Are Tornadoes Getting Stronger? New Research Hints yes…

December 13, 2013

Missed this presentation. Good thing Livescience didn’t.


SAN FRANCISCO — The trail of twisted metal and torn roofs left behind by massive twisters is growing longer and wider, a sign that tornadoes may be growing stronger, climate scientist James Elsner said here Tuesday (Dec. 10) at the annual meeting of the American Geophysical Union.

Beginning in 2000, tornado intensity — as measured by a twister’s damage path — started rising sharply, said Elsner, of Florida State University. “I’m not saying this is climate change, but I do think there is a climate effect,” he said. “I do think you can connect the dots.”

Devastating tornado outbreaks in recent years, such as the massive storm that injured hundreds in Moore, Okla., this summer, have focused attention on whether climate change is altering tornado frequency and strength. Just last week, a heated debate played out in an op-ed on LiveScience and the New York Times over whether tornado-tracking data could answer these questions. One scientist claimed the data show twister numbers are dropping, but tornado experts said changes over time in how weather officials assess tornado size and damage make it difficult to look for climate patterns

Elsner’s solution was to drop the human factor. Instead, he looked at wind speed and the size of the damage path (its length and width) to gauge whether tornado intensity has changed since 1994. (The United States has been almost completely covered by Doppler weather radar since 1994.) Using the damage path to gauge intensity avoids problems such as analyzing tornado strength via the Fujita and Enhanced Fujita scales, which are based on observations by weather service officials, he said.

Elsner analyzed damage paths and wind speeds using a statistical model. The result: a sharp upward spike starting in 2000. He also looked at earlier data, since the 1970s, which showed a much slower rise.

Puzzling out how climate change alters tornados is the big next step, Elsner said. One way this could happen is by adding moisture (via humidity) to fuel storms in Tornado Alley, the storm belt where tornadoes spin up in the United States. Warmer air holds more moisture. But Elsner said it was also important to track tornadoes in Canada, because there are hints that big ridges and troughs in the jet stream’s powerful winds could be triggering more tornadoes up north, and fewer in the United States.

17 Responses to “Are Tornadoes Getting Stronger? New Research Hints yes…”

  1. kingdube Says:

    My heavens. Observations show no increase but now this man has developed a Model that does. Oh boy…just what desired result cannot be extracted from a Model?

  2. Observations by whom, Muller? Hold your horses, bub. Anthropogenic climate change passenger just posted the AGU talk as the last post on Dec. 6.
    It was extracted from data, not models. Dube, your dooby is showing. Remember the thing we talked about with the toilet paper hanging six feet out your behind that everybody was too embarrassed to point out to you? Alright. Just don’t let it happen again. Elsner is not claiming its AGW. He is just pointing out a way to map tornado intensity or energy over time from the data. Its just a beginning. Don’t be so eager to refute something you have not absorbed or comprehended yet. It betrays a dearth of objectivity.

  3. Now its appropriate to talk about water vapor and clouds. There are many positive feedbacks. Water vapor is one of them. Ice and snow albedo another, etc. Water vapor is describes as a greenhouse gas, thus only positive feedback. Its caused by increasing warmth. Its estimated to give us 1C for every 1C from warming. Clouds are more complicated. Its high clouds vs low clouds. Lindzen and Spencer argue negative feedback, but other studies do not support this. Clouds are not the only feedback. They are not even the dominant feedback. In the net, a large amount of evidence supports positive feedback. That is shown in the historical record which shows many abrupt positive temperature excursions, i.e. ice age recoveries, but not the only evidence. Milankovitch starts it, feedbacks, including CO2, kick it into high gear. Now we are supplying the CO2 instead of waiting for the Milankovitch cycle. No more 800 year lag canard BS. No more recycled WUWT nonsense. Class is in session. If you want to play like hooligans, go over and stand in the corner. Gigs up dube, burton, swallow.
    You showed me your mistakes. You are not teaching class. You are not even good students. We don’t have to wait 100 years to wait for water vapor to affect us. The atmosphere is like a kettle of boiling water. The more we heat it, the greater its extremes. More flooding. More droughts. More extremes of every kind. Why? More energy. It has to go somewhere.

  4. astrostevo Says:

    “Puzzling out how climate change alters tornados is the big next step, Elsner said.

    Mor eheta eneergy = more strength in almost all weather systems I’d guess perhaps naively. That includes tornadoes as much as everything else.

    But I am not a climatologist.

    Any reason why more heat energy would mean something other than stronger / more frequent tornados?

    (Asking because I don’t know, quite prepared to hear I’m wrong if I am.)

    • astrostevo Says:

      More heat energy – were meant to be the first words there. Typos. Sorry. (Wish we could edit these comments.)

    • A problem with tornado Genesis is the fact that it is not very well understood. But we do know a number of factors that make it more conducive for strong long track tornadoes. Which is windshear or wind changing with high, preferably a kink in the jetstream, strong temperature gradients, moisture gradients as in dry air and more moist air. Topography makes a difference as well with the location of the Gulf of Mexico, Rocky Mountains, and the Atlantic Ocean which helps to influence all the above components.

