Montreal Protocol leads to healing of Earth's ozone layer hole

Earth’s protective ozone layer, the loss of which risked exposing people to harmful ultraviolet rays from the sun, is healing! In their new report, U.N. scientists say at the current rate, the giant hole over Antarctica would be fully healed by 2066. This achievement is majorly due to the Montreal Protocol of 1987, a landmark multilateral environmental agreement that regulates the consumption and production of nearly 100 man-made chemicals, or ‘ozone-depleting substances’ (ODS).

Ozone is a form of oxygen. In the Earth’s upper atmosphere, known as the stratosphere (15 to 30 kms above Earth’s surface), the ozone layer acts as a barrier to block harmful radiation from the sun. But closer to Earth’s surface, ozone is a common pollutant. Each year, a large hole develops in the layer over Antarctica.
The discovery of a hole in the Ozone Layer was first announced by three scientists from the British Antarctic Survey, in May 1985. Variations in the size of the Antarctic ozone hole, particularly between 2019 and 2021, were driven largely by meteorological conditions. Nevertheless, the Antarctic ozone breach has been slowly improving in area and depth, since the year 2000.

According to Dr. Paul Newman, chief Earth scientist at NASA’s Goddard Space Flight Center, the two chief chemicals that munch away at ozone are in lower levels in the atmosphere. Chlorine levels are down 11.5% since they peaked in 1993, and bromine, which is more efficient at eating ozone, dropped 14.5% since its 1999 peak.

The UN report reaffirms the positive impact that the Montreal protocol has had on the climate. The treaty has also benefitted efforts to mitigate climate change, helping avoid global warming by an estimated 0.5°C. In 2016 an additional agreement to the Montreal Protocol, known as the Kigali Amendment required a phase-down of the production and consumption of some hydrofluorocarbons (HFCs).
The report also warned that efforts to artificially cool the planet by putting aerosols into the atmosphere to reflect sunlight would thin the ozone layer by as much as 20% in Antarctica.

Down to Earth is Science and Environment fortnightly published by the Society for Environmental Communication, New Delhi. We publish news and analysis on issues that deal with sustainable development, which we scan through the eyes of science and environment.