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Comments 47901 to 47950:

47901. Andy Skuce at 06:45 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Can anybody explain where all the water went during the low sea levels in the Miocene? Figure 2a shows Miocene sea levels (green squares) that, mostly, are less or much less than pre-industrial sea levels, some of them comparable to the low-stands during Pleistocene glacial maxima. Miocene climates are generally thought to be warmer than today, with no major northern hemisphere ice sheets and Antarctic ice volumes that fluctuated but were less than today's. RealClimate article on the Miocene

       Moderator Response: (Rob P) Most likely into ephemeral ice sheets in the Northern Hemisphere. The early Miocene period was very warm and is the interval under discussion at Real Climate. The ice sheets most likely formed in the latter part of the Miocene. See below from Zachos(2001):

       

       See also the site linked to in the green box at the bottom of the post. Still lots of research to be to be done to sort out some of the disparities.
47902. Don9000 at 06:43 AM on 7 March 2013
       Cherrypicking to Deny Continued Ocean and Global Warming
       

       As a literary scholar I find the other side's analysis is often as rich in verbal silliness as it is in scientific gobblygook. Here's a pithy verbal pearl of wisdom from Willis Eschenbach's guest post on WUWT, which was posted in response to the Watts post linked to above:

       "the ocean is huge beyond belief"

       The quote can be found here:

       wattsupwiththat.com/2013/02/25/ocean-temperature-and-heat-content/

       Eschenbach makes this profound point in an attempt to back up his notion--or maybe it's a scientific hunch?--that the data on the ocean's heat content or average temperature he is working with is suspect. Here is his complete sentence (the ellipsis is Eschenbach's):

       "I find the claim that we know the average temperature of the upper ocean with an error of only one hundredth of a degree to be very unlikely … the ocean is huge beyond belief."

       In other words, followers of WUWT should have faith in Eschenbach's idea that the temperature rise he's taken the trouble to graph is of no real signficance because the ocean is really, really, really big to the point where Eschenbach, who has possibly thunk about it hard and long, simply can't wrap his mind around the volume of water involved.

       Okay. Fine. I grasp that Eschenbach is trying to imply that there aren't enough sampling points in the vastness of the briny deep to have faith in the stated accuracy of the data, but that is of course exactly the kind of thing scientists take into account when they do their work and present that data. And unlike those scientists, Eschenbach has provided no evidence to back up his claim beyond the aforementioned pearl of wisdom.

       Oddly enough, if we accept that the ocean is so huge that even someone as talented as Eschenberg cannot believe how large it is, and we accept that the data is accurate to the degree scientists say it is, then it should occur to Eschenberg and others that the seemingly trifling increases in temperature he has graphed translate into vast increases in heat content over a short period of time.

       As this is a very scary conclusion and I hate for people to actually worry about such scary things, I take a modicum of comfort from my own belief that it will not trouble the sleep of regular readers of WUWT.

        

47903. jzk at 06:41 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin,

       I have also asked your question of many, and so far have not received a satisfactory answer either.  It is said that the Milankovitch cycle is not "strong" enough to force an ice age or an interglacial, yet it sure seems to be able to reverse a warming trend just as CO2 is higher than at any time in that cycle and continuing to rise.  If that is the case, the Milankovitch forcing must be stronger than the forcing from the CO2 at its peak.  Otherwise, the system would continue to rise and run away.  And it hasn't.

47904. scaddenp at 06:38 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Just a quick point on assymmetry. I dont see that symmetry should be expected. At least two processes are not. Firstly ice sheet/shelf/glacier development versus break up is assymetrical largely because of calving. eg a glacier retreats much faster than it advances. Also affecting albedo is vegetation loss/recovery. The second one is methane (which becomes CO2) from swamps and possibly clathrate though isotope studies suggest swamps are most important. Accumulation is slow process, release very fast.

47905. BillEverett at 06:28 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Rob Honeycutt@8, "biggest" versus "main" is quibbling. I know "biggest" was used in the title of Ally's lecture. I also know he wasn't addressing the general public at the fall 2009 AGU meeting. But Ш used "main" above because that was the word being used here. My point is the greenhouse gases do serve as a thermostat for the climate in the sense that ordinary people understand in their daily lives, and CO₂ is the main greenhouse gas because it has a very long residency. For example, many cooking recipes begin "Preheat the oven to..." Why? Because there is a noticeable time delay between setting the desired temperature and the oven finally reaching that temperature. Using the term "thermostat" or "main thermostat" for the atmospheric CO₂ concentration would make it easier for non-scientists to grasp the fact that the current increased global temperature DOES NOT correspond to the "setting" on the global thermostat any more than the temperature in your oven one or two minutes after you turn it on corresponds to the setting of its thermostat. Depending on the oven and what temperature you set, it might take ten or twenty minutes or even longer to reach the equilibrium temperature. One estimate of the relaxation time for the earth temperature-CO₂ equilibrium is about 700 years (roughly half the turnover time of the thermohaline circulation).
       
