Are tornadoes getting stronger and more frequent? [View All]

[ben_meyers]

Since we are coming into the tornado "season" I thought this was interesting.

Are tornadoes and severe thunderstorms getting more numerous and more extreme due to climate change? To help answer this question, let's restrict our attention to the U.S., which has the highest incidence of tornadoes and severe thunderstorms of any place in the world. At a first glance, it appears that tornado frequency has increased in recent decades. (snip)

However, this increase may be entirely caused by factors unrelated to climate change:
1) Population growth has resulted in more tornadoes being reported.
2) Advances in weather radar, particularly the deployment of about 100 Doppler radars across the U.S. in the mid-1990s, has resulted in a much higher tornado detection rate.
3) Tornado damage surveys have grown more sophisticated over the years. For example, we now commonly classify multiple tornadoes along a damage path that might have been attributed to just one twister in the past.
Given these uncertainties in the tornado data base, it is unknown how the frequency of tornadoes might be changing over time. The "official word" on climate science, the 2007 United Nations IPCC report, stated it thusly: "There is insufficient evidence to determine whether trends exist in small scale phenomena such as tornadoes, hail, lighting, and dust storms." Furthermore, we're not likely to be able to develop methods to improve the situation in the near future.The current Doppler radar system can only detect the presence of a parent rotating thunderstorm that often, but not always, produces a tornado. Until a technology is developed that can reliably detect all tornadoes, there is no hope of determining how tornadoes might be changing in response to a changing climate. According to Doswell (2007): I see no near-term solution to the problem of detecting detailed spatial and temporal trends in the occurrence of tornadoes by using the observed data in its current form or in any form likely to evolve in the near future.

But they are getting stronger Right? Well maybe not.

Are violent tornadoes increasing?(snip)

However, if we look at the statistics of violent U.S. tornadoes since 1950 (Figure 2), there does not appear to be any increase in the number of these storms. In fact, there was only one tornado of EF5 intensity reported during the eight year period 2000-2007, the tornado that devastated Greensburg, Kansas in 2007 (although Canada did report its first EF5 tornado in history on June 22, 2007). The previous eight year period of 1992-1999 had six F5 tornadoes, so we can't say that climate change has caused an increase in the strongest tornadoes in recent years. Note that the EF scale to rate tornadoes was adopted in 2007, but the transition to this new scale still allows valid comparisons of tornadoes rated EF5 on the new scale and F5 on the old scale.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=910&tstamp=200802