archive-org.com » ORG » R » REALCLIMATE.ORG

Total: 1481

Choose link from "Titles, links and description words view":

Or switch to "Titles and links view".
  • A barrier to understanding? « RealClimate
    Academy of Sciences is equally embarassed by this given that their official stated position on climate change stands in stark contrast to the views expressed in this piece mike 107 P Lewis says 3 Jan 2008 at 2 43 PM Re 105 Rod B But no Rod B There is very good phenological evidence for early springs early flowering etc and later autumns delayed senescence that is approaches the scale over which climatology data are assessed statistically Stick to weather fine But don t Enough of weather 108 Paul Middents says 3 Jan 2008 at 3 22 PM Rod B Here are some studies citing long term trends in things like the cherry blossoms are blooming that seem to be pretty well researched and supported Phenological changes reflect climate change in Wisconsin Proc Natl Acad Sci U S A 1999 August 17 96 17 9701 9704 Nina L Bradley et al http www pubmedcentral nih gov articlerender fcgi artid 22273 Freeze and breakup dates of ice on lakes and rivers provide consistent evidence of later freezing and earlier breakup around the Northern Hemisphere from 1846 to 1995 Historical Trends in Lake and River Ice Cover in the Northern Hemisphere Magnuson et al Science 8 September 2000 1743 http www sciencemag org cgi content full 289 5485 1743 These and other studies are summarized in this rather attractive little publication from the University of Wisconsin http www botany wisc edu zedler images Leaflet 13 pdf 109 Marcus says 3 Jan 2008 at 4 03 PM Re 97 Greg on 6 2 1 in the TAR Here is the quote from 6 2 1 In the on dimensional radiative convective models wherein the concept was first initiated lambda is a nearly invariant parameter typically about 0 5 K Wm2 Ramanathan et al 1985 I think it is pretty clear that this number is not the best estimate from the TAR For that you would look at F 3 in the Technical Summary where it notes that climate sensitivity is likely to be between 1 5 to 4 5 degrees C which would be equivalent to about 0 4 to 1 1 K Wm2 Note that 0 75 is smack dab in the middle of the range I think the AR4 updates this by actually giving a probability distribution rather than a range and maybe by shaving off the bottom end of the range Going back to 94 You might consider the following back of the envelope calculation According to the Water Vapor Feedback or Forcing post somewhere between 15 and 34 of the total forcing is attributable to GHGs other than water vapor and clouds If we assume that water vapor and clouds are feedbacks then the 33K of warming we see could possibly be attributed to between 0 15 150 and 0 34 150 W m2 primary forcings This would give you a sensitivity of between 1 5 and 0 65 K Wm2 which is actually higher than the IPCC best estimates Of course this back of the envelope calculation is also rather crude one expects that the water vapor cloud response to be non linear and of course this doesn t include any albedo change feedbacks positive less snow glacier arctic ice retreat etc or negative increased desertification etc 110 pat neuman says 3 Jan 2008 at 5 21 PM Statements 93 made earlier by VirgilM s on Devils Lake need to be corrected Devils Lake was in a state of fluctuation from January 1 of 2000 to January 1 of 2006 However reading on January 1 of 2006 2007 and 2008 below show that the elevation of Devils Lake in ft above mean sea level has been in a state of recession In 2008 Devils Lake will have a short term rise approximate 1 0 ft or less in the elevation of Devils but the lake elevation on January 1 of 2009 will be lowered than the lake elevation was on January 1 2008 I m willing to accept bets on this if there are any takers Observations Jan 1 2006 was 1447 89 ft abv mean sea level Jan 1 2007 was 1446 96 ft abv mean sea level Jan 1 2008 was 1446 79 ft abv mean sea level http waterdata usgs gov nd nwis dv referred module sw format rdb period 730 site no 05056500 Forecast by Pat Neuman Jan 1 2009 less than 1446 79 ft abv mean sea level http nwis waterdata usgs gov nd nwis dv cb 00065 on cb 00065 on format html begin date 2000 01 01 end date 2008 01 02 site no 05056500 referred module sw 111 Marcus says 3 Jan 2008 at 7 08 PM Re 110 Pat Neuman I have to say having looked at the data myself Virgil s arguments are fairly convincing Personally I think arguing about one lake or even one hydrological region doesn t make much sense when looking at climate but it seemed like the two of you were having an argument that would be easy to resolve If I go to the USGS website http waterdata usgs gov nd nwis uv site no 05056500 to get data the first thing I note is that in 2005 they shifted their monitoring station because of excessively high lake levels If I actually then get the data which goes back to 1979 though it is spotty for the first decade it is clear that current lake levels are at historic highs 1995 is the first year it exceeds 1430 feet 1998 the first year it exceeds 1440 feet and only in 2000 did it break 1446 feet the level you list for your January low prediction So I don t understand why you are trying to defend a prediction that the level of Devils Lake is dropping when it is at a level higher than any recorded from 1980 to 2000 112 Bob Tisdale says 3 Jan 2008 at 8 46 PM No 68 Barton Paul Levenson Check the data on your post Go to http lwf ncdc noaa gov oa climate research cag3 na html Scroll down and try inputting Data Type Mean Temperature Period Annual First Year To Display 1998 Last Year To Display 2006 Base period begin year 1998 Base period end year 2006 Output Type Line or Bar Chart Your Choice but select Plot Trend Line Sort By Year Press Submit ANNUAL 1998 TO 2006 TREND 0 35 DEG F DECADE Regards Response Calculate the error bars on the trend 2 sigma is 1 48 deg F dec making this completely insignificant This isn t difficult to check gavin 113 Mike says 3 Jan 2008 at 9 52 PM Sorry I just couldn t resist my cold weather comment I just get tired of hearing the news media blabbing day in and day out about extreme heat waves and blaming it on global warming 114 P Lewis says 4 Jan 2008 at 4 26 AM And just to add to Gavin s comment to Bob Tisdale s 112 Tamino has an excellent analysis of this very topic at Garbage is Forever and at Wiggles 115 Barton Paul Levenson says 4 Jan 2008 at 8 26 AM Bob Tisdale posts ANNUAL 1998 TO 2006 TREND 0 35 DEG F DECADE Those are temperatures for the UNITED STATES I was using temperatures for the WORLD For which the 1998 2006 trend is UP Look again http members aol com bpl1960 Ball html 116 Ray Ladbury says 4 Jan 2008 at 8 53 AM Mike 113 I hope you will forgive our lack of enthusiasm for your rediscovery of Winter 117 pat neuman says 4 Jan 2008 at 1 12 PM It s true that the lake tendency in the 1980s and 1990s was upward However that s history Climate change has now swung the other way toward downward lake levels Devils Lake observations show that the level of Devils Lake has been on a falling trend averages for last three years falling also see comment 110 The dropping levels are now being driven by longer ice free winter periods longer growing seasons warmer temperatures and higher evaporation rates Longer growing seasons in the basin means increasing amounts of water loss from land areas due to higher rates of transpiration and evaporation anuual inflows since 2006 have decreased Water temperatures have been warming more rapidly than average annual air temperatures Lake Superior Annual lake water evaporation from the Great Lakes is greatest in fall when the water temperatures are warmer than air temperatures and due to lake effect snowfall Devils Lake hydrology has also been complicated by human influence for many years including Channel A cut in 1979 overflows to Stump Lake since 2000 and many other channel modifications within the basin None the less the current tendency in Devils Lake water level is recession There is no need to create a diversion from Devils Lake to the Sheyenne River and Red River which has been pushed by those with little or no hydrologic knowledge of the basin On the Great Lakes warmer water temperatures in fall and early winter have resulted in higher losses from lake evaporation 118 VirgilM says 4 Jan 2008 at 6 54 PM Pat Neuman I think my point stands Devils Lake in North Dakota hit a record high in May of 2005 which caused significant problems around the area Your proposed statement in 2000 made no mention of record lake levels that was broken a few times from 2001 to 2005 Your statement said that lake levels would fall becasue of human induced climate change I suspect that your prediction is a personal opinion that you tried to get into a NWS product If it is not then reference me a peer reviewed journal article that modeled the future climate in Eastern North Dakota and specifically said that lake levels will drop for Devil s Lake North Dakota has moved into a drought that last two years That has happened many times in the last 1000 years When that happens lake levels drop because precipitation is a big part of the equation A very small drop in lake levels in the last two years only proves that drought as moved into the area Connecting it with human climate change takes much more work because correlation does not mean causation Where is that work in the journals 119 pat neuman says 4 Jan 2008 at 8 17 PM My experience includes hydrologic model development model calibration and accurate annual operational forecasting the elevation of Devils Lake 30 years gained from first hand experience at the NOAA NWS Kansas City River Forecast Center from 1976 to 1979 and at the NOAA NWS North Central River Forecast in Center im Minnesota officially awarded retirement for 30 years of Loyal Service rendered to the government of the United States by the NWS Central Region director Feb of 2006 120 pat n says 5 Jan 2008 at 3 36 PM VirgilM asked Where is that work in the journals Answer NOAA NWS was a road block for publishing material related to climate and hydrologic change in jounals for many years While at NWS I was told to remove reference to myself as a NWS employee on the paper below even though I had been allowed to do some of the research on the timing of snowmelt runoff shown in the paper on government time http www mnforsustain org climate snowmelt dewpoints minnesota neuman htm 121 Carrick says 17 Jan 2008 at 10 20 AM Gavin Long term trends from the forcing are expected to be around 0 2 0 3 deg decade Therefore you need to be able to get uncertainties down to well below those values in order to find a clear discrepancy Judging from the last thirty years that period is around a decade Seems to me it s more complicated than this If you look at the historic forcings before roughly 1975 if climate models are to be believed there was a rough balance between the positive forcings from CO2 and the net negative forcings associated with aerosol particles I use this figure from the WIki article to illustrate the balancing of these two anthropogenic forcing terms It should be noted that industrialized nations have been reducing their CO2 intensity ratio of CO2 production to GDP e g see this As an aside the total US CO2 production US CO2 production dropped by 2 in 2006 I ve read a press account but don t have a more trustworthy link that ironically Europe s CO2 production increased by 0 4 over the same period Put another way the CO2 contributions from developed nations are decreasing as a percentage of the global anthropogenic CO2 budget It should also be noted that developing nations like China are adding coal burning electric plants at a prodigious rate I heard as high as 1 per day Because these facilities produce copious quantities of aerosols one might expect the relative balance of CO2 forcing to aerosol forcing to shifting back towards a balancing of the two contributions I don t have ready access to global aerosol production so please accept this as just a plausible scenario meant to illustrate a point It may very well be the case in the near future that we reach another period in which global mean temperature either slows or reaches a plateau I would emphasize that this would occur in a manner completely consistent with the climate models and our understanding of anthropogenic climate change Under such a scenario would expect as the developing countries were to continue to industrialize that like us as their industry addresses pollution issues their aerosol production would diminish while their CO2 production would continue to increase tipping us back into an upwards trend in global mean temperature We d end up with a step in the warming trend like seen between roughly 1945 1975 Obviously without the aerosol data this is pure speculation but I m just suggesting that it s important to not take trends like 0 2 C per decade as gospel People who are demanding a definite answer on this on both sides may simply be underestimating the complexity of the anthropogenic forcings terms Response It s a reasonable idea but you forget one crucial fact CO2 accumulates and aerosols don t That means you have a competition between a forcing which is proportional to the total emissions compared to one that is proportional to current emissions At the beginning you can balance them out but in the long term the accumulator is always going to dominate Thus for this to work out you have to start making emissions dirtier and dirtier from here on in That faustian bargain is just not sustainable not least for human health issues Total aerosol in recent decades seems to be going down slightly a big decrease in the US Europe FSR balanced by increases in India and China and so is either near neutral at the moment or slightly positive it depends on the make up of the aerosols ratios of reflective vs absorbing from the different sources The aerosol issue isn t going to go away as an uncertainty but I don t think anyone expects it to be able to cancel the growth of forcings associated with CO2 at present or the near future gavin 122 Carrick says 17 Jan 2008 at 3 36 PM Gavin It s a reasonable idea but you forget one crucial fact CO2 accumulates and aerosols don t That means you have a competition between a forcing which is proportional to the total emissions compared to one that is proportional to current emissions I m really not trying to be argumentative but I understand the relationship between the amount of CO2 emitted by anthropogenic processes and the change in CO2 concentration to be more complex than that For example there are carbon sinks that are affected by the availability of CO2 in the boundary layer It s a nonlinear system and it has memory I m thinking of Inez Fung s work on this You could have e g a step function change in the rate of CO2 emissions and end up with nearly the same total concentration levels due to the response of the other carbon sinks to the increased availability of CO2 in the boundary layer depending on the magnitude of the step function that is To make it clear I wasn t proposing that a long term stable situation could be set up e g increasing our aerosol production to balance the increased CO2 concentrations Rather I was suggesting these changing demographic patterns represents a potentially confounding effect over some short term interval 20 30 years that could mask a very real long term trend in global warming How probably this confounding effect is to be seen obviously you re the expert on this not me My only real point is that because of changing demographics we might expect the net forcings from CO2 and aerosols to change over time and potentially we could be going into a short term lull on climate scales e g 20 years in global warming That is it hasn t stopped just slowed by poor industrial practices in third world nations However this wouldn t signify either a problem with climate models or signify a long term end of the warming period I absolutely agree with your other comments I hope you weren t trying to take my question as a well it s going to flatten out indefinitely so there s no worry Clearly I agree on the need to moderate both CO2 emissions and aerosol production Faustian is a great choice of words by the way for the other scenario whereby global warming is stopped long term because we produce enough pollutants to balance the increased CO2 emissions I wasn t proposing this idea

