planet, but new research from NOAA says it may now have a chance to at least partially recover.

In new research, NOAA found that global concentrations of harmful ozone-depleting chemicals have declined by just over 50% in the mid-latitude stratosphere, from levels seen in 1980. The continued decline, NOAA scientists said , “shows threat to ozone layer recedes below major milestone in 2022”.

Although more slowly, there has also been a decline in concentrations over Antarctica, where a hole in the ozone layer occurs every year. NOAA found that concentrations are down 26 percent from peak values ​​in the region in the 1990s. In 2021, that hole was larger than usual – larger than the size of Antarctica itself, but now NOAA says the Antarctic ozone layer is projected to recover “sometime around 2070”.

International regulations and compliance to manage these chemicals are the reason for three decades of “slow but steady” progress, the agency said.

Stephen Montzka, senior scientist for NOAA’s Global Monitoring Laboratory, said progress is great, but “at the same time, it’s a little humbling to realize that the science is still a long way from being able to say that the issue of ozone depletion is behind us.”

Ozone-depleting gas index (ODGI) versus time calculated for the Antarctic and mid-latitude stratosphere.  As before, the ODGI was derived directly from the Equivalent Effective Stratospheric Chlorine (EESC) determined from our surface atmospheric observations.  / Credit: NOAA

Ozone-depleting gas index (ODGI) versus time calculated for the Antarctic and mid-latitude stratosphere. As before, the ODGI was derived directly from the Equivalent Effective Stratospheric Chlorine (EESC) determined from our surface atmospheric observations. / Credit: NOAA

Scientists have been closely monitoring the ozone since the 1980s, when it was discovered that certain man-made chemicals were “severely damaging” the Earth’s vital protective layer. In 1987, just seven years after the destruction of the ozone by chemicals became more apparent, every country on Earth – for the first and only time – ratified a treaty, known as the Montreal Protocol, to regulate chemicals to protect the Earth.

Among these man-made chemicals are chlorofluorocarbons (CFCs), which people began using in the 1960s in air conditioners, aerosol spray cans, Styrofoam and industrial cleaning products, according to the University Corporation for Atmospheric Research.

Once used, CFCs rise into the stratosphere, where ultraviolet radiation breaks down the compounds and releases chlorine atoms, which along with bromine are dangerous to the ozone, according to the EPA. These atoms are known for destroying ozone molecules – just one chlorine atom can destroy more than 100,000 ozone molecules, the agency said, adding that with these atoms, ozone “can be destroyed faster than it is created of course”.

Hydrochlorofluorocarbons (HCFCs) were developed as a temporary alternative to CFCs, as they have a shorter lifetime in the atmosphere compared to CFCs and do not release as much reactive chlorine into the stratosphere. However, they still have the ability to “deplete stratospheric ozone,” according to NOAA, and production in developed countries was banned in 2020.

And while the success so far is promising, the scientists said, the race isn’t over.

“Ozone recovery is not a foregone conclusion,” they said in their report. “Full recovery is expected only with continued reductions in atmospheric chlorine and bromine in the coming years and continued adherence to the production and consumption restrictions outlined in the Protocol.”

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