RealClimate logo

Rapid attribution of PNW heatwave

Summary: It was almost impossible for the temperatures seen recently in the Pacific North West heatwave to have occurred without global warming. And only improbable with it.

It’s been clear for at least a decade that global warming has been in general increasing the intensity of heat waves, with clear trends in observed maximum temperatures that match what climate models have been predicting. For the specific situation in the Pacific NorthWest at the end of June, we now have the first attribution analysis from the World Weather Attribution group – a consortium of climate experts from around the world working on extreme event attribution. Their preprint (Philip et al.) is available here.

Trends in Tmax globally

In the paper, they show that this event was truly exceptional in the temperature statistics in the region and specifically in Vancouver, Seattle and Portland, but that the geopotential height anomaly (one measure of the ‘heat dome’ or the ridging) was not that far off from the underlying trends. Using various methods to construct the return time for this event, they show that even in today’s climate this was a one in 400 yrs or longer event. Using only data from before 2021, an anomaly this large is estimated to never occur!

What happened?

Everyone is agreed that the specific synoptic situation is unusual. A large ‘omega’ pattern (so-called because of the resemblance to the Greek letter \Omega) set up by a Rossby wave breaking event, intersecting with the topography and the warm temperatures to the south-west that were advected to the PNW. But the question is whether the temperature extremes are being made substantially more likely by underlying climate changes.

First, look the maximum annual daily temperature in the region (according to the ERA5 reanalysis for the historical data and the actual weather forecast analyses since June 1st). There is a real trend of about 4ºC over the last 70 years – roughly 3 to 4 times the trend in the global mean temperature. Nonetheless, the magnitude of the regional anomaly is more than 5ºC above the previous record. That is, literally, phenomenal.

ERA5 regional temperature anomaly
Figure 4 from Philip et al., (preprint).

The temperature anomaly at the local station level is similarly huge at SeaTac airport, Portland International Airport and New Westminster (nr. Vancouver). Note that while the cities might be affected by urban heat island effects that would exacerbate the temperature signal, that would not affect the regional analysis above, nor the situation in village of Lytton, BC which set a massive new all-time Canada-wide temperature record on Tuesday June 29th and promptly burnt down a day later.

However, the situation is a little different if you look at the geopotential height anomalies – these are affected by the synoptic situation as well as the integrated temperature anomalies. In that case, while still record-breaking, the anomaly is not totally beyond expectations. Indeed, the trend in z500 values is similar to the situation in Western Europe last year.

Geopotential maxima trends

Together these analyses suggest a synoptic situation that is rare, but not inconceivable, but with temperature anomalies that are off the charts.


The way that attribution for extreme events works (as discussed previously on RealClimate here and here etc.) is that you look at the situation with and without the anthropogenic global warming signal and calculate the ratio of probabilities. If an event is say, twice as common with the GW, then one can give a fractional attribution of 50% to anthropogenic forcing and the return time is half what it used to be. If it is five times more likely, the attribution is 80% = 100*(5-1)/5 and the return time is a fifth of what it used to be. In this case, we are seeing probability ratios of 150 to 1000s, suggesting that these, improbable, temperatures can be almost entirely attributed to global warming. Without the anthropogenic signal, temperatures this extreme wouldn’t have happened in thousands to tens of thousands of years.

Figure 8 in Philip et al: The GEV fit to the regional anomaly and the probability of regional temperature extremes with and without anthropogenic warming.

Rainfall and soil moisture deficits as a precursor?

In many previous extreme heat events, such as the 2003 European heatwave, rainfall deficits and dry soils the prior spring were shown to have made an important contribution to the temperature extremes, and so it’s worth looking at the same phenomena here. The IMERG data which are mostly based on satellite rainfall amounts do show a moderate deficit in the area over the last four months, but not so much of an effect that it could explain the anomaly on it’s own. The magnitude of this effect will be examined further in the months to come.

Preceding precipitation anomaly

All models are wrong?

This kind of attribution is of course only as good as the models being used. In such a rapid attribution study, that means that the authors depend on an existing database – in this case, from CMIP5 and CMIP6 – and while they screen the models for fidelity in matching this genre of event, it’s possible that there are systematic issues with this class of model for a specific aspect of the situation. For instance, Mann et al., (2018) find that the CMIP5 models have a poor representation of a quasi-resonant (QR) phenomena in jet stream waves that are associated with the ‘omega’ pattern blocking event seen here. [Update: the specific claim in the paper relates to oscillations with wavenumber 6-8, while this event was more of a wavenumber 4 phenomena – see comment #9 below]. The expected trends in QR suggest an increase of about 30% in such events today over the situation in the pre-industrial. If models don’t capture this behaviour, it will make the event seem more unlikely than it really is. This might be resolved in higher resolution modeling specific to this event, but doesn’t really affect the broader conclusions.

Maybe it was just really, really, really unlikely?

Some people still reject these lines of argument, typical of this is Cliff Mass in this recent blog post. For them, the trends in max temperatures are (literally) ignored, and the fact that this phenomenon is being seen around the world is just a series of increasing unlikely combinations of factors that for some inexplicable reason keep happening. But this is really just a case of synoptic myopia – paying too much close attention to the series of specific events that lead to the specific situation, and not seeing the wood for the (burning) trees.

p.s. (8 July): In 2012 we published the highly relevant post Extremely hot, starting like this:

One claim frequently heard regarding extreme heat waves goes something like this: ”Since this heat wave broke the previous record by 5 °C, global warming can’t have much to do with it since that has been only 1 °C over the 20th century”. Here we explain why we find this logic doubly flawed.

Pretty much exactly what happened! And it ends thus:

So in summary: even in the most simple, linear case of a shift in the normal distribution, the probability for “outlandish” heat records increases greatly due to global warming. But the more outlandish a record is, the more would we suspect that non-linear feedbacks are at play – which could increase their likelihood even more.


  1. M.E. Mann, S. Rahmstorf, K. Kornhuber, B.A. Steinman, S.K. Miller, S. Petri, and D. Coumou, "Projected changes in persistent extreme summer weather events: The role of quasi-resonant amplification", Science Advances, vol. 4, pp. eaat3272, 2018.

