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The International Meeting on Statistical Climatology

Filed under: — rasmus @ 6 July 2019

The weather forecast looks sunny and particularly hot from Sunday to Friday, with afternoon temperatures above 30°C every day, and likely exceeding 35°C by the middle of the week. One consequence is that the poster sessions (Tuesday and Thursday) have been moved to the morning as they will be held outside under a marquee.”

 

I have never received a notification like this before a conference. And it was then followed up by a warning from the Guardian: ‘Hell is coming’: week-long heatwave begins across Europe.

 

The heatwave took place and was an appropriate frame for the International meeting on statistical climatology (IMSC), which took place in Toulouse, France (June 24-28). France set a new record-high temperature 45.9°C on June 28th, beating the previous record 44.1°C from 2003 by a wide margin (1.8°C).

 

One of the topics of this meeting was indeed heatwaves and one buzzword was “event attribution”. It is still difficult to say whether a single event is more likely as a result of climate change because of model inaccuracies when it comes to local and regional details.

 

Weather and climate events tend to be limited geographically and involve very local processes. Climate models, however, tend to be designed to reproduce more large-scale features, and their output is not exactly the same as observed quantity. Hence, there is often a need for downscaling global climate model results in order to explain such events.

 

A popular strategy for studying attribution of events is to run two sets of simulations: ‘factual’ (with greenhouse gas forcing) and ‘counterfactual’ (without greenhouse gas forcings) runs for the past, and then compare the results. Another question is how to “frame” the event, as different definitions of an event can give different indicators.

 

Individual heatwaves are still difficult to attribute to global warming because soil moisture may be affected by irrigation wheras land surface changes and pollution (aerosols) can shift the temperature. These factors are tricky when it comes to modeling and thus have an effect on the precision of the analysis.

 

Nevertheless, there is little doubt that the emerging pattern of more extremes that we see is a result of the ongoing global warming. Indeed, the results presented at the IMSC provide further support for the link between climate change and extremes (see previous post absence of evidence).

 

I braved the heat inside the marquee to have a look at the IMSC posters. Several of them presented work on seasonal and decadal forecasting, so both seasonal and decadal prediction still seem to be hot topics within the research community.

 

A major hurdle facing decadal predictions is to design climate models and give them good enough information so that they are able to predict how temperature and circulation evolve (see past post on decadal predictions). It is hard enough to predict the global mean temperature (link), but regional scales are even more challenging. One question addressed by the posters was whether advanced statistical methods improve the skill when applied to model output.

 

A wide range of topics was discussed during the IMSC. For instance, how the rate of new record-breaking events (link) can reveal trends in extreme statistics. There was one talk about ocean wave heights and how wave heights are likely to increase as sea-ice retreats. I also learned how severe thunderstorms in the US may be affected by ENSO and climate change.

 

Another interesting observation was that so-called “emergent constraints” (and the Cox et al, (2018) paper) are still debated, in addition to methods for separating internal variability from forced climate change. And there is ongoing work on the reconstruction of temperature over the whole globe, making use of all available information and the best statistical methods.

 

It is probably not so surprising that the data sample from the ARGO floats shows an ongoing warming trend, however, by filling in the spaces with temperature estimates between the floats, the picture becomes less noisy. It seems that a better geographical representation removes a bias that gives an underestimated warming trend.

While most talks were based on statistics, there was one that was mostly physics-based on the transition between weather regimes. Other topics included bias-adjustment (multi-variate), studies of compound events (straining the emergency service), the connection between drought and crop yields, how extreme weather affects health, snow avalanches, precipitation from tropical cyclones, uncertainties, downscaling based on texture analysis, and weather generators. To cover all of these would take more space than I think is appropriate for a blog like this.

 

One important issue was about data sharing which merits wider attention. The lack of open and free data is still a problem, especially if we want to tackle the World Climate Research Programme’s grand challenges. European and US data are freely available and the Israeli experience indicate that open access is beneficial.

127 Responses to “The International Meeting on Statistical Climatology”

  1. 1

    Hi Rasmus,

    we published the results of our attribution study of that heat wave last Tuesday at https://www.worldweatherattribution.org/human-contribution-to-record-breaking-june-2019-heatwave-in-france/ , inclusing a full write-up of the problems we encountered in matching observations and climate models. It was a perfect illustration of my talk “Attributing heat waves is hard”, as you also mention.

    Geert Jan

  2. 2
    mike says:

    event attribution? you don’t need a weatherman to know which way the wind blows.

    I think the focus on attribution is a successful framing of extreme weather events by the merchants of doubt.

    Warm regards

    Mike

  3. 3
    Mr. Know It All says:

    Heat waves have always occurred around the world.

