By Dr William Gray

It is now over a year-and-a-half since the media explosion following hurricanes Katrina and Rita’s landfalls and several papers saying that the US landfalling hurricanes of 2004-2005 probably had a human-induced global warming component.  With this there was an implication that US hurricane landfall and damage would continue to get worse with time as CO2 amounts continued to rise. 

Although global mean CO2 and Atlantic surface temperatures have increased between the two 50-year periods (1900-1949 compared with 1956-2005), the frequency of US landfall numbers actually shows a slight downward trend for the later period.  It is also to be noted that there were 39 US landfalling major hurricanes (Cat 3-4-5) between 1925-1965 and only 22 in the same length period between 1966-2006 when CO2 amounts were getting higher. 

The increased Atlantic hurricane activity since 1995 is a result of a speed-up of the Atlantic thermohaline circulation – as occurred also in the 1940s-1950s and the late 19th century. The advocates of CO2 are either unaware or unaccepting of this plausible explanation. The alarmist’s position that the overall trend in SSTs and tropical cyclone and hurricane numbers is substantially influenced by greenhouse warming.  Read Bill’s take on the season and the issue here.