tag:blogger.com,1999:blog-9959776.post113904567159721280..comments2024-02-15T04:42:41.606+00:00Comments on James' Empty Blog: Climate sensitivity is 3CJames Annanhttp://www.blogger.com/profile/04318741813895533700noreply@blogger.comBlogger40125tag:blogger.com,1999:blog-9959776.post-44274520077471058622011-02-27T07:03:49.729+00:002011-02-27T07:03:49.729+00:00Thanks, I saw the manuscript but didn't check ...Thanks, I saw the manuscript but didn't check though the sensitivity calc. I agree with the reviewer that it's a bit of a mess but expect it will get sorted out in the review process. I hope that CP will add "comment feeds" of some type to make it easier to keep up with the discussions, they are generally very sparse at the moment and there's no way of keeping informed (other than submitting a comment, then you get emailed with each update).James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-63669648600519903022011-02-26T16:37:36.650+00:002011-02-26T16:37:36.650+00:00Clim. Past Discuss., 7, C26–C31, 2011 www.clim-pas...Clim. Past Discuss., 7, C26–C31, 2011 www.clim-past-discuss.net/7/C26/2011/ © Author(s) 2011. This work is distributed under the Creative Commons Attribute 3.0 License.<br />Climate of the Past Discussions<br /><br />There's currently only one<br />Interactive comment by <br />D. Royer (Referee)<br />droyer@wesleyan.edu <br />"... a novel way to calculate temperature and CO2 for the last 20 Myrs and explore the implications of this association, especially with regards to climate sensitivity.... Overall, the manuscript is in pretty good shape except for the discussion of climate sensitivity...."Hank Robertshttps://www.blogger.com/profile/07521410755553979665noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-39214558844114583272009-11-29T11:24:33.898+00:002009-11-29T11:24:33.898+00:00I think there are enough uncertainties, including ...I think there are enough uncertainties, including the magnitude of the forcing, response, and other boundary conditions, on top of the dubious relevance to the modern system, that it is hard to use directly. But there are certainly people working on all these things.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-27868542790820146462009-11-29T10:39:47.783+00:002009-11-29T10:39:47.783+00:00Apologies if this is a dead thread, but does the P...Apologies if this is a dead thread, but does the PETM offer any constraints on climate sensitivity? Or is the sensitivity of the Eocene planet irrelevant to that of the modern one?C W Mageehttps://www.blogger.com/profile/09706100504739548720noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-86634823383439574482008-11-15T05:11:00.000+00:002008-11-15T05:11:00.000+00:00Cox and Jones?http://secamlocal.ex.ac.uk/people/st...Cox and Jones?<BR/>http://secamlocal.ex.ac.uk/people/staff/pmc205/papers/2008/Hank Robertshttps://www.blogger.com/profile/07521410755553979665noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-31695589376826104752008-09-06T11:46:00.000+01:002008-09-06T11:46:00.000+01:00This comment has been removed by a blog administrator.mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-72889994433855828532008-09-05T02:47:00.000+01:002008-09-05T02:47:00.000+01:00DK did not hypothesize a "thin mixed layer".As I s...<I>DK did not hypothesize a "thin mixed layer".</I><BR/><BR/>As I said before, they did not explicitly provide a number for the depth of the surface layer in their analysis, most probably because it would destroy the credibility of their results. But a relaxation time scale of a few months <I>requires</I> a thin mixed layer because a thick one takes longer to warm up or cool down.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-15332167587762087792008-09-05T01:50:00.000+01:002008-09-05T01:50:00.000+01:00"The diffusion out of their hypothesised thin mixe...<I>"The diffusion out of their hypothesised thin mixed layer cannot be controlled by the diffusion coefficient in the thermocline because their mixed layer is far too thin to reach this thermocline, based on their own figures."</I><BR/><BR/>DK did not hypothesize a "thin mixed layer". They simply added a term representing heat flux into the ocean to their model and estimated how great that flux should be based on first principles. They freely admit that their's is an approximate treatment - the so-called "separability hypothesis" DQ = sDT - but that seems like a reasonable first-order model. <BR/><BR/>So the argument just comes down to how great an additional heat flux out of the ocean you would expect from a peak temperature excursion of approximately -0.5C due to Pinatubo. Wigley et al claim it is of the order of 2W/m2, DK claim more like 0.25W/m2. DK's estimate has the advantage that it does not rely on further modeling. <BR/><BR/>My educated layman's physicist's gut (layman as far as climate science goes, not physics) tells me 2W/m2 out of the ocean seems pretty high given that the temperature difference is generated by a peak forcing of only -3.4W/m2 - it implies that the ocean response is of the same order as the atmospheric response, which seems unlikely given the "impedance mismatch" between the ocean and atmosphere.