tag:blogger.com,1999:blog-8216971263350849959.post8878402232695096902..comments2023-08-07T16:41:49.660+02:00Comments on Die Klimazwiebel: Climate change and extreme flooding linked by new evidence?eduardohttp://www.blogger.com/profile/17725131974182980651noreply@blogger.comBlogger72125tag:blogger.com,1999:blog-8216971263350849959.post-70796987082222430092011-03-18T09:42:20.629+01:002011-03-18T09:42:20.629+01:00@ Eduardo
Here's an interesting paper on the ...@ Eduardo<br /><br />Here's an interesting paper on the subject ...<br /><br />http://www.eas.gatech.edu/files/hall_twyman_kay_influence_diagrams.pdf<br /><br />.. discussed at JC's blog ...<br /><br />http://judithcurry.com/2011/03/15/reasoning-about-floods-and-climate-change<br /><br />RalphAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-10381431258857107452011-03-03T18:25:44.947+01:002011-03-03T18:25:44.947+01:00wflamme,
sure, unfortunately many journalistic re...wflamme,<br /><br />sure, unfortunately many journalistic reports and press releases have to be taken with a grain or two of salt. An intelligent observed would try to look under the carpet and figure out which part is likely true and which part not so likely. In theory, this would be the task of scientist themselves, but unfortunately this seems to be difficult nowadays.<br /><br />Concerning your second comment (an undisturbed observed climate..), this is the nub of all our pains. We cannot observed a climate that is for sure undisturbed. This is the reason why attribution can only be achieved with models, in which undisturbed and disturbed climates can be recreated. This is essentially the method applied by Min et al. <br /><br />You could argue that the present climate is undisturbed, but then of course you reach the conclusion by analyzing observations that... the present climate is undisturbed. This type of circularity cannot be avoided when one has only one Earth and no possibility to conduct experimentseduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-1322384250693900132011-03-02T22:18:42.146+01:002011-03-02T22:18:42.146+01:00eduardo,
these are reasonable objections IMO.
H...eduardo,<br /><br />these are reasonable objections IMO. <br /><br />However I didn't expect it - I was just checking the more general lines of reasoning using a readily availabe sample. After all many scientific media and most of its most popular outlets say that increases are happening already. I don't need to provide examples, do I?<br /><br />Regarding the models: Extreme precipitation is rare by definition and variable by nature. I'm not sure wether the model's results are substantially different from what we could expect when comparing two random samples of observations from an 'undisturbed' climate.wflammehttps://www.blogger.com/profile/18260929727390446009noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-27696979104812634842011-03-01T23:34:38.023+01:002011-03-01T23:34:38.023+01:00@68
I dont see why one should expect the CC relat...@68<br /><br />I dont see why one should expect the CC relationship to be fulfilled for extreme precipitation at regional scale. I would perhaps expect a relationship between mean precipitation in Germany and average temperature over the ocean areas that are the main source of precipitable water for Germany, which probably is the whole North Atlantic. At regional scale, and depending on the season when extreme precipitation occurs, I would even expect a negative relationship: if extreme precipitation occurs in summer, more cloudy summers over land will be associated to colder summers over land. <br />We should not forget that precipitation is not solely modulated by the available water vapor, and that atmospheric dynamics plays an important role. In climate simulations precipitation is predicted to increase in some regions and decrease in others, and even in a given region to increase in some seasons and decrease in other seasons.eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-86313226565342156662011-02-25T19:04:28.759+01:002011-02-25T19:04:28.759+01:00"Mr. Flamme, when did you stop torturing your..."Mr. Flamme, when did you stop torturing your data?"<br /><br />Actually I couldn't. But did they confess?<br /><br />Let's denote extreme precipitation events (e.g some uppermost quantile or top ranks) in a daily record by pairs of observation in precipitation P (of course) and temperature (T) in descending rank order along P, so the pairs become (P1,T1), (P2,T2), ...<br />If there were a strong relationship w/o much noise we could hope to provide a linear estimate in the form of <br /><br />dP/dT =~ (P1-P2)/(T1-T2) =~ (P2-P3)/(T2-T3) = ....