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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.

165 Responses to “Absence and Evidence”

  1. 1
    Dan Miller says:

    Attribution of some extreme events is straightforward. James Hansen, et al, showed that “Extremely Hot Summers” (a summer with an average temperature that is 3-sigma above a 1951-1980 baseline) is now happening over 50 times (5000%) more often than during the baseline. That data is a bit old and the latest numbers show 100X+, but let’s use 50X.

    As Hansen points out, the shift of the temperature “bell curve” to the right is — by definition — global warming. When the curve shifts, items that formerly were 3-sigma events become much, much more likely.

    So, using 50X, when an Extremely Hot Summer occurs now, we know there is a 49 out of 50 chance (98%) that it was caused by global warming and not by a pre-global warming natural occurrence.

    Any extreme event that follows a normal (bell curve) distribution will likely show similar results. Maximum rainfall in 24 hours will likely show a significant impact from climate change. The key is to collect data globally like Hansen did, then the measurement of rare, 3-sigma events can be done satisfactorily and their current probabilities can be assessed and compared to historical data.

  2. 2
    Matthew R Marler says:

    It’s a well-known motto in research that “absence of evidence” is not “evidence of absence”.

    It depends on whether the evidence has been rigorously searched for. In the Pons and Fleishmann apparatus, evidence for fusion is absent (except for the occasional random deviates), and that is rightly taken as evidence of absence of fusion. There was also the Michelson and Morley experiment, which produced the famous absence of evidence for the luminiferous aether. Likewise for evidence of harm from Thimerosol and aspartame.

    McKitrick probably did not write the headine, and it would be good of him to disown it.

    About Pielke Jr, McKitrick wrote this: He found convincing evidence that climate change was not leading to higher rates of weather-related damages worldwide, once you correct for increasing population and wealth.

    In response to Trudeau’s comment: “Extreme weather events are extraordinarily expensive for Canadians, our communities and our economy,” he said, citing the recent tornadoes in Ottawa and wildfires in Western Canada. “That’s why we need to act.”

    I think it’s clear in context that the topic was economic damage, and Pielke is essentially correct: Extreme weather events are not causing more economic damage simply by being more extreme.

  3. 3
    GERALD ZUCKIER says:

    More energy in a fluid system like the atmosphere will of course create a higher frequency of “high-energy events”, which is pretty much a definition of storms; when you have a pot of water on the stove, if you turn up the heat you can see the turbulence increase.

  4. 4
    Dennis N Horne says:

    No so much that figures lie as liars figure…

  5. 5
    BJ Chippindale says:

    The denial community should be required to provide evidence that continuing changes to the makeup of the planet’s atmosphere has no important impact on climate.

    I am tired of repeatedly and perpetually explaining to people that uncertainty is not their friend, that prudent risk management demands immediate and severe action now, and that the discount rate is negative.

    How about we find some way to take the discussion back and force them to answer the questions they absolutely *cannot* answer.

  6. 6
    P S BAKER says:

    Many thanks for this, an excellent analysis – it should get a wide readership … send it to The Guardian (UK) etc?

  7. 7
    Michael Tobis says:

    2 (M R Marler): “I think it’s clear in context that the topic was economic damage, and Pielke is essentially correct: Extreme weather events are not causing more economic damage simply by being more extreme.”

    You are doing that cow thing again.

    a – We have an attribution to PM Trudeau, not a direct quote. e.g. I know from press reports that the PM also mentioned flooding, which McKitrick conveniently elides.

    b – While that specific claim of the PM’s is economic, McKitrick’s screed attempts to attain much broader conclusions. He says “the bottom line is there’s no solid connection between climate change and the major indicators of extreme weather”. This is at best extremely dubious, which is my point.

    c- Pielke has not, to my knowledge, made the claim you attribute to him. Indeed, just yesterday on Twitter (https://twitter.com/RogerPielkeJr/status/1143283175004635136) he said “No matter how you define “heat wave” Europe has seen more of them over the past 125+ years.” (accompanied by a series of graphs of upward trends)

    d – Physical arguments indicate that many classes of severe event, not just heat extremes, are likely to increase. Observational evidence, while perhaps arguably not yet conclusive, increasingly leans in the direction that they are.

    e – To be sure, there certainly is a non-climatic anthropogenic component to increasing damages. The Fort McMurray fire (Canada’s most expensive disaster) would have burned unnoticed had a major settlement not been planted in the boreal forest to extract oil from tar sands. (I am not sure why people choose to take solace in the fact that there are multiple anthropogenic factors in some disasters, but so be it.) But damages are clearly increasing. And the Fort MacMurray fire was certainly exacerbated by an unusually warm and dry period that preceded it.

    f – There is no sensible argument that increasing numbers of increasingly severe events don’t lead to more damage.

