If I Had Ever Been Here Before I Would Probably Know Just What To Do

An argument preferring recurrence questions to attribution questions

We have had a very severe weather event in South Carolina. As I write it is still an extremely serious situation. Before taking off onto the science and implications, it is worth taking note of the human suffering and environmental damage. There have been 14 reported deaths and enormous property damage, much of it to residences without flood insurance, bringing catastrophic and unexpected expense to many households.


Even now, before the rivers have stopped rising, the usual Disaster Tango has ensued, with the dance partners partners each dancing to a different tune. The tunes were “climate change caused it” / “it has nothing to do with climate change”. This dance inevitably follows a severe weather event, especially in the USA. Little is achieved by it.

Both positions are very problematic in my opinion.

We have to look for better ways to talk about these sorts of things, and in my opinion the only way to do that is to stop pointing vaguely at science and instead develop the patience to actually think about the situation. Science is commonly used as a weapon in a polemical battle, but that’s abusing it.

There are reasons to argue from authority, but every severe event begins as an open question. Open questions give us the opportunity to think about science as a rational community of interest, rather than as a pair of competing debate teams.

We should be looking at what science says, and using it to bring the conversation closer to reality. Instead, each side picks their own evidence and uses their favorite points as a cudgel. That may be how politics is done. But it’s not how we attain to a world that is informed by reality.


If you need to quickly decline to dance the “did not/did too” dance, Kevin Trenberth et al have provided a sensible escape:

“The climate is changing: we have a new normal. The environment in which all weather events occur is not what it used to be. All storms, without exception, are different. Even if most of them look just like the ones we used to have, they are not the same. ”

To that, Andy Revkin raises this objection:

“In this piece, Kevin Trenberth’s insistence that greenhouse-forced climate change is in every extreme weather event has no meaning without some quantification. The same could be said for every sunny unremarkable day, as well.”

Of course it is true for every event, remarkable or otherwise, that it is a part of a changed climate! That is not a refutation of Trenberth because it is exactly what he claimed.

To be fair to Revkin, Trenberth is looking at the attribution question itself, while Revkin’s attentions are further down the policy chain. After all, if the world’s climate were to somehow become more benign (however you choose to define that) it would still be a climate change but wouldn’t imply any policy change.

Trenberth is however responding to an overvaluing of the formal attribution question that has plagued climate change conversation from the beginning. When we see something odd in the weather, it is natural to ask whether it is “because of” human interference. This is formalized into scientific questions of various sorts, and the result is often inconclusive or misleading. Climate change is perhaps the only scientific discipline where inconclusive results, rather than being buried, are trumpeted from the mountain-tops by those who would like to imply that nothing at all is known.

Here’s a classic example reported in mass media of work by Marty Hoerling, who is consistently equivocal about finding traces of climate change in actual events on the ground.

It’s to this pernicious pattern that Trenberth et al is responding.

We should simply bypass those questions in public discourse. I propose extending Trenberth et al’s assertion something like the following:

As Trenberth et al. assert, “The climate is changing: we have a new normal. The environment in which all weather events occur is not what it used to be. All storms, without exception, are different. Even if most of them look just like the ones we used to have, they are not the same.” This in itself does not inform us about the extent and immediacy of the climate risk we are taking. What we should care most about is the prognosis for the future climate that is dramatically much more altered than the one we face today. To inform that, we should not look at individual events, even the most extremely destructive ones, without taking a historical perspective and seeking comparable disasters in the past. ”

This is to say that formal attribution is the wrong question. (One might say it is applying frequentist reasoning to very small sample sets, and so necessarily yields inconclusive results.)

You might argue that we should take a Bayesian perspective, to see how events that we see line up with our priors, but that’s problematic as well. That is, we might ask whether this or that particular event tends to confirm or change our detailed expectations. Without, for the moment, getting into why this is a very difficult question to address, I’ll just say that it’s still the wrong question insofar as Revkin’s complaint, (assuming it makes any sense at all) is concerned.


What we care about collectively is whether things are already getting worse because of our actions, not whether our theories are correct in every detail. This, it seems to me, is the quantification Revkin is asking for.

(Regarding sea levels, which did play a role in the South Carolina disaster as well as the Sandy disaster, this is a slam dunk. Definitely, to the extent that sea level is part of the event, human action is partly responsible. Definitely, coastal flooding is worse on account of human interference in the climate system. But let’s leave that aside for now.In other disasters, drought for instance, clearly this is not so. There are very interesting questions at hand in cases where sea level is not involved.)

This brings us around to “recurrence rates”. To speak of recurrence rates seems to me a sounder approach to the climate/disaster connection than speaking of attribution.

To be sure, once one accepts Trenberth’s observation that we live in a changed climate, there is a separate question as to whether human activity dominates the changes. On this matter, the consensus is clear enough; the battles with those who try to squirm out of the concensus won’t go away because we wish they would.

But even so, recurrence conversation gives us something we can talk about together, in a non-oppositional way. It might help us improve the extent of our shared understanding.

If we do accept that climate change is and for the foreseeable future will be human-dominated, then we can make more fruitful use of the disaster record to inform the scope and urgency of the problems we face in coping with our new responsibilities.


The “recurrence rate”, useful though it is in thinking about our situation, is commonly misunderstood.

Of course, “a thousand year recurrence rate” or a “1000-year storm”  means that the expectation of seeing such an event in a given year is 0.001, i.e., that the average 1000 years contains one such event.

Claims like ”a 1000-year recurrence rate” are being bandied about for the South Carolina flood, and being duly mangled by politicians and in turn duly mocked by comedians. The governor of South Carolina seems to have claimed that “South Carolina has seen nothing like this for a thousand years”, as if there were some sort of of millenial clock spurting out weird moisture jets in every year ending in ‘015.


Recurrence time does give us something we can effectively apply quantitative reasoning to. If we are seeing more disasters that one would expect on this quantitative scale, then we could unambiguously apply (non-sea-level-rise) costs to human activities. A recurrence argument is likely to be more fruitful than attribution arguments.

Still, Colbert has a point. We don’t really have a lot of information on the distribution of the rarest events, as typically their occurrence, if any, would be prehistorical. There is much speculation about the shape of the tails of these distributions. Unfortunately, the stranger an event is, the more important it is, but also the less confidence we have in its recurrence rate.

On the other hand, the most extreme events ARE the ones we should be paying the most attention to in evaluating whether climate change has really begun to bite. The current California drought, the Texas drought of 2011, recent heatwaves in Australia, the Pakistan floods and Russian fires of 2010, such events are arguably so far outside the norm that they arguably would simply not occur in a stable Holocene climate. If so, their recurrence times would literally be infinite. It looks that way, but it is intrinsically hard to know this, as any recurrence time longer than the duration of the instrumental record has to be somewhat speculative.

Unfortunately any honestly inconclusive result can easily be twisted to yield aid and comfort to those-who-must-not-be-named; let’s call them the ignorophiles. Of course I mean those who ask “you can’t *prove* anything so why should we change our policy?” We must patiently point out to those wielding this tiresome argument that they are analogous to a doctor, unable to come up with a firm diagnosis, asserting that a patient, however uncomfortable, cannot possibly be sick. Applied science is not afforded the luxury of certainty. The balance of evidence is tricky enough – it is more so when there is a dedicated group trying to dig up ambiguities and red herrings. Strange things are afoot, and we expect them to get stranger, even if we can’t exactly quantify that expectaion.

On the other side of the ledger, there’s something misleading about the way these recurrence times are bandied about. There are plenty of locations on earth, and various sorts of events (wind, rain, flood, drought, snow) to worry about. A 1,000 year event in one place is a big problem for that place, but it sounds scarier than it is. In an unchanging climate, if there are 1,000 places the size of South Carolina and 5 types of events, we’d expect an average five of these a year globally, one per type. A single thousand year event is big news for the people who experience it, and may be a big deal economically or even geopolitically, but it isn’t in itself climate news.

But we have to be willing to roll up our sleeves and dig into the dirt. The recurrence question can provide an honest motivation to engage with the details of the science. However tragic it was, the South Carolina firehose was also a fascinating bit of atmospheric dynamics. We should be able to take the occasion to delve into the details, rather than shrugging it off.

We should be willing and able to say “What’s the recurrence time of such an event? We don’t have a great answer, but it’s a great question!” It’s certainly a better question than “is this our fault? Hell yes!” (or Hell no!”) It opens the door to reasoning and to attention to evidence, rather than shutting it. It engages our minds rather than our guts.

