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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I think it’s important to note that even though I vigorously disagree with the science and economics behind Kyoto, Cap & Trade and “80 by 50″… I don’t object to reasonable efforts to reduce CO2 emissions and increasing the economic efficiency of our energy use.
You can’t create more wealth without more work… And you really can’t do more work with less energy. We can do a lot to squeeze more wealth out of every barrel of oil, MCF of gas, and ton of coal that we burn… But gov’t can’t just arbitrarily and wantonly decide that we will drastically reduce our fossil fuel consumption over the next 40 years without destroying wealth on a scale not seen since the fall of Rome.
A significant reduction in the growth of anthropogenic CO2 emissions is very easily achievable…
– Require new coal-fired plants to sequester carbon emissions.
– Create tax incentives to replace old coal-fired plants with natural-gas fired plants. The US generates ~60% of its electricity from coal – Natural gas yields half as much CO2 as coal does. The most idiotic thing about Waxman-Markey is that the manner in which the carbon credits will be doled out will actually increase our use of coal relative to natural gas.
– Encourage the use of nuclear power… Particularly fast breeder reactors.
– Create tax incentives for solar, wind, geothermal and all of the other “utility infielders” of energy sources. But, don’t try to delude the public into thinking that the utility infielders are all Alex Rodriguez.
– Open up the 60% of US sedimentary basins that are currently off limits to oil and gas exploration… Particularly the 85% of the US Outer Continental Shelf that is currently off limits.
In the interest of full disclosure: I make my living finding oil and gas. So, I do have a vested interest in this area… But, just about everything I know about the relationship between CO2 and climate change was learned in the late 1970’s, when I was getting my BS in Earth Science at Southern Connecticut State (“That fine oil school,” as the President of my first employer called it).
Now back to CO2 proxies…
Both the ice core and plant stomatal index data have advantages and disadvantages.
Ice cores yield long-term continuous time series of data. The process is intuitively easy to understand. But, the Firn Densification Model that has to be used to “age” the gas in the bubbles is, in my opinion, problematic. The firn densification process is also problematic, because it is almost certainly subject to a great deal of mixing of older with newer gas. That’s probably why it only appears to capture a long-term moving average of atmospheric CO2. This plot of the Wood For Trees Temperature Index compares the WFT-TI to the 3rd Harmonic Low Pass Filter of the WFT-TI. It’s quite possible that the SI data are showing us the higher frequency component and the ice core data are showing us the equivalent of the low pass filtered component.
Plant SI data have one very big advantage over ice core data: They can be empirically tested under laboratory conditions to see how SI relates to CO2 changes. We can’t empirically test ice core data to see how the gas bubbles react to hundreds of thousands of years of burial under thousands of feet of ice. The disadvantages to the SI data are that each species has to be calibrated differently. If there are no modern equivalents of the fossil species, the method loses reliability. Some species also seem to have CO2 “ceilings”… Beyond that ceiling, the stomatal density will cease to decline with higher concentrations of CO2. The SI data may also be more subject to local conditions and the ice core data might be a better indicator of CO2 levels free from surface effects.
The scientifically prudent thing to do is to treat both methods as valuable tools… Rather than simply relying on the ice core data to say that atmospheric CO2 levels were a steady 280ppmv prior to capitalism causing them to rise to current unprecedented levels; and then using the SI data to say that pre-industrial warming was also driven by CO2.
An objective use of both tools, tells us that modern CO2 levels are not anomalous when compared to the Holocene or the Roman Warming and that the pre-industrial relationship between CO2 and temperature was one in which temperature changes caused changes in atmospheric CO2 levels.
The atmospheric dynamics are clearly dominated by negative feedbacks .
The dominance of negative feedbacks in natural laws has been known and established for more than 100 years .
Le Chatelier principle says :
.
“If a chemical system at equilibrium experiences a change in concentration, temperature, volume, or partial pressure, then the equilibrium shifts to counter-act the imposed change.”
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While the atmospheric dynamics can’t be strictly reduced to a chemical system only , the natural laws of physics don’t admit divergences which would be arguably a result of any positive feedback .
Despite a wide range of orbital variations , solar radiation variation and atmospheric composition variations (f.ex the early atmosphere contained large amounts of CH4 , NH3 , CO2 and H20 all of them IR active some violently like CH4) , the atmosphere has stayed in a quasi stable state during the last 3.8 billions years .
