Another paper for the Copenhagen train. This is an estimate according to the abstract. Here’s the abstract and the supplemental information, of course the publicly funded paper is behind the AAAS paywall.
From UCLA News: Last time carbon dioxide levels were this high: 15 million years ago, scientists report
By Stuart Wolpert October 08, 2009 Category: Research
You would have to go back at least 15 million years to find carbon dioxide levels on Earth as high as they are today, a UCLA scientist and colleagues report Oct. 8 in the online edition of the journal Science.
“The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,” said the paper’s lead author, Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences.
“Carbon dioxide is a potent greenhouse gas, and geological observations that we now have for the last 20 million years lend strong support to the idea that carbon dioxide is an important agent for driving climate change throughout Earth’s history,” she said.
By analyzing the chemistry of bubbles of ancient air trapped in Antarctic ice, scientists have been able to determine the composition of Earth’s atmosphere going back as far as 800,000 years, and they have developed a good understanding of how carbon dioxide levels have varied in the atmosphere since that time. But there has been little agreement before this study on how to reconstruct carbon dioxide levels prior to 800,000 years ago.
Tripati, before joining UCLA’s faculty, was part of a research team at England’s University of Cambridge that developed a new technique to assess carbon dioxide levels in the much more distant past — by studying the ratio of the chemical element boron to calcium in the shells of ancient single-celled marine algae. Tripati has now used this method to determine the amount of carbon dioxide in Earth’s atmosphere as far back as 20 million years ago.
Aradhna Tripati
“We are able, for the first time, to accurately reproduce the ice-core record for the last 800,000 years — the record of atmospheric C02 based on measurements of carbon dioxide in gas bubbles in ice,” Tripati said. “This suggests that the technique we are using is valid.
“We then applied this technique to study the history of carbon dioxide from 800,000 years ago to 20 million years ago,” she said. “We report evidence for a very close coupling between carbon dioxide levels and climate. When there is evidence for the growth of a large ice sheet on Antarctica or on Greenland or the growth of sea ice in the Arctic Ocean, we see evidence for a dramatic change in carbon dioxide levels over the last 20 million years.
“A slightly shocking finding,” Tripati said, “is that the only time in the last 20 million years that we find evidence for carbon dioxide levels similar to the modern level of 387 parts per million was 15 to 20 million years ago, when the planet was dramatically different.”
Levels of carbon dioxide have varied only between 180 and 300 parts per million over the last 800,000 years — until recent decades, said Tripati, who is also a member of UCLA’s Institute of Geophysics and Planetary Physics. It has been known that modern-day levels of carbon dioxide are unprecedented over the last 800,000 years, but the finding that modern levels have not been reached in the last 15 million years is new.
Prior to the Industrial Revolution of the late 19th and early 20th centuries, the carbon dioxide level was about 280 parts per million, Tripati said. That figure had changed very little over the previous 1,000 years. But since the Industrial Revolution, the carbon dioxide level has been rising and is likely to soar unless action is taken to reverse the trend, Tripati said.
“During the Middle Miocene (the time period approximately 14 to 20 million years ago), carbon dioxide levels were sustained at about 400 parts per million, which is about where we are today,” Tripati said. “Globally, temperatures were 5 to 10 degrees Fahrenheit warmer, a huge amount.”
Tripati’s new chemical technique has an average uncertainty rate of only 14 parts per million.
“We can now have confidence in making statements about how carbon dioxide has varied throughout history,” Tripati said.
In the last 20 million years, key features of the climate record include the sudden appearance of ice on Antarctica about 14 million years ago and a rise in sea level of approximately 75 to 120 feet.
“We have shown that this dramatic rise in sea level is associated with an increase in carbon dioxide levels of about 100 parts per million, a huge change,” Tripati said. “This record is the first evidence that carbon dioxide may be linked with environmental changes, such as changes in the terrestrial ecosystem, distribution of ice, sea level and monsoon intensity.”
Today, the Arctic Ocean is covered with frozen ice all year long, an ice cap that has been there for about 14 million years.
“Prior to that, there was no permanent sea ice cap in the Arctic,” Tripati said.
