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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.

References

  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. http://dx.doi.org/10.5194/nhess-9-635-2009

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

  1. 1
    Alastair B. McDonald says:

    It seems to me to be wrong to state that an extreme event was caused by global warming. All that one can say is that the event was made worse (more extreme) by global warming. The point is that every extreme event has many causes, not least the butterfly that flapped its wings in Brazil causing a tornado in Texas. Forest firs are caused by droughts, carelessly discarded cigarette butts, and a buildup of organic fuel. All three are causes of the fire, but global warming can make its effect worse.

    What one can say is that a record hurricane or wild fire is caused by global warming, but that is because without global warming the event would not be a record. So, many record events are proof of global warming, but those events would still have happened to a lesser extent without global warming. The record was caused by global warming not the event.

  2. 2
    Dan Miller says:

    I posted this in the last thread but it is more appropriate here:

    Jim Hansen, et al, did a great study showing that average summer temperatures that are 3 standard deviations (“3-sigma”) above the 1951-1980 baseline have increased over 100X since the baseline period.
    http://www.columbia.edu/~jeh1/mailings/2016/20160120_Temperature2015.pdf See Figure 6 – top.

    During the baseline period (for the Northern Hemisphere) the probability of a 3-sigma summer was 0.1%. In the 2005-2015 period it was 14.5%. This means when there is a 3-sigma summer now, the chances that it is caused by climate change is >99%. Note that this dramatic change applies to the extremes (the “tail” of the curve), not the average summer.

    I’m wondering if anyone has done a similar study for extreme rain events. We know that “500-year” rain events are common now, but has anyone quantified it like Hansen has done for temperatures? If 500-year rain events in a particular place now happen, say, every 5 years, then when one of these events happen, then you can say there was a 99% chance they were caused by climate change (a shift of the pdf).

  3. 3
    Tim Merlis says:

    I was curious about the blanket statement on single-event attribution (paragraph 3), so I checked the 2016 National Academy of Sciences report on Attribution of Extreme Weather Events in the Context of Climate Change (https://www.nap.edu/catalog/21852/attribution-of-extreme-weather-events-in-the-context-of-climate-change). From its summary section:

    “The ability to understand and explain extreme events in the context of climate change has developed very rapidly over the past decade. In the past, a typical climate scientist’s response to questions about climate change’s role in any given extreme weather event was, ‘We cannot attribute any single event to climate change.’ The science has advanced to the point that this is no longer true as an unqualified blanket statement. In many cases, it is now often possible to make and defend quantitative statements about the extent to which human-induced climate change (or another causal factor, such as a specific mode of natural variability) has influenced either the magnitude or the probability of occurrence of specific types of events or event classes.”

  4. 4
    Hank Roberts says:

    Looks like you answered the question I came to ask:

    … in its Tuesday morning discussion, the National Hurricane Center said the storm is in an environment “ideal for some additional intensification.”

    The hurricane …. is already nearing historical precedent and a theoretical limit for how strong it can get.

    https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/09/05/catastrophic-hurricane-irma-now-a-cat-5-is-on-a-collision-course-with-florida/

    So the “theoretical limit for how strong it can get” is going to change with climate? That, er, blows away a lot of the statistical work on likelihood of damage. (cough) Pielke Jr. (cough)?

  5. 5
    mike says:

    Scientists should not answer the question “was this storm/event caused by global warming?” except to say that this is not the right question to ask about a specific event. The right question is: does the current level of global warming play a part in extreme weather events around the globe? The answer on that one ought to be pretty clear and easy. Maybe a discussion of quantum mechanics, the uncertainty principle, wave v. particle questions, Schrodinger’s cat would be easier to sort out than the silly question: was this storm or event caused by global warming?

    Don’t get sucked into the morass of the wrong questions. That way lies madness.

  6. 6
    hseneker says:

    Climate will do what climate will do as it has for hundreds of millions of years. Meanwhile, decisions and policy need to be based on hard fact.

    There are some crucial, verifiable facts – with citations – about human-generated carbon dioxide and its effect on global warming people need to know and understand at

    hseneker.blogspot.com

    The discussion is too long to post here but is a quick and easy read. I recommend following the links in the citations; some of them are very educational.

