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How we know the greenhouse effect isn't saturated
mgardner @54:
Being a layman like you this discussion is quite challenging and enlightening also for me.
Regarding your three underlined paragraphs / questions I’ll try to provide some information.1. There isn’t a specific altitude there IR attenuation by CO2 or any other greenhouse gas becomes negligible. This depends strongly on the IR wavelength, and varies from sea level in the “atmospheric window” (8-12 microns) to the lower or middle of the stratosphere (25-30 km) in the part of the IR spectrum most strongly absorbed by CO2 (close to 15 microns). The 5 km figure is just an average of this. If CO2 was the only greenhouse gas, the average altitude of heat loss would be much lower (1-1.5 km?) because its absorption is negligible outside the wavelength range 13-17 microns. IR radiation outside this range would therefore escape to space directly from the surface.
2. The forcing from a doubling of CO2 is usually given as about 4 watts/m2, meaning that it would reduce the outgoing longwave radiation (OLR) from 240 watts/m2 to 236 watts/m2 until surface warming restored the balance by increasing the OLR to its previous level.
240 watts/m2 corresponds to 255 K, so how much cooling is needed to reduce the radiation to 236 watts/m2?
According to the Stefan-Boltzmann law, 236 watts/m2 corresponds to 254 K, so a 1 K cooling is sufficient to reduce the OLR by 4 watts/m2. With a lapse rate of 6.5 K per km the answer to your question should be about 150-160 m.
Surprising? A doubling of CO2 raises the average altitude of heat loss by merely 150-160 metres?Don’t forget that most of the IR spectrum isn’t affected at all, while the heat loss from the central part of the CO2 absorption band will rise several kilometres. And the water vapour feedback isn't included here.
3. Sorry, it’s past midnight here in Norway now. I’ll try to write something about the thickness of opaque layers tomorrow if nobody else has anything about that.
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Dikran Marsupial at 09:53 AM on 20 February 2014Dodgy Diagrams #1 - Misrepresenting IPCC Residence Time Estimates
ranyl, like many analogies, the bathtub one only explains a basic concept and there is often little use in extending it. If you are happy with the basic idea, then the next step is to look into simple box models of the carbon cycle, but that is rather beyond the scope of the article.
While increasing ocean temperatures will result in some degassing, it isn't the only thing that determines the strengths of the oceanic source/sink. Another important factor is the difference in partial pressure of CO2 in the atmosphere and the surface oceans, if there is more CO2 in the air than the oceans, the oceans will take up more CO2 to balance the partial pressures. Fossil fuel use has increased the partial pressure in the atmosphere, and this has resulted in an increase in uptake of CO2 into the oceans, which greatly outweighs the effect of the increase in ocean temperatures.
In the ice core data, there is no external (to the carbon cycle) source of atmospheric CO2 causing a partial pressure difference, so CO2 was degassed from the oceans, so the situation isn't quite the same.
The IPCC diagram in the article shows the changes in the various fluxes into and out of the atmosphere since the pre-industrial equilibrium, which shows that both the oceanic source and sink have strengthened (but the sink more than the source).
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Rob Honeycutt at 09:46 AM on 20 February 20142014 SkS Weekly News Roundup #7
Apology accepted and appreciated, Russ. I'll let Tom take it from here.
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ranyl at 09:30 AM on 20 February 2014Dodgy Diagrams #1 - Misrepresenting IPCC Residence Time Estimates
Interesting article.
Do you think that in reality for the analogy that the sink hole should shrink as the ocean warms as well?
Considering the below and increasing forest fires, permafrost melt, increasing severe weather and nutrient limitations of the CO2 fertilizer effect.
"As the world's oceans warm, their massive stores of dissolved carbon dioxide may be quick to bubble back out into the atmosphere and amplify the greenhouse effect, according to a new study.
The oceans capture around 30 per cent of human carbon dioxide emissions and hide it in their depths. This slows the march of global warming somewhat. But climate records from the end of the last ice age show that as temperatures climb, the trend reverses and the oceans emit CO2, which exacerbates warming.
Previous studies have suggested that it takes between 400 and 1300 years for this to happen. But now the most precise analysis to date has whittled that figure down.
Quick response
"We now think the delay is more like 200 years, possibly even less," says Tas van Ommen from the Australian Antarctic Division, in Hobart, who led the study.
The new results come from Siple and Byrd ice cores in western Antarctica. Van Ommen and colleagues dated CO2 bubbles trapped in the ice, and then compared their measurements with records of atmospheric temperatures from the same time period.
As expected, when temperature increased, carbon dioxide followed, but at both Siple and Byrd the time lag was around 200 years – much shorter than previous studies found.
Rising temperatures make carbon dioxide leak from the oceans for two main reasons. First, melting sea ice increases the rate that the ocean mixes, which dredges up CO2-rich deep ocean waters. Second, "when you warm the ocean up, just like warming up a Coke bottle, it drives the gas out," says van Ommen.
Previous estimates used cores from regions with low snowfall, van Ommen says, leading to a very gradual trapping of the carbon dioxide in the ice. This increased uncertainty in timing. Also, many previous studies used only one ice core site."
Just with a smaller sink hole or even the sink hole becoming a source seems more akin to the reality of the situation.
How much more carbon can put in the atmosphere safely?
None?
??
Don't we need to remove CO2 to get the now widely advocated 350ppm by 2100?
Is this a well serious real situation right now or an abstract problem still??
