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Absence and Evidence

Guest commentary by Michael Tobis, a retired climate scientist. He is a software developer and science writer living in Ottawa, Ontario.

A recent opinion piece by economist Ross McKitrick in the Financial Post, which attracted considerable attention in Canada, carried the provocative headline “This scientist proved climate change isn’t causing extreme weather – so politicians attacked”.

In fact, the scientist referenced in the headline, Roger Pielke Jr., proved no such thing. He examined some data, but he did not find compelling evidence regarding whether or not human influence is causing or influencing extreme events.

Should such a commonplace failure be broadly promoted as a decisive result that merits public interest?

ABSENCE OF EVIDENCE VERSUS EVIDENCE OF ABSENCE

Statistics is a vital tool of science, but it is not the only one. It is most effective when dealing with large quantities of data. Using statistical methods to detect the effect of one factor among several amounts to proving that the other factors did not align as a matter of happenstance. The more abundant the data, the less likely such a coincidence.

In the case of extreme weather, the number of sample points is small because extreme events by definition are rare. Up until the beginning of the satellite era, records of past events are often incomplete. There is little we can do to improve the amount of such data at hand. Because the data are irredeemably scarce, and time series short, using purely “frequentist” statistical methods to decide whether or not climate change makes a certain type of severe event more likely will tend to be inconclusive.

Limiting attention only to the most severe storms of a particular type, and then further limiting it to those causing the most extreme financial damage, drastically reduces the number of samples considered, and so further reduces the likelihood that a real trend will be detected.

It’s a well-known motto in research that “absence of evidence” is not “evidence of absence”. It’s well known because it is a common beginners’ error to conflate these. Scientists in training quickly learn that “we find no evidence of phenomenon P” is not the same as “we found evidence that phenomenon P is false”. The proposition in question could well be true but the analysis may lack enough data to show it. (The test is said to be underpowered). Yet a systematic neglect of this simple point is pervasive among those skeptical of the risks of climate change.

Those who wish to avoid vigorous climate policy have gotten a lot of mileage out of inconclusive results.

HOW TO GET INCONCLUSIVE RESULTS

There is, along the periphery of climate science, an enthusiastic audience for null results: people who don’t want to accept the seriousness of climate risk will celebrate any absence of a demonstrated trend or inconclusive attribution. But it’s always possible to obtain a null result, i.e., a lack of statistical significance, if one seeks it, by reducing the amount of data under consideration.

Most science works the other way around, looking for relationships and trends that actually do seem to be happening! There is, under ordinary circumstances an audience for significant results. Were we not operating in a politicized context, detection would be considered more important than lack thereof.

To increase the likelihood of detection, we can look at larger categories of event. For example, in a 2013 report, the European Academies’ Science Advisory Council, examined trends in the specific extremes of heat and cold, precipitation, storms, winds and surges, and drought. The agency found evidence for “overall increases in the frequency and economic costs of extreme events”.

Much of Pielke’s work focuses largely on insurance costs of landfalling hurricanes in the USA, an especially rare phenomenon influenced by numerous factors and one with especially peculiar statistics. It’s an ideal field in which to get a null result, if that’s what the investigator is seeking.

An important point in looking at actuarial damages is that building standards and warning systems have systematically improved. In the absence of a climate-driven trend, we’d expect damages to decline. This counter-argument is made in many places, for example Dr. Kevin Trenberth in a book review:

[Pielke] ignores the benefits from improvements in hurricane warning times, changes in building codes, and other factors that have been important in reducing losses.”

Another approach to hide climate-driven damage is to blur trends. We expect (from physical arguments and models) and find (from observations) increasing precipitation at higher latitudes and decreasing precipitation in dry subtropical latitudes. Aggregating them, the net result is no global trend in drought, and true to form McKitrick celebrates this result as well.

Source: A dryer southwest and wetter northeast, so no overall trend. An example of how averaging can obscure significant results.

Aggregating such non-results and obscured results brings us to McKitrick’s sweeping conclusion.

“There’s no trend in hurricane-related flooding in the U.S. Nor is there evidence of an increase in floods globally. Since 1965, more parts of the U.S. have seen a decrease in flooding than have seen an increase. And from 1940 to today, flood damage as a percentage of GDP has fallen to less than 0.05 per cent per year from about 0.2 per cent. And on it goes. There’s no trend in U.S. tornado damage (in fact, 2012 to 2017 was below average). There’s no trend in global droughts. Cold snaps in the U.S. are down but, unexpectedly, so are heatwaves.”

McKitrick leaves the impression that all these conclusions are unequivocal, and that none of them have been hamstrung by approaches that are unlikely to yield significant trends.

Even at face value these specific claims, combined with a world-weary “and on it goes” isn’t enough to logically support his broad conclusion that “The bottom line is there’s no solid connection between climate change and the major indicators of extreme weather.”

Jumping from specific observations to a broad conclusion, as McKitrick does, is rhetorical, not scientific. In addition to being a logical fallacy, it ignores a great deal of evidence to the contrary. 

“This cow is black, and that one, and that one, and on it goes,” is not enough to prove that all cows are black when there are spotted cows aplenty in the field.

TIME AND TIDE

The evidence to the effect that there is a connection between anthropogenic climate change and increasing severe events, far from being absent, is in fact rapidly accumulating.

McKitrick makes much of Pielke’s role in a 2006 conference on severe weather which released a consensus document, the Hohenkammer Consensus, that was a fair assessment of knowledge at the time. That report asserts that “In the near future the quantitative link (attribution) of trends in storm and flood losses to climate changes related to GHG emissions is unlikely to be answered unequivocally.”

It is in exactly this pool of equivocality that Pielke has been content to operate. But is that pool shrinking?

Both science and climate change itself are advancing at a rapid pace. What was true in the “near future” of 2006 is not necessarily true today! So in using more advanced methods to study a more advanced disruption, has the situation changed?

In fact it has. Methods for attributing individual severe events partially to climate change have emerged. In 2016, the National Academy of Science of the USA issued a report entitled Attribution of Extreme Weather Events In the Context of Climate Change, which enumerates the ongoing efforts. Among its key conclusions:

“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.”

While not without complexity or controversy, attribution studies are complex and subject to the usual debates and disagreements that evolving fields of science undergo. Such work is extensive and carried out by multiple research groups in multiple countries (see also Going To Extremes from this site).

The Bulletin of the American Meteorological Society has, since 2011, been releasing special issues on the subject of extreme event attribution. In recent issues, cases of severe events have been identified that would have been essentially impossible in the undisturbed climate. New examples have been published recently, indicating that heat waves in Europe and North America and in Japan couldn’t have occurred in the absence of human-caused climate change.

So McKitrick’s claim that “the bottom line is there’s no solid connection between climate change and the major indicators of extreme weather, despite Trudeau’s claims to the contrary” is at best out-of-date and ill-informed. Some might call it deceptive.

One can always dismiss evidence one doesn’t like as not “solid”, of course. But by now, there’s quite a lot of evidence to dismiss and McKitrick, rather than addressing it avoids any mention of any of it whatsoever. One expects better from an academic.

