Arguments
CO2 lags temperature - what does it mean?
What the science says...
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CO2 didn't initiate warming from past ice ages but it did amplify the warming. In fact, about 90% of the global warming followed the CO2 increase. |
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Climate Myth...
CO2 lags temperature
"An article in Science magazine illustrated that a rise in carbon dioxide did not precede a rise in temperatures, but actually lagged behind temperature rises by 200 to 1000 years. A rise in carbon dioxide levels could not have caused a rise in temperature if it followed the temperature." (Joe Barton, US House of Representatives (Texas) 1985-2019) - Full Statement
At a glance
Antarctic ice-core data today provide a continuous record on temperature and atmospheric composition that goes back for some 800,000 years. The data track the last few glacial periods and their abrupt endings, with rapid transitions into mild interglacials. But in some of the ice-cores, temperature rises first and is followed, a few hundred years later, by rising carbon dioxide (CO2) levels.
Certain purveyors of climate-myths seized on this observation, claiming it to be “proof” that carbon dioxide doesn't cause climate change. Wrong, wrong, wrong. But how? The answer lies in a beer-can.
In fact, you can do this one yourself. You need two cans of any fizzy beer. On a nice summer's day, take one out of the fridge and place it outside in direct sunshine for a few hours. Leave the other where it is. Then open the two at the same time. The warm one will froth like mad, half-emptying the can and making a mess. What is left in the can will be horrible and flat. Conversely, the one straight from the fridge will just give a “pfft” noise and will be pleasant to drink, being cool and fizzy.
What's that got to do with this myth? Well, you have just demonstrated an important point about the solubility of CO2 in water. CO2 gives fizzy drinks their fizz and it is far more soluble in colder water. As the water warms, it cannot hold onto as much CO2 and it starts to degas. Hence that flat lager.
Exactly the same principle applies to the oceans. When global warming is initiated, both land and the oceans start to warm up. On land, permafrost starts to thaw out, over vast areas. Carbon dioxide (and methane) are released, having been trapped in that permafrost deep-freeze for thousands of years. At sea, that “warm beer effect” kicks in. Thanks to both processes, atmospheric CO2 levels rise in earnest, amplifying and maintaining the warmth. That rise in CO2 thereby caused more of the gas to be released, warming things up yet more in a vicious cycle, known as a positive feedback. Other feedbacks kick in too: for example as the ice-sheets shrink, their ability to reflect Solar energy back out to space likewise decreases, so that heat is instead absorbed by Earth’s surface.
The trigger for the initial warming at the end of an ice-age is a favourable combination of cyclic patterns in Earth's orbit around the Sun, leading to a significant increase in the solar energy received by Earth's Northern Hemisphere. That's no secret. Glacial-interglacial transitions are caused by several factors working in combination – triggers and feedbacks. We've understood that for a long time.
And when you think about it, saying CO2 lagged temperature during glacial-interglacial transitions so cannot possibly be causing modern warming is a bit like saying, “chickens do not lay eggs, because they have been observed to hatch from them".
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further details
That CO2 can lag behind but amplify temperature during a glacial-interglacial transition was in fact predicted as long ago as 1990. In the paper The Ice-Core Record: Climate Sensitivity and Future Greenhouse Warming by Claude Lorius and colleagues published in the journal Nature in 1990, a key passage reads:
"The discovery of significant changes in climate forcing linked with the composition of the atmosphere has led to the idea that changes in the CO2 and CH4 content have played a significant part in the glacial-interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing and by constituting a link between the Northern and Southern Hemisphere climates."
This was published over a decade before ice core records were accurate enough to confirm a CO2 lag. We now know that CO2 did not initiate the warming from past ice ages but it did amplify the warming. In fact, about 90% of the global warming followed the CO2 increase.
Antarctic ice cores reveal an interesting story, now going back for around 800,000 years. During this period, changes in CO2 levels tend to follow changes in temperatures by about 600 to 1000 years, as illustrated in Figure 1 below. This has led some to disingenuously claim that CO2 simply cannot be responsible for the current global warming. Unsurprisingly, such a claim does not tell the whole story.
