International efforts to phase out the use of chlorofluorocarbons and other ozone-depleting substances may be paying off, according to research revealed Friday by the National Institute of Water and Atmospheric Research in New Zealand.
The Antarctica ozone hole is the smallest it has been in the past five years, NIWA said.
While a one-year reduction in the ozone hole can’t indicate a recovery stage, NIWA’s atmospheric experts say the new information adds to a pattern of less severe ozone holes in recent years.
Satellite data combined with ground-base measurements, including the Antarctica New Zealand Arrival Heights observatory near Scott Base, show the hole reached a maximum area of about 22 million square kilometers (about 8.5 million square miles) and a 27 million ton deficit of ozone this year, compared with 24 million square kilometers (about 9.3 million square miles) and a 35 million ton deficit last year.
The largest hole, according to NIWA, was 29 million square kilometers (about 11.2 million square miles) and a 43 million ton deficit, recorded in 2000 and then repeated in 2006.
"We see a lot of year-to-year variation in ozone holes, caused by differences in atmospheric temperature and circulation," said NIWA atmospheric scientist Stephen Wood in a prepared statement. "So we can't definitively say the ozone hole is improving from one new year of observations."
"However, we have now had a few years in succession with less severe holes," Wood said. "That is an indication we may be beginning to see a recovery."
The Antarctic ozone hole forms in August and September each year, remaining until it breaks up in November or December.
Wood said the results are encouraging and indicate that international initiatives, such as the Montreal Protocol, may be showing a positive effect on the Antarctic ozone hole.
The 1987 Montreal Protocol is an international convention phasing out the use of ozone-depleting substances such as chlorofluorocarbons (CFCs) and other manmade halogen compounds.
While it's referred to as a "hole," the term refers to a large area of the stratosphere with extremely low amounts of ozone.
The ozone layer protects all life from the sun's harmful radiation, according to the U.S. Environmental Protection Agency, noting ozone depletion is a global issue and not just a problem at the South Pole.
Less protection from ultraviolet light will, over time, lead to higher skin cancer and cataract rates and crop damage, the EPA says. The U.S., in cooperation with 190 other countries, is phasing out the production of ozone-depleting substances.
CFCs were used in refrigerants, solvents, foam blowing agents, and in other smaller applications, the EPA says. CFCs do not dissolve in the rain, only exposure to strong UV radiation breaks them down, and that releases chlorine atoms that destroy up to 100,000 times their number of ozone molecules.
By contrast, chlorine from swimming pools, industrial plants and volcanoes doesn't reach the stratosphere, but does wash out of the atmosphere when rain falls.
The EPA credits measures taken under the Montreal Protocol for falling emissions of ozone-depleting substances. Natural ozone production process will heal the ozone layer in about 50 years, it says.
Continued monitoring and measurements may reveal soon if "we are really seeing the start of a sustained, long-term recovery,” Wood said in releasing the 2010 Antarctica research.