There is a reason the Montreal Protocol is considered a rarity. Not only did the 1987 multilateral agreement get universal ratification, measures implemented under it have massively aided recovery of the ozone layer. The latest 2022 UN-backed Scientific Assessment Panel to the Montreal Protocol on Ozone Depleting Substances confirms the phase out of nearly 99 per cent of banned ozone-depleting substances (ODS). However, new research shows that the layer's recovery to 1980 levels—before the appearance of the ozone hole—could still be delayed by nearly a decade.
Found in the stratosphere, between 15 km and 30 km above Earth’s surface, the layer of naturally occurring molecule of three oxygen atoms protects the planet by absorbing the sun’s ultraviolet-B radiations that are linked to multiple ailments including skin cancer. Some 100 ODS, such as chlorofluorocarbons and hydrochlorofluorocarbons, which are used in industrial processes and equipment and get released into the atmosphere, damage the ozone layer by reacting with the gas and converting it to oxygen.
The Montreal Protocol phased down the consumption and production of ODS, with different timelines for developed and developing countries. However, it excluded ODS used as feedstocks (such as carbon tetrachloride or CCL4) in the manufacture of other chemicals because their emission rates were estimated to be only 0.5 per cent of the amount produced and it was believed that their production would decline with time. However, feedstock emissions are now substantially higher, and feedstock production and use has been rising rather than falling, finds a new study.
"Despite earlier projections, the reported global use of ODS as feedstock chemicals did not decline after 2000 but has increased by 163% between 2000 and 2024," says the study published in April 2026 in Nature Communications. Due to this, the associated emissions have increased to about 3.6 per cent, finds the study. At current rates, the feedstock-related ODS emissions could delay the "recovery of the mid-latitude stratospheric ozone layer by 7 (6–11) years", until about 2073. So far, the ozone layer was expected to recover to 1980 levels by around 2066 over the Antarctic, by 2045 over the Arctic and by 2040 for the rest of the world, as per World Meteorological Organization.
Falling satellite debris and reentry of rockets from space to Earth have emerged as another threat to the ozone layer …
This article was originally published in the September 16-31, 2026 print edition of Down To Earth