<br /><br />For relative changes we could declare P1 (P2) being 100% with little error, this will result in<br /><br />dP_rel/dT=(1-P2/P1)/(T1-T2) or <br />dP_rel/dT=(P1/P2-1)/(T1-T2)<br /><br />Now that's just what I did - comparing every pair of observation in the station's extremes set with every other pair, seperately noting numerator and denominator. Finally I used OLS to estimate the average dP/dT between them. To speed things up a little I used the top 30 extremes or .99 quantile, whatever set was smaller (resulting in ~400 pairwise comparisons for every station).<br /><br />Helgoland: 0.14% +/- 0.12% (p=0.231)<br />List/Sylt: 0.59% +/- 0.2% (p=0.004)<br />Schleswig: -0.01% +/- 0.14% (p=0.88)<br />Fehmarn: -0.01% +/- 0.1% (p=0.851)<br />Hamburg-Fuhlsbüttel: 0.43% +/- 0.17% (p=0.011)<br />Schwerin: 0.85% +/- 0.12% (p=0)<br />Rostock-Warnemünde: 0.68% +/- 0.12% (p=0)<br />Greifswald: 0.78% +/- 0.16% (p=0)<br />Bremen: 0.05% +/- 0.11% (p=0.668)<br />Hannover: 0.12% +/- 0.09% (p=0.173)<br />Magdeburg: 0.07% +/- 0.09% (p=0.438)<br />Potsdam: 0.28% +/- 0.08% (p=0)<br />Berlin-Tempelhof: 0.57% +/- 0.09% (p=0)<br />Lindenberg: 0.17% +/- 0.08% (p=0.025)<br />Kahler Asten: 0.04% +/- 0.1% (p=0.699)<br />Brocken: 0.09% +/- 0.09% (p=0.337)<br />Görlitz: 0.15% +/- 0.11% (p=0.146)<br />Aachen: 0.15% +/- 0.1% (p=0.131)<br />Erfurt-Bindersleben: -0.11% +/- 0.12% (p=0.301)<br />Fichtelberg: 0.48% +/- 0.08% (p=0)<br />Trier-Petrisberg: 0.37% +/- 0.06% (p=0)<br />Frankfurt M-Flughafen: 0.42% +/- 0.14% (p=0.003)<br />Würzburg: 0.21% +/- 0.1% (p=0.036)<br />Bamberg: -0.05% +/- 0.09% (p=0.477)<br />Hof: 0.19% +/- 0.12% (p=0.108)<br />Saarbrücken Ensheim: 0.3% +/- 0.13% (p=0.019)<br />Karlsruhe: -0.33% +/- 0.12% (p=0.007)<br />Stuttgart Echterdingen: 0.53% +/- 0.09% (p=0)<br />Nürnberg: -0.05% +/- 0.1% (p=0.538)<br />Straubing: -0.15% +/- 0.09% (p=0.063)<br />Augsburg: -0.12% +/- 0.11% (p=0.223)<br />Kempten: 0.33% +/- 0.12% (p=0.005)<br />Zugspitze: 0.16% +/- 0.07% (p=0.017)<br />Hohenpeißenberg: 0.29% +/- 0.11% (p=0.011)wflammehttps://www.blogger.com/profile/18260929727390446009noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-42690327352959647662011-02-24T09:35:42.247+01:002011-02-24T09:35:42.247+01:00eduardo: "Eschenbach makes two errors: he con...<i>eduardo: "Eschenbach makes two errors: he confuses statistical significance with signal strength, and he does not take into account field significance versus individual significance."</i><br /><br />eduardo,<br /><br />Thank you for your response and your spare time sacrifices.<br /><br />Despite Willis' offensive wording that was my first impression, too. However Willis not confuses significance and relevance (now?) although he could be much clearer:<br /><br /><i>Willis: "I put all of those trend numbers in because they are important as an indication of the size of the change that we are looking at. It is a very tiny change if it exists at all. We know that because of the amount of the underlying data which contains no trend at all. This is a different result from e.g. finding a tiny trend that results from the averaging of a large number of significant trends."</i><br /><br />With respect to the effect strength estimate this certainly is true. However accompanying statistical diagnosis would reveal the difference.<br /><br /><i>Willis: "In addition, it indicates that the size of their claimed effect is doubtful. They claim that the number of extreme events in much of the US has increased by 30-50% over the last 50 years … are you seriously claiming that if that happened a simple trend test would not be able to detect a 30-50% change, and that such a 30-50% change would be statistically insignificant in over 90% of the stations?"</i><br /><br />If Min makes that claim in the paper Willis' for sure has a strong point here: Any effect on extremes that general and strong should easily be detectable and should stand well out above gridcell noise. <br /><br />In addition I'm suspicious as well about that PDF fitting. After all that procedure can't produce any new information but only reflect what has been observed already.<br /><br /><br />With respect to DWD data and increase in Germany's extreme precipitation I was looking for a reference procedure not giving percent change over time but percent change over temperature change. That's because I'd like to avoid potential fallacies arising from any indirect two step conclusion.<br />I also don't want to 'waste' that precious dataset by endless multiple testing of ideas (it probably has been to much already).wflammehttps://www.blogger.com/profile/18260929727390446009noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-12848594348607508922011-02-23T23:47:50.012+01:002011-02-23T23:47:50.012+01:00@ Hank
We all like cherries, don't we?