    Yet somehow you pull this all together to “Pielke is essentially correct” that “Extreme weather events are not causing more economic damage simply by being more extreme.” That is spun pretty hard.

    It’s pretty hard to avoid the conclusion that supporting this sort of spin is actually the point of his work. But as far as I know, he carefully doesn’t say this, except specifically in the case of hurricanes, a particularly noisy and problematic time series. Presumably he is aware that the generalization is insupportable. Yet he is happy with McKitrick representing that his work supports such a broad conclusion and more.

    I, for one, am not.

  8. 8
    jgnfld says:

    McKittrick’s MO for years has been to find an isolated factoid, remove any and all context around said factoid, and then make sweeping conclusions.

    The cited article here is no different.

  9. 9
    MMM says:

    “I think it’s clear in context that the topic was economic damage, and Pielke is essentially correct: Extreme weather events are not causing more economic damage simply by being more extreme.”

    As the main post noted, this is not true.

    Imagine a case where the number of hurricanes (or other extreme of your choice) doubles, but where the building codes have improved such that a given hurricane causes half as much damage. In this case, there is no trend in economic damage… but importantly, climate itself is still doubling damages compared to what they would have been. And that’s the part that Pielke & McKitrick and the rest want to sweep under the rug.

    -MMM

  10. 10
    Polar Flyer says:

    Typo in paragraph 7: “…the analysis may lack have enough data to show it.”

  11. 11
    MarkR says:

    Matthew R Marler:
    “I think it’s clear in context that the topic was economic damage, and Pielke is essentially correct: Extreme weather events are not causing more economic damage simply by being more extreme.”

    Really?

    I think the right comparison is “what happened with X” versus “what would have happened without X”.

    McKitrick’s argument looks to be the same as: “Nigeria’s population has increased so AIDS can’t be killing people”. It seems ridiculous to me.

    We know that extreme heat increases can be directly linked to the climate change we’ve caused. Since an extreme heat event causes more damages and death than a period without extreme heat, damages are clearly higher than they would be without those extra events.

    Sure, total losses are affected by protective methods (e.g. air conditioning), but losses from extreme heat are higher than they would be without climate change, even if total losses might be down due to air conditioning.

    I’m not arguing the total effect of climate change here, just that McKitrick’s presented evidence doesn’t support his case. It’s strange he didn’t mention the evidence of enormous increases in extreme heat, the patterns of which match climate model expectations pretty well. It’s strange he only talked about areas where climate models *don’t* tend to expect a signal to emerge just yet.

  12. 12
    Matthew R Marler says:

    5, BJ Chippindale: that prudent risk management demands immediate and severe action now,

    Much is covered in the word prudent. Surely prudent evaluation of proposals ought to take into account their opportunity costs and likely benefits. I am in favor of immediate investment in flood control and irrigation improvement in every jurisdiction that experiences alternations of heavy rain and drought (for example), but CA has neglected its levees and other water works in favor of plans of little likely climate benefit, such as the high speed rail line and solar and wind farms.

  13. 13
    Tom Sager says:

    Wish to share the following on climate and weather:

    “Had he been informed by an indisputable authority that the end of the world was to be finally accomplished by a catastrophic disturbance of the atmosphere, he would have assimilated the information under the simple idea of dirty weather, and no other, because he had no experience of cataclysms, and belief does not necessarily imply comprehension.”
    —Joseph Conrad (Typhoon, 1902)

  14. 14
    Jane says:

    The data on insured losses from environmental disasters in Canada alone is enough proof that something serious is going on … Do we have some data on the USA on the topic?
    jane

  15. 15
    MA Rodger says:

    The article of Pielke Jr has a sub-headline – “And so, many scientists who have the facts and know the truth remain silent.” This is re-stating part of the article’s conclusions which run thus:-

    “The bottom line is there’s no solid connection between climate change and many major indicators of extreme weather that politicians keep talking about, such as hurricanes, tornadoes, droughts, rainfall and floods, despite Trudeau’s claims to the contrary. The continual claim of such links is misinformation employed for political and rhetorical purposes. Powerful people get away with it because so few people know what the numbers show. Many scientists who know better remain silent. And the few who push back against the propaganda, such as Roger Pielke Jr., find themselves on the receiving end of abuse and career-threatening attacks, even though they have all the science in their corner.” [My bold]

    So there can be none of the nonsense @2 up-thread to suggest that Pielke Jr “probably” wasn’t responsible for the sub-headline.
    The headline itself reverses the implied logic within McKitrick’s conclusion. The conclusion implies “many scientists … remain silent” allowing Pielke to be picked on for his stand. (Or perhaps that should that be “to have been picked on” as I assume this comedic carry-on is now finished and he is no longer suffering ‘infamy, infamy, they’ve all got it in f’ me.’) Conversely, the sub-headline asserts that the “many scientists … remain silent” because of the punishment meted out on Pielke Jr.
    But whatever way it is/was, it does beg the question who are these anonymous ‘many scientists’? What are their names? Should we expect anything different than the usual sad list of swivel-eyed denialists?