  7. 7
    dhogaza says:

    hseneker’s blog post that he’s so proud of doesn’t contain an original thought but rather rehashes a long list of tired denialist memes.

    Too bad … I was hoping for some creativity.

  8. 8
    Meme Mine says:

    WELL GEE!
    Unstoppable global warming kinda tends to do that sort of thing!

  9. 9
    rasmus says:

    It’s easier to answer if you have a set of events rather than one event. But if it’s sufficiently extreme, it would be easier to attribute it to physical conditions if you can simulate the event. -rasmus

  10. 10
    Thomas says:

    6 hseneker, you’re a silly silly gullible man Harold. (sigh) Your beliefs and opinions are not worth discussing, period.

  11. 11
    Thomas says:

    The issue here is not one of climate science but issues of semantics, linguistics, logic and how our brains work cognitively.

    Rasmus speaks highly of the article by Joanna Walters. People need to be aware that Joanna is a freelance news, features and travel journalist, based in New York City. This is the type of person that AGW/CC science is continually relying upon to communicate critical factors about scientific based know-how to the public? Sheer luck that someone out there in journalism land will get something right now and then and express in a way that might make a positive difference to people’s knowledge and beliefs. Seriously?

    The most important she said, imo, was this: The Noaa experts (ie AGW/CC scientists) REFUSED to comment on funding issues. My caps!

    Rasmus refs Mike Mann’s article then immediately states this: “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…” and further down states this: “… climate is the same as weather statistics […] This statistics, however, […] (is not) a force that influences the outcomes.”

    Meanwhile Mike had this to say in his article: “There are certain climate change-related factors that we can, with great confidence, say worsened the flooding.” and “Sea level rise attributable to climate change..” and “… we can say is that it (Climate Change) exacerbated several characteristics of the storm in a way that greatly increased the risk of damage and loss of life. Climate change worsened the impact of Hurricane Harvey.”

    iow what Mike said a number of times through his article was precisely the opposite of: “Climate Change (is not) a force that influences the outcomes.”

    This a decades ling conundrum of communicating AGW/CC knowledge in way that is consistent and in a way that can be absorbed in a nuanced and understandable cognitively consistent way by people that makes clear sense to them and builds a know-how about the consequences of AGW/CC that will lead to a change in personal behavior, especially when Voting…. for example for the ongoing sustained funding of NOAA and all other Climate science organisations.

    Which was precisely the point and primary purpose of Joanna’s article …. one that has now been totally lost in this RC article by Rasmus, by the way.

    So here we have Rasmus writing an article about the critical differences between Climate Change and Global Warming in relation to weather and weather events. He is properly trying to CLARIFY these differences and pointing out that Climate Change is NOT a Forcing that has any physical impacts on either “weather” overall and “extreme events” in particular.

    Unfortunately Climate Science is suffers an extreme communication deficit, and has done form the get go. Why? Because the “words” used and the “phrases” and the “framing” being deployed matters more than anything else … much more than any amount of scientific facts ever could. Yet the “experts” directly engaged in Climate Science and the Global Warming phenomena are continually shooting themselves in the foot and have done for decades, imo.

    Take the FAR in 1990 quoting (pg 11 of pdf) …. The Intergovernmental Panel on Climate Change (IPCC) was jointly established by our two organisations in 1988. Under the chairmanship of Professor Bert Bolin, the Panel was charged with:

    (i) assessing the scientific information that is related to the various components of the climate change issue, such as emissions of major greenhouse gases and modification of the Earth’s radiation balance resulting therefrom, and that needed to enable the environmental and socio-economic consequences of climate change to be evaluated,

    (ii) formulating realistic response strategies for the
    management of the climate change issue.

    https://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_full_report.pdf

    Others opinions will vary wildly, however my view is that on both counts the IPCC has been a complete and total failure in achieving it’s two primary goals and reason for being.

    Rasmus, look how the IPCC has “framed” the discussion using the phrase Climate Change. There’s a reason why the deniers jumped upon their simple attack phrase that undermines the whole ‘story’ … Global Climate has always changed. The details the ‘facts’ are irrelevant because that phrase they deploy is in fact absolutely TRUE and ACCURATE in and of itself. That truth then immediately takes up residence by being INTERNALIZED in people’s brains as a given … it is LOCKED INTO PLACE as a Priory belief of what is true.

