ENVIRONMENTAL RISKS - PROJECT SUMMARY

European Windstorms in a Changing Climate: Storm Tracks, Clustering and Multi-peril Extremes

David STEPHENSON, Principal Investigator

• Nationality
  British
• Year of selection
  2009
• Institution
  University of Exeter
• Country
  United Kingdom

Project Informations

Professor David Stephenson is an internationally renowned expert of the statistical analysis of weather and climate. He has developped advanced methodologies that provide deeper understanding of climate variations and improve the quality of forecasts. Since 1998, he has worked with catastrophe modellers in the global reinsurance industry. In 2006, he was also a key founding member of the Willis Research Network, the world’s largest partnership between academia and insurance companies. Professor Stephenson has received Axa funding for his RACEWIN project, which will assess the impact of climate change on European windstorms.

Climate change is a vast area of research. But how precise can mathematical projections be?

We can now make adaptive forecasting of climate change. And instead of just saying “by the end of the XXIe Century, it will be 5 degrees warmer”, we are now trying to make predictions for the next year or the next ten years. It is important for the insurance sector because it allows us to look at the changing rate of hazards. Historical catastrophe models assume that the risk is stationary, but we know that weather events and their rates do change in time. So our predictions get more dynamic.

What do we know of the impact of climate change on storms in Europe?

I'm one of the lead authors for the chapter on “Regional Climate and Extremes” in the next Intergovernmental Panel on Climate Change (IPCC) report. One of our problems today is making statements on that more local scale for the future. Today, the different models get very different answers.

 To what extent can we really predict a storm today ?

There is some predictability of the strong wind patterns in the atmosphere at least a month ahead, a couple of months maximum. We can say whether there is a higher risk of having storms, but we cannot predict exactly where it is going to happen or how many storms there will be. For example, the severe storms that impacted France in December 1999 were due to the persistence of a strong upper level jet stream. We know that this condition provides the energy needed for explosive growth of damaging windstorms. But we could not go further. It is a probabilistic prediction.

 Your RACEWIN project aims at improving these projections. How will you proceed ?

 Starting in October, we will collaborate with the UK Met Office to statistically analyse the storm tracks (which trace the central pressure of a storm all along its way) from a set of high-resolution regional climate model projections for the 21^st century. This will allow us to better quantify trends and clustering in future European windstorms. Clustering measures the tendency of storms to occur together over a short time in a particular region, rather than being randomly distributed. We will look at the dependency between successive storms and between extreme wind speeds and extreme precipitation. In addition, our project will set up a European windstorms research network to help bring together critical mass in this important area of climate science.

 * Note : the IPPC is a scientific intergovernmental body of the United Nations, in charge of assessing the risks of climate change. Its fifth report, a reference document, is due in 2014.

Professor David Stephenson, Director of Exeter Climate Systems University of Exeter, UK

Principal investigator of the AXA RACEWIN project :
European Windstorms in a Changing Climate: Storm Tracks, Clustering and Multi-peril Extremes

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