Regarding the South Carolina floods, I suspect we’ll even find that 1,000 year recurrence is something of an understatement. But before we dig into it, we should think a bit about what a recurrence interval really means. Stu Ostro has some points to make about this question (toward the end of the linked article). I agree with him that it’s considerably more complicated than it sounds at first. But it is neither polarizing nor boring, so I think it’s worth thinking about.

— mt


UPDATE: From Tom Fuller’s blog:

Screen Shot 2015-10-09 at 11.18.39 PM


ATTP has generously added me, Michael Tobis, Ph.D. (Atmospheric and Oceanic Sciences, University of Wisconsin – Madison, 1996), commonly referred to as “mt”, as a co-author of this site, so I guess this doesn’t count as a guest post.

I am a retired climate scientist and much influenced by computer science and information theory. I never aspired to a faculty position or published much in the formal literature, but I am familiar with the science and am personally acquainted with some of the most prominent and impressive climate scientists. I will continue to post smaller climate-related observations and possibly longer pieces of economics – skepticism on my own blog, Only In It For The Gold, but will endeavor to contribute here regularly.

I am working on a book on how to think about disasters in a changing climate.


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104 Responses to If I Had Ever Been Here Before I Would Probably Know Just What To Do

  1. afeman says:

    Bad youtube link.

    [ fixed by our host -mt ]

    What fairly startles me is that a number of stations blew by the 1000 year mark for 5-day precip by several inches.

    http://dipper.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=sc
    via
    http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3142

    It’s difficult to fit that with anodyne (if statistically correct) statements about expecting to find such an occurrence X times a year. This looks like black swan territory, earlier than expected.

  2. RickA says:

    Wasn’t the extraordinary amount of rainfall caused by a hurricane?

    Who can say whether the hurricane was caused by humans?

    Or was made worse by humans?

    All we know is hurricanes hitting the East coast of the USA are lower lately than they were before (over the last decade) – but who knows if that will continue.

    So if the rain caused the flooding, which was caused by a hurricane, and hurricanes are less likely (a big question obviously) – wouldn’t that play into the recurrence rate calculation?

  3. MT,
    Thanks for the post. Very interesting. It’s a topic I had thought of covering, but don’t think I could have done it the justice you have. Maybe related to what you’re getting at here is a sense that there is pressure to try and attribute events, which then leads to various counterclaims if anyone suggests that they can do so. Instead – as you suggest – we should be using science to bring the conversation closer to reality. As you yourself indicate, there are some aspects about which we have more confidence than others – warming, precipitation, sea level rise being some examples. It seems (and maybe this is what you’re suggesting) we should use this type of understanding to try and discuss what we might expect in the future, rather than specifically trying to attribute human influences to specific events.

  4. Willard says:

    How many leading questions can you ask in a single comment, RickA, and is this related to the fact that you practice law?

  5. mtobis says:

    I intend to take on Rick’s questions. A valid point is that extreme events are by nature sui generis. Doing statistics on them is hard.

  6. mtobis says:

    afeman: “looks like black swan territory”

    It’s definitely a black swan; but is it a climate change astonishing outlier or just a regular astonishing outlier?

    Stay tuned; I’m not sure where this will come out exactly but you can be confident that my answer will be some form of “maybe”.

    “earlier than expected”

    I think IPCC and consensus science is remarkably silent on expectations. Still, I tend to agree there is a sort of informal expectation among climatologists that it is early for anthropogenically driven disasters to really pop up out of the noise.

    But are they?

    Which side of this question is falling victim to confirmation bias?

    There are slam dunk questions in science. This isn’t one of them. Fortunately it’s an objective question. Unfortunately, it’s a messy one. Fortunately it’s an interesting one.

    Anyway, I seem to be able to spend hours a day writing about it. Stay tuned, there’s more along these lines to follow, and I intend to mostly avoid the beaten paths.

  7. snarkrates says:

    Extreme value statistics are just a special case of order statistics. Mike, do you know if anyone has looked at how the order statistics are changing. The advantage there is that you have more statistics to work with. Moreover, there are games you can play with not only recurrence, but with increments between the order statistics vs. time (e.g. by how much does the new extreme crush the old one).

  8. RickA says:

    Willard:

    3.

    Probably.

  9. lerpo says:

    “All we know is hurricanes hitting the East coast of the USA are lower lately than they were before (over the last decade)”

    I don’t believe that Joaquin hit the east coast either: http://www.npr.org/sections/thetwo-way/2015/10/02/445264369/joaquin-brings-rain-but-east-coast-likely-to-dodge-direct-hit

    Regarding Atlantic hurricanes in general, the trend seems flat. The last decade appears to be at the higher end. – http://www.gfdl.noaa.gov/historical-atlantic-hurricane-and-tropical-storm-records

  10. Andy Skuce says:

    Excellent post, mt

    RickA: Lawyers never ask questions that they don’t know the answers to. My guess for your answers would be yes, nobody, nobody. Correct me if I’m wrong, I am, frequently.

    My answers, for what they are worth, are: partly, nobody, some experts do. Although if you had me in the witness box I might be restricted to yes/no/don’t know answers.

  11. mtobis says:

    snarkrates, specific examples and references would be welcome.

    That said, the Disaster Tango is about disasters, so the statistics of everyday events are off topic, important though they are in a broader context.

    There are good reasons and bad reasons for the perennial interest in the subject of disasters in climate change, but for the most part the dance tends to be pointless and dull. This is peculiar, given the fact that the question is intrinsically important and interesting.

    It’s time for some new choreography.

  12. izen says:

    ATTP may have a different take on those questions… here’s mine!

    @-RickA
    “Wasn’t the extraordinary amount of rainfall caused by a hurricane?”

    No, the hurricane and the extraordinary amount of rainfall where part of a much larger system of meridional energy transfer.

    “Who can say whether the hurricane was caused by humans?”

    Anyone can say that hurricanes are caused by the way energy flows from the equator to the poles with the process mediated by the phase changes of water. It is never humans who ’cause’ hurricanes.

    “Or was made worse by humans?”

    AGW can cause warmer sea surface temperatures which make the hurricane more intense which MAY be ‘worse’ in one sense.
    However ‘worse’ would seem to imply that the valuation is based on its impact on humans not just its physical characteristics.

    The main way humans make hurricanes worse is by building housing and infrastructure unable to withstand hurricane impacts in areas with a known history of hurricane landfall.

    “All we know is hurricanes hitting the East coast of the USA are lower lately than they were before (over the last decade) – but who knows if that will continue.”

    Archeologists and geologist are the best source for the incidence of hurricane landfall over a longer timescale than a decade. I am not aware of any very prolonged period when hurricanes did not impact the N American Atlantic coast intermittently. Given the geological evidence of intense storms in the Caribbean for most of the Holocene it would seem unwise to bet on the East coast of the USA remaining free of hurricane impact in the future, unless you are expecting the human impacts of AGW to prevent the past pattern.

    “So if the rain caused the flooding, which was caused by a hurricane, and hurricanes are less likely (a big question obviously) – wouldn’t that play into the recurrence rate calculation?”

    GIGO.
    The intense rain was caused by a particular combination of a VERY energetic hurricane driven by exceptionally high SSTs and all the extra water in the atmosphere.
    While the shape of the event is an emergent property of the system and as yet somewhat unpredictable, the conditions that enable such an event are ’caused’ to some arguable extent by AGW.

    The gun-nut goes on a rampage…
    The level of availability of guns determines the recurrence rate of such events.

  13. mtobis says:

    On second thought, it’s interesting that I write a post specifically saying

    > “What’s the recurrence time of such an event?” [is] certainly a better question than “is this our fault?”

    and Rick A responds, in part

    > Who can say whether the hurricane was caused by humans?

    My answer to that part remains that it is very much the wrong question.

  14. I like the analogy of climate change ‘increasing the floor height of the basketball court’ or, for Europeans, ‘making the goals increasingly wider’. It doesn’t become the reason a goal or a basket is scored—that’s still a function of the bounce/roll of the ball and the skills of the players—but it does increase the number of goals or baskets being scored in each game.

  15. RickA says:

    mtobis:

    Ok – it is the wrong question.

    Still – if the rain was caused by a hurricane (it was) – than anytime a hurricane happens it could rain a whole bunch and cause flooding.