Some projections show carbon dioxide levels rising as high as 600 or even 900 parts per million in the next century if no action is taken to reduce carbon dioxide, Tripati said. Such levels may have been reached on Earth 50 million years ago or earlier, said Tripati, who is working to push her data back much farther than 20 million years and to study the last 20 million years in detail.
More than 50 million years ago, there were no ice sheets on Earth, and there were expanded deserts in the subtropics, Tripati noted. The planet was radically different.
Co-authors on the Science paper are Christopher Roberts, a Ph.D. student in the department of Earth sciences at the University of Cambridge, and Robert Eagle, a postdoctoral scholar in the division of geological and planetary sciences at the California Institute of Technology.
The research was funded by UCLA’s Division of Physical Sciences and the United Kingdom’s National Environmental Research Council.
Tripati’s research focuses on the development and application of chemical tools to study climate change throughout history. She studies the evolution of climate and seawater chemistry through time.
“I’m interested in understanding how the carbon cycle and climate have been coupled, and why they have been coupled, over a range of time-scales, from hundreds of years to tens of millions of years,” Tripati said.
In addition to being published on the Science Express website, the paper will be published in the print edition of Science at a later date.
UPDATE: Bill Illis add this graph in comments, which brings up the obvious correlation questions.
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Bill Illis (06:04:54),
Excellent post. I would like to see any CO2=AGW true believer *cough*joelshore*cough* step up to the plate and explain that one for us.
Isn’t climate science wonderful! We can now measure the amount of CO2 (a mixture of carboon and oxygen) in the atmosphere by measuring the ratio of two different elements (boron and calcium) in the shells of long extinct single cell marine animals which lived in the oceans and possibly never emerged into the atmosphere.
Are there just too many assumptions in the chain?
LOL: J.Hansford (23:52:23) :
It’s getting that the Hockey stick shape is becoming a religious symbol to the Warminists
Undoubtely a phallic symbol, as you indirectly suggest.
cba:
(1) Is Venus quite different than Earth? Yes, of course, particularly in the situation it is now where a runaway greenhouse effect has already occurred and the atmospheric composition is now likely very different than it once was. (Including any water that may have been there having boiled away.) Nonetheless, Venus is a “poster child” for the greenhouse effect taken to the extreme. Such a situation is unlikely to be in the cards for Earth (at least not for billions of years)…but that doesn’t mean that we shouldn’t be concerned with what strengthening of the greenhouse effect we are causing.
(2) The percentages that you quote for the amount of the natural greenhouse effect (of 33 C) that is due to CO2 only are in the ballpark of what I have seen. However, the natural greenhouse effect is quite large…and, furthermore, these statements assume that changes in CO2 that occur do not lead to other changes…most notably changes in water vapor. In actuality, the rise in CO2 leads to warming that causes an increase in water vapor concentration which causes more warming, amplifying the radiative effect of the CO2 alone.
(3) I agree with you about the doublings although, as a nitpick, I think the accepted value for the radiative forcing due to a doubling is closer to 4 W/m^2 than 3 W/m^2. (The lowest value that I have seen, mentioned by Lindzen I believe, was like 3.7 W/m^2.) Also, this is a value averaged over the whole planet, not a clear skies value.
Okay, well actually if all of this information is accurate, then 1) it shows that there is NO correlation between CO2 and temperature. 2) it raises questions as to how CO2 will effect the biosphere now. I think rather then trying to scare everyone with CO2 caused warming scientists would have a much better role to play in searching for how CO2 effects the biosphere as in plants and animals.
One interesting question that I never see asked is just how much additional plant life would be needed to consume the CO2 that is being added to the atmosphere each year. How much is 1 part per million in real terms anyway… the atmosphere is a big place…
More then anything I am just curios now… I would love to sit and play with things like this
Joel Shore:
“most notably changes in water vapor. In actuality, the rise in CO2 leads to warming that causes an increase in water vapor concentration which causes more warming, amplifying the radiative effect of the CO2 alone.”
