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Should the official Atlantic hurricane season be lengthened?

Filed under: — Jim Kossin @ 2 April 2021

By Jim Kossin, Tim Hall, Mike Mann, and Stefan Rahmstorf

The 2020 Atlantic hurricane season broke a number of records, with the formation of an unprecedented 30 “named storms” (storms that reach wind-speed intensity of at least 18 m/s and are then given an official name). The season also started earlier than normal. In fact, when ranked by their order in the season, the date of formation of every named storm, from Tropical Storm Arthur to Hurricane Iota was substantially earlier than normal (Fig. 1).

Fig. 1 Average number of named storms by day of the year in the historical record from 1851–2019 (dark blue line). The light blue shading denotes the range between the minimum and maximum number of storms observed by each day. The days of formation for the 2020 named storms are shown by the red squares.

In 2008, after a series of Atlantic hurricane seasons that began earlier than normal, a study was published that explored whether the anomalously early starts may be part of a larger trend (Kossin 2008). The results of that study identified increasing trends in the length of the active hurricane season, with storms forming earlier and later in the season than normal (Fig. 2), but there was quite a bit of uncertainty in the statistical significance of the trends, and additional uncertainty in the century-scale trends (red lines in Fig. 2) due to missing or uncertain data in the earlier part of the record. Still, regardless of statistical significance, there is clearly a very steep trend towards earlier storms in the past four decades (lower green line in Fig. 2), which represent a period of reliable data.

Fig. 2 Time series of the first and last day of storm formation in each season from 1851 to 2020 (lower and upper black lines, respectively) and their linear trends over the periods 1851–2020 (red), 1950–2020 (blue), and 1980–2020 (green).

The official start to the Atlantic hurricane season has been set at June 1st since the 1960s, but this steep trend toward earlier storm formation over the past four decades has spurred many discussions about modifying this date, and the World Meteorological Organization has recently proposed that the National Hurricane Center extend the official start of the hurricane season backwards by two weeks to May 15th. If this pronounced tendency toward earlier storms over the past four decades is defining a “new normal”, then extending the season backwards by two weeks seems entirely supportable. Furthermore, there’s no question that the season length is linked to Atlantic sea-surface temperature (SST), with the season starting about 15–20 days earlier and about 15–20 days later per °C of anomalous Atlantic warming (Kossin 2008).

But this also raises other questions: 1) Can we expect the season to continue to lengthen as global warming from increasing concentration of globally well mixed greenhouse gas (GWM-GHG) continues to warm the Atlantic SSTs? and 2) Is there any process that might drive the new normal back to the old normal, thereby reducing the season length? Answering these two questions is the goal of this article.

While season length is clearly linked to Atlantic SST, it’s not so clear that this is part of a longer-term trend linked to global warming. In fact, there is quite a bit of uncertainty regarding the effect of GWM-GHG warming on tropical storm formation. Although some modeling studies find an increase in storm frequency related to GWM-GHG warming (e.g., Emanuel 2021; Hall et al. 2021; Knutson et al. 2020), many others do not. And some studies actually predict a decrease in frequency of tropical storm formation, both globally and in the North Atlantic (all while allowing those storms that do form to become more intense and produce more rain) (Knutson et al. 2019). If SST warming due to GWM-GHG does reduce Atlantic formation rates, or does not increase them substantially, then there is no clear and obvious expectation that this warming should cause further lengthening of the season.

This answers our first question, at least as far as we can, given the uncertainty in what we know about how formation rates respond to global warming. The answer is no. This doesn’t mean that it won’t happen; only that we don’t understand the physical relationships well enough and we don’t have the consistent numerical modeling results to form a clear expectation.

The statement that GWM-GHG SST warming may not increase storm formation rates might appear incongruent with the earlier statement that the season is about 30–40 days longer on average per °C of anomalous SST warming. But it emphasizes an important point about the relationship between SST and hurricane behavior in general: The hurricane response to SST changes depends on what caused the SST changes (Emanuel and Sobel 2013). In particular, Atlantic SST warming caused by local forcing does increase Atlantic tropical storm formation rates, while Atlantic SST warming caused by increased GWM-GHG concentration may not. The difference is due largely to the differences in the regional atmospheric response that occurs in concert with the SST warming.

The key to understanding this lies in understanding what tropical storms respond to. In particular, they don’t just respond to SST changes, but also how the atmosphere changes as the SSTs change. For example, warming caused by GWM-GHG can cause the atmosphere in some regions to become more stable and drier in the mid-levels (Knutson et al. 2020), and can cause an increase in vertical wind shear over the Atlantic (Kossin 2017; Ting et al. 2019). All three of these factors have a powerful quelling effect on tropical storm formation. So it’s okay to say that SST warming will increase storm formation rates, all other things equal, but all other things are not equal. It depends on what’s driving the warming because the atmosphere will respond differently depending on the driver. The local atmospheric response to warming can be strong enough to actually reduce formation rates in some regions even while that same warming is increasing the local SST.