       Kevin@38, "removal of CO₂ from the atmosphere is a worthwhile endeavor because the decline in temp is the same as the incline has been." Yes and no. If we reduced today's 394 ppm to 350 ppm CO₂, then the temperature would continue to increase for several hundred years because we are still far from the equilibrium temperature for 350 ppm. If you look at the graph, 350 ppm is about 15% higher than the highest peak in the last 800 thousand years. Getting the CO₂ down to 300 ppm might stop the temperature increase. Might. Getting it down to 250 ppm would most likely start a slow cooling. So, yes, reducing the CO₂ level would be good. No, it won't cause a temperature decline UNLESS the reduction in CO₂ is sufficiently large.
       
       In summary, greenhouse gases are the thermostat for the temperature of the earth climate. No greenhouse gases, which is impossible for our planet because there would undoubtedly be a small amount of water vapor in the atmosphere, means a snowball earth with little or no life as we know it. Life, as we know it, has a rather narrow range of tolerable temperatures. In the past different natural factors changed the thermostat setting, rapidly in some cases, where rapidly typically means a time scale of a century or millenium, and slowly in other cases, where slowly typically means a time scale of ten or a hundred millenia or even a million years. If you don't like atmospheric CO₂ "controlling" the temperature of the earth's climate, then you are free to think that whatever it is at a given time that changes the setting of the CO₂ thermostat is what is really controlling the the temperature (via the CO₂ concentration). Currently, humans are cranking the thermostat up and up and up. So, you can say, "No, CO₂ is not 'causing' the climate to heat up. People are 'causing' the climate to heat up by putting more CO₂ in the atmosphere."

47906. Composer99 at 05:28 AM on 7 March 2013
       Cherrypicking to Deny Continued Ocean and Global Warming
       

       From the department of redundancy department...

47907. Don9000 at 05:28 AM on 7 March 2013
       Cherrypicking to Deny Continued Ocean and Global Warming
       

       I'm still having fun with Watts' quote: "Sure looks like a pause to me, especially after steep rises in OHC from 1997-2003. Note the highlighted period in yellow:"

       Parsing this brief passage, I note that Watts has used the word "rises" to characterize the already brief 1997 to 2003 period. I suspect he did so because the data shows, if we use his vague concept of "a pause," that from 1999 to 2001 there was a similar "pause." And before 1997 there were arguably similar pauses from 1993 through 1999, as anyone with a yellow highlighter could show a la Figure 1.

       
       Of course, by subdividing a graph that is alreadly a subdivision in a sense (as it excludes the data for deeper water) into shorter cherry-picked segments, Watts is able to hide or obfuscate the larger trend even as he leaves room for faux sceptics to point to short periods of decline or even short periods of lower rates of increase as evidence that a longer duration trend has reversed or paused.

       I wonder if this kind of manipulation is not in some way linked to a kind of intellectual Attention Deficit Disorder where Watts' followers are concerned. Don't we see the same kind of deluded excitement from the Watts crowd every autumn when the Arctic starts to refreeze?

47908. Composer99 at 05:27 AM on 7 March 2013
       Cherrypicking to Deny Continued Ocean and Global Warming
       

       I have the feeling that, if and when we deploy satisfactory instrumentation to measure heat content in the deeper ocean (below 2,000 m) we won't like the results.

       Previous discussion on deep ocean behaviour has been discussed at Skeptical Science here.

47909. Roger D at 05:26 AM on 7 March 2013
       Cherrypicking to Deny Continued Ocean and Global Warming
       

       Well, sure, if you're gonna be such a stickler as to "consider all the available data".

       (nice post - thanks)

47910. Don9000 at 04:48 AM on 7 March 2013
       Cherrypicking to Deny Continued Ocean and Global Warming
       

       It took a few minutes, but I read through the various links. I have to say that Anthony Watts' post is not exactly a model of scientific rigor. I really love that he sums up on his site this post's Figure 3 in this especially rigorous way:

       
       "Sure looks like a pause to me, especially after steep rises in OHC from 1997-2003. Note the highlighted period in yellow:"

       And then Watts shortly goes on to write the following to underline his highly-rigorous scientific claim by quoting that highly regarded genuine faux physicist and bonifide television character "Dr. Sheldon Cooper":

       "As Dr. Sheldon Cooper would say: 'Bazinga!'"

