Hurricane Florence: climate dynamics context

by Judith Curry

“Impending massive hurricanes bring the best out of weather twitter and the worst out of climate twitter” – Joseph Maykut

Every time we have a tropical cyclone landfall in the U.S., there is an explosion of public statements regarding the role (or not) of human caused global warming on the impacts suffered upon landfall.

This blog post sorts through the various claims, and also provides a way forward for objectively assessing them.

Note, I am almost finished with my big report on sea level rise.  After that, I will begin a comprehensive assessment of the hurricanes and global warming topic. This post is a preliminary taste, before I really dig in and focus on this.

Meteorological recap

Florence originated from a strong African easterly wave that emerged off the coast on August 30.   Heading on a west-northwest trajectory, the system became a tropical storm on  September 1. An unexpected bout of rapid intensification ensued on September 4–5, Florence emerging as a Cat 4.

Wind shear then tore the storm apart and Florence degraded to a tropical storm by September 7. The system regained hurricane strength on Sept 9 and major hurricane status by the following day, becoming a Cat 4 on Sept 10. Afterwards, Florence weakened slightly as it underwent an eyewall replacement cycle.  After some restrengthening wind shear reduced the intensity although Florence continued to increase in horizontal size.  On Sept 14, Florence made landfall on the southern coast of North Carolina as a Cat 1.

The main meteorological impact has been record breaking precipitation, that is continuing as the post-tropical storm  slowly moves across the mid Atlantic states, expecting to exit back into the Atlantic later today.

The forecast for Florence has to be regarded as a success story.  5-7 days lead time was provided for a landfall (or pseudo landfall) near Wilmington, SC.  Florence presented some challenges for intensity forecasting, owing to its very large size and evolving complex structure.

Pre landfall forecasts of storm surge, wind speed and precipitation were qualitatively correct, sufficiently accurate to support emergency management planning 3-5 days in advance.

A full verification report will be forthcoming, comparing track forecasts from the different models (including CFAN’s forecast), plus CFAN’s landfall wind forecasts and precipitation forecasts.

The controversy

In an unusual move, on Sept 12 a ‘pre-event attribution’ analysis was published online [link]:

We find that rainfall will be significantly increased by over 50% in the heaviest precipitating parts of the storm. This increase is substantially larger than expected from thermodynamic considerations alone. We further find that the storm will remain at a high category on the Saffir­Simpson scale for a longer duration and that the storm is approximately 80 km in diameter larger at landfall because of the human interference in the climate system.

This was followed by a USA Today  op-ed by Roy Spencer, entitled Hurricane Florence is not climate change or global warming.  Its just the weather.  The title  pretty much summarizes the article.

Seth Borenstein of AP published interviewed 17 meteorologists climate scientists in an article entitled A warmer world makes hurricanes more intense.  This list included a number of climate scientists/activists  who apparently know nothing about hurricanes, who got most of the space in the article.

Climate Feedback responded to Roy Spencer’s op-ed with a fact check entitled USA Today op-ed ignores evidence to claim climate change had no role in Hurricane Florence.  It includes extensive commentary by Kerry Emanuel that is worth reading.

And finally Jim Hansen has posted an article entitled Global Warming and East Coast Hurricanes.  “So, does global warming have a hand in the magnitude of the Hurricane Florence disaster on the U.S. East Coast? Yes, we can say with confidence, it contributes in several ways.

Another report from Seth Borenstein:  Hurricane rating system fails to account for deadly rains  which makes some very good points.

Attribution methods

The key issue is how different scientists mentally frame the problem of attribution of the causes of extreme weather events.  Here are 4 different frames that I’ve identified:

  1.  It’s just weather (e.g. Roy Spencer).  This is the null hypothesis, and looks to identify more extreme events in the past.
  2. Conditional approach (e.g. Kevin Trenberth, Jim Hansen). Examines basic thermodynamic impacts, and changes in circulation, focused on understanding AGW impacts on basic mechanisms.
  3. Climate model based attribution (pre-event attribution analysis, Fredericke Otto, Myles Allen).  Compares climate simulations without anthropogenic forcing, with simulations including anthropogenic forcing.
  4. Detailed observational analysis that includes not just trends but also mechanistic covariances (e.g. Jim Kossin).

Re #1.  This is indeed the null hypothesis, but we cannot rule out AGW effects based on  this argument.  The detection component of this approach is very useful in identifying previous extremes in historical and paleo records.

Re #2.  The conditional approach is useful in pointing to #4 type observational analyses, but is insufficient on its own for attribution

Re #3.  The climate models simply are not fit for this task. Such analyses implicitly assume the a) climate model sensitivity is correct; b) climate models correctly simulate internal variability; c) climate models correctly simulate extreme events; d) climate models correctly simulate thermodynamic feedbacks; e) climate models correctly simulate large-scale weather events and blocking patterns.

