· Sun's activity blamed for stopping natural repairs
· Fears remain over skin cancer and cataracts
The hole in the ozone layer could grow significantly over the next
few years, reigniting fears over skin cancer, cataracts and damage to vulnerable
According to scientists in Germany, changes in the sun's activity have delayed
natural repairs to the layer of gas high in the stratosphere, and are about to
trigger further ozone loss. They say the ozone layer, which shields the Earth
from the worst of ultraviolet radiation, will not begin to recover until the end
of the decade.
Martin Dameris, who led the research at the Institute for Atmospheric Physics
in Wessling, said: "The ozone hole will stay around for another four to
five years. We can't expect it to start to recover until 2010 and then it will
take another 40 to 50 years to repair completely."
Ozone depletion is a largely forgotten problem since the Montreal protocol
successfully reduced levels of CFC chemicals in the atmosphere, after British
scientists in Antarctica reported they were destroying ozone. But some experts
have been puzzled by the layer's slow recovery.
The German team pins the blame on the 11-year solar cycle, which makes the
amount of solar radiation striking Earth periodically rise and fall. Scientists
already knew the cycle influenced ozone, but Dr Dameris says its role in controlling
the layer's recovery has been overlooked.
Reporting their findings in the journal Geophysical Research Letters, the team
says: "We do not expect recovery, but a return to stronger ozone depletion
and deeper ozone holes in the next few years in line with the expected lower
solar activity." The sun's activity is expected to fall until the "solar
minimum" in 2007/08.
An observed increase in ozone between 1997 and 2003 is partly explained by
a surge in solar activity from 1997 to 2001, they say: "We do not believe
a sustained reversal of ozone depletion started in the late 1990s. A recovery
is only pretended."
They reached their conclusions using a computer model that looked at how the
sun's activity and material spewed into the atmosphere by volcanic eruptions
affected ozone. They say the computer correctly predicted levels of ozone from
1960 to 2003, making them confident it can accurately forecast what will happen
Ann Webb, an ozone scientist at Manchester University, said it would take decades
for the ozone layer to recover fully because the banned CFCs degrade slowly
in the atmosphere.
Some chemicals introduced to replace CFCs still damage ozone, she said, and
there are worrying signs that climate change may be making the situation worse.
Scientists are particularly worried that increased amounts of heat-trapping
greenhouse gases in the lower atmosphere could start to cool the stratosphere,
accelerating ozone loss.
Last spring ozone cover over the UK neared record lows following the coldest
Arctic winter on record.