SO WHAT IS REALLY GOING ON?

While determining exactly which severe events are more likely already under climate change, and which will become so, we should begin by focusing on what is known currently.

Quoting from the aforementioned 2006 consensus document that McKitrick celebrates, it was already known that:

  • Climate change is real, and has a significant human component related to greenhouse gases
  • For future decades the IPCC (2001) expects increases in the occurrence and/or intensity of some extreme events as a result of anthropogenic climate change
  • Direct economic losses of global disasters have increased in recent decades with particularly large increases since the 1980s
  • There is evidence that changing patterns of extreme events are drivers for recent increases in global losses.

McKitrick leaves the reader with the impression that the report had other conclusions. The 2006 report only said that the reasonably inferred causality between human-caused climate change and increasing severe events wasn’t as yet proven.

Since the time of that conference, not only climate change but increases in the frequency of disruptive events have become rather obvious in many regions of the world, including Canada. The evidence has shifted remarkably. 

These are the troublesome events we expect, and many of these troubles appear to be happening with increased frequency and severity.

If someone argues, as they may, that the connection is not yet proven to their satisfaction, they may or may not have a case. Indeed, I (the author of this article) have expressed some concerns about the validity of the single-event attribution approach. But questioning an approach is one thing. To claim or imply that something is disproved by systematically ignoring evidence to the contrary is another thing entirely. To do so is to undermine discourse. It’s simply misleading and irresponsible.

WHAT ABOUT CANADA?

Environment and Climate Change Canada recently released “Canada’s Changing Climate Report”. As with most scientific consensus documents, it is careful to emphasize scientific uncertainty. Its opening sentence is nevertheless unequivocal: “There is overwhelming evidence that the Earth has warmed during the Industrial Era and that the main cause of this warming is human influence. “

Regarding the specific issues raised by McKitrick, the report’s conclusion is

“In the future, a warmer climate will intensify some weather extremes. Extreme hot temperatures will become more frequent and more intense. This will increase the severity of heatwaves, and contribute to increased drought and wildfire risks. While inland flooding results from multiple factors, more intense rainfalls will increase urban flood risks. It is uncertain how warmer temperatures and smaller snowpacks will combine to affect the frequency and magnitude of snowmelt-related flooding.”

Katherine Hayhoe, in an article in Chatelaine, a popular magazine published in Canada, points out that

The Insurance Bureau of Canada estimates “catastrophic losses due to natural disasters have increased dramatically” over the last 10 years, with $1.9 billion of insured loss in 2018 alone. Extreme weather-related losses reported during the ’90s and 2000s averaged around half a billion dollars per year. Even leaving out damages from the record-breaking Fort McMurray wildfires, losses in the 2010s are still three times higher, averaging almost $1.5 billion per year through 2018.”

insured losses from environmental disasters in Canada, in constant dollars via Insurance Bureau of Canada.

This is what climate science expects, and this is what we see. There are conflating influences  – more property value exists, and conceivably it is, for some extraneous reason, more at risk. Still the trend in Canada is particularly striking.

One can argue whether the connection is as yet “proven” in the sense of statistical hypothesis testing, but it’s far from being disproven. To the contrary, it is reasonable to expect the proof to continue to emerge.

SCIENCE, POLITICS AND REASON

Scientists, being humans living on the Earth, are not immune from political and policy preferences. While as scientists they are trained to resist such biases, no one denies that such influences exist and need to be considered. But this cuts both ways.

Of course, taking climate change seriously will require substantial shifts in public policy, and many are threatened by these, whether by direct financial motivation or a strong philosophical preference for laissez-faire organization of society. Those scientists who are most popular among those so threatened are ones who seem to actively look for inconclusive results. In doing so they may advance their own careers, but they hardly advance either science or public discourse.

When one-sided articles like McKitrick’s come out that are rife with logical fallacies, it’s more than a little bit ironic to see them accusing their opposition of bias.

Democracies, including Canada. historically have been especially capable of arguing about contentious issues from common values and shared understanding of facts. Recent adverse trends in political discourse have been very disturbing.

McKitrick’s article is a part of this disturbing trend – it amounts to a personal attack on Prime Minister Trudeau, selecting and bending facts to create a misleading conclusion. The attacks imply that the Prime Minister and his government are casually misinformed, and concede nothing to those with whom the author disagrees.

This is not the way to solve problems or maintain a civil society. Let’s do better.

139 Responses to “Absence and Evidence”

  1. 51
    Dennis N Horne says:

    Definitions are tricky.That’s a reason we need so many damn lawyers… Even a car is quite difficult: some don’t have four wheels. What about a chair that one leg has broken off – most people would recognise it as a chair but a seat with three legs is usually a stool…

    So. I know what weather is. I know what bad weather is. I know what a nice day is. I prefer the climate in Auckland to the climate in London, but Paris is often pleasantly warm and more settled in summer. So I guess I know what climate is, but I am quite content to let someone else define it.

    Finally, I know I am opinionated, insistent and argumentative, and have no expertise in this field, so time to bow out…

  2. 52
    Matthew R Marler says:

    Mal Adapted: Over the last decade, extreme weather and fire events have cost the federal government over $350 billion…These costs will likely rise as the climate changes.

    I am not sure that you are getting Pielke’s point: no doubt the dollar costs have increased, but increased storm intensity, frequency, and duration are not necessarily the reasons. Increased population and inflation mean that for every storm, more high priced assets are at risk; additionally, other factors like the New Orleans ship channel increase the risk of coistly damage.

  3. 53
    David Young says:

    Jan, If you look at the Navier Stokes equations, the driving terms are all in terms of gradients. So for example the gradient of the pressure is there and the gradients of the velocities. Using the ideal gas law, pressure is proportional to temperature so the gradient of the temperature can be argued to enter in some form. Tropical convection is driven by temperature gradients through density gradients (recall the ideal gas law) that drive vertical velocities. It’s really fundamental stuff.

    I would also point out that our current corrupt media is notoriously biased towards exaggerating every event and its significance because that generates clicks and sells yellow sheets. The real crisis of science in our era is the boulderizaiton of science and the translation of that pseudo-science into governmental policy. You hear all kinds of nonsense when popularized science gets politicized. For 60 years we had policy that tried to get people to eat less dietary fat. Companies complied and added more carbohydrates and simple sugars, resulting in soaring obesity and diabetes rates. All driven by a single biased nutritionist named Keyes who created a “consensus” around this.

    Scientists who give Congressional testimony that relies on biased media reports are doing us a disservice. Ignorant politicians make harsh and biased statements. That’s perhaps what McKitrick was trying to respond to. I personally think “damages” is useless for assessing trends in weather events, so he picked the wrong metric. For one thing we are much much more exposed to coastal flooding now than 100 years ago when most coastlines were undeveloped.

  4. 54

    Something which I left out in #22 because it was already long and its focus was upon Statistics, is Dr Tobis’ (IMO) correct discussion regarding:

    Much of Pielke’s work focuses largely on insurance costs of landfalling hurricanes in the USA, an especially rare phenomenon influenced by numerous factors and one with especially peculiar statistics. It’s an ideal field in which to get a null result, if that’s what the investigator is seeking.