The simple fact that we are still here shows that the atmospheric dynamics is intrinsically stable and dominated by negative feedbacks (Le Chatelier principle) .
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This point is also easily explained by the theory of non linear dynamics .
As the climate trajectory has evolved during at least 3.5 billions years in a finite subset of the phase space , it is certain that this subset is an invariant set (attractor) .
The empirical determination of the topology of the attractor (and 3.5 billions of years are largely enough to determine it) insures that the future climate will continue to evolve within the attractor .
One can btw note that attractors in non linear dynamics are the physical equivalents of the Le Chatelier principle in chemistry .
And of course nobody is surprised that the atmospheric dynamics exhibits chaotic behavior whic is another way to say that it evolves within its attractor .
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Obviously the Earth will still visit pseudo periodically ice ages , interglacials , wet and dry periods etc but it will never diverge outside of the attractor whatever happens with its internal dynamical parameters unless its trajectory around the Sun which is the dominating stability factor gets destroyed .
While it can’t be excluded forever , it is certain that the orbit will not be destroyed in the next hundreds of millions years 😉
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You can be very sure that anybody who is talking to you about “tipping points” and “positive feedbacks” in atmospheric dynamics is an award winner in the competition for the biggest crackpot .
Therefore you can simply ignore whatever he/she says .
Dave Middleton (04:06:41),
I agree with your post, except for the proposal to sequester CO2, which is entirely beneficial. More CO2 is better: click.
There has been such a constant, unrelenting drumbeat demonizing this entirely harmless and beneficial trace gas that people tend to assume it is the cause of climate problems. It is not. Increased CO2 has already resulted in higher agricultural yields. And despite their constant squawking, the alarmists are incapable of showing empirically that CO2 is harmful in any way.
P Wilson (17:26:19) :
Altitude for Holocene leaves are easy to determine. Fossil leaves can safely be considered to have grown close to sealevel, since high-altitude fossils are about as common as hens teeth. The altitude effect you write about is a non-problem.
@Smokey (07:56:44) :
If the CO2 is sequestered the “right” way, it can be used for enhanced oil recovery.
I tend to agree with you that we would die from asphyxiation before we ever put enough CO2 into the atmosphere to alter the Earth’s climate or the oceans’ geochemistry… But… It never hurts to reduce anthropogenic impacts on the environment if, and only if, it’s done it an economically beneficial manner.
Dave Middleton (04:06:41) :
I think it’s important to note that even though I vigorously disagree with the science and economics behind Kyoto, Cap & Trade and “80 by 50″… I don’t object to reasonable efforts to reduce CO2 emissions and increasing the economic efficiency of our energy use.
Dave, we can do a lot to promote the efficiency of fossil fuel operated power plants,
insulation of buildings, air conditioning, more efficient engine technologies, etc, etc.
CO2 sequestration however will have the opposite effect.
It takes a lot of energy (and water) to sequester CO2, it takes a lot of energy to compress it and a lot of energy to transport it.
A coal plant will use the double amount of coal if CO2 is taken out.
Because higher CO2 levels promote plant life and reduce the amount of water needed to sustain the plant life cycle, why should we reduce CO2 emissions?
CO2 is not a climate driver.
Therefore there are NO reasonable reasons to reduce CO2 Emissions.
Every cent we spend on the subject is wasted.
Even if we should entirely stop the burning of fossil fuels world wide, it would not have any effect on our climate.
Monckton explains why in the following publication:
October 12, 2009
Climate Myths and National Security
By Viscount Monckton of Brenchley
http://www.americanthinker.com/2009/10/climate_myths_and_national_sec.html
william says:
I think that paragraph is responding to someone else, not me.
TomVonk: I think you may be confused by the way that the term “feedback” is used in climate science. When climate scientists talk about negative or positive feedbacks, they are talking about how processes feed back on a given temperature change…and whether they end up magnifying or reducing that change.
There is another level that one could talk about it, which is at the level of energy balance. I.e., if we make a change in the balance of energy between the sun, earth, and space (e.g., by increasing the level of greenhouse gases), what then happens. At that level, it is in fact correct that the system is dominated by a negative feedback…and that feedback is simply due to the Steffan-Boltzmann (S-B) Equation…I.e., if the Earth starts emitting less energy than it receives, it heats up which causes a negative feedback because the heating increases the amount of energy that it emits. And, you are correct that it would not be sensible to have a net positive feedback at this level.
