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  • Myth vs. Fact Regarding the "Hockey Stick" « RealClimate
    for reconstructing past temperature variability Science 295 2250 2253 2002 Jones P D K R Briffa T P Barnett and S F B Tett High resolution palaeoclimatic records for the last millennium Integration interpretation and comparison with General Circulation Model control run temperatures Holocene 8 455 471 1998 Jones P D Mann M E Climate Over Past Millennia Reviews of Geophysics 42 RG2002 doi 10 1029 2003RG000143 2004 Mann M E R S Bradley and M K Hughes Global scale temperature patterns and climate forcing over the past six centuries Nature 392 779 787 1998 Mann M E R S Bradley and M K Hughes Northern Hemisphere Temperatures During the Past Millennium Inferences Uncertainties and Limitations Geophysical Research Letters 26 759 762 1999 Mann M E Ammann C M Bradley R S Briffa K R Crowley T J Hughes M K Jones P D Oppenheimer M Osborn T J Overpeck J T Rutherford S Trenberth K E Wigley T M L On Past Temperatures and Anomalous Late 20th Century Warmth Eos 84 256 258 2003 Rutherford S Mann M E Osborn T J Bradley R S Briffa K R Hughes M K Jones P D Proxy based Northern Hemisphere Surface Temperature Reconstructions Sensitivity to Methodology Predictor Network Target Season and Target Domain Journal of Climate in press 2004 Soon W and S Baliunas Proxy climatic and environmental changes over the past 1000 years Climate Research 23 89 110 2003 Soon W S Baliunas C Idso S Idso and D R Legates Reconstructing climatic and environmental changes of the past 1000 years Energy and Environment 14 233 296 2003 Comments pop up 9 9 Responses to Myth vs Fact Regarding the Hockey Stick 1 Saheli says 10 Dec 2004 at 3 45 PM Thanks This is a great resource 2 Stephen Berg says 13 Dec 2004 at 11 27 PM Holy cow What a great site Way to go and keep it up 3 Brad DeLong s Semi Daily Journal A Weblog says 17 Dec 2004 at 3 05 PM When Climatologists Attack The climatologists are angry and are on the warpath against the industry funded Tech Central Station RealClimate Temperature Variations in Past Centuries and the so called Hockey Stick coined by the former head of NOAA s Geo 4 John Finn says 22 Dec 2004 at 11 14 AM I have a yet another question In the above article you discuss various myths associated with the hockey stick graph To support your argument you refer to other sources For example see Cook et al 2004 at the end of the myth 1 discussion So I thought ok I ll look up the Cook study and see what it says Now unfortunately I m a total non expert I only started reading about climate change a few months ago so it always possible that I ve misunderstood something Anyway as I was reading the paper it struck me that neither the Cook study nor any of the other proxy studies were in total agreement with the hockey stick Response Your comment is somewhat incorrectly premised There is no uniquely defined hockey stick reconstruction This term as defined in our glossary refers to the general shape common to a number of independent reconstructions see this comparison of various proxy and model based estimates characterized by 20th century large scale warming that exceeds the bounds of the more moderate temperature variations characterizing preceding centuries The details of any individual reconstruction depend however on the regions and seasons represented by that particular reconstruction as discussed above in the discussion of myth 1 In the Cook et al 2004 paper referred to above the authors are indeed careful to emphasise that their conclusions pertain to the warm season and extratropical continental region represented by their particular reconstruction There are a number of important reasons why reconstructions differ depending on seasonal and spatial sampling considerations see the response to comment 3 above and also the discussion in the review paper by Jones and Mann 2004 see section 5 3 therein Jones P D Mann M E Climate Over Past Millennia Reviews of Geophysics 42 RG2002 doi 10 1029 2003RG000143 2004 It is therefore not surprising that past summer extratropical temperature changes such as are reconstructed by Esper et al 2002 and Cook et al 2004 may indeed have differed significantly from annual temperature changes over the entire tropical and extratropical Northern Hemisphere such as are targeted in other reconstructions e g Jones et al 1998 Mann et al 1999 Crowley and Lowery 2000 Mann and Jones 2003 Despite these differences in seasonal and spatial emphasis however the various reconstructions and model estimates are in fact observed to be consistent within estimated uncertainties mike You could argue that all the reconstructions show some agreement up to about 1980 but after that the measured temperature record diverges completely from the proxy records and by the end of the century appears to be at least 0 3 degrees higher than the proxies Response This is not correct Most reconstructions only extend through about 1980 because the vast majority of tree ring coral and ice core records currently available in the public domain do not extend into the most recent decades While paleoclimatologists are attempting to update many important proxy records to the present this is a costly and labor intensive activity often requiring expensive field campaigns that involve traveling with heavy equipment to difficult to reach locations such as high elevation or remote polar sites For historical reasons many of the important records were obtained in the 1970s and 1980s and have yet to be updated The fact that a relatively small number of long high resolution proxy temperature records extend through the most recent decades should not be mis interpreted as evidence against recent warming as sometimes done by certain contrarians The available long records that extend through the present typically do indeed confirm the recent warming For example through a composite of the relatively few very

    Original URL path: http://www.realclimate.org/index.php/archives/2004/12/myths-vs-fact-regarding-the-hockey-stick/ (2016-02-13)
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  • RealClimate » Blog Archive » On attribution
    detect Note that it helps enormously to think about attribution in contexts that don t have anything to do with anthropogenic causes For some reason that allows people to think a little bit more clearly about the problem First off think about the difference between attribution in an observational science like climatology or cosmology etc compared to a lab based science microbiology or materials science In a laboratory it s relatively easy to demonstrate cause and effect you set up the experiments and if what you expect is a real phenomenon you should be able to replicate it over and over again and get enough examples to demonstrate convincingly that a particular cause has a particular effect Note that you can t demonstrate that a particular effect can have only that cause but should you see that effect in the real world and suspect that your cause is also present then you can make a pretty good though not 100 case that a specific cause is to blame Why do you need a laboratory to do this It is because the real world is always noisy there is always something else going on that makes our reductionist theories less applicable than we d like Outside we don t get to perfectly stabilise the temperature and pressure we don t control the turbulence in the initial state and we can t shield the apparatus from cosmic rays etc In the lab we can do all of those things and ensure that hopefully we can boil the experiment down to its essentials There is of course still noise imprecision in measuring instruments etc and so you need to do it many times under slightly different conditions to be sure that your cause really does give the effect you are looking for The

    Original URL path: http://www.realclimate.org/index.php/archives/2010/05/on-attribution/ (2016-02-13)
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  • On mismatches between models and observations « RealClimate
    in Future Changes in Climate section reads For the next two decades a warming of about 0 2 C per decade is projected for a range of SRES emission scenarios Even if the concentration of all greenhouse gases and aerosols had been kept constant at year 2000 levels a further warming of about 0 1 C per decade would be expected The table immediately below said paragraph predicts sea level rise with two significant digits under a variety of scenarios You must be aware that this report has been cited numerous times by Nancy Pelosi Harry Reid Al Gore and many lobbyist organizations pushing cap and trade legislation and many other EPA regulations While I agree that any mismatch between models and observation in all respects is normal and expected it is the very quantity in bold face in the FAR summary that is both mismatched and driving these policy considerations What I was hoping for in this post was some technical leads for the mismatch specific to your bullet point 2 above Is it the fundamental CO2 forcing prediction based on effective radiation temperature to space Or the indirect CO2 forcing predicted due to H2O increases at high altitudes that have not materialized I am probably as aware of any reader here of modeling challenges in general and can appreciate the work your groups have performed but I can also appreciate the implications of the mismatch that prompted your post there is fundamental uncertainty in the interaction of the complex mechanisms that drive climate change including the human effect Response The IPCC report is far more than a single line about the short term ensemble mean trend Even the SPM is substantially more detailed let alone the rest of the report Your claim of a fundamental mechanism that is at play here is simply wrong As I outlined above there are many reasons for mismatches and the shorter the time period the more reasons there are forcings initial conditions internal variability are all likely playing a role as has been demonstrated in a number of recent papers We don t yet have a full synthesis but people are working on it but for you to automatically assume the answer says more about prior beliefs than it does about the evidence gavin 14 Tim Beatty says 13 Sep 2013 at 10 47 PM Ray Ladbury Maybe it s a chicken egg problem but how do you test basic assumption like gridding I would think model disagreement with sample could be attributed to a number of things unrelated to the model 1 the natural event is extreme so the actual population including its sample is outside model limits 2 the sample is not an accurate representation of the population or 3 the population is more complex or dynamic than the sample methods As an example and I don t have data just a thought experiment when we estimate average global temperature and we grid up the planet how do we test that the grid size is appropriate to sample How do assess whether grid size required for accurate population is potentially seasonally or geographically or both dependent Or if the grid is oversampled in certain areas If the model is the only test it could be revealing an extreme population and extreme sample or model error How do we know a model could be exactly accurate but the data it needs 10 10 sq mile sample sets in the ENSO SST region but only an 100 100 sq mi sample sets in Ukraine Maybe it s my ignorance of available data but I don t know how to measure sensitivity to that kind of sampling error It seems the goal is to get the model to agree with the sample but how do test the sample against the population and how do you estimate the variance in the population with the variance in the sample 2012 is different from 2013 Both are represented as a population nature and as a sample of population our measurement of nature Is one of the populations extreme Is the sample correlated well enough to the population Are sampling methods dependent on conditions Do we treat sampling as part of the model or separate 15 AIC says 14 Sep 2013 at 1 10 AM Please a glossary for the various abbreviations in your post Thanks Response Here Let me know if there is anything that is not clear gavin 16 NickC says 14 Sep 2013 at 1 44 AM Gavin would it be safe to assume that you have enough confidence in paleo inferences to have mismatch of models