       The delicious irony I find in Watts' choice to use this line from The Big Bang Theory is derived from the fact that it is used in the television comedy when the character has told a joke or pulled off a prank and is letting his friends know they've been played upon. Should anyone wish to fact check me, there is actually a website devoted to the character's use of the term:

       www.sheldonfan.com/origin-sheldon-coopers-bazinga.html

       Ironically, Watts wrongly seems to think "Bazinga!" is used by the character when he has made a valid scientific point.

       
       I'd say Watts has exercised the same telling degree of intellectual rigor in using the bazinga quote as he's used in presenting his graphic with a yellow line (which, ahem, he only used to highlight the region, don't you know).

47911. Doug Bostrom at 04:47 AM on 7 March 2013
       Arctic sea ice has recovered
       

       Yes, quite striking. Far be it from my place to criticize (because I'm way too ignorant) but the pattern of the last handful of years makes me wonder if we're overestimating the volume of ice left in the Arctic ocean. Those excursions just leap out at the eye. 

47912. Rob Honeycutt at 04:44 AM on 7 March 2013
       Cherrypicking to Deny Continued Ocean and Global Warming
       

       What's continually amazing to me is how the (fake) skeptics will give Anthony Watts a pass on such a blantant error, but turn around and scream all day long about nuances of the statistical significance of trends.  

       It just boggles the mind.

47913. BBD at 04:41 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       James Hansen, Makiko Sato, Gary Russell and Pushker Kharecha have a draft paper Climate Sensitivity, Sea Level, and Atmospheric CO2 which contains the following succinct description of the geological carbon cycle and temperature change over the Cenozoic (65Ma - present):
       
       
       Carbon dioxide is involved in climate change throughout the Cenozoic era, both as a climate forcing and as a climate feedback. Long-term Cenozoic temperature trends, the warming up to about 50 Myr BP (before present) and subsequent long-term cooling, must be primarily a result of the changing natural source of atmospheric CO2, which is volcanic emissions that occur mainly at continental margins due to plate tectonics (popularly "continental drift"). This CO2 source grew from 60 to 50 My BP as India subducted carbonate-rich ocean crust while moving through the present Indian Ocean prior to its collision with Asia about 50 Myr BP (Kent and Muttoni, 2008), causing atmospheric CO2 to reach levels of the order of 1000 ppm (parts per million) at 50 Myr BP (Beerling & Royer, 2011). Since then, atmospheric CO2 declined as the Indian and Atlantic Oceans have been major depocenters for carbonate and organic sediments while subduction of carbonate-rich crust has been limited mainly to small regions near Indonesia and Central America (Edmond and Huh, 2003), thus allowing CO2 to decline to levels as low as 170 ppm during recent glacial periods (Petit et al., 1999). Climate forcing due to CO2 change from 1000 ppm to 170 ppm is more than 10 W/m2, which compares with forcings of the order of 1 W/m2 for competing climate forcings during the Cenozoic (Hansen et al., 2008), specifically long-term change of solar irradiance and change of planetary albedo (reflectance) due to the overall minor displacement of continents in that era.

47914. BBD at 04:40 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin @ 38

       Looking at the graphs in fig 1a, I would argue that is not accurate.  If the rise and fall of the temps and CO2 is from the CO2 feedback loops, then why is the fall so different then the rise?  Clearly, there is a different mechanism at play.

       Please see 37. Perhaps slowing down and reading some of the responses and links might be a good idea at this point.
       

47915. 10in10Diet.com at 04:37 AM on 7 March 2013
       Living in Denial in Canada
       

       Thanks, BobLoblaw, for the link to the article about where we Canadians are getting our oil. I've been pretty obsessively watching climate science for ten years and although I walk the walk in my vegetarian lifestyle, I have no illusion that this individual action does anything but make me feel a bit righteous. However, I certainly have had my head in the sand regarding the sources of our fossil fuels. It's a tricky thing to argue. We live in a country where just about all of us live in homes that use at least $1000 a year in fossil fuel or electricity for heating. Vaclav Smil points out that we could make the biggest difference if we stopped eating so much meat and if we stopped burning fossil fuel to generate electricity. He believes we could transition to very efficient motor vehicles over one decade, if that efficiency were legislated. He's all for well-insulated buildings, but it's unimaginable that we could retrofit every one.

