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  • Debate in the noise « RealClimate
    the fact that no one ever predicted that warming should proceed upward in a smooth line that periodic speedups and slowdowns were expected But nobody ever told me that the appearance of a slowdown in warming might easily go away with better data or better analysis So the implication that the scientists knew this all along takes me by surprise Or am I misinterpreting what you re saying here That s always a possibility since I m not a scientist myself 14 Simon F says 16 Jun 2015 at 3 54 PM As a European I must remind that the global warming has been often illustrated here with the Hadcrut3 score so it is very easy on this side of the Atlantic to understand why many questions came out and why skepticism raised and why proper scientists were embarassed to explain what was going on 15 Mike Flynn says 16 Jun 2015 at 6 10 PM Hi I found this interesting quote from Svante Arrhenius Make of it what you will By the influence of the increasing percentage of carbonic acid in the atmosphere we may hope to enjoy ages with more equable and better climates especially as regards the colder regions of the earth ages when the earth will bring forth much more abundant crops than at present for the benefit of rapidly propagating mankind He seemed to be in favour of global warming 16 John Mashey says 16 Jun 2015 at 9 23 PM Hank if measurements of g were treated like projections in climate science some people would say that nothing that depends on gravity can be done until we know g exactly 17 Victor says 16 Jun 2015 at 10 24 PM Stefan may I ask What is the long term trend you have in mind We see a striking rise in surface temps from 1910 to ca 1940 But that looks a bit early to have been due to f f emissions From 1940 through the late 1970 s we see first a distinct cooling trend followed by a period with little or no trend It s only from ca 1979 1998 only 20 years that we see a strong upward trend apparently coordinated with an equally strong upward trend in CO2 emissions John Cook in Skeptical Science 2009 saw a similar problem over a somewhat shorter period While CO2 is rising from 1940 to 1970 global temperatures show a cooling trend This is a 30 year period longer than can be explained by internal variability from ENSO El Niño Southern Oscillation and solar cycles If CO2 causes warming why isn t global temperature rising over this period http www skepticalscience com The CO2 Temperature correlation over the 20th Century html So if you don t mind I d appreciate it if you could tell us precisely where your long term trend begins and ends Thank you 18 Jan Galkowski says 16 Jun 2015 at 10 30 PM I got about 0 1 per decade simply using a Kalman smoother graphed here http math ucr edu home baez ecological galkowski SmoothingSplineToEstimatePointDerivatives png reported here https johncarlosbaez wordpress com 2014 06 05 warming slowdown part 2 19 Charles Keller says 17 Jun 2015 at 12 24 PM While it is true the hiatus is less flat than originally thought the trend 1999 2014 is lower than suggested by models Indeed the trend if pacific ocean cycles are taken into account would seem to show that the models are on average overestimating climate sensitivity and that rather than ECS being around 3 C it is closer to 2 5 C or perhaps even lower While this is small comfort as the resultant warming will be unacceptable it does suggest that society has more time perhaps a decade to reduce Carbon emissions This is good news In addition I am aware that modelers are looking hard at the climate sensitivities of their models and looking for reasons it may indeed be smaller than simulated Can you comment 20 Barton Paul Levenson says 17 Jun 2015 at 12 31 PM The O Floinn Yes Arrhenius thought global warming would be a good idea He was writing in winter in Sweden in 1896 Also he thought it would take 3 000 years to double carbon dioxide He didn t get the exponential growth thing 21 Charles Keller says 17 Jun 2015 at 12 32 PM While the recent adjustments to the global temperature record are interesting the observations 1999 2014 show less of a trend than previously determined This is good news perhaps giving society more time to reduce carbon emissions However the resultant implication is that climate sensitivity is lower than predicted by computer models down from around 3 C to 2 5 or even closer to 2 C Thus it would seem the models are missing something aerosol or cloud forcing that would be essentially negative feedbacks I am aware that modelers are hard at work looking for such mechanisms Can you comment 22 Barton Paul Levenson says 17 Jun 2015 at 12 32 PM V 17 The long term trend is evident from say 1850 to 2014 where CO2 accounts for 80 of the variance of temperature anomalies Plot the slope Do a t test of a regression of dT against time Tell me what you find Of if you don t like HadCRT do 1880 2014 and use NASA GISS or NOAA figures 23 michael sweet says 17 Jun 2015 at 12 56 PM Victor If you continue to read the Skeptical Science post you linked the next two paragraphs read The broader picture in this scenario is to recognise that CO2 is not the only factor that influences climate There are a number of forcings which affect the net energy flux into our climate Stratospheric aerosols eg from volcanic eruptions reflect sunlight back into space causing net cooling When solar activity increases the net energy flux increases Figure 3 shows a composite of the various radiative forcings that affect climate When all the forcings are combined the net forcing shows good correlation to global temperature There is still internal variability superimposed on the temperature record due to short term cycles like ENSO The main discrepancy is a decade centered around 1940 This is thought to be due to a warming bias introduced by US ships measuring engine intake temperature It does not make you more convincing to post obviously misleading quotes 24 Jim Eager says 17 Jun 2015 at 1 36 PM Victor think about particulate and sulphur aerosols from continuous and ever increasing burning of coal and oil in the complete absence of environmental controls in the post WW2 era and how that would affect incoming solar insolation Bear in mind that CO2 from that same burning would also increase unabated during that same period Now think about the rapid introduction of effective legislation and regulations in Europe and North America to reduce those aerosol emissions and what the temperature trend would do soon after their introduction Now look at the temperature trend for the second half of the twentieth century Really it s not that difficult 25 dp says 17 Jun 2015 at 2 30 PM Surely the quiet period was from about 2003 2013 1998 was an outlier caused by a very strong ElNino Temperatures didn t approach it until several years later 26 Christopher Hogan says 17 Jun 2015 at 2 55 PM At 17 Victor I may be off base but didn t they just cover this two posts ago http www realclimate org index php archives 2015 05 global warming and unforced variability clarifications on recent duke study We found that unforced variability is large enough so that it could have accounted for multidecadal changes in the rate of increase of global average surface temperature over the 20th century If I read that right it s correct that ENSO can t account for it It s likely attributable to AMO and other longer period oscillations This does not necessarily explain the observed variation I ve seen other analyses point to e g hypothesized ill quantified changes in aerosols and particulates It just says that you don t necessarily have to explain it i e that not every multi decade trend requires explanation via forcing Such trends may or may not occur as a result of internal variability of the earth atmosphere system Those results are new and so would not have been factored into the cited skeptical science analysis The article then goes on to nail the key issue in that internal variability is not large enough to account for 20th century overall trend So that gives the empirical answer Somewhere between a few decades and a century is long enough 27 Jim Eager says 17 Jun 2015 at 3 16 PM Charles Keller wrote the observations 1999 2014 show less of a trend than previously determined Charles what you are missing is that the observations for 1999 2014 don t show the long term trend period because 15 years is simply too short a time span for the trend to be resolved from the noise of short term natural variability which means it tells you nothing at all about climate sensitivity What it does tell you is that over short time spans natural variability can overwhelm the underlying long term trend See https tamino wordpress com 2015 04 30 slowdown skeptic and https tamino wordpress com 2015 01 20 its the trend stupid 3 and http moregrumbinescience blogspot ca 2009 01 results on deciding trends html 28 Barton Paul Levenson says 17 Jun 2015 at 3 44 PM CK 20 15 years isn t enough to tell a climate trend You need at least 30 http bartonlevenson com 30Years html http bartonlevenson com NoWarming15Years html 