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  • Raymond T. Pierrehumbert « RealClimate
    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 New On line Classes and Models Marcus Pages Acronym index Data Sources Categories Climate Science Aerosols Arctic and Antarctic Carbon cycle Climate impacts Climate modelling El Nino Geoengineering Greenhouse gases Hurricanes Instrumental Record IPCC Oceans Paleoclimate Sun earth connections Communicating Climate Reporting on climate skeptics Extras Attic Comment Policy Contributor Bio s FAQ Glossary In the News Reviews Supplemental data Tutorials hydrological cycle Open thread RC Forum Scientific practice statistics The Bore Hole Books Contributors Highlights Dummies Guide to the latest Hockey Stick controversy El Nino Global Warming and Anomalous U S Winter Warmth Hurricanes and Global Warming Myth vs Fact Regarding the Hockey Stick On attribution On mismatches between models and observations On Sensitivity Part I Tropical

    Original URL path: http://www.realclimate.org/index.php/archives/2004/12/raymond-t-pierrehumbert/ (2016-02-13)
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  • William M. Connolley « RealClimate
    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 New On line Classes and Models Marcus Pages Acronym index Data Sources Categories Climate Science Aerosols Arctic and Antarctic Carbon cycle Climate impacts Climate modelling El Nino Geoengineering Greenhouse gases Hurricanes Instrumental Record IPCC Oceans Paleoclimate Sun earth connections Communicating Climate Reporting on climate skeptics Extras Attic Comment Policy Contributor Bio s FAQ Glossary In the News Reviews Supplemental data Tutorials hydrological cycle Open thread RC Forum Scientific practice statistics The Bore Hole Books Contributors Highlights Dummies Guide to the latest Hockey Stick controversy El Nino Global Warming and Anomalous U S Winter Warmth Hurricanes and Global Warming Myth vs Fact Regarding the Hockey Stick On attribution On mismatches between models and observations On Sensitivity Part I Tropical Glacier Retreat Water Vapour feedback or forcing Welcome to RealClimate Other Opinions A Few Things Ill Considered Accuweather Climate Blog And Then There s Physics Andrew Dessler Brave New Climate C2ES Christian Science Monitor Climate Change Education Climate Communication Climate Matters Columbia Climate Science Watch ClimateArk ClimateConservative Org Climatedenial org ClimatePhys ClimateProgress ClimateSight Cntr for Enviro Journalism Deep Climate Deltoid deSmogBlog DotEarth Earth Discovery Channel Ecologically Orientated Effets de

    Original URL path: http://www.realclimate.org/index.php/archives/2004/12/william-m-connolley/ (2016-02-13)
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  • Jim Bouldin « RealClimate
    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 New On line Classes and Models Marcus Pages Acronym index Data Sources Categories Climate Science Aerosols Arctic and Antarctic Carbon cycle Climate impacts Climate modelling El Nino Geoengineering Greenhouse gases Hurricanes Instrumental Record IPCC Oceans Paleoclimate Sun earth connections Communicating Climate Reporting on climate skeptics Extras Attic Comment Policy Contributor Bio s FAQ Glossary In the News Reviews Supplemental data Tutorials hydrological cycle Open thread RC Forum Scientific practice statistics The Bore Hole Books Contributors Highlights Dummies Guide to the latest Hockey Stick controversy El Nino Global Warming and Anomalous U S Winter Warmth Hurricanes and Global Warming Myth vs Fact Regarding the Hockey Stick On attribution On mismatches between models and observations On Sensitivity Part I Tropical Glacier Retreat Water Vapour feedback or forcing Welcome to RealClimate Other Opinions A Few Things Ill Considered Accuweather Climate Blog And Then There s Physics Andrew Dessler Brave New Climate C2ES Christian Science Monitor Climate Change Education Climate Communication Climate Matters Columbia Climate Science Watch ClimateArk ClimateConservative Org Climatedenial org ClimatePhys ClimateProgress ClimateSight Cntr for Enviro Journalism Deep Climate Deltoid deSmogBlog DotEarth Earth Discovery Channel Ecologically Orientated Effets de Terre FR

    Original URL path: http://www.realclimate.org/index.php/archives/2004/12/jim-bouldin/ (2016-02-13)
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  • Caspar Ammann « RealClimate