    You cannot shake that by quoting facts and writings lengthy articles that now assert “climate change” is the wrong term to be used 27 years after the IPCC went to Print. Unless and until the global body of climate scientists, and the IPCC (which imho should be disbanded as useless; a waste of money, time and effort if the lack of “results” are rationally taken into logical consideration) start to employ the knowledge of cognitive science, psychology and marketing principles in communicating the essentials of AGW/CC science and WTF to do about it globally and nationally, you are truly wasting your time saying anything in the public domain.

    If you wanted to fly from New York to London, rational people would likely make sure they bought a seat on a plane with a highly qualified expert Pilot.

    It should therefore logically follow that IF climate scientists truly desired to communicate their knowledge to the public and politicians and corporate boards, then rationally and logically they would engage highly qualified experts in the field of Public Communication after realizing and admitting to their own severe limitations in this regard – already historically proven ad nauseum, imho.

    TY maybe some food for thought and then some real action as a result?

  12. 12
    Dennis N Horne says:

    Earth is retaining more energy; the climate system is “charged” with moving it around. So the weather is going to be worse.

    The deniers are merely breaking wind…

  13. 13
    Omega Centauri says:

    I’ve liked the loaded dice analogy. You rolled a pair of one’s and lost your grubstake. You know the house loaded the dice. But, even if they hadn’t you still coulda got that outcome. So how much of your loss is due to the machinations of the house, versus plain old bad luck?

    I don’t like saying global warming made such an such an event worse. GW is actually a very large butterfly, so we are sampling completely different random
    outcomes ( if we were doing a computer Monte-Carlo experiment, we not only changed some of the model parameters, we changed the initial seed for the random number generator). So yes we can say an event we experienced of such and such a magnitude (floods, heat waves etc.) are now more likely, but we can’t say any certain event was worse, because nature is using a whole different set of random numbers.

  14. 14
    Andy Revkin says:

    Great primer. One thing I keep wondering about (in relationship to storms, drought, in particular) is how paleoclimate work so often resets the bar on what is thought of as rare or extreme. I think back to 2002 Noren et al. paper, Shanahan et al. in 2009, and others of that sort. Paleo work on fire patterns in North America (where summer smokiness was the norm way before Western settlement. How much difficulty is added to analysis seeking a signature of greenhouse-forced shifts in extremes given those gaps, and occasional insights?

    Noren: https://www.nature.com/nature/journal/v419/n6909/full/nature01132.html
    Shanahan: https://www.ncbi.nlm.nih.gov/pubmed/19372429
    Fire: http://www.pnas.org/content/109/9/E535.full

  15. 15
    Toby Thaler says:

    Thomas @ 10: correct. I’m surprised RC let him post.

  16. 16
    Thomas says:

    fwiw may be useful to review some of the things said back in 1990.

    eg pg xii
    To improve our predictive capability, we need:
    • to understand better the various climate-related
    processes, particularly those associated with clouds,
    oceans and the carbon cycle
    • to improve the systematic observation of climate-
    related variables on a global basis, and further
    investigate changes which took place in the past
    • to develop improved models of the Earth’s climate
    system
    to increase support for national and international
    climate research activities
    , especially in developing
    countries
    to facilitate international exchange of climate data

    and

    pg xiii
    This Policymakers Summary aims to bring out those
    elements of the main report which have the greatest
    relevance to policy formulation, in answering the following
    questions
    • What factors determine global climate
    7
    • What are the greenhouse gases, and how and why are
    they increasing
    9
    • Which gases are the most important
    9
    • How much do we expect the climate to change
    9
    • How much confidence do we have in our
    predictions
    9
    • Will the climate of the future be very different
    9
    • Have human activities already begun to change
    global climate
    9
    How much will sea level rise
    9
    • What will be the effects on ecosystems
    9
    • What should be done to reduce uncertainties, and
    how long will this take
    9
    This report is intended to respond to the practical needs of
    the policymaker. It is neither an academic review, nor a
    plan for a new research programme Uncertainties attach to
    almost every aspect of the issue, yet policymakers are
    looking for clear guidance from scientists,
    hence authors
    have been asked to provide their best-estimates
    wherever possible, together with an assessment of the
    uncertainties.