Don't we need to adapt, stop carbon emissions asap, somehow remove CO2 from the atmosphere and doesn't that mean transforming everything we do?
Community Adaptation Transformation looks promising, it does mean sacrifices in many areas but does also allow the potential for a transformation of things in an inclusive way that brings people's together in such a way that well being of the environment is championed and an equitable, secure and sustainable future might be realised.
Worth having a look at, considering the extreme weather?
?
Moderator Response:[PS] Fixed link and excessive white space. Please avoid too much block quoting - a link and you comment on it is better.
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Dikran Marsupial at 09:22 AM on 20 February 2014How we know the greenhouse effect isn't saturated
scaddenp that is a very interesting diagram. It was already my understanding that there wasn't really an "opaque layer" and a "translucent layer" with a distinct boundary, but I had no idea that the distinction was anything like as diffuse as is suggested by that diagram. In that case, is probably better not to think of it in those terms, other than as a very crude qualitative model.
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Don9000 at 09:08 AM on 20 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
Wili@2
Your link, when accessed via Firefox, yielded a pop up warning me from connecting:
"This Connection is Untrusted" and so on.
Deleting the "s" from the https fixed this issue.
Moderator Response:[PS] Fixed, thank Don
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Russ R. at 08:44 AM on 20 February 20142014 SkS Weekly News Roundup #7
Rob Honeycutt,
I owe you an apology for my last post @67, as it amounted to, in sports terminology, a "late hit".
Sorry.
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Tom Curtis at 08:03 AM on 20 February 20142014 SkS Weekly News Roundup #7
As a point of clarrification, here are the estimated Equilibrium Climate Sensitivities from Otto et al:
The important values are the "likely" range, of approximately 1.1 to 4.2 C per doubling of CO2 for the full 1970-2009 period, which compares to the "likely" range of 1.5 to 4.5 C per doubling of CO2 given by the IPCC AR5; and the 95% confidence interval of 0.9 to 5.0 C per doubling 95% confidence interval for the full period. The later range is drawn, not from the graph but from their specific statement in the text, which states:
"The most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2–3.9 °C (dark red, Fig. 1a), compared with the 1970–2009 estimate of 1.9 °C (0.9–5.0 °C; grey, Fig. 1a). Including the period from 2000 to 2009 into the 40-year 1970–2009 period delivers a finite upper boundary, in contrast with earlier estimates calculated using the same method14. The range derived from the 2000s overlaps with estimates from earlier decades and with the range of ECS values from current climate models10 (ECS values in the CMIP5 ensemble13 are 2.2–4.7 °C), although it is moved slightly towards lower values. Observations of the energy budget alone do not rule out an ECS value below 2 °C, but they do rule out an ECS below 1.2 °C with 95% confidence. The upper boundary is lowered slightly, but is also very sensitive to assumptions made in the evaluation process (see Supplementary Section S2). Uncertainties include observational errors and internal variability estimated from control simulations with general circulation models."
You will notice that they state the 95% confidence range, but only display the 90% confidence range on the graph.
There is also a confusing point in the graph, in that the broad bands are stated as being the 17% to 83% confidence interval (from which Russ derives his estimate), but the ovals are stated to "... represent likelihood contours enclosing 66% two-dimensional confidence regions". That is, they represent the 17-83% confidence contour allowing for the fact that there is uncertainty not only in the width of each line, but also in its relative placement. I would argue that that is the better comparison to the IPCC values, but Russ's determination of the values is certainly a reasonably reading of the graph. Certainly his "likely" range is more directly comparable to the 90%, or 95% confidence ranges that will become crucial later in the discussion.
For comparison, the IPCC do not give a "most likely" (ie, modal) value, nor a mean nor median value in their estimate (unlike in AR4). They give a likely (17-83%) range of 1.5-4.5 C, and a 1-90% range of 1 to 6 C.
With regard to interpreting Otto et al's comments, I believe Rob Painting has it right. It must be always kept in mind that the confidence intervals given by Otto et al are the confidence intervals based on only the data they look at, and using only the method that they use. Clearly adding more data may change the confidence interval, and need not necesserally narrow it. Further, using different methods on the same data may also change the outcome. Otto et al (with the possible exception of Nic Lewis) are well aware of that. Hence they insist that their results are in the same ball park as other results and reinforce our confidence in that general ball park far more than they create confidence that the specific limits found by any particular study. Looked at this way, Rob Painting is merely recognizing that there are many other emperical studies, which cannot simply be ignored or trumped by a single study no matter how much we like its results. The combined confidence intervals of the many studies is highly unlikely to have its confidence intervals exactly match those of any individual study. It is, however, likely that its central value (whether mode, median or mean) will lie within the 95% confidence interval of the vast majority of the individual studies.
Given that this is merely to restate the point I made @55 above (point 2) in different language (IMO), I would appreciate it if Russ would not respond explicitly to this post, but include any arguments he has on this point in his response to my post @55.
Moderator Response:[PS] If this discussion is going to focus on climate sensitivity, then consider also the "climate sensitivity is low" article
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scaddenp at 06:55 AM on 20 February 2014How we know the greenhouse effect isn't saturated
It would raise the emission height a few hundred meters.
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mgardner at 05:51 AM on 20 February 2014How we know the greenhouse effect isn't saturated
DM (and Phil)
Yes, that's exactly the question, and it should have been obvious, if you had read my language carefully, that I clearly distinguish between "absorption of all possible photons from the emitting plane" (opacity, which is the essence of the original myth about 'saturation',) and "a reduction of the energy emitted from that plane as it traverses the interval" (attenuation). I don't use words randomly.
