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What is the link between hurricanes and global warming?

What the science says...

Select a level... Basic Intermediate

There is increasing evidence that hurricanes are getting stronger due to global warming.

Climate Myth...

Hurricanes aren't linked to global warming

“According to the National Hurricane Center, storms are no more intense or frequent worldwide than they have been since 1850. […] Constant 24-7 media coverage of every significant storm worldwide just makes it seem that way.” (Paul Bedard)

The current research into the effects of climate change on tropical storms demonstrates not only the virtues and transparency of the scientific method at work, but rebuts the frequent suggestion that scientists fit their findings to a pre-determined agenda in support of climate change. In the case of storm frequency, there is no consensus and reputable scientists have two diametrically opposed theories about increasing frequencies of such events.

The background to these enquiries stems from a simple observation: extra heat in the air or the oceans is a form of energy, and storms are driven by such energy. What we do not know is whether we might see more storms as a result of extra energy or, as other researchers believe, the storms may grow more intense, but the number might actually diminish.

What do the records show? When this rebuttal was first published in 2010, the Pew Centre stated, “Globally, there is an average of about 90 tropical storms a year”. The IPCC AR4 report (2007) says regarding global tropical storms: "There is no clear trend in the annual numbers [i.e. frequency] of tropical cyclones."

But this graph, also from the Pew Centre, shows a 40% increase in North Atlantic tropical storms over the historic maximum of the mid-1950, which at the time was considered extreme:

But while the numbers are not contested, their significance most certainly is. Another study considered how this information was being collected, and research suggested that the increase in reported storms was due to improved monitoring rather than more storms actually taking place.

And to cap it off, two recent peer-reviewed studies completely contradict each other. One paper predicts considerably more storms due to global warming. Another paper suggests the exact opposite – that there will be fewer storms in the future.

What can we conclude from these studies? About hurricane frequency – not much; the jury is out, as they say. About climate change, we can say that these differing approaches are the very stuff of good science, and the science clearly isn’t settled! It is also obvious that researchers are not shying away from refuting associations with climate change, so we can assume they don’t think their funding or salaries are jeopardised by research they believe fails to support the case for AGW. The scientific method is alive and well.

Never mind the frequency, feel the width

So far, all we’ve managed is to document here is what we don’t know for sure yet. But we do know there is extra energy in the system now, so could it have any other effects on tropical storms? Here, the science is far less equivocal, and there is a broad consensus that storms are increasing in strength, or severity. This attribute, called the Power Dissipation Index, measures the duration and intensity (wind speed) of storms, and research has found that since the mid-1970s, there has been an increase in the energy of storms.

Recent research has shown that we are experiencing more storms with higher wind speeds, and these storms will be more destructive, last longer and make landfall more frequently than in the past. Because this phenomenon is strongly associated with sea surface temperatures, it is reasonable to suggest a strong probability that the increase in storm intensity and climate change are linked.

Basic rebuttal written by GPWayne

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial


This rebuttal was updated by Judith Matz in September 2021 to replace broken links. The updates are a result of our call for help published in May 2021.

Last updated on 5 July 2015 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.


The image North Atlantic Tropical Storms and Observing Techniques is courtesy of Global Warming Art.

Emanuel's graph of PDI versus temperature was courtesy of Climate 411.

Further reading


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Comments 51 to 93 out of 93:

