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  • November « 2015 « RealClimate
    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 So what is really happening in Antarctica Filed under Climate Science eric 10 November 2015 The recent paper by Zwally et al in the Journal of Glaciology has been widely reported as evidence that Antarctic is gaining mass and hence lowering sea level Is it Expert Jonathan Bamber weighs in Guest post by Jonathan Bamber University of Bristol There have been quite few big media stories related to Antarctica recently including a paper on the irreversible collapse of the marine portion of the West Antarctic Ice Sheet and a NASA funded study that finds contrary to numerous previous results that the Antarctic ice sheet as a whole has been gaining mass between 1992 and 2008 This most recent study received a lot of media attention because it runs counter to what was said in the last IPCC Report Certain parts of the media hailed this as another sign that the impacts of climate change had somehow been exaggerated a risk that the lead author Jay Zwally was concerned about before the research was published So what did Zwally and his colleagues do what did they find and why does it contradict a plethora of previous studies that suggest Antarctica has been losing mass over the same time period More Comments pop up 52 Older Entries Site Google Custom Search Recent Comments What is the best description of the greenhouse effect Jim Eager 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 With Inline Responses Marvel et al 2015 Part III Response to Nic Lewis SteveS Marvel et al 2015 Part III

    Original URL path: http://www.realclimate.org/index.php/archives/2015/11/ (2016-02-13)
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  • October « 2015 « RealClimate
    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 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

    Original URL path: http://www.realclimate.org/index.php/archives/2015/10/ (2016-02-13)
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  • September « 2015 « RealClimate
    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 James Empty Blog Jeff Masters Wunder Blog John Fleck Kate has things to say Maribo Mark Lynas Neven s Arctic Sea Ice Blog Open Mind Our Changing Climate Planet 3 0 PrimaKlima DE Rabett Run

    Original URL path: http://www.realclimate.org/index.php/archives/2015/09/ (2016-02-13)
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  • August « 2015 « RealClimate
    was provided by linking tree ring chronologies to ice cores through two extraterrestrial events More References M G L Baillie and J McAneney Tree ring effects and ice core acidities clarify the volcanic record of the first millennium Climate of the Past vol 11 pp 105 114 2015 http dx doi org 10 5194 cp 11 105 2015 B M Vinther H B Clausen S J Johnsen S O Rasmussen K K Andersen S L Buchardt D Dahl Jensen I K Seierstad M Siggaard Andersen J P Steffensen A Svensson J Olsen and J Heinemeier A synchronized dating of three Greenland ice cores throughout the Holocene J Geophys Res vol 111 2006 http dx doi org 10 1029 2005JD006921 M Sigl J R McConnell L Layman O Maselli K McGwire D Pasteris D Dahl Jensen J P Steffensen B Vinther R Edwards R Mulvaney and S Kipfstuhl A new bipolar ice core record of volcanism from WAIS Divide and NEEM and implications for climate forcing of the last 2000 years Journal of Geophysical Research Atmospheres vol 118 pp 1151 1169 2013 http dx doi org 10 1029 2012JD018603 M Sigl M Winstrup J R McConnell K C Welten G Plunkett F Ludlow U Büntgen M Caffee N Chellman D Dahl Jensen H Fischer S Kipfstuhl C Kostick O J Maselli F Mekhaldi R Mulvaney R Muscheler D R Pasteris J R Pilcher M Salzer S Schüpbach J P Steffensen B M Vinther and T E Woodruff Timing and climate forcing of volcanic eruptions for the past 2 500 years Nature vol 523 pp 543 549 2015 http dx doi org 10 1038 nature14565 Comments pop up 23 Unforced variations Aug 2015 Filed under Climate Science Open thread group 3 August 2015 This month s open thread A traditional time to discuss the Arctic sea ice minimum But NH summer heatwaves and to be fair snow in the southern hemisphere are also fair game Comments pop up 282 Site Google Custom Search Recent Comments What is the best description of the greenhouse effect Jim Eager 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 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

    Original URL path: http://www.realclimate.org/index.php/archives/2015/08/ (2016-02-13)
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  • July « 2015 « RealClimate
