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Why extremes are expected to change with a global warming

Filed under: — rasmus @ 5 September 2017

Joanna Walters links extreme weather events with climate change in a recent article in the Guardian, however, some  reservations have been expressed about such links in past discussions.

For example, we discussed the connection between single storms and global warming in the post Hurricanes and Global Warming – Is there a connection?, the World Meteorological Organization (WMO) has issued a statement, and Mike has recently explained the connection in the Guardian.

We still cannot say that single events are caused by climate change for the simple reason that climate change is not a force.

Rather, climate change is a consequence of changed physical conditions. Indeed, one type of climate change could hypothetically consist of storms just becoming more powerful.

I will explain what I mean with climate change below.

Added insight through statistics
If you want to understand the world, then statistics can provide some insights if you have a large number of observations or measurements. This is especially so if you live in a very complex universe with a lot of complicated factors and it is difficult to solve all the equations representing the physics.

To distill information about the climate, you can sort weather data according to different categories, such as magnitude. Then create a table keeping a count of the number of cases that fall into each category, and you will be able to see what magnitudes are common and what range within which you expect them to fall.

You can also plot this type of statistics as a figure known as a histogram.

The histogram is a crude way of showing how frequently you can expect the measurement to fall into each category.

The frequency is proportional to the probability, and you can fit a smooth probability density function (pdf) to the data.

Typical examples of pdfs include the bell-shaped normal distribution for temperature (left panel in the Fig. 1) and the exponential distribution for 24-hr precipitation (right panel i Fig. 1).

What I mean by climate
I usually say that climate is the same as weather statistics (or more precisely, the statistical characteristics of meteorological variables), providing information about what type of weather to expect and its probability.

This statistics, however, will not tell you what one particular outcome will be (i.e. a weather forecast) nor is it a force that influences the outcomes.

The statistics is a mere reflection of (hidden) underlying forces of physics.

Global warming is one kind of climate change caused by an increased greenhouse effect with an impact on both meteorology and the hydrological cycle. It involves physical conditions which set the stage for evaporation, convection, condensation of water vapour, formation of clouds, and precipitation.

Statistical parameters are surprisingly predictable, and weather statistics is systematically influenced by the physical conditions present.

This dependency to physical conditions is evident from how the temperature and precipitation vary from place to place: typically warmer at low latitudes and cooler at higher altitudes; more rain near the coast and less in the interior.

There is also more intense rainfall in the warm tropics than the cooler extra-tropics, and summer precipitation is often more intense than in winter due to different physical conditions.

probability density functions

Typical probability density functions (pdfs) of temperature (left) and precipitation on rainy days (right).

What I mean by climate change
One definition of a climate change is a shift in the pdf describing the temperature, precipitation, or some other variable.

Such a shift in the pdfs is illustrated in Fig. 1 where the grey shading represents the original climate and the red shading a changed climate.

Some variables are strongly affected by changes physical conditions, others are less so. One indicator for their sensitivity to a climate change can be how their character depends on the season, geography, natural variations, or if they exhibit pronounced long-term trends.

Different kinds of extremes
Extremes are often defined as the tails of the distribution (upper or lower parts of the curves in Fig. 1), which are associated with low probability but magnitudes near observed ranges. The magnitude can be either very high (e.g. heat waves, heavy precipitation, intense wind speeds) or low if the pdf has two tails (e.g. freezing temperatures).

The expression “weather extremes” is a catch-all phrase, and not very useful for describing the actual situations. There is a range of different types of extreme weather events, with different nature and different manifestations.

For instance, there are conditions which are present all the time, such as temperature or barometric pressure (there are no days without temperature or pressure). These can be described by one single pdf to indicate their magnitude at any time.

Some conditions are intermittent, such as rain (it doesn’t rain constantly all the time). There are two aspects characterizing intermittent phenomena: how often do these phenomena take place and how intense are they.

For intermittent phenomena, you need two pdfs: one describing their presence (e.g. a Poisson distribution) and one indicating the magnitude when their are present (e.g. Fig. 1).

Some meteorological phenomena are both rare and violent, such as tropical cyclones, mid-latitude cyclones, tornadoes, hail, and lightning.

The more frequent they are, the greater the chance for seeing very extreme events just because you get a larger sample of events over time.

We can use these ideas as a context for Joanna Walters’s article and Hurricane Harvey.

Tropical cyclones
One thing is that global warming may have boosted its force, but will a global warming result in more frequent tropical cyclones?

The oceans are warming, and these hurricanes represent one mechanism that moves the heat from the surface to high levels in the atmosphere where it can escape to space.

We know that the number of tropical cyclones is influenced by several factors: the seasonal cycle, the geography, ocean temperatures and the wind structure in the atmosphere.

