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Comments 121601 to 121650:

121601. GFW at 11:21 AM on 3 April 2010
        Greenland's ice mass loss has spread to the northwest
        HR, yes there appears to be *some* linkage between sea ice and the glacier flow/calving rate, but it's not quite the same story as how the more permanent ice shelves of Antarctica hold back glaciers there. Sea ice doesn't have the thickness or rigidity of an ice shelf so any back-pressure effect is much weaker. However, the less sea ice there is in general, the less protection Greenland has from warm winds and currents.
121602. HumanityRules at 09:56 AM on 3 April 2010
        Greenland's ice mass loss has spread to the northwest
        Riccardo #54 Is sea ice extent really unrelated to this topic? If it's true that most of the mass loss is due to calving rather than melting in-situ as suggested by many then surely open ocean for longer time periods must have an affect on the rate of ice loss. It would seem common sense that open water facilitates more calving than ice locked sea. The many animations of arctic sea ice suggest there has been change in sea ice freeze in the Baffin/Greenland sea since the 1980's.
121603. Rob Honeycutt at 08:03 AM on 3 April 2010
        A residential lifetime
        @HenryH... You should really watch the Richard Alley lecture that John suggested. It explains the whole issue extremely well. Google: Richard Alley The Biggest Control Knob. The point that Alley makes in the lecture is that Milankovitch cycles can only account for a small portion of temperature change. It's those cycles of orbit, precession, etc that set off feedbacks in CO2 and CH4 that result in the swings in global temps that we see.
121604. Philippe Chantreau at 05:13 AM on 3 April 2010
        The human fingerprint in global warming
        RSVP "For instance, life (as we know it) cannot be sustained without oxygen." That's incorrect. The oxygen in our atmosphere is owed to living organisms. Numerous organisms still exist that do not need oxygen. See for example this: http://www.scientificamerican.com/article.cfm?id=origin-of-oxygen-in-atmosphere
121605. John Russell at 04:33 AM on 3 April 2010
        A residential lifetime
        I like 'gallopingcamel's' suggestion that humans raising the temperature by a few degrees is acceptable on the grounds that we're pre-empting an ice-age that might possibly affect us, to some unknown degree, at some unknown point in the future! If only sceptics were as willing for humans to take dramatic actions to lower temperature by reducing emissions, in the face of the suggested 95% chance that increased temperatures will destroy our children's future.
121606. Ned at 03:59 AM on 3 April 2010
        A residential lifetime
        gallopingcamel writes: I am a little puzzled by your conclusion that a warmer earth would be "inhospitable" given that mammals became dominant during the Eocene when temperatures were much higher than today. Our agricultural system and all our infrastructure are predicated on the idea that climate is more or less constant, such that if the north-central US is a good place to grow wheat now, it will continue to be a good place to grow wheat in the future. Or, as another example, we build a fleet of ships/barges to operate on the Mississippi River or the St Laurence Seaway, with the assumption that water levels will not drop enough to prevent fully laden vessels to move through the system. In other words, there are a million ways in which our infrastructure is designed around a particular climate in particular places. Changes in temperature or more importantly precipitation can wreak havoc with this. You keep arguing that a few degrees of warming is OK because "it's better than another glacial advance." But no one is suggesting we should try to create another round of glaciation! The question isn't "Which is worse, too warm or too cold?" The question is "Which is better, the climate we have built our infrastructure around or a climate that's significantly warmer most places, with very different patterns of precipitation?" Please stop using a non-existent threat of rampaging glaciers as an excuse to ignore the actual threats associated with CO2-driven climate change.
121607. John Russell at 03:28 AM on 3 April 2010
        A residential lifetime
        Tom Dayton: I know, I know; hence my point 2 about the hole in the bucket (...dear Lisa, dear Lisa). I thought it worth making the point about the wider ability of naturally-occurring vegetation to sequester CO2 when left alone to do its thing, which many people choose to overlook. The irony is that not only are humans adding to atmospheric CO2 but -- through a lack of understanding -- we're also blocking the ecosystem's correcting mechanisms which have evolved to protect the existence of life on the planet. This is the basis for Lovelock's 'Gaia' theory.
