Under Water: Scientists Confirm Global Warming Link
By Michael McCarthy
24 July, 2007
It's official: the heavier rainfall
in Britain is being caused by climate change, a major new scientific
study will reveal this week, as the country reels from summer downpours
of unprecedented ferocity.
More intense rainstorms across
parts of the northern hemisphere are being generated by man-made global
warming, the study has established for the first time an effect
which has long been predicted but never before proved.
The study's findings will
be all the more dramatic for being disclosed as Britain struggles to
recover from the phenomenal drenching of the past few days, during which
more than a month's worth of rain fell in a few hours in some places,
and floods forced thousands from their homes.
The "major rainfall
event" of last Friday fully predicted as such by the Met
Office has given the country a quite exceptional battering, with
the Thames still rising. In Gloucester water levels had reached 34 feet,
just 12 inches below flood defences the same level as during the
flood of 1947 although a police spokesman said last night that
the River Severn had stopped rising.
Last night vast areas of
the country around Gloucestershire and Worcestershire were still inundated,
large numbers of people in temporary accommodation, transport links
were widely disrupted, and yet more householders were standing by to
be flooded in their turn, in one of the biggest civil emergencies Britain
About 150,000 residents in
Gloucestershire were left without drinking water when the Mythe Water
Treatment Works in Tewkesbury became inoperable after flooding. Another
200,000 people are at risk of losing their supplies. The water shortages
may last until Wednesday and 600 water tanks were being drafted to the
Panic buying of bottled water
was reported, with supermarkets selling out of stocks, and there were
contamination problems in south London, where 80,000 households and
businesses in the Sutton area were advised to boil their water after
rain got into a tank. Yet another potential danger was from car thieves;
West Mercia police warned drivers who had abandoned their cars in the
floodwater to collect them quickly to prevent theft.
The Great Flood of July is
all the more remarkable for following right on from the Great Flood
of June, which caused similar havoc in northern towns such as Doncaster
and Hull, after a similar series of astonishingly torrential downpours
on 24 June.
Meteorologists agree that
the miserably wet British summer of 2007 has generally been caused by
a southward shift towards Britain of the jetstream, the high-level airflow
that brings depressions eastwards across the Atlantic. This is fairly
normal. But debate is going on about whether climate change may be responsible
for the intensity of the two freak rainfall episodes, which have caused
flooding the like of which has never been seen in many places.
This is because the computer
models used to predict the future course of global warming all show
heavier rainfall, and indeed, "extreme rainfall events", as
one of its principal consequences.
The new study, carried out
jointly by several national climate research institutes using their
supercomputer climate models, including the Hadley Centre of the UK
Met Office, does not prove that any one event, including the rain of
the past few days in Britain, is climate-change related.
But it certainly supports
the idea, by showing that in recent decades rainfall has increased over
several areas of the world, including the mid-latitudes of the northern
hemisphere, and linking this directly, for the first time, to global
warming caused by human emissions of greenhouse gases.
The study is being published
in the journal Nature on Wednesday, and its details are under embargo
and cannot be reported until then. But its main findings have caused
a stir, and are being freely discussed by climate scientists in the
Met Office, the Hadley Centre and the Department for Environment For
Environment, Food and Rural Affairs.
One source familiar with
the study's conclusions said: "What this does is establish for
the first time that there is a distinct 'human fingerprint' in the changes
in precipitation patterns the increases in rainfall observed
in the northern hemisphere mid-latitudes, which includes Britain.
"That means, it is not
just the climate's natural variability which has caused the increases,
but there is a detectable human cause climate change, caused by
our greenhouse gas emissions. The 'human fingerprint' has been detected
before in temperature rises, but never before in rainfall. So this is
"Some people would argue
that you can't take a single event and pin that on climate change, but
what happened in Britain last Friday fits quite easily with these conclusions.
It does seem to have a certain resonance with what they're finding in
The Hadley Centre lead scientist
involved with the study was Dr Peter Stott, who specialises in finding
"human fingerprints" sometimes referred to as anthropogenic
signals on the changing climate.
Last September Dr Stott,
who was not available for comment yesterday, published research showing
that the climate of central England had warmed by a full degree Celsius
in the past 40 years, and that this could be directly linked to human
causes the first time that man-made climate change had been identified
at such a local level.
The human fingerprint is
detected by making computer simulations of the recent past climate,
with and without emissions of greenhouse gases and then comparing
the results with what has actually been observed in the real world.
In Dr Stott's research, and
in the study to be published on Wednesday, the observed rises in temperature
and rainfall could be clearly accounted for by the scenario in which
emissions were prominent.
The conclusions of the new
rainfall study are regarded as all the more robust as they are the joint
work of several major national climate research bodies, led by Environment
Canada, with each using its own supercomputer climate model.
Global warming is likely
to lead to higher rainfall because a warming atmosphere contains more
water vapour and more energy. Since climate prediction began 20 years
ago, heavier rainfall over Britain has been a consistent theme.
© 2007 Independent News
and Media Limited
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