    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 New On line Classes and Models Marcus Pages Acronym index Data Sources Categories Climate Science Aerosols Arctic and Antarctic Carbon cycle Climate impacts Climate modelling El Nino Geoengineering Greenhouse gases Hurricanes Instrumental Record IPCC Oceans Paleoclimate Sun earth connections Communicating Climate Reporting on climate skeptics Extras Attic Comment Policy Contributor Bio s FAQ Glossary In the News Reviews Supplemental data Tutorials hydrological cycle Open thread RC Forum Scientific practice statistics The Bore Hole Books Contributors Highlights Dummies Guide to the latest Hockey Stick controversy El Nino Global Warming and Anomalous U S Winter Warmth Hurricanes and Global Warming Myth vs Fact Regarding the Hockey Stick On attribution On mismatches between models and observations On Sensitivity Part I Tropical Glacier Retreat Water Vapour feedback or forcing Welcome to RealClimate Other Opinions A Few Things Ill Considered Accuweather Climate Blog And Then There s Physics Andrew Dessler Brave New Climate C2ES Christian Science Monitor Climate Change Education Climate Communication Climate Matters Columbia Climate Science Watch ClimateArk ClimateConservative Org Climatedenial org ClimatePhys ClimateProgress ClimateSight Cntr for Enviro Journalism Deep Climate Deltoid deSmogBlog DotEarth Earth Discovery Channel Ecologically Orientated Effets de Terre FR George Monbiot globalchange Grist Climate and Energy Horatio Algeranon Hot Topic HotWhopper

    Original URL path: http://www.realclimate.org/index.php/archives/2004/12/caspar-ammann/ (2016-02-13)
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  • Thibault de Garidel « RealClimate
    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 New On line Classes and Models Marcus Pages Acronym index Data Sources Categories Climate Science Aerosols Arctic and Antarctic Carbon cycle Climate impacts Climate modelling El Nino Geoengineering Greenhouse gases Hurricanes Instrumental Record IPCC Oceans Paleoclimate Sun earth connections Communicating Climate Reporting on climate skeptics Extras Attic Comment Policy Contributor Bio s FAQ Glossary In the News Reviews Supplemental data Tutorials hydrological cycle Open thread RC Forum Scientific practice statistics The Bore Hole Books Contributors Highlights Dummies Guide to the latest Hockey Stick controversy El Nino Global Warming and Anomalous U S Winter Warmth Hurricanes and Global Warming Myth vs Fact Regarding the Hockey Stick On attribution On mismatches between models and observations On Sensitivity Part I Tropical Glacier Retreat Water Vapour feedback or forcing Welcome to RealClimate Other Opinions A Few Things Ill Considered Accuweather Climate Blog And Then There s Physics Andrew Dessler Brave New Climate C2ES Christian Science Monitor Climate Change Education Climate Communication Climate Matters Columbia Climate Science Watch ClimateArk ClimateConservative Org Climatedenial org ClimatePhys ClimateProgress ClimateSight Cntr for Enviro Journalism Deep Climate Deltoid deSmogBlog DotEarth Earth Discovery Channel Ecologically Orientated

    Original URL path: http://www.realclimate.org/index.php/archives/2004/12/thibault-de-garidel/ (2016-02-13)
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  • Global Dimming? « RealClimate
    Global Dimming It seems that over the past 40 years while the amount of sunlight reaching the top of the atmosphere has not changed the amount of sunlight reaching the surface 7 Tom Rees says 19 Jan 2005 at 5 36 AM I thought the basic idea was that if sulphate cooling is greater than we thought then GHG warming must be greater than we thought and therefore climate sensitivity must be greater than previously thought The 10 deg C rise was presented as a warning rather than a prediction i e something that could possibly happen including carbon cycle feedbacks but probably won t Clarification from Peter Cox would be excellent though Perhaps you can get him to blog something 8 BARISTA says 19 Jan 2005 at 8 45 AM cheer up it was only mass hysteria Tim Lambert has picked up on the global dimming story with his usual readable rigour He points to a sceptical post on RealClimate which brings a needed breath of sanity to the story In the process he also pointed to 9 Brian S says 19 Jan 2005 at 5 05 PM Thought I recognized James Glassman s name he s the author of Dow 36 000 I see he s transferring his financial prediction accuracy to climatology More info on him is available at http www disinfopedia org wiki phtml title James K Glassman 10 Ken says 19 Jan 2005 at 5 19 PM If there were no CO2 in the atmosphere average surface temperatures of the Earth would be 15 deg or lower Although only