121608. Tom Dayton at 02:24 AM on 3 April 2010
        CO2 has a short residence time
        I agree with you in general, Hugh. It is best to avoid repeating misinformation even in the context of disproving it, because repeating the disinformation actually publicizes it. That's why I greatly appreciate Doug's approach in this post, of stating the facts. But there is also the problem of icons such as this sacred list of 36 previous studies. That list is used by deniers as evidence that 36 other experts disagree radically with Doug and "a few" other people. That tactic could be neatly parried by saying that all those studies were about residence time of an individual molecule rather than adjustment time. Such a simple statement inserted as a single sentence in Doug's description of residence time would help a lot, I think. But we'd have to be sure such a statement was completely accurate, which is where a student project would be helpful.
121609. Tom Dayton at 02:10 AM on 3 April 2010
        A residential lifetime
        John Russell, the problem is that sequestration by trees (and plants in general) cannot keep up with CO2 increases due to humans. On the relevant thread CO2 Is Not a Pollutant there are some relevant comments containing links to sources: #3 by me followed by #4 by muoncounter. See also the USDA report I linked to in my comment #1 on that thread.
121610. gallopingcamel at 01:42 AM on 3 April 2010
        A residential lifetime
        Marcus (#36), I am a little puzzled by your conclusion that a warmer earth would be "inhospitable" given that mammals became dominant during the Eocene when temperatures were much higher than today. My idea of "inhospitable" would be the period ~74,000 years ago when it was so cold that the human race was near extinction. In spite of the technologies mankind is so proud, it will be very difficult for humanity when the next Ice Age arrives.
121611. Marcus at 01:01 AM on 3 April 2010
        A residential lifetime
        One important point is this-the carbon we're currently burning comes from a time when the planet had CO2 concentrations 10x to 20x higher than at any point during the Quaternary Era. Its important to note that temperatures were a good 4-6 degrees *warmer* then than during the entirety of the Quaternary Era-in spite of the sun being cooler during this earlier time period. This should give some idea of the maximum impact we could expect from raising CO2 emissions *if* we were somehow to burn every ounce of coal & oil ever created. Even if we don't burn that much (indeed, economics will probably demand that we stop burning coal long before this because it will become more expensive to mine than what it can ever be worth-indeed, this day has almost arrived in the bulk of Europe) we'll be able to burn enough to make life on this planet extremely uncomfortable-if not downright inhospitable-for our species. That doesn't sound very intelligent to me!
121612. John Russell at 21:58 PM on 2 April 2010
        A residential lifetime
        A couple of points. 1) Re: trees. Doug Mackie talks of trees as if they have very little effect on CO2 sequestration; "Every tree that grows will eventually die and decompose, thereby releasing CO2." The facts are more complex. True, trees in woods and forests do live and die but in fact the organic matter on the floor of a woodland or forest is gradually increasing (let's face it, that's one of the ways peat is formed) and it ends up as a net CO2 sink. Where they are not being depleted by agriculture or deforestation the world's soils are all constantly deepening. Even where soils are eroding mechanically, that soil ends up washing down rivers and it's that organic matter that ends up making a significant contribution to the sediments accumulating on the bottom of our oceans. 2) Re the CO2 lifetime. I think the discussion tends to over-complicate a simple concept. When describing the working of a business I always use the analogy of a bucket with a hole in the bottom. The work the company does, and product it sells, provides money to fill the bucket; while the costs -- wages, overheads, raw materials purchase -- bleeds money out of the hole in the bottom. Equilibrium is maintained while the inputs match outputs. The same analogy can be applied to atmospheric CO2. If we think of a molecule of CO2 as a molecule of H2O then the time a specific molecule exists in the bucket is irrelevant; all that matters is the balance between inputs and outputs. Increasing inputs will result in the water level rising; increasing output will cause the water level to fall. One can't push this analogy too far, but it does get the point across to some sceptics. It also helps to explain why man's relatively small contribution to the CO2 cycle is so significant. I hope that's useful.
121613. RSVP at 18:53 PM on 2 April 2010
        A residential lifetime
        CBDunkerson Thank you for the reply. Very interesting. & Doug Mackie Also interesting. Aside from the question, your answer brings up an idea... You refer to powering air conditioners and CO2 released for this. Would it make any sense then (i.e., benefit) to prohibit burning fossil fuels for energy during summer months? I would assume not, however, you always hear this point about air conditioners. Maybe air conditioners themselves should be completely banned to simply make people (including the elite) more conscious of global warming.
