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  • Climate Science « RealClimate
    and will come online on Monday called Global Warming II Create Your Own Models in Python or Fortran This takes advantage of new code grading machinery at Coursera to automatically run your code through its paces There is also a peer code review step where you will get feedback on your commenting and variable naming skills and provide feedback to others The class gives detailed instructions to create simple models of time evolution of global temperature the ice albedo feedback drop into snowball Earth an ice sheet and a shallow water circulation model The class is intended for people who are new to programming or new to Python or wish to enhance their understanding and appreciation of some cool science of Earth s climate system The classes are supported by the same interactive on line interactive climate system models as before at http climatemodels uchicago edu with some new additions both of which generate animations of their time dependent solutions One is a Hurricane simulator using a model from Kerry Emanuel which can demonstrate the sensitivity of ocean temperature ocean mixing and atmospheric structure on hurricane evolution The other the Permafrost model is a simulation of a soil or sediment column in which ice and methane hydrate can form The model shows how the brine salinity thermodynamically excludes methane hydrate from forming until you get to the base of the permafrost zone and also how long it takes to warm a soil column by warming the surface This model shows why I do not believe in an imminent methane climate catastrophe from Arctic Ocean methane hydrates Comments pop up 21 Unforced Variations Feb 2016 Filed under Climate Science Open thread group 1 February 2016 This month s open thread Just so you know a lot of people have complained that these threads have devolved particularly when the discussion has turned to differing visions of solutions and have therefore become much less interesting Some suggestions last month were for a side thread for that kind of stuff that wouldn t clog interesting issues of climate science Other suggestions were for tighter moderation The third suggestion is that people really just stay within the parameters of what this site has to offer knowledgeable people on climate science issues and context for the science that s being discussed elsewhere For the time being let s try the last one combined with some moderation The goal is not to censor but rather to maintain somewhere where the science issues don t get drowned out by the noise Comments pop up 103 Older Entries Site Google Custom Search Recent Comments What is the best description of the greenhouse effect Patrick Eriksson What is the best description of the greenhouse effect Kevin McKinney Anti scientists Carbomontanus What is the best description of the greenhouse effect Spencer Marvel et al 2015 Part III Response to Nic Lewis SteveS What is the best description of the greenhouse effect Chris Colose Blizzard Jonas and the slowdown of the Gulf

    Original URL path: http://www.realclimate.org/index.php/archives/category/climate-science/ (2016-02-13)
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  • Marvel et al (2015) Part III: Response to Nic Lewis « RealClimate
    K K Lo E E Matthews S Menon R L Miller V Oinas A O Oloso J P Perlwitz M J Puma W M Putman D Rind A Romanou M Sato D T Shindell S Sun R A Syed N Tausnev K Tsigaridis N Unger A Voulgarakis M Yao and J Zhang Configuration and assessment of the GISS ModelE2 contributions to the CMIP5 archive J Adv Model Earth Syst vol 6 pp 141 184 2014 http dx doi org 10 1002 2013MS000265 A Otto F E L Otto O Boucher J Church G Hegerl P M Forster N P Gillett J Gregory G C Johnson R Knutti N Lewis U Lohmann J Marotzke G Myhre D Shindell B Stevens and M R Allen Energy budget constraints on climate response Nature Geoscience vol 6 pp 415 416 2013 http dx doi org 10 1038 ngeo1836 Comments pop up 12 12 Responses to Marvel et al 2015 Part III Response to Nic Lewis 1 Kevin McKinney says 9 Feb 2016 at 9 40 PM Thanks Gavin Not surprising perhaps but interesting nonetheless 2 Tim F says 10 Feb 2016 at 10 54 AM Lewis appraisal has indeed turned up one error and suggested further sensitivity experiments which have both ended up strengthening the robustness of the basic result Mwahaha This gets to one of the most fundamental flaws of almost all climate deniers the idea of robustness Robust data survives if you find an error and fix it Therefore when the fundamental hypothesis is sound finding an error is not that big a deal and in fact most of the time correcting errors should strengthen rather than weaken any bottom line conclusion that aligns with reality Robust data also survives bootstrapping If you start a temperature correlation in 1998 and end it in 2012 then you get one result Start in 1997 and you get a different result A scientist would say that looks like a noisy trend Instead of focusing on any one result measure the correlation for every fifteen or twenty year window starting as far back as we have data and see whether the average slope is significantly different from zero that is pretty close to basic data smoothing something about the 1998 crowd particularly seems to miss To find data points that particularly bias the conclusion randomly remove points from the set and see how well the overall result holds up Legitimate data is robust You can easily tell the difference between that and spurious conclusions with some basic tests that I almost never see from people who seem particularly motivated to deny warming 3 DF says 10 Feb 2016 at 11 19 AM I just wonder why there are no mentioning of cloud feedback effects in the paper As far as I understand the net surface warming is currently around 0 6 W m 2 Wikipedia Earths Energy budget and the cloud feedback effect is of the same magnitude ref fig 7 10 in IPCC AR5 WGI 4 Matt Skaggs says 10 Feb 2016 at 12 12 PM Thanks for taking the time to write a detailed response to a blog post Gavin wrote Lewis has also suggested that it is statistically permissible to eliminate outliers in the ensembles because he doesn t like the result it is not These are simply post hoc justifications for not wanting to accept the results This is written as a blanket denunciation for post hoc decisions even though the run that Nic Lewis criticized looks wildly implausible As somewhat of a layman it seems that conclusions could only be improved by removing implausible results Can you elaborate a bit on why this would be statistically impermissible Response Calculating the forced response to any particular effect is done by integrating over all the ensemble members which have varying internal variability With a finite ensemble in these simulations there