Ozone layer to recover in 4 decades but aerosol injection may undo gains: UNEP

Ozone layer to recover in 4 decades but aerosol injection may undo gains: UNEP

Subject: Environment

Context:

• The successful phasing out of banned substances as envisioned by the Montreal Protocol has set the stage for a complete recovery of the ozone layer by the 2060s, a United Nations-backed panel of experts said at the American Meteorological Society’s annual meeting January 8, 2023.

Details:

• 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.
• The scientists warned of the detrimental effects of geoengineering technologies such as stratospheric aerosol injection on the ozone layer.

Ozone hole:

• The first ozone hole was discovered in the stratospheric layers over the Antarctic in 1985, which allowed harmful ultraviolet (UV) radiation to pass into the lowest layer of the Earth’s atmosphere (troposphere) where humans live.
• UV radiation is linked with health hazards such as skin cancer, cataracts and other conditions in the eye and reduced immunity.

What is Montreal Protocol?

• The Montreal Protocol was created to reduce the production and consumption of ozone-depleting substances and protect the earth’s vulnerable ozone layer.
• On September 16, 1987, the treaty was opened for signature, and it entered into force on January 1, 1989, following a first meeting in Helsinki in May 1989.
  • The Protocol’s parties meet once a year to make decisions that will ensure the agreement’s successful implementation.
  • The Protocol has been adjusted or amended seven times since its inception – in 1990 (London), 1991 (Nairobi), 1992 (Copenhagen), 1993 (Bangkok), 1995 (Vienna), 1997 (Montreal), and 1999 (Beijing).
  • The protocol called for a ban on the use and trade of 100 ozone-depleting substances (ODS), and 99 per cent of these have been successfully phased out.
• The Kigali Amendment, the most recent amendment, called for the phase-out of hydrofluorocarbons (HFCs) in 2016.
  • These HFCs were used to replace a batch of ozone-depleting substances that had been phased out under the original Montreal Protocol.
  • They are known to be powerful greenhouse gases and thus contributors to climate change, despite the fact that they do not deplete the ozone layer.
  • The implementation of the 2016 Kigali Amendment to the Montreal Protocol for phasing out some hydrofluorocarbons (HFC) can gain from the success of the ODS ban. Reducing the concentration of HFCs can help avoid 3-0.5°C of global warming over pre-industrial levels by the end of this century.
• The Montreal Protocol established a set of practical, actionable tasks on which everyone agreed.

Salient features of the protocol:

• A number of classes of halogenated hydrocarbons that destroy stratospheric ozone are the foundation of the agreement.
  • Hydrofluorocarbons (HFCs) were introduced as non-ozone depleting alternatives to aid in the timely phase out of CFCs and HCFCs.
  • Hydrochlorofluorocarbons (HCFCs) are gases that are used in foam applications, air conditioning, and refrigeration systems all over the world. However, the Montreal Protocol is phasing them out since they damage the ozone layer.
  • HCFCs are both ODS and potent greenhouse gases; the most widely used HCFC has a global warming potential about 2,000 times greater than that of carbon dioxide (GWP).
  • The Parties made the decision to move up the phase-out of HCFCs in September 2007. By 2020, developed nations were supposed to totally phase them out.
• Chlorine or bromine is a component of any substance regulated by the Montreal Protocol that damages ozone (substances containing only fluorine do not harm the ozone layer).
• Nitrous oxide (N2O) is one of the ozone-depleting substances (ODSs) that the Montreal Protocol does not yet regulate.
• The treaty specifies a timeline for when manufacturing of each category of ODS must stop and thereafter be completely eradicated.
• A 10-year phase-in period was given for the developing nations mentioned in Article 5 of the agreement.

Concerns include:

• Geoengineering experiments to reduce global warming can damage the ozone layer.
• The panel examined the potential effects on ozone of the intentional addition of aerosols into the stratosphere, known as a stratospheric aerosol injection (SAI).
• SAI can increase sunlight reflection, thereby lowering the amount of heat that enters the troposphere.
• This method “could also affect stratospheric temperatures, circulation and ozone production and destruction rates and transport.
  • Injection of sulphuric acid into the stratosphere, for example, would damage the ozone layer.
  • Aerosol sprays, like other commonly used substances such as dry cleaning solvents, refrigerants and fumigants, contain ODS.

What is Stratospheric Aerosol Injection (SAI)?

• Stratospheric Aerosol Injection (SAI) is an unproven and hypothetical geo-engineering technique that could limit rising temperatures that are causing climate change.
• Working:
  • It would involve the use of huge hoses, cannons or specially designed aircraft to spray large quantities of sulphate particles into the upper layer of the atmosphere to act as a reflective barrier against sunlight.
  • The research assumes a special aircraft can be designed to fly at an altitude of about 20 km and carry a load of 25 tonnes.