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dana1981 at 03:36 AM on 22 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
To me, anyone who introduces himself as having 6 degrees is trying way too hard to sound credible. It makes me immediately think "there's a reason he said that - probably because he doesn't know what he's talking about but wants to sound credible." And this is of course confirmed by the content of his talks, not to mention the fact that his degrees aren't relevant to climate science. -
Dikran Marsupial at 03:17 AM on 22 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
@sphaerica that would be a "no" then ;o) -
Dikran Marsupial at 03:15 AM on 22 May 2012CO2 has a short residence time
IanC residence time is the length of time an individual molecule of CO2 stays in the atmosphere, rather than the time it takes to decay to zero. C14 is constantly being generated in the upper atmosphere, so it does have a non-zero equilibrium level. The real problem with Essenhigh's paper is that hea appears unaware of the distinction between residence time and adjustment time. His estimate of residence time is completely uncontraversial, the problem is that a short residence time doesn't mean that anthropogenic emissions are not the cause of the long term rise. The link between residence time and the attribution of the rise in his paper is very tenuous. -
Bob Lacatena at 02:31 AM on 22 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Dikran, From DeSmog Blog:- Ph.D. Electrical Engineering, Stanford University, Stanford, California.
- M.S. Electrical Engineering, Stanford University.
- M.S. Statistics, Stanford University.
- M.A. Applied Mathematics, University Of Sydney.
- B.E. Electrical Engineering, University Of Sydney, Sydney Australia, University Medal (1983).
- B.Sc. Applied Mathematics and Physics, University Of Sydney.
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IanC at 02:08 AM on 22 May 2012CO2 has a short residence time
Dikran, For the case of C14, the residence time is the same as the adjustment time. I tend to think of the residence time as the time it takes to reduce X to 0, while the adjustment time is the time it takes for X to approach a particular equilibrium. In the case of the C14, the initial perturbation is so large that 0 is effectively the equilibrium, and the data does support a simple exponential decay to 0. In which case the linear model is valid, and the residence time and adjustment time are the same. IMO, the fatal flaw of Essenhigh2009 is that the equilibrium for overall CO2 is very far from 0, so although his model is 'validated' by the C14 data it doesn't actually carry over to the anthropogenic CO2 problem, as it is in a completely different regime! -
davidpalermo at 02:08 AM on 22 May 2012Who Are the Most Prominent Advocates of Global Warming?
I have been reading that Margaret Thatcher changed her views on Man-made global warming and is now a skeptic. I think that should be addressed. Apparently both deniers and mainstream science supporters are using Thatcher to make their case. What gives? http://www.treehugger.com/corporate-responsibility/margaret-thatcher-hailed-as-champion-for-climate-skeptics.html http://www.guardian.co.uk/environment/2010/jun/22/thatcher-climate-sceptic-monckton -
Dikran Marsupial at 01:57 AM on 22 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
chris, it certainly wouldn't go down well with an English audience, where self-deprecation is more the norm. It does rather beg the question whether any of the degrees are in relevant subjects. More to the point, in research your qualifcations are not a big deal, what matters is the quality and quantity of your publications (as measured by e.g. your h-index) or academic awards or prizes, which show that you can usefully apply what you studied for your degrees. -
Bob Lacatena at 01:50 AM on 22 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Tristan, You forgot Degree Enumeration, which is a rare and highly self-valued field of study. -
Tristan at 00:17 AM on 22 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
John Rocket Surgery, Actual Science, Computational Theology, Psychohistory and Nintendo. Chris No, it's not polite in Australian culture nor any culture I'm aware of. -
chriskoz at 23:25 PM on 21 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Regardeless of the ensuing content of this video, when I hear Evans introducing himself at the start: "Hello, my name is Doctor David Evans [...] I have 6 university degrees..." Something does not sound right. Does anyone know a credible and honnest scientist who introduces him/herself in such boastful way? In Japanese culture for example, it would be considered very very rude, perhaps in English culture he may get away with it: I'm notr sure as English is not my mother tongue. -
Michael.M at 21:22 PM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
