The Island of Doubt

The neverending hurricane-climate story

Posted by James Hrynyshyn on March 4, 2010
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ResearchBlogging.orgIt’s a sore spot for some climate change pseudoskeptics. Any time anyone makes any kind of claim about the effects of a warming planet on tropical storm activity, you can count on a deluge of rejoinders about how shaky the science on the subject really is.


Much is made of Al Gore’s use of an image of hurricane spewing forth from a smokestack on a promotional poster for “An Inconvenient Truth.” And Chris Mooney devoted an entire book to exploring the science, and the battles over and about the science, Storm World. I was commissioned by the Weather Channel a couple of years back to write a feature on the latest scientific developments as several hurricanes tore threw Haiti. The question everyone wants to know is, was Gore right? Will climate change make hurricanes more destructive and/or more frequent?

If you were hoping for a definitive answer, look elsewhere. But if you’re willing to be patient and consider how slowly science moves on such things, then a new paper in Nature Geoscience is worth a read.

“Tropical cyclones and climate change” is remarkable in part because of the authors list. Almost all the big names are there, including Thomas Knutson, Greg Holland, Kerry Emmanuel, Chris Landsea, and six others who haven’t received the same kind of name recognition for one reason or another. The fact that there is now a single document that represents a sort of consensus on the subject isn’t particularly new — a group composed of many of the same scientists issued a World Meteorological Organization statement on the state of the science in late 2006. Back then there was much debate about what warming sea surface temperatures were doing to hurricane trends and the most definitive statement the group could come up with was

…it is likely that some increase in tropical cyclone intensity will occur if the climate continues to warm.

Since then they’ve learned a fair bit. There are still loads of unanswered questions and predictions for specific ocean basins come with much larger degrees of uncertainty than global trends. But here’s the take home message of the new paper, which serves as an update for the 2006 statement, conveniently summarized in a box:

Detection and attribution
It remains uncertain whether past changes in any tropical cyclone activity (frequency, intensity, rainfall, and so on) exceed the variability expected through natural causes, after accounting for changes over time in observing capabilities.

Tropical cyclone projections
Frequency. It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged owing to greenhouse warming. We have very low confidence in projected changes in individual basins. Current models project changes ranging from −6 to −34% globally, and up to ±50% or more in individual basins by the late twenty-first century.

Intensity
Some increase in the mean maximum wind speed of tropical cyclones is likely (+2 to +11% globally) with projected twenty-first-century warming, although increases may not occur in all tropical regions. The frequency of the most intense (rare/high-impact) storms will more likely than not increase by a substantially larger percentage in some basins.

Rainfall
Rainfall rates are likely to increase. The projected magnitude is on the order of +20% within 100 km of the tropical cyclone centre.

Genesis, tracks, duration and surge flooding
We have low confidence in projected changes in tropical cyclone genesis-location, tracks, duration and areas of impact. Existing model projections do not show dramatic large-scale changes in these features. The vulnerability of coastal regions to storm-surge flooding is expected to increase with future sea-level rise and coastal development, although this vulnerability will also depend on future storm characteristics.

To summarize the summary: There’s a good chance that we might see fewer hurricanes or maybe no change in frequency overall, but there’s also a good chance that we’ll see storm intensity grow and more of the most intense storms.

So it would appear there is justification for the linking of global warming and hurricane threats after all. Was Al Gore justified five years ago? At the time, the science was less conclusive, but that’s the way things were tilting at the time. Between then and now, things were in flux, and they still are and likely will be for a while yet. But arguing that there is no science to support the link is simply not congruent with the published literature.

–Knutson, T., McBride, J., Chan, J., Emanuel, K., Holland, G., Landsea, C., Held, I., Kossin, J., Srivastava, A., & Sugi, M. (2010). Tropical cyclones and climate change Nature Geoscience, 3 (3), 157-163 DOI: 10.1038/ngeo779

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Comments

  1. #1 Brian Sandler
    March 4, 2010

    At my website http://bsandler.com there is a description of a machine designed to kill hurricanes.

