Is Global Warming Causing More Tornadoes? Not So Fast, Says Harold Brooks

Recently, I witnessed the destructive power of a tornado nearly firsthand. In Norman, Oklahoma on the evening of May 24, I watched the sky darken and unleash a battery of nickel sized hail. Then a funnel cloud twisted down from the clouds, even as the cloud line itself touched earth in the distance, where a tornado had landed. Later, grass and leaves came flying through the air and stuck to our window, debris propelled from miles away.

It was terrifying—and more than that, awe inspiring. But what happened in Oklahoma that day, while very destructive and deadly, was nothing near the death toll in Joplin, Missouri two days earlier, or in Alabama in April, a month that set a new record for tornado outbreaks. So much tornado destruction this year, and so many deaths, has inevitably led some to ask the question—could global warming be implicated here?

Fortunately, being in Norman, I was also in the place to ask one of our country’s top experts this question—Harold Brooks, a tornado specialist at the National Severe Storms Laboratory. Along with other mainstream scientists, Brooks agrees that “it’s abundantly clear that the surface temperature has increased, and will continue to increase, and the overwhelming evidence is that it’s due to human activities.” Brooks also thinks global warming is likely to impact many weather phenomena–increasing the risk of heat waves, for instance, and stronger precipitation events.

But it doesn’t necessarily mean that every bad weather event is going to get worse,” Brooks continues, and when it comes to tornadoes, “I get really worried when people oversell the case.” After all, if we’re wrong and we go through a series of quiet tornado years in the coming years, it will be just another weapon with which to attack those who want climate action.

Why isn’t Brooks convinced that tornadoes are getting more numerous due to climate change? In short, it’s because the numbers of tornadic outbreaks don’t simply follow the temperature–meaning the problem is much more complicated. “Maximum tornado occurrence doesn’t happen during the summer time, but well before,” Brooks explains, “and the hottest years haven’t seen the most tornadoes.”

Indeed, neither the theory, nor the data, provide enough support at this point to claim that tornadoes should increase in number in a warming world.

Let’s cover theory first: Tornado formation is greatly enhanced by two key atmospheric parameters: convective available potential energy (or CAPE), which is a measure of atmospheric instability, and wind shear, which imparts rotation. (For more explanation, see here.) So one way of examining what will happen to tornadoes in a warming world is to examine how these variables are expected to change.

The answer, according to Brooks, is that it’s mixed—CAPE is expected to go up, but shear moves in the opposite direction. (One paper finding this result is Trapp et al, 2009.) “Physically the most important thing for the tornado problem is the wind shear, and the models predict it should decrease for a warming planet,” Brooks explains.  

In addition to models, there’s the data on tornado occurrence over time. Here again, Brooks doesn’t see a trend related to rising temperatures. “When you look at the big years in the US, it’s the early 1970s for tornadoes,” he says. “That’s the coldest period in the US, and for a long time.” Even in the very warm 2000s, we saw some quiet years for tornadoes.  “If I was going to expect to see an association with global warming, I would certainly expect the 2000s to have many more big years than the 1970s,” Brooks says.

None of this means we shouldn’t worry about global warming, or its weather impacts. And we definitely need to be ever vigilant in tornado prediction and emergency communication to the public. It’s just to say that when it comes to climate change, not every change in every weather phenomena is necessarily a worsening–or easily predictable or measurable. There are many, many things to worry about in a warming world, but at least at this point, it seems we should be cautious about including an increase in tornado activity on that list. 


Harold Brooks is allowed to speak on the subject because he gave his loyalty oath: “Brooks agrees that ‘it’s abundantly clear that the surface temperature has increased, and will continue to increase, and the overwhelming evidence is that it’s due to human activities.’”

Or are you just omniscient rather than omnipresent?

I bet you didn’t get far at school, the teachers kept hearing from you “Oh, yeah? ‘A is for Apple’, is it? You’ve just given a loyalty oath that A is the first letter of Apple so as to brainwash us kids!!!!”.

