Dr. Roger Pielke Jr. points out a new paper for which he is a co-author.
Normalized Tornado Damage in the United States: 1950-2011
in press, Environmental Hazards
Kevin M. Simmons, Daniel Sutter and Roger Pielke, Jr.
In this case, a picture is worth a thousand words:
- Overall we find a decrease in damages since 1950.
- Even so 2011 was one of the 3 most costly years in our dataset.
- Our dataset includes 56,457 tornadoes, of which 33,746 caused some recorded damage.
- Since 1950, in round numbers, tornadoes resulted in about half the normalized damage as did hurricanes and twice that of earthquakes
- The strongest two categories of tornadoes (called EF4 and EF5) represent about 1% of all reported events but have caused almost 45% of all normalized damage.
- The most damage per square mile from1950-2011 has occurred in Massachusetts and Connecticut.
- The most damage overall from 1950-2011 has occurred in Texas and Alabama.
- During the calendar year 80% of damage occurs January-June.
- The most damaging months are April (31%), May (20%) and June (16%).
On climate time scales there is no indication of increasing incidence of tornadoes, and the increases documented over the short (sub-climate) period 2000-2011 are strongly influenced by the large number of events documented in 2011. However, the decreased frequency of high damage events in recent decades as compared to previous decades is a notable feature in the time series and provides strong counter-evidence to claims found in the scientific literature that the atmospheric environment that spawns tornadoes has intensified leading to more intense events on climate time scales (e.g., Trenberth, 2012). Such claims are commonly found in the popular media and also in the insurance/reinsurance sector where they influence public opinion and decision making in business and government. The most recent review by the IPCC found no basis for claiming an increase (or decrease) in tornado incidence or intensity (IPCC, 2012).”
Read his full essay here