Idly casting my still sleep-filled eye over WUWT this Sunday morning (27 June) I was struck and attracted by a most impressive sight – maps of the Northwest USA bedecked in bright hues. These I learned were “Update 3 Northwest USA Heatwave Prediction” published the previous day (26 June) and had been copied from a weather website published by Cliff Mass (who runs a University of Washington high resolution weather prediction system).

What was most striking about the map was the use of vibrant colours, mostly clashing shades reds and yellows for different areas of high temperature predictions. With areas of different colour shaped by the mountains dissected by deep river valleys, the map resembles a blazing fire with bright flames raking the sides of the Olympic Mountains and Cascade Ranges. In other maps the core of the mountains is depicted in brown colours making them resemble burnt-out coals in the centre of the fire.

I immediately thought just how appropriate was the colour scheme predicting a forthcoming heat wave with predicted temperatures expected in places to exceed 110oF.

The only green (=cool) pigments visible were far out in the frigid Pacific. Puget Sound was a solid yellow (= bath water temperatures) hue. I once crossed Puget Sound from Seattle to Victoria in BC by hovercraft.  I have never been so scared in my life. Puget Sound was mind-numbingly cold and seemingly full of inquisitive killer whales. It is also notorious for its escaped and waterlogged logs floating just beneath the surface. I imagined the outcome of my hovercraft hitting a 200 footer at speed, and those intelligent killer whales following behind seemed to have motive. But I digress.

I do appreciate a good colour rendition in a map. I was introduced to the art of using high-confidence colours to sell a prospect to the company exploration manager when I worked for an oil company. But I was warned not to overdo it. Managers might well become suspicious if high confidence colours were overused. So was this temperature prediction map overdoing it? Well possibly, but it attracted me and the map’s validity would soon be judged since it was predicting events only a few days hence – so Cliff Mass and his team must be rather confident.

Soon after I had come to appreciate the map’s fizzing colour scheme, my mind suddenly lurched to whether those suffering from colour blindness could appreciate the maps. Then on to the topic of colour blindness and whether climate alarmists suffered from it – unable to recognise the advancing greenness of semi-deserts. But then friend Wikki came to my aid and I discovered that for those with the commonest form it is red apples that appear green, rather than the reverse. Do they perhaps suffer from a much rarer type – trianopia where green coated landscapes appear as cloaked in a purplish red?  Something must affect their view of the world.

Cliff Mass threatens a sequel relating the heatwave, after it has past, to climate change. Wonder if Anthony will pick that up?


  1. Ron, gosh just imagine Cliff Mass’s maps flickering like yours do. The simulation of a raging hot fire would be even more realistic.


  2. John so many thanks for embellishing my morning bit of whimsy with something with scientific weight and relevance.


  3. You say ‘whimsy’ but I say ‘serious business’. As far as I can see, the ‘Update 3 Northwest USA Heatwave Prediction’ is using the common rainbow colour scheme. The appeal of this scheme to the climate alarmed is that it is evocative of the black body spectrum, with things glowing red hot, etc. However, as far as I am concerned, the key statement in the Nature paper is:

    “The common rainbow colour map should not be used in data visualisation. There is not a single rainbow colour map with similarly bright colours across the colour bar that comes close to being scientific (e.g., ref. 32).”


  4. The original forecast from the 23rd had, to my eye, a striking resemblance to a hobgoblin:

    Or maybe it was yet another psychological quirk of a human mind, this time automatically trying to impose agency on a random pattern (pareidolia).


  5. ATTP,

    Gavin Schmidt may very well be justified in saying that Cliff Mass is guilty of ‘naïve accounting’, but I find that the explanation provided by Gavin renders him no less so.