Maybe, just maybe, the temperature trend us up.

Try a little skepticism on your own dogma.

Loyalty oaths like that are political, not scientific. You know it’s true. Surely that must make at least some of the AGW supporters queasy to be in that company.

Just like “all the scientists were saying it was cooling in the 70’s” that existed only in your brain.

Just like all your “facts” that you spew up here like the pile of useless crud you are.

Oaths like what? The one you made up.

That’s a sign of insanity.

When you put something in quotes, you are explicitly saying that those words were used in that order by the quoted source. It is not considered ethical to do otherwise.

“useless crud,” eh? Is that a promotion?

It doesn’t make it an oath. That is your insanity speaking.

Or your faith.

There’s no real difference in effect, just in motivation.

A pile of crap was indeed your only contribution.

For crying out loud. Do you not realize that name-calling only makes you look like an insecure teenager? No one who is confident in their views would do that. Thinking people on your side of an issue must cringe. It makes the AGW supporters look like a gang of rowdy but loyal soccer fans instead of thinking individuals.

The AGW-skeptic disagreement is fundamentally about numbers. When numbers one person sees as unsupportable are cherished by another, it can be instructive to explore motivations. But even then the goal should be understanding the difference in motives, not silencing the opposition.

You’re a frigging nutcase.

It isn’t name-calling, it’s a statement of actual specifically evidence fact.

You’re a raving lunatic. No matter than you desperately want to beleive you’re an “everyman” (as evidenced by your insistence that everyone uses “faith” to decide issues when it’s patently obvious that the only reasoning you apply to your position is faith only).

But you don’t like to have the mirror of truth shown up to you. You’re not an everyman. You’re not the “reasonable middle ground”. YOU ARE THE FRUITCAKE.

The liar.

The misanthropic speck of flyshit on the dinnerplate of humanity.

It would be teenager of me to be afraid to tell you and everyone the truth about you just because you want to paint it as something adolescent.

It’s only the adolescents who so desperately want to be seen as grown-ups. Adults have enough backbone to ignore the petulant whinings of the lunatic fringe.

As long as you lie, as long as you crap all over the planet and as long as you continue to put yourself ahead of every single other being on this planet, I’ll call you out on it.

You’re a raving lunatic paralysed by a fear that you are a lunatic.

“Adults have enough backbone to ignore the petulant whinings of the lunatic fringe.”

Well then, grow a backbone and ignore me. You’d be doing the blog a favor.

It is a BS filter.

This is a very good post. I find all the talk about linkages between climate change and tornados to be disappointing. It hurts our credibility.

Period. Nobody can prove the storms of 2011 were made worse by climate change.
Nobody can prove the fires in Texas and Russia were the result of global warming.
Nor can anyone prove the heavy rains and floods of 2010 and 2011 were due to CO2 induced climate change.

Perhaps nobody will ever be able to prove it. So as the death toll rises, the crops drown or wither and our planet gets more and more inhospitable, we can all breath a sign of relief. We can’t pin it on Climate Change.

Oh sure you can…..

Come on… go ahead. Nobody believes AGW alarmists anymore anyway so be as silly as you like.

Look here:

Cant get much sillier…..

AGW alarmism doesn’t exist. Even poptart couldn’t find one in several days. Even though he’s spent YEARS being skeptical of it.

All that exists is the caterwauling of the losers in the intelligence race: the denialists.

The number of weather-related disasters reported each year in the world’s poorest countries has more than trebled since the 1980s and the increase cannot be explained by better reporting or an increase in population, a study by Oxfam has found.

An analysis of the natural disasters reported to international relief agencies since 1980 has revealed that while the number of disasters relating to geophysical events – such as earthquakes and volcano eruptions – remained fairly constant, disasters caused by flooding and storms significantly increased. Oxfam looked at disasters in more than 140 countries and found a clear increase over time, rising from 133 disasters a year in 1980 to more than 350 a year in recent years. Steve Jennings, the report’s author, believes the increase could be the result of climate change.