    I’ll say more, though. Risk numbers and event rate numbers look significantly different if you just count U.S. landfalling hurricanes than all hurricanes in the Atlantic basin. Also, if you look at numbers of hurricanes or tropical storms outside of the conventional hurricane reason, those have increased a lot as well. My point is that these are, as Dr Tobis emphasizes, curiously avoided by people like Pielke and McKitrick, who seem to define their sampling space in the most narrow plausible terms.

    Dr Tobis argues

    To claim or imply that something is disproved by systematically ignoring evidence to the contrary is another thing entirely. To do so is to undermine discourse. It’s simply misleading and irresponsible.

    I would go farther and say this practice demonstrates a lack of good faith. When a scholar points out a discrepancy and does not work hard to rationalize how one gets from the basis of the discrepancy to their objection. It is simply good scientific form to work on elucidating the discrepancy, and this is often done in cooperation with the authors of the original study. Noting a discrepancy but then stopping before it is explained may sow doubts about the study, but it is not science, or even good engineering. It is a courtroom tactic.

    Worse, demanding a claim be re-proven when ample literature and argument exists to substantiate the claim wastes everyone’s time. Some might feel such time-wasting is justified based upon ideological reasons, whether or not they admit it, and, so, are guilty of an Argument from Adverse Consequences.

  5. 55
  6. 56
    Michael Tobis says:

    #55 “The steady Navier–Stokes/energy system with temperature-dependent viscosity” has precisely nothing to do with the climate system except insofar as there is a N-S system at its heart. (Two, actually, in the case of climate, plus a nasty visco-elastic continuum problem with sea ice, and a whole lot of interface physics, actually.)

    I suppose it might have practical application, e.g., it might be relevant to lava flows, except insofar as the authors discuss the steady problem in two dimensions.

    If your point is “Jan, If you look at the Navier Stokes equations, the driving terms are all in terms of gradients. So for example the gradient of the pressure is there and the gradients of the velocities.” you could make it in some other way than googling up a random paper with N-S in the title.

    If you want to engage people, explain what you mean by a gradient and why that calls into question the simple “more energy – more bad weather” claim.

    If you just want to look clever with an impenetrable reference, from where I am sitting you have not succeeded.

  7. 57
    Mal Adapted says:

    Matthew R Marler:

    I am not sure that you are getting Pielke’s point: no doubt the dollar costs have increased, but increased storm intensity, frequency, and duration are not necessarily the reasons.

    You apparently didn’t get Dr. Tobis’s point. Pielke may have been talking only about hurricanes, but the OP is about an opinion piece by one Ross McKitrick, well-known professional AGW-denier, appearing in Canada’s business-friendly Financial Post with the headline “This scientist proved climate change isn’t causing extreme weather – so politicians attacked”.

    MT wrote:

    In fact, the scientist referenced in the headline, Roger Pielke Jr., proved no such thing. He examined some data, but he did not find compelling evidence regarding whether or not human influence is causing or influencing extreme events.

    Quoting McKitrick’s OpEd directly:

    “There’s no trend in hurricane-related flooding in the U.S. Nor is there evidence of an increase in floods globally. Since 1965, more parts of the U.S. have seen a decrease in flooding than have seen an increase. And from 1940 to today, flood damage as a percentage of GDP has fallen to less than 0.05 per cent per year from about 0.2 per cent. And on it goes. There’s no trend in U.S. tornado damage (in fact, 2012 to 2017 was below average). There’s no trend in global droughts. Cold snaps in the U.S. are down but, unexpectedly, so are heatwaves.”

    MT’s post is about McKitrick’s exaggeration of RPJr’s claims. One imagines Jr might be annoyed with McKitrick. Anyway, Jr’s analysis posed unrealistic expectations: due to the nature of the data, conventional statistical methods can’t yet detect any historical increase in, for example, hurricane intensity. Nonetheless, there are well-founded predictions that tropical cyclone intensity will increase as AGW proceeds. And while dollar costs of extreme weather have increased in the US, as I cited earlier, of course “increased storm intensity, frequency, and duration” can’t be shown to be the sole causes: every costly disaster has multiple causes ultimate to proximate.

    So, do you think MT’s post will appear as an opinion piece in the FP, perhaps titled “When scientists rigorously show how AGW causes extreme weather, paid deniers attack with specious rhetoric“? If so, would McKitrick be deterred by scientific (i.e. genuine) skepticism? My faint hope, OTOH, is that ridicule, along with appeals to “common sense”, are effective with the mythical uncommitted RC lurker. IOW, to “act as if, speak as if, my whole worldview is of course normatively correct. Overton windows and all that” ;^)!

  8. 58
    nigelj says:

    Matthew R Marler @52

    “I am not sure that you are getting Pielke’s point: no doubt the dollar costs have increased, but increased storm intensity, frequency, and duration are not necessarily the reasons. Increased population and inflation mean that for every storm, more high priced assets are at risk; additionally, other factors like the New Orleans ship channel increase the risk of coistly damage.”

    I agree some of the increased costs are attributable to those human elements, but some of the costs must be attributable to increased storm intensity and increased frequency of droughts, heavy rainfall events and heatwaves etc because many of such events are known to be happening according to the IPCC, and cause physical damage or other problems for people. Its absurd to suggest they don’t cause damage, because its simple cause and effect, and so it costs more money and resources to fix. Economic growth only masks this climate influence. The thing is to work out the proportionality between the costs of the human factors and the climate/ weather factors, which is obviously difficult.

    And the fact that human causes are one factor in increasing costs of weather related events is not proof that weather is not getting worse in some way. McKitrick and Pielke also cherrypick their data to suit their argument.

    Of course global warming is simply causing changes in the weather and whether this is making weather more extreme, or worse or better depends where you live and what you value, but overall higher intensity and higher frequency of heatwaves, droughts, cyclones, and floods etc do not look like they are well compensated for by slightly warmer winters, just as my subjective impression as a layperson living in a temperate climate zone.

  9. 59
    David Young says:

    Well, Michael aside from sarcasm I don’t see anything in you #56. The point is that the Navier-Stokes equations as stated on the third page of my reference only contain the gradient of the temperature.

    I give Jan more credit than you do in that I expect he knows what a gradient is. The paper considers most of the other ways temperature could change the Navier-Stokes equations for example through the viscosity.

    I already stated why global warming might lead to lower temperature gradients. Lower pole to equator temperature gradients and perhaps (even though data is ambiguous) lower vertical temperature gradients in the tropics.

    The simple fact is that more severe weather is a very weak talking point since its really not supported by either theory or data. I’m surprised that you ventured into this area given the weak evidence.

  10. 60
    Matthew R Marler says:

    11 Mark R: “Nigeria’s population has increased so AIDS can’t be killing people”. It seems ridiculous to me.

    I think that is absurd. A Fairer analogy would be: Nigeria’s population is increasing so the increase in the number of AIDS deaths by itself does not imply an increase in the incidence of AIDS.