29 Dennis Just says 17 Jun 2015 at 4 55 PM Richard Hawes from the previous post on this site it seems that difference is due to bucket corrections Someone more knowledgeable than I may be able to help you explain what that is or perhaps the google will help Cheers There is some variation around the 1940s because of the bucket corrections See more at http www realclimate org index php archives 2015 06 noaa temperature record updates and the hiatus sthash hXtDpQck dpuf 30 Victor says 17 Jun 2015 at 9 22 PM 22 Michael first of all I asked a question when did the long term trend referenced by Stefan begin and when did it end Still haven t received a reply but I can wait no problem Secondly regarding John Cook s concern regarding the lack of trend over a 30 year period I m very aware of the hypothesis he offers by way of explanation I analyze his explanation in my book However a hypothesis intended to provide reasons for the absence of an expected trend does not automatically produce the expected trend A trend or lack of trend will remain regardless of how reasonable the explanation might seem And if his observation regarding the lack of warming trend over such a long period is accurate and it certain seems consistent with the data then it looks to me like there was in fact no long term trend after all That doesn t mean the lack of a trend can t be accounted for by some hypothesis But no hypothesis can produce a trend that never existed in the first place In other words Regardless of what one might want to claim regarding what might have caused the trend to not appear in the data the lack of trend remains in the data regardless and the claim of a long term trend cannot therefore be maintained 31 Kevin McKinney says 17 Jun 2015 at 9 38 PM I don t recall anyone saying the hiatus could easily be an artifact of insufficient data See more at http www realclimate org index php archives 2015 06 debate in the noise comment page 1 comment 632625 Mike not sure how far back you want to go But the clearest voice saying this has been statistician Tamino For example here is a piece describing a paper he co wrote in 2011 https tamino wordpress com 2011 12 06 the real global warming signal None of the data sets shows any evidence that the global warming rate has changed recently A truly fascinating result is that increased precision enables us to establish the statistical significance of a warming trend using a shorter time span than with unadjusted data All five data sets show statistically significant warming since 2000 There s also the story about the discussion of the pause in AR5 the comments of the government of Germany may be of some interest in this connection https www ipcc ch pdf assessment report ar5 wg1 drafts WGIAR5 FGD FinalDraftSPMComments pdf 32 Hank Roberts says 18 Jun 2015 at 8 52 AM Victor Still haven t received a reply The real scientists don t appear on command to retype the frequently questioned answers that s why others have repeated the pointers to sources for you to read Again Statistics 101 is what you re lacking here It will change your view of the world if you pass the course Or since you claim to be an academic talk to one of the reference librarians about how to ask better questions You can do it 33 KeefeAndAmanda says 18 Jun 2015 at 11 11 AM Victor wrote on 17 Jun 2015 9 22 PM the lack of trend remains in the data regardless and the claim of a long term trend cannot therefore be maintained There is no lack of an underlying long term ongoing and still positively accelerating global warming since the 1800s in the data If you actually want to see this still positively accelerating global warming starting in the 1800s in the data in a very clear and simple graphical representation and if you accept the existence of up to 60 year oscillations such as the most general one the NMO of Steinman Mann and Miller 2015 which combined the AMO and the PMO a term they used to denote the apparent up to 60 year oscillation in the PDO then a 60 year running mean a 60 year moving average shows this quite nicely and here it is http www woodfortrees org plot gistemp mean 720 This graph gets rid of all these multidecadal oscillations of up to 60 years It shows a graph of global warming since the 1800s that clearly seems to follow the path not of a straight line but of a positively accelerating curve that shows no sign of slowing down even as we speak By positively accelerating curve I mean the curve of a convex function a function whose second derivative on the given interval is positive Note This graph of a 60 year running mean was given by commenter Olof twice at Open Mind in the comment threads under the articles https tamino wordpress com 2015 04 30 slowdown skeptic and https tamino wordpress com 2015 05 19 response in which articles and in comments under these articles Tamino showed via statistical analysis that the global warming underlying all this shorter and longer term variability is positively accelerating consistent with what the 60 year running mean graph clearly shows in a glance I note that this phenomenon of the positive acceleration seemingly showing no sign of slowing down in the 60 year running mean essentially includes all the years covered by the 30 year running mean seen at this article http www skepticalscience com global warming still happening html which includes all the mere slowdown since around 2000 and all the actual downturn 1940s to 1970s and that this difference in mere slowdown and actual downturn is consistent with an upward increasing cycling curve suggested by the 30 year running mean oscillating around a still positively accelerating curve suggested by the 60 year running mean That is when we compare the 30 and 60 year running means we see the broad effect of the NMO appearing becoming more apparent and then disappearing to the point of seeing essentially nothing in the 60 year running mean but the raw continuing positive acceleration of AGW That is this graphical information makes it very easy and clear to see that not only is it true that AGW attribution is clearer and predictions are more certain with the longer the run but that the long term global warming underneath the NMO oscillation is not following the upward path of merely a straight line but as the 60 year running mean graph shows it is following what seems to be the upward path of a positively accelerating curve that shows no sign of slowing down even as we speak If these links don t work then try Google images which shows these graphs when we enter 30 year running mean and then when we enter 60 year running with the parentheses Final point to anticipate an objection to a 60 year running mean As Steinman Mann and Miller showed the NMO with its up to 60 year oscillations exists and so it s about time to fully and appropriately recognize this fact and all its implications 34 Victor says 18 Jun 2015 at 1 21 PM 22 Barton Paul Levenson The long term trend is evident from say 1850 to 2014 where CO2 accounts for 80 of the variance of temperature anomalies Well here s a graph covering that period actually three http www abc net au news 2015 02 02 global average temperature anomaly 281850 201429 6064298 I don t see an upward trend until ca 1910 Things are definitely warmer now than they were in 1850 I ll grant you that But a difference is not the same as a trend no Now from 1910 we see a rather steep upward trend culminating ca 1940 I m

    Original URL path: http://www.realclimate.org/index.php/archives/2015/06/debate-in-the-noise/ (2016-02-13)
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  • IPCC « RealClimate
    10 24 Joules The decision was widely welcomed by the science and policy communities as a great step forward In the past the 2 C goal has allowed some governments to pretend that they are taking serious action to mitigate global warming when in reality they have achieved almost nothing I m sure that this can t happen again with the new 10 24 Joules goal said David Victor a professor of international relations who originally proposed this change back in 2014 And an unnamed senior EU negotiator commented Perhaps I shouldn t say this but some heads of state had trouble understanding the implications of the 2 C target sometimes they even accidentally talked of limiting global warming to 2 I m glad that we now have those 10 24 Joules which are much easier to grasp for policy makers and the public This fictitious newspaper item is of course absurd and will never become reality because ocean heat content is unsuited as a climate policy target Here are three main reasons why More Comments pop up 155 Climate response estimates from Lewis Curry Filed under Climate modelling Climate Science Greenhouse gases Instrumental Record IPCC group 6 October 2014 Guest commentary from Richard Millar U Oxford The recent Lewis and Curry study of climate sensitivity estimated from the transient surface temperature record is being lauded as something of a game changer but how much of a game changer is it really More References N Lewis and J A Curry The implications for climate sensitivity of AR5 forcing and heat uptake estimates Clim Dyn vol 45 pp 1009 1023 2014 http dx doi org 10 1007 s00382 014 2342 y Comments pop up 236 Older Entries Newer 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 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