Which brings us to the question of what a polite response to someone asking a serious question might be. My approach is to make sure I understand the question by asking for clarification rather than lecturing and repeating the same thing multiple times. Then, if I couldn't provide the answer, I would say "I don't know" rather than deflecting by saying "you're missing the point".
So, I'll repeat my questions:
If I understand correctly, we take something like 5km to be the altitude above which attenuation of IR by CO2 is negligible--"where energy radiates freely to space".
Now, without telling me about how it all varies with season and latitude, and all of the complications involved in doing the calculations, can I find out about what that altitude would be if we double the CO2 concentration? Is it 100m higher, or 1km higher, or 4 km or what?
I would also like to know, again, order of magnitude, what the thickness of an 'opaque' 'layer' just below that original 5 km altitude would be. And what the attenuation would be for IR radiation in some CO2 band through that 'layer'.
There's no shame in admitting "I don't know"; that's what I'm doing by asking these questions. But it should be obvious if you are paying attention that I know what I'm asking about.
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Andy Skuce at 05:50 AM on 20 February 20142014 SkS Weekly News Roundup #7
Russ started this discussion @1 with the question :
What exactly would constitute evidence against climate change? Or is climate change an unfalsifiable hypothesis?
There is an excellent post at Bart Verheggen's blog (written by Jos Hagelaars and Hans Custers) that has an extended answer to Russ's question.
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Rob Honeycutt at 05:37 AM on 20 February 20142014 SkS Weekly News Roundup #7
Russ... I've already shown you where it states otherwise in Otto et al, but I'll give the discussion of this over to Tom.
[edit] If you don't have the bandwidth it will be helpful if you keep the discussion directed toward Tom and not bait me with additional comments that I would need to respond to.
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airscottdenning at 05:35 AM on 20 February 2014Dodgy Diagrams #1 - Misrepresenting IPCC Residence Time Estimates
There are at least two important responses to this misunderstanding:
1) from a "communicating science to the public" point of view, consider the catastrophe that would result if CO2 really did have a residnce time of say, 10 years. There's currently about 400 ppm of CO2 in the atmosphere. We would have to ADD 40 ppm every year (about 80 GtC per year) just to maintain the habitability of the planet! This is about 8 times the current emissions from the entire global economy. The world would have ended lon ago when plants ran out of CO2. It's patently absurd, and the fact that we're here shows without a shadow of a doubt that it's not true.
2) More seriously, what we actually know about the fate of fossil CO2 is that the rate of removal depends sensitively on the size of the anthropogenic pulse. A small pulse will decay to 20% of its original size in 1000 years, but a large pulse will take many millennia to decay to that level. This has been especially pointed out by David Archer and colleagues.
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Dikran Marsupial at 05:03 AM on 20 February 2014How we know the greenhouse effect isn't saturated
mgardner, a bit if politeness wouldn't go amiss, KR and I are only trying to be helpful.
Consider a photon emitted by the surface. It is absorbed by a molecule of CO2 in the "opaque layer", however the energy in that photon is transferred by molecular collisions to the translucent layer, where it is emitted upwards by another molecule of CO2 and it leaves the Earth. Now you could say that the opaque layer has attenuated the flow of IR photons, by absorbing this one, but has it attenuated the energy radiated into space? No, becase the energy was transformed, passed on to the translucent layer and then radiated into space. The fate of IR photons leaving the surface of the Earth is essentially irrelevant to the Earths energy budget, as virtually all of them (in the relevant absorption bands) are absorbed by the atmosphere at some point.
Asking about the absorption of photons by the opaque layer suggests you have an incorrect model of the nature of the greenhouse effect. It is what happens at the top of the atmosphere that determines the greenhouse effect, not by what happens near the surface.
As it happens, I am an electronic engineer by training, and I know exactly what attenuation means, the question is attenuation of what, the individual photons (which are irrelevant), or the energy that they carry (which isn't)?
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Phil at 05:02 AM on 20 February 2014How we know the greenhouse effect isn't saturated
DM: "It doesn't really matter how much IR is attenuated in the "opaque layer" as some of the energy of the absorbed photons will still be transmitted to the "translucent layer" via collisions, convection and re-radiation."
mgardner: What exactly do you think "attenuation" means, other than that?
mgardner, I think Dikran is using "attenuation" to refer to absorbtion of the photon. When an IR photon (of the correct frequency) interacts with a CO2 molecule, the photons energy is transferred into a vibration of the atoms within the molecule, in the case of Global Warming this is primarily a bending motion. The photon (which is essentially a packet of energy) is destroyed, and the CO2 molecule starts vibrating more energetically. Thus the photon has been "attenuated".
At some later stage the CO2 molecule will relax into its "slower" vibration; either by emitting a new photon (back or outbound radiation), or by collisions with other molecules.
This response glosses over the quantum mechanics somewhat.
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mgardner at 04:52 AM on 20 February 2014How we know the greenhouse effect isn't saturated
DM@50
I don't have a clue what you mean or think you mean when you use the term "attenuation". Maybe you could use a different word or words?
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Dikran Marsupial at 04:18 AM on 20 February 2014How we know the greenhouse effect isn't saturated
mgardner, the bit that is attenuated by absorption by CO2 will still be eventually transferred upwards by the mechanisms I mentioned, which is why the attenuation of the opaque layer is essentially irrelevant. Consider what happens to the energy absorbed by the opaque layer, if it is not to indefinitely increase in temperature, it must loose the energy either upwards to the translucent layer, or downwards to the surface (back-radiation).