Yet, many scientists would disagree, including Lindzen, Spencer, Christy and Eschenbach. This naive extrapolation of the Clausius-Clapeyron equation is fundamental to the climate model forecasts of runaway warming, yet the resulting behaviour of clouds and convection as a function of this hypothesised warming is ignored completely.
If the climate behaves in this way, then why should this feedback only kick in from levels of CO2 that humans have caused rather than previously?
Joel Shore:
“And, in both [evolution and AGW] cases, we see the same pattern: namely a dramatic divergence of views between the scientific community in the field and recognized scientific authorities (like NAS and AAAS) vs “skeptics” of the theory, with the scientific authorities finding the evidence quite compelling while those dead-set against it do not. ”
Nonsense. There are no scientific positions taken against evolution. And for good reason – we have fossil evidence of a myriad of intermediate species, ordered sequentially in time showing a clear picture of how each form leads to the next and the next; we know how mutations in genes acting through environmental pressure favours the success of the most suitable phenotypes. But you know all that anyway.
Moreover, in order to dismiss evolution you would have to come up with an alternative explanation. Either a) all species were created by the Diety in the forms that have been layed down in the fossil record or b) . . . erhm, there is no explanation b). There is not. If you doubt this, try and think of any alternative explanation. Consequently, some form of evolution (gradual change or punctuated equilibrium) is the only theory that does not involve divine intervention.
Now we come to AGW. Can we think of any alternative explanation? Well, how about natural variation? Not only is this the alternative commensurate with natural law, but it fits with our understanding of an ever changing climate. Unless you believe in hockey sticks, that is.
It doesn’t look like today’s CO2 measurements are the highest in the last 200 years. Apperently, the IPCC, Keeling and others decided to throw out a lot of data to construct the CO2 levels in the 1800s but I find it hard to believe that all of these people were always wrong. And why would the chemical method be less reliable than ice core samples – doesn’t make sense either.
http://www.anenglishmanscastle.com/180_years_accurate_Co2_Chemical_Methods.pdf
Vincent says:
Actually, I don’t think that many scientists still disagree about the effect of water vapor itself…although certainly clouds remain a source of uncertainty. And, clouds and convection are not ignored in the climate models, although as I said, there is a fair bit of uncertainty in regards to clouds. Nonetheless, in all the different climate models produced by all the different groups with all the different parametrizations of clouds, there has not been any that have managed to come up with a significant negative feedback involving clouds.
They have. That’s the point. The sensitivity of the climate to past changes (such as the changes in forcings between the last interglacial and now) is what helps provide an estimate of the climate sensitivity…and supports the idea that the range that is seen in climate models is also the range that appears to operate in the real climate system.
Whenever I see one of these “highest in the last N years” articles, I find myself wondering, “OK, so what were things like before that N years ago cut-off” because usually that’s where one find the embarrassing data that disproves the point being made. The CO2 concentrations during the Carboniferous are estimated to have a mean 800ppm and were up at 1500 ppm during the Early Carboniferous. While one might be right to point out that we wouldn’t really want a Carboniferous climate today, I find myself asking whether there is any evidence that, for example, the oceans became so acidic that they destroyed the shells of sea creatures or evidence of any of the other doomsday scenarios currently being thrown around.
John says:
It is not primarily the CO2 levels that matter as the rapidity of the rise. CaCO3 from limestone rocks acts to neutralize the oceans but it is a slow process relative to the rate at which we are increasing CO2 in the oceans. There is one possible past analog to the current situation, which is the PETM event that occurred about 55 million years ago when there was a large release of greenhouse gases and significant warming (although I don’t think they have good enough time resolution to say how rapid the greenhouse gas increase was relative to today). And, I believe that there were a lot of extinctions and changes in sea life around that time. I’m not really up on the literature for that event but there are a lot of papers about it over the last several years because of the analogy to our current “experiment”.
Joel Shore:
“Are you seriously telling me that you haven’t heard of Science? It and Nature are probably the two most prestigious interdisciplinary science journals in the world! Many scientists would probably sacrifice their first-born child to get a paper in there.”
You are probably right about that. That is why I first started to seriously doubt AGW when I found three factual howlers in a pro-AGW paper in Nature.
That’s the dichotomy.