    Original URL path: http://www.realclimate.org/index.php/archives/2007/12/a-barrier-to-understanding/comment-page-3/ (2016-02-13)
    Open archived version from archive


  • A barrier to understanding? « RealClimate
    may be eaten but it is too late by that time Yes Collapse has its gory points 12 henning says 28 Dec 2007 at 5 09 AM Thanks a lot for that one Gavin Understanding what can be linked directly to AGW and what can t is very important in the political debate Blaming AGW for everything and seeing evidence everywhere would not lead to more public awareness in the long run it would be rather the opposite Personally I would have liked to see somewhat more of this in the Gore thread but never mind 13 A Simmons says 28 Dec 2007 at 7 17 AM I m surprised the article made no mention of the UK government s recently retired Chief Scientific Officer Sir David King who has frequently used Thames Barrier statistics as an example of real world evidence for AGW See for instance this 2004 address to the AAAS and Google has many more examples 14 Akseli says 28 Dec 2007 at 7 27 AM Scotland Norway Sweden Finland and many other places are rising and pushing away water from their coasts Where is all that water going 15 rick says 28 Dec 2007 at 8 20 AM 5 Very interesting info I ve had my own doubts about my local NWS in New York They always seem to be understating the actual temperatures we experience here especially during the Winter 16 Ricks says 28 Dec 2007 at 10 03 AM Mount Kilimanjaro seems a poor example Kilimanjaro s ice has been melting away for more than a century and most of that melt occurred before 1953 prior to the period where science begins to be conclusive about atmospheric warming in that region according to Philip Mote of the University of Washington and Georg Kaser of the University of Innsbruck in Austria Response This is precisely what my bigger point was Kilimanjaro like almost all other tropical glaciers is receding fast These glaciers have existed continuously for 1000 s of years and now the one on Kilimanjaro is disappearing and it really is The important point is that tropical glaciers are receding everywhere see our previous post and that is much more easily attributable to global climate change than any one glacier However Kilimanjaro is a great example of tropical glacier retreat even if on it s own it is not proof of the attribution What gets lost in these discussions is the whole balance of evidence from other sources gavin 17 Don says 28 Dec 2007 at 10 07 AM response to Bird Thompson Actually population growth is trending the right way http www worldbank org depweb english modules social pgr Global rates of growth though still positive are falling Averaged over all of humanity fertility rates were about 6 children per woman 35 years ago now the number is less than 3 We have a huge task ahead of us in feeding 6 billion people now and probably about 9 billion before the total number starts to fall Certainly GW will make feeding the world much more difficult and the knock on effects of secondary pollution will aggravate environmental damage Most overall growth is now in the age structure rather in the number of children per woman The contribution to greenhouse gases is small among peoples with the highest growth rates Burning the coal for air conditioning in the southeastern US probably contributes more CO2 to the atmosphere than does Africa and the parts of Asia and the Middle East where poverty and high birth rates are found GW will harm these impoverished people much more than they will contribute to global warming 18 Barton Paul Levenson says 28 Dec 2007 at 10 25 AM Edward Greisch posts Another thing you have going against you is religion In Collapse How Societies Choose to Fail or Succeed Jared Diamond discusses how religion has played a role in the collapse of some civilizations Christianity contributed to the collapse of the Greenland Viking civilization Religionists will of course resist any change in values regardless of the fact that a change in values is necessary for survival This is an issue of the preachers income In the end the preachers may be eaten but it is too late by that time Yes Collapse has its gory points And yet the Pope has said that global warming is a serious problem and 83 leading evangelicals have signed a statement saying Christians need to act to prevent global warming How about that Response No more discussion of religious issues please gavin 19 pete best says 28 Dec 2007 at 11 32 AM Re 18 what would the pope know on this issue really Although AGW is a serious problem I doubt that it is the main threat in the near term for the first world is some decades off No that accolade goes to peak oil the cost of oil and its global availability Come 2020 we are really going to be struggling with adequate supply All IPCC climate models vastly overestimate global fossil fuels reserves and hence peak fossil fuels will come first with oil happening first of all Maybe we can delay the onset of peak oil by a decade by mining increasingly energy poor oil reserves but the writing is on the wall Once oil peaks extracting coal and gas becomes very difficult so its doubtful they will scale 21st century issues eh 20 henning says 28 Dec 2007 at 11 33 AM I don t understand how even all glaciers put together or all tide barriers or whatever could possibly provide proof for global warming We measure temperatures using termometers we measure percipitation using a bucket on a stick and we measure gas concentrations and radiation using sophisticated sensoring Obviously filming a termometer slowly rising by 2C per decade for 90 minutes won t win you an oscar but when you want to find out how the temperature behaved during the last couple of decades you fire up GISTEMP you certainly don t hike up the Kilimajaro with a yardstick or penetrate your garden with a core driller right 21 Martin says 28 Dec 2007 at 11 40 AM Just a point of detail The floods in 1953 referred to in the article did not actually reach the City of London only going as far as dockland and the east end The 307 deaths were all along the east coast of England from Northumberland to Essex Central London is about 25 miles in land This is something of a technical point because it is certainly true that the people of London were very worried by the 1953 floods and that the case for a Thames Barrier was made but as far as I can tell there were few if any casualties in 1953 up river of the site of barrier 22 Martin Vermeer says 28 Dec 2007 at 11 46 AM Aleksi 14 kirjoitti Scotland Norway Sweden Finland and many other places are rising and pushing away water from their coasts Where is all that water going Well to London for instance Seriously for every post glacial uplift area there is a remote zone that s downlifting very slowly For Fennoscandia it includes Central Europe BTW Gavin the Eastern Schelde Barrier in the Netherlands may be interesting to look at as it is a cleaner example and a longer time base 23 Ray Ladbury says 28 Dec 2007 at 12 00 PM Henning Actually Gavin s point is very important The balance of evidence or the aggregate of the evidence is crucial Drawing conclusions based on data from multiple independent lines of evidence and reasoning makes it much less likely you ll draw erroneous conclusions So it is not the thermometers or the yard sticks or the laser altimetry by themselves that make us so confident about our conclusions but rather all of them together Likewise in evolution it is not any particular fossil that establishes evolution but the aggregate of the entire fossil record 24 P Lewis says 28 Dec 2007 at 12 04 PM Sorry that should have read Full ish details on the UK 1953 floods can be found at the Met Office 25 Ray Ladbury says 28 Dec 2007 at 12 06 PM Pete Best Oh I suspect we will find a way to use the coal plenty of that for decades to come Then there are the clathrate deposits at the bottoms of the oceans already looking into how to use that Humans have plenty of ingenuity to release all the carbon we need to cook our own goose The question is whether we will have the wisdom to apply our ingenuity to making the situation better rather than worse 26 James says 28 Dec 2007 at 12 12 PM Re 20 I don t understand how even all glaciers put together or all tide barriers or whatever could possibly provide proof for global warming It s a cold morning your outside thermometer says 20F You want to know if it gets above freezing while you re away at work and you have a bunch of skeptics claiming your thermometer is out of whack so what do you do Simple put an ice cube outside Go to work If the ice cube s melted when you get home it s a pretty good indication that the temperature got above freezing isn t it If you want to get a bit fancier you could measure how much of the ice had melted do a little math and come up with a figure for degree hours So that s glaciers handy natural sensing devices that integrate temperature and precipitation for you 27 Martin Vermeer says 28 Dec 2007 at 12 48 PM Likewise in evolution it is not any particular fossil that establishes evolution but the aggregate of the entire fossil record Stronger still the fossil record and Linnaeus s family tree and molecular genetics several methodologically different lines of evidence all telling essentially the same story 28 pete best says 28 Dec 2007 at 12 59 PM Re 25 that just not reality if you study the subject Ray There are many interpretations but the IPCC projections for fossil fuel energy reserves are extreme best case scrnarios worse case really and not reality well in many peoples eyes anyway You see OPEC all bumped up their quotas in the 1980 s in order to be able to pump more oil Those rises were not real they were economic and since then many billions of barrels have been used by their proven reserves remain the same However the IPCC took data from these reserves and more besides in the ultimately recoverable reserves range No peak oil or economically more expensive oil is going to be a major destabaliser and if we somehow do find enough oil then climate change will be worse than I expect 29 Ray Ladbury says 28 Dec 2007 at 1 02 PM Re 27 Exactly A single fossil or measurement can mislead A single trend can be misinterpreted However when all the data are telling you anthropogenic CO2 is behind the warming it s bloody unlikely that all the people analyzing all these data are making mistakes in the same direction That seems to be what denialists of anthropogenic climate change or of evolution seem to miss 30 VirgilM says 28 Dec 2007 at 1 36 PM Pat Neuman Re 5 A particular climatic event like the 1993 Midwest Flood in itself isn t proof of anything There has been paleoclimatic research published on such events Midwest River Floods and many such events have occurred in the last 1000 years before significant human arthoprogenic climate forcing Some of those events were much more severe than what was experienced in 1993 So how can you be so sure that the 1993 Midwest Floods was not a natural event Yesterday I read a paper in the journal Earth Science Reviews Cook et al 2007 North American drought Reconstructions causes and consequences In the abstract this paper notes Of central importance to drought formation is the development of cool La Nina like SSTs in the eastern tropical Pacific region So if persistant La Nina conditions causes drought over significant portions of the United States then could it be that persistant El Nino conditions causes floods over significant portions of the United States Going back to the ENSO record during that time Neutral to Moderate El Nino conditions was present over the equatorial Pacific from 1990 to the onset of the 1993 Midwest floods I wonder if such a connection has already been made in published research The point here is that while the National Weather Service sees it s mission to publicize major climatic events as they happen they don t have the research published in journals available to them that tells them if the climatic event is human caused or natural caused Such research only gets published years after the event Many NWS offices have chosen to take the conservative approach in this area to preserve credibility and trust rather than in enguaging in non peer reviewed speculation on the causes of climatic events 31 henning says 28 Dec 2007 at 1 52 PM However when all the data are telling you anthropogenic CO2 is behind the warming Does it A rise in sea level is just that a rise in sea level It can be measured and it can be broken down to various contributions by further investigation The frequency of the closing of some human controlled barrier surely does not even remotely clarify whether there is a rise in sea level let alone that it s cause lies in the warming of our planet and even less so when it comes to the question of what caused this warming You don t have to be a denialist to see that you can stretch an argument only so far 32 Ray Ladbury says 28 Dec 2007 at 2 21 PM Pete I don t doubt that Peak Oil will be a factor but it will be short term I have greate faith in human ingenuity I ve seen it work time and again mostly digging us deeper and deeper into a hole Peak oil means there s more incentive to find new ways to use other energy resources Now those resources could be renewables or they could be coal and clathrates and nukes etc Indeed there may be only a tiny difference in cost between them But that tiny cost multiplied by billions of consumers will make somebody very very rich Look at India When the wood was gone they went further and go more wood When that was gone they used the stubble from their fields Now they use animal dung There s a whole industry processing animal dung for use in cook stoves Economics doesn t stop when things get expensive or even when things are used up It goes on as long as there are sufficient resources to support life just like bacteria in a bottle 33 Ray Ladbury says 28 Dec 2007 at 2 40 PM Henning Yes a rise in sea level says little in and of itself However if a theory predicts a priori that sea levels will rise the rise is evidence that favors that theory over those that predict no rise or falling sea levels Moreover if the theory predicts the rise quantitatively within errors the support for the theory is stronger Similar arguments apply to melting glaciers and sea ice Likewise if one model predicts that night time temperatures will see greater effects than daytime temperatures that favors said model You cannot look at an isolated result or line of reasoning However if you have lots of favor a particular theory moderately strongly the result is no less convincing and maybe moreso than a single smoking gun 34 John Mashey says 28 Dec 2007 at 2 52 PM re 28 peak Oil 1 I recommend the recent paper by Kharecha Hansen Implications of peak oil for atmospheric CO2 and climate which is submitted so its name may change but rather than talk about that here perhaps RC might start a thread for it 2 As far as I can tell a IF that paper is reasonable b IF The Ayres Warr work is reasonable i e that GDP growth is more dependent on exergy efficiency energy used than any other factor i e the Solow residual isn t jsut technology c THEN the idea held by many economists that one can defer climate change mitigation because people in 2100 2200 will be much richer and they can do it i e sometimes described a positive discount rate is seriously wrong d In particular no matter how cheap an iPod with a Terabyte of memory gets things that actually require energy in the real world won t especially when there s effectively no petroleum left Water Nitrogen based fertilizer natural gas Food The Economist The End of Cheap Food a week or two ago Required transport of food needed materials Concrete steel Building dikes and sea walls earthmoving in general As economists would say iPods are not substitutes for these goods Of course we can get more efficient we can electrify use biofuels for the necessary transport stretch the oil gas longer to avoid coal to liquid and burning a lot more coal and maybe it won t be worldwide depression but it s just hard to see how there is not going to be a negative discount rate during much of the next century Anyway the article mentioned above is very useful 35 John Mashey says 28 Dec 2007 at 3 04 PM Oops sorry the URL for previous post was http pubs giss nasa gov docs notyet submitted Kharecha Hansen pdf 36 Hans Kiesewetter says 28 Dec 2007 at 3 13 PM Re 22 the Eastern Schelde Barrier in the

    Original URL path: http://www.realclimate.org/index.php/archives/2007/12/a-barrier-to-understanding/%5C (2016-02-13)
    Open archived version from archive