<BR/><BR/>Of course DK could be wrong, but it just comes down to basic physics: what governs the ocean heat flux change. They argue the ocean heat flux change is proportional to the atmospheric temperature change, with a small constant of proportionality. <BR/><BR/><I>"I can't be bothered generating a reading list for you to learn about the difference between effective diffusion and the abyssal interior value, because it is actually not relevant to this simpler point above which directly refutes their analysis."</I><BR/><BR/>As above, I don't see how you have refuted them. <BR/><BR/><I>"However, a google search found a bunch of it very easily, which suggests you are more interested in wasting my time than actually learning."</I><BR/><BR/>I can assure you I am not trying to waste your time. I would have thought given the references I have already cited that it was obvious that I have indeed been doing my own research (eg - Thorpe above) to try to get to the bottom (no pun intended) of this. My main interest is in understanding what, if anything, we can say about climate sensitivity that does not rely on General Circulation Models. Hence, I would be most grateful if you could post the references you found.mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-39293878785473267272008-09-04T22:56:00.000+01:002008-09-04T22:56:00.000+01:00DK's analysis fails on its own premises. End of st...DK's analysis fails on its own premises. End of story. The diffusion out of their hypothesised thin mixed layer cannot be controlled by the diffusion coefficient in the thermocline because <I>their mixed layer is far too thin to reach this thermocline, based on their own figures</I>.<BR/><BR/>I can't be bothered generating a reading list for you to learn about the difference between effective diffusion and the abyssal interior value, because it is actually not relevant to this simpler point above which directly refutes their analysis. However, a google search found a bunch of it very easily, which suggests you are more interested in wasting my time than actually learning.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-86217097085798315312008-09-04T14:24:00.000+01:002008-09-04T14:24:00.000+01:00It is perhaps excusable that you can't get your he...<I><BR/>It is perhaps excusable that you can't get your head around the physical behaviour of the climate system, but that doesn't mean that everyone else who has studied it is a moron who is missing your supposed insight.<BR/></I><BR/>What a surprisingly aggressive response to my question, which was simply: "Do you have references supporting your assertion that the average ocean heat flux is determined by <I>'Vertical mixing around the boundaries and over steep topography'</I>"<BR/>It wasn't a rhetorical question. I am genuinely curious. And it goes directly to the heart of whether Douglass and Knox's (DK's) model makes sense. <BR/><BR/>DK countered Wigley et al's objections <A HREF="http://www.pas.rochester.edu/~douglass/papers/reply_WAST_2005GL023695.pdf" REL="nofollow">here</A> <BR/><BR/>They came up with a neat modification (eq (3) and (4)) to their original model that allowed them to incorporate ocean heat uptake without changing the functional form of the model, hence all their original fits were still valid. <BR/><BR/>They then estimated the heat flux into the thermocline using a standard (accepted) model, with a thermocline eddy diffusion coefficient of 1.2E-5 m^2/s from Ledwell: <BR/><I><BR/>We estimate s by using this slope<BR/>along with k = 1.2x10-5 m2/s (the eddy diffusion coefficient in the thermocline [Ledwell et al., 1998])<BR/></I><BR/>So if they are wrong, either their basic model is wrong (which seems unlikely - it is just a simple energy balance model after all), or their choice of eddy diffusion coefficient is wrong.mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-70361071403348411962008-09-03T23:01:00.000+01:002008-09-03T23:01:00.000+01:00Mugwump, you talk about the "average diapycnal hea...Mugwump, you talk about the "average diapycnal heat transfer of the ocean", but what Douglass' revised model actually requires is the heat transfer <I>out of the upper mixed layer</I>, which must (according to his ~5 month time scale) be very shallow. However, in his revision, he did not use such a (shallow) heat transfer coefficient, but explicitly used a value appropriate to the ocean interior.<BR/><BR/>Your comments about "huge ocean-induced lag" are just nonsense bluster. The rapid decay of the cold anomaly is (partly) <I>because it is diffused downwards</I>. It is perhaps excusable that you can't get your head around the physical behaviour of the climate system, but that doesn't mean that everyone else who has studied it is a moron who is missing your supposed insight.