Re #4.  This is the way to go, relatively few studies taking this approach.  Results need to  be carefully interpreted in terms of the impacts of natural modes of variability.


The debate on hurricane intensity has been summarized in these previous blog posts:

The punchline is that while we would expect a signal of increased intensity from global warming, any  signal is at present lost in the noise of natural variability.

The point I want to make here with regards to Florence (and this also relates to Harvey, Irma and Maria in 2016) is that these hurricanes (which went to Cat 4 or 5) are over performing their thermodynamic base.  My basis for this conclusion is the operational hurricane forecasts provided by my company Climate Forecast Applications Network.  We make intensity forecasts based on ensemble wind speeds predicted by global weather models, and also apply a statistical thermodynamics based intensity models to these ensembles.  The statistical model assess the thermodynamic intensity potential.  The high intensities and the rapid intensification was driven primarily  by storm dynamics, and not thermodynamics that could be attributable to AGW.

And finally with regards to Florence, she was only a Cat 1 at landfall, after reaching Cat 4 (twice).

From Phil Klotzbach:

Also of interest in this regard.  Part of what did in Florence’s intensification is that it was a victim of its own success.  Look at the cold wake following the track, resulting from wind-driven mixing that brings cold water to the surface.

Size matters

Seth Borenstein’s second article (cited above) makes the important point that Cat 1 is woefully inadequate for describing Florence’s landfall impacts. Florence had a large horizontal extent once it started the eyewall replacement process.  Large horizontal extent directly relates to landfall impacts: storm surge, large horizontal extent and duration of tropical storm level wind speeds, rainfall, and tornadoes.

5-10 years ago, there was interest in the financial/insurance sector in including size in measures of hurricane intensity (e.g. the Carvill Index).   Also the metric Integrated Kinetic Energy (IKE) is a 2-D version of Accumulated Cyclone Energy (ACE)

Is hurricane size relate to global warming?  I’m not aware of any studies that really address this, the most relevant one that I know of is the masters thesis by Angela Fritz (of Washington Post fame, yes she was my student) entitled North Atlantic Tropical Cyclones: A Kinetic Energy Perspective

Here are figures that Angela Fritz created:

R34 refers to the radius of tropical storm force winds

It would certainly be interesting to update this analysis for the N. Atlantic and extend to global.  What I see is that  the big jump in size and IKE occurred in 1995, with the shift to warm phase of the Atlantic Multidecadal Oscillation.  Interpreting this as a trend from global warming would be misleading, although there is possible some component there that could be associated with global warming.

For another perspective on Florence’s size:

Florence’s size was much much smaller than Typhoon Manhkhut in the West Pacific, where tropical cyclones tend to have much larger horizontal extent than in the Atlantic.  Understanding this difference is a prerequisite before attempting to attribute anything related to the horizontal size of Atlantic tropical cyclones to global warming.

Track and stalling

The track for Florence, with a North Carolina landfall,  was unusual for storms on this initial path:

The reason for Florence’s unusual path relates the to presence of a massively large high pressure system across the North Atlantic and Northeastern U.S.  The figure below shows the 1018 hPa isobar, with higher pressure to the north.  Florence was unable to punch through this region of high pressure, and continued moving to the wast towards the Carolinas.

The horrendous rainfall associated with Florence was associated with its stalling once it reached the coast.  Again, this is the presence of high pressure system to blame:

Some of the analyses of Florence cite a paper by Jim Kossin [link] that found  that tropical-cyclone translation speed has decreased globally by 10 per cent over the period 1949–2016.  This is most likely a robust result, although the interpretation of what has caused this remains open to debate.  However, the effect described by Kossin is very different than the out-and-out stall that we saw for Florence and Harvey in 2016.  These are blamed on blocking high pressure systems.

So are these blocking systems changing with global warming?  Rahmstorf and Mann say yes [link], related to Arctic warming.  This is a hotly debated issue, stay tuned for a more detailed analysis of this issue as I work on my new hurricane assessment.  But if you consider multi-decadal to interannual internal variability,  it is pretty difficult to argue for a global warming signal.

Storm surge

The maximum storm surge from Florence was 10-12 feet, although because of the complex coastal geography, surge was felt inland

Jeff Masters of Weather Underground has a good article on Florence’s storm surge [link].  The title of the article is Florence’s 1-in-100-year storm surge breaks all records.

The record for all-time highest water level at Wilmington, NC, where records extend back to 1935, fell.

“Note that sea level in Beaufort has risen by about 0.7 feet since the time of Hazel, largely due to human-caused climate change, and Florence would not have been able to break Hazel’s record without it.”