  • Incertidumbre, ruido y el arte de comparar datos y modelos « RealClimate
    land In other words is an area average a good way to determine the actual global trend Second have the instruments being used to determine sea surface temperature been satisfactorily validated If I recall correctly there have been some problems correctly interpreting readings from the instruments which were launched several years ago Or is this more related to the difference in methods Gavin mentioned 14 David Lea says 11 Jan 2008 at 11 52 AM Gavin thanks for an informative post Does the 2007 value you plot include December I noticed from GISTEMP that Dec 07 was cooler than other months can this be attributed to the strong ongoing La Nina in the Pacific Thanks David Response Yes it does include Dec 07 And indeed it does seem to be related to the La Nina gavin 15 Roger Pielke Jr says 11 Jan 2008 at 12 08 PM Gavin 7 Thanks a few replies You ask How can you read the post above and claim that we re avoiding forecast verification altogether Well my first clue is when you misrepresented why I did and what John Tierney reported You characterized the effort as attempts to validate or falsify IPCC projections of global temperature change over the period 2000 2007 No such claims were made by me and I don t think by Tierney In my post I was careful to note the following I assume that many climate scientists will say that there is no significance to what has happened since 2000 and perhaps emphasize that predictions of global temperature are more certain in the longer term than shorter term And John Tierney wrote you can t draw any firm conclusions about the IPCC s projections a few years does not a trend make So why misrepresent what we said Models of open systems cannot in principle be validated see Oreskes et al 1994 I simply compared IPCC predictions with observations as an example of how to do a verification which is standard practice in the atmospheric sciences but much less so in the climate modeling community and yes I think this is indeed the case Instead of telling your readers all of the reasons that a verification exercise is misguided you might have instead constructively pointed to the relevant forecasts with proper uncertainty bars please do post up the link or better yet simply shown how an analysis comparing 2000 2007 with relevant predictions would have been done to your satisfaction Given that you point to the IPCC AR4 Figure 1 1 in positive fashion I remain confused about your complaint about what I did I don t recall you complaining about IPCC efforts in verification previously How about this We agree that rigorous forecast verification is important There also does not a clear agreement among researchers as to a what variables are most important to verify b Over what times scales c what actual constitutes the relevant forecasts and d what actually constitutes the relevant observational verification databases Then this is a subject to work through collegially rather than try to discredit dismiss or suppress Thanks PS As I stated on my blg If discussing forecast verification in the context of climate model predictions is to be a sign of skepticism then climate science is in bad shape For the record I accept the consensus of IPCC WG I Response Roger I m flummoxed You keep bringing in things that have not been said and rebuttals to arguments that have not been made All we have done is point out statistical issues in two things you compared Oreskes paper is a case in point I have no desire to argue about the semantics of verification vs evaluation vs validation none of that is relevant to the overriding principle that you have to compare like with like In a collegial spirit I suggest you download the model data directly from PCMDI and really look at what you can learn from it You might get a better appreciation for the problems here Verification is not misguided Your attempt at verification was gavin 16 Hank Roberts says 11 Jan 2008 at 12 16 PM John Lederer http scienceblogs com stoat 2007 05 the significance of 5 year tre php 17 Jon Pemberton says 11 Jan 2008 at 12 21 PM Gavin You stated The red line is the annual global mean GISTEMP temperature record though any other data set would do just as well Can you provide graphs of the other data sets I want to see them do just as well Thanks Jon P 18 Earl Killian says 11 Jan 2008 at 12 29 PM If you replace 8 year trend lines with n year at what value of n do they start to faithfully reflect the underlying trend 19 Steven T Corneliussen says 11 Jan 2008 at 12 30 PM I see now that in reporting in item 3 above on the Boston Globe s Jeff Jacoby s contribution in the category of misconstruing weather as climate I probably should have bee explicit my own opinion for what it s worth is that Jacoby s contribution is preposterous 20 B Buckner says 11 Jan 2008 at 12 30 PM Gavin You indicated that the GISS product extrapolates over the arctic region Extrapolate means to infer or estimate by extending or projecting known information How is this done and can you explain why is it valid Is this simply using widely spaced and limited data from within the arctic itself and extrapolating to cover the entire region or extrapolating somehow from the perimeter of the arctic Response This is explained in the GISTEMP documentation but in areas with no SST information like most of the Arctic the information from met stations is extrapolated over a radius of 1200 km That fills in some of the Arctic A validation for that kind of approach would be a match to the Arctic buoy program but I haven t looked into that specifically gavin 21 Boris says 11 Jan 2008 at 12 40 PM In fact IPCC 1990 dramatically over forecast trends as show by the IPCC figure that you reference and that I provide here Roger Your blog post neglects to even mention the good reasons for forecasts to be off namely the Mt Pinatubo eruption Don t you think you owe it to those who read your blog to point out that A The IPCC projections do not include volcanic eruptions and B Your graphs starts immediately before a volcanic eruption that had a large effect on global temperatures I m afraid burying it and IMO downplaying it in your comments does not draw an accurate picture 22 Jim Cripwell says 11 Jan 2008 at 12 42 PM Jon P writes Can you provide graphs of the other data sets I want to see them do just as well I agree And this of course brings up the perennial question Which of the various data sets of average annual global temperature anomaly is closest to the truth When we get some good scientific analysis which brings an understanding of that question we will have advanced the yardsticks a very long way 23 Patrick Hadley says 11 Jan 2008 at 12 43 PM Is there an element of cherry picking in this article Would an illustration using HadCRU or RSS with a moving average of either 5 6 7 or 9 years been as helpful to you in making your point Response The distribution of trends will be very similar most of this variability is due to real weather not instrumental noise But I ll check and report back gavin 24 Paul says 11 Jan 2008 at 12 47 PM As a layman who is trying to understand this issue I ve been struggling with how to assess the forecast skill of the GCMs I think this is an extremely important issue and I wish I could find more information regarding tests that would confirm or falsify the forecasting skill of the GCMs I agree with your point that short term deviations from a trend are not necessarily significant and do not necessarily indicate that the GCM s are unreliable However I think that Roger Pielke Jr has a point when he suggests that accurate short term forecasts are used to show how reliable the GCMs are but inaccurate short term forecasts are attributed to random noise in the actual data This seems like a head we win tails you loose verification method As another example I have read here how the GCM s accurately forecast the effect of the Pinatubo erruption If by accurate you mean that the GCM s predicted that dumping massive amounts of aersols into the atmosphere would cause cooling I am not impressed The mental model that exists in my head would be just as accurate If however by accurate you mean that the GCM s made reasonably close predictions of the extent of the cooling then it seems you are playing the head I win tails you loose game suggested by Roger Pielke s comment Response Huh When did we say that short term predictions were good if they agreed with the models Any test of a model has to be accompanied by an analysis of the uncertainties and if a test happens to be a good match but the uncertainties indicate that was just a piece of luck then it doesn t count Pinatubo is different because the forcing in that case was very strong and so it dominated the short term noise at least in some metrics like the global mean temperature Look at Hansen et al 2007 for more discussion of this Pinatubo is more interesting validation than just for temperatures too though Models get the LW and SW TOA radiation changes they get the changes in water vapour they get the impact on the winter NAO None of those things were programmed in ahead of time gavin 25 Hank Roberts says 11 Jan 2008 at 12 47 PM Walt you said you d been staring at the data and that Hadley was definitely reporting How much statistics do you know Did you do any math People are very good at detecting trends simply by looking at images and very often see what is not actually there This worked to detect large predators imagining a leopard has low cost compared to not seeing a leopard but the same talent leads to gross error imagining a recession is expensive compared to not noticing a recession Looking doesn t suffice for definitely reporting Math may How did you arrive at your conclusion 26 John Lederer says 11 Jan 2008 at 1 05 PM Hank Roberts I understand the problem with short term trends However if someone says the last 6 or 7 years is suggestive that global warming has stopped it is not good form to refute by showing a spread of 8 year trends It just inserts another issue Why 8 for the refutation rather than the 6 or 7 year record advanced in the original assertion Response Because that was what was used by Tierney The spreads for 6 or 7 year trends are even higher gavin 27 steven mosher says 11 Jan 2008 at 1 20 PM The problem here is that you dont have weather variability you have VOLCANO variability If you factor out the volcano effects I recall tamino doing something similiar on his site and then look at the 8 year trend you will get a different picture That might be an interesting excercise Tamino 28 George Robinson says 11 Jan 2008 at 1 24 PM Some interesting comments here and would just like to add my own observations well not my own but reports here in Scandinavia Spitzbergen is having extremely mild conditions and when I say mild well Last week is was the warmest place in Norway about 8C and heavy preciptation at their main weather station 43mm in one day and no it was not snow it was rain There is still no winter sea ice south of the islands neither was there any for the past 2 winters Further south on the mainland of Norway the high plateaus are having huge snow deposits and its only January something like 10 12 meters already on the Jolsterdals glacier Because of the milder winter weather records are being broken all the time with precipitation most likely the record of over 5000mm is in danger 29 Roger Pielke Jr says 11 Jan 2008 at 1 42 PM Gavin Thanks but this is a pretty lame response In a collegial spirit I suggest you download the model data directly from PCMDI and really look at what you can learn from it You are the climate scientist no If you are unwilling to explain what is substantively wrong is my efforts to provide an example of forecast verification then so be it I am quite confident in my conclusions from this exercise as summarized from my blog Prometheus and nothing that you say here contradicts those conclusions whatsoever 1 Nothing really can now be said on the skill of 2007 IPCC predictions 2 By contrast IPCC dramatically over predicted temperature increases in its 1990 report For 1995 2001 and some interesting surprises please tune in next week Gavin if you do decide to provide substantive critiques of the two conclusions above please do share them as I still have absolutely no idea what your complaint about this exercise actually is other than the fact that it took place Response You are again changing the subject Who ever claimed that the 2007 IPCC projections had been shown to be skillful I need to look at the 1990 1992 reports in more detail to comment on point two as I said above If you don t get what my complaint was after all this I am surprised but I will repeat it concisely 1 You need to compare like with like 2 Long term trends have different statistical properties than short term variability 3 Any verification attempt needs to take that into account gavin 30 Jamie Cate says 11 Jan 2008 at 1 52 PM A quick question about the 1997 1998 El Nino and the annual mean growth in atmospheric CO2 concentrations that occurred in 1998 See http www esrl noaa gov gmd ccgg trends Is there a connection that s obvious from the models or other studies Also what s the html tag for the tilde That d be useful to post in a handy location given how often El Nino La Nina events come up 31 Joseph O Sullivan says 11 Jan 2008 at 1 54 PM Roger Pielke Jr is capable of doing good work but too often he just likes to be provocative and will be disingenuous to do it His latest critique of the IPCC is another unfortunate example of the later Roger took a quote from a comment of mine on RealClimate about Environmental Defense s website I wrote that I liked the Q A section where readers could submit questions about climate change Roger on his blog dishonestly claimed that Dr Judith Curry made my comment and claimed Dr Curry was endorsing Environmental Defense s politics Roger then blocked my comments when I tried to correct his mistaken claims Its a bit of a stretch for him to complain that RC is selectively editing his comments 32 Roger Pielke Jr says 11 Jan 2008 at 2 01 PM Gavin Please explain how you accounted for short term variability in your over effort at verification here other than to say they don t mater when looking at trends http www realclimate org index php archives 2007 05 hansens 1988 projections My approach to verification is identical to yours in the Hansen post that you link to And indeed in my first blog post on this I was careful to make the same qualification about short term trends as you do in this current post which I will repeat since you haven t acknowledged it I assume that many climate scientists will say that there is no significance to what has happened since 2000 and perhaps emphasize that predictions of global temperature are more certain in the longer term than shorter term So what is it that you are complaining about again Response If you try and step back from simply trying to be contrary I suggest focusing on the the main principle that you have to compare like with like In the post I did on the 1988 projections I compared long term trends with long term trends It works there because in both the model output and observational data have uncertainties in the long term trends that were small compared to the signal This is not true for 8 year trends The figures you produced show the long term trend and it s uncertainty and the short term variability That is not an appropriate comparison Either put in the full envelope of model output over the same period or just plot the trends and their uncertainty for the 8 year period gavin Response Let me try to explain with a simple example Imagine you want to check the prediction that Colorado gets warmer during spring The prediction is for a roughly sinusoidal seasonal temperature cycle based on solar zenith angle Would you test this prediction against a piece of observational data from 10 17 April Of course not Random weather variability means that a cooling from 10 17 April does not falsify the seasonal cycle nor would a warming verify it in any way because the time period is just too short The variance of weather is larger than the seasonal warming from 10 17 April Do exactly the same exercise for a two month period rather than 8 days and it will make sense The variance of weather is then still the same

    Original URL path: http://www.realclimate.org/index.php/archives/2008/01/uncertainty-noise-and-the-art-of-model-data-comparison/langswitch_lang/sp/ (2016-02-13)
    Open archived version from archive