  11. 61
    zebra says:

    Michael Tobis #47 and other comments,

    I still don’t see that you are contradicting what I said about the science. I said that scale and time were relevant, and I qualified my statement with ”near-term”. I think that covers everything you are saying about rates of change, and equilibria, and energy distribution.

    Where there is (apparent) disagreement is in the matter of near-term effects, and how one might best communicate about them with the general public.

    I always get on people about giving definitions, so I will begin with mine for “near-term”. That would be when the system state is still close enough to the original equilibrium that the constituent phenomena and interactions are readily recognizable. So, we still have hurricanes as we have known them, and we don’t have zero hurricanes, and we don’t have weekly hurricanes. Deserts have not become inland seas, and rain forests have not become deserts. Moist air still meets cold air and it rains…and so on; I’m sure you understand.

    Now, you seem to be arguing that I am incorrect in telling people that the increase in total system energy we have experienced (and future near-term increases) will manifest as changes in those phenomena, and that the resultant disruptions will be problematic in most cases. (Imprecisely put: ‘more energy, worse weather’)

    So far, you haven’t made the case. You’ve repeated the logical error I pointed out before; the fact that lowering the original equilibrium system energy would be disruptive has no bearing on what the effect of increasing it would be. And, with all due respect, I find it a bit insulting that you cite Keith Woolard’s inane #41 as something we should consider a meaningful counterargument. The Denialists are going to produce those kinds of responses no matter what you say. The question is, what can a typical sincerely agnostic person understand, if there are such individuals?

    I think not debates about Navier-Stokes and gradients, or arcane statistical criteria, or dense jargon-filled abstracts, but they can understand things like “more energy means more water vapor means heavier rain when it rains”. I think the Denialists are well aware of that, and are all too successful in manipulating discussions away from simple, correct, descriptions.

  12. 62
    Tadaaa says:

    #61, a good point well made, when trying to communicate complex systems often brevity and clarity (at the risk of losing some fidelity) is a good tactic, especially in conveying the central truth to the semi committed “lurker”

    when answering the question sometimes posed by 911 conspiracy theorists as to why the WTC 1,2 and 7 fell “straight” down

    sometimes an effective response is simply saying “gravity”

  13. 63
    David Young says:

    Of course zebra has it backwards. Communicating that dietary fat is bad for you is unethical if its in fact not supported by science. Truth and rigorous math must come first.

    The science on severe weather is deeply equivocal with competing verbal formulations that mostly lack quantification. The real problem here is that if scientists become indistinguishable from activist yellow journalists, confidence in them will decline to zero.

  14. 64
    MA Rodger says:

    The discussion of the theoretical increase in extreme weather under global warming is one that is flatly denied by that old denialist Dicky Lindzen. I note that he managed to maintain this argument in his 2018 chat to the Gentlemen Who Perfer Fantasy: that polar amplification will reduce the polar/tropics temperature gradient and this refutes the notion of AGW bringing more extreme weather:-

    “Now, the models used to project global warming all predict that this temperature difference will decrease rather than increase. Thus, the increase in temperature extremes would best support the idea of global cooling rather than global warming. However, scientifically illiterate people seem incapable of distinguishing global warming of climate from temperature extremes due to weather. In fact, as has already been noted, there doesn’t really seem to be any discernible trend in weather extremes.”

    I have always felt this idea of a temperature gradient requirement to drive extreme weather is flawed.
    In a climate with no active atmosphere, the gradients are at their highest but there is no extreme weather, just the same weather as it was yesterday/last year. The idea that in a heavily-greenhoused climate with no gradient would be all calm & sedisville on the surface may hold some merit, but inbetween these extremes there would presumably be a point of manimum extreme weather.
    But a heavilly-greenhoused climate with zero gradient? Will it have a calm surface? Bar the loss of albedo due to melting ice, polar amplification is still a big factor in today’s Earth and the diurnal temperature range will also be dropping. Both will require greater energy transfer from tropic to pole, and from day to night.
    I am no expert on Venus, a climate Lindzen cut his teeth on, but does it not shows signs of such energy transfer? Are they ‘calm & sedisville’?

  15. 65
    MA Rodger says:

    Ooops! Broken link from above here. Venus is covered on pp9-10.

  16. 66
    Michael Tobis says:

    #61 “but they can understand things like “more energy means more water vapor means heavier rain when it rains”

    #62 “when trying to communicate complex systems often brevity and clarity (at the risk of losing some fidelity) is a good tactic”

    These are worthwhile points.

    If somebody says ““more energy means more water vapor means heavier rain when it rains” even that is a bit of a short cut which elides some necessary pieces fo the argument, but I probably wouldn’t object. It is MORE true than “more energy means worse weather” which logically implies “less energy means better weather” which is false.

    The important thing, in my way of thinking, is to convey that “anthropogenic climate change is much more rapid than even the rapid climate changes of the Quaternary, and will provide increasingly difficult and sometimes overwhelming challenges to adaptation in both artificial and natural systems”. Yes, that’s a mouthful, but it is in fact the right way to think about it, and I think it’s something people can comprehend. In brief, it’s not the direction of change but the rate.

    To a large extent it’s formed by a response to the actually rather strong denier talking point that there’s no “best global temperature”. Indeed, the optimum is unclear, but the optimum rate of change is VERY clear, and that is as close to zero as we can manage, and MUCH closer to zero than we are managing at present.

    The question of where to put the clarity/fidelity boundary is an old one. There is too much pressure to lean towards clarity away from fidelity, though. This leaves people believing things that are dubious.

    A recent example is the massive hail and flood in Guadalajara, a very striking event, but not one without precedent. Calling it an indicator of climate change as McKibben happily did is possibly arguable, but not overnight.

    There are climate “agnostics” (really that word itself is revealing, isn’t it?) who will see that as excessive, precisely because it is excessive.

    Among the ways in which science remains important to the conversation is to restrain overstatement about the excesses of the excessively alarmed. (Methane emergency etc.)

    Too much of a doomer bent has among its more severe consequences the weakening of the credibility of the actual evidence of the actual very serious situation. (Another is that it supports Macpherson-ite doomer fatalism and withdrawal from the battle to save what can still be saved.)

    The balance can be tricky, especially in the present situation where we are seen as allied with one “side” and against the other “side”. But truth is not a side, really. This sense of alignment is a problem, arguably symptomatic of deeper problems, but a problem nonetheless. Relying on science to align with your talking points is exactly what it means to “put the cart before the horse”.

    In any case, the purpose of science communication (institutional press offices notwithstanding) is to convey the current understanding with the maximum fidelity possible at a given level of sophistication.

    This article is a bit more accessible than many on RC, but it still draws upon a certain level of mathematical sophistication that probably exceeds that of the general public. For that audience at least, “more energy means worse weather” is clearly an oversimplification.

    But for anyone “unnaturally rapid natural climate change stresses adaptation” is a far better formulation in my opinion. It has a lot more fidelity, is equally accessible (most people really don’t have a clear idea what “energy” means to a physicist, after all) and is less open to attack. So why not say that?