Grrr, keyboard with stuck keys.... Most answers to the Haertland-hate-Billboard either took the type of argument to ridiculousness, or answered the science. I propose something other, show people Heartlands own history of industy-paid, fake expertise: A picture of e.g. Fred Singer, withe the subtitle "tabacco-industry paid fake expert from Heartland" (if this seems to harsh, one could just omit the "fake", but I go with tamino on this). Main text: "I still believe smoking does not cause cancer. Do you? Heartland.org" (Haertland.org can be replaced with a source of real information either about Heartlands role in the smoking-debate or with information about the dangers of smoking) Its mirroring the attack; but not with the same logical fallacy, but known facts about the paid lobyying of Heartland. -
Albatross at 16:10 PM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
dalyplanet@15, I really must take strong exception to some of the assertions that you made in your post. While Heartland did remove the billboard, they did so under duress and have remained unapologetic for their actions. In fact, Joe Bast has been bending over backwards to try and justify what they did (see here) and in the process Bast refers to Mike Mann as a "madman". Also, Heartland still stands by its assertion that "....the most prominent advocates of global warming aren't scientists. They are murderers, tyrants, and madmen." You mention Thatcher, while you are entitled to your opinions of her (I am not a particular fan, but what we think of her is irrelevant), it does not change the fact that what she says in the video is supported by the science and in present day by observations. People who have watched the video will not that it also features such greats as Hawking, Sagan and Schneider. It is very unfortunate that you tried to dismiss the Hiroshima analogy as "sensationalism". Ever since the Hiroshoma bomb scientists have been using that analogy to help readers comprehend and understand the huge amounts of energy involved or released during certain processes, and certainly not to engage in sensationalism or appeal to emotion. Telling someone that the earthquake off Japan last March released about 2x10^17 Joules of energy means nothing at all to most people. But they can very much appreciate the huge amounts of energy involved when told that the quake released the energy equivalent to 600 million A-bombs. Similarly, during the Thunderstorm Project, Dr. Braham and his colleagues determined that the amount of energy released in the lifteime of a sing-celled thunderstorm is equivalent to 50 A-bombs. Those are but two of many examples. So when Hansen is trying to convey to a lay audience how much energy is being accumulated each year in the climate system on account of the planetary energy imbalance being imposed by us emitting GHGs, telling them that the increase on the order of 10^22 J/yr would not be helpful. Hence, he like his colleagues, uses the A-bomb analogy, and there is nothing wrong with that. You trying to claim that his stature as a scientist is being reduced for standing up for what is right is not only demonstrably false, but a form of ad hominem argument and possibly in violation of the comments policy. Regardless, that he is an activist (it is sad that some people consider others standing up for what is right to be a bad thing) has no bearing whatsoever on the integrity or value of his findings appearing in his scientific publications. Hansen continues to publish prolifically in prestigious peer-reviewed journals and is very much respected by his peers. -
DaneelOlivaw at 14:59 PM on 21 May 2012Dear Heartland, Stop using Arthur Robinson's Trick to Hide the Incline
Very cool investigation, Mark. I love this kind of in depth stories about climate myths. I commend you for your honesty in contacting the people involved and reproducing their comments (albeit marginally helpful in this case). I'm always amazed with people's obsession in using local records to imply global temperature and their simultaneous reluctance to use *actual* global averages. -
dagold at 13:49 PM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
yes, Climate Reality is going ahead with the billboard campaign. Funny little story- I actually passed along my billboard and website idea to a person who works with Climate Reality and...lo and behold...a week later they came out with their campaign. Actually, it seems we both came up with the idea independent of each other. Great minds think alike? :) -
John Chapman at 13:27 PM on 21 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
The other misleading technique David has is to discuss a modelled trend or rate and then apply it to a start year that is high in the records, so consequently the modelled predictions end up looking higher. As an aside, does anyone know what David Evan's 5 other degrees are in? -
skywatcher at 13:08 PM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
LarryM #12 - Seems like Al Gore has the same idea! - The Climate Reality Project are putting up a bunch of billboards around Chicago to time with the Heartland conference there.