to observation lessen your conviction we remain on a worrying path In other words does it lessen your certainty or just point to gaps in knowledge that will eventually still bear out the overall thrust that anthropogenic contribution is worrying I think it is pertinent to the discussion Response Yes I m not quite sure what specific mismatch you are referring to or just making a general point but on the basic issue should one be concerned about future anthropogenic climate change I have not changed my opinion mainly because that is not based on models at all Models are there to help us quantify the changes and without them we would have much larger uncertainties gavin Also in 12 you say and models are consistent with inferences from paleo could you elaborate on face value it seems incorrect I must be missing something Response Charney sensitivity from paleo is around 3ºC models are in the same range the latest GISS model for instance is around 2 5ºC gavin 17 sue says 14 Sep 2013 at 2 36 AM PS I have no idea what you mean by high confidence in catastrophic anthropogenic global warming gavin 7 SecularAnimist says 13 Sep 2013 at 5 15 PM Alex wrote high degree of confidence regarding catastrophic anthropogenic global warming A high degree of confidence is appropriate given that catastrophic anthropogenic global warming is already occurring right before our eyes all over the world Deniers have to work very hard to ignore it Can you clarify Gavin since you let this comment through moderation Response I have high confidence that anthropogenic effects are dominating current climate change and will increasingly do so in the decades to come The changes that we have seen so far are not catastrophic on a global scale though future changes are going to be much larger and there is a very real risk of substantive damages However when people use the term catastrophic anthropogenic global warming they are not referring to any real science but are attempting to paint anyone who talks about the science as an alarmist AGW is real and growing but whether it turns into a catastrophe is very much up to us gavin 18 Joe says 14 Sep 2013 at 4 50 AM Gavin I ll have to read up on Quine to grasp your deeper epistemological point here but your examples seem far off The faster than light neutrino experiment was an error so of course it didn t falsify special relativity I m sure Feynman didn t claim that errors falsify theories so there s no contradiction of Feynman s dictum here Response You are missing the point entirely Since there is never a perfect experiment or observation error is always a possibility And since you correctly note that erroneous claims do not falsify anything there is always the possibility that an experimental result however conflicting on it s face was actually in error Therefore it is never as simple as Feynman s dictum implies gavin Saying that a map doesn t capture the true landscape or a portrait the true self is very confusing as a lead in to a discussion of climate models Maps actually do capture what they are supposed to capture quite accurately I don t know what you mean by a portrait but it s not going to be a good analogy for a science like climate science Response Sometimes I like to use metaphors Sue me But listen to the Neil Gaiman story first gavin I think it would be bad bad news for climate scientists to start talking this way to start retreating behind vague figurative artistic analogies to describe their ability to cohere with reality Adopting an epistemolgy of lower standards one where hypotheses or theories can t be falsified creates too much room for bias and motivated reasoning Perhaps it wasn t your intention to suggest a sloppy low standards epistemology Climate science is viewed by outsiders and described by Judith Curry as a biased groupthink driven field There is very little that scientists can learn from 20th century epistemologies many of which would make science impossible The last thing climate science needs right now is some wishy washy epistemology Response The last thing any science needs are false epistemologies that are just hoisted up the flagpole in order to ignore the balance of evidence I illustrated my points with real cases where different resolutions have been found to previous mismatches assuming that future mismatches will all be resolved in a single way is a historical and extremely unlikely gavin BTW Alex said there s fundamental uncertainty not that there s a fundamental mechanism 19 Dag Flolo says 14 Sep 2013 at 6 00 AM Fixed a few type errors Hi Gavin Maybe the following example is useful as a clean example ref we compare the result of the computation to nature with experiment or experience compare it directly with observation to see if it works If it disagrees with experiment it is wrong actually doesn t work except in the purest of circumstances and I m not even sure I can think of a clean example Here is a clean example Distance traveled m velocity m s time s The dimensions are traceable to international standards I can measure both distance velocity and time in SI units I can determine the standard uncertainty for all the measured variables from statistics It is falsifiable i can move a body at a certain velocity for a certain time and measure the traveled distance If the traveled distance does not fit with calculated distance within the uncertainty calculated by using the international standard Guide to the expression of Uncertainty in Measurement the model might be wrong Response This is simply a definition of velocity and so the statement is a tautology it cannot be otherwise Thus it doesn t come into the discussion of testing theories gavin The model is useful if I can make predictions which affect my choice of action In my every day life it is useful even within uncertainties of 10 20 caused by uncertainty in predicted velocity when estimating time of arrival If the uncertainty became to high it would not be useful The model is analogue to Increase in global average atmospheric temperature K Effect from CO2 K ppm CO2 Increase in CO2 level ppm CO2 For the model to be useful it must be correct within some level of standard uncertainty for some averaging period And repeatably so for many periods Response You have a very impoverished view of what utility is Is it useful to know that a medical treatment improves outcomes by 0 to 30 in different trials The answer for the FDA is very different than for a patient or a researcher gavin 20 dhogaza says 14 Sep 2013 at 8 05 AM Gavin Flaws in comparisons can be more conceptual as well for instance comparing the ensemble mean of a set of model runs to the single realisation of the real world Or comparing a single run with its own weather to a short term observation These are not wrong so much as potentially misleading since it is obvious why there is going to be a discrepancy albeit one that doesn t have much implications for our understanding This is almost worth a post in itself as these fundamental misunderstandings are the basis for so many skeptical arguments in particular combining the single realization of the real world with an ensemble mean In fact in this thread alex and nickc are both arguing based to some extent on fundamentally misunderstanding this along with an apparent belief in model reality mismatches that don t actually exist to the extent they believe 21 Frank Davis says 14 Sep 2013 at 9 14 AM So if the model doesn t work there s nothing to worry about Response No If there is a mismatch there is maybe an interesting reason for it and people should try and find out what it is gavin 22 Watcher says 14 Sep 2013 at 9 34 AM Gavin Since I m spreading admiration around I reckon you should get some too you had to know a discussion of this type would be lively So let s go to your responses to 18 Just because v D t doesn t mean that all predictions based on Newton s law of motion are tautologies I agree that for some simple theories they are so obvious in retrospect that they seem so For example if I measure v using D t as my rocket leaves the atmosphere it is not a tautology to predict where it will be 5 or 6 years from now so that it can drop a probe on Jupiter Response I didn t say that Newton s Law did not give testable predictions Only that your specific example v D t was a tautology and has nothing specific to do with Newton s Law in any case gavin Ah But maybe it didn t make it to Jupiter Does this falsify the theory No I forgot to account for the orbital motion of Earth and Jupiter so indeed this expensive miss does not invalidate Newton s theory If I understand you correctly this is what you are getting at Response Yes this is more to the point Nevertheless it is surely possible to take into account the appropriate factors calling into use gravitational constants and what not and come up with a better prediction If I include only Earth and Jupiter the result will still be off but I reckon that if I start taking the Sun into account my prediction will start looking a lot better Maybe it needs tweaking a bit due to the lunar fly by before it starts looking really good Response Yup But how do you tell whether any remaining mismatch is due to a missing body or to the difference to general relativity gavin Nevertheless while each of the pieces of this construction comprises equally simply things like D vt and F GMm r 2 the final prediction is not a tautology Response F GMm r 2 is a theory D vt is a definition There is a difference I would venture to say that this is how science is supposed to work and it is perverse to insist that Feynman s philosophy be judged on the basis of the first simplistic experiment It is the job of a scientist to know which theory hypothesis is being tested by a given experiment and is at the root of what I would call a properly designed experiment Maybe we can say that a good scientist is able to take the world of Quine and reduce it to the world of Popper at least to an extent that is good enough Response Agreed Just to belabour the point notice that my Jupiter prediction failed to take into account either the colour of the rocket s paint or the newly discovered earthlike planet around Alpha Centauri or wherever because my scientific judgement tells me that while this leaves me open to the criticism that my model is incomplete I have good reason to believe that these things don t matter in the current context Indeed if pressed I can estimate the impact using the same D vt and F etc and show this to be the case Maybe I launch several probes that all arrive safely and in my mind I elevate my model to a theory of Earth Jupiter space travel Now suppose that next year I launch another probe and this time it misses Does that falsify Newton s laws Perhaps but it s more likely that my theory was incorrect I check things out a bit and notice that this year Mars has moved close to the flight path so previously I got the right answer with an incorrect theory that posited no influence from the planet Mars Scientific honesty requires me to admit to another expensive error and revise my theory to include the new factor and once again attempt the conversion of a Quine to a Popper situation My my I have gone on and I should probably get to the point There is philosophy and there is science If scientists behaved like philosophers nobody would ever get anything done because they d all be too worried about having missed some factor and anyway what if I m just imagining the space probe in the first place In a scientific sense it MATTERS very much what measurements say and I will say again that measurements are the only things that really do matter It s not sufficient to say that they might be wrong or they might be measuring something different from what they seem to and so therefore I might be right even though my theory doesn t agree with them The job of a scientist is to sort through the mess and develop a theory that can account for the measurements Furthermore for that theory to be useful it must be capable of producing verifiable predictions e g the probe will get to Jupiter no matter what year I launch it If the predictions don t work out then the theory must be modified or abandoned Anything less is not science Response I am a scientist not a philosopher and anything I am talking about here comes directly from the practice of science not