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  1. Thanks for this. Attribution is obviously a big issue, and one that tends to be rather a ‘hot button.’

    I should think these will help lend a little clarity.

    Comment by Kevin McKinney — 17 Feb 2011 @ 8:02 AM

  2. Why waste all the time on other super-computers, just ask Watson! It knows all.

    Where is there some raw data on precipitation in the last 100 years?

    I haven’t seen this information. There is always concern that the start and end points for any trend study are not appropriate (both sides are guilty on this IMO). I have read precipitation studies were more difficult due to sparse data, and it seems we would have seen precipitation trend graphs a lot more often by now if it was straight forward. 7% seems to be a large change to not have been noted (vocally) earlier, seems like there is more to this story.

    Are there individual trends like they have for temperature stations?

    Is there any publicly available database?

    [Response: Monthly precip data is part of GHCN, but Pall et al used the data from Alexander et al (2006) which is available via HadEX. – gavin]

    Comment by Tom Scharf — 17 Feb 2011 @ 8:07 AM

  3. Thank you very much. This is exactly what we needed. As you say, it is a lot of work, not an easy thing. I believe you on that. I hope the same things will be done with the 2010 floods in Pakistan, Australia, Brazil, the Philippines, the Russian drought, etcetera. Those results are what we need to tell people.

    The results are still probabilities not absolutes and so will be disappointing to many people. Probabilities will have to do. They are still things we can point to when questioned. When the probabilities get added together, they make an argument that will persuade more people.

    A whole bunch of big storms, floods, droughts and fires are things that can invoke the fear necessary to get action on GW. Probable attribution is so much better than where we were before.

    Comment by Edward Greisch — 17 Feb 2011 @ 8:41 AM

  4. Risk assessment: drought and flooding in the 2050s vs agriculture. As we surely all agree, you don’t remain silent about, say, an approaching asteroid (still far enough away so that a slight push could make it miss earth) until the chance of collision is > 95 percent. How much more likely does impending climate disaster have to be than impending asteroid disaster to result, in practice, to the same level of warning?

    Comment by Pete Dunkelberg — 17 Feb 2011 @ 8:44 AM

  5. Gavin, am interested in your earlier reported brief comment in the context of the Pakistan floods (perhaps here on Real Climate) that a different way of looking at extreme events is asking the question thus: what is the likelihood of such events occurring had atmospheric CO2 levels remained what they were at the time of the Industrial Revolution (276 ppm) rather than what they are now (390 ppm). Very unlikely I think is what you said. Has that any bearing on the above posting?
    Nagraj Adve
    (an activist based in Delhi)

    [Response: That’s not really what I said (I presume you are referring to this New York Times interview?). We know that precipitation intensity has been increasing (the amount of rain that falls in the most intense events) across the northern hemisphere – this was clear in the literature even before the Pall et al paper. And while that doesn’t translate directly to flooding (which is a function of a lot of different factors – previous rainfall, soil moisture, water management policy, etc), it certainly plays a role. The study that Min et al did could be repeated for the Pakistan events and that would certainly be a very interesting result. – gavin]

    Comment by Nagraj Adve — 17 Feb 2011 @ 8:46 AM

  6. THX`Gavin,
    Aware person not a scientist myself just an interested longterm AGW/CC observer & hobby researcher
    RE “… though the El Niño of 1997/8 may have had an outsize effect.”

    Comments like this, eg during recent Aussie weather events where I live, have confused me for some time.

    My uncommon sense tells me that whatever the existing “climate drivers” natural or additional man made, they would sooner or later of themselves feed these El Nino/Nina cycles.

    And yet what often I hear-read is as if these El Nino/a are being treated as a separate/independent “weather influences” … could you explain this to me please?

    As it appears I have missed something along the way that I do not quite understand as yet.

    THX Sean

    [Response: Our ability to attribute changes in ENSO is very poor – both as a function of insufficient historical data and poor simulations of the phenomenon in the global models. So you can’t assume that (specifically) the 1997/1998 El Niño was related to long term climate change. So if you have a data set (as here) that goes from 1950-1999, you need to be aware of the fact that the trends could be affected just by this (potentially coincidental) El Niño. Looking at their figure 2, I don’t think this would change their results significantly, but it would be interesting to do the same study using a dataset that removed the ENSO influence – it might well be clearer. – gavin]

    Comment by Sean — 17 Feb 2011 @ 9:06 AM

  7. Gavin,

    Thanks for this. There’s been a lot of noise about extreme weather the past few months, and it frustrates me, because I think that too much jumping up and down about it does a disservice to the science, and to future expectations of immediate, in-your-face evidence of climate change.

    I’ve tried to ameliorate this, when I could, exactly because actual attribution is so difficult to do.

    Having hard, cold studies to point to, and a calm “well, let’s look at this realistically and understand our limitations” approach really helps, I think.

    Comment by Bob (Sphaerica) — 17 Feb 2011 @ 9:36 AM

  8. 2, Tom Scharf,

    (both sides are guilty on this IMO)

    I get so tired of this. There are no sides. If there is any classification to be made concerning sources of information, then there are scientists who are seeking the truth, and non-scientists who are trying to prove or disprove a predetermined point. Regardless of what that point is, those people are not scientists, they’re ideologues, and they’re doing humanity a disservice.

    But any scientific study you look at is not on any side. It’s just a result of doing research, trying to solve a problem, and the only objective is the correct and truthful answer, whichever “side” it happens to fall on.

    Remember that for real scientists, they’ll ultimately be judged in their chosen careers and lifelong endeavors by posterity. Sooner or later the truth will be known, no matter what anyone says today. Scientists have no incentive whatsoever to choose sides, and in fact have a strong disincentive to avoid bias. They have every reason to be as impartial as they can.

    Comment by Bob (Sphaerica) — 17 Feb 2011 @ 9:42 AM

  9. Gavin: Monthly precip data is part of GHCN, but Pall et al used the data from Alexander et al (2006) which is available via HadEX.

    Likewise, GSOD includes precip data.

    Comment by Ron Broberg — 17 Feb 2011 @ 9:46 AM

  10. RE: \Some extremes will become more common in future (and some less so). We will discuss the specifics below.\

    This statement caught my interest, but I didn’t get what I was hoping for…I would love to see a list, like

    [Event type X] MORE likely in [regions A,B,C]
    [Event type Y] MORE likely in [regions D,E,F]
    [Event type Z] LESS likely in [regions G,H,I]


    PS re-captcha has become really irritatingly difficult IMO

    (because I’m lazy and hoping someone else will do the work of compiling such a list lol)

    [Response: Table 3.8 in IPCC AR4 is a good list, and Joe Romm has a list of recent papers on the subject. – gavin]

    Comment by Kevin Stanley — 17 Feb 2011 @ 10:19 AM

  11. Gavin, I’m somewhat baffled how to interpret the findings of Pall et al. In fact I’m sceptical of the methodology or rather the underlying concept you outline of “fractional attribution”. If a rare event X occurs only when A, B, C, D and E are true, A is 100% attributable to the coincidence, not 20% to each factor. An eclipse occurs because of the alignment of the Sun and the Moon with the observer, it’s not 50% attributable to the position (relative to the observer) of the Sun and 50% to that of the Moon!

    [Response: Not relevant. The question is how much more likely a flood is compared to a previous set of circumstances. If the odds go from 1 in 100, to 4 in 100, that is 3-fold increase in likelihood, and you can attribute 75% of the events to the new circumstances (statistically, not individually). In your example there is no change in anything against which to calculate the increased odds. – gavin]

    Pall et al appear to make a stronger claim than that, because of AGW, flood events in the future will be more frequent, or more severe when they occur. Rather, Pall et al suggest anthropogenic forcings (henceforth “AGW”) in some sense caused the 2000 flood event in the first place.

    [Response: No. This is not the claim. Read the paper more carefully. – gavin]

    There appears to be an implicit assumption, at least in the Abstract (I don’t have full access to the journal) that the floods were just as likely to occur in 2000 as in any other year. Pall et al have therefore determined only how much more likely floods were to occur in 2000 with AGW compared to without AGW. But we know the floods – a rare event, remember – occurred in 2000, and we know forcings affect the state of the climate system. It would therefore be extremely surprising if Pall et al hadn’t found floods in 2000 were more likely with the actual pattern of forcings than with a different pattern. Maybe without AGW floods would have been more likely in 1999 or 2001 or 2013 (remember we’re talking about a rare event) than with AGW.

    Let me put this another way. Weather patterns over the UK, as elsewhere, depend on the ocean heat state (as well as insolation etc). A factor other than AGW affecting the ocean heat state in 2000 was the Pinatubo eruption in 1991. Take this out of the model forcings and I’ll wager floods in Oxford in 2000 become less likely than if Pinatubo were left in.

    Further, I hypothesise that the pattern of change of the ocean heat state following Pinatubo (which led to the loss of a considerable amount of heat) is an underlying cause of the 2000 floods. This pattern of change clearly depends on the forcings in effect. The fact that Pinatubo + AGW (+ any other relevant factors one might come up with) increased the probability of a once in several centuries event in 2000 in particular doesn’t in itself permit statements of the form “AGW makes flood events x% more likely”. We need to look at the entire problem – all the possible flood events under different natural climate forcing scenarios – under AGW and without in order to attribute “blame”. Some flood events will be less likely with AGW than without. But probably (as other research seems to show) more possible flood events are more likely with AGW than without.

    I’m not sure that Pall et al tells us more than that AGW is one of the factors determining the specific weather events that occur, i.e. what we know already, that is, that AGW affects the climate. It doesn’t in itself tell us whether flooding will be more or less frequent and/or severe with or without AGW.

    [Response: I think it is clear that you would want to do more work leading on from this – and doing different test cases is certainly useful. But you are expecting a little much from this study. – gavin]

    Comment by Tim Joslin — 17 Feb 2011 @ 11:29 AM

  12. >Ron Broberg (#9) says:
    17 Feb 2011 at 9:46 AM

    >Likewise, GSOD includes precip data.

    Yes, and GSOD is valuable data for understanding of spatio-temporal distribution of precipitation in extreme cases.

    But GSOD is an uncertain source for evaluation of trends and anomalies of precipitation. When I compared monthly sums in 1990s at several Southeast Asian locations with nationally archived data, I found much discrepancy.

    It is mainly because of failures of transmission. Though failures have become rarer in recent days, past observations are not recovered.

    In additon, WMO’s rule of transmission of synoptic observations is designed far before climate change is an important issue. Precipitation is an optional element. If a synoptic report was successfully transmitted and it did not include the amount of precipitaiton, we cannot distinguish “no precipitation” from “observation missing” for sure.

    So we often need data obtained from individual countries in non-real-time manner. And often (though not always) the national governments have restrictions on redistribution of those data.

    Comment by Kooiti Masuda — 17 Feb 2011 @ 12:10 PM

  13. Gavin.

    A couple of things regarding the Min et al. paper (if you have time).

    I am struggling with the interpretation of the increased trend in “percent probability.” I understand this to mean that over time, there is a tendency to move upwards (to the right) along the cumulative probability curve, let’s say, for annual extreme 1-day precipitation. In other words, there is a tendency for rarer 1-day annual extreme precipitation amounts to occur later in the temporal record. I am interpreting that to mean that there is a trend towards increasing annual 1-day extreme precipitation—but I am not sure how to quantify that change. You describe this result as “the researchers conclude that the probability of intense precipitation on any given day has increased by 7 percent over the last 50 years.” I am not 100% sure this is what the results mean. I don’t think they are assessing the probability of daily occurrence, but instead, the probability of an annual daily extreme of some magnitude. Maybe they are the same thing?

    Also, I don’t understand the authors’ preference for the ANT results over the ALL results. Don’t the observations reflect ALL (i.e. they are responding to all forcings, both natural and anthropogenic)? So, I would think, that to show a positive detection of an anthropogenic influence, you would show that the ALL models fit the observations whereas NAT (i.e., natural forcing only) runs do not. It doesn’t seem to me that the ANT runs would be of much use, other than perhaps to show what the signal may look like without NAT variability. But in this sense, the ANT results wouldn’t be used for detection.

    Thanks for any help in trying to straighten me out about this!


    Comment by Chip Knappenberger — 17 Feb 2011 @ 12:41 PM

  14. Gavin, what do you make of the recent WSJ article claiming that Gilbert Compo’s research proves that there is not a relationship between more extreme weather and AGW? It’s making the rounds on the denier sites. Might be good to address it or realclimate.

    [Response: The WSJ is not a reliable source. There is no discussion of extreme events in the Compo et al paper at all. The 20C Reanalysis project is however very useful (albeit with caveats) and we’ll address that in a future post. – gavin]

    Comment by Shan Wells — 17 Feb 2011 @ 12:48 PM

  15. The 2010 Joint Statistical Meetings included some invited papers on the analysis of extremes relevant to analysis of climate change. Here is one of them:

    This one attempts to define “extreme events” a priori and then model them probabilistically. I expect much more work like this in the future, but I have not seen one published in the peer-reviewed literature since R. L. Smith, “Extreme value analysis of environmental time series: An application to trend detection in ground-level ozone (with discussion)”, Statistical Science, 1989, vol 4, pp 367-393.

    To define an event after it has occurred, such as the simultaneous Russian heat and cold waves in summer 2010, and then post hoc to try to develop a probability model for it that you might have had (had you thought of it in advance), is nearly always a hopeless enterprise.

    Comment by Septic Matthew — 17 Feb 2011 @ 12:51 PM

  16. nuts, I forgot to add: this was a good essay by gavin. Good work.

    Comment by Septic Matthew — 17 Feb 2011 @ 12:52 PM

  17. Gavin, Thanks for your responses.

    The Abstract of the paper seems to be clear that we’re looking at the 2000 Oxford floods in particular, not the increased risk of floods occurring over a specific time period, say 1996-2005. I’ll look at the text when I can access it.

    Pall et al is being interpreted, e.g. in the Guardian, as raising the possibility of legal action based on the supposed increased probability of the 2000 floods.

    But statements of “fractional attribution” are not meaningful – or rather reflect only the limitations of our knowledge, in this case as embodied in climate models, not “how likely an event was to occur” (this is painful to write – the event has occurred, the wave function has collapsed, it’s no longer a probability, it’s a fact!).

    Let me elaborate:

    (1) Statements of “fractional attribution” of meteorological events depend entirely on the characteristics of the climate models employed. Being deterministic for a second, given perfect models (and input data), the 2000 floods are 100% likely to have occurred under AGW (since we know they did, in fact, occur). Under any other scenario, such as “without AGW” they are either 0% or 100% likely. (Note we also need to define what constitutes “floods” since in every scenario a specific different set of meteorological events will have occurred). So statements of “fractional attribution” only reflect our lack of omniscience, not actual real-world probabilities.

    (2) Furthermore, the floods are also either 0% or 100% likely to have occurred if we change one or more of an infinite (or at least very large) number of other factors. I mentioned Pinatubo earlier, but we could “blame” earlier volcanoes such as El Chichon, or the solar cycle, or anthropogenic factors such as historic deforestation or agricultural activity in Europe or North America or Africa, which surely affect weather patterns in England. It’s very likely – I’d say certain – that, with perfect modelling, any number of even minor counterfactuals could be shown to result in no floods in 2000, that is, by the logic being employed, the floods would be 100% attributable to such factors, compared to the counterfactuals. Even with “fractional attribution” (i.e. imperfect modelling) we’re pretty soon going to find we can attribute more than 100% of the event to various causes. With perfect modelling we’re simply going to identify large numbers of necessary causal factors.

    On top of this, there’s the need to take account of the possibility that what might have happened otherwise (i.e. absent AGW) might have been just as bad, as I discussed before. I’m reminded of Stephen Fry’s Making History.

    I really don’t think, unfortunately, that this nascent discipline of attributing specific climate events to AGW is going to stand up in court.