47916. Rob Honeycutt at 04:33 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin @ 46...  This is exactly what I'm talking about with regards to the semantics.  You are interpretting this to mean that CO2 has been a forcing over the past 40my.  No one is making that claim.  

       What is being said is that CO2 is the biggest "control knob."  That doesn't mean that CO2 is controling global temperature.  It means that it is the mechanism that causes the biggest amplification on forcing.

47917. BBD at 04:31 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin @ 38

       Looking at the graphs in fig 1a, I would argue that is not accurate.  If the rise and fall of the temps and CO2 is from the CO2 feedback loops, then why is the fall so different then the rise?  Clearly, there is a different mechanism at play.

       Please see 37. Perhaps slowing down and reading some of the responses and links might be a good idea at this point.
       

47918. BBD at 04:27 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin @ 43

       
       It is widely accepted that the gradual reduction in CO2 levels over the ~50Ma since the Eocene Optimum caused a very gradual cooling *within which* many different climate states occurred (Zachos et al. 2008).

       
       This is how CO2 and sea levels can broadly correlate over the last ~40Ma.

        

47919. Kevin8233 at 04:24 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Sorry, but you are just engaging in pedantry as far as I can see.

        

       ( snipped)

       I did not make any claims as to the last 100 years.  This article is talking about the past 40 million, so any discussion about anthropogenic CO2 is off topic.

       Moderator Response: (Rob P) - sloganeering snipped.
47920. Rob Honeycutt at 04:23 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin said... " If temp leads CO2, clearly, CO2 can't be dominate control of temp!"

       This is absolutely wrong.  I think you're getting twisted up in the semantics of the analogies and thus missing the point of the actual published research.

       Think of it as gears.  CO2 is the cog in the system that causes the greatest amplification on a given forcing.  It doesn't matter if there is a delay in the response or not.    

       What we are doing by burning fossil fuels is taking what is normally a CO2 response, and we're turning into a forcing.

47921. Don9000 at 04:13 AM on 7 March 2013
       Arctic sea ice has recovered
       

       

47922. Dikran Marsupial at 04:13 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin, there have been other occasions where CO2 has led temperature changes (e.g. uplift of Appalacians leading to increased chemical weathering, reduction of atmospheric CO2 and cooling temperatures), and there is also the fact that if CO2 is released by anthropogenic emissions then obviously any temperature change will lag emissions.  Sorry, but you are just engaging in pedantry as far as I can see.  Viewing CO2 as a thermostat is misleading as it can also be a forcing, calling it a control knob likewise doesn't tell the whole story as it often acts as a feedback.  This pedantry seems to be aimed at avoiding the key point of the story, which is that our anthropogenic emissions are twisting the control knob on the thermostat, and paleoclimate tells us that there is good reason to expect that to have a significant effect.

47923. Don9000 at 04:10 AM on 7 March 2013
       Arctic sea ice has recovered
       

       The most recent PIOMAS current ice volume anomaly graphic (31 January 2013) suggests to me that the Arctic Ocean is beginning to behave much more like a seasonally frozen lake or pond than a permanently frozen large expanse of ocean that melts around the edges. Note in particular the annual pattern in the graphed data from the 2010 maximum to the end of January, 2013:

        http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAnomalyCurrentV2.png?%3C?php%20echo%20time%28%29%20?

47924. Kevin8233 at 04:02 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Composer99,

       First, I should like to draw your attention to the fact that the graph in figure 1(a) goes backwards in time as you go from left to right. So what you are actually seeing is that CO2 and sea levels are dropping very gradually, with brief interludes and irregularities, and then rise very drastically.

       Thanks, I am used to seeing this the other way around, and did think it looked odd.  But that doesn't counter my points.

       

       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years

       Just pointing out that the title of this article can't be accurate.  As I pointed out, and everybody agrees, CO2 didn't start or end any of the ice ages.  I also pointed out 1 paper for, and yes, someone pointed out one against, temp leading CO2.  If temp leads CO2, clearly, CO2 can't be dominate control of temp!

       Sorry about the multiple points, but they are all so closely related.

       Moderator Response: [RH] Fixed image width.
47925. Rob Honeycutt at 03:33 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin...  Just to be completely clear here, even if CO2 does lag (noting the most recent research suggesting there is no lag), that doesn't in any way cast doubt on the role of CO2 as a greenhouse gases, nor does it cast doubt on the warming effects of man-made CO2 from burning FF's.  It's a complete non-issue with regards to published research.

