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Climate Hustle

The link between hurricanes and global warming

Posted on 9 September 2008 by John Cook

With an intense 2008 hurricane season, the link between hurricanes and global warming is once again in the spotlight. Does climate change have any effect on hurricanes? Or is the recent rash of hurricanes a biproduct of the same chaotic weather that spewed out Hurricane Katrina in 2005 followed by a quiet season the following year. A new paper published in Nature, The increasing intensity of the strongest tropical cyclones (Elsner et al 2008) addresses this question.

Hurricanes have already been observed to be increasing in intensity in the North Atlantic (Emanual 2005).  However, Elsner extends this to each ocean basin using global satellite data, looking for any trend in wind speed since 1981. Figure 1 plots the long term trend of maximum wind speed (eg - whether hurricanes are getting stronger or weaker) against different strength hurricanes. This tells us not only whether hurricanes are overall getting stronger but also how different strength hurricanes are being affected.

Figure 1: Trends in  tropical cyclone maximum wind speeds by quantile, from 0.1 to 0.9 in increments of 0.1. The point-wise 90% confidence band is shown in grey. The solid red line is the overall trend and the dashed red lines delineate the 90% point-wise confidence band about this trend.

Overall, there is a statistically significant upward trend (the horizontal red line). But more significantly, Elsner found weaker hurricanes showed little to no trend while stronger hurricanes showed a greater upward trend. In other words, stronger hurricanes are getting stronger.

While Elsner found no trend in the overall number of hurricanes, the increasing intensity means there are an increasing number of storms with a maximum wind speed exceeding 210 kilometres per hour (category 4 and 5 storms). The inevitable conclusion is that as sea temperatures continue to rise, the number of Category 4 and 5 hurricanes hitting land will inexorably increase. That coupled with rising sea levels is a bleak prospect.

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Comments

Comments 1 to 26:

  1. Interesting. Ned Potter did a blog at ABC News (US) that indicated this may have something to do with an eastward shift in their origin. I argued that the shift in origin was likely due to climate shift (climate change), meeting with much resistance by some because I indicated not AGW. It is a very interesting topic.
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    Response: Elsner 2008 isn't just looking at particular region such as the North Atlantic but globally across all ocean basins. But it also begs the question, if warming sea temperatures are not lending more energy to hurricanes making them stronger, why not?
  2. John
    I don't know but I would speculate that warer air and cooler seas would tend to intensify storms because of the increased temperature differential. Would not a smaller differential lead to less violent storms?
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  3. that s/b warmer air (dropped the m), sorry.
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  4. PS in the hurricanes thread Alan M. posted a comment with a link that seems relavent. This is a subject that I find puzzling. I do understand that warmer oceans would have more energy stored but NASA indicated that the oceans did not warm, so I am puzzled.
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    Response: If you're referring to the argument that oceans are cooling, that's a short term cooling over the last few years which is not unusual over the last 30 years that has shown long term warming and a corresponding long term increase in hurricane intensity.
  5. Not sure what Quietman is referring to, but this subject is indeed an "ink bottle."

    From looking at what I can comprehend, it seems that the SSTs/lower trop. temp. differential is an important factor in the rate of storm intensification.

    The past 2 Atlantic seasons have seen some of the fastest intensifying storms ever recorded.

    Still, the significance of hurricane/tropical storm activity is somewhat unsure. RC had a post on this some time ago that pointed to major difficulty with the evolution of data quality/quantity.

    http://www.realclimate.org/index.php/archives/2008/02/tropical-cyclone-history-part-ii-paleotempestology-still-in-its-infancy/langswitch_lang/
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  6. John
    Yes, that is the part I dont get. The intense storms are very recent (not the last 30 years but the last 10 maybe) and this is when the oceans don't show warming? I am not positive but was that not the issue of the missing ocean heat? So is it the hot spots or the cold spots where these storms originate? The 2005 paper talks about the tropics and they mention hotter air. But I thought it was primarily the opposing air currents meeting at the equator that iniates cyclones and hurricanes so I am having difficulty following the logic. I am not being skeptical about this, I just don't understand what they are saying, it's like something is being left out or assumed.
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  7. This isn't really about initiating storms. The number of storms is very much a matter of debate but from what i know it would be very hard to establish a trend there. How the storms intensify is a different problem.