    I’d advise the climate science community to stick to what we already have, i.e. statements of the form that “floods will be x% more likely”.

    [Response: I cannot speak to the legal consequences of any particular method of attribution, but Myles Allen has discussed this speculatively in regards to the 2003 European heat-wave. I can’t see any reason why some use of this information would not useful though. Since we will never be able to say with absolute 100% confidence that single effect A happened because of cause B in the real world – even if something goes from almost never happening to happening all the time – a fractional attribution makes a lot of sense. I wouldn’t be at all surprised to find that something similar was used in medical malpractice cases for instance.

    Comment by Tim Joslin — 17 Feb 2011 @ 12:55 PM

  18. Yup, first comment on new DotEarth is from Judith Curry!

    Comment by Susan Anderson — 17 Feb 2011 @ 1:02 PM

  19. Gad, and JC points to the Huffington Post for coverage.
    Bad source, generally. Proof if needed that “left” need not mean “scientific”

    Comment by Hank Roberts — 17 Feb 2011 @ 1:50 PM

  20. [Response: Not relevant. The question is how much more likely a flood is compared to a previous set of circumstances. If the odds go from 1 in 100, to 4 in 100, that is 3-fold increase in likelihood, and you can attribute 75% of the events to the new circumstances (statistically, not individually). In your example there is no change in anything against which to calculate the increased odds. – gavin]


    Your reply to Tim is centered on the issue I have with attribution studies. I believe that I understand the method used to derive the increase in likeliness of a type of extreme event due to global warming, but the trouble begins when the results are used to say something meaningful about real extreme events, or at least what the media make of it. I think most journalists and laypeople understand the results in some kind of twisted way similar to what Tim formulated, that is, as applicable to a particular extreme event that they’re considering, and not to the statistics of these extreme events. Taking your 75% number as an example, I think they understand something like this: “75% of the strength of this extreme event is attributable to global warming”, or “There’s 75% chance that this event would not have occurred without global warming”.

    But they’re bound to understand it this way if the event is extreme enough, because the right way to understand it often leads to no useful conclusion. Indeed, as you point out, the right way to look at it is in statistic terms, that is to compare the statistics of the model with pre- and post-industrial revolution conditions to the statistics of the real world, and see whether the real trend in the statistics is well reflected in the model runs, statistically speaking. Then one could conclude that the current statistics of extreme events can only be explained by human influence. Unfortunately what extreme events tend to do for a living is to be rare. If we’re talking about a once-in-a-century event (the striking figure often used in the media), then we’ll need quite a few centuries before we can say anything meaningful about their statistics. As for the paleo data on extreme events at the scale of centuries, I guess it depends on the exact type of event but I imagine it cannot be so comprehensive either ?

    To put it another way. One can compare the records of global surface temperatures to model runs with and without anthropogenic greenhouse gases, and meaningfully (with some quantifiable degree of confidence) conclude that the trend cannot be explained without the human influence. I don’t see a similar “point of contact” between models and reality as far as attribution studies of extreme events are concerned, given that what we need to compare are modeled statistics (which we can always have by making many model runs) and meaningful real statistics, (which are hard to get) ?

    Comment by Mathieu — 17 Feb 2011 @ 2:36 PM

  21. Not having access to the full Min et. al. study I’d be curious to see how natural fluctuations in multi-decadal cycles such as the PDO and AMO during the time frame in question were filtered out to find the 7% attribution to AGW specifically, or is this kind of filtering even relevant in this kind of study?

    Comment by R. Gates — 17 Feb 2011 @ 3:25 PM

  22. As a layperson (to climatology, tho not my field), who would be much more interested in avoiding the false negative of failing to mitigate a true serious problem, I look at ACC this way: We live in a warmed & warming world….that is my null hypothesis. When they get to .05 on my null (95% confidence that ACC is not happening, and extreme events cannot in any way at all be attributed to ACC), then I will still continue to mitigate, bec it saves me lots of money.

    But I’ll be a happier camper.

    Here’s how I tried to explain science to folks on my environmental studies program committee:

    I just heard the good news that Egypt is free now to pursue true democracy. Could anthropogenic climate change have played a role — a straw out of many that helped break the camel’s back?…

    It seems one of the factors was extraordinarily high food prices…Of course, there are many factors that determine food prices…On the supply side there have been some terrible weather events…floods, droughts, severe storms, wildfires, heatwaves, and ?? I’m thinking this hard freeze here that killed most of the veggies in my garden [due to a strongly negative arctic oscillation].

    Now weather is not climate, but climate is all weather…or, weather at a statistically aggregated level…

    So while scientists cannot attribute Hurricane Katrina, drought, or other extreme weather events to climate change, they can say climate change increases the risk of these occurring. And that’s because scientists are focused on the “null hypothesis.” That is, they assume climate change is not happening and not having any impact whatsoever, unless the probability of climate change not happening and having no impact gets way way down to, say, 5% or less (which the first climate change studies did in 1995). I know that sounds bonkers crazy like a double negative…It’s called avoiding the false positive of making an untrue claim, or avoidance of being the boy who called wolf when there really wasn’t one…which could harm scientists’ reputations & science in general.

    Imagine, say, a bell-shaped curve based on the null hypothesis that climate change is not happening (and not having an impact on increasing extreme weather events), and there is this really long tail out to infinity; and supposing we get an off-the-charts category 7 hurricane in January, we still cannot attribute it or its extra intensity or unusual seasonality to climate change, even if there is only a one in kazillion chance it might occur without climate change having an effect – that is, it is way out there in the very tiny tail of this null hypothesis curve that fades out into infinity — the tail that says, afterall, anything’s possible.

    We laypersons, on the other hand, would strive to avoid the false negative…So in my books, as a layperson & not a scientist, it looks like climate change has contributed to food prices going off the charts, and the poor in many parts of the world becoming all that more desperate.

    I like these attribution studies mention in this post, but the denialists seem forever stuck out on the long tail of “anything’s possible in a non-ACC world, it’s all within what’s natural.”

    Comment by Lynn Vincentnathan — 17 Feb 2011 @ 3:47 PM

  23. Good radio science on this, from NPR’s Richard Harris:
    goes into various questions, beyond these specific studies; he emphasizes these studies are about precipitation events.

    Comment by Hank Roberts — 17 Feb 2011 @ 3:47 PM

  24. If any of you folks are interested, I just made a site which will allow everyone to collaboratively research this very topic. A lot of the stuff I read about global warming becomes a immensely time-consuming task to verify. With, we can divide the work and don’t have to repeat other peoples’ efforts. Check it out sometime. Right now the main claims are about global warming.

    Comment by Wizbang09 — 17 Feb 2011 @ 3:53 PM

  25. RE the possibility that negative arctic oscillations may also be expected to become more frequent in a warming world (see ), here is an effect on Mexican agriculture at :

    February’s freezing fury has left a path of crumpled crops, pummeled harvests and dashed dreams in the countryside of northern Mexico. Hardest hit was the northwestern state of Sinaloa, known as the “Bread Basket of Mexico,” where about 750,000 acres of corn crops were reported destroyed after unusually cold temperatures blanketed the north of the country in January and early February.

    Altogether, more than 1.5 million acres of corn, vegetable, citrus and other crops were either damaged or destroyed in Sinaloa, with a preliminary economic loss of approximately one billion dollars.

    The source of about 30 percent of Mexico’s grains and vegetables, Sinaloa also exports food products to the United States.

    Other northern states also experienced the widespread destruction of winter crops…

    Comment by Lynn Vincentnathan — 17 Feb 2011 @ 3:59 PM

  26. “I wouldn’t be at all surprised to find that something similar was used in medical malpractice cases for instance.”

    I think that there is some case history in the pollution field, actually: when multiple sources produce a particular pollutant that has been fingered as “at cause” in a sickness or mortality incident, the blame gets apportioned between the sources as some function of their contribution to the exposure. I think. Its been a few years since I took environmental law… (if only I could remember the case name, but I can only remember a small subset, like Daubert, American Trucking, and cases by the judge “Learned Hand”, because how cool of a name is that?)


    Comment by M — 17 Feb 2011 @ 5:03 PM

  27. Interesting Nature accompanied Richard Allan’s comment piece with a photo of floods in York in 2000.

    These floods set a record high. They were one inch higher than the previous record. This occurred in 1625 when, IIRC, AGW was in its preconception stage.

    Comment by Dave Andrewsa — 17 Feb 2011 @ 5:04 PM

  28. Whizbang09 #24 Thanks, but I had a look at your website, and it is pointless, irrelevant and utterly lacking credibility. You may gather a group of like minded individuals there, and waste one anothers’ time, but the real work will be done elsewhere, by others.

    Comment by One Anonymous Bloke — 17 Feb 2011 @ 5:10 PM

  29. Hi,

    it thought it has been demonstrated that the atmosphere holds 4% more water vapour now then it did at the start of the 20th century and that 2010 has had the heaviest rainfall globally. In theory its going to rain more in certain places?

    Comment by pete best — 17 Feb 2011 @ 5:11 PM

  30. Mathieu #20 wrote:

    I think most journalists and laypeople understand the results in some kind of twisted way similar to what Tim formulated…

    seemingly misunderstanding my position.

    Mathieu, I agree with what you say in your post, but I think you need to look carefully at what Pall et al claim. They do in fact seem to be saying something analogous to your strawman example of “There’s 75% chance that this event would not have occurred without global warming”, to wit:

    …we generate several thousand seasonal-forecast-resolution climate model simulations of autumn 2000 weather, both under realistic conditions, and under conditions as they might have been had these greenhouse gas emissions and the resulting large-scale warming never occurred. Results are fed into a precipitation-runoff model that is used to simulate severe daily river runoff events in England and Wales (proxy indicators of flood events). The precise magnitude of the anthropogenic contribution remains uncertain, but 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%.

    i.e. that they can somehow determine the increased likelihood due to AGW of an actual past extreme (once in some centuries) meteorological event. I’m arguing that this is not a meaningful exercise – i.e. against the “twisted” position. The increased likelihood due to AGW of the particular event was in fact infinite (or 0% if it would have happened anyway), i.e. in the AGW case the event was 100% likely since it did, in fact, happen, i.e. if they’d used perfect models (and data) all those run “under realistic conditions” would have correctly hindcast the 2000 Oxford flood event and all those run under a given scenario of “conditions as they might have been” would have also consistently either predicted flooding that year, or, more likely, predicted no flooding. Any other estimate, such as the PDF Pall et al came up with, merely reflects modelling inaccuracy, interesting to know though that may be.

    Comment by Tim Joslin — 17 Feb 2011 @ 5:34 PM

  31. One paper says

    In the future, there will be more precipitation in the high latitudes of the NH and less precipitation in the mid-latitudes.

    The other papers suggests-

    In the future, there will be more precipitation in the mid-latitudes and less in the high latitudes of the NH.

    Which one is correct?

    [Response: Since neither of these statements are to be found in the papers mentioned, your question is moot. I strongly advise reading the papers before asking questions – even the titles would have been informative. – gavin]

    Comment by OG — 17 Feb 2011 @ 5:40 PM

  32. Andy Revkin shows his ignorance of probability & statistics once again at:

    It is, of course, not possible to give a laboratory course in comments to dotearth.

    Comment by Edward Greisch — 17 Feb 2011 @ 5:48 PM

  33. Wizbang09: doing science by popular vote?


    Just no.

    Comment by Didactylos — 17 Feb 2011 @ 6:03 PM

  34. For OG: the claims you copypasted are amateur opinion; just above where you found them the writer says “My dunce head reading … is- One paper says-“

    Comment by Hank Roberts — 17 Feb 2011 @ 6:12 PM

  35. Gavin, on your response to #14: my first reaction was yours, that WSJ isn’t a reliable source. That the 2nd paragraph starts with “Some climate alarmists” is a clear giveaway. That this sort of strident propaganda can appear in a top internationally read financial paper is disappointing but not surprising.

    But I went and skimmed through the paper anyway: interesting but nothing to support what WSJ wrote. I suspect Compo may have been taken a tad out of context, as in intending to say something like this is new stuff we’re working on, I looked for something and didn’t find it, rather than the definitive spin WSJ put on it, that this is a conclusive study that shows nothing is happening. I look forward to your more detailed article on 20C Reanalysis.

    Comment by Philip Machanick — 17 Feb 2011 @ 7:57 PM

  36. I’ve been living in Australia since 2002, and I have found the number of once in a century events surprising (hot dry weather leading to massive bush fires as well as deluges). In some areas, a once in a century flood has happened twice the same season. Brisbane’s recent floods were caused by double the rainfall of the 1974 floods, and only less severe because a flood mitigating dam was completed in the interim. At one point 70% of Queensland (land area 1.7-million km2) was under water. If this is what happens when rain fall is only a few per cent outside norms (assuming the southern hemisphere is not very far from the northern trend), what will happen when climate change starts getting serious?

    Comment by Philip Machanick — 17 Feb 2011 @ 8:06 PM

  37. Pressure to quantify and statistically determine the probability of local weather anomalies will continue to grow as population pressure mounts. Economic models notwithstanding, private companies will fund their own climate models when the cost of not doing so bumps up against profit margins. The real or imagined cost of a statistically stretched climate forecast based on regional models will soon be felt by all of us. Insurers motto “When in doubt, price it in” will overshadow policy and good science.

    Comment by Lloyd Smith — 17 Feb 2011 @ 8:23 PM

  38. More ponderings by an informed non-scientist:
    * Assuming storms are driven by temp/pressure/energy gradients.
    * If warming warms the poles relatively more than the tropics, then the horizontal temperature gradients may actually decrease.

    [Response: depends on whether you look at the surface or the tropopause, and depends on whether there is any ice around. – gavin]

    * If warming warms the lower atmosphere more than the upper atmosphere, then the vertical gradients will likely increase.

    [Response: Depends again – the upper troposphere is predicted to warm more than the surface – at least in the tropics. It is the stratosphere that is cooling. – gavin]

    * Are there compensating feedbacks that amplify or neutralize these effect?
    * What are the controlling variables that determine the whether dissipative structures (storms) are self-organized (cyclonic) vs random-chaotic?
    * How does this play out for the different kinds of “extreme events” and their differing responses to forcings and feedbacks?

    [Response: It’s far more complicated than anyone can hand-wave about. The increase in water vapour as the surface warms is key, but so might be changes in boundary layer stability, rossby wave generation via longitudinally varying responses at the surface, impacts of the stratopshere on the steering of the jet, and the situation is completely different again for tropical storms.- gavin]

    Comment by DougO — 17 Feb 2011 @ 9:03 PM

  39. Changes in ocean salinity can be a useful indicator of chagnes in the hydrological cycle, since the ocean integrates those changes. Those studying the subject might be interested in the following three articles.,2010,helm

    Comment by The Elf — 17 Feb 2011 @ 10:25 PM

  40. The authors of the studies did stress how difficult these were to do. My article for the global news service IPS which is careful to point out these impacts result from a fraction of the heating to come.

    Comment by Stephen Leahy — 17 Feb 2011 @ 10:30 PM

  41. About 6 years ago when I first took an interest in AGW it was all about warming and droughts. Snow and cold were a thing of the past. Now it appears that it can be attributed to pretty much everything.

    All recent ‘extreme events’ on investigation appear not to be extreme when compared to known events in the past few hundred years before AGW. Snow and cold in Europe in the early 1800’s, floods in Australia in the mid 1800’s etc. You can easily check these on the WEB and I’ve not found anything recently that has not occurred more often or to a greater extent in the past. Interested to hear if there are.

    Of course climate changes (by its very nature) but linking current trends to AGW appears very tenuous (even by your research) and bearing in mind the uncertainties and the media and political need for the correlation to stick, its very dangerous ground to attribute anything. We just do not know. This will just muddy the waters even further and loose confidence in climate science by me and I suspect the public at large.