Figure 1: Vostok ice core records for carbon dioxide concentration and temperature change.
The initial change in temperature as an ice-age comes to an end is triggered by cyclic changes in Earth’s orbit around the sun, affecting the amount of seasonal sunlight reaching Earth’s surface in the Northern Hemisphere. The cycles are lengthy: all of them take tens of thousands of years to complete.As both land and oceans start to warm up, they both release large amounts of CO2 into the atmosphere, from melting permafrost and from warming ocean water, since CO2 solubility in water is greater in cold conditions. That release enhances the greenhouse effect, amplifying the warming trend and leading to yet more CO2 being degassed. In other words, increasing CO2 levels become both the cause and effect of further warming. Once started, it’s a vicious, self-reinforcing cycle - an excellent example of what science refers to as a positive climate feedback.
Indeed, such positive feedbacks are necessary to complete the shifts from glacial to interglacial conditions, since the effect of orbital changes alone are too weak to fully drive such variations. Additional positive feedbacks which play an important role in this process include other greenhouse gases like methane - you may have seen videos of that gas bubbling up through icy lakes in permafrost country and being ignited. Changes in ice sheet cover and vegetation patterns determine the amount of Solar energy getting absorbed by Earth’s surface or being reflected back out to space: decrease an ice-sheet’s area and warming will thereby increase.
The detailed mechanisms for the above general pattern have of course been investigated. In a 2012 study, published in the journal Nature (Shakun et al. 2012), Jeremy Shakun and colleagues looked at global temperature changes at the commencement of the last glacial-interglacial transition. This work added a lot of vital detail to our understanding of the CO2-temperature change relationship. They found that:
1) The Earth's orbital cycles triggered warming in the Arctic approximately 19,000 years ago, causing large amounts of ice to melt, flooding the oceans with fresh water.
2) This influx of fresh water then disrupted ocean current circulation, in turn causing a seesawing of heat between the hemispheres.
3) The Southern Hemisphere and its oceans warmed first, starting about 18,000 years ago. As the Southern Ocean warms, the solubility of CO2 in water falls. This causes the oceans to give up more CO2, releasing it into the atmosphere.
4) Finally, CO2 levels may lag temperature in some ice-core records from Antarctica, but in some other parts of the world the reverse was the case: temperature and CO2 either rose in pace or temperature lagged CO2. Figure 2 demonstrates this graphically and shows how things are never as simplistic as purveyors of misinformation would wish.
Figure 2: Average global temperature (blue), Antarctic temperature (red), and atmospheric CO2 concentration (yellow dots). Source.
Last updated on 14 February 2023 by John Mason. View Archives
For a longer view of the correlation between CO2 concentrations and global temperatures, look no further than this reconstruction of the past 540 million years of such from Scotese (Scotese 2021 - Phanerozoic paleotemperatures: The earth’s changing climate during the last 540 million years):
Link to paper
Link to uploaded graphic
And leaving the last word on the subject to Scotese, a true expert in the field:
Thanks, MAR. I see that the story at The Conversation mentions one of the references linked in the Intermediate tab of this post (Parrenin et al, 2013).
Thanks Bob. I was just looking for something clearer. Don't really like the presentation on the intermediate and advanced tabs (forgot about those tabs, btw). Something with the lines closer together and the association clearer. With the lines colored and over each other. Thanks for your and other's efforts.
I did see one that made me gasp that blamed it somehow on jupiter and dust. Huh?
The analogy was cute, that the observation that CO2 rises lag temperature rises, means that the Temp rise causes the CO2 rise, is a bit like saying that chickens do not lay eggs because they have been observed to hatch from them. I would submit that, by the same token, opining that CO2 increases cause global warming is a bit like saying that chickens to not hatch from eggs, because they they’ve been observed to lay them.
This all suggests (as inferred) a co-dependent process.