    This report is a summary of our understanding in 1990

    Although continuing research will deepen this under-
    standing and require the report to be updated at frequent
    intervals, basic conclusions concerning the reality of the
    enhanced greenhouse effect and its potential to alter global
    climate are unlikely to change significantly

    Nevertheless, the complexity of the system may give rise to surprises

    and first mention of “global warming” on pg xi
    The main greenhouse gas, water vapour, will increase in response to global warming and further enhance it”

    and next on pg xiii
    “Introduction: what is the issue ? […] through the enhanced
    greenhouse effect, by past and continuing emissions of
    carbon dioxide and other gases which will cause the
    temperature of the Earth’s surface to increase – popularly
    termed the “global warming”

    and pg xv
    “Water vapour will increase in response to global warming and further enhance it, this process is included in climate models….”

    and then this:

    How will climate extremes and extreme events change?
    “Changes in the variability of weather and the frequency of
    extremes
    will generally have more impact than changes in
    the mean climate at a particular location. With the possible exception of an increase in the number of intense
    showers
    there is no clear evidence that weather variability will change in the future.”

    and

    “If the large-scale weather regimes, for instance
    depression tracks or anticyclones, shift their position this
    would effect the variability and extremes of weather at a
    particular location
    , and could have a major effect However, we do not know if, or in what way, this will happen “

    https://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_full_report.pdf

    Now, 28 years later, apparently, and despite all the scientific work that’s been done and all the Policy Makers talk that has occurred, some people STILL DO NOT KNOW … or at claim not to know! (sigh)

    While others argue endlessly about what are the “appropriate” words and phrases what can be said and not said about “climate change” and “global warming” and their now obvious inter-connectedness and systemic causation regards 21st century “extreme weather events”.

    (sheesh) or as those from my grandparents era said when utterly exasperated: “Strewth Doreen!”

  17. 17
    Astringent says:

    Thomas @11

    It should therefore logically follow that IF climate scientists truly desired to communicate their knowledge to the public and politicians and corporate boards, then rationally and logically they would engage highly qualified experts in the field of Public Communication after realizing and admitting to their own severe limitations in this regard – already historically proven ad nauseum, imho.

    Thomas, you write as if climate scientists were some sort of organised group that stands apart from society. Are you perhaps projecting from the reality of the denialist ‘side’? Climate scientists are scientists, funded by the public, by politicians, by corporate boards. They don’t, necessarily, have an agenda beyond one of understanding the wonderful complexity of nature. Some are fantastic communicators, some are not. Science isn’t a gladiatorial sport where you have ‘sides’ and winning.

    Society can choose to listen to it’s experts or not – the world will keep turning. If you wanted to fly from New York to London, rational people would likely make sure they bought a seat on a plane with a highly qualified expert Pilot. Yes, and if half way across the Atlantic the pilot said ‘buckle your seat belt, it’s getting bumpy’ rational people would listen to the pilot, not to a random person in the next seat claiming it was all a conspiracy by the UN to keep good air passengers from eating pretzels.

  18. 18

    Andy,
    Doesn’t this somewhat miss the point?
    One thing I keep wondering about (in relationship to storms, drought, in particular) is how paleoclimate work so often resets the bar on what is thought of as rare or extreme.
    The key thing (as I understand it) is how changing the climate is going to influence events that we currently regard as extreme and, hence, rare. I don’t really see that such events might have been more common at some epoch in the past as all that relevant.

    If anything, I think a key point in the post (and it would be good to check that this is what Rasmus was getting at) is that climate change will almost certainly impact the distribution of events and, hence, will almost certainly influence those events that we currently regard as extreme/rare.

  19. 19

    #8–If this is the same ‘meme mine’ that I’ve encountered at cbc.ca, look for some (more) seriously stupid posts coming. I sense a disturbance in the Force–near the Bore Hole….

  20. 20
    Mal Adapted says:

    Toby Thaler:

    I’m surprised RC let him post.