According to the IPCC AR5, however, there are little indications of a change in the number of tropical cyclones, although they are becoming more intense (p. 107, TS.5.8.4 Cyclones):

that it is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged, concurrent with a likely increase in both global mean tropical cyclone maximum wind speed and rain rates

I believe the jury is still out on the question of the number of tropical cyclones because the IPCC’s assessment has so far not included studies on the relationship between the number of tropical cyclones and the area of high sea surface temperature, such as the analysis shown in Fig 2 (1).

Fig. 2 shows predictions with a simple model that predicts the number of tropical cyclones (NTC and n) in the North Atlantic based on the area of warm sea surface (A) and the NINO3.4 index. It was created in R using the script tropicalcyclones.R which also retrieves the data. The model was calibrated over the period 1900-1960, and the predictions provide reasonable similar evolution of the North-Atlantic tropical cyclones outside this period. (PDF-version).

The analysis in Fig. 2 shows a crude prediction of the number of tropical cyclones (n) in the North Atlantic based on the area of warm ocean surface (A), and we see a roughly similar trend in these predictions as in the HURDAT2 tropical cyclone record.

One caveat with such empirical studies, however, is that the data record is incomplete and there is a risk that the analysis presents a false picture.

Nevertheless, the IPCC AR5 presents an outlook of increasing extreme precipitation in tropical cyclones making landfall (p. 106, Table TS.2), which is relevant for the flooding connected to Harvey.

Flooding may also become more severe from changes in the landscape, as explained by John Vidal in an article in the Guardian.

I think Joanna Walters’ article about extremes and climate change describes the current situation well, and we should not be too surprised.

A change in the pdf reflects a climate change, and in most cases its range and tails tend to follow the part of the curve that represents the more common conditions. 

We must assume that it is only the exceptional cases where the tails of the pdf are unaffected. Furthermore, an increase in the number of tropical cyclones would increase the number of more cases with extreme rainfall.


  1. R.E. Benestad, "On tropical cyclone frequency and the warm pool area", Natural Hazards and Earth System Science, vol. 9, pp. 635-645, 2009.

167 Responses to “Why extremes are expected to change with a global warming”

  1. 51
    Night-Gaunt49 says:

    “ideological left wing fascism”?

    So we are supposed to know that that means? Calibrate it for us by an explanation of what it really means. Something concrete,not leaving it to everyone to silly putty it into ever crack of their psyche any way they want.

    Better yet just illustrate it and we can figure it out here. But you can’t so you name it for us to fit into your ideological construction you learned from others. Tell us, did they explain it to you or simply tell you those words, ““ideological left wing fascism”? If they did that as I suspect you are the programmed ideological dupe to do their dirty work. The Think Tanks of the Reich Wingers who don’t care what happens to us and the Earth so long as they make every last dollar of every gigaton of carbon left in the earth. And so it takes us from science into the slippery, dirty, muck filled world of political ideology. Something we should flush down the neurological toilet.

    Dan DaSilva nothing in science is 100%, but the facts from all areas can make it in the 90% of probability. But nothing can reach your 100% level of certainty it isn’t happening. Or if it is happening humans cannot be the reason since we are so small. Get enough ants and they can take down an elephant. We leave a foot print upon our world far larger than ourselves.
    Don’t forget logistics which is usually dispensed with just to show everyone staing a few feet away from each other covering Zanzibar to show how small we are ignoring all the effects of what we do to live.

  2. 52
    nigelj says:

    Dan De Silva

    “No victims here just healthy skepticism.”

    There’s no healthy scepticism in your posts. Just accusations of dishonest motives and climate scams, accusations of fudged data and fudged models, political comments, all without anything in the way of EVIDENCE. That’s unhealthy scepticism of the emotive and corrosive sort. It adds nothing to human knowledge or insight.

    Add all the usual tired old irrational climate myths. Victor and Know All are much the same. Plus a total lack of anything genuinely new. I have a feeling this has all been said before.

  3. 53
    Marco says:

    Dan DaSilva, climate is governed by physics. The stock market is not. Your comparison therefore makes little sense.

    Also, you must believe in a vast conspiracy of ideology trumping science, considering that climate science and its conclusions are literally independent of the country where the scientists work, as well as their political views (some exceptions can always be found). You may want to consider whether your “skepticism” isn’t really your own ideology kicking and screaming. I can only speak for myself, but know how it feels when ideology clashes with scientific findings – I’d prefer AGW and its impacts to be false. I really would like that to be. But my own evaluation of the science draws me to the conclusion that it isn’t false, and that has definitely rattled some of my ideological views. Ideology lost, fortunately.