However, this overlooks the same thing that MOST public blogs overlook, and that is the quantum mechanical mechanism on IR radiation (per greenhouse warming theory) has never been proven, and is actually false. New research indicates the fundamental error in the theory, presumes that Heat is ADDITIVE (eg. The Earth’s energy ‘budget’). The quantum process for Thermal transference is not additive. It is a function of frequency resonance. This is why microwave ovens work. Solar heating occurs because the spectrum of frequencies included in sunlight (which reaches the Earth’s surface) sets the maximum temperature which the recipient object may reach. An object in an oven set to 400 degrees will never reach 500 degrees no longer how long it is in the oven, because heat transference is not additive over time. The low energy IR waves received by CO2 molecules will naturally dissipate into the atmosphere with negligible net effect upon the atmosphere, but will never cause planetary ‘heating’ because, per thermodynamic law, no object can heat something beyond the temperature it possesses. Irradiated CO2 molecules can never heat the earth beyond the temperature frequency that already exists within the earth, which generated the IR light waves to begin with. IR Radiation does not raise the temperature of the Earth. The greenhouse warming theory is flawed. THAT is why the universally accepted historical record shows zero correlation between atmospheric CO2 levels and average temperature over the entirety of the past 4 Billion years. Zeroing in on the last 400k or 800k years, and pointing to an anomaly amounts to cherry picking, which disregards the other dynamics in play, such as Milankovitch Cycles. Note: Ozone depletion CAN increase surface temperatures because the range of UV frequencies that reach the surface is expanded.
RBurr @654 : Your ideas are interesting, to some extent.
But your ideas are based on semantics, not on physics. And sadly, the Greenhouse Effect cannot simply be talked away.
Education is the path forward for you. Good luck !
Ah, RBurr's comment at 654 is indeed an odd duck. While demanding "proof", he is badly short on providing any "proof" for his wild assertions. He alludes to "new research" (Where? By who? What publication?), but then just asserts a bunch of old misconceptions.
RBurr's assertions on "quantum mechanics" can be roughly lumped into a denial of the conservation of energy, a gross misunderstanding of the concept of temperature (individual molecules don't have temperature, and temperature is not a property of radiation), with a mix of "violates the second law" bunk.
There are other threads here at SkS where such topics can be discussed (and have been, at length).
A little learning is a dangerous thing;
drink deep, or taste not the Pierian spring:
there shallow draughts intoxicate the brain,
and drinking largely sobers us again.
RBurr @ 654
1) CO2 lags temperature rise at the end of an ice age because CO2 evolves from ocean waters as the temperature rises. This is Henry’s Law. In that case, temperature rises first due to the Milankovitch Cycles. Note that ice age temperatures cool slowly and warm rapidly. Modern CO2 emissions are different because they come from burning fossil fuels. Therefore, temperature rises as a result of CO2. Cause and effect in both cases is clear in both cases, and different in both cases.
2) The quantum mechanical mechanism on IR radiation that explains the greenhouse warming theory has been proven. It is based on fundamental principles of energy balance and radiant energy transfer and has been verified by massive amounts of data, cross-checks, and validation.
3) The Earth’s energy “balance” is fundamental:
Input = Output + Accumulation
Output is reduced as greenhouse gases increase. Thus, energy accumulates.
4) Your description of quantum mechanics does not make sense. Quantum mechanics is fundamental to the specific frequencies (i.e., wavelengths) that are absorbed and emitted by CO2, CH4, and H2O. There is a huge amount of energy carried by IR radiation. It is naturally emitted (not dissipated) and lost to outer space by IR. By the overall global energy balance at steady state:
Input solar = Reflected solar + Emitted IR
Accumulation is zero at steady state, as before CO2 emissions of the industrial revolution.
5) The hot object in this case is the sun at about 5800 Kelvin. That is more than hot enough to warm the earth. The temperature profile is 5800 K of the sun to 288 K (60F) of the Earth 217 K of the lower stratosphere to 2 K of outer space. Increasing CO2 reduces the energy loss to space at specific wavelengths (e.g., approx. 13-17 microns). The absorptance/emittance lines in that range increase, meaning that energy is emitted from a cold 217 K instead of a warm 288 K. This upsets the energy balance. The balance is restored by accumulating energy until the surface temperature increases enough to make up the reduction by CO2. Nothing about this violates either the 1st or 2nd law of thermodynamics. Some mistake the 2nd law by describing the energy balance being at steady state, but the steady state was upset by increasing GHG.