one air molecule in 2500 is CO2 this is sufficient to raise the temperature to 15 deg How does one reconcile the 30 deg C sensitivity for a 100 decrease in CO2 with the estimated 3 deg C sensitivity for a 100 CO2 increase I would think that the sensitivities for 100 CO2 change would be of comparable magnitude Regarding the Faustian bargain has anyone looked at the theoretical feasibility of introducing some kind of biologically benign synthetic aerosol into the atmosphere to counteract GHG warming Clearly this approach should only be considered to prevent catastropic warming effects such as melting the Greenland ice sheet or destabilized methane hydrates Response Firstly the response to CO2 is non linear Secondly I think the 30 oC value you are quoting is for the total greenhouse effect not just CO2 Lastly I haven t heard of the aerosol idea but others e g iron fertilisation of the oceans have been semi seriously proposed and in the case of iron some experimental work done William 11 David says 19 Jan 2005 at 5 50 PM Can any of the experts lurking here refer me to any updates to the anthropogenic direct effect aerosol radiative forcing digram Figure 6 8 Figure 401 in the TAR I am familar with the Liepert et al ground based work which shows fairly consistent reductions in surface solar radiation upto the 1990s and the apparent linkage of this to the evaporation paradox The question is whether this increase in aersol forcing is continuing or if cleaner burning technologies have reversed the trend Many Thanks David 12 Pat Neuman says 19 Jan 2005 at 6 02 PM The Arctic is warming more rapidly than IPCC scientists had anticipated in 2001 What is the amount of additional greenhouse gases now expected from more rapid permafrost thawing in the Arctic What about feedbacks from methane burps in warmer waters These questions should be addressed before one concludes as gavin did above that The suggested doubling of the rate of warming in the future compared to even the most extreme scenario developed by IPCC is thus highly exaggerated while these extreme notions might make good television they do a dis service to the science 13 Beate Liepert says 19 Jan 2005 at 6 41 PM A comment and or answer to David s question New studies on ground based observations extending to 2000 are currently in the publication process In General without details your suspicion seems correct that there is reversing tendency in direct aerosol forcing in highly industrialized areas But these papers will be out soon Beate 14 Ferdinand Engelbeen says 19 Jan 2005 at 8 08 PM While particulate emissions over the Western world decreased since the mid 1970 s the emissions in developing countries increased rapidely in the past halve century The global trend in general leveled It is difficult to find exact results of the most comprehensive investigation on aerosols the INDOEX over SE Asia on the open internet but there is one interesting investigation done in the Indian Ocean where a highly aerosol contaminated area in the NH was compared to a far less contaminated one in the SH See http meteora ucsd edu jnorris reprints io cloud pdf If aerosols act as cloud seeds and prolong the cloud s lifetime there should be different trends between the two regions Which is not the case Sulphate aerosols give more reflection of sunlight thus should have a cooling effect Soot aerosols absorb more sunlight and increase tropospheric warming Both have a dimming effect But where is the balance between the two And what is the ultimate effect on surface temperature According to the investigation There is a strong increasing trend in sea surface temperature over the northern Indian Ocean during the 1952 96 time period and Soot was a sizeable fraction of the aerosol mix and caused substantial absorption of solar radiation Satheesh and Ramanathan 2000 infer from satellite and surface measurements that aerosol heating in the lower atmosphere over the northern Indian Ocean at local noon is 1 3 K day an increase of 50 100 over aerosol free solar heating Thus the balance is that soot has more positive effect than the combined direct and indirect negative effects of sulphate and other aerosols It seems that at least the regional effect of aerosols in S E Asia is warming not cooling Thus any reduction there would have a cooling effect Further dimming also occurs at places where there is no or a minor trend in aerosols Antarctica 9 dimming no trend in aerosols Australia continuous increasing dimming minute change in aerosols and no in cloud cover Still a lot of research to do 15 dave says 19 Jan 2005 at 10 15 