  4. 54
    jgnfld says:


    Your blogger has some points, but right from the get-go makes a fundamental error: He bases his arguments on SST anomalies from the 1981-2010 period. I know of no scientist predicting statistically observable rises in hurricane frequency, intensity, precipitation amount or track over only a few decades. So what he has defeated with his logic is a completely straw-based position.

    If he would redo his analysis going back to anomalies from preindustrial times, he might could have a point as extreme events are notoriously hard to pin down statistically without very large samples. But as it stands, his “careful analysis” is worthless w.r.t. human-caused warming in the modern era.

  5. 55
    Victor says:

    #52 nigelj says:

    “Add all the usual tired old irrational climate myths. Victor and Know All are much the same.”

    Sorry, but the raw data on CO2 level and global temperature is not a myth. And what that data shows, in graph after graph after graph, is the absence of a clear and consistent correlation between CO2 levels and global temps. A large chunk of the rise in temperature that’s produced all those “record breaking” years took place between 1910 and 1940, a period where the effects of CO2 level rise were minimal. (“After all, the greenhouse effect could not have been responsible for much of the warming that had come between the 1890s and 1940, when industrial emissions had still been modest.” from “The Discovery of Global Warming,” Spencer Weart –

    Without that early period of warming — cause unknown — we would not be seeing record temperatures today. That’s not a myth but a fact. Whether it’s “tired” or not changes nothing. What sounds like a myth to me is the notion that this warming was some sort of rebound effect due to the relative lack of volcanic eruptions. A rebound from what, exactly?

    The leveling off and/or cooling of world temperatures between 1940 and 1979 is also not a myth. It can clearly be seen in just about every representation of the data. NOT a myth. What sounds like a myth to me is the notion that this cooling was caused by the very activity that produced the increase in CO2 levels that are supposedly the root cause of “global warming”: the burning of fossil fuels. Why? Because somehow the particulates emitted by this same process blocked out the sun’s rays and somehow compensated for the warming produced by the same source. Now THAT sounds like a myth to me. If global warming can be negated by the same process that produced it, why that’s quite a trick indeed!

    We’ve been all over the so-called “hiatus” after 1998 so there’s no point in going over all that again. You can pick and choose whether to believe Fyffe et al. or Karl et al., but that does NOT negate the FACT that there was never any long term correlation between CO2 and global temperatures during the entire course of the 20th century aside from the last 20 years. FACT not myth. Where we find myths is in the many, often contradictory attempts to explain these facts away.

  6. 56
    Mal Adapted says:

    David Young:

    Cliff Mass’ blog post on Harvey carefully analyzing the facts and data on it. Basically, there is no evidence that Gulf Coast rainfall has increased or that it will increase in a warmer world.

    Yes, Mass seems to be acquainted only with frequentist statistical methods. He finds that within conventional 30-year norms for extreme rainfall, and the contemporaneous synoptic-scale conditions that influenced Harvey’s stall over SE Texas, no influence of climate change on Harvey’s rainfall is detectable. He appears to consider the observed trend of GMST irrelevant.

    A just-published paper by Mann, Lloyd and Oreskes in Climatic Change argues for a Bayesian approach, as more congruent with the physical foundations of weather and climate:

    Using a simple “proof-of-concept,” we show that such an approach will, under rather general assumptions, yield more accurate forecasts.

    Their approach appeals to me and to James Annan, and I expect we’ll see a lot more of it.

    In an opinion piece in the Graun, Mike Mann sensibly didn’t mention Bayesian statistics, but merely went over the physical reasons why we expect hurricanes to deliver more rain now than they did 30 years ago. Mass dismissed Mann’s opinion piece, although from his terse reply to a comment on his blog post it’s not completely clear just why:

    Michael Mann is wrong for a number of reasons, but in his direct statements and his implications. Facts are facts….cliff mass

    That seems rather cavalier. IMO facts must be analyzed in a theoretical framework. Theory predicts both warmer sea surface waters in the Gulf of Mexico, and more precipitable water in the air column over SE Texas, relative to 30-yr norms. Both were observed before and during Hurricane Harvey. In turn, the warmer Gulf surface water and the additional atmospheric H2O should on average produce heavier rainstorms. Higher-than-expected precipitation rates and totals were both observed as Harvey made its slow and erratic way along the Gulf coast.

    Yet while rainfall amounts and intensities may have been ‘unprecedented’, they weren’t unprecedented enough for Mass. He says they were extreme only because Harvey ‘stalled’ (bolding in original):

    And the results are clear: human-induced global warming played an inconsequential role in this disaster.

    Why did Houston Get So Much Rain?