200 Responses to “Rapid attribution of PNW heatwave”

  1. 51
    MA Rodger says:

    I see the troll J Doug Swallow @43 has posted a reasonable question for once (although the reasoning on the troll’s part was likely that he thinks his question will prove here infernally awkward).
    “Could what is written above also be applied to these historical heat waves on the East Coast?”

    The two heat waves mentioned are over a century old.
    The first mentioned is 1896 Eastern North America heat wave which wasn’t very hot but still proved deadly. In Boston it did provide the hottest day of the year but this was cooler than the previous year’s maximum and also the maximum of two years later. Similarly in New York higher maximum temperatures had been recorded in previous years and again two years later The 1986 heat wave was deadly not because of the heat but because it was hot-&-humid as well as other factors. The Wikithing page on the heat wave linked above states “A majority of the deaths were of working-class men in their twenties who performed manual labor.”
    Thus the 1896 Eastern North America heat wave does not compare.

    The 1911 Eastern North America heat wave still provides Boston with its all-time record high temperature (but not Massachusetts and in New York City it never did) and at Boston it was at-the-time a step up from the previous record maximum of +5°F. But this step-up is a lot less than the step-up at Lytton of +9.3°F which occurred with a lot more than a couple of decades of preceding temperature data.
    Thus the 1911 Eastern North America heat wave does seemingly bear some comparison but as a heat wave of considerably less intensity.

  2. 52
    Piotr says:

    One of the consequences of this heat wave (and the future ones elsewhere) would be many more people buying air condition. (The International Energy Agency expects space cooling energy needs to triple by 2050).

    It will
    – increase the demand for electricity, and at the worst possible time: since in the US and probably most of the world – the maximum demand for electricity is already in summer (i.e. as discussed in FV – while being the best season the solar and good for wind, it is the worst season for the gas, coal, and nuclear, which are thermodynamically least efficient (the temp. difference between steam and coolant the lowest)

    – even more importantly it would release through leakage of Hydrofluorocarbon (HFC) used in them:
    The most abundant HFC is 3,790 times more damaging to the climate than carbon dioxide over a 20-year period

    So another positive feedbacks for AGW. Hopefully, easier to counter than others (provided that we find the political will):

    A paper from 2013 concludes that:
    “avoiding production and use of high-GWP (global warming potential) HFCs by using technologically feasible low-GWP substitutes to meet the increasing global demand can avoid as much as another 0.5 ◦C warming by the end of the century).”

  3. 53
    Ray Menard says:

    I was rather delighted to see an attribution study out the door so quickly and vigorously get picked up by the media. It’s changed the conversation in the Pacific Northwest just a many folks are still smelling the consequences of dead shellfish near the mud flats of Puget Sound, trying to save their landscaping, watching the dramatic change in snow on Mount Ranier and many other lingering effects in their lives. I hope quick turn arounds, based on evidence, such as this, become common after extreme events. I also hope they survive peer review mostly intact.

  4. 54
    Russell says:


    It will be interesting to see how the usual California skeptics try to spin the hottest climateball yet pitched in their direction, as Furnace Creek is 200 miles from the nearest urban heat island, and their cartoonist may not be up to the occasion:

  5. 55
    nigelj says:

    Killian @41

    “The glaring example is nigel. He must be beat about the head and shoulders for days, weeks or even years before he shifts his stance”

    Hes wrong. And nobody is more fixed minded than Killian, not even Victor or KIA amazingly enough. Killian should be in the Guiness Book of World Records worlds most stubborn person. Look at discussion between Killian and myself, Piotr, BPL, EP, KM etcetera. And what is Killian doing wasting this websites time with evidence free nasty, insulting personal accusations made against a fellow warmist, made on an article about heat wave attribution? Its despicable and off topic.

  6. 56
    Richard the Weaver says:

    Gavin: Literally you appear to not be able to see what is right in front of you.

    RtW: and now we get to see if you’re honest. My suggestion is to respond properly. My guess is that you will demonstrate your lack of substance instead.

  7. 57
    Richard the Weaver says:

    Mike: Connect the dots. Read the handwriting on the wall.

    RtW: Why would anyone do such an unprofitable thing?? NOBODY will get richer than a denier by admitting such stupid truths

  8. 58
    Richard the Weaver says:

    Ray: One cannot say climate change was THE CAUSE,

    RtW: because ’cause’ is a stupid word that has no meaning in probability. There are always multiple threads.
    Go ahead. Give me an example that says otherwise

  9. 59
    Richard the Weaver says:

    Zebra: would anyone like to offer their opinion as to what the probability of occurrence of that heatwave under discussion on Earth-B would be?

    RtW: precisely zero to a zillion decimals. Duh. Is that your point?

  10. 60
    jacob l says:

    well to get to the bottom of the cliff mass thing
    I downloaded my local iera tmax from klimate explorer and counted the days above 25c
    what I found was that the decades where indeed not significant p value of .16,
    but when i did years I got a p value of 0.0451 significant.

    The decade data is as follows
    any thoughts on how to analyse??
    Thanks jacob l

  11. 61
    Richard the Weaver says:

    About Mike on Cliff,

    Yep, it would be nice if folks cared about whether the biosphere survives more than they care about whether their previous drunken claim is correct.

    But that isn’t the planet we’re living on. As proven by Cliff

    Either that or doctorates are as valuable as toilet paper

    Seriously, does Cliff sound smarter than Victor or KIA?

  12. 62
    zebra says:

    Question For Meteorologists,

    Would you characterize a “wavier” jet stream as a more or less energetic state than the “standard” condition?

    My first guess is more, but it is really just a simplistic assumption because molecules would be traveling longer distances.

    Thanks for any elaboration beyond my limited two-dimensional conceptualization.

  13. 63
    Jan says:

    Hello Folks, so i ask again: Where did the air mass come from which descended over the Northamerican West… This would realy interest me, because we see a planetary circulation that becomes more meridional…

    Here are many experts, so you should know – or are most of you only good in statistics? The mechanistic analysis tells you the probability of such events – statistics won’t help you in a novel climate system!

    And forget your 30 year climate definition to detect a trend. Because what we see now in many fields and regions is that our planet leaves natural variability and what we see now are no more exceptions but the beginning of a robust trend since the last ~6 years because of the new warming jump that took place from 2012 onward.