  • Uncertainty, noise and the art of model-data comparison « RealClimate
    In other words is an area average a good way to determine the actual global trend Second have the instruments being used to determine sea surface temperature been satisfactorily validated If I recall correctly there have been some problems correctly interpreting readings from the instruments which were launched several years ago Or is this more related to the difference in methods Gavin mentioned 14 David Lea says 11 Jan 2008 at 11 52 AM Gavin thanks for an informative post Does the 2007 value you plot include December I noticed from GISTEMP that Dec 07 was cooler than other months can this be attributed to the strong ongoing La Nina in the Pacific Thanks David Response Yes it does include Dec 07 And indeed it does seem to be related to the La Nina gavin 15 Roger Pielke Jr says 11 Jan 2008 at 12 08 PM Gavin 7 Thanks a few replies You ask How can you read the post above and claim that we re avoiding forecast verification altogether Well my first clue is when you misrepresented why I did and what John Tierney reported You characterized the effort as attempts to validate or falsify IPCC projections of global temperature change over the period 2000 2007 No such claims were made by me and I don t think by Tierney In my post I was careful to note the following I assume that many climate scientists will say that there is no significance to what has happened since 2000 and perhaps emphasize that predictions of global temperature are more certain in the longer term than shorter term And John Tierney wrote you can t draw any firm conclusions about the IPCC s projections a few years does not a trend make So why misrepresent what we said Models of open systems cannot in principle be validated see Oreskes et al 1994 I simply compared IPCC predictions with observations as an example of how to do a verification which is standard practice in the atmospheric sciences but much less so in the climate modeling community and yes I think this is indeed the case Instead of telling your readers all of the reasons that a verification exercise is misguided you might have instead constructively pointed to the relevant forecasts with proper uncertainty bars please do post up the link or better yet simply shown how an analysis comparing 2000 2007 with relevant predictions would have been done to your satisfaction Given that you point to the IPCC AR4 Figure 1 1 in positive fashion I remain confused about your complaint about what I did I don t recall you complaining about IPCC efforts in verification previously How about this We agree that rigorous forecast verification is important There also does not a clear agreement among researchers as to a what variables are most important to verify b Over what times scales c what actual constitutes the relevant forecasts and d what actually constitutes the relevant observational verification databases Then this is a subject to work through collegially rather than try to discredit dismiss or suppress Thanks PS As I stated on my blg If discussing forecast verification in the context of climate model predictions is to be a sign of skepticism then climate science is in bad shape For the record I accept the consensus of IPCC WG I Response Roger I m flummoxed You keep bringing in things that have not been said and rebuttals to arguments that have not been made All we have done is point out statistical issues in two things you compared Oreskes paper is a case in point I have no desire to argue about the semantics of verification vs evaluation vs validation none of that is relevant to the overriding principle that you have to compare like with like In a collegial spirit I suggest you download the model data directly from PCMDI and really look at what you can learn from it You might get a better appreciation for the problems here Verification is not misguided Your attempt at verification was gavin 16 Hank Roberts says 11 Jan 2008 at 12 16 PM John Lederer http scienceblogs com stoat 2007 05 the significance of 5 year tre php 17 Jon Pemberton says 11 Jan 2008 at 12 21 PM Gavin You stated The red line is the annual global mean GISTEMP temperature record though any other data set would do just as well Can you provide graphs of the other data sets I want to see them do just as well Thanks Jon P 18 Earl Killian says 11 Jan 2008 at 12 29 PM If you replace 8 year trend lines with n year at what value of n do they start to faithfully reflect the underlying trend 19 Steven T Corneliussen says 11 Jan 2008 at 12 30 PM I see now that in reporting in item 3 above on the Boston Globe s Jeff Jacoby s contribution in the category of misconstruing weather as climate I probably should have bee explicit my own opinion for what it s worth is that Jacoby s contribution is preposterous 20 B Buckner says 11 Jan 2008 at 12 30 PM Gavin You indicated that the GISS product extrapolates over the arctic region Extrapolate means to infer or estimate by extending or projecting known information How is this done and can you explain why is it valid Is this simply using widely spaced and limited data from within the arctic itself and extrapolating to cover the entire region or extrapolating somehow from the perimeter of the arctic Response This is explained in the GISTEMP documentation but in areas with no SST information like most of the Arctic the information from met stations is extrapolated over a radius of 1200 km That fills in some of the Arctic A validation for that kind of approach would be a match to the Arctic buoy program but I haven t looked into that specifically gavin 21 Boris says 11 Jan 2008 at 12 40 PM In fact IPCC 1990 dramatically over forecast trends as show by the IPCC figure that you reference and that I provide here Roger Your blog post neglects to even mention the good reasons for forecasts to be off namely the Mt Pinatubo eruption Don t you think you owe it to those who read your blog to point out that A The IPCC projections do not include volcanic eruptions and B Your graphs starts immediately before a volcanic eruption that had a large effect on global temperatures I m afraid burying it and IMO downplaying it in your comments does not draw an accurate picture 22 Jim Cripwell says 11 Jan 2008 at 12 42 PM Jon P writes Can you provide graphs of the other data sets I want to see them do just as well I agree And this of course brings up the perennial question Which of the various data sets of average annual global temperature anomaly is closest to the truth When we get some good scientific analysis which brings an understanding of that question we will have advanced the yardsticks a very long way 23 Patrick Hadley says 11 Jan 2008 at 12 43 PM Is there an element of cherry picking in this article Would an illustration using HadCRU or RSS with a moving average of either 5 6 7 or 9 years been as helpful to you in making your point Response The distribution of trends will be very similar most of this variability is due to real weather not instrumental noise But I ll check and report back gavin 24 Paul says 11 Jan 2008 at 12 47 PM As a layman who is trying to understand this issue I ve been struggling with how to assess the forecast skill of the GCMs I think this is an extremely important issue and I wish I could find more information regarding tests that would confirm or falsify the forecasting skill of the GCMs I agree with your point that short term deviations from a trend are not necessarily significant and do not necessarily indicate that the GCM s are unreliable However I think that Roger Pielke Jr has a point when he suggests that accurate short term forecasts are used to show how reliable the GCMs are but inaccurate short term forecasts are attributed to random noise in the actual data This seems like a head we win tails you loose verification method As another example I have read here how the GCM s accurately forecast the effect of the Pinatubo erruption If by accurate you mean that the GCM s predicted that dumping massive amounts of aersols into the atmosphere would cause cooling I am not impressed The mental model that exists in my head would be just as accurate If however by accurate you mean that the GCM s made reasonably close predictions of the extent of the cooling then it seems you are playing the head I win tails you loose game suggested by Roger Pielke s comment Response Huh When did we say that short term predictions were good if they agreed with the models Any test of a model has to be accompanied by an analysis of the uncertainties and if a test happens to be a good match but the uncertainties indicate that was just a piece of luck then it doesn t count Pinatubo is different because the forcing in that case was very strong and so it dominated the short term noise at least in some metrics like the global mean temperature Look at Hansen et al 2007 for more discussion of this Pinatubo is more interesting validation than just for temperatures too though Models get the LW and SW TOA radiation changes they get the changes in water vapour they get the impact on the winter NAO None of those things were programmed in ahead of time gavin 25 Hank Roberts says 11 Jan 2008 at 12 47 PM Walt you said you d been staring at the data and that Hadley was definitely reporting How much statistics do you know Did you do any math People are very good at detecting trends simply by looking at images and very often see what is not actually there This worked to detect large predators imagining a leopard has low cost compared to not seeing a leopard but the same talent leads to gross error imagining a recession is expensive compared to not noticing a recession Looking doesn t suffice for definitely reporting Math may How did you arrive at your conclusion 26 John Lederer says 11 Jan 2008 at 1 05 PM Hank Roberts I understand the problem with short term trends However if someone says the last 6 or 7 years is suggestive that global warming has stopped it is not good form to refute by showing a spread of 8 year trends It just inserts another issue Why 8 for the refutation rather than the 6 or 7 year record advanced in the original assertion Response Because that was what was used by Tierney The spreads for 6 or 7 year trends are even higher gavin 27 steven mosher says 11 Jan 2008 at 1 20 PM The problem here is that you dont have weather variability you have VOLCANO variability If you factor out the volcano effects I recall tamino doing something similiar on his site and then look at the 8 year trend you will get a different picture That might be an interesting excercise Tamino 28 George Robinson says 11 Jan 2008 at 1 24 PM Some interesting comments here and would just like to add my own observations well not my own but reports here in Scandinavia Spitzbergen is having extremely mild conditions and when I say mild well Last week is was the warmest place in Norway about 8C and heavy preciptation at their main weather station 43mm in one day and no it was not snow it was rain There is still no winter sea ice south of the islands neither was there any for the past 2 winters Further south on the mainland of Norway the high plateaus are having huge snow deposits and its only January something like 10 12 meters already on the Jolsterdals glacier Because of the milder winter weather records are being broken all the time with precipitation most likely the record of over 5000mm is in danger 29 Roger Pielke Jr says 11 Jan 2008 at 1 42 PM Gavin Thanks but this is a pretty lame response In a collegial spirit I suggest you download the model data directly from PCMDI and really look at what you can learn from it You are the climate scientist no If you are unwilling to explain what is substantively wrong is my efforts to provide an example of forecast verification then so be it I am quite confident in my conclusions from this exercise as summarized from my blog Prometheus and nothing that you say here contradicts those conclusions whatsoever 1 Nothing really can now be said on the skill of 2007 IPCC predictions 2 By contrast IPCC dramatically over predicted temperature increases in its 1990 report For 1995 2001 and some interesting surprises please tune in next week Gavin if you do decide to provide substantive critiques of the two conclusions above please do share them as I still have absolutely no idea what your complaint about this exercise actually is other than the fact that it took place Response You are again changing the subject Who ever claimed that the 2007 IPCC projections had been shown to be skillful I need to look at the 1990 1992 reports in more detail to comment on point two as I said above If you don t get what my complaint was after all this I am surprised but I will repeat it concisely 1 You need to compare like with like 2 Long term trends have different statistical properties than short term variability 3 Any verification attempt needs to take that into account gavin 30 Jamie Cate says 11 Jan 2008 at 1 52 PM A quick question about the 1997 1998 El Nino and the annual mean growth in atmospheric CO2 concentrations that occurred in 1998 See http www esrl noaa gov gmd ccgg trends Is there a connection that s obvious from the models or other studies Also what s the html tag for the tilde That d be useful to post in a handy location given how often El Nino La Nina events come up 31 Joseph O Sullivan says 11 Jan 2008 at 1 54 PM Roger Pielke Jr is capable of doing good work but too often he just likes to be provocative and will be disingenuous to do it His latest critique of the IPCC is another unfortunate example of the later Roger took a quote from a comment of mine on RealClimate about Environmental Defense s website I wrote that I liked the Q A section where readers could submit questions about climate change Roger on his blog dishonestly claimed that Dr Judith Curry made my comment and claimed Dr Curry was endorsing Environmental Defense s politics Roger then blocked my comments when I tried to correct his mistaken claims Its a bit of a stretch for him to complain that RC is selectively editing his comments 32 Roger Pielke Jr says 11 Jan 2008 at 2 01 PM Gavin Please explain how you accounted for short term variability in your over effort at verification here other than to say they don t mater when looking at trends http www realclimate org index php archives 2007 05 hansens 1988 projections My approach to verification is identical to yours in the Hansen post that you link to And indeed in my first blog post on this I was careful to make the same qualification about short term trends as you do in this current post which I will repeat since you haven t acknowledged it I assume that many climate scientists will say that there is no significance to what has happened since 2000 and perhaps emphasize that predictions of global temperature are more certain in the longer term than shorter term So what is it that you are complaining about again Response If you try and step back from simply trying to be contrary I suggest focusing on the the main principle that you have to compare like with like In the post I did on the 1988 projections I compared long term trends with long term trends It works there because in both the model output and observational data have uncertainties in the long term trends that were small compared to the signal This is not true for 8 year trends The figures you produced show the long term trend and it s uncertainty and the short term variability That is not an appropriate comparison Either put in the full envelope of model output over the same period or just plot the trends and their uncertainty for the 8 year period gavin Response Let me try to explain with a simple example Imagine you want to check the prediction that Colorado gets warmer during spring The prediction is for a roughly sinusoidal seasonal temperature cycle based on solar zenith angle Would you test this prediction against a piece of observational data from 10 17 April Of course not Random weather variability means that a cooling from 10 17 April does not falsify the seasonal cycle nor would a warming verify it in any way because the time period is just too short The variance of weather is larger than the seasonal warming from 10 17 April Do exactly the same exercise for a two month period rather than 8 days and it will make sense The variance of weather is then still the same but

    Original URL path: http://www.realclimate.org/index.php/archives/2008/01/uncertainty-noise-and-the-art-of-model-data-comparison/langswitch_lang/zh/ (2016-02-13)
    Open archived version from archive