Source: “Weather disasters in the poorest nations ‘have trebled since 1980s’ “ by Steve Connor, Science Editor, The Independent, May 23, 2011

It has been 27,658 days since the most powerful hurricane to ever hit the US struck. CO2 was well below the safe level of 350 ppm at the time.

It has been 6,849 days since a category five hurricane struck the US.

It has been 985 days since any hurricane hit the US. The longest hurricane-free spell since before the Civil War.

You realize that we would all be dead with zero CO2 in the atmosphere, right? The lowest safe amount is probably around 200 ppm. Go too low and photosynthesis grinds to a halt.

CO2 isn’t what’s wanted from an internal combustion engine.

Therefore it’s waste.

When you throw waste out into the streets, air or rivers, that’s called “polluting the environment”.

However, libertards, all for THEIR OWN FREEDOM and hang anyone else’s, see the censure against poisoning the environment (and therefore mutualising the cost of cleaning up whilst privatising the profit of being dirty) as an infringement of their liberties.

‘course when your dog shits on their lawn, they’re the first ones to call the police…

They’re a bunch of hypocrites.

Safe level of CO2 for extended living is 5000ppm.
8000 ppm is safe for periods of a week or two.
An ideal level for Planet earth would be 1000 to 1500 ppm.
The average CO2 level over the past 600 million years was 1250 ppm..

The periods of maximum life and Biodiveristy were in the 4000+ range.

CO2 is plant food and very benificial for life on our little rock.

I am doing my part by driving my car lots.

You must be a stooge of the fossil fuel industry…

Don’t think fossil fuels will do the trick to get it that high. You’d need to increase the temperature of the ocean CO2 reservoir to shift the equilibrium vapor pressure. But that would mean dreaded warming.

Who was it that wondered: if the environmentalists had a thermostat and could control the earth’s temperature, what temperature would they pick? Could they pick one at all?
Do they know what they want?
Or do they just know what they don’t want?
Or does what they want have nothing to do with temperature?

CO2 causing warming? You don’t think so.
Humans affecting the planet? You don’t think so.

but when it comes to denial?

GCRs causing warming? Yup, gotta be.

You’re a credulous moron.

I think you have the GCR-cloud-albedo hypothesis backwards.
But carry on…

As in: we already know that GCRs can be CCN’s.

That’s why we use cloud chambers to detect charged elementary particles.

This is not news.

Now, as to “albedo”, what’s the albedo of high cloud, applesauce?

And what happens if the cloud cover increases?

And what happens to the earth’s temperature when the albedo changes as destined by the answer above?

Or have you no idea what you’re talking about? Again.

That’s the spirit. Act as if you understood it all along. No one will notice. Besides, that’s why you post as anonymous, right?

You see, the way it happens is that a charged particle will strip electrons off some atoms in a gas it passes through. These charged particles will attract polar molecules (such as H2O). In a super-saturated environment, this will accrete more water and eventually (if there’s enough water vapour to stop the droplet evaporating), become visible. The charged particle continues and makes more charged molecules and so you can see the trail of the charged particle as a trail of droplets of water.

This is not news.

As I said,
Charles Thomson Rees Wilson (1869–1959), a Scottish physicist, is credited with inventing the cloud chamber

See the date? It’s not a new thing.

To YOU, maybe.

But as we’ve seen, you don’t actually read anything to inform your opinions, you just jump straight into having one, so maybe you read that this paper “destroys” AGW and just jumped straight into “this must be new”.

And my point was that as soon as research was published on cloud formation mechanisms, the AGW apologists would begin hand-waving denials. And here they are, right on cue.

The fact that cloud chambers already existed is so far off the point as to be laughable. No one had ever quantified the effect of various particles on the atmosphere. Much more research will be done, unless you all succeed in suppressing it. It can then be included in the vaunted models. If you’re an honest scientist, you don’t desist improving the model because it gives you the result you want. Do you see the AGW people saying “Great, more data to help us refine our models! Thanks!” That’s what good scientists would say.