      So in a warming planet will you have more tornadoes or stronger tornadoes that probably is not a real good question to answer. As the planet warms the Great Plains and the South may have more frequent droughts therefore fewer tornadoes.

      So in my humble opinion it looks like there has been a slight shift eastward of long track tornadoes as well as a slight shift in the season starting earlier and ending earlier which a slight increase in intensification. Best guess is you would probably see it continue shifting East ( and earlier) then start shifting more North with fewer tornadoes on its northerly progression . Because of increasing blocking patterns you probably have years with fewer tornadoes while other years will have an exceptional number of tornadoes.
      [48 States assume]

      • I would guess the weakening Jet Stream, and weakening temperature diff between equator and poles would make tornadoes less frequent, though.

        Which maybe explains what we see?

  5. Great comments, all. Thanks for the links, passenger. Zimmerman am interested in increasing tornado intensity and this empirical study is of breakthrough importance. It has parallels in the hurricane debate. Intuitively, storm intensity grows with energy or heat, and that is average temperature. IPCC is making a general statement about damaging storms. Derechos are a relatively unheard of phenomena that is becoming more widespread and intense. (Sorry, no science here) by that, I mean I don’t even recall it being spoken before. In any case, the point is not that any single type is increasing or more intense, but that aggregate of violent storms is increasing. Ultimately, we look at insurance info, like Munich RE, to see that weather related casualty is increasing. That’s the empirical data.

  6. Wow . Sorry. My spell checker is ruining me. Zimmerman does not even belong there. Should be “I am”. How a computer does that is beyond me.

  7. From the essay:

    “Puzzling out how climate change alters tornados is the big next step, Elsner said. One way this could happen is by adding moisture (via humidity) to fuel storms in Tornado Alley, the storm belt where tornadoes spin up in the United States.”

    I brought this up previously, but it seems particularly relevant here. There has been a recent study that suggests tornadoes will increase in intensity. They were specifically looking at severe thunderstorm conditions, but the connection to tornadoes is made.

    Previously it was considered an open question as to whether tornadoes would increase or decrease in frequency or severity:

    “Climate researchers have previously hypothesized that global warming will increase CAPE [(convective available potential energy)] and cause an overall decrease in wind shear, which created uncertainty about the net effect.”

    Global warming is likely to increase severe thunderstorm conditions in U.S., research finds

    However, it appears that while wind shear will decrease with global warming, it does not decrease sufficiently to be the determining factor on days of high CAPE:

    “Although the climate model experiment does indicate an overall decrease in the average amount of wind shear, the researchers found that the bulk of that decrease occurs on days that produce levels of CAPE that are much lower than is normally seen during severe storms.

    “The net effect is that the increases in CAPE on other days drive increases in the occurrence of severe thunderstorm environments.”


    The technical paper is open access:

    Robust increases in severe thunderstorm environments in response to greenhouse forcing (open access)
    PNAS 2013 ; published ahead of print September 23, 2013, doi:10.1073/pnas.1307758110

    • Wonderful reference, Timothy. Cuts to the chase directly. Thunder storm intensity increases with global average temp. Wind, rain, flooding, and so on. My point is, more energy is dissipated somewhere. If energy is increased, everything that intercepts it must deal with it. That means us. All infrastructure. The most vulnerable? Probably crops. Think hail, high wind, flooding, drought, …. Co2 is plant food is pretty myopic on that note.

      • It makes sense to think that increased temperatures will result in higher absolute humidity and more moist air convection. However, with Arctic amplification you are decreasing the poleward temperature differential, and this will slow the jet stream, which paradoxically becomes less energetic, decreasing the wind shear that, for example, is responsible for the initial formation of what is essentially a horizontal rotating tube of air that develops into a tornado. A layman’s intuition would likely miss these factors, and to properly take them into account requires both quantitative modeling and empirical studies. I personally would expect tornadoes to become more severe, but I am no expert, and am quite willing to defer to those who are.

        • Quite correct and the proper attitude to take with respect for those dedicating their lives to study. From a system perspective, it’s hard to imagine a gentler world with more energy in it. We may be concentrating on one violent weather phenomena and ignoring another. I was thinking derecho. The Munich re data points to an increase in weather related casualty. This study shows the beginnings of tornado intensity increase. I think historical hurricane studies may suffer from similar inaccuracies. Then there is the general destruction from wind, hail, flood, etc. Drought is another issue. We need more analysis and data. This paper is a good start.

  8. My apologies. I actually went to skeptical science and found a link to peters 2007 video on water vapor. That’s a good place for class to start. It’s just ridiculous that deniers are recycling long debunked garbage like 600 year lag and water vapor. Watch the video, by all means. It’s entertaining and enlightening. Sweet.

  9. […] Missed this presentation. Good thing Livescience didn't. LiveScience: SAN FRANCISCO — The trail of twisted metal and torn roofs left behind by massive twisters is growing longer and wider, a sign that tornadoes may be …  […]

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