The Earths energy budget is determined by the difference in incoming and outgoing radation. How many times the energy is transferred within the atmosphere before it is finally radiated out is irrelevant to the Earth's energy budget.
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mgardner at 04:12 AM on 20 February 2014How we know the greenhouse effect isn't saturated
DM and KR @48 and @47
DM: "It doesn't really matter how much IR is attenuated in the "opaque layer" as some of the energy of the absorbed photons will still be transmitted to the "translucent layer" via collisions, convection and re-radiation."
What exactly do you think "attenuation" means, other than that?
KR: "The "...thickness of an 'opaque' 'layer' just below..." would be all the way from that altitude to the ground."
Well, no, it wouldn't be. There's some point below a given altitude h (e.g. 5km) at which photons emitted (in a given band) will not reach h. That's dependent on the density profile. And below that, there's another such point, and so on. What I don't know is how many such points exist before I reach the surface.
Look, there's nothing I'm asking that an actual expert would have trouble with-- it's the most basic of the physics of this subject.
So I'm leaving my question open for anyone who either has some ballpark numbers in their memory or can specifically refer me to where I can find them, or who can explain to me why they don't exist.
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Dikran Marsupial at 04:07 AM on 20 February 20142014 SkS Weekly News Roundup #7
I have to say that it ought to be obvious that if someone agrees to step out of a discussion in order for there to be clarity, then continuing the discussion with them is rather bad form. This is especially the case if you start by making an accusation such as "This looks like a pretty unreasonable attempt to spin the result as nothing new for sensitivity...".
This seems to me to be a shameless attempt to get Rob back into the discussion in order to avoid the clarity of a one-to-one discussion with Tom. I can't imagine why you might want to avoid the clarity of a one-to-one discussion with Tom! ;o)
I suggest we don't rise to the bait and leave Tom to discuss this with Russ.
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Russ R. at 03:57 AM on 20 February 20142014 SkS Weekly News Roundup #7
Rob Honeycutt,
"Their conclusion is not that ECS is lower that other estimates. They're saying their results are consistent with other estimates."
This looks like a pretty unreasonable attempt to spin the result as nothing new for sensitivity... It implies a marked lowering of the IPCC "likely" range. Although the paper does not explicitly mention it, the "likely" range for equilibrium climate sensitivity using the full 40y of data seems to be about 1.3-3C (reading off the graph by eye, the lower end may be off a bit due to the nonlinear scale).
Please note, this isn't my opinion. I'm quoting James Annan, and last I checked, he's a bona fide, peer-reviewed climate scientist, whom SkS has often cited in the past.
""Russ... But can you not see that you're doing exactly what Otto et al are cautioning against? "
"Do you not get what they are talking about when they say "based on the energy budget of the most recent decade"? They're not saying the most recent decade gives them a better estimation of ECS (which you seem to be implying)."
I'll be discussing this in detail with Tom Curtis. Stay tuned.
[-snip-]
Moderator Response:[RH] Snark not necessary or constructive.
[PS] If you want a serious discussion, then by all means go ahead. If you simply want to troll other commentators, then please find another venue for your entertainment.
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YubeDude at 03:42 AM on 20 February 2014Dodgy Diagrams #1 - Misrepresenting IPCC Residence Time Estimates
The birth of a meme...
"either did not understand the distinction between residence time and adjustment time and/or didn't bother to adequately check what was actually written"
Would love to get an ongoing list of the sites that will post and tweet and repeat until little meme is able to cross the street without holding anyones hand; soon little meme will be riding a bike and going off to university; they grow up so fast.
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Russ R. at 03:19 AM on 20 February 20142014 SkS Weekly News Roundup #7
Thank you Tom,
I don't have the bandwidth to maintain numerous parallel debates threads (I have a full time job and a fiancée who's becoming increasingly annoyed with me for paying more attention to climate blogs than to her.)
I'll make a few concluding comments to others here been patiently awaiting responses, and I'll continue discussion with you.
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YubeDude at 03:08 AM on 20 February 20142014 SkS Weekly News Roundup #7
@64
His is a tsunami of irony; he decries the use of manipulative and misleading rhetoric by using manipulative and misleading rhetoric...”Hey kettle, you’re black!” Said the pot unabashedly and with a total lack of self awareness.
Not sure what I enjoy more, his fluid use of language and the wave upon wave of subtle yet obvious sophistry or that awesome goatee. -
Composer99 at 02:49 AM on 20 February 20142014 SkS Weekly News Roundup #7
I would say Tom Harris' title is correct - climate rhetoric can and does undermine rational decision-making; only it happens that it is his content (and his climate-related work in general) that constitutes the undermining rhetoric.
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YubeDude at 01:58 AM on 20 February 20142014 SkS Weekly News Roundup #7
@62
Here is the link and a couple of excerpts...
"It is not surprising that language has always been an important weapon of war. Delivered with rhetorical flare, language has driven ordinary citizens to perform heroic acts of self-sacrifice in defence of their countries, while pushing others to incomprehensible acts of stupidity and barbarism.
Rhetoric is key in the political battle over climate change. With global warming virtually non-existent during the past 17 years..."
And of course...