In the North Atlantic, examples of local SST warming mechanisms that can increase Atlantic storm formation rates are:

This brings us back to our second question: Is there any process that might drive the new normal back to the old normal, thereby reducing the season length? The external local forcing of Atlantic SST caused by decreasing sulfate and dust aerosols is bounded (concentration cannot become less than zero), so the resulting warming cannot be easily projected into the long term. It’s also (hopefully) unlikely that we would revert back to increasing sulfate pollution, so this doesn’t seem a likely candidate for a reversal of the warming trend. However, it is certainly possible that Saharan dust, which is carried over the Atlantic in the trade winds and exhibits variability on decadal to multidecadal timescales (Evan et al. 2016), could increase again in concentration. This would have a cooling effect on Atlantic SST, as well as a stabilizing effect on the regional atmosphere (Dunion and Velden 2004), and would be expected to reduce tropical storm formation frequency for some (possibly prolonged) period.

Internal AMOC variability has been argued to exhibit some decadal to multidecadal behavior (e.g., Zhang et al. 2016), in addition to a long-term decline (Caesar et al. 2021). But evidence for oscillatory internally-driven North Atlantic SST variability, sometimes referred to as an Atlantic Multidecadal Oscillation (AMO), is becoming increasingly challenged and disputed (e.g., Mann et al. 2020). If this variability is not oscillatory, then it is not predictable, and expectations that the “AMO should transition back to a cool phase soon” (e.g., Klotzbach et al. 2015) are not clearly supported. In fact, there is evidence that past observed decadal-to-multidecadal Atlantic SST variability, which is often considered to be the fingerprint of an internal AMOC oscillation (i.e., the AMO), may be entirely externally driven by volcanic eruptions (Mann et al. 2021). In this case, there is no reason to expect a transition to a period of cooler SST anytime soon, since there is no predictability in how volcanic eruptions will occur over these timescales. That being said, it is possible that the past cooling periods due to volcanic eruptions could occur again, just as it’s possible for Saharan dust concentrations to increase again, and either of these could plausibly cause a period of reduced Atlantic hurricane activity and season length.

This answers the second question. There is no clear support for expecting the season to begin to shrink for any extended period, except for the random chance that it could. That is, it’s not clear and is likely not predictable how the Atlantic regional drivers of tropical storm frequency, both internal and external, will vary in the immediate or long-term future.

As an important addendum to this discussion, the uncertainty in projected storm formation rates creates uncertainty in projections of risk in general because it introduces uncertainty into the typical measures of risk (e.g., return periods), which rely on absolute measures of storm frequency. We are much more confident that when a storm does form, it’s more likely to become stronger (and much more dangerous), which increases the proportion of strong storms (Knutson et al. 2019; Kossin et al. 2020). But translating this to an expectation of more strong storms (and thus shorter return periods), rather than proportionally more, must carry the extra uncertainty of storm frequency projections along with it. It’s a clear imperative at this time to continue to focus scientific resources on reducing these uncertainties.

To summarize, based on the observed increase in early-season tropical storm formation over the past 40+ years, a strong argument can be made for moving the official start of the hurricane season to May 15th, with the understanding that this may be the new normal and there is no oscillatory or predictable agent that might return things to the old normal anytime soon. For longer time-scales where GWM-GHG warming tends to dominate, there is no clear and obvious expectation, based on our present knowledge, that the Atlantic hurricane season should become progressively longer into the 21st century.


Jim Kossin is a NOAA / NCEI scientist.

Tim Hall is a NASA / GISS scientist.

Mike Mann and Stefan Rahmstorf are co-founders and regular authors of RealClimate.

Kerry Emanuel and Adam Sobel also provided helpful input.