    Comment by Titus — 17 Feb 2011 @ 11:22 PM

  42. Tim @11,17, and more.

    I think you need to separate out the effects of the botterfly effect, from changes in the longterm statistics in climate. Beyond a few months, the only thing that can be said is statistical in nature. I personally should be held responsible for the 2000 flood, because in 1995 I steped on a botterfly. If I had not, and it got to flap its wings the chaotic sampling of the weather in fall 2000 would have been totally different, and that flood wouldn’t have happened. Similar to, being blamed by a roolette player for his losing a crucial bet because I hapenned to breath out, and perturbed the details of the balls trajectory. Weather is inherently chaotic, and trying to attribute the definite ocurrance of an event to any one cause just can’t be done. Any one of a gazillion other tiny changes would have averted it (possibly causing a worse diasater somewhere else). What we are trying to attribute here is proof of loaded diz, not an effect on a given roll of them.
    Curses on the spam checker. I’ll try to deliberately mispell some words
    and try again.

    Comment by Thomas — 17 Feb 2011 @ 11:22 PM

  43. Titus – the addition of the Wivenhoe Dam was supposed to hold the flood level a specified number of meters below the 1974 level. It failed to do so. The Wivenhoe Dam was designed to make it unlikely it would have to make a large release of water to defend the dam wall’s structural integrity. The dam’s managers had to do do just that. Try to think it through. To compare flood events somebody who knows what they are doing has to account for all of that relevant factors that contributed to the flooding and then analyze the mitigation effect of all the existent mitigation infrastructure. Once that work is completed, it’s very possible the 2011 Brisbane flood will fully compete with recorded history.

    Comment by JCH — 17 Feb 2011 @ 11:54 PM

  44. Thanks Gavin. Having read both papers last night and struggled a bit, must say your succinct summary is seriously impressive.

    Comment by GlenFergus — 17 Feb 2011 @ 11:56 PM

  45. @Titus #41 – I have read other people say that Australia has had worse floods and precipitation than has occurred this year. When investigated it appears they are comparing one or two floods in a particular area with only one of the floods this season. I have yet to see evidence that the total sum of floods since September 2010 across the whole of Australia has ever been experienced over a similar time period in the recent past. Can you please provide a link to your claim? Does your reference (if any) include the repeated flooding of Queensland and record rain and floods in Victoria (repeated), Tasmania, Western Australia, South Australia, the Northern Territory and NSW (ie in every state and territory except the tiny ACT)?

    I have seem reports of extensive floods in parts of Queensland in the 1800s on the BoM site, but have not seen the reports to which you might be referring for the whole country.

    (I know this isn’t relevant to the discussion, because weather from more than a century ago was responding to different climate and weather forcings than is the weather of today.)

    Comment by Sou — 18 Feb 2011 @ 12:21 AM

  46. Titus, #41 and
    Show beyond any doubt that, no matter what you may have been “reading” “about 6 years ago” (bearing in mind that IPCC AR4 was based on existing resources) everything we’ve seen is within the bounds of predictions. Or, to be more accurate, stretching the bounds of predictions.

    Please start your entire argument again from the beginning, this time with respect to the facts.

    Comment by One Anonymous Bloke — 18 Feb 2011 @ 2:22 AM

  47. Sou @45 & JCH @43 Thanks for comments.

    Here’s a link to some flood history:

    The current level got to about 4.5m. That’s less than 1974 at 5.5m and a lot less than several in the 1800’s (in fact 2 were almost twice as large).

    I admit this is just one area but take a look around the site and others for more examples.

    Not sure of the effect of dams but it will no doubt be an interesting an needed study for the future. My point being that extremes are pretty much the norm in celestial time frames.

    Comment by Titus — 18 Feb 2011 @ 2:28 AM

  48. @Thomas #44:

    I understand that Pall et al are trying to account for the butterfly effect, it’s just that in hindcasting a specific flood that actually happened rather than floods in general (in contrast seemingly to the methodology adopted to assess the probability of European heatwaves comparable to that in 2003), we’re left with no way of separating forecast inaccuracy from real-life randomness. If we thought weather forecasting models were inaccurate solely because the weather doesn’t “know” what it’s going to do there’d be no point in investing in bigger and bigger supercomputers would there? I hope we’re not starting to confuse model behaviour with real-world behaviour! The fact is the 2000 Oxford floods really happened whether they were predicted by 10% of the model runs or by 100%, so they weren’t made 20% or 90% more likely because of AGW, they were infinitely more likely.

    Comment by Tim Joslin — 18 Feb 2011 @ 3:30 AM

  49. One approach that might be fruitful I saw during a discussion on the Brisbane floods and the operation of the Wivenhoe dam. With modern recording equipment, it’s relatively easy to calculate the quantity of rain falling in any given period – in this case 2 or 3 days.

    So this person simply said what if this quantity of water was larger than previous rainfall events by the 4% estimated for the increase in water vapour held in the whole of the atmosphere. When he did that and subtracted it from the total rainfall, hey presto!, the Brisbane flood would either not have happened at all or have been relatively minor. Haven’t seen anything similar for the flash flooding in the Toowoomba area.

    Someone who knows what they’re doing could do some work on the basis (that occurs to me as a naive non-scientist) that localised effects would involve more than the 4% average for the whole globe / whole atmosphere.

    But it’s a good logical, rather than scientific, exercise to quantify the point where we move from the 0% to 100% likelihood of not seen before effects from extreme weather.

    Comment by adelady — 18 Feb 2011 @ 3:58 AM

  50. Titus says, “All recent ‘extreme events’ on investigation appear not to be extreme when compared to known events in the past few hundred years before AGW.”

    I have to say that it takes a special sort of studied obtuseness to look at all the events we are hearing about–unprecedented heat waves in Russia, flooding in Oz, S. America, etc. and say “Meh!” I have to wonder how far you’ll take the act. When you are up to your navel in floodwaters, will you still be proclaiming it’s no big deal? But then, it is your progeny who will bear the brunt of your complacency, so why should you care?

    Comment by Ray Ladbury — 18 Feb 2011 @ 5:01 AM

  51. #3 and #32 Edward Greisch
    “The results are still probabilities not absolutes and so will be disappointing to many people.”

    Science doesn’t deal with absolutes (that by definition have no reference points)- it only deals with probabilities.

    and therefore “Andy Revkin shows his ignorance of probability & statistics once again ” is perhaps not surprising.

    Comment by Hugh Laue — 18 Feb 2011 @ 7:00 AM

  52. @ Titus, yes, as you point out the link you provided is indeed limited to a very small geographic area (two adjacent cities in south east Queensland).

    This spring and summer with the extra strong La Nina, there have been multiple record precipitation events right across the nation in number of events as well as size of the flooding (especially the vast areas flooded in Victoria and central Australia as well as Queensland). I hope BoM will prepare a report on these events as a whole and comment on whether there has been any precedent. The fact that so many records have been broken multiple times this season, makes it unlikely there has been any recorded precedent.

    Comment by Sou — 18 Feb 2011 @ 8:10 AM

  53. Is there any such attribution study about the Katrina?

    Comment by Alexandre — 18 Feb 2011 @ 8:24 AM

  54. “I’ve not found anything recently that has not occurred more often or to a greater extent in the past. Interested to hear if there are.”

    Iowa had 2 “100 year floods” in a decade.

    Comment by Jeffrey Davis — 18 Feb 2011 @ 8:49 AM

  55. #48, Tim Joslin–

    \The fact is the 2000 Oxford floods really happened whether they were predicted by 10% of the model runs or by 100%, so they weren’t made 20% or 90% more likely because of AGW, they were infinitely more likely.\

    Perhaps I misunderstand, but it appears to me that this statement is you \confusing the model with the reality.\ That is, the ‘x% more likely’ is modeled, not ‘real.’ Or to put it another way, what did happen does not erase what could have happened in our ex post facto calculation of the probabilities.

    The corollary of what you are arguing is that attribution studies are completely impossible, since past events are always more or less ‘certain.’

    (Well, not in the denierverse, I suppose, as nothing is ever at all certain there.)

    Comment by Kevin McKinney — 18 Feb 2011 @ 9:32 AM

  56. Titus wrote: “All recent ‘extreme events’ on investigation appear not to be extreme when compared to known events in the past few hundred years before AGW.”

    That is simply not true. The extreme weather events occurring all over the world are in fact extreme by historical standards, and are in some cases unprecedented. And what is truly unprecedented — and truly alarming — is the fact that these extreme events are occurring all over the world at the same time.

    “Several diverse extreme weather events are occurring concurrently around the world, giving rise to an unprecedented loss of human life and property … Climate extremes have always existed, but all the events cited above compare with, or exceed in intensity, duration or geographical extent, the previous largest historical events … The occurrence of all these events at almost the same time raises questions about their possible linkages to the predicted increase in intensity and frequency of extreme events, for example, as stipulated in the IPCC Fourth Assessment Report published in 2007.”

    World Meteorological Organization, August 2010

    Comment by SecularAnimist — 18 Feb 2011 @ 9:52 AM

  57. Titus:

    How high would the flood be without the 1,450,000 ML of flood mitigation provided by Lake Wivenhoe?

    Do I need to draw a line connecting the 1974 floods and the building of Wivenhoe Dam?

    “It is anticipated that during a large flood similar in magnitude to that experienced in 1974, by using mitigation facility within Wivenhoe Dam, flood levels will be reduced downstream by an estimated 2 metres.”

    As for the figures from pre-1900: apply large error bars. Big error bars.

    Comment by Didactylos — 18 Feb 2011 @ 10:02 AM

  58. RE #32, we have the scientists who require .05 p or less (95% confidence) on their claims and the industrialists and denialists who require 99 to 101% confidence.

    Why do the people, potential and real victims, the media, and policy-makers stand somewhere between this 95% to 101% confidence. They should be way out on the other side of precaution when the risks are so high (maybe requiring 50% or even 5% confidence). It just amazes me.

    Hurricanes Katrina, Andrew, and all other extreme weather events that can even by a new, remote, or quasi logical hypothesis be linked to CC over the past 50 years, in my books ARE caused (or enhanced) by CC. If someone can prove at the .01 alpha level that they are NOT…like I said, I’ll still keep mitigating, bec it saves money, and it also mitigates lots of other environmental and nonenvironmental problems.

    Comment by Lynn Vincentnatnathan — 18 Feb 2011 @ 10:17 AM

  59. Would it be safe to say, from a lay parson’s perspective, this: evidence of a causal link between “AGW” and some types contemporary extreme weather events has grown but there is not yet a consensus view?

    When is a consensus view likely to appear? The next IPCC report? Or is some other body (eg NAS) planning to report on this question?

    Comment by Mike — 18 Feb 2011 @ 11:01 AM

  60. Mike, as a “lay parson” you may not be aware of how a “consensus statement” works. Have a look at a few from many different areas of science:

    Comment by Hank Roberts — 18 Feb 2011 @ 11:14 AM

  61. Mike #59 Waiting for “Consensus” is a waste of time – whether or not it makes a good political comforter. It buys in to the “false and misleading dichotomy” that science can be settled (or unsettled). For further reading I can recommend Dr. Gavin Schmidt’s article Unsettled Science

    Comment by One Anonymous Bloke — 18 Feb 2011 @ 11:36 AM

  62. Hank Roberts #60 Obviously ‘consensus’ has a scientific use that the laity are unaware of, this is another example of how the use of a word by scientists can be misrepresented. People hear “consensus” and translate it according to their lay definition. How to avoid this? Good question.

    Comment by One Anonymous Bloke — 18 Feb 2011 @ 11:45 AM

  63. Re 59 Mike,

    There is consensus that it is pretty close to impossible to ascribe any particular event to climate change, but that the pattern of events makes it clear that climate change is happening.

    With one event, it is possible to give some sense of how likely the event is in our current climate, how likely it might have been in preindustrial times, and so ascertain a higher or lower probability of it happening today.

    Some heat waves are just hot times. Others, perhaps because they last longer, or because the temperature remains high at night, so humans and other living things don’t have a chance to recuperate, seem to be higher probability events today. Higher night temperatures, in particular, is one of the fingerprints of higher atmospheric greenhouse gas levels.

    Comment by Karen Street — 18 Feb 2011 @ 11:55 AM

  64. This just in:
    NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100
    Study underestimates impacts with conservative assumptions

    And for the current discussion why not link to the CP post?

    Two seminal Nature papers join growing body of evidence that human emissions fuel extreme weather, flooding that harm humans and the environment

    Comment by Biochar — 18 Feb 2011 @ 12:20 PM

  65. @56 – Secular Animist. Thanks for the great quote from the WMO! I hadn’t seen that before. Very concise though scary.

    Comment by Bay Bunny — 18 Feb 2011 @ 12:40 PM

  66. All in all, it it extermely difficult to attribute extreme events to climate change. Another analysis is presented here:

    Comment by Dan H. — 18 Feb 2011 @ 1:05 PM

  67. “A whole bunch of big storms, floods, droughts and fires are things that can invoke the fear necessary to get action on GW.”

    Certainly true. However, that same whole bunch of fearful stuff could just as easily draw more determined inaction if it were determined that the extremes are not attributable, or minimally attributable, to AGW. I’m surprised there was no cautionary note from RC attached to the statement I have quoted above, but perhaps that caution has been expressed elsewhere on this or another thread. I hope it has. Overreaching has not been good for the cause of late, and I hope no gun is jumped on this important issue.

    Comment by Andronicus — 18 Feb 2011 @ 1:10 PM

  68. 51, Ray Ladbury: I have to say that it takes a special sort of studied obtuseness to look at all the events we are hearing about–unprecedented heat waves in Russia, flooding in Oz, S. America, etc. and say “Meh!”

    Depending on how you define a “region” (an island, a river, a pair of non-overlapping areas east of Moscow, a city, a mountain range, a 1degree by 1degree area of the South Atlantic, a peninsula, an isthmus, a gulf, a bay) there are thousands to hundreds of thousands of “regions” of the world, partially overlapping in some cases, not always (perhaps never) statistically independent, seldom linearly related. In every region there are multiple measures every day: rainfall, accumulated rainfall over the last week or month, maximum temp, number of consecutive days with a max temp above 90F, minimum temp, max and min wind temps, etc. With this many opportunities over a poorly defined (or undefined, or defined post hoc) sample space, it would be a rare year that did not have multiple extreme events (“unprecedented”, or “unprecedented since 1100AD”, or “unprecedented in the historical record”) under any reasonable probability model. The actual number of extreme events would fluctuate randomly from year to year. To show from recent records that the actual frequency of extreme events has increased is hard, and non-intuitive. The two papers that are the focus of gavin’s essay are honest attempts to address the issue of whether particular events, identified post hoc, can provide reasonable evidence. In their case, hard work yielded little; the works are, however, reasonable models to try to improve upon in the future.

    What you called “studied obtuseness” I would call “intellectual rigor”. “Studied obtuseness” would be the continued avoidance of statistical methods devoted to the analysis of extremes.

    Comment by Septic Matthew — 18 Feb 2011 @ 1:20 PM

  69. ” if it were determined that the extremes are not attributable, or minimally attributable, to AGW”

    People say that kind of stuff all the time and the idea that if AGW were simply of natural origin then we shouldn’t or couldn’t do anything about it. If people believed that kind of stuff generally, they wouldn’t go the doctor, farm, work, eat, clothe themselves, etc. Death is as natural as it gets and yet we constantly work to put off the day of reckoning.

    Comment by Jeffrey Davis — 18 Feb 2011 @ 2:17 PM

  70. 67 Andronicus: “I hope no gun is jumped on this important issue.”
    Surely the gun went off in 1988 when James Hansen testified before Congress.

    Comment by Edward Greisch — 18 Feb 2011 @ 2:47 PM

  71. Edward, the NPR Science Friday just pointed that those who do science are convinced not by any individual opinion but by the weight of the evidence.

    If you point to individual items you’ll get argument about opinions.
    If you point to the weight of the evidence you’ll have a chance of educating people. You can’t point to the same thing tomorrow — more evidence comes in every day.

