Climate Change/Severe Weather Connection Heats Up

Climate scientists are starting to face off again on thorny weather questions, as they did in aftermath of Hurricane Katrina.

Some climate scientists are actively exploring an issue climate activists may see as the Holy Grail of climate policy — the connections between extreme weather events and global warming.

Much of the interest started with Hurricane Katrina in 2005, which triggered a controversial debate among many in the climate community.

Similar attribution storms have since arisen over the 2010 Russian heat wave, the spate of deadly tornadoes that ripped through the Midwest in 2011, and now the unseasonably warm weather that blanketed large portions of the U.S. in March.

The latter event is proving as controversial and potentially as divisive to the climate community as Katrina was.

Kevin Trenberth, a senior scientist with the National Center for Atmospheric Research (NCAR), recently wrote in the journal Climatic Change:

The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.

Heidi Cullen, Climate Central’s chief climatologist, echoed this framing in an interview with the Daily Beast earlier in the week: “All weather is now born into an environment that is warmer and moister because of man-made greenhouse-gas pollution.”

In the interview, Cullen provided a sophisticated and elegant explanation for how the climate system works, comparing it to an “orchestra” and the way it produces many different sounds. But the interviewer’s focus was on understanding how global warming is affecting current extreme weather events. On this, Cullen offers an analogy that is also becoming a popular explanation: “Climate change stacks the deck for certain types of extreme weather events.”

How mainstream media and climate activists then translate all this involves a delicate dance. Consider this: A recent Yale University poll found that more Americans are increasingly linking the March heat wave and recent drought and tornado episodes of the past year to climate change.

Some press stories* on the poll’s findings interpret this development as a clear sign that the reality of global warming finally is starting to sink in with people.

Not surprisingly, Roger Pielke Jr., a University of Colorado climate policy scholar, asserted that such media coverage only reinforces a faulty understanding of the link between climate change and severe weather.

Regardless, as The New York Times article noted in its story on the Yale poll:

Advocacy groups seeking policies to limit climate change say that extreme weather is giving them an opening to reach the public.

A group called is planning a worldwide series of rallies on May 5, under the slogan “Connect the Dots,” to draw attention to the links between climate change and extreme weather.

But well-regarded Houston Chronicle science reporter Eric Berger cautions that it is problematic for activists to overly rely on the poll’s findings:

On one hand climate activists will welcome this report as it suggests the American public has found an aspect of climate change that concerns them. This has been a real challenge because the prospect of some nebulous, future warming has not galvanized the public nor their politicians to action.

On the other hand, attributing extreme weather to climate change is a bit like playing with fire.

A recent IPCC report on climate and extreme weather took a fairly moderate view, saying of losses due to climate change, “In many regions, the main drivers for future increases in economic losses due to some climate extremes will be socioeconomic in nature, (rather than climate extremes).”

Some climate scientists, fearing what they consider to be an over-play of the climate change/severe weather link, are pushing back. Cliff Mass, a University of Washington atmospheric scientist, recently wrote on his blog:

It is happening frequently lately. A major weather event occurs — perhaps a hurricane, heat wave, tornado outbreak, drought or snowstorm — and a chorus of activist groups or media folks either imply or explicitly suggest that the event is the result of human-caused (anthropogenic) global warming.

In a candid passage in that blog posting, Mass also implicates some in the climate science community for fostering this impression:

It is somewhat embarrassing for me to admit this, but part of the problem is that a small minority of my colleagues — people who should know better — are feeding the extreme-weather/climate hype in the mistaken belief that by doing so they can encourage people to do the right thing — lessen their carbon footprint.

John Mike Wallace, a National Academy of Sciences member and also a climate scientist at the University of Washington, struck a similar (but somewhat gentler) theme in a recent Los Angeles Times op-ed. He wrote that, “we must consider the possibility that the apparent weirdness of the weather in March isn’t all that weird if viewed in a larger historical context. In this respect, it’s noteworthy that large areas of the U.S. were just about as warm in March 1910 as they were in March 2012. With weather, weird things happen every now and again.” (Wallace’s “Forum” column in the American Geophysical Union’s EOS, of March 13, 2012, is also well worth reviewing. Andrew Revkin’s Dotearth blog has a useful examination of the issue and links to Wallace’s column (PDF) and more.)

Wallace leaves no doubt about his concerns over a warming climate: “If global warming continues as projected, the global consequences of deteriorating conditions in the tropics will soon be a lot more serious than a foretaste of summer weather in late winter.”

But in the politicized climate debate, activists (and perhaps also some of Wallace’s scientist colleagues) may regard some of his remarks as not very helpful.