are always 5 you only get to estimate that With more resources you could do much larger ensembles and have a better estimate of course The key however is to integrate over the whole space of internal variability which includes variations in the North Atlantic Ocean convection There will be ensemble members that have decreases and some with increases but if you just remove runs with negative responses you are obviously biasing your sample It is much better to use the spread to estimate the sampling uncertainty gavin 5 MartinM says 11 Feb 2016 at 2 14 AM First of all thanks for putting the time in on this That said there seem to be some errors in the corrected table S1 The ECS iRF value for land use efficacy is given as 1 27 which is inconsistent with the corresponding ECS in fig 1 of 4 2 K The latter figure as well as my own attempt at reproducing the numbers give an efficacy of 1 83 For the TCR ERF case my numbers broadly agree with your efficacies but most of the TCRs listed in fig 1 are inconsistent to varying degrees The ECS ERF case is trickier since I m considerably less confident in my own numbers here but there are definitely inconsistencies between table S1 and fig 1 for several entries a land use ECS of 3 K doesn t fit with an efficacy of 1 64 similarly ozone ECS of 1 2 K vs efficacy 0 7 and volcanic ECS of 1 K vs efficacy 0 73 FWIW my numbers for those are land use ECS 2 9 K eff 1 26 ozone ECS 1 4K eff 0 62 volcanic ECS 1 75K eff 0 76 On a slightly more positive note the error bars on your efficacies look too wide to me by about 50 Entirely possible it s my own calculations that are wrong but it might be worth double checking just in case you have some more positive results lurking in there Response I ll check the numbers later today But the error bars are

    Original URL path: http://www.realclimate.org/index.php/archives/2016/02/marvel-et-al-2015-part-iii-response-to-nic-lewis/ (2016-02-13)
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  • Aerosols « RealClimate
    flavours signify etc There is an impressive list of attendees with a very diverse range of views on just about everything and so I am looking forward to very stimulating discussions More Comments pop up 26 The mystery of the offset chronologies Tree rings and the volcanic record of the 1st millennium Filed under Aerosols Climate Science Paleoclimate group 19 February 2015 Guest commentary by Jonny McAneney Volcanism can have an important impact on climate When a large volcano erupts it can inject vast amounts of dust and sulphur compounds into the stratosphere where they alter the radiation balance While the suspended dust can temporarily block sunlight the dominant effect in volcanic forcing is the sulphur which combines with water to form sulphuric acid droplets These stratospheric aerosols dramatically change the reflectivity and absorption profile of the upper atmosphere causing the stratosphere to heat and the surface to cool resulting in climatic changes on hemispheric and global scales Interrogating tree rings and ice cores Annually resolved ice core and tree ring chronologies provide opportunities for understanding past volcanic forcing and the consequent climatic effects and impacts on human populations It is common knowledge that you can tell the age of a tree by counting its rings but it is also interesting to note that the size and physiology of each ring provides information on growing conditions when the ring formed By constructing long tree ring chronologies using suitable species of trees it is possible to reconstruct a precisely dated annual record of climatic conditions Ice cores can provide a similar annual record of the chemical and isotopic composition of the atmosphere in particular volcanic markers such as layers of volcanic acid and tephra However ice cores can suffer from ambiguous layers that introduce errors into the dating of these layers of volcanic acid To short circuit this attempts have been made to identify know historical eruptions within the ice records such as Öraefajökull 1362 and Vesuvius AD 79 This can become difficult since the ice chronologies can only be checked by finding and definitively identifying tephra volcanic glass shards that can be attributed to these key eruptions sulphate peaks in the ice are not volcano specific Thus it is fundamentally important to have chronological agreement between historical tree ring and ice core chronologies The ice cores record the magnitude and frequency of volcanic eruptions with the trees recording the climatic response and historical records evidencing human responses to these events But they don t quite line up More Comments pop up 44 Older Entries Site Google Custom Search Recent Comments What is the best description of the greenhouse effect Patrick Eriksson What is the best description of the greenhouse effect Kevin McKinney Anti scientists Carbomontanus What is the best description of the greenhouse effect Spencer Marvel et al 2015 Part III Response to Nic Lewis SteveS What is the best description of the greenhouse effect Chris Colose Blizzard Jonas and the slowdown of the Gulf Stream System doiknow What is

    Original URL path: http://www.realclimate.org/index.php/archives/category/climate-science/aerosols/ (2016-02-13)
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  • Climate modelling « RealClimate
    K Folland G R Harris and J M Murphy Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model Science vol 317 pp 796 799 2007 http dx doi org 10 1126 science 1139540 N S Keenlyside M Latif J Jungclaus L Kornblueh and E Roeckner Advancing decadal scale climate prediction in the North Atlantic sector Nature vol 453 pp 84 88 2008 http dx doi org 10 1038 nature06921 Comments pop up 45 NOAA temperature record updates and the hiatus Filed under Climate modelling Climate Science Instrumental Record gavin 4 June 2015 In a new paper in Science Express Karl et al describe the impacts of two significant updates to the NOAA NCEI née NCDC global temperature series The two updates are 1 the adoption of ERSST v4 for the ocean temperatures incorporating a number of corrections for biases for different methods and 2 the use of the larger International Surface Temperature Initiative ISTI weather station database instead of GHCN This kind of update happens all the time as datasets expand through data recovery efforts and increasing digitization and as biases in the raw measurements are better understood However this update is going to be bigger news than normal because of the claim that the hiatus is no more To understand why this is perhaps less dramatic than it might seem it s worth stepping back to see a little context More References T R Karl A Arguez B Huang J H Lawrimore J R McMahon M J Menne T C Peterson R S Vose and H Zhang Possible artifacts