    Comment by Hank Roberts — 18 Feb 2011 @ 3:13 PM

  72. Karen Street wrote: “There is consensus that it is pretty close to impossible to ascribe any particular event to climate change …”

    It is impossible to attribute a particular weather event to any one particular cause. All weather events, extreme or otherwise, arise from numerous interacting causes and conditions.

    And anthropogenic global warming is now a pervasive and inescapable condition that influences all weather events. We are experiencing the weather of an anthropogenically warmed, and rapidly warming, Earth. There is no more “natural” weather.

    Comment by SecularAnimist — 18 Feb 2011 @ 4:22 PM

  73. @Kevin McKinney #55:

    Maybe I am confused, since I understand the rationale behind Pall et al is to make progress towards determining the AGW fraction of attributable risk (FAR) for the case of a particular single exemplar extreme real-world precipitation event, the autumn 2000 floods in England. The point is not to tell us just something about the models, or about the increased risks of flooding in a warmer world in general, though that is in fact all the study does, IMO.

    Pall et al’s assessment of the AGW FAR is surely highly sensitive to modelling skill, specifically of the actual event (their “A2000 climate”). Yet they don’t discuss at any length the skill of their climate model in actually forecasting the autumn 2000 floods when initialised to April 2000. They only go as far as to show some apparent skill in the correlation of the pattern of mean 500 hPa geopotential height with precipitation (their Fig 1) and in reproducing something similar to the real-world runoff power spectrum (Fig 2). From their Fig 3, their model does not appear to be incredibly skilful, predicting runoff as or more severe than actually occurred around 20-30% of the time (and there’s no information as to whether the model under or overestimates rainfall in other years nor any discussion of interannual runoff variability or other way to assess the skill in terms of the range of outcomes above and below what actually occurred).

    This whole methodology will only make sense once we have models which can accurately hindcast the extreme event with some reliability. Thinking a bit further along these lines, we could then run a suite of, in this case, A2000s and just discard outliers, say 10%, with the remainder taken as defining the extreme event parameters, in this case an average daily rainfall range (for example, maybe 0.38 to 0.44mm in the 2000 flood case). Then perhaps we could run the same model with the range of possible counterfactual (no AGW) initial values (Pall et al’s A2000N suite) and get to the FAR directly (without the awkwardness of having to talk about the increased risk of something that is known to have happened) – discarding the extreme 10% again, we would simply calculate the proportion within the event parameters as previously determined (if some more extreme remain we have problems!). There are still a few assumptions to be challenged in court, though.

    The idea is to determine a FAR for AGW as might be done for smoking, say. But in the case of smoking you have data on a real population of smokers and non-smokers. You only have to make one not particularly heroic assumption, i.e. that the risks for the individual whose loved ones are bringing the law suit were typical of the population of smokers as a whole. In the case of specific events under AGW there is a population of one. Another method is needed, and IMO simply “pretending” there’s a large population by a series of parallel universe model runs is, to say the least, somewhat problematic.

    Comment by Tim Joslin — 18 Feb 2011 @ 4:29 PM

  74. Septic Matthew, The Russian heat wave by itself was nearly a 3 sigma event. We are having flooding in enough areas that it has played a role in bringing global food prices to a record high. This is not merely a phenomenon that affects a couple of regions. It is global, and it is just what the theory predicts. Ignoring that is not intellectual rigor, but intellectual rigor mortis.

    Comment by Ray Ladbury — 18 Feb 2011 @ 6:00 PM

  75. Mike@59,
    The consensus theory of Earth’s climate predicts just this type of increase in extreme weather events, so no, I don’t think your statement is correct. Put another way, an element of a theory becomes part of the consensus when you cannot understand or predict system behavior correctly without it. It is very likely that if you didn’t take into account the increasing energy, water vapor, etc. in the atmosphere, that you not predict the increased severe weather.

    Comment by Ray Ladbury — 18 Feb 2011 @ 6:05 PM

  76. Wow, almost a year from submission to publication. Intense.

    This has been a burning question in my mind. I’m looking forward to reading these two carefully, and to seeing more papers like this in the future. Thanks for the post.


    Comment by Peter Kalmus — 18 Feb 2011 @ 6:55 PM

  77. 74, Ray Ladbury: Septic Matthew, The Russian heat wave by itself was nearly a 3 sigma event.

    Since you missed my points, I’ll repeat them: Earth experiences dozens at least of 3 sigma events every year, under any realistic probability models; you really need to study up more on the statistical analysis of extremes if you are going to promote some statistical inferences based on extremes.

    [Response: You mean earth experiences more than three ‘extremes’ every month?! That’s what ‘dozens’ per year would mean.–eric]

    Comment by Septic Matthew — 18 Feb 2011 @ 8:02 PM

  78. I find the Meehl et al 09 study pretty neat, which showed that since 2000 the ratio of the number of record high to record low temperatures is about 2:1, projecting to increase to about 50:1 by end of century. Goes to show also that even in a warmer world you can still get record lows.

    Comment by chris colose — 18 Feb 2011 @ 9:01 PM

  79. On the face of it, one would not expect that an increase in greenhouse gases sufficient to increase the average temperature of the Earth by a degree or so would have a dramatic effect on ‘extreme events’ in general. Some types of events would probably become a bit more common in some places, and some would become less common in others.

    The alternative hypothesis is that for some reason this minor addition of a trace gas systematically and consistently causes bad weather, rather than having a fairly neutral effect overall. Maybe it does, but convincing people of this will require more than anecdotal evidence about floods here and heatwaves there, in one particular year.

    I suspect that our best assessments of the most likely changes in weather patters will be a good deal less terrifying than some of the posters here would like. (Even when beneficial changes are downplayed, as is usually the case.)

    [Response: Maybe we’ve only had a degree or so of warming so far, but depending on climate sensitivity and how much coal we can (or will) burn, global mean temperatures could well rise by 7C or even more. That is why there is so much interest in trying to use the present climate change to try to get some early warning of how bad things can get. You only have “suspicions” based on neither observations nor physics, just prejudice. Other people are working hard to try to make some sense observationally of this difficult problem Your suspicions don’t help anybody very much, so people should just take them for what they are worth. –raypierre]

    Comment by Gerry Quinn — 18 Feb 2011 @ 11:22 PM

  80. @ Quinn #79 – How do you define ‘bad weather’? Perhaps you define a drought as ‘bad weather’. Yet a drought in, say, the UK would be a mild summer where I live. Or maybe you define ‘bad weather’ as torrential rain? Torrential rain in a tropical rainforest is the norm in the wet season, yet where I live summer is dry and torrential rain causes flash floods and month long floods and ruins crops.

    Extreme or bad weather can only be defined relative to what constitutes ‘normal’ weather for a particular locality. In other words, ‘consistently bad weather’ as you’ve put it would constitute a change in the climate, which has ramifications for local agriculture, building design and construction, infrastructure such as roads, rail and water storage, indoor air conditioning (or climate control’) and even the siting of dwellings and infrastructure.

    The change in weather (extreme weather and unprecedented weather) is already taking place a good deal more quickly than some people expected. And the weather is measured, it’s not just anecdotes of someone gazing out their window. What constitutes terrifying for some might not for others. Staring down a wildfire is quite nerve-wracking, as is holding onto a barbed wire fence for several hours, hoping not to drown in a swiftly flowing current of water. Drought is a slower form of ‘terrifying’.

    People in some localities might not be subject to extremes of weather. In other localities people are flip-flopping from one extreme to another, including unprecedented extremes. (eg In this part of the world it is flip-flopping from unprecedented heat and long drought to unprecedented rain intensity and extreme floods – and this has been going on for more than a decade.)

    Comment by Sou — 19 Feb 2011 @ 12:04 AM

  81. SM, how about some sources? You sound like you know the literature or have written some of it. What are you reading or recommending others read?

    Something like this?
    Rougier: Probabilistic inference for future climate using an ensemble of climate model evaluations

    Comment by Hank Roberts — 19 Feb 2011 @ 2:07 AM

  82. Septic Matthew in your comment #72 on attribution of weather causes and natural weather:

    I really don’t think a synoptic or mesoscale meteorologist would agree with your remarks. In a very strict sense you may be right, but of course we don’t necessitate that every picokelvin of the temperature gradient around a frontal system or every microscopic and turbulent feature associated with a mid-latitude cyclone be accounted for. Saying that we can’t attribute causes to an emerging weather system is just as absurd as saying we can’t attribute causes to climate change. Here in Wisconsin for example, it’s usually pretty easy to identify storm systems that originate by the rockies, perhaps due to deformation of a temperature gradient down the leeward side of the mountain.

    I think it’s very easy to brush off synoptic/mesoscale dynamics and the rather powerful field of meteorology when we talk about climate, and I know at least know a few people I have everyday contact with who get irritated at climate people because of this. I think a better marriage of these fields is really going to have to happen to get a better grip, especially, on the issue of extremes.

    Comment by chris colose — 19 Feb 2011 @ 2:34 AM

  83. Tom Wigley wrote

    The relative importance of human factors varies greatly according to both the spatial scale and the variable considered. As a general rule, the smaller the spatial scale, the smaller the ratio of human-to-natural influences. Furthermore, the magnitude of the human influence relative to natural variability for temperature is, generally, much larger than for variables like precipitation (see Box 1) and atmospheric circulation (Barnett and Schlesinger, 1987; Santer et al., 1991). These differences are important in understanding future changes. As we continue to perturb the environment with the byproducts of industrial and agricultural activity, so the signal of anthropogenic climate change will continue to grow relative to the background noise of natural variability. For global-mean temperature, anthropogenic warming will become rapidly more and more obvious. However, for other variables like precipitation, and for changes at smaller spatial scales, the human signal will emerge from the background noise much more slowly. In some cases, it may be many decades before we can clearly see these signals.

    in his Pew Center report The Science of Climate Change: Global and U.S. Perspectives in 1999.

    We have “long” since passed the point where the anthropogenic influence on global mean temperature has emerged from the background noise. And it seems to me we are on the cusp of being able to attribute smaller scale features an anthropogenic influence with reasonable probability.

    Comment by P. Lewis — 19 Feb 2011 @ 3:59 AM

  84. Didactylos #57. Good points. It goes further than that. Wivenhoe exceeded nominal 100% capacity 4 times before the flood. 100% represents the level below flood mitigation capacity. The dam is completely full at 225%, and went to 191% the last time it was emptied. This is a very serious situation because the dam is not designed to be overtopped. It has sacrificial gates that would have opened before that happened so a disaster arising from the dam collapsing is unlikely, but the fact that we arrived at that situation from a drought crisis in 2007 when the dam dropped to 15% is a hint that we are seeing wilder climate swings than in the past. The saving of 2m no doubt relates to one event when the dam holds back a flood. I saw a claim that the total rainfall feeding into the dam was double that of the 1974 flood. It’s just plain stupid or a consequence of only reading the Murdoch media to claim this event was of a lesser scale than the 1974 flood.

    As to whether this is a once-off event or part of a pattern, there’s still science to be done, but I wouldn’t wait if there’s action that can be taken now.

    Comment by Philip Machanick — 19 Feb 2011 @ 4:31 AM

  85. Brisbane floods:

    BOM rountinely publishes monthly weather summaries including comments on point and areal extremes. January isn’t out yet, but will appear shortly here (December is worth a read). There will also be a flood event summary, which, as I guess you know, will appear here.

    Not all of the Wivenhoe flood storage window was used. It peaked at a bit over 1000GL, for a total of ~1350GL in the Somerset Dam / Wivenhoe Dam cascade. I think Wivenhoe will have reduced Jan’11 by more than the 2m hindcast for Jan’74, because the proportion of the event rain on that sub-catchment was higher this time. Recall that Somerset was in place for both floods and also has a substantial flood storage window (~300GL). So if you wanted to adjust for flood mitigation, I’d be adding about 0.5m to Jan’74 and maybe 3m to Jan’11 (crude estimate from one who lives in the town and works in the field…).

    Pre-1900 errors; yep, up to a point. The 1893 flood heights are known exactly. The flood of record (1841) is a bit of a guess. First european visitor was only 1821.

    You seem to be arguing that the Jan’11 flood was not particularly extreme. That, of course, is correct (I’d put it at only about 1 in 50, but that’s a controversial view). I think you should re-read Gavin’s brief explanation of what “extreme event” means in the context. It’s not “biggest possible” or even “biggest recorded”; really just “unusually big” (yeah, rubbery…). So in that sense Jan’11 is one, and what might be able to said is that events like it are becoming more frequent. Any evidence of that in the Brisbane record (so far)? Nup, not on the face of it. Elsewhere? Seems to be, now.

    The really odd (and little mentioned) thing about Jan’11 was that it wasn’t a cyclonic event, unlike the other big ones on the record. Attributers could do worse than have a look at that.

    Comment by GlenFergus — 19 Feb 2011 @ 4:58 AM

  86. Septic Matthew, And since you missed or chose to ignore my points, I will also repeat them:

    The Russian heat wave affected a very large area. It was well outside the norms for any historical event. The extent of the flooding this year has come very close to causing food insecurity for the first time since the ’80s–despite all of the advances in farming and yields.

    What is more, these are precisely the sorts of events that theory predicts. I think you would have a very difficult time explaining the trends without added greenhouse forcing. Indeed that is what this research indicates.

    Comment by Ray Ladbury — 19 Feb 2011 @ 7:42 AM

  87. Gerry Quinn,
    Might I suggest that you sit down and estimate exactly how much energy an increase in temperature of 1 degree C represents for the atmosphere plus the first hundred meters or so of ocean. Now consider that this is an AVERAGE and that the distribution of energy is not uniform and is subject to fluctuations–as in any thermodynamic system. I would suggest that this increase is more than sufficient for any sort of extremes we are seeing.

    Comment by Ray Ladbury — 19 Feb 2011 @ 7:45 AM

  88. Septic Matthew said “Earth experiences dozens at least of 3 sigma events every year”

    This is just daft. Earth experiences millions of extreme events every year. We have no clue exactly how many. Extremes are only extreme when you look at a specific event in a specific place. This means that when comparing extremes, it is essential to compare extremes from the same class.

    Thus, you cannot compare a 3 sigma record high temperature day in Springfield with a month-long heatwave covering a big chunk of eastern Europe.

    So, let me close with a quote: “you really need to study up more on the statistical analysis of extremes”.

    Comment by Didactylos — 19 Feb 2011 @ 9:25 AM

  89. While we’re talking 3 sigma events, how rare is permafrost melting? After all, it isn’t called “Oftenfrost.”

    [Response: The term “Permafrost” refers to the situation where there is always a layer left deep down that remains frozen throughout the year. In any place where the surface temperature goes above freezing for part of the year, there is an active layer that melts and refreezes annually. High latitude warming manifests itself primarily in increase in the depth of the active layer. –raypierre]

    Comment by Jeffrey Davis — 19 Feb 2011 @ 9:59 AM

  90. is not “…anecdotal evidence about floods here and heatwaves there.”

    This whole methodology of determining how badly the dice are loaded will only make sense once we have models which can accurately hindcast each individual occurrence of snake eyes, the extreme event, with some reliability.
    In other words, the “how can you predict the climate if you can’t predict the weather” argument is brought up yet again.

    Comment by Brian Dodge — 19 Feb 2011 @ 10:14 AM

  91. Chemotherapy causes hair to fall off. Even so, it´s hard to pinpoint which ones fell because of the chemo and which would be the ones that would fall off anyway, in the normal rate.

    It looks like we’ll go bald claiming that we cannot determine wether it’s becauso fo the chemo or not.

    Comment by Alexandre — 19 Feb 2011 @ 10:25 AM

  92. Chemo & baldness
    The difference is we have a pretty good idea how much baldness to expect in the absence of chemo. And can predict with chemo.