PM This is strange I thought I would just go ahead and e mail Peter Cox to get his thoughts here If you do a Google search on Peter Cox climate the first link you currently get is Peter Cox s Position Available dated October 22 2004 What follows is a job description Perhaps he is indisposed at the moment for whatever reason Anyway here s some Hadley Centre research Chris Jones and Peter Cox issued prior to his statements in the BBC interview an AGU news release May 2003 New Climate Model Predicts Greater 21st Century Warming I believe this news release gives his statements some context Global dimming is not mentioned The research article has the title Strong carbon cycle feedbacks in a climate model with interactive CO2 and sulphate aerosols and appeared in Geophys Res Lett 30 9 1479 I can not find the original on the web 16 Mark Bahner says 19 Jan 2005 at 11 32 PM Responding to my quotes of Peter Cox in comment 5 Gavin Schmidt writes Without access to the full interview you don t know the context in which Dr Cox was speaking He may have been asked Let s just imagine that climate sensitivity was twice as big as you thought what would that imply for the UK under the top end IPCC scenario Absent further information you cannot conclude that he was saying these impacts were likely or even plausible Mugging of scientists in such ways is not unknown First of all I cut pasted four paragraphs Nearly 200 words Unless the BBC deliberately cut out his caveats he certainly was quoted enough to provide his own context But more importantly if Peter Cox was misquoted or quoted out of context why wouldn t the Hadley Centre Met Office issue some sort of statement on their website They certainly don t appear adverse to commenting on public events e g their nifty promotional piece for The Day After Tomorrow http www metoffice com corporate pressoffice 2004 pr20040430 html I especially love the movie poster with Big Ben Top notch science there Response I think you re being unreasonable The site actually says The timescales depicted may be unrealistic but some of the science behind the movie is real enough And if you follow the immeadiately following link on the page you get a discussion of the gulf stream and its possible shutdown and a clear statement that modelling results don t show this just a 20 slowdown and that the probablility of a shutdown is low I would have written the lead somewhat differently to emphasise more clearly how unscientific the movie is but they clearly aren t supporting the movie William 17 dave says 20 Jan 2005 at 12 41 AM I am a bit put off by Mark Bahner calling Peter Cox on the carpet after I originally mentioned him in comment 4 Bahner on his BLOG says The IPCC Third Assessment Report s TAR s projections for methane atmospheric concentrations carbon dioxide emissions and atmospheric concentrations and resultant temperature increases constitute the greatest fraud in the history of environmental science I just want to make sure that I am not associated with that position I have no doubts about the fact that climate change is happening and that the warming trend is real and unusual given the GHG aerosol forcings I am also interested in the apparently more extreme climate modelling results Hadley Centre is getting but I ll have to be sold on those I will say that humans have screwed up the atmosphere so much with these direct climate forcings and their indirect effects as mentioned in the original post that we don t know if we re coming or going sometimes with respect to climate Global dimming indeed It looks like the climate effects over time will be quite damaging We just don t know the full extent of it and how or when it will happen abrupt non linear changes And that disturbs me very much As Wallace Broeker says Climate is an angry beast and we are poking at it with sticks Perhaps some posts on paleoclimate are in order To tell some of these people that the Holocene is basically an anomaly and that climate can change at least regionally very fast and has done so often in the Pleistocene Especially if you poke it with sticks 18 Ajax Bucky says 20 Jan 2005 at 2 48 AM It won t be possible to just publish accurate scientific information about anthropogenic climate forcing and leave it at that and expect the general public to respond in a prudent and rational way Especially and I say this to you Mark Bahner when for their whole lives they ve been subjected to the most virulent forms of hucksterism and conscienceless deception the human mind is capable of This debate is not happening in a Socratic community of scholars it s