theorising about it However as I m sure the philosophers reading will be happy to know there is some connection between what scientists actually do and how it is modelled by philosophers It s not a perfect model though of course gavin 23 Jan Galkowski says 14 Sep 2013 at 9 41 AM This is a personal perspective of the subject from that of a practicing statiscian and only a very amateur climate guy In the case of Earth s climate as a source of observations there s an additional difficulty As Slava Kharin observed in slides for the Banff Summer School 2008 There is basically one observational record in climate research See Slide 5 http www atmosp physics utoronto ca C SPARC ss08 lectures Kharin lecture1 pdf And this is an issue For there is enough variability in Earth s climate that if the system were initialized again say 50 years back and somehow magically all the external inputs to the system kept exactly the same the result would be a little different There is a debate about how big this internal variability is see Kumar Chen Hoerling Eischeid Do Extreme Climate Events Require Extreme Forcings http dx doi org 10 1002 grl 50657 with climate amateur but statistician me coming down on the side of not as much as you might think My reasons are complicated and I ll write them up in an upcoming paper I m putting on arXiv org that being a critical review of the statistics in the recent NATURE CLIMATE CHANGE paper by Fyfe Gillett and Zwiers shared first with those authors There are different flavors of variability beyond internal and external See http hypergeometric wordpress com 2013 08 28 overestimated global warming over the past 20 years fyfe gillett zwiers 2013 for more But the point is such variability makes modeling even harder for not only are the general parameters of the physical system necessary to get right but if prediction is a goal actually TRACKING the actual realization Earth is taking is part of the job Slava Kharin argues and I agree that the one observational record reality means a Bayesian approach is the only sensible one That s not universally held in geophysical work however Nevertheless it s important I think to parse properly what this all means The reason why we want models is to help understand what data means and what physical effects are important how much and how We of course also want to use them for policy predictions but using these as predictive devices is a tricky business Statistically speaking NONE of that should be taken to mean the long term projections are off in expected values in any significant way Forcings are forcings and AB INITIO physics says that extra energy needs to go someplace and be dissipated throughout the primarily fluid systems of Earth somehow The devil is in the latter details as are the impacts But they will occur even if amounts and timings will be off as they necessarily must be So called two sample comparisons are tricky in complicated systems Most direct techniques for doing so assume constant variation over large swaths of samples That kind of approach tends to give large Regions of Probable Equivalence ROPEs which of course are less useful that otherwise When this is done for predicting elections say something called stratification is used where observations are qualified by in this case spatial extent time of day and other auxiliary variables and the response state of atmosphere considered as conditioned on these and the model evaluated comparably where it can be Alas sometimes doing that leaves few observations or few model runs to compare That s okay if a Bayesian approach is used Not so much otherwise Gavin said all this but I wanted to second his view giving mine as well as put a note about my ongoing hard look at Fyfe Gillett and Zwiers 24 Watcher says 14 Sep 2013 at 9 42 AM I have to echo some of the comments made above concerning the reliance on paleo studies The notion that proxy ESTIMATES of temperature 1000 years ago when there was no anthropogenic CO2 are a superior test of AGW theory than current temperature MEASUREMENTS in the presence of a significant anthropogenic CO2 component strikes me as absurd Response Here s a test If you read something written by someone who basically knows what they are talking about and it seems absurd to you ponder at least for a second or two that it might be your interpretation that is at fault rather than the statement If you did and perhaps followed the links you would realise that my comment had nothing whatever to do with temperatures 1000 years ago But nice try gavin 25 prokaryotes says 14 Sep 2013 at 10 03 AM Models tap into the physical world processes but focus only on a given range of frequencies Therefore any interpretation conclusion is prone to human error To understand future states better it appears to involve as much data as possible which would also increase error rate It would help to identify tipping point systems of the spectrum better The conclusiveness the reliability should increase with data spectrum ratio I really like to read another post on CMIP5 combined modelling with all methane forcings But even a small data model for instance analogous albedo Daisyworld seems to be reliable in predicting trends Also i find this interesting The treatment of signal and noise in constructing climate scenarios is of great importance in interpreting the results of impact assessments that make use of these scenarios If climate scenarios contain an unspecified combination of signal plus noise then it is important to recognise that the impact response to such scenarios will only partly be a response to anthropogenic climate change an unspecified part of the impact response will be related to natural internal climate variability However if the objective is to specify the impacts of the anthropogenic climate signal alone then there are two possible strategies for climate scenario construction attempt to maximise the signal and minimise the noise do not try to disentangle signal from noise but supply impact assessments with climate scenarios containing both elements and also companion descriptions of future climate that contain only noise thus allowing impact assessors to generate their own impact signal to noise ratios Hulme et al 1999a Link When it comes to science messaging i think it would help to point out more often general agreements predictions and underestimation and why 26 csoeder says 14 Sep 2013 at 10 05 AM re maps and models I think that James Gleick was spot on in his book Chaos Only the most naive scientist believes that the perfect model is the one that perfectly represents reality Such a model would have the same drawbacks as a map as large and detailed as the city it represents a map depicting every park every street every building every tree every pothole every inhabitant and every map Were such a map possible its specificity would defeat its purpose to generalize and abstract Mapmakers highlight such features as their clients choose Whatever their purpose maps and models must simplify as much as they mimic the world Gleick p 278 279 27 Radge Havers says 14 Sep 2013 at 10 08 AM Joe Saying that a map doesn t capture the true landscape or a portrait the true self is very confusing as a lead in to a discussion of climate models Maps actually do capture what they are supposed to capture quite accurately I don t know what you mean by a portrait but it s not going to be a good analogy for a science like climate science Huh Here Be Dragons The good cartographer is both a scientist and an artist He must have a thorough knowledge of his subject and model the Earth He must have the ability to generalize intelligently and to make a right selection of the features to show These are represented by means of lines or colors and the effective use of lines or colors requires more than knowledge of the subject it requires artistic judgement Erwin Josephus Raisz 1893 1968 The foremost cartographers of the land have prepared this for you it s a map of the area that you ll be traversing Blackadder opens it up and sees it is blank They ll be very grateful if you could just fill it in as you go along Blackadder II British Comedy set in Elizabethan times A map is the greatest of all epic poems Its lines and colors show the realization of great dreams Gilbert H Grosvenor Editor of National Geographic 1903 1954 When our maps do not fit the territory when we act as if our inferences are factual knowledge we prepare ourselves for a world that isn t there If this happens often enough the inevitable result is frustration and an ever increasing tendency to warp the territory to fit our maps We see what we want to see and the more we see it the more likely we are to reinforce this distorted perception in the familiar circular and spiral feedback pattern Professor Harry L Weinberg 1959 in Levels of Knowing and Existence Studies in General Semantics There is no such thing as information overload only bad design Edward Tufte If you want a database that has everything you ve got it It s out there It s called reality Scott Morehouse Director of Software Development ESRI our earth is a globe whose surface we probe no map can replace her but just try to trace her Steve Waterman The World of Maps 28 Hank Roberts says 14 Sep 2013 at 11 36 AM data spectrum ratio 29 SecularAnimist says 14 Sep 2013 at 11 37 AM Gavin wrote in reply to 17 The changes that we have seen so far are not catastrophic on a global scale To paraphrase Tip O Neill all catastrophe is local And when local catastrophes are occurring everywhere at once that s global The millions of people all over the world who have already experienced mass destruction of their homes livelihoods food supply and or water supply as a result of AGW driven climate change and extreme weather might not agree that the changes we have seen so far are not catastrophic Which is of course why the primary mission of the deniers at this point is to deny any link between global warming and these ongoing and rapidly escalating effects to argue in essence that yes the world is warming and yes we are experiencing exactly the sort of effects that climate science has predicted for a generation would result from that warming but no those effects are not the result of the warming So what is causing them According to the deniers nothing They are just our imagination 30 SecularAnimist says 14 Sep 2013 at 11 45 AM I wrote yesterday 7 A high degree of confidence is appropriate given that catastrophic anthropogenic global warming is already occurring right before our eyes all over the world Deniers have to work very hard to ignore it And right on queue for a perfect example see the piece in today s Washington Post by Bjorn Lomborg perhaps the hardest working denier in show business Sure your decades of smoking cigarettes have given you lung cancer And yes you are coughing up blood But you can t attribute every bloody cough to the cancer There are always bloody coughs every once in a while It s just natural variation you see And it doesn t mean you are going to experience globally catastrophic effects from the cancer like you know death 31 prokaryotes says 14 Sep 2013 at 12 25 PM Hank Roberts Re Spectrum Ratio see also Vautard R and M Ghil 1989 Singular spectrum analysis in nonlinear dynamics with applications to paleoclimatic time series Physica D 35 395 424 Link or Singular spectrum analysis 32 prokaryotes says 14 Sep 2013 at 12 32 PM And Spectral signal to noise ratio 33 Lichanos says 14 Sep 2013 at 12 36 PM If you want a database that has everything you ve got it It s out there It s called reality Scott Morehouse Director of Software Development ESRI Gads As a daily user of ESRI software for more than 20 years I shudder at the thought of their executives being taken as authorities on anything but sales I suppose he thought he was being clever but the notion of reality as a database is absurd After decades of producing books along the lines of Modeling Our World The ESRI Way I guess they believe their own propaganda 34 Berényi Péter says 14 Sep 2013 at 1 30 PM I wonder if there is a non equilibrium quasi steady state non reproducible thermodynamic system one with a vast number of internal degrees of freedom other than the terrestrial climate system which is successfully described by a computational model If its dimensions are small enough to make it fit