  17. 67

    It seems to me that the Pielke argument that increased damages are due to increased wealth and population would be a whole lot stronger if the rise in non-climatic disasters such as earthquakes were commensurate with the trend observed in climatic ones. But my understanding is that that is not the case.

  18. 68

    David Young says:

    Jan, If you look at the Navier Stokes equations, the driving terms are all in terms of gradients.

    A gravitational field does have a gradient, but does this guy (who is supposedly an expert on fluid dynamics employed by Boeing) think that the gravitational gradient has a stronger driving pull than the first-order uniform gravitational force?

    You have to wonder how Boeing can keep their airplanes in the air if this is who they hire ;)

  19. 69
    JCH says:

    … Companies complied and added more carbohydrates and simple sugars, resulting in soaring obesity and diabetes rates. All driven by a single biased nutritionist named Keyes who created a “consensus” around this. … Communicating that dietary fat is bad for you is unethical if its in fact not supported by science. Truth and rigorous math must come first. – David Young

    Can you link to a scientific paper that has used rigorous math to prove what has caused obesity to soar?

  20. 70
    zebra says:

    #66 Michael Tobis,

    First, around here I am consistently the anti-doomer with respect to the science, so we are in agreement on that subject. But I see that there are some areas where we are not.

    I really don’t understand what your statement with respect to rate of change is supposed to be about. It is not an alternative to mine in bold at #61, which deals specifically with the question of weather events given the existing rate of change in system energy. I thought that was the main point of the discussion, and I think there is an important principle in scientific reasoning to consider here.

    Maybe you could clarify this by addressing my actual statement. Do you disagree with it? If you don’t disagree, then we can proceed to discuss how to approach communicating about attribution, and communication in general.

  21. 71

    “…the actually rather strong denier talking point that there’s no “best global temperature”. Indeed, the optimum is unclear…”

    Two points on that.

    1) Perhaps not, but the fact that biological adaptation occurs over tens of millennia or more–if we are talking about really significant changes (as from, for example, homo [whatever] to modern humans)–would suggest as a first-order approximation that existing biota are pretty well adapted to conditions that have prevailed for the last couple of million years. Therefore, departing too radically from said conditions is biologically risky.

    2) Since the Quaternary–ie., the last couple of million years, give or take–has been characterized by an alternation between glaciations and warmer interglacial periods such as the present, it would further seem that we–meaning, “the planetary biota”–are probably experiencing at present the *upper* part of the range to which we are adapted. (Elizabeth Kolbert makes this point in her Pulitzer-winning “Sixth Extinction.”) Hence, we are currently quite close to exceeding conditions to which we–meaning, again, “all Earth’s biota”–have most recently been adapted.

    https://upload.wikimedia.org/wikipedia/commons/6/60/Five_Myr_Climate_Change.png

  22. 72
    zebra says:

    #63 David Young,

    I’ll ask you the same question I asked Michael. I said:

    I always get on people about giving definitions, so I will begin with mine for “near-term”. That would be when the system state is still close enough to the original equilibrium that the constituent phenomena and interactions are readily recognizable. So, we still have hurricanes as we have known them, and we don’t have zero hurricanes, and we don’t have weekly hurricanes. Deserts have not become inland seas, and rain forests have not become deserts. Moist air still meets cold air and it rains… and so on; I’m sure you understand.

    Now, you seem to be arguing that I am incorrect in telling people that the increase in total system energy we have experienced (and future near-term increases) will manifest as changes in those phenomena, and that the resultant disruptions will be problematic in most cases.

    OK, can you tell me what is incorrect about that statement in bold? Or “untruthful”, or “backwards”?

  23. 73
    Adam Lea says:

    64: “I have always felt this idea of a temperature gradient requirement to drive extreme weather is flawed.”

    In the case of storms I don’t think it is. Windstorms are effectively heat engines, where heat moves from a warm place to a cold place, and in the process some of that heat energy is converted to kinetic energy (wind). In this case, it is temperature differences that influence the intensity of the storm. In hurricanes, it is the temperature difference between the ocean and tropopause which determines the theoretical maximum potential intensity. In extra-tropical windstorms, it is horizontal temperature differences which influence the strength of the jet stream, and the intensification of perturbations along the polar front. That is why in NW Europe, the strongest and most destructive windstorms occur in the autumn and winter months, when the temperature difference between the tropics and the north pole is greatest. The role of storms is to transfer heat from the tropical regions (where incoming solar radiation exceeds outgoing longwave radiation on average), to the polar regions (where outgoing infra-red radiation exceeds incoming solar radiation on average. It is therefore not unreasonable to ask whether mid-latitude storms in the northern hemisphere will decrease in intensity on average due to polar amplification reducing the equator to pole temperature gradient.

  24. 74
    MA Rodger says:

    Adam Lea @73,
    It is indeed “not unreasonable to ask whether mid-latitude storms in the northern hemisphere will decrease in intensity on average due to polar amplification reducing the equator to pole temperature gradient.”
    But that is not what the denialists are arguing. They are asserting that all extreme weather events will be diminished by global warming’s polar amplification.
    While this is not something I have thought through entirely, the polar amplification in winter will tend to be due to more energy shifting polewards as the albedo (certainly within the Arctic circle) will not be much of a factor with the sun below the horizon. And the TLT records do appear to show more amplification in winter than in summer. (RSS TLT certainly shows this.) So the winter gradient will have reduced the most (although large to start with) but presumably the amplification means the energy sent poleward will have increased even though the gradient is diminished.

    On a different point, the denialist messaging, I note Woy Spencer has a blog in which he tries to magic away any global-warming-induced extreme weather. He presents three “facts” usually “ignored” that, if better known, would mean “few people with the ability to think for themselves would conclude that our greenhouse gas emissions had much of an impact” on extreme weather.
    The three “facts” are (specifically in the context of the recent record temperatures in France) ♣ We should expect Record Temperatures to occur because the data recorded only covers a limited length of time, and even if the rate of Record Temperatures were increasing, you cannot blame that on global warming (apparently), ♣ If you have a Record heatwave, there will also be an associated colder bit of the world and also the global average will be singularly unimpressive (thankfully), ♣ Finally Woy is “convinced” that we shouldn’t trust the temperature record because of the Urban Heat Islands, and remember Capn Willard Watts whose grand voyage of discovery led to the discovery of this elusive archipeligo (which is all incredibly convincing).

  25. 75
    Keith Woollard says:

    Zebra @72
    What is wrong with that statement is that you are just making stuff up. What possible science says it will mostly be problematic?

    This is the inherent problem with this post, and the attitude of the vast majority of the climate evangelicals…. things used to be in equilibrium (rubbish) and perfect (rubbish) and any change is bad (rubbish)

    What is wrong with your statement – see my 41

  26. 76

    #73, Adam–

    Here’s a thought on temperature gradients.

    On a hemispherical scale, we know that the temperature gradient should decrease, because the poles (Arctic now, Antarctic presumably in the future) warm faster than the equator.

    But does that necessarily mean that temperature gradients over smaller scales decrease, too? Or is it possible that for some time at least, remaining isotherms in the mid-latitudes ‘crowd together’, and thus preserve local gradients even as those on larger scales decrease? How uniform are latitudinal gradients now, and how may they be expected to change?

