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Recently, two DKos diaries (http://www.dailykos.com/..., http://www.dailykos.com/...) have taken bitterly opposed viewpoints on how much we should try to link bad weather events to global warming. The actual differences in their viewpoints were, however, rather subtle. I believe we can reach a consensus on this issue. My motivation is partly just to avoid unnecessary friction among the good guys, but I'm also guided by a somewhat different sense of the underlying science.

Let's start with the non-controversial points. I think we all agree that:

1. Anthropogenic global warming is very real, and is going to become much more intense.

2. On general grounds, we know that weather is very sensitive to such effects, so weather patterns are going to change a lot and probably already have changed significantly, in addition to the obvious temperature increases. One systematic change can be predicted with confidence, a world-wide increase in precipitation due to warming oceans.

Now let's look at the parts where the science is a little trickier.

Some of the discussion has centered around distinguishing between individual events and statistical patterns. Causation of individual events is not really worth discussing, because weather is so extraordinarily sensitive to tiny "butterfly" effects that even the smallest change in climate or land use etc. will give an entirely different set of individual storms than would otherwise have occurred.  The only meaningful subject for weather causation arguments is the statistical pattern.

We have seen a lot of claims that there will be more extreme weather, usually implying that there will be more large storms of various types. That may turn out to be true, but the scientific certainty of it is not remotely close to that of the basic warming effect. Global warming actually reduces the temperature contrast between the arctics and the tropics, so it reduces the strength of one of the principal drivers of weather patterns. Claims that AGW increases the net energy flow through the weather system are false. That flow is just set by the total amount of solar energy absorbed. AGW probably slightly increases cloud cover, so it's likely to reduce the net energy flow through the weather system. So this leads to point 3:

3. the calculations about which particular changes to expect in storm patterns are far more uncertain than the global climate calculations. That includes estimates of net number of severe hurricanes, etc.

4. So we don't want to claim that we know the changes in storm statistics are due to global warming with the same confidence that we know what's causing the warming and how much it will grow.

Nevertheless, there's another meaning to the claim that we will see "more extreme weather", captured by the phrase "global weirding". We may not know much about the details of what will happen to storm patterns, but we are very confident that they will change. Therefore:

5. People in most areas will experience weather that's weird, unfamiliar for their area, and for which their infrastructure and habits are unprepared. That's true even if the net number of severe storms worldwide doesn't change.

So when people find persistent weird weather changes, we should be open about saying that such changes could be due to global warming.

It'll be interesting to see if the various people who were slugging it out over this issue can find consensus on these points.

Originally posted to docmidwest on Sun Jun 19, 2011 at 10:32 AM PDT.

Also republished by Science Matters.

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Comment Preferences

  •  It's just a silly pie argument (2+ / 0-)
    Recommended by:
    radmul, docmidwest

    And really, people haven't agreed even on point #1.  Big oil and their minions have been out spreading lies about global warming for decades.  So, don't stop saying it.  We need to do something about it.

    Republicans: Taking the country back ... to the 19th century

    by yet another liberal on Sun Jun 19, 2011 at 10:46:26 AM PDT

  •  Well I'm Seeing Severe Weather With Reduced (6+ / 0-)

    temperature extremes. First large low rotations I ever saw came recently in a sub 80f supercell whose trailing cold air was warmer than 60f. Your statement that a reduction in temperature contrast is an AGW prediction is the first time I for one have seen that, and it comes after several years of puzzled observation of storms after returning to my childhood home from a decades absence.

    Intense low contrast storms are not just unusual, they're novel to my experience anywhere, and as a decades long sailor I've been observing and employing the weather more than the average citizen. Still obviously not a scientist.

    That shouldn't be possible except that AGW also predicts increased moisture levels, and increased atmospheric moisture is a known energy source for storms that could make up for the slack in temperature differential.

    So my practice-based generations long experience with several years of weather is seeing a pattern that fits 2 predictions of climate change, good enough for me to link it as a claim of soft agreement with the predictions as long as I don't use an absolute.

    It's a kind of silly argument in terms of politics because a time in which we might be nearing action is not presently foreseeable. We're not jeopardizing anything helpful by erring on the extreme.