"Carbon is a solid, naturally occurring, non-toxic element found in all living things. It forms thousands of compounds, much more than any other element. Medicines, trees, oil, even our bodies are made of carbon compounds."
If Tom will allow me, I believe what he is trying to say is Carbon is harmless and that there is "virtually" no warming; along with saying that language (albeit purposefully mendacious and manipulative) can encourage stupidity. I do believe he got this last part right; the first part not so much.
Opinion: Climate rhetoric undermines rational decision-making FEBRUARY 4, 2014
Moderator Response:[RH] Shorten link that was breaking page format.
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Dikran Marsupial at 01:36 AM on 20 February 2014How we know the greenhouse effect isn't saturated
mgardner wrote "And what the attenuation would be for IR radiation in some CO2 band through that 'layer'."
FWIW, I think you are missing the point, what matters is the temperature of the atmosphere from which outbound photons are not absorbed. It doesn't really matter how much IR is attenuated in the "opaque layer" as some of the energy of the absorbed photons will still be transmitted to the "translucent layer" via collisions, convection and re-radiation. As it happens, IIRC, the opaque layer isn't actually saturated either, but it would make no real difference if it was, or whether it had enough CO2 to be saturated ten times over. What matters is the energy of outbound IR that isn't absorbed on its way out into space.You may find part 2 of the RealClimate blog post of some interest as well.
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How we know the greenhouse effect isn't saturated
mgardner - The "...thickness of an 'opaque' 'layer' just below..." would be all the way from that altitude to the ground. And it's not, properly speaking, a single opaque to transparent transition, but rather increasing mean path length (10's of meters to kilometers) with decreasing GHG density, until ~50% or more of the IR photons in GHG frequencies are escaping to space.
Some additional resources for you: Trenberth et al 2009, Earths Global Energy Budget, figure 1:
Also an excellent GHG Java simulation from PHET that shows absorption re-emission events varying with GHG concentration, as well as the ability to run some glass plate "layer" experiments.
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mgardner at 00:30 AM on 20 February 2014How we know the greenhouse effect isn't saturated
HK et al
I did some more searching and came up with this:
If I understand correctly, we take something like 5km to be the altitude above which attenuation of IR by CO2 is negligible--"where energy radiates freely to space".
Now, without telling me about how it all varies with season and latitude, and all of the complications involved in doing the calculations, can I find out about what that altitude would be if we double the CO2 concentration? Is it 100m higher, or 1km higher, or 4 km or what? I can eyeball that the temp changes between 5-10C in 1 km.
I would also like to know, again, order of magnitude, what the thickness of an 'opaque' 'layer' just below that original 5 km altitude would be. And what the attenuation would be for IR radiation in some CO2 band through that 'layer'.
This is what I'd like to see represented on a graphic. I'm beginning to realize that there may not be one anywhere with that kind of resolution, and perhaps I will set up a chalkboard, draw some diagrams, take a picture, and post it here to have you guys check it out.
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Composer99 at 00:15 AM on 20 February 20142014 SkS Weekly News Roundup #7
Unrelated to what will hopefully be a fruitful discussion between Tom Curtis & Russ R., I see the Vancouver Sun opinion piece describes some recent misinformation efforts by Tom Harris (who you may recall was sending young minds down the path of denial while teaching at my alma mater).
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michael sweet at 20:53 PM on 19 February 20142014 SkS Weekly News Roundup #7
Chris:
I think everyone sees what is going on and understands why. Tom has decided that he has the patience to continue with this discussion anyway. I think this is a good learning experience for the rest of us to see how to deal with this type of intrangience, which is common on other blogs. If nothing else, it shows that SkS interacts with people who think blog posts trump peer review.
I have learned a lot from reading Tom's last couple of posts. It will be interesting to see where it goes.
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Dikran Marsupial at 19:58 PM on 19 February 20142014 SkS Weekly News Roundup #7
Tom, sure, best of luck, it is fortunate that Russ has someone with the patience to go over all of this in detail, lets hope that he can make some use of it.
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wili at 18:37 PM on 19 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
Anyone interested in keeping up with all things related to accelerated sea level rise should keep an eye on postings by ASLR here
Moderator Response:[PS] Fixed link
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Cedders at 14:37 PM on 19 February 2014Extreme weather isn't caused by global warming
Of course! There's a roughly exponential factor besides the difference in temperatures. "water holding capacity of air increases by about 7% per 1°C warming" Trenberth KE (2011) Changes in precipitation with climate change. Clim Res 47:123-138
Thanks for sorting that out for me, Rob.
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Tom Curtis at 12:52 PM on 19 February 20142014 SkS Weekly News Roundup #7
Rob @57, thanks. I hope the dental bills are not too high ;)
Chriskoz @58, my understanding of the weekly news roundups is that they do not have a specific topic. For that reason I switched the discussion with Russ from another thread so we could explore a wide range of issues necessary to show that the issues he raised, and which I quoted @28 do not allow inaction on climate change as a rational choice (or at least, not if we take equity to be a genuine value). I certainly do not want my discussion of those issues to interfere with discussion of other independent issues Russ has raised here.
Moderator Response:[PS] Your understanding is correct.
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chriskoz at 12:31 PM on 19 February 20142014 SkS Weekly News Roundup #7
This thread has gone way off topic.