    Recently, there was a heat wave in Alaska. Some local temperature records were set, but the 1915 state record high of 100 F remains. Inconvenient fact: 1915, had essentially PRE INDUSTRIAL CO2 concentrations. The record cold temperature, -79.8 F, occurred in 1971. Inconvenient fact: CO2 concentrations were significantly above PRE INDUSTRIAL levels in 1971. Both records occurred in the interior of the state, known for it’s extremes. Source:

    https://en.wikipedia.org/wiki/U.S._state_temperature_extremes

    The recent heat wave affected mostly south central Alaska around Anchorage. Local records were broken but the records replaced occurred on dates in 1926, 1953, and 1969 – long before current CO2 levels. Source:

    https://www.oregonlive.com/environment/2013/06/unusual_heat_wave_strikes_alas.html

    In conclusion, record heat waves cannot be attributed to AGW, since they have occurred long before CO2 concentrations began to rise. We are running cool here in the PNW – 60s and 70s – lower than normal.

  4. 4
    rasmus says:

    Yes, it’s true that heatwaves have been around before, but your reasoning is flawed. It is the character of such heatwaves that is changing: their frequency and their intensity. We can gauges this change trough record-breaking statistics.

  5. 5
    rasmus says:

    The real question is if the particular event is a result of the global warming/climate change, or if it just as easily could have happened if there was no climate change.

  6. 6
    Nemesis says:

    Don’t ignore the drought, it’s just devastating, millions of trees are dying all over Europe, trees contribute to weather and precipitation as well, take away the trees and you will get more heat, more drought. Farmers are suffering badly too. And we will get ugly fresh water scarcity in the near term future.

    You know, the northern hemisphere speculated to PROFIT from climate heating, harr harr, what a joke, what an ignorant, selfish delusion :) Why should only India, Pakistan, Africa ect suffer from climate heating? Bring on the heat, bring on the drought to the belly of the beast (namely Europe, the US, Australia et al), I like to see that climate heating (and it’s harsh consequences) is for everyone, I call it:

    Justice.

    Cheers from Germany.

  7. 7
    zebra says:

    #5 rasmus,

    The real question is if the particular event is a result of the global warming/climate change, or if it just as easily could have happened if there was no climate change.

    I think the real question is why you guys with advanced educations involving physics continue using language that plays into the Denialist game-plan.

    I would ask you to apply your expertise to this simple thought experiment:

    On a parallel Earth, all history is identical. Humans evolve, expand, develop agriculture and industrial technology, exactly as we know it, quantitatively and qualitatively.

    But in this parallel universe, carbon that has fossilized and been extracted, when burned, produces a CO2 that does not absorb radiant energy.

    So, what is the probability that the exact “particular event” under consideration would occur on that planet?

    To me, this is a question that does not require running a complicated model or fancy statistical analysis on past events. I would say that it is effectively zero, given that that planet’s climate system will have had a different history with respect to the amount of energy retained over the preceding time period.

    Do you disagree?

    Why is there this reluctance to be more precise and clear about what we definitively know and don’t know?

  8. 8
    rasmus says:

    Good point. There is no doubt that climate change is causing more extreme weather events, and when you look at patterns of record-breaking temperatures, then the probability is essentially zero. But the calculations must be done the proper way. You may object to attempts attributing single events, however, there are groups that that do that, and this was discussed at the IMSC. And what’s the point of attributing single events when there may be exceptional freak events? I guess it’s to indicate whether it is something we can expect more of in the future. After all, it is the emerging pattern of severe weather conditions that we need to prepare for.

  9. 9

    #3, KIA–

    What this post essentially says is “Because not all records have fallen in a perfectly uniform pattern, therefore nothing unusual is happening.”

    Of course, that’s just silly. There are many thousands of weather stations, and weather is highly variable in the first place. So of course there are going to be exceptions and outliers to the overall pattern. Always have been, always will.

    But what matters is that overall pattern, which is that we observe warming pretty much everywhere in the world, and as a natural consequence we consistently see many more record highs being set that record lows. And yeah, that goes for Alaska, too–and in fact, more strongly than most US locations, thanks to Arctic amplification.

    Let’s take as an example that Anchorage location cited. There’s a list of top 10 warmest/coolest dates for the month of July available here:

    https://w2.weather.gov/media/afc/July%20Climate%20Records.pdf

    The other months are similarly available, too, of course, but let’s keep it straightforward by looking at the current month.

    An understandable way of analyzing these numbers would be to ‘bin’ them by decade. That is, we just count how many top 10 warmest/coldest days or months–we’ll look at both daily and monthly records–fall within a given decade, and see what falls out.

    First, here’s a list of daily highs and lows by decade, with the lows in parentheses.

