The link between climate change and tornadoes is unclear. Here’s what we know so far

In the aftermath of last Friday’s deadly tornado outbreak, federal emergency officials say they are bracing for more severe and more frequent weather disasters, raising questions about whether there’s a link between climate change and tornadoes. While scientists are confident that climate change is increasing natural disasters, causality is trickier in the case of tornadoes. John Yang reports.

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  • Judy Woodruff:

    In the aftermath of last Friday's deadly tornado outbreak, federal emergency officials say they are bracing for more severe and more frequent weather disasters.

    As John Yang reports, that is raising questions about whether there's a link between climate change and tornadoes.

  • John Yang:

    Judy, while scientists are confident that climate change is driving an increase in some natural disasters, in the case of tornadoes, they say it's a bit trickier.

    Victor Gensini is an associate professor of geographic and atmospheric sciences at Northern Illinois University.

    Mr. Gensini, thanks so much for being with us.

    So many superlatives being used to describe this tornado outbreak on Friday night. Help us put us — put this into perspective. How major of an event was this?

  • Victor Gensini, Northern Illinois University:

    It's very likely to be historic.

    The National Weather Service right now is still surveying the longest tornado that started just north of Little Rock, crossed into the Bootheel of Missouri, into Northwest Tennessee, and finally into Kentucky, where it did its most prolific damage.

    We think the tornado right now has a path length somewhere near 250 miles. That would put it at first place, if you will, the most historic tornado path length in history, only to surpass the infamous Tri-State Tornado of March 18, 1925. That tornado had a path length of 219 miles.

  • John Yang:

    And to put that in perspective, I mean, the — a tornado track is generally — I mean, a long one could be 50 miles.

    And tornadoes generally lose their energy pretty quickly.

  • Victor Gensini:

    Most tornadoes are under five miles. It's pretty hard to get a tornado 50 miles, let alone talking about one that was on the ground for 200 miles.

    So, yes, as I was watching this tornado unfold on Friday evening, I got a pit on my stomach watching radar. I knew exactly what was happening at the surface. And it was just a matter of time until we saw some of those devastating pictures on Saturday morning.

  • John Yang:

    Help us understand, what do we know and, maybe more important, what do we not know about the link between climate change and tornadoes?

  • Victor Gensini:

    Right now, the link is still muddy.

    There have been studies that have shown a mean increase in overall severe weather in the future, but also an increase in the variability. I think the best analogy right now is honestly Major League Baseball during the steroids era. We couldn't say for certain if a home run was due to steroids, but when you look at the batting averages and the number of home runs over the season, it becomes pretty clear that steroids was having, right, an impact during the season.

    I think the same thing can be said here about tornadoes. We're just not sure right now if something like Friday evening was the direct result of climate change.

  • John Yang:

    Why is that? Why don't we know yet?

  • Victor Gensini:

    It's mostly due to the small scale. Tornadoes are actually on a very small scale relative to things like hurricanes or wildfires or drought.

    And that link, when you start to go down really small to the storm scale vs. the large climate scale system, makes these types of questions very, very hard to unpack from a scientific perspective.

  • John Yang:

    When you talk about sort of looking backward to try to figure it out, what have we seen? What changes have we seen in tornadoes in recent years?

  • Victor Gensini:

    Great question.

    Really, the only thing that we can hang our hat on right now is a pretty significant downward trend in the Great Plains of the United States. So, you think of Texas, Oklahoma, Kansas, your colloquial Tornado Alley, they have actually seen a decrease in the number of significant tornadoes that are over the last 40 years.

    And there's been a significant increase in places in the mid-South, like Kentucky, Missouri, Tennessee, Mississippi, Alabama, some of these areas that are — have been hit hard recently.

    And I think that's a really important thing, because we have a lot more assets, a lot more people as you get east of the Mississippi River, due to the increased population density.

  • John Yang:

    Any idea what that tells us or what that suggests, why that might be, that shift?

  • Victor Gensini:

    We think it's due — partly due to climate change and partly due to natural variability.

    To what extent? What percentage of that shift is being caused by climate change? These are all questions that are really good, and that research groups like us at NIU are still trying to unpack.

  • John Yang:

    And what are the implications for the future, from your research and what you're learning from your research?

  • Victor Gensini:

    Well, I think there's two things.

    I think we want to understand what the future holds for these extreme events, like those of Friday evening. And on the flip side, we also want to understand the changing footprint of society. Both of those go hand in hand in understanding the future of tornado disasters like what we witnessed last week.

    And I'll tell you, looking ahead, even here tomorrow, it looks like another significant severe weather event possible across the Siouxland area. It only takes one event, right, to make your day, one tornado event to make your day a very bad day. And I think there's going to be a lot of questions about what happened to that Amazon warehouse and what happened to that candle factory on Friday evening.

  • John Yang:

    Victor Gensini of Northern Illinois University, thank you very much.

  • Victor Gensini:

    Thanks, John.

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