Since the response of the Earth on this level of energy flows is always going to be dominated by this negative feedback, climate scientists have instead essentially said, “Yes, we know that the Earth’s climate system will re-adjust to a change in radiative forcing by equilibrating to a new temperature (because of what one could call the negative feedback due to the S-B Eqn) but an interesting question is how the new temperature equilibrates to compares to what would happen if the level of CO2 changed while keeping everything else in the climate system constant. If the new equilibrium temperature is higher than this, we will call this a (net) ‘positive feedback’ and if it is lower than this, we will call this a (net) ‘negative feedback’.” One aspect of this definition of feedbacks is that a positive feedback does not necessarily lead to an instability. It has to be of sufficient magnitude to do this; otherwise, it simply leads to a magnification of the temperature response one obtains in the absence of feedbacks. (The mathematics of this is basically that of a convergent infinite series likethe geometric series 1 + 1/2 + 1/4 + 1/8 + …, which converges to the value 2.)
And, just as a point out, it is not correct to say that physical processes are usually dominated by negative feedbacks. For example, whenever one observes an interesting pattern in nature, it is usually due to a positive feedback…in fact, one strong enough to lead to an instability. One example is that of the growth of dendrites (like snowflakes) in which a bump on a surface actually grows faster than the surrounding surface. Another example are wavy patterns that winds can form on sand (including the formation of sand dunes themselves). Yet, another is the “washboard” effect that one can get on a dirt road. Of course, if the positive feedback leads to an instability, then the system doesn’t remain unstable forever but rather runs off to a part of phase space with stability is restored. Hence, for example, the divergence that led to the greenhouse instability that is believed to have occurred on Venus did not lead to the temperature of Venus rising forever…Eventually it stabilized.
At any rate, for the earth’s climate, such a greenhouse instability is very unlikely to be in the cards (at least for the sun at its current irradiance). However, there is nothing that says that the net feedbacks cannot be positive and hence magnify a temperature change, where feedbacks are defined in the way that I have described.
Joel. Forget the Steffan Bolzmann equation applied to the climate or the idea that accumulating gas means greater heat.
Its nonsense, and you’re perfectly aware it is.
see:
http://wattsupwiththat.com/2009/10/04/a-borehole-in-antarctica-produces-evidence-of-sudden-warming/
P Wilson (20:55:08
In the climate, forcings are such things as solar energy, ocean circulation, ocean heat gain v heat loss, orbital disposition, and a few others. Feedbacks are atmospheric factors such as ghg’s, clouds, precipitation etc which result from the forcings. Forcings always over-ride the feedbacks, incurred with a time lapse
so, using the global warmer’s logic, 15 million years ago the neanderthals were driving lots of SUV’s and burning too much coal in their industrial plants? since a rise in CO2 levels is man-made, after all…
craig says:
The poor logic that you speak of is purely your own. It is sort of like saying, “The firemen say that the big fire in the L.A. area last month was started by arson. We know ecologists have claimed that forest fires occurred before homo sapiens around. Does that mean the firemen think that neanderthals were arsonists?” We know that the rise in CO2 levels since the industrial revolution is due to man because we have multiple lines of evidence, some of them very strong, that point to this.
P Wilson says:
You mean the thread where you have propounded this nonsense and I have very patiently treid to explain to you why you are wrong and how we have empirical evidence and in fact whole technologies based on the correctness of the S-B Equation?
I have no idea why you think that “Forcings always over-ride the feedbacks”. The distinction between forcing and feedbacks is somewhat artificial, in fact. “Forcings” are defined as things that are externally forced onto the system whereas “feedbacks” involve responses of the system. However, whether something is considered a forcing or a feedback sort of depends on how you define the system.
As a practical matter, one often tends to define the system as narrowly as one can and still have it such that the system responses do not somehow have the possibility of (significantly) altering the forcing. Hence, we tend to talk about the orbital oscillations that trigger ice ages as a forcing because the response of the earth’s climate does not (to any significant extent) alter the earth’s orbit around the sun. And, in the context of ice ages, the changes in greenhouse gas levels or changes in earth’s albedo are often thought of as feedbacks because they are triggered by the orbital oscillations. However, people sometimes also refer to them as other “forcings” and it is hard to say that one is correct or the other wrong, although one or the other might be more useful depending on context.
