It is now verified that the earliest 2017 tornados — first tornados of the season — struck several communities in east-central Minnesota (a few miles north and south of me). So what you say? Especially because it was a mere F1 and didn’t hurt anyone!
This is an important event because the earliest recorded tornado of the year in Minnesota was previously March 18th, and that was in 1968. This tornado, striking on March 6th (confirmed yesterday by the NWS) is way earlier than that!
One tornado, near Zimmerman went for nine miles.
A second tornado appears to have passed through the community of Clark’s Grove as well. That one may have been on the ground for over 12 miles.
Neither tornado was large, but there was a lot of damage to property and trees.
Needless to say, the frequency of storms in general, and their severity, are expected to rise with climate change. Part of that seems to be the lengthening of the storm seasons. More time, more storms.
This is a segment of The Big Picture with Thom Hartmann, in which climate scientist Professor Michael Mann provides important perspective on the link between climate change and other disasters such as tornadoes. (See also: The Meaning of the Fort McMurray Fire).
For more information on the science showing the link between climate change and weather patterns, discussed in the video by Professor Mann, see these items:
<li><a href="http://scienceblogs.com/gregladen/2015/03/12/new-study-on-how-global-warming-changes-the-weather/">New Study On How Global Warming Changes The Weather</a></li>
<li><a href="http://scienceblogs.com/gregladen/2014/08/14/more-research-linking-global-warming-to-bad-weather-events/">More Research Linking Global Warming To Bad Weather Events</a></li>
<li><a href="http://scienceblogs.com/gregladen/2013/09/28/global-warming-and-extreme-weather-climate-agw/">Global Warming and Extreme Weather – #climate #agw</a></li>
<li><a href="http://scienceblogs.com/gregladen/2013/06/04/linking-weather-extremes-to-global-warming/">Linking Weather Extremes to Global Warming</a></li>
<li><a href="http://scienceblogs.com/gregladen/2016/04/20/this-is-the-worst-coral-bleaching-episode-in-australias-history/">“This is the worst coral bleaching episode in Australia’s history”</a></li>
Al Franken likes to joke about having run the most efficient campaign for Senate ever, referring to when he beat incumbent Norm Coleman by just a couple of hundred votes (on the first count … the number went up during the grueling recount). Now, we have an example of the most efficient ever tornado hunt.
This is in Russia where, apparently, every single vehicle has a dash cam just in case something interesting happens. You see the guy back out of his garage, see the tornado coming down the street, and when he tries to drive back into his garage for safety … well, just have a look:
Are there more tornadoes because of global warming? Are they stronger? Do they occur more frequently outside of the usual tornado season, or are they more common in areas that formerly had few tornadoes?
There are problems with all of these questions, and the main problem is the fact that the tornado data isn’t very informative.
Here’s the raw data from the NOAA tornado database, showing the number of tornadoes per year of all intensities greater than one mile long on the ground:
(Click on the graph to see the whole thing in case it isn’t showing for you.)
This looks like more tornadoes are happening. We could leave it at that but we’d be doing bad science if we did so. The problem is that over time, the way tornadoes are observed and measured has changed, and owing, probably, to changes in population distribution in the region that gets most of the tornadoes in the US, there may be a number of tornadoes in the earlier years that were not observed. But, we don’t know that. In fact, we have no idea whatsoever how to make these data useful. These data could represent a reasonably accurate picture of tornado frequency over time in the US, or they might not, but we have no quantification of how biasing effects might work over time.
A while back I tried to see if I could make the data speak more clearly by measuring the total length and width of tornadoes in the database and adding them up for the period 1990 to 2012. This eliminated the problem of missing tornadoes because I was only looking at recent times when the data would be better. The resulting graph looks like this:
(Click on the graph to see the whole thing in case it isn’t showing for you.)
This seems to show a dramatic increase in overall effects of tornadoes. But, it turns out that the way “width” of tornadoes was measured was changed during this period, so these data are still not that useful.
Why am I showing you bad data? Here’s why. Consider the possible interpretations of graphs like these. For example:
1) There are more tornadoes over time, possibly because of global warming.
2) There are fewer tornadoes over time, despite global warming.
3) We can’t say anything about changes in frequency, severity, or land coverage of tornadoes over time because the data suck.
4) The evidence shows that there is no effect of global warming on tornadoes over time.
If this was a multiple choice question, the correct answer would not be 1, because the data are not useful. The correct answer would not be 2, because the data are not useful. The correct answer would be 3, because the data are not useful.
But often, we hear people who want to minimize the effects of global warming and deny the importance of climate change claim that number 4 is true. But we can’t say this because … wait for it … the data suck! The data as presented here are not sufficient to say that there are more tornadoes, but the default fallback null model is NOT that there is no relationship between climate change and tornado frequency, severity, or landscape coverage.