References

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  2. K. Emanuel, "Response of Global Tropical Cyclone Activity to Increasing CO2: Results from Downscaling CMIP6 Models", Journal of Climate, vol. 34, pp. 57-70, 2021. http://dx.doi.org/10.1175/jcli-d-20-0367.1
  3. T.M. Hall, J.P. Kossin, T. Thompson, and J. McMahon, "U.S. Tropical Cyclone Activity in the 2030s Based on Projected Changes in Tropical Sea Surface Temperature", Journal of Climate, vol. 34, pp. 1321-1335, 2021. http://dx.doi.org/10.1175/JCLI-D-20-0342.1
  4. T. Knutson, S.J. Camargo, J.C.L. Chan, K. Emanuel, C. Ho, J. Kossin, M. Mohapatra, M. Satoh, M. Sugi, K. Walsh, and L. Wu, "Tropical Cyclones and Climate Change Assessment: Part II: Projected Response to Anthropogenic Warming", Bulletin of the American Meteorological Society, vol. 101, pp. E303-E322, 2020. http://dx.doi.org/10.1175/BAMS-D-18-0194.1
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  9. M.E. Mann, and K.A. Emanuel, "Atlantic hurricane trends linked to climate change", Eos, Transactions American Geophysical Union, vol. 87, pp. 233, 2006. http://dx.doi.org/10.1029/2006EO240001
  10. N.J. Dunstone, D.M. Smith, B.B.B. Booth, L. Hermanson, and R. Eade, "Anthropogenic aerosol forcing of Atlantic tropical storms", Nature Geoscience, vol. 6, pp. 534-539, 2013. http://dx.doi.org/10.1038/ngeo1854
  11. A.H. Sobel, S.J. Camargo, T.M. Hall, C. Lee, M.K. Tippett, and A.A. Wing, "Human influence on tropical cyclone intensity", Science, vol. 353, pp. 242-246, 2016. http://dx.doi.org/10.1126/science.aaf6574
  12. A.T. Evan, D.J. Vimont, A.K. Heidinger, J.P. Kossin, and R. Bennartz, "The Role of Aerosols in the Evolution of Tropical North Atlantic Ocean Temperature Anomalies", Science, vol. 324, pp. 778-781, 2009. http://dx.doi.org/10.1126/science.1167404
  13. M.E. Mann, B.A. Steinman, D.J. Brouillette, and S.K. Miller, "Multidecadal climate oscillations during the past millennium driven by volcanic forcing", Science, vol. 371, pp. 1014-1019, 2021. http://dx.doi.org/10.1126/science.abc5810
  14. A.T. Evan, C. Flamant, M. Gaetani, and F. Guichard, "The past, present and future of African dust", Nature, vol. 531, pp. 493-495, 2016. http://dx.doi.org/10.1038/nature17149
  15. J.P. Dunion, and C.S. Velden, "The Impact of the Saharan Air Layer on Atlantic Tropical Cyclone Activity", Bulletin of the American Meteorological Society, vol. 85, pp. 353-366, 2004. http://dx.doi.org/10.1175/BAMS-85-3-353
  16. R. Zhang, R. Sutton, G. Danabasoglu, T.L. Delworth, W.M. Kim, J. Robson, and S.G. Yeager, "Comment on "The Atlantic Multidecadal Oscillation without a role for ocean circulation"", Science, vol. 352, pp. 1527-1527, 2016. http://dx.doi.org/10.1126/science.aaf1660
  17. L. Caesar, S. Rahmstorf, A. Robinson, G. Feulner, and V. Saba, "Observed fingerprint of a weakening Atlantic Ocean overturning circulation", Nature, vol. 556, pp. 191-196, 2018. http://dx.doi.org/10.1038/s41586-018-0006-5
  18. M.E. Mann, B.A. Steinman, and S.K. Miller, "Absence of internal multidecadal and interdecadal oscillations in climate model simulations", Nature Communications, vol. 11, 2020. http://dx.doi.org/10.1038/s41467-019-13823-w
  19. P. Klotzbach, W. Gray, and C. Fogarty, "Active Atlantic hurricane era at its end?", Nature Geoscience, vol. 8, pp. 737-738, 2015. http://dx.doi.org/10.1038/ngeo2529
  20. J.P. Kossin, K.R. Knapp, T.L. Olander, and C.S. Velden, "Global increase in major tropical cyclone exceedance probability over the past four decades", Proceedings of the National Academy of Sciences, vol. 117, pp. 11975-11980, 2020. http://dx.doi.org/10.1073/pnas.1920849117

29 Responses to “Should the official Atlantic hurricane season be lengthened?”

  1. 1
    J Doug Swallow says:

    I’m not sure if this report from NOAA fits well into the narrative that Tim Hall, Mike Mann, and Stefan Rahmstorf want for folks to believe. Since Jim Kossin is with NOAA, he is aware of this report, I hope.
    F. Summary for Atlantic Hurricanes and Global Warming
    In summary, neither our model projections for the 21st century nor our analyses of trends in Atlantic hurricane and tropical storm activity support the notion that greenhouse gas-induced warming leads to large increases in either tropical storm or overall hurricane numbers in the Atlantic. While one of our modeling studies projects a large (~100%) increase in Atlantic category 4-5 hurricanes over the 21st century, we estimate that such an increase would not be detectable until the latter half of the century, and we still have only low confidence that such an increase will occur in the Atlantic basin, based on an updated survey of subsequent modeling studies by our and other groups. A recent study finds that the observed increase in an Atlantic hurricane rapid intensification metric over 1982-2009 is highly unusual compared to one climate model’s simulation of internal multidecadal climate variability, and is consistent in sign with that model’s expected long-term response to anthropogenic forcing. These climate change detection results for rapid intensification metrics are suggestive but not definitive, and more research is needed for more confident conclusions. A slowing of tropical cyclone propagation speeds over the continental U.S. has been found since 1900, but its cause remains uncertain.
    Therefore, we conclude that it is premature to conclude with high confidence that increasing atmospheric greenhouse gas concentrations from human activities have had a detectable impact on Atlantic basin hurricane activity, although increasing greenhouse gases are strongly linked to global warming. (“Detectable” here means the change is large enough to be distinguishable from the variability due to natural causes.)
    https://www.gfdl.noaa.gov/global-warming-and-hurricanes/

  2. 2
    Mitch says:

    I am not certain why Doug Swallow (#1) posted that information since it doesn’t bear on the length of hurricane season. The first storm will form when becomes warm enough in the late spring to develop a cyclone, and when a stable lower atmospheric layer is not present.

