tag:blogger.com,1999:blog-9959776.post1573684829816144955..comments2024-02-15T04:42:41.606+00:00Comments on James' Empty Blog: A sensitive matterJames Annanhttp://www.blogger.com/profile/04318741813895533700noreply@blogger.comBlogger204125tag:blogger.com,1999:blog-9959776.post-42750744551770644002014-02-26T17:06:50.684+00:002014-02-26T17:06:50.684+00:00Firstly, people don't build models with a give...Firstly, people don't build models with a given TCR to order. The TCR emerges as a result of all the little bits of physics that the models contain.<br /><br />And according to some, the "or so" covers roughly the range that the models fill anyway.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-58415748022233739702014-02-26T04:19:28.724+00:002014-02-26T04:19:28.724+00:00
We have had 70 years of experience / data that gi...<br />We have had 70 years of experience / data that gives us experimental data for TCR estimate, and it seems to line up with 1.3C or so.<br /><br />So why are there models running around with TCRs much higher than that?<br />While there is questions about validity on other scores, it seems the TCR seems a direct enough one to fix.Patrick McGuinnesshttps://www.blogger.com/profile/05419236602900154573noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-48040300953810985672013-03-03T03:36:39.425+00:002013-03-03T03:36:39.425+00:00Wow, a second page of comments. I didn't know ...Wow, a second page of comments. I didn't know blogger even did that!<br /><br />Thor, I agree the planet doesn't seem to have warmed quite as much as expected, and my interepretation is that the sensitivity is probably a bit lower than expected. It is possible that a change towards more La Nina conditions might be acting a little bit to mask the forced response, but I don't think it is plausible that this will act as a strong long-term effect.<br /><br />People haver certainly investigated the effect of stopping emissions abruptly - note that aerosol emissions will also stop, as they are largely tied to fossil fuel burning. Thus the immediate effect (weeks to months) would actually be an increase in forcing. (Recent black carbon research may change this perspective, actually). David Archer is one name to look out for if you are interested in the 10,000 yer time scale.<br /><br />CO2 would only drop subtantially on the decadal time scale, maybe 2ppm per year or so. And this rate of decrease would slow over time.<br /><br />Even in 10y, we may know quite a lot more, just from temperature data. Just about everyone is predicting a return to the previous trend in a few years, so if it doesn't happen, they will have to re-evaluate things. Rate of learning depends on sensitivity, we would learn faster for a low sensitivity. But we aren't limited to new temperature data, as the recent research on aerosols and black carbon shows...James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-44395158448268938932013-03-01T01:32:32.229+00:002013-03-01T01:32:32.229+00:00Hi James,
I am interested in your commentary and s...Hi James,<br />I am interested in your commentary and sometimes read realclimate.org<br />and in this article here<br />http://www.realclimate.org/index.php/archives/2013/02/2012-updates-to-model-observation-comparions/ they don't seem to update temp estimates, and stick to about 3K for a CO2 doubling.<br /><br />I have a few questions/comments. The warming in the last decade certainly hasn't accelerated, and as far as I am aware neither has ocean heat content in the 0-700m range. What is expected here, is it possible that more heat is going somewhat permanently into the lower ocean, or will it come out again with say a change in the PDO?<br /><br />2. Is it possible the PDO or ENSO cycle becomes less cyclical and more like a negative feedback by going into a permanently cool phase as a response to a warming world/CO2 increase?<br /><br />3. I regard the transient climate response as more important than the steady state response to a doubling of CO2 because I din't expect CO2 levels to stabilize. Once we stop using fossil fuels, surely they will drop, perhaps relatively quickly. Are there graphs of what will happen to the temp if say in 50-70 years we have stopped using fossil fuels almost completely and CO2 levels are dropping. Surely we won't reach the maximum steady state temp corresponding to the max CO2 level, especially if we continue to emit the same amount of cooling aerosols.