Peter Sinclair has a post linking together the tornado question and a spate of climate science denialism in this post: Tracking the Truth About Tornadoes. Go have a look.
In that post Sinclair quotes Michael Mann:
Actual atmospheric scientists know that the historical observations are too sketchy and unreliable to decide one way or another as to whether tornadoes are increasing or not…
So one is essentially left with the physical reasoning…
…warm, moist air is favorable for tornadoes, and global warming will provide more of it. But important, too, is the amount of “shear” (that is, twisting) in the wind. And whether there will, in a warmer world, be more or less of that in tornado-prone regions, during the tornado season, depends on the precise shifts that will take place in the jet stream — something that is extremely difficult to predict even with state-of-the-art theoretical climate models. That factor is a “wild card” in the equation.
So we’ve got one factor that is a toss-up, and another one that appears favorable for tornado activity. The combination of them is therefore slightly on the “favorable” side, and if you’re a betting person, that’s probably what you would go with.
I’d like to add to this: Storminess in “Tornado Alley” is likely to increase. It may be more straight line winds and severe thunderstorm, more ALH (amazingly large hail), or more tornadoes. Personally, I suspect it will be all of this but with the actual rate of tornado formation varying a great deal from year to year, depending on effects such as wind shear, but that’s just a gut feeling. Vertical wind shear may help attenuate the development of tornadoes when it is happening, but it won’t make the energy go away, and that energy may be manifest in other ways through storms that don’t happen to form tornadoes. We’ll see, I guess.
At the time that Samaras, his son, and his colleague, were crushed to death inside their tornado-chasing car, which was apparently rolled by the force of 200-300 mile an hour winds over a distance of a half mile or so, it was said by numerous news sources that this car had been trapped by a traffic jam caused by looky-loos who wanted to see the tornado and/or people sent out on the roads by a local weather reporter to “escape.” So, that apparent fact was part of the underpinning of the original post (below).
Later analysis of the situation indicates that there was indeed a traffic jam enhanced risk for several storm chasers, caused by the ill advised comments from local media (as described below) but that this happened after Samaras and his crew were killed, in a different location, and that this happened to not cause any deaths.
Here is what the tornado did: It grew from a big tornado to a bigger tornado, to what might be the largest tornado ever observed with instruments, in a matter of seconds, and it made a fast jog to the right, not an unusual thing for a tornado to do, but unanticipated by the storm chasers. Samaras’ car was perhaps too slow and too light, and the road was not amenable to fast driving. The tornado caught up with him and his crew and ended them.
Since I wrote this post, I’ve received many emails telling me that the premise is wrong, that traffic from too many storm chases did not contribute to the death of Samaras and others. At the same time, many helpful comments have been added to the post. I decided to let the comments speak for themselves, because, after all, this post was written three or four days after the event, and the comments reflect more recently available information and analysis.
I do regard some of the complaints I’ve gotten, especially some of the really nasty ones I’ve gotten by email, to be excuse making. Amateur chasers don’t want there to be strong evidence that what they do endangers themselves or others, so they want chaser-enhanced traffic jams to be taken out of the picture. They can’t have this, because the traffic is a factor, but yes, Samaras and his crew were not killed this way.
So, regarding the question of traffic: first, I know. I am hereby referring you and all readers to the comments. Also, read the wikipedia on Tim Samaras for more details, and watch this YouTube video (embedded below as well).
Second, the point is still valid. In the case of the El Reno tornado, traffic in combination with road bottlenecks (over a river) did in fact cause a number of storm chasers (and go watch the video to get an idea of how many storm chasers there were!) to get jammed up. They didn’t happen to be overrun by a killer tornado at the time.
Yes, lets get the facts straight, which the comments below and the information added here help do. I appreciate that, it is a good idea. But let us not let the fact that Samaras and his crew were killed in a manner that did not relate to traffic obviate further consideration of the “drive to the fire” problem. Look at that video. Skip Talbot makes this point. Pay attention to what he says.
If you want to walk down Main Street, in downtown America, you can do that, because it is America. This is a free country and public space is public. But if the Acme Office Building, on Main Street, is on fire, broken glass is blowing out of windows and fire trucks and other emergency vehicles are trying to gain access to the building and nearby fire hydrants, and ambulances are trying to get in to pick up injured, and out to bring them to hospitals, you can’t walk down Main Street. The police can close off that street and nearby streets and as annoying or inconvenient as that may be, they are not taking away your rights. They are acting in the interests of public safety.
We’ll get back to that in a moment.