121614. Doug Bostrom at 17:39 PM on 2 April 2010
        A database of peer-reviewed papers on climate change
        Harold, McKitrick's essay is well written, but I once I spent a few moments checking his characterizations I ended up with a fairly firm conclusion not in his favor. McKitrick describes Dr. Rasmus Benestad as "a blogger at Real Climate", technically true, then McKitrick goes on to dismiss Benestad's failure to follow up on an invitation to submit a comment to JGR with the rather snide remark, "Yes, yes, time pressures: I understand. I guess blogging takes up a lot of time." Here's Dr. Benestad's bio as provided to Real Climate: I am a physicist by training and have affiliations with the Norwegian Meteorological Institute (met.no) and the Oslo Climate Group (OCG) [My views here are personal and may not necessarily represent those of RegClim, OCG, met.no, or the mentioned societies]. I have a D.Phil in physics from Atmospheric, Oceanic & Planetary Physics at Oxford University in the United Kingdom. Recent work involve a good deal of statistics (empirical-statistical downscaling, trend analysis, model validation, extremes and record values), but I have also had some experience with electronics, cloud micro-physics, ocean dynamics/air-sea processes and seasonal forecasting. In addition, I wrote the book ‘Solar Activity and Earth’s Climate’ (2002), published by Praxis-Springer, and I was a member of the council of the European Meteorological Society for the period (2004-2006), representing the Nordic countries and the Norwegian Meteorology Society. Here is Dr. Benestad's record of publications: Rasmus Benestad's Publication list Ross McKitrick jumps directly into characterizations of others' work as "fabrications" and swiftly moves to arguable distortions such as Dr. Rasmus Benestad being simply "a blogger," of course leaving a credulous reader with the impression that Benestad is insufficiently credentialed. I suppose McKitrick is trying to harm the credibility of his opponents, but instead such tactics leave me wondering how much fact-checking I'm required to do in order to attach any credibility to his claims. Life is too short, I won't bother and I must leave the question of whether he was fairly treated in the hands of other, more easily believed folks, such as editors and reviewers with sufficient proven reliability to be found working for reputable journals. If most of those persons chose not to publish McKitrick's work, my vote of confidence must go to them because for me McKitrick has ruined his own credibility by swerving into rank hyperbole.
121615. iskepticaluser at 17:04 PM on 2 April 2010
        CO2 has a short residence time
        Tom's comment #3 refers to lack of time and knowledge in pursuing an understanding of climate change, so I'll throw this out there, though it's a bit off topic. Regular readers of this blog come here often because we find the science fascinating, but I think that fascination can be a handicap when we're trying to communicate the central urgency of AGW to folks who may have a lot of other issues on their minds. If I were presented with the "iconic list" either in rebuttal or simple confusion, I would be tempted to simply by-pass it and say "Look, we KNOW (from direct and proxy measurements) that the planet's CO2 blanket is more than a third thicker than it was before the industrial revolution. We KNOW (through carbon isotope signatures) that we're the ones thickening it. We KNOW that CO2 traps infrared - we can measure the effect both in the lab and from satellites. And we KNOW that global (atmospheric and ocean) temperatures are rising." If anyone appreciates these basic facts, they'll GET global warming. Hockey-sticks, tropical troposphere hot-spots and ENSO variability are secondary issues that may or may not interest a general audience, but they are not critical to the basic narrative. It's important to address denialist arguments when they arise. But it's more important to be able convey - really well - the ESSENCE of the AGW threat. Widespread familiarity with, and repetition of, that central chain of evidence will be the most powerful antidote to whatever head-in-the-sand nonsense happens to be floating around.
121616. Doug Mackie at 16:03 PM on 2 April 2010
        A residential lifetime
        Johnd #24 And the heat capacity of seawater is...(hint: greater than air). As suggested above The long thaw makes scary bedtime reading. Emphasis on the long.
121617. Doug Mackie at 15:53 PM on 2 April 2010
        A residential lifetime
        RSVP #10 "Is residence time affected by temperature? And if so, what is the nature of this feedback?" I assume you mean residence time and not lifetime? If so then, no, residence time is not directly controlled by temperature. However, while I hate to give another equivocal answer, it depends: Residence time, as explained above, is simply size of reservoir divided by rate of throughput. Temperature will not directly alter the size of the reservoir, i.e. amount of CO2 in the atmosphere. (Though perhaps warming will mean less burning of fossil fuels for heating but equally it may lead to increased consumption to run air-conditioners etc). Temperature may have secondary effects on throughput rates: One removal process for CO2 is dissolution in the ocean. This is a physical process and the bottleneck is large scale circulation. Which is, in part, driven by winds and temperature gradients. (Though as a complicating factor warm water can hold less dissolved water than cold water).