    To your Question For Meteorologists. I’am not one but i read many studies on that topic and what the experts write is, that a wavier Jet-stream losses energy (speed). One is the declining pressure difference between tropics and Arctic during winter.

    Then that a jet that meanders more strongly losses its energy because of the turns it makes – it was compared with a car – driving straight or in curves.

    Another cause are sudden stratospheric warming events which occur when the jet flows over a ridge and shoots into the stratosphere where it dissipates.

    And last there exist the possibility that the jet breaks down because of the extreme curve it makes – Rossby wave breaking.

    Further just ridges and troughs (which occur now much more frequently and are getting extremer along the zonal direction) in the atmosphere should also be enough to slow down the jet stream, because it meanders not only in the north/south direction but also in height.



  14. 64
    tamino says:

    Re: #60 (jacob l)

    When you use 10-year averages, you reduce the available data to a mere 7 data points. That makes it very hard to establish statistical significance, especially since you lose two degrees of freedom (slope and intercept, if you’re doing linear regression) so you only have 5 degrees of freedom left.

    Also note: the data can’t be negative, so a linear regression model isn’t the best. I suggest Poisson (or quasi-Poisson) regression.

    When I do this with the ERA5 data averaged over the study region outlined in the attribution paper, I do get statistical significance, even using 10-year averages. Exactly what region are you examining?

  15. 65
    Piotr says:

    Zebra (49) “ It’s The Physics Stupid, apparently many here can’t explain the physics, so they engage in weird analogies and supernatural mind-control explanations, much like the Denialists

    Brave words from somebody whose entire presence here is built around … correcting others on their definitions and on basing one’s arguments not on physics, but on splitting words.;-) But let’s read further, it gets better:

    Zebra (49)” No, Piotr, the “long-term global average temperature” does not affect anything, because that value is an effect, not a cause” [emphasis by Zebra]

    Huh? I wrote: “the global warming does affect local weather extremes “

    The “ long-term global average temperature ” is NOT the same as the “global warming”, Genius – the former being a METRIC that describes the latter: the accumulation of heat. And that’s WHY I choose “ the global warming” and NOT “ long-term global average temperature”.

    But please do condescendingly lecture me and others (like IPCC) that … “It’s The Physics Stupid” and “perhaps because you yourselves are indeed out of touch with the physical nature of physics… we’re not doing QM or GR here, people“.

    Zebra (49): “ Piotr (and others): You can’t “shift the distribution”, because you are not God. The distribution moves to the right because the individual measurements are higher, not the other way around.”

    so … WHY are these “individual measurements” higher, Mr. Zebra. God?

    To sum it up:
    – I and the “others”, e.g. IPCC (the graph on the shifting distribution is from IPCC 2007), argue that humans DO affect climate (here: by shifting the temp. distribution to the right)
    – zebra ridicules the notion by: “your are not God“.

    So who of these two has “ accepted Denialist Propaganda framing“:

    – Sen. James Inhofe [R], the chair of the U.S. Senate Committee on Environment and Public Works from 2003 to 2007 and again from 2015 to 2017:
    “The hoax is that there are some people who are so arrogant to think that they are so powerful, they can change climate. Man can’t change climate.”; “my point is, God’s still up there. The arrogance of people to think that we, human beings, would be able to change what He is doing in the climate is to me outrageous.”

    – Rep. John Shimkus [R], Ranking Member of the Subcommittee on Environment and Economy:“The Earth will end only when God declares it’s time to be over. Man will not destroy this Earth”

    – Zebra: “You can’t “shift the distribution”, because you are not God.”

    P.S. Speaking of God, you’re familiar with Matthew 7:5?

  16. 66
    Piotr says:

    Zebra(62) Would you characterize a “wavier” jet stream as a more or less energetic state than the “standard” condition? My first guess is more, but it is really just a simplistic assumption because molecules would be traveling longer distances.

    less. Arctic is heated up more than mid lats -> smaller difference in temps.-> smaller difference in air pressure -> weaker the forcing driving the Jet Stream from W->E -> chaotic departures N or S increase in relative strength to the W->E and have more time to develop -> Jet Stream more wavy -> sucking more cold air south and warm air north -> possibly one reason for more extreme weather events in N.America

    Or my another “ pointless analogy“: a river
    – not very wavy near the source (steep slope – large driving force of gravity)
    – vs meanders of the same river downstream, on the flatter terrain.

  17. 67
    Piotr says:

    Let me get it right, Killian (41) – you travelled from the Forced Responses to the discussion on “Rapid attribution of PNW heatwave“, to comment on Mike’s criticism Clifford Mass claims on that heatwave, and all that – so you can …talk about Nigel?

    And your “guilt by association” rhetoric comes at a price – not only it is dishonest toward Nigel, but also … elevates the climate change deniers: when you try to take down Nigel by implying that he is no better than deniers, this comes at the price of implying that the deniers ain’t that bad, since they are no worse than Nigel.

    Your hostility toward Nigel and other “warmists” on this group is consistent with fundamentalist all-or-nothing mind. To such minds – people on our side who nevertheless differ from us in minor ways, or don’t acknowledge our greatness and/or prophetic qualities – are seen as “traitors”, and as such WORSE than an open enemy.

    That’s why fundamental islamists may tolerate unbelievers, but never apostates. And that’s why fundamental Christians we often much more hostile to the Jews than to the pagans – for the pagans “know not what they are doing”, while the Jews
    were given a chance to embrace the Son of God, and they refused. (Toutes proportions gardées – your biting repartees are not that lethal).

    So now that you know it, you can change. Just kidding. ;-)

  18. 68
    Stephen Berg says:

    Re: #62 and 63,

    A wavier jet stream may or may not be more energetic than a more zonal (i.e. west-to-east or straight) flow. It would depend on the actual flow speed aloft. A wavy jet stream with an average flow speed of 120 kts would likely be more energetic than a zonal flow with flow speed of 80 kts. However, many wavy jet stream situations can be stronger or weaker than that. Stronger jet streams, however, can result in greater upper-level diffluence, which can generate cyclogenesis or produce short wave patterns at the surface from ascending air that can support storm or precipitation formation in many situations.

    The arguably more important feature of wavy jet streams, however, is the presence of greater vorticity advections and their association with cyclogenesis and anticyclogenesis. In the section from crest to trough, negative vorticity is promoted, generating high pressure at the surface (drier conditions), whereas in the section from trough to crest, positive vorticity is promoted, generating low pressure at the surface (more precipitating systems).