of data biases in the recent global surface warming hiatus Science vol 348 pp 1469 1472 2015 http dx doi org 10 1126 science aaa5632 B Huang V F Banzon E Freeman J Lawrimore W Liu T C Peterson T M Smith P W Thorne S D Woodruff and H Zhang Extended Reconstructed Sea Surface Temperature Version 4 ERSST v4 Part I Upgrades and Intercomparisons Journal of Climate vol 28 pp 911 930 2015 http dx doi org 10 1175 JCLI D 14 00006 1 Comments pop up 85 Global warming and unforced variability Clarifications on recent Duke study Filed under Climate modelling Climate Science Instrumental Record IPCC group 13 May 2015 Guest Commentary from Patrick Brown and Wenhong Li Duke University We recently published a study in Scientific Reports titled Comparing the model simulated global warming signal to observations using empirical estimates of unforced noise Our study seemed to generated a lot of interest and we have received many inquires regarding its findings We were pleased with some of coverage of our study e g here but we were disappointed that some outlets published particularly misleading articles e g here here and here Since there appears to be some confusion regarding our study s findings we would like to clarify some points see also MM4A s discussion More References P T Brown W Li E C Cordero and S A Mauget Comparing the model simulated

    Original URL path: http://www.realclimate.org/index.php/archives/category/climate-science/climate-modelling/ (2016-02-13)
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  • Greenhouse gases « RealClimate
    better workshops I ve attended it was focussed deep and with much new information to digest some feel for the discussion can be seen from the ringberg15 tweets I ll give a brief overview of my impressions below More Comments pop up 83 Climate Sensitivity Week Filed under Aerosols Climate modelling Climate Science Greenhouse gases Instrumental Record IPCC Paleoclimate statistics gavin 22 March 2015 Some of you will be aware that there is a workshop on Climate Sensitivity this week at Schloss Ringberg in southern Germany The topics to be covered include how sensitivity is defined and whether it is even meaningful Spoiler yes it is what it means how it can be constrained what the different flavours signify etc There is an impressive list of attendees with a very diverse range of views on just about everything and so I am looking forward to very stimulating discussions More Comments pop up 26 How do trees change the climate Filed under Carbon cycle Climate Science Greenhouse gases group 27 October 2014 Guest commentary from Abby Swann U Washington This past month an op ed by Nadine Unger appeared in the New York Times with the headline To save the climate don t plant trees The author s main argument is that UN programs to address climate change by planting trees or preserving existing forests are high risk and a bad bet Ed There is more background on the op ed here However I don t think that these conclusions are supported by the science The author connects unrelated issues about trees conflates what we know about trees from different latitudes and fails to convey the main point tropical trees keep climate cool locally help keep rainfall rates high and have innumerable non climate benefits including maintaining habitat and supporting biodiversity More Comments pop up 49 Older Entries Site Google Custom Search Recent Comments What is the best description of the greenhouse effect Patrick Eriksson What is the best description of the greenhouse effect Kevin McKinney Anti scientists Carbomontanus What is the best description of the greenhouse effect Spencer Marvel et al 2015 Part III Response to Nic Lewis SteveS What is the best description of the greenhouse effect Chris Colose Blizzard Jonas and the slowdown of the Gulf Stream System doiknow What is the best description of the greenhouse effect James Powell Unforced Variations Feb 2016 Jim Galasyn What is the best description of the greenhouse effect Jack Barrett With Inline Responses Marvel et al 2015 Part III Response to Nic Lewis SteveS Marvel et al 2015 Part III Response to Nic Lewis steve s Marvel et al 2015 Part III Response to Nic Lewis Andrew Kerber Blizzard Jonas and the slowdown of the Gulf Stream System Hank Roberts Blizzard Jonas and the slowdown of the Gulf Stream System doiknow Marvel et al 2015 Part III Response to Nic Lewis MartinM Anti scientists Don McKenzie Marvel et al 2015 Part III Response to Nic Lewis Matt Skaggs Anti scientists mikeworst

    Original URL path: http://www.realclimate.org/index.php/archives/category/climate-science/greenhouse-gases/ (2016-02-13)
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  • Instrumental Record « RealClimate
    and apparent acceptance in the scientific community there are reasons to be skeptical of the existence of a hiatus or pause in global warming Ed see also this previous post We have examined this issue in a series of three recent papers which have converged on the conclusion that there is not now and there never has been a hiatus or pause in global warming More Comments pop up 92 And the winner is Filed under Climate modelling Climate Science Instrumental Record IPCC group 17 November 2015 Remember the forecast of a temporary global cooling which made headlines around the world in 2008 We didn t think it was reliable and offered a bet The forecast period is now over we were right the forecast was not skillful Back around 2007 8 two high profile papers claimed to produce for the first time skilful predictions of decadal climate change based on new techniques of ocean state initialization in climate models Both papers made forecasts of the future evolution of global mean and regional temperatures The first paper Smith et al 2007 predicted that internal variability will partially offset the anthropogenic global warming signal for the next few years However climate will continue to warm with at least half of the years after 2009 predicted to exceed the warmest year currently on record The second Keenlyside et al 2008 forecast in contrast that global surface temperature may not increase over the next decade as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming This month marks the end of the forecast period for Keenlyside et al and so their forecasts can now be cleanly compared to what actually happened This is particularly interesting to RealClimate since we offered a bet to the authors on whether the results would be accurate based on our assessment of their methodology They ignored our offer but now the time period of the bet has passed it s worth checking how it would have gone More References D M Smith S Cusack A W Colman C K Folland G R Harris and J M Murphy Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model Science vol 317 pp 796 799 2007 http dx doi org 10 1126 science 1139540 N S Keenlyside M Latif J Jungclaus L Kornblueh and E Roeckner Advancing decadal scale climate prediction in the North Atlantic sector Nature vol 453 pp 84 88 2008 http dx doi org 10 1038 nature06921 Comments pop up 45 Older Entries Site Google Custom Search Recent Comments What is the best description of the greenhouse effect Patrick Eriksson What is the best description of the greenhouse effect Kevin McKinney Anti scientists Carbomontanus What is the best description of the greenhouse effect Spencer Marvel et al 2015 Part III Response to Nic Lewis SteveS What is the best description of the greenhouse effect Chris Colose Blizzard Jonas and the slowdown of the Gulf Stream System doiknow