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  • IPCC « RealClimate
    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 Debate in the noise Filed under Climate Science Communicating Climate Instrumental Record IPCC Reporting on climate stefan 15 June 2015 Last week there was an international media debate on climate data which appeared to be rather surreal to me It was claimed that the global temperature data had so far shown a hiatus of global warming from 1998 2012 which was now suddenly gone after a data correction So what happened One of the data centers that compile the data on global surface temperatures NOAA reported in the journal Science on an update of their data Some artifacts due to changed measurement methods especially for sea surface temperatures were corrected and additional data of previously not included weather stations were added All data centers are continually working 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 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 global warming signal to observations using empirical estimates of unforced noise Sci Rep vol 5 pp 9957 2015 http dx doi org 10 1038 srep09957 Comments pop up 36 Older Entries Site Google Custom Search Recent Comments What is the best description

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  • A new sea level curve « RealClimate
    30 years but since the weights of the filter decline away from the central point I cited the half width this is like citing an effective width for a Gaussian weighting curve The filter can produce smooth sea level curves which are as long as the original unsmoothed curves so it does not end before the original data and you can see the rate curves go as far as the sea level curves in Fig 1 Of course the treatment of the end points where data are not available across the full filter width introduces some uncertainty Luckily this is not a big issue here because the rate at the end for the last 20 years we know very well from the satellite data If one wants to discuss changes in rate within the past twenty years one should really only use the satellite data for that and not the rate curves from the tide gauges shown here stefan 8 t marvell says 15 Jan 2015 at 1 03 AM For public consumption it would be nice have a clean line but one that can be justified I would suggest the median of the 7 estimates for each year Why do the Wenzel Schroter estimated trends differ in the early years from the others 9 Neil White says 15 Jan 2015 at 3 30 AM t marvell 5 As far as I can tell having read the papers and discussed this with one of the authors part of the technique Wenzel and Schroter use is to fill the early part of the shorter nearly always later records with a linear fit to the existing data this tends to damp down the variability early in the 20th century leading to the straight lines smaller variability earlier in the century in both figures One could also argue that the variability in the early part of the century in some of the other time series is too large because of the increasingly sparse data distribution as we go back in time Some of the estimates have error bars that take this into account Some don t I think it would be interesting to see versions of these figures that only use time series with believable error bars Neil 10 warrenlong says 15 Jan 2015 at 5 35 AM Wili 4 said It looks as if the rate of rise graph stops at about 2003 Has the rate remaind stable now at about 3 mm yr over the last ten years or so Or has the rate continued to increase Wili I believe the Purkey Johnson 2014 said 3 4mm and then we have the following paper http www atmos washington edu bitz 514 2013 RecentChangesInGreenlandAntarctica 2013 pdf 11 stefan says 15 Jan 2015 at 7 34 AM Hi Carling Eric Bob and Jerry nice work and very interesting paper I hope you will join the discussion to better understand the method and differences especially compared to Church White Towards this I d love to see these two tests 1 Run your reconstruction method with exactly the same tide gauges as used by Church White to see what part of the difference is due to analysis method and what part due to different input data 2 You used your reconstructed field as truth to test how the Church White method performs with that What do you get when you use their reconstruction as truth and test how your method performs on that Also it would be great to see a map of the different trends in order to understand the regional structure of the differences Cheers Stefan 12 Nichol Brummer says 15 Jan 2015 at 10 51 AM If I understand correctly both methods try to calibrate their tide gage data by comparing with the satellite data And all the non satellite data has trouble to cope with water being moved around by wind and weather which can also have effects on time scales as long as those for which we have satellite data wouldn t that mean that there is a nearly irreducable systematic effect due to weather wind pushing around the oceans in the satellite era The only way to correct for that would be if there are trustworthy models for describing these movements of ocean water in the satellite era I m also very curious if there is an explanation for those periods with a hiatus in sea level rise Are those real or is there an instrumental explanation 13 Victor says 15 Jan 2015 at 11 29 AM According to all the curves going back that far sea levels appear to have begun their rise sometime around 1880 Is there any evidence that worldwide fossil fuel emissions would have been high enough at that early date to already be affecting sea level And if as Stefan reminds us above there is a considerable delay between atmospheric warming and sea level rise that means FF emissions would have to have been warming the atmosphere to a considerable extent already by mid 19th century or earlier Does that seem likely Response Given the multi decadal variability you can t really tell when a significant rise above the noise started Also I don t believe all this multi decadal stuff is real global sea level change rather than data noise The problem is much worse furthest back in time when there is few tide gauges stefan 14 Robert says 15 Jan 2015 at 2 28 PM Interesting article But a minor point I wonder if there is a typo in your first paragraph You write Up to about 1970 the new reconstruction of Hay et al runs at the top of the existing uncertainty range OK I see that so I guess I m looking at what you are looking at But then next sentence For the period from 1880 AD however it shows the same total increase as the current favorites by Church White Did you mean 1980 and not 1880 And the following sentence Starting from 1900 AD it is about 25 mm less Did you mean 2000 AD and not 1900 AD Are these typos or am I missing something wouldn t be the first time or do I just need to clean my glasses Response I meant it as I wrote it not sure what is unclear for you stefan 15 BobR says 15 Jan 2015 at 2 44 PM You imply the satellite data does not suffer uncertainty with respect to local conditions like the tide gauges do How do we know the elevation of the satellite Is it referenced to some land based point If so the satellite data would be subject to those local conditions How is the change in satellite elevation reflected in its data Does it have perfect elevation or one at least below the margin of error These are questions that popped up as I read this good summary article Thank you 16 sidd says 15 Jan 2015 at 3 28 PM I see 3 2 0 4 mm yr in Purkey 2014 and Hay 2015 gives 3 0 0 7 mm yr so they agree to within error 17 Robert says 15 Jan 2015 at 5 23 PM Stefan there are possibly two sources of my confusion First when you write Up to about 1970 I can read that as incorporating the period from 1880 and I can read the period from 1880 as incorporating the period Starting from 1900 But you are treating these as 3 distinct periods Perhaps if you included both start and end dates for the periods you are comparing I would have seen it more clearly Also it may be possible that I am confusing the colors the color for the Hay curve is somewhat similar to the color for the Church White 2011 curve at least on my screen Or perhaps I am missing something else Response I see When saying up to about 1970 I am talking about where the curve runs Hay is the uppermost After that I am talking about the total rise from 1880 to present which is the same in Hay and Church White and from 1900 to present which is about 25 mm less in the former because in 1900 Hay is about 25 mm above Church White as you can see in the graph stefan 18 Neil White says 15 Jan 2015 at 6 24 PM BobR 13 Answers to some of your questions are here http www cmar csiro au sealevel sl meas sat alt html The satellite altimeter data is referenced to an ellipsoid which is in turn referenced to the centre of the Earth so the satellite