    We are called to speak for the weak, for the voiceless, for victims of our nation and for those it calls enemy.... --ML King "Beyond Vietnam"

    by Gooserock on Sun Jun 19, 2011 at 10:52:07 AM PDT

  •  Clue: Life is not simple (1+ / 0-)
    Recommended by:
    cassandracarolina

    People want simple answers and clear-cut dividing lines. When does a fetus stop being a micro-organism and become a human being? Is the Joplin tornado outbreak due to global warming? 100%? 50%? 1%?

    The real world is complicated, no matter how simple you may be.

    Don't let millionaires steal Social Security.

    by Leo in NJ on Sun Jun 19, 2011 at 11:09:38 AM PDT

    •  simple answers? (1+ / 0-)
      Recommended by:
      palantir

      Maybe for Joplin, we can just say "Not so far as we know" and leave it at that. For Katrina, on the other hand, we can honestly say "These storms might not be dumping so much water if there were no global warming. Between rising sea levels and increased precipitation, AGW is probably going to really fuck up NO."

      Michael Weissman UID 197542

      by docmidwest on Sun Jun 19, 2011 at 11:16:26 AM PDT

      [ Parent ]

      •  Katrina's really not a great example... (1+ / 0-)
        Recommended by:
        palantir

        you have a strong storm (Cat. 3 at landfall) hitting a below-sea-level bowl head on, combined with terrible evacuation management.

        Gets a lot of press.

        But it doesn't really demonstrate anything.  What about last year's Atlantic hurricane season?  No one cares, because nothing big hit the coast.  But it's weather trends that you need to be considering to see if they're real...not individual weather events.

        •  right (3+ / 0-)

          I agree completely that a Katrina-like event could easily happen without any AGW. On the average, however, there's good reason to think that such events are likely to be wetter than they would be with cooler oceans. That's something that people should be interested in. For tornadoes, we don't even know the sign of the relevant statistical changes, if any.

          Michael Weissman UID 197542

          by docmidwest on Sun Jun 19, 2011 at 11:47:16 AM PDT

          [ Parent ]

          •  well, thankfully we haven't had another season (2+ / 0-)
            Recommended by:
            RunawayRose, palantir

            like 2005 since...well...2005--so we can hope the season was a one-off at least for now.  I did read a couple of reports that show that the consensus is for the top-of-the-line hurricanes to strengthen as you're saying, but the overall number to decrease--but no consensus on whether or not that has started--when it will start...etc..

            Guess we'll have to wait and see....

            take an umbrella though.

    •  Basically ... (6+ / 0-)

      My argument is that we need to highlight that extreme weather is occurring within a context of climate disruption / global weirding. That we MUST be discussing this because, far too often, severe weather and extremely 'unusual' weather patterns (multiple 100+ or 500+ year weather events; droughts; heat temperature records; etc ...) are passing without any discussion of climate change. In the general public / policy / political discussion, climate disruption is far under discussed rather than overdiscussed ... even as it remains impossible to point to one specific event and state that it occurred "because of climate change".

      Blogging regularly at Get Energy Smart NOW! for a sustainable energy future.

      by A Siegel on Sun Jun 19, 2011 at 11:21:46 AM PDT

      [ Parent ]

  •  Until coastal cities are underwater (1+ / 0-)
    Recommended by:
    palantir

    those who are too ignorant or are in denial or are receiving $$ from energy companies to resist the evidence of AGW, will do nothing.  They will wring their hands some day and either say "See, we told you climate was cyclicle" or "Jeeze, maybe you WERE right."  In the meantime, I'm hoping scientists can work within gov't agencies to try to counteract some of the effects and smarter individuals will move to higher ground.  Climate change deniers, like right-wing Teapublicans will never see the evidence as truth, will never admit they were wrong and will continue to cling to their guns and Bibles.  We are wasting our time trying to change their minds or appease them.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe." A. Einstein

    by moose67 on Sun Jun 19, 2011 at 11:50:15 AM PDT

  •  Global Climate Change is real but not sudden (2+ / 0-)
    Recommended by:
    weatherdude, evergreen2

    On a very hot summer day a couple of years ago a neighbor asked if this was global warming.  My comment was that while global warming was real, it wasn't sudden.

    Here is a blog entry from a very well know University of Washington professor of atmospheric science, Dr. Cliff Mass:
    ...let me make clear that I am not a global warming denier, but a mainstream atmospheric scientist who believes human-induced global warming is inevitable and a major threat if we don't deal with......Folks, we are in the early days of the warming and most of the action is yet to come. We need to be very careful on jumping to conclusions too early, since that only aids the deniers and skeptics who are just looking to pounce on excessive claims.
    http://cliffmass.blogspot.com/...

