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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. -
Bob Lacatena at 08:22 AM on 20 May 2012CO2 lags temperature
Dougal, I'm heading out, but no, it is not the closeness of the orbit. There are multiple factors, including axial tilt, precession, shape of the orbit (ellipse versus circular), and others. Distance changes very little. I'll explain more later. -
Dougal at 08:06 AM on 20 May 2012CO2 lags temperature
@Sphaerica 358: Sorry, it was not the relative rate of warming to cooling I was raising, but the fairly constant (albeit different) rate in both. Unusual in a cyclic system where rates are less at the peaks and maximum at the mid points. But since you raise it, why is it easier to melt than freeze - is it because melt water runs off exposing more of the cold ice sheet and maintaining a larger temperature incline at the sheet compared to when it is growing as water freezes it heats the local air reducing the temperature incline and so rate of growth? Possibly also because it can welt whenerver the temperature is high enough, while to grow it needs an equivalent cold temperature and water. -
Dougal at 07:59 AM on 20 May 2012CO2 lags temperature
@Sphaerica 355: That seems a bit disengenuous - it is the closeness of the orbit that is causing the longer NH summer and shorter NH winter which increases the icemelt and reduces the ice growth which leads to temperature change which amplifies the ice sheet change. I believe from what you said that the amount of cooling/heating is related to the size of the ice sheets - larger ice sheets, more reflection. Similarly the length of NH summer/winter is related to the closeness of the orbit adjusted on a shorter period cycle by tilt and wobble - closer orbit, longer summer, reduced ice sheets, more cooling. Lastly the temperature also changes the CO2 level (in the past) and warmer oceans release more C)2 which increases the warming and reduces the ice sheets, etc. So these three factors combine cause increasing warming the warmer the planet gets. So at the end of a glacial period we have minimum CO2, and maximum ice sheets, while the orbit is getting closer at a cyclic rate - why isn't there balance and a slow shift to warming? Is there something that causes the ice sheets to start melting quickly despite only small change in NH winter/summer, extensive ice sheets and sustained high CO2? That is what I can't reconcile. Do any of the linked reports have graphs which include the Milankovitch cycle, or anywhere that has the Milankovitch cycle data which I can then combine with that from Petit (2000) to generate my own analysis? In fact I think that is what I will need to do, to lok closely at the rate of change which appears to spike massively at the 'tipping points'.Moderator Response: TC:Suggesting that another poster is disingenuous is sailing close to the wind on the comments policy, especially with regards to the clauses about no ad hominens, and the requirement to not be inflammatory. If a moderator deems you to have violated the comments policy, they may warn you, snip the offending text, or simply delete the entire comment. The later is by far the easiest procedure, so by violating the comments policy you make your post a hostage to fortune. A word to the wise... In this case I have given you the benefit of the doubt and assumed you are not suggesting that Sphaerica is dishonest (which would violate the comments policy), but only that he has not discussed all the relevant facts. If you continue to counter corrections to your factual errors with similar suggestions, I will not continue giving you the benefit of the doubt. -
Tom Curtis at 07:58 AM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
dana1981 @13, to be more specific, a theory is "not even wrong" when it is so confused a hypothesis as to be meaningless. Rationalwiki gives the example:"2 + zebra ÷ glockenspiel = homeopathy works"
and goes on to say:"The strict definition of "not even wrong" applies when the premises of an argument are known to be false (based on observational evidence or similar), or when they are used to describe theories which cannot possibly be falsifiable or provide meaningful predictions. For example, any physical theory based on the existence of the aether, and any biological idea based on evolution by Lamarckian inheritance would be classed as not even wrong. In this case, it is a type of formal logical fallacy as using incorrect or non-applicable premises will always yield an incorrect answer. As the premises are wrong the conclusion is certainly incorrect, but the conclusion is at least correct based on said premises. The term "not even wrong" therefore describes this situation. For a clear but silly example, one can say that "this chair is made of hard, solid wood, therefore I can sit on it". This is perfectly true, except in the case where the chair is made of jelly. The conclusion is correct based on the premise, but the premise is clearly not applicable. Therefore we the conclusion is not even wrong."