To put things back on track, I want to recall the reason this whole haywire discussion started: Russ@1 critique that the two of the articles above (by Nicholas Stern and Justin Gillis) are using seemingly contradictory arguments to suit the common cuase, to quote Russ:
you [presumably Nick & Justin] can't use an argument (i.e that specific weather is clear evidence of climate change) when it suits your cause (as with heat in Australia) and then turn around and argue the opposite when it doesn't suit you (as is being done with the cold in the US)
Russ does not explain what he means by "specific weather" and "your cause", but later @4, he explained that he means "particular local weather event" and "your belief that global warming is a serious problem that requires urgent policy action".
Mod [JH] asserted the articles do not apear contradictory if you read them in full. Why no one picked on that? Indeed, after reading them, I found out that:
1. Both Nick & Justin are talking about global weather events. Nick is talking about several "extreme event", like recent floods in UK, typhoon in Philipines, heat waves in OZ, to prove his point that weather has gone crazy worldwide, with unprecedented damages. Justin is taking about recent cold and warm temperature extremes, arguing that the globe is indeed warming on average, despite his fellow US citizens opinions: "it cannot be global warming because it's so cold here". So it is clear for me, that both article do not talk about "particular local weather event" only, as suggested by Russ@1@4
2. I note that only one author (Nick) is advocating policy actions in his article. Justin does not talk about any policies. So, it's incorrect suggest that a "belief that global warming is a serious problem that requires urgent policy action" is a commonpiece of those two.
Therfore I conclude, that Russ in his post@1 either:
- intentionally misrepresents the content of the articles he's commenting about, or
- does not care about the content of the articles and if his comments are accurate and in the proper context
In either case, he uses the distorted interpretation of the articles as an excuse to create a strawman argument, according to his agenda. In the ensuing discussion, he's been jumping from topic to topic, continuing to cherry-pick the data and selective-quoting from articles presented to him, creating further strawman arguments.
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denisaf at 12:19 PM on 19 February 2014Customizable Global Warming Widget Metrics
Why select this one example of the malfeasance of the technological systems of civilization. What about metrics that depict the rate of loss of aquifer water, top soil, nutrients in soil, forests, flora and fauna, irreplaceable natural material resources (including oil), marine food chain.
Moderator Response:[PS] because this site is dedicated to debunking climate myths. Lets not go offtopic please however worthy the sentiment.
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Rob Honeycutt at 12:01 PM on 19 February 20142014 SkS Weekly News Roundup #7
You got it, Tom.
I'll just sit in the corner over here and grind my teeth. ;-)
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Tom Curtis at 11:34 AM on 19 February 20142014 SkS Weekly News Roundup #7
Could I make a request to other participants on this forum that they leave it to me to respond to Russ in relation to his responses to my post @28 and following discussion. I know there is plenty to respond to in what he writes, and of necessity I am not covering all points. However, just from the points I am covering it is becoming plain that Russ is very, and inconsistently selective in which evidence he will admit. Adding more voices to the debate will distract from that point, and also make it less likely the discussion will continue to the end where it covers those areas Russ incorrectly percieves as his strong points.
Moderator Response:[PS] This is a reasonable request and I would ask participants note the "No dogpiling" rule. Corrections or further elucidations of comments would help but please dont add new distractions.
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chriskoz at 11:27 AM on 19 February 20142013 Among Top Ten Warmest on Record
Dave@1,
I second that. And it's a pity that such good, information-rich article as this one receives so little commentary attention from our fellow bloggers while the Weekly News Roundup #7 thread is going haywire feeding a troller (user-named Russel R.) who has high-jacked it to feed his strawman arguments.
It's worth noting that the global temperature data used in this WMO report may be biased low if it does not include the CW2014 correction for lack of coverage in Arctic (look at figure 2 therein and compare to to figure 1 in this article, which one do you think should go to the resources page?) Looks like data the figure 1 in this article is based on combined NCDS/GISS/HadCRUT, so it's probably less biased than HadCRUT itself, but it's still revealing to compare it to CW2014 Hybrid data where 2013 comes up warmer than 1998.
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Tom Curtis at 11:26 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ @47:
1) Fundamentally the Transient Climate Response (TCR) is a function of feedbacks and thermal inertia. By definition, the Equilibrium Climate Sensitivity (ECS) is the response after thermal equilibrium with the oceans is reached, and, ergo, is not a function of inertia. On the other hand, thermal inertia is a confounding factor in calculating the ECS from empirical data. Getting these details right matters.
Turning to the substance of your comment, you claim that "...geological evidence points to a planet see-sawing between two relatively stable equilibrium climate conditions, which suggests high sensitivity in the middle of the range, and low sensitivity at either end of the range". That, however, is the reverse of the true situation. As global temperature falls, ice sheets creep towards the equator in the NH. As the edge of the ice sheet, and perhaps more importantly, the southern limit of winter snowfall creeps closer to the equator, it must deal with more direct sunlight, with the consequence that the albedo effect becomes greater and you have a stronger climate sensitivity. Conversely, with rising temperature, humidity rises, and with it the strenght of the water vapour feedback. In fact, water vapour concentration rises with the fourth power of temperature so that in the right conditions, increasing temperature mean that water vapour can force a runaway greenhouse effect. The right conditions include strong enough insolation, and fortunately for the Earth is safe from that outcome - but that does not preclude an increasing climate sensitivity with increased temperature due to a strengthening WV feedback.