6) Neither the Milankovitch Cycles nor the Schwabe Cycles (sunspots) explain the cause of modern global warming. The long-term Milankovitch Cycles have not been in a period of significant change for the last 12,000 years after warming from the last ice age. Measured radiosity data from the sun show that short-term Schwabe Cycles have not changed significantly either and do not explain modern warming.
The mention of quantum mechanics warrants further discussion so one is not baffled or misled by a misrepresentation of it. Besides, the science is fascinating, and the concept is not that hard to understand. All molecules above absolute zero have internal energy. They vibrate, bend, and stretch in a limited number of ways that depend on their structure and ability to interact with electromagnetic radiation. Absorption and emittance of a photon changes the internal energy level by a discrete amount, which gives rise to discrete absorptance/emittance lines. CO2 is a linear, non-polar molecule that can stretch symmetrically and asymmetrically, but also polarizes temporarily when it bends. When molecules in the atmosphere have absorptance/emittance lines that fall within the wavelength range of IR at moderate temperatures by the Planck distribution, they become greenhouse gases. Discrete lines for CO2 and H2O are illustrated in Figure 3 in Introduction to an Atmospheric Radiation Model.
One more comment about the “quantum process” which is described incorrectly by RBurr @ 654. CO2 is “additive” and increasing. Thus, it is affecting the accumulation term in the global energy balance.
What an absolute joke of site this is. This isn't science, its a bunch of clowns that can't handle critisism and a hall monitor running around telling people what they can and can't say. Its no wonder that out of the dozens of comments I've read on this thresd, not ONE, gives a straight answer to the question that's at the heart of the entire theory of human driven climate change. You and those you parrot better be right.
[BL] If your goal is to get banned, so you can go and tell your friends that Skeptical Science is unwilling to listen to your wisdom, then you are off to a good start. You'll save us all a lot of time if you just post a comment saying "please ban me".
If your goal is to actually discuss any of the science, then you actually have to be willing to make a specific, supported, scientific statement that is related to the discussion topic of the original post, then you'll need to read and follow the Comments Policy. There is a link to the policy above the box you used to post your comment.
The first two statements of the Comments Policy are:
...but there are a couple more that you have violated in your brief rant. Surely someone of your great intellect will be able to read the policy and identify which rules you have broken.
Please note that posting comments here at SkS is a privilege, not a right. This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.
Please take the time to review the policy and ensure future comments are in full compliance with it. Thanks for your understanding and compliance in this matter.
Wavefunction @659 :
Hmm. Now that you have vented your emotions
. . . perhaps you would be so kind as to make an On-Topic comment that is interesting and relevant.
Or try posting at the WattsUpWithThat blogsite, where about 80% of comments are venting & echo-chambering of non-science.
Wavefunction @659 raises an important point.
As a professional engineer with an MBA I have pursued developing a well justified understanding, open to being improved by justified criticism, of what is required to develop sustainable improvements.
Everyone should welcome and engage in learning based on ‘justified’ criticism of developed beliefs and justified criticism of poorly justified or unjustified criticism. That is how ‘scientific understanding improves’, including how this site’s content has constantly improved. It is also how businesses and political groups can learn to be more sustainable (less harmful and more helpful actions have more of a future).
The persistence, and in some cases the tragic growth or regrowth, of unjustified confidence in harmful misunderstandings is an undeniable problem. An aspect of that problem is the unjustified angry responses to sensible efforts to increase awareness and improve understanding that help people learn to be less harmful and more helpful members of humanity.
Correction of tragically popular misunderstandings, especially misunderstandings regarding harmful profitable activity (including excusing or denying harm done because of perceived benefits), is essential to the development of sustainable improvements for the benefit of all children now and into the distant future.