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DSL at 13:07 PM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
dalyplanet, I'll point out the obvious: comparing someone to Hitler is intended to cast the target as, at the very least, a mass murderer (through indirect means). It is a sensational comparison, meant to ring those little bells of paranoia inside the heads of those who are unable or unwilling to think critically beyond a certain point. Anyone who accepts the theory of AGW is a mass murderer, according to the logic of the billboard. Measuring the energy budget imbalance in Hiroshimas is also sensational, but the comparison is not meant to suggest that the energy will end up destroying whole cities, leaving us with a radioactive nightmare. It's simply a way to put the size of the energy imbalance into perspective. A few extra Wm2? What's the big deal? And what's a Wm2? Oh, throughout the whole system it's that much? Ok then. -
Rob Honeycutt at 12:34 PM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
dalyplanet... Heartland also took a lot of hits from skeptics of global warming. They took hits from just about everyone. It was an incredibly poorly calculated "experiment" on their part. Margret Thatcher is being presented because she, like Reagan, was a staunch conservative but still understood the threat of global warming. The amount of energy released in Hiroshima is a standard reference used is all kinds of contexts, not just this. It's an accurate measure of how much energy is being retained by the planet through a change in radiative balance. Hansen is not reducing his stature at all. He is showing his concern for the consequences we face. -
chriskoz at 12:22 PM on 21 May 20122012 SkS Weekly Digest #20
Have you checked another fingerprint of climate change reported by realclimate here?. That's based on Durack et al. (2012) research about the change in salinity from ARGO data spanning 1950-2000. I don't have access to the full text of Durack et al. (2012), so I'm asking a question to someone who has: how Durack came out to the number of hydrological cycle sensitivity of ~8%/°C. How did he justify the surface salinity is due to change in precipitation and not other factors like the currents? That's an interesting number quantifying the increased intensity of floods and droughts we are facing in the warmer world. Apparently this number is higher than that predicted by ocean-atmospheric circulation climate models. I think SkS should also say their comment on that interesting new research. -
dalyplanet at 12:20 PM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
Heartland took hits from many that do not agree with catastrophic warming and Heartland removed the billboard post haste. Margret Thatcher is really just another politician to be taken with a grain of salt. Hansen's Hiroshima bit is rather sensationalism as that particular incident is highly emotionally charged and can be construed in the same manner as Heartlands ill conceived billboard. His forays into activism are reducing his stature as a scientist. -
Riduna at 11:52 AM on 21 May 20122012 SkS Weekly Digest #20
Toon of the Week Nice ball, nice sentiments - but a green greenland and Antarctica! -
dana1981 at 09:24 AM on 21 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Hairy @20 - we can only refute myths so many times. If the denialists continue to repeat the same long-debunked myths, that says a lot about their credibility, or lack thereof. Frankly I'm not sure why anyone listens to Evans, who's just some computer programmer who clearly doesn't even understand basic climate science and shows no interest in getting his facts right. -
PT_Goodman at 07:38 AM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
Of course, this sort of nonsense from Heartland should not affect someone's opinion on AGW one way or another. But I would walk away from any group who behaved this badly, even if it were SkS. The science of AGW will--actually, it does--does stand on its own. Remembering the Falklands War, I don't have a high opinion of Thatcher myself. That too, is a separate issue. -
funglestrumpet at 07:12 AM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