into the lab and studied that way in controlled experimental runs so the model is verified properly it is even better A system is reproducible if for any pair of macrostates A B A either always evolves to B or never Response Define successfully gavin 35 Martin Vermeer says 14 Sep 2013 at 2 13 PM A model doesn t have to be perfect just better than the competition Like you don t have to out run the lion just the other guy 36 Lee A Arnold says 14 Sep 2013 at 2 52 PM Gavin you have hit upon one of my favorite topics There was a related discussion here Naomi Oreskes Kristin Shrader Frechette Kenneth Belitz Verification Validation and Confirmation of Numerical Models in the Earth Sciences SCIENCE Vol 263 No 5147 Feb 4 1994 pp 641 646 Note that your argument applies analogously to natural language too To help climate change communication in the public debate I have been trying to create a natural language style flow chart cartoon language that illustrates the principles of the lack of precise prediction in complex systems for purposes of elementary pedagogy This is not climatology it is non mathematical general systems to picture different things in the same format I am happy to report that it has had SUCCESS in counteracting denialist arguments in the comments section under the new Lomborg opinion column in the Washington Post Here is the thing I did http www youtube com watch v SIvcQTXdjTg list PLT vY3f9uw3AcZVEOpeL89YNb9kYdhz3p And here is the complete list of the series http www youtube com playlist list PLT vY3f9uw3AcZVEOpeL89YNb9kYdhz3p They are all exactly one minute long The food web cartoon 3 takes a similar approach 37 Abhay says 14 Sep 2013 at 2 58 PM With regard to comparisons evaluation may be a proper word here of models to using satellites it is worth pointing out that this is a big research field in its own There are various approaches for comparing these two and each approach has its own advantage and limitation For example 1 one can do a traditional comparison whereby one compares means standard deviations etc with satellite based estimates This will tell you if a model captures the overall range of values and spatial variability but will not tell you anything about how good any particular process is simulated 2 Another way would be to carry out a process oriented comparison wherein one focuses on a set of processes or natural variabilities e g ENSO NAO or Indian Ocean Dipole and investigate how good a particular model reproduces climatology of certain variables during those processes variabilities in reference to similar climatology from the satellites But this approach will not have the advantage of the first one 3 One could also employ satellite simulators so as to avoid comparing apples to oranges The simulators take model data of a certain geophysical variable and carefully simulate it in a way particular satellite sensor would have seen that variable This ensures a fair comparison And it not only takes care of mismatches and sampling issues between models and satellites but also different sensitivities of different satellite sensors to geophysical variables 4 Eventually one could combine any or all of the approaches above which I think would be the most stringent litmus test of the models All of this of course only applies if you have satellite based data sets which in most cases go back to 1979 for comparison 38 Ray Ladbury says 14 Sep 2013 at 3 04 PM At this point it would not seem out of place to quote Richard Hamming The purpose of computing is insight not numbers The same can be said of models A model need not even be the best to accomplish this Tamino s 2 box model is a case in point as its simplicity allows the important contributors to climate to be isolated and assessed On the other hand the denialist model Oh yeah There is no denialist model And you guys wonder why no one intelligent takes you seriously 39 Berényi Péter says 14 Sep 2013 at 3 09 PM Response Define successfully gavin In case the system can be studied experimentally in a controlled lab environment definition of successfully is straightforward Both the experiment and model simulation can be run as many times as necessary with controlled parameters As the system is supposed to be non reproducible only statistics of macroscopic state variables are comparable of course but with enough runs that can be made to converge to an arbitrary degree provided the model is correct If it is not divergence is clearly visible that is

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  • On sensitivity: Part I « RealClimate
    something different if the change in temperature from the last GM is 6 K approximately 1 3 change again versus 4 K approximately 1 2 change again In other words if climate sensitivity is toward the low end 2 K is more dangerous than we currently give it credit for and arguments for low risk because of low sensitivity are less valid because that means that more ecological changes occur for a given temperature change than currently thought 6 David B Benson says 3 Jan 2013 at 3 11 PM Quite helpful Gavin Well done 7 Tom Scharf says 3 Jan 2013 at 4 30 PM A useful post Correct me if I am wrong but this appears to be walking back the CS numbers a bit 3C seems to be heading towards 2 5C I am encouraged as I have been a somewhat vocal critic that when models have been over estimating the temps fairly consistently that it somehow wasn t translating into lower CS estimates or constraining the upper range Many forcings were being twiddled to account for observations namely aerosols but the main CO2 forcing seemed to be the third rail Response Huh Forcing is not the same as sensitivity For reference GISS ModelE had a sensitivity of 2 7ºC and GISS E2 has sensitivity of 2 4ºC to 2 8ºC depending on version All very mainstream gavin 8 richard pauli says 3 Jan 2013 at 4 33 PM Thanks for this crucial science on sensitivity A crucial subject for understanding This leads to questions about micro sensitivity People are thinking about their individual impact to global warming Generalities of carbon footprint try to package the message but fail We might want to know the impact of specific actions Certainly operating a carbon fueled car has real consequences although for any one vehicle they are very slight A single cylinder emission is the lowest unit of micro sensitivity One person in a car might have a few million per day or a pound of CO2 per mile traveled It s like pissing in a trout stream one person may not do more harm than scare away the fish but with millions along the shores all streaming away all day pretty soon it is the yellow river of death Somewhere we need to measure cognitive sensitivity to human impacts of global warming Perhaps the visual display would be like a car s tachometer it would measure ineffectual use of CO2 The micro sensitivity meter would indicate how effectively carbon fuel is used to deploy clean energy It would sit right on the dashboard 9 SecularAnimist says 3 Jan 2013 at 5 20 PM Tom Scharf wrote models have been over estimating the temps fairly consistently That s simply not true Contrary to Contrarian Claims IPCC Temperature Projections Have Been Exceptionally Accurate 27 December 2012 SkepticalScience In this post we will evaluate this contrarian claim by comparing the global surface temperature projections from each of the first four IPCC reports to the subsequent observed temperature changes We will see what the peer reviewed scientific literature has to say on the subject and show that not only have the IPCC surface temperature projections been remarkably accurate but they have also performed much better than predictions made by climate contrarians 10 wili says 3 Jan 2013 at 5 45 PM This was just posted at SkSc Time varying climate sensitivity from regional feedbacks Time varying climate sensitivity from regional feedbacks Armour et al 2012 FULL TEXT Abstract The sensitivity of global climate with respect to forcing is generally described in terms of the global climate feedback the global radiative response per degree of global annual mean surface temperature change While the global climate feedback is often assumed to be constant its value diagnosed from global climate models shows substantial time variation under transient warming Here we propose that a reformulation of the global climate feedback in terms of its contributions from regional climate feedbacks provides a clear physical insight into this behavior Using i a state of the art global climate model and ii a low order energy balance model we show that the global climate feedback is fundamentally linked to the geographic pattern of regional climate feedbacks and the geographic pattern of surface warming at any given time Time variation of the global climate feedback arises naturally when the pattern of surface warming evolves actuating regional feedbacks of different strengths This result has substantial implications for our ability to constrain future climate changes from observations of past and present climate states The regional climate feedbacks formulation reveals fundamental biases in a widely used method for diagnosing climate sensitivity feedbacks and radiative forcing the regression of the global top of atmosphere radiation flux on global surface temperature Further it suggests a clear mechanism for the efficacies of both ocean heat uptake and radiative forcing Citation Kyle C Armour Cecilia M Bitz Gerard H Roe Journal of Climate 2012 doi http dx doi org 10 1175 JCLI D 12 00544 1 http www skepticalscience com new research 52 2012 html 11 wili says 3 Jan 2013 at 5 53 PM And this Late Pleistocene tropical Pacific temperatures suggest higher climate sensitivity than currently thought Late Pleistocene tropical Pacific temperature sensitivity to radiative greenhouse gas forcing Dyez Ravelo 2012 Abstract Understanding how global temperature changes with increasing atmospheric greenhouse gas concentrations or climate sensitivity is of central importance to climate change research Climate models provide sensitivity estimates that may not fully incorporate slow long term feedbacks such as those involving ice sheets and vegetation Geological studies on the other hand can provide estimates that integrate long and short term climate feedbacks to radiative forcing Because high latitudes are thought to be most sensitive to greenhouse gas forcing owing to for example ice albedo feedbacks we focus on the tropical Pacific Ocean to derive a minimum value for long term climate sensitivity Using Mg Ca paleothermometry from the planktonic foraminifera Globigerinoides ruber from the past 500 k y at Ocean Drilling Program ODP Site 871 in the western Pacific warm pool we estimate the tropical Pacific climate sensitivity parameter λ to be 0 94 1 06 C W m 2 1 higher than that predicted by model simulations of the Last Glacial Maximum or by models of doubled greenhouse gas concentration forcing This result suggests that models may not yet adequately represent the long term feedbacks related to ocean circulation vegetation and associated dust or the cryosphere and or may underestimate the effects of tropical clouds or other short term feedback processes Citation Kelsey A Dyez and A Christina Ravelo Geology v 41 no 1 p 23 26 doi 10 1130 G33425 1 In general as we get better and better data and as models include more and more feedbacks are studies moving toward higher and higher sensitivities That had been my impression but perhaps this is the result of selective reading on my part Response I would need to check but I think this is a constraint on the Earth System Sensitivity not the same thing see the first figure gavin 12 David Stern says 3 Jan 2013 at 8 35 PM I m increasingly thinking that what we really need is an estimate of the sensitivity of the system to an injection of carbon dioxide including the feedback from the carbon cycle etc I suppose that is the Earth System Sensitivity in this terminology Using sensitivities where carbon dioxide concentrations is an exogenous variable could underestimate the cost of emissions impacts 13 Geoff Beacon says 4 Jan 2013 at 4 38 AM Surely the models described are all lagging behind the real world The CMIP5 models seem to predict an Arctic free of summer sea ice in a few decades but the real world trend is for this to happen in the next few summers So why