The p...@ Hank<br /><br />We all like cherries, don't we?<br /><br />The patterns are first shown in upcoming humid winds in autumn and wintertime. There would be no mountain effects otherwise.<br /><br />RalphAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-66531505135348247192011-02-23T23:32:12.703+01:002011-02-23T23:32:12.703+01:00Ralph picked the cherry from that link: "one ...Ralph picked the cherry from that link: "one of the wettest villages in Spain is not on the Atlantic coast but in Andalucia. Grazalema in the Sierra de Grazalema has an average of 2,153 mm of rain a year. The warm, humid winds blow in from the Atlantic and cool and condense as they pass over these limestone peaks. The wettest points are certainly on the Galician -Portuguese border and parts of Northern Navarra."<br /><br />That's a mountain effect, not a seasonal pattern.<br /><br />Look at the links to cities in the Andalusian region: <br />http://www.iberianature.com/material/Spain_climate/climate_spanish_cities.htm<br />typical pattern of winter, not summer, rainfall.Hank Robertshttps://www.blogger.com/profile/07521410755553979665noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-90594688305010621102011-02-23T23:18:49.902+01:002011-02-23T23:18:49.902+01:00@ Eduardo
I was aware of this kind of "argum...@ Eduardo<br /><br />I was aware of this kind of "argument" with your first attempt on N° 57 ("maybe the reason is that being both behind a pay wall") - and then decided just to ignore it.<br /><br />Honestly - and for all those who don't have the opportunity to read the full text, are you trying to tell us that the abstracts of the two papers discussed here are quite misleading?<br /><br />"Please, pay attention to the meaning of all words"<br /><br />I do, I do.<br /><br />"the models predict an increase in extremes and in others a decrease in extremes when driven by increasing GHG"<br /><br />No comment.<br /><br />"The paper Pall et al. claims that GHG increased those odds. It does not say that GHG *caused* the floods"<br /><br />Rhetorics, sorry - just notice how the issue is interpreted not only by the Guardian but by the authors themselves and the cited supporters, by the public in general.<br />A communication problem as Gabriele Hegerl says?<br /><br />"Prof. Sutton, or whoever quoted him here, is wrong"<br /><br />Sutton is one of the supporters mentioned above.<br /><br />"in Spain rain comes in winter not in summer. And extreme precipitation in Spain occurs in autumn, not in summer. So there must be something else"<br /><br />How about high (summer) and low pressure (autumn) phases, wind transporting moist air from the atlantic and the mediterranean ocean?<br /><br />"The warm, humid winds blow in from the Atlantic and cool and condense as they pass over these limestone peaks"<br /><br />http://www.iberianature.com/material/Spain_climate/Rainfall_Spain.htm<br /><br /><br />RalphAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-41853984957836610942011-02-23T22:22:55.929+01:002011-02-23T22:22:55.929+01:00@53
it is more complex that at first sight, depen...@53<br /><br />it is more complex that at first sight, depending on your background. You can have an impression <a href="http://www.nonlin-processes-geophys.net/14/305/2007/npg-14-305-2007.pdf" rel="nofollow"> here </a>, although the calculation you did may be a good starting point. You could count the number of positive and negative trends, and establish its statistical significance by generating artificial surrogate station data when the trend has been destroyed: reshuffling in time all data. Do this 1000 times, repeat the calculation of the trends and count how many are positive. If the number of positive trends in the original data set is larger than the 95% quantile in your 1000 realizations, then you may have detected something.<br /><br />Perhaps you have been following the discussions in this thread. I would add a few comments: <br />precipitation will not increase according to CC, but less, in the range of 1-2 %/K, see <a href="http://europa.agu.org/?view=article&uri=/journals/gl/gl1104/2010GL045953/2010GL045953.xml&t=gl,2011,Frieler" rel="nofollow">here</a> This is because there are also dynamical and energetic constraints to the increase of precipitation. I am not sure now (I am on holiday :-) whether this is true for extreme precipitation as well. It is in general not valid anyway, since models predict a decrease of extreme precipitation for some areas, since they predict a global increase of precipitation but a decrease in the subtropics. So the story is much more complex when one goes from the global mean to finer spatial scales, quantiles and seasons.<br />For Germany I would not be surprised that you dont find the 6%/K CC increase. Regionally there are many more factors than contribute to changes in precipitation than the increase in specific humidity. In winter, for instance, the changes in the storm tracks at mid latitudes (the path of mid-latitude low-pressure systems, which in the present climate seem to be focused on Hamburg and roundabouts..); in summer maybe land use changes may affect convective precipitation, etc etc...eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-63048666188643236562011-02-23T21:21:44.897+01:002011-02-23T21:21:44.897+01:00@ 60
Ralph,
