Human induced emissions influence weather extremes, shows report
Human induced greenhouse gas (GHG) emissions substantially increased the likelihood of devastating floods occurring in England and Wales in autumn 2000, research has found.
Human induced greenhouse gas (GHG) emissions substantially increased the likelihood of devastating floods occurring in England and Wales in autumn 2000, research has found.
The floods damaged nearly 10,000 properties and led to insured losses estimated at £1.3 billion. Research conducted by the University of Oxford and published in the journal Nature this week (17 February), showed a two-in-three chance that the odds of heavy, intense precipitation occurring were increased by human induced GHG, by a factor of two or more.
The water-holding capacity of the atmosphere is expected to increase roughly exponentially with temperature, and that atmospheric water content is increasing in accord with this theoretical expectation. The study, ‘Anthropogenic Greenhouse Gas Contribution to Flood Risk in England and Wales in Autumn 2000’, suggests that human induced global warming may be partly responsible for increases in heavy precipitation.
The study suggests that, although floods in 2000 could have occurred in the absence of human influence on climate, GHG emissions can now be blamed for increasing the odds of floods occurring at that time. The precise magnitude of the difference that is down to human influence is still uncertain.
Dr Pardeep Pall, who initiated the research as a doctoral student at Oxford University’s Department of Physics, said: “This study is the first of its kind to model explicitly how such rising greenhouse gas concentrations increase the odds of a particular type of flood event in the UK, and is the first to use publicly volunteered computer time to do so.”
Using a detailed computer climate model, developed at the Met Office Hadley Centre, researchers simulated the weather in autumn 2000, both as it was, and as it might have been had there been no GHGs since the beginning of the 20th Century.
The process was repeated thousands of times using a global volunteer network of personal computers participating in the climateprediction.net project. The results were analysed in order to determine the impact of emissions on extreme weather.
In collaboration with Risk Management Solutions (RMS) - developers of risk models for the insurance industry - the team fed the information from these weather simulations into a flood model, and found that GHG emissions very likely increased the chances of floods occurring in autumn 2000 by more than 20 per cent. The study found that the effects may have even doubled the odds of the damaging inundations occurring.
Dr Dag Lohmann of RMS, a co-author on the paper, said: “Studies like this are helpful, since we need to know how risks are changing to provide our clients with accurate models of risk today.”
Dr Richard Harding, of the Centre for Ecology and Hydrology (CEH) Wallingford and the coordinator of the EU WATCH project which co-funded this research, said “climate change is only one of many factors affecting local flood risk, but understanding it is clearly important if we are to plan how to adapt.”
Dr Peter Stott, of the Met Office, also a co-author, said: “This study is the first step toward near real-time attribution of extreme weather, untangling natural variability from man-made climate change.”
Members of the public can still participate in follow-up studies, supported by Microsoft Research, Oxford University’s Smith School for Enterprise and the Environment, the Met Office, and the Natural Environment Research Council. Further research anticipates assessing how anthropogenic emissions might have changed the odds of a whole host of weather-related events – including floods and droughts – in regions across the world.
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