    So your recurrence rate is really a – how often are we hit by a hurricane rate.

    Based on Roy Spencer’s post, I am going to guess a recurrence rate of about 100 to 125 years.

    I believe he found flood stage seven feet higher in 1903 or 1908? Going off memory.

    So two data points.

    So I would say the 1 in 1000 year thing is probably hyperbole.

  16. RickA says:

    Andy:

    Yes – I do think that the flooding was caused by the hurricane and that we really have a difficult time with predicting how many hurricanes there will be and how many will hit the USA. I really think we have a hard time attributing any particular hurricane to humans.

    But I don’t disagree with mtobis – it is a good idea to look at how often something might happen when planning on how to deal with what might happen – so this is a good discussion.

    Lets get even more specific.

    Lets postulate that it can rain 24 inches in a fairly short period in NC (or SC) or anywhere on the East Coast. It wouldn’t be the worst thing ever to change building codes going forward to plan for 24 inches of rain in a 24 or 48 hour period, and try to divert, store and handle.

    For example – how expensive would it be to build a house which could be jacked up two feet (if necessary). On a going forward basis obviously. Compared to a house which couldn’t be jacked up?

    I have no idea – but I will guess a couple thousand bucks.

    Might be a good idea to put that into the building codes if your house is in a 500 year flood plain, and especially if it is a 100 year flood plain.

  17. I don’t quite understand the fixation on the hurricane. Bear in mind, Joaquin did not make landfall on the continental US.

    The more important factor was the very strong upper level low which set up the efficient conveyor belt or “atmospheric river” of moisture from the Caribbean. Joaquin happened to be one gear in the machine of this conveyor belt which made the larger, synoptic-scale system that much more efficient at moving massive quantities of moisture. As izen points out, this disaster was the byproduct of a larger scale system in the atmosphere which moves energy from the equator towards the poles in each hemisphere.

    The detection/attribution of an anthropogenic signal in hurricane statistics is probably a much harder question than the detection/attribution of the pattern in upper-level dynamics which enabled the flooding in the first place. And since there are more of these events per year, the statistics might be a bit easier, too – although attributing any changes in those statistics to things that humans have done is still a Very Hard Question.

    Overall, I think there’s far too much eagerness to pin individual extreme weather events on climate change (with the exception of droughts and heat waves).

  18. Willard says:

    > My answer to that part remains that it is very much the wrong question.

    Who’d thunk?

    ***

    > Based on Roy Spencer’s post […]

    Perhaps I missed a citation, but which post?

  19. RickA says:

    izen said “No, the hurricane and the extraordinary amount of rainfall where part of a much larger system of meridional energy transfer.”

    You went one level to high for me with that comment.

    At that point – you might as well say it was caused by Fall – or even the sun. To abstract.

    No – I think it is safe to say the rain was caused by the hurricane – does anybody disagree with me?

  20. RickA,

    No – I think it is safe to say the rain was caused by the hurricane – does anybody disagree with me?

    Hmmm, even that seems simplistic. Would it have rained without the Hurricane? I guess we could say that the Hurricane carried warm, moist air, to a region where the air cooled, the moisture condensed out, and it rained. I’m not sure that I would call that “caused”. There are more interesting questions worth answering, which – I think – is the point of MT’s post.

    Roy Spencer’s post seems to be making the same point that MT – and others – have made.

  21. izen says:

    @-RickA
    “No – I think it is safe to say the rain was caused by the hurricane – does anybody disagree with me?”

    I do obviously.

    NONE of the rain that fell came from the hurricane. it came from an already extant local weather system.
    How do you justify claiming that the rain was CAUSED by the hurricane when it was at most a distant influence?

  22. RickA says:

    ATTP:

    It is not whether it would have rained without the hurricane – but would it have rained as much as it did without the hurricane.

    But – ok – forget the hurricane.

    Lets just look at how often it rains 24 inches or more in a 24, 48 or 72 hour period (say in SC).

    Still seems like every 100 or 125 years.

    Maybe even once every 50 or 60 years?

    Not my field – so I will wait for mtobis’s recurrence rate (or anybody else’s).

    Mine is just a guess.

  23. RickA says:

    izen:

    Sorry – I am not sure what you are talking about.

    The clouds which were over SC and which dropped all the rain were part of Joaquin.

  24. BBD says:

    mt wrote:

    Claims like ”a 1000-year recurrence rate” are being bandied about for the South Carolina flood, and being duly mangled by politicians and in turn duly mocked by comedians. The governor of South Carolina seems to have claimed that “South Carolina has seen nothing like this for a thousand years”, as if there were some sort of of millenial clock spurting out weird moisture jets in every year ending in ‘015.

    Before we get too sidetracked by RickA, does anyone know more about where the 1000 year claim came from or on what basis it was made?

  25. mt says:

    Hurricane? Not hurricane? It’s complicated.

  26. BBD says:

    I think it’s important to remember that while it is risky for anyone to make strong claims about AGW based on a single extreme weather event, it is *equally* risky for anyone to use a single weather event as ‘evidence’ that AGW is not happening / happening but not serious etc.

  27. RickA,
    As I understand it, the amount of rainfall exceeds any event in SC in recorded history. The problem with calling it a 1-in-a-1000 event is that we don’t have data that allows us to make such a claim, not that it isn’t indeed an extreme event for that location. Also, as MT points out, if you consider 1000 different locations, you would expect there to be 1-in-a-1000 event at – on average – one of those locations every year. So, a single 1-in-a-1000 event (if it is indeed such a thing) isn’t necessarily indicative of anything. It’s important – I think – to consider the overall picture, not a single event.

  28. izen says:

    http://www.cnbc.com/2015/10/05/1000-year-flood-hyperbole-or-hard-science.html
    “The reference is to a statistical measure — 1 in 1,000. It means that there is a 1 in 1,000, or 0.1 percent, chance that such a rain event or flood will occur in any given year. There are also 500-year and 100-year rain events, which have probabilities of occurrence of 0.2 percent and 1 percent, respectively.”

    It got mentioned on the Roy Spencer thread, with further links to distribution and asymmetric long tails; and dismissed as clearly impossible to estimate probabilities of 1:1000 events from a mere 100 throws of the die.
    But then there be dragons…

    @-mt
    “Hurricane? Not hurricane? It’s complicated.”

    Selective framing of causation is often a problem, –

    “It is not whether it would have rained without the hurricane – but would it have rained as much as it did without the hurricane.”

  29. Magma says:

    RickA: Lets just look at how often it rains 24 inches or more in a 24, 48 or 72 hour period (say in SC).
    Still seems like every 100 or 125 years.
    Maybe even once every 50 or 60 years?
    Not my field – so I will wait for mtobis’s recurrence rate (or anybody else’s).
    Mine is just a guess.

    I don’t know whether RickA is trying to be annoying with these sort of questions and uninformed guesses or if it’s accidental.

    In over a century of weather records, South Carolina’s maximum 24-hour measured rainfall was 14.8″. Almost all of the cases where 24-hour rainfall exceeded 10″ occurred when a named hurricane or tropical storm made landfall. The highest predicted 4-day rainfall with a 1000-year precipitation frequency for the entire state (North Myrtle Beach on the north coast) is only 20.5″. Wide areas of the state received over 20″ of rain over four days in the recent storm without Joaquin making landfall.

    http://www.dnr.sc.gov/climate/sco/ClimateData/data/24_hr_pcpn.php

  30. Magma says:

    A number of points relevant to the rainfall totals are discussed here, mostly accompanied by non-technical graphics.
    http://www.weather.com/news/news/south-carolina-historic-flood-rainfall-record-extreme

  31. Magma says:

    From the preceding Weather Channel source:

    This week’s storm deluged the Carolinas for the better part of five days, so we took a look at the wettest five-day intervals on record in South Carolina history. At the start of this month, the top five were:
    17.44 inches in downtown Greenville (Aug. 22-26, 1908)
    17.37 inches in Kingstree (July 12-16, 1916)
    17.08 inches at Charleston International Airport (July 8-12, 1973)
    16.93 inches in Gillisonville (Aug. 27-31, 1898)
    16.80 inches in Myrtle Beach (Sept. 15-19, 1999)

  32. afeman says:

    The NOAA link I posted goes directly to the recurrence rates for SC.

  33. afeman says:

    Also, the point about expecting a random 1/1000 event among 1000 locations seems complicated by geographical autocorrelation — you don’t expect rare events to randomly happen adjacent to each other.