many of your objections arise because...@ 60<br />Ralph, <br />many of your objections arise because you have not been able to read the original paper and you are basing your comments in indirect accounts of those papers, some of them also inaccurate. Not your fault, of course, <br /><br />'Both studies dont take into account natural variability'<br />This is what Judith Curry wrote. You pointed to that blog.<br /><br /><br />"There is no need for a accurate attribution of GHG warming. Actually, none of the studies uses temperature data"<br /><br />??? Eduardo, please. First read your last point above, then ...<br />"Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events"<br /><br />Please, pay attention to the meaning of all words. The last sentence makes the connection between GHG and extreme precipitation. The first sentence involves GHG *warming*. I repeat that the study by Min et al. does not requite that the models *accurately* simulate GHG warming. They could underestimate it, and yet the pattern of extreme precipitation trends could be detected. I have to explain again, those studies are based on detection of spatial patterns of trends (here rising, there decreasing), and not whether or not the *magnitude* of the trends is correctly simulated.<br /><br />'Of course the authors or their models suppose that more CO2 will lead to higher temperatures which lead to an increased water evaporation, thus to more precipitation.'<br /><br />Not correct. The pattern of trends in extreme precipitation has positive and negative values. therefore in some areas the models (at least the mean across all models) predict an increase in extremes and in others a decrease in extremes when driven by increasing GHG.<br /><br /><br />"Why should averaging be problematic?"<br /><br />Instead of opening a new thread, let me cite Michael Blastland: "the world is a soup of sometimes wildly varying ingredients. The<br />average is like the taste and tells us how the ingredients combine. That is important, but never forget that some ingredients have<br />more flavour than others and that these may disguise what else went into the pot."<br /><br /><br />Nice sentence, but what the Min e al study did was to average over several gridcells to match the resolution of model and observed grids. To me it seems a reasonable thing to do. They are not averaging 'different ingredients'.<br /><br />“"The model runs incorporate those (aerosols) forcings"<br />I'm not convinced they do it appropriately. But this , of course, is a weak objection due to the fact that we have no detailed viewon these models.<br /><br />The original claim ( I dont know now by whom) was these studies dont incorporate the effect of aerosols forcings. The answer is that they do. If the original claims had been that it is doubtful that the effects of aerosols is incorporated realistically, it could be argued. I have the impression that we are moving goals here. <br /><br />“Pall et al.: "it is very likely that global anthropogenic greenhouse gas emissions substantially increased the risk of flood occurrence in England and Wales in autumn 2000"<br /><br />That is exactly what I wrote. The paper Pall et al. claims that GHG increased those odds. It does not say that GHG *caused* the floods. This latter type of attribution is impossible.<br /><br /><br />“Professor Rowan Sutton: "The increase in extreme precipitation has a firm foundation in basic physics, the scientists said, as a warmer atmosphere can hold more water"<br /><br />Professor Sutton, or whoever quoted him here, is wrong. A simple counter example is that in Spain rain comes in winter not in summer. And extreme precipitation in Spain occurs in autumn, not in summer. So there must be something else. See also my comment above. Models predict a *decrease* of extreme precipitation in some areas when driven by GHG.eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-26266549338837659932011-02-23T21:20:30.381+01:002011-02-23T21:20:30.381+01:00Found at:
http://online.wsj.com/public/page/letter...Found at:<br />http://online.wsj.com/public/page/letters.html<br /><br />Severe Weather Is Driven by Many Factors<br /><br />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.<br /><br />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.<br /><br />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.<br /><br />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.<br /><br />Thank you for this opportunity to clear up any inadvertent misunderstandings about our work, which can be found at: http://onlinelibrary.wiley.com/doi/10.1002/qj.776/full<br /><br />Gilbert P. Compo<br />Research Scientist<br />University of Colorado at Boulder<br /><br />Jeffrey S. Whitaker<br />Meteorologist<br />National Oceanic and Atmospheric Administration<br /><br />Prashant D. Sardeshmukh<br />Senior Research Scientist<br />University of Colorado at Boulder <br />------Hank Robertshttps://www.blogger.com/profile/07521410755553979665noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-80433160249892908462011-02-23T19:54:36.116+01:002011-02-23T19:54:36.116+01:00@ Eduardo
"most of them (posts on JC's b...@ Eduardo<br /><br />"most of them (posts on JC's blog) are not related to those papers specifically"<br /><br />OK, like in all open blogs it is a mass discussion but the main issue concerns "Attribution of Extreme Events". You might ignore a good part of the posts and taking in account at least some of the others.<br /><br />"Both studies do take into account natural variability"<br /><br />Not my words. I talked about "atmosphere/ocean feedbacks"<br />Pall et al.: “As atmosphere–ocean feedbacks were not believed to play a major role during autumn 2000, we use an atmosphere-onlymodel, with sea surface temperatures (!) (SSTs) and sea ice as bottom boundary conditions.”<br /><br />"There is no need for a accurate attribution of GHG warming. Actually, none of the studies uses temperature data"<br /><br />??? Eduardo, please. First read your last point above, then ...