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Kevin C at 08:50 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
Not sure if anyone's answered Kevin's question about what triggers the descent back into a glacial?
Basically the glacial state is the equilibrium for icehouse earth. The Milakovitch peaks concentrate enough of the (almost constant) solar radiation in the latittude band where most of the land ice is which temporarily shifts the equilibrium, and the feedbacks take over to do the rest. Once the Milankovitch peak is over the feedback alone is not sufficient to maintain the interglacial state, causing a gradual descent back into a glacial.
That's also why interglacials tend to be shorter than glacials.
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Rob Honeycutt at 08:48 AM on 7 March 2013Conspiracy Theorists Respond to Evidence They're Conspiracy Theorists With More Conspiracy Theories
Brandon... Isn't that a little like asking what the conspiracy was behind the JFK assassination that conspiracy theorists claims? It's not about the actual conspiracy. They create a story line out of what they perceive to be inconsistencies.
The point is the ideation of conspiracies, which is exactly what McIntyre engaged in. Rather than attempting to look for a logical explanation, or even simply ask Dr Mann any questions, he went off in his own direction connecting dots to form a story line that had no basis in reality. That's what conspiracy theorist do. That is what McIntyre did in this case, as well.
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Brandon Shollenberger at 08:46 AM on 7 March 2013Conspiracy Theorists Respond to Evidence They're Conspiracy Theorists With More Conspiracy Theories
Ah, thanks. Sorry about that!Moderator Response: [RH] No problem. -
Chris Colose at 08:42 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
Since my comment #16, there's still confusion of timescales in the discussion of feedbacks and "control knobs." There's also some misunderstandings of Richard's AGU presentation. He said himself that CO2 does not explain "everything" and he was looking at the broadest view of climate in a geologic perspective, and telling it as a historian. That was his choice for giving a ~60 minute presentation on over 4 billion years of climate history, and I think it was a good choice, but obviously it's not fully inclusive. Rather clearly, CO2 is not the principle driver behind abrupt climate changes, ENSO dynamics, regional climate variability, and it only tells part of the story over glacial-interglacial cycles (a CO2-focused perspective is valuable in the tropics, not so much at higher latitudes where the orbit and cryospheric feedbacks dominate and have a different structure than projected global warming changes).
On geologic timescales, the weathering feedback being discussed (which by the way goes back at least to Walker and Kasting's paper in 1981) has classically been invoked to be important for long-term CO2 evolution. This comes back in discussions of the Ordovician climate, the Neoproterozoic snowball deglaciation, the evolution of climate in the last 60 million years, etc...for a recent discussion of the Cretaceous to Cenozoic problem, see e.g., this paper. This mechanism has also worked its way into the planetary science community as a viable mechanism to expand the limits of the habitable zone in the search for extrasolar life, and could conceivably work on any planet with plate tectonics and liquid water. Keep in mind that this mechanism works on timescales longer than orbital, so you can still get considerable temperature fluctuations on sub-million year timescales, or can have positive carbon cycle feedbacks, operating primarily from the ocean or biosphere (as is evidently the case for the glacial-interglacial problem in the last several million years).
The 'control knob' concept on geologic timescales comes not only from the fact that CO2 is a big player in climate evolution over geologic time, but also because CO2 can interact with the climate through a variety of negative carbon cycle feedbacks (on million year timescales), and positive carbon cycle feedbacks (on glacial-interglacial timescales), and thus inserts its role in climate evolution almost everywhere we can look. It's only on rather short (decadal) timescales that we usually don't need to think about boundary condition changes from CO2. For the timescales in which carbon cycle feedbacks tend to be positive, it's not a 'thermostat' anymore, but still a 'control knob.' And in the case of glacial-interglacial changes, that control knob is very good at communicating the orbitally-paced fluctuations to the equator and globally.
Other mechanisms do not work as a thermostat or control knob because they don't interact with the climate. The sun, for example, changes independently of the climate. Moreover, solar evolution over geologic time is a one-way street, gradually brightening at ~7-8% per billion years. On shorter timescales, the changes are usually too small for a lot of purposes. Volcanic activity displays no to weak dependence on the mean climate state (there might be issues with the ground temperature or ice sheet loading on the crust, but these are probably small). These things are very important for understanding climate evolution on all timescales. Volcanic forcing, for example, is very important for the last millennium and there's still some uncertainty in these forcing reconstructions. But volcanoes don't get up and organize themselves to blow up every year and cause an ice age.