<br /><br />4. How long before we will actually know in a lot more detail what will happen? <br />Will more data, faster computing power, or simply time make the difference. Surely by 2040 data itself will have massively constrained our uncertainty even without advances in understanding.Thor Russellhttps://www.blogger.com/profile/07856410399322399878noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-50433642093935143082013-02-17T00:54:10.546+00:002013-02-17T00:54:10.546+00:00Of course compliments are always welcome :-) But (...Of course compliments are always welcome :-) But (to explain what I meant) blogger has gone into manual approval mode for comments which makes it hard to carry on a conversation, especially if I miss some email notifications.<br /><br />I'm sure Isaac Held will appreciate your discussions over there :-)James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-34445441250671104552013-02-16T14:19:40.812+00:002013-02-16T14:19:40.812+00:00James, I thank you as well for hosting the interes...James, I thank you as well for hosting the interesting discussions - thanks for your patience regarding my perhaps naive ideas. :-)<br /><br />By the way, for those interested in the aerosols vs internal variability issue an interesting post serendipitously appeared today at Isaac Held's blog - <a href="http://www.gfdl.noaa.gov/blog/isaac-held/2013/02/15/35-atlantic-multi-decadal-variability-and-aerosols/" rel="nofollow">link</a>Alex Harveyhttps://www.blogger.com/profile/10591760549272940968noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-22069061538890049732013-02-16T06:52:20.875+00:002013-02-16T06:52:20.875+00:00James, I want to thank you for an interesting and...James, I want to thank you for an interesting and informative post and discussion.David Younghttps://www.blogger.com/profile/17029429374522399227noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-42226753607724791622013-02-15T22:56:00.623+00:002013-02-15T22:56:00.623+00:00Well blogger has now decided that this conversatio...Well blogger has now decided that this conversation should be drawing to a close.<br /><br />I don't disagree with their judgement :-)James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-13080919805595693742013-02-15T18:19:32.970+00:002013-02-15T18:19:32.970+00:00If the aerosol cooling hypothesis is so rock solid...<i>If the aerosol cooling hypothesis is so rock solid why can't you just point me to a rebuttal of either Tsonis et al. or Thompson et al.? You don't find this odd?</i><br /><br />Because no-one believes it presents any contradiction to the idea of aerosol cooling?<br /><br />I'll give you an example why not: <a href="http://s18.postimage.org/krqopdyeh/csirohist_nh_sh.png" rel="nofollow">This image</a> shows a comparable NH-SH SST plot from the CSIRO CMIP5 model output. Viewed in terms of the Thompson et al. study I would identify from this time series an abrupt NH cooling in the late 1960s, which is obviously too quick to have been caused by anthropogenic aerosols.<br /><br />Trouble is that we know the anthropogenic aerosol cooling influence in this model is considerably large.<br /><br />When looking at noisy datasets these types of apparent patterns can pop up, but you have to be cautious of what they really mean. In the case of the SST datasets analysed by Thompson et al. it looks to me that natural variability (volcanic influences, ENSO etc.) have conspired to make a relatively gradual trend look like a sudden one.<br /><br />Unfortunately their attempt to account for such natural variability doesn't really improve the picture. They apply equal-sized adjustments to each hemispheric dataset for volcanic and ENSO effects. This might be ok for most volcanoes but the 1963-4 Mt Agung eruption had distinctly assymetric hemispheric effects with an SH bias. Their adjustment left the SH still feeling the cold, while making the NH too warm. Their ENSO adjustment I'm also not too sure about - I believe it tends to effect SH SSTs more (?).Paul Shttps://www.blogger.com/profile/15275182941476518621noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-65127062583017919932013-02-15T18:04:32.686+00:002013-02-15T18:04:32.686+00:00Alex,
