Researchers in their study claimed that the hole in the Earth’s ozone layer over Antarctica has begun to heal. They said that in September 2015 the hole was around 4 million square kilometers smaller than it was in the year 2000, an area roughly the size of India.
The gains in the protective layer can be credited to the long term phasing out of ozone-destroying chemicals which was adopted in the 1989 Montreal Protocol.
Findings of the Study
• Industrial chlorofluorocarbons that cause ozone depletion have been phased out under the Montreal Protocol.
• A chemically-driven increase in polar ozone (or “healing”) is expected in response to this historic agreement.
• Fingerprints of September healing since 2000 was identified through
a) Increases in ozone column amounts
b) Changes in the vertical profile of ozone concentration
c) Decreases in the areal extent of the ozone hole
• Along with chemistry, dynamical and temperature changes contribute to the healing, but could represent feedbacks to chemistry.
• Volcanic eruptions episodically interfere with healing, particularly during 2015 (when a record October ozone hole occurred following the Calbuco eruption).
This is the first clear evidence of healing after the thinning of the layer was first reported in 1980s. The then report suggested a hole in the ozone layer above Antarctica every that was of an average of about 18 million square kilometers in September 1987 and widened to nearly 25 million square kilometers in September 2000.
The study was published on 30 June 2016 in the journal Science. Susan Solomon, the lead author of the study along with his team carried out detailed measurements of the amount of ozone in the stratosphere between 2000 and 2015.
What helped in finding the hole in Ozone in 1980s in Antarctica?
Extreme cold conditions and large amount of light helped the scientists to find thinning of the ozone over Antarctica. These two factors helped in producing Polar Stratospheric Clouds and the chlorine chemistry in these clouds helps in destroying the ozone.
The ultraviolet (UV) light of the sunlight on striking the chlorofluorocarbons (CFCs) into the atmosphere breaks their chemical bonds and freezes chorine. These free chlorine atoms helps in striping oxygen from Ozone molecules (O3) to form chemicals, destroying the ozone itself.
The ozone hole reaches its peak size in October, and by November, the stratosphere heats up enough to break apart this polar vortex fill the hole.
Ozone layer lies at the lower edge of the stratosphere at a distance of about 20 to 30 kilometer above the Earth’s surface. The layer protects the planet from the Sun’s ultraviolent radiation.
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