After a large and violent tornado went through Moore Oklahoma a few days ago, several people in various media outlets including CNN mentioned that given the (seemingly enigmatic) lack of good shelter in homes and public buildings in Oklahoma, that a good option to protect yourself in case a tornado comes your way is to drive away. In some but not all cases, this advice was qualified; If you know several hours in advance that there is a high probability that a tornado will come through your area, then it is a good idea to just go away and be somewhere else. This advice sounds reasonable, but it really isn’t. During the United States tornado season, it seems that we experience repeated tornadoes and other severe storms in a given area over several days. That area might include three or four of the several states that make up “Tornado Alley.” However, within that area, the exact location of a killer tornado isn’t predictable at the scale of several hours. So, if you live in Oklahoma City and figure there may be tornadoes coming later in the day, there is nothing to guarantee that driving north to Aunt Millie’s house in Enid, OK will not put you in the path of one of the tornadoes that happen to form that day. A tornado could hit Oklahoma City, or it could hit Enid.
So, the driving away several hours in advance isn’t really smart, because you don’t know that far in advance where “away” might be. Perhaps, the day before tornado-warned storms are expected, you could fly to France, but that is not really an option for most people.
The unqualified version of that advice is “If there is a tornado coming your way now, get in your car and drive away fast.” That is also bad advice. The reason that is bad advice is very simple. If you are directly hit by a strong tornado, ending up in the vortex, and you are in the bathtub of your home on the lower floor, you’ve got a pretty good chance of survival. Despite the horrible fact that some two dozen people died in the Moore tornado last week, there were tens of thousands of people directly in that tornado’s path, hiding out in low interior rooms within their homes or other buildings, who survived. Alliteratively, if you are in a car and hit by the vortex of an F3 or stronger tornado, your chances of survival are much lower. Roughly speaking, this is the equivalent of driving down the highway at several tens of miles an hour and suddenly flipping, three or four times. Or, perhaps, you are driving down the highway at 40 mph along with a dozen other cars also driving down the highway and suddenly you are all flipped. Then, when the car is done flipping, it gets flipped again. And again. And for several minutes you car is shoved around on the surface like you were a puck in a game of air hockey, with the car slamming into other cars and other cars slamming into you, and each car being turned over now and then. To make this point, here are photographs from major media of a handful of examples of cars that got hit with the vortex, most but not all from this latest tornado:
I admit that a flattened house may look pretty bad, may even look worse than a mushed up car, but generally speaking the interior lower floor room in a house that is badly messed up by a tornado is a survivable shelter, while there is no such shelter in your car.
So, let’s go back to the advice again. Say you are sitting in your home and you know there is a tornado coming and you are watching TV and the following breathless reporting is happening. Pay special attention to what the weather forecaster says starting at 4:35:
“… if you can drive south, anywhere around Whitewater Bay, State Fair Park, the Ballpark, downtown Oklahoma City, southwest Integres, US Grant District, Rose State college, Midwest City regional medical center, Midwest City, and Parts of Del city, you need to drive south now….” (approximate transcript)
The Oklahoma City metro district has about 1.3 million people. Of those areas mentioned in this quote, “Downtown OK city” has about 7,600 people living in it. Del City has 21,000 people in it. What this weather forecaster just did was to advice a couple/few tens of thousands of people in the path of a tornado to get in their cars and drive in the same direction.
That wasn’t the only broadcaster telling people to evacuate instead of hunker down.
The thing is, this tornado was heading roughly from west to east into a highly populated area. News casters were telling people in the direct line of the tornado do “drive south.” But then the tornado made a turn and headed straight for the “south” that people were being told to drive to. Here is a compilation of broadcasts and events documenting this:
I have no idea how many of the people in the viewing area of this station saw or heard this report and responded by driving into the path of the tornado. Of those who did I don’t know how many of them were primed to use “drive away” as a strategy by earlier chatter in major media outlets, and elsewhere such as twitter and other social media. I’m not sure how many people actually got in their cars and “drove south.” We do know, however, that the highways in the area became jammed with cars, and the vicinity around the intersection of I35 and I40 was described as a “parking lot.” One thing we do know is that many people who “drove south” to get away from the tornado in fact drove directly into its path, created a traffic jam, and most of the deaths associated with this tornado were among those people in those cars.
Three experienced tornado “chasers” … actual meteorological scientists … were killed when their truck (one of the vehicles depicted above, probably) was destroyed by the tornado. Other professional meteorologists, from The Weather Channel, were injured. As of this writing, the death toll stands at 13 with another 6 (though I’ve also heard 7) people still missing.
Every time I went down to Oklahoma [with storm chasers] I was struck by the number of people tagging along. Often scores, even hundreds of chasers would converge on the same cell by late afternoon. It’s a free country – you’re obviously free to drive when and where you want, and I certainly don’t want that to change, but something has to be done to avoid another tragedy like the one that killed 9 motorists Friday evening, including 3 professional tornado researchers Tim Samaras, his son, and intercept partner.