<br />"Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events"<br /><br />Of course the authors or their models suppose that more CO2 will lead to higher temperatures which lead to an increased water evaporation, thus to more precipitation.<br /><br />Blog entry, see above: "a global average temperature increase will cause a global average increase in the amount of water vapour, which will cause an increase in average precipitation globally"<br /><br />and ...<br /><br />"Global warming was found to have most likely doubled the risk of the 2000 floods"<br /><br />and ...<br /><br />"models seem to underestimate the observed increase in heavy precipitation with warming"<br /><br /><br />"Why should averaging be problematic?"<br /><br />Instead of opening a new thread, let me cite Michael Blastland: "the world is a soup of sometimes wildly varying ingredients. The average is like the taste and tells us how the ingredients combine. That is important, but never forget that some ingredients have more flavour than others and that these may disguise what else went into the pot."<br /><br />"The model runs incorporate those (aerosols) forcings"<br />I'm not convinced they do it appropriately. But this , of course, is a weak objection due to the fact that we have no detailed view on these models.<br /><br />"It is the Pall paper that assumes that feedbacks are not important"<br /><br /> You're right. My mistake.<br /><br />"The Pall et al paper claims that GHG inceases the odds of having England-2000 style floods, not that those particular floods were caused by GHG - something impossible to attribute of course"<br /><br />Pall et al.: "it is very likely that global anthropogenic greenhouse gas emissions substantially increased the risk of flood occurrence in England and Wales in autumn 2000"<br /><br />A communication problem? Wrong message?<br />Please read the blog entry and the Guardian article: "Global warming made the floods that devastated England and Wales in the autumn of 2000"<br /><br />"The Min et al paper does not claim that GHG leads to more or less extreme precipitation globally. It just identifies a pattern of increasing in some place and decreasing in other places"<br /><br />???<br />Professor Rowan Sutton: "The increase in extreme precipitation has a firm foundation in basic physics, the scientists said, as a warmer atmosphere can hold more water"<br /><br />"I am not sure I understand what you mean here"<br /><br />The attribution of specific events to GHG emissions.<br />Eduardo: "something impossible to attribute of course"<br /><br />RalphAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-83482666731845905222011-02-23T17:52:10.803+01:002011-02-23T17:52:10.803+01:00@51
Wflamme,
Eschenbach makes two errors: he conf...@51<br />Wflamme,<br /><br />Eschenbach makes two errors: he confuses statistical significance with signal strength, and he does not take into account field significance versus individual significance.<br /><br />To the first point: a signal (correlation, difference in means, etc) can be strong and yet not statistical significance, due to the lack of data, e.g. the series are too short. on the other hand, a signal may be very weak (correlations as low as 0.05) may be statistical significant if I have a lot of data (say a time series with several millions of data. So when he says, the trends are not statistically significant and there fore there is no signal, he makes a mistake. It just may be, although not necessarily, that the data are not enough. This is why one may look at many records and search for a certain, theoretically prescribed pattern. For instance I may have 100 independent short records of whatever variable. All display a positive trend, but due to the length of each record, none of the trends is statistically significant. It does not mean that the signal is not there, it just means that the series are too short. But when I realize that all series display a positive trend , the odds that this happens by chance are very very very small, and therefore the overall pattern of trends is highly statistically significant. I have the impression that Eschenbach has not grasped this if I understand his responses well.eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-2213495711403143652011-02-23T17:38:55.527+01:002011-02-23T17:38:55.527+01:00Continued
-'There are the
uncertainties in the...Continued<br />-'There are the<br />uncertainties in the (raw) data (HADEX RX1day dataset)'<br /><br />Yes, data of extremes are more uncertain than seasonal means and it may very well be that the phasing-in of better measurements systems produces an artificial upward trend in extreme rainfall . One could argue here that this may be the reason why the northern hemisphere average trend in extreme rainfall is underestimated in models - observations would be biased upwards. But I would agree in general, there are issued with data quality of extremes<br /><br />-'the use of averaged data with<br />questionable models' Here I dont see the problem. Why should averaging be problematic ?<br /><br />- 'the choosen time-frame, increasing negative<br />aerosol forcings'. This is not a problem because the model runs incorporate those forcings. Als, which time frame can be otherwise be chosen? we have basically one sets of observations<br /><br />- 'and regarding the Min et al. paper -<br />atmosphere/ocean feedbacks'. No , you are not correct here. It is the Pall paper that assumes that feedbacks are not important. The Min et al paper considers full feedbacks: it uses the IPCC simulations with atmosphere-ocean couple models. Also, the Min et al. paper does not deal with floods but with extreme precipitation.