Nobody here (nor any scientist that you or ...Alex, <br />Nobody here (nor any scientist that you or anyone here referred to) claims "that this mid century cooling business is settled".<br /><br />As Steve there are many past climate events for which we lack the data to explain with certainty, and this is just one of them.<br /><br />There is hardly ever "certainty" in scientific work, but that is not a valid reason to give uncertainty undue weight by overemphasizing doubt, misinterpreting peoples comments and creating strawman arguments.Rob Dekkerhttps://www.blogger.com/profile/04955911975945629265noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-27517800981464476682013-02-15T15:26:56.679+00:002013-02-15T15:26:56.679+00:00Mikel,
well, we can and we do observe the forcing ...Mikel,<br />well, we can and we do observe the forcing of aerosols on a regular base. Downwelling irradiance measurements, data from AERONET and EARLINET (Europe), or satellite imagery are operationally available. Extensive field campaigns provide further evidence and guidance as to whether the measured effects are aerosol related and to what extent. Clear-sky and all-sky measurements in different regions of the planet tell us a lot about their impact. We also have some confidence in the emission estimates, such that the aerosol composition isn't a mystery after all. Sure, it is difficult to know exactly what is going on at each particular moment, but the global numbers have converged considerably over the last few years. This is expressed in the reduction of the uncertainty range for the aerosol forcing as shown in the leaked AR5 SOD.KarSteNhttps://www.blogger.com/profile/16117301462523147860noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-59245694383133143402013-02-15T11:24:30.435+00:002013-02-15T11:24:30.435+00:00Steve, no I am not throwing things at the wall.
...Steve, no I am not throwing things at the wall. <br /><br />I don't see how you or anyone can honestly claim that this mid century cooling business is settled. Plenty of scientists are skeptical that aerosol cooling is necessarily the right answer.<br /><br />I suppose my argument isn't strong insofar as I'm mostly dropping names of doubting scientists but on the other hand the existence of doubting scientists does show there is a controversy.<br /><br />You say above,<br /><br /><i>this is only a debate because of the very limited data available for the time.</i><br /><br />I find this a strange thing to say. It sounds like, "our beliefs are correct, and all doubters will know it as soon as we have data to prove it". Isn't that circular?<br /><br />And how can you imply that Tsonis et al. is not relevant here? The Tsonis theory is taken seriously by many. And I don't see any fundamental contradiction between Tsonis et al. and Thompson et al.<br /><br />But what I do find strange is the lack of debate about all this despite the obvious existence of opposing theories in the literature. If the aerosol cooling hypothesis is so rock solid why can't you just point me to a rebuttal of either Tsonis et al. or Thompson et al.? You don't find this odd?Alex Harveyhttps://www.blogger.com/profile/10591760549272940968noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-74461095451906238912013-02-15T05:12:15.475+00:002013-02-15T05:12:15.475+00:00Alex, now you're just throwing things at the w...Alex, now you're just throwing things at the wall. Personally, I spend my time on this subject attempting to gain a coherent understanding of the climate system, in particular large-scale circulation changes (and so yes, I've seen all this material before). You seem interested in the opposite. Good luck and so long.Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-23072588470530149352013-02-15T04:34:21.373+00:002013-02-15T04:34:21.373+00:00Steve, Revkin's opinion is hardly what matters...Steve, Revkin's opinion is hardly what matters here.<br /><br />The authors of the paper - being very big names in climate science - believe that aerosol cooling is not the right explanation of the mid century cooling.<br /><br />And then there are others making arguments like this independently - e.g. <br /><br />Tsonis, A. A., K. Swanson, and S. Kravtsov (2007), A new dynamical mechanism for major climate shifts, Geophys. Res. Lett., 34, L13705, doi:10.1029/2007GL030288.<br /><br /><i>The standard explanation for the post 1970s warming is that the radiative effect of greenhouse gases overcame shortwave reflection effects due to aerosols [Mann and Emanuel, 2006]. However, comparison of the 2035 event in the 21st century simulation and the 1910s event in the observations with this event, suggests an alternative hypothesis, namely that the climate shifted after the 1970s event to a different state of a warmer climate, which may be superimposed on an anthropogenic warming trend.