    I’m not. Posts like hseneker’s show that contrary to the accusations of some AGW deniers, RC does not censor them as a rule. Why should it? hseneker has done himself no favors by catching the attention of RC regulars 8^D!

    At least hseneker is a relatively polite denier, who presents himself here as a DK-afflicted volunteer. If any commenter should be banned from RC, it’s the “Meme mine” ‘bot in its various permutations. Its comments are never anything but crude mockery of the scientific consensus for AGW. Most of us don’t bother responding anymore.

  21. 21
    Mitch says:

    Thomas #11
    …The most important she said, imo, was this: The Noaa experts (ie AGW/CC scientists) REFUSED to comment on funding issues. My caps!…

    Federal employees are statutorially obligated not to lobby congress, so do not undertand why you think the refusal has meaning.

  22. 22

    OK, I was a sport and had a look at hseneker’s blog. It was all downhill after the title.

    The defining moment for me was the citation for the claim that the “Medieval Warm Period” was slightly warmer than the present–it dates back to 1999, the very year that the second Mann, Bradley and Hughes paper came out, basically redefining the field of paleoclimatology (and pretty much putting paid to the ‘warmer MWP’ idea hseneker puts forward.)

    Gee, why would anyone ignore the last 18 years of bibliography in a field where research has metaphorically exploded in volume, scope and sophistication?

    ‘By their cites ye shall know them.’

  23. 23
    Ann Kah says:

    The jet stream, swinging more wildly now in a pattern that has been connected to climate change, is responsible for freaky weather patterns; here in northern Ohio, we have had more than a week of temps in the 50-70° range in August, typically the hottest month of the year. The devastation due to hurricane Harvey is in large part due to stalling over Houston and dumping prodigious amounts of rain, because the jet-stream weather patterns kept it entrained in one spot. The warmth of the water, especially in the Gulf of Mexico, is only part of the hurricane story.

    Check this out: https://thinkprogress.org/jet-stream-harvey-bd146d428ed1/

  24. 24
    rasmus says:

    A changing climate implies changed pdf, and the tails of the pdf will respond to the changes in the bulk of the curve (the area under the pdf curve must be one by definition because the probabilities of all possibilities add up to unity). -rasmus

  25. 25
  26. 26
    Thomas says:

    21 Mitch, well for one, The Guardian is an international newspaper, not Congress. Not all statutes, regs and laws are good ones or logical or ethical. Given the reality of funding in the US and the Congressional dysfunctions and the number of resident ‘lunatics’ there, I find that quote really telling and important.

    17 Astringent suggests: “Thomas, you write as if climate scientists were some sort of organised group that stands apart from society.”
    Actually I write to the reality. Climate scientists are an extremely disparate group often speaking at cross purposes and entering fields outside their expertise level, plus that the IPCC efforts to achieve it;s goals have been a failure.

    Whereas it is my view that there needs to be, should be, a very well organised group of high end climate scientists that need to take charge of the direction of AGW/CC communication of the most critical aspects of the current state of knowledge and take that to the populace in programmed structured globally directed way using the best experts known to man in that field of public communication tech.

    And that those who support the work of AGW/CC scientists to do whatever they can to support such public information work to finance it via crowd funding operations, again which is set and managed by that ‘group of scientists’ and their PR Marketing firm.

    Sorry, I thought the intent and the reasons why was already clear. HTHs

  27. 27
    Thomas says:

    Scientific analysis is one thing, usually undertaken by experts in their field. Understanding that analysis and what it ‘means’ is another thing entirely for Joe Public.

    Scandinavia has a Regional Climate. Due the ‘forcings'(?) linked to AGW that climate is changing. The Gulf States of the USA likewise has a Regional Climate. And again due to ‘forcing’ linked to AGW that climate is changing.

    As I understand “climate” is a statistical evaluation of weather stats across time, usually across a ~30 year period for ease of comparison and having clear “standards.”

    As far as I know, Scandinavia does not have Hurricanes. This is because of it’s ‘…….’.

    What is ‘…….’?

