Hole in ozone layer recovering

By Paul Harper

Photo / Supplied
Photo / Supplied

The hole in the ozone layer over Antarctica appears to be recovering, with new satellite images showing the hole the smallest it has been in the past decade.

The findings, from the European Space Agency (ESA), suggest international efforts to phase out of human-made chlorofluorocarbons (CFCs) have been effective.

Since the beginning of the 1980s, an ozone hole has developed over Antarctica during the spring, resulting in a decrease in ozone concentration of up to 70 percent.

According to the ozone sensor on Europe's MetOp weather satellite, last year the hole was the smallest seen in the last 10 years, the ESA said in a statement.

Long-term observations also show the Earth's ozone has strengthened following international agreements to protect the vital layer of the atmosphere.

International agreements on protecting the ozone layer - particularly the Montreal Protocol - have stopped the increase of CFC concentrations, and a drastic fall has been observed since the mid-1990s.

However, due to the long-lifetimes of CFCs in the atmosphere, it may take until the middle of the century for the stratosphere's chlorine content to returns to levels similar to the 1960s, the ESA said.

Ozone depletion is more extreme in Antarctica than at the North Pole because high wind speeds cause a fast-rotating vortex of cold air, leading to extremely low temperatures. Under these conditions, CFCs have a stronger effect on the ozone, depleting it and creating the infamous hole.

Over the Arctic, the effect is far less pronounced because the northern hemisphere's irregular landmasses and mountains normally prevent the build-up of strong circumpolar winds.

The reduced ozone over the Southern Hemisphere means people here are more exposed to cancer-causing ultraviolet radiation.

- nzherald.co.nz

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