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-29732239653046558692008-09-03T13:57:00.000+01:002008-09-03T13:57:00.000+01:00Vertical mixing around the boundaries and over ste...<I>Vertical mixing around the boundaries and over steep topography are far greater - Douglass's value refers to the extremal low value in the deep interior, not a representative average.</I><BR/><BR/>The average depth of the ocean is 3,790m. Two thirds of the earth's surface is covered by ocean greater than 200m deep. Therefore, it is much more likely that the <I>average</I> diapycnal heat transfer of the ocean is determined by the interior than it is by the boundaries or regions of steep topography. Do you have references supporting your assertion to the contrary?<BR/><BR/><I>"I guess that the reason he does not explicitly discuss the implied depths in his paper is that the inconsistency would be too stark."</I><BR/><BR/>I doubt that is the reason. The original paper included no ocean heat-flux, and fit the data very well. You don't even need the model to see that a huge ocean-induced lag is unnecessary to explain the data. Just eyeballing the data, you can see the eruption, the response, and then the relaxation back to equilibrium with a lag of about 6 months. If there is a big ocean lag in there it is not significantly impacting the temperature response.mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-51466667441567385892008-09-03T07:10:00.000+01:002008-09-03T07:10:00.000+01:00You also seem to be confusing the ocean interior d...You also seem to be confusing the ocean interior diffusion with the basin average. They are not the same! Vertical mixing around the boundaries and over steep topography are far greater - Douglass's value refers to the extremal low value in the deep interior, not a representative average.<BR/><BR/>Note also that he has already effectively claimed in the first paper that the ocean mixed layer is very shallow - so for the effective diffusion out of the bottom of that layer, he should use a diffusion coefficient appropriate for 50m depth or thereabouts, not 500m. <BR/><BR/>No-one credible considers his analysis reasonable, and I guess that the reason he does not explicitly discuss the implied depths in his paper is that the inconsistency would be too stark.<BR/><BR/>It is not "parsimonious" to ignore factors that are known to be important, and then produce a spurious and misleading argument to attempt to defend the initial error.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-19753930876594494252008-09-03T04:27:00.000+01:002008-09-03T04:27:00.000+01:00Modern estimates of the effective diffusion seem t...<I>Modern estimates of the effective diffusion seem to agree with Wigley et al and disagree with Douglass.</I><BR/><BR/>I am curious to which modern estimates you refer. Ledwell's 1998 SF6 tracer experiments established an eddy diffusion coefficient of around 10-5, which is what Douglass uses. Wigley uses values between 10 and 40 times that. <BR/><BR/>The book "A Turbulent Ocean" by S A Thorpe has an interesting discussion on <A HREF="http://books.google.com/books?id=Ax2d94PODgIC&pg=PA39&lpg=PA39&dq=eddy+diffusion+coefficient&source=web&ots=MbWaPQLtQB&sig=Lpht8clFU9mMyuzDt9XTI8KxDAk&hl=en&sa=X&oi=book_result&resnum=8&ct=result#PPA39,M1" REL="nofollow">pages 39-40,</A> which describes the smaller tracer-derived numbers as the correct "modern" value.<BR/><BR/>Regardless, describing Douglass as "rubbish" because he used recent, published values for the eddy diffusion coefficient seems rather unfair. The model and analysis in Douglass is, in my opinion, an object lesson in parsimony.mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-3319614017089829452008-09-03T02:20:00.000+01:002008-09-03T02:20:00.000+01:00Well I'm puzzled, because I definitely did reply s...Well I'm puzzled, because I definitely did reply some time ago, but it doesn't seem to have stuck...<BR/><BR/>Douglass do try to salvage their original work by claiming that they original error has negligible effect, but their apparent confusion between the ocean interior diffusion and the effective basin-wide diffusion (substantially larger, due to topographic effects over ridges and near edges, and convection) makes it pretty dubious. And using a quote from the SAR for something written in 2005 is decidedly odd. Modern estimates of the effective diffusion seem to agree with Wigley et al and disagree with Douglass.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-88333676644845907902008-09-02T15:38:00.000+01:002008-09-02T15:38:00.000+01:00No response? Do you agree then that Douglass is no...No response? Do you agree then that Douglass is not "rubbish" as you put it? If so, how do you think inclusion of his results will modify your sensitivity estimate?mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-83732862427851457482008-08-26T12:55:00.000+01:002008-08-26T12:55:00.000+01:00Douglass completely ignored the ocean heat uptakeT...