According to NOAA, sea level has risen at these locations by the following amounts:

  • Wilmington:  average rate of SLR of 2.3 mm/yr, or 9 inches per century.
  • Beaufort:  average rate of SLR of 3.04 mm/yr, or 12 inches per century

So, how much of this sea level rise can we blame on warming (human caused, or natural)?  Karegar et al. (2016) provides a GPS-based analysis of vertical land motion on the U.S. Atlantic coast:

  • Wilmington: -1.41 mm/year, for a value of absolute sea level rise of 0.9 mm/yr
  • Beaufort: -1.13 mm/year, for a value of absolute sea level rise of 1.9 mm/yr

It is somewhat surprising to see such different values of absolute sea level rise for two locations that are relatively close, but this probably depends partly on how close the GPS station is to the actual tide gauge.  In any event, the maximum amount of sea level rise that could be blamed on human caused global warming (assuming all warming in last century is human caused) is substantially less than the sea level rise measured at tide gauges.

According to Masters, that little boost of sea level rise made the difference in breaking the record Beaufort.  However the amount of sea level rise that you can potentially blame on human caused global warming is substantially smaller than what is measured at tide gauges, owing to vertical land motion.


Florence set tropical rainfall records for North Carolina and South Carolina, there was also considerable flooding inland as far north as Massachusetts.

To what extent can we blame this substantial rainfall on human caused global warming.  Well, the major cause of the large rainfall (same as for Hurricane Harvey) was the stalling and slow motion of the storm.

What of the claims that the warm sea surface temperatures in the Atlantic contributed to the heavy rainfall?  Well the Atlantic surface temperatures weren’t particularly warm in the main development region of the North Atlantic where Florence spun up its intensity.  The warm Atlantic temperatures were further north and didn’t particularly influence Florence’s intensity.

The basic thermodynamic argument is that warm surface temperatures result in a larger equilibrium vapor pressure (then wave hands) and therefore more rainfall in tropical cyclones.  It is not implausible to imagine that warmer sea surface temperatures could contribute to increased rainfall in tropical cyclones (#2 style of attribution argument).

Well, for this argument to be convincing, the following analyses need to be done (a #4 approach):

  • Look at the liquid water path and precipitation data from microwave satellite back to ~1979 for all Atlantic tropical cyclones (best to extend globally as well).  I used to be very active in this research [link]  I need to catch up on this research but I suspect that there has not been much done re tropical cyclone water climatology.
  • Calculate the “characteristic life time” (CLT) of the condensed water (sum of liquid and ice) and water vapor may be determined by dividing their amounts by rainfall rate.  Also the precipitation efficiency is the precipitation divided by the condensed water
  • Relate above parameters on a storm by storm basis to the local sea surface temperatures.
  • Assess the influence of SST on liquid water path, precipitation, characteristic life time and precipitation efficiency.
  • If no significant relationship with SST, then give up.  If significant relationship with SST, then assess the relationships in context of the Atlantic Multidecadal Oscillation, etc.

I’m not signing up to do these things, but I’m laying out what needs to be done.


I’ve scratched the surface of the complex issues surrounding the weather and climate dynamics of Florence, but the take home point is that convincingly attributing any of this to human caused global warming is very challenging, and the strategies used by the mainstream climate community to do this (#2, #3) are woefully inadequate and misleading to scientists, the public and policy makers.

62 responses to “Hurricane Florence: climate dynamics context

  1. Re #1. This is indeed the null hypothesis, but we cannot rule out AGW effects based on this argument.

    We also cannot rule in any AGW effects based on any actual data. Warming does change things, but there is no proof or reason to believe any warming was not natural.

  2. Roy W. Spencer

    there are so many different kinds of records that can be devised to be broken, and so many different locations where they can be broken, is it any wonder that records keep being broken? How about 11 years without a Cat 3+ landfall…a 1 in 250 year event? Did AGW cause that? What about the 50% decrease in landfalling major hurricanes since the 30s and 40s (based on the linear trend)? Did AGW cause that? A lot of what we are hearing is based upon cherry picking. My point is that natural variability is so large, even on multi-decadal time scales, how can one ever decide what role humans have? Yet, that is the FIRST explanation given now for every weather disaster…as if weather disasters haven’t happened before. If a Cat 1 hurricane causes this much fuss, what will it be like when the next Cat 5 hits, which, statistically, we are just about due for.

    • Roy Spencer:

      Please quit trying to prove that nothing has changed or that conditions are better or worse, earth and oceans have warmed and things have changed. It may be better and/or worse, some better and some worse, but what is important is that we did not cause it. Climate change is and always has happened and it was and is not our fault.

      Alex Pope

      • Sadly not so. Some forms of climate change are possibly attributable to human influence. Farming practices causing salinity and desertification for instance..
        But as the man said there are not only many different records that can be thought of there are many different ways ( including CO2) that might or might not cause climate change.
        I believe we will have terraforming and climate change capacities in the not too distant future.
        I doubt that any significant effect is being had on hurricanes presently or that any meaningful signal could be extracted at present. Natural variability is too great.

