Human-Caused Climate Change Contributed to Half of Extreme Weather Events Analyzed in New Study

By Tom Yulsman | September 6, 2013 9:57 am

A screenshot from an animation of Hurricane Sandy based on images from the GOES-14 satellite, acquired October 29, 2012. (Click to watch.) The animation reveals the storm’s detailed cloud structures as it approached the U.S. coastline. (Source: NOAA Environmental Visualization Laboratory.)

Figuring out what caused an extreme weather event like Hurricane Sandy, seen in the animation of satellite images above, can be something like trying to determine what caused a car wreck.

In the case of a wreck, was it the fact that the driver had consumed alcohol? Or that it was a dark and stormy night and the roads were very slick?

In the case of an extreme weather event, bad stuff happens all by itself, just like dark and stormy nights. So an event like Hurricane Sandy can occur and cause havoc just because of natural variability. Yet, just as driving drunk can help determine the outcome of driving on a slick road in the dark, human-caused climate change can make the outcome of a natural event more extreme.

Teasing apart these details and saying something meaningful and accurate about human influences on extreme weather events has been one of the great challenges facing scientists. Now, 19 studies by 18 research teams gathered together in a special issue of the Bulletin of the American Meteorological Society show that scientists are getting better at that detective work. (In their conclusion, btw, the researchers use a similar car crash analogy as the one above to explain the challenges they face.)

The headline conclusion of the report is that we humans contributed to half of 12 extreme weather and climate events around the world in 2012 examined by the research teams. These include spring and summer heat waves in the United States,  the inundation from Hurricane Sandy’s storm surge, the record low Arctic sea ice extent in 2012, and some extreme rainfall events.

But there is much, much more to the report. So in coming days, I’ll be going through it in detail and sharing what I’ve learned, along with comments from scientists. I hope to have the first one posted before the end of the day, so please check back.

  • disqus_atlq8Zmtsd

    I look forward to seeing what you have to say about it. I hope you provide emphasis on why this needs to be taken with a grain of salt.

    “we have reason to believe” is a far cry from “yes”

    • Tom Yulsman

      I won’t be emphasizing why this is not meant to be taken seriously, which is what I think “with a grain of salt” means. It is a very serious report. But I would like to do a post emphasizing, among other things, the caveats in the report, which the authors were very clear and transparent about. I’m also hoping to speak with Marty Hoerling, one of the co-authors, who is a cautious scientist who has taken quite a bit of heat for research showing that certain specific extreme weather events widely considered to be caused by anthropogenic climate change actually were the result of natural variation. He is at NOAA here in Boulder, and I’d like to speak with him in person. So it may take a little while.

      You should read the report. It is quite interesting.

      • disqus_atlq8Zmtsd

        You are doing exactly what I mean with the “grain of salt” comment. I believe in healthy skepticism and discernment.

        I’m too used to news sites reporting this sort of thing as the establishment of new facts instead of a compilation of evidence.

        I’ll refrain from that sort of comment in the future, because I think you’ve demonstrated that you are committed to educating people on the issue instead of on what they “should” think. My apologies.

        • Tom Yulsman

          No need to apologize! You are constructive and civil. Hooray! I have become too sensitized by the climate wars, which I’ve tried valiantly to check out of. (Mostly successful now with ImaGeo, but I still can get sucked in on Twitter and Facebook, I’m afraid.) Over the years I’ve been excoriated from all sides — I’ve been called an “alarmist,” a “warmist,” AND a “delayer” (which I guess is better than a “denier”). I’ve also been told that I should be put up against a wall and shot.

          • disqus_atlq8Zmtsd

            Well, go extreme enough and we all should be shot.

            And of course there is the opposite end that says we are natural, and thus everything we do is natural effectively absolving us of any responsibility for the world around us.

            at a purely philosophical level it does start to get pretty interesting. I mean, its pretty easy to define sustainability as the moral high ground (the pandas deserve to go extinct argument not withstanding), but I think most of us would agree that we have a slightly higher standard to live up to than self preservation (more or less what sustainability amounts to in the long term).

            this tangent being irrelevant to the fact that nowhere in the scientific method is there a step that tells you to agree with your conversational partner.

          • Tom Yulsman

            Excellent! I’m tempted to start a post with this clip.

          • disqus_atlq8Zmtsd

            I used to HATE that part of the movie because I always roll my eyes at our tendency for irrational self loathing.

            Then I started realizing that

            a) there is some small amount of truth to it
            b) there are people that embrace that whole heartedly

            Now its one of my absolute favorite clips for ironic reasons.


    Now, 19 studies by 18 research teams…
    Impressive numbers, however I doubt they were working in secrecy, maybe they shared data and/or conclusions. A common theme in this connected world.

  • DMAllen

    “…show that scientists are getting better at that detective work…”
    Ha, more in agreement possibly or more arrogant? When extreme events have not increased and remain similar to past times, how can they attribute it to human caused climate change. I would love to present these 18 scientist groups with extreme weather data from a period, unbeknownst to them, before the recent increase in emissions and concentration of CO2, and I’d bet the farm they’d come up with the same group think analysis.

  • Claus Mohr

    I believe that this is the same magazine that very recently announced that the global temperature has not changed in the last 15 years, in fact the Pacific Ocean is cooling. Make up your mind.

  • Dee Baig

    This calls for need for more action on climate change. We can still undo most of the damage by planting more trees and protecting forests. This should take in most of the carbon released in atmosphere. Trees not only make the place look greener but they also help reduce global warming. We should really start planting them soon on a wide scale, since they will take a few years to grow.


  • OWilson

    So, did each “study” miraculously arrive at the same 50% causation conclusion independently, or is that the average finding?
    If the latter is the case, it is no better than a coin flip, statistically.
    And, 19 studies? All trying to prove the AGW hypothesis?

  • twinkly_violet

    what about HARRP technology in America. Are they programed all this earth disaster to test their capabilities?



ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


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