Paul is right. This is a free country, or at least we want it to be a free country, and being able to freely travel on public thoroughfares is part of that. If you want to walk down Main Street, in downtown America, you can do that, because it is America. But if the Acme Office Building, on Main Street, is on fire, broken glass is blowing out of windows and fire trucks and other emergency vehicles are trying to gain access to the building and nearby fire hydrants… you can’t walk down Main Street… you are not really free to walk or drive up and down Main Street to take pictures of the event. Public safety officials have the right and responsibility to restrict access to Main Street and areas nearby in order to save lives and property.
Until proven otherwise, I will assume that the special category of people known as “Professional Storm Chasers” like Tim Samaras and his crew as well as Reed Timmer, and others, are risking their own lives to make observations and collect data that help us understand tornadoes better, to make better predictions about storm behavior, and thus to make better predictions about unfolding storms. Also, their data helps us to better understand the dynamics of what happens in tornadoes which can help make safer structures. Reed Timmer and Sean Casey and their crews modified vehicles that successfully survived being in powerful tornados (for Mythbusters fans, you may have seen these two teams’ vehicles go head to head with a jet engine to see how they would survive tornado strength winds on the episode Storm Chasing Myths).
But the hundreds, or even thousands of non-professional “storm chasers” are probably not contributing to the science of tornadoes and tornado safety. Rather, they are jamming roads in the very places where a traffic jam can be deadly if a tornado happens to pass over the gaggle of cars stuck in place. If you watch the Discovery Channel’s Storm Chasers show, you will notice that as the seasons progress the professional storm chasers encounter more and more traffic as they try to move to the predicted path of oncoming tornadoes to drop data collecting probes or carry out direct intercepts (where the specially modified vehicles equipped with data collection devices are directly hit with a tornado).
There is a great irony to the deaths of the three storm chasers from Twistex. Tim Samaras’s strategy was never to get into the direct path of a tornado. Rather, his team would predict the path and drop machines on the ground designed to directly measure variables such as temperature, humidity, wind and so on, but with the team and their vehicles getting out of the way before the tornado comes. It is probably true that Samaras abandoned attempts at dropping probes more often then strictly necessary, cautiously avoiding rain-wrapped tornadoes where they would not have been able to see where the tornado was, in order to be extra safe. It is also true that the relatively cautious “drop and run” strategy meant that they missed getting their equipment in the direct path of a tornado more often than not. I can only assume that Tim Samaras had no intention of being in the path of the the tornado that killed him, his son, and his colleague, but was unable to get out of the way because of the traffic jam.
And that traffic jam was probably caused by the exodus of people following very bad advice, and possibly as well as non-professional storm chasers moving in on the likely path of the storm.
I suggest that law makers in tornado alley states consider legislation making it a violation to intentionally drive into or near the path of known or likely tornados. This is not an especially enforceable regulation but having such a thing on the books would probably encourage amateur storm chasers to think twice about putting others in danger by contributing to blocked roads. Such a law or regulation could be more general, specifying that police have the authority to direct people generally in relation to emergency disaster zones that have not happened yet. In other words, it is now probably legal and appropriate for police or fire departments to close off roads or direct traffic or tell people not to drive in a particular area where there is currently a major fire, explosion, storm devastation, and so on. A new law or regulation merely needs to specify that tornado-related disasters that have not happened yet (because the tornado hasn’t formed or has not yet arrived) can be considered in this public safety action. In fact, one could argue that a new law is not needed and this power is already available to police and emergency response agencies. That might be preferable because making a new law to address particularistic new circumstances that are already covered by existing law, regulation, and best practice is probably a bad thing. But a law or explicit regulation, or even a well publicized set of best practices in the interest of public safety, might make the point that needs to be made, thus discouraging people from making decisions that endanger others.
One might argue that if someone wants to drive their car into the path of a tornado they should be allowed to do so because it is a free country. But once your car is inside an F3 or F4 tornado, that is no longer your problem alone. Because of your action, your car has become a very large and dangerous projectile. You shouldn’t be allowed to do that.
Such a regulation or law would also require consideration of a certification of “professional” status for actual professional storm chasers. This, in turn, would require storm chasers to make their case that they are professionals that are doing something worthwhile, and that they take appropriate action related to their own safety and the safety of others. In fact, we probably need more professional storm chasers, and among storm chasers my feeling is that we need a better more comprehensive research design. For example, most storm chasers are individuals or small teams, and they benefit with direct contacts with actual tornadoes, and often fund their work this way as they sell their video to news outlets. But what about big storms that don’t drop tornadoes? It seems to me that we should be collecting equivalent data from storms that do and storms that do not drop tornadoes, because, after all, one of the things we want to know more about is the difference between those two types of storms.
Tim Samaras, his son Paul Samaras and their colleague Carl Young were killed yesterday when their research vehicle was crushed almost beyond recognition by a Tornado they were “chasing” in Oklahoma.