  • Uncertainty, noise and the art of model-data comparison « RealClimate
    time to better info 69 Walt Bennett says 11 Jan 2008 at 10 27 PM Re 48 Hank You misunderstood my post Also did you see my followup with links to the references I made My point was not Hey isn t it statistically significant that Hadley shows two consecutive years of cooling My point was Is Hadley right NASA GISS seems to think it has kept on warming I m just trying to understand the Hadley data at face value 70 Hank Roberts says 11 Jan 2008 at 10 29 PM Oh Jon you mentioned Eli s notes on sea ice and said you wished he had something Did you click his link The comparison of the poles that you wished for is at the source Eli gives The charts there that are pulled automagically from the databases are working now the hand edited one will be updated in a week or two to fill out the 2007 year I just asked nicely about that yesterday myself grin 71 Hank Roberts says 11 Jan 2008 at 10 51 PM Charles a moving average gives you a different look than a trend line There s an excellent treatment of this here in a rather famous website http www fourmilab ch hackdiet e4 signalnoise html Like most attempts to characterise a complicated system by a single number a scale throws away a great deal of the subtlety The scale responds with a number that means something or other If only we knew what Over time certainly the scale will measure the cumulative effect of too much or too little food But from day to day the scale gives results that seem contradictory and confusing We must seek the meaning hidden among the numbers and learn to sift the wisdom from the weight The right way to think about a trend chart is to keep it simple The trend line can do one of three things Go up Go down Stay about the same That s it The moving average guarantees the trend line you plot will obviously behave in one of these ways the short term fluctuations are averaged out and have little impact on the trend He addresses the reason that the moving average you ask for may not give a clear picture on the same page http www fourmilab ch hackdiet e4 figures figure737 png The familiar moving average trend line is drawn as before The dashed line is the best fit to all 90 days But obviously it misses the point Short term straight line trend lines provide accurate estimates Excel workbooks are provided at the site to try out the different methods of charting See also everything else wonderful site 72 PaulM says 11 Jan 2008 at 11 11 PM It is now raining in mid winter where before it would be snow I need no other proof or to be told weather is different than climate Again in mid winter it is now rain and if it does snow it is a wet snow and melts a few days later before there would be snow on the ground from Thanksgiving until Easter now it is raining in January I am old enought to know the pattern has changed by what I have experienced and what I am experiencing now 73 Joseph O Sullivan says 11 Jan 2008 at 11 35 PM Re 31 my comment and 34 Roger Pielke Jr s reply My tone was unduly harsh Roger Pielke Jr does like to provoke discussion To do this he will make controversial statements on his blog Its common in some academic circles but its likely to be misunderstood in a public forum like a blog I did not like see my comment used in a way I thought was inappropriate The misquote did occur and I submitted comments and several where not admitted After the posts moved on one my milder comments made it through After that I had all but one of my comments admitted on other posts I do not think that Roger Pielke Jr does not respect Dr Curry but I do think he was trying to stir things up This is the post http sciencepolicy colorado edu prometheus archives climate change 000904hurricanes and globa html 74 Andre Narichi says 12 Jan 2008 at 12 08 AM I am not convinced by much of this You take a data set of 30 years and say that the initial warming observed of less than 20 years is a long term trend and can be relied upon but you say the past 7 years of statistically indistinguishable temperature data is short term climatic fluctuation and can be ignored note this short term fluctuation isn t fluctuating There are no errors bars in the graph put them in and you can draw your trend lines with much more latitude And because the recent observed stasis is 7 years you ignoring errors chose an 8 year grouping which is bound to drag the stasis back towards the rising section of the graph because you are giving it less weight than the data in the centre of the graph YOU are the denialists denying data Finding ways to prove it isn t what it is and making it conform to your worldview 75 Walt Bennett says 12 Jan 2008 at 12 21 AM I made a chart from the updated NASA GISS anomaly data and I think it came out fairly well http bp1 blogger com hb0jssUZaPY R4hNSaRKHzI AAAAAAAAABM Gabp4uz77ag s1600 h anom gif I plot gross annual anomalies a score of 1200 would be a mean anomaly of 1 C per month along with 5 10 and 30 year running means I d appreciate any feedback as to method and conclusions 76 Bob North says 12 Jan 2008 at 12 42 AM First of let me qualify my post by saying that I come here as a believer a questioner and a skeptic By that I mean that I am a believer in that I find the evidence for long term global warming since at least the 1880s overwhelming and apparently irrefutable Secondly basic physics thermodynamics dictate that increasing concentrations of greenhouse gasses will have an affect on the overall climate However I am a questioner in that I am not as fully convinced of the magnitude of the impact of anthropogenic versus non anthropogenic causes of the warming trend but readily concede that the current warming trend is at least in part due if not substantially due to anthropogenic releases of CO2 and other GHGs Finally I am a skeptic that has some experience in much simpler modeling mostly ground water contaminant fate transport in that I have much less confidence in our current ability to accurately model future climatethan is often portrayed in the popular press or even on websites such as this In other words I believe we can with near certaintude say that if global temperatures continue to rise there will be a rise in sea level due to the melting of glaciers and thermal expansion of the oceans but that projections of drought hyper intensive storms mass extinctions and other calamities etc are somewhat less certain As an educated layman my take on this is Much Ado about Nothing I have read and re read Tierney and Pielke s posts and what I get out of both of them is that they are saying you can read whatever you want out of the recent 2001 2006 Global temperature estimates ehy are very clear in stating that the recent Global temperatures neither prove or disprove the overall AGW model What Pielke did say is that the most recent number will provide cherry pickers with ammunition to quibble about this that or the other thing Tierney correctly noted that there is a wide range of variance in the estimated global temperature anomalies and that depending on where you fall on the sociological spectrum denier questioner skeptic advocate disciple will help dictate which estimate you will rely on most What both Tierny and Pielke seem to be asking for is continued and further refinement of the models as we gather additional climate data In other words don t become defensive and just say short term perturbations don t affect the validity of the MODEL continue to try to make the model account for the short term perturbations The models are nothing more than our attempts to account for all the variables that do drive climate change Bob North Bob North 77 Thomas says 12 Jan 2008 at 12 50 AM Gavin a man with the patience of a saint My question has to do with how well behaved the psuedo climate system as defined by GCM runs is I work in FEA engineering and it is quite common for such systems to contain bifurcations whereby a large collection of runs will demonstrate two or more general solutions superimposed of course with shortterm noise Have any of the climate models shown such behavior I E do you see situtaions where some fraction of the runs with the same parameters and forcings but perturbed initial conditions show more than a single solution trend 78 John Mashey says 12 Jan 2008 at 1 17 AM Another way to see that data is take the GISTEMP data compute 8 year regressions via SLOPE and put that series into as scatter plot whihc gives one line that graphs the slopes of the blue lines The only times the slopes go below zero are those around the volcanoes 79 cce says 12 Jan 2008 at 1 46 AM Re 57 Here is the 12 month moving average for NASA GISS Hadley CRU UAH and RSS temperature analyses from January 1979 to October 2007 NASA GISS and Hadley CRU are land ocean instrument data while UAH and RSS are lower troposphere satellite data http cce 890m com temp compare jpg Here is the raw data for each analysis including the linear fit With both of the instrumental analyses the slope is 0 17 degrees per decade In the UAH satellite analysis it is 0 14 degrees per decade In the RSS satellite analysis it is 0 18 degrees per decade In all cases the anomalies are adjusted up or down so as to give the linear regression for each analysis a y intercept of zero http cce 890m com giss jpg http cce 890m com hadcrutv jpg http cce 890m com uah jpg http cce 890m com rss jpg In short the anomalies are where you d expect them to be given the warming signal plus natural variability and the fact that each analysis uses different methods 80 Barton Paul Levenson says 12 Jan 2008 at 6 53 AM Looks like we re about to have a big volcanic eruption in Ecuador So temperature will go down by 0 2 K for a couple of years and we ll have to put up with two more years of deniers saying See global warming stopped 81 Jim Cripwell says 12 Jan 2008 at 7 12 AM Ref 52 If you want to see the sort of thing I am talking about I am afraid you need to go to Yahoo Climate Skeptics and download the graphs I uploaded under the title Rctner I fully realize that there a pseudo infinite number of such graphs and these three are merely examples 82 Daniel C Goodwin says 12 Jan 2008 at 7 27 AM Thanks much for the crystal clear diagram and discussion Contrary to some readers who are growing weary of it I m delighted to see RC giving the other side enough rope like this Your main point which you have now repeated 60 zillion times is irrefutable as is your observation that the exercise in question violates the simple principle that LIKE SHOULD BE COMPARED WITH LIKE You haven t tried shouting yet I suppose but I doubt that would prove any more effective In the face of an argument which could hardly be framed more crisply your dissenter has no more interesting stratagem than feigning deafness Like a World Wrestling Federation spectacle this classic thread has been a grossly unfair fight and a lot of fun 83 Gautam Kalghatgi says 12 Jan 2008 at 9 01 AM I understand that between the 1940s and 1970s global mean temperature did not change much and this has been ascribed to increased particulates arising from industrialisation So if you take a 30 year average between say 1945 and 1975 and then again between 1975 and 2005 the latter average should be significantly higher What is the proper explanation for this What changed in the 70s Surely particulate emissions on a world scale did not decrease in the 1970s though it might have in some industrialised countries What about increasing use of coal by China and India say and the consequent increase in particulates in the recent past Would this not be expected to have a dimming effect and a reduction in global temperatures Response Not all aerosols are the same Some such as black carbon released by coal burning actually have a surface warming impact Sulphate aerosols and secondarily nitrate aeresols which do have a surface cooling impact increased substantially in burden from the 1940s through the 1970s decreasingly markedly with the passage of the Clean Air Acts of the 1970s and 1980s The various issues you raise have been discussed many times before here and in links provided Start here here and here mike 84 lgl says 12 Jan 2008 at 9 28 AM These comparisons are flawed since they basically compare long term climate change to short term weather variability What is short term weather variability Isn t it obvious that the warming had to stop after a 5 W m2 drop in the energy input to the climate system in 2002 http isccp giss nasa gov zFD an9090 TOTnet toa gif It should be equally obvious that the 90s had to get much warmer than the 80s because of a much higher energy input at TOA But the explanation is that there was one type of quite stable weather between 1994 and 2000 and a totally different type of weather between 2002 and 2005 and probably longer capable of reducing the radiation by 5 W m2 What is this assumption based on Response The ISCCP data is great but can t be relied on for trends due to difficulties in tying different satellite records together The implication that albedo has suddenly increased to Pinatubo levels without anyone else noticing or a rapid decrease in temperatures is surprising to say the least gavin 85 Ray Ladbury says 12 Jan 2008 at 9 35 AM cce says in 79 In short the anomalies are where you d expect them to be given the warming signal plus natural variability and the fact that each analysis uses different methods Of course the denialists will say it s clear the warming stopped in 2000 and in 1998 and in 1995 and in 1991 and in 1987 At least Pielke and Douglass et al are sufficiently sophisticated to realize that the only way to attack the anthropogenic hypothesis is to simply deny that warming is occurring Unfortunately since all the science and the evidence support a warming trend they can t get beyond misusing statistics and saying No it isn t 86 John Lederer says 12 Jan 2008 at 9 53 AM A couple of small comments 1 Pielke is right that so long as the four major sources of global temperature disagree what one sees is largely a matter of which record one looks at This is quite troubling since the members of each pair the two surface records and the two satellite records essentially have the same raw data The differences between members of the pairs is thus a difference in after the fact adjustments Surely those can be ironed out and agreement reached on the better methods The increased divergence of GISStemp and HadleyCRU and between UAH and RSS suggests that rather than being reconciled the differences are growing Very troublesome Response Not really The trends for the most part are similar given the underlying uncertainty and there are defendable reasons for the various choices made in the different analyses Reasonable people can disagree on what is best in these cases and so rather than being troubled one should simply acknowledge that there are some systematic uncertainties in any large scale climate metric That uncertainty feeds into assessments of attribution and the like but is small enough not to be decisive Of course assessing the reason for any divergence is important and can lead to the discovery of errors such as with the UAH MSU record a couple of years ago but mostly it is due to the different choices made gavin 2 For assessing global climate change the absolute trend lines are apt However for assessing man caused global warming the neutral trend line would not be zero Since the Little Ice Age we have naturally warmed Should not this be taken into account In other words a trend of some figure say 6 C per century should be regarded as neutral for purpose of assessing a man caused trend Response There is no neutral trend that can simply be regarded as natural volcanic and solar forcing changes are not any different to GHG forcing when it comes to attribution and modeling If instead you propose that the 20th Century trends are simply some long term intrinsic change then you need to show what is going on No such theory exists The trends can however be explained quite adequately from the time series of forcings including natural and human caused effects gavin 87 Jim Cripwell says 12 Jan 2008 at 9 56 AM In 68 Hank writes Jon Pemberton Seems to me you re asking others to do an impossible amount of work

    Original URL path: http://www.realclimate.org/index.php/archives/2008/01/uncertainty-noise-and-the-art-of-model-data-comparison/comment-page-2/ (2016-02-13)
    Open archived version from archive