altimeter data is effectively referenced to the centre of the Earth 19 Hank Roberts says 15 Jan 2015 at 7 12 PM How do we know the elevation of the satellite Triangulation from known points using the speed of light and accurate clocks Same method the GPS system uses Do you now how long a nanosecond is physically That is how far light travels during that time This far http highscalability com blog 2012 3 1 grace hopper to programmers mind your nanoseconds html 20 Hank Roberts says 15 Jan 2015 at 7 14 PM In case that link failed try this one http 3 bp blogspot com zH99SS8Ga0U Ta36kWgQM0I AAAAAAAABAs k6WOz2POw5k s1600 Nano hanger jpg 21 James Newberry says 15 Jan 2015 at 9 35 PM If you look sideways at the curves of Figure 1 you can discern an acceleration of the rate of sea level rise This is also apparent in Figure 2 If that acceleration trend continues unabated through any significant portion of the planet s ice sheets then we could lose all seaports like NYC Boston Seattle and coastal communities natural and man made Seems like a serious national and international security threat to me as in clear and present danger 22 Hank Roberts says 15 Jan 2015 at 9 48 PM Also for BobR the other important part of how the satellites are located precisely is many measurements not only one Each individual measurement has some error If we only had one thermometer or one satellite altimeter we d be limited to that single instrument s error limits Someone with better and newer statistics than I have should explain how accuracy goes up with more measurements explain it better it s a basic tool much used and the reason it works isn t easily obvious without Stat 101 23 Hank Roberts says 15 Jan 2015 at 9 49 PM someone Oh yeah it s 2014 You can just oogle it https www google com search q how does taking more measurements increase accuracy 24 Bob Kopp says 16 Jan 2015 at 7 44 AM Hi everyone Responding to Stefan s response to Wili I m not sure I agree that one should always use satellite data over the last 20 years instead of tide gauge data It depends on the question Satellite data are denser but they have different data gaps for example they don t exist in the polar regions where some of the biggest effects associated with the proximity of shrinking land ice sources occur They also measure a slightly different vaeiable sea surface height aka geocentric sea level ie the height of the sea surface relwtive to the planet s center of gravity rather than sea level proper aka relative sea level ie height of the sea surface relative to the solid Earth Satellite data are better for some questions but if you want to compare sea level over the last 20 years to earlier sea level I think you re actually better off not changing your metric or using a statistical method that incorporates both and recognizes fhe differences between them Stefan good suggestions in 11 We are working on a reconstruction using only Church White s tide gauges and I ll have to think about the idea of using their EOF reconstructions We are preparing to deposit all 622 of our tide gauge reconstructions and intend to generate some maps when we write the data descriptor Nichol we don t use satellite data in our calibration Our physical patterns are based on the physics of glacier ice sheet melt static equioibrium fingerprints glacial isostatic adjustment models and an ensemble of GCMs to inform the ocean dynamic contribution 25 Chris Dudley says 16 Jan 2015 at 9 33 AM Hank 22 It is pretty easy to see why taking many throws of a die can suss out if the die is weighted much better than taking just a few 26 wili says 16 Jan 2015 at 1 17 PM This study http www ocean sci discuss net 11 2029 2014 osd 11 2029 2014 print pdf seems to be going around the denialosphere where they are claiming it shows that there is no acceleration in the rate of slr Interestingly even that claim implies that they accept that there is some sea level rise They point especially to the right hand graph in figure 10 page 2069 as showing a possible recent decrease in rate of slr in the last decade or so I m afraid I m a bit out of my depth in pointing out what might be wrong with this What exactly is that graph measuring It seems to me that this is too short a time frame to tell us much And it also conveniently for denialists apparently ends at 2011 when there was an anomalous drop in sea level because so much of it ended up temporarily on land as deluges in Australia and a few other places But I don t feel particularly confident in assessing this study Any help would be most appreciated 27 prokaryotes says 16 Jan 2015 at 1 17 PM Message The new analysis suggests that the acceleration in the past two decades is 25 percent higher than previously thought Carling Hay 28 Bob Kopp says 16 Jan 2015 at 2 09 PM I should note one element of the paper not highlighted in this write up the closing of the 1901 1990 sea level rise budget In ch 13 of IPCC AR5 WG1 the authors note that the two reasonably well modeled components of the sea level budget thermal expansion and glaciers add up to about 1 1 mm y Given the previous sea level trend estimate of about 1 5 mm y there is a gap that requires either that these two components both be at the high end of projections or that there is a significant contribution from Antarctica and or Greenland The lower trend found by our study is consistent with the median projected sums of thermal expansion and glacier mass loss implying that no net contribution from polar ice sheets is needed over 1901 1990 By contrast there is of course a significant contribution over the past 20 years observed directly and seen along with greater thermal expansion in the 3 0 mm y rate of rise over 1993 2010 29 Neil White says 16 Jan 2015 at 6 27 PM It seems to me that the biggest difference between the new GMSL curve and most of the others is the flat spot in the new curve from about 1950 to 1970 This more or less corresponds to the flat spot in the global mean temperature series There is a belief in some quarters that the sea level generally lags behind global mean temperature If you were to replace that bit of the new curve with a section with the same slope as many of the others then all of the curves would more or less lie on top of one another Many of the other curves have a jump up in the late 1950s which contributes to the slope over this time span whereas the Hay et al curve doesn t There are jumps in a number of tide gauge records at this time probably partly related to an El Nino event Some other shorter time series e g Holgate and Woodworth 2004 http onlinelibrary wiley com doi 10 1029 2004GL019626 full also show a fairly steep increase in GMSL over this period This study uses a fairly simple tide gauge averaging technique Why is the Hay et al GMSL curve so flat through this period Response Hi Neil I noticed the same thing and wondered whether a flat bit can indeed shift the whole curve thereafter this would be the case if the method reconstructs sea level increments from the data and then produces the proper sea level curve by time integration An equation shown in the methods section suggests that is the case but when I raised this with the authors they said no How is this in your method I think this is a key issue that needs clarification stefan 30 t marvell says 16 Jan 2015 at 7 58 PM The satellite estimates show an upward linear trend from 1993 2014 for GMSL http www aviso altimetry fr en data products ocean indicators products actualitesindicateurs des oceansniveau moyen des mersindexhtml html The seven estimates in this post show expodental trends maybe even quadratic trends in recent years That s vastly different from a linear trend The satellite data are better There isn t much difference between satellite data and the seven estimates in the amount of GMSL growth in the past few decades but the shape of the curves of course suggest very different future trends 31 MARodger says 17 Jan 2015 at 5 30 AM wili 26 If you examine Fig 10 Right hand panel of Ablain et al 2014 you may be less eager to suggest of the delusionist position even that claim implies that they accept that there is some sea level rise The zero rise is actually closer to the top of the graph than the bottom What the graph does show is signs of

    Original URL path: http://www.realclimate.org/index.php/archives/2015/01/a-new-sea-level-curve/ (2016-02-13)
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  • Diagnosing Causes of Sea Level Rise « RealClimate