<br /><br />-'Uncertainty: are we really able to attribute extreme (regional) events<br />with high certainty to anthropogenic GHG emissions - and to exclude<br />natural factors the same time?<br />No, none of this papers does that. The Pall et al paper claims that GHG inceases the odds of having England-2000 style floods, not that those particular floods were caused by GHG - somethuing impossible to attribute of course.<br /><br />The Min et al paper does not attribute any event in particular to GHG, but , repeat, identifies the expected (from modelling) pattern of extreme precipitation change in the observations. <br /><br /><br />-'There are/were quite a lot of similar papers in these last years<br />claiming that GHG emissions would lead to an increased number of<br />droughts. A change in conjuncture cycles or in "marketing strategies"?'<br />The Min et al paper does not claim that GHG leads to more or less extreme precipitation globally. It just identifies a pattern of increasing in some place and decreasing in other places.<br /><br /> -'<br /> Signals that<br />obviously show such weak correlations that they are difficult to detect<br />in the statistical noise.'<br /><br />Yes, thy are difficult to detect, but the Min et al. paper does just that.<br /><br />-'Coupling weather events with an non-linear, chaotic system remains a difficult task' I am not sure I understand what you mean here. Climate models are chaotic and have weather events..(?)eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-11713979404252563192011-02-23T17:38:17.753+01:002011-02-23T17:38:17.753+01:00Ralph,
no, sorry. I have quickly gone through the...Ralph,<br /><br />no, sorry. I have quickly gone through the comments posted in Judith Curry's blog,a nd it seesm to me that most of the m are not related to those papers specifically. Some are even discussing carbon tax. This is what I want to avoid. A mass discussion like that very often goes astray and in the end nothing really clear comes out - at least in my experience.<br /><br />there seems to be lost of confusion about those papers, and maybe the reason is that being both behind a pay wall, few of the commenters seem to have read them in the first place ! here I would say Nature should be more open with certain papers that are promoted by Nature itself - they should be open access. <br /><br />But JC makes some mistakes in her opening text. She writes for instance '<br /> and it does not recognize the role of natural internal variability such as <br /> the Arctic Oscillation, La Nina, etc in producing floods.' This is not correct. Both studies do take into account natural variability- this should be very clear for any expert who has read the papers. It can be argued that they do so assuming that the natural variability simulated by models is close enough to reality, and this may be questionable. But to say that they do not take that into account is simply, and surprisingly, wrong.<br /><br />To your comments:<br /><br /><br />- 'to accept<br />the attribution of the last 150 years warming to GHG effects as<br />accurate'. No, this is not correct. There is no need for a accurate attribution of GHG warming. Actually, none of the studies uses temperature data<br /><br />-' models are not good at<br />simulating historic rainfall at regional scales.'<br /><br />This one I would buy. It is indeed difficult for models to simulate precipitation properly, even more extreme precipitation, and even more focusing at a certain region like England and Wales, with complex coast lines.eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-88181507784842250952011-02-23T16:45:43.640+01:002011-02-23T16:45:43.640+01:00@ Eduardo
"other aspects that cannot be dism...@ Eduardo<br /><br />"other aspects that cannot be dismissed"<br /><br />Why don't you - just ignoring the title - follow Eschenbach's thread - and the discussion where he answers different questions, like the one linked by wflamme (N° 51)? <br />Or follow the debate over at J. Curry's blog where both papers are discussed in a more civilized manner I hope ... http://judithcurry.com/2011/02/16/attribution-of-extreme-events-part-ii<br /><br />Among other difficulties first and above all we would have to accept the attribution of the last 150 years warming to GHG effects as accurate. Besides that there is the fact that models are not good at simulating historic rainfall at regional scales. There are the uncertainties in the (raw) data (HADEX RX1day dataset), the quality/homogeneity of the used data, the use of averaged data with questionable models, the choosen time-frame, increasing negative aerosol forcings - and regarding the Min et al. paper - atmosphere/ocean feedbacks, the increase in land use with more impervious surfaces leading to a higher flood potential etc. - just to mention some of the problems. By the way: the floods in England and Wales (20009 were not record-breaking in a historical context.<br /><br />Uncertainty: are we really able to attribute extreme (regional) events with high certainty to anthropogenic GHG emissions - and to exclude natural factors the same time?<br />There are/were quite a lot of similar papers in these last years claiming that GHG emissions would lead to an increased number of droughts. A change in conjuncture cycles or in "marketing strategies"?<br /><br />Looking at historical floods and other extreme weather events, one can hardly pretend we would see more an more severe ones of them in present times.<br />OK, the authors talk about identifying "signals". Signals that obviously show such weak correlations that they are difficult to detect in the statistical noise.<br /><br />Coupling weather events with an non-linear, chaotic system remains a difficult task ... Do standard statistical techniques give useful results when they are applied to these type of events?<br />When I read sentences like "approximately two-thirds” or "limited availability of daily observations” it all ends up in pure speculation.<br /><br />RalphAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-4885646217138504842011-02-23T00:22:29.536+01:002011-02-23T00:22:29.536+01:00Ralph,