    I’d also have to ask — are supposed 1000 year events happening all the time and we just don’t record or hear about them? Or are we imposing the wrong PDFs?

  34. izen says:

    @-RickA
    “For example – how expensive would it be to build a house which could be jacked up two feet (if necessary). On a going forward basis obviously. Compared to a house which couldn’t be jacked up?
    I have no idea – but I will guess a couple thousand bucks.
    Might be a good idea to put that into the building codes if your house is in a 500 year flood plain, and especially if it is a 100 year flood plain.”

    If this was government mandated there might be some pushback from the property developers and builders. Two feet may be insufficient, and difficult to aply to larger retail or commercial buildings.

    It is rather authoritarian, next it will be requiring property owners to have a government regulated ‘Obama-Floodcare’ insurance if they live in a 100 year floodplain.

  35. RickA says:

    izen:

    It is rather authoritarian.

    I am not advocating it, just indicating it could be done.

    In Minnesota, the local building code has requirements on the maximum height of a residential home, the R value of the windows and insulation, the thickness of the studs and a host of other issues. So it certainly wouldn’t surprise me in the least.

    As to flood insurance – yep – they sure could do that.

    If they can force everybody to have health insurance, they can force everyone to have flood insurance (or pay a penalty). Again, not in favor – but they could do it.

  36. snarkrates says:

    Rick, The hurricane remained >800 miles off shore! And the precipitation was all up and down the East coast! Are you proposing that the hurricane caused the rain via telekinesis?

  37. Magma says:

    @afeman: as you infer, the temporal and spatial autocorrelation is substantial.

    @ izen: here’s a relevant article from the Charleston Post and Courier:
    http://www.postandcourier.com/article/20151007/PC16/151009476

  38. RickA says:

    snarkrates:

    Look – I am from Minnesota, so what do I know about hurricanes?

    This is the kind of stuff I read:

    http://www.upi.com/Top_News/US/2015/10/03/Flooding-from-Hurricane-Joaquin-continues-in-Carolinas/4681443884245/

    This article said:

    “The eye of Hurricane Joaquin is currently located well away from the U.S. East Coast although its bands continue to dump massive amounts of rain on the mainland.”

    So I got the impression that the hurricane caused the rain.

    Maybe “caused” is the wrong word.

    Maybe I should say the rain was correlated with the hurricane and but for the hurricane it wouldn’t have rained so much in SC?

  39. BBD says:

    RickA?

    I am not advocating it, just indicating it could be done.

    Stilts by Jove! Panic over.

  40. Kevin O'Neill says:

    snarkrates writes: “Rick, The hurricane remained >800 miles off shore! And the precipitation was all up and down the East coast! Are you proposing that the hurricane caused the rain via telekinesis?”

    No, not telekinesis, but teleconnections – via direct outflow of moist tropical air from Joaquin feeding the ‘noreaster’ that hit the US east coast. The fact the hurricane remained offshore was predicted in advance by models several days out – as was rain caused *by* the hurricane. From Jeff Masters Wunder Blog, Oct 2nd, Thousand-Year Rains Possible In Carolinas

    The latest 3-day Quantitative Precipitation Forecast from NOAA’s Weather Prediction Center is calling for 10 – 15″ inches of rain for the majority of South Carolina, including the cities of Charleston and Columbia.

    This forecast assumes that Hurricane Joaquin will not come anywhere close to the state. The rain will be due to what meteorologists call a “Predecessor Rain Event” (PRE) (see this paper on them, h/t to Stu Ostro of TWC: http://journals.ametsoc.org/doi/pdf/10.1175/2010MWR3243.1). In a Predecessor Rain Event, tropical moisture well out ahead of a landfalling tropical cyclone interacts with a surface front and upper-level trough to produce heavy rainfall, often with significant inland flooding. The PRE can develop well to the left or right of the eventual track of the tropical cyclone. Slow-moving Hurricane Joaquin is perfectly positioned to transport a strong low-level flow of super-moist tropical air that has water vapor evaporated from record-warm ocean waters north of the Bahamas westwards into the Southeast U.S. Once this moisture hits land, it will encounter a cut-off upper low pressure system aloft, with a surface front beneath it, which will lift the moist air, cooling it, and forcing epic amounts of rainfall to fall. The air will also be moving up in elevation from the coast to the Piedmont and Appalachians, which lifts the air and facilitates even more precipitation. Satellite imagery is already hinting at development of this connection of moisture between Joaquin and the Southeast low and frontal system.

  41. Ken Fabian says:

    How likely some event is has to be tricky to determine – and has to be with respect to prevailing climatic conditions. One in ten thousand years, when prior ten thousand year periods include ice sheets across N. America, Asia and Europe can make it misleading and even meaningless. This kind of measure of likelihood is one commonly used and it seems more comprehensible to the general public (not so sure that’s actual rather than just apparent) but surely the prevailing climate state – ie the actual climate and weather processes in play are the key elements.

    Also I’m not sure communication with the public is the crucial crux; more important is with those who hold relevant positions of trust and responsibility, including mainstream media. They need to be well informed or capable of taking the expert advice they receive seriously. That will flow through to the broader public. Not sure how that could be made to happen except by trial and error and attrition that eventually overwhelms self interested uncertainty and reluctance to act – and almost certainly cost us more decades of our window of opportunity to get a handle on the climate problem.

  42. Andy Skuce says:

    Most flood insurance is, at least in Canada, just for basement flooding in the case of sewer back-up or burst water pipes “Overland” flooding is specifically excluded as a risk. Many people in Calgary found that out, to their surprise, when the big floods hit in 2013. The government paid up.

    Living on the west coast, in the one-in-300-year Big One belt, I have earthquake insurance. Like most people, I had never read the fine print, but I did after the Calgary flood. I found that there is a huge deductible, 10% of the value of the home. So, if you have a house with a replacement value of, let’s say, $300,000, the first $30 k of damage is on you. Wood-frame houses built on rock are unlikely to be completely destroyed (except by tsunami, which is not generally a covered risk), so the EQ coverage is of limited benefit. I am sure that most people here assume they are covered for all damage.

    Ultimately, damage for big natural (or anthropogenically enhanced) disasters can’t be covered by private coverage, at least not at rates people can pay. It’s up to the government to pick up the bill and to reduce their exposure by limiting development in high-risk areas. Of course, it’s too late to stop people settling in Miami, New Orleans, LA, San Francisco, Seattle or Vancouver, so we’ll just have to act surprised when disaster strikes and hope that the rest of our countries will bail us out.

  43. mt says:

    Well, this is handy: http://dipper.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html

    (Works most places in the US, but not Texas. Grumble.)

  44. Jim Eager says:

    Watch the 7 second time lapse animation up thread a few times.

    There is no hourly time scale, but the first 2 seconds clearly shows the broad swath of cloud and rain of the preexisting low pressure system unrelated to Joaquin, including bands of heavy rain over the Carolinas *before* any influence from Joaquin. Then at the 5 second mark a strong flow of moisture develops and extends northward from Joaquin up to the preexisting low system (the teleconnection that Kevin mentioned), which rapidly develops into the relentless “firehose” directed at Charleston and then virtually locks onto the region even as Joaquin veers east and then north.

    Rick A is correct that it was the hurricane that supplied the extraordinary moisture that turned what would have been a heavy but unremarkable rain event into a 1 in a 1000 year record breaker, but Rick is not correct that it was the hurricane that caused it. Rather, it was the simultaneous confluence of the strong nor’easter and the proximity of Joaquin to feed it. Without the preexisting low Joaquin would not have had much effect on the mainland, but without Joaquin the preexisting low could not have dumped anywhere near that much water.

    That said, climate change also had an effect in that it produced a warmer sea surface temperature that enhanced evaporation to feed Joaquin, and the warmer air temperature that allowed the atmosphere to hold more moisture to fall as rain at landfall.

  45. Eli Rabett says:

    Ask not if SC floods caused by climate change. Ask were SC flood caused by high sea surface temps, which WERE caused by climate change. That is a whole lot easier to make the salient point about.

  46. Michael Hauber says:

    I don’t think the link can be proven by statistics. But can we get a physical link and mechanism? Increased SST and increased moisture carrying capacity in a warmer atmosphere is an obvious mechanism, but from memory the numbers are something like 4% extra water vapor per degree of warming? Not enough to be interesting in my opinion.