</i>Alex Harveyhttps://www.blogger.com/profile/10591760549272940968noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-35258802362944687332013-02-15T03:55:33.349+00:002013-02-15T03:55:33.349+00:00Ales, read the whole Revkin post, at the end of wh...Ales, read the whole Revkin post, at the end of which it becomes clear, and he agrees, that science-by-press-release had the effect of way over-stating the significance of the paper (which wasn't even novel since Trenberth & Shea had previously spotted the issue). And indeed, there's now been several years and 28 cites and... no excitement. Sorry. Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-81934446998431360222013-02-15T03:48:57.002+00:002013-02-15T03:48:57.002+00:00Alex, this is only a debate because of the very li...Alex, this is only a debate because of the very limited data available for the time. Karsten correctly points out that the resolution of this debate in favor of a given explanation won't mean much.<br /><br />Why you even brought it up is a mystery. As I said above, there are many past climate events for which we lack the data to explain with certainty, and this is just one of them. Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-47290707183384036852013-02-15T03:22:18.712+00:002013-02-15T03:22:18.712+00:00Karsten,
You seem to be misrepresenting the views...Karsten,<br /><br />You seem to be misrepresenting the views of the Thompson et al. authors - all of whom individually are big names in climate science.<br /><br />From the accompanying Nature News article -<br /><i>The ocean cooling also coincides with a 0.2 °C drop in global mean temperature from the late 1960s to the mid-1970s ... . Researchers have blamed this short-lived cooling, more pronounced in the Northern Hemisphere, on a build-up of sunlight-blocking sulphate aerosols from fossil fuels, which began to clear in the 1970s as pollution controls took hold.<br /><br />Thompson and his colleagues think a circulation change in the North Atlantic is a more likely culprit. ... Michael Mann ... isn't so sure. ...</i><br />http://www.nature.com/news/2010/100922/full/467381a.html<br /><br />To make it clearer that Nature News wasn't misrepresenting them Andrew Revkin solicited their views in email at the same time and printed it on his blog:<br />http://dotearth.blogs.nytimes.com/2010/09/22/a-sharp-ocean-chill-and-20th-century-climate/<br /><br />There were other comments at the time from researchers, e.g. Roger Pielke Sr. <br />http://pielkeclimatesci.wordpress.com/2010/09/23/comment-to-andy-revkin-on-the-dot-earth-post-a-sharp-ocean-chill-and-20th-century-climate/<br /><br />So you are entitled to your views about aerosol cooling but you can't claim there is no controversy or on-going debate.Alex Harveyhttps://www.blogger.com/profile/10591760549272940968noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-64118694786136746472013-02-14T18:30:56.604+00:002013-02-14T18:30:56.604+00:00And yes, the high share of non-absorbing aerosols ...<i>And yes, the high share of non-absorbing aerosols exerts a strong negative forcing also today.</i><br /><br />Karsten,<br /><br />The crux of the issue is this: If we cannot really observe the strong negative forcing of sulfates at the surface over the most polluted areas because their effect is confounded by other forcings such as warming aerosols, how can we be so sure that the total aerosol *global* effect at the surface is strongly (or even weakly) negative? How do we know that the absorptive aerosols effect counteracts the scattering aerosols effect less in the non-polluted areas so as to produce a global negative forcing?Mikel Mariñelarenahttps://www.blogger.com/profile/16104103451964316348noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-10931017881976933412013-02-14T14:55:14.697+00:002013-02-14T14:55:14.697+00:00Mikel,