  16. 16
    nigelj says:

    Matthew R Marler @2, there is a huge difference between the absence of evidence in a laboratory experiment where people control everything and know what they are looking for, and looking for something in historical weather patterns that could so easily be hidden by lack of historical data, and obscured by other factors.

    “Pielke is essentially correct: Extreme weather events are not causing more economic damage simply by being more extreme.” This doesnt make a lot of sense to me. More extreme weather has to cause more physical damage and so economic damage, by definition. An improving economy might make it easier to deal with the damage, but is still moving resources into repairing storm damage, so something else loses out.

  17. 17
    Dennis N Horne says:

    #2 Matthew R Marler: “I think it’s clear in context that the topic was economic damage, and Pielke is essentially correct: Extreme weather events are not causing more economic damage simply by being more extreme.”

    Or, heads I win, tails you lose.

    Add more energy to the climate system the weather is worse. Predicted. Observed. Measured.

  18. 18
    Peter Jones says:

    GERALD ZUCKIER (3)

    You said “More energy in a fluid system like the atmosphere will of course create a higher frequency of “high-energy events”, which is pretty much a definition of storms”

    Most countries outside of the tropics, have a 20 to 30 degrees Celsius difference between winter and summer. So in summer, there is a huge increase in the amount of energy in the atmosphere.

    Do you associate summer with a higher frequency of storms?

    Why do most people prefer summer to winter?

  19. 19
    Michael Tobis says:

    #17 “Add more energy to the climate system the weather is worse.”

    This comes up a lot from the bleachers, but Is this true? Had we instead come up with a massive industrial process to deplete CO2 would the weather have gotten better?

    I don’t think it works like that. I don’t know if I’ve heard a case made for it by a scientist.

    The reasons to expect more severe weather with rapid change are manifold.

    I think the main one is that with climate change you are getting (at best) someplace else’s weather. Someone just argued to me that Paris getting Bangkok’s weather this week is no big deal, because people in Bangkok live with it all the time. But it is severe weather in Paris, as people aren’t acclimated or skilled in dealing with those conditions – their buildings aren’t set up for it, etc.

    A more energetic atmosphere could conceivably be a less active one. Polar amplification reduces meridional gradients, weakening the jet stream. Many of the weather problems we see in middle latitudes, the current European heatwave among them. are arguably traceable to a weaker jet stream, allowing for more meandering and hence locally persistent anomalies.

    The climate system is complex, and causality is tricky business. The good news about that is it’s a beautiful and fascinating object of study. The bad news is that it’s sometimes hard to communicate succinctly and correctly.

  20. 20
    Matthew R Marler says:

    17 Dennis N Horne: Add more energy to the climate system the weather is worse.

    Maybe, but Pielke’s analysis shows that, corrected for inflation and population, the damage hasn’t been getting more costly.

    However, energy transfer rates, hence storm intensities, depend on the difference between atmospheric temp and surface temp, and predictions from that are all over the place, since CO2 warms the atmosphere first, reducing the difference (very, very slightly).

  21. 21

    @Michael Tobis,

    “A more energetic atmosphere could conceivably be a less active one.”

    Really? Clausius-Clapeyron and transfers of energy higher into atmosphere because of latent heat of water? Deeper energy gradients at atmospheric fronts? More energy in top 2000 meters of oceans? More extreme precipitation in 24 hours?

    Sure, storm systems can slow because of amplification, but that also means they have more “time on station” to do damage.

  22. 22

    I’m not sure which Pielke-Jr article McKitrick is referring, and, whichever it is, I mean one with technical details (link?), but, nevertheless, I wanted to gently disagree with part of Dr Tobis post above. Consider

    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.

    To the extent that Pielke-Jr is running some kind of hypothesis test for determining attribution, the problem isn’t Statistics, it’s wrong-headed and out-of-date statistical technique.

    It is not true that inference and estimate rely upon “large quantities of data”. Sometimes, in fact, relative small amounts of well chosen data are far more powerful: Think of an experimental design with controls and balance. That’s important to remember. In many engagements I have with Big Data people, I need to emphasize that the size of your dataset isn’t the raw size, it’s the number of replicas of unique combinations of explanatory variables you have. If most in a big dataset have but one observation, that’s not a big dataset at all. If there is a wide range in the numbers of replicas, that’s a problem with balance, and it can even harm seemingly non-parametric techniques like cross-validation.