let us try to mix things up. You pointed ...Ralph,<br /><br />let us try to mix things up. You pointed us to Eschebach post – I had not read it before. So I read it and saw that it was technically not correct. You seemed to agree, but you again suggested that that post may contain other aspects that cannot be dismissed. Which ones exactly ? I am happy to read the technical details more closely and perhaps learn a bit doing that. <br /><br /><br />'Precipitation without floods, ok - but floods without precipitation?' <br />well, that is exactly the point. You may have trends in precipitation and/or extreme precipitation and not to have them in floods or flood-related damage, which is what seems to be observed. <br /><br />“If - as you say - GHG signals do not dominate the variability or the<br />trends of extreme precipitation - what are we exactely talking about -<br />and telling the politicians?”<br /><br />I said that the Min et al paper does not claim that GHG dominate the trends in extreme precipitation. I do not know whether or not that is true, but the paper does not claim it, as far as I understand it.<br />What do we say to politicians? Thats the dilemma we were discussing before. Let me illustrate it with a further example. Let us assume for the moment that we know that the observed trend in global mean surface temperatures is mainly caused by trends in solar irradiance. However, we also observe that the trend in stratospheric temperature is negative, and no other forcing than GHG can produce this negative trend. This is similar to pattern detection. We would have detected a signal of GHG, although the effect of GHG may be not dominant in the observations of surface temperature in our example. What we say the politicians is a matter of taste.I would go for telling them everything.<br /><br />The Pall et al. paper on England and Wales floods is technically of a different sort, and is almost exclusively based on model results and basically only on one model . I think that therefore the uncertainties in this paper are larger. <br /><br />“I don't think that's where it exactely started with the rather biased<br />Guardian report and its odd testimonials.”<br /><br />To be honest I havent read the Guardian report. Probably it is biased, I would not be surprised. But then why dont you discuss that report instead of the watssupwiththat weblog ?eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-30550855618815593792011-02-22T23:47:06.623+01:002011-02-22T23:47:06.623+01:00@ Eduardo
Don't let us waste more time on lam...@ Eduardo<br /><br />Don't let us waste more time on lamenting over bad manners. At least you can see Eschenbach being confronted with a lot of critical questions. WUWT is not just a meeting place for brainless headbangers and "claqueurs".<br /><br />"Floods and extreme rainfall ... are not the same thing":<br /><br />Talking about severe river runoffs in England and Wales, flood water has to come somewhere from.<br />Precipitation without floods, ok - but floods without precipitation?<br />Pielke Jr.: "Precipitation is to flood damage as wind is to windstorm damage"<br /><br />If - as you say - GHG signals do not dominate the variability or the trends of extreme precipitation - what are we exactely talking about - and telling the politicians?<br /><br />It's all about uncertainties - and open minded research and debates. <br />I don't think that's where it exactely started with the rather biased Guardian report and its odd testimonials.<br /><br />RalphAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-61685708280158034842011-02-22T21:44:05.165+01:002011-02-22T21:44:05.165+01:00eduardo,
a simple question (I hope):
How would I...eduardo,<br /><br />a simple question (I hope):<br /><br />How would I go about to find empirical evidence for the ~6.5%/K extreme precipitation increase (CC equation) in german weather service's daily data?wflammehttps://www.blogger.com/profile/18260929727390446009noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-88813903918550131302011-02-22T18:06:56.018+01:002011-02-22T18:06:56.018+01:00Ralph ,
the problem I see is not to be a lightwei...Ralph ,<br /><br />the problem I see is not to be a lightweight. Everyone should be able to comment on published work. The problem I do see is that he comments with a style that appears aggressive, dismissive, when at the same time the contest of his post are quite questionable.<br /><br />In @4 you wrote that the results of those studies are uncertain. Sure, the Min et al. Study for example, is based on the assumption that control simulations the ones where the external forcing is kept constant) can reproduce the right amplitude of internal climate variations) This is very difficult to prove, since those internal variations cannot be observed directly (the real climate is always forced). This happens in virtually any scientific study. There are always some underlying assumptions. But this is not reason to qualify a paper as a flood of bad science. <br /><br />Floods and extreme rainfall. They are not the same thing, as Roger Pielke also underlines. And again, the Min et al study detects the GHG signal in extreme precipitation. It does not say that GHG dominates the variability or the trends of extreme precipitation. These are tow different things and it may well be that the press releases or further comments failed to split that suble difference.<br /><br />I would disagree with Curry when she says that the motivation to detect the GHG signal in extremes is political. The group where Min is working have detected the GHG signal systematically in many other variables, e.g. rainfall, sea-level-pressure, etc, and this is a natural extension of that work. One only needs to google detection and attribution. One may see political motives everywhere, but this is not the most parsimonious explanation in this caseeduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-34250439353759754892011-02-22T11:34:34.287+01:002011-02-22T11:34:34.287+01:00@eduardo (#45)