  • Uncertainty, noise and the art of model-data comparison « RealClimate
    temperature records are compared Response They are referenced in model simulations at least Krakatoa which is after the 1850 1880 start date for most simulations see http pubs giss nasa gov abstracts 2007 Hansen etal 3 html gavin 116 lucia says 12 Jan 2008 at 8 31 PM Gavin In answer to 2m you discussed the multiple response times of various components of the planet Could you point me to a reference that describes how the response time to Pinatubo the deep oceans or any other components Thanks in advance Response Where do you want to start Google 14C distributions in the ocean the seasonal cycle glacier retreat etc The literature on responses to Pinatubo is also pretty extensive Hansen et al 1992 Wigley et al 2005 in response to Douglass If you want to be more specific I could probably be more helpful gavin Response If you don t have access to the Wigley et al 05 paper which indeed addresses this most directly you can find some discussion in the IPCC AR4 report which is publicly available See page 61 of chapter 9 of the Working Group I report warning its 5 MB in size and may take a minute or two to download depending on the speed of your internet connection mike 117 Walt Bennett says 12 Jan 2008 at 8 42 PM I m sad I provided references for Hank and he has yet to follow up with me even though he is still active in the thread And nobody has a comment on the graph I labored most of the night to create I m feeling neglected Predictions 1 We are due for a spike year We haven t realy spiked since 2002 and it is about time for another one based on what I see on the historical graph 2 On any scale 5 year 10 year or 30 year it is unmistakable that the warming trend continues The rate may be slowing or accelerating we should know the answer to that in 5 years However cooling would be the wrong word no matter how you look at the last 9 years when all are well above the 1951 1980 mean and 2 of them exceeded 1998 As I have been saying the spike has become the norm Is that not news 118 Hank Roberts says 12 Jan 2008 at 9 17 PM Walt did you see Gavin s inline response at 86 It seemed to me to answer your question as well as you could hope for though it was in response to someone else asking something similar I m just another reader here not a climatologist I can hardly answer questions like the one you asked Is Hadley right I doubt anyone could If you mean do their published measurements reflect the instruments they used likely so You could ask what their error bars are for short term measurement those will be relatively large compared to their error bars for long term trends those will be relatively smaller perhaps 119 Walt Bennett says 12 Jan 2008 at 9 32 PM Re 118 Hank I am specifically asking anybody 1 Can Hadley s SST measurements be considered reliable to the same extent land measurements can 2 Is it correct to allow the extrapolated SST signal to dominate the reconstructed climate signal I suppose that rolls back to question 1 but also the method by which overall SSTs are determined I assume there are very few measuring points on the open ocean what method is used to extrapolate the overall temp and has it been in any way verified with for example spot sampling from passing ships My intuition is telling me that the warming is clear detectable and accelerating at least here in the northeast U S and from what I read the same is true in many other places We have visual evidence of rapid change in the Arctic region and I suspect we will be seeing much the same soon in certain parts of the Antarctic continent even moreso than we have already seen There may be some confusing year to year feedbacks but the overall trend is clear to me If we have SST measurements that seem to offset the warming there is bound to be less concern about the overall increase in global temp If it turns out that the methods used to determine overall SSTs were severely in error we would be looking back and asking Why did we let ourselves believe overall global temps were stable when all of the visual evidence told us that the warming was continuing 120 Anna Haynes says 12 Jan 2008 at 9 41 PM Idea someone should run a Debunking for Dollars site where anyone with a denialist talking point could submit it with a PayPal donation of appropriate size get said point addressed instead of sitting around at Dot Earth and elsewhere complaining that RealClimate won t address the point for the 152nd time If there are conflict of interest issues the money could go to a charity And multiple people could do the debunking to spread the load I ve just now registered the url as a precaution and would be happy to help defray the costs of setting up the site 121 Hank Roberts says 12 Jan 2008 at 11 27 PM Walt when you write this If we have SST measurements that seem to offset the warming there is bound to be less concern about the overall increase in global temp you re now talking PR political spin not science It doesn t matter what your political beliefs say would be good PR or good spin or good press if you want to talk about the science What matters is getting good information The models have all indicated areas that will be warmer and areas that will be cooler over time Hadley in particular has that 10 year look into the model s future that I already pointed to But look at any of the pictures of what may occur and you ll see areas warmer and other areas cooler Getting it right is what matters Not getting it one way for PR 122 lucia says 12 Jan 2008 at 11 35 PM Mike Thanks for the citation I have a fast connection I ve glanced at that and it appear to be a summary literature review type document So while it doesn t contain what I m looking for I suspect I can order some of ther referenes to find the basis for some numbers It should help Gavin Thanks I d probably be more specific if I had a clue what types of things existed I m interested in papers that specifically describe how that set or particular authors estimate time scales rather than simply citing other authors and mention what someone esle found I have for example Schwartz 2007 Heat Capacity Time Constant and Sensitivity of Earth s Climate System which suggested the climate system can be modeled as a simple lumped parameter and then found a time constant based on the autocorrelation of surface temperatures Schwartz cites a number of papers in section 4 I m in the process of trying to get them and familiarize myself with the sorts of approaches used but Schwartz doesn t for example cite Hansen 1992 He does cite a Hansen 1996 Geophys Rev Letters He also cites Wigley 2005 I assume Hansen wrote more than 1 paper in 1996 Anyway as I know you criticized Schwartz s paper it occurred to me you might cite papers Schwartz did not I guess as long as you are writing about this topic and you answered a question mentioning these time constants I m asking hoping to find which papers describing time constants you think are most worth reading rather than simply googling It sounds like the Wigley paper s that Mike you and Steven Schwartz all cite must be a good start If it s not I ll probably be able to trace back through the references 123 Dusty says 12 Jan 2008 at 11 50 PM The sun is quiet and has been on a downturn for a few years Why are cooler ocean temps any surprise It is possible that the sun will soon enter a relatively extended quiet period What ramifications that would have on our climate remains to be seen In reply to comment 120 Why are all of us with open minds labeled debunkers Are open minds now a bad thing Thanks but I will keep my open mind and skepticism readily handy for both sides Everyone these days seems to have an agenda If the oceans are cooling Thats great If not that is great too This whole thing makes me miss the old days when everyone thought nuclear war was inevitable 124 Bryan S says 13 Jan 2008 at 12 33 AM Re 107 Gavin you say none of the resolutions of issues that you mention have made it into the literature yet and I m happy to refrain from commenting on papers that don t yet exist Ah but they will be in the literature soon A steak dinner at your favorite steakhouse if the OHC gain for 2004 2005 2006 and 2007 turns out to be more than statistically insignificant in any refereed paper on the issue If less then you buy at mine If the result is overturned later I will refund your dinner in kind Are you having any of it Maybe afterward we can get down to business talking about some interesting climate science P S The beef is better down here in Texas 125 John says 13 Jan 2008 at 12 35 AM How well do the CGM models used in the various generations of IPCC studies capture the effects of the two volcanoes highlighted in the main article I gather that volcanic aerosols are specified in model runs up to present One would expect that they should show the two cooling pulses Has anyone plotted model outputs for the few years around these eruptions 126 Hank Roberts says 13 Jan 2008 at 12 35 AM Dusty is there some correlation between sunspot cycles and El Nino La Nina ENSO published somewhere Cite please Hadley s prediction for the next decade doesn t involve the sun missing a cycle And the sun s on the upswing first sunspot of the new cycle happened 127 John Mashey says 13 Jan 2008 at 2 04 AM As per 78 an even better way to get over all this arguing about 7 years 8 years etc goes like this 1 Download the GISTEMP data year anomaly I used 1977 2006 2 Compute N year SLOPEs centered on each year N years 3 1978 2005 7 1980 2003 11 1982 2001 15 1980 1999 19 1978 1997 3 Do a scatter plot of the 5 series which shows how the slopes vary over time for a different number of years 4 One finds 3 7 11 15 19 018 017 017 017 016 MEAN Not much difference 074 023 008 007 003 STDEVP Standard deviation decreases strongly 135 069 036 030 020 MAX 130 022 006 006 011 MIN 265 091 030 024 010 range Range shrinks strongly unsurprisingly 5 People sometimes argue with any specific series length as cherry picking but by showing multiple lengths on one chart that clearly isn t happening The chart is another way to show what anybody should know but some people seem to not understand or don t want to a If you pick a short span in a noisy series you can prove anything b As series get longer the variability shrinks and that is obvious on the chart 6 And in this particular case once you get to 11 years there are no negative slope series min 006 i e even Pinataubo doesn t do it 128 Walt Bennett says 13 Jan 2008 at 3 12 AM Re 121 Hank I fear that you have once again missed my point I do not intend to be so obscure I am singularly focused on getting it right I have asked a battery of questions on that very subject and have gotten zero response The point if there was one to my question was is it possible that we are getting it wrong with regard to SST cooling Hadley s own graph shows that the ocean tends to warm when land warms Why in the last two years has that not been the case What would the explanation be for the oceans overall to be cooling for what to my eyes seem to be at least the last two years http www metoffice gov uk research hadleycentre CR data Monthly NMAT SST LSAT plot gif 129 Timo Hämeranta says 13 Jan 2008 at 6 30 AM Re 60 etc on Ocean Heat Content OHC please see the new study Johnson Gregory C Sabine Mecking Bernadette M Sloyan and Susan E Wijffels 2007 Recent Bottom Water Warming in the Pacific Ocean Journal of Climate Vol 20 No 21 pp 5365 5375 November 2007 online http www pmel noaa gov people gjohnson gcj 3m pdf Abstract Decadal changes of abyssal temperature in the Pacific Ocean are analyzed using high quality full depth hydrographic sections each occupied at least twice between 1984 and 2006 The deep warming found over this time period agrees with previous analyses The analysis presented here suggests it may have occurred after 1991 at least in the North Pacific Mean temperature changes for the three zonal and three meridional hydrographic sections analyzed here exhibit abyssal warming often significantly different from zero at 95 confidence limits for this time period Warming rates are generally larger to the south and smaller to the north This pattern is consistent with changes being attenuated with distance from the source of bottom water for the Pacific Ocean which enters the main deep basins of this ocean southeast of New Zealand Rough estimates of the change in ocean heat content suggest that the abyssal warming may amount to a significant fraction of upper World Ocean heat gain over the past few decades 130 Hank Roberts says 13 Jan 2008 at 6 44 AM Hmmm was it a low sunspot number or was it bad observing conditions due to volcanic activity Interesting idea http ntrs nasa gov search jsp R 522471 id 4 qs Ntt 3Dsunspot 26Ntk 3Dall 26Ntx 3Dmode 2520matchall 26N 3D4294826660 2B53 26Ns 3DHarvestDate 257c1 Volcanism Cold Temperature and Paucity of Sunspot Observing Days 1818 1858 A Connection Author s Wilson Robert M Abstract During the interval of 1818 1858 several curious decreases in the number of sunspot observing days per year are noted in the observing record of Samuel Heinrich Schwabe the discoverer of the sunspot cycle and in the reconstructed record of Rudolf Wolf the founder of the now familiar relative sunspot number These decreases appear to be nonrandom in nature and often extended for 13 yr or more The drop in equivalent annual mean temperature associated with each decrease as determined from the moving averages measured about 0 1 0 7 C The decreases in number of observing days are found to be closely related to the occurrences of large cataclysmic volcanic eruptions in the tropics or northern hemisphere Interesting to think that the counts of sunspot numbers could actually have been counts of dirty air days and the variations in temperature due not to sunspots but volcanic activity far around the Earth I don t know where this idea when if anywhere Just happened on it 131 Lynn Vincentnathan says 13 Jan 2008 at 9 36 AM RE this post it s a good thing there are some scientists around like you folks to do the science I m thinking sci fi on this a world in which journalists do the science Title Maybe THE NEW DARK AGES 132 Lynn Vincentnathan says 13 Jan 2008 at 9 50 AM I saw a program on Nat Geo RING OF FIRE around the Pacific Ocean It said volcanism is higher now than thousands of years ago and that it could get a lot worse If it does and it gets extremely worse like 251 mya ago then I m guessing the initial impact might be an aerosol cooling effect but that once that clears from the atmosphere then it would be leaving GHGs behind for a very long time to cause increased GW But before the denialists start gloating about this we should consider that we might need those very fossil fuels we are wastefully burning now to help us keep warm during the cold snap So either way whether volcanism is due to increase drastically or not we ve got to cease and desist from our fossil fuel burning right now 133 pat n says 13 Jan 2008 at 10 31 AM From the referenced Jan 10 2008 article Dr Pielke suggests that more scientists do reality checks However Pielke fails to mention that U S scientists have run into a road block in attempting to do reality checks on climate change with National Weather Service climate and streamflow data Pielke ought to know that to be true in his having received funding from NOAA NWS in years past 134 Imran says 13 Jan 2008 at 11 15 AM I think what the original article was tapping into is the general publics observation that there has been no meaningful global temperature rise in the last decade This is at odds with the alarmism that is continually being preached I agree with the point that the IPCC predictions are not meant for the short term but they create a credibility problem for themselves when the alarmist predictions don t materialise in the short term Looking at the global HADCRUT3 data set and overlaying the IPCC 2001 report range of predictions clearly shows the global

    Original URL path: http://www.realclimate.org/index.php/archives/2008/01/uncertainty-noise-and-the-art-of-model-data-comparison/comment-page-3/ (2016-02-13)
    Open archived version from archive

  • Uncertainty, noise and the art of model-data comparison « RealClimate
    trend 613 MikeN says 21 Apr 2009 at 7 39 PM Well going off the post at the top which shows various trends over short periods as part of general weather variability I m assuming a flatline comes from this and not some external forcing not in the models In that case then I think basic math would suggest that the lower end of warming is more likely than the higher end A flatline should be more likely in a 2C model than a 6C model correct 614 Duae Quartunciae says 22 Apr 2009 at 1 58 AM Hi MikeN This question has come up in another discussion and both Mike and I would love to get a more informed third opinion If I may rephrase the question I think Mike is asking What does the frequency of lulls tell us if anything about the climate sensitivity Sensitivity estimates for climate range from about 1 5C to 4 5C per 2xCO2 or equivalently from about 0 4 to 1 2C per unit forcing W m 2 Should different sensitivities result in a different frequency of lulls Can we use information about the range of variation in the short term 8 year slope to help constrain the sensitivity estimates 615 Mark says 22 Apr 2009 at 2 38 AM You d have to know how the chaotic system reacts Short answer no Long answer theoretically and in general An example is to take the variations in temperature and go how much of that is matched out by solar variation you then subtract a variation at that frequency until you get a line that is more straight than before And do that with all other variables Though that gives more the attribution rather than the sensitivity And is subject to a lot of error But that s not looking at the lulls either 616 Dave Occam says 22 Apr 2009 at 11 19 AM Dave so were you agreeing with me that a 10 year flatline if it happens would have to lower the confidence ranges for temperature increase by 2100 Are you addressing me MikeN I accidentally double posted I meant to direct my post to Martin Vermeer In case you were asking my opinion Statistically speaking I would not look at a select 10 year period a selection already biases the result but rather the full record from the date of the prediction s I would consider the prediction suspect if we got a couple years outside my bounds over the next decade exempting years of a major episodic event I think if temperatures hug the lower bound over the next few years it would make the upper 2030 bound an unlikely occurrence but not necessarily the upper 2100 bound Some models and scenarios produce very slow increases in temperatures in the first couple decades but accelerate more in the later years For example scenario A2 of the 6 SRES scenarios Fig 9 15 of my reference produces the smallest increase in temperature in 2030 but the second highest in 2100 for all models So far the IPCC predictions are holding their own Hypothetically speaking if they should require modification in the future to levels outside current bounds then I don t think we can say at this point if it is because of inaccurate models forcing sensitivities initial conditions or natural changes that were not anticipated So we couldn t say much about 2100 temperatures till that was resolved 617 MikeN says 29 Apr 2009 at 4 35 PM I think if temperatures hug the lower bound over the next few years it would make the upper 2030 bound an unlikely occurrence but not necessarily the upper 2100 bound OK not necessarily unlikely but wouldn t it then make the lower 2100 bound more likely than the upper 2100 bound Duae has hypothesized that a high positive feedback model that produces a 6C warming is as likely to produce lulls as a low feedback model that produces warming of 2C Any opinion on this By the way I don t wish to compare models of different carbon scenarios but rather models with different feedback variables 618 Dave Occam says 30 Apr 2009 at 10 39 AM Re 617 By the way I don t wish to compare models of different carbon scenarios but rather models with different feedback variables But the IPCC prediction envelope encompasses both when the authors determined the bounds of this envelope they had both in mind The bounds of their prediction were based on expert judgment not statistical computation If you want to tease out more information than what they summarized you need to address specific models and or specific scenarios but then how do you choose statistically speaking And then adding confidence limits for a chosen model is problematic for experts not to mention lay readers Re 617 OK not necessarily unlikely but wouldn t it then make the lower 2100 bound more likely than the upper 2100 bound Short answer I am not qualified to say but IMO I still think not necessarily despite the intuitive attractiveness of your assumption It all depends on how you determine likelihood and how well the causes of the slower than expected warming are understood in the future of your hypothetical scenario But we are just splitting hairs By the time we reach 2030 they will have greater understanding of climate better data and models and be able to narrow the range of plausible outcomes However there will always be some natural variation that is beyond prediction At this point in time I don t see that it matters in terms of decisions that have to be made today regarding policy around GHG emissions that affect resource spending prior to 2030 619 Mark says 30 Apr 2009 at 11 21 AM but wouldn t it then make the lower 2100 bound more likely than the upper 2100 bound It doesn t MAKE the upper bound less likely