    Original URL path: http://www.realclimate.org/index.php/archives/category/climate-science/instrumental-record/ (2016-02-13)
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  • Marvel et al (2015) Part 1: Reconciling estimates of climate sensitivity « RealClimate
    Bayesian estimation of climate sensitivity based on a simple climate model fitted to observations of hemispheric temperatures and global ocean heat content Environmetrics vol 23 pp 253 271 2012 http dx doi org 10 1002 env 2140 D T Shindell Inhomogeneous forcing and transient climate sensitivity Nature Climate Change vol 4 pp 274 277 2014 http dx doi org 10 1038 nclimate2136 Comments pop up 30 30 Responses to Marvel et al 2015 Part 1 Reconciling estimates of climate sensitivity 1 Eli Rabett says 5 Jan 2016 at 12 05 AM The implication being that the geographical separation of most of the forcings and CO2 to an extent at least low down in the atmosphere near cities would allow one to tease out a better estimate for TCR or in other words to define a local regional TCR 2 Barton Paul Levenson says 5 Jan 2016 at 6 40 AM I would very much like to see your time series data especially for aerosols Response Here gavin 3 Chip Knappenberger says 5 Jan 2016 at 9 15 AM Gavin Thanks for the article What about the notion that in the real world the forcings don t act in isolation and therefore the spatial and temporal distribution is more homogenous when the forcings are taken together than in the isolated model runs This increased homogeneity then may alter the how quickly the land and ocean temperatures respond and make a different to the projection of the forcing onto the ocean and hence the ocean heat content change and return the real world combination of forcing efficacy closer to that of CO2 Thanks for your thoughts Chip Response That s a testable proposition even if it s unlikely to be true given that these are relatively small perturbations on a complex system where you would expect linearity to hold And wouldn t you know it we have already tested it gavin 4 PaulS says 5 Jan 2016 at 10 52 AM Hi Gavin The low net historical iRF efficacy result appears to be dominated by very strong cooling aerosol efficacy However capturing the full aerosol cloud forcing requires an interactive troposphere which presumably is not included in the iRF calculation Isn t this result largely a consequence of the iRF setup not reflecting the full aerosol forcing rather than efficacy Though AR5 s aerosol forcing estimate was weighted strongly by satellite studies which only looked at the cloud albedo effect plus an ad hoc positive longwave adjustment so maybe it makes sense in practice For the ERF result the low net historical efficacy result appears to be dominated by low GHG efficacy Would historical GHG have a substantially different spatial structure than CO2 alone or are there other factors affecting efficacy here The robust low efficacy of Ozone is interesting Would be good to see how well this is supported across models 5 Barton Paul Levenson says 5 Jan 2016 at 11 12 AM Unless I m reading the documentation wrong perhaps I am this is data from simulations Are there time series estimates for aerosols available that are from observations Or at least some kind of accounting based model 6 Chip Knappenberger says 5 Jan 2016 at 12 15 PM Thanks for the link to the other Marvel et al 2015 paper Let me summarize my understanding to make sure that it is in line with your findings and their implications Basically your conclusions are that the combination of historical forcings from all causes has resulted in less of a rise in the global average surface temperature than would have occurred had the change in total forcing been due to CO2 alone Do I have this right Response Yes gavin As a check of this one could comparing the climate model simulations of temperature change using the historical forcing runs with the temperature change produced by the same models under CO2 only forcing runs at times of equivalent total forcing change Presumably the temperature rise would be greater in the latter set of runs Is this also correct Response Yes And yes this is effectively what is done in comparing the actual TCR which comes from a 1 increasing CO2 run gavin Thanks for bearing with me 7 Jim Baird says 5 Jan 2016 at 12 28 PM Should we not be unrealising a lot more radiative imbalance by creating energy moving surface heat to the ocean abyss through heat engines In part this is a conversion of global warming to global energy and the relocation of the remaining heat makes minimal impact on the temperature of the massive ocean deep 8 ScienceNotDenial says 5 Jan 2016 at 6 18 PM What about the feedbacks that are not normally well represented by ECS and normally fall into the Earth System Climate Sensitivity stuff like the Arctic Ice cover which now has trends over decades closer to what was seen on centuries in paleoclimate http i713 photobucket com albums ww133 Sane Person Arctic 20Meltdown Sea Ice models v reality 2012 jpg Response Sea ice change is specifically included in calculations of ECS It isn t an additional feedback gavin 9 Hank Roberts says 5 Jan 2016 at 11 48 PM interactions between forcing agents Any speculation on the likelihood of other unexpected interactions emerging either among known chemical compounds or novel ones We know that new persistent organic chemicals continue to be invented and produced Chlorofluorocarbons were a surprise and if industry had chosen to produce analogous bromine compounds instead we d have been toast before we identified the problem see Crutzen s Nobel speech http www nobelprize org nobel prizes chemistry laureates 1995 crutzen lecture pdf This brings up the nightmarish thought that if the chemical industry had developed organobromine compounds instead of the CFCs or alternatively if chlorine chemistry would have run more like that of bromine then without any preparedness we would have been faced with a catastrophic ozone hole everywhere and at all seasons during the 1970s probably before the atmospheric chemists had developed