Willis' has adressed this in h...@eduardo (#45)<br /><br />Willis' has adressed this in his comment here:<br />http://wattsupwiththat.com/2011/02/20/nature-unleashes-a-flood-of-bad-science/#comment-603940<br /><br />See the inline links as well.wflammehttps://www.blogger.com/profile/18260929727390446009noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-34521122783580852522011-02-22T11:12:38.679+01:002011-02-22T11:12:38.679+01:00@ Eduardo
Eschenbach might be an academic lightwe...@ Eduardo<br /><br />Eschenbach might be an academic lightweight in your eyes (talking about his style would be another issue) and there are some misunderstandings in his comments indeed. <br />So if you don't wish to give it much credibility, why do you preeminently focus on that post? You could answer him directly on WUWT.<br /><br />I didn't mention WE as a "crown witness" to show that the Min et al. paper is not correct - but he is asking some justified questions. <br />From my part there are no judgements besides the ones in post N° 4.<br /><br />Pielke Jr. doesn't just talk about "climate-disaster economic losses" as you try to make us believe. <br />He writes: "A recent study of trends in long time series of annual maximum river flows at 195 gauging stations worldwide suggests that the majority of these flow records (70%) do not exhibit any statistically significant trends. Trends in the remaining records are almost evenly split between having a positive and a negative direction"<br />... and<br />"I expect that many will still want to connect the dots between greenhouse gas emissions and recent floods. Connecting the dots is fun, but it is not science."<br /><br />Werner's question "is this about politics or about science?" is answered by Judith Curry ("Attribution of Extreme Events, Part I and II"):<br />"Not sure what the motive is for the attribution of extreme events, other than to build political will for climate change policies"<br /><br />Revkins comment is an interesting piece of scientific reporting under post normal conditions. Interesting because Revkin seems to be more cautious and reserved than he used to be about a year ago.<br /><br />While the quality of Gavin Schmidt's prediction "some extremes will become more common in future and some less so)" finally opens the door to climate astrology.<br /><br />I still recommend the two links listed in N° 11.<br /><br />RalphAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-4551293609198546532011-02-22T00:45:34.894+01:002011-02-22T00:45:34.894+01:00@ 46
Ralph,
if one entitles his weblog as a '...@ 46<br /><br />Ralph,<br /><br />if one entitles his weblog as a 'flood of bad science' , and starts off with a serious misunderstanding, which is highlighted several times in the text, you would agree that I am not very inclined to give much credibility to the text as a whole. Actually, that webpost is as drastic and lacking nuance as most press-releases that I have happened to read about the Min et al study. <br /><br />If you have specific question about the methods, we can discuss them here and try to clarify what Min et al did. Also, you can explain us here why do you think that the Min et al. paper is not correct, or why do you think that wattsupwiththat is justified. But other than that, I'd rather not enter in general comments about other blogs<br /><br />Roger Pielke explained that there are no detectable trends of normalized climate-disaster economic losses, which I have no reason to doubt- actually I believe that this is true as well. I do not see a contradiction with Min et al. We should not forget that Min et al.'s claim is that they were able to detect a certain signal in the observed noisy record of extreme rainfall. As far as I understand, they did not claim that trends in extreme rainfall are only caused by GHG or even that GHG are the most important cause for trends in extreme rainfall. <br /><br />The implicit conclusion is indeed that, given that the signal is there, and given that GHG concentrations will continue growing and other forcings will not, GHG will at some point become the dominant cause in the future.<br /><br />It may be that of the some fuss about this study is confusion about these subtle differences .<br /><br />Revkin warns that there are uncertainties in this study – as in many others. I would also agree.eduardohttps://www.blogger.com/profile/17725131974182980651noreply@blogger.comtag:blogger.com,1999:blog-8216971263350849959.post-39182088689414662872011-02-21T23:45:34.806+01:002011-02-21T23:45:34.806+01:00eduardo, georg, hans, ralph:
the anthropologist i...eduardo, georg, hans, ralph:<br /><br />the anthropologist is confused: is this about politics or about science? Looks like an uncontrolled back and forth or switching from one field to another. Is it possible that those models are political themselves, deep inside?Werner Krausshttps://www.blogger.com/profile/15094636819952421339noreply@blogger.com