    Original URL path: http://www.realclimate.org/index.php/archives/2008/01/uncertainty-noise-and-the-art-of-model-data-comparison/comment-page-13/ (2016-02-13)
    Open archived version from archive

  • Model-data-comparison, Lesson 2 « RealClimate
    warming say error estimates representing the noise Likewise the trend in the observational evidence would consist of only three parallel straight lines as displayed by Tamino The smoothed black line in Stefan s fig 1 1 which is not straight would therefore still contain too much insignificant noise to be very useful 3 What does the theory i e the models have to say about estimates of the acceleration 4 Tamino estimates that we may have to wait till 2015 before being able to detect that global warming since 2000 has stopped Is it agreed that positively accelerated warming might not show up until then or is this long wait unecessary if we start with 1975 instead of 2000 Tamino is a statistician Response Answering all this properly would need a scientific paper but here is what I can say in five minutes As we argued in Lesson 1 you need something around 15 year averaging to determine a robust trend given the interannual noise in the data If you want to see whether the trend is changing accelerating you d need to look at a much longer interval still IPCC has done something like that in Figure TS6 on page 37 of the technical summary This graph shows that warming has progressively accelerated i e over the last 25 years warming was faster than over the past 50 years etc Trend over the past 25 years 0 18 50 years 0 13 100 years 0 07 150 years 0 05 all in degrees C per decade more digits and error bars are given in the link stefan 58 Chuck Booth says 12 Apr 2008 at 10 59 AM Re 55 tom watson So despite your education and work experience in your field you rely on The National Business Review for scientific information I hope you had higher standards when seeking information related to your job 59 Martin Vermeer says 12 Apr 2008 at 11 41 AM Tom Watson 55 I am an EE with 4 decades of work about how electromagnetic radiation and matter interact I have spent thousands of hours trying to understand how CO2 has some property that allows for the storage of the trillions and trillions of BTU required to globally warm the earth It would have been better use of your time to first figure out that CO2 has a property affecting the transport of heat rather than its storage 60 Hank Roberts says 12 Apr 2008 at 11 59 AM the lead author of the IPCC chapter Says who Which author Which chapter Which IPCC report Show me a more recent source than this one for that statement Publication Date June 1 2001 Publisher The Heartland Institute The Third Assessment Report TAR of the United Nations Intergovernmental Panel on Climate Change IPCC expected to be released sometime in 2001 is already coming under heavy criticism from various directions But none has been more devastating than the one delivered on March 1 by one of the report s lead authors Lindzen Please check your calendar 61 Hank Roberts says 12 Apr 2008 at 12 16 PM Correspondence not a Letter Good point Has anyone asked the Editors there how they reviewed this Quoting from the link Chris provides Correspondence provides readers with a forum for comment on papers published in a previous issue of the journal or to discuss issues relevant to the geosciences Titles for correspondence are supplied by the editors In cases where a correspondence is critical of a previous research paper the authors of the criticized paper are given the opportunity to publish a brief reply Criticism of opinions or other secondary matter does not involve an automatic right of reply Refutations are always peer reviewed Other types of Correspondence may be peer reviewed at the editors discretion 62 David B Benson says 12 Apr 2008 at 1 10 PM Jamie 50 wrote It may be true that I will never understand the science in all its intricacies Probably not Nobody understands earth s climate in all its intricacies tom watson 55 A better use of your time is to explaore and read the following links http www realclimate org index php archives 2007 05 start here http www aip org history climate index html 63 Richard Ordway says 12 Apr 2008 at 1 24 PM 9 Joc but increasing scepticism I have developed towards Climate Change aka global warming Well Joc you re in good company Only 130 countries out of 130 agreed unanimously and signed on paper in 2007 2008 that it is unambigious that the Earth is warming and that it is highly likely that humans are causing it Included are the oil countries of Saudi Arabia and Venuzuela that stand to lose big time as well as Australia the USA europe Russia China etc etc etc Further With the July 2007 release of the revised statement by the American Association of Petroleum Geologists no remaining scientific body of national or international standing is known to reject the basic findings of human influence on recent climate Wikipedia 2008 http en wikipedia org wiki Scientific opinion on climate change So I am impressed Joc that you disagree I am talking to a real expert here 64 John OConnor aka joc says 12 Apr 2008 at 3 55 PM not sure if this posted correctly the first time if so please ignore this copy I have decided to post under my full name rather than just joc My apologies for the delay in responding to some of the comments on my possibly intemperate remark 9 earlier Thank you to those who responded considerately to it and particularly Matthew Brunker 53 in detailing exactly what he meant in 7 The sarcasm in 63 is best ignored 130 out 130 countries agree by that do you mean political leaders signing a document There are many things leaders do that don t have the full backing of their countries Right now I have a fairly busy day job family and other commitments hence the delay in replying I am unable to peruse and comment while at work for various reasons not least that I am paid to work at IT not browse I should clarify first my scepticism is more to the alarmism that is raised regarding the potential effects of climate change rather than climate change itself It is obvious that the climate is changing and always has I don t have a huge problem either with the proposition that man has a significant effect However I do have issues with the magnitude of the effect and also how we deal with it preferring to concentrate on adaption and wise development etc rather than an outright drive to reduce carbon emissions That is not to say pollution reduction is important that itself is crucial to make our environment liveable in It also makes a lot sense to reduce our energy consumption for a lot of other reasons For example we have changed some our energy practices at home e g use of low energy light bulbs at key locations in the house to reduce our electricity bill simply because our energy bill was way too high However and I think this is one of Lomborg s main views I think it makes far more sense to invest wisely and strategically in our future by trying to avoid catastrophes and loss of life This to me means not building in flood plains and also taking note of why the loss of life in countries in Bangladesh is so much greater in the face of floods rather than in say New Orleans It is facile to simply blame this on global warming and not to look into the development and infrastructure issues Likewise there was a lot of silly hysteria in England last year over the floods maybe it was due to climate change though a recent report seems to deny this What was obvious though and has been for some time was that floods do occur from time to time there and it is plain daft to continue building on flood plains and covering the run off areas with concrete and ashphalt I also have issues those to try and label everyone who is sceptical as being either a denialist or somehow or other connected with Big Oil This does not help your argument or any campaign related to it I m not connected and never have been connected with big oil or power companies In fact the company I work for stands has bought into carbon trading in a big way and possibly stands to make a lot of money out of it Although I trained in EE I haven t actually worked for it though I retain a strong interest in it e g I am an IEEE member and would agree that Spectrum does give a very good case for AGW and various mitigating technologies There have incidentally being some very interesting essays on the effectiveness of the whole peer review process in it s sister publication Computer in the last year or two that would go against Gavin s apparent faith in it I agree to a point with Ray Ladbury 13 regarding ignorance but I would also note that sometimes you RC and other scientists have a habit of making science sound like a High Priesthood that unless you are admitted to it you don t have a clue and therefore your argument can t be taken seriously Ok as I noted earlier my initial comment was a bit inflammatory too I hope it won t be taken as simply trolling Meltwater 22 and BPL 23 are correct scepticism based on a reaction to people isn t very logical However I do have a problem with L Brown 26 and the whole acceleration of warming The reality here is that we have been doing real temperature measurements over a relatively short period of time an astonishingly short period of time The remainder of the measurements are by using proxies e g ice cores Even Gavin has admitted recently that the proxy analysis keeps throwing up surprises I have no doubt that the calibration of the proxy data in comparison to the real current measurements are improving but I still have my doubts about it I also have a lot of doubts about how much we should depend and believe in computer models to help us evaluate future climates This is based on the practical realities of the complexity of programming My specialty is Release and Configuration Management a constant battle to ensure that very bright and able developers actually deliver reliable software to a demanding production environment It is also based on the little matter of the actual stability of the atmosphere and the daily demonstrated inability of the current Met Office systems to predict the actual weather beyond 3 5 days OK I know that this is weather not climate as RC but climate is an equally complex and chaotic system Finally as regards arrogance in Universities it has been my personal experience that while there have been some wonderful academics I was privileged to study under two in particular there is also a lot of self serving arrogance Unfortunately this also does come across sometimes in some of the articles here and some of the put downs It is always worthwhile to remember that a little courtesy can go a very long way in convincing someone Manu D 54 makes this point very well I could write a lot more and would like to but other work beckons 65 David B Benson says 12 Apr 2008 at 5 19 PM John OConnor aka joc 64 Here are two links to explore and read as time allows http www realclimate org index php archives 2007 05 start here http www aip org history climate index html and here is a graph of global temperatures since 1850 CE http tamino files wordpress com 2008 04 t3v jpg While reading and noticing the temperature has risen noticably for the past 50 years or so keep in mind that agriculture depends upon the remarkably steady climate of the Holocene Since we are rapidly headed out of that optimum temperature and precipitation pattern range there is quite a serious danger that we will leave agriculture behind 66 Lawrence Brown says 12 Apr 2008 at 5 55 PM In comment 42 Ike Solem refers to the term clean coal Sounds like the PR people in the coal industry are earning their keep Coal contains sulfur and mercury can contaminate surface and groundwater resources through acid mine drainage and can cause black lung disease to name a few of its drawbacks The term clean coal is an oxymoron no offense to anyone No matter how you slice it or sequester its burned biproducts coal is very dirty 67 tamino says 12 Apr 2008 at 6 14 PM Re 57 Geoff Wexler The temperature time series since 1975 don t support acceleration of global warming They re consistent with a constant warming rate plus red noise bearing in mind that noise can include physical processes which are essentially unpredictable like volcanic eruptions and el Nino But while there s no statistical reason to deny a strictly linear warming the physical likelihood of a strictly linear progression is vanishingly small The true signal is almost certainly nonlinear but the data so far don t enable us to confirm or quantify its nonliner behavior A straight line is perfectly consistent with the data but the thick black smoothed line shown by Stefan is also perfectly consistent with the data We simply don t yet have enough data to discriminate between these plausible alternatives On my website I addressed a comparison between the alternative hypotheses of continued warming at an unchanged rate and global warming stopped in 2001 which seems to have superceded its predecessor global warming stopped in 1998 There s no reason to believe that global warming stopped in 2001 any more than there s valid reason to believe that global warming stopped last Thursday But the data since 2001 are so sparse and the time span so short that of course it can t be disproved statistically In my opinion it s foolish of the statistically ignorant and unethical of the statistically savvy to exploit the naivete of the common person with such a claim It s rooted in the fact that most people have no real idea of the unavoidability of noise or its likely effect I also posted about what conditions would disprove this claim statistically by 2015 that will probably have happened but it depends on the data 68 Geoff Wexler says 12 Apr 2008 at 7 05 PM re 64 I think it is both important to try to be both rigorous and non rigorous on different occasions and to know the difference We should thank our lucky stars that the most alarming papers are rather controversial otherwise we might become too depressed especially as there is political paralysis But there is a difference between arguing that the climate sensitivity GW caused by doubling of CO2 is unlikely to be as high as 6 degs C and to ignoring that possibility altogether I think that the debate about this kind of issue is one of the most important of all The stronger the argument against this kind of estimate the better provided the arguments are valid In so far as 6 degs remains a reasonable but unlikely possibility I think it should certainly not be ignored Would an engineer be allowed to design a bridge or a nuclear reactor on the basis of a complete disregard of low probability outcomes The USSR did it with their nuclear reactors and according to a colleague of Gorbachov it may have contributed to the downfall of communism Finally I note that you raised a similar topic to that of my previous comment i e the acceleration of warming But my views are quite different from yours in the following ways 1 I don t agree about the need to invoke ice cores That may be an academic problem of interest to the professionals but it involves much longer time scales and no human influence The question I asked has nothing to do with the physics and just refers to the statistical analysis of the recent data It may well be possible to isolate the acceleration if not yet then soon because of the accumulation of more data 2 Even if the observed acceleration turned out to be effectively zero now it may well rise later depending on the emissions scenario or the onset of new positive feedbacks 3 The only good result would be the onset of negative acceleration A continuation of the linear trend of about 2 degs century would still be of extreme concern 69 Alex Burton says 12 Apr 2008 at 7 19 PM I am an electrical engineer too I work in research on solar thermal energy systems The control systems knowledge that being an electrical engineer gives me makes me very worried about GW We have a control system with seemingly slow responses governmental society mob psychology being asked to control the worlds climate system which apparently has nonlinearities and quite a fast response in comparison to that of the control system Add to that a delay of the order of 10 years between observed consequences melting warming etc and emissions and you have yourself a system that any student of control systems will tell you is most likely to go unstable Given this basic information I am surprised that electrical