the necessary knowledge to identify the problem and the appropriate techniques for the necessary critical measurements Noting that nobody had given any thought to the atmospheric consequences of the release of Cl or Br before 1974 I can only conclude that mankind has been extremely lucky that Cl activation can only occur under very special circumstances This shows that we should always be on our guard for the potential consequences of the release of new products into the environment Continued surveillance of the composition of the stratosphere therefore remains a matter of high priority for many years ahead How s that surveillance coming Anyone publishing 10 Mike M says 6 Jan 2016 at 12 39 PM This might be much the same question Chip Knappenberger asked but in a different form for Otto et al 2013 the estimated TCR without taking account of the efficacies is 1 3ºC which is on the low side of other estimates but with this effect accounted for it is closer to 1 8ºC Does this mean that in Figure 1 the ratio of the slope of the green line to the slope of the purple line is 1 8 1 3 Response Almost The correction is to the TCR slope which is CO2 only and the GHG slope is not quite the same Close though gavin 11 Chris Colose says 6 Jan 2016 at 9 15 PM Thanks for the post I must be confused but why do the volcanic only forcings red dots hover around a positive value in the first graph Even the negative values don t seem negative enough even after decadal averaging I was initially wondering how well volcanic periods would fall cleanly on a regression line if the spatial structure of the forcing was that relevant in setting the efficacy factor since some events have been expressed differently e g Pinatubo pretty symmetric El Chichon in the North Agung in the South 12 Dan H says 8 Jan 2016 at 12 32 PM How well known is the assumption that climate sensitivity is a constant This would accurately explain the temperature response in a closed controlled system but can we say the same in an open and chaotic system such as the Earth s atmosphere Obviously over a rather large range 0 100 CO2 it would not hold But over how wide a range can we assume a constant response 13 Aubrey Meyer says 8 Jan 2016 at 1 41 PM In the light of the Comment Question Answer above re quoted below can you please advise what the adjusted RF atmospheric CO2 values should now read for RCP scenarios 2 5 4 5 6 0 8 5 Requote for Otto et al 2013 the estimated TCR without taking account of the efficacies is 1 3ºC which is on the low side of other estimates but with this effect accounted for it is closer to 1 8ºC Does this mean that in Figure 1 the ratio of the slope of the green line to the slope of the purple line is 1 8 1 3 Response Almost The correction is to the TCR slope which is CO2 only and the GHG slope is not quite the same Close though gavin 14 Todd Friesen says 8 Jan 2016 at 8 58 PM Question for Gavin or Kate or anyone Based on NASA s CMIP5 forcing model year 2012 has a greenhouse forcing of 3 54 Wm2 ozone has 0 45 Wm2 atmospheric aerosols have 0 89 Wm2 combined direct indirect and land use has 0 19 Wm2 all based on iRF If I apply the adjustments specified in the paper based on TCR to make equivalent to GHGs then I get revised forcings of 3 54 0 24 1 19 and 0 68 respectively Put it all together results in a forcing of 1 91 W m2 out of a total of 3 78 for GHGs and Ozone I ve ignored volcanoes and solar for simplicity The ratio would be 1 79 W m2 out of 3 66 W m2 with the aerosol adjustments in Schmidt 2014 Is my understanding correct that aerosols and land use then offset half of the GHG Oz forcing So instead of 0 9C of warming relative to pre industrial we would have closer to 1 8C without them The AR5 chart measuring human contribution to warming from 1950 2010 shows a much smaller aerosol offset ie 0 9C of warming without other anthro instead of 0 7C of warming with The IPCC chart appears to assume no adjustments to the iRF I would appreciate comment to see if I m understanding the implications here clearly Goals of limiting warming to 1 5C or 2 0C aren t going to be easy without aerosol offsets which could dissipate quickly as we reduce CO2 pollution Thank you very much for sharing the study publicly 15 Chris Machens says 9 Jan 2016 at 7 15 AM Re Dan H 12 asked How well known is the assumption that climate sensitivity is a constant A quote from Gavin http www realclimate org index php archives 2013 01 on sensitivity part i In practice people often mean different things when they talk about sensitivity For instance the sensitivity only including the fast feedbacks e g ignoring land ice and vegetation or the sensitivity of a particular class of climate model e g the Charney sensitivity or the sensitivity of the whole system except the carbon cycle the Earth System Sensitivity or the transient sensitivity tied to a specific date or period of time i e the Transient Climate Response TCR to 1 increasing CO2 after 70 years As you might expect these are all different and care needs to be taken to define terms before comparing things there is a good discussion of the various definitions and their scope in the Palaeosens paper http www nature com nature journal v491 n7426 full nature11574 html I have no estimates but with all the inertia in the system Ocean and Air and with changes taken place in these systems transient constraints a transient response will likely be on the higher estimate scale Because for instance the capability to sequester carbon by natural systems will be impaired until the system settles at a new climate equilibrium state 16 Kevin McKinney says 9 Jan 2016 at 9 14 AM I suppose this is close to OT but it s well worth checking out Dr Marvel s blog Her writing is crisp and funny and despite the wisecracking has some rather thoughtful things to say For instance Climate models are highly misunderstood A surprising number of people seem to be under the impression that a model is basically a large diorama and that climate scientists are hired based on their ability to safely use plastic scissors construction paper and googly eyes http marvelclimate blogspot co uk m 1 17 dc says 10 Jan 2016 at 5 54 PM Nic Lewis has a post at WUWT claiming the conclusions of Marvel et al have no credibility ironic that he posts it at WUWT The main argument seems to be the usual WUWT models are wrong garbage but there are some more technical points around efficacy values that are harder for non experts to evaluate http wattsupwiththat com 2016 01 10 appraising marvel et al implications of forcing efficacies for climate sensitivity estimates anyone care to comment Response It s mostly confused but we ll have some sensitivity tests to address a couple of the technical points next week gavin 18 Hank Roberts says 10 Jan 2016 at 8 21 PM What s an impulse response