    We need to look at the reason for a hurricane season. It is an announcement to the public of the time frame that they need to be ready to face a hurricane. With that in mind, it is better to extend the season. It can always be adjusted back if further information comes to light.

  3. 3
    Piotr says:

    Mitch(2) I am not certain why Doug Swallow (#1) posted that information since it doesn’t bear on the length of hurricane season. The first storm will form when becomes warm enough in the late spring to develop a cyclone, and when a stable lower atmospheric layer is not present

    That’s because the Occam’s Razor suggests that “J. Doug Swallow” is an AI program.

    Ask your self – what is a simpler explanation
    a) that we have an actual HUMAN, STUPID ENOUGH to think that CO2, thanks to the higher molecular weight, falls to the ground (proving that there is Intelligent Designer) AND AT THE SAME TIME able to write DOZENS long posts weekly, covering diverse aspects of climatology and biogeochemical cycles, keep track of the current deniers talking points and the links they used to the scientific literature, following updates on multiple websites (here of GFDL),and, apparently sending emails to some long-time participants of RC.
    or
    b) that it is bot, a poor-man’s version of the IBM Watson that by searching Internet for answers – handily defeated best human competitors in “Jeopardy”

    Hmm, which is a simpler answer ?

    And once you allow that “Doug Swallow” is an AI bot – everything falls into place – it can SEARCH any topic, but it has not idea what it found – whether different articles with the same keyword relate to each other:

    That’s why in this thread JDS recognized phrase “Atlantic hurricane”, posted text containing this keyword, but which “doesn’t bear on the length of hurricane season“, which is subject of this thread.

    The AI cannot also figure out whether the text it found supports or contradicts other texts – see a comment in an earlier post:
    Kevin: “ The funny thing about JDS’ aeronautical tale was that it nicely refuted his own point! […] That is, of course, the exact opposite of the thesis he was trying to defend. (I.e., that pressure determines temperature.)

    Both characteristics are illustrated in the mentioned CO2/Intel Design debacle – after being programmed that CO2 is good, JDS started to search for articles supporting it:
    1) First it found a standard denialist text that CO2 is good because plants need it for food.
    2) Then it connected that to a file from a creationist folder – and voila:
    JDS: “here is intelligent design because all of the living organisms that utilize CO₂ exist on the surface of the Earth ”.

    3. Then it found a 3rd article, saying:” carbon dioxide invaded the low lying valleys, killing more than 1500 people and 6000 head of cattle. ”.
    Unfortunately, while this supports text 1, but it shoots in the back text 2, because either the Intelligent Designer is not so intelligent, or at least not so benign, as the creationist article tried to persuade us.

    Again, with JDS being a software – all that makes sense – you and I would see immediately that text “3” shoots text “2” in the back, but the JDS AI program could not. Obviously, the ability to search Internet is easier to program than understanding.

    Still, the designers of the JDS must be proud – their software has been passing the Turing test for a long time now, and not in some comment section of a newspaper or on a fan page of Kim Kardashian, but on the Real Climate science blog!

    And the Beta version of the JDS succeeded in tying-up RC participants, redirecting their attention and energy away from discussing things that client want to distract from – the science of climate change or ways to mitigate it. Do a few patches here and there, and the JDS will be ready for the wide release.

  4. 4

    Jim,
    This is all very believable except it all hinges on the false statement you make:-
    “Still, regardless of statistical significance, there is clearly a very steep trend towards earlier storms in the past four decades (lower green line in Fig. 2), which represent a period of reliable data.”
    Rasmus made the same mistake in the near identical post https://www.realclimate.org/index.php/archives/2020/12/the-number-of-tropical-cyclones-in-the-north-atlantic/ in December last year.

    You make the assumption that because we have reliable data it is consistent but that is far from the case. What I did is calculate and plot the mean Longitude from HURDAT2 Vs year. Obviously you can do that, but here is a plot:-
    https://photos.app.goo.gl/Nt86JYYJWjLMkZVp6
    For the period up to about 1940 there is no real trend as the vast majority of observations are done from land. Following that there is a very obvious eastward shift as our ability to remotely measure storms increases. Clearly it is unlikely that that this easterly shift actually exists, and so it can be used as a proxy for our improvements in detection.

    If you were correct, then the 40 years between 1940 and about 1980 would show the easterly shift and then it would remain flat, as the first 90 years were. But that is not the case, the trend continues to the present day.

    Clearly the data shows we are continuing to better detect storms.