    Daily Highest (Lowest)

    50s: 1 (5)
    60s: 2 (1)
    70s: 2 (1)
    80s: 1 (1)
    90s: 1 (0)
    00s: 2 (1)
    10s: 1 (0)

    Whereas the distribution of record highs is fairly flat across the decades, the same cannot be said for the lows, which are clearly skewed toward the 1950s. It appears that Anchorage has been seeing rising daily minimums.

    (Of course, the numbers for July 2019 have yet to be determined, so the ’10s’ are missing potential data points relative to the other decades. Probably should have done June for that reason, but whatever.)

    More interesting yet, and probably much more indicative are the monthly highs, because the averaging should decrease the overall variability. Here’s the list, in the same format:

    Monthly Highest (Lowest)

    50s: 0 (3)
    60s: 0 (0)
    70s: 1 (1)
    80s: 1 (2)
    90s: 2 (0)
    00s: 3 (2)
    10s: 3 (1)

    Here we see a clear trend on the warm side: neither the 50s nor 60s even show up in the list, and of 10 warmest years, 6 occurred this century. On the cool side, the 50s are the leading decade, accounting for 3 of 10 places in the top 10. Overall, 7 of the top 10 coolest years occurred in the last century.

    With apologies to Bob Dylan, you don’t need a statistician to see which way the trend goes.

  10. 10
    zebra says:

    #8 rasmus,

    Thanks for your response, but I guess we disagree.

    I conclude that the probability of a particular event absent the effect of CO2 is zero, based on the effect CO2 does have on the net energy balance of the climate system. There is no question of “proper” calculations or “looking at the patterns of record-breaking temperatures”. It is trivially obvious that a system which can be influenced by (metaphorical) butterfly wings is not going to produce the identical output under such a different input.

    I don’t object at all to the academic exercises that some may engage in, but to how this topic is communicated.

    You (not just you personally of course) keep using language that confuses cause and effect. It makes no sense to talk about “the link between climate change and extremes”, because events in aggregate is the climate. A lot of extreme events is climate change; it is not the cause of climate change.

    What exactly is the objection to saying “the link between extreme events and the increased energy in the system caused by CO2”? In my experience educating “the public”, that is something they would easily understand and accept (tribal politics aside). And further explanation would be much easier.

  11. 11
    mike says:

    you say: “The real question is if the particular event is a result of the global warming/climate change, or if it just as easily could have happened if there was no climate change.”

    Zebra and I are in complete agreement. This is the wrong question. It is a distraction and opportunity for the merchants of doubt to market doubt to the unsophisticated.

    Then you say:

    “… what’s the point of attributing single events when there may be exceptional freak events? I guess it’s to indicate whether it is something we can expect more of in the future. After all, it is the emerging pattern of severe weather conditions that we need to prepare for.”

    So, the presentation should be: “we see the recent extreme weather event (insert particulars) in the context of the emerging pattern of sever weather conditions. A single event attribution calculation for this specific event indicates (insert particulars), but single event attribution and analysis is not the best means to assess this event. This recent extreme weather event is best assessed within the emerging pattern of severe weather conditions that arise from global warming.”

    Don’t waste a lot of effort on the single event attribution, move quickly to the pattern of severe weather events that is much more easily attributed to climate change. Avoid discussion of the monetary impact of extreme events as that is an opening for the merchants of doubt to insert changes in built infrastructure that raises costs for current weather events when compared to similar events in the past that happened with less built infrastructure. The issue to raise is the emerging pattern of extreme weather events. If you think droughts, floods, forest fires, heat waves, etc. are great, then global warming is your vehicle. Global warming has changed the pattern of extreme weather events and we have more extreme weather events now on a warmed planet. The data are quite clear on this:

    https://nca2014.globalchange.gov/highlights/report-findings/extreme-weather

    https://www.scientificamerican.com/article/climate-change-and-extreme-weather/

    I am enjoying the cool NW weather that MKIA mentions. It’s too bad that our NW forests are suffering from changes in snowpack and rainfall. I see a lot of trees in native, old growth forests that appear to be stressed by changes in NW water patterns. I think this is part of the emerging pattern of changed weather and it will lead to long term changed in Cascadia.

    Thanks for your work, Rasmus,

    Mike

  12. 12
    DukeSnide says:

    KnowItAll,
    CO2 was rising in 1915, also in 1923, 1956, and 1969.

    How many times can you be completely wrong?

  13. 13
    mike says:

    I think this approach avoids the denialist-preferred framing of single event attribution:

    https://www.carbonbrief.org/frances-record-breaking-heatwave-made-at-least-five-times-more-likely-by-climate-change

    “A preliminary analysis by scientists at the World Weather Attribution network finds that the average temperature of such a heatwave in France is now “4C higher” than it would have been a century ago, the authors say.