If ice core-derived paleo-CO2 values are quantitatively correct – CO2 and temperature have only correlated for about 30 years out of the last 600 million years in a manner supportive of the AGW position.
If fossil plant stomata-derived paleo-CO2 values are quantitatively correct – A century-scale rise from 280ppmv to 380ppmv CO2 is wholly unremarkable and has been the norm in every warming period since the early Holocene; including the MWP, Roman Warming and Holocene Thermal Maximum.
So… Either CO2 didn’t cause the late 20th century warming; or the late 20th century rise in atmospheric CO2 levels was mostly caused by the late 20th century warming.
The fact that delta-CO2 lagged behind delta-T in the Pleistocene ice cores and that fossil plant stomata data suggest that Holocene CO2 levels have always risen to the mid to high 300’s ppmv… Coupled with the total non-correlation of temperature and CO2 throughout most of the Phanerozoic tells this geoscientist that the IPCC are barking up the wrong tree.
Joel Shore:
“I don’t think they have good enough time resolution to say how rapid the greenhouse gas increase was relative to today”
It is good enough to show that temperatures started rising a few thousand years before CO2 (as usual):
http://igitur-archive.library.uu.nl/dissertations/2006-0906-200913/full.pdf
(chapter 7 in particular)
obviously joel, you were not paying attention to my post. The fact that Venus has an extremely long day precludes any reasonable similarity with Earth.
There has been no evidence to suggest that Venus had any significant water in the past as that would have undoubtedly helped reduce CO2 via inorganic processes. Since there is virtually no signficant power coming in to the surface from the Sun, there is no “greenhouse” effect present. The surface is just not being heated by large amounts incoming solar radiation there. Note that the actual greenhouse effect is really the blocking of convection rather than the radiative blocking of some fraction of IR.
As for CO2 doubling effects being closer to 3 or to 4 W/m^2 , it totally depends upon what altitude you desire to select for the comparison point. It also depends upon whether you take into account only absorption or whether you consider absorption and emission.
“…unlikely to be in the cards…” That’s a good laugh. At the Earth’s surface, there’s about 10 metric tons of atmosphere above you in every square meter column of atmosphere. To have the same amount of CO2 in our atmosphere as that of Venus would require the addition of over 90 metric tons of CO2 in every square meter atmospheric column over the surface of the Earth. Atmospheric pressure would have to become around 93 bar at the surface. It still would not be very close to the same thing as we’d need to more than triple the atmospheric nitrogen amount as well.
And more warmth leads to more water vapor cycle which leads to more convective heat transfer and leads to more cloud cover and greater albedo – reducing the incoming radiation reaching the surface . So What! Feel free to presume for no reason that we just happen to live with the one CO2 doubling range where by the effects are super amplified by h2o so the results are far greater than any additional CO2 doublings or any prior doublings. Just remember – as mentioned – there’s about 11 CO2 doublings (actually halvings) that one could have with similar consequences for power absorption AND the net results of all of these – plus all other effects of GHG gases amounts to a total of around 33 Kelvins rise. Essentially, all of this is due to h2o vapor with CO2 contributing a total of around 10% so it averages around 0.3 Kelvins per doubling for CO2 only. Considering that H2O is going to exist in the atmosphere regardless of the presence of any CO2 or minor variation in T, you now have the limitations of just how much of that positive feedback you want to claim for this rather unique CO2 concentration that is so much more sensitive LOL.
You cannot quantify CO2 averaged between clear sky and clouds. Clouds can essentially block IR totally – that means there is no CO2 blocking effect difference. What does it matter that CO2 would block 3.7 W/m^2 when you have practically 100% blocking due to cloud cover?
This of course brings up another major falacy. That is the presumption that this is a radiative only environment with a unique temperature required for radiative balance. If you consider a new variable, cloud cover fraction (for now a single number of some nonexistant typical average cloud) that can vary between 0 % and 100 %. If you plot incoming solar power versus outgoing IR, you will find that the intersection of those curves defines this balance point. I will not go into the details here of the details concerning how but suffice to say clear sky incoming solar is far greater than totally overcast sky incoming solar – as is outgoing IR. What it means though is that one can change the cloud cover and achieve radiative balance without changing the temperature even though there is a change in atmospheric absorption. IE, there’s not a unique temperature required which must rise if there’s an increase in CO2 absorption gases in the atmosphere.