    With the reduced temperature gradients caused by Arctic Amplification, these wavy jet stream patterns are moving more slowly and are more “malleable” (can become even more wavy), resulting in both these high and low pressure systems prevailing over an area for a longer duration, intensifying the resulting dry and wet conditions over each respective region. This may result in these sorts of heat waves from persistent sun and slow subsidence (and resultant warming of descending dry air) in the high pressure zones. Flooding situations may also develop in the low pressure zones from precipitating systems (possibly including intense mesoscale convective systems) that are sometimes stationary or moving more slowly out of an area, giving possibly 100-200 mm or more rainfall over a small area, overwhelming watersheds and substantially raising water tables.

  19. 69
    jgnfld says:


    Running a normal linear regression with 1 and 5 degrees of freedom is mathematically “legal”, but as a statistical test, it simply has no power to detect any reasonable difference. The differences would have to be truly PHENOMENAL. (Hint: Various sources suggest minimum numbers of data values that should be present before doing a time series trend analysis, NONE even remotely suggest using 7 total degrees of freedom.)

    For example, if, in the past 20 years, there had been even 30 and 40 records set in the 2000s and 2010s respectively, the result STILL would be just outside of .05 significance. There just is no statistical power to be had with so few observations.

    Other routes:

    Some nonparametric stats can be helpful:
    A one-way chi square is highly significant in showing that there is _some_ sort of dependency going on here. Just not what particular kind (though that’s pretty obvious by eye, isn’t it?). Various other general nonparametric tests would show this as well.

    In many areas (hydrology in particular), a Mann-Kendall one way test (which tests for monotonically increasing/decreasing values over time) is common. However it too doesn’t perform well on such limited data.

    All this simply points out yet again that using extreme values to predict anything or make any solid inference is fraught with power issues. Which is why denier-types dearly love using them.

  20. 70
    John Pollack says:

    Jan @63 As a partial answer to your question, the air mass that “descended on the Northamerican West” was mostly a regional creation. Keep in mind that we are not looking at some large body of air which is displaced, essentially unmixed, from some part of the planet and put in another place. It only takes a few percent of the surrounding air converging into a region to create a ridge. The air mass was heated from above by having the air descend and compress. It was heated from below by extra solar radiation being absorbed by unusually dry ground across the drought-stricken west.

    What about the circulation from the tropics to the subtropical high that you referred to earlier? This is an average tendency, once you filter out all of the shorter term weather. It is a simplification to help understand the overall tendencies of the planetary circulation.

    In the same way, the jet stream is not some solid entity. It is a formation that air flows through, entering in one place and leaving in another. Jet streams form and dissolve, and vary in strength. If they lose energy, it goes into the surrounding atmosphere. For example, a net loss of energy from a jet stream could go into powering the descending air in an adjacent high pressure area.

  21. 71
    John Pollack says:

    Zebra @62 I would say that to obtain an answer, you would have to define your terms better. A “jet stream” is not a distinct entity that can be separated from the rest of the atmosphere. They are discontinuous, and there can be two or three bands of strong winds that might be called a “jet stream” at different latitudes and elevations at the same longitude.

    “Wavy” is another tricky term. I’ve seen a lot of different definitions to define the magnitude of “waves”, “blocks” etc. These are simplifications, somewhat identifiable formations within complex fluid flows.

    There is a good definition of “energy” but I’m not sure it is the one you would care to focus on. The kinetic energy of the atmosphere is the mass- weighted integration of the square of the wind speed through a defined volume. In general, the energy is greatest in the winter, due to the stronger temperature gradient between high latitudes and tropics, which supports stronger winds. The flow of the atmosphere may be manifested in different configurations of waves and jet streams for the same total energy. If you want to include thermal energy and latent heat energy, it gets even more complicated.

  22. 72
    Chas says:

    That ERA5 “regional” temperature plot in the post seems dubious since it shows nothing of the 2009 heat wave that produced the prior record high of 103 in Seattle. Portland reached 106 then as well, 1 degree short of its record (according to NWS data), but the ERA5 plot shows a 2009 max temp of about 90, so it seems either the region doesn’t include Seattle and Portland, or the region is so big as to render the 2009 PNW heat wave as geographically too small to notice.

    Also, NWS data for Seattle, which goes back to the late 1800s, shows max temps of 100 in 1941 and 1955, both not shown in the ERA5 plot (Portland temps for 1941 and 1955 were 103 and 98). And if it reached 100 twice in 15 years prior to AGW is it really accurate to say 107 (the new Seattle record) would happen only “thousands or tens of thousands of years” without AGW?

    Its also not clear what the attribution is claiming. Is the claim that, absent AGW, it would have been in the 70s as usual, or is the claim that it would have been something like 104 instead of 107? The former is a big deal, the latter not so much.

    And finally, the NWS data for Seattle does show gradually rising max temps with a slope of 0.028 by my simple spreadsheet calculation. Max temp data for SeaTac (i.e. the airport south of the city) only starts in 1945 but its slope is more than double at 0.0716. The Seattle slope is roughly half that of the ERA5 plot, despite being a city susceptible to the heat island effect. It seems like a lot of the attribution analysis depends on the ERA5 data, but frankly that data doesn’t seem like it accurately represents the PNW given its failure to show the previous heat extremes in Seattle and Portland. Maybe the attribution analysis is really only valid for a heat wave that is geographically as large as the recent one, which I gather was much larger than the previous ones.

  23. 73
    hexghost says:

    As a PNW resident, I do follow C.M a lot (even though he never approves any of my comments on his blog), and so his article about the heat wave was very interesting. Anecdotally it sure felt wrong, but, not being a climatologist or even good with statistics, I found it hard to find anything obviously incorrect in his post. As mentioned perhaps by earlier commenters, “slick science” can be very convincing, especially if the source has a good track record for local meteorological events.

    Thanks to all the other commenters and of course post authors, as I really appreciate this content.

  24. 74
    Karsten V. Johansen says:

    Again and again we hear the same question being repeated: when will science be able to predict precisely the amount of global heating etc.?