  1. David: In addition to the comments by Dikran and DSL, I should like to note that the additional energy in the system resulting from greenhouse warming is not evenly distributed, temporally or spatially. As such the potential exists for larger gradients leading to more intense storm activity, as suggested by the Intermediate version of this article and comment #47 (although as per that comment and the IPCC SREX more research is needed to confirm whether this is occuring).
  2. To Dikran: Look up "perpetual motion machine of the second kind." As I already said, it doesn't violate conservation of energy, it violates the second law--that entropy tends to increase, not decrease. For what it's worth, I have a doctorate in physics. To DSL: As you can see if you read what I wrote, I'm not claiming that the conclusion of the argument is wrong--I don't know if it is. I'm claiming that the argument is wrong. The argument didn't say that global warming would occur more in hotter air than in cooler air, which is what your argument would require--whether it's true I don't know. It said that because there was more thermal energy available, storms would be either more frequent or stronger. That's bad physics, for the reason I explained.
  3. "For what it's worth, I have a doctorate in physics."
    That's a crap argument. And I've heard many.
    "it doesn't violate conservation of energy, it violates the second law"
    If you are going to argue the 2nd Law meme, take it to the appropriate thread.
  4. David Friedman @48, a hurricane is formed by updrafts forming over warm waters. The updraft carries warm water vapour to high altitudes, cooling it in the process. This progressively condenses the water vapour, releasing latent heat. The release of latent heat slows the cooling of the air in the updraft which is cooling due to adiabatic expansion as it rises. This allows the air to rise faster, increasing the rate at which fresh water vapour is drawn into the system and hence strengthening the storm. Should a hurricane pass over land, the lack of water vapour being drawn into the updraft results in a rapid weakening of the storm. With increased heat, there is more water vapour in the atmosphere. This preferentially strengthens storms because in stable air or downdrafts, there is little condensation of water,and hence little release of latent heat. Given this, the brief description in the basic rebuttal is true, if simplistic. It does not constitute a fallacious argument, as you maintain, because it is not an argument. The reason it is not an argument is because there are other significant factors, and it is unclear what the actual effect of this additional available energy in the form of increased water vapour will have. It merely points out that increased energy may have one of (at least) two potential effects without detailing the mechanisms involved.
  5. Daniel, I dont think David is arguing that "AGW violates the 2nd Law" which is loony tunes stuff. I believe is arguing the mechanism proposed in the article for hurricane formation violates 2nd Law. However, it isnt clear to me why David thinks the argument of "more thermal energy in the atmosphere can create bigger storms" violates second law. The article notes empirical evidence but for discussion of the physical evidence then that cites for: Emanuel, K. (2005), Increasing destructiveness of tropical cyclones over the past 30 years, Nature, online publication; published online 31 July 2005 | doi: 10.1038/nature03906 Knutson, T. K., and R. E. Tuleya, 2004: Impact of CO2-induced warming on simulated hurricane intensity and precipitation: Sensitivity to the choice of climate model and convective parameterization. Journal of Climate, 17(18), 3477-3495. in scholar might be worth looking at.
  6. I agree with David that the statement is factually incorrect. A hurricane is a Carnot heat engine, and its efficiency e is dictated by the ratio of the temperature between the heat source (T_H) and heat sink (T_C) i.e. e = 1- T_C/T_H The Carnot engine is the most efficient engine you can have within the limits of the second law. If both T_C and T_H increase with T_C increasing more, you will end up in a situation where more thermal energy actually results in less energy available to the storm itself. The conclusion "more energy to drive storm" therefore violates the second law. Fortunately of course the Tropopause is cooling and the surface is warming, so T_C/T_H is decreasing and the efficiency is going up, and therefore the conclusion holds. The reasoning should however be adjusted I think.
  7. David Friedman Looking up perpetual motion machine of the second kind gives "2. Also called perpetual motion of the second kind motion of a hypothetical mechanism that derives its energy from a source at a lower temperature. It is impossible in practice because of the second law of thermodynamics. I'm pretty sure that the energy source (the sun) is at a higher temperature than the Earth. ;o) According to Wikipedia, "A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. ..." Well I have a Crookes' radiometer in my workshop, which does just that, so there must be more to it than that. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However it does violate the more subtle second law of thermodynamics (see also entropy). The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics. As Tom points out, storms are formed by updrafts over warm water that take warm moist air up higer into the atmosphere, which is cooler. Thus there is no contravention of the second law of thermodynamics, as far as I can see. Your PhD in physics means very littlle. I have a PhD as well, and I am an active researcher in my own field (essentially statistics), and have a h-index over 20. Does that mean that my arguments on statistics have any greater strength than if they came from somebody else? No not really. There is also the point that the authors of the papers on which this article is based also have PhDs, and more importantlty are also experts on this particular topic. You would be better off explaining your scientific objection in more detail in a more moderate manner, the postuting does you no favours at all, it just isn't the way science should be done.
  8. Phil, since David is either being purposefully obtuse or simply unclear, I clarified my assessment with "if". Hence, if the root argument he makes is based on a misunderstanding of the greenhouse effect, the comments could then stay here or go to one of the more applicable GHE threads. If it is based on a misunderstanding of the applicability of the 2nd Law, then it should go as directed. Either way, my comment holds.
  9. Dikran, Kelvin's version of the second law states that No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work. i.e. some of the heat extracted from the warm source must be transferred into the cooler reservoir. Effectively the 2nd law states that not only do you need a cold reservoir to receive the heat that is not converted to work, there is also an upper limit to how much work you can extract. Any statement indicating otherwise amounts to a violation of the second law, and any machine that is more efficient then what 2nd law allows is a perpetual machine. Having a cooler reservoir is necessary but not sufficient to comply with the second law. You also have to make sure that the machine does not do more work than the second law allows.
  10. cheers Ian, you do a much better job of explaining the issue! It seems to me one of those things where a straightforward presentation for the general public isn't actually the whole truth, but is enough to convey the basic idea. Perhaps there needs to be an advanced version of the post?
  11. I still don't see where the comment in question: "The background to these enquiries stems from a simple observation: extra heat in the air or the oceans is a form of energy, and storms are driven by such energy. What we do not know is whether we might see more storms as a result of extra energy or, as other researchers believe, the storms may grow more intense, but the number might actually diminish." is claiming that "all energy" is being converted to mechanical. 1. The background to these enquiries stems from a simple observation. 2. extra heat in the air or the oceans is a form of energy 3. and storms are driven by such energy. 4. What we do not know is whether we might see more storms as a result of extra energy 5. or, as other researchers believe, the storms may grow more intense, but the number might actually diminish. Is it in point 3, the "such" of which I read as "increased lower trop and sea surface temp"?