BTW, another little tidbit concerns the fact that a small rise in ghg absorption also tends to cause a reduction in atmospheric layer temperatures in order to maintain energy balance due to the geometry of the system. Greater absorption causes greater emission for a given wavelength at a given temperature.
Vincent (11:24:50)
go to:
http://wattsupwiththat.com/2009/10/04/a-borehole-in-antarctica-produces-evidence-of-sudden-warming/
P Wilson (17:25:56)
for an explanation.
I can crunch some further mathematics if need be
william (18:17:38) :
Ah. So you work in the steel industry? I have heard nothing from you about shutting that hugely CO2 polluting industry down.
According to your lights the industry you work in is destroying the planet. Have you no shame?
Honor dies where interest lies?
tty says:
Actually, that is not exactly what that paper claims. What they claim to show is that the rise in C-13 depleted carbon happened after the warming. As they note, a rise in CO2 from a pool of carbon having the same isotopic composition as the carbon in the atmosphere (such as from the oceans) could have occurred earlier.
Vincent:
Well, there are plenty of people out there who are claiming there is no empirical evidence for evolution. And, there are indeed scientists (including Roy Spencer) who don’t believe in it. Of course, neither you nor I think they are correct but that doesn’t stop them from making these arguments. And, that is exactly my point. One cannot judge the state of the science by whether there are people vocally claiming that there is not the empirical evidence and so on and so forth.
That is why the scientific enterprise has evolved the way it has (pun sort of intended), with peer-review and bodies of scientists themselves set up to evaluate the current state of the science.
And, by the way, I am not claiming that the exact quantitative amount of uncertainty exists in evolutionary theory and in AGW. I agree that there are at this point larger uncertainties regarding climate sensitivity than would be true for analogous issues in evolutionary theory.
But, the basic point remains that the correct way for the science to be judged, including what uncertainties exist and how great they are, is within the scientific process itself and that lots of people screaming from the sidelines that “empirical evidence doesn’t exist” or what-have-you is more a measure of how the science interferes with their belief system than a measure of where the science actually is.
cba says:
According to this http://en.wikipedia.org/wiki/Runaway_greenhouse_effect it is simply not known whether or not Venus had significant water in the past or not.
I guess I don’t understand your logic here. I don’t see how your argument that very little of the solar energy makes it to the surface means there is no greenhouse effect present. Something has to be keeping the surface at a highly elevated temperature relative to the radiative temperature that would produce the emission to balance the incoming solar radiation.
I guess my point is that the 3.7 W/m^2 number is the global mean radiative forcing, which I believe already includes the effect of clouds. Also, the statement about blocking due to cloud cover is, I believe, a confusion regarding how the greenhouse effect works. What matters at the end of the day is the increase in CO2 causing an increase in the effective radiating level. That is, it is not just a matter of whether the IR gets out without being absorbed or not but rather at what level the last absorption and subsequent emission of radiation occur for those IR photons that then escape into space. So, if you have low clouds then they don’t really have much impact as they are below the effective radiating level. High clouds above the radiating level can have more impact. In fact, this is the reason why low clouds tend to cause a net cooling (higher albedo and less effect on outgoing IR) whereas high clouds tend to cause a net warming (lower albedo and more effect on outgoing IR).
I may be missing your point but this logic seems sort of circular to me. If you assume that H2O is a minor feedback, then, yes, that limits how much of the current greenhouse effect could be due to CO2. However, if you assume that H2O is a significant feedback then a very large fraction of the greenhouse effect can be due to CO2 combined with the feedback on H2O. I.e., it could be that as you draw down CO2, H2O is drawn down enough that most of the greenhouse effect disappears…and, of course, the albedo effects change too. Clouds change but, probably more importantly, there is a lot more ice and hence significantly more reflection of solar radiation. This means that, in fact, a planet with all the CO2 removed and most of the water vapor locked out of the atmosphere could be considerably more than 33 C colder because it could be essentially a “snowball earth” scenario with a large albedo. (I am not sure how large the albedo could realistically get.)
