The Empire Strikes Back

Over at Prometheus there has been a response from Robert Muir-Wood of RMS. He states:

The political response to the 'insurance crisis' currently underway in Florida is looking for someone to blame. Cat modelers are simply the messengers relaying news concerning the significance of a period of significantly higher hurricane activity that has persisted in 9 out of the last 12 years and that climatologists, as polled at the most recent expert elicitation, expect to continue for a decade or more longer. There is a need to get journalists and politicians in Florida to focus more attention on the reasons for the increase in hurricane activity and, in particular, the role of climate change.

Its enough to make me a little misty.

Anyway...I responded over there:

Robert Muir-Woods states: "Cat modelers are simply the messengers relaying news concerning the significance of a period of significantly higher hurricane activity that has persisted in 9 out of the last 12 years and that climatologists, as polled at the most recent expert elicitation, expect to continue for a decade or more longer."

LEt's look on the NOAA data on the storms hitting the US since 1994.

2005: 6 (4 Cat3, 2 Cat1)
2004: 6 (1 Cat4, 2 Cat3, 1 Cat2, 1 Cat1)
2003: 2 (1 Cat2, 1 Cat1)
2002: 1 (1 Cat1)
2001: 0
2000: 0
1999: 3 (1 Cat3, 1 Cat2, 1Cat1)
1998: 3 (2 Cat2, 1 Cat1)
1997: 1 (1 Cat1)
1996: 2 (1 Cat3, 1 Cat2)
1995: 2 (1 Cat3, 1 Cat2)
1994: 0

26 storms in a 12 year period (2.1667 per year). 8 of those 12 years had 2 or fewer storms hit. Since historically we have averaged around 1.75 storms a year, I hardly think 2 storms a year is "significantly higher."

Other 12 year periods that had above average numbers of storms includes:

1932-1944, 24 storms
1942-1953, 26 storms
1944-1955, 29 storms

It is interesting to note that in the five years following the 1944-1955 12 year period (29 storms, 2.41/year), only 7 storms hit (1.4/year).

The claim that "significantly higher hurricane activity that has persisted in 9 out of the last 12 years" is simply false. Since hurricanes can only hit in full integers (i.e. one at a time), it is dishonest to claim a year that has 2 hurricanes is an example of "higher activity" when the average is around 1.75. It would be much more honest to claim it is an example of bouncing around the mean.