    There has been lots of speculation about slowing down of weather systems which allows them to stay in one spot for longer, which is certainly relevant to this case. A big part of this event was the fact that the length of time that the heavy rain fell for. Another factor to consider is convective aggregation. This was speculated as a possible mechanism in a paper that attempted to revive the IRIS effect recently. The theory being that in a warmer world tropical convection will have a stronger tendency to cluster together, which would produce more intense flash flooding rainfall type events. Anecdotally I have witnessed a surprising number of heavy convective rainfall events in Eastern Australia in recent years. I’m not sure if this is climate change, or because I have better access to radar etc to track in detail what is happening in each rain event.

    As for Joaquin’s role in this event I feel it was relatively minor, and to some extent the event happened in spite of the fact that Joacquin and the highest precipitable water values were well out to sea. From my experience watching similar events in Australia I’d guess that similar moisture influx could have easily occurred without a hurricane, and that if there had been a hurricane positioned in Florida the amount of moisture may have been much higher.

  47. Ethan Allen says:

    “Regarding sea levels, which did play a role in the South Carolina disaster as well as the Sandy disaster, this is a slam dunk. Definitely, to the extent that sea level is part of the event, human action is partly responsible. Definitely, coastal flooding is worse on account of human interference in the climate system. But let’s leave that aside for now.In other disasters, drought for instance, clearly this is not so. There are very interesting questions at hand in cases where sea level is not involved.”

    This assertion would appear to need some references?

    When one does water levels in the coastal zone, one usually separates the tides from the storm surge from the sea level rise.

    As to sea level rise NOAA suggests 3.16 mm/yr (+/- 0.22 mm/yr) for Charleston SC (which roughly speaking is one foot per century or 0.3 meters per century).

    As to the water level event itself, it just so happens that something occurred on the 28th of September (the 18.6-year nodal tide), which for Charleston was +8.4043 ft MLLW and four days later the water level was only about ~0.2 ft higher (the preliminary NOAA data has it at 0.264 ft but likely with some smoothing that number will be about 0.2 ft higher, say +8.6 ft MLLW).

    As to the pure storm surge alone that would appear to be 1.0-1.5 ft higher than the in situ astronomical tide, so really not much of a true storm surge to speak of (the NOAA predicted tide is flatlined or has zero slope, it only caries harmonics up through the annual Solar (SA) harmonic). What that basically means is that the current NOAA predicted tide is, very roughly, one foot below the in situ astronomical tide due to … you guessed it … sea level rise.

    Also, if you all are going to talk about climate extremes, in this case, I would want to look only at the precipitation index (or whatever it might be called) as a function of time. I’m sort of thinking that this was some sort of rare rain event. If we had, oh say 10,000 years of precipitation data (which we don’t, but I am sort of wondering what the total duration of precipitation data there is for SC), we could perhaps make some claim as to return period provided the data were very roughly stationary at say longer than millennial time scales.

    As such, I’m sort of wondering about Tropical Storm Claudette which occurred in 1979 …
    https://en.wikipedia.org/wiki/Tropical_Storm_Claudette_(1979)

    Which, you know, dropped up to 45 inches of rain in Texas. I guess that happened before there was all this talk of climate change? If that were to happen today and hit say Houston TX dead center .. oh boy … Mann would be screaming bloody murder or some such. When all you have is climate change on your mind, as presented to us by the MSM, perhaps every weather event is a climate change event. Don’t know myself, but it does seem as though that pump has been primed so to speak.

  48. Victor Petri says:

    @mt

    I have been wondering about this piece of information and I’d hope you could give your take on it.
    The so-called accumulated Cyclone energy, which does not seem to be in a particular rising trend.

  49. MT can comment more, or correct anything I get wrong, but I think there are a number of things to bear in mind. One possible outcome is that the number of cyclones/hurricanes goes down in a warmer world, but that the frequency and intensity of the strongest increases. That signal, however, is not something that we would yet expect to definitively have seen. There is actually some evidence for this in some ocean basins (see Elsner et al. 2008) but it’s still inconclusive. It would also be surprising if enhanced sea surface temperatures don’t lead to an increase in the strength of cyclones/hurricanes. One possibility, though, is that cyclones/hurricanes move to higher latitudes and so occur over the same kind of sea surface temperatures as before. However, if that did happen, they would be occuring in places where they were once rare.

    Additionally, the impact of a cyclone/hurricane isn’t only it’s intensity/strength, it’s also the precipitation, and storm surge. Warmer air carries more moisture and warming leads to sea level rise. So, even if we don’t see an increase in cyclone strength, doesn’t mean that the impact in the future will be the same as it is today.

  50. verytallguy says:

    Victor,

    your graph appears to show a couple of things:

    1) The importance of considering the source of data in evaluating it
    2) How ill-advised looking at a single metric in evaluating a complex subject can be

    Let’s look at them individually.

  51. Ethan Allen says:

    Also, your link here …
    http://www.wunderground.com/blog/stuostro/comment.html?entrynum=36

    Points to this tweet here …

    Now that one looked really suspicious, like it is an actual road, the old beach road or what’s left of the old beach road. That part of the beach has been known to be eroding for at least 35 years (the people that were at the FRF before I was there for a short one year stay in 1983 knew this already).
    http://wtkr.com/2015/10/07/nc-12-could-reopen-thursday-morning/

    So, I guess I forgot to mention nearshore waves and what’s known as wave setup. It’s been awhile, so I won’t hazard a guess on that one.

    On the 2nd there were 4 meter wave heights and on the 4th there were 5 meter wave heights in Duck NC. Now I guess I need to look at some offshore NOAA buoy data.

    The NOAA tide gage at the end of the FRF Pier (say 1800 ft offshore) suggest 2.5 ft storm surge and looking at the Charleston Harbor SC tide gage (6-min records back further than what I was looking at in my previous post)) it does appear to be 2 ft storm surge (both relative to the NOAA predicted tide). So it’s very likely that the storm surge on the open coast proper was somewhat higher in SC.

  52. Victor Petri says:

    @vtg
    What do you think I ask this question for if not exactly that?
    @attp
    Thanks. The measurements in itself you do consider valid?

  53. vp,
    I don’t know. I’ve seen nothing to make me think that it isn’t. In fact, I can’t see any reason why it wouldn’t be valid. The more interesting question is what it’s telling us and its relevance.

  54. verytallguy says:

    So, first, a case study in evaluating sources.

    Victor provides a link to a graph badged as “policlimate” but nothing more. The website itself is “policlimate”, not one I’m familiar with.
    Here’s my internal hierarchy:

    Most reliable: Authoritative literature from reputable organisations – publications by IPCC, Met office, NOAA etc.
    Next: Peer reviewed literature, with a caution that for a non-expert this can be easy to misinterpret and also cherry pick
    Lower down: Commentary likely from personal experience to be based on reliable science. Skeptical science, for instance
    Next: Unknown commentary – eg Victor’s graph from “policlimate”
    Bottom: Known biased sources. WUWT for instance, is directly in opposition to known facts

    Let’s have a look at “policlimate”.

    There’s not much there, but it immediately brings up a red flag with a post “cross posted to WUWT”. I now know this is unlikely to be a reliable source of information. The articles appear to be written by a name I’m unfamiliar with “Dr Ryan N Maue”

    Let’s google that name. The second link takes us to the graph, which has a cite to a peer review paper by Maue. That’s good, at least the data itself is likely to be accurate.

    Next on the list is a link to “Joe Bastardi and the Weatherbell team”

    The name “Bastardi” sticks in the mind. Let’s google him, and the Wiki helpfully shows us “Bastardi is an outspoken contrarian regarding human-induced global warming.[13][14] His views are sharply at odds with analyses by working scientists in the field.[15][16]”

    Not until the second search page does Dr Maue’s apparent employment at Florida State university as a meteorology professor turn up, however the university’s staff directory doesn’t show him, so maybe he’s left, or my search is awry.

    So, we find that Dr Ryan Maue writes for anti-scientific websites and is closely linked to a notorious climate change denier. However, he likely is or was a meteorology professor and does publish in peer reviewed literature. So his graph is most probably accurate, but it would be ill-advised to take his data or opinions as representative of the field. In fact it’s probably likely that graphs promoted by Dr Maue are actively misleading.

  55. verytallguy says:

    Now, let’s look at the actual graph.