function in a climate model http onlinelibrary wiley com doi 10 1002 2014GB005074 epdf An impulse response function for the long tail of excess atmospheric CO2 in an Earth system model 19 Salamano says 11 Jan 2016 at 5 37 AM Re 17 I would also be interested to hear more about the regression model used for the iRF efficacy estimates potentially creating the seemingly un physical situation where a zero forcing causes a non zero effect on temperature Response You should note that there are lags in the system that extend beyond a decade Thus expecting each decade s temperature and forcing to line up perfectly is too optimistic Instead one expects temperatures to lag forcing by some amount and this leads to a small shift in the temperatures w r t the forcing An alternate way of doing the calculation using the last decade minus first decade is effectively equivalent to forcing the regression through the origin and was tested in the paper it does not significantly impact the results gavin 20 Nic Lewis says 11 Jan 2016 at 7 22 AM Chris Colose you asked why do the volcanic only forcings red dots hover around a positive value in the first graph The explanation I give in my technical analysis of Marvel et al at Climate Audit is that in Figure 1 the iRF for volcanoes appears to have been shifted by 0 29 W m2 from its data values available at http data giss nasa gov modelforce Fi Miller et al14 txt Why not check it out and see whether my analysis is confused as has been suggested here Response You are confused because you are using a single year baseline when the data are being processed in decadal means Thus the 19th C baseline is 1850 1859 not 1850 We could have been clearer in the paper that this was the case but the jumping to conclusions you are doing does not seem justified gavin 21 MartinM says 11 Jan 2016 at 1 09 PM The explanation I give in my technical analysis of Marvel et al at Climate Audit is that in Figure 1 the iRF for volcanoes appears to have been shifted by 0 29 W m2 from its data values Nope Look at the purple line in Figure 1 ten decadal averages where the forcing file contains 163 years of values The mean of the first 63 volcanic values is 0 29 W m2 Nothing s been shifted you re just looking at a different timespan Response Yup The baseline is 1850 1859 the first decade To be fair that wasn t explicitly stated in the paper gavin 22 Nic Lewis says 12 Jan 2016 at 10 12 AM Gavin you write You are confused because you are using a single year baseline when the data are being processed in decadal means Thus the 19th C baseline is 1850 1859 not 1850 We could have been clearer in the paper that this was the case but the jumping to conclusions you are doing does not seem justified Thank you for providing this information To clarify does this imply that 1850 59 was used as a baseline for all the delta T and delta Q values as well as for iRF 23 MatthewRMarler says 12 Jan 2016 at 1 02 PM Is the full paper available for downloading The Supporting Information is available for downloading from NatureClimateChange but not the main paper I d like to print it out for study 24 Todd Friesen says 12 Jan 2016 at 3 01 PM 23 Matthew The full paper is available for free but it makes a difference how you access it If you click the link in the footnotes to this blog post it will show the full paper after a brief pause If you accessed it through nature com you will encounter a paywall 25 MatthewRMarler says 12 Jan 2016 at 11 20 PM 24 Todd Friesen thank you but that link will not let me download 26 nobodysknowledge says 22 Jan 2016 at 6 00 AM Todd Friesen says Question for Gavin or Kate or anyone Is my understanding correct that aerosols and land use then offset half of the GHG Oz forcing So instead of

    Original URL path: http://www.realclimate.org/index.php/archives/2016/01/marvel-et-al-2015-part-1-reconciling-estimates-of-climate-sensitivity/ (2016-02-13)
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  • Marvel et al (2015) Part 2: Media responses « RealClimate
    case you had to read six paragraphs down to get the message people would care about and even argue heatedly about which could have sparked headings like Global Warming From CO2 Likely Lowballed Instead the web special opened with Estimates of future global temperatures based on recent observations must account for the differing characteristics of each important driver of recent climate change which sounds a bit ho hum if not well duh The whole second paragraph was taken up with definitions and so on The heading Examination of Earth s Recent History Key to Predicting Global Temperatures didn t seem to be on point at all 5 patrick says 5 Jan 2016 at 8 04 AM it is always a struggle to concisely say why a paper is interesting while not overselling it or being too technical Very well observed Ditto paragraph 2 I appreciated the release very much and was glad to have it Disinformers saw fossil fuels and cooling together in the same sentence and they popped like bovine methane They would not have read the next two sentences or cared to comprehend the whole paragraph You clarify it they ll blur it on purpose It s the method And it s the full extent of their capacity But this does point out the need for educating about aerosols both to further understanding of climate science and to protect human health as the case may be I appreciated the topical December 7 image in the release especially because I was looking at how the BBC World Service More or Less trivialized and obscured a good recent paper by Rohde and others on the health effects of pollution notably around Beijing notably from particulate matter of less than 2 5microns etc They also obfuscated probabalistic statements about flooding events What they did was they made a hash they pretended it was ice cream and they put a cherry on top Thank you CM for all of your remarks It s a dilemma no doubt whether to try to do more with the release which suits people like me or to do less to minimize potential handles for disinformers to grab The abstract is brief and clear on what the paper is about and the release linked that plus some supplementary materials 6 CM says 5 Jan 2016 at 10 57 AM Patrick 5 Good point about the picture which matters I ve also been told that the reading most people take away from a newspaper story is the heading and the picture caption The caption did a very good job using the current interest story in the picture to make the study s point about the unequal geographical impact of aerosols or so I thought 7 patrick says 5 Jan 2016 at 3 07 PM CM 6 Copy Press release team please copy Thanks for your informed perception I subscribe to all of your remarks On top of everything pun intended I can now characterize what the BBC World Service has been doing thanks to remarks by CM at 4 It s the