Also, do you have a reference for your statement of how many halvings one can do before you are out of the logarithmic regime? I would think the issue would become more complex as one gets away from the actual current climate as it would depend on the concentration of the other gases…especially water vapor (and clouds)…in the atmosphere.
Finally, I agree with you in principle that a change in cloud fraction (or other cloud properties) is an important feedback that can impact what the final climate sensitivity is. No doubt about it. However, because clouds have a mixture of effects (both warming and cooling as described above), the effect of a change in clouds is not as dramatic as it would be if there didn’t tend to be partially canceling effects.
At any rate, I think the empirical evidence regarding climate sensitivity as determined, e.g., by looking at the paleoclimate record (particularly the last glacial maximum vs now) and the eruption of Mt Pinatubo do not favor a significant negative cloud feedback.
And, of course, all of the current climate models with all their different pedigrees and cloud parametrizations all seem unable to produce a significant negative cloud feedback. Admittedly, it could be possible that they all suffer from some similar fundamental misconception, but the fact that nobody has been able to come up with a significant negative feedback and still presumably have a reasonable climatology and explain the various paleoclimate events and response to Mt Pinatubo seems to argue against this.
However, I do agree that understanding the cloud feedbacks and the resulting climate sensitivity is the most fundamental question in the basic science. And, frankly, I think that the “skeptic” movement would do better for themselves, at least scientifically, if they focused on this issue rather than arguing about really nutty things like whether the current rise in CO2 is due to humans, whether basic radiative physics equations like the Stefan Boltzmann Equation are correct, and whether or not the atmospheric greenhouse effects violates the 2nd Law of Thermodynamics. These other issues may be good to focus on if the goal is just to confuse the public but if the goal is actually to convince the scientific community then I think it would be wise to focus on real scientific issues rather than manufactured ones.
I’m sorry but this post from Bill Illis is worth re-posting again….and again….and again.
Pay attention especially to the last paragraph:
Bill Illis (06:04:54) :
The important aspect about using the paleoclimate data is that there is no “lagged warming” explanation available for the Hansen’s of the world.
The lags in the climate system can only be as long as 1,500 to 3,000 years as a maximum.
The paleo data extends beyond those lags so when you see CO2 staying at 250 ppm for 10 million years, then one can be sure that other things are impacting the climate beyond CO2/GHGs and these other factors must, in fact, be far more important.
If CO2/GHGs were as dominant as the theory says, then the last 20 million years should have been one big long ice age. Maybe not as big as the last glacial maximum but the glaciers should have extended into the mainland of North America for the entire period. Well, they didn’t and, in fact, it was much warmer than today in the period.
I’m assuming the cognitive dissonance of actually looking at the data and seeing that it does not match up with the theory, means they just don’t look at it anymore (or believe it). Which means they are constantly trying to find ways to adjust it. This is another one of those.
Irrefutable, incontrovertible words.
Chris
Norfolk, VA, USA
Joel Shore:
“Well, there are plenty of people out there who are claiming there is no empirical evidence for evolution. And, there are indeed scientists (including Roy Spencer) who don’t believe in it.”
That such people exist is irrelevant to my rebuttal. You are trying to equate the climate change skepticism with creationism by drawing attention to a single commonality – that both claim a lack of empirical evidence for the theory they are attacking – while ignoring the important differences. It matters not what theological beliefs Dr. Spencer holds re evolution, because he has not written a paper that attempts to refute it, and if he had written such a paper it should stand and fall on its own merit.
When individuals attempt to refute evolution they do so to support a single agenda – to retain belief in the literal Biblical story of creation. As I have previously posted, the ONLY alternative to evolution is creationism, which is totally different to the AGW hypothesis. There we see a whole spectrum of alternative views ranging from extreme positive feedbacks, milder feedbacks, no feedbacks and negative feedbacks.
