Increasing tornado outbreaks—is climate change responsible?

December 1, 2016
A tornado near Elk Mountain, west of Laramie Wyoming on the 15th of June, 2015. The tornado passed over mostly rural areas of the county, lasting over 20 minutes. Credit: John Allen/Central Michigan University

Tornadoes and severe thunderstorms kill people and damage property every year. Estimated U.S. insured losses due to severe thunderstorms in the first half of 2016 were $8.5 billion. The largest U.S. impacts of tornadoes result from tornado outbreaks, sequences of tornadoes that occur in close succession. Last spring a research team led by Michael Tippett, associate professor of applied physics and applied mathematics at Columbia Engineering, published a study showing that the average number of tornadoes during outbreaks—large-scale weather events that can last one to three days and span huge regions—has risen since 1954. But they were not sure why.

In a new paper, published December 1 in Science via First Release, the researchers looked at increasing trends in the severity of tornado outbreaks where they measured severity by the number of per outbreak. They found that these trends are increasing fastest for the most extreme outbreaks. While they saw changes in meteorological quantities that are consistent with these upward trends, the meteorological trends were not the ones expected under .

"This study raises new questions about what climate change will do to severe thunderstorms and what is responsible for recent trends," says Tippett, who is also a member of the Data Science Institute and the Columbia Initiative on Extreme Weather and Climate. "The fact that we don't see the presently understood meteorological signature of in changing outbreak statistics leaves two possibilities: either the recent increases are not due to a warming climate, or a warming climate has implications for tornado activity that we don't understand. This is an unexpected finding."

The researchers used two NOAA datasets, one containing tornado reports and the other observation-based estimates of meteorological quantities associated with tornado outbreaks. "Other researchers have focused on tornado reports without considering the meteorological environments," notes Chiara Lepore, associate research scientist at the Lamont-Doherty Earth Observatory, who is a coauthor of the paper. "The meteorological data provide an independent check on the tornado reports and let us check for what would be expected under climate change."

U.S. tornado activity in recent decades has been drawing the attention of scientists. While no significant trends have been found in either the annual number of reliably reported tornadoes or of outbreaks, recent studies indicate increased variability in large normalized economic and insured losses from U.S. thunderstorms, increases in the annual number of days on which many tornadoes occur, and increases in the annual mean and variance of the number of tornadoes per outbreak. In the current study, the researchers used extreme value analysis and found that the frequency of U.S. outbreaks with many tornadoes is increasing, and is increasing faster for more extreme outbreaks. They modeled this behavior using extreme value distributions with parameters that vary to match the trends in the data.

Annual 20th, 40th, 60th and 80th percentiles of the number of E/F1+ tornadoes per outbreak (6 or more E/F1+ tornadoes), 1954-2015 (solid lines), and quantile regression fits to 1965-2015 assuming linear growth in time (dashed lines). Credit: Michael Tippett/Columbia Engineering

Extreme meteorological environments associated with severe thunderstorms showed consistent upward trends, but the trends did not resemble those currently expected to result from global warming. They looked at two factors: convective available potential energy (CAPE) and a measure of vertical wind shear, storm relative helicity. Modeling studies have projected that CAPE will increase in a warmer climate leading to more frequent environments favorable to severe thunderstorms in the U.S. However, they found that the meteorological trends were not due to increasing CAPE but instead due to trends in storm relative helicity, which has not been projected to increase under climate change.

"Tornadoes blow people away, and their houses and cars and a lot else," says Joel Cohen, coauthor of the paper and director of the Laboratory of Populations, which is based jointly at Rockefeller University and Columbia's Earth Institute. "We've used new statistical tools that haven't been used before to put tornadoes under the microscope. The findings are surprising. We found that, over the last half century or so, the more extreme the , the faster the numbers of such extreme outbreaks have been increasing. What's pushing this rise in extreme outbreaks is far from obvious in the present state of climate science. Viewing the thousands of tornadoes that have been reliably recorded in the U.S. over the past half century or so as a population has permitted us to ask new questions and discover new, important changes in outbreaks of these tornadoes."

Adds Harold Brooks, senior scientist at NOAA's National Severe Storms Laboratory, who was not involved with this project, "The study is important because it addresses one of the hypotheses that has been raised to explain the observed change in number of tornadoes in outbreaks. Changes in CAPE can't explain the change. It seems that changes in shear are more important, but we don't yet understand why those have happened and if they're related to global warming."