cherry on the hash fallacy So NASA GISS press release team don t pull back The good news is the world wants press releases and you have the credibility Comments from the experimenters are a good thing An informal edge is o k 8 MA Rodger says 6 Jan 2016 at 12 51 PM The post in describing the nonsense from the Express Daily Rail and also scientific chaos mild confusion solved by plucky researchers as being newsworthy perhaps misses the idea that newspapers TV channels can be institutionally in denial The BBC s Roger Harrabin has facebooked on this in recent days Are the BBC climate change deniers as well as featuring on a Radio 4 complains programme on the same subject linked on Facebook and 5 mins from 15 30 back in December A TV journo is a bit different to a print journo but Harrabin is pointing to the small amount of time available to put a TV story across perhaps 110 words But the journalist is not in control of what the editor allows to be put on air and his words may be edited down to fit the space by the journo or by the editor and probably in a rush Simply the news is part of the media It is entertainment Thus we get The Terminator at Paris COP21 And we don t get mention of AGW with every climate weather story just as sunrise goes without mention on the media for days on end But the sunrise is not the subject of denial mis information A typical problem occurred 5 1 16 when the BBC TV evening news gave a short item on the UK s December weather being of record warmth and record wet The 300 word version is posted on line here but that wasn t what appeared on the telly which was very short The recordness of December s weather was drowned out by saying it was only since 1910 rather than since records began And the causes were given but with zero climate change comment Instead we got only El Nino the Jetstream All this from memory the on line version was off line by the time I got to look there Folk like Harrabin at the BBC are properly signed up to AGW but reluctant to bombard the audience with AGW at every turn My previous resistance to the inevitable climate mention on every flood news story remains he says But beyond that the editors presenters at the BBC do show signs of being less sighed up and the message while not overtly denialist does not prevent a denier taking a denialist message from the coverage That of course is wrong But when there are folk involved in the process that do not see denial as a problem as well as folk who are more concerned with the entertainment factors than the denialist problem an institutionally denialist outcome should be no surprise Newspapers are more word hungry than TV but otherwise the same applies I would also suggest with the Express the Daily Rail other right wing papers that they are likely to see a bit of down right denialism as good for business Such is their readership 9 Kevin Malone says 6 Jan 2016 at 7 05 PM late to comment but here goes as a biologist working on salmon issues in the Pacific Northwest I cannot emphasize enough that when trying to communicate complex issues to the Public points have to be easily understood and presented using terms examples they understand etc In reading Real Climate and climate change type articles I am always amazed how poorly this field communicates info to the Public My pet peeve is where the expected change in temperature is almost always presented in degrees C and not F I would guess that 80 percent of the US population could not define C or convert it to F The same knowledge level applies to anything dealing with the metric system Secondly when talking to the Press you need to talk like Bill Nye the Science Guy not Albert Einstein In my experience you can never assume that what you believe to be common knowledge is actually that The Press and Public have short memories and are not involved in the issue on a day to day basis Yes at one time they may have known about aerosols but that may have been two years ago and they moved on to other topics This one of the major reasons that businesses etc provide Press releases that clearly describe salient take home points and also if they are well done provide info on what the report etc doesnt say The Press generally spends little time questioning these releases and lots of time simply repeats whats stated As scientists we generally write our papers recognizing what the scientific critiques weaknesses may be and trying to address these in the paper The same effort should be given to thinking about how vested interests will use the information presented in the paper 10 t marvell says 7 Jan 2016 at 11 54 AM Responsible reporters would contact GISS to make sure they understand things There is contact info in the press release Did the Express and Mail reporters do that Did any other reporters 11 Hans Kiesewetter says 8 Jan 2016 at 3 15 AM KM 9 Indeed Communication is difficult It starts with understanding your public I have difficulties understanding degrees F In my part of the world not US 95 is not able to convert F to C without some kind of conversion tool General comment Thanks for the combination of a technical post part 1 and a separate communication post part2 I like that 12 AntonyIndia says 8 Jan 2016 at 11 19 PM What is your comment on Nicholas Lewis review of your article on climateaudit org http climateaudit org 2016 01 08 appraising marvel et al implications of forcing efficacies for climate sensitivity estimates Response Mostly confused but there are a couple of points worth following up on Should have the relevant sensitivity tests available next week gavin 13 Phil says 9 Jan 2016 at 6 34 PM t marvell 10 I engaged the Daily Mail over their misreporting of the Cryosat2 paper in July 2015 documented by Jim Hunt here During my communication with the Mail I suggested that since they had gone so badly wrong with their calculation they contact the authors for clarification Their response back contained phrases like UCL researchers say So I forwarded it to Rachel Tilling lead author and asked her did you say these things Her answer was unequivocal the UCL team that published the paper had not been contacted by the Mail and they UCL team did not and would never have said the things that the Mail in their private email to me claimed they did Quite who the UCL researchers the Mail did talk to a Classics PhD in the post room perhaps were who knows The whole idea that the Mail may be responsible reporters seems laughable they appear to have an agenda and will print anything they can find or interpret that supports it 14 Halfkidding says 9 Jan 2016 at 7 42 PM The herd or tribal instinct of humans is being magnified by modern communications One complexity is that people can instantly become members of many tribes via modern communications If one understands that news organizations are