    Using climate models, the authors conclude that such an increase in heatwave intensity was made at least five times more likely by human-caused climate change.

    However, they note that there are “large uncertainties” in their analysis and the true influence of climate change could be higher.”

    I don’t think there is anything inherently wrong with looking at single event attribution except that it is a framing that is particularly advantageous to the merchants of doubt.

    Cheers

    Mike

  14. 14
    MarkR says:

    Hi Mr. Know It All, do you support using the same logic to say that deaths cannot be attributed to nuclear bombs, since they have occurred long before nuclear bombs started exploding?

  15. 15
    Hank Roberts says:

    > … drought, … devastating, millions of trees are dying all over Europe

    Ironically, there’s this:

    https://www.smithsonianmag.com/science-nature/forests-around-chernobyl-arent-decaying-properly-180950075/

  16. 16
    DasKleineTeilchen says:

    Heat waves have always occurred around the world

    seriously, MrKIA?!? you really take that road *again*?

    In conclusion, record heat waves cannot be attributed to AGW, since they have occurred long before CO2 concentrations began to rise

    5 “once-in-a-century”-heatwaves in europe in the last 20 years, go figure

  17. 17
    rasmus says:

    Climate can be regarded as weather statistics, and while the butterfly effect plays a role in the unfolding of the weather, we want to assess how changes in the physics influences the statistical characteristics of the weather. Eg the maximum temperatures or rainfall amounts. These statistical traits are often predictable and give an indication of risks associated with the weather.

  18. 18
    Dan says:

    KIA,
    Your continued failure to understand climate science is appalling. You are on a web site run by climate scientists yet you think somehow you know something that thousands of peer-reviewed climate scientists do not. That has been pointed out to you umpteen times yet you make no effort to learn. Epic critical thinking failure, junior. Read the peer-reviewed science. Specifically, the Bulletin of the American Meteorological Society which last year documented specific events which were either caused or enhanced by global warming. Including heat waves. Stop flaunting your scientific ignorance and failure to learn. Obviously you can’t admit to being completely wrong. Insecurity will do that.

  19. 19
    Russell says:

    4.
    Right, but some memorable events may have had ancillary anthropogenic causes unrelated to contemporary climate forcing.

    Ihe summer of 1915 was a real scortcher in Siberia, but besides dessication, the proximate cause of the forest fires that devastated hundreds of thousands of square kilometers may have been the lack of Smokey The Bear billboards along the newly opened Trans-Siberian Railroad .

  20. 20
    Mr. Know It All says:

    5 – rasmus
    “The real question is if the particular event is a result of the global warming/climate change, or if it just as easily could have happened if there was no climate change.”

    Thanks for the reply, but that’s a trick question. :) As I pointed out, there have always been heat waves for as long as humans have been around, probably since day 1. And there has always been climate change. Change is the only constant in the universe. Some adapt and survive. Some don’t.

    But my previous comment answered your “real” question. Yes, similar heat waves have occurred many times before what we are now calling climate change (AGW) existed. ;)

  21. 21
    Dan Miller says:

    I will repeat my comment from another thread since it is appropriate here…

    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.

    Note that this method of attribution does not use models… it is based solely on temperature records.

    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.

  22. 22
    rasmus says:

    This is a claim that must be backed up with data and analysis. So far, the numbers indicate that it is not the case.

  23. 23
    rasmus says:

    You can check the data on https://ocdp.met.no. With all the data, you can find some cases with heatwaves in the earlier times, but point is that the pattern (occurrence) of such extremes have changed and that they now are more common. This is the also an underlying factor of the the event attribution.

  24. 24
    Nemesis says:

    @Hank Roberts, #15

    Hehe, so ironically, the environment around Chernobyl does NOT recover as many claimed. But I don’t see any connection of the Chernobyl catastrophe (want more nuclear power to “save the planet?”^^) in 1986 and the devastating drought in Europe^^ The trees all over Europe simply dry out, two extreme drought years in a row, ever more soil compaction, the bark beetle (who loves heat and drought) and ever more decreasing groundwater tables is enough to kill the trees. Just have a look at the drought map for Germany:

    https://www.ufz.de/index.php?de=37937

  25. 25
    Al Bundy says:

    Dan,
    It has been pointed out to you umpteen times that KIA is essentially a rock yet you make no effort to learn that attempting to influence a rock is extremely silly. Epic critical thinking failure, junior. (And I resemble that remark frequently)

    :-)

  26. 26

    kia 3: record heat waves cannot be attributed to AGW, since they have occurred long before CO2 concentrations began to rise.

    BPL: Forest fires happened naturally for millions of years, so there’s no such thing as arson.