In the Andrew Lacis worldview, the 'control knob' concept revolves moreso around the fact that CO2 is the most important non-condensing greenhouse in Earth's atmosphere, is very long-lived, and is most capable of changing on anthropogenic warming timescales. The CO2 in the atmosphere is required to maintain a significant water vapor greenhouse, and any CO2 modifications in the future (likely to be the most dominant forcing over the next century) will set the stage for any water vapor or cloud responses. Of course, other forcings could offset this tendency, but they tend to either be too small (solar variations), too slow (Milankovitch), or too short-lived (volcanoes, ENSO) to get in the way of making confident projections of late-century climate. In this case, it's the uncertainty in climate response (sensitivity) and emission scenarios that dominate, rather than minor issues in how forcings are specified or what initial conditions you need to deal with (as in the decadal-projection problem). -
Brandon Shollenberger at 08:26 AM on 7 March 2013Conspiracy Theorists Respond to Evidence They're Conspiracy Theorists With More Conspiracy Theories
The proprietor of this blog, John Cook, recently promoted a Facebook post written by Michael Mann via Twitter. The post claimed this post by Steve McIntyre contained talked of conspiracies, saying McIntyre:chose to invent an entire conspiracy theory involving not just me, but multiple scientists, the AGU, IPCC, etc.
John Cook also favorably commented on the post, saying:I find it interesting that Steve McIntyre automatically lunges towards a conspiratorial explanation of events. Stephan Lewandowsky published a paper last year showing a significant association between climate denial and conspiratorial thinking. The response to the research from climate deniers was a host of new conspiracy theories. We document the originators of these conspiracy theories in the paper Recursive fury: Conspiracist ideation in the blogosphere in response to research on conspiracist ideation: Lewandowsky_2013. The chief originator of conspiracy theories? Steve McIntyre.
This associated the paper this post is about with Mann's claims, and that leads to an important question. What conspiracy did McIntyre supposedly allege? As far as I can see, he blames everything in that post on Michael Mann. That cannot possibly be talk of a conspiracy.Do you believe McIntyre's post an example of conspiratorial ideation as Mann claims? If so, what conspiracy did he discuss?Moderator Response: [RH] Fixed link that was breaking page format. -
Rob Honeycutt at 08:10 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
jzk... Except that Lindzen stands virtually alone in such statements regarding glacial-interglacial cycles.
And you also managed to completely dodge my point that the direct radiative effects of CO2 are well accepted. Please read my following post @61 about the properties of CO2.
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jzk at 08:04 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
Rob Honeycutt,
Actually when presented with that very issue, that CO2 is necessary to drive interglacials and glacials, Richard Lindzen said "I don't think there is any case to be made for that." He has further cited Roe's "In Defense of Milankovitch" which states "Thus, the relatively small amplitude of the CO2 radiative forcing and the absence of a lead over dV/dt both suggest that CO2 variations play a relatively weak role in driving changes in global ice volume compared to insolation variations."
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Rob Honeycutt at 08:01 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
jzk... What you also don't seem to yet understand is that it's not the radiative effects of CO2 alone that are what makes CO2 the biggest control knob. The direct radiative forcing of CO2 is not that much greater than Milankovitch cycles (AFAIK). But it's the other properties of CO2 that make it important. The fact that it's a long lived, well-mixed, non-condensing atmospheric gas is what makes it the control knob that it is.
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Rob Honeycutt at 07:56 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
jzk... As has been pointed out in this thread many times now, the most recent research suggests that there may not be a lag. And even if there is a lag, that doesn't in any way disprove the relationship between CO2 levels and global temperature.
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Rob Honeycutt at 07:51 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
BillEverett @52... If I understand Dr Alley's work (specifically his "Biggest Control Knob" lecture), the CO2 rock weathering thermostat idea comes from Dana Royer's work. And then there is also Andrew Lacis' work on the CO2 thermostat that describes the mechanism on shorter time scales.
I'm quibbling over the "main" vs "biggest" exactly because of the semantics issue that Kevin seems to be misunderstanding. The problem seems to arise from how the thermostat changes.
Kevin seems to be saying, if the temp goes up before the thermostat (CO2), then CO2 can't be the thermostat. Where he's getting it wrong is, he's not comprehending the forcing and feedback aspects of the thermostat, and I think that's where quibbling over phrasing becomes important.
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jzk at 07:41 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
scaddenp,
During the last 400,000 years, when temperature levels were highest, CO2 levels were also at their highest (of the cycle so far) and the reusultant forcing from the CO2 was at its highest. Yet, that, very powerful forcing, according to AGW theory, is not enough to overcome the forcing from all else because temperature starts dropping and CO2 levels continue to rise. If CO2 forcing is stronger than everything else, how can that be?
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Rob Honeycutt at 07:28 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
jzk... Actually, the forcing from Milankovitch cycles and the direct radiative effects of atmospheric are very well understood and calculated. Not even the Richard Lindzen's and Roy Spencer's of the world dispute these figures.
I would suggest that if you're not getting a satisfactory answer, then maybe you aren't reading or comprehending the research.