121618. Doug Mackie at 15:28 PM on 2 April 2010
        A residential lifetime
        Alexandre #20: In the short term (centuries) CO2 in the atmosphere will slowly come to equilibrium with CO2 in the oceans. By definition this means that the final concentration of CO2 in both boxes will be greater than it was in preindustrial times. Exactly how much greater depends on the time scale we use and the total amount of fossil CO2 released. The oceans will acidify as a result of this process. This is a whole post in itself but I direct your attention to the UN Convention on Biological Diversity : “Ocean acidification is irreversible on timeframes of at least tens of thousands of years and is determined in the longer term by physical mixing processes within the ocean that allow ocean sediments to buffer the changes in ocean chemistry. Warming of the oceans as a result of global climate change may also reduce the rate of mixing with deeper waters, which would further delay recovery.”
121619. Harold at 15:10 PM on 2 April 2010
        A database of peer-reviewed papers on climate change
        You have an understandable emphasis on peer review as a validation for the various scientific arguments for/against AGW. However, peer review is not necessarily a level playing field. For an enlightening (and somewhat entertaining) look at the efforts of Ross McKitrick to get one of his papers through peer review, check out this link.
121620. shargash at 15:07 PM on 2 April 2010
        A residential lifetime
        HenryH@9 "Why should it happen today in another way like in former times?" There has never before in the history of the earth been a fossil fuel-burning, industrialized civilization. THAT is why what is happening today is different than in former times.
121621. Chris G at 13:26 PM on 2 April 2010
        A residential lifetime
        Having said that, now I'm not sure if the increase in temperature is inherently logarithmic, or if the net effect is a log because the higher increase in energy loss makes it that way. Might have to go dig that one up.
121622. Chris G at 11:38 AM on 2 April 2010
        A residential lifetime
        HenryH (#9) If you are asking why the earth hasn't headed toward a truly runaway greenhouse effect, another way to answer that is that the temperature increase due to an increase in a GHG is logarithmic in nature. It continually increases, but the rate of increase (1st derivative) continually declines. On the other hand, the amount of energy lost from radiation is proportional to the 4th power of the absolute temperature; energy loss accelerates rapidly with an increase in temperature. A new equilibrium, at a higher temperature, will always be reached, where the curves intersect again.
121623. Doug Bostrom at 04:50 AM on 2 April 2010
        Tree-rings diverge from temperature after 1960
        Malcolm, the research you wish for is very much in play. Simply bounce over to Google Scholar, try searching on "plant metabolism anthropogenic C02" or "plant metabolism acid rain" and you'll see what I mean. The first term produces some 7,000 results, the second (being the subject of earlier interest) over 45,000. Plugging in better terminology for search terms will yield more and better results.
121624. Riccardo at 04:32 AM on 2 April 2010
        Tree-rings diverge from temperature after 1960
        MalcolmMcDonald, "surely we need to know what's going on?" i agree but it's not up to climate scientists. I'd be tempted to ask for more research funds, but you know, people would think it's just the standard complaint from scientists.
121625. MalcolmMcDonald at 03:59 AM on 2 April 2010
        Tree-rings diverge from temperature after 1960
        I don't think this is good enough. The "divergence" is evidence, surely, of some severe environmental stress, one that could at any moment start to impact on our food supplies. If this was any other branch of regular science, an expermiment would be rigged up, 6 or 16 greenhouses in a row, one with increased CO2, one with reduced CO2, one with artificial acid rain, one with extra ultra-violet and so on and so forth. We'd have at least parts of the answer in 12 months. Why is nobody treating this problem as a matter of urgency, surely we need to know what's going on?