Learning about required corrections of thoughts and beliefs is also necessary for the successful repair of the damaging results of the popularity and profitability of ‘lack of awareness and misunderstandings’. Popular and profitable lack of awareness and misunderstanding can be very resistant to ‘justified criticism that would improve and correct it’.
I welcome justified criticism to improve that understanding.
[BL] I disagree that Wavefunction has raised any interesting points. He starts with an insult, continues with name-calling, and makes a wild claim that none of the "dozens of comments" he has read (on a topic that had 658 comments on it before he posted) "gives a straight answer" to some unspecified "question that's at the heart of the entire theory of human driven climate change".
The comment deserved to be deleted in its entirety, due to it's lack of anything specific, its tone, and its numerous violations of the policy - but it also deserves to be left up for anyone that reads it to see what Wavefunciton's behaviour is.
You have used Wavefunction's comment to make what are interesting and valid points. Reasonable discussion, justified criticism, avoiding angry unjustified response. All are worthwhile goals. The Comments Policy begins with:
The purpose of the discussion threads is to allow notification and correction of errors in the article, and to permit clarification of related points. Though we believe the only genuine debate on the science of global warming is that which occurs in the scientific literature, we welcome genuine discussion as both an aid to understanding and a means of correcting our inadvertent errors. To facilitate genuine discussion, we have a zero tolerance approach to trolling and sloganeering.
Genuine discussion requires a willingness to provide clear communications. Wavefunction hasn't even come close.
OnePlanet @661 : yes.
Now we await Wavefunction's first piece of "justified criticism".
Patience may be required ...
[BL], I agree. That is why I focused my reponse on wavefunction's unjustified criticism "...can't handle critisism [sic]...". To be honest, I had a faint hope that opening with the suggestion that wavefunction's comment raised an important point would get them to read my full comment.
Eclectic, I agree. Also, a lack of a justified response by wavefunction would indicate that they "can't handle, learn from or deliver, justified criticism".
[BL] Hope is a good thing....
during a recent discussion the below paper was mentioned regarding the lag of CO2 and temperatur. it's a very recent paper and doesn't pear to have been discussed on here.
[long link]
I would like to hear your thoughts on it.
[BL] Link activated.
The web software here does not automatically create links. You can do this when posting a comment by selecting the "insert" tab, selecting the text you want to use for the link, and clicking on the icon that looks like a chain link. Add the URL in the dialog box.
Blusox69 @664 :
Are you referring to the new 10/July/2024 article by Dr Demetris Koutsoyiannis ? (your link is not activated)
If so, then you will find that some previous articles by Dr K. have already been discussed on the SkS website here.
IIRC, those articles showed gross errors in his understanding of climate physics. If you can show that Koutsoyiannis has made a large step forward in his understanding of climate mechanisms ~ then I (among others) would be happy to spend time analysing his new July paper. But you would need to make a good case that it wasn't just Dr K. seeking to recycle/republish his old erroneous ideas.
Over to you, Blusox69.
.
btw, the title of his new paper is: "Stochastic assessment of temperature-CO2 causal relationship in climate from the Phanerozoic through modern times". ~A rather discouraging title, which suggests that he is relying on a statistical analysis [which might well be misleading] rather than looking into the actual physical mechanisms which produce climate effects. Real science requires real demonstrated mechanisms of physical action.
Blusox69 @664,
The paper you link-to is Koutsoyiannis (2024) 'Stochastic assessment of temperature–CO2 causal relationship in climate from the Phanerozoic through modern times' which is hot off the press. The author should immediately ring alarm bells being a known perveyor of crazy denialism.
This SkS thread deals with the Temp → CO2 → Temp relationship prior to recent times when mankind began to increase atmospheric CO2 levels by burning fossil fuels and clearing forests.
The author of Koutsoyiannis (2024) also co-authored Koutsoyiannis & Kundzewicz (2020) 'Atmospheric Temperature and CO2: Hen-Or-Egg Causality?' which addresses a different relationship and does so with eye-bulging stupidity.