    It is essential that anyone who tries to construct a statement of causality should provide an assessment for both components of the causal narrative, i.e. the probability of necessity (PN) and the probability of sufficiency (PS). Despite the fact that Gavin recognizes that there is a role to play for both ‘ultimate cause’ and ‘proximate cause’ he does not seem to be interested in following this through and evaluating how both play their part in the determination of PN and PS. Instead, by restricting himself to matters of fractional attribution, he attempts to construct a causal statement based entirely upon a value for PN. This mistake is commonplace amongst those who comment upon matters of climate attribution, but that does not make it right. In cases where there are several proximate causes strongly influencing the outcome, it is quite possible for a very high figure for PN to be, nevertheless, combined with a low figure for PS. By saying only that ‘If the odds of an event have doubled then climate change is 50% responsible’, Gavin is completely overlooking the sense in which proximate causes can also be said to be responsible. To complete the causal statement he should add something along the lines of ‘But given that the probability of sufficiency is only 0.005, this makes the proximate causes 99.995% responsible’. The apparent paradox here lies in the loose and ambiguous use of the word ‘responsible’. He should really try to avoid such words.

    The bottom line is that two people arguing over the ‘contribution of global warming’ without accounting for both PN and PS are both guilty of naïve accounting.

    Liked by 1 person

  6. I live in White Rock, British Columbia , near the US-Canada border and the forecasts here have somewhat underestimated the highs. It’s currently 38C even at a station near the ocean. Definitely feels hot as many of us don’t have air conditioning in coastal BC. Of course the media are attributing the “heat dome” 100% to climate change.
    I was struck by the Cliff Mass analysis in his blog where he states:
    “So without global warming, a location that was 104F would have been 102F. Still a severe heat wave, just slightly less intense.”
    He has taken the average regional warming of 1-2 F over the past 50 years and added it to the forecast highs. This seems much too simplistic to me as the average warming has nothing to do with an extreme weather anomaly. Hence his conclusion:
    “Let me end with the golden rule of temperature extremes: the bigger the temperature extreme the SMALLER the contribution of global warming. Think about that.” Think indeed!


  7. Potentilla, I have been to White Rock back in the 1980s, looking for a house. But nothing came of my move and eventually I moved back to the U.K.
    You have my sympathies regarding the current weather, I suspect trying to sleep at night when temperatures are in the twenties (centigrade) and dew points are high must be the worst. I’ve only experienced those temperature conditions at night in Regina but then humidities were low.

    Obviously ATTP doesn’t think much of Cliff Mass


  8. I have now read Cliff Mass’s blog post, in which the offending map appears, and I was astonished to read the following:

    “The situation is so extreme that I had the colors altered to better define high temperatures.”

    This is like saying ‘The situation is so extreme I had the data altered to over emphasise how extreme it was.”

    Anyone who has read the Nature paper I cited earlier (“The misuse of colour in science communication”) would know that Cliff is breaking every rule in the book. And yet, at the end of his blog post he proclaims that he is “trying to communicate the best science”.

    Yes, but in the least scientific way.

    I am having so much fun with this that I now, belatedly, realise that I should have registered the value of Alan’s article by liking it.

    Liked by 1 person

  9. And having now read the Cliff Mass post, I am even more certain that he is simply analysing the situation from the perspective of probability of sufficiency. What he actually says is:

    “So without global warming, a location that was 104F would have been 102F. Still a severe heat wave, just slightly less intense. Let me end with the golden rule of temperature extremes: the bigger the temperature extreme the SMALLER the contribution of global warming. Think about that.”

    What he should be saying is:

    “Let me end with the golden rule of temperature extremes: the bigger the temperature extreme the SMALLER the probability of sufficiency. Think about that.”

    Neither Gavin or Cliff appear to have the required grasp of causal analysis theory to properly express themselves, and so they argue past each other, using words such as ‘responsible’ and ‘contribution’. This is a perfect example of the misunderstandings that I alluded to in my article ‘A Brief Primer in Causation’, when I said:

    “The fact that causality has this duality (probability of necessary cause and probability of sufficient cause) leads to many differences of opinion when attribution statements are discussed, with the alarmed usually focusing upon PN and sceptics focusing upon PS. Worse still, the individuals concerned are often unaware that this is the true nature of their dispute.”