happening in the crowded alleys of a black market where slaves and stolen art are sold right next to fresh produce and brand new bicycles As has been hinted at here there is resistance to factual debate on climate change that amounts to intrigue as Sir David King said he was being followed around the world by people in the pay of vested interest groups that want to cast doubt on the science of climate change It s the height of folly to infer that this is not the case to pretend that the men whose selfish decisions were and are responsible for this whatever it is disaster dilemma looming extinction transitional threshold are not still running the world politically and economically They are But only because the majority the great majority of decent people in the U S especially have been and are being kept in the dark about what s happening Speaking to those decent people in plain and honest language under such circumstances while easily derided is a brave and responsible thing to do Responding to someone of King s stature and proven integrity with scorn isn t a mistake it s an act of cowardice and duplicity Comment I ve allowed this through but its pushing the boundaries This is a science site please remember that William 19 O Linde says 21 Jan 2005 at 11 59 PM Things almost never happen as expected The degree of incorporation of an unknown number of gases and particles not only CO2 methane methyl bromide CFC substitutes and the other known as GHG is not known and we would need maybe more than a century to have an estimate at the same time new compounds would be incorporating in the atmosphere We created something that never existed before We cannot talk of air as we study in Chemical texts We are living in a bottle of a kind of garbag air Thermodynamics governs us we are not governing it nor can we know what are billions of souls doing what are industries throwing to our lungs and nature s lungs less can we change the minds of educated and poor illiterate people in case we had the Truth I find Pat Neuman Dave and some others are right We have to be cautious Since the middle 1980 s I was reading climate changes could lead to something not pleasant sea level rise and all the etc then in the 1990 s the projections were not too dramatic but serious I felt the estimates were low and things would get worse than predicted Then in 1998 some of us felt the future was going to be a kind of disaster if not thinking seriously about how to behave For more than two decades some of us are used to find that the predictions are almost always wrong Obviously How on Earth can we know about millions of parameters interacting Computer models can only spit what computers are fed I feel Wallace Broeker knows the beast and is right We have to continue doing things the best way possible because we know almost nothing still I will paste a bit from a post by Lee A Arnold somewhere in Prometheus brilliantly written Perhaps concern over uncertainty in complex adaptive open systems should be investigated by inductive generalization from observations of the dynamics of a wide range of such systems ecosystems social systems computer systems immune systems economic systems It is curious that the following things are never admitted as facts about the world but here goes the observer would note of all of these systems that they undergo oscillations within apparent parameters and occasionally flip into new regimes they often demonstrate novel emergence and that increased forcing whether of native elements or exotic ones increases the rates of oscillation and catastrophic shifts sometimes after a quieter period of sub threshold build up The observer would also see that these events are not tractable to analytic prediction beforehand due to any or several of various regular functions including definition modeling measurement calculation experiment control and repeated verification Yet it will remain a fact that even though you can t predict any exact occurrence or its timing all complex systems will show these general dynamics At that point we opt for the Precautionary Principle as your grandma already knew It is a curious defect of mentality that economic predictions of experts are held to be sacrosanct by the same crowd that dumps on the climate scientists But surely economics is far less determinative Surely our economic system will rise to the challenge of working in almost any climate policy Indeed the climate debate is not exactly a conflict over values unless one of them is greed It has been registered time and again that aside from a few serious climate scientists