If you ever watched Storm Chasers, the show on Discovery Channel (it is on Netflix) you may know of these guys. Tim Samaras’s team was “TWISTEX” … they drove pickup trucks with extremely well engineered systems for deploying “probes” that would collect data from tornadoes passing overhead. Their methodology was to get in and out before the tornado came through, and to the extent that we can figure out what was going on in real life from the Discovery Channel show, the TWISTEX team was about a 4 on the 1-5 scale of safety consciousness. For storm chasers that is. Some teams have vehicles that allow them to go into storms up to about F3 strength, and others stay way away from the storms, but TWISTEX attempted to put probes in the storm’s path but always avoided direct contact and Tim Samaras seemed especially careful.
It seems that traffic on roads in the vicinity of tornadoes had become an increasingly serious problem for storm chasers working in Tornado Alley. This was due, I think, to a lot of amateur storm chasers flocking to the vicinity where a storm was expected to drop a tornado. But yesterday was worse. According to news reports I saw yesterday, a lot of people in Oklahoma fled oncoming tornadoes in their cars rather than seeking shelter. I’m not sure what possessed them to do this. Certainly, it would not have been recommended by authorities. I’d like to find out what sort of information went around suggesting this to people … Twitter? Ignorant AM radio jockey? … or was it just massy “hysteria.” Anyway, apparently all of the deaths in yesterday’s Tornado were the result of people being in cars in stead of where they should have been. And, it appears that Tim Samaras, his son, and his colleague were killed because they were in the middle of one of these traffic jams.
Yes, people, it turns out that ignorance can be fatal.
Just so you know, a car is not the place you want to be when you are hit by a tornado.
Imagine standing next to Parable Creek, an imaginary rocky brook in New England. The water is rushing past you from left to right, around the rocks that emerge tall above the surface of the stream, mounding over the top of those that are lower down. The deepest parts of the steam are relatively flat but show ripples that belie the presence of other rocks and sunken branches that are well below the water line.
While you are observing a young boy of about 11 years old comes along, carrying his fishing pole. “Hey mister, how’s it going?” he says, as he steps into the stream. “I’m going fishing over there,” he says pointing in the direction of a mill pond a mile or so away. As he crosses the stream you notice that whenever he puts is foot down, some of the water mounds up on the upstream side as it rushes by him. He continues across the stream and climbs the opposite bank, running off to his destination. You wish him good luck with his fishing and return to your observations.
You can see large eddies here and there that seem to persist though they may change shape or grow or shrink a little. Smaller eddies, mini vortexes, form in certain parts of the stream, and rush down slope only to disappear as the water crashed into an obstruction. Every here and there there is a splash caused by the rushing water hitting a rock or branch just the right way.
Now, imagine that you are a compulsive data collecting scientist standing next to the rocky brook with nothing else to do for a while. So you start measuring things. Every where you see a mound of water built up in the current alongside a rock, that is a bit of kinetic energy (water moving) converted momentarily in to potential energy (water rising against gravity). So you estimate the number of mounds and their collective mass. This is a measurement of one form of energy in the stream.
You make a prediction. If the amount of water coming down this stream increases for a while, the total energy of the stream will increase, and this will be visible as an increase in total potential energy in the mounds you’ve been measuring.
Coincidentally it has been raining heavily upstream and just as you have formulated your hypothesis you see the water rising. Aha! A chance to test your prediction. At first, your hypothesis seems supported. As the water rises, the relative height of the mounds increases, and some new mounds form. You take some quick measurements, by eye, and note that the total potential energy stored in water mounds has increased, presumably as an effect of more overall energy in the stream. You gain confidence in your theory and congratulate yourself on your brilliance.
But then, as the water level continues to rise something different happens. More and more of the stream is now above the obstructing rocks. Therefore, there is less conversion of kinetic to potential energy. Most of the mounds disappear and the overall surface of the stream is much smoother. You take a new set of measurements and estimate that the total potential energy stored in water formed into mounds is an order of magnitude LOWER than your original measurement. Apparently, you think, something is wrong with this stream.
Just then a troop of Brownies comes along. The little girls want to cross the stream to take a short cut to their picnic grounds. They ask, “Hey, Mister, do you think it is safe to cross this stream?”
You had a nice theory linking total energy and a specific observation, which seemed to be confirmed by some of your research. The total energy of stream flow is linked to the total mound-i-ness of the stream’s surface. Now, the stream’s surface is smoother than it was before. Therefore, the total energy of the stream is at the low end of its known variation. A while back you saw a small boy cross the stream with no problem. Clearly, it is safe to cross now.
So, you say, “Actually, I’m sure it is quite safe. Go ahead and cross, and have a nice day!”
The brownies jump happily into the stream and start wade through the water. Half way across the stream, one by one but over just a few seconds of time of time, they are carried away by the water and drown.
“Hmmmm,” you think. “Maybe I had that wrong.”