    I'm not sure that it is really possible to say that the past 30 years show no ocean warming.

    According to this paper, the past 30 years have seen significant ocean warming:
    http://www.nature.com/nature/journal/v453/n7198/abs/nature07080.html

    Before Emmanuel, this paper looked at increased SSTs and found them to be the best explaining factor for higher intensity storms:

    http://www.sciencemag.org/cgi/content/abstract/1123560v1
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  8. Philippe
    I see what you mean by ink bottle. I still remember Diana from when I was growing up on Long Island. There were a few nasty storms back then. But they seemed to have been lass intense until recently. I am more curious in what caused the lull.
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  9. John
    While not proof of anything, an interesting related article on The Worst Hurricanes at Live Science.
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  10. Quote prof. William Gray, Colorado Uni....

    "Consider, for example, the intensity of U.S. land-falling hurricanes over time -- keeping in mind that the periods must be long enough to reveal long-term trends.
    During the most recent 50-year period, 1957 to 2006, 83 hurricanes hit the United States, 34 of them major.
    In contrast, during the 50-year period from 1900 to 1949, 101 hurricanes (22% more) made U.S. landfall, including 39 (or 15% more) major hurricanes."

    for full report see....
    http://online.wsj.com/public/article/SB118541193645178412.html

    It would be interesting to see the history of Pacific storms and see how they compare....another one on the list....
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  11. Another what on what list? Not on the list of real science papers, or otherwise scientific references that Mizimi is pointing to. So far you got us Beck, who manages to fumble with his own made up BS, and a WSJ article. Impressive. Last I look, WSJ was not about science.

    Where are the figures coming from? If Gray is using NOAA data and applying the corrections suggested by Nyberg et al., is he aware of the fact that they seem to misunderstand Landsea's recommendations and apply his numbers wrongly? Is it just raw NOAA data for early century numbers? What are we talking about?

    The WSJ article does not include a single reference and offers no clue whatsoever to where these numbers are coming from. As we have already discussed, past hurricane activity is a highly contentious area and the uncertainty renders almost impossible a discussion of trends in storm frequency. The intensity ranking of past storms is also a considerable problem.

    What's funny is that even by these numbers the latter part of the century has a higher percentage of the storms hitting that were major storms (34/83 vs 39/101), which is in fact in agreement with the expectations of real climate scientists studying hurricane activity.

    Gray is one train late (and some of his ideas about climate defy the laws of physics, but that's another story). I have not heard any serious climate science researcher claiming that GW was the cause of more tropical storms. What they hypothesize (and support rather well) is that GW makes for storms likely to be more intense and to intensify more rapidly.

    So what exactly is your point?

    And why discuss only the hurricanes hitting the US? The ones going to Central America or dissipating over the North Atlantic don't count? What happens to the numbers once you include all storms?
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  12. Philippe
    Mizimi refers to a personal "to do" list of things to read up on.
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  13. It is interesting the reduction in OHC is just brushed off as "short term cooling". There is a reason why since 2003 the oceans have stopped gaining heat. It cannot be ignored since it is at the core of the AGW argument. See Hansen et al 'Earth's Energy Imbalance: Confirmation and Implications'.

    Amazing. Ten years of OHC rise and it becomes the "smoking gun" for AGW. Five years of cooling and it is "short term" insignificance. Where is the missing heat?

    Isn't the real truth about hurricanes as is the case in other aspects of climate that "scientists" really don't know as much as they portend? Cloud dynamics, convection, solar and others are not well understood either.

    http://www.agu.org/pubs/crossref/2008/2008GL033950.shtml

    This paper is still in press (need subscription to view abstract), so will link to this blog:
    http://climaterealist.blogspot.com/2008/09/new-paper-us-hurricane-counts-are.html

    Now, what makes anyone think that small changes in solar activity does not also affect earth's climate as a whole?
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    Response: Several years of ocean cooling is not unusual over the last 50 years of ocean warming. Solar activity certainly does have an effect on earth's climate - it's believed the 11 year solar cycle has an impact on global temperature of around 0.1C. So it wouldn't be surprising if this had an impact on hurricane intensity which is increasingly being linked to sea surface temperatures. More on the link between sun and climate...
  14. #11
    Philippe >> "Another what on what list? Not on the list of real science papers, or otherwise scientific references that Mizimi is pointing to. So far you got us Beck, who manages to fumble with his own made up BS, and a WSJ article. Impressive. Last I look, WSJ was not about science....

