This year’s ozone hole over Antarctica has shown signs of steady recovery, ranking as the fifth smallest since 1992, according to Nasa and Noaa (National Oceanic and Atmospheric Administration scientists. Early observations suggest the hole is breaking up nearly three weeks earlier than in previous years, reflecting the long-term impact of global efforts to reduce ozone-depleting chemicals under the Montreal Protocol.During the height of this year’s ozone depletion season, from September 7 to October 13, the average size of the ozone hole was about 7.23 million square miles (18.71 million square kilometers).The ozone hole reached its largest single-day size this year on September 9 at 8.83 million square miles (22.86 million square kilometers), around 30% smaller than the largest ozone hole ever observed in 2006, which had an average area of 10.27 million square miles (26.60 million square kilometers). Using satellite records dating back to 1979, this year’s ozone hole ranks as the 14th smallest over 46 years of observations.“As predicted, we’re seeing ozone holes trending smaller in area than they were in the early 2000s,” said Paul Newman, a senior scientist at the University of Maryland system and longtime leader of NASA’s ozone research team. “They’re forming later in the season and breaking up earlier.”Noaa and Nasa scientists say this year’s monitoring confirms that international controls on ozone-depleting chemicals under the Montreal Protocol and its amendments are driving the gradual recovery of the ozone layer. Stephen Montzka, senior scientist with Noaa’s Global Monitoring Laboratory, said, “Since peaking around the year 2000, levels of ozone depleting substances in the Antarctic stratosphere have declined by about a third relative to pre-ozone-hole levels,” as quoted by Noaa.“This year’s hole would have been more than one million square miles larger if there was still as much chlorine in the stratosphere as there was 25 years ago,” added Newman.Weather balloon data showed that the ozone layer directly over the South Pole reached its lowest concentration of 147 Dobson Units on October 6. The lowest value ever recorded over the South Pole was 92 Dobson Units in October 2006.Laura Ciasto, a meteorologist with Noaa’s Climate Prediction Center and a member of the ozone research team, noted that natural factors such as temperature, weather, and the strength of the polar vortex also influence ozone levels. “A weaker-than-normal polar vortex this past August helped keep temperatures above average and likely contributed to a smaller ozone hole,” she said.
What is ozone and why we need it
Earth’s ozone layer, located in the stratosphere between 7 and 31 miles above the surface, acts as a protective shield against harmful ultraviolet (UV) radiation. Reduced ozone levels allow more UV rays to reach the Earth, which can cause crop damage and increase risks of skin cancer and cataracts. Ozone depletion occurs when chlorine- and bromine-containing compounds, such as CFCs, reach the stratosphere and react with ozone molecules. Though now banned, these substances remain in old products like building insulation and landfills, and will gradually decrease over time. Scientists project that the Antarctic ozone hole could fully recover by the late 2060s.