    Answer: By the time science could have been able to predict the heat-driven collapse of the so-called civilization (already in full swing), science will already be long gone. Because a) it will since long have been forbidden, crushed, uprooted etc. by the already long roaring fascistic idiocy and raving madness that grips the leading lights of mankind, the hyper-rich and hyper-gready psychopaths and the stupid majority always following their orders, whenever they sense even a tiny fraction of something true approaching their minds (all this is already happening at full speed in front of our eyes), and b) mankind itself will therefore be in a state of full collapse or probably already long gone.

    The truth is: what is called capitalism/growth etc. in reality is *the collapse of mankind*. Everything points to the unpleasant fact that our species does not differ from any other except by this: we are able to manipulate our environment on earth so enormously much further than any other species, that we, through our unstoppable growth and consumption, create a global ecological catastrophe of geological proportions, destroying not only ourselves by destroying our environment, but on top of that creating the biggest mass-extinction of life on earth since at least 66 million years.

  25. 75
    nigelj says:

    Zebra @49

    “No, Piotr, the “long-term global average temperature” does not affect anything, because that value is an effect, not a cause.”

    This is pedantic nonsense and its not actually what Piotr said anyway. Implicit in the term increasing global temperatures is warmer global air mass and THAT affects local weather. Which it does. How would it not?

  26. 76
    J Doug Swallow says:

    #50 William Jackson says: “Comparing apples and oranges are you not JDS, 1896 was in a time of little or no AC not to mention that Boston is not the Pacific North West! You seem confused.” Have it however you want; but it was the overall temperature that was phenomenal in both the deadly 1896 and 1911 New England heat waves. Since I have been to both Boston and also to the Pacific Northwest many times, I should thank you for caring enough about me to point that out. What have you to inform me about regarding this report that follows?
    Heatwave of July 1936
    The “Dust Bowl” years of 1930-36 brought some of the hottest summers on record to the United States, especially across the Plains, Upper Midwest and Great Lake States. For the Upper Mississippi River Valley, the first few weeks of July 1936 provided the hottest temperatures of that period, including many all-time record highs (see tab below).
    The string of hot, dry days was also deadly. Nationally, around 5000 deaths were associated with the heat wave.
    In La Crosse, WI, there were 14 consecutive days (July 5th-18th) where the high temperature was 90 degrees or greater, and 9 days that were at or above 100°F. Six record July temperatures set during this time still stand, including the hottest day on record with 108°F on the 14th. The average high temperature for La Crosse during this stretch of extreme heat was 101°F, and the mean temperature for the month finished at 79.5°F – 2nd highest on record.

  27. 77
    Jan says:

    Hello Folks,

    so i took a look at the real stuff – highly interesting! When i learned one thing in my endeavor to understand the Earth System: Its always the behavior in the real world that is the main thing.

    This Website is the tool to understand the coupled atmos/ocean circulation systems of Earth besides the theories:,9.88,401

    The 250hPa layer is quite interesting. Here best you go back to Mai 2021. Nice to see how the southern double jet structure disturbes and modulates the northern jet. First the northern jet gives birth to the southern structure by splitting up over the central North Pacific and later the southern structure of the jet disturbs again the northern jet more to the east some days in advance of the event. So the double jet structure was obviously involved in this event which is said to increase in occurrence – so QR theory applies not literally here but the main principle holds true – the southern jet disturbs the northern one – and nice to see how it goes both ways as all (tele)connected subsystems function in the Earth system!

    Further on the 500hPa level it is highly interesting to see how an air mass is advected from the tropical Atlantic over the Amazon to travel along the North American west coast up right to the area of the heat wave. This happened till the 24.06.2021 – then conditions calmed in this layer till 29.06.2021. So my question would be here to the experts – was this air mass involved in the heatwave? Was it part of the high pressure system of the heat wave? Because this air mass could have created some extreme adiabatic heating over the region.

    Further of interest is the 850hPa and 1000hPa level – here in the advance of the event close to nothing was happening in the area of interest besides the air from the Pacific was blocked at the coast, so it could not reach the American Northwest during the time of the heatwave and in advance of the event – what is of interest here is that in the eastern and western North Pacific marine heatwaves increase non-linearily because of circulation changes (e.g. decreasing mixing events during winter, cold air outbreaks from the Arctic etc.), decreasing mixed layer depth and increases in stratification across the North Pacific – all good precorsors for marine heatwaves. So the marine heatwave in the eastern North Pacific in 2021 was maybe also involved – dry conditions over the area of interest by blocking moist air from the ocean to reach the continent in advance of the event.

    Play a little around with the animation and look at how the heatwave evolved at the different levels of our atmosphere…

    My personal opinion: it took our novel climate system 5 years to produce such an extreme event over the area (2019 something similar happened over western Europe) after the warming jump of 2012 to 2016. So my first guess would be that this is the median time for such events to occur under present-day climate because several precursors of this event were not exceptional but quite common under today’s climate (see link) – but the future will show!

    Here is the first attribution study on the event which is also interesting to read:

    All the best


  28. 78
    Jan says:

    Sorry Gavin to keep on commenting, but the issue with the new scale of extremes happening across the NH since 2016 is vital to understand what is coming at us.

    The event of 2021 was preceded by the heatwave in western Europe in 2019 exceeding historical max values by several degrees.

    Then in 2020 we had the exceptional heatwave across large parts of Siberia also exceeding past max values by several degrees.

    I ask myself what can produce suddenly temperatures in these latitudes being several degrees hotter than any event in the historical context or even more important the recent past. And for me the only explanation that makes sense besides cloud cover, wind conditions, dryer conditions, and high pressure systems (that we had also in the past) is that air masses come from farther south more northward, because it’s the air closer to the tropics that has the most energy.

    And such events are now common, because they happened 2019, 2020 and 2021. They are not a freak event under today’s climate system, or more precise of today’s circulation system.

    If science makes the mistake to use long time statistics to understand these events and not mechanics we will keep on gravely underestimating climate change, because the knock on effects of these events are frightening.

    The same we see with flooding – just the floodings of the central US in 2019 and the mind blowing scale of the flooding across India, Bangladesh and China in 2020 – what a synoptic scale flooding event! And flooding and Methane seems to be the issue – just one event can produce several million tonns of methane with the current methane increase of ~8ppb being in the range of ~25M tonns – so each Mt of methane more you see in the ppb graph. In 2020 we had an increase of >14ppb – from December 2020 to December 2021 even of >20ppb.