    • Landfall is tricky, seems to be driven by the AMO phase and where the warm water is. When the warm tongue extends to east atlantic, TC’s rapidly intensify and head north. Current pattern looks like cold phase of AMO (not clear that this is the shift yet). Then all of this is spiced by variations in the Pacific. In principle, AGW could shift TCs away from the US by making the eastern Atlantic warm

      • In principle, natural climate change could shift TCs away from the US by making the eastern Atlantic warm

      • Again, AGW has not been proved with actual data!
        Natural Climate Change has been proved by past data!

        Natural Climate Change has always has always happened and it did not stop. In principle, Natural Climate Change is most likely the only thing going on that is significant, we do know that happens, it is just not considered by climate scientists. Suddenly, natural cycles stopped and change now only occurs with man-made CO2.

        Michael is one more storm to test the people who say warming did not cause any change. Warming must cause change, for better and/or worse. Man did not cause it, that is the major issue! Again and again, Luke-Warmers cause more alarmism! Prove AGW or quit promoting it!

  3. The basic thermodynamic argument is that warm surface temperatures result in a larger equilibrium vapor pressure (then wave hands) and therefore more rainfall in tropical cyclones. It is not implausible to imagine that warmer sea surface temperatures could contribute to increased rainfall in tropical cyclones (#2 style of attribution argument).

    That is not what modern consensus climate alarmism is all about. It is not about if warming causes any change, why would it not?

    It is about if what is happening is natural and necessary and normal, and there is no data that proves it is not normal, natural and necessary.

    What is happening is a repeat of past warming phases of past cycles and is inside the bounds of what happened in the past.

  4. Salvatore del Prete

    It is ridiculous to even entertain the thought that non existent AGW, which has hi jacked all natural variability which was in a warming mode from the end of the Little Ice Age to 2005 had any climatic impact on this event much less the global temperature rise.

    My point will be proven now – over the next few years as global temperatures continue to fall in response to all natural climatic factors now transitioned to a cold mode.

    If there is any validity to AGW , the global temperatures should continue to rise now-next few years, but they will not because AGW does not exist.

    What controls the climate are the magnetic field strengths of both the sun and earth. When in sync as they are now(both weakening) the earth should grow colder.

    In response to weakening magnetic fields the following occurs:

    EUV light decreases – results in an weaker but more expansive polar vortex. Greater snow coverage.

    UV light decreases – results in overall sea surface oceanic temperatures decrease.

    Increase in GALACTIC COSMIC RAYS- results in changes to the global electrical circuit, cloud coverage , explosive major volcanic activity.

    In other words during periods of very weak long duration magnetic field events the earths cools due to a decrease in overall oceanic sea surface temperatures and a slightly higher albedo due to an increase in global cloud/snow coverage and explosive volcanic activity.

    Thus far all overall global temperature trends for the past year or two have been down and I expect this trend to continue.

    • The warm periods during the most recent ten thousand years each lasted a few hundred years. This warm period will last the same, it will not get a lot warmer or a lot colder for several hundred years. What will happen is a repeat of what has happened. There will be warmer and colder excursions during this warm period, but nothing that will matter in the longer time.

      • Salvatore del Prete

        I say the warm period is coming to a close.

      • This warm period will continue longer just like past warm periods continued longer. Little colder cycles will not last long. This warm period must continue and promote the snowfall that rebuilds ice on land in the NH. It will get colder after the ice is sufficient volume to advance and cause colder.

  5. Dr. curry,
    Living on the northern South Carolina coast I confess to having been distracted and did not pay attention to CFAN forecasts or discussion. Florence went ashore 90 miles to my NE and although as a tropical storm came within 30 miles, it’s meaner and windier days were behind it. Saw about 12 inches of rain but little wind above 50mph from the west or south. Will you be discussing CFAN’s products leading up to landfall and which models you consider to be worthy of note?

  6. It strikes me that you do believe in #AGW. Correct ?

  7. From Seth’s AP disaster . .
    “For every degree the air warms, it can hold nearly 4 percent more water (7 percent per degree Celsius) . .”
    Since the mainstream’s shrill here is about AGW – not naturally occurring GW – can we please begin to separate the two? Isn’t the ‘consensus’ view such that AGHG’s had really experienced the rapid rise until sometime between 40-60 years ago, and as such, the human footprint in GT’s isn’t really considered to be observable until sometime within that time period.
    The warming (0.5C +/- between 1910-1945 surely is generally agreed to be almost, if not entirely naturally occurring, w/ the warming (the other 0.5 C in this last cycle) considered to me ‘mostly” (what? over 50%) man-made?
    So what do we end up with? Say 0.25 to 0.35C (or 0.4 – for the greedy) of the total GW is potentially AGW.
    Therefore – if GW is having an impact on tropical cyclone intensity/size/precip/forward speed, then the cause of that is (among other possibilities) is naturally occurring with perhaps a fraction of it having some human influence.
    Note: I was very giving, in my opinion, in that presentation.