As far as creationists claiming that there is no empirical evidence for evolution, they always concentrate on one area – the fossil record – and try to infer that no intermediate forms exist such as would definitively show one species evolving into another. The fallacy of this logic involves division ad infinitum, such that however many intermediate forms are unearthed, you can always ask for a smaller and smaller subdivision. And by focussing on this, they deliberately ignore knowledge of molecular biology with provides the theoretical framework that predicts how evolution will happen. All these predictions are borne out, as for example, that speciation will occur under geographic isolation. There have been some modern confirmations of the theory that explain how some birds develop enormously oversized display feathers which would appear to impose a burden rather than a benefit. It turns out that if you factor in sexual preference for these feathers by females, and then run the genetic models, you get exactly these phenotypes as predicted by evolution.
To compare the richness of evolution with the paucity of AGW is to insult everyone from Darwin, Huxley, Gould, Dennet, Dawkin’s, thousands of field scientists ect, who together, have painstakingly gathered evidence and woven together a beautiful theory.
Reply: Ok, I know I am the number one enforcer of no evolution/creationism/ID posts, but this one makes a comparison that goes beyond debating evolution so I am allowing it. HOWEVER, no more on the subject in this thread or any debate of the merits of evolution or creationism in any other thread. ~ charles the admittedly inconsistent moderator
Joel Shore:
“Nonetheless, in all the different climate models produced by all the different groups with all the different parametrizations of clouds, there has not been any that have managed to come up with a significant negative feedback involving clouds.”
You are confusing climate models with empirical evidence. If you had written that scientists had examined dozens of earth-like planets and not found any significant negative feedback involving clouds, then this would be empirical evidence in favour of positive feedback. But to say what you have just said, is in fact to say something like “of all the different ways that modellers program cloud behaviour in their models, none of them involve negative feedback.”
Do you see the difference?
“Joel Shore
According to this http://en.wikipedia.org/wiki/Runaway_greenhouse_effect it is simply not known whether or not Venus had significant water in the past or not.
”
As I stated – no evidence to support…
“I guess I don’t understand your logic here. I don’t see how your argument that very little of the solar energy makes it to the surface means there is no greenhouse effect present…”
Evidently, look at the supposed concept called the greenhouse effect – SW in, LW blocked… Only a fraction of incoming solar power gets in. It’s not night time but it’s not bright daylight there on the surface. What’s more, you’ve simply have to remember that the temperature is twice that of Earth, crudely speaking and that the peak emission wavelength has shifted according to Wein’s law which means that the effects are a bit different. You should also keep in mind that daytime there is a season, not half a day. Considering that this is not causing massive atmospheric turbulence since there is little mixing going on compared with Earth’s atmosphere, it is not putting much energy into that eerie twighlight that exists.
“I guess my point is that the 3.7 W/m^2 number is the global mean radiative forcing, which I believe already includes the effect of clouds.”
As stated, it is a calculation based upon radiative transfer information through clear skies. Given an atmospheric column such as is typical in concentrations, pressures, temperatures, then at a certain altitude, such as 22km or 45km or ???? there will be 3.7 or 3.5 or …. less power making it past that level when CO2 has been doubled in a clear sky.
Your comment on clouds there means that the radiation is blocked from the surface. When dealing with radiation, you get a blackbody curve only from solid/liquid materials. For gas, you get the molecular spectra. Perhaps you’re trying to say that given more ghgs, the atmosphere above the clouds will radiate more not less??
outa time – will try to continue later today
Joel Shore:
“Actually, that is not exactly what that paper claims. What they claim to show is that the rise in C-13 depleted carbon happened after the warming. As they note, a rise in CO2 from a pool of carbon having the same isotopic composition as the carbon in the atmosphere (such as from the oceans) could have occurred earlier.”
Exactly, and this rules out *all* CO2-based mechanisms that have been suggested for the PETM:
– Methane outgassing
– World-wide peat fires
– Volcanic CH4/CO2 production from coal beds
– Oxidation of recently uplifted marine deposits
– Cometary impact
All of these would show up strongly in the C-13 ratio.
As you say, CO2 dissolved in ocean water would not affect the isotope ratio, however this requires “something” to warm the oceans enough to liberate large amounts of CO2.
So, as I said before, the warming comes first, the CO2 later, AS USUAL.