A paper comes out on cloud formation.


It doesn’t change AGW’s conclusion: the majority of the warming since the middle of last century is due to human influence on the climate.

Yet somehow you denialists go all “Teh end of teh smientists!”.

How is it “hand-wavey” to say that the GCR’s are outnumbered by other CCN’s at ground level? You can go look the figures up for yourself.

What’s hand-wavey is posting up that a paper comes out about cloud formation and then go “See! AGW false!”.

But you’ve never yet formed an opinion by reading something, you’ve decided what your opinion will be before any information enters your head.

And what a *skeptic* would say is “Is this paper actually correct”.

Didn’t, did you. No.

So you are of the opinion that this paper is really just saying “here’s a better way to model GCR-produced clouds” and that this is, in your words, “really big” at the same time?

Well, lets have a look at the paper itself, shall we?
We have studied sulfuric acid aerosol nucleation in an atmospheric pressure reaction chamber using a 580 MeV electron beam to ionize the volume of the reaction chamber. We find a clear contribution from ion-induced nucleation and consider this to be the first unambiguous observation of the ion-effect on aerosol nucleation using a particle beam under conditions that resemble the Earth’s atmosphere. By comparison with ionization using a gamma source we further show that the nature of the ionizing particles is not important for the ion-induced component of the nucleation. This implies that inexpensive ionization sources - as opposed to expensive accelerator beams - can be used for investigations of ion-induced nucleation.

So let’s have a look at that last sentence again, the “take home” message:

“This implies that inexpensive ionization sources - as opposed to expensive accelerator beams - can be used for investigations of ion-induced nucleation.”

Tell me, where did you get your opinion of what this paper was about when you described it as something useful for climate science, given that we don’t use expensive accelerator beams to modify the climate.

Where is your source?

It can’t be the paper.

So where did you get your opinion? You say you form them yourself by reading the actual facts, but the actual facts in this case do not support your conclusion.

Where did you get your opinion from?

Note how applesauce has not answered anything but, having being given some skeptical questions about this hypothesis in the face of known elements (anyone who has washed their car knows about dust being a huge aftereffect of rainfall).

Yet, despite styling itself as “skeptical”, shows no sign of anything approaching skepticism. Not even (as it insists should have been done in the case of this paper under their mischaracterisation of the paper’s utility) with “that’s interesting, maybe that ought to be included in their theory”.

Again this is obstinacy, not skepticism: applesauce is ALWAYS RIGHT and AGW ALWAYS WRONG. Anything that supports applesauce’s preconceptions MUST be accepted uncritically. Anything that goes against applesauce’s preconceptions must have been wrong.

Safe limits for working is 1000ppm, so you’re out by a factor of 5 there. And indoors the CO2 concentration is higher because you are in it and there’s nowhere near the level of airflow as there is in the blue room.

However, there IS one fact that you got right: deniers hate people.

You do know that if we have only CO2 we’d all choke to death, right?

And the plants would all die.

Even with all this “plant food” around.

Just have a look at Venus as to what that “plant food” can do for plants…


1000ppm indoors is toxic.

Since indoors CO2 levels are higher than it is outdoors, the global CO2 that would give that level of toxicity is less by some amount.

I think you need to read this:

OSHA permissible exposure is 5,000ppm continuously.
OSHA permissible short term exposure is 30,000ppm.

If you’re trying to make a case that fossil fuel emissions could some day create toxic levels in the atmosphere, you can’t.

Did you even read your link before you made your opinion?

5000ppm for 8 hours.

What planet are you going to be living on for the other 16?

That just shows you’re an idiot.

However, we’d all love to know where you formed that opinion from.

the stats come from the Navy, NASA, the government and the Mining industry.
The average CO2 level in well ventilated buildings is around 1000.
In mines it routinely goes to 5000 and on Space stations, 5000 is considered safe for long duration and 8000 for short. (weeks)\
Again, Dont take my word, go look it up.
390 ppm is in fact dangerously low and barly adequate to sustain life.