  8. I would like to discuss with you via email the history of Grand Solar Minimums. With e-mail I can send you some graphs and discuss the fall of great empires and dynasties. Mayan’s, Aztecs, Roman, Viking’s are just a few examples of GSM activity and global destruction events. I also have some great observations of what is disrupting our Sun. The perturber can also be traced through history. Sir Isaac Newton searched for it. Carlos found it. The connection of these cycles in Biblical history. Judgement events like Noah’s flood and the destruction of Sodom and Gamorrah! All these seem to fall on a roughly 400 year cycle. Cycles of cycles both within and along side. Currently there are many underwater volcanoes erupting that are not being discussed. Fresh volcanic pumice washing ashore in Northern California and Lake Michigan are just two places. Heat anomalies in the oceans of volcanoes erupting in three locations I have monitored and these are just the few we have found. Lastly I would recommend reading up on the work of Carlos Munoz Ferrada. The events he described almost 100 years ago are now coming into play. I have searched for a way to email you and am not finding the link?

  9. Media caught exaggerating to make flooding seem as bad as possible. I simply don’t believe anything I see in the yellow journalism media that is simply returning their roots in 19th century press corruption and naked partisanship.

    • Don Jr. uses an image of Cooper from years ago, and you blame the media.
      Don Jr. claimed Cooper is kneeling. He wasn’t.
      I think you should look into why Jr. would lie about this.

      • He might not have been kneeling but his cameraman was in calf deep water. That is undeniable. There were many sources for those pictures, not just Don Jr.
        Also, a reporter was canoeing on a street. Pedestrians walked into camera shot. Water was ankle deep. The reporter’s paddle must have been scraping pavement.
        I hope you’re not defending these clowns, who exaggerate the storms impacts for ratings.

      • Also it was Ike not Florence, which seems like a major fact to get wrong.

      • It doesn’t matter if it was Tinkerbell, the point is the media overly dramatizes events to get eyeballs. It’s entertainment to them, not news.

      • When the “media” digs up a 10-year-old archive photo and calls it Florence, that is either a major journalistic bumbling or a deliberate (and successful) attempt to fool unwitting people like Don Jr.

      • You guys still don’t get it. Don Jr. posted the pic of Cooper from waters NOT from Florence, then you blame Cooper for posting pics during Florence that were (get ready for it) not from Florence.

        And Cooper was not kneeling.

        I guess you like fake news. You seem to have this gene for wanting lies instead of facts.

      • Now Breitbart claim Don Jr. never said this was Florence when he posted the picture but it was in support of his claim that CNN wants to make his father look bad even though Ike was in 2008 when Bush was ending his presidency, so that doesn’t explain it either. Truth is he was taken in by fake news or Twitter stuff and posted it out like a good bot. If the media want to make Trump look bad they only need to post him throwing paper towels to Puerto Ricans. There’s plenty deep water Florence material out there too. They would not need to fake anything because of reality.

  10. sheldonjwalker

    An introduction to Alarmist statistical testing (also called hypothesis testing).


    Rule 1. Never specify a null hypothesis.

    If you can’t “prove” that your favoured hypothesis is true, then it is easier to claim that you are still correct, if you don’t have a null hypotheses.


    Rule 2. Insist that a slowdown or pause, must be statistically significant, before you will accept that it exists.

    Slowdowns and pauses are both “negative” results. They exist when there is NO statistically significant result.

    By saying that you will not accept that a slowdown or pause exists, unless it is statistically significant, you are effectively saying that you will NEVER accept that a slowdown or pause exists, even if it lasts for 10,000 years.

    Compare the Alarmist belief, with this statement. “I will never accept that the apple barrel is empty, unless there are a statistically significant number of apples in it”.

    Slowdowns and pauses should be specified in the null hypothesis. Remember rule 1, never specify a null hypothesis.


    Rule 3. Looking for a slowdown or pause, in “noisy” temperature data, is like looking for a black cow on a moonless night. They are hard to see.

    An Alarmist is like a person who has cow manure on their shoes, who insists that there are no black cows around, on a moonless night.


    Sorry, I only had 5 minutes to put this together. I have a hypothesis, that Alarmists make a lot more stupid statistical mistakes, than the ones that I have described here. But I am not going to specify a null hypothesis (because I know that I am right, and I don’t want to allow the possibility that I might be wrong).

    • “By saying that you will not accept that a slowdown or pause exists, unless it is statistically significant, you are effectively saying that you will NEVER accept that a slowdown or pause exists, even if it lasts for 10,000 years.”