    In fact, there is now a rich set of methods for embodying domain knowledge in statistical models, namely, the Bayesian hierarchical modeling approach, whether these derive from meteorology or climate science or baseball statistics. Judging from literature in say, Journal of Climate, few papers appear aware of these techniques, preferring to argue piecemeal from grounding in the domain. That’s okay, but large comprehensive studies are hard, and it’s unfortunate that these modern methods aren’t better understood and used.

    Deniers and doubters, in my experience, are the least likely to be aware of such methods, and I find many instances, whether in denial-oriented assessments of temperature or sea level changes, where Statistics is practiced as if by rote, and with a lot of confusion. Time series seems to be a particular tripping point.

    Others have noted these kinds of blemishes, but often such underscores don’t go on to indicate what should be done. There are many sound statistical analyses which demonstrate any of these claims, from the statistical significance of temperature rises, to increased damage from storms, to droughts and heatwaves, to phenological aberrations in species migrations. There is no doubt these are true.

    There are many wonderful Bayesian analyses which can serve as examples. Schmittner, et al from Science in 2011 is wonderful (“Climate Sensitivity Estimated from Temperature Reconstructions of the Last Glacial Maximum”). There are several papers where Professor Mark Berliner is a co-author, like his “Uncertainty and Climate Chance“, or, with Professor Levine, “Statistical Principles for Climate Change Studies“. The latter paper addresses the nuances of hypothesis testing, showing that while it seems simple, it is clouded with delicate assumptions. Smashing that all aside and oversimplifying, it’s that p-values (themselves) are random variables.

    Statistics as a field hasn’t left these questions alone. The American Statistical Association has, like many scientific organizations, a formal statement on climate change. But, too, the status of Statistics in climate change science has been examined. There have been special issues of journals.

    I also urge readers to be open-minded about applying techniques from machine learning and related areas to geophysical problems. They certainly have their faults and limitations, opacity in explanation being one formidable issue. But as O’Gorman and Dwyer showed in 2018 , ML techniques are beginning to make their presence felt in geophysics. See also Rasp, Pritchard, and Gentine in a 2018 PNAS.

  23. 23
    Dennis N Horne says:

    #19 Michael Tobis: “This comes up a lot from the bleachers, but Is this true? Had we instead come up with a massive industrial process to deplete CO2 would the weather have gotten better?”

    Well it certainly would have been colder, and ultimately “Snowball Earth”. So, yes settled weather!

    Isn’t weather, in simple terms, just the climate system moving energy around.

    The bottom line is, “Absence of proof is not proof of absence” is an aphorism, not science. Same applies to “More CO2 – more energy – more climate – worse weather”. Perhaps a lot closer to reality than the special pleading from McKitrick and Pielke.

  24. 24
    zebra says:

    #19 Michael Tobis,

    “a more energetic atmosphere could conceivably be a less active one”

    A couple of points that might help with communication:

    -You are responding to “add more energy weather gets worse”, but your example of stalled systems due to meandering jet stream is, in fact, “worse” weather.

    -With respect to “less active”, isn’t that a matter of scale and time? At some point in the future, the system might reach such an equilibrium, but in the near term, the energy will still be unevenly distributed, (and perhaps more unevenly?), so “activity”, in the sense of transferring energy, would not diminish.

    So, I think the “more energy” explanation is a pretty reasonable way to explain things to the public; it doesn’t really matter if “less energy” would lead to difficulties, because they would not be physically the same ones we will be dealing with due to CO2.

  25. 25
    Michael D Sweet. says:

    Tamino has several posts about extreme weather.

    https://tamino.wordpress.com/2012/11/03/unnatural-catastrophes/
    this post has a graph that compares weather related costs with geophysical events. The geophysical events control for increase in population and stronger building.
    As is easily seen (no statistics needed), geophysical events stay the same while weather events increase dramatically. I think this graph alone shows Pielke and Mckittrick are wrong.

    These additional posts are relevant.
    https://tamino.wordpress.com/2016/01/22/extreme-trends-detection-is-hard/

    https://tamino.wordpress.com/2018/08/02/climate-disasters-billions-and-billions-of-dollars/

    https://tamino.wordpress.com/2012/11/03/catastrophes-how-many-more/

  26. 26
    barn E. rubble says:

    RE: Dennis N Horne says:
    “No so much that figures lie as liars figure…”

    Then there’s the old quote, “There are three kinds of lies: lies, damned lies, and statistics”

  27. 27
    Dan Hughes says:

    Evidence of existence of potential, is not evidence of existence of outcome.

    Evidence of existence of outcome, is not evidence of causality.