    If you were to break my plot into 2 (at 1940) or 3 (at 1940 and 1980) then those slopes could be used to attempt to correct your plots to account for the observational error

  5. 5
    J Doug Swallow says:

    #2 3 Apr 2021 at 12:22 PM Mitch says: “I am not certain why Doug Swallow (#1) posted that information since it doesn’t bear on the length of hurricane season”. Perhaps missed this when he read my post;
    “Therefore, we conclude that it is premature to conclude with high confidence that increasing atmospheric greenhouse gas concentrations from human activities have had a detectable impact on Atlantic basin hurricane activity, although increasing greenhouse gases are strongly linked to global warming. (“Detectable” here means the change is large enough to be distinguishable from the variability due to natural causes.)”

  6. 6
    J Doug Swallow says:

    #2 Mitch says: “It is an announcement to the public of the time frame that they need to be ready to face a hurricane. With that in mind, it is better to extend the season”. Mitch needs to understand what is being said in this NOAA report; “these same models project future decreases in Atlantic tropical storm frequency in response to increasing greenhouse gas concentrations”.
    There is increasing evidence from modeling studies at GFDL/NOAA and the UK Met Office/Hadley Centre (UKMO) that the increase in tropical storm frequency in the Atlantic basin since the 1970s has been at least partly driven by decreases in aerosols from human activity and volcanic forcing. Natural variability may also have contributed to recent changes. The recent GFDL and UKMO studies do not imply that the increase in Atlantic tropical storm frequency since the 1970s will continue into the future: these same models project future decreases in Atlantic tropical storm frequency in response to increasing greenhouse gas concentrations.
    • There is evidence for a slowing of tropical cyclone propagation speeds over the continental U.S. over the past century, but these observed changes have not yet been confidently linked to anthropogenic climate change.
    https://www.gfdl.noaa.gov/global-warming-and-hurricanes/

  7. 7

    I’m not sure if this report from NOAA fits well into the narrative that Tim Hall, Mike Mann, and Stefan Rahmstorf want for folks to believe.

    And I’m not sure that there *is* a such a “narrative.” It seems more likely that JDS is projecting his own storytelling urges onto the authors.

    JDS aside, though, it strikes me that there may be a bit of an excluded middle in the authors’ discussion of their “first question,” i.e., “Can we expect the season to continue to lengthen as global warming from increasing concentration of globally well mixed greenhouse gas (GWM-GHG) continues to warm the Atlantic SSTs?”

    That is, it seems to me that, in the abstract at least, you might see the TS PDF shift shape such that an extended season continues to lengthen even as storm formation rates during the season drop. One can imagine a scenario in which total seasonal storms remain roughly the same, but spread over more time. (All else equal, you’d see out of season storms decrease, just because of the shortening of the off-season, and therefore also a slight drop in the annual storm total.)

    I’ve no idea if that’s physically plausible, given the atmospheric variables discussed. But it does suggest that perhaps the linkage between storm formation rates and season length could be more complex than the discussion suggested.

  8. 8

    M 2: I am not certain why Doug Swallow (#1) posted that information since it doesn’t bear on the length of hurricane season.

    BPL: JDS is a global warming denier who comes here to cast doubt on the science.

  9. 9
    John Pollack says:

    Mitch @2 I’m in agreement that we need to take a deeper look into the intended purpose of a “hurricane season” declaration. Despite the title of the discussion, the research presented is more about the climate science of the length of the season, and the uncertainties involved, than about the official season length. Good stuff, yes.
    In fact, hurricane researchers and the NHC have generated a lot of good stuff in the past few decades that isn’t being communicated very well. There is a real discrepancy between the amount of important information in the NHC discussions and what gets into the short warnings and media takeup, let alone public awareness. Granted, it has to go through an international bureaucracy before changes in procedure are implemented. However, that has occurred for hurricane names and category rankings in general.
    So, yes, extend the hurricane season, since it has been starting earlier. I would also like to see a lot more detail in the category ratings. First, add a “+” or “-” to the category for storms that are expected to change intensity by a category in the next 24 hours. Perhaps a “++” for storms that show potential for rapid intensification.
    Next, I’d like to see something analogous to what the Storm Prediction Center has implemented for Day 1 and 2 convective outlooks. Not only is there an overall hazard rating, but it is broken down into hazards in three different categories. For tropical cyclones, there could be a multi-part rating if portions of the storm are forecast to make landfall within 24 hours, with one ranking for wind, one for storm surge, and one for excessive rain. That way, a storm that is category 1 for wind, or in the process of becoming extratropical, could still be highlighted as a much higher category if major flooding is expected. The media could interpret this as “well, the winds have died down a lot, but this storm is still a category 4 based on the enormous flooding that we expect, so don’t let your guard down yet!”