Pity Thatcher was chosen as a focus, otherwise it is an excellent video. Perhaps Mr Sinclair doesn't realise just how much she is still reviled by a sizeable portion of the U.K. population, and I choose my words with care as I am a member of that group. If you want to find out how good the U.K. accident and emergency services are, go into a bar in what used to be a Welsh mining village and say out loud that you think Mrs Thatcher is a lovely person. Mind you, it is doubtful that anyone would actually call an ambulance for you. -
Hairy Zelden at 06:14 AM on 21 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Thanks for the thorough discussion. Evans comes across as oh so professional in the video. I force myself to watch the first part as well, and I'm surprised you didn't also remark on how he (as do so many others) misrepresents Hansen's 1981 projections, and claims to refute them. -
LarryM at 02:52 AM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
I second the congratulations and thanks to dagold #7 for the best new idea I've heard in a while, namely spreading the word about the reality of climate change on billboards linked to an excellent website. I suppose Heartland gets some credit for the inspiration! For future such endeavors, I suggest putting part of the answer to the billboard question "Guess who believes in climate change?" right on the billboard, such as the line from the website, "The Pentagon and every National Science Academy in the world for starters...". There's some guy named Obama with a million dollars to spare and a sympathetic superPAC who should see this idea and have a lightbulb go on... -
Dikran Marsupial at 02:33 AM on 21 May 2012CO2 has a short residence time
IanC Essentially yes. The key point is that C14 is not replenished, so it can only tell you about the residence time not the adjustment time. -
IanC at 02:14 AM on 21 May 2012CO2 has a short residence time
Dikran, I read Essenhigh's paper, and my impression is that he is using CO2 with C14 to validate his linear model, and then use that as an argument against short adjustment/equilibration time for CO2 in general. Is this a correct interpretation? -
JMurphy at 01:15 AM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
I just wanted to congratulate dagold for actually paying-out money for that billboard, and setting-up a website to go along with it. It sounds like a good idea but not something that everyone can or would want to fund. Well done, sir ! -
Martin A at 00:25 AM on 21 May 2012CO2 has a short residence time
Dikran M, IanC: Thank you. I need to try and work out some examples for simple models with significant nonlinearity so I can get a feeling for what's really going on. -
dhogaza at 00:23 AM on 21 May 2012Who Are the Most Prominent Advocates of Global Warming?
Rob, it's always best to be accurate when talking about historical people, and as a matter of face, Hilter was a dog lover, often photographed with his shepard "Blondi" while chancellor. I'm a cat person, too, so photos like this: LINK Make me feel good about myself :) :) :) Napolean disliked cats, too? Maybe cats are too independent-minded for your average dictator type ...Moderator Response: [RH] Link was breaking page formatting, and sorry, I somehow killed the link as I was trying to fix it. If you repost think link I'll fix it again. -
muoncounter at 23:10 PM on 20 May 2012CO2 lags temperature
Recall, too, that glacial advance requires snowfall, compaction and buildup. That's inherently a multi-year process. Once the glaciers spread beyond their valleys to become continental ice sheets, that process must occur over a vast geographic area, inevitably slowing it down. Deglaciation can start the first year there is less accumulation. For direct evidence of how fast that can be, consider the catastrophic flooding that results from ice dam collapse. There is no analogous 'fast process' on the buildup side. -
Bob Lacatena at 23:05 PM on 20 May 2012CO2 lags temperature
Dougal, Note that I'm not saying that this is the reason or even necessarily a factor. I'm just pointing it out to give a clear example as to how the two transitions are asymmetric and therefore do not need to parallel each other like the motion of a bouncing ball or a yo-yo. -
Bernard J. at 17:22 PM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Dana1981 at #13. James Hansen states the 400,000 Hiroshima bombs equivalence at 7:45 in his video "Why I must speak out about climate change". -
Bernard J. at 17:08 PM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Just to follow up on Andylee's comment at #12... 400,000 HB/day = 400,000 HB/(24*60*60)second = 4.63 HB/second -