a tribe then one can understand that selecting to work for one and then being selected requires one to abide by the tribes rules Among the most important rules in news organizations is to always demonstrate neutrality In order to appear neutral one must give equal credence to all or more typically both sides of an argument or debate hat tip to Jay Rosen Look him up A sample https www youtube com watch v ms548AkFP5s It is probable that most every working writer for major print organizations and writers of copy for news readers know that AGW is a fact That has nothing however to do with their job as journalists and reporters The tribe requires neutrality 15 sue says 10 Jan 2016 at 3 43 AM Gavin The obvious error is that they thought it was news that aerosol emissions have partially cancelled out some of the warming one would expect with greenhouse gas emissions Now if this was the 1980s they might have had a point but the fact that aerosols are an important climate forcing have a net cooling effect on climate and in part arise from the same industrial activities that produce greenhouse gases has been part of mainstream science for 30 years Isn t 30 yrs ago in the 80 s 1985 86 16 Hank Roberts says 10 Jan 2016 at 10 54 AM For Sue about climate science aerosols and the 1980s https www aip org history climate Winter htm Gavin s description of the timeline is consistent with the history there That s a link into Spencer Weart s frequently updated online History of Global Warming also found on every RC page in the right hand sidebar under Science Links where it s abbreviated cryptically as AIP Discovery of Glob Warm The big government s at the time were still considering whether a preemptive nuclear first strike might be a good strategy the idea that World War III could be won in a few days or a week and without a lot of collateral damage or not Aerosols were arguably a concern and still very much news as the issue become mainstream science You had to be there 17 Ray Ladbury says 10 Jan 2016 at 11 33 AM Dudes they don t call it the Daily Fail for nothing 18 Paul K says 12 Jan 2016 at 5 24 AM Gavin You say that Nic Lewis is confused I am also confused In fact I think that anyone who says that they are not confused by Marvel et al is just failing to understand the situation Completely independently from Nic Lewis I set up a non parametric convolution model of GISS E2 R This uses the step forcing data from the published CO2 instantaneous quadrupling experiment to define the unit step forcing responses for temperature and net flux The temperature and net flux responses for any arbitrary forcing series can then be forward modeled by convolution of the forcing data with the unit impulse response or by superposition of the incremental forcing values with the unit step response Analytically the integrals yield an identical result Numerically they give 3 sf accuracy with a TS of 6 months First test was to see whether GISS E2 R conforms to a linear system since this is one of the important assumptions made in Marvel et al Using the concentration vs forcing data from Hansen 2005 and Hansen s value of 9 27 for Fi for 4xCO2 I derived with high order accuracy since it is not log linear the forcing vs time profile for the 1 p a experiment and then used this to predict the temperature and net flux evolution of the 1 p a experiment The temperature and net flux predictions match almost perfectly with the published data lending support for the view that GISS E2 R conforms to a linear system The TCR predicted by the emulation model is 1 376 deg K vs a published TCR of 1 4 I then predicted the 20th century historical run using the Fi iRF values from Miller as used in Marvel et al Without any efficacy corrections i e Weighted efficacy 1 0 this yields temperature and net flux predictions for the 20th Century historic run which correspond very closely with the published values The only clearly evident correction required is to the volcanic efficacy where the GCM response is slightly lower than the emulation model Overall this would lend strong support for the view that using Hansen s forcing data Fi basis very little is required in terms of total weighted efficacy correction to the historic mix of forcings Miller stated that the GISS E2 R CO2 forcings were almost identical to those from GISS E These are the forcings I have used in the above analysis On the other hand Marvel et al uses a value of Fi for 2xCO2 which is almost 10 lower than Hansen s value Since my system is linear the use of the lower Fi value would rescale my results pro rata but would still not justify the massive adjustment to TCR implied in Marvel et al It would be truly helpful if we could have a clear statement from GISS on what the Fi Fa and ERF forcings really are in GISS E2 R over a range of CO2 concentrations as per Hansen 2005 It is impossible to reconcile Miller s statements with the values used in Marvel et al Only with these data is there any chance of testing the Marvel et al conclusions Even with the values cited in Marvel I cannot reproduce her results So yes I am confused 19 Patrick says 13 Jan 2016 at 11 43 AM I cordially invite you guys to the OCEAN TUNNELS group on Facebook to solve earths global warming problem here https www facebook com groups 1548937018758434 Ocean Tunnels offer us a way out of this quagmire of which there seems to be no other solution to So instead of dilly dallying around for decades on end lets put an end to it once and for all 20 Edward Greisch says 15 Jan 2016 at 6 14 AM 13 Phil and everybody else There is no point in trying to correct a provoker Punching the tarbaby just gets you more stuck in the tar You can do your best to word your paper carefully but in the end your only recourse is to not communicate with such people They are purely looking for a way to cause trouble emotional trouble if possible As journalists they are also looking for a way to create controversy as a method of selling newspapers The more you try to correct them the more newspapers they can sell So your job is to put them out of business by making controversy as difficult to find as possible Make your paper sound like a very boring history As we found over the past half century we have today found the same old thing Aerosols bla bla bla provoker A person who provokes a troublemaker English Wiktionary 21 patrick says 16 Jan 2016 at 6 26 AM 20 Edward Greisch Not really Not always You have to be good Really good It s a particular calling And it s a great service for example https twitter com climatehawk1 status 683838014909321216 The disinformation dissected here is logging 283

    Original URL path: http://www.realclimate.org/index.php/archives/2016/01/marvel-et-al-2015-part-2-media-responses/ (2016-02-13)
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