should policy makers care what these models predict as climate sensitivity I suppose it is an interesting scientific problem but we should bear in mind that most or all of them are on the optimistic side Quite apart from the known underestimated feedbacks more forest fires melting permafrost the decomposition of wetlands new possibilities turn up What if we see more Great Arctic Cyclones pop up in coming years to speed very unwelcome climate changes Don t you think we re seeing changes that exceed predictions already Lots of droughts floods and snow I would be interested in your take on frankenstorm Sandy A sign of climate change or just blowing in the wind 14 James Annan says 4 Jan 2013 at 5 48 AM Since the AGU Wiley publishing switchover seems to have anihilated the Hargreaves et al paper hopefully only temporarily here s my own copy of it Response James thanks One of my papers disappeared this way too Mildly annoying I added a link in the post which we ll remove once AGU sorts things out eric 15 Alex Harvey says 4 Jan 2013 at 6 40 AM Thanks for this interesting post 16 Philip Machanick says 4 Jan 2013 at 11 34 AM If sensitivity is the response to a given injection of CO 2 how can we measure this directly when the CO 2 level is constantly increasing Response That isn t the point Sensitivity is a measure of the system and many things are strongly coupled to it including what happens in a transient situation although the relationship is not as strong as one might think The quest for a constraint on sensitivity is not based on the assumption that we will get to 2xCO2 and stay there forever but really just as a shorthand to characterise the system Thus for many questions such as the climate in 2050 the uncertainties in the ECS are secondary gavin 17 Hank Roberts says 4 Jan 2013 at 12 05 PM Palaeosens 2012 the reference in footnote 1 is http www nature com nature journal v491 n7426 abs nature11574 html Making sense of palaeoclimate sensitivity PALAEOSENS Project Members Paywalled but the Supplementary Information 4 8M PDF is available 18 Ric Merritt says 4 Jan 2013 at 1 14 PM Geoff Beacon 13 You may indeed be able to cite cases where models are lagging behind the real world Arctic sea ice measurements below a past prediction do constitute such a case But comparing different future predictions of an Arctic free of summer sea ice cannot logically be cited today as a discrepancy between a past prediction and the real world as measured Please don t confuse these 2 situations which are quite different If you want to bet on an ice free Arctic by some appropriate definition by some date in a couple years you can probably find a place to do it but that s a different thing from pointing out how a past prediction missed something in the real world 19 Geoff Beacon says 4 Jan 2013 at 4 02 PM Ric Merritt 18 I actually did make money betting on the Arctic sea ice this year but I would like to point out the bets were motivated more by anger than avarice Just look at the plots taken from CMIP4 and CMIP5 models when they are compared with measured extents from NSIDC data then tell us where you would place your bet for a summer free of sea ice I d expect to see the Arctic essentially free of ice during September within three years What s your bet Neven s Sea Ice Blog has some pieces that will help The real AR5 bombshell Models are improving but can they catch up 20 Hank Roberts says 4 Jan 2013 at 5 03 PM Ideally one would want to do a study across all these constraints with models that were capable of running all the important experiments the LGM historical period 1 increasing CO2 to get the TCR and 2xCO2 for the model ECS and build a multiply constrained estimate taking into account internal variability forcing uncertainties and model scope This will be possible with data from CMIP5 How soon Is there any coordination among those doing this before papers get to publication so you know what s being done by which group and all the scientists are aware of each other s work so they taken as a group can nail down as many loose ends as possible 21 Jim Larsen says 4 Jan 2013 at 5 10 PM Volume has a more immediate signal than extent In other words measuring extent masks the problem Since we now can talk with either term it is a disservice for the IPCC to speak extent I suggest the whole sea ice section be re written with a volume centric view I m betting all those models more or less worked for extent up to 2011 would turn into models were way off on volume through 2012 22 Hank Roberts says 4 Jan 2013 at 5 11 PM Oops I see that s been answered http www metoffice gov uk research news cmip5 CMIP5 is an internationally coordinated activity to perform climate model simulations for a common set of experiments across all the world s major climate modelling centres and deliver the results to a publicly available database The CMIP5 modelling exercise involved many more experiments and many more model years of simulation than previous CMIP projects and has been referred to as the moon shot of climate modelling by Gerry Meehl a senior member of the international steering committee WGCM 23 Lennart van der Linde says 4 Jan 2013 at 5 16 PM How does this submitted paper by Hansen et al fit in http arxiv org ftp arxiv papers 1211 1211 4846 pdf Do I understand correctly that this paper suggests a current CS of about 4 degrees C and earth system sensitivity of about 5 degrees and seems to rule out CS values lower than 3 degrees They also speak about sea level sensitivity as being higher than current ice sheet models show It seems about 500 ppm CO2 could eventually mean an ice free planet much lower than the circa 1000 ppm that ice sheet models seem to estimate Any thoughts on this approach and these conclusions 24 Hank Roberts says 4 Jan 2013 at 7 53 PM Splendid word I d guess a typo in the Hansen conclusion 16 CO2 is conceivable but of course governments would not be so foolhearty 25 meteor says 5 Jan 2013 at 4 24 AM Gavin This is not the subject but it seems that in AR5 sorry it is the leaked version the mean total aerosol forcing is less 30 than this same forcing in AR4 0 9W m2 against 1 3W m2 On this link http data giss nasa gov modelforce RadF txt NASA GISS provides a total aerosol forcing in 2011 of 1 84W m2 I think that if it is easy to conciliate a 3 C sensitivity with 1 84W m2 it seems impossible with 0 9W m2 the new IPCC mean forcing maybe a 2 C sensitivity works better So is there another aerosol effect different of the adjustment accounted by the models or other things Response That file is the result of an inverse calculation in Hansen et al 2011 You need to read that for the rationale The forcings in our CMIP5 runs are smaller gavin 26 Paul Williams says 5 Jan 2013 at 7 56 AM On the studies of sensitivity based on the last glacial maximum what reduction in solar forcing is used based on the increased Albedo of the ice sheets snow and desert It doesn t appear to be outined in the papers 27 Jack Wolf says 5 Jan 2013 at 9 31 AM This is off topic but I was wondering about the Alaska earthquake this morning and its impact on the methane hydrates along the continental shelf Info on this would be helpful 28 Dan H says 5 Jan 2013 at 12 07 PM Geoff My bet would be the opposite Historically a new low sea ice extent area is set every five years with small recoveries in between My bet would be that 2012 was an overshoot and that the next three years will show higher extents and areas The next lower sea ice will occur sometime thereafter 29 Lennart van der Linde says 5 Jan 2013 at 5 35 PM Looking again at Hansen s submitted paper leaves me guessing his earth system sensitivty in the current state a little more than 5 degrees C more like 6 8 degrees Any other interpretations 30 Jim Larsen says 5 Jan 2013 at 7 06 PM 26 Paul W asked On the studies of sensitivity based on the last glacial maximum what reduction in solar forcing is used based on the increased Albedo of the ice sheets snow and desert It doesn t appear to be outined in the papers Yes the obvious questions that make the most sense are often missing What s the total watts m2 of the initial orbital push from LGM to HCO totally silent on this and what s the total increase in temperature 4 6C Combine the two and you ve got a total system sensitivity for conditions during an ice age I ve heard that sensitivity for current conditions is probably higher but regardless isn t that the first thing one would want answered about climate sensitivity 1 What was the initial push historically 2 What was the final result pre industrial temps 3 What is the current push RC often touches on the last two but the answer to the all important first question is rarely if ever I don t ever remember seeing an answer mentioned even though it seems to be the best way to derive some sort of prediction about the future that doesn t rely on not ready for prime time systems Has anybody ever heard

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  • Tropical Glacier Retreat « RealClimate
    of evidence put forth in support of the precipitation hypothesis is that the retreat of the Kilimanjaro glaciers began in the late 19th century before the beginning of significant anthropogenic warming and coincided with a shift to drier conditions as evidenced by a reduction in the level of Lake Victoria This is indeed a convincing argument in favor of the early phase of the retreat up to around 1900 being precipitation driven It would be a fallacy however to conclude that the late 19th century precipitation drop is the cause of the continued retreat and ultimate demise over the subsequent century or so After all precipitation went down in the late 19th century and Lake Victoria found an equilibrium at a new lower level without drying up and disappearing Why should it be any different for the Kilimanjaro glacier which is also a matter of finding an equilibrium where rate of mass in equals rate of mass out The association of the initial retreat with precipitation changes has no bearing on this question Most of the field studies cited in support of the dominance of precipitation effects for East African glacier retreat only support the role of precipitation in the initial stages of the retreat up to the early 1900 s For example Kruss 1983 has this to say about the Lewis glacier on Mt Kenya A decrease in the annual precipitation on the order of 150mm in the last quarter of the 19th century followed by a secular air temperature rise of a few tenths of a degree centigrade during the first half of the 20th century together with associated albedo and cloudiness variation constitute the most likely cause of the Lewis Glacier wastage during the last 100 years This conclusion is repeated in Hastenrath 1984 Moreover if one only looks at the Lake Victoria level since 1880 one gets the mistaken impression that the high precipitation regime in 1880 was somehow normal and that the subsequent shift to drier conditions puts the glacier in a much drier environment than it had previously encountered The fact is that wet dry shifts of a similar magnitude are common throughout the record It would be more correct to say that 1880 represented the center of a wet spike lasting hardly a decade a very short time in the life of an 11 000 year old glacier and that the subsequent drying represented a return to normal conditions as illustrated in the accompanying long term lake level graph from Nicholson and Yin 2001 In fact a few wet years around 1960 and a moderate shift to wetter conditions in subsequent years restored the Lake Victoria level to within 1 5 meters of its high stand This level is comparable to the level in the decade preceding the 1880 wet spike and considerably greater than the values estimated for the earlier half of the 19th century Even more significantly the Kilimanjaro glacier survived a 300 year African drought which occurred about 4000 years ago as inferred from the ice core record Thompson et al 2002 This drought was so severe that it has even been implicated in the collapse of a number of civilizations that were subjected to it If the Kilimanjaro glacier has survived earlier precipitation fluctuations what is different this time around that is causing its imminent disappearance if not for something associated with anthropogenic climate change Figure 4 Lake Victoria level data after Nicholson