121626. FerdiEgb at 03:12 AM on 2 April 2010
        The human fingerprint in global warming
        Tarcisio José D'Avila at 05:14 AM on 30 March, 2010 I question the assertion that the relationship c13/c12 may indicate that the increase of CO2 in atmosphere is the result of burning fossil energy. The absorption of CO2 by oceans and plants tend to dominate the CO2 released by decomposition of organic matter (CO2 cold). CO2 of all sources is quite rapidely mixed within a few days to a few months within each hemisphere. The passing of the ITCZ (at the tropics) from the NH to the SH takes some more time, currently some 14 months to reach the South Pole. The 13C/12C ratio is a good indication of the source: besides fresh organics and fossil organics, all other sources of carbon have a higher 13C/12C (d13C) ratio. That are volcanic eruptions, carbonate rock wearing and (deep) ocean degassing. But how can we make a differentiation between fresh organics and fossil one's? There are two ways: fresh organics have some 14C built in from cosmic rays or nuclear tests. That is used for carbon dating, up to some 60,000 years. Fossil carbon is completely depleted of 14C. The decline of 14C in the atmosphere was observed around 1870 and carbon dating had to be corrected. The second method is from the oxygen balance: We know how much fossil fuels were sold (taxes!) and how much oxygen that needs. The oxygen use since about 1990 was measured and there is somewhat less used than calculated. That means that the whole organic world acts as an oxygen source, thus a (preferentially 12C) CO2 sink (photosynthesis...). Thus the decrease in d13C is from fossil fuel burning and nothing else.
121627. FerdiEgb at 02:52 AM on 2 April 2010
        The human fingerprint in global warming
        Arkadiusz Semczyszak: The ice core with the highest resolution (8 years for 2 out of 3 ice cores of Law Dome) and a spread of only 1.3 ppmv (1 sigma). These have an overlap of about 20 years (1960-1980) with the atmospheric data taken at the South Pole. There is practically no CO2 gradient at the South Pole. Moreover, ice cores with completely different temperature profile and accumulation speed all show the same CO2 levels for the same gas age within a few ppmv. Ice core CO2 start to increase and d13C to decrease around 1850. That is at the same moment that this happens (at a different level) in the upper oceans as has been measured in coralline sponges. Stomata (index) data show the same increase in CO2 for the past century (they are calibrated... against ice cores!), but rather unreliable indicators for past changes, as they react on local/regional CO2 levels over land, which are heavily influenced by land changes over time...
121628. michael sweet at 02:38 AM on 2 April 2010
        A residential lifetime
        In the post at RC, Matthews and Weaver appear to have not considered that if CO2 emmision is stopped, aerosol emmisions will also stop. The aerosol emmsiions currently cool the globe (amount uncertain) so temperatures would immediately rise. It looks like their model needs some more work, although it is an interesting way to look at the problem.
121629. FerdiEgb at 02:20 AM on 2 April 2010
        A residential lifetime
        Tom Dayton, Thanks for the link... It seems somewhat overdone at RC: Around 2000 there still was some heat "in the pipeline" from the oceans. But that completely disappeared in a few years time. Thus if we should stop our CO2 emissions today, in a period of about 40 years the extra CO2 (some 100 ppmv today) would be halved, including the forcing (+ feedbacks) related to that amount of extra CO2. Thus cooling the atmosphere down as can be seen in the graph for the Bern model, or maybe faster, as the Bern model is rather conservative.
121630. johnd at 02:11 AM on 2 April 2010
        A residential lifetime
        If the rate of ocean transfer of CO2 is controlled by the slow circulation and turn over, taking roughly 500-1000 or so years, then surely the heat transfer will be subject to the same slow circulation and turn over.
121631. Ned at 01:27 AM on 2 April 2010
        A residential lifetime
        Normally I wouldn't try to speak for David Archer, but having read quite a bit of his work (including The Long Thaw -- I concur with your recommendation of it, BTW) my guess is he'd probably say that: (a) Our distant descendants in AD 52010 would probably be able to prevent the onset of the next glacial advance if necessary without any help from us, and (b) In the meantime there's much more danger from warming (which is actually happening) than from cooling (which isn't). I'm all in favor of prudent concern for the future, but I think we should probably focus on the next couple of centuries rather than some hypothetical condition tens of thousands of years in the future.
121632. Ned at 01:18 AM on 2 April 2010
        A database of peer-reviewed papers on climate change
        Poptech, sorry I missed your post. Don't take the moderation personally. Like Doug, I've had a number of my own comments excised. I take it as a reminder to be polite and not to accuse others of lying or dishonesty. Sometimes the bad habits I pick up at other blogs can be hard to shake. Back on topic ... John, thanks for setting up this database. Is there any particular way you'd like to have the titles handled? I noticed several people had been using the article title, followed by author's name and year in parentheses (e.g., Interactive investigation of climate science topics via a collaborative web portal (Cook et al. 2010)). That seemed like a good idea to me, so I adopted it....