In the context of our current “experiment”, the increase in greenhouse gases is usually considered to be a forcing since it is being imposed by humans and one can argue that there is not a significant way in which the response will alter the forcings. (Although one could also argue that the climate response will likely cause us to take action to lower our fossil fuel emissions, so in some broad view I suppose here there is some ambiguity.) The changes in water vapor and clouds that result are then feedbacks. It is worth noting that “water vapor” could in principle be a forcing if it was the case that human emissions could significant alter its concentration in the atmosphere by our emissions; however, since we can’t, it is often noted that “Water vapor is a feedback, not a forcing,” or, in other words, the way we are going to end up changing water vapor is through the response of the system to our emissions of the long-lived greenhouse gases like CO2.
Another ambiguity comes when one considers possibilities that the warming from our greenhouse gas emissions could cause further emissions (e.g., due to releases from the melting of permafrost in the arctic). Usually, these are considered to be feedbacks, although there may be contexts where it is useful to consider them as forcings.
By the way, this ambiguity also can lead to some real issues worthy of thought. For example, estimates of the climate sensitivity have been derived by estimating the change in temperature and change in total forcings between the last glacial maximum (LGM) and now. In that context, the change in albedo due to land ice and vegetation changes and the increase in CO2 and aerosol levels have all been considered forcings…and this estimate leads to a climate sensitivity of ~0.75 C / (W/m^2), which translates to around 3 C for a doubling of CO2 levels.
However, James Hansen has pointed out that for our “current experiment”, we generally just consider the forcing to be the change in CO2 levels and any change in ice albedo as part of the feedback. As a result, we may be underestimated the climate sensitivity that we should really expect from doubling CO2…In fact, he estimates from the LGM that it should about double to 6 C per CO2 doubling. However, other scientists argue that most of the ice sheet disintegration / melting will likely take much more than a century to occur (although there is certainly debate about this) and also that there is less land ice to melt (and hence less albedo change) in going from our current climate to a warmer climate than there was in going from the LGM to now, so 6 C per doubling is too high.
Ther notion that more gas will cause greater temperature is what is in question. It was established a long time ago that c02 absorbs 8% of heat. if outgoing temperature is 3C then c02 absorbs 0.8C . It doesn’t increase the temperature by 0.8C – just that it stays at around 3C for a while longer than if there was no c02. This effect is established by the 1st 100ppm of c02 at cool temperatures. The higher the temperature, the more evasive heat is of c02 – and this factor is crucial. That 8% figure might well be downsized – as its not certain what the global average temperature is emitted by the earth. All we know is ground temperatures – not what they emit. That figure cannot increase to 53%
Incidentally, on that bore hole in the Antarctic thread, I did the mathematics with the S-B equation to emphasise the point. I’m not sure your responses were entirely patient.
addendum to “It was established a long time ago that c02 absorbs 8% of heat. if outgoing temperature is 3C then c02 absorbs 0.8C . It doesn’t increase the temperature by 0.8C – just that it stays at around 3C for a while longer than if there was no c02.”
should read
It was established a long time ago that c02 absorbs 8% of heat. if outgoing temperature is 3C then c02 absorbs 0.08C . It doesn’t increase the temperature by 0.08C – just that it stays at around 3C for a while longer than if there was no c02.
By feedbacks one is referring to ghg’s amongst other things, but lets concentrate on those.
you maintain
In our “current “experiment”, the increase in greenhouse gases is usually considered to be a forcing since it is being imposed by humans and one can argue that there is not a significant way in which the response will alter the forcings.”
THis is inferred from the 30% addition of c02 according to ice measurements, which is another act of deduction – and since thats a gross simplification of data adjustment, its deductively inferred that there must have been a delicate balance before the industrial period. However, There is also a logical error in claiming that the 3% of CO2 which humans put into the atmosphere accumulates over time to 30%, while the 97% of CO2 which nature adds to the atmosphere does not accumulate and in fact shrinks to 70% of the total. The notion that water vapour – a significant ghg compared to any other can change dramatically with precipitation and evaporation- rather upsets the delicate balance conjecture.
Anyhow, given that precipitation and evaporation, and clouds, associated with ocean heat is caused by the sun, or geothermal activity, theres a strong case, that c02 is a proxy of the climate and that it is an extraneous feedback, which is independent of water vapour -except that oceans also emit vast amounts of c02 during warming phases also
P Wilson says:
I have to say that these two sentences (and in fact the whole paragraph) qualifies as about the most bizarre statements on AGW, radiation physics, or any scientific subject that I have ever read. I really don’t know where to begin! What is an “outgoing temperature”? What do you mean by CO2 absorbs 8% of heat? Why does 8% of 3 C equal 0.08 C? What does the last sentence even mean?