    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 James Empty Blog Jeff Masters Wunder Blog John Fleck Kate has things to say Maribo Mark Lynas Neven s Arctic Sea Ice Blog Open Mind Our Changing Climate Planet

    Original URL path: http://www.realclimate.org/index.php/archives/2015/07/ (2016-02-13)
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  • June « 2015 « RealClimate
    to improve their database and they therefore occasionally present version updates of their global series NASA data are currently at version 3 the British Hadley Centre data at version 4 There is nothing unusual about this and the corrections are in the range of a few hundredths of a degree see Figure 1 This really is just about fine details More Comments pop up 59 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 Unforced Variations June 2015 Filed under Climate Science Open thread group 1 June 2015 This month s open thread Some interesting trends in ocean heat content surface temperatures multiple oddly reported papers which are often linked to ambiguous press releases etc But at least we aren t working in political science Comments pop up 264 Site Google Custom Search Recent Comments What is the best description of the greenhouse effect Jim Eager 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 With Inline

    Original URL path: http://www.realclimate.org/index.php/archives/2015/06/ (2016-02-13)
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  • May « 2015 « RealClimate
    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 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

    Original URL path: http://www.realclimate.org/index.php/archives/2015/05/ (2016-02-13)
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  • April « 2015 « RealClimate
    always occurs very soon or immediately after lightning But hearing thunder gives you only a general prediction of when the next lightning will be observed One would correctly deduce that lightning causes thunder That s progress But it would not tell you the cause of the lightning in the first place For my part I ve long been a skeptic about the old idea that the D O variations are ultimately driven by meltwater and or iceberg fluxes into the North Atlantic the Day after Tomorrow scenario if you will There are only 6 clearly identified Heinrich events that is layers of terrestrial sediment in ocean sediment cores from the North Atlantic evidence for massive iceberg discharges from the Laurentide ice sheet but there are at least 23 D O events It more likely that there is intrinsic variability in the coupled ocean atmosphere system as found for example in a long simulation with the climate model CCSM4 by Peltier and Vettoretti 2014 and 2015 though there is debate about the validity of the very low values for ocean vertical mixing used in those simulations Iceberg discharges are then just the consequence not the cause of changes in ocean circulation as argued recently by Alvarez Solaz et al 2013 and also suggested by Barker et al 2015 who found that on average evidence for icebergs in the North Atlantic follow rather than precede the abrupt coolings at the end of some D O events That doesn t mean that the huge ice and meltwater fluxes associated with Heinrich events don t have an impact most modeling work suggests that they would But it may be important in this context that our results show no dependence of the 200 year lag on whether or not a Heinrich event has occurred that is there is no evidence that Heinrich stadials the cold periods during which Heinrich events occur are unusual with respect to ocean seesaw dynamics The role of these events in millennial scale variability therefore remains an important and open research question see e g Margari et al 2010 In the meantime our precise observations of the phasing of D O and AIM events provide an important new constraint against which to validate model simulations designed to capture the dynamics of these interesting features of the climate system UPDATE The News Views article about our article by Tas van Ommen is worth a read Available here subscription based only I m afraid Notes The ability to obtain such small uncertainties is owing to four main things First we have very high resolution measurements of methane in both the WAIS Divide and the Greenland cores methane is globally well mixed and so abrupt changes in methane must happen at the same time within a year in cores from both regions This means that we can synchronize the age of the gas trapped in the bubbles within the cores very precisely Second