who make useful points in the real debate all of the anti warming people are paid industry hacks The idea that economics trumps climate should be exactly reversed on our best and most comprehensive understanding of the processes involved The human race will do just fine although some people may have to find another job End of Arnold s excerpt 20 Tom Rees says 24 Jan 2005 at 10 17 AM This may be what Peter Cox was referring to maybe the Horizon journalists mistook celsius for fahrenheit wouldn t be the first time Strong carbon cycle feedbacks in a climate model with interactive CO2 and sulphate aerosols By the end of the 21st century the authors state the increase in carbon dioxide and decrease of sulphates will cause a substantially higher global warming of 5 5 degrees Celsius 9 9 degrees Fahrenheit compared with 4 degrees Celsius 7 degrees Fahrenheit when these interactions are neglected 21 JC says 24 Jan 2005 at 10 43 AM In response to Ferdinand Engelbreen s reply Sulphate aerosols give more reflection of sunlight thus should have a cooling effect Soot aerosols absorb more sunlight and increase tropospheric warming Both have a dimming effect But where is the balance between the two And what is the ultimate effect on surface temperature Here s your answer http www ncpa org iss env 2002 pd011402d html Scientists Say Antarctica Is Cooling Not Warming 22 Tom Rees says 24 Jan 2005 at 12 00 PM A more recent paper by Jones Cox http camels metoffice com MiscReport01 html Perhaps someone here could give their opinion of it Both low Q SO4 low climate sensitivity and high Q SO4 high climate sensitivity combinations are consistent with the historical climate record But they lead to very different future climates when the sulphate cooling

    Original URL path: http://www.realclimate.org/index.php/archives/2005/01/global-dimming/ (2016-02-13)
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  • Global Dimming II « RealClimate
    day anthropogenic and natural aerosols and green house gases called present day scenario 1985 In the second simulation we reduce the aerosols to the natural concentrations called pre industrial 1885 and keep the greenhouse gases constant at present day level 1985 This is what you would assume as a scenario when we clean up aerosols See table 4 AP experiment in the paper we turn the argument around and discuss the effect of aerosol increase The result is a temperature increase of 0 8 degree Celcius in this particular model MPI Hamburg Note that this model does not include ocean dynamics Subjectively I find 0 8 degree a lot hotter 2 I agree my 2004 paper provides counterintuitive arguments Let me please explain it in more detail and I hope you ll see my point The key is the difference between moisture storage and moisture fluxes GHGs modify storage and fluxes and aerosols modify fluxes When temperature increases in the atmosphere due to GHGs the moisture holding capacity should go up following the Clausius Clapeyron formulation The simulated model atmosphere is indeed moister absolute humidity goes up It is relative humidity not absolute humidity that governs cloud formation Relative humidity is fairly constant because it depends on other meteorological factors such as circulation e g ITCZ Once cloud formation takes place in a moister atmosphere these clouds hold more water and should be optical thicker Optically thicker clouds reduce sun light Reduced sunlight reduces evaporation Now you say this should lead to moisture starvation in the atmosphere Correct but BUT there is another way to increase atmospheric moisure Leave moisture in the atmospheric storage for a longer time with the same or less fluxes in and out Lifetime of water vapor goes up from 10 to 10 1 2 days The indirect effect as it is simulated in this model reduces precipitation efficency and helps keep rel humidity and cloud cover constant This is indeed as you mention important to actually tip the balance towards reduced evaporation in a moister and warmer world Note the the indirect effect is highly uncertain Hence you are right that indirect aerosol effect is important But moisture can increase because the atmosphere can hold more due to warming Hence it IS the combination of both Incidentally even in greenhouse gas only simulations when you have an increase in rainfall and evaporation this increase is not as great as you d expect from Clausius Clapeyron because of the fairly constant rel humidity and cloud coverage Even in greenhouse gas only simulations the lifetime of water vapor increases The lifetime effect counteracts the increases in rain