Rivers Of Air
Air flowing over the surface of the land is a bit like water running down a stream or river. The air interacts with the ground (especially things like mountains). There are different layers, mounds, streams, and eddies of air that interact with each other. The overall form of movement is shaped by the spin of the earth, the tendency of warm air to form in certain areas (i.e., near the equator, or over water during winter and over land during summer, etc.) which causes the air to pile up and spill into nearby eddies. There are all sorts of ways in which batches of air interact, and when you thrown in differential amounts of moisture in different air masses, and things like night vs. day, and so on, you get the surface of Parable Creek. Metaphorically. In real life, we call the The Weather.
When the total energy in the system of air movement changes the way those crazy zany air masses move and what sorts of weather form can also change. For example, there is in total more energy on the hemisphere (north vs south) that is sticking its face towards the sun. It seems that one result of this is that the hemisphere with more energy (the summer end of the earth, as it were) has hurricanes, severe thunder storms, tornadoes, and so on while the hemisphere with less energy has less of that stuff.
However, a tornado is like a small eddy in the stream, and a hurricane like a large eddy, and a line of thunderstorms like the outer edge of one the mounds and the rainstorms are like the splashes at the edge of the log and so on and so forth. As Parable Creek’s level rises, exactly which phenomena are predominant changes, even as the total ability of the stream to wash away Brownies increases to the level where it can also wash away Girl Scouts and eventually Brawny Construction Workers and Bikers. Having said that, while a rocky stream converts to a large and deep river by adding a LOT of water, which may have a smooth surface despite the total energy of the river being orders of magnitude greater than Parable Creek’s energy, the system of air movement is not likely to become smoother owing to various limitations in the system.
Too Much Variability
You can’t measure the energy in the stream by only looking at one of the many phenomena that are the manifestations of that energy. In order to understand the relationship between global warming and storminess, it is minimally necessary to measure all of the storminess and find some way to combine it.
I remember when I first moved to Minnesota. That summer we had numerous straight line wind events of the sort never seen before. Maplewood, a community near where I lived famous for it’s tree lined streets lost almost all of its trees in one storm. That same storm also took out most of the stock of most of the new car companies in that town, famous for its numerous car lots. The cars were pitted with hail stones. Every single home for about three miles along a street right near where I lived had it’s vinyl or aluminum siding drilled with hundreds of holes and dents from large hail stones being driven by a 60–100 mile per hour wind. It was one of the worst weather years in Minnesota, with insurance companies practically going bankrupt.
There were only a few tornadoes in the area that year.
The next year there were hardly any straight line wind storms of the magnitude just described. But that is the year of the Saint Peter tornado. It was one of the largest tornado events ever; It was a twister that lifted and dropped a couple of times, so ‘nato-pedants divide it into multiple events, but that’s absurd. It was an F3 and F4 event, and it tracked for 67 miles and was up to one and a half mile wide.
There were a lot of tornadoes that year.
The atmosphere over central and southern Minnesota had a lot of energy those two years, for whatever reason. If we want to understand the total energy, and its effects on life and property, we would be doing a disservice to our pursuit of understanding if we failed to consider both straight line winds and tornadoes together (though obviously also separately).
The Big Picture
Weather comes in bands. The biggest and most obvious band is the Intertropical Convergence Zone, a band of thunderstorms that rings the entire planet and is pretty much always active. Another band is the arid band that rings the earth; actually there are two of them, one in the Northern Hemisphere and one in the Southern Hemisphere. Almost every major desert on the earth is in one of those bands. In fact, any desert that is not in one of those bands has to explain itself, and the excuse is usually a mountain rain shadow. Conversely, any wettish areas in those bands also have some ‘splainin to do. The southeastern US is in the Northern Hemisphere’s arid band, but the Gulf of Mexico keeps that region pretty wet much of the year.
Severe weather is also patterned in these bands, to some extent. Hurricanes form in the bands just north or south of the Intertropical Convergence Zone. Tornadoes tend to be confined to subtropical and southern temperate bands away from the equator. In a sense, one could say that most tornadoes that are not spinoffs from hurricanes occur in a certain band either north or south of the equator, and if we are going to count tornado activity, measure its total intensity, etc., we should be looking more globally at those zones, not just parts of those zones.
This of course applies to national borders as well. Tornadoes occur in the US but also in Canada, but the most easily available tornado data for North America is always presented as US tornadoes. Also, years are tricky. Events that span Jan 1st are hard to track if we count things by calendar years.
Some have been harping about the “tornado drought of 2012” as evidence that there is not an increase in tornadoes owing to global warming. Well, there are very few US tornadoes in January, but the January with the most tornadoes ever (in our records) was January 2012. Also, Canada had a lot of tornadoes in 2012. Has anyone looked to see what the combined US and Canadian count would be? And, how do you count a Canadian Tornado? The very fact that a tornado forms 1000 miles north from where most occur has something to do with the nature and distribution of atmospheric energy across the plant’s surface. I’m not making a specific claim about the distribution of tornadoes across time and space. I am saying, rather, that counting tornadoes within an arbitrary boundary in space (or time) can be misleading.