  12. Dikran, Yes it is really a subtle point, and I probably won't have picked it up either if David hadn't point out the problem. However no matter how simple the argument is, I agree that the argument should be as accurate as possible. Given that the strength of a hurricane theoretically depends on temperature contrast between the surface and tropopause, rather than the temperature itself, we should make that clear. I suggest that instead of "extra heat in the air or the oceans is a form of energy, and storms are driven by such energy", we can replace it with "due to the greenhouse effect, the surface is warming relative to the top of the atmosphere, which in turn increases the amount of energy available for driving hurricanes." I believe it is consistent with the physics, yet avoids the need to discuss the thermodynamics. An advance version, where the thermodynamics can be examined in greater detail, will certainly be useful. When I attended a talk given by Kerry Emanuel a few months ago I was quite fascinated by the theory, and found thermodynamics to be interesting for once!
  13. To IanC--thank you for understanding the argument. While I'm correcting the page, there is a related but still more subtle error on it: "Recent research has shown that we are experiencing more storms with higher wind speeds, and these storms will be more destructive, last longer and make landfall more frequently than in the past. Because this phenomenon is strongly associated with sea surface temperatures, it is reasonable to suggest a strong probability that the increase in storm intensity and climate change are linked." The mistake is in the "because" phrase. Since sea temperature and air temperature are not perfectly correlated, high sea temperature will correlate with a high difference between sea and air temperature. So the evidence doesn't tell us whether it is the sea temperature or the temperature difference that is related to storm intensity. This one is interesting partly because it echoes a famous error in economics. The Phillips Curve showed an inverse relation between inflation and unemployment--suggesting that by accepting some level of inflation one could hold down unemployment. When the attempt was made, it didn't work (hence "stagflation") because the real relation was not with the inflation level but the difference between the actual and anticipated level--and once a country maintained an inflation rate of (say) 5% for a while, people came to anticipate it, and the unemployment rate went back up.
  14. Curious if anyone's heard of this fellow and his paper on worldwide hurricane activity: Best I can tell, he's not actually a climate scientist and his paper isn't actually peer-reviewed, but Google his research links to about a thousand denier sites.
  15. Hurricanes Worldwide 1970-2012
    Based on data from Maue, RN (2011): Global Frequency . I have studied the development of the number of tropical cyclones during the years January 1970 through September 2012 divided into the Northern and Southern Hemisphere. I would like to thank R.N. Maue for collecting data on tropical cyclones and making data public.
    The reason why I have made this analysis is that there have been mistrust in the climate skeptical world to the predictions made by IPCC, and using the data from R.N. Maue it should be possible retrospectively to verify or falsify the prediction made using elementary statistical tools. In addition to this, I was not aware of the differences found below between the Northern and Southern Hemisphere.
    The following graph shows the development of the number of tropical cyclones for the years January 1970 through September 2012.
    Please use zoom to see details.
    The number of Major Hurricanes is significantly growing in the Northern Hemisphere and the Southern Hemisphere, while the Tropical Storms are significantly decreasing in the Southern Hemisphere.
    This is in line with IPCC’s prediction of increasing number of Major Hurricanes and a decreasing number of Tropical Storms.
    Since hot sea water is the fuel for tropical cyclones, I understand why we will see an increasing number of Major Hurricanes. But I do not understand why the number of Tropical Storm is expected to decrease in the future as they already have done.
    There is a positive correlation between then number of Tropical Storm, Hurricane and Major Hurricane within the Northern Hemisphere and the Southern Hemisphere respectively.
    If you look at a shorter time span than 43 years, other observations could be made. For the years 2009-2012 the number of tropical cyclones is smaller than expected. However, 4 years are a too few years to put forwards a statement on a general trend. Please be aware that 2012 only includes 9 month so far.
    There is an apparent difference in the development of the number of tropical cyclones in the Northern and Southern Hemisphere. There is more tropical cyclone in the Northern Hemisphere, approx. 68% out of the total number of tropical cyclones.
    The following picture shows some of the differences between the Northern and Southern Hemisphere in respect of tropical cyclones:
    The tropical cyclone prone area is much large in Northern Hemisphere than in the Southern Hemisphere.
    When you look at number of Major Hurricanes per month, it appears that there is a remarkable difference in their distribution per month. In the following graph, I have shifted the month to produce frequency distribution by season.
    The number of Major Hurricanes for the Northern Hemisphere shows a left skew distribution with a gradually decreasing trend after the peak at the month of September, while the number of Major Hurricanes for the Southern Hemisphere shows a more abrupt decreasing trend after the peak at the month of March.
    The tropical cyclone season is 12 months for the Northern Hemisphere and 9 months for the Southern Hemisphere.
    There is a 6 and 12 month cyclic variation in the number of tropical cyclones. This follows from the seasonal shift between the Northern and Southern Hemisphere and from a spectral analysis not shown here. The following graph shows the number of Tropical Storms worldwide for the years 2000-2012 by month:
    I have used a generalized linear model with a linear trend and two harmonic terms with a cycle and 6 and 12 month to respectively in order to produce the graph above.
    Please use zoom to see details.
    The variation originates from merging the figures from the Northern and Southern Hemisphere, each with its own cyclic variations. The model explains 65% of the total variation. There is no significant trend and approx. 87 Tropical Storms are expected annually.
    In total the number of tropical cyclones in the Southern Hemisphere makes up 32% of the total number of tropical cyclones.
    The tropical cyclones prone area in the Southern Hemisphere makes up 42% of the total tropical cyclones prone area. This number is found by counting 5 * 5 degree squares on the map page 505 Marine Safety Information Chapter 35 Tropical Cyclones where tropical cyclones occur. As a first guess, this is probably OK to do so, but a better estimate is wanted.
    The number of tropical cyclones in the Southern Hemisphere, calculated in proportion to tropical cyclone prone area, equals 0.42*6690= 2803. The actual number is 2134. This is significantly lower.
    This leads to the following questions? 1) Why is the tropical cyclones prone area smaller in the Southern Hemisphere than in the Northern Hemisphere?
    2) Why is the number of tropical cyclones in the Southern Hemisphere in proportion to area smaller than the in the Northern Hemisphere?
    3) Are these findings in line with IPCC’s predictions?
    Atlantic cyclones - biased information As a result of the dominance of US based news media worldwide, the information about the tropical cyclones in the Atlantic region is more dominant than from the other parts of the world. This can lead to an incorrect understanding of trends and causes, since the number of tropical cyclones in the Atlantic region accounts for only 12.6% of the total number of tropical cyclones. The Atlantic Tropical Storms, Hurricanes and Major Hurricanes accounts only for 13.1 %, 12.7 % and 10.8 % of the total number of Tropical Storms, Hurricanes and Major Hurricanes respectively.
    More details can be found in the statistical analysis of tropical cyclone data from R.N.Maue Worldwide Hurricane analysis.
  16. Seems like this thread is in need of some updating.