<I><BR/>Douglass completely ignored the ocean heat uptake<BR/></I><BR/><BR/>They addressed that in their followup responses I linked to above. In fact the ocean heat uptake fit very neatly into their model. Once included, it made little difference to their estimates.mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-46949649183771757822008-08-26T11:27:00.000+01:002008-08-26T11:27:00.000+01:00Douglass completely ignored the ocean heat uptake,...Douglass completely ignored the ocean heat uptake, which is a huge red flag. Everyone knows that this is a major uncertainty, and every plausible climate model suggests it is a substantial effect. It is not credible that the authors and reviewers were not aware of this, assuming they have a rudimentary awareness of the field. Yet Douglass and Knox don't even mention it!<BR/><BR/>You may not realise that GRL basically allows authors to pick their own reviewers, which means that complete nonsense occasionally gets through.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-91511892684431996452008-08-26T01:09:00.000+01:002008-08-26T01:09:00.000+01:00Can you explain why you think Douglass is rubbish?...Can you explain why you think Douglass is rubbish? From my reading his is a simple, physical energy balance model that fits the data very well. <BR/><BR/>Also, Douglass did not claim that his sensitivity results from Pinatubo necessarily established anything about 2XCO2 sensitivity, given that the feedbacks in each case are probably very different (unlike 2XCO2, Pinatubo belched enormous quantities of crap into the atmosphere)mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-80560414598874031732008-08-26T00:08:00.000+01:002008-08-26T00:08:00.000+01:00I think Douglass' stuff is rubbish (and no reviewe...I think Douglass' stuff is rubbish (and no reviewer suggested it rated a mention).<BR/><BR/>In more detail, the natural variability happened to oppose the Pinatubo cooling, so the forced response was actually greater than the observed change. And GCMs with much larger sensitivity than Douglass would allow, still simulate the cooling rather well. So although I would agree that this and other eruptions point towards moderate sensitivity, they by no means prove it is negligible.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-61478898058355897812008-08-25T14:15:00.000+01:002008-08-25T14:15:00.000+01:00I am curious why you did not reference Douglass an...I am curious why you did not reference <A HREF="http://www.pas.rochester.edu/~douglass/papers/2004GL022119_Pinatubo.pdf" REL="nofollow">Douglass and Knox</A> which shows that the climate sensitivity estimate from Pinatubo is much smaller, and probably cannot be used to derive a 2XCO2 estimate because of the different processes involved in a volcanic eruption (see also <A HREF="http://climate.envsci.rutgers.edu/pdf/DouglassKnoxComment2005GL023287.pdf" REL="nofollow">Robock</A>, <A HREF="https://e-reports-ext.llnl.gov/pdf/319378.pdf" REL="nofollow">Wigley et. al.</A> and Douglass and Knox <A HREF="http://www.pas.rochester.edu/~douglass/papers/reply_Robock_2005GL023829.pdf" REL="nofollow">response to Robock</A> and <A HREF="http://www.pas.rochester.edu/~douglass/papers/reply_WAST_2005GL023695.pdf" REL="nofollow">Wigley et. al.</A>mugwumphttps://www.blogger.com/profile/17843895243809398396noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-16081314551833679572008-07-05T17:53:00.000+01:002008-07-05T17:53:00.000+01:00Any new citation info? it should go here: http://...Any new citation info? it should go here: http://home.badc.rl.ac.uk/lawrence/blog/2006/03/07/climate_sensitivity_and_politicsHank Robertshttps://www.blogger.com/profile/07521410755553979665noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-2914485407262790262008-02-23T23:49:00.000+00:002008-02-23T23:49:00.000+00:00Thanks Hank,I'd seen a glimpse of that at the AGU ...Thanks Hank,<BR/><BR/>I'd seen a glimpse of that at the <A HREF="http://julesandjames.blogspot.com/2007/12/agu-science.html" REL="nofollow">AGU</A> and wondered where the full paper was. Will probably blog it once I've had time to read it.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-34475513330110445852008-02-23T16:32:00.000+00:002008-02-23T16:32:00.000+00:00http://www.agu.org/pubs/crossref/2008/2007GL032759...http://www.agu.org/pubs/crossref/2008/2007GL032759.shtml<BR/><BR/>ChylekHank Robertshttps://www.blogger.com/profile/07521410755553979665noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-49275747020526761832007-01-16T13:03:00.000+00:002007-01-16T13:03:00.000+00:00Earl,
I certainly don't believe that 3C of warmin...Earl,<br /><br />I certainly don't believe that 3C of warming will "lead to millions of deaths", and I don't think there is any scientific support for such a position. It will cause changes, for sure, and if we could stop all anthropogenic carbon emissions for free then I'd be all for it, but as things stand we have to consider the trade-offs between current economic growth and future climate changes, both of which contain uncertainties.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.com