    1 5 mm year or 1 8 mm year http www aviso altimetry fr en data products ocean indicators products actualitesindicateurs des oceansniveau moyen des mersindexhtml html Correct 12 Hank Roberts says 8 Jan 2015 at 9 02 PM For Jon Evjen consider that less than 30 percent of planet Earth s surface is land the rest is ocean and a bit of ice here and there You can look up the areas where oil and water have been extracted and yes there s subsidence well documented and some of it seems a big scary number on the vertical dimension in human terms Heck California s still mining water like crazy now knowing that most aquifers after they collapse can t un collapse That s a one time use Water checks out it never checks back in Yet we suck Examples abound including some under the ocean e g http en wikipedia org wiki Ekofisk oil field there are several maps there On a map of the world areas mined for water or oil and the subset of those that are instances of compaction and sinking are very very small in comparison to the surface of the oceans viewed from satellites That s why they say negligible above I know it sounds like dismissal or a brushoff if you haven t looked at the numbers and the maps to be told that s not a big enough number to matter the natural response is why not The trick here is mostly we amateurs I m definitely not a scientist can figure some of this stuff out and await correction we know where people have drilled and pumped out water and oil and gas and we know where the surface has collapsed It s a big deal for those living on it but not compared to the area of the ocean looked at in these recent studies These studies aren t using measurements of sea level at the coastline As they say above satellite altimetry has provided high resolution measurements of sea surface height These data are used to estimate local and global sea level variations That s not height against the levee or seawall at New Orleans That s height from orbit over the broad expanse of the ocean 13 Hank Roberts says 8 Jan 2015 at 9 10 PM Good news for Chinese ocean science and a discussion of how data is collected and some of the problems with the old methods http www theguardian com environment climate consensus 97 per cent 2014 nov 28 chinese scientific revolution tackle climate change 14 sidd says 9 Jan 2015 at 12 40 AM Thank you Prof Purkey and Prof Johnson for many years of stellar work I recall your paper from 2010 doi 10 1175 2010JCLI3682 1 showing significant abyssal below 4000m warming and freshening in the Southern ocean I believe von Schuckmann doi 10 1029 2008JC005237 2009 also saw a freshening above 2000m in the Southern Ocean Could this signal have anything to do with increased ice melt I do not suggest that the fresh water originated from the ice but are there any plausible circulation changes that might have affected both I have in mind something like the wind driven intrusions of CDW onto the continental shelf although i am hard put to extract a mechanism for freshening extending below 4000m sidd 15 Ray Ladbury says 9 Jan 2015 at 5 39 AM Fritz Since water is a fluid its surface will conform to minimum gravitational potential energy that is it will deform due to the local gravitational field which is proportional to the mass present locally That ice represents a whole helluva lot of mass but since the mass is decreasing water will flow away from the glacial regions as they melt Make sense 16 Kevin McKinney says 9 Jan 2015 at 10 48 AM This would be better on the Unforced Variation thread but we don t have one for January yet and this does respond to Hank s 13 From that link comes this quote from John Abraham While in many parts of the world like Australia and the USA in particular funding for basic research is decreasing in China things are different Funding is increasing in critical scientific areas Perhaps more importantly in China scientists are respected In my country as well as in Canada and Australia whenever you tell people you are a scientist you must prepare for a negative reaction Perhaps it is because we understand human evolution the history of the universe climate change or the causes and effects of acid rain as just some examples Understanding basic science is a threat to many people in my country Just being a scientist means I represent those things that are an anathema It is a very sad state when the people who are most needed to help us navigate our social problems are dismissed by a sizable population This is not the case in China My Chinese colleagues get support from their government their media and the larger society They don t have to wade through hate mail upon coming to the office in the morning Now that is a sad story well not the Chinese part 17 Russell Seitz says 9 Jan 2015 at 10 52 AM Ray the presence of seriously thick ice in both Antarctica and Greenland complicates the view you offer isostasy makes mile high ice sheets indent the Earth s deformable crust and the base of ice sheets that thicken over geological time can as is spectacullarly the case under central Greenland end up a kilometer below sea level a lot of moulin water ends up in such inland depressions instead of flowing into the sea Still there is hope for sea level rise mitigation as long as you like chowder 18 Chris Dudley says 9 Jan 2015 at 11 41 AM It is worth noting that University of Hawaii is studying divesting from fossil fuel companies http www hawaii edu news 2015 01 08 uh to study divesting from fossil fuel companies 19 fritz says 9 Jan 2015 at 1 33 PM Thanks Ray if I follow your explanation the remaining part of Antarctic must gain Ice and gravitational potential as does the South Atlantic why 20 Mal Adapted says 9 Jan 2015 at 3 59 PM Prof Steig inline to my 6 Local land subsidence presumably has a negligible effect on global sea level as measured by satellite instruments Response Not presumably It IS negligible eric Thanks I didn t have a citation readily available while you OTOH can say that with authority 8 Response What I meant is that I cannot imagine it is anything but negligible If I am somehow wrong I am happy to be corrected eric 21 Hank Roberts says 9 Jan 2015 at 4 44 PM A more relevant to this topic quote from that article I linked the Chinese Academy of Sciences hosted a small workshop which involved scientists from around the world that work on a device called the Expendable Bathythermograph or XBT The obscurity of the conference speaks volumes it didn t get much if any press attention This fact tells a lot about the host nation XBTs are devices that are used to measure ocean temperatures They were developed many decades ago Each year hundreds of thousands of these devices are dropped into the world s oceans A huge database stretching back to the 1960s is available for climate studies The problem is that the devices are designed to be well expendable and cheap When their wire spool runs out the wire breaks and the torpedo like device detaches from the ship and sinks to the ocean floor The expendable nature of the device has forced the cost per device to be low As a result no pressure sensors were installed on the devices so water depth cannot be determined directly So understanding the accuracy of XBT fall rates the rate that they descend in the water is one of the most important and difficult issues in all of climate science devices have changed as the years have passed fall rates depend on the temperature of the water All of this makes for time and spatially varying fall rates real mess Despite this only a small handful of scientists are actively working to improve XBT accuracy and the Chinese Academy of Sciences decided to bring them all together This unique group of individuals met for three days to try to hammer out a best practices standard While we don t know yet what the outcome is from this meeting we see that China has taken a leading role as a scientific player 22 WJ Long says 9 Jan 2015 at 9 06 PM I guess the only dumb question is the one not asked So why would the Indian and Atlantic sectors of the Southern Ocean be considered to act as one during the study period because of changes in the Weddell gyre Would not the effect be proportional to the areas in question thus allowing for observational differences 23 Everett F Sargent says 10 Jan 2015 at 1 24 AM 11 Chris Dudley Here s an Accepted Article version https informedgreencifers files wordpress com 2014 11 jgrc20949 pdf 24 Ray Ladbury says 10 Jan 2015 at 8 40 AM Think about what happens when the ice flows into the oceans on a rotating Earth Where will the water go on a rotating sphere 25 Ray Ladbury says 10 Jan 2015 at 8 41 AM Russell Agreed but these are second order effects and the ground does rebound over time The net change is still less mass at the poles 26 Chris Dudley says 10 Jan 2015 at 10 39 AM Everett 23 Thank you The first sentence gives global sea level rise of 3 2 mm per year That makes it plain what they are doing This passage in this article starts to do it Over recent decades very roughly half of the observed mean sea level rise is owing to changes in ocean density with the other half owing to the increased in ocean mass mostly from melting glaciers and polar ice sheets The exact proportion has been difficult to pin down with great certainty But this article never gets back the the proportion 27 Hank Roberts says 10 Jan 2015 at 6 38 PM this article never gets back the the proportion This article adds a third term and so the proportion is different I could wish for a list of other possibilities that were considered and ruled out as possibly whether individually or in combination making some considerable change to the total snark Plastic garbage patch expansion can that affect sea level Spurious signals fooling the