47926. grindupBaker at 03:31 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       @1.Kevin "..do they just happen to go up and down together, perhaps each caused by something else..". It's known as hard physics that CO2x2 will force back ~3.5Wm-2 (skeptic Lindzen says 3.4). By simple math that power would raise ocean temp. to full depth by 1 C in 147 years with no other factors. Ocean mixing to depth takes ~1,000 years so it will be less than 147 years for top, say, 1000m. So you ask whether something known to be enough to melt massive ice was simply a coincidence in time with some mysterious other thing never seen (that you cannot suggest yourself) that does precisely the same. I'm sure not. What think you ? 

47927. Dikran Marsupial at 03:27 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       BTW Kevin, if you want to get to the bottom of something, the fastest way to do so is to discuss one issue at a time, or ask one question, or make one point.  If you branch off into three or four points in every post it more or less guarantees that many of them won't get answered.  Indeed a common tactic in rehtorical debate is to do just this precisely in order to prevent getting to the bottom of the key issue.  If someone is genuinely interested in scientific truth, a good indication is generally that they will keep to the point and narrow the discussion to ever more focussed questions that identify the key issues.

47928. Dikran Marsupial at 03:21 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin, I don't see any dissconet there with regard to water vapour.  The principal difference is that CO2 is a long-lived GHG, whereas water vapour is a greenhouse gas, but its "adjustment time" in the atmosphere is a matter of days, so it only has a lasting effect on the atmosphere if it is amplifying something else that does (e.g. CO2).

       "What caused the temp to drop?" largely Milankovic cycles, as has already been pointed out.  Orbital cycles are sometimes favourable to initiating a glaciation, sometimes unfavourable.
       

       I would also agree that CO2 in paleoclimate has been mostly a feedback, hence it has been a thermostat, rather than a "control knob", although there have been events where it has initiated warming rather than merely amplifying it (e.g. end of "snowball Earth").
       

       However CO2 as well as being a feedback can also be a forcing (which is what anthropogenic emissions are doing), hence it can also be a "control knob" that we can use to set the thermostat.  However in my opinion, going on about knobs or thermostats is missing the point.  Paleoclimate shows that CO2 has a substantial effect on climate, hence if we double the atmospheric CO2 concentration (or more) we should expect it to have a substantial effect.
       

       The difference in slope between the start of  a glaciation and the end has already been explained by composer99 above.
       

47929. Kevin8233 at 03:08 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Dikran,

       Now before we go onto more advanced issues, please can you explicitly state whether you agree with this, and if you don't agree, please explain why not.

       Yes and no.  Terrible answer, but I'll go on.  I agree with the initiation aspect, although I attribute more than just an initiation here, substantial "forcing" as well.  I even agree, up to a point, with the feedback mechanism.  The main problem I have is this:

       The temp leads the CO2, the CO2 generates more heat trapping, the temp goes up...etc.  Yes, I understand the Boltzman limitations, however, there is still a disconnect.  On another thread here, the feedback loop for watervapor is equal to the temp increase from CO2 - for every temp increase due to CO2, you can expect the same temp increase from watervapor, and maybe some more from the other feedbacks - CO2 climate sensetivity - and since these temps and CO2 concentrations (for the glaciation graphs) are all lower than in the present when this sensetivity relationships were "calculated", they should still all hold up (probably even increase).  None of this yet disputes your scenario. Yet.

       Why does it end?  The CO2 lags the temp.  What caused the temp to drop?  Another timely astronomical event?  It can't be from "diminishing returns" of the CO2 feedback loop, as I stated above, these are all at lower than present values.  Since these ice ages all end, and end with regularity (the same regularity that they start with) there must be some other, regular, forcing component to end them.

       Since there is another component that starts them, and another that ends them, I will gladly point out that CO2 really can't be the big control knob.  Since it really is something else that starts and stops them, it is not too much of a strech to find that this something else also controls or dictates the magnitude of these changes.

        

       Also, on another thread, it is stated that the removal of CO2 from the atmosphere is a worthwhile endeavor because the decline in temp is the same as the incline has been.  Looking at the graphs in fig 1a, I would argue that is not accurate.  If the rise and fall of the temps and CO2 is from the CO2 feedback loops, then why is the fall so different then the rise?  Clearly, there is a different mechanism at play.

47930. BBD at 03:07 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       I'm surprised nobody has so far mentioned Shakun et al. (2012). This study explores the process by which increased summer insolation at high NH latitudes initates deglaciation and entrains powerful positive feedbacks that ultimately result in full glacial termination. There is an excellent article about S12 at RealClimate by Chris Colose (recently spotted in comments upthread) and also here at SkS.

