By Sharon Atieno

The ozone layer, a thin part of the earth’s atmosphere which absorbs most of the sun’s harmful ultraviolet radiation, is on track to recover within four decades.

This is according to the United Nations (UN)-backed Scientific Assessment Panel to the Montreal Protocol on ozone-depleting substances (ODSs) quadrennial assessment report, published every four years.

The report finds that if current policies remain in place, the ozone layer is expected to recover to 1980 values (before the appearance of the ozone hole) by around 2066 over the Antarctic, by 2045 over the Arctic and by 2040 for the rest of the world.

This recovery is a result of phasing out nearly 99% of banned ODSs including chlorofluorocarbons (CFCs), bromine-containing halons and methyl bromide, hydrochlorofluorocarbons (HCFCs), carbon tetrachloride (CCl4), and methyl chloroform.

Exposure to ultraviolet rays can result in sunburns, premature aging of the skin, eye problems, and even skin cancer among other effects.

The Montreal Protocol, a global agreement to protect the Earth’s ozone layer by phasing out the chemicals that deplete it, was adopted in 1987. This was followed by strong declines in the emissions of ODSs which led to a decline in the abundances of chlorine and bromine- which contribute to ozone depletion.

Additionally, compliance with the 2016 Kigali Amendment to the Protocol, which requires a phase-down of production and consumption of some hydrofluorocarbons (HFCs), is estimated to avoid 0.3–0.5°C of global warming by 2100.

HFCs are commonly used in air conditioners, refrigerators, aerosols, foams and other products. While these chemicals do not deplete the ozone layer, some of them have high global warming potential (GWP) ranging from 12 to 14,000.

According to the UN, overall HFC emissions are growing at a rate of 8% per year and annual emissions are projected to rise to 7-19% of global carbon dioxide emissions by 2050. Thus,  uncontrolled growth in HFC emissions challenges efforts to keep global temperature rise at or below 2°C this century.

“Ozone action sets a precedent for climate action. Our success in phasing out ozone-eating chemicals shows us what can and must be done – as a matter of urgency – to transition away from fossil fuels, reduce greenhouse gases and so limit temperature increase,” said World Meteorological Organization (WMO) Secretary-General Prof. Petteri Taalas.

With the intentional addition of aerosols to the stratosphere, known as stratospheric aerosol injection (SAI) being proposed as a potential method to reduce climate warming by increasing sunlight reflection, the Assessment has found that this method can reverse the gains made in the ozone layer.