    The proximate cause of the disaster is clear: the extreme rainfall was the result of a hurricane/tropical storm that pulled in huge amounts of water vapor off the Gulf of Mexico (and beyond), and which came into the Texas coast and then stalled for days. All tropical storms/hurricanes bring large amounts of rain during landfall. What was different here was the stalling and sitting over the same region for days.

    So if you want to explain why this event was so unusual, you must shed light on the lack of motion after landfall of this strong hurricane/tropical storm.

    Maybe. Why it stalled is interesting to scientists, but perhaps not to some victims of Harvey-generated flash flooding. In Baton Rouge last year and in Houston two weeks ago, some minor depressions in the landscape flooded for the first time, just because it had never rained that hard on the adjacent higher ground before. More accurate forecasts probably wouldn’t have helped residents in those soon-to-be-discovered stormwater sumps. If they know that AGW is changing all weather, however, they’d be imprudent to assume it won’t rain that hard again for the next 500 years.

  7. 57
    Thomas says:

    45 David Young, good blog post imo. But why be surprised about the media engaging in “hand-waving arguments”? That’s what they are paid to do. Arguing with “media reports” even those written by agw/cc scientists about singular specific events is in itself counter-productive in my view.

    One major reason the ‘denialist’s propaganda war’ have been so successful sowing doubt in climate science prognostications is that battles are more easily won following the “divide and conquer” theory of war. On this agw/cc (war zone) issue the deniers have a distinct advantage because the “experts/scientists” were and remain already “divided” and fighting among themselves 24/7, and they do it IN PUBLIC. So, imv, Cliff Mass is just another ‘public’ example of that… the rest show up in the media 24/7.

    46 Racetrack Playa, seems like logical and plausible approach. What’s been said to date doesn’t appear to be working out that well. The two conflicting sides are further apart than ever, and the public as confused as ever. The result is further unnecessary conflict with neighbors arguing with their neighbors about “who” is right and “who” to believe.

  8. 58
    Thomas says:

    Was Yasi Australia’s biggest cyclone?
    Dr Jeff Kepert , head of the High Impact Weather Research Team in the Bureau of Meteorology and Professor Jonathan Nott from the Australasian Palaeohazards Research Unit with James Cook University.

  9. 59
    Thomas says:

    Acts of God, human influence and litigation by Sophie Marjanac, Lindene Patton and James Thornton
    Developments in attribution science are improving our ability to detect human influence on extreme weather events. By implication, the legal duties of government, business and others to manage foreseeable harms are broadening, and may lead to more climate change litigation.
    @ and

  10. 60
    Tokodave says:

    Marco @ 53

    “Climate is governed by physics” Absolutely.
    Just to back this up: Physics. Never takes a day off. Always bats last. Always!

  11. 61
    Dan DaSilva says:

    re 50
    What is not understood is that skepticism should be a default state. A skeptic does not have to prove anything, he waits for the proof. That is not “flaunting intellectual laziness and ignorance”.

    For example the famous Hockey Stick mixes observation data and proxy data on the same curve, does not rise to the level of good charting techniques let alone proof.

  12. 62
    Mr. Know It All says:

    25 – Russel
    Your “link” to 200 F temperature difference in the hurricane went to the self-admitted “Chronicle of Idiocy” vvats up with that. No info on the 200 F delta T.

    28 – Lynn
    Harvey was not a 1000 year storm. It isn’t even the worst storm Houston has seen since Europeans moved in. Houston has received as much rain as Harvey dumped in 3 days in a single 24 hour period – see hurricane Claudette.

    49 – CCH
    Quote: “There is no evidence that mainstream climatologists are driven by ideology nor that ideology influences the peer review process. None. Not only that, the science is quite robust going back almost two hundred years.”

    So, why didn’t AGW become a thing until recent decades?

  13. 63
    Mal Adapted says:


    skeptic does not have to prove anything, he waits for the proof. That is not “flaunting intellectual laziness and ignorance”.

    Oh, FFS, who told you that’s what a skeptic does? Why do you trust that person more than you trust climate scientists?

  14. 64
    JCH says:

    For example the famous Hockey Stick mixes observation data and proxy data on the same curve, does not rise to the level of good charting techniques let alone proof. …

    I’ve seen this written many times. Who makes this claim? Can you cite a textbook, or a peer-reviewed paper? Because, to be honest, your claim makes little sense.

  15. 65
    CCHolley says:

    DaSilva @61

    What is not understood is that skepticism should be a default state. A skeptic does not have to prove anything, he waits for the proof. That is not “flaunting intellectual laziness and ignorance”.

    Oh it is understood; however, systematic rejection of evidence and the avoidance of undesirable facts or conclusions is NOT skepticism. It its denial.

    For example the famous Hockey Stick mixes observation data and proxy data on the same curve, does not rise to the level of good charting techniques let alone proof.