  28. 28
    Lynn says:

    I was thinking that a comparison could be made between what the probability was of Harvey’s intensity, stalling (re also how CC impacts lingering Rossby waves), precip, and inundation (related also to sea level & sea level rise)…

    1. under CC is not happening, no warming (the average before CC took off around 1980). They are saying it was a 1 in 1000 year storm, so there might be some idea, with a prob of ?? less than .001

    2. under CC (warming, precip, sea rise, impact on Rossby waves) to date. Maybe it would be bumped to a 1 in 50 year storm or 1 in 20 year storm, with a prob somewhere greater than .05

    Or, like life expectancy calculations of life expectancy at age 5 …. Given a Cat 1 hurricane, what is the likelihood it will turn into a Cat 2, 3, 4, 5, now 6 it seems under pre-CC conditions and under current CC conditions.

    Just some ideas that might help people to see the difference betw a non-CC, pre-1980 world and the current CC situation we have now.

  29. 29
    Eric Swanson says:

    Harold Seneker @ 6 points to his blog post, which features a paper by John P. Bluemle (REF #9). That paper’s main thrust is a re-plot of data from Keigwin’s 1996 paper in SCIENCE. Apparently, Bluemle cherry picked a modified version of Keigwin’s data, derived from a paper by Robinson’s OISM which incorrectly plotted the data. Not to mention that the original Keigwin data presented pairs of data points, each of which represented an average value of the 14C from within the particular slice of the core, thus there’s no way to set an exact date for each point. There aren’t any confidence limits (error bars) mentioned, either. And, of course, the Sargasso Sea temperature isn’t even close to a hemispheric temperature average.

    Sorry, Harold, your blog is just a regurgitation of well known denialist crap.

  30. 30
    Mal Adapted says:

    Kevin McKinney:

    Gee, why would anyone ignore the last 18 years of bibliography in a field where research has metaphorically exploded in volume, scope and sophistication?

    No doubt you were asking rhetorically, but of course AGW-deniers will only cherry-pick two centuries of climate science for rhetorical ammunition, and dismiss the rest as a plot to impose world soshulizm and pollute our precious bodily fluids. If hseneker were actually interested in keeping up with the multiple lines of peer-reviewed evidence supporting the consensus of working climate scientists, he wouldn’t be a denier, and he probably wouldn’t have a blog.

  31. 31
    Thomas says:

    Sarah Perkins-Kirkpatrick – Research Fellow, UNSW – September 6, 2017
    “…. climate scientists should not expect everyone to be as concerned as they are when they show a plot of increasing global temperatures.

    Cli-fi has the potential to work in the exact opposite way, through compelling storylines, dramatic visuals, and characters. By making people care about and individually connect to climate change, it can motivate them to seek out the scientific evidence for themselves.”
    https://theconversation.com/can-cli-fi-actually-make-a-difference-a-climate-scientists-perspective-83033

  32. 32
    Jan Samohyl says:

    Regarding the connection between changing climate and an individual weather event, why not try the following:

    Calculate the probability that event is influenced by humans. Then roll dice for the probability. And then give the media the short answer based on the dice roll.

    If anyone will raise doubts about what you did, explain them the procedure.

  33. 33
    Ray Ladbury says:

    Kevin McKinney: “Gee, why would anyone ignore the last 18 years of bibliography in a field where research has metaphorically exploded in volume, scope and sophistication?”

    Why obviously to counter the well known liberal bias of reality!

  34. 34
    Dan DaSilva says:

    The model is indeed simple, ridiculously so. Oh but wait it is “calibrated”. Another word for fudging your model to meet past results. This my friends is not science it is mental masturbation.

  35. 35
    Dan DaSilva says:

    “Gee, why would anyone ignore the last 18 years of bibliography in a field where research has metaphorically exploded in volume, scope and sophistication?”

    Exploded alright, but what is the cause of the explosion? Not science but ideological left wing fascism trying to shutdown debate by screaming denier.

  36. 36

    Dan DaSilva, #35–

    “Exploded alright, but what is the cause of the explosion? Not science but ideological left wing fascism trying to shutdown debate by screaming denier.”

    Oh, BS, pure and simple. That “explosion” we are talking about is in the peer-reviewed literature, where one mention of a loaded term like “denier”–or for that matter, “fascism”–will make pretty darn sure your paper will never see the light of day. And, pray tell, how does a plethora of reconstructions, new and improved methodologies, better analyses, etc., “shutdown debate?” Any reasonable accounting would say it promotes debate–or at least, understanding.