    The same counts for wood fires – for example, in California we reached the prognosis of burned area for 2040 already in 2020 – with 2021 on the track to become even again much more worse. The same we see in the Arctic – and the Arctic has a huge potential to burn.

    If we keep on thinking that all these events were freak events in their own nature we will keep on underestimating climate change to the extreme. Or in short: 1.2°C was to much because the extremes of the last 2 years where not outliers but the new “norm”!

    Here is the link to Siberia: – on this web page you can watch the events unfold in “real” time from a circulation point of view.

    and allways sorry for my slopy writing, but i do not want to spend to much time with my comments – see them as food for thought!



  29. 79
    Adam Lea says:

    62: “Would you characterize a “wavier” jet stream as a more or less energetic state than the “standard” condition?”

    I would say less, because the wind speed in a wavier jet stream tends to be lower. From my experience of looking at upper level charts, it is zonal jet streams which have the strongest winds.

  30. 80
    Anthony Banton says:

    Zebra, Jan:
    I am a retired UKMO meteorologist (on the bench – not research).
    Actually the PJS strength is driven by the DeltaT between the temperate and polar regions – the vertical temp profile through both air-masses having greatest horizontal DeltaT at around the 300mb level.
    There are 2 aspects to it:
    Whilst the PJS has more energy (momentum) when zonal (strong), when the opposite (meridional) applies, further drivers are brought into play.
    Eg: In the case of a Spanish Plume event over the UK where a slowly approaching upper trough (left exit of the JS) overrides warm/moist air sourced from the Spain then the resultant divergence aloft “sucks up” that air as it advects north and the potential instability is released in the form of thunderstorms. If the air is sufficiently warm/moist then self sustaining storms can merge into an extreme rain/lightening areas.
    Of course in a slow moving, wavy JS then weather also can get “stuck” and give prolonged wet, and under the JS ridges heat/drought.
    For an energetic PJS think the Oct ‘87 Storm, where a “Jet streak” of over 200kt overshot a region of baroclinicity (region of horizontal Delta T – often a frontal zone) and the extreme vorticity advection brought by the jet will combine with/induce warm advection and explosive cyclogenesis will occur. Result: extreme winds on the south side of the storm but with the thing rapidly moving away east.

    If anyone is interested in a laugh:
    I recently engaged m’lord Monckton over at the Unmentionable Blog that is WUWT.
    Trolled him rather just to show Denizens the lengths of his obfuscation and lies re the Hu, Wu Et Al 2019 paper on the attribution of GW.
    Credit must go to Nick Stokes for the initial come-back at him.
    He got nowhere of course and must be careful to not go to far as he is a long-term regular there – and though Watts would dearly love to get rid of him, he has given him no excuse to do so. The patience of the man is beyond me!
    Essentially m’lord insists the paper attributes (warming) of only 70% to CO2 and 30% to NV. (It is the partitioning to the modulation of warming through the period that they refer).
    This despite a graph showing that NV ends up zero-sum at the end of the period and CO2 is clearly shown to be 100% of the cause of warming.
    Never expected him to admit fault of course … but the 30% NV contribution to warming that doesn’t exist, magically becomes “little more than 50%” !!
    You just couldn’t make it up.
    There were many “I am most grateful to” s.
    And …. “Is of course correct” s.
    This was post he had authored re the Bode feed-back in an amplifier that he reckons is analogous to climate.
    Just his latest ABCD causation theory snake-oil sold to the faithful there.
    He appeals to “eminent colleagues” for their expertise FFS.
    Several times (I kept at it) he employed his other “Monckton Schtick” of, after a bit, of going/frying, of “And as usual Mr Banton has no discernible scientific input”.
    Couldn’t make it up.

    Anyway if you can stomach it it’s here ….

  31. 81

    According to NASA JPL there will be an extreme coming up soon in sea level height, which will be caused by expected cycling of long-period tidal forces.

    I placed the “wobbling” moon mechanism in context here as the mainstream media placed some spin on it.

  32. 82
    4thCorner says:

    Other useful measures to assess trends in local or global temperature include nightime lows and shifts in the date of budbreak in widely planted shrub and tree species.

  33. 83

    Tamino @ #64 – isn’t that exactly what you did (only you did more) as described in your #35? Only you just split it into “before and after year 2000”

  34. 84
    J Doug Swallow says:

    #51 MA Rodger says something that could have best gone unsaid where MA Rodger feels compelled to begin his dissertation with the usual name calling. He rambles on and ends with this comment; “Thus the 1911 Eastern North America heat wave does seemingly bear some comparison but as a heat wave of considerably less intensity.” I realize that this comment will never be posted by the powers that be on this site that has never come to understand what Walter Lippman so aptly observed; “Where all think alike, no one thinks very much.”

    Over the 11-year span from 1930-1940, a large part of the region saw 15% to 25% less precipitation than normal. This is very significant to see such a large deficit over such a long period of time. This translates to 50 to 60 inches of much needed moisture which never arrived that decade. For an area which only averages less than 20 inches of precipitation a year, deficits like this can make the region resemble a desert. Deficits like this are the equivalent of missing three entire years of expected precipitation in one decade. Figure 2 is a map of the precipitation departures from normal in terms of a percentage of normal (total precipitation divided by normal precipitation) for the Dust Bowl region for 1930 to 1940.

  35. 85
    Michael Corn says:

    If you want to understand Cliff’s motivation, you need only look at the nature of the responses posted on his blog. Most of them are hero-worship, media critics, and climate change deniers as well as people who seem to dislike urban dwellers. While Cliff does not call himself a climate change denier, he is clearly a climate change minimizer. He characterizes the effect of climate change on the Pacific Northwest as modest, making it a bit more pleasant place to live with a longer growing season. In a recent television interview on Northwest Now, Cliff mostly dismissed the depth of the climate change problem by simply saying “These are technical problems we can solve” (pretty close to an exact quote). Cliff mostly refuses to post comments on his blog that are critical of his positions. He generally refuses to post citations to other views as well. There is a reason he has been fired from two different Seattle area public radio commentary jobs.