and evaporation due to the Clausius Claperyron In these GHG experiments however the lifetime effect is small compared to the Clausius Clapeyron effect Thus it is plausible to get a warmer moister darker world where it rains less 4 Peter J Wetzel says 20 Jan 2005 at 6 10 PM Thank you I understand and accept that The GHG warmed atmosphere maintains a greater moisture reservoir through which moisture cycles more slowly than its pre industrial counterpart That is what your model reveals and it is also fairly intuitive Still there remains a question in my mind about the relative importance of the GHG warming and the aerosol indirect effects on global dimming If I understand you correctly the model you use demonstrates that a net reduction in solar radiation a portion of the dimming is caused by the GHG warming effect alone However there is a lack of consensus among the 10 models quoted in IPCC TAR on this issue See Fig 7 2 with the accompanying statement that In response to any climate perturbation the response of cloudiness thereby introduces feedbacks whose sign and amplitude are largely unknown first paragraph I would appreciate your perspective on this Specifically what fraction of the dimming would you estimate from your work to be caused by the GHG warming And finally if it is fair to make this request how much would you estimate this fraction to vary among the 10 models quoted in IPCC TAR 5 Beate Liepert says 20 Jan 2005 at 8 00 PM The relative importance of GHG warming and indirect effect and a revised version of the IPCC TAR of the cloud feedback is exactly what I am working on Results should be out soon Sorry I can t tell more Patience Beate 6 Peter J Wetzel says 20 Jan 2005 at 9 43 PM Reluctantly I shall wait As Gavin and Mike recently posted regarding peer review science normally advances in baby steps The quantum leaps that the general public perceives are almost always the result of a long and unheralded period of foundation building behind the scenes I hope you will post here when a paper is accepted Best wishes Pete 7 Ferdinand Engelbeen says 21 Jan 2005 at 4 54 AM Some more questions 1 The emission of sulphate aerosols in Europe is drastically reduced since the mid seventies 70 The largest effect of this reduction should be found downwind of the main sources According to the Hadcm3 model a difference of 5 K in north Scandinavia Russia over a 10 years time span But there is no difference in trends attributable to aerosols between less contaminated area s and the area with the highest contamination See aerosols 2 An investigation in Switzerland presented at the latest dimming conference on your pages see dimming conference shows that the reduction in surface solar insolation was compensated by increased downward LW radiation This was attributed to the measured increase of water vapour But should one not expect less water evaporation with decreased insolation And what part of the SW of incoming sunlight is absorbed by water vapour and how much W m2 Response due to the complexities of the system there is no need for decreased evap if its occurred to result in lower WV In fact a bit speculative it can be the other

    Original URL path: http://www.realclimate.org/index.php/archives/2005/01/global-dimming-ii/ (2016-02-13)
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  • Pollution-Climate Connections « RealClimate
    D Fernandes and C Jang Linking ozone pollution and climate change The case for controlling methane Geophys Res Lett 29 1919 doi 10 1029 2002GL015601 2002 Hogrefe C B Lynn K Civerolo J Y Ku J Rosenthal C Rosenzweig S Gaffin K Knowlton and P L Kinney Simulating changes in regional air pollution over the eastern United States due to changes in global and regional climate and emissions J Geophys Res 109 D22301 doi 10 1029 2004JD004690 2004 Mickley L J D J Jacob B D Field and D Rind Effects of future climate change on regional air pollution episodes in the United States Geophys Res Let 30 L24103 doi 10 1029 2004GL021216 2004 Comments pop up 8 8 Responses to Pollution Climate Connections 1 Dano says 26 Apr 2005 at 10 35 AM Good piece Loretta and the GRL paper looks good A question many of the precursors to O3 formation are VOCs and my study area trees contribute a significant fraction of VOCs to the atm Tree canopies also can change the boundary layer mixing in cities making it harder for wind to sweep out the goop in the air Were you able in your work for this paper to contact anyone and explore whether elevated CO2 levels decrease tree metabolic rates and thus decrease VOC emissions Best D 2 Tim says 27 Apr 