       
       Very briefly, the process works like this:

       - By ~19ka, mid/high latitude NH temperature increase causes sufficient melt from NH ice sheets for freshwater flux to inhibit NADW formation and halt AMOC
       
       - NH *cools* as equatorial -> poleward heat transport stops
       
       - With the NH ‘heat sink’ turned off, the SH *warms*, as it must
       
       - Deep water warming in SH causes release of carbon from ocean sediments. This strongly positive feedback globalises and amplifies the warming
       
       - NH melt resumes, fully engaging strongly positive ice albedo feedback
       
       - Deglaciation accelerates until largely complete by ~11.5ka. Holocene interglacial begins
       
       The supposed lag between GAT and Antarctic CO2 disappears. Along with a pseudo-sceptic 'argument'.
       

47931. Composer99 at 03:02 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin:

       With regards to your inquiries:

       [...] Except for the fact that the glaciation graphs tend to be saw toothed in shape, not sinusoidal.

       1. What causes this regularity? With the built in pauses?

       2. More importantly, what causes the sharp drop off? Both CO2 and sea level drop rather drastically. Apparently, this is natural, as it repeatedly happens again and again. Why won't it happen again?

       First, I should like to draw your attention to the fact that the graph in figure 1(a) goes backwards in time as you go from left to right. So what you are actually seeing is that CO₂ and sea levels are dropping very gradually, with brief interludes and irregularities, and then rise very drastically.

       With that in mind, the answer to your question #1 is that it takes much longer to form the massive North Hemisphere ice sheets than it does to melt them.

       Another factor to consider is that there are several different sets of orbital changes (or wobbles as I have called them upthread) and these have different periodicity, which can accelerate or decelerate climate changes (when these are driven by orbital changes, unlike in the present).

       Your question #2 has already been responded to.

47932. Rob Honeycutt at 03:01 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       LaughinChance @ 30...  It's interesting that your link goes to a website called "Global Warming Hoax."  And then when you click the link to locate the source of the statement, the link is dead.

       Not winning any style points on that one.

47933. Jeffrey Davis at 02:50 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       What is sinusoidal is the game of whack-a-mole on rebunked talking points. 

47934. DSL at 02:45 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       LaughinChance, note Parrenin et al. (2013).  Abstract (my emphasis): 

       "Understanding the role of atmospheric CO2 during past climate changes requires clear knowledge of how it varies in time relative to temperature. Antarctic ice cores preserve highly resolved records of atmospheric CO2 and Antarctic temperature for the past 800,000 years. Here we propose a revised relative age scale for the concentration of atmospheric CO2 and Antarctic temperature for the last deglacial warming, using data from five Antarctic ice cores. We infer the phasing between CO2 concentration and Antarctic temperature at four times when their trends change abruptly. We find no significant asynchrony between them, indicating that Antarctic temperature did not begin to rise hundreds of years before the concentration of atmospheric CO2, as has been suggested by earlier studies."

       So who ya gonna believe?  Al Gore on video?  British court responding to a graph? Flying Spaghetti Monster?  Science?

       Or are you suggesting that CO2 can only be a feedback; when we put it into the atmosphere, it's radiatively inert?

47935. Dikran Marsupial at 02:39 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       laughinchance - a lot of the change in temperature was caused by CO2 and CO2 changes lag temperature changes by 800+ years.  There is no contradiction there, it is just what you would expect if the natural carbon cycle provided positive feedback amplifying the effects of orbital variation.

47936. DSL at 02:31 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Yes, they did.  Now, what does it mean to you?

47937. LaughinChance at 02:26 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Curiously the British Court that defended Al Gore's film found the opposite to be true...

       Among the inaccuracies was this:The film suggests that evidence from ice cores proves that rising CO2 causes temperature increases over 650,000 years. The Court found that the film was misleading: over that period the rises in CO2 lagged behind the temperature rises by 800-2000 years.

       http://www.globalwarminghoax.com/news.php?extend.29 (among numerous citations!)

47938. Rob Honeycutt at 02:25 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       BillEverett said... 'I am unhappy with Ally's calling CO2 simply earth's main control knob."

       Actually, Dr Alley calls CO2 the "Biggest Control Knob."  That would be very different than saying it's the "main" control knob.  

       I have somewhat of an enhanced version of this analogy.  You can maybe think of the whole system as a very complex and sloppy set of gears and pulleys.  A forcing is something like solar variation or orbital changes that are actively turning one or more of the gears, and those gears are in turn driving a broad series of other gears and pulleys.  Each of those turns at different rates and has a net effect on global temp.  CO2 happens to be just one of the cogs in the system that has the largest effect on global temp.  Even when a separate forcing is doing the work, that forcing is pushing the "big knob" (CO2) to have the largest effect.