If climate science is to remain the leading front in the battle over climate change, activists will have to allow time for the science to play out on the climate change/extreme weather connection. And that means we may soon see a full-throated debate within the climate science community along the lines of what occurred in the aftermath of Hurricane Katrina.

*The survey was conducted by a team led by Yale Forum Publisher and Director of the Yale Project on Climate Change Communication Anthony Leiserowitz (see Yale Forum article).

Keith Kloor

Keith Kloor is a New York City-based freelance journalist who writes often about the environment and climate change.
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13 Responses to Climate Change/Severe Weather Connection Heats Up

  1. Matt Skaggs says:

    Scientists should be very wary of “just so” stories, and that is exactly what the “stacked deck” argument amounts to. The folks at Realclimate similarly refer to a “shifted distribution,” in which more extreme events must be more likely, as though it were an established fact, even though they have absolutely no facts to back it up. There is also a strong undercurrent of post hoc fallacy, in which extreme events in the recent past are assigned a probability indicating how unlikely they were, even though comparable events have occurred in the past.

  2. Is The Yale Forum becoming a hotbed of denialist rhetoric?

    What do you mean by “activists”? These people are realists!

    Let Cliff Mass get his ideas published in the peer-reviewed literature where climate scientists can discuss them — his unsubstantiated ideas in a blog post are not worthy of a real scientific discussion.

    That recent IPCC report was heavily watered down, thanks to stealth deniers like your buddy Roger Pielke, who is not a climate scientist.

    John Mike Wallace’s views on the off-the-scale March heat wave are again just opinions and are not substantiated by any sort of peer-reviewed research.

    What is your point, here, Keith? All I can see is a lot of innuendo and false balance designed to confuse the uninitiate and lead one to believe that the horrific extreme weather events of the past 3 years are just stuff that happens every once in a while, when in fact many extreme weather events are so off the scale that people like Jeff Masters hardly have words left to describe them.

    Yet again you have written something here that is unworthy of this forum.

  3. BBD says:

    From Cliff Mass’s blog (link in Keith’s article; emphasis as original):

    (2) If we haven’t seen trends in extremes that does not mean that we won’t see them in the future when the impact of anthropogenic greenhouse warming increases substantially. The earth is only starting to warm up due to mankind’s influence on greenhouse gases. The big action… including changes in extremes… is AHEAD of us. Activist types have made a huge mistake in thinking they need to point to observed changes in extremes to make their case for dealing with GW. They are particularly making a mistake when they make claims that have no scientific basis. Global warming skeptics and deniers have made the huge mistake of assuming that a lack of clear changes in the atmosphere during the past decades says something about what will happen in the future, since most of the GW impacts have not yet occurred Ironically, the activist types are providing the deniers with a potent weapon, since it is pretty easy to disprove many of the activist claims of human-induced global warming enhancing past and current extreme weather.


    I believe the science is fairly clear…the impacts of global warming due to human-enhanced greenhouse gases will be be very significant, that the effects will increase gradually at first, but then accelerate later in the century. There will be substantial impacts on extremes, but the magnitudes and spatial distributions will be complex, and we don’t necessarily have a good handle on it at present.

  4. Scott Mandia says:

    I am with Kevin Trenberth and Heidi Cullen on this one. Climate is the canvas and weather is the picture painted on that canvas. Humans have changed the canvas so now all weather has been influenced by human activity – some more than others and some easier to prove than others.

    Munich RE: and other insurance corporations also agree that climate-related losses are increasing even when accounting for more people being put into harm’s way.

    BTW, Jeff Masters has a nice summary of the record March here:

    There is an interesting paper by Francis and Varus, 2012 that shows Arctic amplification has weakened the jet allowing more NH amplitude and blocking patterns that increase the likelihood of extreme weather such as that in the US the past several years. See: Evidence linking Arctic amplification to extreme weather in mid-latitudes at

    One point I like to make clear to those that will listen is that if we never have another hurricane or tornado there are enough high confidence impacts that have increased risks and costs that we need to take action now. These include: heat waves, drought, fires, floods, and ocean acidification.

    Let us buy some “fire insurance” now while it is cheaper.

  5. keith Kloor says:


    You’re welcome to choose sides. This post isn’t advising which side to take; it’s only pointing out that that the global warming/severe weather attribution debate is shaping up to be every bit as contentious and controversial as the one that took place right after Katrina.

    Incidentally, here’s another highly respected climate scientist who weighed in late last year.

    So you can see, this issue has already been building into a highly charged debate–not just in the media but within the climate community, as well.

    • Keith,

      How this is playing out shows just how wrong some are when they state that there is tribalism within the scientific community about the primary cause of climate change – human activities. To get thousands of scientists and all international science academies to agree on something is quite a feat.