    Causality demands existence of unique dependency between evidence and potential.

  28. 28
    zebra says:

    #18 Peter Jones,

    Expanding on my reply to Michael Tobis, I think that if the goal is to communicate, there has to be some precision of language.

    As I understand the predictions with respect to hurricanes, increasing energy in the atmosphere would lead to perhaps fewer storms overall, but an increase in the intensity of those that do occur.

    Gerald’s comment was pretty much on track, if not perfectly precise; your response is really unclear.

    If we increase energy in a complex non-linear system, we would expect excursions in some metrics for existing phenomena in the near term. It makes no sense to compare winter to summer; the correct comparison is summer storms to summer storms and winter storms to winter storms.

    So, are you saying that increasing energy in the system will have no effect? Or are you saying that some people would like to have milder winters, putting aside all the other negative consequences?

    The latter is not really relevant to the science.

  29. 29

    The same tactics–that is, inappropriate averaging and excluding various alternate forms of evidence–were used to try to “prove” that the Syrian drought ‘didn’t happen.’

    That, in spite of the fact that accepting that the drought “didn’t happen” would pose the question “Why was it, then, that the nation experienced significant shortfalls in wheat production, a 90% loss of the barley crop, and livestock mortality of 50-100% among more than 100,000 livestock owners? Or that 800,000 people were reported to have lost the means of livelihood?”

    https://lb.boell.org/sites/default/files/uploads/2010/12/drought_in_syria_en.pdf

  30. 30

    More recently, a more sophisticated version, possibly better motivated.

    https://www.eurekalert.org/pub_releases/2017-09/uos-nrd090717.php

    Selby and colleagues’ article finds that:

    “Although northeast Syria did experience an exceptionally severe drought prior to its civil war, this drought was not necessarily caused by human influences on the global climate…”

    [Ah–“Necessarily.”]

    “Though the 2006/07 to 2008/09 drought did contribute to migration away from northeast Syria, this was on nothing like the scale which has been claimed (most likely 40-60 thousand families, rather than the 1.5 million people often quoted), and was probably more caused by economic liberalisation than by the drought…”

    [And yet the Massoud Ali report from 2010, cited above, says that:

    Estimates from the Ministry of Agriculture and Agrarian Reform show that 40-60,000 families migrated to other areas in Syria in July of 2010, with thirty-five thousand families migrating from the al-Hasaka governorate alone. However, in light of the continued internal migration, which is taking place at all times of the year, the real figures are likely to be much more than what is stated in the official numbers.]

    So how is it, exactly, that Selby et al found the *exact same number of climate refugees for the entire crisis* as the Ag Ministry found for July 2010 alone?

    “There exists no meaningful evidence that drought-related migration was a contributory factor in the onset of the civil war.”

    [And the definition and criteria for “meaningful” were what, exactly?]

    It is certainly correct to “interrogate” accepted wisdom and any specific research results. But it seems to me that Selby et al are rather overstating their results, along the lines of the topic here.

  31. 31
    Mal Adapted says:

    Jane:

    The data on insured losses from environmental disasters in Canada alone is enough proof that something serious is going on … Do we have some data on the USA on the topic?

    This NOAA NCEI release shows the frequency of billion-dollar US weather and climate disasters rising steadily in the last 30 years. Will Mr. Marler argue with NOAA’s numbers?

  32. 32
    Mal Adapted says:

    Dennis N Horne:

    Add more energy to the climate system the weather is worse. Predicted. Observed. Measured.

    Yep, pretty much. Or else the additional heat retained by rising atmospheric CO2 is magically cancelled, and some other magic is driving the weather. Once again: how hard can something so basic really be to understand?

  33. 33
    Brian Mapes says:

    Another well-known motto in research is that “extraordinary claims require extraordinary evidence”.

    Some of this debate seems to boil down to who gets to decide which claims have become ordinary, or even null hypotheses (presumed true, Occam’s beneficiaries of the mightiest power: doubt), versus which claims are extraordinarily (perhaps extraordinarily “inconvenient” to accept…). There’s bluster: act as if, speak as if, your whole worldview is of course normatively correct. Overton windows and all that. Science is not immune to this simian posturing game. Well, better to notice it explicitly.

  34. 34
    William B Jackson says:

    According to Canadian sources Syrian families tend to be large with twelve members being common amongst refugees they resettled so sixty thousand families could easily reach a total of 600 thousand or more. And I suspect the minimization of families to forty to sixty thousand is wrong headed. Denial is denial!