    However, it is also worth noting that climate scientists can make the mistake of thinking that a probability of necessity is all you need for a full statement of causation, and no one blinks an eyelid. And yet as soon as someone starts to emphasize the perspective afforded by probability of sufficiency you get the likes of Gavin Schmidt dismissing them as ‘naïve’ and the likes of Ken Rice calling them ‘silly’.

    Speaking of Dr Rice, where did he go?

    Liked by 1 person

  10. John just a minor point but from one point of view the colour scheme used in the maps might be considered more appropriate than a scientifically more accurate graded colour scheme. If Cliff and his team wished to convey the potential danger of the high temperatures to a general public, then I for one consider their efforts reasonable and appropriate. Hobgoblins aside, the similarity to a hot fire was what drew my attention and I’m sure that of many in the affected area.


  11. John,

    Speaking of Dr Rice, where did he go?

    Better things to do.

    “So without global warming, a location that was 104F would have been 102F. Still a severe heat wave, just slightly less intense.

    Except, this misses the main point. If we assume that the distribution of events remains normal with the same standard deviation, then a shift of the mean might imply – in a simple sense – that every event shifts by an amount equal to the shift of the mean. However, if for example, you shift the mean by one standard deviation, what was a 4 sigma event becomes a 3 sigma event, or a 3 sigma event becomes a 2 sigma event. That’s a big change in the probability of that event occuring. So, an event that may never have occurred over the timescale considered, could become an event that does occur.

    According to Cliff Mass, this would suggest that this event was not influenced by the shift of the distribution, which seems like a rather bizarre conclusion.


  12. Alan,

    I only sort of agree with you. It blurs the boundary between science and activism and I guess a lot of the discussion here at Cliscep reflects a concern for that boundary.


  13. ATTP,

    “According to Cliff Mass, this would suggest that this event was not influenced by the shift of the distribution, which seems like a rather bizarre conclusion.”

    No, no and thrice no. He is not saying that at all. He is making a case for the probability of sufficiency and you and Gavin insist on judging him as though he is arguing about the probability of necessity. That is the main point.


  14. John,
    To go back to your comment about Gavin’s point, I don’t think it’s correct to regard the ultimate cause and the proximate cause as two separate influences. Every climate event will have a set of proximate causes (whatever physical atmospheric processes that operated to produce that event). Understanding the proximate causes will typically not tell you if climate change played some kind of role. To do that you’d need to understand the impact that climate change has had (the ultimate cause). So, the suggestion is that one way to assess the impact of climate change is to consider the probability of that event in an unchanged climate and then compare that to the probability of that event in a changed climate.

    Hence, if we shift the distribution so much that an event occurs that had an extremely low probability of occuring in an unchanged climate, one might conclude that climate change played a significant, or even dominant, role. That doesn’t mean that the proximate cause would be atmospheric processes that had never occurred before. It would just mean that climate change has shifted the underlying climate state to the point where it becomes possible for an event to occur that had never occurred before.

    There may well be other ways to assess this, but this seems like a reasonable way to estimate the impact of climate change.


  15. Firstly, I’m going to take issue with the use of the term ‘ultimate cause’ in this instance. If one is performing a root cause analysis, in which a succession of events lead to a particular outcome, one can point to the initiating cause as being necessary for what followed. That does not, however, address the question as to whether the initiating event was sufficient for the final outcome. There may be several intervening events that were equally or more necessary and it may not even be possible to discern a single initiating event anyway. By referring to climate change as the ultimate cause of a specific weather event, one affords it a status that is unwarranted. It may provide the backdrop against which extreme weather events may become more likely, but that doesn’t make it an ultimate cause in the root cause analysis sense.