    Gray is one train late (and some of his ideas about climate defy the laws of physics, but that's another story). "

    And a damn fine story too, I'll bet. LOL!

    Are you seriously suggesting that Prof. William Gray's more than 40 years of tropical meteorological research experience is not "real science", as you call it.



    This attitude of denegrating well respected scientists who don't agree with your world view is reminiscent of Creationist tactics! It is certainly not a scientific approach.
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  15. Healthy skeptic, you really think I'm pulling this out of my rear-end? Denigrating scientists and accusing them of intellectual dishonesty, fraud, etc is so common among skeptics, it seems to be all they have.

    Even the moderate Quietman has no problem about accusing all the RC contributors of being biased and suggests that their funding is a cause of their "views" despite the fact that they do not receive funding from anyone to keep up the site. I've never heard you protest because he was denigrating these scientists.

    Do you even know what some of Gray's claims are? Have you checked the existing research about his claims?

    Find me the published papers that Gray would, according to you, be alluding to in the WSJ story, then we talk again. Gray is a respected expert on hurricane forecasting. He has published many papers on that subject and tropical meteorology. His track record of publications on climate science is quite different.

    But, as I said, if you have papers that would be of interest, link them. That what this site is all about.

    However, save us the memo circulated for the 2006 conference on hurricane and tropical meteorology, it is not a peer-reviewed science paper. Gray still calls on deep water upwelling from the tropics into the THC in this piece, an idea that has been discredited for a long time. He also seems to believe that evaporation can somehow make energy disappear. He makes all sorts of claims on historical behavior of the THC that do not have supporting evidence.

    Nobody is infaillible. Interesting is the fact that Gray testified in Congress that the Termo Haline Circulation was accelerating (while there was no real oceanographic evidence of it), leading to increased hurricane activity, then changed his theory when evidence was published that the THC was actually slowing down. As glider says, scientists don't know everything about hurricanes, which are really more a feature of weather than of climate.
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  16. Philippe
    Re: "all the RC contributers"
    No, just one, but it made me loose all respect for the site. There are plenty of other sites with pro-AGW authors that I can and do respect (like this one).
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  17. Re #10 and #14 (Mizimi and HealthySkeptic)

    Why should we take account of the appeals to authority of a 78 year old retired scientist just because he happened to be an authority on hurricanes during his working career? Gray is demonstrably wrong in many of his assertions, and as with all science, his comments should be judged according to the evidence, and not because he's given platforms for bombastic assertions, and you might happen to like what he says.

    If you look at the numbers that Gray asserts about hurricane numbers, for example (Mizimi reproduced these in post #10), you can see the first problem. As Gray presumably knows full well (after all he's published on the very subject - see Goldenberg et al, 2001 below), the issue is not about total numbers/frequencies of hurricanes and tropical storms, but the increased numbers of high category (Cat 4 and 5) storms in a warming world. That's pretty obvious from reading John Cook's top article.

    Gray's other major assertion that is in complete contradiction with the evidence is his insistence that global warming is the result of internal variation in the ocean circulations.

    One may as well point out the other rather unfortunate habit of Gray which is to use ludicrous strawmen and other fallacious "arguments" with which to attack the straightforward science. So he is wont to state, for example, that hoary chestnut of contrived ignorance that climate models are no good because they can't predict the weather two weeks ahead [***]! Gray is either being incredibly ignorant of the science or mendacious...take your pick.

    [***]http://www.washingtonpost.com/wp-dyn/content/article/2006/05/23/AR2006052301305_pf.html


    Putting aside Gray, the issue is reasonably clear, even if this is an area of climate science, and the consequences of man-made global warming, that are not very well-defined as yet. The following seems pretty straightforward:

    (i) everyone seems to agree (Gray, included) that recent years (last couple/few decades) has seen enhanced activity of hurricanes and tropical storms in terms of intensities (Goldenberg et al, 2001; Emanual, 2005; Hoyos et al, 2006; Curry et al, 2006; Elsner et al, 2008).