You know the theological question, “Could God make a rock that was too heavy for him to lift?” Well, the theological question here is: “Can God make someone with enough patience to not be driven to insanity by his creation of the most patience-trying person in existence?” I think Scott Mandia said it best when he quoted Mark Twain saying something like “It’s not what people don’t know that scares me but what they do know that just ain’t so.” I don’t mind that you don’t know that much atmospheric radiative physics. In fact, I have just been learning it myself…and the whole way that the greenhouse effect operates is pretty subtle and led some pretty smart people astray until it was settled about half a century ago. However, the scary part is how you say completely incorrect or incomprehensible things about it with such absolute surety and confidence and then refuse to budge on them when confronted with clear evidence that they are incorrect (and then either repeat them or make more incorrect or incomprehensible statements).
The Earth has got colder for ten years. The only thing that seems to be getting hotter is the adjusted data. So the weather outside gets colder and we are told of another record month. As the snow falls the outrageous claims of alarmism become more and more hollow.
How will the scientists who have perpetrated this tomfoolery be treated by the public.
over the wavelength spectrum from short wave to long wave of the earth’s “energy budget”, 8% of heat corresponds to the outgoing total micrometre range -which is what the combined wavelength that c02 intercept.
this is nothing new.
Out going temperature, my mistake, should be expressed as re-emitted heat from the earth’s surface.
If temperature at ground level is 3C then it follows that if that ground level is emitting heat, it is getting colder. C02 absorbs 8% of emitted heat
“P Wilson (18:22:26) :
over the wavelength spectrum from short wave to long wave of the earth’s “energy budget”, 8% of heat corresponds to the outgoing total micrometre range -which is what the combined wavelength that c02 intercept.
this is nothing new.
Out going temperature, my mistake, should be expressed as re-emitted heat from the earth’s surface.
If temperature at ground level is 3C then it follows that if that ground level is emitting heat, it is getting colder. C02 absorbs 8% of emitted heat
”
shows the typical missunderstandings. Where ever molecular absorption can occur, so can molecular emission. Were the CO2 in your example to be at 3 C along with the surface, there would be no net absorption of power. Were the CO2 in your example to be at 4 C and the surface at 3 C, the CO2 would radiate more heat than it absorbed. The geometry of the situation though does dictate that the CO2 must be cooler than the surface because it will radiate more power than it receives were it to be at 3 C.
Another misconception is that you don’t have continuum radiation other than from the Earth’s surface. Where ever you have significant clumps of molecules in the liquid or solid phase, you get a continuum. Clouds have ice or water droplets, hence they radiate a continuum although at a lower temperature so less total power.
FInally, convection and conduction have always been a critical factor so it isn’t just radiative.
As for Joel Shore, it seems you must have forgotten to continue your commentary on my earlier post from last week. Good choice but I wouldn’t recommend taking on TomVonk instead as you are in a different league and have the wrong type of equipment and ball.
Agreed with all your points, with only exception to replace the term *carbon dioxide” above ground with “atmosphere/air” above the ground – c02 transmits heat in all directions
cba says:
Yeah…Sorry. I am a little overwhelmed here and responding to what you have posted actually takes considerable thought (and, to do it justice, even some further education on my part). I’ll just say quickly that although I don’t think we agree on everything about Venus, we agree on the main point that the Earth and Venus are quite different in several ways so we might as well leave it at that.
As for what the 3.7 W/m^2 represents, I see us as sort of at an impasse on that. The IPCC make a quite direct statement that this includes clouds. You claim to have played around with radiative transfer codes and think it doesn’t. So, I don’t know really what else to say. (I did want to mention that I think that your statement that the climate models “do still not properly handle clouds” may be a bit of a red herring in this context. I agree that the cloud feedback is a difficult issue for the models but we aren’t talking about that. We are talking about just getting clouds in the initial state approximately correct, for which there is quite a bit more likelihood that they can do at least enough to not significantly effect the radiative forcing number.)