    Secondly, no one, including myself, or Cliff, is for one moment arguing that proximate causes are more relevant than distal causes. Fractional attributions of risk are equivalent to calculations of the probability of necessity and, as such, address the question of how much more likely the event has been made by climate change. But that is only half of the story when talking about a specific weather event. For any event (Y), there are always two questions to be asked:

    a) Given that X and Y have happened, what is the probability that Y wouldn’t have happened if X hadn’t happened?

    b) Given that neither X or Y has happened, what would be the probability that Y would have happened if X had happened?

    The former is the one you are concentrating upon. The latter question is no less fundamental, however, to the question of causation. It is the probability of sufficiency and it cannot be ignored if you want to fully understand the causation of an event. Unfortunately, however, when X is climate change, anyone who focuses upon the latter question is immediately accused of trying to deny the relevance of X. Nothing could be further from the truth.

    I am conscious that we are getting very off-topic as far as Alan’s post is concerned. If we want to continue the discussion, perhaps we should consider choosing a different thread.


  16. John and Ken, please be my guest. I wrote my post on a whim, believing that a few readers might just be interested in my early morning, almost ephemeral, thoughts about a resemblance between a heatwave prediction map and the flames in a fire. From this, the post has been transformed by you into a serious discussion about the rights and wrongs of colour representation of data and, wouldn’t you know it, attribution science. I couldn’t be pleaser.


  17. ATTP,

    You seem to have gone quiet again. Presumably it’s because you have better things to do than respond to comments that you elicited. Perhaps it would help if I were to be more direct and succinct in my response to your previous comment.

    a) You use the term ‘ultimate cause’ inappropriately. It is no more appropriate to suggest that climate change is the ultimate cause of an extreme weather event than it is to say that moving to an area with higher covid prevalence was the ultimate cause of catching covid.

    b) You have expended effort explaining to me how event attribution works when it should be obvious from what I have said previously that I already understand. How probability of necessity is calculated with regard to climate is a given. I am talking instead about the need to also consider probability of sufficiency in order to complete the causal statement in respect of a specific weather event.

    c) We are having this discussion because you referred to Cliff Mass’s ‘golden rule’ as being ‘silly’. I am suggesting that you only consider it silly because you insist on interpreting it as a statement regarding probability of necessity when it is, in fact, alluding to sufficiency. Do you know how probability of sufficiency is calculated? I’ll cite you the relevant paper, if you show any interest.

    Liked by 1 person

  18. Full disclosure: I’ve slightly edited my previous comment. Instead of giving what I now realize was a misleading hint, I have offered instead to cite the relevant paper.

    Liked by 1 person

  19. Fascinating commentary today at WUWT about the heatwave in the Pacific Northwest by both Anthony Watts and his commentators. One of the latter points out how local the heat anomaly is – that the average temperature over the whole USA is actually down 1 degree F. Talking of global warming….


  20. Alan,

    >”One of the latter points out how local the heat anomaly is…”

    Try telling that to the BBC. You might like to check out what the BBC’s ‘Visual Journalism Team’ managed to conjure up by using a common rainbow colour map, employing deliberately evocative colours and an inventive calibration that de-emphasises the locality of the phenomenon and portrays even those parts shivering in 10-15oC as being in peril of melting:

    What was it that the ‘misuse of colour paper’ said? Not even close to scientific!


  21. I can imagine the ‘team’ huddled around the computer, endlessly twiddling knobs until they get the desired effect. Then one shouts from the back, “For God’s sake you morons. Don’t use blue!”

    Yes, nowhere near scientific, but very near to journalistic.


  22. ATTP,

    Yes, I am keen to highlight the paper, if only for the following reason:

    “We have shown, with simple examples, that it is important to distinguish between necessary and sufficient causality. Such a distinction is, at present, lacking in the conventional event attribution framework. Any time a causal statement is being made about a weather or climate-related event, part of the audience understands it in a necessary causation sense, while another part understands it in a sufficient causation sense, which can give rise to many potential misunderstandings. Introducing the clear distinction may thus clarify discussions.”

