Now for a topic that is close to the heart for many inhabitants of New Orleans – hurricanes. The devastation caused by the events in 2005 by hurricane Katrina led to most of the inhabitants of New Orleans to be displaced and caused news and debate around the world for months – still today, nearly two years on from the events many inhabitants are still homeless.
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A hurricane can be modeled as a vortex, with a depth of only around 50 – 100 ft, but being miles across. Katrina was a Category 5 hurricane which brought water levels to around 30 ft at the coastal lines and was the sixth strongest Atlantic hurricane ever recorded.

Greg Holland from the National Center for Atmospheric Research, Boulder, Colorado, talked about understanding extreme hurricanes. Hurricane activity has increased substantially since the 1970’s, Holland pointed out that in his simulations just a 5 m/s increase in wind speeds can lead to a 100% increase in category 5 hurricanes – which he says seems to correlate well with observed behavior.

Of course the economic costs can be great of the devastation brought from a hurricane such as Katrina, which has now cost around $140 per household in the US. A following talk from Harold Brooks from National Severe Storms Laboratory, in Norman Oklahoma, showed another aspect of climate change – large hail stones. He showed that the frequency of large hail fall (i.e that the size of a baseball – still going on the baseball theme) is increasing by about 6% a year, and the ‘favorable severe environment’ for such weather conditions is increasing by 0.8 % per year. Both exploding just after the 1980’s.

Town planning was also a subject under scrutiny, with Holland pointing out the lemming like way we are build more and more communities next to the coast on some of the dangerous places like on marsh land.

However, it was noted during the session that Katrina is likely a few hundred year event, but this, however, now remains to be seen.