    Comment by Punksta — 19 Feb 2011 @ 10:52 AM

  93. So SM, you’re claiming some expertise in ‘statistical analysis of extremes’ — reading? cites?

    Comment by Hank Roberts — 19 Feb 2011 @ 12:18 PM

  94. Gerry Quinn wrote: “On the face of it, one would not expect that an increase in greenhouse gases sufficient to increase the average temperature of the Earth by a degree or so would have a dramatic effect on ‘extreme events’ in general.”

    On the contrary. On the face of it, that’s exactly what one should expect, because it is what the climate models have been predicting, and it is now occurring just as predicted.

    Comment by SecularAnimist — 19 Feb 2011 @ 1:31 PM

  95. #91 Punksta. You have read the article, haven’t you? The one about prediction and attribution at the top of the page… Seems a bit daft to make assertions that can be proven false by using the scroll bar.

    Comment by One Anonymous Bloke — 19 Feb 2011 @ 2:41 PM

  96. 92, Hank Roberts: So SM, you’re claiming some expertise in ‘statistical analysis of extremes’ — reading? cites?

    At the risk of some repetition from my previous posts,

    R. L. Smith, Extreme value analysis of environmental time series: An appication to trend detection in ground-level ozone (with discussion), Statistical Science, volume 4 pp 367-393, 1985.

    S. G. Coles, An Introduction to Statistical Modeling of Extreme Values, Springer, 2001.

    The 2010 Joint Statistical Meetings included some invited papers on the analysis of extremes relevant to analysis of climate change. Here is one of them:

    Ray Ladbury and Didactylos, I think your last posts were attempts to goad me into an emotional response. If you’ll think about them for a few days, I think you’ll see what I mean.

    I think I’ll have to leave you all and master raypierre’s book. It’s a gold mine of information for a skeptical point of view: uncertainties and omissions are clearly presented, along with what is known.

    Comment by Septic Matthew — 19 Feb 2011 @ 4:45 PM

  97. Hello gents,

    Balancing the science with public policy is such a pain in the patootie. Sadly, this sort of post is irrelevant in terms of risk assessment because risk assessment is based on worst-case possibilities, home insurance, life insurance, e.g., where the risks are so overwhelming they must be addressed.

    The worst case scenario of me drinking 6 beers on a Friday night? A hangover. The worst case scenario wrt climate? Civilization being shaken to its knees and even collapsing. (One of the well-known collapse writers and researchers has turned pessimistic where he was formerly hopeful, e.g., per a private conversation and Taleb is famously pessimistic about our properly dealing with risk.)

    This is one of those rare times when I ask: Did you really need to post this? People are looking for ways to avoid acting, and the worse conditions get, the more they will grasp for straws. When asked, please answer honestly, but choosing proactively to post something that far too many will see as, “Scientists can’t equate squat to squat!” is perhaps worth reconsidering.

    The trends are clear enough, aren’t they? Need we always deal with the provable? Or do we all really believe Pakistan and Russia and Arctic Sea Ice and Tennessee floods and Australian floods and methane clathrate emissions and… would all be happening concurrently at 1850 temps?

    I’ll go close the barn door now.

    Comment by ccpo — 19 Feb 2011 @ 5:03 PM

  98. 77, eric in comment: [Response: You mean earth experiences more than three ‘extremes’ every month?! That’s what ‘dozens’ per year would mean.–eric]

    I missed this. The answer is yes, approximately, but the number fluctuates randomly.

    The extreme is with respect to the distribution of measures in the region and season. Like the Russian heat wave, most of these are not defined in advance (with respect to region and season), but identified post-hoc and cherry-picked to suit. Concomitant with the Russian heat wave was a Siberian cool wave; bloggers chose the event that matched their AGW beliefs. Had anyone chosen in advance a region large enough to include (and average together) them both, the event would have been nothing unusual.

    Another recent example was the swath of record low high temperatures in south central US. Had it been a swath of record high low temperatures it would have been exactly what is predicted by AGW. Instead, it’s just a set of locally correlated hundred-year (or 150-year) extreme events of no importance.

    The situation is analogous with coincidences: they are much more common than commonly supposed, but people do not notice most of them unless something draws their attention; the coincidences noticed after Pres Kennedy was assassinated have spawned a whole genre of literature and movies.

    If at this point you are thinking I am extreme (!), then start over from the top with gavin’s essay and the two focus papers. The statistical analysis of extreme events identified post-hoc is really hard.

    Comment by Septic Matthew — 19 Feb 2011 @ 5:10 PM

  99. “The WSJ is not a reliable source. There is no discussion of extreme events in the Compo et al paper at all. The 20C Reanalysis project is however very useful (albeit with caveats) and we’ll address that in a future post. – gavin]”

    There was certainly nothing in the Compo et al paper to justify the WSJ’s assertion that “The weather isn’t getting weirder” and “…researchers have yet to find evidence of more-extreme weather patterns over the period, contrary to what the models predict”.

    Gilbert Compo has submitted a letter to the WSJ regarding their misrepresentations of his work, which he expects to be published on Wednesday Feb 23rd – I hope they publish it in full. Look out for it.

    Comment by Icarus — 19 Feb 2011 @ 8:09 PM

  100. Icarus #99: good to see that but any chance that the Compo letter will appear here? I don’t read WSJ regularly because I like to know what’s going on and could easily miss it if published there.

    Comment by Philip Machanick — 19 Feb 2011 @ 8:51 PM

  101. SM, okay, you point to stuff ten or more years old; I pointed to recent work; have you any thoughts about the current papers?

    Comment by Hank Roberts — 19 Feb 2011 @ 9:08 PM

  102. Septic Matthew, How interesting that you seem to think a response that sticks to facts is trying to goad you.

    I agree that one can tell little from any single event–however extreme. However, when you start seeing more large events than expected and when the effect of those events begins to have global consequences (e.g. food insecurity), that’s a pretty good indication that something important has changed. We’re there.

    Comment by Ray Ladbury — 19 Feb 2011 @ 9:20 PM

  103. I have to mostly concur with ccpo.

    Meanwhile, I notice that people here continue to spend much time engaging with trolls and nitwits, while ignoring important posts, such at the one that (should have) directed the august posters here attentions to the recent study highlighted at climate progress on tundra destabilization.

    Maybe it’s just me, but if we have crossed crucial tipping points, I would kind of like to know it–just ’cause I prefer knowing the truth, especially from sites like this.

    Has the tundra and the ESAS (see N. Shakhova’s recent work) crossed a threshold that those mature enough to handle very hard truths should know about?

    (By the way, I completely trust wall street and everything that its Journal puts out–they’ve done ‘a heck of a job’ with the economy, and I think we should turn the care and nourishing of the livability of the entire planet over to them right away [/sarconol])

    Comment by wili — 20 Feb 2011 @ 12:24 AM

  104. Septic @ 98: Sorry, but this is completely incorrect. I have not gone back to look at it, but I’m certain both the high and low were probably related to the same phenomenon. Rather, the cut-off that created the heat wave probably prevented Moscow from participating in the cold wave. It was anomalous. Moreover, the concern about highs and lows is not abou any one, but about the preponderance of new highs to new lows being at about 2:1 as opposed to a more typical 1:1-ish.

    Further, your contention the US lows were not anything unusual is also largely incorrect. The lows went as far as Mexico and are related (known, but not proven) to the Arctic oscillation which is related to levels of sea ice and higher than usual Arctic temps.

    I can’t (yet) prove it, but we both know it’s so.


    Comment by ccpo — 20 Feb 2011 @ 12:52 AM

  105. #73: I think smoker lawsuits are workable analogies to the Pall case, although toxic exposure suits like #26 mentioned are better. Re:

    “The idea is to determine a FAR for AGW as might be done for smoking, say. But in the case of smoking you have data on a real population of smokers and non-smokers. You only have to make one not particularly heroic assumption, i.e. that the risks for the individual whose loved ones are bringing the law suit were typical of the population of smokers as a whole.”

    A lawsuit brought by a single smoker would be very similar to the hypothetical lawsuit brought over the flooding. We do have data on the real population of extreme events pre and post climate change, and the assumption that a particular smoker is “typical” could be challenged in court. Again, though, asbestos or other toxic exposure suits would be more appropriate analogies.

    Gavin suggests medical mapractice might also be a good example. Sounds plausible to me, although I don’t know the field.

    Comment by Brian Schmidt — 20 Feb 2011 @ 12:04 PM

  106. IEHO, these papers alert us to be watchful, and are an interesting effort at postdiction of climate effects on a local level, but one should be cautious about accepting them at full face value yet.

    Signing on enthusiastically to the next hot thing immediately risks looking foolish the next day. But this is interesting. Other than that Eli’s read on the thing is a good try to determine what the unperturbed boundary values were for a local climatology and whether they have been exceeded when the climate is perturbed.

    Comment by Eli Rabett — 20 Feb 2011 @ 4:26 PM

  107. The “livability of the entire planet” – I like that. Cf. the Devonian, 8 times pre-industrial CO2, life flourished like crazy.

    But I no more expect this post wil be accepted than my previous one drawing attention to Phil Jones’s admission of no warming in 15 years.

    [Response: This comment probably deserves to be just Boreholed, but I think it at least provides a useful occasion to remind people that in the Devonian nobody was trying to feed 9 billion humans with plants and animals that are largely adapted to the climate of the past few million years or less. Heck, there weren’t even any mammals yet, for that matter, not much animal life on land. Seed plants had just barely gotten underway on land, and insects were just getting going. So I don’t think that you can exactly conclude it would be harmless to go back to a Devonian climate in the next couple thousand years. –raypierre]

    Comment by Michael H Anderson — 20 Feb 2011 @ 5:40 PM

  108. Michael, for crying out loud, everyone here knows that you have taken Phil Jones’ comment out of context and misrepresented his meaning. If you actually do not know what his meaning was, you will have to look it up, because I am not about to tell you. If you don’t do that, then you will simply continue to make a fool of yourself. Your choice.

    Comment by Ron Taylor — 20 Feb 2011 @ 9:37 PM

  109. Michael #106. You are out of your depth. Tread water, listen, learn. Thrashing around like that will just induce a feeding frenzy.

    Comment by One Anonymous Bloke — 20 Feb 2011 @ 9:54 PM

  110. thanks for the excellent clarification – the four bullet points are fundamental and I’ll be adding them to my teaching powerpoints!!

    Comment by paul haynes — 21 Feb 2011 @ 6:00 AM

  111. Speaking of life “flourishing” with AGW, the Humboldt Squid is doing nicely; hake, and the fishermen who catch them, not so much –

    “Coincident with the arrival of Dosidicus in 1997, the numbers of hake declined, then recovered after the squid observations dropped off, from 1999 through 2001. When Dosidicus returned in 2002, the numbers of hake dropped again and have remained very low (Fig. 3). Numbers of hake have been significantly lower during periods when Dosidicus was present (1997–1999 and 2003–2005; Mann–Whitney U test, U = 1,176, n = 196, two-tailed P = 0.000),”

    “‘There’s very strong evidence that the squid expansion had a huge impact on the hake fisheries,’ says Field, who helped organize a symposium on the animal in 2007. ‘It looks like they’re doing the same migration as hake, which concerns me.'”

    Then there’s the “flourishing” of mosquito populations –
    “Recent disease outbreaks are consistent with model projections that warmer, wetter conditions will lead to greater transmission potential at higher altitudes and elevations. Mosquito-borne diseases are now reported at higher elevations than in the past at sites in Asia, Central Africa, and Latin America (Epstein et al., 1998).”
    “In New York City, an encephalitis outbreak in summer 1999 claimed three lives… West Nile virus as being responsible for this outbreak…which had not been previously documented in the Western Hemisphere”

    “The results of the empirical estimation indicate that climate conditions have an increasingly significant impact on the probability of people being infected by dengue fever. ” Estimating the economic impacts of climate change on infectious diseases: a case study on dengue fever in Taiwan Wei-Chun Tseng, Chi-Chung Chen, Ching-Cheng Chang and Yu-Hsien Chu

    It’s not all AGW gloom and doom; take jellyfsh, for instance –
    “Two centuries worth of data shows that jellyfish populations naturally swell every 12 years, remain stable four or six years, and then subside.
    2008, however, will be the eighth consecutive year that medusae, as they are also known, will be present in massive numbers.
    The over-exploitation of ocean resources by man has helped create a near-perfect environment in which these most primitive of ocean creatures can multiply unchecked, scientists say.
    “When vertebrates, such as fish, disappear, then invertebrates — especially jellyfish — appear,” says [Ricardo] Aguilar [research director for Oceana, a international conservation organisation].
    The collapse of fish populations boost this process in two important ways, he added. When predators such as tuna, sharks, and turtles vanish, not only do fewer jellyfish get eaten, they have less competition for food.”

    “Researchers also don’t know why the giant jellyfish are becoming more regular visitors to Japan’s shores.
    In the early 1900s large numbers of the giants were reported only every 40 years or so.
    But in recent years the jellyfish have been appearing with alarming frequency: Japan experienced unusually large outbreaks almost every year between 2002 and 2007.”

    Probably just a coincidence that it correlates with global warming, right?

    Wrong. (And perhaps relevant to
    “In eleven species studied from subtropical, temperate and subarctic environments, warm temperatures were related to large population sizes;”
    “Because climate changes have complex ecosystem-level effects, the proximate causes of jellyfish increases are difficult to deduce. Therefore, the effects of temperature, salinity and prey on asexual production of new medusae from the benthic polyps of scyphomedusae and hydromedusae also are reviewed. Experiments on temperate species show greater and more rapid production of medusae at warmer temperatures.”
    Climate effects on formation of jellyfish and ctenophore blooms: a review Jennifer E. Purcell, Journal of the Marine Biological Association of the United Kingdom (2005)

    “Data obtained since 1958 from the continuous plankton recorder show an increasing occurrence of jellyfish in the central North Sea that is positively related to the North Atlantic Oscillation (NAO) and Atlantic inflow to the northern North Sea.”
    Climate-related increases in jellyfish frequency suggest a more gelatinous future for the North Sea Attrill, Martin J., Jade Wright, Martin Edwards,Limnol. Oceanogr., 52(1), 2007, 480-485 | DOI: 10.4319/lo.2007.52.1.0480

    “Complicating future predictions will be the possibility that, if climate change exceeds some critical threshold, some marine systems will switch to a new state that might not only be less favourable than the present one, but also prove impossible to reverse.”

    With a little more push from humans, the ocean ecosystems might return not to the Devonian, but even further; Richardson et al[1] note
    “The potentially durable switch to a jellyfish-dominated system is reminiscent of the ancient, rudimentary ecosystems of the Cambrian, and has convinced some authors [26,53] that human stressors are propelling marine ecosystems ‘way back to the future’”

    Gibbons, M.J. and Richardson, A.J. (2008) Patterns of pelagic cnidarian abundance in the North Atlantic. Hydrobiologia 616, 51–65, cited by the Heartland Institute as a rebuttal to Attrill, “showed that variations in jellyfish abundance over 50 years in the oceanic North Atlantic are temperature dependent, with more jellyfish occurring in warmer years.”
    Richardson et al., in [1] suggests(with his tongue firmly in his cheek, IMHO; maybe Idso and Monckton at Heartland should read rather than cherrypick?) –
    “One potentially appealing response is to harvest more jellyfish for human consumption. Jellyfish are important culturally as a gourmet food in Chinese banquets, and are the ultimate modern diet food [56].”
    Richardson’s reference 56, Jellyfish as food, Hsieh et al, point out that “…the carbohydrate content in jellyfish is negligible for calorie calculations (Table 1). The calculated caloric value for a normal serving (100 g) of RTU is less than 20 Kcal.”
    “Amino acid analysis shows that tryptophan, a limiting amino acid, is either not detectable or is found in small amounts in jellyfish tissue (Kimura et al., 1983). Thus, the nutritional quality of jellyfish protein quality is low” and is only ~5 g per 100g serving.