As noted by Dikran Marsupial, your evidence for the convenient ECS plateau we are supposed to occupy also has it wrong. The Earth has in fact experienced at least two, and probably more runaway cooling events. Further, our nearest neighbour, Venus, has experienced a runaway warming event (which unlike the cooling events are not, for practical purposes, reversible). Physics does not change between planets. If increasing temperatures drives increasing climate sensitivity from the WV feedback (necessary for a runaway warming event) in Venus, then they drive the same effect here. Fortunately we are protected from the final outcome of such an event by lower insolation, and had greater protection in the past when the Sun was cooler, though CO2 concentrations were higher.
That raises another point, for the strength of feedbacks also depends on the strength of insolation. Consequently, climate sensitivity would have been lower in the deep past than now with the same configuration of continents (the additional factor effecting climate sensitivity). That is something that should be born in mind when looking at paleoclimate results, particularly from the deep past (pre-tertiary).
To summarize, your comforting belief is the opposite of what would be expected from basic principles. Further, it is based on claims that runaway cooling and warming events do not happen, despite the fact that several runaway cooling events have occurred on Earth, and a runaway warming event has occurred on our nearest, and most physically similar planet. Rather than being at a local high in terms of climate sensitivity, we are likely at a local low, with higher climate sensitivities likely for both warmer and cooler conditions.
2) Despite my heavy emphasis on observational estimates of ECS in my preceding post, many of which are paleo estimates (for which estimates of anthropogenic aerosol forcing, and thermal inertia are irrelevant), you again focus solely on computer models. The evidence climate scientists present for their theories are not restricted to the evidence you feel you may be able to rebut. Simply ignoring contrary evidence as you are currently doing is no basis on which to form views about scientific facts.
So, seeing you choose to ignore it, here is again a presentation of observational climate sensitivity estimates, in this case all from paleodata:
In addition to ignoring all the inconvenient empirical estimates, you again focus on Otto et al. The two main problems with Otto et al (IMO) are that they are only a partially observational estimate, and the method is erratic in its results, suggesting we should not place a large amount of weight on those results, and certainly not to the exclusion of other results.
First, to estimate ECS, Otto et al require an estimate of the increase in Global Heat Content (GHC) over the reference period from 1860-1879. There are no ocean heat content measures over that period on which to base an observational estimate. As they need a value for that period, they used model data to provide their baseline reference. Otto et al's result is critically dependent on this model determined value.
Further, Otto et al had no observational estimates of forcings over the period 2006-2010, and used the RCP 4.5 projections instead. Consequently their values for the final decade have even less of an empirical basis then the other values.
It is possible to eliminate the model dependence by applying their method, and using 1970-1979 as the reference period. The results for each decade is as follows:
1980s: 3.49 C/doubling
1990s: 2.70 C/doubling
2000s:2.58 C/doubling
The range of values obtained in that excercise also indicates the erraticness of the method. This method is heavilly influenced by decadal variations in the data, and effect partially concealed in their published results by the long time span used in the estimate, and by an odd discrepancy between their estimate of GHC in the 1970s and that obtained from other sources.
For completeness, two further problems with Otto et al are the use of HadCRUT4 which does not include the Arctic and hence underestimates recent warming. In addition, the HadCRUT4 record prior to 1880 consists effectively of the North Atlantic region (including the east coast of the US, and Western Europe), plus the sea routes to Brazil, South Africa, India and Australia. It is not a global record, and is heavily biased by data from the North Atlantic. There is a reason, a very good reason, why GISS and the NCDC start their temperature records in the 1880s (by which time temperature records are almost global, with the exclusion of Antarctica).
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mgardner at 11:21 AM on 19 February 2014How we know the greenhouse effect isn't saturated
HK @43
A noble effort, but I already understand all this, and it doesn't answer my question or my concern about communicating it to others, which I thought was a major purpose of the blog. KR@44 is saying that it is possible to answer my question, but apparently I have to acquire and become proficient with MODTRANS, run my numbers, and whip up the graphics on my own time.
Here's an example of what I'm looking for:
A nice image and explanation, I think. If I were explaining this to someone, I would use it, and I think most sincere 'students' would get it. But if someone then asked me "what about that saturation thing I've heard about", I would like to be able to zoom in on the zone at the top of the troposphere, and show a similar diagram with some approximate values.
I could elaborate, but I'm not sure if there is any point if there's no source of information.
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Rob Honeycutt at 11:07 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ... I have to ask you honestly when you read this...
"The most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2–3.9 °C,..."
Do you not get what they are talking about when they say "based on the energy budget of the most recent decade"?
They're not saying the most recent decade gives them a better estimation of ECS (which you seem to be implying). They state that that may not be the case, and that their estimations remain consistent with previous estimates of ECS.
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Rob Honeycutt at 10:09 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ... But can you not see that you're doing exactly what Otto et al are cautioning against?
Their conclusion is not that ECS is lower that other estimates. They're saying their results are consistent with other estimates.
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Russ R. at 09:10 AM on 19 February 20142014 SkS Weekly News Roundup #7
Rob Honeycutt,
"You might actually take the time to read Otto 2013 before making such assertions as that they estimate CS at 2C."
I did read Otto et al (2013).
Quote:
"The most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2–3.9 °C,..."
Moderator Response:[PS] It would save a lot of tedious detail if you would spell out why you think a CS of 2 is nothing to worry about, preferably with reference to impacts in the IPCC WG2. Since I would assume that you reject the Stern review, it would also help discussion if you spell out what sources inform your opinion when discussing impacts and costs. Thank you.
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Russ R. at 08:47 AM on 19 February 20142014 SkS Weekly News Roundup #7
Dikran Marsupial,
In one post @49 you managed the trifecta of: a) quoting me out of context, b) making a strawman argument, and then c) accusing me of trolling.
