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The hole in Earth’s ozone layer that forms over Antarctica each September was the smallest observed since 1988, NASA satellite measurements from this year have revealed.

Details

• The ozone hole reached its peak extent on September 11, covering an area about two and a half times the size of the U.S. — 7.6 million square miles in extent — and then declined through the remainder of September and into October, according to scientists from NASA.
• Ground- and balloon-based measurements from the National Oceanic and Atmospheric Administration (NOAA) also showed the least amount of ozone depletion above the continent during the peak of the ozone depletion cycle since 1988
• NOAA and NASA collaborate to monitor the growth and recovery of the ozone hole every year.
• The Antarctic ozone hole was exceptionally weak this year. This could be partly attributed to the success of the Montreal Protocol.

About the Ozone layer

• Ozone depletion describes two related phenomena observed since the late 1970s: a steady decline of about four percent in the total amount of ozone in Earth's stratosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone around Earth's Polar Regions. The latter phenomenon is referred to as the ozone hole.
• There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric phenomena.
• The main cause of ozone depletion and the ozone hole is man-made chemicals, especially man-made halocarbonrefrigerants, solvents, propellants, and foam-blowing agents (chlorofluorocarbon (CFCs), HCFCs, halons), referred to as ozone-depleting substances(ODS).
• These compounds are transported into the stratosphere by the winds after being emitted at the surface.^[2] 
• Once in the stratosphere, they release halogen atoms through photodissociation, which catalyze the breakdown of ozone (O₃) into oxygen (O₂). Both types of ozone depletion were observed to increase as emissions of halocarbons increased.
• The concerns of ozone depletion and its subsequent harmful effects led to the adoption of the Montreal Protocol in 1987, which bans the production of CFCs, halons, and other ozone-depleting chemicals. The ban came into effect in 1989. Ozone levels stabilized by the mid-1990s and began to recover in the 2000s. Recovery is projected to continue over the next century, and the ozone hole is expected to reach pre-1980 levels by around 2075.
• The Montreal Protocol is considered the most successful international environmental agreement to date.

About the Montreal Protocol

• The Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force on 1 January 1989, followed by a first meeting in Helsinki, May 1989. Since then, it has undergone eight revisions, in 1990 (London), 1991 (Nairobi), 1992 (Copenhagen), 1993 (Bangkok), 1995 (Vienna), 1997 (Montreal), 1998 (Australia), 1999 (Beijing) and 2016 (Kigali, adopted, but not in force). 
• As a result of the international agreement, the ozone hole in Antarctica is slowly recovering.
• Due to its widespread adoption and implementation it has been hailed as an example of exceptional international co-operation.

Source

The Hindu