       The difference today is, we are directly moving that CO2 knob ourselves.  It's still a sloppy system of gears and pulleys, and thus there is some delay in the net effect, as well as uncertainties with what the exact effect will be.  But there is no doubt, based on our understanding of how the system works, that we're fiddling with the big knob.

47939. CBDunkerson at 01:52 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin, yes in the past CO2 levels have naturally gone up to ~280 ppm, dropped down to ~180 ppm, and repeated over and over again.

       You ask, "Why won't it happen again?"

       We're at ~400 ppm CO2 and climbing. Completely outside the bounds of that 'natural cycle'. The natural ~100 ppm CO2 drop from that cycle would normally occur over the course of next few tens of thousands of years... we have already increased CO2 by more than that 100 ppm and are still putting enough in to offset the entire decline every fifty years.

       So, basically... the phase of the Milankovitch cycle which in the past has caused CO2 levels to drop will 'happen again'. It will just be insignificant in comparison to the rate at which we are increasing CO2 levels.

47940. Dikran Marsupial at 01:43 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin, the ice ages are generally understood to be initiated by changes in the Earth's orbit (i.e. Milankovic cycles), which explains the regularity (point 1).  Note very carefully that I said "initiated", rather than "caused".  This is because the changes in insolation caused by the variation in orbit is not sufficient to cause the observed change in the Earths temperature, so we know that there must be some feedback mechanism that amplifies the effect of the Milankovic cycles.

       One of these feedback mechanisms is the carbon cycle.  As the world warms up, the oceans release CO2 into the atmosphere, which is a greenhouse gas, which causes a bit more warming, so a bit more CO2 is released and so on.  Fortunately there are also negative feedbacks (principally the Stefan-Boltzman law), so this process doesn't continue forever.

       Now before we go onto more advanced issues, please can you explicitly state whether you agree with this, and if you don't agree, please explain why not.

47941. CBDunkerson at 01:32 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       I've been looking at sea level rise maps. At 24 meters Bangladesh and the Netherlands essentially cease to exist... along with various island nations, the U.S. state of Delaware, half of Florida, and most of the major cities on the planet. We'd better hope this study is wrong, actual rise is on the low end of the uncertainty range, or the timescale is in the thousands of years, because even a 'several hundred years' timescale for this kind of sea level rise could be economically devastating.

47942. Kevin8233 at 01:28 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       shoymore,

       There are others, and more recent, but it doesn't much matter.

        

       dr2chase,

       all well and good.  Except for the fact that the glaciation graphs tend to be saw toothed in shape, not sinusoidal. 

       1.  What causes this regularity?  With the built in pauses?

       2.  More importantly, what causes the sharp drop off?  Both CO2 and sea level drop rather drastically.  Apparently, this is natural, as it repeatedly happens again and again.  Why won't it happen again? 

47943. dr2chase at 01:05 AM on 7 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       I'll have a shot at explainging this to Kevin.  The climate has two positive feedback mechanisms of (usually, hopefully) limited range -- albedo, and greenhouse gasses.  Shrinking ice sheets increase heat absorption leads to more shrinking ice sheets leads to more heat absorption -- but they cannot shrink past zero.  There appears to be a mechanism where increase GHGs (CO2 and CH4) lead to increased warmth leads to increased GHGs -- perhaps because of reduced solubility in the ocean, perhaps because of methane hydrate releases.

       The initial kick that usually leads to change, either cooling or heating, does not need to be large -- if it is large enough to push either feedback mechanism into action, the feedback takes over, and then the change (ahem) snowballs.  This is why, in the case of the natural warming out of ice ages, you see the CO2 lagging the change -- the initial kick out of equilibrium is not large, and precedes the first increase in CO2.  But that first increase in CO2 leads to more warming -- which precedes the next increase in CO2.  And the next increase leads to more warming, etc.  This is consistent both with (1) the lag you see written about and (2) claims that CO2 is the cause of most of the warming.  You might argue that really this is all about ice caps and albedo, and that would be reasonable, except that we already know that CO2 is a greenhouse gas of no small power (else we would not be here to have this discussion, because the planet would be far colder, even colder than it is during ice ages).

       The reason, now, that we see CO2 rises not lagging temperature increases is because the CO2 increase is both artificial and rapid -- the earth (in particular, the oceans) are slow to warm, and we have also outrun any historically observed feedback effects.  