      What is your point? You seem to be too concerned about fluctuations with that obvious warming to admit that it is warming. Are you really saying that the earth is cooling, but we have to be looking at certain cherry-picked years to see it?

      “Skeptics” need to read about BEST and determine if their gut feelings are really more important than the science.

      “Skeptic” example: A local university employs a physics professor who claims that he doesn’t know if the earth is warming, because he hasn’t run the numbers himself. I asked him if he ran the number to see if the atomic weights were correct. He is not a “skeptic” at all, but there’s not enough time and money to fund these guys to come to the same conclusions that Muller and Curry did.

  11. Here’s a critical review of Emanuel 2005, the origin of the PDI measure. (Power Dissipation Index).

  12. Reblogged this on Climate Collections.

  13. It would be nice to be educated someday why in
    “The high intensities and the rapid intensification was driven primarily by storm dynamics, and not thermodynamics that could be attributable to AGW.”
    storm dynamics doesn’t seem to have anything to do with thermodynamics or what the distinction may mean in this context.

  14. The challenge of determining AGW attribution to the storm surge is increased by the “ hardening “ of the coastal environment over the last 200 years with the introduction of millions of tons of concrete and buildings, thereby reducing the capacity to absorb the volume of water from the storm. Just as building in the flood plain up river within a watershed alters the flow dynamics of storm waters feeding the lower reaches of that watershed, the hurricanes involve a reversal of that process, but the impact is the same. It raises the water levels that would have occurred in the absence of all that development. Even without the construction on the coast, the very long term effects on the geomorphology at the land/water interface have changed from land use practices and alterations many miles upstream from the coast. Who knows what the storm surge would have been at the same location 500 years ago since that coastal environment would have had a much different look and capacity to withstand the same storm.

    And then, as nicely explained in the link on vertical land motion, the geological and groundwater extraction effects have to be part of the equation in apportioning the CO2 share. As Karegar noted “Subsidence along parts of the Atlantic Coast constitutes the largest amplitude proglacial forebulge collapse on earth.” But, as he further explains, other processes are at work as well, to add to the subsidence problem.

    How many times I’ve wished I had been a warmist. All of this complexity just dissipates and poof I’ve concluded it’s CO2. What a wonderful world it would be.

  15. Here are some comments by David Nolan published on NBC website: Hurricane Florence raises questions about link between climate change, severe storms Storm expert David Nolan explains what we know and what we’re still trying to figure out.
    My synopsis:

    • A: Whether or not severe weather is actually getting more severe is not clear. It is clear that the most extreme rainfall events have increased in frequency, and this is consistent with our understanding of how global warming will change the weather.
      = Science.

      A: The main reason is that warmer air can hold more water vapor. So when air rises and forms clouds and then rain, more water is released and then more water falls to the ground as rain.
      = Science.

      “In theory, global warming (for whatever causes) should produce more moisture and extreme rainfall. In practice there is no evidence that this has happened.”
      = What?

      • Q: But there’s no evidence that climate change is making hurricanes more frequent?

        A: There is not. Unfortunately, the existing modern records of hurricanes are only of good quality for about 60 years. Because hurricane activity varies so much from year to year, then it’s not long enough to say for sure if there is a clear trend upward due to global warming. = Science
        A: Many scientists these days are trying to better understand “rapid intensification,” which is when a hurricane’s winds increase by two or more categories in a single day. But there has been a lot of progress on that, and the computer models have become pretty good at predicting this, just as they are for Hurricane Florence right now.

        The other very popular topic is how hurricane activity will (or will not) change with global warming. While everyone seems to think it will make it worse, there is no proof of that yet. = Science

      • Hard to rain with no water vapour in the air so the more vapour the more chance of rain than if no vapour.
        But the frequency of extreme rainfall events lessens with increasing heat as larger hurricanes form less frequently.
        Is more than baseless assertions.

      • Typing in a #AGW denier blog won’t change a single thing or influence public

  16. Salvatore del Prete

    Ron saw your comments on WUWT under the solar constant article. Exactly correct.

  17. Jeff Masters effort on the storm surge from Florence, is significant, however it leaves me a bit confused – a quick search on Google for ‘hurricane hazel + storm surge’ presents a lot of 15′ to 18′ high storm surge . . like this from the NWS:

    “Hurricane Hazel was the deadliest and costliest hurricane of the 1954 … The hurricane brought a storm surge of over 18 feet to a large area of the North Carolina”

  18. Reblogged this on Tallbloke's Talkshop and commented:
    A sort of post-mortem look at various issues surrounding Hurricane Florence. If pressed for time, ‘the take home point is that convincingly attributing any of this to human caused global warming is very challenging’ – see the summary.

  19. Here’s Mike Seidel of the weather channel trying to bring out the worst of Hurricane Florence, and getting caught out.