    Perhaps Lord Monckton, echoing another infamous member of the nobility, believes we should “let them eat jellyfish.”

    [1] The jellyfish joyride: causes, consequences and management responses to a more gelatinous future Anthony J. Richardson, Andrew Bakun, Graeme C. Hays and Mark J. Gibbons, Trends in Ecology and Evolution Vol.24 No.6

    Comment by Brian Dodge — 21 Feb 2011 @ 11:23 AM

  112. re: 110 and the spread of disease

    Dengue Fever is now showing up in Florida.

    Comment by Jeffrey Davis — 21 Feb 2011 @ 11:50 AM

  113. RE #79 & (Even when beneficial changes are downplayed, as is usually the case.)

    I have to admit that when I moved to the Lower Rio Grande Valley in 2002, I secretly felt a bit happy that GW had a silver lining, and embarrassed I felt good about it, bec of all the other very serious harms it causes (but continued my household mitigation measures nevertheless & even more — like going on GreenMountain wind energy). In our area you can’t grow things in summer — too hot — so fall-winter-spring is our growing season. Except rarely in some years we get a killing freeze for a day or so, usually end of Dec, Jan. So with GW, I reasoned, these freezes would become less frequent & maybe non-existent.

    Now some are saying they maybe become more frequent caused by negative arctic oscillations (see ). As happened this year (in Feb, & 2 hard freezes really doing in my plants) and last year (Dec 4, 2009), killing much of my vegetable garden. So much for the silver lining.

    And I’m really mad at those darned people profligately emitting their GHGs AND (the kicker) denying any culpability, like sons of Cain. Can’t you darned profligate GHG emitters give a person a break?

    I wonder how the Mexicans feel after losing over a $billion of their crops a few weeks ago to the same freeze? See

    Comment by Lynn Vincentnatnathan — 21 Feb 2011 @ 12:06 PM


    Comment by Some Anonymous Bloke — 21 Feb 2011 @ 6:05 PM

  115. I’d just like to add to #85 Glen Fergus. Despite its position today as an industrialised, modern nation Australia is quite young. The first European settlers arrived here some 12 years after the American War of Independence.

    By 1850 the national population was only 405,356 spread over an area the size of the USA. Due to this it will be hard to draw comparisons to modern times and trends. We might know that a mjor flood occurred in 1862, but there is no way to accurately define the full extent or area covered. All we can know is that it was about “this high” in “this place”.

    My own State, Queensland (where Yasi hit) doesn’t enter the records until 1859 with a population of 23,520. The bottom line is that there could have been 5 Cat 5 cyclones every year before then and we wouldn’t know anything about them.

    I’m sorry, but I think the Australian data is too short and sparse to draw many conclusions from. The only certain thing is that we always have been and always will be a “Land of drought and flooding rains”.

    I also agree with Glen that too little attention is being paid to the non cyclonic nature of the recent event.

    Comment by JohnB — 21 Feb 2011 @ 11:51 PM

  116. Brisbane floods , Toowoomba is on the great dividing range west of Brisbane
    where the inland tsunami event began

    Comment by john byatt — 22 Feb 2011 @ 4:36 AM

  117. Minor Nitpick: The CPDN team tries to be careful to use “Non-Industrial” rather than “Pre-Industrial”. There are obvious differences: Pre-industrial does not have current solar forcing whereas non-industrial does have current solar forcings.

    So perhaps a change would be in order from:

    “Then they repeated the same experiments with pre-industrial conditions (less CO2 and cooler temperatures).”

    to something more like

    Then they repeated the same experiments with non-industrial conditions (pre-industrial anthropogenic forcings like CO2 so cooler temperatures but natural forcings like solar at current levels).

    Comment by crandles — 22 Feb 2011 @ 5:49 AM

  118. Lynn,
    Many other locations experienced favorable growing conditions over the past 30 years also. This was mainly a result of higher low temperatures, resulting in fewer freezes and a longer growing season (in some places up to two weeks). Summer highs have changed very little over that timeframe, resulting in less parchment.
    Additionally, much of the Midwest and Plains have experienced an increase in rainfall further increasing crop yields. Areas in the Desert Southwest have been reporting more drought-like conditions, which may be affecting your area.
    Southern states (and Mexico) have experienced fewer freezes in recent years than in decades past. This resulted in farmers growing crops in region that are not ideal. If conditions return to those in the 1960s and 70s, then these farmers will experience many crop failures due to the cold weather.

    Comment by Dan H. — 22 Feb 2011 @ 9:32 AM

  119. 118, Dan H,

    And what’s your point? That climate change will be good, or that it just hasn’t slammed us yet quite as hard as we can expect it to?

    To answer those questions, visit this site: Climate Wizard

    Choose “precipitation” and “mid century” from the radio buttons and stick to the USA.

    Doesn’t look too bad, though, does it? A bit wetter up north, a bit drier in the south east.

    But wait… that’s just an annual average. What if (as is the case) there are severe drops in precipitation during the growing seasons, but increases after it’s too late (or during the winter, when it hardly matters)? Or dangerously useless increases for very short periods (meaning floods and crop damage instead of moisture patterns that feed crop growth)?

    Choose different measurement periods from the drop down menu (e.g. “June”) to see what I mean.

    Hint 1: local precipitation is not so much dependent on local temperatures as more complex patterns involving distant regions and factors, which are in turn affected on average by climate. Warmer temperatures at one locale do not necessarily mean drought, and vice versa.

    Most models project a serious water deficiency for the American south and south west with climate change. And in that realm, one or two horrible months could kill an entire season of crops, no matter what you are trying to grow, or what the annual average is.

    Hint 2: It is still very early in the climate change issue. You can’t point to anything now and say “see, it’s not so bad,” or “yeah, things are worse for them, but better for those other people over there.” It’s too early to tell for sure.

    You’re going to have to wait fifty years to see what your calm patience with the issue has done to everyone else’s future.

    Comment by Bob (Sphaerica) — 22 Feb 2011 @ 10:29 AM

  120. Ray Ladbury @87

    Might I suggest that you sit down and estimate exactly how much energy an increase in temperature of 1 degree C represents for the atmosphere plus the first hundred meters or so of ocean. Now consider that this is an AVERAGE and that the distribution of energy is not uniform and is subject to fluctuations–as in any thermodynamic system. I would suggest that this increase is more than sufficient for any sort of extremes we are seeing.

    What nonsense. For a start, a difference of 1 degree in the relevant region is equivalent to an 0.3% increase in the average temperature of 290K or so. That’s if absolute temperatures meant anything in this context, which they don’t. Temperature differences are what count in terms of available energy. Now you might be able to make a case on the basis of specific temperature differences, or increased moisture content of warm air, or whatever. Even then, you will be hard-pressed to make any such simple argument for dramatic changes based on actual local values, which fluctuate greatly about the average.

    Comment by Gerry Quinn — 22 Feb 2011 @ 11:59 AM

  121. Secular Animist @94

    Gerry Quinn wrote: “On the face of it, one would not expect that an increase in greenhouse gases sufficient to increase the average temperature of the Earth by a degree or so would have a dramatic effect on ‘extreme events’ in general.”

    On the contrary. On the face of it, that’s exactly what one should expect, because it is what the climate models have been predicting, and it is now occurring just as predicted.

    Actually, the models do *not* predict dramatic changes from a degree or so of warming (and, for obvious reasons to do with the size of typical temperature fluctuations on a less than global scale, one would be have to be very suspicious of any model that did).

    That is one reason why the IPCC have selected 2 degrees of warming as a reasonable target. It’s not expected to do anything particularly terrible.

    Comment by Gerry Quinn — 22 Feb 2011 @ 12:12 PM

  122. Bob,
    Your post seems to indicate that the desert southwest and western Texas received an increase in precipitation during the past 50 years. Changing to seasonal or monthly precipitation did not seem to have a large effect on the growing season. I was also surprised to find such a large area of the US witness a temperature decrease over the past 50 years, especially in the summer and fall months. In fact, it appears that the entire temperature increase occurred from January – April, and was restricted to the Northern Plains and Western States. This is probably why we witness such a large extension in the growing season.

    Comment by Dan H. — 22 Feb 2011 @ 1:12 PM

  123. > an 0.3% increase in the average temperature of 290K

    Your calculation ignores a significant change occurring at 273.15 K.
    Your percent increase needs to be calculated against that as the zero mark.

    You do too know what I’m talking about. Deal with it.

    [Response: % changes in temperature are simply meaningless. – gavin]

    Comment by Hank Roberts — 22 Feb 2011 @ 1:30 PM

  124. Gerry Quinn @121 — The current ~0.7 K increase is already bad enough. A full 2 K is likely to be rather rugged on us all.

    Mark Lynas’s “Six Degrees”:

    Comment by David B. Benson — 22 Feb 2011 @ 2:03 PM

  125. Worth following on this topic–posts by Zorita:

    Comment by Hank Roberts — 22 Feb 2011 @ 3:11 PM

  126. Gerry Quinn @ 120 and 121

    As a weather forecaster, I would expect some rather dramatic changes in extremes with a 1C rise in temperatures. This is especially relevant in the sub/tropics, and in more poleward locations that receive subtropical advection. That’s because this would also raise the dew points by about the same 1C. Considering energy partition at fairly typical tropical temperatures and RH (70% for a crude estimate) over 2/3 of the extra thermal energy goes into evaporating water. This latent energy is made available downstream by increasing the CAPE (convectively available potential energy), thus energizing thunderstorms, tropical systems, etc.

    Models are typically not gridded finely enough to resolve convective instability. That’s why an important task for warm season forecasting in the mid latitudes of the humid U.S. is evaluating the low level moisture, and the potential for instability. Even 1C extra dew point at, say, 850 mb is enough to cause a “loaded gun” barely capped airmass to blow in spectacular convection.

    Poleward transport of moisture and instability by narrow low level jets, another feature not well resolved by models, also results in many flooding episodes, as well as severe convection.

    Considering that the capacity of air to hold water vapor increases nearly exponentially with temperature, I think a 1C increase is truly a big deal, and will add substantial extra energy to some already strong systems, models or no.

    Comment by John Pollack — 22 Feb 2011 @ 3:45 PM

  127. John Pollack @126 — Exceptionally clear. Thank you.

    Comment by David B. Benson — 22 Feb 2011 @ 4:30 PM

  128. Amazon has two books entitled \Statistics of Extremes\.

    Gumbel’s 1957 Dover Book ($16.47 )


    Jan Beirlant, Yuri Goegebeur, Johan Segers, and Jozef Teugels ($108.44)

    I bought one with an extremal price.

    Comment by John E. Pearson — 22 Feb 2011 @ 10:45 PM

  129. John Pollack @126
    Certainly water vapour content is the most plausible large effect of an increase in average temperature; as you indicate, evaporation and condensation are ways of transferring large amounts of free energy, some of which can presumably end up in a variety of weather events.

    Of course extra water vapour has other effects as well. For one thing it is the mechanism for amplification of the basic CO2 greenhouse effect. And assuming that the amount of rainfall is in some way responsive to the average water vapour content, presumably higher temperatures can drive an increased number of extreme rain events. On the other hand, more rain, on the face of it, should mean less drought, so it’s not all bad.

    However, when we talk about the effects of an extra degree, we need to remember the main point I was making. The temperature at the Earth’s surface varies very widely. The average annual temperature varies globally over a wide range, depending not just on latitude and altitude but on many other factors. And at every location the temperature also varies, in some places more than others. It varies between day and night, it varies between seasons, and it varies day to day, week to week, month to month, and even over years, in response to weather systems of various longevity. The longest term weather systems shade into climate, which itself varies, and not just due to anthropogenic causes.

    It varies everywhere by much more than one degree. Which means that on most days, it is sometimes 1 degree hotter than it is today. Do we quake in fear when the weather forecast says temperatures will rise by one degree next week?

    Short version: a change of one degree in average temperature is surely not going to move any region of the world into a novel climatic regime! I can readily believe that, for example, flooding events, heatwaves, or what have you might become a bit more likely in many places. But basically, these are going to be happening in places that might expect such events anyway.

    A small change in global average temperature may certainly have statistically significant global average results. And it may well interact with other processes to make climates evolve differently than they would have otherwise, for better or worse – or, almost certainly, for better AND worse. But I don’t find the prophecies of doom in the comments here (not referring to your post) remotely credible.

    Comment by Gerry Quinn — 23 Feb 2011 @ 6:25 AM

  130. Gilbert Compo very kindly emailed me the following, regarding the recent WSJ article about the Twentieth Century Reanalysis Project and trends in extreme weather:

    I wanted to let you know that our letter has appeared at
    Severe Weather Is Driven by Many Factors

    While we appreciate the opportunity to discuss our work, we found that the resulting opinion piece “The Weather Isn’t Getting Weirder” (Feb. 10) does not accurately reflect our views.

    As for the statement that the Twentieth Century Reanalysis Project, which is a synthesis of weather observations going back to 1871, shows “little evidence of an intensifying weather trend”: We did not look at weather specifically, but we did analyze three weather and climate-related patterns that drive weather, including the North Atlantic Oscillation. And while it is true that we did not see trends in the strength of these three patterns, severe weather is driven by many other factors.

    The lack of a trend in these patterns cannot be used to state that our work shows no trend in weather. Many researchers have found evidence of trends in storminess and extreme temperature and precipitation in other weather data over shorter periods.

    Finally, the article notes that the findings are “contrary to what models predict.” But models project forward, while our analysis looked back at historical observations. We see no conflict between the 100-year-projection of changes in weather extremes resulting from additional carbon dioxide and the fact that our look back at three indicators showed no historical trend.

    Thank you for this opportunity to clear up any inadvertent misunderstandings about our work, which can be found at:

    Gilbert P. Compo
    Research Scientist
    University of Colorado at Boulder

    Jeffrey S. Whitaker
    National Oceanic and Atmospheric Administration

    Prashant D. Sardeshmukh
    Senior Research Scientist
    University of Colorado at Boulder

    Comment by Icarus — 23 Feb 2011 @ 12:55 PM

  131. I agree with the excellent post by Gerry (129) and was actually thinking something similar the other day. I was watching a TV bit about Stephen Hawking and the black hole information destruction controversy and wondered if this idea could (loosely) have any relevance to climate or specifically to the earth’s temperature history. Does our climate gobble up temperature information like a black hole? Much is being claimed about the alleged direct effects of a 0.5 degree temperature increase (last 30 years) on our climate system. The idea that there is some type of memory mechanism in the atmosphere that “remembers” minor long-term temperature trends is something that is taken for granted but never really proven. If this temperature “information” is not stored and it is obliterated daily, how could it possibly drive climate variations or create increases in “extreme events”? As Gerry said, how could minor long-term trends drive weather when they are completely and utterly obliterated by hourly, daily, seasonal, and dynamical temperature swings? The only ones that can and do remember or record minor long-term trends are us! (And some would claim we do a poor job at that) If we were talking about a clearly observed long-term temp trend of say 5 degrees or higher then it might be worth having this discussion. We just don’t have anything close to that! The air, ground, and even the oceans have no built in mechanism to be able to remember the slight long-term temp trends that some people are attributing to almost every negative event on the planet. This small signal is completely obliterated by much higher amplitude signals – plus there is nothing to filter or store it anyways! A few weeks ago here in Texas the highs were in the low 20’s and couple days later the highs were in the 70’s. 99.99999 percent of us and most of our ecosystem survived that crazy up swing in temperature. Why would we not be able to survive a 0.5 degree change over 30 years? Worry about this seems like extreme exaggeration. So are people claiming that climate instability is caused by the upward shift in temperature itself? Like claiming that there is some type of climate “inertia”? (Another poorly proven concept) Again, our planet can survive DAILY temp swings much greater then any claimed long-term trend without more instability being introduced. Some regions of the planet experience diurnal and seasonal changes that are vastly greater then other regions of the planet. Do these regions have vastly more unstable weather? That would be a good test for this theory, would it not? So can anyone here prove that there exists something like a memory mechanism in the atmosphere? Also, can anyone here prove that there is any type of climate inertia mechanism where the mere existence of long term trends cause “instability”?