satellites maybe You can be sure fans of other imaginative possiblities will be trying to come up with numbers that add up to a propitious sum that will suit their fancies 28 Mal Adapted says 10 Jan 2015 at 9 04 PM While local land subsidence may have a negligible effect on SLR over decades to millenia at 10 to 100 million year time scales the relationship of global sea level to continental drift is apparently well established YMMV but IMO the prospect of climate chaos within our lifetimes can t detract from the wonder of geologic processes working in deep time 29 Edward Greisch says 11 Jan 2015 at 7 56 AM What is the temperature measurement system in the Argo floats How accurate and precise is it 30 Chris Dudley says 11 Jan 2015 at 10 07 AM Hank 27 No I think they are looking just at steric and mass contributions seeking a better separation between them I m complaining about making it clearer that this is their over all object They did this immediately in their paper but have not been as plain in a popular article 31 Hank Roberts says 11 Jan 2015 at 12 20 PM for Edward Greisch in case this helps LMGTFY Short answer as i read it after a few minutes research with oogle it depends as with other measurements using a variety of devices over the years a lot of work goes into answering that question A bit from one early paper as just one example 253 Journal of Oceanography Vol 60 pp 253 to 258 2004 Short Contribution Stability of Temperature and Conductivity Sensors of Argo Profiling Floats 31 May 2003 After recalibration of the temperature and conductivity sensors of three Argo profiling floats recovered after operations for four to nine months the results indicate that the floats basically showed no significant drift either in temperature or salinity and adequately fulfilled the accuracy requirement of the Argo project 0 005 C for temperature and 0 01 psu for salinity More than a decade later they re still working on improving this e g A Preliminary Study on Quality Control of Oceanic Observation Data by Machine Learning Methods well worth a glance Pasting your question into Scholar and then limiting the results to recent years will give you a few solid hours reading if you want to go into that http scholar google com scholar as sdt 0 5 q temperature measurement system in the Argo floats 3F hl en as ylo 2014 I m not a robot check I m not a librarian check I m some guy on the Internets check double check could be wrong 32 wili says 11 Jan 2015 at 7 48 PM Nice article Reading the title though I was hoping for a review of all the slr relevant articles over the last year with perhaps an estimation of what they spell wrt how fast and how far we might see sea levels rise in this century and the next Any chance that something like that might be in the works Or if it already exists somewhere I d be happy for a pointer in that general direction 33 michael sweet says 11 Jan 2015 at 9 30 PM This Skeptical Science article states that sea level declined about 3 meters over the past 4 5 000 years due to sea floor subsidence That is about 0 7 mm yr Is this subsidence correct and continuing and does it affect your calculations significantly Should this be added to either the expansion or the mass increase number 34 prokaryotes says 12 Jan 2015 at 12 42 AM Related Sea level rise What the experts expect http www realclimate org index php archives 2013 11 sea level rise what the experts expect 35 Tom Scharf says 12 Jan 2015 at 2 02 PM What matters to society is RSL coastal not GSL If the middle of the ocean increases faster than RSL then this is of little policy importance The global map showed a lot of the GSL was out in the middle of nowhere in the Indian ocean as I recall The latest IPCC report had little to say about the connection between RSL and GSL only that RSL is regional and varies Most people assume that average RSL will rise at the same rate of GSL but I wonder about that What seems to be a disconnect to me is that NOAA tide gauges seem to average 2mm year versus GSL estimates of 3mm year It suggests that RSL is rising slower than GSL which would seem to be an important point The increased volume isn t making it to the coasts As for acceleration almost all the NOAA gauges on their website show a very near linear trend some going back 100 years or more at some locations The JASON data shows a near linear increase over the past 20 years of 3 2mm year and is supposedly calibrated to RSL tide gauges The IPCC SLR models expected sea level rise to be 3 7mm year at this point and this 15 observational difference suggests the models have overestimated the rate of acceleration There is no good explanation for this there are theories it might be pause related but it is noted that SLR did not pause with the temperatures from 1940 to 1970 according to tide gauges At what point would the SLR models be revisited if the discrepancies persist 36 Mal Adapted says 12 Jan 2015 at 2 59 PM michael sweet This Skeptical Science article states that sea level declined about 3 meters over the past 4 5 000 years due to sea floor subsidence Fascinating I did not know about that I want to thank Jon Evjen for raising an interesting question whether he intended to or not 37 Jim Eager says 12 Jan 2015 at 5 20 PM Mal not mentioned in that 2012 piece by Rob Painting is thermal contraction as a factor in that 4 5000 year decline in sea level Global mean temperature has been slowly declining since the Holocene climate maximum of 5 6000 years ago which is plenty long enough for that cooling to be integrated at least in part into the ocean so some part of that sea level decline would be expected to be due to steric change no 38 Hank Roberts says 12 Jan 2015 at 6 30 PM sea floor subsidence Distinguish at least two very different forms there One what Jon Evjen asked about local subsidence like New Orleans experiences That s been very fast as it has in similar places New Orleans is sinking locally because of pumping oil and water out of the sedimentary basin https www google com search q 22new orleans 22 groundwater oil pump subsidence ie utf 8 oe utf 8 Two post ice age change very slow due to a mile or two of ice having melted off of one side of a very thick rigid solid piece of the Earth s crust There areas tipped teeter totter fashion one side sinking under the ice cap the other side

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  • Oceans « RealClimate
    warming seen in the observations during 2001 2013 One simple way to address this is to examine what is different about the recent decade compared to the preceding decade when the global mean SAT metric accelerated This can be quantified via decade mean differences or via multi decadal trends which are roughly equivalent if the trends are more or less linear or if the focus is on the low frequency changes More References G Foster and S Rahmstorf Global temperature evolution 1979 2010 Environ Res Lett vol 6 pp 044022 2011 http dx doi org 10 1088 1748 9326 6 4 044022 M A Balmaseda K E Trenberth and E Källén Distinctive climate signals in reanalysis of global ocean heat content Geophys Res Lett vol 40 pp 1754 1759 2013 http dx doi org 10 1002 grl 50382 M H England S McGregor P Spence G A Meehl A Timmermann W Cai A S Gupta M J McPhaden A Purich and A Santoso Recent intensification of wind driven circulation in the Pacific and the ongoing warming hiatus Nature Climate Change vol 4 pp 222 227 2014 http dx doi org 10 1038 nclimate2106 Comments pop up 95 The global temperature jigsaw Filed under Aerosols Climate modelling Climate Science El Nino Instrumental Record Oceans statistics stefan 17 December 2013 Since 1998 the global temperature has risen more slowly than before Given the many explanations for colder temperatures discussed in the media and scientific literature La Niña heat uptake of the oceans arctic data gap etc one could jokingly ask why no new ice age is here yet This fails to recognize however that the various ingredients are small and not simply additive Here is a small overview and attempt to explain how the different pieces of the puzzle fit together Figure 1 The global near surface temperatures annual values at the top decadal means at the bottom in the three standard data sets HadCRUT4 black NOAA orange and NASA GISS light blue Graph IPCC 2013 More Comments pop up 83 Sea level rise What the experts expect Filed under Climate Science IPCC Oceans stefan 23 November 2013 In the long run sea level rise will be one of the most serious consequences of global warming But how fast will sea levels rise Model simulations are still associated with considerable uncertainty too complex and varied are the processes that contribute to the increase A just published survey of 90 sea level experts from 18 countries now reveals what amount of sea level rise the wider expert community expects With successful strong mitigation measures the experts expect a likely rise of 40 60 cm in this century and 60 100 cm by the year 2300 With unmitigated warming however the likely range is 70 120 cm by 2100 and two to three meters by the year 2300 More Comments pop up 71 Sea level in the 5th IPCC report Filed under Climate Science Communicating Climate IPCC Oceans stefan 15 October 2013 What is