  2. #2 jebyrnes
    March 4, 2010

    I’ve been curious about this same issue for extratropical storms. Separate reviews by Easterling et al. and Meehl et al. in 2000 were somewhat ambiguous, although an increase in the intense rainfall events seemed evident. More recently, I’ve been looking into the EL Niño literature, and again finding ambiguity, with a great review by Latif and Keenlyside in 2008. What is intriguing, though, the trends seen in the data on El Niño’s. Gregis and Fowler have an awesome piece in 2009 looking at El Niño frequency and intensity from the 1500s on, showing that in the last century, and even the last decade, we’ve been getting more frequent intense ENSO events. This is coupled with an intriguing uptick in the frequency and intensity of large winter wave events from storms (great work by Bromirski, Graham and Diaz, and a new Ruggiero et al in press).

    I’m not a climate modeler by any stretch, but quite curious about what to make of solid observational evidence of trends versus uncertain model predictions. I do hope the two reach parity sooner or later so that we have a firmer leg to stand on with respect to extreme weather events.

  3. #3 Ferro
    March 4, 2010

    Kindly note that they are REAL sceptics, not “pseudo” and I think that this is true for good reason. While global warming may be present, there is no credible evidence that humans are having any effect upon climate. The Earth has been, both, much warmer and much colder than it is now. My concern is that governments are going to pass laws that will result in hugely expensive “solutions” to a problem that does not exist. When those “solutions” have no effect, then new, even more expensive “solutions” will be mandated, ad nauseam.

  4. #4 maxwell
    March 4, 2010

    Wait a second.

    This is the paper where the authors state,

    ‘Moreover, despite some suggestive observational studies, we cannot at this time conclusively identify anthropogenic signals in past tropical cyclone data.’

    right?

    Since it is, how you can you possibly make the claim

    ‘So it would appear there is justification for the linking of global warming and hurricane threats after all.’

    ?

    Such a statement is completely contradictory to what science has to say to this point. You’ve seemed to have forgotten that simply because a model can produce an outcome does not mean that outcome has occurred.

    But hey, you’ve proven that you’re not that interested in science anyway, so it’s just about expected.

    See you next time…

    The key word is “conclusively.” The quote mined above is entirely consistent with this excerpt from the abstract:

    “However, future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11% by 2100.”

    Also, the authors only said they couldn’t find data in the past to link storms and global warming. Since there’s no data on the future, projections are all we have to go on. Sorry if that’s not good enough for you.
    –jh

  5. #5 mandas
    March 4, 2010

    maxwell

    Ummmmm – did you actually read the WHOLE post, or did you just see the quote that you wanted to mine, then cut and pasted it to support your view? How about you go back and read it again, then click on the link and read the WHOLE paper, not just the abstract.

    When (if you do), you will find that James summarised the paper perfectly. For example, take this quote from the paper:

    “….dynamical and statistical/dynamical downscaling tools for tropical cyclone activity have improved, and evaluations of these tools have become more convincing. These improvements have encouraged us to raise our confidence levels concerning several aspects of cyclone-activity projections. These include our assessment that tropical cyclone frequency is likely to either decrease or remain essentially the same. Despite this lack of an increase in total storm count, we project that a future increase in the globally averaged frequency of the strongest tropical cyclones is more likely than not — a higher confidence level than possible at our previous assessment….”.

    So, as far as identifying which one here is ‘interested in science’, I’m going for the person who read the whole paper, then provided an accurate summary. That would be James.

    But the award for the person who has shown no interest in science, because of a continued insistence on a dogmatic view not supported by any data, and for a continued failure to do any research……. goes to…… maxwell!Congratulations! You are an idiot.

  6. #6 maxwell
    March 4, 2010

    mandas,

    I read the paper two weeks ago when Roger Pielke Jr. featured it on his blog. What is amazing is that considering all of the improvements that have been to our understanding, as you make very clear to point out in your comment, the authors still say that there is NO substantial link between human emitted greenhouse gases and past tropical storms. That is, in my opinion, the only worthwhile statement in the paper because hurricane predict is far from a precise science, even in the long run.

    It is particularly important in the context of this post because James makes it seems as though this paper proves such a link when, according to the authors of the paper, it does not exist.

    I find the following statement extremely interesting, however.

    ‘…because of a continued insistence on a dogmatic view not supported by any data…’

    How does the fact that the ‘data’ in this case shows no connection between greenhouse gas emissions and hurricane activity affect your impression of this situation? In fact, there is no other ‘data’.

