CO2 and Tornadoes

Well, you now have a simple algorithm for sorting flakes and politicized hacks from honest scientists -- anyone who is going around this week saying that the tornadoes in Alabama this week were due to manmade CO2 sit firmly in the former category.  First up, Dr. Roy Spencer

If there is one weather phenomenon global warming theory does NOT predict more of, it would be severe thunderstorms and tornadoes.

Tornadic thunderstorms do not require tropical-type warmth. In fact, tornadoes are almost unheard of in the tropics, despite frequent thunderstorm activity.

Instead, tornadoes require strong wind shear (wind speed and direction changing rapidly with height in the lower atmosphere), the kind which develops when cold and warm air masses “collide”. Of course, other elements must be present, such as an unstable airmass and sufficient low-level humidity, but wind shear is the key. Strong warm advection (warm air riding up and over the cooler air mass, which is also what causes the strong wind shear) in advance of a low pressure area riding along the boundary between the two air masses is where these storms form.

But contrasting air mass temperatures is the key. Active tornado seasons in the U.S. are almost always due to unusually COOL air persisting over the Midwest and Ohio Valley longer than it normally does as we transition into spring.

For example, the poster child for active tornado seasons was the Superoutbreak of 1974, which was during globally cool conditions. This year, we are seeing much cooler than normal conditions through the corn belt, even delaying the planting schedule. Cool La Nina years seem to favor more tornadoes, and we are now coming out of a persistent La Nina. The global-average temperature has plummeted by about 1 deg. F in just one year.

An unusually warm Gulf of Mexico of 1 or 2 degrees right now cannot explain the increase in contrast between warm and cold air masses which is key for tornado formation because that slight warmth cannot compete with the 10 to 20 degree below-normal air in the Midwest and Ohio Valley which has not wanted to give way to spring yet.

The “extra moisture” from the Gulf is not that important, because it’s almost always available this time of year…it’s the wind shear that caused this outbreak.

More tornadoes due to “global warming”, if such a thing happened, would be more tornadoes in Canada, where they don’t usually occur. NOT in Alabama.

Thus we yet again run into the logic of the marketing campaign to change the effect of CO2 from global warming to climate change, as if CO2 could somehow make for random climate changes without the intermediate step of warming.

We all draw upon fallible memories to come to conclusions about whether events are more or less prevalent today, and in many cases our memories fail us (often due to observer bias, in particular the increasing frequency of an event in the media being mistaken for the increasing underlying frequency of the event).  I will say that my memory is that the seventies were the time in my life with the most severe weather (including horrible regional famines) and the seventies were the coldest decade of my life so far.

Anyway, tornadoes are something we can measure, rather than just remember, so let's go to the data:

In An Inconvenient Truth, Al Gore and company said that global warming was increasing the number of tornadoes in the US.  He claimed 2004 was the highest year ever for tornadoes in the US.  In his PowerPoint slide deck (on which the movie was based) he sometimes uses this chart (form the NOAA):

Whoa, that’s scary.  Any moron can see there is a trend there.  Its like a silver bullet against skeptics or something.  But wait.  Hasn’t tornado detection technology changed over the last 50 years?  Today, we have doppler radar, so we can detect even smaller size 1 tornadoes, even if no one on the ground actually spots them (which happens fairly often).  But how did they measure smaller tornadoes in 1955 if no one spotted them?  Answer:  They didn’t.  In effect, this graph is measuring apples and oranges.  It is measuring all the tornadoes we spotted by human eye in 1955 with all the tornadoes we spotted with doppler radar in 2000.   The NOAA tries to make this problem clear on their web site.

With increased national doppler radar coverage, increasing population, and greater attention to tornado reporting, there has been an increase in the number of tornado reports over the past several decades. This can create a misleading appearance of an increasing trend in tornado frequency. To better understand the true variability and trend in tornado frequency in the US, the total number of strong to violent tornadoes (F3 to F5 category on the Fujita scale) can be analyzed. These are the tornadoes that would have likely been reported even during the decades before Dopplar radar use became widespread and practices resulted in increasingtornado reports. The bar chart below indicates there has been little trend in the strongest tornadoes over the past 55 years.

So itt turns out there is a decent way to correct for this.  We don’t think that folks in 1955 were missing many of the larger class 3-5 tornadoes, so comparing 1955 and 2000 data for these larger tornadoes should be more apples to apples (via NOAA).

Well, that certainly is different (note 2004 in particular, given the movie claim).  No upward trend at all when you get the data right.  I wonder if Al Gore knows this?  I am sure he is anxious to set the record straight.