  10. 10
    Russell Seitz says:

    I’m in favor because I presently live ~75 cm above sea level, where vorticity is often reckoned to be a Bad Thing :

    https://vvattsupwiththat.blogspot.com/2021/04/another-reason-to-extend-hurricane.html

  11. 11
    nigelj says:

    Piotr @3 says JDS is most likely an AI programme if you apply Occams Razor. Ha ha that is an extremely clever post, but JDS has given some sarcastic responses to one of my posts and I’m not sure AI is capable of that human sort of touch. There are other possible explanations: Its well known that some people display deliberate stupidity due to political ideology, or vested business interests, or religious beliefs ( and his posts do suggest an interest in creationism), this possibly building in the case of JDS on a great deal of innate shortcomings to begin with. This would explain the bizarre statements about C02 and intelligent design.

    The huge output of long posts requiring a great deal of in depth research may simply be explained by him being both very driven and retired, or alternatively he’s paid to do it by some organisation, or alternatively copious use of crack cocaine. These are all still fairly simple explanations.

  12. 12
    Susan Anderson says:

    “want for folks to believe” is a most peculiar distortion, and has nothing at all to do with the scientific process. Conspiracists and tubthumping ranters do that. Scientists spend their time, intelligence, and considerable skills avoiding this kind of BS.

  13. 13
    J Doug Swallow says:

    #4 3 Apr 2021 at 9:16 PM Keith Woollard says:
    Jim, This is all very believable except it all hinges on the false statement you make:-
    “Still, regardless of statistical significance, there is clearly a very steep trend towards earlier storms in the past four decades (lower green line in Fig. 2), which represent a period of reliable data.” Keith Woollard demonstrates that he has a firm idea what this discussion is about, unlike Piotr, whose post shows that he basically has NO idea what the topic is. These facts below makes one wonder how non occurring hurricanes can be coming earlier? Since this information is true, I do not expect it to make it by the moderator’s inspection.
    This from a previous RC article by “rasmus @ 23 December 2020” should, if RC believes what they post, add credence to this information below.
    “2020 has been an unusual and challenging year in many ways. One was the record-breaking number of named tropical cyclones in the North Atlantic (and the Carribean Sea). There has been 30 named North Atlantic tropical cyclones in 2020, beating the previous record of 28 from 2005 by two”.
    https://www.realclimate.org/index.php/archives/2020/12/the-number-of-tropical-cyclones-in-the-north-atlantic/

    (CNSNews.com) — Saturday, June 24 marked the completion of a record 140 straight months since the last major hurricane made landfall in the continental United States, according to the National Oceanic and Atmospheric Administration(NOAA).
    The last major hurricane to hit the continental U.S. was Hurricane Wilma, which struck Florida on Oct. 24, 2005. According to NOAA, four major hurricanes hit the continental United States that year. They included Wilma, Rita, Katrina, and Dennis.
    But since Wilma, no Category 3 or above hurricane has made landfall in the continental United States, making June 24, 2017 the end of a record 140 months without a major hurricane strike.
    Prior to this 140-month stretch without a major hurricane strike, the longest major hurricane drought was the 96 months between September 1860 and August 1869.
    http://www.cnsnews.com/news/article/gage-cohen/record-140-months-major-hurricane-strike-us

  14. 14
    Peter Ashby says:

    The project to plant a belt of trees across the Sahel could well act to reduce Saharan dust storms since if it is every finished that number of trees will change the local climate making it wetter and thus reducing dust levels. Over what area? We don’t know. But if successful it might stimulated further planting to further green the desert or it might happen naturally as the forested zone increases in size though that is likely to be local in origin.

    But as with other things all things are not equal in terms of the Sahara, we are interfering probably positively.

  15. 15
    jgnfld says:

    @jds “The last major hurricane to hit the continental U.S.”

    Q: What does the continental US have to say about the globe?

    A: Somewhat less than 2%.

  16. 16

    #15, jgnfld–

    Yes, the “major hurricane drought” meme was always dumb, for the reason you pinpointed.

    But it’s even dumber not to note that since it ended we’ve been hit by four: Harvey (2017), Irma (2017), Michael (2018), and Laura (2020). Plus, outside CONUS but in the Atlantic basin, Maria (2017). Plus, several highly damaging ‘minor’ hurricanes like Matthew and Sally. (Matthew actually was a major hurricane–in fact, it set a record for time at or above Cat 4–but not when it hit the US.)

  17. 17
    J Doug Swallow says:

    #15 6 Apr 2021 at 7:18 PM jgnfld says: “Q: What does the continental US have to say about the globe?
    A: Somewhat less than 2%.” I wonder if the one who will not use his real name for probably good reason, jgnfld, realizes how severely some of that 2% suffered from this particular hurricane in 1900?
    The Great Galveston Hurricane of 1900 was the deadliest hurricane to ever hit the United States and caused between 8000 and 12000 deaths.
    http://geology.com/hurricanes/largest-hurricane/

    Hurricanes have also been around for a long while, it seems.
    “As they approached New England, an unusually powerful early season hurricane struck, known as the “Great Colonial Hurricane of 1635″, and the James and the Angel Gabriel were forced to ride it out just off the coast of modern-day Hampton, New Hampshire.”
    “The 30 Deadliest US Hurricanes / Tropical Cyclones (1851 – 2006)”
    http://www.wunderground.com/hurricane/usdeadly.asp

  18. 18

    JDS 17: Hurricanes have also been around for a long while, it seems.