  36. 86
    Stephen Berg says:

    Regarding Clifford Mass, I would like to say that, yes, his stances on human-caused climate change and the effects of the climate crisis on the planet are very problematic and reduce the momentum towards addressing this emergency. These are major issues that only he can come to grips with as he sees his region burn and melt, though sadly his influence can send some less informed people wayward. However, I will say from a more meteorological perspective that he has done some great work on understanding precipitating systems, particularly in the Pacific Northwest, especially with respect to atmospheric river events and onshore flow patterns.

    This thread has left me with some mixed feelings, as I do respect Dr. Mass’ work quite a bit, but feel very upset over his mischaracterizations of the climate crisis and his dismissal of many of the studies which have shown that this heat wave and wildfire calamity over the PNW and Western Canada are matching to the ‘T’ what climate change modelling scenarios have been showing is far more likely with anthropogenic warming, including the World Weather Attribution study.

    Please, Dr. Mass, begin see the light, like Dr. Richard Muller has.

  37. 87
    Stephen Berg says:

    *That should read “Please, Dr. Mass, begin to see the light, like Dr. Richard Muller has.” (If you can edit this for me, moderators, I would really appreciate it!)

  38. 88
    tamino says:

    Re: #83 (Keith Woollard)

    No. Computing, then analyzing, decadal averages means you end up analysing one data point per decade. Splitting the data into two parts (pre- and post-2000, omitting 2021) doesn’t mean I end up analyzing two data points; I end up analyzing two *sets* of data (of several thousand data points each).

  39. 89
    jacob l says:

    re 64 tamino
    thankyou for your reply!
    The region is north western montana -115.3e by 48.5n
    close to where I live but up in the mountains
    I was thinking that the average caused the error bars to grow faster that the signal. But all things I know about stats indicate that 7 is a small number to being analysis on.
    Though I don’t know much mostly how to get the computer to do the work.
    thanks jacob l

  40. 90
    Jan says:

    Hi Anthony Banton,

    thanks for your reply – especially i do now understand more what a baroclinic atmosphere looks like in reality – in knew the different definitions of both concepts but was not sure about what a baroclinic atmosphere looks like – so frontal zones are one expression of it.

    I always learn through studies the Earth System – so i learn from the top to the bottom – they only explain the great concepts but not the foundations – so i know all the different discussions and theories of the observed changes ;) So one could say that a more merdidonal circulation creates a more baroclinic atmosphere because of greater differencies of the air masses (temp. moisture) crashing into one another happening more often…

    ah and by the i really would be happy if you let people like Cliff or what his name was be and stick to the topic of this heatwave or extreme events in general, because i was hoping to be able here to discuss/learn in this blog from the pros to deepen my understanding of Earth!

    And as a present for you Anthony i link this study which i found quite interesting, besides all the other circulation systems and how they change – it was the final piece to make me understand what the madden-julian-circulation (somehow i refrained for many years to really go into it) really is. And how and why its changing its fascinating ;)

    Also it shows that in terms of extreme events we should really observe what is going on in the oceans in terms of mixed layer depth, stratification, and vertical heat transport and how circulation changes are involved in a two sided fashion of cause of effect! The main issue here: marine heatwaves, droughts and collapsing biomes…

    All the best


  41. 91
    nigelj says:

    J Doug Swallow @84 really seems to confuse things in the most incredible way possible. For example MAR says “Thus the 1911 Eastern North America heat wave does seemingly bear some comparison but as a heat wave of considerably less intensity.” JDS replies I realize that this comment will never be posted by the powers that be on this site that has never come to understand what Walter Lippman so aptly observed; “Where all think alike, no one thinks very much.” Over the 11-year span from 1930-1940, a large part of the region saw 15% to 25% less precipitation than normal. ”

    This JDS guy doesn’t seem to realise heatwaves and droughts are different things. For his benefit heatwaves are unusually hot periods while droughts are unusually dry periods. Or is he high jacking the thread to try to quote every past extreme weather even he can find? Judging by the numbers of similar comments in the borehole he must spend hours, entire days in this pointlessly silly exercise.

    JDS breathlessly quotes the 1930s dustbowl as if this somehow suggests more recent droughts and heatwaves are nothing to worry about or are not influenced by global warming. In fact causes of the 1930s dustbowl were an unusual combination of regional conditions. It means a future event like this could be made EVEN WORSE by global warming. Refer below for causes of the dust bowl.

    The other important thing that JDS cant seem to grasp judging by this post and past nonsensical commentary, is that heatwaves and droughts are weather events or regional climate events of limited duration, but there is evidence modern climate change (oops global warming go keep Zebra happy) is making both heatwaves AND droughts worse:

    And JDS claiming MAR doesn’t think very much. Looks like its JDS that doesn’t think very much. I mean oh the irony.

  42. 92
  43. 93
    MA Rodger says:

    I see the troll J Doug Swallow @84 expresses objection to be called a troll yet happy up-loads his nonsense even though he says he “realize[s]” that his comment “will never be posted by the powers that be on this site.” The censorship of his comments (which are all on display in the Borehole so even when they fail to appear in-thread, the troll fails to “realize” that his comments are always “posted”): the censorship he arrogantly believes is because the points he makes are entirely valid but are at odds with the views of “the powers that be on this site” which presumably he considers to be non-valid views and in need of correction.

    So, hey, maybe after all J Doug Swallow isn’t a troll but instead just incredibly stupid. Certainly he fails to grasp that science is evidentially-based and not simply dreamt up by foolish whimsy.
    Such a conclusion would fit with his comment @84 which again strays from the heatwave in the US West, this time linking to a NOAA web page that compares drought back in the Dust Bowl with drought in the same region a decade ago. I’m not sure of the relevance to the discussion here. The droughts of the 2000s in that region weren’t so bad, certainly compared with the Dust Bowl and also compared with the early 2010s as the NOAA Drought numbers for Texas and Oklahoma show.

    Of course if you want to see signs of scary numbers going in the wrong direction, look no further than the NOAA Drought numbers for US ‘West Region’, a place which actually is experiencing the hot weather under discussion here.

  44. 94
    Willard says:

    > There is a reason he has been fired from two different Seattle area public radio commentary jobs.