    Here's the most recent news :

    ~ ~ ~ ~ ~ ~ ~ 

    Recent intense hurricane response to global climate change
    Greg Holland, Cindy L. Bruyère  |  March 2013,

    An Anthropogenic Climate Change Index (ACCI) is developed and used to investigate the potential global warming contribution to current tropical cyclone activity. The ACCI is defined as the difference between the means of ensembles of climate simulations with and without anthropogenic gases and aerosols. This index indicates that the bulk of the current anthropogenic warming has occurred in the past four decades, which enables improved confidence in assessing hurricane changes as it removes many of the data issues from previous eras. We find no anthropogenic signal in annual global tropical cyclone or hurricane frequencies.

    But a strong signal is found in proportions of both weaker and stronger hurricanes: the proportion of Category 4 and 5 hurricanes has increased at a rate of ~25–30 % per °C of global warming after accounting for analysis and observing system changes.

    This has been balanced by a similar decrease in Category 1 and 2 hurricane proportions, leading to development of a distinctly bimodal intensity distribution, with the secondary maximum at Category 4 hurricanes.

    This global signal is reproduced in all ocean basins. The observed increase in Category 4–5 hurricanes may not continue at the same rate with future global warming. The analysis suggests that following an initial climate increase in intense hurricane proportions a saturation level will be reached beyond which any further global warming will have little effect.

    Full article:

  17. Klaus @ 65, I think yet the answer to your questions 1 and 2 is to be found in the Sea Surface Temperature. This map of SST shows that the hurricanes appear, as expected, in the warmest areas :Sea Surface Temperature


    [DB] Reduced image width to 450.  Click on image for larger version.