    (ii) everyone seems to agree that the enhanced intensity of tropical storms and hurricanes is related to the enhanced sea surface temperatures (SST) that have been directly measured. In fact it was William Gray that first established a causal link between hurrican intensity and SST way back in 1968.

    (iii) it seems pretty well established that enhanced SST during the period of enhanced high category hurricanes is largely the result of the global warming measured during this period (Barnett, 2005; Trenberth and Shea, 2006; Elsner, 2006). If the Earth warms, the SST warms, and it is the thermal energy in the surface waters of the sea that provide the destructive power of tropical storms.

    Barnett, T. P. et al (2005) Penetration of human-induced warming into the world's oceans Science, 309, 284–287.

    Elsner JB (2006) Evidence in support of the climate change - Atlantic hurricane hypothesis Geophysical Research Letters 33 L16705

    Elsner, JB et al (2008) The increasing intensity of the strongest tropical cyclones. Nature 455, 92-95 (see link in John Cook's top article).

    Emanual K (2005) Increasing destructiveness of tropical cyclones over the last 30 years Nature 436, 696-688 (link in John Cook's top article).

    S. B. Goldenberg, C. W. Landsea, A. M. Mestas-Nuñez, W. M. Gray (2001) The Recent Increase in Atlantic Hurricane Activity: Causes and Implications
    Science 293, 474 - 479

    C. D. Hoyos et al. (2006) Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity Science 312 94 - 97.

    K. E. Trenberth and D. J. Shea (2006) Atlantic hurricanes and natural variability in 2005 Geophysical Research Letters, VOL. 33, L12704

    etc. etc.


    ---------------------------------------------------
    here's some of the abstracts of papers cited above:

    C. D. Hoyos et al. (2006)Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity Science 312 94 - 97.

    Abstract: "To better understand the change in global hurricane intensity since 1970, we examined the joint distribution of hurricane intensity with variables identified in the literature as contributing to the intensification of hurricanes. We used a methodology based on information theory, isolating the trend from the shorter-term natural modes of variability. The results show that the trend of increasing numbers of category 4 and 5 hurricanes for the period 1970–2004 is directly linked to the trend in sea-surface temperature; other aspects of the tropical environment, although they influence shorter-term variations in hurricane intensity, do not contribute substantially to the observed global trend."

    Barnett, T. P. et al (2005) Penetration of human-induced warming into the world's oceans Science, 309, 284–287.

    Abstract: "A warming signal has penetrated into the world's oceans over the past 40 years. The signal is complex, with a vertical structure that varies widely by ocean; it cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models. We conclude that it is of human origin, a conclusion robust to observational sampling and model differences. Changes in advection combine with surface forcing to give the overall warming pattern. The implications of this study suggest that society needs to seriously consider model predictions of future climate change."


    **K. E. Trenberth and D. J. Shea (2006) Atlantic hurricanes and natural variability in 2005 Geophysical Research Letters, VOL. 33, L12704

    Abstract: "The 2005 North Atlantic hurricane season (1 June to 30 November) was the most active on record by several measures, surpassing the very active season of 2004 and causing an unprecedented level of damage. Sea surface temperatures (SSTs) in the tropical North Atlantic (TNA) region critical for hurricanes (10° to 20°N) were at record high levels in the extended summer (June to October) of 2005 at 0.9°C above the 1901–70 normal and were a major reason for the record hurricane season. Changes in TNA SSTs are associated with a pattern of natural variation known as the Atlantic Multi-decadal Oscillation (AMO). However, previous AMO indices are conflated with linear trends and a revised AMO index accounts for between 0 and 0.1°C of the 2005 SST anomaly. About 0.45°C of the SST anomaly is common to global SST and is thus linked to global warming and, based on regression, about 0.2°C stemmed from after-effects of the 2004–05 El Niño."