Better understanding of how climate affects tornado activity can help to predict in the short-term, a month, or even a year in advance, and would be a major aid to insurance and reinsurance companies in assessing the risks posed by outbreaks. "An assessment of changing tornado outbreak size is highly relevant to the insurance industry," notes Kelly Hererid, AVP, Senior Research Scientist, Chubb Tempest Re R&D. "Common insurance risk management tools like reinsurance and catastrophe bonds are often structured around storm outbreaks rather than individual tornadoes, so an increasing concentration of tornadoes into larger provides a mechanism to change loss potential without necessarily altering the underlying tornado count. This approach provides an expanded view of disaster potential beyond simple changes in event frequency."

Tippett notes that more studies are needed to attribute the observed changes to either global warming or another component of climate variability. The research group plans next to study other aspects of severe thunderstorms such as hail, which causes less intense damage but is important for business (especially insurance and reinsurance) because it affects larger areas and is responsible for substantial losses every year.

Explore further: Extreme tornado outbreaks have become more common, says study

More information: "More tornadoes in the most extreme U.S. tornado outbreaks," Science, science.sciencemag.org/lookup/doi/10.1126/science.aah7393

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31 comments

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Paulw789
1.7 / 5 (12) Dec 01, 2016
Would be nice study if the actual data supported it at all. But it doesn't.
mememine69
1.4 / 5 (9) Dec 01, 2016
CO2=Y2K

97% of all scientists are now also 99% certain that the effects of climate change "could be real" and worse than the effects of unstoppable global warming of the entire planet Earth.

But they are more than 99% sure the planet isn't flat and smoking WILL cause cancer.
antigoracle
1.9 / 5 (13) Dec 01, 2016
LOL
It's always amusing to see how manmade globull warming always started at the minimum point of the dataset. Never mind that the data shows that it was higher prior to that point.
JongDan
1 / 5 (1) Dec 01, 2016
Probably just better documentation. A bit like how the number of earthquakes seems to be growing, but the lower the magnitude, the faster the number is growing.
gkam
2.2 / 5 (13) Dec 01, 2016
Well, according to Reverend Pat, these-here things are Acts of God, and are in response to really bad sinning, . . nasty stuff. I guess that is why all the deadliest tornadoes are inflicted on the Bible Belt.
tblakely1357
Dec 01, 2016
This comment has been removed by a moderator.
rrrander
1.9 / 5 (9) Dec 02, 2016
Remember after Katrina, how all the kooks and hand-wringers said hurricanes on the east coast of the U.S. would become stronger and more frequent? It went the opposite way. In 60 years, the enviros, the intellectuals have made one wrong prediction after another. When will they learn?
Anonym
1.8 / 5 (10) Dec 02, 2016
The Mighty Wurlitzer of "Global Warming-Anthropogenic Global Warming-Climate Change-Climate Disruption-Climate Armageddon" plays on.

Guess what? NOAA just released a study that found there has been NO upward trend in tornado activity at all since 1954 (the start date of the study).

http://www.spc.no...adj.html

Insured losses are another matter --- population density has increased a lot since 1954, and inflation (and fraud) have driven the dollar amount of losses higher, of course. It's counter-intuitive, but insurance companies profit from big disasters because a onetime spike in claims can be used to justify a permanent increase in premiums. And the warming meme plays well before state regulators when seeking rate increases.
antigoracle
1.7 / 5 (11) Dec 02, 2016
Taking their lead from that other infamous cult, the Church, the AGW Cult continues to ignore and rewrite history. How much manmade CO2 was responsible for the most extreme weather ever of the 1930s?
http://www.trinit...bowl.htm
cantdrive85
2 / 5 (12) Dec 02, 2016
Increasing tornado outbreaks—is climate change responsible?

What a stupid title, AGW is ALWAYS responsible for EVERYTHING.
julianpenrod
2.3 / 5 (9) Dec 02, 2016
I warned for a long time that the number of tornadoes per year was increasing, that the number today is about seven or eight times what it was in 1950. I was told that I didn't know what I was talking about. I was told there are more people today to see tornadoes, that's why more are reported. The population grew only 200 percent since 1950, but the number of tornadoes by more than 600 percent! I was told better equipment indicated the presence of tornadoes. That means more than 1000 tornadoes per year were managing to hide somewhere for half a century. The Oklahoma Climatological Survey shows tornado numbers were nearly constant at 180 per year before 1950. It's chemtrails causing this, like chemtrails are the cause of climate change.
gkam
1.9 / 5 (9) Dec 02, 2016
Really? "Chemtrails"?