47944. John Hartz at 00:48 AM on 7 March 2013
       2013 SkS Weekly Digest #9
       

       Doug Hutchenson:

       You can access a profile of Judith Curry at Source Watch by clicking here. 

       I presume that Curry is not included in the SkS Misinformers section because updating that section has not been a particlarly high priority activity for members of the SkS volunteer author team.  I would also note that neither DeSmog Blog nor Real Climate have posted a profile of Curry.  

47945. Physicist-retired at 00:03 AM on 7 March 2013
       China Takes a Leading Role in Solving Climate Change
       

       JoeT,

       Your links provide some meaningful information, and are much appreciated. 

47946. Composer99 at 23:03 PM on 6 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       BillEverett:

       With regards to your point (1), if memory serves (it has been some time since I have watched the video), I do not recall Alley referring to CO₂ as a control knob in his speech (although it is referred to as such in the title of the presentation).

       He does, I am much more certain, note that the combination of volcanic CO₂ emissions and rock weathering of CO₂, taken together, regulate the climate in a manner similar to a thermostat (the word 'thermostat' or some synonym is used).

       Since the term 'control knob' is used prominently in the title of the presentation, your criticism still stands, as far as I can see.

47947. BillEverett at 19:49 PM on 6 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       A few points (in addition to seconding or thirding the Tom Curtis motion@19):

       1. I am unhappy with Ally's calling CO₂ simply earth's main control knob. We encounter lots of control knobs in our everyday lives (or at least we used to in the predominantly analog era): volume control knob, screen brightness control knob, etc. These control knobs work virtually instantaneously. We have had very few control knobs that take significant time to see the effect of turning the knob. The most common examples (perhaps the only examples familiar to most people) is a thermostat: the thermostat for controlling home temperature, the thermostat in the refrigerator, the thermostat for the oven in the kitchen. I wish Ally had originally called CO₂ earth's main thermostat.

       2. In the older Antarctic ice core data, while CO₂ lagged temperature_, CH₄ was leading by more than CO₂ was lagging. With the recent indication that the relative age of the air bubbles and the surrounding ice in the Antarctic core data need adjusting, the CH₄ lead would increase as the CO₂ lag decreases. As is known, CH₄ is converted to CO₂ and H₂O in the atmosphere on the time scale of a decade. Both CH₄ and H₂O are greenhouse gases, but their residence times in the atmosphere are relatively short. The residence time of CO₂ is on the order of a millenium, which is why it is the main greenhouse gas for long-term climate control.
       

       3. The atmospheric CO₂ concentration does not directly control the sea level. Sea level is controlled by the amount of water in the oceans and the temperature of that water (water expands when it warms). When water is stored on land as ice, that water is not running quickly to the sea.. The causal chain is thus: high atmospheric CO₂ results in increased temperature, which means warmer oceans and less land ice (more water ran into the sea), and consequently a higher sea level. On the other hand, low  atmospheric CO₂ results in decreased temperature, which means cooler oceans and more land ice, and consequently a lower sea level.

47948. shoyemore at 18:39 PM on 6 March 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Kevin #12,

       The paper you cite was published in 1999.

       I suggest it has been superseded by these papers published much more recently:

       http://www.nature.com/nature/journal/v484/n7392/full/nature10915.html

       http://www.sciencemag.org/content/339/6123/1060.abstract

       From the second:

        Here we propose a revised relative age scale for the concentration of atmospheric CO₂ and Antarctic temperature for the last deglacial warming, using data from five Antarctic ice cores. We infer the phasing between CO₂ concentration and Antarctic temperature at four times when their trends change abruptly. We find no significant asynchrony between them, indicating that Antarctic temperature did not begin to rise hundreds of years before the concentration of atmospheric CO₂, as has been suggested by earlier studies.

       http://www.nytimes.com/2013/03/01/science/earth/at-ice-age-end-a-smaller-gap-in-warming-and-carbon-dioxide.html?_r=1&

47949. Doug Hutcheson at 18:35 PM on 6 March 2013
       China Takes a Leading Role in Solving Climate Change
       

       China is taking climate change seriously

       That's good to know. May it long continue.

       Is the Australian reduction in carbon emissions from the electricity sector and energy demand legitimately able to be sheeted home to the Carbon Tax, or are there other factors in play? (Good news if it is due to the tax.)

47950. Doug Hutcheson at 18:20 PM on 6 March 2013
       2013 SkS Weekly Digest #9
       

       I was looking for material on Judith Curry, to counter a comment in another forum, but she does not appear on the 'Climate Misinformers' page (unless I have misread). Any reason for her absence from the rouges' gallery?

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