we have very high resolution measurements of the nitrogen isotope ratio 15 N 14 N in atmospheric N 2 also trapped in the bubbles in the cores This isotope ratio provides information on the age difference between the gas and the ice because gravitational settling increases the 15 N 14 N ratio this depends on the thickness of the firn the permeable ice between the surface and the impermeable ice at depth where bubbles are trapped The deeper the firn the longer it takes to trap gases and the larger the age difference It s the age of the ice that we re actually interested in because this not the gas trapped within the ice is what the δ 18 O measurements are made on Fourth this age difference is much smaller at WAIS Divide than in any other long Antarctic record it is at most 500 years compared with e g 4000 years at Vostok Finally we also have unprecedentedly high resolution measurements of δ 18 O and very high quality borehole temperature measurements which together provide a very robust measure of the temperature variations through time Data The data from the paper are all available in the Supplement to the paper The timescale and the oxygen isotope data from our lab what most people will be interested in are available at the National Snow and Ice Data Center at doi 10 7265 N5GT5K41 References Barker S J Chen X Gong L Jonkers G Knorr D Thornalley Icebergs not the trigger for North Atlantic cold events Nature 520 333 336 2015 http dx doi org 10 1038 nature14330 Blunier T J Chappellaz J Schwander A Dällenbach B Stauffer T F Stocker D Raynaud J Jouzel H B Clausen C U Hammer and S J Johnsen Nature vol 394 pp 739 743 1998 http dx doi org 10 1038 29447 Böning C W A Dispert M Visbeck S R Rintoul F U Schwarzkop The response of the Antarctic Circumpolar Current to recent climate change Nature Geoscience 1 864 869 2008 http dx doi org 10 1038 ngeo362 Buizert C Cuffey K M Severinghaus J P Baggenstos D Fudge T J Steig E J Markle B R Winstrup M Rhodes R H Brook E J Sowers T A Clow G D Cheng H Edwards R L Sigl M McConnell J R and Taylor K C The WAIS Divide deep ice core WD2014 chronology Part 1 Methane synchronization 68 31 ka BP and the gas age ice age difference Clim Past 11 153 173 2015 http dx doi org 10 5194 cp 11 153 2015 EPICA Community Members One to one coupling of glacial climate variability in Greenland and Antarctica Nature vol 444 pp 195 198 2006 http dx doi org 10 1038 nature05301 Fyfe J C and O A Saenko 2005 Human Induced Change in the Antarctic Circumpolar Current J Climate 18 3068 3073 http dx doi org 10 1175 JCLI3447 1 Grootes P M M Stuiver J W C White S Johnsen and J Jouzel Comparison of oxygen isotope records from the GISP2 and GRIP Greenland ice cores Nature vol 366 pp 552 554 1993 http dx doi org 10 1038 366552a0 He F J D Shakun P U Clark A E Carlson Z Liu B L Otto Bliesner and J E Kutzbach Northern Hemisphere forcing of Southern Hemisphere climate during the last deglaciation Nature vol 494 pp 81 85 2013 http dx doi org 10 1038 nature11822 Margari V L C Skinner P C Tzedakis A Ganopolski M Vautravers N J Shackleton The nature of millennial scale climate variability during the past two glacial periods Nature Geoscience 3 127 131 2010 http dx doi org 10 1038 ngeo740 NEEM Community Members Eemian interglacial reconstructed from a Greenland folded ice core Nature vol 493 pp 489 494 2013 http dx doi org 10 1038 nature11789 Pedro J B T D van Ommen S O Rasmussen V I Morgan J Chappellaz A D Moy V Masson Delmotte and M Delmotte The last deglaciation timing the bipolar seesaw Climate of the Past vol 7 pp 671 683 2011 http dx doi org 10 5194 cp 7 671 2011 Peltier W R and G Vettoretti Dansgaard Oeschger oscillations predicted in a comprehensive model of glacial climate A kicked salt oscillator in the Atlantic Geophys Res Lett 41 7306 7313 2014 http dx doi org 10 1002 2014GL061413 Rind D G Russell G Schmidt S Sheth D Collins P deMemocal J Teller Effects of glacial meltwater in the GISS coupled atmosphere ocean model 2 A bipolar seesaw in Atlantic Deep Water production Journal Geophysical Research 106 pp 27 355 27 365 2001 http dx doi org 10 1029 2001JD000954 Roe G H and E J Steig Characterization of Millennial Scale Climate Variability J Climate 17 1929 1944 http journals ametsoc org doi full 10 1175 1520 0442 282004 29017 3C1929 3ACOMCV 3E2 0 CO 3B2 Rosen J L E J Brook J P Severinghaus T Blunier L E Mitchell J E Lee J S Edwards and V Gkinis An ice core record of near synchronous global climate changes at the Bølling transition Nature Geosci vol 7 pp 459 463 2014 http dx doi org 10 1038 ngeo2147 Schmittner A O Saenko and A Weaver Coupling of the