Rob Honeycutt at 15:50 PM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
Miffedmax... I thought of using dogs in that statement but somehow it lacks the same umph. Maybe it's just me. And I'm a cat person. -
Tristan at 15:11 PM on 20 May 2012Peer review process was corrupted
Otter For some significant set of the 'skeptics' there is no beating them. That global warming is not dangerous/not happening is to them, an axiom. By virtue of that 'fact' the peer review process must be corrupted and any morsel of information that could possibly be taken to be indicative of such corruption is unreservedly true and able to be extrapolated to all of climate science. I was once a regular on one such blog until I realised that it was negatively affecting my mood. -
Bob Lacatena at 14:53 PM on 20 May 2012CO2 lags temperature
Dougal, You have enough to chew on for now about Milankovitch cycles, but to give you one very direct and easy to understand example as to why de-glaciation is fast, while re-glaciation is slow, consider simply the surface area of a sphere, or more importantly, the circumference. For understanding purposes only, imagine two cases, one with ice that covers the entire northern hemisphere all the way down to the equator (our oversimplified and exaggerated "glacial" state) versus one with ice that extends only as far south as the northern coast of Greenland. Look at a globe. If you were to change the seasons in a way that the ice in the first case retreats 5 degrees further north, and in the second case extends 5 degrees further south... Each scenario affects temperature by changing the overall albedo of the planet. But the effect near the equator is much, much greater, through the combination of (a) covering far more surface area (and in that way changing the total energy reflected by a greater amount) and (b) changing the albedo in a more important place (i.e. year round 12 hour days of very direct light at the equator versus half a year of long days and half a year of no daylight and with very indirect light at the pole). So you have an asymmetric situation, one in which a change from glacial-to-interglacial (retreat of ice from the equator, far south) produces a much stronger feedback than the change from interglacial-to-glacial (advance of ice from the pole, far north).
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otter17 at 14:28 PM on 20 May 2012Peer review process was corrupted
DSL, thanks for the support and ideas on how to logically approach this. From a logical perspective, I suppose I had a decent idea how to respond. My main questions for evidence centered around the following question. Why hasn't this story been blown wide open by an investigative journalist or a huge government inquiry? Extraordinary claims require extraordinary evidence. I wanted to kind of test my debate skills and I remained calm/rational throughout, but I probably won't be going back. -
skywatcher at 14:01 PM on 20 May 2012CO2 lags temperature
Just to add a small part to the discussion here, at least one of the feedbacks involved in enhancing the Milankovitch signal is decidedly asymmetric - ice sheet accumulation/ablation. Ice melt and loss through calving or increased flow always has far greater potential to operate at a much higher rate than ice accumulation through precipitation or slowing of ice flow. This can be seen in concepts as simple as the AAR on a valley glacier - the accumulation-ablation area ratio. The accumulation area is usually ~60% of a glacier's mapped area, to compensate for the higher rate of loss through melt per unit area of a glacier. Bigger mechanisms in ice sheet buildup or loss are similarly asymmetric. It's eaasier to melt very large volumes than to add large volumes. -
DSL at 13:39 PM on 20 May 2012Peer review process was corrupted