    BPL: Forest fires have burned due to natural causes for millions of years, so there’s no such thing as arson.

    Same logic.

  19. 19
    Piotr says:

    To the designers of the AI discussion program “J. Doug Swallow” (17)
    – either your program is unstable – invariably drifts off the subject or drags up from its memory unrelated ones
    – or you furnished it with a substandard vocabulary – apparently missing the definitions of: “ global ” and “ climate “.

    Quite an oversight, if I may say so, for a bot tested on its ability to challenge “anthropogenic global climate change”.
    To make things worse – its computational engine apparently cannot detect the inequality between “2%” and “100%”.

    If you do not correct these issues promptly, the outcome of the Turing test of your software may be in question. Be best!

  20. 20
    Richard Caldwell says:

    Piotr,

    I enjoy your rapier-sharp-and-accurate wit. It does sting sometimes, though…

  21. 21
    jgnfld says:

    @18 Re. “same ‘logic'”…

    I’d argue it’s worse since JDS is now arguing that 2 singular events in the past half millenium apparently provide him with all the “proof” he needs state that there is no global warming trend now.

    For the more theoretically minded, hurricanes are already extreme events and as such are notoriously weak at identifying trends: No power as you throw away all but the most extreme data before you even start. Limiting the analysis to only major hurricanes is even worse as you throw out even more data before you start. (This neglects the fact that hurricanes do not respond to rising/falling temps directly or linearly and so are poor indicators of temp trends in the first place.)

    But now JDS has recursed even that idiotic misuse of extreme-values to a whole new level by taking only the 2 most hurricane extreme events of the past half millenium–in a delimited area of the globe no less–to “prove” there is no global warming trend! Or, more succinctly, “Let’s throw away all but the most extreme 2 datapoints for the last half millenium before we do our warming trend stats or make any conclusions about trends”. Great “science”!

  22. 22
    J Doug Swallow says:

    Can we believe anything that we read on the web? Note that this site, in two different places, tells its gullible followers that the Great Galveston Storm was in 1990 when anyone who knows any history knows that it was in 1900. It is very easy to become dubious and also very sick of this dishonest nonsense. The truth, on occasion, would be greatly appreciated . What do you ‘think’, Piotr?
    The five deadliest hurricanes in US history
    • The Great Galveston Storm (1990) – the estimated death toll is from 8,000 to 12,000.
    • Hurricane Maria (2017) – the estimated death toll is around 5,000. Initial estimates were only 64 in Puerto Rico; new reports showed incredibly more.
    • The Okeechobee Hurricane (1928) – the estimated death toll is around 3,000.
    • Hurricane Katrina (2005) – the death toll is 1,833. Tens and thousands of people were displaced.
    • The Chenière Caminada Hurricane (1893) – The Great October Storm killed nearly 1,400 people, almost the population of a town.

    The Five Deadliest Hurricanes in US History
    (by estimated deaths) 12,000 The Great Galveston Storm (1990)
    https://comparecamp.com/hurricanes-statistics/

    Galveston Hurricane 1900
    This hurricane was the deadliest weather disaster in United States history. Storm tides of 8 to 15 ft inundated the whole of Galveston Island, as well as other portions of the nearby Texas coast. These tides were largely responsible for the 8,000 deaths (estimates range from 6,000 to 12,000) attributed to the storm. The damage to property was estimated at $30 million…
    https://www.nhc.noaa.gov/outreach/history/#galveston

    [Response: Congratulations on finding that someone on the internet was wrong. – gavin]

  23. 23
    Richard Caldwell says:

    Peter Ashby: The project to plant a belt of treaes across the Sahel could…
    …and thus reducing dust levels. Over what area? We don’t know.

    RC: the Amazon (and the Atlantic ocean)? Less dust/natural fertilizer along with the ongoing trees-to-hamburgers project doesn’t sound healthy for a rain forest.

    But the advancing desert has been increasing dust exports to South America, I’m sure, so maybe the project is bringing things back to “normal”.

    Regardless, I still think the Amazon is toast. Time to start thinking about triage.

    And how does African dust export affect hurricanes?

  24. 24

    #17, JDS–

    The Great Galveston Hurricane of 1900 was the deadliest hurricane to ever hit the United States…

    And in other news, President McKinley is still dead.

  25. 25
    Piotr says:

    J. Doug Swallow(22) “ Can we believe anything that we read on the web?

    Dear Designers of the AI program “J. Doug Swallow”, wasn’t the very reason for going with AI that it could learn? Obviously it has not worked so far, so could you in your JDS manually adjust:
    – either ​its vocabulary, indicating the difference between “ anything” and “everything“, and between “can” and “should“?)
    – or its logic circuit: finding a trivial typo on one Internet site does not invalidate the entire Internet; and a claim could be “ dishonest” or “nonsense“, but rarely “dishonest nonsense“.