    •  That was my argument, albeit (0+ / 0-)

      it didn't come across as well as I'd hoped and had to clarify in the comments. The fallout was either 1) because people are too lazy to read beyond the title, or 2) because people refuse to believe that extreme weather events just happen -- we can't have an active few weather years without something more sinister occurring behind the scenes.

      The fallout continues, I see. C'est la vie -- no skin off my nose.

      If you say "gullible" real slow, it sounds like "green beans."

      by weatherdude on Sun Jun 19, 2011 at 01:51:12 PM PDT

      [ Parent ]

      •  I'm curious (Bayesian) (0+ / 0-)

        as to whether you agree with the points in the diary. They seem to agree explicitly with your arguments, although with some more emphasis on the likelihood of big changes of some sort.

        I guess I'm trying to be Bayesian here. The theory-based prior probability for big weather changes is very high. The particulars are mostly lost in the details of the crude models. Therefore, in full awareness that weird things happen all the time for no particular reason, we should still acknowledge the likelihood (not certainty) of some AGW-induced weirdness before some sort of formal rejection-of-the-null test is passed.

        Michael Weissman UID 197542

        by docmidwest on Sun Jun 19, 2011 at 01:59:11 PM PDT

        [ Parent ]

  •  Global Temps have been cooler over last 6 months (0+ / 0-)

    compared to the same months of the prior year.  In fact, not one of the past 6 months has even been close to the temps of the prior year.
    http://data.giss.nasa.gov/...

    So I don't see how anyone can make the case that recent weather has been caused by climate change.  The global temps are simply going in the wrong direction.

    •  Nip in the air this morning (0+ / 0-)

      so I guess, drop the whole thing? Seriously, have you been actually following the science at all?

      Michael Weissman UID 197542

      by docmidwest on Mon Jun 20, 2011 at 08:35:34 AM PDT

      [ Parent ]

      •  My point (0+ / 0-)

        was that recent weather events cannot be attributed to AGW because for the last six months, temps each month have been down dramatically from the prior year.

        Unless you are prepared to say that declining temps caused these unusual weather events, then AGW must be irrelevant.

        Where is the science that says declining temps cause unusual weather events?  I always understood the science to be that climate IS NOT weather and vice versa. You disagree?

        •  Agreed that (0+ / 0-)

          the weather events so far have not been statistically changed in an compellingly clear way by AGW. It'll be interesting to see if some more reliable evidence of anomalies shows up in the next few years. The first thing to look for, I suppose, will be simple increased net precipitation, since that's expected for warmer oceans.

          As for the relation between climate and weather, if there's a climate change, then changes in typical weather patterns will occur. Predicting those changes reliably is hard. I'm not sure what it means to even ask if climate "is" weather etc. They mean different things but both are aspects of one big dynamical system.

          Michael Weissman UID 197542

          by docmidwest on Mon Jun 20, 2011 at 09:21:23 AM PDT

          [ Parent ]

          •  "one big dynamical system" (0+ / 0-)

            and that system is the jet stream for which no long term prediction model exists.

            Obviously our weather in the northern hemisphere is primarily a function of the jet stream's meanderings.  Until some scientific model convincingly relates the jet stream's dynamics to AGW, then our weather is not a function of climate change.  Nobody can predict the jet stream based on AGW.

            •  "Not a function"? (0+ / 0-)

              Don't you mean "not a predictable function"? That's kind of my point. The weather system's response to AGW is hard to predict not because it's insensitive but because it's too sensitive, i.e. chaotic.

              Michael Weissman UID 197542

              by docmidwest on Mon Jun 20, 2011 at 02:13:20 PM PDT

              [ Parent ]

              •  Chaos Theory (0+ / 0-)

                As you know, chaotic systems can be predictable.  But so far, nobody has produced any reliable predictions that relate our weather to AGW.

                Of course there has been a lot of speculation, but there is no science.  Therefore, there is substantial risk that AGW will be discredited when people try to claim a causal relationship between weather events and climate change without any scientific proof of such causation.

                •  That point was (0+ / 0-)

                  central to my post. However, I qualified it with the thought that if there are persistent changes in patterns which had previously been stable, it would reasonable to say that the overall system change was probably responsible.

                  Saying "there is no science" is a silly exaggeration. Saying that the science is still quite sketchy, much sketchier than basic AGW science, is accurate and necessary to preserve credibility.

