A depiction of the ozone hole over Antarctica, courtesy NOAA.
Ozone-depleting chemicals decreasing in atmosphere, but weather plays big role in year-to-year variability
Staff Report
FRISCO — The ozone hole over Antarctica didn’t change much from last year, scientists said this week, pointing to weather and climate variability as key factors in year-to-year variability.
The single-day maximum area was similar to that in 2013, which reached 9.3 million square miles. The largest single-day ozone hole ever recorded by satellite was 11.5 million square miles) on Sept. 9, 2000. Overall, the 2014 ozone hole is smaller than the large holes of the 1998–2006 period, and is comparable to 2010, 2012, and 2013.
“Year-to-year weather variability significantly impacts Antarctica ozone because warmer stratospheric temperatures can reduce ozone depletion,” said Paul A. Newman, chief scientist for atmospheres at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Under the Clean Air Act, NASA and NOAA have been monitoring ozone-depleting gases and stratospheric depletion of ozone from the ground and with a variety of instruments on satellites and balloons since the 1970s.
“The ozone hole area is smaller than what we saw in the late-1990s and early 2000s, and we know that chlorine levels are decreasing. However, we are still uncertain about whether a long-term Antarctic stratospheric temperature warming might be reducing this ozone depletion,” Newman said.
With the increased atmospheric chlorine levels present since the 1980s, the Antarctic ozone hole forms and expands during the Southern Hemisphere spring (August and September). The ozone layer helps shield life on Earth from potentially harmful ultraviolet radiation that can cause skin cancer and damage plants.
Starting in 1987, the Montreal Protocol agreement regulated ozone depleting substances, such as chlorine-containing chlorofluorocarbons and bromine-containing halons. The 2014 level of these substances over Antarctica has declined about 9 percent below the record maximum in 2000.
Scientists aren’t sure if the ozone hole trend over the last decade is a result of temperature increases or chlorine declines. An increase of stratospheric temperature over Antarctica would decrease the ozone hole’s area. Satellite and ground-based measurements show that chlorine levels are declining, but stratospheric temperature analyses in that region are less reliable for determining long-term trends.