As for the big picture, you presumably believe that the cloud feedback is negative and this results in a much lower climate sensitivity (since your disagreement between 3 and 3.7W/m^2 for the radiative forcing is not enough to make that big a difference)? How do you think this is compatible with evidence on climate sensitivity from the Last Glacial Maximum to now, i.e., what big forcing do you think they missed or underestimated? And, what about the response to the Mt Pinatubo eruption?
Right…The change in temperature caused by the drop in CO2 will then cause lower absolute humidity and you get the water vapor feedback, whose strength seems to be fairly well-determined these days. By the way, the (full-scale) climate models don’t assume a constant RH…and, in fact, they don’t find exactly a constant RH although globally averaged it appears to be about the case and the strength of the feedback is about the same as if they were to assume a constant RH.
Not quite. I think what you mean to say is the net effect of clouds is a negative radiative forcing, which is true…although it is smaller than one might expect because of the partial cancellation between the shortwave and longwave effects. It also depends on cloud type as high clouds (as long as they are not too thick) have a positive forcing and low clouds have a negative forcing.
To diagnose the feedback due to clouds, you have to know what clouds do as the climate warms. It is not that obvious what will happen with them since, for example, both the temperature and the absolute humidity increase in such a way that the relative humidity is roughly constant, at least on a globally-averaged scale.
I agree that it is wavelength-dependent. And, at the infrared wavelengths of interest, the earth’s surface apparently has an emissivity very close to (e.g., within a few percent of) 1. (I think I read somewhere that the one exception is certain desert surfaces where it can get as low as 0.7.)
How so?
cba says:
Okay, but…
(1) If this is the case, why is it that so much of the effort on the part of “skeptics” is expended arguing silly points such as contesting whether the current rise in CO2 in anthropogenic, whether increased CO2 really causes additional radiative forcing, whether cherry-picked time periods of around ten years with little temperature trend in a least-squares fit really constitute a falsification of AGW, etc. Why don’t they send most of their time and effort arguing the issues where there is truly some room to debate such as about cloud feedbacks and climate sensitivity?
(2) From a practical point of view, what sort of implications does this have for using science to inform public policy? Do we just ignore the current scientific view in the peer-reviewed literature and as re-iterated by almost all the major scientific societies in favor of the view promulgated by the Heartland Institute? Seriously, the implication to me seems to be that the “skeptics” should focus on actually doing serious science to overturn the current scientific view. And, while there do seem to be a few scientists (like Roy Spencer) doing this, there in general seems much more effort spent promulgating nonsense.
Joel
The change in temperature caused by the drop in CO2 will then cause lower absolute humidity and you get the water vapor feedback, whose strength seems to be fairly well-determined these days. By the way, the (full-scale) climate models don’t assume a constant RH…and, in fact, they don’t find exactly a constant RH although globally averaged it appears to be about the case and the strength of the feedback is about the same as if they were to assume a constant RH.
Given that there is no recorded drop in temperature caused by a change in c02, unless you’re referring to recent drops of temperature caused by increasing c02 it would be appropriate to say a change in temperature occurs through the drop or rise in temperature of oceans. temperature is not so important. Precipitation counts, which increases through warmer oceans, and that releases a lot of heat into the atmopsphere, associated with and a global heat loss
Even the most avid proponents of AGW have less contempt for evidence than Joel, but I digress slightly. Any heating of the atmopshere by greenhouse gases would have caused precipitation to decrease. Yet the result is the opposite. Whilst present theory is fond of assuming a feedback from water vapour and ignoring the water vapour feedback from solar forcing then given that there are thousands more vapour molecules than c02 molecules, and which absorb heat at three times the value of c02, a 1% change in water vapour is equvalent to a 200% change in c02. As independent variables, it pretty much follows on that the water vapour feedback has 2 characteristics. The first is that it overwhelms c02. The second is that it is variable, going up to 4,000ppm and providing 65-70% of the ghg effect. clouds represent 25% of the greenhouse effect. Relative humidity depends on latitude. Given the higher the temperature, the lower the humidity, theres generally little over deserts and more toward the poles.
On the S-B constant – it doesn’t apply as there are no connections between a theoretical calculation and an empirical measurement. If the number is so unquestionable, why can’t they determine where it came from? It ends up being quite a quagmire that the climate has great difficulty following, since scientists who use it find it impossible to make calculations that have any meaning or application – and that makes it all the more difficult for impartial scientists to unravel.
“Not quite. I think what you mean to say is the net effect of clouds is a negative radiative forcing, which is true…although it is smaller than one might expect because of the partial cancellation between the shortwave and longwave effects.”