It is in the sense that the premises of Evan's arguments, eg, that the ocean heat content data before 2003 is worthless, are known to be false that his arguments are not Evan wrong. That sense is an extension of its original, and literal meaning in which claims are "not even wrong" if they are so vague, poorly constructed as to be literally incapable of falsification by any data. -
Dougal at 07:40 AM on 20 May 2012CO2 lags temperature
@Sphaerica Thanks you for those. Sorry for the long post, but needed to try to explain the piece I was missing. I will address if I may also in parts. 357: So it relative to a nominal temp, thanks. Change (as I understand it) just didn't make sense (to me anyway). -
andylee at 06:41 AM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Dana, reference is at TED Talks @ 7:45 Also referenced in Peter Sinclair's excellent video @ 7:24 -
littlerobbergirl at 06:37 AM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
Another source of 'potholes' is big dams. Couple of those filled recently. -
littlerobbergirl at 06:19 AM on 20 May 2012Climate Change Consequences - Often Unexpected
The sewers went in long before the sewage treatment plants - i guess basilget et al welcomed the odd storm surge to give the system a really good flush now and then - they were designed to take it hence the upside down egg shape. So we have a 70s work around bolted onto a victorian 'just move it away a bit' system, just as we do with flue gas abatement. We use a resource, drinking water, to move another rescource, humanure, then add another resource, rainwater, and let it spill out into our rivers where it is least wanted. London mixed sewage overflow events now happen dozens of times a year instead of a couple; partly because of higher water use, partly more high rainfall events but also stupid things like front gardens being paved over with impermeable hard surfaces. I swam in raw sewage as a child i thought those days were over sigh. -
dagold at 05:16 AM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
Well, being the motivated climate activist citizen...I actually had a billboard put up in Minneapolis, Minnesota last Tuesday with the text "Guess who believes in Climate Change?" in response to the Heartland Billboard. My billboard directs you to the website: www.itsphysics.org Please go take a look-the first page lists quotations of various scientific and military organizations advocating action on climate change. Then (culled from this site over the years!) page 2 explains the BASIC physics of climate change. I wanted to put up my billboard in Chicago this week on the Heartland billboard site,but the billboard company wanted $1000 for a day (Minneapolis only charged $300...oh well) -
GCNP58 at 04:04 AM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
@ralbin #3: word. -
dana1981 at 03:25 AM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
John Hartz @11 - there's a phrase "that's not even wrong" for something incredibly fundamentally wrong. "Evan" is a little wordplay on "even" in that phrase. andylee @12 - do you have a link to the 400,000 Hiroshima bombs comment? 2 per second is correct, based on the increase in ocean heat content, though it has also accelerated in recent decades/years, so perhaps that's what Hansen referred to. -
Dikran Marsupial at 03:23 AM on 20 May 2012CO2 has a short residence time
Martin A Indeed in my paper I use a linear model, but it is only a local approximation of the real system. Linearisations of this type are quite common in physics and are good for getting the basic message across, but as I said in the paper it isn't really up to making useful quantative predictions. I think the problem is that you have the outflow being proportional to the volume, however this does not give a reasonable local approximation and you need a linear function of the volume instead (i.e. outflow = k v(t) + C). I think your model is perhaps too simple. This is the principal difference between your model and the one in my paper, so I assume it is where the difference lies. I intitally used a proportional model (as Essenhigh did) but found that if you plot the proportional relationship with the observations it gives an extremely bad approximation, which is why I used linear regression to get a better approximation. -
muoncounter at 03:17 AM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
Nitpick: No one really advocates global warming (except a few Barents sea crab fishermen frequently seen on the Discovery Channel). Perhaps it would be better to say 'The most prominent advocates of global warming science' Because the implicit message of Heartland is "Those who advocate science are ..." -
R. Gates at 03:04 AM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
We can only hope that Heartland's "Murders, Tyrants, and Madmen" statement is brought to the attention of even more of Heartland's sponsors and that even more will flee this organization that seems to have increasing difficulties managing its public messaging. How anyone will stay connected with this organization on any level is beyond me. -
andylee at 03:02 AM on 20 May 2012David Evans: All at Sea about Ocean Warming and Sea Level Rise
According to Jim Hansen the energy imbalance is equivalent to 400,000 Hiroshima bombs per day - this is nearly 5 bombs per second, not 2 as stated above. -
ralbin at 02:55 AM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
This is, of course, excellent. But this is the same Mrs. Thatcher who stated "there is no such thing as society" and whose strident advocacy of neoliberalism played a significant role in undermining the legitimacy of dealing with environmental problems. This makes her recognition of global warming more salient but it shouldn't obscure her significant culpability for the difficulties experienced in developing sensible policy responses to global warming. -
Alexandre at 02:24 AM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
Why don't we have politicians like that nowadays? Maybe the deniers were indeed successful in manufacturing the controversy in the meantime. It became a touchy subject now. -
Daniel Bailey at 01:26 AM on 20 May 2012CO2 lags temperature
"And with all of that said, the next orbital configuration to really get us into a true glacial state isn't supposed to be for another 10,000 to 20,000 years"
Earlier, Tyrrell et al 2007 examined this, concluding that we have already skipped the next glacial epoch. Furthermore, Tyrrell concludes that if we continue our present fossil fuel consumption, we will skip the next 5 glacial epochs. With that said, per Tzedakis et al 2012, “glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv” (for reference, we are at about 396 right now…and climbing). With the millennial atmospheric lifetime of CO2, no glacial epochs will be occurring the next million years… -
otter17 at 01:09 AM on 20 May 2012Hockey stick is broken
It seems that the link to the reconstruction data is broken (third link in the 'Further Reading' section). Current Link (broken): http://www.ncdc.noaa.gov/paleo/pubs/ Suggested Link: http://www.ncdc.noaa.gov/paleo/data.html -
Bob Lacatena at 01:02 AM on 20 May 2012CO2 lags temperature
Dougal, Just to state it a little more directly (as to why the rise is fast, but the decline is slow)... it's a lot easier to melt the ice sheets and thereby increase CO2 and heat the planet, than it is to reduce the CO2, and thereby cool the planet and create new ice sheets. The two processes are not exact, diametric opposites. Hence the difference. -
dorlomin at 01:01 AM on 20 May 2012Who Are the Most Prominent Advocates of Global Warming?