    Personally, I have no idea what the answers may be. But perhaps they are sensible questions?

  27. 77
    zebra says:

    #76 Kevin McKinney,

    Kevin, yes, this is a complicated topic. I just posed on UV (#3) a question about the jet stream, because I for one need a more detailed understanding of how it works.

    If we look at those maps where there is now a mass of warmer air the entire N-S distance of the USA, next to a mass of colder air of the same extent, there is clearly a significant E-W temperature difference.

    I’m hoping someone can suggest a reference that has graphics or animations showing how the air moves.

  28. 78

    #75, KW–

    There are numerous issues with your #41, rather remarkably, considering how short it is.

    One is general: the incredibly simplistic assumption that ‘warmer is better.’

    Another, more specific, one is the faulty assumption that people don’t go northwards for tourism in large numbers. For instance:

    In 2012, over 16 million tourists arrived in Canada, bringing US $17.4 billion in international tourism receipts to the economy. Domestic and international tourism combined directly contributes 1% of Canada’s total GDP and supports 309,000 jobs in the country.

    https://en.wikipedia.org/wiki/Tourism_in_Canada

    A third concerns the inverse case–the assumption that people will still want to visit the tropics when climatic conditions in those areas exceed norms experienced during our proximate evolutionary history. For instance, I can’t help but wonder what the ongoing heat wave in India and Pakistan has done for/to tourism to those countries? Certainly, it’s had its impact on the school system:

    https://www.news18.com/news/india/delhi-govt-to-suspend-remedial-classes-for-10-and-12-standards-due-to-heat-wave-2215647.html

    https://en.wikipedia.org/wiki/2019_heat_wave_in_India_and_Pakistan

    Fourth is the whole framing of these issues in terms of tourism, as opposed to more central endeavors, like, you know, agriculture. Where people choose to go is one thing; where they must live, quite another. And speaking of which:

    [We] have heard from innumerable Guatemalans that the most fundamental driver of emigration is desperation — and, to an extent that most Americans don’t appreciate, this desperation often reflects drought and severe weather linked to climate change.

    “Food doesn’t grow here anymore,” Jorge Jorge said. “That’s why I would send my son north.”

    There are other factors as well, and the despair also reflects a marginalization of Mayan communities that goes back hundreds of years, presided over in the capital by an incompetent kleptocracy. But climate change is aggravating the desperation.

    “The weather has changed, clearly,” said Flori Micaela Jorge Santizo, a 19-year-old woman whose husband has abandoned the fields to find work in Mexico. She noted that drought and unprecedented winds have destroyed successive corn crops, leaving the family destitute, adding, “And because I had no money, my children died.”

    https://www.nytimes.com/2019/06/05/opinion/guatemala-migrants-climate-change.html

    Sounds like a real tourist paradise.

    The bottom line for me is essentially biology: not only we, but most of the rest of the planet’s biota, are adapted to the prevailing conditions of the Quaternary period, the temperature range of which we are presently at the upper end. Climate change is a process by which humanity forcibly ‘de-adapts’ the planetary biota, and at a very rapid clip.

    Re-adaptation will be unimaginably slow and costly. So slow, in fact, that recovery will not occur in timeframes that are humanly relevant in any except an evolutionary sense.

  29. 79
    Ray Ladbury says:

    I would point out that more water vapor also translates to more latent heat when that water vapor condenses to liquid water–and that can translate to a very significant gradient over a small space. Weather is local–that’s why they report in on your 10 o’clock news.

  30. 80
    Mal Adapted says:

    Kevin McKinney:

    …the actually rather strong denier talking point that there’s no “best global temperature”. Indeed, the optimum is unclear…

    Two points on that…

    Good comment. I think your two points distill down to this: the optimum GMST is the one that results in the fewest mass casualties, as the globe stabilizes at it. Urban civilization arose while it was cooler on average than today, as global temperatures slowly declined from the Holocene Climatic Optimum. The explosive population growth of the last couple of centuries occurred while it was as much as a degree cooler than now. The technological infrastructure to sustain today’s >7 billion people is relatively fixed. Moving production of dozens of staple crops with their preferred climates will be expensive, in money and tragedy. So will migrating people, of course. One way or another, the poorest of the poor will be pushed over the edge of disaster. Meanwhile, new extremes of weather are already taking their toll. The total cost is certain to rise with GMST. Failing global decarbonization over the next few decades, we assuredly ain’t seen nothin’ yet. The appropriate response, IMHO, to “What’s the best global temperature?” is to ask “What’s the best number of homes, livelihoods and lives lost getting to it?”

  31. 81
    Adam Lea says:

    I am glad this article was published.

    I have done some investigation of regional (wind) storminess trends (north Atlantic and UK mainly) as part of my job and found that over the last 40 years, there is no significant upward trend. Atlantic storminess is highly correlated with the North Atlantic Oscillation, which has no long term trend. Along with the tropical cyclone ACE timeseries not having a significant upward trend over the last few decades, my line manager took the view that there is no evidence of a climate change link to storminess in recent decades, given that since 1980 global warming has been most rapid. He went as far as stating at any insurance-related seminar that cliamte change will have little influence over storm-related losses in the near future at least (say 15-20 years), and that future insured loss trends will be dominated by population and wealth trends. I always felt uncomfortable with this conclusion, as it seemed that a warming climate should have some effect, in particular, anything related to water, but I couldn’t think of a solid rebuttal because if the trends in the data werent there, where was my evidence? This article has filled in the missing link, in that it is possible that climate change is having an effect on storminess, but it is currently being masked by the noise (natural variability), so we may not see a standout link directly in the data for maybe a few decades. Of course we can’t afford to wait that long before taking action, because it will be too late.

    It also requires care if looking at north Atlantic storminess trends, because you can show whatever trend you want by choosing your start and end years. Look at the 1960’s to the 1990’s and you will see an upward trend. Start in the early 1990’s to the present day and you will see a downward trend, simply because of the multi-decadal cycle of the NAO.

  32. 82
    Adam Lea says:

    MA Rodger @74: Yes I can see faulty thinking in those Woy Spencer quotes. It is true that when one part of the world experiences abnormal warmth, another part will experience cool temperatures, because high and low pressure systems advect warm air toward the poles, and advect cool air toward the tropics. However it is not either/or, the natural variability is superimposed on any climate trend, so in a warming climate, the hot extremes will get worse and the cold extremes less so. 2010 was a warmer than average year globally despite a strongly negative NAO resulting in a freezing cold winter over much of Europe, and cool wet summer weather in the UK in 2012 was caused by Greenland blocking, with a downstream trough in the jet stream over the UK bringing slow moving low pressure systems, and at the same time the blocking high advected very mild air into the Arctic, aiding in the record sea ice low that year. Unfotrunately those who try to deny global warming by saying it is unusually cold in XYZ at the moment either don’t get this, or choose to ignore it and hope people don’t notice.