The last chart is dated - am I hiding something?  Nope, here is the update (from here)

By the way, note the 2nd to last bar, which I believe it the 2008 bar (this chart is really hard to read, but it is the only way I have found the data from the NOAA).  In spring of 2008, the media went nuts with a spring spate of tornadoes, saying that the apocalypse was here and this was the ultimate proof of global warming.  In particular, ABC ran a story about how the frequency was twice the previous year.  Beyond the insanity of drawing long term trends in a noisy system from 2 data points, notice that the previous year was virtually the lowest number in half a century, and despite being twice as high, 2008 turned out to be an average to lower-than-average tornado year.  This is what the media does with the climate issue, and why you can trust almost none of it.

Update: By the way, 10 of the top 10 deadliest tornadoes occurred before 1955?  An artifact of increasing wealth, better construction, and in particular better warning and communication systems?  Likely -- it is no accident, I think, these all occurred before the popularization of TV.  However, remember this argument when you see charts of increasing property damage from hurricanes.  These are also an artifact of increasing wealth, but the other way around -- more rich people build expensive houses on the beech, the more property damage from hurricanes irregardless of hurricane strength or frequency.

Update#2:  The entire outbreak may be the third deadliest in the century.


  1. Scott Miller:

    Here in Kansas they overcall tornadoes by Doppler signature (rotation). And it has become a major local media event, with huge weather centers with multiple screens (like a war center) at most competing local broadcasters. It has caused some consternation when the weather guy or the NWS calls a tornado, and they have a storm chaser on staff who runs after it and it doesn't look that bad on the ground. Every storm becomes a crazy event, and usually ends up being just wind and hail, although the hail has been significant the last few years, again because people take pictures of the hail with their phone cameras and send them into the station.

  2. Ignoramus:

    A suggestion for a hypothesis: Tornadoes peak on something like a 30- to 40-year cycle.

    As illuminating as the correcting graph above is, it would be more stark if it only showed the F5s. If memory serves, over half of the F5s ever recorded were on that single two-day period back in 1974. Now that's a Holy Shit Headline.

    My other evidence for periodic tornado cycles:

    "The Wizard of Oz" was written around 1900, presumably following popular interest in tornadoes. We needed to have a lot of White inhabitants living in Tornado Alley for several decades to validate tornadoes, which are intensely localized, short-lived and inherently unbelievable. Finger of god, blow me. No one believes Indians.

    The Oz movie came out in 1939, following the extreme weather of the 1930s. Coincidence?

    By the way, you can read Oz as populist political allegory. I'm intrigued with populist politics these days.

    In the Oz book it's "silver slippers", not ruby. Thus, something like:

    Strawman: Farmers, who think they need a brain.

    Tinman: Factory workers, who think they need a heart.

    Yellow Brick Road: Gold standard, vs the proposed silver standard following the discovery of the Comstock load. Quaint that we used to argue over which precious metal to use to anchor the dollar.

    Emerald City: New York, home of the financiers.

    Cowardly Lion: William Jennings Bryan?


  3. Jonathan:

    Maybe it's just my poor reading comprehension, but your first paragraph leads me to expect that Dr. Spencer falls in with the "flakes and politicized hacks", which makes reading his remarks very confusing.

  4. Gil:

    There you go - tornados of a century ago were so powerful it could create a rift in space and sent you to another dimension. And people today complain!

  5. Zach:

    I live in Kansas, and I couldn't care less about tornadoes. They're so localized as to make them irrelevant in my day to day life. When the sirens go off, I head to my front porch, not my basement. Tornado activity doubles this year? All that means to me is that I better not be emotionally invested in any network dramas, as they're going to get preempted by the weather woodies from my local stations. I used to dread April and May while 24 was running.

  6. Zach:

    My previous comment is not to say that I don't care about the destruction they leave behind. I do; what happened in the south is horrible and I don't wish that upon people. I just do not fear tornadoes in my day to day life.

  7. Scott Miller:

    Zach, you are exactly correct. We in Kansas all run to the front porch to see if we can see the tornado.
    At work we had a manager visiting from Minneapolis corporate HQ. He heard that we were under a tornado watch. He asked his colleagues, "Where do you go when the sirens go off?". They replied "outside to watch the tornado." He was horrified. He meant "where is the shelter?".
    And TV is even worse because the local TV stations cover all of central and western Kansas. It is more than 300 miles to the Colorado border, and many hours away. Yet we see all of their warnings. Inevitably interrupts the season finales of our fave shows, and the Stanley Cup playoffs.