[To explain this stupidity, the measured CO2 record of recent decades has wobbles caused by El Niño impacting rainfall patterns and thus reducing vegitation growth in tropical regions. This effect is enough to slow the draw-down of CO2 and accelerate the atmospheric CO2 increase from human emissions, delaying the absorption of perhaps 15Gt(CO2) over a matter of months. Such a wobble is quite visible on the measured CO2 record. The whole process has been measurd from satellites.
An El Niño also causes a wobble in global average temperature and this temperture wobble arrives earlier than the CO2 wobble This is the situation Koutsoyiannis & Kundzewicz are measuring, a Temp wobble preceeding a CO2 wobble.
What Koutsoyiannis & Kundzewicz entirely fail to explain is the long-term rise in CO2 due to human emissions. This becomes eye-bulgingly stupid when they address the source of this long-term CO2 rise if it is due to rising temperature. They "seek in the natural process of soil respiration" and also "ocean respiration" but fail to actually look and find it. This should be no surprise. While warming biosphere and oceans would release CO2, the CO2 content of the biosphere & oceans is today increasing not falling, not exactly what you'd expect in a CO2 source.]
I cannot say I have read Koutsoyiannis (2024) properly. After a lot of blather, it tells us it there are questions to be asked about the role of CO2 within the climate system. Is it a GHG? Is it "decisive" in this role? Is the GH-effect enhanced in the last century? Are human emissions increasing the GH-effect? Are human emissions "decisive" in this regard? Is mankind the cause of rising CO2 levels? Is CO2 increasing global temperature, or visa versa, or both?
Koutsoyiannis (2024) then lists a bunch of references to support the assertion that "conventional wisdom" is wrong although the science behind the "conventional wisdom" is rather unwisely (and unscientifically) ignored. Note that all nine of Koutsoyiannis's bunch of references is authored by Koutsoyiannis. He has, according to himself, managed to overturned the scientific understanding of our planet's greenhouse effect.
And this new paper, Koutsoyiannis (2024), proceeds to use 12,000 words examining the temporal relationship between CO2 and global temperature for periods back 541million years. I have not read those 12,000 words but they certainly comprise more eye-waterlingly stupid blather.
Thanks for the replies so far. I read the paper over a few times and it didn't sit right with me. Under section 4.1 he neglects to show data or even graphs for the CO2 to T as he states they "did not provide useful results". Straight away that rang alarm bells. I've never omitted data from my studies, even if the results were not useful as it lays the foundation for being accused of cherry picking data/results. I'm not a statistician, but I'm sure the same logic would be applied to their work too.
Blusox69:
The previous Koutsoyiannis paper that MA Rodger refers to - "On Hens, Eggs, Temperatures and CO2: Causal Links in Earth’s Atmosphere" - was subject to an analysis by Giacomo Grassi, in a guest blog post here at SkS in late May.
Koutsoyiannis has a habit of repeating the same errors paper after paper after paper, so I doubt there is much point in trying to read the entire "new" paper. In the abstract, he once again concludes "unidirectional causality", which defies physics. The abstract implies that he is using the same "stochastic methodology of assessing causality" that has been shown to be wrong before.
A key issue, buried in MA Rodger's reply to you, is that they use detrended data - ΔT and ΔCO2 - which hides the current cause of CO2 rise (steady input of CO2 from burning fossil fuels).
There are links to other discussions of previous Koutsoyiannis works on the SkS blog post (and comments) I link to in my first paragraph.
When considering lead/lag with CO2 and temperatures, there are two fundamental concepts to understand. One is Henry’s Law that dissolved CO2 in water will reach equilibrium with CO2 concentration in the air. The other is the overall global energy balance. At steady state equilibrium, nothing changes. Change occurs when there is an upset in the equilibrium. Major ice ages are caused by the major Milankovitch solar cycles which upset the energy balance. During the onset of ice ages, water gets colder and CO2 dissolves. The reduced greenhouse effect of lower CO2 concentrations allows more radiant energy loss to space. At the end of an ice age, CO2 evolves, reducing energy loss to space. This is the first time in the history of the planet that anthropogenic greenhouse gas emissions have upset the equilibrium CO2 concentration in air first. This time, the overall global energy balance has been upset by greenhouse gases rather than by responding to changes in solar irradiation.