  27. 27
    zebra says:

    #21 Dan Miller,

    Dan, I am just using your comment to illustrate what I have been saying to rasmus about terminology:

    “the shift of the bell curve to the right is, by definition, global warming”

    and

    “there is a 49 out of 50 chance that it [a particular event] was caused by global warming”

    You may say that I am being pedantic or nit-picky on this, but in all the decades I have followed the topic, this kind of language has clearly been an aid to the Denialists in their attempts to obfuscate the science. We here know what you are trying to say, but you can’t expect the public to sort it out.

    As I asked rasmus, why is it so difficult for people with a scientific background to just consistently begin with the fact that CO2 has caused the total energy in the climate system to be higher than it would be without CO2?

    What rasmus says at #17 is fine for me, if prefaced with that.

    I would say that the shift in the bell curve is caused by the increase in system energy, and the increased probability of the particular EHS is caused by the increase in system energy. Much less confusing to the public, and much less open to misleading nonsense from the Denialists.

  28. 28

    One does not have to show that extreme heat has occurred, but only that the frequency of these events appears to be accelerating. For example, a study of hailstone sizes and their damages in North America over the last 5-6 decades reveals a significant trend: “However, 5 of the nation’s 10 most damaging hail events since 1950 occurred during 1992-2006 (Changnon, et al., 2009). http://webh2o.sws.uiuc.edu/pubdoc/CR/ISWSCR2009-12.pdf.

    Large hailstone sizes, say, above 2.0 to 2.5 cm, need further study on a world-wide basis.

  29. 29

    BPL, #26–

    “BPL: Forest fires happened naturally for millions of years, so there’s no such thing as arson.”

    Just so. Is there already a formally named “Fallacy of single causation?” ‘Cause if not, I’m calling dibs!

  30. 30
    Tony Loman says:

    I am a social scientist. People in my profession use case studies to illustrate causal relations that have been established or at least strongly suggested statistically based on many individual observations. Event attribution reminds me of this. A high temperature event, a flood caused by intense rainfall, an extended drought are all case examples. Attributing extreme events to climate change is not illogical as some here have suggested–go read one of the methods papers freely available on the web. But single events are ultimately not convincing by themselves because counterexamples can always be found, like some that have been mentioned by commenters. The stronger arguments come from analysis of changing frequencies, like increasing rates of intense rainfall events, increasing frequencies of high temp events, etc. and the use of inferential statistics. This is what Rasmus is saying in comment 17, I think. Event attributions are useful, in my opinion, but to be convincing they must be placed in the context of broader analysis of statistical patterns and the physics of climate change.

  31. 31
    Jim Eager says:

    By using the false logic gambit of “heat waves (droughts/forest fires/floods/hurricanes) happened long before CO2 concentrations began to rise” KIA demonstrates himself to be either a clueless fool impervious to facts and logic, or a wilfully devious disinformer determined to ignore facts and logic. Either way his posts belong in the Bore Hole.

  32. 32
    Dan says:

    re: 25.
    Al,

    I too resemble that remark! :-) However, I will never let someone who flaunts their ignorance over and over again (whether science or supporting hate re: the Pittsburgh shooter who was one of his brethren) just repeat their lies, as if it somehow gives him more validity. His failure to learn is inexcusable, whether he is granite or quartz! :-)

  33. 33
    Dan Miller says:

    #27 Zebra

    “the shift of the bell curve to the right is, by definition, global warming” comes from Jim Hansen and is accurate. The shift shows that the global temperature has increased and, therefore, the globe is warming. QED. It does not claim what caused the warming. If your body temperature rises by 3ºC, we can say you have a “fever” even if we do not know what caused the fever.

    I agree with you that the buildup of greenhouse gases in the atmosphere causes more energy to build up in the Earth system and this this is what has caused what we call “global warming” and “climate change”.

    But it is still correct to say that a 3-sigma Extremely Hot Summer has a >98% chance of being caused by “Global Warming”, “build up of energy in the Earth system”, or “manmade release of GHG into the atmosphere.”, though to show the connection to humans the statement does require more back up to show the link between the release of GHG and the warming.

  34. 34
    Al Bundy says:

    Zebra,
    It astounds me that you expect folks with advanced degrees to be sentient. It is obvious that 99.999% of humans are not sentient, and well over 1% of humans have advanced degrees.
    Then factor in that MOST humans are motivated by self-enrichment and self engrandizement, and that the rich can illuminate the doofuses who enrich the rich…

    And yet you all wonder why the system you all agree is the be all and end all doesn’t work.

    DUH! Because it’s a stupid system designed by morons who wanna be gods.

  35. 35
    zebra says:

    #33 Dan Miller, #30 Tony Loman,

    Sorry Dan, it is not correct to say:

    1. The shift of the bell curve to the right is global warming.

    and

    2. The 3-sigma EHS has a 98% chance of being caused by global warming.

    That’s because you are now saying that the event was caused by the shift of the bell curve. Events are not “caused by” statistics, they are caused by physics. In fact, that bell curve is derived from the aggregate values of the very individual events you are talking about, right?