  33. 83
    David Young says:

    As usual Paul P your red herring (buried in an adhominem) is wrong and irrelevant. The Navier-Stokes equations only involve the gradient of the temperature. Likewise it’s only the pressure gradient that enters. The velocity terms all involve gradients even though the velocities themselves also enter. I doubt if anyone else reads or cares about your comments as they are usually wrong. You are only harming yourself with such emotional outbursts. I am only responding to make sure those who aren’t mathematicians aren’t fooled.

  34. 84
    Michael Tobis says:

    #71 – In my opinion, yes, precisely. I agree with every word.

  35. 85

    David Young said:

    “… the driving terms are all in terms of gradients.”

    and then dug himself a deeper hole by continuing to ignore the obvious.

    No one could deny that a force acts as a “driving term” in fluid dynamics, as anybody that was near a swimming pool or watched a video during the California earthquake can understand. That’s called a forced response.

    Or just consider tides in which the driving term is a changing gravitational force.

    You were originally responding to Jan Galgowski’s comment “fluid dynamics remains subject to Conservation of Energy constraint”. Since conservation of energy and momentum involves the system as a whole, you really need to be careful about making authoritative blanket statements regrding the driving terms.

  36. 86
    Michael Tobis says:

    See also https://climatefeedback.org/evaluation/financial-post-commentary-misrepresents-scientific-understanding-of-weather-extremes-ross-mckitrick/

    To make matters here a bit more interesting, I would draw your attention to this from Caldeira, in considering a particularly extreme event:

    “Can we say that that 2015 precipitation was not a consequence of climate change because there is no significant preceding trend, or do we say that the 2015 event was likely caused by climate change because there was no historical precedent? Obviously, the case is not clear. There are many people who today tend to attribute such anomalous events to climate change, regardless of a lack of underlying mechanistic understanding.” [end quote]

    This is very relevant to the question of single-event attribition. If an especially extreme event happens that doesn’t align with trends or anticipated trends, should we say “that event was made LESS likely by anthropogenic climate change”?

    At some point we have to appeal to physics, not just statistics.

  37. 87
    David B. Benson says:

    David Young @ 83 — From the Wikipedia article on Navier-Stokes, there is an additive term denoted by g for the body accelerations such as gravity and electrostatic accelerations…

  38. 88

    MT said:

    “At some point we have to appeal to physics, not just statistics.”

    I tend to agree, except for the fact that precipitation requires special care because it favors fat-tail statistics. Thus, the fat-tail of precipitation statistics suggests that the “Normal” sigma that Caldeira is applying (2015 was 6 sigmas above average for USA central stations) holds less significance here.

    In short the reason that fat-tail stats apply is that rainfall is what’s called a ratio distribution, in that it includes numerator (precip volume, etc) and a denominator (transit time of front, etc) to calculate. And so any variation in the denominator stretches the distribution into fat-tail territory.

    So in practice, what is needed is insight guided from the physical problem formulation, and not just blind application of normal/gaussian thin-tailed statistics.

  39. 89
    zebra says:

    #86, #88 Michael Tobis and Paul Pukite,

    “at some point we must appeal to physics, not just statistics”

    Michael, the point I have been trying to make here is that, with respect to communicating this topic, your horse and your cart are reversed. I made the point on the next post as well.

    You didn’t answer whether you agreed with my earlier statement (#61), so I will offer this for you (or anyone qualified) to agree/disagree:

    Any event that we observe has effectively zero probability of occurring absent the effect of anthropogenic CO2 on the global energy balance.

    I say this without any data analysis or numerical model, but because it is trivially obvious that if you change the input to the (complex non-linear) climate system, you will not get an identical output.

    So, there’s attribution, and then there’s attribution. To communicate/explain “climate change” clearly, you have to begin at the beginning, and you can’t misinterpret “climate change the effect” as “climate change the cause.”

  40. 90
    Dan Hughes says:

    #68, #83, #84, #85 #87

    The gravitational force is a conservative force. It is the gradient of a scalar potential. The scalar potential is given by Newton’s Law.

    The electrostatic force is a conservative force. It is the gradient of a scalar potential. The scalar potential is given by Coulomb’s Law.

    Look it up.

    I suspect there’s a trend here: conserved quantities are universally expressed as gradients of driving potentials.

    [It is very unfortunate that this off-topic perpendicular got started by a purely ad hominem comment containing not a single thread of fact relating to the original post. It is doubly unfortunate that RealClimate has allowed that comment to remain. The comment is exactly the kind that RealClimate boosts that it will never allow.]

  41. 91
    Mal Adapted says:

    David Young:

    As usual Paul P your red herring (buried in an adhominem) is wrong and irrelevant.

    As usual Mr. Young you’re misusing “adhominem”. The argumentum ad hominem is to reject your claim because you’re the one making it, rather than on its merits. But as Paul Pukite has made clear, he rejects your Navier-Stokes claim for the same reason Dr. Tobis does: because it’s incorrect. He then implicitly challenges your claim to authority arising from your personal history. That’s not a red herring, it’s highly relevant: it bears on your otherwise puzzling persistence in making already-refuted technical arguments. You clearly don’t grasp the topic of climate well enough to know you’ve been corrected, yet you soldier on. Paul invites the rest of us to infer you are afflicted with the Dunning-Kruger effect. You know a little science, so you think you know enough to contradict the consensus of trained, disciplined specialists, while demanding to be treated with respect. They respond with sarcasm because facts and logic don’t work on you, and you haven’t earned their respect. You don’t recognize your own incompetence, nor the aggregate genuine competence represented on RC. If you did, you’d have nothing to say here.

  42. 92

    Dan Hughes gyrations reminds me of his contorted reasoning in defending Judith Curry when she tried to apply Bose-Einstein statistics to droplet and ice nucleation. (Look it up) All I do is point out someone trying to BS their way through physics and suddenly it becomes ad hominen?

  43. 93
    David Young says:

    Mal, What a silly and technically content free comment. My point is of course technically correct. The temperature enters the Navier-Stokes only as the gradient. I even provided a reference. You might try to read it if its not too technical for you. There has been no refutation.

    Gravitational forcing in the equations is of constant over time so that can account for absolutely nothing in terms of changes in weather. It’s a silly point designed to discredit by throwing up dust to confuse.

    Your so called “concensus” of “trained” scientists is very weak because the data is not conclusive. The IPCC says that there is only weak evidence of increases in severe weather. It is you my friend who have no evidence and no expertise.

  44. 94

    Mal Adapted suggested that Dr.Young may be afflicted with D-K.

    The top-level post is on precipitation, which is an atmospheric effect, but then why did Young link in #55 to a paper on viscosity in regard to incompressible Navier–Stokes equations?

    Earlier Young had stated: “Using the ideal gas law, pressure is proportional to temperature so the gradient of the temperature can be argued to enter in some form.”

    Navier-Stokes applies to both gaseous fluids and liquid fluids, so it appears that Young’s one-track mind focusing on aerodynamics prevents him from considering the nearly incompressible ocean where the ideal gas law clearly does not apply.

    And as David Benson said in #87, his neglect of gravity as a driving term is nuts, considering Young makes the accusation “It seems to be based on misconceptions about fluid dynamics.”