    The above quote is taken from the paper, and it reflects my own concerns. The paper starts out in a deceptively facile manner but quickly reveals its relevance and, IMHO, profound importance. You will also note that it is not in any way a climate denier’s charter. It simply offers a wider and more insightful way of looking at D&A. Enjoy:

    Click to access r451-reprint.pdf


  23. John,
    Thanks. I think that is related to what I was suggesting in an earlier comment that there might be multiple ways to do this. For example, if you consider all the possible causal factors (anthropogenic forcings, natural forcings, and internal variability) then if the resulting PN (wrt anthropogenic forcings) is high enough, then the PS may not matter.

    If the resulting PN is high enough, then human responsibility is established and a ruling may in theory follow, as it does in litigation cases. In any case, as in the imprudent shooter example, PS does not matter here, only PN does.

    However, when consider future planning, both PN and PS become relevant. According to the paper, at least, PN is more relevant when considering taking action (If we reduce the forcing will it reduce the frequency of these events) but PS might be relevant if we’re considering what we might do if we don’t take action (i.e., if we don’t take action, will the frequency of these events be maintained).

    So, as the paper says:

    To summarize, depending on the context, PN, PS, or both may be relevant and can help answer different causal questions.

    which seems perfectly reasonable to me.

    The problem I can see with insisting on PNS is that it’s the probability that the event would occur in the present of (in this context) increased anthropogenic forcings, but would not occur in their absence. However, we are still interested in how climate change might impact events that could still occur in the absence of climate change, we’re not only interested in events that would not have occurred at all in the absence of climate change.


  24. ATTP,

    As I said, the paper is not a denier’s charter. Actually, the part of the paper that asserts that a high PN renders a low PS irrelevant as far as culpability is concerned is the one part that I am not sure of. I can think of a number of situations where a low PS may mitigate culpability notwithstanding a high PN, and I am unconvinced that the climate change example does not fall into such a category. Certainly this is the case where forest fires are concerned, in which lit matches, cuts in fire services and poor forest management are factors. Anyway, we shall see what attitude the courts take when the litigation starts.

    >”However, when consider[ing] future planning, both PN and PS become relevant. According to the paper, at least, PN is more relevant when considering taking action (If we reduce the forcing will it reduce the frequency of these events) but PS might be relevant if we’re considering what we might do if we don’t take action (i.e., if we don’t take action, will the frequency of these events be maintained).”

    Actually, I think the important distinction is between avoidance and mitigation. PS is certainly of more interest to insurance companies. Even a low PS may concern them because they have to take the longer view.

    >”The problem I can see with insisting on PNS…”

    I believe the main problem with insisting upon a high value for PNS is that it sets the bar too high for making a causal case.

    To return to my initial point, I still believe you and Gavin were misjudging Cliff Mass, mainly because he was pointing out how the causal case looks from a sufficiency perspective and you were reading this as a denial of the necessity perspective. As he said:

    “Is global warming contributing to this heatwave? The answer is certainly yes. Would we have had a record heatwave without global warming. The answer is yes as well.”

    The Hannart paper may be aligning with comments you have made subsequently but it does not support your initial criticism of Mass. He was simply trying to take on board the duality of causality. If anyone was being naïve, it was Gavin Schmidt.


  25. If the likes of Gail Tverberg are anyway correct then the industry needs an oil price of around $120 a barrel to make developing new fields profitable. So it seems to me that the oil majors have every reason to be cautious about developing new fields. It also could be that they see defeats in the courts as a face-saving way of withdrawing from increasing difficult and unprofitable markets.

    The five major western oil companies only control about 15% of world oil production, the remainder being supplied by national companies. So the Grauniad’s attack on oil seems more like an inter-elite fight than anything more serious. When they start attacking the likes of Aramco, the Saudi oil producer, we will know they are serious about shutting down the oil industry.