    Two points here.

    Who says it is not good charting?

    And, although questioning the original Hockey Stick study may be legitimate skepticism, the rejection of the results after multiple other studies using various different proxies came to the same conclusion is denialism.

  16. 66
    nigelj says:

    Victor @55, your particular interpretation of correlations is a myth. You interpret an imperfect correlation as no correlation. Its been pointed out 100 times that CO2 and temperature since 1850 correlate imperfectly, but are still statistically significant, and that’s all that is required to establish a correlation.

    By analogy the correlation between tobacco smoking and lung cancer and emphysema is imperfect,as the majority of lung cancer is in smokers but not all, but its a a red flag and statistically significant. Plus we have causation for smoking in laboratory studies. Only a fool still believes theres no connection between smoking and disease.

  17. 67
    nigelj says:

    Dan de Silva

    “For example the famous Hockey Stick mixes observation data and proxy data on the same curve, does not rise to the level of good charting techniques let alone proof.”

    Why not? You don’t say. Data is spliced together all the time in science and engineering, all you need are common baselines.

  18. 68

    #61, DDS–

    “For example the famous Hockey Stick mixes observation data and proxy data on the same curve, does not rise to the level of good charting techniques let alone proof.”

    So, if someone wanted to show the relation between instrumental and proxy data, you’d have them keep them on separate charts? What, you think the data would start having sex or something?

  19. 69

    And while we are at it, the ‘famous Hockey Stick’ is here, in case someone would like to draw their own conclusions.

  20. 70
    Marco says:

    Dan DaSilva, there is a difference between skepticism and contrarianism, and also between skepticism and laziness.

    To say that a skeptic does not need to ‘prove’ anything, he waits for the ‘proof’, *is* intellectually lazy: just sitting in your chair and say with every little bit of evidence thrown at you “I don’t believe it”. A good skeptic does not automatically believe things, but *actively* looks at the evidence provided. A good skeptic will also consider their own biases.

    The example you provide is clear evidence of intellectual laziness: a proper skeptic would have wondered how the surface record compares to the proxy record and have *asked* for the two to be plotted on the same chart. Moreover, a good skeptic would have looked for other data and sources…and found them to give a very similar picture. A good skeptic would also have asked himself whether he truly had the expertise to judge the data. Did you ever do that, Dan?

  21. 71
    Marco says:

    “Without that early period of warming — cause unknown — ”

    Victor, why do you insist on showing your ignorance of the scientific literature?

    Here, I’ll be nice and point you to an easy-to-read explanation:

    If it’s too easy, there’s always the advanced description:

    You may want to look first on the skeptical science website before you claim “unknown” again. It goes through a lot of the pseudoskeptic talking points, so I’m sure you’ll find a response to most of the nonsense you apparently have subscribed to.

  22. 72
    Astringent says:

    #61 Dan, you really need to distinguish between scepticism applied as a scientific method, which usually goes ‘that’s an intriguing result, but I wonder if they thought of X, I’ll just check’ and pseudoscepticism, which seems to go ‘that’s a result I don’t believe, but I can’t be bothered to actually do any work on it, so i’ll just stuff my doubts on a blog’

  23. 73
    Dan says:

    re: 61. Wow, you a master of putting your foot in your mouth. Clue for you: Science is not nor has it ever been about waiting for “proof”. Science is about hypotheses, data collection, analyses, more hypotheses and peer-review. “Proof” is a mathematical concept. Once again you are showing you have absolutely no clue about the scientific method and worse yet you are making no effort to learn. That is clearly “intellectual laziness and ignorance”. Classic examples actually. The fact that you know very little about how science is down yet somehow think you know something that every major climate science organization and peer-reviewers in the world knowis the absolute height of ignorance and arrogance. And you completely wrong about mixing proxy data and observational data. It’s been done for centuries. It is called “science”. You might want to look up the word.

  24. 74
    Dan DaSilva says:

    re 50, Quote:
    “Due to the complexity there is some tuning for some parameters that are not well constrained.”

    Not well constrained in this case means not well understood.

    Given a few variables you can curve fit any past history. Look at Fourier transforms for example. Did you now that a few climate scientists have even been known to comment on how well climate models fit past data?

    Remember we are all ignorant just some are more so. As far as intellectual laziness that could be from accepting authority without skepticism.

  25. 75

    Victor: what that data shows, in graph after graph after graph, is the absence of a clear and consistent correlation between CO2 levels and global temps

    BPL: Victor, I have a homework assignment for you. Go look up the correlation coefficient and learn how to calculate it. Then do it for temperature anomalies and CO2 levels. If you need help finding the raw data, I can point you to it.

