The recent announcements by NASA and NOAA that this year’s Antarctic ozone hole is slightly smaller than average could be further confirmation that the 1987 Montreal Protocol, an international treaty is phasing out production of ozone-depleting substances, is working as expected.
On the other hand, it could mean only that the weather helped save more Antarctic ozone than in some previous year.
The hole is an area in the atmosphere with low ozone concentrations. It is normally is at its biggest this time of year. NASA says on average it covered 8.1 million square miles this season. That’s 6 percent smaller than the average since 1990.
A NASA release quotes the agency’s chief atmospheric scientist, Paul A. Newman, as saying. “The main reason for this year’s result is local weather. The upper air has been almost 2 degrees warmer than normal in the globe’s southernmost region. That has led to fewer polar stratospheric clouds. These clouds are where chlorine and bromine, which come from man-made products, nibble away at ozone.”
NOAA’s James Butler, director of NOAA’s global monitoring division at the it’s Earth System Research Lab, told the Associated Press the new figures are “sort of encouraging news. It’s not getting worse. We can’t say yet that it’s a recovery.”
Either way, since ozone-eating substances hang around 50 years or longer in the atmosphere, scientists don’t expect the hole to become history until around the middle of this century.
NASA tracks the amounts of stratospheric ozone globally with satellites while NOAA follows what’s happening over Antarctica with ground measurements and balloons that carry ozone measuring instruments 20 miles into the air over the U.S. South Pole station.
When asked about this year’s reports, Susan Solomon, who won a 1999 National Medal of Science for her ozone hole work, responded by email with a reference to her 2004 article in Nature magazine warning scientists and journalists against reading too much into the annual reports of the hole’s growth or shrinkage.
In this article she says measurements showing global reductions in the amounts of ozone-eating substances in the lower atmosphere are a better gauge of what’s happening over the long run. These measurements continue to show a decrease.
The 1985 discovery of the ozone hole by British researchers in Antarctica led to global concern that the whatever was causing huge decreases in ozone in the stratosphere over Antarctica each Southern Hemisphere spring could eventually occur elsewhere. This set off alarms because stratospheric ozone blocks extremely dangerous ultraviolet energy from reaching earth’s surface.
In the 1980s Solomon and her colleagues at the NOAA’s Earth System Research Laboratory in Boulder, Colo., hypothesized that interactions involving ozone and chlorofluorocarbons (the source of the chlorine Newman refers to) on ice particles in clouds in the Antarctic stratosphere destroy ozone. This was one of several hypotheses
She led the 1986 and 1987, expeditions to Antarctica that helped confirm the NOAA hypothesis and helped lead to the Montreal Protocol. Their work and the work of other scientists in the 1980s showed what causes huge decreases in the amount ozone over Antarctica and led to the Montreal Protocol.
Here are the basics of the Antarctic ozone hole:
1. Antarctic’s temperatures begin plunging in March as the continent moves into months of darkness and a strong vortex of stratospheric winds forms over Antarctica.
2. The Vortex blocks outside air from arriving with more ozone.
3.Polar-stratospheric clouds, which concentrate ozone-destroying substances form.
4. In September when the sun returns it melts the clouds, dumping the ozone-eating substances into the air and supplying energy for chemical reactions that destroy ozone.
5. Ozone levels reach the lowest levels in October and begin recovering as the vortex weakens and outside air arrives to replenish ozone.
Solomon, who is now the Ellen Swallow Richards Professor of Atmospheric Chemistry & Climate Science at the Massachusetts Institute of Technology, said in 2008 that she hoped to be around to celebrate the mid-century end of the ozone hole.
“In an ideal world I’d find a way to be [in Antarctica] at the time. I don’t know how at that age, maybe I can go on a cruise ship,” Solomon said.
While interesting, this month’s Antarctic ozone levels aren’t a signal for Solomon to purchase tickets.