        Response: I've done either but lately I've been adding the (Cook 2010) at the end just to add some useful info - it's handy to see at a glance who wrote it and when it was written.
        
        That web portal paper sounds like a cracker :-)
121633. gallopingcamel at 01:18 AM on 2 April 2010
        A residential lifetime
        quokka (#12), Great video! I thought it was excellent. John Cook is right about Richard Alley's "American Idol" appeal; he will not be able to give up his day job as Harvard's Tom Lehrer was able to do.
121634. gallopingcamel at 01:15 AM on 2 April 2010
        A residential lifetime
        doug_bostrom (#7), Thus far I have not offered my opinion as I see no point in annoying the thoughtful people who hang out here. David Archer has some very interesting speculations with huge implications if true. Archer is trying to model the effects of large CO2 emissions (up to 5,000 Gtonne C) over 500,000 years. He suggests that high emissions could delay the onset of the next Ice Age: http://geosci.uchicago.edu/~archer/reprints/archer.2005.trigger.pdf
121635. Alexandre at 01:04 AM on 2 April 2010
        A residential lifetime
        Doug, Thanks for the guest post. I read the oceanic uptake can only remove part of the extra atmospheric carbon, and the rest would have to rely on the geological response of rock weathering, stretching the process to hundreds of thousands years. Do you agree?
121636. Tom Dayton at 00:43 AM on 2 April 2010
        A residential lifetime
        FerdiEgb wrote "Thus it seems that the CO2 sink in the deep ocean will continue for a long period, removing most of the extra CO2 in relative short time (half lifetime around 40 years), for 99% of the current amounts, the moment we stop all emissions." There is a study also described in the RealClimate post Climate Change Commitments, projecting the rate of global temperature change if humans suddenly stopped all our CO2 emissions.
121637. Ned at 23:04 PM on 1 April 2010
        A residential lifetime
        HenryH writes: More CO2 and CH4 -> higher temperatures. Higher temperatures -> more extra CO2 and CH4 by releases from the ocean and the land and its flora and fauna. What is the goal of this escalating effect? Why does it happen never in the last several billion years? Not sure what you mean by "goal" but this happens all the time, and not just with CO2 and CH4 but with other feedbacks. Some initial forcing causes the climate to change (comet impact at Chicxulub, change in solar irradiance, anthropogenic emissions of CO2, large-scale emissions of CO2 from flood basalt episodes, ...) This warming (or cooling) is then amplified by various positive feedbacks involving further increases (or decreases) in CO2 and CH4 as you note, as well as water vapor, albedo, etc. There are also negative feedbacks that reduce this amplification. The glacial/interglacial cycle is a good example of this. The initial Milankovich forcing is enough to get the process started, but the full magnitude of the swing in temperatures would not occur without the positive feeddbacks.
121638. Ned at 22:53 PM on 1 April 2010
        A residential lifetime
        HenryH writes: The glacial periods are driven by the distance between the sun and the earth, not by the CO2! First of all, it's not "the distance between the sun and the earth," it's the eccentricity of the earth's orbit, obliquity of its axis of rotation, and precession. More to the point, there have been plenty of other cases where changes in temperature were driven by changes in CO2. See, for example, this comment and the rest of that thread. There are lots of examples of CO2 causing warming (or decreases in CO2 causing cooling). The fact that some fires are caused by lightning does not mean that other fires are not caused by arson. The current warming is obviously caused by greenhouse gases, not by Milankovich cycles, which don't operate on decadal to century timescales.....
121639. thefrogstar at 22:33 PM on 1 April 2010
        A residential lifetime
        If the word "flux" was more widely used (or understood) then it might help put across these points. That, and the difference between "equilibrium" and "steady state". (As the old joke goes: "Old chemists never die, they just reach equilibrium")
121640. HenryH at 22:14 PM on 1 April 2010
        A residential lifetime
        Yes, indeed, weathering is removing CO2 from the atmosphere... But this process cannot explain the rapid up and down in the CO2 concentration in the atmosphere. The glacial periods are driven by the distance between the sun and the earth, not by the CO2!
