Ozone hole maximum is up on 2007

13 October 2008

The 2008 ozone hole over Antarctica is larger than the 2007 hole by two million square kilometres. But this doesn't beat the 2006 record.

Ozone hole extent

The ozone hole above Antarctica on 7 October 2008 (European Space Agency)

This year, the ozone hole over the South Pole - as measured by the European Space Agency's Envisat satellite - rose to 27 million square kilometres in area at the start of October. In 2007, it reached 25 million square kilometres compared with the record-breaking 2006 ozone hole - 29 million square kilometres. This is about the same size as the North American continent.

The hole reaches its largest point each year at the start of October during the Antarctic spring season.

Ozone is a protective layer found at around 25 kilometres in the upper atmosphere that acts like an umbrella, shielding us from harmful ultraviolet rays, which can cause skin cancer, cataracts and harm marine life.

Depletion of ozone is caused by extremely cold temperatures at very high altitudes combining with ozone-destroying gases, such as man-made chlorofluorocarbons (CFCs), which were phased out under the 1987 Montreal Protocol. CFCs last for a long time in the atmosphere and persist at levels of around 3·5 parts per billion by volume.

Scientists at the British Antarctic Survey's Halley Bay research base in Antarctica were the first to notice that ozone depletion could be a problem. Geophysicist Joe Farman's ground-breaking discovery appeared in Nature in 1985 and acted as an early warning signal which led to tougher controls on CFC emissions in the Montreal Protocol.

This year is up there with the worst years for the ozone hole.

- Dr Neil Harris

Although the use of CFCs was phased after the Montreal Protocol, the fact that they persist in the atmosphere means levels are higher now than in 1985. Scientists have estimated that the hole over Antarctica won't get back to 1980s levels until 2060.

In 2000, the ozone hole reached a peak not broken until 2006. Although its size has varied since 2000, it still hasn't got much smaller.

"This year is up there with the worst years for the ozone hole," says Dr Neil Harris, a chemistry researcher at Cambridge University.

The hole over Antarctica won't get back to 1980s levels until 2060.

Atmospheric chemistry experts think the hole must be recovering, because we're using less CFCs, but because the time it takes for CFCs to disappear, the ozone hole has been at its worst over the last ten years.

Planet Earth reported last week that, according to scientists from the National Centre for Atmospheric Science, climate change might have been an even bigger problem than it currently is had the Montreal Protocol not reduced CFCs levels in the upper atmosphere over Antarctica.

The UK funds the European Space Agency's Earth observation satellites through NERC's annual space budget of £42m. Envisat is the world's largest Earth observation satellite.