  35. 35
    patrick027 says:

    Energy in the climate system: There’s heat energy (enthalpy), there’s available potential energy (APE) – the energy that could be converted to kinetic energy if all horizontal density and pressure variations were allowed to dissipate via (dry or moist as in CAPE) adiabatic inviscid overturning of fluid; there’s the kinetic energy, and there’s the rate of adiabatic inviscid kinetic energy generation (gross, and net – because some motions in the atmosphere (and ocean) function as a heat pump; the gross would be balanced by viscosity/frictional dissipation) and APE net generation. …

  36. 36
    Michael Tobis says:

    “So, are you saying that increasing energy in the system will have no effect? Or are you saying that some people would like to have milder winters, putting aside all the other negative consequences?”

    Neither.

    The system cannot behave as before. Among the consequences, locally unprecedented condition, which we will experience as extreme events, are nigh inevitable, and we are starting to see them.

    But “more energy, worse weather” is not itself a solid argument. The system is quite a bit more complicated than that. I mentioned the weakened summer jetstream. For a second example, increased subtropical drought, which is a kind of severe event we expect more of and are starting to see more of, would be the same as *reducing* local (moist convective) energy exchanges.

    I’m not the one saying we aren’t seeing more disasters!

    But getting things wrong has consequences for credibility. Maybe you don’t have to get it right, but I do.

  37. 37
    Michael Tobis says:

    #27

    “Evidence of existence of potential, is not evidence of existence of outcome.

    Evidence of existence of outcome, is not evidence of causality.

    Causality demands existence of unique dependency between evidence and potential.”

    Well, howdy, Dan!

    This is all true in its way. But earth sciences cannot be particularly experimental. Causality can rarely if ever be proved in an observational science in the way it can be in an experimental one.

    Nevertheless, we know things. We come to certain conclusions with considerable confidence. One way is with validated predictions.

    Increased heat, increase in heavy convection, drying subtropics, polar amplification, stratospheric cooling, not to mention global warming itself – these are emerging from the observational data as was predicted in advance. Valid predictions are worth something.

    Standards of frequentist “proof” from experimental science may not be the right standard. Is it more likely than not that anticipated shifts which actually appear are appearing for the reasons we anticipate? (In this case, many serious people think so.) Are these shifts consequential? (Again, this appears to those who think about it most to be far more likely than not.)

    That all said, you are indeed, as #33 suggests, shifting the burden of proof. In the present case my burden is light.

    My claim in the article is only that McKitrick’s “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 a rhetorical trick, one that relies far too heavily on the word “solid” and delivers an extremely misleading impression.

    Whether or not you find the evidence credible, there’s plenty of candidate evidence. Argue against those lines of argument if you like. But dismissing them as if they were non-existent is unreasonable and unacceptable.

    If McKitrick says “nothing is solid” he has to say why “everything is non-solid”. It’s too big a claim to be made so casually, never mind then using this broad and dubious claim to attack the Prime Minister.

  38. 38
    Matthew R Marler says:

    31, Mal Adapted: This NOAA NCEI release shows the frequency of billion-dollar US weather and climate disasters rising steadily in the last 30 years. Will Mr. Marler argue with NOAA’s numbers?

    with increased population and steady inflation, the number of billion-dollar assets at risk has increased. There have been other non-weather-related changes that increase the costs of disasters, such as the New Orleans ship channel that contributed to the damage cause by Hurricane Katrina.

  39. 39
    David Young says:

    I’m actually surprised by the naivety of this post and the comments. It seems to be based on misconceptions about fluid dynamics. “More energy” in the system tells us nothing. Changes in flow patterns depend on the dynamics very strongly. It’s also usually the gradients of quantities like temperature that are important and not the absolute level. Thus its more important how vertical temperature gradients change than how much the SST’s warm. If the tropical hot spot was actually real for example, it would probably mean less severe storms. Warm air holds more water vapor. But it can precipitate out only when the warm air cools as it rises. Thus the gradient is the controller for precipitation.

    As Brian points out there is a lot of posturing going on here too. Some severe events seem to increasing like flooding while others are decreasing such as drought and tornadoes. However, there is a lot of weather noise in all this. Perhaps more important than the posturing is why we are not doing a better job of adapting to all severe weather events, which happened in the past and will continue to happen? We don’t even prepare for the past, much less the future. One logical response would be to stop subsidizing building in flood prone areas such as coastlines by providing federal flood insurance. We can’t even agree on such a simple and common sense measure. Perhaps too many rich and politically vocal people live in these areas.

  40. 40
    patrick027 says:

    re my 35 – (cont.) … I will add that while the negative lapse rate feedback would by itself suggest a reduced temperature difference between net radiant heating and net radiant cooling, thus tending to reduce the efficiency of conversion of convected heat to work, the tropopause is should rise; if the tropopause temperature warms less than the surface or cools, then perhaps… well it depends…

    One thing I wonder about – the polar jet in the mid-troposphere in the Northern hemisphere should slow down with decreased horizontal temperature gradient, it’s been my understanding that higher up, the westerlies (subtropical and polar??) are expected to speed up. What effect does that have?