hemispheres in observations and simulations of glacial climate change Quaternary Science Reviews vol 22 pp 659 671 2003 http dx doi org 10 1016 S0277 3791 02 00184 1 Steig E J et al Q Ding J W C White M Küttel S B Rupper T A Neumann P D Neff A J E Gallant P A Mayewski K C Taylor G Hoffmann D A Dixon S W Schoenemann B R Markle T J Fudge D P Schneider A J Schauer R P Teel B H Vaughn L Burgener J Williams and E Korotkikh Recent climate and ice sheet changes in West Antarctica compared with the past 2 000 years Nature Geosci vol 6 pp 372 375 2013 http dx doi org 10 1038 NGEO1778 Steig E J Climate change The south north connection Nature vol 444 pp 152 153 2006 http dx doi org 10 1038 444152a Stocker T F and S J Johnsen A minimum thermodynamic model for the bipolar seesaw Paleoceanography vol 18 pp n a n a 2003 http dx doi org 10 1029 2003PA000920 Vettoretti G and W R Peltier 2015 Interhemispheric air temperature phase relationships in the nonlinear Dansgaard Oeschger oscillation Geophys Res Lett 42 1180 1189 http dx doi org 10 1002 2014GL062898 WAIS Divide Project Members Onset of deglacial warming in West Antarctica driven by local orbital forcing Nature 500 440 444 2013 http dx doi org 10 1038 nature12376 WAIS Divide Project Members Precise interpolar phasing of abrupt climate change during the last ice age Nature http dx doi org 10 1038 nature14401 Comments pop up 65 Nenana Ice Classic 2015 Filed under Climate Science Instrumental Record gavin 25 April 2015 Unsurprisingly to anyone looking at the exceptionally warm winter on the West Coast of North America the Nenana Ice Classic had another near record early breakup on Friday netting some lucky winner s around 300 000 in prizes More Comments pop up 10 The return of the iris effect Filed under Climate modelling Climate Science group 24 April 2015 Guest commentary from Andy Dessler TAMU When a new scientific hypothesis is published two questions always occur to me Did the authors convincingly show the hypothesis was correct If not is the hypothesis actually correct The answers to these two questions may not be the same A good example is Wegener s theory of continental drift his idea was fundamentally correct but he lacked the data and physical mechanisms to convince the rest of scientific community It would take several decades before enough data were gathered that the scientific community wholeheartedly endorsed plate tectonics In 2001 Prof Richard Lindzen and colleagues published his iris hypothesis Lindzen et al 2001 The hypothesis has two parts First in a warmer climate enhanced precipitation efficiency will lead to less cloud being detrained into the troposphere from convection Second with less cloud cover more infrared radiation can escape to space thereby creating a strong climate stabilizing negative cloud feedback that prevents significant warming from increasing greenhouse gases Within a few years a number of analyses made clear that the evidence provided by Lindzen et al had problems e g Hartmann and Michelsen 2002 Lin et al 2002 Lin et al 2004 Su et al 2008 Lindzen and colleagues responded to these critiques but few were convinced by their arguments By 2006 when I submitted an analysis of tropospheric water vapor that investigated whether there was an iris in that one of the reviewers pointedly questioned why anyone was still working on this issue I subsequently withdrew the paper Nevertheless just because Lindzen et al did not convincingly demonstrate their case does not mean the iris hypothesis is wrong With that idea in mind a new paper by Mauritsen and Stevens 2015 revisits the iris hypothesis The most important part of their work was to simulate the iris in a climate model by artificially tweaking the model s convective parameterization They do this by increasing the rate of conversion of cloud water to rain as the climate warms thereby reducing the amount of detraining condensate in a warmer climate In effect this imposes a tweak that mimics the iris effect it is not a demonstration that the iris effect emerges from any physical mechanisms What they find is that even though cloud cover is reduced as the climate warms it does not generate a strong negative cloud feedback While reducing cloud cover does indeed let more infrared energy out it also lets more sunlight in These two effects while independently large act in opposite directions The net effect is the small residual of their difference For runs with the strongest iris the model s climate sensitivity is reduced from 2 8 C for doubled carbon dioxide to 2 2 C still well within the IPCC s canonical range It s also worth