  26. John,
    I’m not quite sure how Cliff can make this claim:

    Would we have had a record heatwave without global warming. The answer is yes as well.

    unless he means that at some point this region would probably have experience a heatwave, even in the absence of climate change. It may well be true, but it doesn’t seem all that informative.


  27. ATTP,

    I think there may be two ways of thinking about Cliff’s assertions:

    a) There was so much internal variability on display that one has to concede that the PS for the temperatures achieved was very low.

    b) There was not enough variability to explain the temperatures achieved, so one has to concede a high PN, but there was still more than enough to have broken the previous records without recourse to the contribution made by global warming, i.e. the PN was high with regard to the actual temperatures achieved but low with respect to those that were necessary to break the previous record.

    I think both statements may be true but perhaps the latter is more relevant.


  28. John,
    Except, you can’t separate out the various causal factors without some kind of model. Clearly, a complex set of climate factors (or, physical climate processes, whatever term seems most suitable) combined to give this climate event (heatwave). And one can clearly analyse the atmospheric data to determine what these processes were. However, that alone doesn’t tell you if climate change played a role, or how much of a role. To do that, you’d need to somehow compare how likely such a set of events might be in the absence of anthropogenic forcings, and in their presence (and you could presumably use this kind of analysis to determine PN and PS). So, unless Cliff has done something like that, it’s hard to see how he can make a confident statement about the emergence of a record heatwave in the absence of global warming (as I said earlier, this is probably true in the sense that one would probably eventually emerge, but this is not particularly informative).


  29. I think Cliff is just conjecturing. I don’t for a minute think he has performed any D&A on this one – but you can bet your life that someone will, or already has. Let me know if you hear anything. If they publish values for p1 and p0 as well as for the FAR then we will be able to use the Hannart-Pearl equations to calculate PN, PS and PNS. Wouldn’t that be fun?


  30. ATTP,

    With our discussion having reached a natural conclusion, I had promised myself that I would let the matter drop. However, having just re-read your responses, it occurs to me now that there are still a couple of points that remain to be made.

    Firstly, despite the fact that both you and Gavin criticised Cliff Mass’s attribution argument because of a supposed misunderstanding of how necessity works, and despite the fact that I have demonstrated that Cliff was not actually arguing from the perspective of necessity, you have not, at any point, acknowledged your error.

    Secondly, after reading the Hannart et al paper that I’d cited, you drew attention to the authors’ statement that ‘when consider[ing] future planning, both PN and PS become relevant.’

    You said that this “seems perfectly reasonable to me”.

    Back in June 2020, I told you this on your website:

    “You need both PN and PS for a full causal narrative and you need a full causal narrative to decide the best policy for managing the risks.”

    It’s such a shame that the idea didn’t strike you as perfectly reasonable back then. In fact, you didn’t pay any attention whatsoever. You only sprang to life when defending Willard’s unwarranted censorship of my complaint regarding his behaviour.

    In fact, if you had read and taken on board my ‘Brief Primer on Causation’, posted here on Cliscep back in March 2020, you would already have understood all you need to know about the relevance of PN and PS, since it was in that article that I quoted Hannart:

    “PS is the appropriate focus for the planner when assessing the future costs that inaction will imply, but PN is at stake when assessing the future benefits of enforcing strong mitigation actions. Policy elaboration requires both sides of this assessment; thus both PN and PS are of interest here.”

    Liked by 1 person

  31. Well, here’s more grist to the Ridgway/aTTP mill:

    “Climate change: US-Canada heatwave ‘virtually impossible’ without warming”

    “The searing heat that scorched western Canada and the US at the end of June was “virtually impossible” without climate change, say scientists.

    In their study, the team of researchers says that the deadly heatwave was a one-in-a-1,000-year event.

    But we can expect extreme events such as this to become more common as the world heats up due to climate change.

    If humans hadn’t influenced the climate to the extent that they have, the event would have been 150 times less likely.

    Scientists worry that global heating, largely as a result of burning fossil fuels, is now driving up temperatures faster than models predict.”


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