Charlie Brown @ 669:
One needs to be careful about referencing Henry's Law when it comes to CO2. CO2 does not just dissolve in water - it ends up dissociating and forming carbonic acid. This complicates the solubility equations.
SkS has a very good series on ocean acidification - in 20 parts. The 9th part discusses Henry's Law. The entire series is summarized in the 19th and 20th posts in the series.
Bob Loblaw @ 670:
That level of water chemistry is not needed to convey or understand the concepts of equilibrium and lead/lag for CO2 and temperature. It would be needed to go on to explain acidification or total dissolved carbon.
As someone agnostic to climate change, I'd like to point out that the beer can analogy doesn't propose that CO2 causes warming and, indeed, supports the notion that CO2 levels follow temperature changes caused by other means.
I am trying to find reproducible studies that prove CO2 contributes to increased warming at all, but I can only find anecdotal evidence, which is not evidence at all. It merely demonstrates CO2 follows warming, which we all agree on.
If one fills a greenhouse with higher concentrations of CO2, it doesn't get any hotter. This has been tried many times.
Is someone able to provide any experiments to prove CO2 contribution to warming?
Many thanks.
JBomb @672 :
There's more than half a century of scientific investigation showing that CO2 causes warming. And yet you yourself have been unable to find anything of that?
Permit me to be skeptical about your "agnosticism".
Perhaps you have wandered onto an inappropriate website ~ you would be happier trying WattsUpWithThat website (where over half the participants are "agnostic" about the mass of evidence that the globe is warming at all).
JBomb @672,
I would say that the planetary greenhouse effect is not well described. And as you say, an actual greenhouse will radiate the same (and thus cool the same) regardless of its CO2 levels. The level of radiation will depend on temperature.
One difference between an actual greenhouse and our planet's atmosphere is that greenhouses are far-more leaky than our atmosphere which is very stable with little upward and downward air movement. Thus, outside a hurricane a packet of air will take a week or so to travel the 10 miles up to the top of the troposphere at the tropics, and the same to come back down again, roughly. This is because, as the air rises it cools and expands, this all in balance with the atmosphere as a whole. And if this were not the case, hurricane-strength winds would be the result at ground level.
That said, consider the concentration of CO2 per volume in the atmosphere. At higher altitudes, the pressure is less and the molecules including the CO2 are more spaced out. So at some point, the radiation absorbed and emitted by CO2 will begin to emit upward and out into space, cooling the planet.
The greenhouse effect works because an increase in the CO2 concentration will make that radiation escaping into space happen higher up in the atmosphere. And that will be a cooler part of the atmosphere. Cooler gas radiates less. So with increased CO2 the cooling of the planet will be less. And to reach equilibrium, the planet has to warm.
That is how the greenhouse effect works. The various aspects of its working can be shown by experiment. But other than a full-scale experiment, pumping CO2 into a planet's Earth-like atmosphere, the full mechanism in action would be difficult to demonstrate by experiment.
Eclectic at 673,
We agree on most issues regarding Climate Science. At 673 you said "There's more than half a century of scientific investigation showing that CO2 causes warming."
In the 1850's scientists first measured the emission lines of carbon dioxde and noted that if carbon dioxide increased in the atmosphere it would heat the Earth (170 years ago). In about 1898 Arhennius calculated the temperature increase from a doubling of carbon dioxide and got a result not too far off the current estimates (125 years ago). In 1965 the National Academy of Science told President Johnson that climate change would be a big problem in the future (60 years ago).
The science of climate change has been understood by scientists for much longer than half a century. I find that many novices think that climate science was only recently developed when in fact it is well established, long understood that carbon dioxide will heat the Earth.
I think we should say "There's more than 170 years of scientific investigation showing that CO2 causes warming". Jbomb need only look at the absorbtion lines of carbon dioxide to see convincing experimental evidence that the Earth will warm with more carbon dioxide in the air.