    My general critique, that includes Hansen and others, not just rasmus and Dan, and filters down to the news reporters, is that at this point people keep employing the terms “global warming” and “climate change” inconsistently, and confusing the discussion. To me, it seems much clearer to say:

    1. The increased probability of the individual EHS is caused by the increased system energy.

    and therefore

    2. The shift in the bell curve is caused by the increased system energy.

    Please feel free to explain what is “wrong” with this statement.

    Tony,

    I said that I was fine with rasmus #17 if it were prefaced by:

    “Anthropogenic CO2 has caused the total energy in the climate system to be higher than it would be without that CO2.”

    Which, as you say, establishes context.

    Perhaps, as a social scientist, you could give an opinion about this communication issue I am raising. You say:

    “But single events are ultimately not convincing by themselves”

    Convincing of what?

    That to me is the crux of the problem.

  36. 36
    Killian says:

    Hello Rasmus,

    I didn’t have the patience to wade through all the comments as zebra’s was enough to make my head explode and mike’s was in the ballpark of what I want to say. Zebra is correct in that the framing is off, but his/her how is also off.

    The real issue with attribution is no one event can really be proven to *just* be climate. And climate doesn’t work that way; it’s basically weather at the meta scale.

    What is important for attribution is that EVERY event can, and should be, assumed to be affected. That is, attribution is really about *magnitudes* of events, not causes of a given event, per se.

    This simple shift in framing also makes the case much easier to make.

  37. 37
    Adam Ash says:

    Well this nice positive feedback example shoves the curve another notch to the right, to (wink) difficult to attribute it to anthropogenic forcings.

    Unprecedented Arctic megafires are releasing a huge amount of CO2

    https://www.newscientist.com/article/2208610-unprecedented-arctic-megafires-are-releasing-a-huge-amount-of-co2/

  38. 38
    Nick O. says:

    #3 – Mr Know It All, also elsewhere under other numbers and as ‘Mr KIA’

    A question for you, if I may.

    Do you think it possible that human kind could ever, by whatever means, change the climate of the Earth?

  39. 39
    Mr. Know It All says:

    32 – Dan
    “…I will never let someone who flaunts their ignorance over and over again (whether science or supporting hate re: the Pittsburgh shooter who was one of his brethren) just repeat their lies,…”

    Ditto here, so let us review some facts and dispel yours:

    https://www.usatoday.com/story/opinion/2018/10/29/donald-trump-robert-bowers-racist-anti-semitic-synagogue-shooting-column/1800755002/

    LINK TO DODGY BLOG REMOVED BECAUSE IT WAS INAPPROPRIATE AND NOT RELEVANT – please behave (Rasmus)

    26 – BPL
    Record heat waves could be caused by AGW, but they may also be caused by whatever has always caused them – perhaps the same forces that caused the ice age to end. We know who starts many forest fires – the big guy in the sky. ;)

    28 – Donald
    “…For example, a study of hailstone sizes and their damages in North America over the last 5-6 decades reveals a significant trend: “However, 5 of the nation’s 10 most damaging hail events since 1950 occurred during 1992-2006 (Changnon, et al., 2009).”

    Perhaps our exploding population, a much discussed topic here, has resulted in a larger percentage of the land occupied by humans so more hail storms and damage are recorded. In the 60s there was a hail storm in the Midwest that dumped baseball and softball sized hail stones. My grand parents kept some in their freezer to show us. I have not seen any even close to that size since then.

  40. 40
    Victor says:

    Excuse me, but what exactly is meant by the term “climate change”? And what exactly are extreme events being attributed to when we attribute them to “climate change”?

    Yes, as seems clear, it is now roughly 1 degree celsius warmer, worldwide, than it was in 1900, as indicated in, for example, the following graph, one of many that could be cited: http://berkeleyearth.org/wp-content/uploads/2019/01/GlobalAverage_2018.png. Just about everyone is in agreement on that, including the great majority of skeptics.

    So what, exactly, was the purpose of the conference you attended, Rasmus? If most attribution studies agree that there is some sort of trend toward more extreme weather events, based on an increase in temperatures over the last 120 years or so that hardly anyone denies, then what, pray tell, is the point? The attribution studies you mention focus on the (presumed) effects of temperature increments of fractions of a degree over a very long period. One can’t help but wonder how such tiny increments over such a long period could have such devastating effects, but perhaps they do. So what does that tell us? As far as I can tell, the attribution studies you’ve referenced tell us nothing about what has caused the temperature to rise. But since the term “climate change” seems to have CO2 emissions built into it, the two are assumed to go hand in hand.