    Young appears to be very confused or is spouting this stuff intentionally to create FUD for the casual reader of RC. Alas, someone has to unwind all this stuff for the benefit of that same reader.

  45. 95
    Dan Hughes says:

    This off-topic discussion was initiated by Paul Pukite at Comment #68. A short summary follows.

    Paul first quotes David Young by this statement:

    Jan, If you look at the Navier Stokes equations, the driving terms are all in terms of gradients.

    And then Paul said:
    A gravitational field does have a gradient, but does this guy (who is supposedly an expert on fluid dynamics employed by Boeing) think that the gravitational gradient has a stronger driving pull than the first-order uniform gravitational force?

    There is not a single word in Paul’s statement that can be attributed to David. David said:, . . . the driving terms are all in terms of gradients. David did not say; . . . the gravitational gradient has a stronger driving pull than the first-order uniform gravitational force. Those words were made up out of thin air, or some very dark place where the Sun never shines, by Paul.

    In my comment #90 I attempted to indicate that the gravitational force is a conservative force and that as such its fundamental representation is in fact the vector gradient of a scalar potential. I consider this to be of such a basic nature that I assumed it was not necessary to supply explicit citations. I correct that assumption here.

    The basic mathematical and physical nature of conservative forces is summarized in this Wiki entry, in which it says;

    The term conservative force comes from the fact that when a conservative force exists, it conserves mechanical energy. The most familiar conservative forces are gravity, the electric force (in a time-independent magnetic field, see Faraday’s law), and spring force.

    Many conservative forces and the associated vector gradients and scalar potentials are summarized in this Wiki entry. In particular, the scalar potential for Newton’s Law is developed.

    As far as the specific matter of the gravitational term in the Navier-Stokes-Fourier equations, and David’s characterization, let’s take a look at what Professor Richard Feynman has to say about that. In this Chapter of his lectures, Feynman presents Equation (40.4), a step along the way toward the Euler form of the momentum equations. The second term on the right-hand-side of Equation (40.4) is the vector gradient of a scalar potential. He describes these forces just above the equation as being external forces like gravity or electricity.

    In other words, at the fundamental level, the gravity term in the N-S-F equations is a gradient; exactly as characterized by David Young. The scalar potential, which is given by Newton’s Law (see Wiki entries above), could be substituted into the momentum equation and all subsequent mathematical operations and applications could be carried out with that representation.

    However, for a vast number of applications which occur on or near Earth’s surface, it is much more convenient to assume that the magnitude of the gravity vector is constant, and that is the number that almost universally appears in the equations for such applications.

    Footnotes:

    1. Paul’s characterization in parentheses; (who is supposedly an expert on fluid dynamics employed by Boeing), along with this: You have to wonder how Boeing can keep their airplanes in the air if this is who they hire ;), should never have been accepted by RealClimate. Again, the complete lack of any connection with the subject of the original post is a defining property of almost all of Paul’s comments.

    2. By the way, a search for any indications that Judith Curry applied Bose-Einstein statistica to nucleation of ice will prove to be futile. Judith and none of her colleagues have ever made such applications. No one at all, anywhere or at anytime, has ever made such applications.

    This complete BS comment by Paul is an additional illustration of his Standard Operating Procedure (SOP) when participating in blog discussions.

    3. I assumed that all this was well know because the concept is the basis of a first-year pop quiz that asks for the distance from Earth to its Moon at which the attraction of a object by each is equal.

  46. 96
    Matthew R Marler says:

    92, Paul Pukite: Judith Curry when she tried to apply Bose-Einstein statistics to droplet and ice nucleation. (Look it up)

    In a few pages out of almost 800 pages of quite dense and informative writing (Thermodynamics, Kinetics, and Microphysics of Clouds), Vitaly Khvorostyanov and Judith Curry suggest that Bose-Einstein statistics might provide a better fit to the data than other distributions. That’s all. It’s analogous to Gauss conjecturing that the normal distribution (the limit of the probability of favorable outcomes in a long run game) might be accurate for measurement errors of the locations of astronomical objects. It frequently happens that probability distributions have applications in realms beyond the narrowly defined circumstances for which they have been derived.

  47. 97
    Matthew R Marler says:

    86, Michael Tobis: At some point we have to appeal to physics, not just statistics.

    Mathematical Physics seldom contains a complete and accurate description of anything. Instead, it contains simplifications and approximations. Therefore, at some point we have to appeal to statistics, not just physics, in order to determine which, if any, physical description of a system is accurate enough for practical purposes (including the practical problem of designing the next experiment.)

  48. 98
    David Young says:

    Lets clarify this so no one is confused by all the irrelevant dust being thrown up.

    1. There are external “forces” in the Navier-Stokes such as gravity forces. These generally are close to constant just like solar insolation and so have only a minor effect on weather or indeed climate. This is particularly true for severe storms which are almost totally a function of gradients in temperature and pressure.

    2. The other terms in the Navier-Stokes are all given in terms of gradients. Temperature in particularly enters only as its gradient. This gradient from pole to equator is what drives mid attitude weather. Likewise the vertical gradient drives convection.

    3. I gave a reference going through in complete detail all the ways temperature enters the equations. Most of the effects are weak, for example, the effect on viscosity.

  49. 99
    Fred Magyar says:

    Mal Adapted @ 80 says:

    Moving production of dozens of staple crops with their preferred climates will be expensive, in money and tragedy. So will migrating people, of course. One way or another, the poorest of the poor will be pushed over the edge of disaster.

    Indeed and I agree with that statement. Unfortunately there are a number of complicating factors. Especially when dealing with plant physiology, biochemistry and numerous levels of interactions between plants and their various pests.

    This is a truly eye opening talk by Dr. John Trumble, University of California, Riverside, It underscores a number of other issues related to increases of atmospheric CO2 and increases in temperature.

    https://www.youtube.com/watch?v=emFGiIJvce8
    Climate Change, Insect Biology, and the Challenges Ahead

  50. 100
    Dan Hughes says:

    At #94, Paul Pukite said:

    And as David Benson said in #87, his neglect of gravity as a driving term is nuts, considering Young makes the accusation “It seems to be based on misconceptions about fluid dynamics.” [ bold by edh ]

    At #87, David Benson said:

    David Young @ 83 – From the Wikipedia article on Navier-Stokes, there is an additive term denoted by g for the body accelerations such as gravity and electrostatic accelerations…

    Note the stark contrast between what Paul Pukite claims David Benson said, and what David Benson actually said. David Benson did not say that David Young neglects gravity as a driving term in the Navier-Stokes equations.

    It was Paul at #68 who made up the false claim (aka, a blatant lie) that Young omits the gravity term. See #95 for how Paul Pukite pulled a false statement out of nowhere to make up the claim.

    Paul cannot specify where David Young has ever indicated that the conservative gravitational force, which is a vector gradient of a scalar potential, does not appear in the N-S-F equations.

    It is abundantly clear that Paul Pukite’s Standard Operating Procedure is maximum obfuscation, with falsehoods and purposeful mis-characterizations thrown in for added effects. Paul Pulite seldom addresses technical matters as actually stated.

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