engineers the field most associated with control systems aren t jumping up and down about GW more than anybody else Alex 70 Steve Latham says 12 Apr 2008 at 7 54 PM I know that some work has been done modeling changes in oceanic acidity as carbon emissions increase I ve never seen a comparison of these models with those of temperature changes Presumably they are simpler or have much more certainty associated with them I imagine that changes in acidity would be relatively monotonic if that term can be applied in it s relationship to atmospheric CO2 I mention this for two reasons First with relevance to the current thread I m curious to learn about how tight the relation is over time between atmospheric CO2 measures and ocean acidity Second since the negative effect on the oceans of increasing acidity is uncontroversial why does there seem to be so much more focus on temperature Is it because it s so obvious or bland that the media don t pick up on it and nobody of any occupation denies it Or is it because the science of this issue is relatively young 71 Jim Eager says 12 Apr 2008 at 9 35 PM Re Tom Watson 55 Tom as others have pointed out CO2 does not absorb heat and store it very quickly it either radiates that energy back out in any direction as new IR photons and those photons in turn strike and excite other greenhouse gas molecules or it transfers the energy to other gas molecules IR inert gas or greenhouse gas as kinetic energy through collision Either way the energy remains active in the atmosphere for longer than it otherwise would before reaching space thus warming the entire atmosphere not just CO2 In addition it s not just CO2 that is at work here Ordinary water vapour is also a greenhouse gas as is methane nitrous oxide chlorofluorocarbons and a number of lesser trace gasses Water vapour is many times more abundant than CO2 and thus has a much greater capacity to intercept IR photons but unlike with CO2 human activity does not add more water vapour to the atmosphere because of relative humidity it will just condense and precipitate out The only way to add more water vapour is to increase temperature which will happen as increasing CO2 continues to add more warmth to the atmosphere In fact this is already happening at the poles where the current warming is highest and polar air is now able to hold more water vapour thus acting as a feedback adding even more warming 72 tom watson says 12 Apr 2008 at 9 41 PM Chuck Booth Says 12 April 2008 at 10 59 AM Re 55 tom watson So despite your education and work experience in your field you rely on The National Business Review for scientific information I hope you had higher standards when seeking information related to your job tom watson replies Well Chuck One s standards are simply a function of one s methods I read first I think about it I determine if the writer is using logic and sense I don t assume any person because of their education or background is to be disregarded because of some phony idea of my own self genius I also reported how I came to read that article I also asked is this true http climatedebatedaily com Martin Vermeer Says 12 April 2008 at 11 41 AM to Tom Watson 55 It would have been better use of your time to first figure out that CO2 has a property affecting the transport of heat rather than its storage tom watson replies I find it interesting that you made that statement I believe it is a silly miss interpretation of the point of my original post And in that you don t seem to know how to be specific I will point out that even CO2 has a property called it s specific heat and plants by the way fix hydrogen to CO2 to create hydrocarbons the O2 from the water is what goes back into the air So you say CO2 has a property affecting the transport of heat rather than its storage I am working on my what the hell is air page but this is very very rough and not peer reviewed http toms homeip net global warming what the hell is air html 73 Ken Coffman says 12 Apr 2008 at 9 49 PM Excellent a rarified gas does not store energy it transports it Thanks for the clarification 74 Holly Stick says 12 Apr 2008 at 9 49 PM 69 Alex Burton s comment on control systems is fascinating because it s from an unfamiliar professional viewpoint yet clear enough for me nonengineer nonscientist with some understanding of ecosystems to understand what he means I think Maybe someone should make a blog or a wiki on how to explain the likely effects of global warming to various professionals in terms that they will understand How to explain AGW to an electrical engineer an economist a city planner etc 75 Timothy Chase says 12 Apr 2008 at 9 57 PM Off Topic Al Gore has a new slide show Al Gore New thinking on the climate crisis http www ted com talks view id 243 76 Miss Priss says 13 Apr 2008 at 1 02 AM In response to comment 66 I think you re splitting hairs a bit Mr Brown clean coal is a term that simply refers to a specific method of refining via chemicals steam and gasification so as to better rid coal of its sulfur dioxide I actually grew up in the mining industry soft rock and hard and even worked for a time in the coal industry indeed clean coal is cleaner at least in the sense that the carbon dioxide and the flue are recouped About coal however and the widespread use thereof your point is well taken And it s the anti nuclear groups we have to thank for that preponderating use In fact uranium generates gigantic amounts of energy in a very small space which wind and solar combined cannot come close to and yet those who say otherwise those who are anti nuclear in other words have brought the world 400 million more tons of coal used per year because for thirty years now since 1979 following the Three Mile Island accident we ve been using more and ever more coal In fact the meltdown of the uranium core in 1979 at Three Mile Island was so overblown by anti nuclear groups that it went virtually unnoticed how the containment vessel at Three Mile Island had done its job and prevented any significant release of radioactivity To the good Mr Daniel Goodwin in comment 39 above your hostility toward industrialization echoed and answered incidentally here http blog askmisspriss com p 64 is something you would do well to reconsider As Thomas Hobbes famously noted life before industrialization was solitary poor nasty brutish and short 77 Richard Pauli says 13 Apr 2008 at 1 14 AM All scientists should immediately halt whatever they are doing and regard these two charts Global Average Temperature vs Number of Pirates http www venganza org about open letter All Theories Proven With One Graph by Don Grace of Florence Alabama http www jir com graph contest index html OneGraph 78 John Mashey says 13 Apr 2008 at 2 08 AM re 64 John O Connor I also have a lot of doubts about how much we should depend and believe in computer models to help us evaluate future climates This is based on the practical realities of the complexity of programming My specialty is Release and Configuration Management 1 You are almost certainly over generalizing from the kind of software with which you are familiar a common problem I m familiar with it also many current R CM tools are remote descendants of work we did 30 35 years ago at Bell Labs to help manage software to meet telephone company reliability standards Some of these were 200 300 person projects Most were smaller thank goodness 2 We had a similar case in http www realclimate org index php archives 2007 11 bbc contrarian top 10 wherein a well educated scientist was convinced that climate models couldn t be useful because he was used to models protein folding where even a slight mismodel of the real world at one step caused final results to diverge wildly just as a one byte wrong change in source code can produce broken results See 197 where I explained this to him and 233 where light dawned and if you re a glutton for detail 66 75 l 89 1230 132 145 151 166 for a sample Climate models aren t the same as weather models 79 Ian Castles says 13 Apr 2008 at 2 50 AM Re 67 Tamino I take your point that there s no reason to believe that global warming stopped in 2001 any more than there s valid reason to believe that global stopped last Thursday But by the same line of argument doesn t it follow that there s no valid reason to assert as the IPCC did in Chapter 9 of the WGI contribution to AR4 that Six additional years of observations since the TAR SHOW that temperatures ARE CONTINUING to warm near the surface of the planet p 683 EMPHASES added If six years is too short a period from which to conclude that warming has stopped how can it be a long enough period from which to show conclusively that warming is continuing 80 Geoff Wexler says 13 Apr 2008 at 5 08 AM re 67 Thanks for discussing my comment First a correction I quoted your starting point as 2000 instead of 2001 This mistake of mine was provoked by Jeremy Paxman on BBC 2 s Newsnight who asked his interviewees whether it was true that there had been no global warming this century i e since 2000 Leading UK contrarian Nigel Lawson said yes and ex climatologist Chris Rapley ex BAS now Science Museum also said yes but then added that there were always short term fluctuations This suggested that the whole period of eight years was being dismissed as a fluctuation I thought that Rapley s answer might have been slightly stronger and so I checked out your site I then decided that it was a pity that you had not been on Newsnight to repeat that a the least square fit this century was positive in contradiction to Lawson s suggestion and b that it was insignificant anyway as Rapley had argued but rather vaguely I agree about the physics except that I think that it makes for more clarity to talk about one thing at a time which is why I liked your approach unethical of the statistically savvy I wonder how you would classify Nigel Lawson He was the UK s chancellor for several years He and his colleague Nigel Calder also from Channel 4 s Swindle programme have been busy writing popular books Perhaps Realclimate might consider reviewing them Response I reviewed Calder s book here and we discussed Lawson s arguments a while ago If there is something new in his latest book we might revisit it gavin 81 Jim Eager says 13 Apr 2008 at 9 04 AM Re Tom Watson 72 Tom right away I see one problem with your what the hell is air page It appears that you are assuming that water vapour is equally mixed throughout the atmosphere when it is not As you go higher in the atmosphere and as temperature drops the atmosphere holds less and less water vapour as it condenses out There is relatively little in the upper troposphere and almost none in the stratosphere CO2 on the other hand is well mixed throughout the entire troposphere and into the stratosphere In fact above the mid troposphere CO2 dominates water vapour as a greenhouse gas It appears that your basic premise is the there is too little CO2 in the atmosphere to make a difference argument If so you need to do some more homework before you page is ready for prime time 82 Jim Cripwell says 13 Apr 2008 at 9 10 AM Please excuse an off topic item I have just found the following http nsidc org arcticseaicenews index html which is the 2008 news from NSIDC on this year s Arctic ice melt I believe NSIDC may put out a forecast for the expected amount of ice in the Arctic in September 2008 in the near future 83 tamino says 13 Apr 2008 at 9 34 AM Re 79 Ian Castles Whether or not the six additional years indicate further warming depends on exactly what years they re talking about Six years is a very short time but if the trend and the noise both go up then it s possible to get statistical significance in spite of the brevity of the time span If they re referring to 1999 0 to 2005 0 or 2000 0 to 2006 0 then the numbers support their claim if they re referring to 2001 0 to 2007 0 then the numbers don t support the claim This is true using either GISS or HadCRU data Despite passing or failing significance tests in a broader sense drawing conclusions from a mere six years of data given the noise level is at best dicey There s also the nontrivial issue of the statistical impact of choosing from a number of possible starting and ending points in this case passing significance for a mere six years depends on the strong warming observed from 1999 to 2001 In my opinion whether it s defensible or not their statement is ill advised 84 Lawrence Brown says 13 Apr 2008 at 10 03 AM Referring to comments 57 by Geoff Wexler and 64 by John O about my comment re that global warming is accelerating I was referring to a comment in the 2007 IPCC report IPCC 2007 Summary for Policy Makers The Physical Science Basis It states under the heading Direct Observations of Recent Climate Change The linear warming trend over the last 50 years 0 13C 0 10C to 0 16C per decade is nearly twice that for the last 100 years The rate of increase over a longer term than that discussed in the correspondence by Roger Pielke Jr is increasing At least according to the latest IPCC report 85 David B Benson says 13 Apr 2008 at 11 07 AM Miss Priss 79 wrote As Thomas Hobbes famously noted life before industrialization was solitary poor nasty brutish and short I believe he was referring to life before govenments If not then he was certainly wrong about life during high medieval times life was communial wealthy enough to be able to support extensive religious holidays and the nasty brutish and short bit was reserved for common soldiers Industrialization has not been an un mixed blessing somehow there are more poor people in the world with an increasing number of who s lives have become nasty brutish and short 86 David B Benson says 13 Apr 2008 at 11 10 AM Lawrence Brown 84 Yes You can see it yourself here http tamino files wordpress com 2008 04 t3v jpg entitled temperatures since 1850 although I believe the graph to show 5 year running averages 87 Barton Paul Levenson says 13 Apr 2008 at 12 06 PM tom watson writes I am an EE Saw it coming with 4 decades of work about how electromagnetic radiation and matter interact I have spent thousands of hours trying to understand how CO2 has some property that allows for the storage of the trillions and trillions of BTU required to globally warm the earth I have concluded that if e MC 2 then CO2 driving climate temperatures is a hoax You have concluded wrong CO 2 doesn t store energy other than in the conventional way of having a non zero Kelvin temperature It absorbs infrared light heats up a bit and radiates like any hot object whereupon some of the radiation goes back to the ground heating the ground up If you want to understand the process I recommend reading through a book like John T Houghton s The Physics of Atmospheres 3rd ed 2002 or Grant W Petty s A First Course in Atmospheric Radiation 2006 and of course working all the problems Or for a quick precis try here Greenhouse 101 It is easy to demonstrate that the radiative equilibrium temperature of the Earth is well below freezing Earth is habitable at 288 K mean global annual surface temperature instead of 255 K because of the greenhouse effect If it didn t exist we wouldn t exist either 88 Jim Cripwell says 13 Apr 2008 at 12 09 PM Ref 83 I agree basically with everything Tamino says However it seems to me that there are two legitimate questions that can be asked about what is happening to global temperature anomalies The first question is Have temperatures risen in recent history e g over the last 40 years I think pretty well everyone agrees that the answer to that question is Yes It is quite legitimate to put a straight line fit through the data points and measure the average rate of rise of temperature The second question is What is happening to temperatures now whenever now happens to be As of this time now is April 2008 Or in other words what is the slope of the temperature time graph as of now Is it positive or negative It seems to me that there ought to be statistical methods to answer this question and they probably only use data for a few recent years I cannot see why temperatures taken 10 years or more ago tell us very much about what the slope of the temperature time graph is as of now My own very limited analysis convinces me that the current slope of the temperature time graph is negative 89 Martin Vermeer says 13 Apr

    Original URL path: http://www.realclimate.org/index.php/archives/2008/04/model-data-comparison-lesson-2/comment-page-2/ (2016-02-13)
    Open archived version from archive



  •