    If you want to demonstrate not only that increased temperatures are causing weather events to be more extreme, but also that CO2 emissions are causing the temperatures to rise, and are thus the ultimate cause of the alarming trends you’ve identified, then it is necessary to establish a clear and consistent correlation between the two. None of the studies you’ve referenced appear to have bothered with that little detail, as though it could simply be taken for granted.

    I see this same confusion arising over and over again, in both the scientific literature and the popular media. “Climate change” may or may not be responsible for extreme events, there may or may not be a significant trend in the direction of a temperature-induced increase in extreme events. But only very rarely do I see any attempt to link such claims to CO2 emissions in any systematic manner. In far too many cases the link is simply assumed.

  41. 41
    Dan Miller says:

    #35 Zebra:

    I believe you agree that the increase in global average temperature (i.e., “Global Warming”) is caused by increased system energy. So I can use those terms interchangeably in this context. Of course, just saying something is caused by increased system energy begs the question of what caused the energy to increase. I assume/hope you agree that the primary cause of the increased system energy is the increase of atmospheric greenhouse gases due to the burning of fossil fuels. So the actual 98% “cause” of the EHS is the burning of fossil fuels (and the other things humans did to cause increased system energy and global warming).

    Just using the phase “increased system energy” does not inform the public about the cause of the increase in EHS and, therefore, is not particularly useful.

    If a bomb goes off, the media should not report it as an “increase in localized energy”.

  42. 42
    William B Jackson says:

    Am I alone in thinking perhaps Mr KIA doesn’t? False equivalence seems to be his stock in trade!

  43. 43
    Killian says:

    Re #30 Tony Loman said But single events are ultimately not convincing by themselves because counterexamples can always be found… The stronger arguments come from analysis of changing frequencies, like increasing rates of intense rainfall events, increasing frequencies of high temp events, etc. and the use of inferential statistics. This is what Rasmus is saying in comment 17, I think. Event attributions are useful, in my opinion, but to be convincing they must be placed in the context of broader analysis of statistical patterns and the physics of climate change.

    Agreed. The overall enhancement of typical patterns is more accurate than attributing whole events.

  44. 44
    rasmus says:

    The purpose of IMSC is to discuss and share climatological analysis and work on statistics, and climate change is just one subtopic. There is also a field known as detection and attribution, which involves both identifying trends and changes and finding their causes. Regardless of cause, it is important to detect trends in order to be prepared. When it comes to attributing to man-made climate change, one usually uses simulations with climate models that include and exclude the suspected forcings/causes.

  45. 45
    libertador says:

    #10 Zebra
    “I conclude that the probability of a particular event absent the effect of CO2 is zero, based on the effect CO2 does have on the net energy balance of the climate system. There is no question of “proper” calculations or “looking at the patterns of record-breaking temperatures”. It is trivially obvious that a system which can be influenced by (metaphorical) butterfly wings is not going to produce the identical output under such a different input.”

    I think attribution science does something else, than you describe. They define a specific event type, for example a heat wave as temperatures exceeding a certain value in a specific region relative to season. Such an event type does not a probability of zero to occur in a nonchanged climate. To be relevant such research has to carefully define event types, in order to properly define event types of relevant interest.
    Further one could ask the question in which way the more specific event is influenced by a changed climate state. For such different kind of research see e. g.: http://dx.doi.org/10.1038/nclimate2657.

  46. 46
    zebra says:

    Dan, right there in the part of #35 addressed to Tony, and in earlier comments, I emphasized the need to first connect the increase in energy to the increase in CO2.

    But you are still making a very fundamental error in your language and/or reasoning here. And it is the same error that Denialists like KIA and Victor employ (see just above) to obfuscate the issue. (Thanks, guys, for helping me make my point.)

    You define Global Warming as the increase in GMST. But the increase in GMST is a statistic, just like the shift in the bell curve discussed in #35; it can’t be a cause for individual events. Both statistics are derived from the individual events and measurements.

    It is understandable that the language got sloppy when people started communicating about the subject decades ago, but this is now a mature science, and there should be standard definitions that everyone agrees to use consistently… and in particular, they should be provided to journalists.

    To put things in context, as Tony said, so people can understand what’s happening, we need to articulate the causal chain correctly. (And more often.)

    So, the level of CO2 determines the system energy, and the system energy determines the value of whatever individual measurements we make, all else being equal. (see #7)

    The mechanism by which higher system energy affects the individual metric is first explained by physics; then, as rasmus says, we develop statistics to allow us to make predictions about future consequences. The attribution exercise is part of that latter process.

  47. 47

    V 40: One can’t help but wonder how such tiny increments over such a long period could have such devastating effects, but perhaps they do.