and Yin 2001 The lake acts somewhat like a huge rain gauge so that lake level is a proxy for precipitation Data before 1840 is not based on individual year level measurements but historical reports of general trends Kaser et al also argue that surface and mid tropospheric Kilimanjaro height temperature trends have been weak in the tropics in recent decades One of the papers cited in support of this is the analysis of weather balloon data by Gaffen et al 2000 which covers the period 1960 to 1997 It is true that this study shows a weak cooling trend in mid tropospheric temperatures over the short period from 1979 1997 but what is more important is that the study shows a pronounced mid tropospheric warming trend of 2 degrees C per decade over the full 1960 1997 period Moreover few of the sondes are in the inner tropics spatial coverage is spotty and there are questions of instrumental and diurnal sampling errors that may have complicated detection of the trend in the past decade Analysis of satellite data by Fu et al 2004 reveals a tropical mid tropospheric temperature trend that continues into the post 1979 period at a rate of about 16 degrees C per decade When one recalls that tropical temperatures aloft are geographically uniform this data provides powerful support for the notion that East African glaciers in common with others have been subjected to the influences of warming Set against this is the surface temperature record from the East African Highlands reported by Hay et al 2002 This dataset shows little trend in surface temperature over the location covered during the 20th century However surface temperature is more geographically variable than mid tropospheric temperature and is strongly influenced by the diurnal cycle and by soil moisture The large decadal and local variability of surface temperature may have interfered with the detection of an underlying temperature trend more noise less signal It is unclear whether this estimate of temperature trend is more relevant to Kilimanjaro summit conditions than the sonde and satellite estimate Because of the great deal of energy needed to remove mass by sublimation the ablation rate will be very insensitive to changes in conditions whether air temperature or precipitation determined surface reflectivity in circumstances where all ablation is due to sublimation The discussion in Kaser et al is often misread as meaning that the high cold Kilimanjaro glaciers are only influenced by sublimation However there is both theoretical and observational evidence that melting now occurs on the horizontal surfaces of the Kilimanjaro Northern Ice Field and contributes to ablation Moelg and Hardy 2004 Thompson et al 2002 According to Thompson et al 2002 Melt features similar to those in the top meter did not occur elsewhere in the NIF or SIF cores Thus there is evidence that the Kilimanjaro glacier has recently entered a new ablation regime If the melting were solely due to the albedo reduction coming from the 19th century precipitation reduction it should have shown up much earlier Kaser et al also specifically identify melting as the main mechanism for retreat of vertical ice cliffs Once melting comes into the picture ablation rate becomes much more sensitive to air temperature Energy and mass balance studies on Kilimanjaro cover barely two years and define neither trends nor the long term ablation rate Nonetheless the studies can be used to provide some preliminary estimate of how much precipitation or temperature change must be invoked to explain the current net ablation of the glacier According to Moelg and Hardy 2004 if air temperature were 1 degree C colder than at present the potential ablation would be reduced by 14 2 millimeters per month liquid water equivalent This is a far from insignificant change amounting to 32 of the measured net ablation during the short period for which data is available This sensitivity estimate is not the last word on the subject because of uncertainties in the approximate formulae used to compute the terms in the energy balance and neglect of possible effects of water vapor feedback on the surface budget As for precipitation Moelg and Hardy 2004 tentatively conclude that the glacier might be in positive mass balance if snowfall were increased to its 1880 maximum rate even if temperature is held fixed at its present value In this estimate only 4 2mm per month of liquid water equivalent are due to the mass added by enhanced precipitation the vast majority of the effect 72mm per month of decreased ablation is due to the effect of precipitation on reflectivity Concerning this effect one should note that the measured ablation differed by a factor of two between the two years studied even though annual mean snowfall was similar in both years This underscores the fact that ablation via the reflectivity effect depends on the seasonal distribution of snowfall This unpleasant fact undermines efforts to relate glacial history to proxy data like lake level history which are sensitive only to annual means A further point of note is that the calculated sensitivity of ablation to precipitation is as high as it is only because of the occurrence of melting The sensitivity would be reduced if sublimation were really the only ablation mechanism It might well be that the snowfall rate of the 1880 s was so large that if it had persisted it would have allowed the glacier to survive despite whatever warming it suffered in the 20th and 21st centuries But what significance is there in the thought experiment of holding precipitation fixed at its maximum 19th century value given that other parts of that century were evidently no wetter than today To be convincing any model used in precipitation vs temperature attribution studies of Kilimanjaro retreat would have to pass the test of accounting for why previous dry periods in the 11 000 year history of the Kilimanjaro glacier did not cause the glacier to disappear No model has yet been subjected to this test Employing much the same palette of facts and observations as invoked by Kaser et al one could paint this rather different picture of what is going on The Kilimanjaro glacier has waxed and waned since the time of its inception about 11 000 years ago An unusually wet decade around 1880 put the glacier into strongly positive mass balance bulking up its mass Early 20th century explorers found the glacier recovering towards equilibrium from this anomalous state However rather than finding a new equilibrium in the 20th century the glacier has continued to retreat and is now on the brink of disappearing Though air temperature has so far remained below freezing melting has begun to occur and the glacier is suffering net ablation over its entire surface Air temperature increases similar to those observed aloft since 1960 amplified by associated increases in humidity account for a significant portion of the enhanced ablation leading to this strongly negative mass balance but the exact proportion is highly uncertain because of the short span of energy and mass balance observations However changes in the distribution of snowfall through the year conceivably linked to increases in sea surface temperature may have reduced the reflectivity of the glacier and played an even bigger role in forcing the retreat than changes in air temperature alone 4 ENTER THE SKEPTICS When the interesting and thought provoking work of Kaser et al emerged from the machinery of the skeptics disinformation operation it had mutated beyond all recognition The reports put out by the Heartland Institute here and here are typical The first of these which came out under the banner Global Warming Fears Melting is headed by a quote from Patrick Michaels starting Kilimanjaro turns out to be just another snow job and goes downhill from there All subtlety tentativeness context and opposing evidence has been lost The study is presented as a broadside on one of the central tenets of global warming in a fashion echoing skeptics coverage of the hockey stick issue Even when the work is quoted directly it is quoted without the context needed to make sense of the claims Notably the quote Mölg and Hardy 2004 show that mass loss on the summit horizontal glacier surfaces is mainly due to sublimation i e turbulent latent heat flux and is little affected by air temperature through the turbulent sensible heat flux is intended to give the impression that air temperature can make no difference whereas we have seen that the results of Moelg and Hardy 2004 are compatible with several ways in which air temperature can affect ablation The skeptics press especially as echoed in Crichton s State of Fear states that the Kilimanjaro retreat can have nothing to do with anthropogenic global warming because it began in the 1880 s before any appreciable CO 2 response is expected The error in this reasoning was discussed in the previous section This situation here is reminiscent of the ubiquitous Little Ice Age problem It is a fact of life for attribution studies that the climate changes associated with the end of the Little Ice Age overlap with the beginning of the era of industrial warming Thus a graph will always give the superficial impression that the present trends are just a continuation of something that began before human influences were much in the picture leading one into the fallacy that the causes of the beginning of the trend are the same as those responsible for its continuation The Heartland Institute s propagation of the notion that the Kilimanjaro glacier retreat has been proved to be due to deforestation is even more egregious They quote an article published in Nature by Betsy Mason African ice under wraps Nature 24 November 2003 which contains the statement Although it s tempting to blame the ice loss on global warming researchers think that deforestation of the mountain s foothills is the more likely culprit Elsewhere Heartland refers to this as a study The study is in reality no scientific study at all but a news piece devoted almost entirely to Euan Nesbit s proposal to save the Kilimanjaro glacier by wrapping it in a giant tarp The article never says who the experts are nor does it quote any scientific studies supporting the claim The Mason news article is what Crichton quotes as peer reviewed research proving that it is deforestation not global warming which is causing the Kilimanjaro glaciers to retreat George Monbiot s article in The Guardian documents a similar case of systematic misrepresentation of glacier data by skeptics A November 26 2003 New York Times editorial contributed to the spread of the deforestation legend by repeating Mason s statement verbatim and without attribution The Times coverage in Andy Revkin s March 23 2004 article was far more balanced and informative though you d never know it from the quote concocted by Heartland Now the pendulum has swung commented the March 23 New York Times The authors wrote that the dry weather both limited the snows that help sustain tropical glaciers and by reducing cloud cover allowed more solar energy to bathe the glacier In dry cold conditions the ice vaporized without melting first a process called sublimation There was no evidence that rising temperatures had caused the melting The omission of the original article s long passage between the two quotes gives the misleading impression that it is the pendulum of scientific opinion in the community of researchers that has swung In reality what Revkin was saying was that so far as activism goes the pendulum had swung towards the use of Kilimanjaro by global warming skeptics Even the admirable Revkin doesn t get it quite right On horizontal surfaces observations and modeling show a role for melting in both the baseline ablation and the sensitivity of ablation to precipitation and temperature melting is the dominant ablation mechanism on vertical ice cliffs and though Kaser et al find no evidence about rising temperatures it is only because the in situ studies don t cover a long enough period to detect trends Elsewhere where Revkin wrote that most scientists agree that for more than a century its ice has been in a retreat that is almost assuredly unstoppable and was not caused by humans it would have been more accurate to state that the agreement is for the most part only that the beginning phase of the