1500 would be far preferable.
And since its insulating value decreases exponentially as its density increases, that concentration would not increase temperatures enough to even offset the cooling we will get in the next 20 years from the real climate driver; the sun.

“390 ppm is in fact dangerously low and barly adequate to sustain life.”

Bugger. So the 180ppm killed off all the plants, then?

And how did we manage to survive with 2 million years of <280ppm!

1000ppm is when you are NOT ALLOWED TO WORK THERE. As in “toxic to human life”.

Aside from the fact that this is all way off topic, you are both wrong, which you must know since the correct information is readily available online. 390 ppm is hardly “dangerously low” since Earth vegetation has done just fine with this amount of CO2 (and less) for quite some time.

Secondly, that 1000 ppm is toxic is absurd. 1000 ppm is typical indoors. 10,000 ppm is fine for 8 hours, and 30,000 is okay for 15-30 minutes. The actual limits vary between different regulating authorities, but nowhere is 1000 ppm considered toxic.

FYI - Very high concentrations (e.g. >100,000 ppm or so) are a little painful … stick your head in a dry ice chest and take a deep breath sometime.

And in those rare cases when it is often the case, the health-and-safety laws require proper ventilation.

1000ppm is the limit for someone to work there (8 hours).

We don’t have somewhere to rest after those 8 hours if the entire planet is at 1000ppm.

says 5000ppm, indoors often at double or more outside (2500ppm required)

says 1000ppm.

says 1500ppm.

And so on.

anonymous’s carefully selected numbers miss a few things:

“…Due to a moderate La Niña, the 2010 Atlantic hurricane season was well above average, with the most number of named storms since 2005. The 2010 Atlantic season ties with the 1995 Atlantic hurricane season and the 1887 Atlantic hurricane season for the third largest number of named storms, with 19, and it also ties with the 1969 Atlantic hurricane season for the second largest number of hurricanes, with 12.[2] In addition, the activity in the north Atlantic in 2010 exceeded the activity in the northwest Pacific Typhoon season. The only other known time this event happened was in 2005.[3]…”

And the comment about the level of CO2 is irrelevent.

Like it or not. the US is just a part of the world, not the whole world.

We have hurricanes when it’s less than 350. We’ll have them when it’s more than 350.

The number of hurricanes in the USA has increased markedly (three- to five-fold) since the beginning of records in the USA.

CO2 has increased 35%.

What do YOU think caused the hurricanes to increase in number so dramatically? God?

According to NOAA, there are fewer now than 100 yeas ago.
Go look it up again.

you are simply echoing alarmist lies.

The denier-anaonymous blathers:

“It has been 27,658 days since the most powerful hurricane to ever hit the US struck. CO2 was well below the safe level of 350 ppm at the time.

“It has been 6,849 days since a category five hurricane struck the US.

“It has been 985 days since any hurricane hit the US. The longest hurricane-free spell since before the Civil War.”


In the northern hemisphere, hurricanes are hurricanes wether they hit the US maimlaind or not.

In the southern hemisphere “hurricanes” are called “typhoons”.

Both hurricanes and typhoons are tropical cyclones.

It is more important for scientists to be accurate than for them to provide talking points for arguments about climate change.

Tornadoes have complicated causes. Dr. Brooks finds that some record tornado seasons have happened in cooler years, so that means a warmer temperature is not the most important factor in causing tornadoes.

I think they are still working on learning how tornadoes work, so maybe they do not yet have a complete explanation for why a record-breaking tornado would occur at any particular time.

More about extreme weather:

“…The study of long-term statistical trends shows an increase in heat waves and heavy rainfalls, Hayhoe said.

But for tornadoes, the jury is still out, because the historical record is too patchy.

Climate change may enhance one precursor of tornadoes while diminishing another one, she said. “We will need a lot more data and modeling before we can say for sure which effect will dominate.”…”

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