the Ban-Weiss paper is indeed the best refe...Mikel,<br />the Ban-Weiss paper is indeed the best reference I know of which demonstrates the height dependency of absorbing aerosols (thanks Paul for this addition). The mid-20th-century cooling is mostly sulfate-driven which makes attribution much easier indeed. One striking feature is, that land cooled more than ocean at that time. A rather incontrovertible fact that oceans can't be the driver. They do play their role, no doubt about that, but you need aerosols to explain most of the observed global temperature pattern. And yes, the high share of non-absorbing aerosols exerts a strong negative forcing also today.<br /><br /><br />Alex Harvey,<br />In fact, Thompson et al. 2010 elaborate on the Great Salinity Anomaly (GSA). They clearly mention that the drop is neither explicable with aerosols nor with multidecadal ocean variability. It's a bit puzzling though why Nature found it worthwhile to be published. IMHO not really surprising news. GSA also seems fairly well understood (see <a href="http://www.knmi.nl/publications/fulltexts/bravo_revised_minor.pdf" rel="nofollow">Gelderloos et al. 2012</a>). Xu and Ramanathan don't argue for the aerosol cooling, they just take it for granted as it is a non-controversial issue. They merely try to answer the question whether the observed latitudinal forcing response is a robust feature in all transient climate states. In doing so, they must account for the strong inter-hemispheric asymmetry in aerosol forcing in order to not render the analysis useless.<br /><br />In my point of view, you fail to understand, that decadal ocean variability (e.g. the extremely strong NAO positive phase in the North Atlantic in the early 1990s which is subject of the Sutton and Dong 2012 paper) and aerosol forcing are two entirely different things. Both non-controversial issues, supported by a vast amount of evidence. They are there! We know it! We just haven't managed to quantify exactly how oceans respond to different external forcing factors at different time-scales yet. And there are a bunch of different time-scales to consider (decadal to multi-centennial variability for the AMOC alone). However, it is clear that ocean variability interferes with aerosol forcing as well as with any other forcing.KarSteNhttps://www.blogger.com/profile/16117301462523147860noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-80095056407063819202013-02-14T11:55:51.505+00:002013-02-14T11:55:51.505+00:00Alex,
I don't understand Thompson et al.'...Alex,<br /><br />I don't understand Thompson et al.'s attribution of the abrupt change in NH-SH to an NH cooling event. If you look at the NH and SH time series next to each other it seems to me the more obvious change is an abrupt warming in the SH - an apparent step-change from a relatively cool period between 1946-70 to a warm period from 1970-present.Paul Shttps://www.blogger.com/profile/15275182941476518621noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-73942209005427835552013-02-14T10:25:52.727+00:002013-02-14T10:25:52.727+00:00James/Steve,
Yes I have reconsidered and agree th...James/Steve,<br /><br />Yes I have reconsidered and agree that ice sheet forcing is a bad example. I was thinking of the difficulties understanding ice-albedo feedbacks in the present climate where we have satellite observations - but of course to get the LGM forcing we don't need to understand why the ice moved - just where it moved from and to where. Okay.<br /><br />I think the other points I have made still stand.Alex Harveyhttps://www.blogger.com/profile/10591760549272940968noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-789818400574877722013-02-14T08:14:30.006+00:002013-02-14T08:14:30.006+00:00James, you are right. I confused Forster and Grego...James, you are right. I confused Forster and Gregory 2006 with Gregory and Forster 2008, which does attempt to estimate the Transient Climate Response (TCR) from past temperature records and estimated forcing.<br />http://www.gfdl.noaa.gov/cms-filesystem-action?file=user_files/ih/papers/gregory_forster.pdf<br /><br />Incidentally, they obtain a TCR of 1.3 - 1.7 - 2.3 K (in your triad notation (P.S. I really like that notation since it captures the relevant points in the PDF very nicely).<br /><br />The interesting thing about their result that is that not just that the median is very close to the Equilibrium Climate Sensitivity (ECS) from the Forster and Gregory 2006 paper, but also that the 5%-95% uncertainty range is very tight.<br /><br />This triggered an idea. Since we know that ECS must be greater than TCR (since ocean heat capacity is surely positive), and that F&G 2006 used a completely different method that G&F 2008, isn't it possible to statistically constraint the ECS result from F&G 2006 (or any other ECS estimate) with the PDF of TCR from G&F 2008 ?