Even I can think of better conspiracies.

You're joking, . . . right?

But if it isn't chemtrails and sinning by the evangelicals, it just MAY be AGW!!

HeloMenelo
3.3 / 5 (7) Dec 02, 2016
LOL
It's always amusing to see how manmade globull warming always started at the minimum point of the dataset. Never mind that the data shows that it was higher prior to that point.

It's always amusing to see how antiscience gorilla and his puppets rake in the 1 out of 5 rankings, boy, has he ever gotten past even one during the past 15 years ? ? lol... wake up sleep, type monkey babble on physorg get 1 out of 5... repeat 24/7 365 days a year....Well done monkey, and as always, along with the 1s comes the bananas ;) :D
HeloMenelo
3.3 / 5 (7) Dec 02, 2016
Taking their lead from that other infamous cult, the Church, the AGW Cult continues to ignore and rewrite history. How much manmade CO2 was responsible for the most extreme weather ever of the 1930s?
http://www.trinit...bowl.htm


How much monkey business have you churned out on physorg the past 15 years ? By the looks of things it clearly seems to us all more monkeying than business.. ;)

and your sock cantdrive still can't drive ;)
julianpenrod
1.9 / 5 (9) Dec 02, 2016
Chemtrails began around 1950 with the advent of jet use worldwide. They were invisible then but caused the formation of the first new cloud species since the founding of the Cloud Atlas, cirrus intortus and the skyrocketing of tornado numbers from an approximately constant 180. In 1997, it appears, the air became saturated with chemical, forcing new contributions to precipitate out, which is why chemtrails became visible. 1997 is exactly the beginning of the spate of manifestations including the worst el Nino events, the worst hurricane season, the warmest years, the accelerated melting of glaciers, hundred degree heat waves from London to Siberia, the formation of the second new clopud species, undulatus asperatus. The carbon dioxide in the air increased only a few percent in that time, far too little to cause these effects.
TrollBane
2.6 / 5 (5) Dec 02, 2016
Another troll parroting the "Mighty Worlitzer" phrase. Probably a bot. Certainly not thoughtful or original.
howhot3
3.7 / 5 (6) Dec 02, 2016
Can anyone give me information on this AGW Cult thing? Are there references to it somewhere I can look up and read about? The reason I ask is, it seems to be a pretty cool Cult with amazing capabilities like increasing tornado out breaks, melting the polar ice caps, destroying glacier, acidifying oceans, destroying crops, heating up cities and making everything just plain miserable most people, animals and things. That's pretty powerful voodoo. Where do I sign up? Tryump U?
TheGhostofOtto1923
3 / 5 (2) Dec 02, 2016
cirrus intortus
Perhaps Julien was thinking of this?

"(Exorcízó te, immundíssime spíritus, omnis incúrsio adversárii, omne phantásma, omnis legio:
in nómine Dómini nostri (Jesu Christi) eradicáre, et effugáre ab hoc plásmate Dei.
Ipse tibi ímperat, qui te de supérnis coelórum in inferióra terrae demérgi praecépit.
Ipse tibi ímperat, qui mari, ventis, et tempestátibus imperávit.)"

-but I don't think it's a cloud in the classic sense.
Can anyone give me information on this AGW Cult thing? Are there references to it somewhere I can look up and read about?
Yes. See above.
howhot3
4 / 5 (5) Dec 02, 2016
Which I'm sure you will translate. I suspect the are the same as this quote from the "Inferno" by Dante;
"Amor, ch'al cor gentile ratto s'apprende
prese costui de la bella persona
che mi fu tolta; e 'l modo ancor m'offende.

Amor, che a nullo amato amar perdona,
Mi prese del costui piacer sì forte,
Che, come vedi, ancor non m'abbandona..."

Google it; but basically "They yearn for what they fear for." So for the climate denier, they yearn for climate change because that is what they fear for; their destruction.

antigoracle
1 / 5 (8) Dec 02, 2016
Can anyone give me information on this AGW Cult thing? Are there references to it somewhere I can look up and read about?

LOL.
Look at what his man crush, Al, pooped out and how unsurprising he's blind to the fact that he is seeking what he is in the middle of. How else else could he worship his False "Prophet" Al, when he is the worst sinner of what he preaches.

https://www.googl...ypocrisy
gkam
1.6 / 5 (7) Dec 02, 2016
No, not Trump U.