    While at this – how about putting some negative feedback loops to dampen its emotional overreactions? Cause your JDS, it destabilizes _really_ quick: in the span of a single post it jumped from a typo on one website to questioning of the value of the Internet! AND to brooding over the human condition:
    It is very easy to become dubious and also very sick of this dishonest nonsense. The truth […] would be greatly appreciated“. Hamlet 2.0?

    And what’s with JDS’s attribution routine??? I mean, why does it ask me about the typo on somebody else’s webpage?

    But relax, it’s not all bad, far from it – I was REALLY impressed that your JDS believes itself to be … human, the human warts and all: like becoming unhinged by a … simple typo! (“It is very easy to become dubious and also very sick of this dishonest nonsense”)
    And the typo that set JDS off was so trivial: what’s the worse that could happen if you read on one webpage that Galveston hurricane was in 1990? I mean, unless you have just bet on that everything in the final round of “Jeopardy”…

    Which ALSO shows how GOOD is your work: the IBM “Watson”, which kicked the human asses, computer’s hands-down, in Jeopardy – did it by quick scanning of MULTIPLE webpages – so a typo on ONE of them would have never thrown it off from the right answer! Yet, apparently, your JDS does not know it could do it too! And in a very human-like display – it gets all emotional over the possibility of being tricked into becoming a “gullible follower” of such a perfidious typo. Bravo!

  26. 26
    J Doug Swallow says:

    [Edit: I realize you have no idea how boring your kind of context-free factoid spamming is. Please be more interesting or don’t bother. – gavin]

  27. 27

    I despair for the future of science sometimes.
    We have here “respected” scientists making snide remarks about people pointing out mistakes! Really Gavin? Isn’t science about being correct?
    And a number of people complaining that JDS is cherry picking by focussing on North America – when the actual post is about North Atlantic storms!
    What JDS is attempting to do (albeit a little clumsily) is to show that there is no trend in the North Atlantic storms, he has done it via selecting news and human impacts.

    But really the reason I despair is the lack of response to the obvious error I pointed out in my comment #4. Please Jim Kossin, Tim Hall, Mike Mann, Stefan Rahmstorf, Kerry Emanuel or Adam Sobel can you explain why you believe the last 40 years of observations are consistent in the face of the data showing otherwise?

    Between the six of you, how many papers have you authored that have assumed Hurdat2 is a complete and consistent record of all North Atlantic storms. And if you believe that, how do you explain the easterly migration?

  28. 28

    In my comment #4, I had a link to a plot where I averaged all the locations of all the tracks for each year.

    Here is a plot of both latitude and longitude generated in much the same way as Jim Kossin did.
    https://photos.app.goo.gl/y4ZcNCbqXHAEBrKx7
    For each storm, we took the peak windspeed location and then averaged those locations over each year. It shows much the same thing as my first plot, but using the same logic as Jim.

    Note that after converting to true X/Y values, magnitude of the longitudinal shift is 6.4 times the value of the latitudinal shift

  29. 29
    Piotr says:

    Keith Woollard (27) “ I despair for the future of science sometimes. We have here “respected” scientists making snide remarks about people pointing out mistakes!

    True that, Keith! I despair too when scientists disrespect our J. Doug Swallow! They don’t like him pointing out their mistakes of not believing that … the Intelligent Designer made the CO2’s molecular weight high, so it would drop to the ground to offer itself to all the living organisms requiring it for survival! Or kill humans and cattle, who knows.

    Or when he points to the mistake of not seeing the virtue of the increasing CO2 emissions: JDS: “Carbon dioxide is a nutrient, not a pollutant, and all life– plants and animals alike– benefit from more of it. All life on earth is carbon-based and CO2 is an essential ingredient.
    https://www.realclimate.org/index.php/archives/2021/01/climate-adaptation-summit-2021/comment-page-2/

    I can already see, J. Doug Swallow, after his usual morning walk on water, hears a man drowning. “Help!“, the man shouts. “Coming right up!”, exclaims J Doug Swallow. But instead of tossing the man a lifeline, he …. teaches him:
    The life on Earth depends on water. You, my dear fellow, would not last 3 days without water! So embrace it, be one with the life-giving water!“. Then he turns, and slowly walks away, smiling to himself.

    And I find it equally infuriating when “respected” scientists do not appreciate, the defender of J Doug Swallow, the great Keith Woollard, my personal hero, who, among other, disproved the effect of global warming on precipitation because “you will find NO correlation” between … local temperature in Perth or Sydney and local rain at that place: https://www.realclimate.org/index.php/archives/2021/01/climate-adaptation-summit-2021/

    Shame on you, “respected” scientists, for not acknowledging your mistakes, shame on you! And:
    All Hail The Swallow! All Hail The Woollard!