    [Response: The number of mistaken assumptions in your text are legion. Who has claimed that the “we will not survive” 0.5 deg C rise in 30 years? This is a strawman. For comparison, the last ice age was only about 5 or 6 deg C colder than today, and that was effectively a different planet. The change by 2100 will be the same order of magnitude if we are unlucky – this is not some trivial change we are talking about. – gavin]

    Comment by xavier — 23 Feb 2011 @ 1:57 PM

  132. GQ 129: Short version: a change of one degree in average temperature is surely not going to move any region of the world into a novel climatic regime!

    BPL: Wrong. We’re talking about the planet’s mean annual surface temperature. A 1 degree change in that is enough to move agricultural growing belts hundreds of miles. Want the math?

    Comment by Barton Paul Levenson — 23 Feb 2011 @ 4:15 PM

  133. xavier:

    First mistake: the temperature increase is defined as the accumulation of “hourly, daily, seasonal, and dynamical temperature swings” over a suitably long period. It’s not the other way around.

    Second mistake: the planet has a very good memory. Some processes will accumulate weather data over a year, and record them. Tree rings, glacier terminations, and many others do this for local weather. Other mechanisms integrate weather data over wider areas, which brings us to –

    Third mistake: the ocean is the “memory” that drives the climate system. It is where most of the heat is stored. And the heat in the top layers of the ocean has been steadily increasing recently, for mindbogglingly obvious reasons.

    Fourth mistake – oh, I just don’t care any more. Think about it carefully, and write in actual paragraphs next time, and you may get a less dismissive response.

    Comment by Didactylos — 23 Feb 2011 @ 5:22 PM

  134. Gerry Quinn @ 129

    While I agree that a 1 degree temperature increase is not likely to lead to a planetary scale disaster, it can certainly worsen local disasters. Daily fluctuations are certainly large, but there are times when a degree can make a difference. For example, a 1 degree increment to our dew point last summer would certainly have made a difference, when the dew point was already a rarely-observed 27C. The same applies in general to convective systems fueled by latent heat energy.

    I am also not as sure as you that a 1 degree increment will not move any region of the world into a novel climate regime. Paleoclimatic evidence says that there really can be tipping points, e.g. the Younger Dryas.

    Comment by John Pollack — 23 Feb 2011 @ 10:54 PM

  135. BPL,
    Better check your math. Travelling North from Dallas, TX in order to Oklahoma City, Wichita, Topeka, Omaha, Sioux Falls, Aberdeen, and Fargo, all incrementally about 125 further north, the average temperature decrease between each is 1.7C. Therefore, all things being equal, a 1C increase would move agriculture about 75 miles north. However, things are not all equal, as the recent temperature increase was observed primarily in the coldest values; nighttime lows and winter. Hence, agriculture is more likely to expand northward rather than move.

    [Response: Agriculture is much more vulnerable to temperature/precip extremes than to changes in the mean, and so estimates of agricultural impact need to think much more about the how the peak daily temperatures will change for instance, than the annual mean. And the impact of that is decidedly non-linear. – gavin]

    Comment by Dan H. — 24 Feb 2011 @ 8:23 AM

  136. Of course Gavin,
    But since the peak temperatures have changed much less than the average, the agricultural impact would be much less. As I stated previously.

    [Response: Stating it doesn’t make it so. You would need to actually look at the data and the projections. – gavin]

    Comment by Dan H. — 24 Feb 2011 @ 11:08 AM

  137. Actually what laypersons & policy-makers should be focused on is not whether this flood or that hurricane can be attributed in part to CC. That’s water under the bridge & for scientists to debate & figure out.

    What we should be focused on is mitigating CC to avoid such events in the future, and here the science is stronger: CC is expected to increase the risk of floods, droughts, and higher hurricane intensity. That’s somewhat a more solid statement, and that’s what we should be trying to mitigate, not events that have already happened.

    Comment by Lynn Vincentnathan — 24 Feb 2011 @ 11:22 AM

  138. The two papers are behind a paywall, but the Supplemental Information for Lin et al is available here:

    The work is admirable and exemplary. From a skeptical perspective it should not be believed until it has been critiqued, debated and replicated, but the work was really carefully done and I hope it inspires others. It does cite the book by Coles, op cit.. You can read a thorough critique on a skeptical blog: but the critic is detailed but nihilistic (can be pronounced to rhyme with “denialistic”, but usually isn’t), that is the critic concludes that the paper is rubbish and ought not even to have been published. That’s an extreme (!) conclusion. Like the famous MBH98, it can be improved upon, but it’s pioneering.

    Comment by Septic Matthew — 24 Feb 2011 @ 11:39 AM

  139. Dan H. should also make the aquaintance of a farmer and a gardener sometime, or read something about phenology, and learn something about the temperature-and-timing requirements for various crops. That would change his mind. Google would like to befriend him. Various producers of fruits and vegetables would have opinions on the practicality of his advice so far.

    Just e.g.:

    Sustainable Orchard Management System For Intermountain Orchards …
    Temperature data generated by orchard weather stations will be … Fruit production in the intermountain west is besieged with problems. To cope with these problems ….
    Google: “sustainable orchard management”

    Comment by Hank Roberts — 24 Feb 2011 @ 12:06 PM

  140. RE #135, there are studies coming in that show the increasing diurnal minimum temps (night temps) are now harming certain crops….and CC increases the average night temps faster than the day temps. The study also says that in the future the increaing day temps (above a certain point) are expected to harm crops.

    Welch, et al. “Rice Yields in Tropical/Subtropical Asia Exhibit Large but Opposing Sensitivities to Minimum and Maximum Temperatures.” PNAS 107(33):14562-14567.

    Then factor in extreme weather events (including perhaps more frequent negative arctic oscillations that freeze-kill crops in areas where it’s too hot to grow crops in summer), and we could be facing serious food shortages.

    And we can’t expect the Arctic region to become the bread-basket of the world….people who live there tell me the soil is very poor. And when you look at the area on a globe rather than a flat map, there’s not as much acreage as it seems.

    And then there’s the impact of CO2….more pest damage, and harm to crops, esp at much higher levels….harm to seafood (fish, corals, shellfish). See:

    -Högy, et al. 2009. “Effects of elevated CO2 on grain yield and quality of wheat: results from a 3-year free-air CO2 enrichment experiment.” Plant Biology 11: 60-69.
    -Oh & Richter. 2004. “Soil acidification induced by elevated atmospheric CO2” Global Change Biology 10.11: 1936-1946.
    -Hunter, M. D. 2001. “Effects of Elevated Atmospheric Carbon Dioxide on Insect-Plant Interactions.” Agricultural and Forest Entomology 3: 153-159.
    -Munday, et al. 2010. “Replenishment of fish populations is threatened by ocean acidification.” PNAS 107(29):12930-12934.
    -Doney, et al. 2009. “Ocean Acidification: The Other CO2 Problem.” Ann Rev of Marine Sciences 1: 169-192.
    -Hoegh-Guldberg, et al. 2007. “Coral reefs under rapid climate change and ocean acidification.” Science 318: 1737-1742.

    Not to mention death by hydrogen sulfide, which is expected to increase:

    Krump, et al. 2005. “Massive Release of Hydrogen Sulfide to the Surface Ocean and Atmosphere During Intervals of Oceanic Anoxia.” Geology 33.5: 397-400.

    Comment by Lynn Vincentnathan — 24 Feb 2011 @ 12:11 PM

  141. Compare and contrast Dan H’s blithely sanguine comments with this new article by the “alarmists” at The Economist:

    A special report on feeding the world: No Easy Fix
    The Economist
    February 24 2011


    Global warming upsets the world’s water cycle, increases the burden of pests, desiccates soil and reduces yields …

    An increase of 2°C in global temperatures … could cause a 20% fall in wheat yields. This would exceed any possible gains from warming in areas currently too cold to grow crops and would also offset the benefits of rising carbon-dioxide concentrations …

    Climate change also affects the rhythm of the seasons. Winters arrive later or spring earlier. Rainy seasons become shorter, milder or more intense …

    In 2009 Oxfam, a British charity, asked thousands of farmers in a dozen countries what worried them most about climate change. Their biggest concern was not higher temperatures but disruptions to the natural cycle …

    When the International Food Policy Research Institute (IFPRI) tried to work out the impacts of climate change on the main cereal crops, almost all its results suggested that yields in 2050 are likely to be lower than they were in 2000, sometimes much lower. Almost half the forecasts showed yield reductions of 9-18% by 2050. One came up with a drop in rainfed-maize yields of 30%. The most vulnerable crop turned out to be wheat, with the largest losses forecast in developing countries. The Indo-Gangetic plain, home to a seventh of mankind and purveyor of a fifth of the world’s wheat, is likely to be especially hard hit.

    And by the way, the Economist article only addresses agricultural food supplies and does not even discuss the serious negative effects of AGW on oceanic food webs which are a major source of protein for human consumption.

    Comment by SecularAnimist — 24 Feb 2011 @ 1:54 PM

  142. Hank,
    You seem to be unaware of the increase in agricultural output during the past century. While much of that is undoubtedly due to technological advances, the climatic changes have also contributed. TO say that all crops have benfitted equally is simplistic. However, many crops here in the Midwest have benefitted from the longer growing season and higher rainfall.

    [Response: The monetary value of wheat, corn and soybeans in North Dakota and Minnesota in 2010 is more or less irrelevant to a general discussion of the effect of climate change on agriculture. Both production, and monetary value, vary widely with economic and other non-climatic factors.–Jim]

    One of this country’s staples is wheat production. Cehck out the Kansas wheat yield since 1979. Is it a coincidence that the highest yield was observed in 1998?

    Comment by Dan H. — 24 Feb 2011 @ 2:13 PM

  143. Climate change also affects the rhythm of the seasons. (…)

    Their biggest concern was not higher temperatures but disruptions to the natural cycle …

    In my area we’ve had a shift for years now that I’ve been refering to as “false spring” – it missed the usual mid Feb period [La Nina?], but I’m expecting it to show up in early March to fool many things to break dormancy too early and be subject to damage from late frost. The Feb warm periods have been resulting in tree fruit not getting enough winter chill-hours to produce fertile bloom, so light crops and/or trees that wind up throwing blooms in late summer or fall!!

    In addition for the last few years there’s been a mid summer period when we get a 1-5 day spell so hot that veggie blossom set ceases, and if it’s late enough it prevents any subsequent set having time to mature, particularly hard on the tomato crop which doesn’t like the warm overnight temps.

    DanH really does need to try growing his own food to cure his myopia – I suspect he may have the opportunity within a few years, if he wants to keep eating.

    Comment by flxible — 24 Feb 2011 @ 2:34 PM

  144. flxible,
    I do grow a lot of my own food. This past year I had a very poor apple crop, by a bumper pear yield. My beans, peppers, and squash all had excellent seasons. My peas were hampered by a spring hail storm which hit at the most inopportune time. I was harvesting broccoli into december – had to clear the snow off the plants first.
    I am appalled at all the people who think that agriculture is in serious trouble, when all the recent evidence points to the contrary. Speculation about future events when not based on real world data does not count as evidence Secular. Now if we were substantially cooling the plant, that would cause a large disruption.

    Comment by Dan H. — 24 Feb 2011 @ 2:56 PM

  145. Dan H wrote: “However, many crops here in the Midwest have benefitted from the longer growing season and higher rainfall.”

    Dan H follows that assertion with a link to an Ag Week article about 2010 record harvests in North Dakota and Minnesota.

    The article that Dan H cites says absolutely NOTHING about attributing those yields to “the longer growing season and higher rainfall”.

    On the contrary, the article quotes North Dakota Commissioner of Agriculture Doug Goehring who attributes the yields to “the type of seed genetics we are getting, the good research and breeding programs, and the better equipment we have”.

    The article also notes that “many parts of the United States have had bad growing years recently”.

    Comment by SecularAnimist — 24 Feb 2011 @ 3:10 PM

  146. DanH, you ask “Is it a coincidence that the highest yield was observed in 1998?”

    Well, I don’t know, and nothing you’ve posted seems to say (though I might have missed something in the Kansas report.) Absent serious consideration of the question, it could indeed be coincidence. Pace Jethro Gibbs, they do happen.

    The only attributive statement I came across was in the North Dakota item. The quote was:

    “That just tells you something about the type of seed genetics we are getting, the good research and breeding programs, and the better equipment we have. The fact is we are doing a better job of managing the crop.”

    Nothing there about temps.

    Is there something out there that actually supports the claim that rising temps in the Midwest have benefitted farmers? ‘Cause there doesn’t seem to be much in the links pointed to.

    Comment by Kevin McKinney — 24 Feb 2011 @ 3:11 PM

  147. Dan H wrote: “Speculation about future events when not based on real world data does not count as evidence Secular.”

    The drought in Russia which caused Russia to ban all wheat exports, and the ongoing drought in China, and the drought followed by flooding in Australia, are “real world data”.

    Skyrocketing global food prices driven by crop failures are “real world data”.

    Comment by SecularAnimist — 24 Feb 2011 @ 3:15 PM

  148. > Dan H
    > You seem to be unaware of the increase in agricultural output
    > during the past century.

    This is so unrelated to anything I posted that I wonder if you’re for real.
    Could you make a greater effort to pass your side of the Turing Test here?

    Comment by Hank Roberts — 24 Feb 2011 @ 4:05 PM

  149. Papers to the people!
    Min et al 2011, Pall et al 2011

    Comment by Pete Dunkelberg — 24 Feb 2011 @ 4:34 PM

  150. Min etal – will this link written with blanks instead of %20s work better?

    How about just this:
    or Zwiers et al Nature 2011.pdf

    Comment by Pete Dunkelberg — 24 Feb 2011 @ 4:41 PM

  151. Dan H 142: Is it a coincidence that the highest yield was observed in 1998?

    BPL: Sigh. Yes, Dan, it almost certainly is. Please read an introductory statistics book.

    Comment by Barton Paul Levenson — 25 Feb 2011 @ 5:55 AM

  152. “But since the peak temperatures have changed much less than the average, the agricultural impact would be much less. As I stated previously.”
    [Response: Stating it doesn’t make it so. You would need to actually look at the data and the projections. – gavin]
    Dan H. — 24 Feb 2011 @ 11:08 AM

    I’m happy to oblige-

    “Here we report that annual mean maximum and minimum temperatures have increased by 0.35°C and 1.13°C, respectively, for the period 1979–2003 and a close linkage between rice grain yield and mean minimum temperature during the dry cropping season (January to April).”

    Looks like Dan nailed it, but –

    “Grain yield declined by 10% for each 1°C increase in growing-season minimum temperature in the dry season, whereas the effect of maximum temperature on crop yield was insignificant. ” ibid.

    “…the agricultural impact would be much less…” Well, much less rice, anyway.

    “Surprisingly, observed variations in average growing-season temperatures of ±2 °C in the main wheat growing regions of Australia can cause reductions in grain production of up to 50%. Most of this can be attributed to increased leaf senescence as a result of temperatures >34 °C.”

    “We conclude that the recipe for a world record includes a combination of cultivar and sowing date that will lead to grain growing through the solar radiation peak, a cool but sunny summer, and attention to agronomic detail so that no growth constraints apply.” (Leibigs Law)
    Future headline – “Lindzen Iris Effect predicted to reduce crop yields, by limiting Solar Radiation during critical growing period!!!” &:>)

    “Is it a coincidence that the highest yield was observed in 1998?”
    Comment by Dan H. — 24 Feb 2011 @ 2:13 PM

    according to Agricultural Outlook/August 1998, Economic Research Service/USDA
    “U.S. winter wheat plantings were down from a year earlier, suggesting a smaller crop in 1998. However, generally favorable weather, especially during harvest, will boost the winter wheat yield to a record 46.6 bushels per acre.” Less productive land was left fallow, which also drives up yield/ha.
    “..average protein content of hard red winter (HRW) wheat is reportedly below normal…” one of the observed “benefits” of more CO2, eh? I say, let them eat cake! (for those who don’t cook, pastry flour is lower in protein than bread flour).