    The correlation between the two is extremely strong. It was measured a long time ago and it has held for the past 167 years. You need to stop saying there’s no correlation, because that is just plain wrong. False. Counterfactual.

  26. 76

    DDS 61: For example the famous Hockey Stick mixes observation data and proxy data on the same curve, does not rise to the level of good charting techniques let alone proof.

    BPL: Proof is for mathematics or formal logic. Science deals in evidence, not proof.

    Fourteen independent studies have confirmed the “Hockey Stick.” Go read the NAS report.

  27. 77
    Ray Ladbury says:

    Dan DaSilva: “What is not understood is that skepticism should be a default state. A skeptic does not have to prove anything, he waits for the proof.”

    Wow, how do you get so much wrong in only 25 words? First, science is not about proof. It is about evidence. Second a true skeptic does not wait for proof. She–or he–goes out and finds evidence. The evidence implicating anthropogenic CO2 is overwhelming, whether YOU understand it or not.

    Second, your contention that mixing different data sources in a multi-century reconstruction is bad science is just dumb. Ever hear of the galactic distance scale? Ever hear of the stratigraphic record? Hell, ever hear of the standard model of particle physics?

    A scientist uses the evidence available to develop a coherent picture of the phenomenon–again, your inability to understand that picture does not constitute an indictment of it.

  28. 78
    jgnfld says:


    Your claimed “disproof” of global warming is that CO2 and temperatures should be lockstep. No climate scientist that I know has made that statement, So, it can hardly be a disproof climate change that lockstep change does not occur.

    What is in lockstep w.r.t. CO2 and the atmosphere is the backradiation contribution from CO2. How that backradiation affects the energy balance equilibrium, the climate directly, and various sinks involved in climate is in no way a lockstep matter. Rather it is a complex system. But more backradiation over time will warm the whole system.

  29. 79
    JCH says:

    What is not understood is that skepticism should be a default state. A skeptic does not have to prove anything, he waits for the proof. …

    But you’re not waiting. And, skepticism is the default state of every single climate scientist I have ever read. Your claim is preposterous.

    That is not “flaunting intellectual laziness and ignorance”.

    Except when it is.

    For example the famous Hockey Stick mixes observation data and proxy data on the same curve, does not rise to the level of good charting techniques let alone proof. …

    I have read on the internet the claim of the inappropriateness of mixing proxy data and the thermometer record on a graph many many times. I somewhat doubt you have been skeptical of this claim, which is absurd on its face.


    We collected relevant observational and measured annual-resolution time series dealing with climate in northern Europe, focusing in Finland. We analysed these series for the reliability of their temperature signal at annual and seasonal resolutions. Importantly, we analysed all of the indicators within the same statistical framework, which allows for their meaningful comparison. In this framework, we employed a cross-validation procedure designed to reduce the adverse effects of estimation bias that may inflate the reliability of various temperature indicators, especially when several indicators are used in a multiple regression model. In our data sets, timing of phenological observations and ice break-up were connected with spring, tree ring characteristics (width, density, carbon isotopic composition) with summer and ice formation with autumn temperatures. Baltic Sea ice extent and the duration of ice cover in different watercourses were good indicators of winter temperatures. Using combinations of various temperature indicator series resulted in reliable temperature signals for each of the four seasons, as well as a reliable annual temperature signal. The results hence demonstrated that we can obtain reliable temperature information over different seasons, using a careful selection of indicators, combining the results with regression analysis, and by determining the reliability of the obtained indicator.

  30. 80
    Thomas says:

    “A skeptic waits for the proof.”

    Fine .. but what is the number of the Bus Stop where you’re waiting? Because thousands of climate scientists have been driving around in circles for 4 decades trying locate you Dan DaSilva while you’ve been sitting there waiting. You, my dear sir, deserve so much better than to be kept waiting!

  31. 81
    Thomas says:

    56 Mal Adapted, well said.

  32. 82
    Thomas says:

    in 55 Victor asserts “FACT not myth”, repeatedly.

    I counted 11 (falsehoods) aka Myths regurgitated by Victor in that one 4 paragraph comment. How many can you count?

  33. 83
    jgnfld says:

    Uh, you do know that aggregating readings from thermometers in selected locations is a proxy for the “real” temperature anomaly, right? Tree ring data, bore hole data, etc., etc., etc., are “observations” every bit as much as thermometer aggregation. Even one reading from one thermometer is a proxy.

    I know of no charting textbook that says 2 or more different proxies cannot be incorporated into one graph–most especially if they are properly calibrated to each other. Could you please provide a professional reference for your not so “skeptical”–but instead rather downright dogmatic–opinion that such is not “a good charting technique”?

    As one example, plotting bucket versus engine intake sea surface temperatures (versus buoy temperatures) showed clearly that calibration was required to match up the two series. “Good charting technique” actually demands calibration of the one proxy to better match the other proxy.