    Scratching my own itch:

    We turn to our regular commentators for their expertise and points-of-view when it comes to sports, food and the weather. But if a commentator, even on his own independent platform, delivers rhetoric that is offensive and inaccurate, we cannot support it. This is the case today with Cliff Mass. His post on his personal blog compares recent events in Seattle to Kristallnacht, the 1938 pogrom carried out by Nazi Germany, and draws distorted, offensive parallels between protesters and Nazi Brownshirts. We abhor the comparison and find it sensationalized and misleading — it does not reflect who we are and what we stand for at KNKX.

    Not sure what happened the first time.

  45. 95
    zebra says:

    Thanks to everyone who answered on the jet stream question. I had been thinking “it must be complicated in three dimensions”, and it is even more complicated than I ever imagined. Much to think about.

    John P, yes, the first step is always definitions, and I was intentionally a bit ambiguous to draw out as much information as possible. But let’s just clarify what I was initially visualizing, for a very simplified model.

    When we look at the typical two-dimensional representation, the entity “jet stream” is obviously longer when it is wavy. So how do you guys define the cross-section along the path (which determines the volume), and how does the density vary (if it does) between more meridional v zonal states?

  46. 96
    zebra says:

    Piotr #65,

    Piotr, you like to parse the comments of others but maybe you should read your own words more critically before you post them. From the comment I was critiquing:

    Global warming increases the frequency of heat waves in two ways:
    a) effect of the higher mean: shifting the Gaussian distribution to the right…
    heat waves are stronger, because the same departure starts from a higher mean.

    “The departure starts from a higher mean”???? But you claim you are not confusing the metric with the physics?

    And this is the entirety of what you then said:

    Local weather extremes, being local and short compared to the time-scale of climate (say, 30 years), have negligible contribution to the value of the long-term global average temperature

    say, effect of 1 week of 20C colder than usual weather in Texas (0.7mln km^2):

    (-20C)*(0.7mln km2/510mln/km2)*(7d/(365d/yr*30yr))= – 0.00002 C from the 30-yr average, or -0.0006C from the global avg. temp that year

    So while local weather extremes have negligible contribution to the value of the long-term global average temperature, it is not true the other way around – the global warming does affect local weather extremes (the 2 distribution effects discussed above).

    So you did all that calculation about how minor the effect of the extreme was on the mean, and you then said “it is not true the other way around”… but now you want to pretend that you weren’t implying again that the shifting of the mean somehow affected the extreme????

    You are, indeed, allowing the Denialists to “own” you, because you adopt their framing when you try to refute their points.

  47. 97
    Reality Check says:

    Cliff Mass July 13, 2021
    Flawed Heatwave Report Leads to False Headlines in Major Media ‘

    Cliff writes
    ‘…claim is not supported in the document or by the rigorous science …in fact, the material in the attribution report contradicts this assertion. I will provide substantial evidence that the heatwave attribution report, which has not been submitted for peer-review, is profoundly flawed, with serious technical and interpretative errors.

    As I shall demonstrate, the study is deeply flawed, does not support the claims in the headline bullets, and has serious scientific and other errors. If submitted to a journal for peer review, it would be rejected.

    It’s funny to me because here is another example of someone getting their nose out of joint because the news media print crappy headlines and are poor at communicating detailed scientific studies. But why blame the study authors for that? Makes no sense to me.

    Besides, the study doesn’t “claim climate change caused the heatwave” anyway. Ít’s far more nuanced than that, as many here would already know.

    The way I read it, the major emphasis of their study analysis findings is found on page 30-31

    Although this extreme heat event is still rare in today’s climate, the analysis above shows that the
    frequency is increasing with further warming. A number of adaptation and risk management priorities that
    emerge as the risk of extreme heat continues to rise locally and around the globe. It is crucial that local
    governments and their emergency management partners establish heat action plans to ensure well
    coordinated response actions during an extreme heat event – tailored to high-risk groups (Ebi, 2019)

    In other words, starting to warn the most
    vulnerable early as temperatures start to rise
    , this can include temperatures at which the general
    population is not yet acutely at risk. In cases where heat action plans and heat early warning systems are
    already robust, it is important that they are reviewed and updated to capture the implications of rising
    – every five years or less (Hess and Ebi, 2016).

    AS Cliff notes himself — The final section “Recommendations” promotes policy changes and specific adaptation recommendations.

    Which were sane, rational, responsible actions at that.

    Seems to me it wasn’t only the ‘news media’ that missed the main point, Cliff did too. Yet being öf the media” himself he’s still shocked and surprised that news media headlines do not present the nuanced analysis of a 31 page paper? Wow. Who knew the media are unreliable and can OVER-HYPE and Over-Emphasize cherry-picked aspects far beyond reason and miss the main take-away points.

    Bloggers do too. But there’s nothing like a good beat up to attract attention to a cause or oneself.

  48. 98
    Anthony Banton says:

    Just thought I’d share this Gavin.

    I posted this up on WUWT a day or 2 ago from the EPA website.
    Go there today to repost – NOT THERE.
    Go to find it at WU (not there).

    There is still a Google postage stamp however – so see if this posts …–kmiyxlBnmFBPGFpHB7qKo1Ww&usqp=CAU

    This is the address of the Graph …

    Which now returns…
    “Sorry, but this web page is not available for viewing right now”


    [Response: Google takes me directly to – gavin]

  49. 99
    Jean-François Fleury says:

    Very nice to see an analysis of what occured about NWP. But actually, the climatic disorders were on a hemispheric scale. There have been also heatwaves in middle-orient, in Russia, in North-West India, in Siberia and there have been almost continuous rains and thunderstorsms above France during May, June and the first half of July with a culmination in France the 19-21 June and an other the 13-16 July in France, Belgium and Germany. Japan has also been well served. Perhaps, it could be necessary, and welcomed, to enlarge the scale of your analysis instead of limiting it to the territory of NWP.

  50. 100
    Susan Anderson says:

    Tamino has a new post!
    Northwest Heat Wave
    btw, these extremes have been so off the charts that the mainstream media is publishing multiple articles including attribution almost every day now. I could post some links I collected if anyone wants: most likely nobody here really needs them.

Leave a Reply

Comment policy. Please note that if your comment repeats a point you have already made, or is abusive, or is the nth comment you have posted in a very short amount of time, please reflect on the whether you are using your time online to maximum efficiency. Thanks.