Ozone depleted by record amount over Arctic: UN

This image shows how large the Arctic ozone hole, shown in blue, was in 2006. This year’s ozone hole is even larger, according to the World Meterological Organization. (IMAGE/NASA)

POSTMEDIA NEWS

The legacy of the ozone-destroying chemicals, such as those that once filled aerosol sprays and refrigerators, continues to be felt in the Arctic, where the ozone has been depleted this spring like never before.

The World Meteorological Organization said Tuesday that the Arctic experienced an “ozone column loss” of about 40 per cent from the beginning of the winter to late March.

The highest ozone loss previously on record was about 30 per cent over the entire winter.

Ozone forms an atmospheric shield that protects the Earth from ultraviolet rays.

“The Arctic stratosphere continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities,” said Michel Jarraud, Secretary General of the UN agency, in a statement.

“The 2011 ozone loss shows that we have to remain vigilant and keep a close eye on the situation in the Arctic in the coming years.”

The depletion comes despite what the UN weather organization calls “very successful” international efforts to reduce the amount of chemicals in the air that can destroy the ozone layer — following a high-profile campaign by environmental activists in the 1980s.

The UN organization called the record ozone depletion over the Arctic the environmental hangover of the chemical pollution that was long pumped into the atmosphere.

Ozone-depleting substances, such as chlorofluorocarbons and halons, which were once used in refrigerators, spray cans and fire extinguishers, stay in the atmosphere for decades.

“It will take several decades before their concentrations are back down to pre-1980 levels,” the weather organization said in a statement.

It gathered its latest assessment through ground-level observation as well as from balloons and satellites over the Arctic.

Weather conditions vary widely in the Arctic from year to year, and that has an effect on how much ozone depletion is seen annually.

Some Arctic winters experience almost no ozone loss, while cold stratospheric temperatures can result in substantial ozone loss, the agency said.

Even though this past Arctic winter was warmer than average at ground level, it was colder in the stratosphere than for a normal Arctic winter.

The stratosphere is the second major layer of the atmosphere, above the troposphere and below the mesosphere. It starts at about 10 kilometres in altitude and reaches up to an altitude of about 50 kilometres.

About 90 per cent of the ozone in the atmosphere is found in the stratosphere. That ozone is commonly referred to as the ozone layer. It absorbs ultraviolet light and protects life on Earth from harmful ultraviolet radiation from the sun.

The Montreal Protocol on Substances that Deplete the Ozone Layer was signed in 1987, in a bid to reduce ozone levels to pre-1980 levels. It has since been revised several times, and has been ratified by nearly 200 countries.

The accord helped phase out ozone-depleting substances — such as chlorofluorocarbons and halons.

The World Meteorological Organization said that, thanks to the accord, the ozone layer in the Arctic is expected to recover around 2025-2035.