    That said, in any case, the original MBH paper did NOT “mix [what you define as] observation data and proxy data on the same curve”. The aggregated thermometer data and the tree ring proxy data were clearly graphed as separate lines using separate symbols (see Fig. 5, p. 783 of In MY definition of “skepticism, I would say that examples of why to ignore insufficient evidence should at the very least provide real evidence as opposed to ignorantly or dishonestly fabricated evidence. But maybe that’s just me.

  34. 84
    Pekka Kostamo says:

    Political consultant Frank Luntz (see Wiki) gives professional help to politicians in choosing the right words. So his focus group compared two expressions: “global warming” and “climate change”. He found that “climate change” was much less alarming. Thereafter president George W. Bush used always that terminology, and so do the climate scientists. Climate is always changing.

    The goal is to keep global warming below 2 degC with respect to the pre-industrial time. You get what you measure. Unfortunately I do not know where we stand now. Nobody reports it to the general public. For some reason all scientists and their istitutions use their own peculiar yardsticks and reference levels.

  35. 85
    Russell says:

    Hurricane Irma has turned a new Facebook page in climate engineering , :
    46,000 gun owners agreed to join in a effort to quell the storm by shooting into it

  36. 86
    Adam Lea says:

    In my part of the world (the UK) it feels like something has changed in the last 10 years. Back in my childhood I remember the weather was typically very changeable, a few days of rain followed by a few days of dry weather sort of thing. In 2007 we had one of the wettest summers on record thanks to stagnated weather patterns resulting in a persistent trough and low pressure during July. This repeated again in the dreadful summer of 2012. It is curious that both these wet summers coincided with record lows in Arctic sea ice. Summer Greenland blocking (which is linked to poor summer weather in the UK) has increased significantly over the last 10 years. The weather since then has seemed to stagnate more frequently (my perception), e.g. the freezing cold December 2010, the soaking wet and stormy winter of 2013/14, and the predominantly blocked weather from August 2016 to July 2017. I wonder if the Arctic sea ice decline has reached, or is close to some threshold where it significantly feeds back on the mid-latitude weather via changes in the jet stream, leading to more meridional slow-moving large waves in the jet stream, rather than zonal westerly flow which steers low pressure systems through quickly.

  37. 87
    Paul Donahue says:

    Why is Gavin allowing the comment section of his blog to be dominated by so-called “skeptics” all repeating the same tired old scientifically invalid points that have been refuted a thousand times? They are not contributing to the discussion here which is supposed to be hard, real science.

    Regrettably, it may be time to get rid if the comment section – as is increasingly the practice of many bloggers and news media sites?

  38. 88
    Dan DaSilva says:

    RE 87
    Maybe Gavin is interest in more than just a echo chamber. Thanks Gavin.

  39. 89
    Dan DaSilva says:

    RE #80
    Would you like a list of things that I think have been pretty well proven?

    Short list:
    CO2 is a green house gas
    Vaccines work
    Men and Woman are different
    Communism is bad

  40. 90

    R 85: 46,000 gun owners agreed to join in a effort to quell the storm by shooting into it

    BPL: Idiots on parade.

  41. 91
    Mal Adapted says:

    Paul Donahue, long-time RC regulars learn to skim’n’scroll. Assuming Gavin is the moderator-in-chief, heavier moderation is asking a lot of him; he works for a living, you know. Also, by allowing AGW-deniers to comment here, RC demonstrates it does not ‘censor skepticism’.

    If nothing else, engaging the committed deniers in ‘free and robust debate’ is an ever-flowing source of savage glee ;^]. No matter how hard you punch them, they always swing right back in your face, unaffected and ready for your next hit.

  42. 92
    CCHolley says:

    Mr. KIA @62

    So, why didn’t AGW become a thing until recent decades?

    You should try learning something about the history of the science.

    Here is a good place to start:

    The Discovery of Global Warming: A History

    Of course, based on your track record on here, you won’t bother. Apparently, to you, knowledge is a dangerous thing.

  43. 93
    Ray Ladbury says:

    Paul Donahue,
    Would you rather they comment here, where their BS will be called out and corrected, or at WTFUWT, where it will be amplified by the echo chamber of stupid?

  44. 94
    Radge Havers says:

    ~ 85 Russell


    I’m sharing that link.


  45. 95
    CCHolley says:

    DaSilva @74

    Not well constrained in this case means not well understood.

    No it does not. It means difficult to model.

    Given a few variables you can curve fit any past history. Look at Fourier transforms for example. Did you now that a few climate scientists have even been known to comment on how well climate models fit past data?