      I understand why you wrote this article because the extreme weather discussion is sexy but will it appeal to those that think there is debate about the other risks that I mentioned? That is the danger here.

      Scientists see the forest but this story, for the most part, highlights the tree.

  6. I can understand where people like Mass are coming from but what I notice from here in Australia is that much of the “debate” about climate is centred in the US and it can sometimes be easy for people in the US to lose sight of the fact that we are dealing with a global phenomenon. There needs to be a seminal study that looks at weather extremes across the globe in the last 50 years so that the real picture can be laid bare, because it is easy for someone in the US midwest to sit back and say, “Heck, we’ve had tornadoes before,” and “Heck, we’ve had droughts before.” It is human nature for people to make judgments based on their own experience. This also extends out to scientists as well as they try and put their science across to the public. They will tend to focus locally, especially when linking climate to weather. Weather is a local thing, but when you can make people relate to other places globally, perhaps the message will get through.
    we are all aware of the weather extremes in the USA with temperature records broken at both ends of the scale as well as droughts and floods. In China and India there have also been records broken year after year. In Russia they have had record droughts. In Australia we had the two largest cyclones on record hit in the last 6 years followed by record floods as well as new record heatwaves in the west. Europe too has had record heatwaves in some places and record floods in others and the list goes on and on from continent to continent and when viewed in a global context it would appear obvious that AGW, which is established, is having an effect. It just needs to be investigated within a global framework and reported accordingly.

  7. Steven Schuman says:

    It’s always good to know weather records were never broken in the past. Maybe the dust bowl days can be exorcised like the medieval warming period. I grew up in the fifties and I well remember what all strange and severe weather was attributed to– that darn atomic bomb testing. Witches are everywhere I tell ya!

  8. Bob Koss says:

    Here is what NOAA says about weather.
    The state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc. Weather refers to these conditions at a given point in time
    (e.g., today’s high temperature), whereas Climate refers to the “average” weather conditions for an area over a long period of time (e.g., the average high temperature for today’s date).”

    So, NOAA defines climate as the long term statistics of the observed weather. Statistics can be useful, but being non-physical they certainly can’t affect any weather event.

    Yet Trenberth says:
    “All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.”

    According to Trenberth not only does a change in the statistics of weather affect weather events, that change apparently only goes toward warmer and moister. It seems the possibility of the statistics moving toward cooler, dryer or some other combination isn’t even on his radar.

    It seems to me he has the relationship backwards. Weather events affect climate.

  9. Bruce says:

    What is the point of this forum? I came here because I thought it would look at all aspects of global warming and not just promote the alarmists’ viewpoint. And yet, in the case of this post, the first reasonably balanced one I’ve read on here, the likes of Tenney Naumer and Scott Mandia are all over it criticising it for providing, what was it, “false balance”? If the forum is only supposed to be about the alarmist point of view then please say so prominently in your “about” section so that you don’t waste people’s time.

    I can’t help but feel that, since we’ve had no statistically significant warming for 15 years, activists have now moved on to extreme weather events as they think this will resonate more with a public which has shown itself to be quite sophisticated where “global warming” is concerned.

  10. You are describing a debate between humans, not a physical reality.

    Years ago such a debate as this might have been about angels on the head of a pin, flat earth, or phlogiston. None of this addresses the reality. Only the personalities and stances of the those making arguments.

    More properly, should this be posted to a blog on debate or rhetoric?

  11. Hank Roberts says:

    >> no significant warming

    “… This assertion is entirely fabricated, as the Met Office explained by publishing David Rose’s inquiry and the Met Office’s responses. Quoted from here.

    Aren’t there any fact checkers at Yale?

    Leaving uncited false assertions unanswered makes the blog treacherous for new readers — kids may believe talking points that you fail to question, even those widely known by older readers to be bogus.

    Scott Mandia above:
    > … blocking patterns that increase the likelihood of extreme weather such as that in the US the past several years. See: Evidence linking Arctic amplification to extreme weather in mid-latitudes at

    Current news:
    “… The storm will idle somewhere between the mid-Atlantic and New England because of an unusual atmospheric condition called “blocking,” meaning a series of high-pressure systems pockmarking the United States will essentially block the storm in place, forcing it to spin like a top over one area before it eventually loses energy.”,0,2716397.story

  12. Peter says:

    Just a question. I have seen on Youtube that a insurance company had a graph with weather extreme events and that it had increased by 150 % since 1980. Is that something you might agree on? Do someone has the source for that? If correct, three of five extreme weather events is due to climate change (if there isn’t any other strange unknown reason). And isn’t that meaning that it’s more cost effective to cut emissions than not doing it?