  18. A new denialist argument that I'm seeing more and more is that because the USA experienced fewer hurricanes in 2013 than in some previous years, global warming has stopped or is disproven!

  19. That is such a collossal disconnect in logic that words fail me...

  20. My analysis of the number of tropical storms only covers the period 1970-2012. This is the weak point, as far as I do not have data going back further. Therefore, I do not know if the development is caused by natural variations or if it is a result of the global warming. However the development is in line with the expectation from the global warming.

  21. The graph of North Atlantic cyclone numbers in the post could do with updating. The 10-year average has concinued to rise and now sits above 16 per year.

    Atlantic cyclone numbers

    N Atlantic hurricane numbers & major hurricane (catagory 3+) numbers have also risen but less dramatically and have presently their own little "hiatus." Add the argument about unreliable data prior to the 1970s, and it is difficult to establish with any certainty an AGW signal above the 'natural cycles'. The same goes for N Atlantic Accumulated Cyclone Energy (see here - usually 2 clicks to 'download your attachment').

    Globally, beyond the N Atlantic,  the data is even less reliable prior to 1970 (as Klaus Flemløse @70 would likely agree). So that Atlantic tropical cyclone graph is a bit of a rare beast.

  22. This is in response to the unfolding disasters in the Carribean and Florida and the fact that this thread is a little out of date.

    Recent relevant update from NOAA:

    It seems that fresh data and recent analysis haven't changed things much.

  23. On further reflection, it appears that NOAA is suggesting that frequency is essentially constant and intensity is (may be?) increasing over time.

  24. The article linked to by SingletonEngineer has been repeatedly cited and linked to by more than one mainstream climate scientist who has been interviewed by the media about the climate change-hurricane* connection in recent articles about Hurricanes Harvey, Irma, Jose, and Katia.

    Global Warming and Hurricanes: An Overview of Current Research Results posted on the website of NOAA’s Geophysical Fluids Dynamics Laboratory (GFDL). It was last revised on Aug 30, 2017.

    *North Atlantic basin only.

  25. Over the past couple of weeks, I have posted links to the following articles about the climate change-hurricane connection on the SkS Facebook page.

    Did Climate Change Intensify Hurricane Harvey? by Robinson Meyer, The Atlantic, Aug 27, 2017

    Climate change did not “cause” Harvey, but it’s a huge part of the story by David Roberts, Energy & Environment, Vox, Aug 28, 2017

    Could Hurricane Harvey Deal A Fatal Blow To Climate Change Skepticism? by Jared Keller, Pacific Standard, Aug 28, 2017

    Harvey Shows How Planetary Winds Are Shifting by Eric Roston, Bloomberg News, Aug 30, 2017

    Does Harvey Represent a New Normal for Hurricanes? by Robinson Meyer, The Atlantic, Aug 29, 2017

    Katrina. Sandy. Harvey. The debate over climate and hurricanes is getting louder and louder by Chris Mooney, Energy & Environment, Washington Post, Aug 30, 2917

    What Hurricane Harvey says about risk, climate and resilience by Andrew Dressler, Daniel Cohan & Katharine Hayhoe. The Conversation US, Sep 1, 2017

    Three things we just learned about climate change and big storms: Can the lessons of Harvey save us? by Paul Rosenberg, Salon, Sep 4, 2017

    Denying Hurricane Harvey’s climate links only worsens future suffering by Dana Nuccitelli, Climate Consensus - the 97%, Guardian, Sep 5, 2017

    Harvey and climate change: why it won't change minds by Amy Harder, Axios, Sep 5, 2017

    Hurricane Harvey's aftermath could see pioneering climate lawsuits, Analysis by Sebastien Malo, Thomson Reuters Foundation, Sep 5, 2017

    On Climate, Hurricanes, And Growth by Joseph Majkut, Niskanen Center, Aug 31, 2017

    First Harvey, now Irma. Why are so many hurricanes hitting the U.S.? by Nisikan Akpan, PBS News Hour, Sep 6, 2017

    The science behind the U.S.’s strange hurricane ‘drought’ — and its sudden end by Chris Mooney, Energy & Environment, Washington Post, Sep 7, 2017

    Hurricane Irma is one of the most powerful Atlantic hurricanes ever: what we know by Brian Resnick, Science & Health, Vox, Sep 7, 2017

    6 Questions About Hurricane Irma, Harvey and Climate Change by Sabrina Shankman, InsideClimate News, Sep 6, 2017

    President Trump, hurricanes Harvey and Irma are sending you a message, Opinion by Andrés Oppenheimer, Miami Herald, Sep 7, 2017