  20. Re the storm surge –

    Why does Jeff Masters cherry pick Wilmington

    Florence was 10-12 ft. But Hazel in 1954 was 18 ft.

  21. One thing that makes me very suspicious about weather attribution is that they never seem to tell us what weather we would have had instead.

    For instance with Florence, we would have had the storm anyway without global warming. So what would it have been like?

    2 mph weaker? One inch less of rain?

    None of these things would scare anybody, yet they try to give the impression that weather is much more extreme now.

    And that is not even mentioning the bad weather we don’t get anymore! Like Dustbowl Droughts, Indian monsoon failures, Sahel droughts..

    The list could go on and on

  22. Thanks Judith – you get a ✨from me. The limits of intrinsic – I like to call it that because of intrinsic Earth dynamics – climate variation grow with the length of a record. This is famously a Hurst effect seen in Nile River records over more than a millennia.

    Rn = Smax – Smin

    where Rn is a time rescaled hydrological storage variation that is more extreme the longer the record length.

    The famous Moy et al 2002 – – sediment record shows change in the Pacific state over the Holocene. This has implications for flood and drought globally and even – in the coupled global system – Atlantic hurricanes.

    The record of sedimentation is influenced by warm or cool states in the eastern Pacific. It is based on the presence of greater and less red sediment in a lake core. More sedimentation is associated with El Niño. It has continuous high resolution coverage over 11,000 years. It shows periods of high and low rainfall alternating with a period of about 2,000 years. There was a shift from La Niña dominance to El Niño dominance that was identified by Tsonis 2009 as a chaotic bifurcation – and is associated with the drying of the Sahel. There is a period around 3,500 years ago of high ENSO activity associated with the demise of the Minoan civilisation (Tsonis et al, 2010). Red intensity was over 200 at times – for comparison red intensity from 1997/98 was 99.

    My feeling is that the 20th century was relatively balmy and that we had better get ready for foreseeable weather surprises.

  23. Pingback: Scientists Throw Cold Water On Claims Linking Hurricane Florence To Global Warming - The Global Warming Policy Forum (GWPF)The Global Warming Policy Forum (GWPF)

  24. I’ll plow this ground, beat this dead horse, yet some more. Maybe somebody will step up and ‘splain scientifically how/why I’ve got it wrong – or not.

    Radiative Green House Effect theory: (Do I understand RGHE theory correctly?)

    1) 288 K – 255 K = 33 C warmer with atmosphere – rubbish. (simple observation & Nikolov & Kramm)
    But how, exactly is that supposed to work?

    2) There is a 333 W/m^2 0.04% GHG up/down/”back” energy loop that traps/re-emits per QED simultaneously warming BOTH the atmosphere and the surface. Good trick. Too bad it’s not real. – thermodynamic nonsense.
    And where does this magical GHG energy loop first get that energy?

    3) From the 16 C/289 K/396 W/m^2 S-B 1.0 ε BB radiation upwelling from the surface. – which due to the non-radiative heat transfer participation of the atmospheric molecules is simply not possible. (TFK_bams09)

    No BB upwelling & no GHG energy loop & no 33 C warmer means no RGHE theory & no CO2 warming & no man caused climate change.

    Got science? Bring it!!

  25. Great article! Just has one minor error with the landfall: Wilmington is in North Carolina, not South.

  26. “The forecast for Florence has to be regarded as a success story. 5-7 days lead time was provided for a landfall (or pseudo landfall) near Wilmington, SC.”

  27. Notable differences in what is said to be “already evident” in three conflicting statements.

    Curryja: Kerry Emanuel has said that it it will be mid-twenty-first century before we’d expect to see any climatological signal in the observations …

    Kerry Emanual: “In many metrics, it [human influence] is already evident (e.g. for rain*).”
    (Leaving one to wonder what the other “many metrics” are.)

    NOAA offers the assessment: In the Atlantic, it is premature to conclude that human activities–and particularly greenhouse gas emissions that cause global warming–have already had a detectable impact on hurricane activity.

    Once again in more detail.
    curryja writes: “Climate Feedback responded to Roy Spencer’s op-ed with a fact check … It includes extensive commentary by Kerry Emanuel that is worth reading.”

    In the article Roy Spencer is quoted:
    “for humans have any influence on hurricanes at all, it probably won’t be evident for many decades to come”
    To which Kerry Emanual comments:
    “In many metrics, it is already evident (e.g. for rain*). Waiting for the signal to emerge unambiguously before acting would be foolish …”
    Notably, while Emanuel refers to “many metrics” he names only one. The remainder of his comments refer to his perspective on how the “best available evidence” should impact public policy.