121641. FerdiEgb at 22:11 PM on 1 April 2010
        A residential lifetime
        Seems that it is very difficult to explain the difference between residence time and excess lifetime. The first is governed by the exchange rate over the seasons, which is about 20% of all CO2 in the atmosphere, leading to an average residence time of a CO2 molecule (whatever the source) slightly of over 5 years. The second is governed by the sink rate, which is only 0.5% of any extra amount of CO2 in the atmosphere (whatever the source), slightly under halve of human emissions (land use changes not included). This sink rate remained remarkably constant in the past 110 years: 55% of the emissions (as quantity, not as individual molecules) remained in the atmosphere, 45% were absorbed by oceans and vegetation. That the sink rate remained constant was recently confirmed, which means that the oceans still are not saturating. The very long tail need some criticism: only when enormous quantities of oil and coal are burned (3000-5000 GtC according to Archer, we are now at a total 320 GtC), the deep oceans will increase substantially in CO2/carbonate content which only slowly will decay. With the current total of emissions, the deep oceans only increased in DIC (dissolved inorganic carbon) with less than 1%. Thus only less than 1% of the current total of emissions would stay in the atmosphere for an extremely long period. Further, the deep oceans are a quite good sink. The main sink of the oceans is in the NE Atlantic, where the THC moves cold water rich(er) in CO2 directly into the deep. That may come back in over a thousand years (mixed with the rest of the deep ocean) in the tropical Pacific. The surface/deep ocean exchanges are about 100 GtC/year, but based on the isotopic dilution of the fossil d13C fingerprint, some 60 GtC is directly or indirectly exchanged between the atmosphere and the deep oceans, including most of the 4 GtC sink rate. Thus it seems that the CO2 sink in the deep ocean will continue for a long period, removing most of the extra CO2 in relative short time (half lifetime around 40 years), for 99% of the current amounts, the moment we stop all emissions.
121642. CBDunkerson at 21:57 PM on 1 April 2010
        A residential lifetime
        RSVP, the relationship between global temperatures and the amount of time that CO2 levels remain high is somewhat complicated. In general, cold water is a much better CO2 sink than warm water. This can be seen in maps showing net change in ocean pH from acidification... the greatest change is found near the poles where the water is colder and absorbs more CO2. Indeed, if the oceans got warm enough they could eventually reach the point where they were releasing more CO2 than they were sequestering. However, warmer temperatures and higher CO2 concentrations also mean more plant life up to a point... and while most of that plant life just briefly stores CO2 before dying and releasing it again, some percentage finds its way to the bottom of the oceans and is locked away there by cold deep sea temperatures. In a further complication, the 'snowball Earth' scenario shows that cold isn't an absolute benefit for sequestering CO2 because if it gets cold enough the oceans freeze over... and ice doesn't absorb CO2. This happened around 700 million years ago. The Earth nearly froze solid, but because there was so much ice all the CO2 going into the atmosphere from volcanic sources STAYED there and eventually built up enough to warm the planet. Setting aside the extremes and taking the balance of forces we'll see diminishing returns on carbon sequestration as the temperature increases. The most recent studies show conflicting results on whether this 'saturation' and accelerated atmospheric accumulation has begun. Not that it really matters on any practical timescale. One need only look at the ice core records to see that every time CO2 levels have risen ~100 ppm (usually taking a couple thousand years, but only about 150 in the current case) it has then taken around 100,000 years to slowly descend back down to that previous level. So, unless we have some way of vastly increasing the speed of carbon sequestration, comparable to the vast increase in its release we have introduced through burning fossil fuels, we've got a clear record that natural processes will require 100,000+ years to reverse the increase we have NOW (~390 ppm from 278 before the industrial revolution) and much longer as we continue to use fossil fuels going forward.
121643. quokka at 21:09 PM on 1 April 2010
        A residential lifetime
        On a lighter note, it seems that Richard Alley is something of a musician. Geoman: http://www.youtube.com/watch?v=7-yJyM2s6ow&feature=related
        Response: That has to be one of the nerdiest songs I've ever seen. Gotta love Richard Alley, what a character.