    The only ones trying to shut down the scientific conversation are those currently holding the purse strings in Washington. And maybe those who support them by falsely, baselessly and hypocritically accusing researchers of ‘political bias’.

  37. 37
    Brian Dodge says:

    If one (that one being Rasmus, or perhaps Tamino, who have the tools, expertise, and data/polynomial fits)extended the ranges to 55 degrees C and 1000mm/day, and divided the points on curve 1 by the points on curve 2, wouldn’t the result be the relative increase in probability from condition 1 to condition 2?
    I suspect that although currently the probability of lethal wet bulb temperatures, or catastrophic rain events are very low, because of the shapes of the curves and “the Statistical parameters are surprisingly predictable, and weather statistics is systematically influenced by the physical conditions present” that their relative increase and risk are much higher than most people appreciate.

  38. 38
    Dan says:

    re: 34. “Oh but wait it is “calibrated”. Another word for fudging your model to meet past results. ”

    Wow, it is quite embarrassing of you to come on a site hosted by peer-reviewed (you know, one of the foundations of all science) climate scientists when you have absolutely no clue about the scientific method. Hint: It is how science has been conducted for centuries and something you should have learned in grade school. Seriously. But no, you lazily regurgitate what someone told you and what you want to believe without a shred of science to support you.

  39. 39

    Da Silva, if anyone has tried to shut down debate, it’s you deniers. Climate scientists have been accused of lying, fired, threatened with nooses and with gang rape of their children, and had eviscerated animals left on their porches. Don’t play the victim with us, please, because we know exactly what’s happening. Any traces of fascism are all on your side. Why don’t you go back to Stormfront? I’m sure they’ll be interested in your input there.

  40. 40
    CCHolley says:

    The model is indeed simple, ridiculously so. Oh but wait it is “calibrated”. Another word for fudging your model to meet past results. This my friends is not science it is mental masturbation.

    This tripe is particularly irksome to me as a category five hurricane, most likely exasperated by the effects of global warming, bears down directly at my home.

  41. 41
    Dan DaSilva says:

    re #38
    Peer-review can be a problem, if peers who review are ideological peers with science taking a seat further back on the bus.

    re #38
    As far as calibration, try making a model of the stock market, back test and calibrate it. The model will make money in the past but do not bet your mama’s farm on future results.

    re #39
    No victims here just healthy skepticism.

    A man who has no doubt is a man with no self awareness. Compare your views and attitudes while sober with those while drunk, has anything changed? When drunk you will be cocksure of yourself just as when you are sober.

  42. 42
    Nemesis says:

    “ideological left wing fascism”

    Hahaha, nice try, made my day :’D

  43. 43
    jgnfld says:

    @41

    The problems you point out with peer review have, in fact, occurred. Unfortunately for your thesis where they have occurred is with denier “science”.

    You are conflating hindcasting with calibration. In the modeling world, these are 2 entirely different things as every professional here is completely aware of. It really makes you look foolish when you make such freshman mistakes.

    “A man who has no doubt is a man with no self awareness.”

    Your post provide good evidence of this assertion.

  44. 44
    Mal Adapted says:

    Dan DaSilva, after dropping the mask of reason, tries his clumsy hand at reason again. His three points are transparently misconceived, and hugely ironic in the bargain. I suggest responses merely link to the SkepticalScience list and/or the relevant RC articles, for the benefit of any genuine skeptics that might be lurking.

  45. 45
    David Young says:

    Since Mann’s article in the Guardian is mentioned here, I will provide a link to 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.

    The bottom line in this analysis is that both observations of the past decades and models looking forward to the future do not suggest that one can explain the heavy rains of Harvey by global warming, and folks that are suggesting it are poorly informing the public and decision makers.

    http://cliffmass.blogspot.com/search?updated-max=2017-09-04T08:13:00-07:00&max-results=20

  46. 46
    Racetrack Playa says:

    I think you want to look at the concept of “fractional attribution” rather than an either-or approach of attributing a given event to “natural cause” vs. “anthropogenic cause.”