    But they are not curve fitted. Read the paper. However, common sense says one should check models against the past to see how well they fit, but they are NOT tuned to do so. Again, read the paper.

    And models are not the end all to our understanding of AGW. They are just another tool. Arrhenius was able to calculate the climate sensitivity of CO2 back in 1894 using basic physics. As was Hulbert in 1931 and then again Plass in 1955. All with results similar to today’s models.

    Remember we are all ignorant just some are more so. As far as intellectual laziness that could be from accepting authority without skepticism.

    Pure arrogance. I do not accept anything without a due level of skepticism and thorough investigation of the facts and evidence. I also am well aware of the limits of my knowledge. However, I have a strong intellectual curiosity that continually drives me to seek answers and learn. It is quite apparent by what you post that it is you who is intellectually lazy and unaccepting or unaware of your ignorance.

  46. 96
    hendric says:

    62 Mr. Know It All
    Are you sure about Hurricane Claudette? Looking at the wiki, it gives a max of 6.5 inches in TX. Nowhere near the numbers from Harvey.

    Perhaps you meant Tropical Storm Allison?
    (goto rainfall tab, scroll to bottom)

    And while Houston got a lot of rain in a short period from Allison, Harvey hammered the whole SE of TX.

    Having 15% more water in the air doesn’t increase the intensity of events by 15%, or the likelyhood of events by 15%. These black-swan events are at the long-tail of the distribution – say 3 standard deviations. Even a small shift will cause a much larger increase of these events to the right of some arbitrary line. For the chance of black-swan events to increase proportionally, the chances would have to be flat. But because the chances increase as you get closer to the mean, every small shift right gives a larger and larger change to black-swan odds.

    Look at the distribution. 3 o is .1%. If the distribution shifts 1 standard deviation, the odds of a similar strength event skyrocket to 2.2%.

  47. 97
    Victor says:

    #66 nigelj says:

    “Victor @55, your particular interpretation of correlations is a myth. You interpret an imperfect correlation as no correlation. Its been pointed out 100 times that CO2 and temperature since 1850 correlate imperfectly, but are still statistically significant, and that’s all that is required to establish a correlation.”

    Statistical significance has a purely technical meaning for statisticians and should not be interpreted as significance in any other sense. A good explanation can be found in this Scientific American article, aptly titled “Statistical significance and its part in science downfalls”:

    Some excerpts:
    “Statistical significance testing can easily sound as though it sorts the wheat from the chaff, telling you what’s “true” and what isn’t. But it can’t do that on its own. What’s more, “significant” doesn’t mean it’s important either. A sliver of an effect can reach the less-than-5% threshold.”

    “The over-simplistic approach to statistical significance has a lot for which to answer. As John Ioannidis points out here, this is a serious player in science’s failure to replicate results.”

    Here’s the post referenced above: “Why Most Published Research Findings Are False,”
    John P. A. Ioannidis.

    From the summary:

    “Simulations show that for most study designs and settings, it is more likely for a research claim to be false than true. Moreover, for many current scientific fields, claimed research findings may often be simply accurate measures of the prevailing bias.”

  48. 98
    Brian Dodge says:

    Re CO2 temperature correlation

    Y’all are cherry-picking a short term rise, and ignoring short term falls, to try to score political points with the scientifically illiterate.

    google “red noise climate”

  49. 99
    nigelj says:

    Thomas @57, yes you are right, the climate experts and even the “warmists” are sometimes divided, sometimes in public.It’s a tough one because if they squabble, it’s a bad look to the public and confusing. But if they all agree they are accused of being conformists or engaged in group think or a giant conspiracy. So lets not judge too harshly.

    And any field of science will have argument. I think all one can hope for is avoid things degenerating into bickering and personal squabbles, and at least have a united front on the basics.

  50. 100
    Jim Baird says:

    Cheng, L., at al., say “the increase in (ocean heat content) OHC observed since 1992 in the upper 2,000 meters is about 2,000 times the total net generation of electricity by U.S. utility companies in the past decade [U.S. Energy Information Administration, 2016].”

    Concerning the heat capacity of the full ocean depth, they say, “Any increase in heat contributes to the thermal expansion of seawater and, consequently, SLR [Church et al., 2013]. Any energy added in Earth’s system also causes land-based ice to melt, further contributing to SLR by adding water to the ocean.

    Since the ocean is warming to a depth of 2000 meters in any event, and since it is major storms that are pushing heat to those depths, we should be deriving the economic benefit of such a relocation.

    What’s more the coefficient of thermal expansion of sea water is less in the deep, one half at a depth of 1000 meters, than the surface, heat moved to these depths produces less sea level rise and is unavailable to melt polar ice.

    We need to be fueling the planet with hurricane fuel.

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