Then, there is the problem we have with all of these storm types, especially tornadoes and hurricanes, of how to actually measure them. Even using standard severity scales, tornadoes can be very different from each other in ways that are not counted in the usual statistics. An F3 tornado that is extra wide and stays on the ground for 100 miles involved significantly more energy than an F4 that formed momentarily and disappeared. Indeed, the different kinds of tornadoes (funnel vs. wedge, for example) really may be very different (but closely related) weather phenomena that should be examined separately at the very same time we combine vastly different storm types to measure and understand at a larger, global scale.
Tornadoes are not a good canary, in the canary in a coal mine sense. But they are obviously important. When we see people stating clearly and plainly that we need not be concerned about the frequency of tornadoes increasing with global warming, we should ask why they are saying that. We should be concerned with increasing storminess … there is almost no way that is not going to happen, and likely, it already has. If tornadoes are part of that increase storminess, we may want to get smart about it fast. For instance, we might want to take seriously the problem of schools and workplaces, where people tend to concentrate, having actual storm shelters instead of just hallways that some administrators says is a storm shelter, for protection when a big tornado comes along. Don’t you think?
There are good reasons to believe that global warming leads to more storminess, but the exact nature of that transition is unclear and hard to measure. Part of the reason for this difficulty is that a given type of storm may become more likely under certain conditions caused by climate change, while a different kind of storm may become less likely, with the “storminess” overall increasing but doing so indifferent ways across time. Also, the most severe, and thus possibly the most important, weather events are infrequent so it is difficult to see changes over time with any statistical confidence. I address many of these issues here and here.
Looking at the raw data, it is clear that there are “more tornadoes” over time in the US. Have a look at this graph:
At first glance, his graph makes it look like there are a lot more tornadoes, but there is a strong effect of observer error; earlier tornadoes were simply missed much of the time, so the big increase you see here, while it may reflect an underlying increase in number of tornadoes, is not reliable and cant’ be taken as evidence. However the later years shown here, from 1950-something to the 1990s, seems to show an increase that could be taken as meaningfull
However, when people speak of tornadoes they often show this graph as evidence that there are not more of them over time:
Looking only at this graph it looks like the number of tornadoes per year in the US is pretty variable but not increasing, as one would expect if global warming was causing more of them.
There is a problem with this graph, however. Actually, a couple of problems (other than those pointed out here). The main problem is that the most frequent tornadoes are left off this graph. If we look at F0 grade tornadoes, not included here, we see that they have actually increased in frequency over time. If we include ALL tornadoes, and not just the kinds that don’t seem to increase in frequency over time, we get this graph:
Compare the scales of the last two graphs. It turns out that the number of tornadoes at the smaller end of the scale goes up quite a bit. It might be hard to see. The upper graph goes up to 900, the lower graph goes up to 1900. So, if we add all the data instead of just select data, we get many hundreds more tornadoes per year.
The proportion of tornadoes that are F0 increases over time as shown here:
… and the overall distribution of tornadoes by strength changes over time as shown in this very cool graph:
As I point out here, one of the contributing factors to variation over time in tornado frequency is the fact that we have somewhat arbitrary boundaries in which we measure them. For instance, the US-Canada border provides an arbitrary line across our data set. By not counting all North American tornadoes the same way, we may be adding unnecessary variability to the data. To demonstrate this, have a look at this graph showing tornado frequency per year in France and Germany, two countries that are right next to each other:
This shows a few things. For one thing, they don’t have too many tornadoes in that part of the world. For another thing, there is an increase in overall frequency over time, and this is not because of lack of reporting. The reporting problem in the US is partly because the western and central states were relatively empty in the old days, and also more technology was available for spotting tornadoes later. But the European and US data have the same shape over a similar time span, but France and Germany do not have the missing observations owing to vast unoccupied (sort of) territories.
But the main thing I want to demonstrate with this graph is the fact that dividing a largish area of land up into arbitrary units can cause your data go go all flooey. Increased variability in data owing to partitioning is a well known phenomenon and this is what it looks like.
Another part of the problem is that the largest storms, which may be the most important ones, have a great deal of variation in their occurrence. Compare any of the graphs above of all tornadoes or all excluding the F0 tornadoes of this graph of just the largest storms:
Not only is there a lot of variation in numbers of tornadoes at the larger end of the scale, but I suspect there is a lot of variability among the tornadoes in each class in terms of overall energy represented. An F4 tornado that lasts five minutes compared to an F4 tornado that lasts 20 minutes are hugely different, but this is not reflected in this sort of data.
Here is a graph showing the amount of storm damagein adjusted dollars over time in the US (pink) with average temperature (blue). Clearly, the total amount of damage goes up, and probably for a number of reasons including there being more stuff to damage, but also, likely overall increases in storminess including hurricanes, tornadoes, severe thunderstorms, etc.