    I downloaded wheat production and temperature stats from
    98-99 wheat crop yield was fourth out of the 6 year period 98-04, so although global T anomalies were high in 98, yields were not globally higher. in Oz, the three most productive years averaged 0.22 deg C temperature anomaly, the three least productive years averaged 0.40 deg C T anomaly.

    Comment by Brian Dodge — 25 Feb 2011 @ 5:22 PM

  153. Dan H., Near as I can tell, people arrive at opinions in two ways–science and making crap up. Why not try science.

    Comment by Ray Ladbury — 25 Feb 2011 @ 8:40 PM

  154. Gavin,

    The Pall et al paper relates directly to a project I’m working on, so I’ve looked at it further since my initial comments on this thread. I noted in my #73 that the paper does not include evidence of the skill of the model in forecasting flooding in a particular year, i.e. the extent to which it reproduces the actual conditions in autumn 2000. It also fails to establish the bias of the model, i.e. how the flood threshold chosen in the modelling exercise (0.41mm/day runoff) relates to real world flooding levels.

    It now seems to me that the reason Pall et al did not attempt to quantify their model’s skill and bias is because they thought they didn’t need to.

    They write that:

    “Crucially, however, most runoff occurrence frequency curves in Fig 3 remain approximately linear over a range of extreme values, so our FAR estimate would be consistent over a range of bias-corrected flood values.”

    But Fig 3 has a logarithmic scale!

    In fact, a simple inspection of Fig 3 suggests to me that the increased risk of flooding due to AGW (their FAR or fraction of anthropogenic risk) is quite sensitive to the bias of their model suite.

    Do you agree?

    I’ve discussed this issue in more detail on my own blog.

    Comment by Tim Joslin — 26 Feb 2011 @ 4:21 AM

  155. Well, it’s happened. A long time denialist on another blog has linked to this thread to claim that no extremes in weather can ever be connected to GW (which, of course, he doesn’t believe in anyway). This guy is a past master at misrepresenting articles and cherry picking data. Of course, other than this case, he describes RC as a completely biased, unscientific, unreliable, alarmist site. Thank you for not letting “what they might say” get in the way of presenting the clearest, most accurate account of unfolding events and science as you can. No matter what we say, they will always attempt to misrepresent and distort it one way or the other. We can’t let fears of how intentional mis-informers might warp our positions stop us from having these important discussions.

    Meanwhile, can we nominate posters for the borehole? If so, may I humbly nominate DanH. He seems to be the latest in a long series of people who manage to come here and hijack the thread so that all posters are responding to his idiocy rather than discussing the very real and enormously important issues, issues that are otherwise clearly and thoroughly presented and discussed only here and in a very few other locations.

    In the mean time, can we all resist the temptation to constantly feed such trolls?

    It only encourages them.

    Comment by wili — 27 Feb 2011 @ 2:59 PM

  156. Dan H. #142:

    One of this country’s staples is wheat production. Cehck out the Kansas wheat yield since 1979. Is it a coincidence that the highest yield was observed in 1998?

    Coincidence. 2003 was also a good year and the continental US was unusually cool that year. I haven’t tried correlating the data since it’s in the form of graphs in the PDF you pointed to and I’m not going to look up usable data. If you want to make a case do the stats yourself.

    wili #155: I agree with the general view that you don’t feed trolls but while they are still posting here well-considered rebuttals can be read by others who actually want to be informed. Remember always when you talk here, it’s not a private conversation like email (oops, that’s not private either).

    Comment by Philip Machanick — 27 Feb 2011 @ 4:50 PM

  157. I guess we can conclude this whole blog with the old tired joke that when, for one hour, I have one leg in the deep freezer and the other leg in the oven I should on average be quite comfortable. Except that at the end of one hour I will have to have both legs amputated. Get a grip.

    Comment by Joseph Sobry — 27 Feb 2011 @ 6:37 PM

  158. #157–

    Even if it were not such an old joke, the humor quotient would be rather low–poor old Eastern Australia is still rather in mind.

    Comment by Kevin McKinney — 27 Feb 2011 @ 8:15 PM

  159. Not much word on recovery that I could find with a quick search. But crop losses are estimated at a billion and a half.

    Comment by Kevin McKinney — 27 Feb 2011 @ 8:20 PM

  160. Kevin, I thought your billion and a half was a bit low. They say that’s only for Yasi, but the wording makes me think it’s also for the SE Queensland flooding.

    So it doesn’t account for grain crops lost and damaged throughout NSW, Vic and SA. The big issue for this in light of the Russian and Chinese wheat harvest problems is that the moisture encouraged swelling and sprouting before the heads could be harvested. So the decreased value reflects the fact that these damaged crops are not just lower quality, they’re suitable only for animal feed. So the apparent “harvest” is quite a bit less than you might think because a large part is not suitable for flour making.

    And I’ve seen pictures of Vic vineyards with flood debris hanging off the wires – a month before harvest. Not an encouraging prospect for crushing if some of that filth stays stuck between the berries.

    I think the total losses for this summer’s mayhem will probably be more than some of the worst drought years. (At least in a drought year you don’t waste money on seeds, cultivation, fertilisers and the rest when you =know= no crop is possible.)

    Comment by adelady — 27 Feb 2011 @ 9:52 PM

  161. #123 Hank:

    Hmph. Current global average is +14 C.

    Mitigation target by 2100 is +16 C. Not many climatologists are confident it will be reached.

    Probable by 2100 is +18 C (i.e. UK Gov. “prepare for” statement, considering achievable political realities)

    Seems there are many climatologists who hold +20 C quite possible in a somewhat longer time frame.

    And then they say +24 C can not be excluded as a long term equilibrium temperature. Average global temperature, that is.

    My grandson, recently born, and his pals may well experience the year 2100 first hand. Will it be a happy time?

    Comment by Pekka Kostamo — 27 Feb 2011 @ 11:45 PM

  162. @ adelady #160. Don’t forget to factor in the fungal and other disease outbreaks in grapes and other fruit, particularly stone fruit, as a result of the unseasonal excessive humidity this summer. It’s not just the extensive areas under actual flood that suffered.

    Plus the costs of not being able to travel the most direct route to almost anywhere in Victoria and many places in Queensland. With so many roads closed for extended periods, the cost of travel and transport must have gone up quite a lot.

    Comment by Sou — 28 Feb 2011 @ 2:33 AM

  163. #160–It may be too low for all I know; I can’t claim the estimate as in any real sense ‘mine’–just a figure that I found in a couple of minutes of searching. It did say “floods,” but with no more specificity than that. And the sources are pretty murky, too–“estimates from [unnamed] grower groups.” So how comprehensive the estimates are remains an open question.

    It’s clear, though, that the number is purely for *crop losses*: “Damage to machinery, infrastructure and processing factories will push the total damage bill higher.” (And this number, too, is presumably specific to growers, and would exclude, say, municipal infrastructure.)

    Comment by Kevin McKinney — 28 Feb 2011 @ 7:13 AM

  164. Pekka, I agree. The change coming is enormous; whatsisname back there tried to pretend it’s not much by comparing before and after to a baseline zero Kelvin.

    Comment by Hank Roberts — 28 Feb 2011 @ 11:35 AM

  165. On the topic of extremes, we still seem to be right on the edge of record ice extent lows for this time of year, just barely above the level of ’06.

    Of course, this year’s ice is much thinner and much more ‘rotten’ than that of five years ago.

    Given all this, this late in the year, is there any chance that we WON’T set a new record low extent (and of course total volume) this September? Can we rule out a major recovery this late in the season?

    And on possible causes of future extremes–is there any more new on the seabed methane front? A Shakhova and Semiletov slide presentation “Methane release from the East Siberian Arctic Shelf and the Potential for Abrupt Climate Change” from December circulating on the web mentions that ‘prorating’ exact measurements from one location to all other known ‘hot spots’ of methane release in the East Siberian Arctic Shelf would give a figure of 3.5 Gt methane release going on right now. But other sources talk about something more like 7 Mt of gradual release currently occurring. Are these merely upper and lower bounds of possible release? The upper one seems pretty scary. Is prorating in this case not intended as an actual prediction but rather a kind of ‘what if’ imaginative exercise?

    From the slide presentation (…/1A_Shakhova_Final.pdf)

    “Interpretation of acoustical data recorded with deployed multibeam sonar allowed moderate quantification of bottom fluxes as high as 44 g/m2/d (Leifer et al., in preparation). Prorating these numbers to the areas of hot spots (210×103 km2) adds 3.5Gt to annual methane release from the ESAS. This is enough to trigger abrupt climate change (Archer, 2005)” Figures seem to be taken from Leifer et alia (2009-in preperation).

    Comment by wili — 28 Feb 2011 @ 3:55 PM

  166. Sorry, this might be a better link to the symposium:

    Comment by wili — 28 Feb 2011 @ 3:58 PM

  167. #165–“Given all this, this late in the year, is there any chance that we WON’T set a new record low extent (and of course total volume) this September? Can we rule out a major recovery this late in the season?”

    Yes, and no. The variability means that early prediction is very tough–the long term is dominated by melt, but the short term is dominated by wind, more than anything else–though it’s not the only highly significant weather variable. (Cloudiness can have a big, big impact, to name just one.)

    All that said, it is (or should be) food for thought just how low the current (possibly annual maximum) extent is. (Of course, ice volume is most likely at an all-time low for this time of year. Bring on the Cryosat data–!) And one of the regulars at Neven’s sea-ice blog just calculated that the February mean was a whisker *below* ’06.

    Comment by Kevin McKinney — 28 Feb 2011 @ 4:54 PM

  168. #158 Kevin, I was afraid I would be misunderstood and I was.
    The joke was only directed at people who think that a small change in globally averaged temperatures can not have any serious consequences.
    I only tried to point out that a benign (comfortable) looking average may be computed from a set of data with some really extreme and horrendous data points.
    The whole point is that a small shift in global average temperatures may well have some extremes in local times, places and various aspects of the weather with consequences that we will not like. To wit all the heat waves, floods and cold spells (currently ongoing here locally), that we have seen in the last few years or so.
    The consequences will not only be in the local climate but also in many other areas such as the economy the environment etc. etc. I do not know what the final tally will be in Australia, Pakistan and Russia just to name a few. Perhaps we should ask Mr. Lomborg how much damage we can suffer and still increase the wealth so we can take on global warming in a few decades.

    Comment by Joseph Sobry — 28 Feb 2011 @ 8:20 PM


    “Natalia Shakhova1, Igor Semiletov
    Methane release from the East Siberian Arctic Shelf and the Potential for Abrupt Climate Change

    Specific features of the Arctic shelf methane hydrates
    • More sensitive to warming:because only 1/3 of energy required to convert deep ocean hydrates to free gas (54.2 kJ/mol) requires to convert to free gas Arctic hydrates (18,2 kJ/mol);
    • More vulnerable because they have naturally been experiencing warming by as
    much as 17˚C while deep oceanic hydrates were warmed by less than 1˚C;
    • More significant in their accumulations:
    because their spatial concentration is many folds greater as well as
    pore occupancy (20-100% vs. 1-2% of deep oceanic hydrates);
    • More potential for abrupt releases …

    Comment by Hank Roberts — 28 Feb 2011 @ 8:42 PM

  170. Oh, and that Arctic permafrost? Here’s what’s happening to warm it:

    ” Snow and ice help control how much of the Sun’s energy Earth soaks up. Bright white snow and ice reflect energy back to space. Because that energy does not get absorbed, it does not go into Earth’s climate. As a result, snow and ice cool the planet. This effect is called a climate forcing because snow and ice directly influence the climate. …

    The image shows how the energy being reflected from the cryosphere has changed between 1979 and 2008. When snow and ice disappear, they are replaced by dark land or ocean, both of which absorb energy. The image shows that the Northern Hemisphere is absorbing more energy, particularly along the outer edges of the Arctic Ocean, where sea ice has disappeared, and in the mountains of Central Asia.

    “On average, the Northern Hemisphere now absorbs about 100 PetaWatts more solar energy because of changes in snow and ice cover,” says Flanner. “To put it in perspective, 100 PetaWatts is seven-fold greater than all the energy humans use in a year.” Changes in the extent and timing of snow cover account for about half of the change, while melting sea ice accounts for the other half.

    Flanner and his colleagues made both calculations by compiling field measurements and satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Very High Resolution Radiometer, and Nimbus-7 and DMSP SSM/I passive microwave data. The analysis is the first calculation of how much the energy the entire cryosphere reflects. It is also the first observation of changes in reflected energy because of changes in the entire cryosphere.

    Comment by Hank Roberts — 28 Feb 2011 @ 9:12 PM

  171. Thanks Kev and Hank.

    Sounds to me as though the death rattle (Cheyne-Stokes) has already set in. Time to inform the next of kin?

    Comment by wili — 28 Feb 2011 @ 11:50 PM

  172. #168–I got your point, and it’s a good one. Sorry for a response that perhaps came off more humorlessly than I intended.

    “Ask Mr. Lomborg. . . ?” Ah, you are a joker!

    Comment by Kevin McKinney — 1 Mar 2011 @ 4:07 AM

  173. Hank # 170 – hmm could it be that Arctic permafrost turning out like that is a positive feedback? Leading to warming greater than that caused simply by excess CO2?

    Comment by guthrie — 1 Mar 2011 @ 7:59 AM

  174. Wili,
    I would not read too much into the recent dip in Arctic sea ice quite yet (I assume you are looking at the same DMI data I am). While we are currently barely above the low maximum of 2006, you should note that 2006 had the highest minimum of the past few years, resulting in one of the smallest overall melts from winter to summer. Conversely, 2008 saw about a million more square km of ice in the winter and a million less in the summer.
    The Arctic Ocean was quite warm through the end of 2010, but has cooled down in January, as has the Northern Pacific and Atlantic. The sudden decrease may just be a blip due to winds or circulation patterns, opposite to the spring jump last year. Changes in Arctic Ocean SST should give an indication of thingfs to come.

    Comment by Dan H. — 1 Mar 2011 @ 8:37 AM

  175. Hank posted this in 170.

    Anybody know why the forcing increased in the US southwest?

    Comment by John E. Pearson — 1 Mar 2011 @ 10:59 AM

  176. Guthrie, it is definitely a feedback. That is why it is alarming, even if it is at much lower levels than the presumably upper-end estimate of 3.5 Gt/year of methane mentioned in the slide show (“The Bad News” slide toward the end).

    It seems our resident troll continues to have trouble reading, or perhaps is just addicted to picking convenient cherries. To repeat myself:

    Of course, this year’s ice is much thinner and much more ‘rotten’ than that of five years ago.

    Comment by wili — 1 Mar 2011 @ 11:13 AM

  177. Wili, thanks in turn for the link to the RS impacts issue. I’ll be perusing that. As to “Cheynes-Stokes” (or not), I suppose that there’s a definitional problem there, analogies being what they are. I wouldn’t claim we’re there yet; but I suspect, FWIW, that the demise of the Arctic icecap is all but unavoidable at this point.

    Just when it can be expected is another question, with recent projections/predictions (made with varying degrees of professionalism) ranging from the next couple of years out to about 2050. Also FWIW, I expect to see it, but I don’t necessarily expect to live to 2050.

    Comment by Kevin McKinney — 1 Mar 2011 @ 11:51 AM

  178. #175–

    “Know?” Can’t claim that. But I’d presume that persistent drought in the southwest in recent years is part of the picture.

    Better informed thoughts?

    On southwestern drought and future water supply:

    Comment by Kevin McKinney — 1 Mar 2011 @ 12:07 PM

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