Angela Merkel. Phd quantum chemistry. Conservative femail politician, pro action on global warming. -
Bob Lacatena at 00:57 AM on 20 May 2012CO2 lags temperature
Dougal, On the graphs, "temperature change" means increase or decrease from a chosen baseline (our current climate). The data is from this paper by Petit (2000) and is done by proxy (O18 isotope levels), and as such is relative to current O18 isotope levels (which are indicative of current temperatures). This is why it is presented as "difference from today" rather than an absolute value, because what is being used to present the data is a difference, not an absolute, in something else. [It's rather like measuring the change in the tide. You can see how much the water level has risen by looking at a marker on a pole, without necessarily knowing how deep the water is beneath the pole. You can confidently say the water has risen X inches -- the change -- but it doesn't really make sense to bother to try to make that into an absolute depth.] -
Bob Lacatena at 00:48 AM on 20 May 2012CO2 lags temperature
Dougal, To translate what I just explained... there are basically tipping points. Once the ice sheets start to grow, that continues and the planet falls into a glacial state. It will remain there until a variety of orbital factors combine to toggle the system in the other direction. The rise is then fast once the change has been kick-started. I'm unsure exactly why the opposite is so gradual, except that it is really sort of the natural state of the planet (to be partially ice-covered, that is), but it takes a very, very long time to draw down CO2 once it has been increased. That CO2 blanket keeps the planet warm and the ice sheets from expanding even though otherwise the orbital configuration "wants" the planet to be in a glacial state. And with all of that said, the next orbital configuration to really get us into a true glacial state isn't supposed to be for another 10,000 to 20,000 years (it's not that easy to compute), so that at least is not really worth discussing. -
Bob Lacatena at 00:43 AM on 20 May 2012CO2 lags temperature
Dougal,I would expect the gross heat effect from the Milankovitch cycles to be a maximum when closest and least when furthest (with smaller variations caused by tilt and wobble)...
I think this points to a misunderstanding of what happens due to orbital variations. The earth does not get warmer or colder due to distance from the sun. It actually doesn't get very much warmer or colder at all due to the variations in orbit. All that changes is the length and intensity of the seasons in each hemisphere. Because the northern hemisphere is mostly land, particularly in that sensitive area around the poles (Siberia, Canada), while the southern hemisphere is mostly water, then the length and duration of the northern hemisphere summer becomes key. If summer is too short and cool, then ice sheets can grow and expand in the NH. These reflect a lot more of the incoming sunlight than either open water, tundra or vegetation covered land. That actually changes the temperature of the planet and cools it off. Conversely, when the axial tilt and other factors conspire to lengthen/strengthen the NH summer, the ice sheets will have longer to melt and less time to grow back in winter. The earth will absorb more sunlight/energy (instead of reflecting it back into space). This will warm the earth, and add to the retreat of the ice sheets. Then CO2 adds its punch on top of that. -
Bob Lacatena at 00:38 AM on 20 May 2012CO2 lags temperature
Dougal, I'll answer your post in parts, because it is so long. I'm not entirely sure I understand all of what you're saying, because you seem to include some misunderstandings in there. First, the simple and most important point:What I am missing is why the extra man-made forcing is such a critical factor for earth's climate.
Because the amount of carbon available to the system has been well constrained in the last 800,000 years to pretty much stay below 300 ppm, even at peak. There simply wasn't enough carbon to go around for feedbacks to keep adding CO2 beyond that. It took man, digging up 337 Gt of carbon (and counting) that had previously been sequestered underground in fossil form to provide a source of carbon that would allow levels to rise above 300 ppm. A large portion of the temperature rise from glacial to interglacial is due to CO2 feedbacks due to the 100 ppm increase. So why wouldn't a further 100 ppm, 200 ppm or more greatly influence temperatures?
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