                  For the most part we seem to be saying something quite similar, but there's obviously something about the way that I put it that's bugging you. I'm not 100% clear which part you want changed.

                  Michael Weissman UID 197542

                  by docmidwest on Mon Jun 20, 2011 at 07:49:12 PM PDT

                  [ Parent ]

                  •  NO Science (0+ / 0-)
                    Saying that the science is still quite sketchy, much sketchier than basic AGW science, is accurate

                    "Sketchy" science is no science.  You are into cold fusion territory which could easily discredit AGW, particularly in the current political climate.

                    •  huh? (0+ / 0-)

                      When people are trying to do some difficult science, things often start out sketchy then gradually solidify, based on tough theory interacting with data. (I'm not exactly revealing some new secret here.) You seem to propose that science springs full-grown from the forehead of Zeus. That's the only way I can interpret your claim that the earlier more uncertain stages are nonexistent.

                      Cold fusion is a terrible analogy. It violated very well-known established science. So there were very strong prior reasons to think it was crap, and the dopy original papers did nothing to dispel that.  Saying that AGW will change weather patterns is more or less a given, barring some weird coincidence. Claiming to now know in detail what the changes will be is over-reaching, but not like trying to overturn established laws.

                      Michael Weissman UID 197542

                      by docmidwest on Tue Jun 21, 2011 at 07:51:27 AM PDT

                      [ Parent ]

        •  Down dramatically? 0.3C? (0+ / 0-)

          Don't forget these are global averages.  What are the US anomalies?  

          The anomaly is still +0.4-0.5C globally.

          "Don't dream it, be it" - Brad, Janet and Frank

          by captainlaser on Mon Jun 20, 2011 at 07:15:59 PM PDT

          [ Parent ]

  •  Am I missing something? (0+ / 0-)

    This does not compute:

    Claims that AGW increases the net energy flow through the weather system are false. That flow is just set by the total amount of solar energy absorbed.

    I am not a climate scientist, but I think this statement is false and shows a lack of knowledge of the major mechanism of AGW theory.

    The problem is not the amount of solar energy absorbed, but rather the amount of solar energy retained. Light energy absorbed on the surface is re-transmitted as heat, in a wave length that, pre Industrial Revolution, passed back out through the atmosphere. The way CO2 and the other greenhouse gasses function in that role is by preventing that re-transmitted energy from leaving the atmosphere.

    So I believe the net energy available to weather is increasing over time.

    •  Basically false (2+ / 0-)
      Recommended by:
      engine17, synductive99

      The amount that gets turned to kinetic energy in the system is not constant because of changes in albedo and holding of energy. Global warming by definition means more energy enters the system. However, how this works and the exact balance of forms of energy is an open question and was actually the basis for my wife's dissertation. Her dissertation (which in many ways is beyond me) did seem to indicate that the system will maximize entropy rather than kinetic energy in the system as warming occurs, if I am understanding her adequately. But the bottom line is the question of what happens to the added energy being retained in the system due to global warming is among the more controversial issues and the basis of current study. THe diarist may well be right in that the amount of energy that gets added to the kinetic energy point (driving weather systems) may be closer to constant than the simple addition of net energy would suggest.

      Again, this is not my specialty. Just trying to pass along my wife's comments. I guess the talking points from her are a.) YES clearly the total amount of energy is clearly increasing, but b.) what that actually means for weather patterns is still an open question, though most climatologists agree that increased weather extremes and increased storminess are likely, but not givens and will vary from  location to location.

      FREEDOM ISN'T FREE: That's why we pay taxes. Read the PROGRESSIVE DEMOCRAT Newsletter

      by mole333 on Sun Jun 19, 2011 at 04:31:47 PM PDT

      [ Parent ]

      •  Please interpret... (1+ / 0-)
        Recommended by:
        mole333
        the system will maximize entropy rather than kinetic energy in the system as warming occurs

        Does this basically mean the system would rather store energy as heat than introduce it as kinetic energy in  a storm?

        Do I gather correctly that some models suggest dramatically wilder weather and less temperature increase, and you wife's calls for a smaller increase in wild weather with temperature rising more rapidly?

        When did you wife do her thesis?

        •  Here's the abstract... (1+ / 0-)
          Recommended by:
          synductive99

          You can probably interpret it as well as I can:

          http://pubs.giss.nasa.gov/...