    So yes, I have a dogmatic view that only claims supported by observations should be given the credence that you would like to give to everything that supports your political position. It’s called ‘the scientific method’. You might want to look into it.

  7. #7 Steve Bloom
    March 4, 2010

    James, this week’s Nature cover article (also with KE as a co-author) would make for an interesting compare-and-contrast.

  8. #8 mandas
    March 4, 2010

    maxwell

    “….That is, in my opinion, the only worthwhile statement in the paper…”

    Wow, you really do like to quote mine don’t you. I think I adopt the position of accepting that there actually may be something more of substance in the rest of the paper, rather than just deciding arbitrarily what should or shouldn’t be used based on my own dogma.

    And since the subject of the paper is both past observations and future trends in cyclones, and since the authors predict a change in cyclone intensity as a result of climate change, then I tend to think that any statements in the paper on that issue are also ‘worthwhile’.

    And you continue to make misstatements about what James has said. This:
    “….James makes it seems as though this paper proves such a link when, according to the authors of the paper, it does not exist….”
    is nonsence. He does no such thing. Try reading his words again. You know, where he says:

    “…Will climate change make hurricanes more destructive and/or more frequent? If you were hoping for a definitive answer, look elsewhere……..There’s a good chance that we might see fewer hurricanes or maybe no change in frequency overall, but there’s also a good chance that we’ll see storm intensity grow and more of the most intense storms. So it would appear there is justification for the linking of global warming and hurricane threats after all. Was Al Gore justified five years ago? At the time, the science was less conclusive, but that’s the way things were tilting at the time. Between then and now, things were in flux, and they still are and likely will be for a while yet….”

    Once again, pretty clear if you read the whole thing. Things aren’t definite……..things still in flux…but a good chance of less but more severe events (because of climate change).

    What part of that don’t you understand?

  9. #9 maxwell
    March 5, 2010

    mandas, I didn’t think I would have to break it down for you since you seem to be an English-speaking individual, but in case you are not here we go.

    James states

    ‘So it would appear there is justification for the linking of global warming and hurricane threats after all.’

    The word ‘appear’ means that one can ‘see’ a specific thing, whether that be a trend in data or a bird on a tree. ‘Justification’ means that there is reason to believe a specific claim. ‘Linking’ means connection between two different specific things.

    Given those ‘definitions’, James is saying that one can see a reason to believe there is a connection between hurricanes, in some general way, and global warming, a theory that people are affecting the climate of the earth in a negative way.

    While the paper makes many predictions for what will happen in the coming decades in terms of many parameters that define hurricanes, the only statement of interest concerning the connection between global warming and REAL OBSERVATIONAL DATA is that such a connection does not exist.

    That may change, as you point out, but until it does James’ statement that the one can see a reason to believe that a connection between hurricanes and global warming exists in any way is falsifiably wrong.

    Are things a bit clearer now?

  10. #10 Lance
    March 5, 2010

    maxwell,

    mandas is determined to make the barely higher than 50/50 conjecture of the authors, “…we project that a future increase in the globally averaged frequency of the strongest tropical cyclones is more likely than not…” the issue here rather than the observation based facts that conclusively demonstrate that there is no evidence to support this conjecture.

    Why am I not surprised.

  11. #11 maxwell
    March 6, 2010

    James,

    as per your response, even if we only have projections to go on, on which I agree, one cannot make a claim that there is a link between hurricanes and global warming FROM A PREDICTION!

    Physical models and the computer simulations of physical models are essential for getting a complete understanding of the world around us. They are, however, only part of the method science uses to determine fact from fiction. All simulations must be tested against reality. It’s known as validation. That’s why our government spends billions of dollars each year on experimental science.

    So no, basing our knowledge of a link between CO2 forced warming and hurricanes on some computer simulation predictions is not good enough for me. In any other field, it would be good enough to accept as fact. The scientific method is taught in such a way that we assume that the null hypothesis is valid until proven otherwise. In this case, without observations of such a link, according to the scientific method, the null hypothesis should be assumed. Therefore, until it is measured, there is no link between global warming and hurricanes, independent of what is predicted for the future.