The ozone layer, which protects us from potentially harmful ultraviolet sunlight, was 40 per cent thinner last month than the average between 1979 and 1982. Though not a "hole", this continues a downward trend: last year, the March level was 24 per cent down on the 1979-1982 levels.
The risks of enjoying sunny weather are much greater in Britain early in the year compared with summer. The ozone layer always thins in March - meaning that unprotected sunbathing in spring can be more hazardous in the long term.
Last November, an expert panel of scientists told the Government that 8,000 extra skin cancer cases would be caused in Britain by increased UV exposure. At present, there are 80,000 cases annually in this country.
The report said children today will face a lifetime risk of skin cancer which is 4-10 per cent higher because of ozone damage. The increase in ultraviolet light is also expected to affect crops and animals, plankton in the sea, and synthetic materials, although it is not yet possible to gauge the damage.
Worldwide, the average ozone layer has a thickness of 300 "Dobson units" - about equal to two stacked 1p pieces. In March, the Arctic level fell to 219 Dobson units. In the Antarctic, the ozone "hole" measures about 100 Dobson units.
"Some people have got the message that the sun can be dangerous," said Kate Law, head of clinical programs at the Cancer Research Campaign. "But a good proportion only take protection when they're abroad because they think that's where the danger is. A recent survey found that one in 12 people here insisted that the sun doesn't cause cancer - so there's still some work to do."
The most important precaution to take is to make sure that children are well-protected from the sun, she said. Studies have shown that high exposure to ultraviolet light when young gives a predisposition to skin cancer later in life.
"I was in Regent's Park today with a TV crew talking to people. The problem is that they don't like being lectured, though it was nice to see that the children were properly covered up, wearing baseball caps, long shorts and long-sleeved shirts, even if their parents weren't."
Britain has accused the United States of dragging its feet on implementing steps to reduce the greenhouse emissions that are blamed for climate change and global warming, writes David Usborne in New York.
John Gummer, the Secretary of State for the Environment shocked UN delegates by visibly fulminating at the close of a speech delivered on behalf of the US government by America's ambassador to the UN, Bill Richardson.
Mr Richardson later told British officials he had been "yelled at" by Mr Gummer, who was seated next to him.
In his own speech Mr Gummer said: "The US has the capability to deal with the serious disruptions that climate change will bring, but the rest of the world does not.
"In 25 years' time, when countries are facing starvation or inundation, who is going to pick up the tab? ... The sadness in America is that politicians have not been willing to communicate to their public what is at stake here."
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