2005 at 6 07 AM Unfortunately there isn t yet much understanding of the large amount of interannual variability in blocking high pressure systems seen in the last few decades So it is very hard to make a prediction of what might happen to blocking in a climate change experiment Whilst it is important to consider the possible effects of climate change on problems such as this I think it is best to emphasise that the dominant cause is the availability of the precursor pollution and that reducing this pollution by making changes to transport systems and industry is the best way of tackling this problem 3 Dan says 27 Apr 2005 at 7 16 AM Biogenic VOCs are highly reactive and the emissions are substantial especially in humid warm seasons I wonder in the case of blocking patterns leading to drought and well above normal temperatures if biogenic VOC emissions might actually decrease Short of the vegetation actually dying from the drought of course 4 Dusty Bradshaw says 29 Apr 2005 at 11 12 PM I know this study focuses on ambient air pollution but has anyone looked into trends to see if we humankind in developed nations stay indoors more during heat waves thereby subjecting ourselves to increased levels of indoor air pollution Common sense tells me to stay in where its cool when its hot Should we be asking if indoor air pollution will become a bigger issue as summers get hotter due to the effects of Global Warming DB 5 Ferdinand Engelbeen says 2 May 2005 at 5 36 AM I have the impression that the prediction of future climate pollution links is rather speculative In the not so long past the worst pollution was during cold calm high humidity weather at the time coal was used in open fire places leading to the infamous pea soup smog in London killing elderly people Since that time SO2 and lead were reduced with over 80 PM10 with over 60 and NOx with over 40 in all Western countries As NOx is the main driver for low level ozone formation it s further reduction should have a large impact About biogenical VOC s these are mainly formed in summer where high temperatures and secondly high light photosynthesis are the primary drivers Natural VOC s exceed anthropogenic emissions with a factor 3 8 Some interesting literature about biogenical VOC s http boreal fmi fi biphorep report chapter7 pdf and http ethesis helsinki fi julkaisut mat kemia vk hakola biogenic pdf 6 Loretta says 2 May 2005 at 6 02 AM Responses 1 and 3 Yes the emissions of volatile organic carbon VOCs from vegetation play a role in ozone formation In cities like Atlanta with lush vegetation biogenic VOCs together with anthropogenic nitrogen oxides can have a significant impact on regional pollution The emissions of biogenic VOCs increase rapidly as temperatures increase But plants also respond to changing CO2 While some plants may flourish in an enriched CO2 atmosphere VOC emissions may decrease And as Dan points out below vegetation may also suffer from heat or water stress in a changing climate It s a complicated picture I did not include any of these biogenic effects in my simple sensitivity study I kept emissions of pollution precursors constant All I wanted to see was this if I increase the long lived greenhouse gases like CO2 in the model and let the climate respond what happens to the patterns of air circulation What I found was that stagnation events lasted longer in the future model atmosphere On the other hand Hogrefe et al 2004 did include the biogenic VOCs that Dano and Dan are talking about Of the effects listed above Hogrefe et al 2004 considered only the temperature effect on biogenic VOC emissions They found a 10 50 increase in these emissions with climate change over the eastern U S Unfortunately there isn t yet much understanding of the large amount of interannual variability in blocking high pressure systems seen in the last few decades So it is very hard to make a prediction of what might happen to blocking in a climate change experiment 2 I agree with Tim that more work is needed to understand what controls cyclone and anticyclone variability in the observation record A number of model studies such as our own have found a decline in cyclone number in a future atmosphere The model trends can be explained with mechanisms such as the flattening of the temperature gradient from equator to pole Improving our understanding of present day variability will give us greater confidence in what these models

    Original URL path: http://www.realclimate.org/index.php/archives/2005/04/pollution-climate-connections/ (2016-02-13)
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