    In contrast, in the transcript of this in Oct 2017 interview curryja says:
    “JC: Kerry Emanuel has said that it will be mid-twenty-first century before we’d expect to see any climatological signal in the observations, because natural variability is so large. And weather roulette — sometimes crazy things happen, and then they don’t have anything to do with climate. By the time you have a long enough time — and this is assuming that we have some substantial warming over the next thirty years — if we do have substantial warming over the next thirty years, probably by 2050 we would start to be able to tease out a signal.” —
    Was the universal qualification of “any” in the “any climatological” assertion a bit too broad?

    In the meantime NOAA’s GFDL offers this assessment:
    Global Warming and Hurricanes: An Overview of Current Research Results
    Last Revised: Sept. 20, 2018
    “In terms of detection and attribution, much less is known about hurricane/tropical cyclone activity changes, compared to global temperature. In the northwest Pacific basin, there is emerging evidence for a detectable poleward shift in the latitude of maximum intensity of tropical cyclones, with a tentative link to anthropogenic warming. In the Atlantic, it is premature to conclude that human activities–and particularly greenhouse gas emissions that cause global warming–have already had a detectable impact on hurricane activity.” –

  28. Pingback: Weekly Climate and Energy News Roundup #329 | Watts Up With That?

  29. Pingback: Weekly Climate and Energy News Roundup #329 |

  30. Pingback: Nothing Unprecedented about The Sea Surface Temperatures for Tropical Storm-Hurricane Florence’s Full Storm Track | Bob Tisdale – Climate Observations

  31. Pingback: Nothing Unprecedented about The Sea Surface Temperatures for Hurricane Florence’s Storm Track | Watts Up With That?

  32. Pingback: Nothing Unprecedented about The Sea Surface Temperatures for Hurricane Florence’s Storm Track |

  33. Pingback: The temperature of the ocean floor for the storm trajectory of the hurricane in Florence | Tech News

  34. Pingback: Nothing Unprecedented about The Sea Surface Temperatures for Hurricane Florence’s Storm Track – Climate Collections

  35. Tomas Milanovic

    Excellent post Judith , I enjoyed it .
    I would like to add an element to the attribution categories .
    When the subject of study is an identified event (f.ex Florence) then, as you said, it is pure dynamics . Post fact basically everything can be understood and explained because , again , it is just dynamics and at these time and space scales the dynamical meteorological equations and their numerical solutions are reliable enough .
    Why didn’t it go north ? Obvious, there was a high pressure . Etc .
    But because all slow and/or weak processes are irrelevant for these dynamical equations, eventual climate changes are pretty much by definition indetectable in any analysis of an individual event .
    So Roy Spencer is right – Florence (or any other name) is “just weather “.

    Any “climatic” attribution must then cross the large divide between the pure “simple” dynamics of a single event and the statistics over a very large time scale of similar events .
    But then a null hypothesis is absolutely needed because if one wants to conclude on a statistical significance it is necessary to analyse and explain the difference between a measured time series and the null hypothesis .
    The null hypothesis is necessarily [CO2] = constant
    But how can one define the distribution of the dynamical parameters for this null hypothesis ?
    Well certainly not empirically because we have only 1 measured time series and we can’t do experiments with hundreds of Florences while imposing [CO2] = constant .
    So the null hypothesis is necessarily theoretical .
    And here the danger is similar to what Robert Ellison reminded about the Hurst phenomenon .
    We can eliminate at once the climate models for reasons you already mentionned – climate models are unable to compute the dynamics of Florence or any meteorological event at the relevant time and space scales .

    So what is left ?
    Well you must make a theoretical postulate .
    Either you postulate that the observed time series is non stationnary and is composed of a sum “deterministic trend” + “stochastic stationnary process” .
    Or you postulate that the observed time series is stationnary and results from interaction between multiple time scales .
    Both belong to what you called the attribution methodology N°4 but are fundamentally different .

    Postulate 1 implies that the null hypothesis is the “stochastic stationary process” so that tautologically the “deterministic trend” is what allows you to do the attribution . Useless to add that you don’t know that the system (e.g weather because climate is just an average of weather) can be defined in that way . It is only a postulate which leads to a self fulfilling prophecy .

    Postulate 2 implies nothing about the null hypothesis and the Hurst phenomenon is an example which governs among others hydrological processes . Dimitri Koutsoyiannis published a number of interesting papers where he proves that when the postulate 1 is applied to a Hurst process , dramatical errors take place in estimating the statistical momenta (e.g the variances and autocorrelations are largely underestimated) from where follow dramatical errors in statistical predictions . The correct way to study a Hurst process (or more generally ergodic chaotic processes) is to look for interaction of processes at multiple time and space scales . This is typically what happens when one considers that weather and its statistics are dominated by oceanic oscillations at multiple time scales .
    Of course, as the postulate 2 doesn’t allow to define a null hypothesis , it doesn’t help with cheap and easy “attributions” which can be done with postulate 1 so that statistical studies in climate are generally done with postulate 1 .