121644. CoalGeologist at 18:07 PM on 1 April 2010
        Greenland's ice mass loss has spread to the northwest
        The current dialog on climate change involves more than just a compilation and interpretation of scientific evidence. We are confronted with diametrically opposed viewpoints on nearly every line of evidence, centered specifically on the question of human attribution. Thus, an equally important issue--and doubtless MORE important in many discussions--is whom to trust as authorities. SkepticalScience.com has placed a priority on evidence reported the peer-reviewed scientific literature, without reference to politics, accusations of deception, or inferences of nefarious goals of climate researchers. From this standpoint, the reference to "Alarmists" in the original Post (#20) by GeoGuy might have been regarded as inconsistent with the Comments POlicy, as the term means "One who causes others to become alarmed without cause". In other words, it implies an intent to cause fear, but without a valid reason. Fortunately, the subsequent discussion has focused exclusively on whether various skeptical arguments can be supported or refuted, based upon evidence in the scientific literature. The term "alarmist" has not appeared again (until now :-( !! ) Bravo to GeoGuy and all respondants to a civil dialog that has been both interesting and informative. The purpose of my present post is to note that we have more to learn from this discussion than arcane details about the rates and underlying causes of loss of ice mass in Greenland, including: 1) Implying an underlying "motive" to those who merely report or discuss research findings is not helpful, assuming the goal is to gain an unbiased understanding of what these findings show, and 2) Asking skeptical questions is not only not wrong, it's the right thing to do in scientific inquiry, assuming that the skeptical hypothesis(es) is testable and refutable by well-documented, verifiable evidence. Anyone who questions the willingness of this site to actively entertain skeptical arguments would do well to read back through the posts and replies.
121645. Ian Love at 17:57 PM on 1 April 2010
        A residential lifetime
        re HenryH: "Why should it happen today in another way like in former times?" It is quite simple - we humans are pushing extra CO2 out with the result that the natural balance is upset, and heat is rapidly being absorbed by Earth. The evidence is in the rapid growth of atmospheric CO2 level. Our time scale is tens of years, the natural one is millenia or even millions.
121646. RSVP at 17:54 PM on 1 April 2010
        A residential lifetime
        Is residence time affected by temperature? And if so, what is the nature of this feedback?
121647. HenryH at 17:48 PM on 1 April 2010
        A residential lifetime
        More CO2 and CH4 -> higher temperatures. Higher temperatures -> more extra CO2 and CH4 by releases from the ocean and the land and its flora and fauna. What is the goal of this escalating effect? Why does it happen never in the last several billion years? Is the climate a ball on a knife edge? The last 65 million years demonstrates that the temperature was explicitly forced by the continental drifts, by the distance between the sun and the earth and by the solar activity. All that time the CO2 and CH4 concentrations in the atmosphere was following the temperature situation. To argue the converse is definitely impossible! Why should it happen today in another way like in former times?
        Response: This is a good question and I strongly recommend viewing the lecture The Biggest Control Knob: Carbon Dioxide in Earth's Climate History by geologist Richard Alley for an excellent overview of the whole issue. Carbon dioxide is removed from the atmosphere by rock weathering. As the earth warms, rock weathering activity removes CO2 from the atmosphere at a faster rate. This acts like a natural thermostat stopping the Earth from getting too hot.
        
        Conversely, when it gets colder, rock weathering slows both due to lower temperatures and ice sheets covering continental surfaces. This leads to a rise in atmospheric CO2 levels which warms the Earth. Again, CO2 acting like a natural thermostat stopping the Earth from getting too cold.
        
        However, rock weathering will not save us from human CO2 emissions now. It's a very slow process - the amount of CO2 removed is several orders of magnitude smaller than the amount of CO2 we're emitting into the atmosphere.
121648. Ebel at 17:22 PM on 1 April 2010
        A residential lifetime
        The mixing of individual destiny with all is not only for CO2 a popular argument of denier. There would be a saturation of the greenhouse effect: photons from the surface do not reach the space. But there, where the atmosphere absorbs strongly, it also emits strongly. That's photons from the surface not reach the space, but others - who cares? Unfortunately, the climate-scientists support that with transparency curves.
121649. Doug Bostrom at 17:05 PM on 1 April 2010
        A database of peer-reviewed papers on climate change
        Poptech, you should read and comprehend the Comments Policy. John Cook is determined to keep a civil tone on this site. As opposed to being a rejectionist I myself am an "alarmist" and found it took me a fair while to be recalibrated from veering, wild hysteresis I'd developed hanging around other climate sites. Several of my posts were permanently interred before I caught on.
121650. Jeff Freymueller at 16:42 PM on 1 April 2010
        Greenland's ice mass loss has spread to the northwest
        #58 CoalGeologist, yes that is exactly the figure I was thinking about. Thanks!

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