Antarctic Ozone Hole Gets Bigger Annual Cycle Expected To Worsen For Several More Years

The annual depletion of ozone high over Antarctica has steadily worsened over the past 10 years and has reached about the most severe levels possible, says a co-discoverer of the so-called ozone hole.

“Basically the situation is we’ve not seen any slowdown at all. If anything there’s an acceleration of the depletion,” said meteorologist Jonathan Shanklin.

Ozone is a form of oxygen that shields against harmful ultraviolet rays from the sun. The ozone destruction is caused by pollution from compounds containing chlorine or bromine.

The Antarctic depletion begins in August and hits its high point in October, as chlorine and bromine destroy ozone within high-altitude clouds.

Ozone levels then begin to climb as warmer temperatures make the high-altitude clouds disappear and ozone-rich air pours in from elsewhere.

Shanklin’s research suggests that the minimum ozone levels have gone about as low as possible in the past three years - less than 40 percent of the amount measured in the 1960s.

International agreements have been signed to counter the pollution, which Shanklin said is expected to peak in the late 1990s.

“We should start seeing things improve thereafter,” Shanklin said. Yet, “it still will be perhaps 50 years before the ozone hole disappears” because the chlorine compounds persist a long time in the atmosphere.

Shanklin, who works for the British Antarctic Survey, is one of three scientists who announced the discovery of the ozone hole in 1985, based on ozone decreases since the mid1970s.

In today’s issue of the British journal Nature, he and a colleague present an update of data recorded over Halley in Antarctica.