    We’ll google “Tropical storm intensity ACE” and see what turns up. Wiki gives a description of the metric, which appears to be total tropical storm energy in a season. So it includes number as well as intensity of storms.

    What do we expect to happen under global warming?

    Here’s from the top of my hierarchy, IPCC AR5, WGI table SPM.1

    Increases in intense tropical cyclone activity is “More likely than not in the Western North Pacific and North Atlantic” – but not until the late 21st century. Before that, “low confidence”.

    So we don’t *expect* Maue/Victor’s graph to show a trend yet.

    Interestingly, we *do* already expect (early 21st century) “Heavy precipitation events.
    Increase in the frequency, intensity, and/or amount of heavy precipitation”, ie events like the one under discussion here.

    Let’s see what we can find of a descriptive nature to help our understanding:

    If we google “cyclone intensity trends” the bottom link takes us to Kerry Emmanuel’s page. Dr Emmanuel appears to be a reliable source, an MIT professor with many papers in high impact journals.

    His page on cyclone trends http://eaps4.mit.edu/faculty/Emanuel/publications/tropical_cyclone_trends provides a link to a very interesting FAQ and essay http://wind.mit.edu/~emanuel/anthro2.htm which helps fill in some basic understanding of the area for an ignoramous like me.

    So, my summary of the graph:
    1. it’s accurate
    2. it’s irrelevant
    3. it doesn’t help in finding reliable information on the subject

    And much more widely and importantly it teaches us that if you are interested in learning, you need a reliable source.

  56. verytallguy says:

    So, Victor, why did you post that graph?

  57. Victor Petri says:

    @vtg
    To find out if its accurate and relevant.

  58. verytallguy says:

    Victor,

    To find out if its accurate and relevant

    C’mon Victor. I think my efforts deserve a little more. There are many graphs on the interweb.

    Why did you post *that* graph?

  59. Victor Petri says:

    Because:
    “I have been wondering about this piece of information and I’d hope you could give your take on it.
    The so-called accumulated Cyclone energy, which does not seem to be in a particular rising trend.”

  60. verytallguy says:

    Yes Victor, but there are many pieces of information out there.

    What led you to wonder about *that* piece of information?

    Tell all.

  61. Victor Petri says:

    Because:
    it “does not seem to be in a particular rising trend” iow, in contrast with an increase in extreme weather events.
    Sorry, I don’t know what else you’d like me to say, I think all I said was pretty straight forward and understandable.

  62. verytallguy says:

    Victor,

    I’m interested in the motivation.

    What led you to the graph?

  63. izen says:

    Atlantic Hurricane energy – ACE – is known to shift on a decadal timescale in response (or as part of) the AMO – the atlantic pressure dipole between Iceland and the Azores. There are hyperactive decades, and low energy periods when total energy can be less than half the long-term ocean average. Other oceans also have apparent decadal trends, some show an inverse correlation, when ACE is high in the Eastern Pacific is is probably low in the West pacific area.

    While there is a trend in more very strong hurricanes, the variability and ocean cycles make any trend in global ACE undetectable. More here-

    http://www.wunderground.com/hurricane/accumulated_cyclone_energy.asp?basin=ep

    Hopefully vtg would find this a slightly more credible source than a Bastardi production!

  64. Magma says:

    Victor, leaving aside the question of how useful a metric the NOAA’s accumulated cyclone energy (ACE) really is, why did you use a three-year-old graph when an up-to-date one is available that undercuts your ‘analysis’?

    http://models.weatherbell.com/tropical.php

    The accumulated cyclone energy (ACE) metric [Bell et al., 2000], analogous to the power dissipation index (PDI) [Emanuel, 2005] convolves intensity and duration information for each individual TC observed in the global tropical basins. ACE is calculated by squaring the 6‐hourly
    intensity estimates reported in the best‐track database and integrating over individual lifecycles or seasons partitioned according to basin or hemisphere.

    R.N. Maue (2011) Recent historically low global tropical cyclone activity, Geophysical Research Letters http://onlinelibrary.wiley.com/doi/10.1029/2011GL047711/abstract

  65. RickA says:

    verytallguy:

    I noticed that the ACE was projected to increase – “but not until the late 21st century.”

    A lot of climate science is like that.

    Sea level is only rising about 8 inches per century, but sometime in the future is expected to accelerate to a much faster rise.

    Warming is below projections – but it will increase at a faster rate sometime in the future.

    Hurricanes will get much worse – but not until late in the 21st century.

    Based on the previous predictions or projections I would take all these far future predictions/projections with a grain of salt.

    It is interesting that the further in the future something is predicted, the firmer the prediction seems.

    Personally, I think it is a very good idea to get satellite data through an entire ocean cycle of about 60 years – so until 2039 ish.

    I have no doubt we will do that – gather more data over many more years – and hopefully our understanding of the climate will grow over time.

    Right now our climate predictions are terrible (at least in my opinion).

    I hold out hope that by 2039 we will have a much more accurate look at natural cycles and natural variation and will be able to subtract that out of our projections, to leave behind a better (but probably smaller) number for human caused warming.

    We will see.

  66. mt says:

    I believe Maue’s graph is correct. ACE is the best global measure of total tropical storm activity, especially insofar as their (smallish) effect on the global circulation is concerned. The variability is striking and I believe unexplained.

    I also believe that it is demonstrated, per ATTP, that there is an increase in very powerful storms; perhaps you should ask folks in the Philippines about that. Joaquin certainly fit that pattern as well.

    Maue may hang around with dubious company, but as far as I know he is scrupulous about data.

  67. Victor Petri says:

    @Magma
    Say, what is my ‘analysis’?
    If you mean that it “does not seem to be in a particular rising trend.” Your graph would lead to the same conclusion. Moreover, we already established that we would only expect global warming to play a possible major role in cyclone energy from about 50 years from now:
    http://wind.mit.edu/~emanuel/anthro2.htm
    Btw, I just took the most recent one that I could find quickly.
    When searching for ‘accumulated cyclone energy’ images
    https://www.google.nl/search?q=accumulated+cyclone+energy&biw=1305&bih=394&source=lnms&tbm=isch&sa=X&sqi=2&ved=0CAYQ_AUoAWoVChMIgcXG4MO1yAIVA4pyCh3u4wCM
    And not wanting to take something from wattsupwiththat.

  68. Victor Petri says:

    @vtg
    I now remember what led me to the graph, I read the article in Geophysical Research Letters, to which, as a geophysicist, I have a subscription.

  69. Willard says:

    > I read the article in Geophysical Research Letters

    You have a link, VP?

  70. Paul S says:

    izen,

    Note there is a large discontinuity in the WUnderground global ACE – from 2012 only East Pacific and Atlantic basins are included in the total.

  71. Willard says:

    Thanks, VP.

    I think the graph Magma wanted to link [is in PNG and can’t be included.]

  72. Victor Petri says:

    @Willard
    Yeah, I know, and looked at it as well, ‘no particular rising trend’ seems a reasonable conclusion still.

  73. Magma says:

    @ Willard: you’re correct and for some reason the plot image doesn’t show even though the old plot used by VP is also a png file. If I click on the ‘missing image’ icon it does open up in a new window. At any rate, it’s the second plot in the linked Weatherbell page directly underneath.

  74. mt says:

    It’s interesting to see how this thread, which was yet another futile attempt on my part to go around ClimateBall and have a real conversation, has devolved into the usual ClimateBall pattern, this time on the hurricane playing field. It’s especially ironic, as hurricane Joaquin, though unusual and powerful in itself, was only one feature of several that made the SC flood event happen. This is obvious; dozens of closely observed hurricanes have passed from the Bahamas to east of Bermuda before, with nothing similar happening in Carolina.

    But as long as we’re on the subject, I’d like to pick up on ATTP’s “One possibility, though, is that cyclones/hurricanes move to higher latitudes and so occur over the same kind of sea surface temperatures as before. However, if that did happen, they would be occurring in places where they were once rare.”

    This is indeed a systematic issue with global metrics.

    It doesn’t only matter THAT severe events happen; it matters WHERE they happen. Heat waves do more damage in colder climates and cold snaps do more damage in warm climates, because the infrastructure and experience isn’t there to cope. Consider the mortality in the Paris and Chicago heat waves a few years back, in heat events that wouldn’t even be noticed here in Texas.