    What We Know about the Climate Change–Hurricane Connection by Michael E. Mann, Thomas C. Peterson & Susan Joy Hassol, Scientific American, Sep 8, 2017

    As Hurricanes Irma and Harvey Slam the U.S., Climate Deniers Remain Steadfast by Marianne Lavelle, InsideClimate News, Sep 8, 2017

    Ask the Experts: How Did 2 Such Powerful Hurricanes Occur Back to Back? by Annie Sneed, Scientific American, Sep 7, 2017

    Another Way Climate Change Might Make Hurricanes Worse by Faye Flam, Bloomberg News, Sep 8, 2017

    Will Irma Finally Change the Way We Talk About Climate? by David Wallace-Wells, Daily Intelligencer, New York Magazine, Sep 9, 2017

    Irma and Harvey lay the costs of climate change denial at Trump’s door by Bob Ward, The Observer/Guardian, Sep 9, 2017

    Hurricane Irma Linked to Climate Change? For Some, a Very ‘Insensitive’ Question. by Lisa Friedman, Climate, New York Times, Sep 11, 2017

  26. More articles of note:

    Four little discussed ways that climate change could make hurricanes even worse by Chris Mooney, Energy & Environment, Washington Post, Sep 11, 2017

    How global warming could push hurricanes to new regions by Bob Berwyn, Pacific Standard, Sep 11, 2017

    'I Don't Expect The Season To Be Done': A Hurricane Expert On What's Still To Come by Kate Wheeling, Pacific Standard, Sep 12, 2017

  27. A new article with some background at Science of Doom:

    Impacts – XIV – Tropical Cyclones and Climate Change 1

    Kevin Walsh and coauthors in 2016: "At present, there is no climate theory that can predict the formation rate of tropical cyclones from the mean climate state"

    In general, relative SST (local sea surface temperature minus the tropical mean sea surface temperature) being more important than absolute SST for TC development has the weight of climate scientists behind it. 

    Climate models struggle to reproduce the more intense TCs (tropical cyclones) in the recent climate and papers come with many caveats about the difficulties of predicting the future.

  28. Another argument about gw and hurricanes is that the latter will work as a negative/damping feedback on the former, since hurricanes transfer energy out to space (among other places), and the more intense the hurricanes become, the more energy they will transfer. I'm trying to find reliable numbers to show that to the extent that this might happen, it is insignificant compared to the approximately half-million A-bombs worth of extra energy ghg's are preventing from gettin into space every day.

    I don't see this in the already-long list of denialist arguments, but maybe I missed it?

  29. wili @78,

    I did have some useful NOAA(?) numbers for the energy fluxes associated with tropical cyclones but they are not falling to hand. However there is literature that presents data. Although this is a bit less authoritative-looking, the literature (& this is from papers to hand rather than from a proper search) does seem quite definitive that hurricanes act to warm the planet rather than cool it although the mechanisms are not that simple.

    Tropical cyclones do simplistically pump energy out of the ocean which will cool the planet. They also mix warm surface waters down into the ocean which, as the post-cyclone surface is cooler and thus easier to warm, will allow ocean warming. (These hurricane-warmed ocean depths won't just sit there but will enhance poleward heat fluxes, as discussed below.) The net size of the ocean-atmosphere flux from global tropical cyclones has been assessed globally using ARGO data at +1.9PW during the passage of storms but becomes a net negative -0.3PW when subsequent enhanced warming following the storm is included. The global figures when divided between hurricanes and lesser storms shows that it is hurricanes which are responsible for the net total being negative (Net total for just hurricanes equals 0.75PW cooling = a global 1.5Wm^-2), with 0.8PW of ocean cooling during the storm but followed by 1.5PW of subsequent ocean warming. For lesser storms the net ocean cooling remains positive 1.0PW cooling during the storm with 0.6 subsequent warming. This suggests that in a world with more hurricanes but fewer less-powerful tropical storms (a possibility that many denialists deny), there will be as a result bigger heat fluxes into the oceans.

    A further mechanism for cooling the planet is that the ocean mixing caused by tropical cyclones will impact poleward heat transfer to some extent, enhancing it in the oceans, reducing it in the atmosphere. But when the effect is set up in a climate model, the impact becomes a net warming effect due to the spread of humid atmospheres and such-like. So, of the ~2ºC global warming resulting from poleward heat fluxes (which are roughly 5 PW in each direction), perhaps some 0.2ºC results from tropical cyclones and would be boosted by increased cyclone activity. (That could be equated to a climate forcing using ECS=3 of +0.25Wm^-2).

    So in terms of A-bombs, the increase in that +0.25Wm^-2 of warming from today's tropical cyclones will be small and will also be A minus.