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  • Oceans « RealClimate
    ones Fig 1 Sea level curves calculated by different research groups with various methods The curves show the sea level relative to the satellite era since 1992 Graph Klaus Bittermann All curves show the well known modern sea level rise but the exact extent and time evolution of the rise differ somewhat Up to about 1970 the new reconstruction of Hay et al runs at the top of the existing uncertainty range For the period from 1880 AD however it shows the same total increase as the current favorites by Church White Starting from 1900 AD it is about 25 mm less This difference is at the margins of significance the uncertainty ranges overlap More References C C Hay E Morrow R E Kopp and J X Mitrovica Probabilistic reanalysis of twentieth century sea level rise Nature vol 517 pp 481 484 2015 http dx doi org 10 1038 nature14093 Comments pop up 43 Diagnosing Causes of Sea Level Rise Filed under Climate Science Oceans eric 8 January 2015 Guest post by Sarah G Purkey and Gregory C Johnson University of Washington NOAA I solicited this post from colleagues at the University of Washington I found their paper particularly interesting because it gets at the question of sea level rise from a combination of ocean altimetry and density temperature salinity data This kind of measurement and calculation has not really been possible not at this level of detail until quite recently A key finding is that one can reconcile various different estimates of the contributions to observed sea level rise only if the significant warming of the deep ocean is accounted for There was a good write up in The Guardian back when the paper came out Eric Steig Sea leave rise reveals a lot about our changing climate A rise in the mean sea level can be caused by decreases in ocean density mostly reflecting an increase in ocean temperature this is steric sea level rise It can also be caused by an increase in ocean mass reflecting a gain of fresh water from land A third and smaller contribution to mean sea level is from glacial isostatic adjustment The contribution of glacial isostatic adjustment while small has a range of possible values and can be a significant source of uncertainty in sea level budgets Over recent decades very roughly half of the observed mean sea level rise is owing to changes in ocean density with the other half owing to the increased in ocean mass mostly from melting glaciers and polar ice sheets The exact proportion has been difficult to pin down with great certainty More References S G Purkey G C Johnson and D P Chambers Relative contributions of ocean mass and deep steric changes to sea level rise between 1993 and 2013 J Geophys Res Oceans vol 119 pp 7509 7522 2014 http dx doi org 10 1002 2014JC010180 Comments pop up 52 Older Entries Site Google Custom Search Recent Comments What is the best description

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  • Ice-core dating corroborates tree ring chronologies « RealClimate
    Eastern history Trees can guide us in reconstructing the past As my co author Mike Baillie quipped in his book A Slice Through Time Dendrochronology and Precision Dating The trees don t lie and they were there Thanks to the research of Sigl et al 2015 this statement is looking all the more true 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 F Miyake K Nagaya K Masuda and T Nakamura A signature of cosmic ray increase in ad 774 775 from tree rings in Japan Nature 2012 http dx doi org 10 1038 Nature11123 I G Usoskin B Kromer F Ludlow J Beer M Friedrich G A Kovaltsov S K Solanki and L Wacker The AD775 cosmic event revisited the Sun is to blame Astronomy Astrophysics vol 552 pp L3 2013 http dx doi org 10 1051 0004 6361 201321080 D Güttler F Adolphi J Beer N Bleicher G Boswijk M Christl A Hogg J Palmer C Vockenhuber L Wacker and J Wunder Rapid increase in cosmogenic 14C in AD 775 measured in New Zealand kauri trees indicates short lived increase in 14C production spanning both hemispheres Earth and Planetary Science Letters vol 411 pp 290 297 2015 http dx doi org 10 1016 j epsl 2014 11 048 F Miyake K Masuda and T Nakamura Another rapid event in the carbon 14 content of tree rings Nature Communications vol 4 pp 1748 2013 http dx doi org 10 1038 Ncomms2783 S E Coulter J R Pilcher G Plunkett M Baillie V A Hall J P Steffensen B M Vinther H B Clausen and S J Johnsen Holocene tephras highlight complexity of volcanic signals in Greenland ice cores Journal of Geophysical Research Atmospheres vol 117 pp n a n a 2012 http dx doi org 10 1029 2012JD017698 C Barbante N M Kehrwald P Marianelli B M Vinther J P Steffensen G Cozzi C U Hammer H B Clausen and M Siggaard Andersen Greenland ice core evidence of the 79 AD Vesuvius eruption Climate of the Past vol 9 pp 1221 1232 2013 http dx doi org 10 5194 cp 9 1221 2013 C U Hammer H B Clausen and W Dansgaard Greenland ice sheet evidence of post glacial volcanism and its climatic impact Nature vol 288 pp 230 235 1980 http dx doi org 10 1038 288230a0 Comments pop up 23 23 Responses to Ice core dating corroborates tree ring chronologies 1 Chris Ho Stuart says 5 Aug 2015 at 8 59 AM Does this have any implications for ice core timing beyond the normal range of dendrochronology Specifically a common talking point has been the time gap between onset of temperature increase coming out of the last glacial maximum and the start of CO2 rise It s been generally accepted for some time that the was an 800 year lag with the temperature rise starting first and CO2 rise following after In popular debate over AGW this has been used by deniers as proof that CO2 doesn t cause temperature rise while conventional science has that CO2 as a feedback can still be responsible for most of the temperature increase of the several thousand years involved For instance at real climate Dec 3 2004 What does the lag of CO2 behind temperature in ice cores tell us about global warming Recent research has since called into question the existence of this lag at all Synchronous Change of Atmospheric CO2 and Antarctic Temperature During the Last Deglacial Warming by F Parrenin et al in Science 1 March 2013 Vol 339 no 6123 pp 1060 1063 DOI 10 1126 science 1226368 Parrenin et al are also proposing a revision to time scales of Antarctic ice cores I m not sure of the state of play in all this at present and I m wondering if your work is at all relevant to the issue of time difference between onset of temperature rise and CO2 rise at the end of the most recent glacial 2 Chris Baisan says 5 Aug 2015 at 12 38 PM Great news Congratulations on the vindication 3 Max Torbenson says 5 Aug 2015 at 1 02 PM Other recent papers that may be of interest on this subject http www clim past discuss net 11 2933 2015 cpd 11 2933 2015 html http geology gsapubs org content early 2015 07 28 G36914 1 abstract 4 Arthur Smith says 5 Aug 2015 at 1 10 PM Great and clear article But how do we know the tree rings are right and ice cores are wrong 5 Chris Baisan says 5 Aug 2015 at 9 25 PM Arthur S we know the tree ring chronologies are correct because unlike the ice cores there are literally hundreds of independently dated times series in both hemispheres that can be cross checked with each other either directly when in the same climatic region or indirectly as in the case of the radiocarbon spikes discussed here The first paper describing the spike was based on material from Japan and gave a calendar date This calendar date has been verified using tree ring material from other continents There is a global network of tree ring sites and they all agree only the ice cores were out of sync and the dating of them has always included error bars unlike the tree ring chronologies Chris H the next logical step is to run the Be analysis on the ice cores back and verify the calendar dates with single year radiocarbon analysis of dated tree rings This will cover the last 12k years Further back there are floating sequences of one to several thousand years of crossdated tree rings that cover parts of the last 20k years That will help with the ice dating however if the CO2 signal and temperature signal have the same source same ice core then there are other issues at work 6 John Pollack says 5 Aug 2015 at 10 59 PM 4 The tree rings are right because tree ring series from both hemispheres show a carbon 14 spike at 774 5 CE due to exceptional solar activity If the tree rings were wrong one or several of these series would be displaced by several years 7 Greg Simpson says 5 Aug 2015 at 11 44 PM Recent research has since called into question the existence of this lag at all That seems a little odd Assuming the underlying cause of glaciations is the Milankovitch cycles I don t see how there could not be a lag I have no clue about how large it should be though 8 Max Torbenson says 6 Aug 2015 at 2 03 AM Chris Ho Stuart The fact that the Greenland and Antarctic ice cores or rather GICC05 and AICC2012 are synchronous for the Holocene is largely