Otter, the best thing to do is ask those people to imagine what the world (and the practice of science) would be like if what they believed were true. It would mean that these dozens of journals across many disciplines stopped publishing any science that did not agree with the "eco-radical" ideology. Now, in order for this to be a bad thing, scientists would have to be producing science that didn't agree with the eco-radical position. These scientists, if they existed, would undoubtedly be talking to each other constantly--through email, blogs, conferences, etc.--and they would undoubtedly, by now, have begun to discover the "eco-radical" journal editor agenda (identified already by these comment stream nutters who've never written a formal hypothesis in their lives). They would then have a choice: continue to work but not publish (bye bye job - and integrity), speak out, seek legal counsel, or start a new journal. None of this has happened. Or, rather, it has allegedly happened to a couple of people whose scientific work has been found lacking and who, in fact, have acknowledged the poor work. There is no widespread call for journal editors to step down. The halls of academia are not filled with whispered bitterness at the eco-radical agenda. Quite the opposite. The overwhelming majority of scientists are, by the comment nutters' definition, "eco-radicals." They all have secret code words and communication networks, and they're all "watermelons." I mentioned Tamino's blog to a statistician colleague of mine in the context of finding examples of essentially Dunning-Kreuger. He gave me a surprised look and noted that this climate stuff had been effectively put to rest rather robustly over a decade ago. Yes. It has. Yet there are still a few nutters (the paid and the psychologically needy) and plenty of people who don't know enough to know that the nutters are nutters. The internet: damned with it and, thanks to corporate-controlled mass media, damned without it. But of course, the actual best way to respond is as you have done: ask for evidence. It never shows up. -
Daniel Bailey at 13:20 PM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Just as an FYI, April 2012 was the 427th consecutive month with ocean temperatures warmer than the 20th century average. The last time the ocean temperatures were below average was September 1976 [Source]. Global land+ocean temps in April were the 4th-warmest April temps on record. In fact, the last month with below-average temperature was February 1985. That makes 325 consecutive months with global land+ocean temps temperatures above the 20th Century average [Source]. And the beat goes on... -
miffedmax at 12:32 PM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
As a former history student and cat person, I just want to point out Hitler (like Napoleon) disliked cats. But the point is taken. -
otter17 at 09:55 AM on 20 May 2012Peer review process was corrupted
I was on a, uh, less than credible anti-science blog recently, and some of these guys in the comments were absolutely berating me for not believing that the journals were taken over by eco-radicals. I was skeptical and repeatedly asked for evidence of this, but only got a reference to what looks to be an opinion piece by Dr. Lindzen from 2008. Title: "Climate Science: Is it currently designed to answer questions?" Now, I guess the best way to deal with this type of widespread accusation is to treat it like a conspiracy theory? I mean, it is sad that people will go to these lengths to conclude that their blog conducts better science than the peer reviewed literature, but there you go. I stood my ground, and made mention that there are a whole host of other groups outside of the journals that also have analyzed the science and deemed climate change a credible threat (US Department of Defense, US Climate Action Partnership, etc). So, I guess this is the appropriate response (before backing away in utter surprise). -
Tom Curtis at 09:22 AM on 20 May 2012CO2 lags temperature
Dougal @367, better to ask a question and be thought a fool, than to be silent and remain one! Not, of course, the I or Sphaerica think you are foolish. Quit the contrary, it is the mark of wisdom to ask questions. So, in your further reading, if you have additional questions, by all means ask them. @362, in fact the response of global temperatures to the Milankovitch Cycle is far more typical than you believe. Compare the chart of insolation at 65 degrees North in the NH summer below to the temperature increases other than at 30 to 90 degrees North in the following chart:
As you can see, tropical and SH temperatures do follow the changes in NH summer insolation, although they are significantly lagged. What is more, SH temperatures are following NH insolation patterns, while NH extratropical temperatures do not. Clearly something very complicated is going on here, and Shakun et al offer a partial explanation.
Given that, I recommend you read the SkS article on Shakun et al carefully, and follow up questions on this point there.