          And here is the Lorenz paper she is working to extend (yes...she is taking up a subject from 1955!)

          http://eapsweb.mit.edu/...

          And here's a lecture by Lorenz that seems easier to understand to me.

          Not sure I can interpret clearly since I am not up on the math or physics associated with it...I'm personally a biologist.

          FREEDOM ISN'T FREE: That's why we pay taxes. Read the PROGRESSIVE DEMOCRAT Newsletter

          by mole333 on Sun Jun 19, 2011 at 06:29:04 PM PDT

          [ Parent ]

          •  hard to tell from the abstract, but... (1+ / 0-)
            Recommended by:
            mole333

            she found that the climate models under-estimated potential energy, at both the larger (zonal) and smaller (eddy) geographical scales, for the recent climate (1997-2000). Thus, actual effects were stronger than the models predicted.

            And she appears to have found that, under a doubled CO2 climate (i.e. probably late-21st century):
            • Over a large (zonal) scale, potential energy is reduced from the recent climate;
            • At a small geographic scale, potential energy is reduced during winter months (DJF) but she didn't study other seasons (climate studies typically focus on 1-2 seasons only).

            Has her dissertation been peer-reviewed and published?

            Thanks for sharing this interesting and highly-specialized research.

            "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy" Hamlet, 1:5

            by synductive99 on Sun Jun 19, 2011 at 11:23:42 PM PDT

            [ Parent ]

            •  Sorry to not be following up... (0+ / 0-)

              I am in the midst of preparing my own presentation for a meeting and am leaving for that meeting and some vacation tomorrow. So I am not at the computer much.

              She has submitted papers related to her dissertation work but it isn't published yet. Her adviser was one of the top names in the field but is also argumentative, so they are, shall we say, working with the reviewers and editors at the moment. My wife has moved on to another job which extends the work to other geographical locations, but needs to publish what she has already done, which may mean getting her adviser to stop arguing and the two of them do some more analysis. She is up for it but also has to balance her new work. Her former adviser is a big name and the current head of her current job (not her current boss) are both HUGE names in the field. She is personally still new and not well known and she is the type to grind huge amounts of data very carefully but not dramatically. So her work both old and new is still in process towards publication. I sympathize since even in my very different field my best publication was one (cited over 120 times) that was very meticulous and critical but not dramatic. She may well be following my approach.

              FREEDOM ISN'T FREE: That's why we pay taxes. Read the PROGRESSIVE DEMOCRAT Newsletter

              by mole333 on Mon Jun 20, 2011 at 12:42:03 PM PDT

              [ Parent ]

        •  modeling efforts (0+ / 0-)

          Again, my point is that these are serious current research questions, as opposed to the existence and approximate magnitude of AGW.

          Michael Weissman UID 197542

          by docmidwest on Mon Jun 20, 2011 at 08:08:34 AM PDT

          [ Parent ]

    •  Heat content vs. heat flow (0+ / 0-)

      Warming means more energy resides in the system. The content of the system  and the flow through it are two different things. (Think of a lake fed and drained by rivers.) In heating driven by solar changes, there's more net flow. In heating driven by the greenhouse effect, there's initially less outward flow until the temperature builds up enough to drive the flow back into balance.

      So your description of the warming mechanism is correct. Weather is a strongly driven dynamical system, not just an aspect of near-equilibrium energy sitting around. My point is that, in estimating how much energy gets dumped into various large-scale weather modes, people have to do serious modeling, not just some rule-of-thumb "more energy flow means more strong weather".
      The state of that modeling is not close to the state of the simpler AGW modeling. We can drag down the reputation of the latter by confusing it with the former.

      Michael Weissman UID 197542

      by docmidwest on Mon Jun 20, 2011 at 08:07:05 AM PDT

      [ Parent ]

  •  Thank you for this diary. (2+ / 0-)
    Recommended by:
    evergreen2, docmidwest

    I have been trying to say exactly this in the comments sections for I don't even know how many diaries about extreme weather events.  I just have not been able to say it as succinctly or clearly as you just did.  

    Have to be careful around here though, just saying that there is no consensus on the effects of global climate change on weather can get you called a troll and yelled at by the less scientific of the choir.  All we can do is continue trying to educate on the climate system (I really need to finish my paleoclimate series).