    Elsner JB (2006) Evidence in support of the climate change - Atlantic hurricane hypothesis Geophysical Research Letters 33 L16705

    Abstract: "The power of Atlantic tropical cyclones is rising rather dramatically and the increase is correlated with an increase in the late summer/early fall sea surface temperature over the North Atlantic. A debate concerns the nature of these increases with some studies attributing them to a natural climate fluctuation, known as the Atlantic Multidecadal Oscillation (AMO), and others suggesting climate change related to anthropogenic increases in radiative forcing from greenhouse-gases. Here tests for causality using the global mean near-surface air temperature (GT) and Atlantic sea surface temperature (SST) records during the Atlantic hurricane season are applied. Results show that GT is useful in predicting Atlantic SST, but not the other way around. Thus GT "causes" SST providing additional evidence in support of the climate change hypothesis. Results have serious implications for life and property throughout the Caribbean, Mexico, and portions of the United States."
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  18. Thanks Chris, nice to have someone with more awareness of the current litterature to give us pointers.
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  19. Yes indeed, nothing like someone with "more awareness" to give us "pointers"... as long as those pointers are pointed in the right direction, right? :)
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  20. If you have other pointers, HS, by all means post the links, I've already invited you to do so earlier on this thread.
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  21. http://www.newscientist.com/article/dn10796-global-warming-link-to-hurricanes-likely-but-unproven.html

    http://www.newscientist.com/article/dn13226-hurricane-study-whips-up-a-storm.html

    "Global warming is likely to affect cyclones and hurricanes, concludes a new statement from 125 experts, but they say the evidence for this to date is inconclusive."

    "There could be an effect but it's impossible to say for sure," says Julian Heming of the UK Met Office. The statement was issued at the end of a workshop organised by the World Meteorological Organization (WMO).

    "The workshop concluded that the increasing economic damage caused by tropical cyclones is to a large extent the result of "increasing coastal populations […] and, perhaps, a rising sensitivity of modern societies to disruptions of infrastructure"."

    Some of the debate centres around our ability to detect hurricanes which has improved markedly since the deployment of sateliites and would thus affect our perception of hurricane numbers and intensity.
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  22. Thanks for the assist Mizimi!
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  23. Noteworthy: Global and Northern Hemisphere Tropical Cyclone Activity [still] lowest in 30-years
    IMO
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  24. Perhaps this is a bit OT, but I'm wondering if, from the above graph and text, any qualitative inferences can be made about the _apparent_ recent increase in extreme weather events around the world. In an Amazon Discussion (of all places), I suggested that one could not prove that the flooding in North Dakota was due to GW or due to global cooling, if that's your predisposition. My uncertainty: is weather (worldwide) is now truly more dynamic, or does weather simply appear to be so, due to better/more reporting of extreme weather events.

    Any comments or links that may help provide some insight are welcome.
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  25. #24

    The graphs at the website QM points to in #23 show a steep decline in cyclone activity in both hemispheres
    ( if you go to the bottom of the page both hemispheres are shown over a time series from 1970 to 2009).
    This suggests that there is decreasing overall energy in the climate system as both the frequency and intensity have fallen to historic lows. This correlates ( at face value) with satellite data showing a cooling trend over the last decade. So one might argue that weather is becoming less dynamic...but the sensitivity of our instrumentation has improved and the sensitivity of our societies to weather based disruption has increased..so it 'seems' the weather is more dynamic.
    One possibility that may give some further insight is to access a meteorological database that logs windspeed and use that as an indicator.
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  26. Some Science!

    Global warming theory actually predicts strongest warming in the Arctic and secondary the Antarctic, with little change in middle to lower latitudes for several years, or decades.

    The idea that mid latitude storm intensities, tropical system enhancement, and severe weather events would be minimal due to less baroclinic stress (a decrease in solenoids) or less atmospheric density differences over a horizontal distance, ...if CO2 were actually causing major changes in the atmosphere.

    If such changes are taking place, must be from other forcing factors (maybe solar intensity fluctuations, and related magnetic flux changes).

    The weather should, at least if we assume CO2 warming is dominating, becomes more benign, with some trend toward increased moisture in the normally dry Arctic. Mid latitudes will be largely unaffected, and the tropic certainly not affected.

    The numerical models all, I repeat ALL, have parameterized processes that are very subjective,not directly included in the quasigeostrophic computations, and contribute strongly to errors in the computational output of said models. Algebraic coefficents, or fudge factors, then become necessary, largely ruining the value of the forecasts.
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