But their course "How to Bankrupt Yourself to Billions" was a real hit.
Anonym
3 / 5 (4) Dec 03, 2016
@Trollbane: Not a troll, not a bot. The link is real; NOAA is real; the tornado uptick is not, per NOAA. What's your point? Did you look at the link? Are you a bot?

(The "Mighty Wurlitzer" is not my phrase. It was how Frank Wisner, CIA deputy director of plans way back when, described the CIA's propaganda apparatus --- a multitude of disparate voices, all singing the same tune, albeit with differing lyrics. The CIA funded thousands of writers and journalists on the Left and the Right to advance its agenda. This effort later morphed into Operation Mockingbird, which included the insertion of CIA "assets" into US newsrooms. Maj. Gen. Edward Lansdale later refined Wisner's Mighty Wurlitzer concept: his idea was to develop "themes" for psychological warfare which exploited mass psychology to mold public opinion along lines desired by CIA. The Climate Change tune, you will notice, swells in intensity ahead of important policy-making meetings, such as the recent treaty negotiations.)
philstacy9
1.4 / 5 (10) Dec 03, 2016
"The climate hoax is ending and the peddlers will surely have their comeuppance."

http://www.americ...nge.html
gkam
2 / 5 (8) Dec 03, 2016
Any time I see a name like "American Thinker" I realize it is another hateful screed by those who inflicted "WMD!" on us. They mass murdered hundreds of thousands of civilians looking for the weapons which were never there.

And we knew it.

It was to steal their oil. Why is the entire Bush Crew not in prison?
gkam
2.1 / 5 (7) Dec 03, 2016
Them scientists have inflicted these-here tornadoes on us. It's a liberal plot to make conservatives not like Our Trump. Wait and see - I predict Oklahoma will have earthquakes.

Liberals are doing it and blaming it on oil and gas! I read it at Breitbart.
Zzzzzzzz
5 / 5 (5) Dec 03, 2016
Only an anti-science delusional dumb phark could translate the above article into validation for his/her delusion of choice. Of course that sort goes through life desperately searching for opportunities to do just that with every waking moment. It must be one of the most miserable existences possible.
TheGhostofOtto1923
3 / 5 (2) Dec 03, 2016
Which I'm sure you will translate. I suspect the are the same as this quote from the "Inferno" by Dante;
"Amor, ch'al cor gentile ratto s'apprende
prese costui de la bella persona
che mi fu tolta; e 'l modo ancor m'offende.
Why don't you try Google translate? Or accuser/opposer. Worked for ne.
howhot3
3.8 / 5 (4) Dec 03, 2016
Can anyone give me information on this AGW Cult thing? Are there references to it somewhere I can look up and read about?

LOL.
Look at what his man crush, Al, pooped out and how unsurprising he's blind to the fact that he is seeking what he is in the middle of. How else else could he worship his False "Prophet" Al, when he is the worst sinner of what he preaches.

Something from Dante's Divine Comedy sounds like an appropriate reply;

"Through me you pass into the city of woe:
Through me you pass into eternal pain:
Through me among the people lost for aye.
Justice the founder of my fabric moved:
To ar me was the task of power divine,
Supremest wisdom, and primeval love.
Before me things create were none, save things
Eternal, and eternal I shall endure.
All hope abandon, ye who enter here."

Anthropogenic Global Warming though is not divine.

HeloMenelo
4 / 5 (5) Dec 04, 2016
Can anyone give me information on this AGW Cult thing? Are there references to it somewhere I can look up and read about?

LOL.
Look at what his man crush, Al, pooped out and how unsurprising he's blind to the fact that he is seeking what he is in the middle of. How else else could he worship his False "Prophet" Al, when he is the worst sinner of what he preaches.

https://www.googl...ypocrisy


monkey goes bananas again.. a passion for monkeying and bananas like no other :D
Phys1
4.4 / 5 (7) Dec 04, 2016
"The climate hoax is ending and the peddlers will surely have their comeuppance."

http://www.americ...nge.html

Do you mean that Trump will be a vindictive dictator that will persecute those who disagree with him until the bitter end, like Hitler and Stalin did?
You may well be right.
Phys1
4.3 / 5 (6) Dec 04, 2016
@sadisticle
his man crush,

Your brains are swarming with visions of this and crushed baby heads.
The leader of the Sturm Abteilung, Ernst Rohm, was much like you.
You two could have been friends !

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