  8. James Bradley:

    In addition to wealth effects, disaster property value damage estimates are almost never expressed in inflation adjusted dollars.

  9. Ron H.:

    I, like Jonathan, am confused by your paragraph before, and the one after your quote from Dr. Spencer's article.

    If, in fact, you consider Dr. Spencer to be a flake, political hack, or AGW to Climate Change marketeer, I don't see how you got that impression from his article. He explains tornadoes as resulting from wind shear, not temperature.

    My previous experience of Dr. Spencer leads me to believe he is a firm skeptic as regards catastrophic AGW. In fact his article, which you quote, starts with the following:

    "I see the inevitable blame-humanity game has been reinvigorated by the recent tornado swarm."

    And, as he says on his web site: "Climate change — it happens, with or without our help."

    I wouldn't attribute these words to a climate change alarmist.

  10. John Moore:

    As an active storm chaser, I'm in touch with a bunch of the scientists involved in tornado research. Most of them are strong proponents of AGW theory, but I have yet to hear one of them attribute any weather event to it.

    As for false alarms and tornado rate... the NWS attempts, after the fact, to validate which warnings were associated with actual tornadoes and which were false alarms. Thus they do their best to clean the tornado climate data. As an aside, the false alarm rate is above 70% - mostly because too often the NEXRAD doppler radar system cannot tell a tornadic from a non-tornadic supercells - which came as a surprise once the system was deployed.

  11. rmark:

    'When the sirens go off, I head to my front porch, not my basement'

    And in Oklahoma, we do the same. I do open the cellar door, just in case. My dad has talked about the 1947 Woodward tornado, and how hot it was at midnight that night in Oklahoma City.They sprayed the house and bushes down with the garden hose trying to cool down enough to sleep.

  12. the other coyote:

    I checked a book out of the library this weekend called "The Children's Blizzard" by David Laskin. It is specifically about a horrid weather event on Jan. 12, 1888, where a blizzard swept across the Dakota plains, killing hundreds - many children, on their way home from school - who were caught outdoors and unprepared.

    The author discusses the big snow years of the 1880's (remember Laura Ingalls Wilder's "The Long Winter" - which was 1881?) and how these massive storms are created. It's really fascinating and took me back to a college class entitled "Weather and Climate". What I found refreshing in the book is not a single mention of "global warming" or "manmade climate change." The author talks, correctly, about the transfer of energy between hot and cold zones, as the earth seeks equilibrium. Exactly what I remember from college. And yes, I am old enough to predate the hoax of global warming; I was in college in the decade between the "global cooling" panic of the 1970's and the "global warming" panic of the 1990's.

    Does it ever seem to anyone that for all its polish and veneer of "science" and "civilization," we aren't really that far away from the Aztecs, believing that man has upset the gods and demanding human sacrifice to appease them?

  13. IgotBupkis, President, United Anarchist Society:

    Ah, small quibble with your word usage, Warren:

    Update#2: The entire outbreak may be the third deadliest in the century.

    "the century" in this context usually refers to the "current century", that is, the 21st Century.

    More than likely your meaning, and certainly far less ambiguously open to interpretation, would be carried by adding two words (in bold):

    Update#2: The entire outbreak may be only the third deadliest in the last century.

  14. Smock Puppet:

    > Does it ever seem to anyone that for all its polish and veneer of “science” and “civilization,” we aren’t really that far away from the Aztecs, believing that man has upset the gods and demanding human sacrifice to appease them?

    I believe your analysis to be correct, but limited far more to postmodern libtards than to anyone else a part of modern civilization.

    ... And they want to cut out your heart and sacrifice it to Mother Gaia, too, donchakno?

  15. IgotBupkis, President, United Anarchist Society:

    BTW -- You, and others, may find these American Heritage pieces of interest:

    The Blizzard Of ’88 (1988 - about your 1888 blizzard)

    The Great Blizzard Of ’88 (1977 - ditto)

    Blizzard (1988 -- about a blizzard in 1931 in Colorado)

    All are excellent reading about the blizzard you mentioned and another deadly one.

    I've found old issues of AH -- particularly those over 20 years old at the moment -- quite fascinating. Not only do they provide information of historical interest, but older ones also encapsulate attitudes and ideas that are no longer viable or taken for granted. Of particular interest, for example, are any articles written about the USSR or the Cold war prior to around 1988. Not only are they informative about the intended topic, but they're interesting to read with the knowledge of what was to come, as well.