    All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident. - Schopenhauer

    by BlueberryTomatoSoup on Sun Jun 19, 2011 at 05:06:52 PM PDT

  •  Nice topic, a couple of comments... (0+ / 0-)

    Good diary to try and flesh out the nuances of this popular issue. Here's some additional material to develop the discussion:

    A. Please clarify your statement that:
    "...Claims that AGW increases the net energy flow through the weather system are false. That flow is just set by the total amount of solar energy absorbed..."

    I'm not understanding your point (sorry for being obtuse), isn't the cause of AGW that greenhouse gasses absorb IR radiation reflected from earth's surface (more accurately, IR wavelengths excite the atoms of greenhouse gasses, bumping electrons into higher orbitals), therefore increased greenhouse gasses means increased energy entrained in the atmosphere, and increased energy available to drive storms?

    B. It seems not very rigorous to cite the Butterfly Effect...can you offer citations to studies that quantify the sensitivity of weather extremes to minute effects? i.e. what proportion of recent extreme events can be attributed to normal variability in the climate system?

    Regarding normal variability, 3-4 years ago, in the trade publication Stormwater, Gary Oberts addressed stormwater professionals who were being approached by clients concerned about receiving two 100-year storms in a single year. The joint probability of two 1% events in a single year is 1/100 x 1/100, i.e. 1/10,000. This is not normal variability.

    Likewise, communities in central New Hampshire, encompassing a radius of perhaps 30-40 miles, have experienced at least a 75-year rainfall event every year for the last seven years. One of these, which I personally modeled, was over 3x greater than anything on record, and equated to a 1/100,000 annual probability based on the 20th century historical record. Again, clearly not normal variability.

    C. The general topic you raise, "Attribution" (i.e. can weather events be attributed to climate change), has been a fairly hot topic within the climate community over the last several years. The party line is that "no single event can be attributed to climate change". However, earlier this year several studies, published in the rigorous, and scientifically conservative journal Nature, challenged the party line:

    Pall P, Aina T, Stone DA, Stott PA, Nozawa T, Hilberts AGJ, Lohmann D, Allen MR (2011) Anthropogenic greenhouse gas contribution to flood risk in England and Wales in autumn 2000. Nature V470 pps 382-385

    ...in nine out of ten cases our model results indicate that twentieth-century anthropogenic greenhouse gas emissions increased the risk of floods occurring in England and Wales in autumn 2000 by more than 20%, and in two out of three cases by more than 90%.”

    ------------------
    Min S-K, Zhang X, Zwiers FW, Heger GC (2011) Human contribution to more-intense precipitation extremes. Nature V470 pps 378-381

    “...Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas."

    Moreover:
    "...Changes in extreme precipitation projected by models, and thus the impacts of future changes in extreme precipitation, may be underestimated because models seem to underestimate the observed increase in heavy precipitation with warming...”

    "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy" Hamlet, 1:5

    by synductive99 on Sun Jun 19, 2011 at 11:01:33 PM PDT

    •  Thanks for these questions (0+ / 0-)

      A. See my comment above. Increased trapped thermal energy is different from increased net energy flow. There's no simple map from the net trapped energy to net changes in weather strength. If the increased heat makes the temperature more homogeneous, less energy may end up flowing through large scale patterns.

      B. My point is that all individual weather events are "caused" by little changes, since it's a chaotic system. Therefore, even in normal times, it's completely pointless to discuss the systematic causes of individual events. All that make sense is to discuss the effects of various changes on the statistical distribution of events. The claims that AGW will make more net extreme events of various sorts are still very shaky, in contrast to the basic AGW science.

      On your various unlikely events: This requires a very rigorous distinction between ex post facto statistics and predictive stats. The reason is that there are enormous numbers of potential weirdities in an enormous number of locales. So there are always lots going on with nominally small p-values. In my opinion the best framework for evaluating whether to say there's evidence of AGW-driven weirding is Bayesian statistics. These allow one to realistically take into account predictions, but also when done properly avoid giving false positives via unintentional ex post facto stats.

      C. Right. We can't say "this event was caused by AGW" but in some cases it looks justified to say: "these events wouldn't be happening so much without AGW." I think we're on the same page there. I have no criticism of that Nature article (and no expertise to criticize it.) The point here is that that this is more cutting edge, with more uncertainty, in contrast to AGW itself. Increased net gobal precipitation, BTW, remains the main obvious first-order weather implication of AGW, unlike various predictions about storms.

      Michael Weissman UID 197542

      by docmidwest on Mon Jun 20, 2011 at 08:28:04 AM PDT

      [ Parent ]

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