    See Stott et al. 2015, “Attribution of extreme weather and climate-related events”
    http://www.hvonstorch.de/klima/pdf/stott-et-al.2015.pdf

    The concept of fraction attributable risk (FAR)was first applied in 2004 in an analysis of the European heat wave of 2003. This was the first instance of an event attribution study providing a direct link between anthropogenic climate change and an individual extreme climate event. To achieve this result, the probability (P1) of a record warm summer in a particular European region was compared with its probability (P0) had anthropogenic influences on climate been absent.

    That’s clearly the best way to think about the problem. However, another major issue is that of attribution based on the thermodynamic state responses to global warming vs. the atmospheric dynamics, with the latter being far more problematic:

    Some attribution assessments that link events to dynamically driven changes in circulation have been criticized on the grounds that small signal-to-noise ratios, modeling deficiencies, and uncertainties in the effects of climate forcings on circulation render conclusions unreliable and prone to downplaying the role of anthropogenic change. Instead, it is argued, it is more useful to consider how changes in the climate’s thermodynamic state have affected the impact of a particular event.

    For hurricanes, then, you’d want to ask what the sea surface temperature, subsurface ocean heat content, and atmospheric water vapor content would have been if, say, fossil fuel use had been eliminated 100 years ago, and atmospheric CO2 remained at about 300 ppm. Under such conditions, you’d still have active hurricane seasons, but the overall average strength and associated precipitation would be decreased by some fraction. Notably, issues such as why a given hurricane stalled or took a particular track (problems in dynamics) could not reliably be attributed to anthropogenic climate change, unlike intensity (which is clearly related to the thermodynamic state of the atmosphere and oceans).

  47. 47

    DDS: Peer-review can be a problem, if peers who review are ideological peers with science taking a seat further back on the bus.

    BPL: I take it you’ve never actually had a paper peer-reviewed. Peer review is not to enable submitters, it is to weed them out. Peer reviewers find everything wrong with your paper that they possibly can. The idea is to make it as hard as possible to get a new idea past the gates–because you cannot know in advance which one of the 20 new ideas that day are valuable and which are dead ends. In short, peer review is designed to be as hard as possible, and on purpose. You don’t just vote your friends in.

  48. 48
    nigelj says:

    Dan De Silva @41

    “As far as calibration, try making a model of the stock market, back test and calibrate it. The model will make money in the past but do not bet your mama’s farm on future results.”

    You pick a poor example because modelling stock market behaviour is notoriously difficult because its chaotic and based on irrational human psychology. Nobody has figured out a useful model with the correct formulas, its a huge challenge, might be impossible, so hindcasting is never going to even get to a useful stage at current state of knowledge. Its like accurately predicting short term weather! Pretty approximate.

    Physical processes like climate are a bit easier to model as they are less chaotic.

    I’m no climate scientist, but I know models in all fields are based on clusters of formulae, and these formulae are often derived from real world data partly by trial and error, and adjusting terms until they can reliably predict past and future data. Its not fudging, its just hard work, and its how formula that work are developed in all fields of science, engineering etc.

  49. 49
    CCHolley says:

    DaSilva @41

    Peer-review can be a problem, if peers who review are ideological peers with science taking a seat further back on the bus.

    Baloney. 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. The burden is on the so called skeptical scientists to show why the science is wrong and to date they have not been able to do so.

    As far as calibration, try making a model of the stock market, back test and calibrate it. The model will make money in the past but do not bet your mama’s farm on future results.

    False equivalency. Models are based on physics. Due to the complexity there is some tuning for some parameters that are not well constrained. The claim that they are tuned to to match the 20th century warming is false.

    See: THE ART AND SCIENCE OF CLIMATE MODEL TUNING

    No victims here just healthy skepticism.

    Nope. Healthy skepticism would be backed by facts and evidence.

  50. 50
    Dan says:

    re: 41.
    “re #38
    Peer-review can be a problem, if peers who review are ideological peers with science taking a seat further back on the bus.”

    Further proof that you have absolutely no clue about the peer review process and the difficulty involved in getting a paper reviewed. Again, you have never learned the scientific method. That is unequivocal. You are desperately reaching for any excuse to defend a non-valid point. Just because you do not want to or can not understand the science it does not mean it is any less valid. Stop flaunting intellectual laziness and ignorance.

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