pointing out what this study doesn t prove It doesn t validate Lindzen et al s original hypothesis in fact it does the opposite even with an iris effect the sensitivity does not become negligible Additionally there is little evidence that the rate of conversion of cloud water to rain actually changes with temperature although Mauritsen and Stevens show that incorporating the iris into the model does improve the model s simulations of some aspects of the climate system even though it doesn t change climate sensitivity much I view this as a what if calculation of the impact of such a process Future research may validate this or it may not This kind of calculation is one of the reasons why we like using models of course Another argument against the iris comes from my work looking at the cloud feedback in response to short term climate variability If the iris provided a strong negative feedback then we would expect to see it in response to short term climate fluctuations Analysis of observations doesn t show anything like that Dessler 2013 Overall I think the debate over the iris hypothesis is a testament to the efforts the scientific community goes through to evaluate challenges to theories and find ways to improve our understanding of the climate for instance see Bill Ruddiman s post from last week This is one of the most important reasons I have such high confidence in the scientific process for figuring out how the universe works References R S Lindzen M Chou and A Y Hou Does the Earth Have an Adaptive Infrared Iris Bull Amer Meteor Soc vol 82 pp 417 432 2001 2 3 CO 2 http dx doi org 10 1175 1520 0477 2001 082 2 3 CO 2 D L Hartmann and M L Michelsen No Evidence for Iris Bull Amer Meteor Soc vol 83 pp 249 254 2002 2 3 CO 2 http dx doi org 10 1175 1520 0477 2002 083 2 3 CO 2 B Lin B A Wielicki L H Chambers Y Hu and K Xu The Iris Hypothesis A Negative or Positive Cloud Feedback Journal of Climate vol 15 pp 3 7 2002 2 0 CO 2 http dx doi org 10 1175 1520 0442 2002 015 2 0 CO 2 B Lin T Wong B A Wielicki and Y Hu Examination of the Decadal Tropical Mean ERBS Nonscanner Radiation Data for the Iris Hypothesis Journal of Climate vol 17 pp 1239 1246 2004 2 0 CO 2 http dx doi org 10 1175 1520 0442 2004 017 2 0 CO 2 H Su J H Jiang Y Gu J D Neelin B H Kahn D Feldman Y L Yung J W Waters N J Livesey M L Santee and W G Read Variations of tropical upper tropospheric clouds with sea surface temperature and implications for radiative effects J Geophys Res vol 113 2008 http dx doi org 10 1029 2007JD009624 T Mauritsen and B Stevens Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models Nature Geoscience vol 8 pp 346 351 2015 http dx doi org 10 1038 ngeo2414 A E Dessler Observations of Climate Feedbacks over 2000 10 and Comparisons to Climate Models Journal of Climate vol 26 pp 333 342 2013 http dx doi org 10 1175 jcli d 11 00640 1 Comments pop up 33 An Online University Course on the Science of Climate Science Denial Filed under Climate Science mike 22 April 2015 Guest post from John Cook University of Queensland For many years RealClimate has been educating the public about climate science The value of climate scientists patiently explaining the science and rebutting misinformation directly with the public cannot be overestimated When I began investigating this issue my initial searches led me here which was invaluable in increasing my understanding of our climate and making sense of misinformation RealClimate has inspired and empowered a host of climate communicators such as myself to step forward and help make climate science more accessible to the general public To further the work of educating the public and empowering people to communicate the realities of climate change the Skeptical Science team has collaborated with The University of Queensland to develop a MOOC Making Sense of Climate Science Denial MOOC stands for Massive we ve already had thousands of students sign up from over 130 countries Open available for free to everyone Online web based no software required Course The course examines the science of climate science denial Why do a small but vocal minority reject the scientific evidence for climate change What techniques do they use to cast doubt on the science And we examine the all important question based on scientific research how should we respond to science denial Several strands of research in cognitive psychology educational research and a branch of psychology called inoculation theory all

    Original URL path: http://www.realclimate.org/index.php/archives/2015/04/ (2016-02-13)
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