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scaddenp at 07:20 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
jzk. On a global scale milankovich forcing vary solar by 1/m2 but at high latitudes the forcing very much higher. (40 I think??) It easily can force high latitude change to albedo. However, albedo feedback alone is insufficient to create the global change. (Ie what you see is a change in forcing in NH affecting climate in SH where the forcing is the in the opposite way). However, there is no problem explaining the global change when you factor in the changes to GHG that are forced by the milankovich changes eg see Hansen et al 2012 and see how closely albedo + GHG does at reproducing the ice age cycle, assymetry and all. As always, not a bad idea to read the appropriate chapter in IPCC WG1 (chp 6).
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Greg54 at 07:08 AM on 7 March 2013George Will - Still Recycling Classic Climate Change Myths for The Washington Post
Will's column was carried in our newspaper (the Holland, MI Sentinel), and I wrote a letter to the editor in reply before seeing this section of scepticalscience.com : http://www.hollandsentinel.com/opinions/x171156157/LETTER-George-Will-perpetuates-myth-about-science
I wish I had seen the article here beforehand, so that I could have included a link to it. I think it's really important to address the climate change denials that misrepresent science, scientists, and their motivations in even small newspapers every time we see them. There are lots of folks who still get most of their news from such sources, and who are more likely to take a challenge from within their own community more seriously than one that originates from elsewhere.
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shoyemore at 06:47 AM on 7 March 2013Cherrypicking to Deny Continued Ocean and Global Warming
Don9000,
I spent some time today explaining to some deniers that you cannot just cherry-pick a reference value of zero, do a statistical test with your data for a significant difference in your mean value from the reference value (of 0), and then say that the "true" mean value "must be 0" if there is no significant difference.
A perfect example of the "begging the question" fallacy, assuming the result you want to prove as part of your "proof". The "reference value " of 0 has no justification in the data, but these guys were agog at the genius of Anthony Watts, who had given them their heart's desire.
I think my efforts will be in vain, because the main people these deniers want to fool is themselves. And they wll keep going back to the Watts' and McIntyres for re-assurance.
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Don9000 at 06:47 AM on 7 March 2013Cherrypicking to Deny Continued Ocean and Global Warming
Oops. I see I changed Eschenbach into Eschenberg in the second to last paragraph above. Mea culpa.
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Andy Skuce at 06:45 AM on 7 March 2013Carbon 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.
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Don9000 at 06:43 AM on 7 March 2013Cherrypicking 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.
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jzk at 06:41 AM on 7 March 2013Carbon 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.
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scaddenp at 06:38 AM on 7 March 2013Carbon 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.
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BillEverett at 06:28 AM on 7 March 2013Carbon 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." -
Composer99 at 05:28 AM on 7 March 2013Cherrypicking to Deny Continued Ocean and Global Warming
From the department of redundancy department...
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Don9000 at 05:28 AM on 7 March 2013Cherrypicking 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?
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Composer99 at 05:27 AM on 7 March 2013Cherrypicking 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.
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Roger D at 05:26 AM on 7 March 2013Cherrypicking 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)
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Don9000 at 04:48 AM on 7 March 2013Cherrypicking 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). -
Doug Bostrom at 04:47 AM on 7 March 2013Arctic 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.
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Rob Honeycutt at 04:44 AM on 7 March 2013Cherrypicking 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.
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BBD at 04:41 AM on 7 March 2013Carbon 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. -
BBD at 04:40 AM on 7 March 2013Carbon 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.
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10in10Diet.com at 04:37 AM on 7 March 2013Living 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.
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Rob Honeycutt at 04:33 AM on 7 March 2013Carbon 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.
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BBD at 04:31 AM on 7 March 2013Carbon 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.
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BBD at 04:27 AM on 7 March 2013Carbon 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. -
Kevin8233 at 04:24 AM on 7 March 2013Carbon 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. -
Rob Honeycutt at 04:23 AM on 7 March 2013Carbon 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.
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Don9000 at 04:13 AM on 7 March 2013Arctic sea ice has recovered
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Dikran Marsupial at 04:13 AM on 7 March 2013Carbon 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.
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Don9000 at 04:10 AM on 7 March 2013Arctic 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?
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Kevin8233 at 04:02 AM on 7 March 2013Carbon 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. -
Rob Honeycutt at 03:33 AM on 7 March 2013Carbon 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.
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grindupBaker at 03:31 AM on 7 March 2013Carbon 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 ?
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Dikran Marsupial at 03:27 AM on 7 March 2013Carbon 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.
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Dikran Marsupial at 03:21 AM on 7 March 2013Carbon 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.
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Kevin8233 at 03:08 AM on 7 March 2013Carbon 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.
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BBD at 03:07 AM on 7 March 2013Carbon 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'. -
Composer99 at 03:02 AM on 7 March 2013Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
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.
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Rob Honeycutt at 03:01 AM on 7 March 2013Carbon 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.
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Jeffrey Davis at 02:50 AM on 7 March 2013Carbon 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.
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DSL at 02:45 AM on 7 March 2013Carbon 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?
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