due to the temporal flexibility used in the comparison Veres et al 2013 Climate of the Past 9 p 1739 write we used a set of absolute markers from the GICC05 depth age relationship with artificially small uncertainties to force the model not to deviate from the chronology Furthermore the analysis uses tie points of 50 year uncertainties for this period which is probably larger than the actual discrepancy in dates between IntCal and GICC05 When looking beyond the Holocene the Antarctic ice core dates are younger than the GICC05 equivalents for the same events By GI 22 and GI 23 it is on the order of millennia see Veres et al Some of the further analysis suggested above can be found in the articles I linked to previously 9 t marvell says 6 Aug 2015 at 2 43 AM Re Post 1 Does this mean that there is now annual data that is generally considered accurate for both CO and world temperature going back well over 1000 years Is it readily available 10 Jonny McAneney says 6 Aug 2015 at 3 46 AM Arthur Smith Chris Baisan explains scientifically why it is the tree rings that are correctly dated and not the ice cores But to further his statement we also know that it is the tree rings that are correct and not teh ice cores because of historical documentation To reiterate a point made in a previous post see figure 3 here http www realclimate org index php archives 2015 02 the mystery of the offset chronologies tree rings and the volcanic record of the 1st millennium we have historical records of recorded phenomena consistant with volcanic dust veil events in 44 BC AD 536 and AD 627 These dates match the formation of frost damaged rings in bristlecone pine in 43 BC AD 536 and AD 626 7 However when we look at the GICC05 they have acid at 50 1 BC AD 529 2 and AD 619 2 Of course in fairness they do have acid at around 534 AD which Larsen et al 2008 argued was the cause of the AD 536 dust veil event which we now know to be the AD 540 eruption The nature paper of Sigl et al 2015 uses the radiation events of 774 5 and 993 4 to tie trees to ice cores creating two synchronisation points One could again question if the trees are telling the truth with respect to their dates By comparing the onset of the radiocarbon signal between northern and southern hemispheric trees the timing of the 774 775 event has been refined to be March 775 6 months Guttler et al 2015 This timing agrees quite well with dated Chinese records see Zhou et al 2013 and references within http www cbpf br icrc2013 papers icrc2013 1149 pdf But here is the pertinant section In the evening on the Chinese lunar calendar day of 11 Dec 774 i e 17 Jan AD775 in the east and above Moon there were more than ten bands of white lights like the spread silk penetrating and covering eight grand constellations named in Chinese corresponding to the sky composed of Taurus Auriga m Gemini q Cancer l Orion V Orion e Taurus d Hydra and a Leo and the lights were ceased gradually after middle night as recorded in the Old Tang Book a Chinese Chronicle 7 The auroras described are actually located in a wide region from east to west and from north to south in Earth s northern hemisphere The records indicated clearly that time to see auroras is most probably from 5 00 6 00 PM to 1 00 2 00 AM therefore the event lasted about 8 hours In Tang dynasty the natural abnormal events were observed and recorded by qualified officers so the records are highly trustable and the work was conducted in the Tang capital Xian which is located in a geomagnetic latitude at lower twenties The low geomagnetic latitude indicates that the solar particles which caused very strong auroras are very intense and with higher energies This might not seem that remarkable until one considers that this observation was recorded in the Tang capital Xian which is around the 34th parallel implying that this was an extremely energetic auroral event 11 Jonny McAneney says 6 Aug 2015 at 4 34 AM Chris Ho Stuart I am not a climate scientist so I cannot answer definatively your question but I will give it a shot within my own limited understanding If I make any errors hopefully others will point it out My understanding is that much of the temperature reconstruction of the past is obtained from measurement of d18O within ice core strata Similalry past CO2 concentration is also reconstructed from ice core layers Thus one would assume that if the measurements were taken from the same core then absolute dating does not matter too much with respect to any correlation between CO2 and temperature since one is dealing only with that core s internal chronology Issues would probably arise if you are comparing proxy data between different ice cores which would depend upon the degree of established synchroniety between cores 12 Jonny McAneney says 6 Aug 2015 at 4 56 AM Chris Baisan Thank you for your responses to the other posters I just wanted to enphasis a point you make regarding syncronising tree rings with ice cores using 14C and 10Be As of 2102 2013 Miyake et al had not identified any further rapid increases in 14C other than AD 774 5 and AD 993 within the previous three millennia but I am sure that this wont stop them or others looking for further excess radiocarbon signals within tree ring records If I remember correctly Miyake et al were guided to the 775 and 993 events through the radiocarbon calibration curve which prompted them to do high precision measurements i e at annular resolution 14C measurements around these dates Similaly for 10Be measures in ice cores where annular resolution measurements were taken because of the radiocarbon measurements It might be a tall order to obtain annular resolution of radiocarbon from trees and 10Be from ice cores for the twelve millennia of tree ring data Radiocarbon and 10Be resolution is currently at five to ten year resolution perhaps even coarser for 10Be I cant recall at the moment There is no doubt that complete annularly resolved 14C and 10Be chronologies would be highly desirable but obtaining them might be quite a costly endeavour 13 Chris Baisan says 7 Aug 2015 at 10 50 AM Yes Jonny a strategy is required A matter of determining the most efficient way to target portions of the radiocarbon calibration curve 10Be numbers There are many reasons to want single year numbers across the whole span of the RC calibration curve but obtaining financing is a stumbling block for sure 14 Richard Caldwell says 7 Aug 2015 at 12 58 PM I just want to say that I m amazed that ice cores can resolve to even a decade Snow and stuff mixes together as ice forms I tip my hat to scientists for even trying to solve this issue I d probably just declare tree rings right and move on Perhaps we re smarter than we think Perhaps we ve got a chance Folks are generally self absorbed and self interested but folks are also generally good 15 A G Gelbert says 7 Aug 2015 at 5 18 PM Fascinating article This added empirical evidence of temperatures in the past will help to silence the fossil fuel industry funded critics of climate change science As a side issue does this mean Carbon 14 dating will require some equation adjustments due to the identification of high proton extra terrestrial events 16 Chris Baisan says 7 Aug 2015 at 11 09 PM A G Gelbert Musing As has been mentioned above the calibration curve is derived mostly from 10 year increments and some 5 year which introduces a smoothing error but mitigates noise At the time calibration work was begun the mass required for each increment was considerable and testing single years wasn t practical in most cases Now the mass required is no longer a barrier because of technical advances but the cost is a barrier The effect of the wiggles in the curve is that the potential error or uncertainty of a radiocarbon date varies through time not from counting or measurement error which is also a factor so in some periods the resolution of the method is poor in others very good The spikes don t have a simple effect because near the spike year of or just following the dating error is potentially very large while either side of the effect the error is reduced if the spike is included accounted for in calibration curve This applies to typical organic samples not tree ring samples with annual layers Overall effect of identifying and accounting for spikes should be a reduction of dating error generally with some specific exceptions An unknown sample with annual layers that include the spike could theoretically be dated with uncertainty almost eliminated if one does dates for multiple layers I am not sure how the calibration people will handle this but there is active interest in the subject and it will be addressed in some fashion 17 Barton Paul Levenson says 8 Aug 2015 at 9 46 AM RC folks are also generally good BPL Explain how generally good folks produced Auschwitz the GULAG and a world where 1 9 of the people are starving 18 Hank Roberts says 8 Aug 2015 at 10

    Original URL path: http://www.realclimate.org/index.php/archives/2015/08/ice-core-dating-corroborates-tree-ring-chronologies/ (2016-02-13)
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