retreat was not caused by humans On the whole though Revkin did a fine job with the essential science A good impression of the main thrust of his article is given by the following intact quote We have a mere 2 5 years of actual field measurements from Kilimanjaro glaciers unlike many other regions so our understanding of their relationship with climate and the volcano is just beginning to develop Dr Douglas R Hardy a geologist at the University of Massachusetts and an author of the paper wrote by e mail Using these preliminary findings to refute or even question global warming borders on the absurd In short Kilimanjaro may be a photogenic spokesmountain no matter what the climatic agenda but it is far from ideal as a laboratory for detecting human driven warming The debate over it obscures the nearly universal agreement among glacier and climate experts that glaciers are retreating all over the world probably as a result of the greenhouse gas buildup These climate skeptics are making generalizations not only to the rest of the tropics but the rest of the world Dr Hardy said And in fact global warming may be part of the whole picture on Kilimanjaro too 5 AIR TEMPERATURE ROLE CLEAR FOR OTHER TROPICAL GLACIERS Generally speaking lower glaciers which extend below the elevation where above freezing air temperatures occur are more sensitive to temperature Kaser and Osmaston 2002 calculate that such tropical glaciers are even more temperature sensitive than midlatitude glaciers A warming of 1 degree C is sufficient to raise the equilibrium line below which net ablation occurs by fully 300 meters As we ve already seen warming is by no means unimportant to the 20th century retreat of the Lewis glacier Mt Kenya in E Africa In other cases the role of warming is yet more clear Data from the tropical and subtropical Andes suggest that changes in precipitation and cloud cover in the latter portion of the 20th century are minor and that changes in these quantities are unlikely candidates for explaining Andes glacier retreat see the discussion in Francou et al 2003 Tropical Andes temperature increased at a rate of at least 1 degrees C per decade since 1939 and the rate has more than tripled over the past 25 years Specific humidity content of the air has increased as expected as part of the conventional water vapor feedback but in fact relative humidity also increased between 1950 and 1990 indicating a stronger water vapor feedback than given by the conventional assumption of fixed relative humidity Detailed studies of the energy balance and ablation of the Zongo and Chacaltaya glaciers support the importance of air temperature increase and identify the increase in downward infrared radiation as the main way that the effect of the warmer air is communicated to the glacier surface Wagnon et al 1999 Francou et al 2003 In the subtropical Himalayas there is evidence from ice core isotopic data and from nearby stations for unusual 20th century warming Thompson et al 2003 These are in the outer Northern Hemisphere subtropics Thus we have evidence for a warming effect on glaciers over a range of tropical latitudes in S America evidence for warming in the Northern subtropics in Asia some evidence for a role of warming at the Lewis glacier in E Africa evidence for general tropical mid tropospheric warming from sondes and satellites and a firm theoretical reason to believe tropical free tropospheric temperature to be geographically uniform It would take a rather perverse though not impossible set of circumstances to leave Kilimanjaro out of the picture 6 CONCLUSIONS AND PERSPECTIVES Kilimanjaro has attracted special attention not because it is an unusually important indicator of tropical climate change but because it is well known through the widely read Hemingway short story If anything it is the widespread retreat of the whole population of tropical glaciers that provides the most telling story Perhaps one can regard the Kilimanjaro glaciers as a kind of poster child standing in for this whole population It is not yet clear whether this photogenic and charismatic poster child is a good choice for the role Certainly if Hemingway had written The Snows of Chacaltaya life would be much simpler Based on what is now known it would be highly premature to conclude that the retreat and imminent disappearance of the Kilimanjaro glaciers has nothing to do with warming of the air and even more premature to conclude that it has nothing to do with indirect effects of human induced tropical climate change On the contrary a study of the glaciers long history argues powerfully that the recent retreat is happening in an environment significantly different from that which the mountain experienced during past equally dry periods To better understand what Kilimanjaro and other tropical glaciers are telling us about climate change one ultimately ought to drive a set of tropical glacier models with GCM simulations conducted with and without anthropogenic forcing greenhouse gases and sulfate aerosol There are substantial challenges to doing so uncertainties in modeling the energy balance terms general difficulties in modeling regional climate change and insufficient resolution of mountains and their mesoscale circulation patterns The time is ripe to make the first attempts at this and hopefully such efforts will bear fruit within the coming decade The attempt to reconcile simulated warming patterns with the tropical glacier record will shed a lot of light on the influence of a range of climate feedback factors including convection clouds and water vapor and the ability of models to faithfully represent them Because of the strong effect of fresh snowfall on the ability of a glacier to absorb sunlight it is likely that changes in precipitation amount or pattern will prove to be part of the story An interesting thing to watch is the effect of precipitation trends over the next decade or two Most GCM s predict that while some parts of the tropics get drier in response to anthropogenic greenhouse gas increases the net tropical precipitation increases Thus some areas of the tropics should experience substantial increases in precipitation which at high elevations will come in the form of snow If tropical glaciers continue to retreat despite an increase in precipitation that will constitute a powerful case for the role of air temperature Interestingly East Africa is one region where IPCC models predict precipitation increases for the coming century It will be the height of irony if it turns out that the IPCC models are right but that Kaser et al are also right that the Kilimanjaro glacier therefore begins to advance again AND that proves to help confirm the validity of the global warming forecasts Keep a close eye on the real time radar satellite monitoring of the level of Lake Victoria here More understanding will result as detailed accurate glacier and regional climate modeling becomes possible This enterprise will not only help in understanding the nature of modern climate change but will permit us to decode the record of past climate changes hidden in tropical glaciers The general understanding of how the climate system responds to natural and anthropogenic forcings will improve as a result Ultimately this is much more interesting and much more important than whether or not Greenpeace chose wisely in picking a place to unfurl their banner Acknowledgements Many thanks are due to Doug Hardy Thomas Moelg and Lonnie Thompson for many patient and illuminating discussions concerning theory and observations of tropical glaciers References For a summary of some of the highlights of the work by Moelg and Hardy and other co workers of the Innsbruck Glacier Group see Moelg s comment 61 to our the RealClimate posting on Worldwide Glacier Retreat Byers AC 2000 Contemporary Landscape Change in the Huascaran National Park and Buffer Zone Cordillera Blanca Peru Mountain Research and Development 20 52 63 Francou B Vuille M Wagnon P Mendoza J and Sicart J E 2003 Tropical climate change recorded by a glacier in the central Andes during the last decades of the twentieth century Chacaltaya Bolivia 16S JOURNAL OF GEOPHYSICAL RESEARCH VOL 108 NO D5 4154 doi 10 1029 2002JD002959 Fu Q Johanson CM Warren SG and Seidel DJ 2004 Contribution of stratospheric cooling to satellite inferred tropospheric temperature trends Nature 429 55 58 Gaffen DJ Santer BD Boyle JS Christy JR Graham NE Ross RJ 2000 Multidecadal changes in the vertical te mperature structure of the tropical troposphere Science 287 1242 1245 Hastenrath S 1984 The Glaciers of Equatorial East Africa Reidel Dordrecht Hay SI Cox J Rogers DJ Randolphs SE Stern DI Shanks GD Myers MF Snow RW 2002 Climate change and the resurgence of malaria in the East African highlands Nature 415 905 909 Kaser G Hardy DR Mölg T Bradley RS and Hyera T 2004 Modern glacier retreat on Kilimanjaro as evidence of climate change Observations and Facts Int J Climatol 24 329 339 Kaser G Osmaston H 2002 Tropical Glaciers Cambridge University Press Cambridge Kruss PD 1983 Climate change in East Africa a numerical simulation from the 100 years of terminus record at Lewis Glacier Mount Kenya Zeitschrift f ur Gletscherkunde und Glazialgeologie 19 43 60 Mölg T Hardy DR 2004 Ablation and associated energy balance of a horizontal glacier surface on Kilimanjaro Journal of Geophysical Research 109 D16104 doi 10 1029 2003JD004338 Nicholson SE and Yin X 2001 RAINFALL CONDITIONS IN EQUATORIAL EAST AFRICA DURING THE NINETEENTH CENTURY AS INFERRED FROM THE RECORD OF LAKE VICTORIA Climatic Change 48 387 398 Pierrehumbert RT 1995 Thermostats Radiator Fins and the Local Runaway Greenhouse J Atmos Sci 52 1784 1806 Porter SC 2001 Snowline depression in the tropics during the Last Glaciation Quat Sci Rev 20 1067 1091 Sobel AH Nilsson J Polvani LM 2001 The weak temperature gradient approximation and balanced tropical moisture waves JOURNAL OF THE ATMOSPHERIC SCIENCES 58 23 3650 3665 Thompson LG Mosley Thompson E Davis M Lin PN Yao T Dyurgerov M and Dai J 1993 Recent warming ice core evidence from tropical ice cores with emphasis on Central Asia Global and Planetary Change 7 145 156 Thompson LG Mosley Thompson E Davis ME Henderson KA Brecher HH Zagorodnov VS Mashiotta TA L in PN Mikhalenko VN Hardy DR Beer J 2002 Kilimanjaro ice core records evidence of Holocene climate change in tropical Africa Science 298 589 593 Thompson LG Mosley Thompson E Davis ME Lin P N Henderson K and Mashiotta TA 2003 TROPICAL GLACIER AND ICE CORE EVIDENCE OF CLIMATE CHANGE ON ANNUAL TO MILLENNIAL TIME SCALES Climatic Change 59 137 155 Wagnon PW Ribstein P Francou B and Pouyaud B 1999 Annual cycle of energy balance of Zongo Glacier Cordillera Real Bolivia Journal of Geophysical Research 104D4 3907 3923 Comments pop up 17 17 Responses to Tropical Glacier Retreat 1 dave says 23 May 2005 at 11 26 PM Reading this I am struck by how such small warming changes in the tropics have set off big changes in low latitude high altitude glaciers just as small changes in the Milankovitch variables create large scale climate changes making the Ice Ages and interglacials over thousands of years In this case however the changes are very rapid these glaciers have been robust over the same time scale many millennia The misleading use of Kilamanjaro deforestation by skeptics is reprehensible given the general meltdown Glad to see Lonnie Thompson s work here on RC The proverbial Canary in the Coal Mine Thanks for the post 2 Ed says 23 May 2005 at 10 56 PM Thank you for the article What impact if any does soot and black carbon from fires have on the glaciers of Kilimanjaro Response I was wondering about soot myself given that the high reflectivity of pristine snow plays such a role in the energy budget of all glaciers On Kilimanjaro the Kibo peak more properly the albedo measurements have only been in for a little while and have not yet been published The modeling in Moelg and Hardy is done using an albedo model for clean snow and ice which yields similar values to those measured in the Antarctic It will be interesting to see if the measured albedo in situ calls for some revision in this It occurs to me that it would be possible to check for dust and snow effects directly by just melting snow ice and filtering but I m not aware that this has been done with an eye to determining