First, you ignored the first half of my comment, thereby distorting my argument. If you hadn't selectively quoted me you would have seen that my full comment was:
" I would make a case that climate sensitivity was both higher and lower at different points in our planet's history, and will diminish if temperatures continue to rise. Were this not the case, the planet would have experienced runaway warming (or cooling) in the past when temperatures and CO2 levels were much higher (and lower) than they are today."
You only quoted the second part, starting at "Were this not the case..." Then you linked to a reference that has nothing to do with the point I was making.
Why do I say the post had nothing to do with my argument? Because it concluded:
"Thus arguments that Ordovician glaciation disproves the warming effect of CO2 are groundless. On the contrary, the CO2 record over the late Ordovician is entirely consistent with the notion that CO2 is a strong driver of climate."
Since I'd already acknowledged above that "the forcing component of increased GHG concentrations is straightforward enough," I'm already on-the-record as being in agreement with this article's conclusion.
I wasn't arguing that CO2 doesn't impact temperatures. I was arguing that sensitivity is not a constant across all climactic states. An argument which you selectively omitted.
Lastly, you accused me of trolling because before responding to Tom Curtis I failed to consult with a 3+ year old SkS post on the Late Ordovician, which refuted a claim I never made. Really?
Moderator Response:[PS] Snark, accusations, some attitude issues and a failure to read comments and responses carefully by both sides are creating unnecessary heat in an otherwise useful discussion. Could everyone please dial it back and focus the issues? kudos to Russ R for spelling out his position in @41 and to Tom Curtis for a considered response. More like this please.
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How we know the greenhouse effect isn't saturated
mgardner - The interception probabilities are due to the total GHGs above the emission point and atmospheric temperatures, which are entirely quantitative but not reducible to a simple expression. That's why tools such as MODTRAN are used, running line-by-line computations with discretization over many layers.
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How we know the greenhouse effect isn't saturated
mgardner & others:
Let’s try another approach and see if it helps:
1. The Earth receives 240 watts of solar energy per square metre on average when its spherical shape and albedo is taken into account.
2. To maintain a stable temperature, each square metre has to lose 240 watts back to space. This heat loss can only be in the form of infrared radiation because convection (dominant within the troposphere) and conduction is impossible in a vacuum.
3. The Earth’s average surface temperature is about 288 K (15oC), which corresponds to an IR emission of 390 watt/m2. That’s 150 watt/m2 more than needed to balance the energy received from the sun.
4. In order to avoid a dramatic cooling, the Earth’s heat loss to space has to occur from a level in the atmosphere where the emission equals 240 watt/m2. By using the Stefan-Boltzmann law (j* = T4 x 5.67x10-8) one find that this emission intensity corresponds to a temperature of 255 K (-18oC).
5. This means that the average altitude of heat loss to space is (288-255)/6.5 ≈ 5 kilometres above the sea level. Note that this altitude depends very strongly on the frequency of the emission. Some frequencies are hardly absorbed at all and therefore able to escape directly to space from the surface (see image in my post @23), while others can’t escape before they reach the lower or middle stratosphere because CO2 absorbs so strongly even in very low concentrations.
6. More CO2 and other greenhouse gases make the atmosphere at the altitude of heat loss more opaque to infrared, so the IR emissions from this altitude can’t escape to space so easily any more. As a result, the altitude of heat loss is pushed upwards to a thinner part of the atmosphere with fewer CO2 molecules above.
7. This new altitude of heat loss is colder and emits less heat to space, meaning that the Earth as a whole loses less heat to space than it receives from the sun.
8. As a result, the Earth has to warm until its heat loss to space increases enough to restore the balance between incoming and outgoing energy.
Did this help, or did I just create more confusion?
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sidd at 06:43 AM on 19 February 20142014 SkS Weekly News Roundup #7
Re:Climate sensitivity as a function of CO2
from
Climate Sensitivity, Sea Level, and Atmospheric CO2
James Hansen, Makiko Sato, Gary Russell and Pushker Kharecha
NASA Goddard Institute for Space Studies and Columbia University Earth Institute, New YorkFig 7b)
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Rob Honeycutt at 06:31 AM on 19 February 2014Customizable Global Warming Widget Metrics
Maurice... The temperature has gone up at a rate of something around 0.11C per decade since 1998. So, you're wrong from the outset here. Add to that the increase in ocean heat content and you have quite a lot of heat accumulating in the climate system.
If you believe the figures are in error then it is incumbent upon you to demonstrate how you would calculate the figures and show how they are correct.
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Composer99 at 06:28 AM on 19 February 2014CO2 was higher in the past
eric7866:
First, solar output, on the largest scale, changes extremely slowly over geological timescales, but is extremely significant when it changes. A few % increase in solar output will, in a billion years or so, render the Earth uninhabitable. So it's no surprise that a few % decrease in solar output going back into the geological past requires an immense amount of atmospheric greenhouse gases to compensate. That said, geologically-significant changes in solar output are not something that has the effects consistent with what we have seen of global warming over the last 150 years.
Second, today's global mean surface temperatures are cold compared to most of the Phanerozoic. (Although given sufficient unabated warming our species may yet have the opportunity to experience surface temperatures consistent with, say, the Late Cretaceous).
Third, if you think that scientists studying present and paleoclimates are "discounting" any forcing agent in any situation, you are simply mistaken.
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