<br /><br />That would be a constraint on the low end of the ECS PDF, which, combined with the high-end constraints (of not using a uniform prior) should result in a nicely constrained ECS estimate from the F&G 2006 study. Are such inter-study constraints allowed statistically, and acceptable by a larger scientific community ?<br />Rob Dekkerhttps://www.blogger.com/profile/04955911975945629265noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-45376567432357023952013-02-14T07:10:58.252+00:002013-02-14T07:10:58.252+00:00"Now, I wonder how I'd go at getting a pa..."Now, I wonder how I'd go at getting a paper published that requested people to draw fewer conclusions please."<br /><br />Easy, you'd run some numbers indicating that much if not most of what's currently understood about climate is wrong. And you'd have plenty of company -- papers like that get published with some frequency. <br /><br />Re Thompson et al. (2010), they discuss an interesting question but AFAIK there's no definitive answer as yet (although maybe check the SOD). Whether it's measurement error (or misinterpretation, more to the point) or the AMO or a freshwater injection or internal variability (with or without an anthropogenic component) doesn't seem to be crucial to the big picture, especially since the phenomenon (if that's what it was) reversed itself after a while. Or maybe I'm just not clear as to your point. <br /><br />If we see another one it'll be a different story since adequate instrumentation is now in place. If not, it may be a mystery permanently, along with many other such.<br /><br />Serendipitously, this <a href="http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20091/abstract" rel="nofollow">paper</a> just appeared. It's a reminder that much of the ocean-atmosphere circulation is changing, including the AMOC. Expect lots of interesting consequences. Little AMOC wobbles are going to seem like small potatoes.<br /><br />Also: "it seems God-like" This is perhaps more a case of a sufficiently advanced technology seeming like magic, per Clarke. Or maybe it's just that flattery is the sincerest form of flat-earthery. :)<br /> Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-77644557995013238302013-02-14T06:11:09.622+00:002013-02-14T06:11:09.622+00:00Steve,
Re Thompson et al. (2010), maybe you shoul...Steve,<br /><br /><i>Re Thompson et al. (2010), maybe you should check more thoroughly before putting too much weight on it.</i><br /><br />Fair enough. So I've had a closer albeit quick look at the abstracts citing it and I do see one paper by <a href="http://earthjustice.org/sites/default/files/black-carbon/Latitudinally-asymmetric-response.pdf" rel="nofollow">Xu and Ramanathan 2012 GRL</a> that appears to argue for aerosol forcing as the cause of mid century cooling. I note that these authors take the Thompson et al. 2010 Nature article as implying measurement error - which is odd because that doesn't seem to be what Thompson et al. actually said.<br /><br />Meanwhile, as far as I can see, most other papers citing Thompson et al. do so favourably and in the explanation of natural variability in the 20th century climate.<br /><br />E.g.<br /><br />Sutton and Dong, (2012): 'Atlantic Ocean influence on a shift in European climate in the 1990s', Nature Geoscience, 5, 788–792, doi:10.1038/ngeo1595.<br /><br />Wu, Z., N.E. Huang, J.M. Wallace, B.V. Smoliak, and X. Chen, (2011): 'On the time-varying trend in global-mean surface temperature', Climate Dynamics, Volume 37, Issue 3-4, pp 759-773, DOI:10.1007/s00382-011-1128-8.Alex Harveyhttps://www.blogger.com/profile/10591760549272940968noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-75189814074396848662013-02-14T05:00:30.957+00:002013-02-14T05:00:30.957+00:00Alex,
There's a vast amount of evidence of a ...Alex,<br /><br />There's a vast amount of evidence of a heavily-glaciated planet at the LGM, including sea level changes, isostatic rebound, direct geological evidence...really, you are barking up a very silly tree here. There are some minor quibbles about the precise boundaries of the ice sheets and how they varied over time, and there are several subtly different ice sheet reconstructions. None of this matters at all for the general picture, however.<br /><br />(In fact, the "LGM" was not really a contemporaneous state globally, ice was retreating in some areas and expanding in others throughout this interval. However this really is a minor detail on the global scale.)James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.com