soot content Perhaps if one of the glacier observing crowd out there is reading this they can chime in Given the altitude if I had to guess I d guess that soot and dust was not playing a big role at this site rtp 3 Michael Jankowski says 24 May 2005 at 8 51 AM Analysis of satellite data by Fu et al 2004 reveals a tropical mid tropospheric temperature trend that continues into the post 1979 period at a rate of about 16 degrees C per decade Wasn t the referenced Fu et al 2004 the Nature article that John Christy and Roy Spencer claimed was due to improper methodology they had previously throw into the trash Wasn t it the article whose methodology was criticized in another Nature publication later in the year Tett and Thorne particularly when it came to the tropics Didn t Fu susequently change his methodology for a publication later that year in the Journal of Climate Response This comment has largely been addressed by subsequent responses Fu did not change his methodology but rather re computed the results using somewhat different methods as a cross check and indeed found that the results were robust Teasing reliable trends out of satellite data will never be easy and I m not claiming that Fu will necessarily be the last word on this subject Still it s a very defensible methodology What is clear is that Spencer and Christy s analysis was contaminated by stratospheric cooling effects Fu provides one way to compensate and no doubt other ways will emerge in the future If we had a completely reliable instrumental record of tropical mid tropospheric warming we wouldn t be talking so much about using tropical glaciers as indicators of climate change would we What strikes me as strange in the satellite business is that in a subject where everybody agrees that the data analysis is hard and difficult to do Spencer and Christy just accepted their original analysis no matter how inconsistent it appeared with other data and trumpeted it widely One cannot fault them for making mistakes in this area but one can fault them for leaving it to other groups to find and correct their mistakes rtp 4 dave says 24 May 2005 at 11 02 AM Re 3 Here s a good discussion of the dispute about Fu et al 2004 at ClimateArk called The tropospheric data do conform 5 Stephen Berg says 24 May 2005 at 11 05 AM Re 3 The Fu article must have still reached the requirements under the peer review process if it made it into Nature I guess the later criticism even if it were valid did nothing to throw the article s findings into disrepute Maybe the Tett and Thorne criticisms were taken into account and Fu improved on the previous study which would make the J of Climate article s findings even more solid 6 Brian Jackson says 24 May 2005 at 12 05 PM Many thanks for the interesting and detailed article Regarding the satellite data there is a detailed 4 Mb pdf article by Scott Church which I found informative page 59 onwards discusses the Spencer and Tett and Thorne criticisms Along the same lines have you considered a RealClimate article on the satellite record Even though the exact warming trend seems to be hotly contested and not clear it would at least be a useful counter to those claims still repeated that it doesn t show warming or falsifies the surface record as well as being interesting in its own right Response It would be an excellent idea to have a RealClimate piece on the satellite record I volunteer to do that in the Fall after Fu s new article comes out provided somebody reminds me If there are any takers who want to do it sooner please be my guest rtp 7 Michael Jankowski says 24 May 2005 at 2 09 PM Re 4 I ve seen conflicting reports of what the Dec 2004 Journal of Climate trend was reported to be Spencer says it s as low as 0 09 deg C decade for the whole troposphere which is much closer to what Christy and Spencer report for the lower troposphere But I ve seen press releases claim Fu shows a full 0 2 deg C decade which is what the Nature article had claimed Maybe those are just the high and low end estimates based on error The Tett and Thorne criticisms were published at basically the same time as Fu s JofC article so I m not sure they were incorporated Christy and Spencer still see methodological flaws they feel introduce errors Re 5 One of Spencer and Christy s complaints was that they didn t get an opportunity to review and comment on Fu s article despite being arguably the top experts in the area and despite usually getting to review submissions on the topic They found some of the errors embarassing and unacceptable for publication Other people see otherwise but it still seems peculiar they wouldn t have been asked to review Re 6 That s a lot to digest I did see a few things upon cursory review of the section on Fu that I have issues about I ll have to revisit it when I have a lot of free time 8 Joseph O Sullivan says 24 May 2005 at 6 15 PM This is a great post It took a long time to read it all but it is very informative Many thanks to Raymond Pierrehumbert and to Thomas Moleg for the comment on the previous post I like to think that I have learned a good amount of the basics of climate change science from reading Realclimate I am going to but some of my new found knowledge to the test re 1 my educated guess about the effects of soot on glaciers would be if the soot were to settle on the glaciers it would have the same effect of natural soil and rock Snow reflects most of sunlight but soot like soil and rock has a lower albedo am I using the term correctly and instead of reflecting sunlight absorbs it When the soot absorbs the sunlight it warms and could increase the melting of the glacier On the other hand this is a big maybe soot and other pollution when it is in the air I am guessing could reduce the strength of sunlight that reaches the glacier and this possibly could reduce the melting If I don t know what the heck I m talking about please feel free to tell me Response You are mainly correct Soot levels in alpine glaciers for instance are much larger than in Greenland because of the proximity to the sources and the same is likely to be true for tropical glaciers near areas of biomass burning However although this can have an effect on the albedo as can dust from the Sahara most mountain glaciers are extremely dirty already and are only really bright when there is fresh snow fall Maybe someone knows a study that has specifically addressed that for tropical glaciers gavin Response The ablating tongue regions of midlatitude Alpine glaciers are very dirty Oerlemann s albedo parameterization gives albedos as low as around 3 for ablating ice which looks a lot like pure dirt In their Kilimanjaro modelling Moelg and Hardy adjusted the albedo model to give values more like those of clean Antarctic ice and get reasonable looking ablation with these values That suggests that the high Tropical glaciers are

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    AM Great post thanks One thing you could add to it and maintain over time would be a list of climate focused blogs Many of us maintain links to other blogs with a climate change focus and this helps create community and spread awareness Since you ve got a good following and are well respected maintaining a clearing house list of such blogs in this this post would be a great community service Here s a list of those I m currently following via RSS Many of these I list in my blog s blogroll and some of them I am cross linked with and would be pleased to be cross linked with all of them http climatedenial org http climateprogress org http www climatesciencewatch org http jameshowardkunstler typepad com http deconsumption typepad com http www globalissues org http globalisation and the environment blogspot com http fergusbrown wordpress com http initforthegold blogspot com http www realclimate org http reasic com Not all of these are single issue blogs but climate issues form a significant part of all of them Best wishes Dennis samadhisoft com 26 Mike Donald says 23 May 2007 at 7 25 AM I find sourcewatch a goodun for finding out the background of sceptics http www sourcewatch org index php title SourceWatch 27 Andrew says 23 May 2007 at 7 28 AM This is one of those pages that will be useful for years to come You guys to great work on the site thanks 28 Ray Ladbury says 23 May 2007 at 7 57 AM Rod B what would you suggest to make the suggestions fair and balanced I personally don t know of any skeptical websites that deal in actual science I mean would you suggest that a biology department offer a course on creationism just to be fair and balanced I m reminded of a scene from the play Greater Tuna a very funny play that revolves around the only radio station in the town of Tuna Texas In one scene the Station Manager is interviewing a concerned citizen who is advocating the removal of several books from the Library One book that is subject to his wrath is Uncle Tom s Cabin When asked why he replies incredulously Why it only presents one side of the slavery issue There are some issues that only have one side and the science of climate change is such an issue There is still room for legitimate debate about how bad things are going to get although I think the IPCC has mostly been quite conservative in their analysis There s lots of room for debate about how we handle the issue I have yet to hear anyone present a coherent case for the so called skeptic s point of view on the science Have you 29 Craig Allen says 23 May 2007 at 8 18 AM Re 20 Sliver cells solar panels Lawrence that is bloody amazing I found a good blurb on it here 5 to 7 years to recoup the cost of your solar panel instead of 20 as is the case with current solar voltaic products on offer And they ll be mass produced and flooding the market within a couple years That makes at least five new Australian kick ass zero CO2 energy technologies that I know of that are all on the cusp of blitzing the energy market Go Aussie It would be good to have section in the new resources page that is devoted to solutions Well done again RealClimate 30 FurryCatHerder says 23 May 2007 at 8 20 AM Re 20 Very unlikely I recently priced 175 watt Solarworld panels that have a module efficiency of 24 Being 15 times more efficient is just impossible One thing I d like to see for the Okay so maybe you are right but we ll die without our fossil fuels crowd is links to alternate energy and energy savings I know I ve got to be the official alternate energy poster child these days but there are people who might do something if they thought they could have their cake and eat it too 31 LochDhu says 23 May 2007 at 8 24 AM A beginner s page shouldn t use anacronyms like IPCC AR4 and TAR without saying what they mean like International Panel on Climate Change IPCC 32 Anil Baysan says 23 May 2007 at 8 38 AM If you wanna see the latest MELTDOWN live via SATELLITE CAMERA on NORTH POLE visit http www globalwarmingcam com and connect to SatCam weather satellite You will not believe your eyes 33 Liz Kalaugher says 23 May 2007 at 9 51 AM Great list of resources thanks Here s another one which I guess could go under Informed but in need of more detail here at http environmentalresearchweb org we re providing free updates on the latest research in climate change and other environmental change topics as well as on potential solutions such as renewable energy 34 Chris Squire says 23 May 2007 at 10 15 AM The Royal Society UK has Climate change controversies a simple guide at http www royalsoc ac uk page asp id 6229 New Scientist magazine has Climate change A guide for the perplexed at http environment newscientist com channel earth climate change dn11462 Grist has How to Talk to a Climate Skeptic at http gristmill grist org skeptics I particulalry like dthe entry explaining about the Vinland grapes It is anecdotes like this which impress the non scientists and make them think that perhaps the sceptics are on to something after all 35 NU says 23 May 2007 at 10 45 AM Someone mentioned the EdGCM model you can download and run Perhaps better for beginners is Ben Matthews Java climate module which is interactive and lets you play around with various parameters in realtime Also mentioned previously on this site is Kerry Emanuel s Phaeton s Reins which is one of the best introductory

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