The United States is having its deadliest tornado year in the past decade and could set a record for most twisters by year’s end. There seem to be two or three possible causes.
According to this story in the New York Times (”A Busy Year as Tornadoes Wreak Havoc“, by Brenda Goodman) some 868 tornadoes were reported through May 18, a pace similar to that of 2004, which saw a record 1,819 tornadoes. At least 100 people have been killed through mid-May, the highest tornado-fatality count since 1998.
We had more tornadoes early in the year than we usually do. Goodman notes, “From 1953 to 2005, an average of 19 tornadoes struck in January and 21 in February … In 2008, 136 tornadoes were reported in January and 232 in February.” The South, an area not usually hit by many tornaodes, has seen a big jump.
Indeed, if you look at the NOAA Storm Prediction Center’s “Monthly Tornado Statistics” page, you’ll see that January-May of this year are all above the 3-year average for tornadoes. May is twice the 3-year average, February was nine times that average and January was four times that 3-year average.
The Times story quotes scientists as saying the possible causes include La Niña, a Pacific Ocean weather phenomenon that causes warmer winters in the Southeast U.S. In addition, meteorologists could be counting more tornadoes because they are better at detecting them than in past years.
Then there’s the question of climate change — is it playing a role as well? Robert J. Trapp of Purdue University says the trend is for an increase in conditions that can create severe weather. During this century, his work shows, if temperatures rise 2-6 degrees Celsius, the number of days with conditions that could form severe thunderstorms could double in cities in the South and along the Eastern seaboard.
The Intergovernmental Panel on Climate Change noted in its “Climate Change 2007: The Physical Science Basis” report, that “There is insufficient evidence to determine whether trends exist … in small scale phenomena such as tornadoes, hail, lightning and dust-storms.”
Bottom line: Right now we don’t have the data to say that climate change is helping to cause more tornadoes. But indications are that rising temperatures during this century will make tornadoes and other severe weather events more likely.
P.S.: For a good graph of tornado reports from 1950-2006, and a discussion of the climate-tornado relationship, see Andrew Revkin’s dot.earth blog entry from February 7.
If only some of us were hundreds of years old! If so, those oldsters among us could help us see whether the very strange weather we’re having now is really only an ordinary occurrence after all. Some sort of decades-long cycle between stable and unstable weather patterns. But since no one alive today has a memory extending back so far … and since even our scientific measurements are unreliable back more than a few decades … all we can do is wonder …
Deborah
I believer the weather conditions are entirely the products of human occupation on the earth.
The butterfly effect.
I live in the country. In the early mornig hours when I walk, I am passed by multipe schol busses The “wind” created by just one
bus is astounding. Multiply this times the billios of modes of transporation and you have a vast weathr changing effect.
earthquakes: imgine any solid sphere, for exaple an orange. Suck all the juice out (oil dilling), drill holes in it scooping out the flesh (mineing) and what effect does it have on the structre?
God Bless.
While it has been an active year, you really can’t compare any data prior to the mid 1990s to what is happening now. Stats from the National Weather Service (NWS) have been based on much more strenuous efforts to verify warnings. In some respects this may lead to more tornadoes being counted that otherwise would not be (good), but also has led to a bit of “tornado inflation” as well (bad). If there is a warning you can bet the NWS will scour the countryside looking for damage which frankly sometimes may or not be tornado damage. Taking to professional meteorologists and those in academic circles, using past tornado and severe weather after 1995 has become difficult because it has become contaminated by marginal, and some might say, non-severe reports motivated by warning verification. IMO it has lowered the severe weather bar.
All the above aside, it has been an active year and with an upswing in loss of life with injury to people and property. I am thinking and hoping this is an aberration. While I think the NWS does a good job in most cases, I sometimes think there are too many watches and warnings which have led to public complacency.
Andrew
Temperature shifts from global warming in and of themselves are not a direct cause of this phenomenon. However, the temperature volatility exacerbated by climate change, in combination with prolonged periods of drought, are a direct cause. I live in an active tornado zone (Central Florida) and fret for the future of my family and home as climate change worsens.
Here’s an update. TheDailyGreen had an item today noting that NOAA has released updated tornado data indicating that the preliminary count for this year has far exceeded the 10-year average for an entire year! See http://www.thedailygreen.com/environmental-news/latest/tornadoes-47061101
NOAA projects the actual tornado count won’t be much lower than the 10-year average for a year — and we’re not half way through this year!
For the NOAA data and graph, go to http://www.spc.noaa.gov/climo/torn/monthlytornstats.html
-Dan
The author of this article is a scientist? Goodman sais that the south is an area that does not normally see many tornadoes? I have to ask which or what south are you talking about? The American south ,’espeacilly parts of Mississippi,North Alabama and Tennessee’is after all known as the ‘Dixi Belt’.The Dixi Belt,’as anyone who has seriously studied the subject knows’is a region of secondary tornado occourance maxima,that is not that far behind the midwestern tornado belt in terms of tornado occourance.Actually if someone were to refere to the American south as tornado alley,many real experts would not correct them.It was not that long ago,that Mississippi and Alabama were actualy ranked ahead of oklahoma in terms of tornado casualties.Some of the deadliest tornado outbreaks in history have occoured exclusivly in the south,and nearly every major national outbreak has included the southern states.It is also a fact that the state of Florida expeareances more tornadoes per square mile than any other state.Per square mile,there are two counties in south Mississippi that are the most tornado prone counties in the country.I could be wrong,but I seem to recall that those two counties are Jones and Newton. The southern states also experience two distinct tornado seasons.One being the early and mid spring,and the second being much of the fall.The later is often highlighted by spin up tornadoes spawned by tropical systems.To say the south is a region that does not normally expeareance’ many ‘tornadoes,is like saying it is seldom dry in Southern California.It just aint so ! Maybe if Goodman was from the Dixi belt and not New York,she would know that!?