  41. 41
    Keith Woollard says:

    “Add more energy to the climate system the weather is worse. Predicted. Observed. Measured.”

    laughable.

    Let me see, which has nicer weather, Perth or the south pole?

    Which direction do 90% of the world go for holidays? towards the poles or the equator?

    I am just remembering back to those hazy lazy days of the snowball earth – glorious weather it was then

  42. 42
    Dennis N Horne says:

    #36 Michael Tobis. “But “more energy, worse weather” is not itself a solid argument.”

    If more energy does not mean worse weather, what are we worried about? After all, it’s weather we have every day, not climate. “Climate” is a statistical invention.

    Furthermore, an old friend of mine, with more professional qualifications than you could fit on an appointment card, said he wasn’t worried about the temperature going up a couple of degrees. On the face of it it’s a reasonable comment. But it isn’t a matter of the temperature just going up everywhere a nice 2C. It’s the sort of “thinking” or trick we are chastising McKitrick for.

  43. 43
    Ray Ladbury says:

    Barn E Rubble,
    I prefer my own amended version: Any damned fool can lie with statistics. What takes skill is using them to tease out the truth.

    When I read a scientific paper, the question I ask myself is whether I now understand things better than I did before. If I do, it was a good paper. If not, it was crap.

    I have never read anything by a denialist that illuminated anything. If your whole schtick is wailing, “Oh, it’s all just too complicated,” you’re never going to understand very much.

  44. 44
    zebra says:

    #36 Michael Tobis,

    My question at #28 was directed at Peter Jones, not you… I was addressing your #19 with my #24, which I think still applies here:

    -With respect to “less active”, isn’t that a matter of scale and time? At some point in the future, the system might reach such an equilibrium, but in the near term, the energy will still be unevenly distributed, (and perhaps more unevenly?), so “activity”, in the sense of transferring energy, would not diminish.

    and from #28:

    If we increase energy in a complex non-linear system, we would expect excursions in some metrics for existing phenomena in the near term.

    Putting aside the subjective term “worse” weather, I don’t see what exactly you are disagreeing with here.

    I understand your point that if you have a completely dry desert, there will be no evaporation of water. But getting to a completely dry desert is in itself an excursion. And then, the completely dry desert will still be absorbing and emitting the (increased) energy in some form.

    I’m in complete agreement with everything else you are saying, but I don’t see how the generalization about increasing system energy… as a way to communicate with the public… could be used to impugn anyone’s credibility.

  45. 45
    Mal Adapted says:

    Brian Mapes:

    Another well-known motto in research is that “extraordinary claims require extraordinary evidence”.

    Some of this debate seems to boil down to who gets to decide which claims have become ordinary, or even null hypotheses (presumed true, Occam’s beneficiaries of the mightiest power: doubt), versus which claims are extraordinarily (perhaps extraordinarily “inconvenient” to accept…). There’s bluster: act as if, speak as if, your whole worldview is of course normatively correct. Overton windows and all that. Science is not immune to this simian posturing game. Well, better to notice it explicitly.

    An incisive comment, thanks for the explicit notice 8^). My normatively correct worldview: of course science isn’t immune to simian posturing – it’s performed by simians. A genetic disposition to social posturing arose early in our ancestry. Science, OTOH, is a relatively recent, cultural adaptation. Having accurate predictions of the future helps individual Homo sapiens avoid hazards and exploit opportunities, but genes can only adapt to current selection pressures, and only from one generation to the next. Predictive capability evolved culturally instead, propagating across individual brains and accumulating extra-genetically over generations.

    Because “the first rule is you must not fool yourself and you are the easiest person to fool”, science is necessarily a collective, i.e. social enterprise. While its progressive (i.e. self-correcting, cumulative) results have enabled our present population size, like all adaptations it’s as good as it is and no better, nor has it abolished other salient adaptations. It merely turns out that of all the methods we’ve evolved for making predictions, only science is more accurate than magic, and only because it’s a way for practitioners to try hard not to be fooled. Suitably applied, it can help each of us avoid deception by our other adaptations, and by other socially-adapted humans. It seems to require arduous training and discipline, however. Sadly, the necessary cognitive faculties don’t easily propagate, culturally or otherwise 8^(.

    Through the Overton window: climate science predicts a fearsome future with high confidence, unless collective action is taken against AGW soon. Since science hasn’t sufficiently overcome self-deception to motivate effective action, other social adaptations will be decisive. IMHO, AGW-denial must not be regarded as respectable.