    BPL: Here’s a hint. The mass of the atmosphere is 5.148 x 10^18 kilograms (Trenberth and Smith 2005). Its heat capacity is about 1,006 J/K/kg. So a 1 K increase in its mean temperature means 5.179 x 10^21 joules of energy have been added to the system. At 4.184 x 10^6 J/kg, this is the equivalent of 1.238 x 10^15 kg of TNT, or 1.238 million megatons, the equivalent of 61,900,000 times the energy of the bomb that leveled Hiroshima.

  48. 48
    Mr. Know It All says:

    38 – Nick
    “Do you think it possible that human kind could ever, by whatever means, change the climate of the Earth?”

    Sure, I even believe CO2 may be contributing to warming. I also think there could be other reasons for warming since global warming and cooling have occurred since the earth was formed. Extreme weather events which have occurred occasionally throughout all of recorded history such as floods, hurricanes, heat waves, tornados, snow storms, cold snaps, hail storms, cannot be attributed to AGW because they also occurred before AGW.

    If I believed the warming was 99% AGW, I still would not give the left political power to solve it because of all the damage they would do with that power. If AGW is real, soon it should be apparent to everyone and we will deal with it. I also think it’s possibly part of the big plan that HE has for us. If so, it is even possible that we can’t solve it.

    Thus, in answering your question, I have also answered the question from Mr. Jackson in 42 above.

  49. 49
    Karsten V. Johansen says:

    The discussion about rethorics is not without importance. The main thing is to keep focused on what decides our fate as a human society. To know what we are talking about and trying to achieve.

    The fenomenon we call or subsume under the word climate does not know what we think when we use the word or other words. It doesn’t care. The laws of nature just react to what we are doing. We are in dire need to at last leave the illusions of the bible (“In the beginning was the word” etc.) behind.

    Extreme weather events are not a result of climate change, this problem is pure fiction, since their averages together with the rest of the weather are what we define as climate change or “global warming” = global heat catastrophe really. We need to use words that give a good and impressive description of the phenomenons in case. Global warming doesn’t. It sounds cosy. A indian peasant dying under the sun in plus 50 degrees C doesn’t feel warm, he feels like in a sweltering hell. Here we encounter as scientists the problems connected with scientific language conventions. The objectification of the language (re)creates the old illusions from the bible word equals reality. In the mathematic language numbers equals reality. Neither is true, far from. Truth is what we experience in real life and death as human beings and, whether we understand it or not, therefore as integral parts of nature.

    A science who helps us as human beings must learn to use a language which calls a spade a spade. This puts that science in deep conflict with our class-society, which hates all talk of the reality when the reality does not money in the “right” pockets. Our society will not speak realistic about the real causes behind fx. the current flooding in Washington and even of the cellar in the white house, because that does threaten fx. the prices in the real estate market. This creates a significant pressure on every scientist working in connection with these phenomenons to so to speak silence his inner voice when it tells him things he knows his upper commendeurs doesn’t like to hear or read. There you have the main problem of all science today in the global crises coming from the frontal collision between our socalled “economic” system, which demands endless exponential growth in use of fx energy and other materials and the natural fundaments of it, which definitely forbids that endless growth (it is only possible in the mathematical phantasies of socalled economists and their bosses).

  50. 50
    Mal Adapted says:

    rasmus:

    There is also a field known as detection and attribution, which involves both identifying trends and changes and finding their causes. Regardless of cause, it is important to detect trends in order to be prepared.

    Thank you, rasmus, for your lucid, thorough explication of the diversity of questions worth investigating in climate science. IIUC, a principal goal of climate-change detection and attribution is to assign a quantitative fraction of weather causation to anthropogenic global warming. Yet even without that, as you pointed out in an earlier comment, climate is represented by the statistics of weather. IOW, we know climate is changing because the ranges and means of multiple weather parameters are changing. And we know from physics that the changes are at least partially due to AGW. That is, we know that all weather is now occurring in an anthropogenically changed climate.

    Certainly, the more we about the causes of extreme weather, the better we can prepare for new extremes. Yet we also recognize that the more ultimate causes of climate change are economic. When we count the social costs of fossil carbon, we count not only a non-zero fraction of the direct costs of extreme weather, but some fraction of the costs of preparation for it. “Lukewarmers”, who acknowledge that climate is changing anthropogenically but claim that “adaptation” is less costly than rapid decarbonization, are overlooking the open-ended character of both direct damages and the costs of preparedness, for at least as long as atmospheric CO2 continues to rise.

    Lukewarmers also overlook the reality that the costs of AGW fall disproportionately on those who make the least contribution to global fossil carbon emissions and have the least resources with which to adapt to hotter heat waves, bigger wildfires, more flash floods and higher storm surges, but that’s another comment.