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IanC at 09:15 AM on 20 May 2012CO2 has a short residence time
Martin A, One thing that needs to be emphasised is that there is a very big difference between a linear model and a linearised model. If we are dealing with an ODE of the form dX/dt=F(X), saying that it is a linear model means: F(X) is precisely AX+B for all X. A model linearised about (X*) means F(X) ~ C(X-X*) + D for points near X*. Typically X* is chosen to be be an equilibrium point so D is usually 0. 1/A and 1/C give you the adjustment time, but only in the linear model will 1/A give you the resident time as well. The reason is that because the residence time depends on the X and magnitude of the flow, which is explicitly given in the linear model (|AX| and B). On the other hand, information about the absolute magnitude of inflow and outflow is not readily available in a linearised model. It is of course possible that there is some nonlinear F(X) such that upon linearising, 1/C happens to give you the resident time, but unless you know F(X) a priori you cannot assume such a thing. -
Dougal at 08:57 AM on 20 May 2012CO2 lags temperature
@Sphaerica 363: Sorry, I am obviously mistaken in my understanding of the Milankovitch cycle and how it affects global temperature, I need to read up more on it. I wasn't meaning to imply you were dishonest above, just that it appeared you weren't addressing my question - this appears to be caused by my misunderstanding of the Milankovitch cycle - my fault all round. @Tom 364: As mentioned, my understanding of Milankovitch needs to be repaired (starting with your link), so my lack of immediate response is not ignoring you, I am paying attention, but think it best I shut up and lurk at least until I have done some more research on it (and stop confirming I am a fool). :) Thank you all for your comments, you have given me some very useful avenues of research, I will definitely be back. This is the most informative factual site I have found on the topic so far. Cheers -
Bob Lacatena at 08:44 AM on 20 May 2012CO2 lags temperature
362, Dougal,But since you raise it, why is it easier to melt than freeze - is it because melt water runs...
Again, your model is so simple that you're missing it. The main factors are CO2, seasonal insolation and albedo. Think about it. I am (really) heading out now. I'll explain in more detail when I return. -
Bob Lacatena at 08:43 AM on 20 May 2012CO2 lags temperature
Dougal, The problem is that you're still stuck on "closeness." Let me explain the orbital factors a little more clearly. First, consider the seasons. The reason that there is a summer and a winter is primarily not that the earth is closer to the sun in the summer... if so, then how come both hemispheres don't have their summer at the same time? The reason is axial tilt. Sunlight hits the northern hemisphere more directly, and so more strongly and for longer days, in the summer, and the opposite in winter.
But this axial tilt doesn't stay the same. Over time it changes, both in direction relative to the sun and in degree (sometimes more straight up, and possibly a few degrees more tilted than now). So does the overall shape of the orbit.
Consider, too, that even if the earth were closer to the sun during one season, it would be further in another... the net sunlight received by the Earth would vary very little in total.
When you abandon your too simplistic view of closer/farther you realize that multiple factors must all align to knock the system out of "glacial mode."
Read this post.
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Tom Curtis at 08:35 AM on 20 May 2012CO2 lags temperature
Dougal @361, I believe you and Sphaerica are talking past each other. Averaged over the year, the Earth was neither closer to, nor further away from the Sun during the Last Glacial Maximum (LGM) or the Holocene Climactic Optimum (HCO). That is what Sphaerica is suggesting. You appear to be suggesting the opposite, but I think you are actually talking about the position of the Earth during Northern Hemisphere summers. Even then you are only partially correct. There are a number of factors which effect the strength of NH summers, of which the most important is the obliquity of the Earth, ie, the tilt of its axis. Because of the tilt of the Earth's axis, incoming sunlight is closer to the zenith in around June and July in the NH, resulting in greater insolation even though the Earth is further from the sun at that time. Thus axial tilt is a dominating factor in determining the timing of the seasons (at least currently). Where orbital eccentricity the primary factor, then NH and SH would experience summer at the same time. In addition to obliquity (axial tilt) and eccentricity (how close the Earth approaches the Sun at its closest approach each year) the other important factor is correlation between the two. The LGM was ended because precession resulted in the NH summer coinciding with perihelion (closest approach), and hence with particularly warm NH summers. Currently the axial tilt is such that NH summers more or less coincide with aphelion (furthest distance). Ignoring all three relevant factors, of failing to specify that what is modified is NH summer insolation, so that it is the configuration during the NH summer that is relevant can only lead to confusion. Finally, I refer you to this excellent article for further discussion.
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