    So, back to tropical storms, it’s timely to watch the remnants of Hurricane Oho as they approach Alaska and British Columbia. Fortunately the storm seems to be missing the main population centers, but peculiarly it seems to be doing that by heading NORTH of Vancouver…

    Of course, disasters in Canada don’t matter to the American press very much. And Juneau is a small town. But this will be interesting, and its right in line with the sort of question I am asking.

  75. Willard says:

    Then perhaps Weatherbell’s server prevents hotlinking images.

  76. Willard says:

    > has devolved into the usual ClimateBall pattern

    It’s an audit.

    Audits never end.

  77. verytallguy says:

    Rick,

    it’s interesting that you both hold out that we don’t have enough data and equally have an opinion on what the unknown data will likely show.

    MT, on climateball, not sure if that was aimed at me or not. I hoped to show with my contribution that examining things thrown in from the contrarionosphere can nevertheless lead to something worthwhile (my brief research into VPs throwaway graph show that it was well touted by contrarians when it first energed)

    In my case it was to Kerry Emmanuel’s essay and FAQ; I think that’s worthwhile vs what sort of signal can emerge.

    The visual correlation of storm intensity vs SST Emmanuel presents seems remarkable. I don’t have the expertise to critique it though, perhaps others do.

    Some discussion of the subtelies here

    http://www.realclimate.org/index.php/archives/2015/03/severe-tropical-cyclone-pam-and-climate-change/

  78. Excellent to see mt here. Good idea, nice complementarity. Agree with him about the Climateball, but unfortunately anytime you post in a public location, the naysayers and distracters will do what they can to undermine the discussion.

    I formulated for myself what I believe is a credible statement about Sandy and the complex engine that included Joaquin had some of those qualities. It had three elements that are on the rise with our heat-trapped planet: it was ginormous; it was a hybrid (married a Northeaster, which is quite a thing in my neck of the woods); and it was late in the season. Joaquin and the system that produced these floods miss the “out of season” piece. I like to look at water vapor animations, partly because they are beautiful, but I can see that every big storm acts like a cog dragging a belt (or some such) thousands of miles. Over time, I can say that the increased energy is notable. These engines also push heat north and into the higher atmosphere (once upon a time I hoped this could dispel heat right out of our system, but that turns out not to happen) and seem to relieve the excessive accumulated energy, which is not a good thing, as the moved heat helps melt polar ice eventually. For a while it will be counterintuitive, sending cold south in winter because of a broken polar circulation, but eventually the Arctic will no longer be cold and icey enough to rebalance the system in the way that makes us all so comfortable on our habitable earth.

    Also, not being a scientist but accustomed to analytical honesty, I note that pulling the discussion into technicalities about individual events is a fine way to derail the obvious and necessary conclusion, which is that worldwide trends over time (a flexible and expanding item) cannot be discredited without this microfocus.

    Well, it’s only a comment so I will not tighten up my ramble, being short for time, but note again that it’s the trends, it’s the trends, it’s the trends. I continue to be puzzled by minds that are unable to mentally walk and chew gum at the same time, noting individual events (weather) but keeping the biggest available information over time and space (climate) in mind.

  79. Eli Rabett says:

    WRT hurricane frequency and strength, James Elsner is the go-to anti-Hoerling, although a lot less monotone Elsner primarily looks at the statistics of storms. His strongest conclusion

    Worldwide the strength of the strongest hurricanes is increasing due to rising ocean temperatures. According to our new research, the upward trend is most dramatic over the North Atlantic and is separate from changes caused by El Niño.

    supported by a ton of publications and presentations (he also tweets). Any discussion of the issue should involve his work.

  80. Magma says:

    mt: “I believe Maue’s graph is correct. ACE is the best global measure of total tropical storm activity… as far as I know he is scrupulous about data.”

    I had no issues with Maue and I hope my comment wasn’t read that way. However, speaking as a non-meteorologist, ACE and its graphical treatment here seem flawed. First, if it’s to be used as a proxy for energy the hurricane or cyclone’s size should be used as well, since those parameters are not directly (or even strongly?) correlated. ACE overweights small hurricanes/cyclones with high wind velocities and underweights large storms with low velocities.

    Second, a 24-month running average can hide a good deal of physically-meaningful information. And conversely you can obtain a result resembling the ACE time series plot simply by calculating the running mean of a series of random numbers.

    A modified and improved ACE would include a storm size factor, such as the square of the radius at a particular wind speed (such as the widely used 34/35 knot threshold), and would break down the data by individual storm as well as month. Filtered regional or global products can readily be generated from finer-grained data, but as it stands now one can only infer so much from the ACE plots used.

  81. mt says:

    Susan, the more commonplace an event type, the easier it is to identify trends.

    It’s much harder with the most extreme one-offs like the SC flood or Sandy. We can count the one-off weirdnesses we see, but we cannot count the ones in the hypothetical unaltered world that we don’t see.

    There are scientifically interesting questions here that are separate from what you and I think are the urgent political and ethical ones. It is my hope that by addressing them we can turn down the flames, and maybe everyone interested in science can reconsider their positions calmly.

    These days it seems unlikely, but anyway these questions are interesting enough to give it a try.

  82. RickA says:

    I think MT does have a good idea about the recurrence rate. However, I don’t know how we can discuss the recurrence rate of a specific unusually high quantity of rainfall in SC without looking at what typically causes (or is associated with) large rainfall events in SC.

    Large quantities of moisture usually come to SC either from the Atlantic, up from the Gulf or down from Canada (in the winter). I suppose some heavy rain comes from the West also, but I am not sure how these events compare to the ones which come up from the Gulf or from the Atlantic..

    It is my layperson impression that the heavier rains usually come from systems that come up from the Gulf or up the coast from the Atlantic.

    But I think any specific discussion of a recurrence rate has to look at how often the events which create the unusual amount of rainfall occur.

    Or am I missing something?

  83. It would also be surprising if enhanced sea surface temperatures don’t lead to an increase in the strength of cyclones/hurricanes.

    That depends on the temperatures of the atmosphere.

    Radiative Forcing is conceived of as a top down process ( forcing at the tropopause works its way down to the surface ):

    The atmosphere is modelled to warm more and faster than the oceans. Such soundings seem to indicate increased, not decreased static stability. Indeed, if the tropical upper tropospheric hot spot were to actually have occurred, one would expect decreased strength of tropical storms.

    But it is not the strength of Joaquin which caused flooding. Indeed, very weak tropical depressions can cause great flooding. It was the persistence of the ‘training’ flow that caused the flooding. Early on, this was due in part to upper level outflow from the very distant Joaquin ( remember the low level flow was AWAY from South Carolina and TOWARD Joaquin ) but also due to a strong mid-latitude cyclone to the west, which is the result of cold air mass intrusion from the polar regions. Later, it appears this event was entirely due to the mid-lattitude cyclone:

  84. TE,
    MT knows more about this than I do, but as I understand it, the energy for a cyclone comes from the sea surface. What I think you’re pointing out is that we might see a reduction in the frequency of tropical cyclones. That doesn’t change, though, that we might see an increase in the frequency and intensity of the strongest cyclones, even if we see a reduction in the number of cyclones overall.

  85. Willard says:

    > However, I don’t know how we can discuss the recurrence rate of a specific unusually high quantity of rainfall in SC without looking at what typically causes (or is associated with) large rainfall events in SC.

    Simple: when discussing the recurrence rate of Event E of type T, we stop focusing on the probable causes of T-Es [NB], and talk about other aspects of it, e.g. its impacts. That we don’t know what causes T-Es exactly doesn’t mean we can’t for instance evaluate their possible impact.

    The big problem here, IMHO, is that we need events to talk about types. Another big problem is that there’s always room to raise concerns about the choice of types. A smaller problem might be to decide a metric to estimate impacts.

    Some may argue that the smaller problem is brokerable in an honest manner.

    [NB]: I assume that science usually quantifies over types of events, not specific events, i.e. tokens.

  86. Jim Eager says:

    Michael Hauber, the Clausius-Clapeyron relation predicts an increase in atmospheric moisture capacity of around 7% per degree C, assuming no change in relative humidity.

  87. mt says:

    TE: “Radiative Forcing is conceived of as a top down process ( forcing at the tropopause works its way down to the surface )”

    I’m not exactly clear on what this means but I am pretty sure it’s wrong. Where did you get the diagrams from?

