UK Climate change doubled likelihood of devastating UK floods of 2000

17/2/2011 Guardian Global warming made the floods that devastated England and Wales in the autumn of 2000, costing £3.5bn,between two and three times more likely to happen, new research has found. This is the first time
scientists have quantified the role of human-induced climate change in
increasing the risk of a serious flood and represents a major development in
climate science.
“It shows climate change is acting here and now to load the dice towards more
extreme weather,” said Myles Allen of Oxford University, who led the work, which
he started after his own home was nearly flooded in 2000. It will also have
wider consequences, say experts, by making lawsuits for compensation against
energy companies more likely to succeed.
It may also have billion-dollar consequences by determining which countries
benefit from the future $100bn-a-year UN adaptation fund which aims to build
resilience against the impacts of climate change.
“This is ground-breaking work,” said Professor Bob Watson, chief scientific
adviser to the department of the environment and former chair of the
Intergovernmental Panel on Climate Change. Until now, he said, scientists could
state that global warming was expected to cause more extreme weather, but not
that it was to blame for any specific event. “The research shows human-induced
climate change is not an issue for the next decades or century: it is an issue
facing us today.”
Chris Huhne, secretary of state for energy and climate change, said: “The
evidence for human influence on climate is now even more compelling. Climate
change is not a distant threat, it is a clear and present danger – and one that
we can do something about.”
The work makes lawsuits against major polluters more likely, said barrister
Richard Lord QC, an expert on climate litigation at Brick Court Chambers in
London: “Showing that the chance of an event occurring has increased by say 100%
or 200% gives you a much better chance of showing causation. It gets you around
one of the legal obstacles.”
Lord said he could foresee such cases – which are already being attempted in the
US – succeeding if international negotiations fail to control greenhouse gas
emissions and the damage caused by climate impacts continues to increase.
Between September and November 2000, over 500mm of rain fell in the UK, the
wettest autumn since records began in 1766. More than 10,000 homes were flooded
and £3.5bn of insurance claims were made. After Allen’s home was nearly flooded,
his colleague, Pardeep Pall, suggested using modelling to determine the role of
global warming, but the amount of computing time required was formidable. To
solve that problem, Allen used his project, through which
members of the public have donated over one billion hours of PC time to running
The team ran models simulating the real weather and, crucially, models of the
region’s weather as it might have been in a world without human-produced
greenhouse gases. The models were run thousands of times to enable the
probability of the extreme floods to be determined in both scenarios, taking
40,000 years of computing time. Global warming was found to have most likely
doubled the risk of the 2000 floods, but there is a one in 10 chance that the
increased risk was as high as 700% or as low as 20%.
The involvement of those who volunteered computer time was essential, said
Allen: “I think it is absolutely fantastic what they do. It’s a great credit to
them.” Allen’s team had previously shown that the scorching heatwave that struck
Europe in 2003, leading to many thousands of premature deaths, was made four to
six times more likely as a result of global warming. But the continent-wide
nature of the heatwave meant it could be studied using broad climate models. The
flood study required far more detailed modelling. “We did the easy problems
first,” said Allen.
The Met Office is now in the process of setting up a service that will use its
supercomputers to calculate the role of climate change in exacerbating extreme
weather on a regular basis. “In future, it will not be enough for weather
services to predict the weather, they will have to explain it,” said Allen, who
is careful to note that some weather events may become less common due to
climate change. His new WeatheratHome project is using home PCs to examine
projected weather in greater detail.
Apart from litigation, the broader implications of being able to link climate
change to specific weather events include determining which natural disasters
have been heavily influenced by warming and which have not, and which should
receive international adaptation funds as a result. “We are going to have to
have a rational approach to assess risks and that would be the way to decide the
priorities for spending on adaptation,” said Watson. “It will make for a more
cost-effective way of using the money.”
Another study, also published in Nature, shows for the first time that the
increase in extreme rain, snow and hail predicted as a consequence of global
warming is real. The researchers, led by Professor Francis Zwiers at the
University of Victoria, Canada, found that increases in intense rainstorms over
land in the northern hemisphere, as measured by rain gauges, mirrored the
projections from climate models and could not be explained by natural climate
In fact, the models appear to underestimate the increase in intense rain. “The
models may be giving us an overly rosy scenario,” said Professor Rowan Sutton, a
climate scientist at the University of Reading, who was not involved in the
research. The increase in extreme precipitation has a firm foundation in basic
physics, the scientists said, as a warmer atmosphere can hold more water.
Overall, Sutton said, the new studies of extreme rain and flooding emphasise
that climate change is having a tangible impact now. “It is not just affecting
global average temperatures, it is affecting aspects of climate that really
matter to people – and to societies and economies – in serious ways.”
Citizen science
More than 300,000 members of the public in at least 100 countries have donated
spare PC time to the project. Their contributions add up
to a total of about one billion hours of processing time, which might have cost
$120m if bought commercially.
The colossal computing power is needed to run many repetitions of complex
climate models in order to assess the probability of particular changes in
climate due to global warming. has completed 80,000,000
years of modelling since its launch in 2003.
The group’s new project, WeatheratHome, increases the ability of the modelling
to predict weather on a regional scale into the 2020s and 2030s. This is even
more computationally intensive but promises information that is more useful on
the ground. In particular, the project will examine Europe, southern Africa and
the western US.
So far about 60,000 model years have been run, said team leader Myles Allen. “If
anyone else wants to sign up, we have plenty of work for them!”
Other distributed computing projects include the astronomy project
Einstein@home, whose team discovered a new pulsar in 2010 and published a paper
about it in the journal Science. Another is Folding@home, which examines the
complex process of protein assembly and has produced more than 70 papers to
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