Extreme Meteorological Events

The joint meeting between the Civic Society and the Royal Geographical Society brought Dr Gregor Leckebusch from Birmingham University to talk to us about extreme weather events, more particularly wind storms. In a packed meeting, members were given a high powered talk into the latest theories behind the generation of major storms, especially in the North Atlantic. Following the experiences of recent years, are we faced with a more turbulent climate in the future and if so, why?

Well, as with all matters associated with the weather, nothing is quite straightforward. Many factors influence our weather and they all react together in different ways and over time. What we do know is that humidity, temperature and air pressure work together to generate storms. In particular, it has now been proven that pressure differences in the North Atlantic between Iceland (low) and the Azores (high) can generate steep pressure gradients which are an essentail ingredient for a wind storm. But why do these severe pressure gradients occur? Well, thinking has now linked them to sea temperatures, with warmer Gulf Stream waters to the south and cooler Arctic waters to the north. Changes are now taking place in the balance between both and that in turn could lead to a propensity for stronger storms. The time factor comes into play, however, because, as we know from watching the television weather forecast, it's relatively easy to forecast two or three days ahead, but not so straightforward to predict months ahead. Things are improving, however, because Gregor explained that forecasting the likelihood of storm winds two or three years ahead was now possible - based on changes to the climatic factors which take time to impact on us. He was asked, for instance if the large iceberg that has broken loose in Antarctica when melting would have an impact on our climate. The short term answer is "no" but the dilution of the salt water in the longer term (say, 100 years) could have an impact. Similarly, the slow melting of the Arctic icecap will change water temperature gradients in the North Atlantic which will influence the weather by 2050.

Much of Gregor's work is of interest to insurance companies. They want to know what is the likelihood of more and stronger storms and where they are most likely to impact. From his forecasts they can derive areas of higher risk upon which our premiums are based.

Gregor is a most competent authority on the analysis of climatic influences. Without doubt his talk stimulated all our "little grey cells". Our grasp of the subtle complexities of our climate was improved, although none of us could hope to emulate Gregor's sophisticated explanation.

Roger Hockney
April 2014