    If you increment infrared optical thickness via a greenhouse gas, you get a radiative imbalance at the top of the atmosphere. Incoming shortwave radiation (mostly visible light) is converted to heat and thence to outgoing longwave radiation, essentially at the surface, but less of it escapes to space. The balance is restored, to first order, when the planet warms enough to make up for the deficit. To zero order, the atmosphere is best regarded as primarily heated from below.

    As a complication, aerosols are directly heated mid-atmosphere to about half the extent that the surface is heated, but that doesn’t help your case.

    The tropopause is dynamically important, but radiatively it is not a particularly special point.

    A planet with an atmosphere with greenhouse gases but no oxygen has no ozone layer and hence no stratosphere and hence no tropopause, but it still has a greenhouse effect.

    There’s some pseudoscience about lapse rates which I can’t make any sense of and I am guessing you’ve fallen victim to it. But there’s no physical reasoning to it.

    “The atmosphere is modelled to warm more and faster than the oceans. Such soundings seem to indicate increased, not decreased static stability.”

    All else equal, it would mean relatively greater destabilization over land, I suppose, but a great deal is unequal in this proposition. The most important distinction, I think, is that in a hurricane the ocean is an active supplier of latent heat energy, and its capacity to do so rises steeply with temperature. So your comparison doesn’t actually, um, hold water.

    ” Indeed, if the tropical upper tropospheric hot spot were to actually have occurred”…

    sigh.

  88. RickA says:

    Willard:

    I don’t want to put words in MT’s mouth.

    However, he was talking about a recurrence RATE – not the impact of the event.

    I interpreted his proposal to be trying to find out how often these events would occur (the rate at which they recur).

    I agree that talking about the impact of an event is very different than trying to figure out how often a particular type of event might happen.

    In fact – they are not the same thing at all.

  89. Ethan Allen says:

    vtg,

    Yes I’m just now getting into Kerry Emanuel’s stuff on tropical cyclones.

    The more general link for that figure is here …
    Papers, Data, and Graphics Pertaining to Tropical Cyclone Trends and Variability
    http://eaps4.mit.edu/faculty/Emanuel/publications/tropical_cyclone_trends

    There is an Excel file there and Dr. Emanual uses a ‘tapered boxcar’ FIR filter (weighted 1-3-4-3-1-) to produce the graph you have shown.. The R^2 he reports is from an OLS fit (I can reproduce the smoothed figure and R^2 from the Excel file)

    When it comes to FIR filters I always check the autocorrelation structure as these exhibit well known nodal anti-nodal behaviors. The 0th anti-node is the zero-lagged autocorrelation, the 1st node, in this case, is the lagged by 5, and for a true iid time series this should be zero. It’s usually the 1st anti-node that could get one into trouble if the R^2 is reasonably large (I’ll check in a bit).

    Anyways, Dr. Emanual will be giving a talk at this fall’s AGU meeting …
    On the Cause of the Great North Atlantic Hurricane Drought of the Late 20th Century (Invited)
    https://agu.confex.com/agu/fm15/preliminaryview.cgi/Session7977
    (I’m sort of hoping all presentations are recorded and available online)

  90. mt says:

    I re-read Willard’s last several times. I think he’s indulging his tendency to be obscure.

    Specifically, I think he is saying we can discuss the distribution of severe rainfall (“impact”) in SC without reference to causality (‘types”) (“tropical storm”, “frontal boundary”, “mesoscale convective complex”, “weird Joaquin spinoff event type thingy”).

    Meteorologists seldom disagree on taxonomy of severe events. They even have a name for this sort of related-to-a-hurricane thing which I’ll come up with soon. I think he’s saying this would gum up the works unnecessarily. If that’s the point, I agree.

    I don’t know what the dig at Roger (“broker’) has to do with anything.

  91. Willard says:

    > I interpreted his proposal to be trying to find out how often these events would occur (the rate at which they recur).

    MT’s proposal was even larger than that:

    We have to look for better ways to talk about these sorts of things, and in my opinion the only way to do that is to stop pointing vaguely at science and instead develop the patience to actually think about the situation.

    I think it’s quite possible to talk about reccurence rates without having to delve into issues of causality. Reinsurers seem to do that all the time. I also mentioned impacts to parry a popular ClimateBall line.

    Finally, MT warns against overvaluing of the formal attribution question that has plagued climate change conversation from the beginning.

  92. Willard says:

    MT,

    I was saying three things.

    First, we need to distinguish between types and tokens:

    Token physicalism is the view that every particular thing in the world is a physical particular. Here is one formulation of this idea:

    [Token physicalism] For every actual particular (object, event or process) x, there is some physical particular y such that x = y.

    […]

    Type physicalism […] holds that that every property (or at least every property that is or could be instantiated in the actual world) is identical with some physical property. Here is a statement of this sort of idea:

    [Type physicalism] For every actually instantiated mental property F, there is some physical property G such that F=G.

    http://plato.stanford.edu/entries/physicalism/

    The distinction type/token is useful in contemporary philosophy. The de re/de dicto distinction is also useful when discussing reference.

    Second, I don’t think (climate) science should be so fine-grained as to be able to explain, predict, or simply quantify over singular events. This idea at least goes back to Aristotle’s Metaphysics. Under that view, attribution and causality are simply not the right concepts for singular events.

    Third, this limitation is problematic when dealing with journalists, who need to write stories about singular events. Even when they talk about generalities, they need to write about specific persons and specific events to be read. I suspect this accounts for one of the frustrations between scientists and journalists.

  93. Willard says:

    > Meteorologists seldom disagree on taxonomy of severe events.

    Here’s an example of a “choice of type” I had in mind:

    The vulnerability concept requires the determination of the major threats to these resources from climate, but also from other social and environmental issues. After these threats are identified for each resource, then the relative risk from natural- and human-caused climate change [from] (estimated from the GCM projections, but also the historical [record], paleo-record and worst case sequences of events) can be compared with other risks in order to adopt the optimal mitigation/adaptation strategy.”

    https://pielkeclimatesci.wordpress.com/2011/08/04/an-application-of-the-use-of-the-historical-climate-record-to-assess-extreme-events-by-john-neilsen-gammon/

    If we consider that a concept depends upon its operationalization, then yes, scientists are disputing taxonomy all the time.

    The quote is from NG’s, but citing Senior’s is useful because of the fall of his editorial, where once again someone, someone somewhere confirms what he keeps saying since so long.

  94. mt says:

    “If I had ever been here before
    I would probably know just what to do
    Don’t you?
    If I had ever been here before on another time around the wheel
    I would probably know just how to deal
    With all of you
    And I feel
    Like I’ve been here before
    Feel
    Like I’ve been here before
    And you know it makes me wonder
    What’s going on under the ground, hmmm
    Do you know? Don’t you wonder?
    What’s going on down under you
    We have all been here before, we have all been here before”

    – Crosby, Stills, Nash and Young

  95. MT,
    Can I clarify why you think DaveJR’s question is the right question to ask. Is it simply because it’s essentially asking why things are different to what we would have expected in a world without enhanced atmospheric CO2?

  96. Roger Jones says:

    TE,

    you don’t have the process right. The radiative forcing happens in the atmosphere and that’s where the heat starts, but it goes straight into the ocean. The warming of the atmosphere does not happen in situ, but comes from a warming ocean. That’s why the energetics of the hydrological cycle should be seen as a thermodynamic phenomenon, not a radiative one.

    To add to MT’s point, the warming is greater over the land, but it is generated from ocean-atmosphere interactions and not an atmosphere warming in place.

  97. I still don’t get why if you are counting extreme precipitation events you have to not include the most extreme ones. This is catnip for deniers.

  98. Susan,
    I’m not sure if that is quite what is being suggested. I thought it was more that really extreme events are so rare that it is difficult to make any statistically meaningful claims about them, given that the sample is so small.

  99. Thanks, yes, I realize my point is sideways to the discussion (and even irrelevant in these rarefied circles). I 100% get that the sample size is small. However, regarded as part of “extreme precipitation events” they are significant.

    I’m a lot better informed than most laypeople, but given my position in this donnybrook, I can state unequivocally that the regular layperson regards the argument about cyclonic events as “proof” that things are more confused than they are. My suggestion is that it be made clear every time this is discussed that cyclonic events are only one part of a complex system, and are part of the record and that understanding that there has been an increase in extreme precipitation events is clear.

    Let me say once again I’m very very pleased to see mt here, haven’t had much time for all this, but plan to read his material carefully.

  100. Pingback: A few thoughts | …and Then There's Physics

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