Context:
The ozone ‘hole’, once considered to be the gravest danger to planetary life, is now expected to be completely repaired by 2066, a scientific assessment has suggested.
Relevance:
GS I- Geography
Dimensions of the Article:
- What is Ozone Layer
- What are Ozone Holes?
- Ozone creation and destruction
- Improvement in the ozone hole
What is Ozone Layer?
- Ozone layer, also called ozonosphere, is a region of the upper atmosphere, between roughly 15 and 35 km (9 and 22 miles) above Earth’s surface which contains relatively high concentrations of ozone molecules (O3).
- Approximately 90 percent of the atmosphere’s ozone occurs in the stratosphere, the region extending from 10–18 km (6–11 miles) to approximately 50 km (about 30 miles) above Earth’s surface.
- The ozone layer effectively blocks almost all solar radiation of wavelengths less than 290 nanometres from reaching Earth’s surface, including certain types of ultraviolet (UV) and other forms of radiation that could injure or kill most living things.
What are Ozone Holes?
- The ‘ozone hole’ is not really a hole — it refers to a region in the stratosphere where the concentration of ozone becomes extremely low in certain months.
- The ‘ozone holes’ most commonly talked about are the depletions over Antarctica, forming each year in the months of September, October and November, due to a set of special meteorological and chemical conditions that arise at the South Pole, and can reach sizes of around 20 to 25 million sq km.
- Such holes are also spotted over the North Pole, but owing to warmer temperatures than the South Pole, the depletions here are much smaller in size.
Ozone creation and destruction
- The production of ozone in the stratosphere results primarily from the breaking of the chemical bonds within oxygen molecules (O2) by high-energy solar photons. This process, called photodissociation, results in the release of single oxygen atoms, which later join with intact oxygen molecules to form ozone.
- The amount of ozone in the stratosphere varies naturally throughout the year as a result of chemical processes that create and destroy ozone molecules and as a result of winds and other transport processes that move ozone molecules around the planet.
- Over the course of several decades, however, human activities substantially altered the ozone layer.
- Ozone depletion, the global decrease in stratospheric ozone observed since the 1970s, is most pronounced in polar regions, and it is well correlated with the increase of chlorine and bromine in the stratosphere.
- Those chemicals, once freed by UV radiation from the chlorofluorocarbons (CFCs) and other halocarbons (carbon-halogen compounds) that contain them, destroy ozone by stripping away single oxygen atoms from ozone molecules.
- As the amount of stratospheric ozone declines, more UV radiation reaches Earth’s surface, and scientists worry that such increases could have significant effects on ecosystems and human health.
Improvement in the ozone hole
Successful Implementation of the Montreal Protocol
- The ozone hole has been steadily improving since the year 2000 due to the successful implementation of the Montreal Protocol.
Ozone Layer Expected to Recover to 1980 Values
- The latest scientific assessment has said that if current policies continue to be implemented, the ozone layer is expected to recover to 1980 values by 2066 over Antarctica, by 2045 over the Arctic, and by 2040 for the rest of the world.
Climate Change Co-Benefit of Eliminating Ozone-Depleting Substances
- The elimination of ozone-depleting substances also has a significant climate change co-benefit, as these substances happen to be powerful greenhouse gases, several of them hundreds or even thousands of times more dangerous than carbon dioxide, the most abundant greenhouse gas and the main driver of global warming.
Compliance with Montreal Protocol Averts Additional Warming
- The report stated that global compliance with the Montreal Protocol would ensure the avoidance of 0.5 to 1 degree Celsius of warming by 2050, meaning that if the use of CFCs and other similar chemicals had continued to grow, the world would be 0.5 to 1 degree Celsius warmer than it already is.
- In 2016, with the objective of addressing climate change, the Montreal Protocol was amended to extend its mandate over hydrofluorocarbons, or HFCs, which have replaced CFCs in industrial use.
- HFCs do not damage the ozone layer, but are very powerful greenhouse gases.
Kigali Amendment Aims to Eliminate HFCs and Prevent Further Warming
- The Kigali Amendment to the Montreal Protocol aims to eliminate 80-90 per cent of the HFCs currently in use by 2050, which is expected to prevent another 0.3 to 0.5 degree Celsius of global warming by the turn of the century.
-Source: Indian Express