  46. 46
    Michael Tobis says:

    #39 “I’m actually surprised by the naivety of this post and the comments. It seems to be based on misconceptions about fluid dynamics.”

    You didn’t actually read the post, did you?

    #42 “Climate” is a statistical invention.

    “Climate” is an overloaded term, but that’s a topic for another day.

    “If more energy does not mean worse weather, what are we worried about?”

    Rapid change is disruptive. The more rapid the worse. It will be perceived as extreme weather regardless of whether it’s abrupt cooling or abrupt warming.

    There is no ideal state of the system, but there is an ideal rate of change, which is near zero, which was the case during human history and very much not the case during the preceding two million years.

    If your comments can be read as pro-ice-age you open yourself to attacks like #41.

    #44 ” I don’t see how the generalization about increasing system energy… as a way to communicate with the public… could be used to impugn anyone’s credibility.”

    Again, see #41.

  47. 47
    Michael Tobis says:

    #24 & #44

    “With respect to “less active”, isn’t that a matter of scale and time? At some point in the future, the system might reach such an equilibrium, but in the near term, the energy will still be unevenly distributed, (and perhaps more unevenly?), so “activity”, in the sense of transferring energy, would not diminish.”

    Hmm. Yes and no… I think there’s a good question lurking here regarding equilibration.

    The atmosphere alone has a rather short equilibration time, and insofar as greenhouse gas accumulation is concerned it can be treated as a quasi-equilibrium, (as in undergraduate engineering thermodynamics).

    However, the climate system includes the ocean, and the ocean equilibration time is comparable to the time scale of the anthropogenic disruption. I think this has to matter for the transient response of the climate system.

    I’d be interested to hear details from anyone more current on contemporary GCM work, but it’s always bothered me that there’s a general assumption that all climate change will be monotonic.

    An example that is salient is whether Great Lakes levels will go up or down. People have made both claims. This is of course a target for mockery, which I have also seen. But in a period of rapid climate shifts, couldn’t we in principle have alternating periods where mid-continent moisture swings one way and then the other, driven by decadal timescale transients in the oceans?

    That said, I don’t think this argument follows directly from energy.

    Sure, much more energy at the surface is disruptive. But much less energy at the surface is too! Atmospheric heat content is not the right measure of climate disruption, because that argues in favour of an artificial ice age, something that is now well within our collective capacity.

    I therefore suggest that there is a much stronger and more accurate case in focusing on rate of change of heat content than in the amount of heat itself.

  48. 48
    Mal Adapted says:

    zebra:

    I’m in complete agreement with everything else you are saying, but I don’t see how the generalization about increasing system energy… as a way to communicate with the public… could be used to impugn anyone’s credibility.

    What zebra said, MT.

  49. 49
    Mal Adapted says:

    Mathew Marler:

    31, Mal Adapted: This NOAA NCEI release shows the frequency of billion-dollar US weather and climate disasters rising steadily in the last 30 years. Will Mr. Marler argue with NOAA’s numbers?

    Why, yes he will:

    with increased population and steady inflation, the number of billion-dollar assets at risk has increased. There have been other non-weather-related changes that increase the costs of disasters, such as the New Orleans ship channel that contributed to the damage cause by Hurricane Katrina.

    OK: according to the US Government Accountability Office,

    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.

    While according to the Fourth National Climate Assessment,

    Without substantial and sustained global mitigation and regional adaptation efforts, climate change is expected to cause growing losses to American infrastructure and property and impede the rate of economic growth over this century.

    IOW: by saying climate change isn’t getting more costly, RPJr is out on a limb at best.

  50. 50

    #33 : @Brian Mapes

    … null hypotheses (presumed true, Occam’s beneficiaries of the mightiest power: doubt) …

    As I noted in #22, we can collectively do vastly better than significance testing today.

    #39 : @David Young

    Changes in flow patterns depend on the dynamics very strongly. It’s also usually the gradients of quantities like temperature that are important and not the absolute level. Thus its more important how vertical temperature gradients change than how much the SST’s warm.

    Okay, but fluid dynamics remains subject to Conservation of Energy constraints. There might be resonances at all scales in the system which are local traps for energy, but in total, the energy available for all traps and non-captured is constrained by the energy in the climate system. Big enough resonances can modulate and delay or accelerate expression of additional energies being available. Eventually, however, all the reachable states get visited and the new increments of energy get distributed.

    The fluid dynamics and various oscillations might mess up clear projections of century scale impacts, but that doesn’t mean they won’t happen. And these are complicated enough that no one can say if, on the whole these will be benign. If there’s a powerful local resonance, it might capture and hold energy away from the rest of the system for a time, but equilibration is inevitable. Moreover, the same nonlinearities could accelerate impact of additional energies, as well as restrain them for a bit.