The greatest loss of heat is at the tropics where there is a lot of vapour. That competes with heat that c02 would otherwise absorb and re-emit. Clouds are a temperature-cloudiness equation which send IR back to space. High altitude clouds also have a cooling effect. As increased cloud cover folds to increased water vapour with colder air temperature the result is increased snowfall which we see happening. Given the solar origins of cloud cover, from 2000-2006 they were thinning – but since the climate is cooling. Neither AGW nor sceptics can explain these autonomous warming and cooling events.
Joel,
emissivity in the IR for practically everything around the Earth’s surface is rather close to 1, usually in the 0.9x before you get too far into the IR. This is also rather independent of the emissivity / relfectivity involved in the visible (or solar spectral area). Albedo for some deserts (which involves visible and NIR) is quite high as compared to most other surfaces – my recollections are as much as 0.4 which at those wavelengths would reduce emissivity substantially. I don’t know that I’ve seen any substantial surface material with that low an emissivity in the IR area of interest for thermal radiation.
As mentioned here (I think it was here a few days back) such things as RH vary with T even if absolute H doesn’t and one finds that the absolute humidity varies with temperature assuming a fixed RH, but these are rather close to linear while radiative is a log effect. As for AH itself being a function of temperature, I don’t know that to be the case. I always hear that RH supposedly tries to maintain a value independent of temperature which I don’t find all that well supported. Besides, there has to be sources of liquid water to evaporate for there to be variations with rising T. Direct solar heating is likely to create more h2o vapor but that is subject to existing cloud cover. Cloud cover is a function of many factors including more than a little bit of unknown circumstances. Consequently – it’s not something that can be accurately modeled even in principle.
However, we do know what typical tropical conditions on the short term tends to be like in the way of daily cloud formation, sometimes to the point of rain, followed by dissipation of the clouds at dusk. We also know there are tremendous convective effects involved as well.
The recent ipcc claims 3.7w/m^2 for an overall average, apparently even including cloud cover. There’s a problem with that as the original source of that – an earlier ipcc publication – doesn’t substantiate that clouds and cloud cover enter in. I also mentioned that while I have done radiative transfer modeling, that you could probably go to a modtran calculator online and play with the parameters to satisfy yourself concerning my comments. In standard scientific dialog, a number 3.7 is the equivalent of expressing a number ranging from 3.65 to 3.75. The number 3 would have the equivalent range of being between 2.5 and 3.5. You’ll also note that since the prior ipcc publication, their value dropped by 15% to 3.7 as they stated.
I don’t follow your suggestion that clouds only need some initial state. Some measurements of albedo over the last 30 yrs have indicated that albedo has changed by as much as 10% over a fairly short term (in years) and that it is not something with a specific base state. A 10% change in albedo results in a change in power balance amounting to over 10 W/m^2. That’s a tremendously large variable, far greater than anything ghg changes have caused. Some of this cloud cover variation appears due to chaotic internal oscillations. Unfortunately, too little is known about real world cloud cover and its variations and effects over the long term. It does call into question any sensitvity studies that do not include this variable.
as for the peer reviewed lit. approach, climate science has be extremely negligent in following accepted scientific proceedures in the realm of disclosure and have in some works considered important failed to use minimally acceptable statistical methodology. This site has analyzed some of the most fundamental instrument records concerning temperature measurement and found it to be a far cry from being minimally acceptable. There has certainly been enough exposed to call into question whether or not the bulk of the fundamental literature on the subject may even be assumed to be correct. Certainly the various investigations into such reliability have been quite fruitful in bringing out serious, if not fatal, flaws.
concerning your reference to ‘skeptics’ as being indicative of anything to do with the nature of the argument, it’s not relevent. They may or may not have a valid argument. The nature of the scientific method is such that nothing is ever proven, only disproven. The piling on of ‘supporting’ evidence goes to give people some level of comfort concerning a scientific hypothesis but only one actual contradiction by valid data is required to prove that hypothesis false forever more. And, sometimes, it turns out that the data is actually wrong.
Unfortunately, the vast number of those at the agw feed trough do not study and verify the basics. In fact, there is a tremendous lack of verification concerning the basics and that which exists is often not independent and is done by associates. Active efforts to prevent legitimate independent analyses have been documented along with findings of serious problems once those efforts at prevention were overcome.