  30. Recommended supplemental readings...

    How to talk about hurricanes now by John D Sutter, Health, CNN, Oct 10, 2018

    The Hurricanes, and Climate-Change Questions, Keep Coming. Yes, They’re Linked. by Henry Fountain, Climate, New York Times, Oct 10, 2018

    Is climate change making hurricanes worse? by Daniel Levitt & Niko Kommenda, Weather, Guardian, Oct 10, 2018

    Yes, Hurricane Michael is a climate change story by Pete Vernon, Columbia Journalism Review (CJR), Oct 12, 2018

    Note: The Daniel Levitt & Niko Kommenda article include outstanding graphics. 

  31. Did anyone here respond to the recent article in Nature apparently documenting that hurricanes in the US have shown no trend, either in frequency or intensity or (the authors' index of) damage caused?

    And while I'm asking, recently published a compilation of stats on global cyclones that seems to show the same pattern so far globally. (This one NOT peer reviewed or published in maybe the most prestigious scientific journal.) 

  32. Sorry, rookie error. I refreshed the page to see if anything had changed and my browser entered my post again. And I don't see how to delete the duplicate. 


    [DB] While the moderators usually notice, should it happen again just ask for the duplicate to be removed.

  33. Norm Rubin,

    Can you link the article you are talking about so we can find it?

  34. @ Norm Rubin #82

    Here's one response to pseudo-science poppycock written by Paul Homewood and posted on the GWPF website:

    GWPF’s “Incoherent” Climate Reports Misrepresent IPCC; Chairman’s Resignation Unrelated, ClimateDenierRoundup, DailyKos, Jan 18, 2019

  35. All I can find this minute is the abstract and citation  with the full text behind Nature's paywall. I thought I'd read it  but I've never paid for a Nature subscription is the link.

    And here's a paste of the contents, FWIW:

    Nature Sustainability
    Analysis | Published: 26 November 2018

    Normalized hurricane damage in the continental United States 1900–2017
    Jessica Weinkle, Chris Landsea, […]Roger Pielke Jr
    Nature Sustainabilityvolume 1, pages808–813 (2018) | Download Citation

    Direct economic losses result when a hurricane encounters an exposed, vulnerable society. A normalization estimates direct economic losses from a historical extreme event if that same event was to occur under contemporary societal conditions. Under the global indicator framework of United Nations Sustainable Development Goals, the reduction of direct economic losses as a proportion of total economic activity is identified as a key indicator of progress in the mitigation of disaster impacts. Understanding loss trends in the context of development can therefore aid in assessing sustainable development. This analysis provides a major update to the leading dataset on normalized US hurricane losses in the continental United States from 1900 to 2017. Over this period, 197 hurricanes resulted in 206 landfalls with about US$2 trillion in normalized (2018) damage, or just under US$17 billion annually. Consistent with observed trends in the frequency and intensity of hurricane landfalls along the continental United States since 1900, the updated normalized loss estimates also show no trend. A more detailed comparison of trends in hurricanes and normalized losses over various periods in the twentieth century to 2017 demonstrates a very high degree of consistency.

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    Nature Sustainability
    ISSN 2398-9629 (online)

    NatureAbout us [clipped...] 

    I believe the item linked in post 84 is aimed at the second item I was asking about  


    [DB] A full copy is here.

  36. Norm Rubin,

    I am not an expert on hurricanes but I read some.

    Nature Sustainability is not the same journal as Nature.  It is less prestigious.

    These authors have been making this argument for a long time.  From what I have read it appears that they are in the minority but there is not a consensus on this topc.

    Analysis of USA only data seems inappropriate to me. There are not many hurricanes and the record is noisy.  The USA is only 3% of the Earth's surface.  You would expect that noise would be bigger than the signal.

    This article documents that strong hurricanes (force 4 and 5) have increased in number over the entire Earth.  They reference at least 4 other papers that find an increase in the most powerful hurricanes.  There appear to be less force 1 and 2 hurricanes so the total number of hurricanes is about the same.  There is much more signal to noise in an analysis of the entire Earth.  It stands to reason that if there are more force 4 and 5 hurricanes (which cause most of the damage), there will be more damage caused.  An analysis of world  wide damage for the past 40 years would be more meaningful than a USA only analysis with a longer record.

    The paper I cited claims that sea surface temperatures have only been elevated enough to affect hurricanes for 40 years so the earlier data in your cited paper is not as valuable.

    Jeff Masters discusses the catastrophic hurricanes that struck the USA in 2018.  He discusses modeling that attributes 50% of Florence's rainfall to warming.  Similar attribution has been made for Harvey's rainfall in Texas last year.