There are many who do not want to link increases in severe weather to global warming. They are probably wrong. Global warming seems to increase severe weather overall. The best way to deny this is to cherry pick the data by ignoring variability across space, leaving out entire categories of storms, or focusing on just some kinds of storms. I suspect the size and severity of tornadoes at the larger end is increasing now, but did not start increasing until recently; time will tell if this is right. But overall tornadoes are so variable across time and space that they are not a reliable canary, as it were. But overall storminess seems to be on the increase, in accordance with expectations from the basis physics of climate, under warming conditions.
Do you hear that loud, repeated smashing sound coming from the general direction of the Upper Midwest and Plains? That’s us. Here in Minnesota, we have been breaking high temperature records left and right. Most of the TV weather reporters are wearing slings, eye patches, and bandages around their heads, it’s been so intense. And, on Monday night, we had the second earliest tornado recorded in the state. It was a baby; it messed up some trees and damaged some sheds down in Elysian, in farm country.
I remember taking a stroll a few years back with a distant relative in the Ozarks, Arkansas, and we talked by a house with a strange looking hatch thingie next to it. He pointed to it and said “Looky thare, those folks gots themselves a Fraidy Hole.”1 A “Fraidy Hole” is a place where you go if you are ‘fraid of tornadoes.
Sunday, May 22nd, 2011: That is a day people around here will never forget. I remember standing in the maw of my open garage holding an iPad with the weather radar running on it. The weather map showed that a tornado was on top of me. Amanda, Julia and Huxley were in the basement preparing for the worst. But, strangely, the rain was falling striaght down and there was not a whiff of wind.
People are asking me: Is the recent spate of tornadoes caused by global warming? The usual answer to that question is that you can’t answer the question because a tornado is not caused by climate … it is cause by weather … and global warming (which is real, and which is cause by humans) is climate change.
However, that is not really the best answer to the question. Ultimately, I want to propose an analogy for how to think about this question, but first, a stab at a good answer, which if modified could probably be improved:
Sad item one: There has been a second death, related to the cleanup. Details.
Sad item two: After passing through one of the more urban areas of Minnesota, the north side of the City of Minneapolis, the tornado crossed the Mississippi River, which includes a fair amount of rather wild country. And there, within the boundaries of the city but along the river, it struck and destroyed the local Great Blue Heron rookery. Details of this event are provided by BirdChick who is also the conservation officer who discovered the damage. Read: Minneapolis Heron Rookery Destroyed By Tornado
Finally, I just want to extend my good thoughts and kudos to Minneapolis Mayor RT Rybak. Here’s what you need to know: If you don’t live in North, but you live in the Twin Cities, then you know of North as a dangerous slum, a blighted African American neighborhood where there are frequent shootings, arsons, kidnapping, and where the police gather in clusters wearing bullet proof vests and carrying big-ass firearms, just in case. Most of these stereotypes are held and passed around by people who’s families fled North a generation ago, to the newly minted suburbs, or who have never been there, mainly out of fear.
Well, North does include a good proportion of the African American population of the city, and it also does include something close to half of the crime that happens in the city, and it is where you will, in fact, find a good number of any sort of events commonly noted on the local evening news happening. But that is because it is, well, about half of the city. North Minneapolis is quite large, and North does not include any of the la-la-shi-shi upper middle class and wealthy neighborhoods (which are in South) and it does not include the University Campus (which is in South and Southeast) and it does not include downtown (which is neither North nor South, by our local nomenclature), so North defaults, statistically, to something close to the average. It is actually a diverse area with all sorts of people living in it (not that tornado victims have to be “diverse” to be our sisters and brothers in need). Despite the obnoxious remarks made by local readers on the WCCO news reporting web pages about the tornado, in which people actually referred to the tornado as appropriate Karma for those living on the dole in Section Eight Housing, I’d wager that the majority of homes destroyed or damaged in this event were working class owner-occupied. And, I quickly add, do we really want to throw people who rent under the bus in a society in which people who own have almost single handedly destroyed our housing market with unchecked greed married to unmitigated ignorance? I don’t think so.
The other night the local new station, especially Fox 9 but to some extent the others as well, breathlessly reported widespread looting in North Minneapolis. They showed the owner of a liquor store saying “well, you know how it goes … unprotected property, and this is what they will do” wink wink nod nod. They showed clusters of Minneapolis police standing around with big scary looking long-guns and other weapons, donning their bullet proof vests, and looking tough.
In response to this, the mayor came out and made it clear that there was NOT widespread looting in the city. There were a couple of incidents. They were managed. What really happened was this: Everybody in the affected area took a look around them and immediately tried to do what they could do to help their neighbors. Yes, the news mentioned that as well, but they sullied the sense of community with their sensationalist reporting of non-events. And RT had the balls to set them straight. Thanks for that, RT.