     To me it stands to reason that if there are more category 4 and 5 hurricanes and they produce twice as much rain due to warming than more damage will be caused by hurricanes.  There were several strong hurricanes at the start of the limited USA record analyzed in the Weinkle et al paper which affect the statistics.  

    I expect it to be a long time (decades) before the USA only record of hurricanes shows statistically significant change in hurricanes since there are so few and the record is noisy.  The worldwide record already shows increases in powerful hurricanes which cause the most damage. 

    I doubt there will be much commentary on this paper by scientists unless deniers make wild claims about it.  Since it is a valid paper if you choose to make the argument that hurricanes have not changed you can, but it is not a strong claim when the world record is examined.  The fact the US damage was so severe in 2018, after the Weinkle paper was published, is suggestive but not statistically significant yet.  

  37. Somewhat old now, but Pielke's work has been discussed over at Tamino's Open MInd in the past:

      Slightly newer discussion of hurrixcane frequency at RealClimate. The post presents some behaviour by Pielke that is, shall we say, not particularly flattering.

  38. Norm Rubin,

    The RealClimate link that Bob Loblaw has above shows that using only landfalling hurricanes reduces the available data by a factor of over 1000.  They specifically argue that this is an inappropriate method of data analysis because it allows the noise to overcome the signal.  It appears that the paper you cited has been prebunked.  I seem to have been too kind in my post.


    Thanks for the great links.  I see your posts on other sites.  Always well informed.

  39. Thanks folks, that's what I was looking for. More the science and stats part than the ad hominem stuff, since I was raised to be able to learn from a fool, and I also don't mind learning from people who are biased or sometimes wrong  I try to avoid tribalism in politics generally, and I find it especially rampant and ugly in the climate wars. 

    But it will take me a while to get through it all. 

    Just offhand, of course the US mainland is not nearly the whole world, but it's probably the part that's been keeping the best records of hurricanes for the longest. When you lose your keys in the dark, it may be smart to look first under the streetlights, type thing. Of course, of all possible statistical outcomes, a finding of no significant trend is most easily produced by a too-small sample, so I "get" the criticism. 

  40. Norm Rubin:

    Hot off the press:

    4 Climate-Influenced Disasters Cost the U.S. $53 Billion in 2018 by Daniel Cusick, E&E News/Scientific American, Jan 23, 2019

  41. GPWayne

    Thank you for the rebuttal regarding frequency of tropical storms.  Could you please comment on this 2017 article [Truchelut, R.E. and Staehling, E.M. 2017. An energetic perspective on United States tropical cyclone landfall droughts. Geophysical Research Letters 44: 12,013-12,019.] which is cited by climate skeptic websites?  It claims there was a drought of energetic hurricanes; i.e. hurricanes above a Cyclone Energy of 100 kt, from 2006 to 2015.  It also claims "a statistically significant downward trend since 1950, with the percentage of total Atlantic Accumulated Cyclone Energy (ACE) expended over the continental U.S. at a series minimum during the recent drought period."  On the face of it, ACE sounds like a good measure of hurricane activity.

    Thanks in advance for your response

  42. "a statistically significant downward trend since 1950, with the percentage of total Atlantic Accumulated Cyclone Energy (ACE) expended over the continental U.S. at a series minimum during the recent drought period."

    Current global ACE is 103% of normal.

    Whats Up With That???

    Denier blogs lie.  Do not trust them.

  43. Ritchieb,

    Strong hurricanes are not very common events.  The USA is only about 3% of world surface area.  You expect a lot of year to year variation in rare occurances measured over a small area.  That includes periods of lower activity.  The global trend is more very strong hurricanes (along with more weak hurricanes and less moderate hurricanes).

    From your reference: 

    "The 2017 Atlantic hurricane season has been extremely active both in terms of the strength of the tropical cyclones that have developed and the amount of storm activity that has occurred near the United States. This is even more notable as it comes at the end of an extended period of below normal U.S. hurricane activity, as no major (category 3 or higher) hurricanes made landfall from 2006 through 2016."

    If the deniers are claiming that there are less strong hurricanes hitting the USA because of AGW (or whatever reason they propose) they have to also note the large damages in the past three years.  I note that Hurricane Sandy was not a major hurricane when it hit New York and occured during the "Hurricane drought", along with other very damaging storms.  I doubt that New Yorkers consider 2012 a "major hurricane free" year.  In addition, hurricane forward speed has decreased worldwide causing much greater flooding (like Harvy, Barry and TS Imelda).  That appears to be AGW linked.  

    Scientifically it is interesting to seek explainations for unusual events. Random chance is the best explaination for this issue.

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