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Comments 4651 to 4700:

4651. Bob Loblaw at 12:08 PM on 12 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      The original emailer has sent in a follow-up to the Skeptical Science contact page, asking about black-body radiation and differences between emissions at 255K and 288K. A temperature of 255K is the commonly-cited radiative temperature at which the earth-atmosphere system emits IR radiation to space, while 288K is the commonly-cited global mean temperature for the earth's surface. The difference is a measure of the role of the atmosphere - the greenhouse effect - and this difference is predicted to continue to rise as atmospheric greenhouse gases continue to increase.

      The blog post focuses on atmospheric absorption, not emission, but atmospheric absorption by CO₂ is a key factor in the greenhouse effect. So, how might that temperature difference - 288K at the surface, 255K at high altitude - affect this process?

      A few of the comments to the post touch on aspects of IR emission, and in figure 2 and comment #10 I mentioned Planck's Law, which governs radiation emission. Figure 2 was intended to show the difference between solar (5800K) and terrestrial (255K) sources of radiation, but does not touch on differences for the range of temperatures within the earth-atmosphere system. The recent follow-up email asked to see Planck curves for 255K and 288K (and to see them on a linear scale), so here is that graph:

      

      The horizontal axis is wavelength in μm, and the vertical axis is energy in W/m²/μm.

      There are three obvious features:

      • At the hotter temperature, the area under the curve is much larger. This area represents the total energy emitted. Hotter sources emit more energy overall.
      • At the hotter temperature, the peak happens at a slightly shorter wavelength. Hotter sources shift a larger proportion of their emissions to shorter wavelengths.
      • The 288K curve always lies above the 255K curve, so even at a specific wavelength, the hotter source emits more radiation than the cooler source.

      The "hotter source" explains why I used a logarithm scale in figure 2. The sun emits a lot more energy than the earth. There is also one more "feature" to figure 2: I scaled the solar output so that instead of giving the intensity at the surface of the sun, where it is emitted, I scaled it down to the value appropriate at the earth's orbit around the sun. That was the only way to get the two lines to graph anywhere close to each other.

      So, if we look back at our discussion of the Beer-Lambert Law, what difference does the source temperature have on the absorption of IR radiation? (The original email had mentioned 15 μm, which we see is a little to the right of the peak in the above graph.)

      Well, it turns out that the temperature of the source has absolutely no effect whatsoever on the absorption according to the Beer-Lambert Law.

      • In the blog post, note that the equations for the Beer-Lambert Law do not have temperature in them.
      • You can add a subscript to the Beer-Lambert Law to indicate wavelength, as the absorption coefficent is highly-dependent on wavelength, but it does not matter what temperature the source was at that emitted the radiation.
      • It also does not matter what the temperature is at the location the absorbing is happening.

      Why is this? Well, there are several factors:

      • The Beer-Lambert Law just tells us the probability that a single photon will be absorbed.
      • Each individual photon is either absorbed, or not. Do, or do not. There is no try.
      • If the photon is absorbed, all the energy goes into the molecule that does the absorbing (and is then transferred to heat all gases through molecular collision).
      • If the photon is not absorbed, then the photon will continue along its way, and be transmitted through the atmosphere.
      • An absorption coefficient of 0.01 means that there is a 1% chance that a single photon will be absorbed. It does not mean that each photon loses 1% of its energy - it means that 1% of all the photons lose 100% of their energy and the oher 99% lose none.

      And all 15 μm photons are the same.

      • They travel at the same speed, and they contain the same amount of energy.
      • They do not contain more energy if they were emitted from a source at 288K than if they were emitted from a source at 255K.
      • The source at 288K that is emitting more total energy at 15 μm is not emitting higher-energy 15 μm photons, it is just emitting more of them.
      • The difference between the two curves in the graph above is just that a 288K source emits more photons at all wavelengths, compared to the 255K source. The 288K source can do this because it has more energy (it's hotter!) that can be transformed into radiation.

      When CO₂ absorbs a 15 μm photon in the atmosphere, it has no way of knowing if that photon was emtited from the surface at 288K, a kilometre away at 270K, or a metre away at 255K. It is just another 15 μm photon carrying the same amount of energy that every other 15 μm photon carries. And that amount of energy just happens to fit nicely into the different energy states that CO₂ likes, so it is easy for CO₂ to absorb it.

      So, the CO₂ will absorb the photon, and that heat is added to the local atmosphere, and it does not matter if the location where it is absorbed is warmer or colder than where the photon was emitted.

4652. One Planet Only Forever at 02:33 AM on 12 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      Because of the perspective I presented @12 I appreciate that the ways that the changes of climate will affect developed food production are more significant concerns regarding the attribution of human causes to climate change.

      Every regional developed food production system is at risk, and needs to attempt to adapt to the changes if the regional climate changes (with no guarantees that the climate changes will support continued food production). And the more significant, and more rapidly, the regional climate changes occur the more harm is done to the global developed food production system. Sustainable total global food production, and systems developed to ensure that every human gets at least basic decent nutrition, is the measure that matters. The studies I have seen indicate that, globally, any regional positives of global warming are outweighed by regional negatives. And until the human impacts causing rapid climate change are actually ended, or are clearly on track to being ended, it is hard to know what future climate conditions food producers and distributors will need to try to adapt to.

      Not knowing if the peak climate impact will be 1.5C, 2.0C, 2.5C, 3.0C, 3.5C means there is no way to plan new developments or revise existing developments for the demands of the future. But what is known is that the future of humanity is more damaged by more warming.

      Attribution of climate change impacts to actual events that are seen to be harmful is essential to help convince the fence-sitting pragmatic moderates that it is harmful to compromise or ‘balance’ the understanding of the need to end harm done by human pursuits of benefit with the desires of people who want to benefit from continuing or expanding understandably harmful unsustainable actions.

4653. Eclectic at 14:47 PM on 11 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      Wilddouglascounty  ~  so far in this discussion, my mind has not been subtle enough to discern the effect of the distinction, or difference, that you draw between the concept of global warming vs increased greenhouse gasses in the atmosphere.

      To clarify your position: how would you describe the distinction (regarding increase in extreme weather events) in the - strictly hypothetical - case that the current rapid global warming were instead being caused by an ongoing rise in total solar irradiation?

      Admittedly there is the crucial difference that such global warming would be beyond direct human intervention in its causation ~ but otherwise the nett effects would mimic AGW.   But how would one (i.e. you) draw distinctions in the wording of attribution?  And why so?

4654. wilddouglascounty at 02:23 AM on 11 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      #11 David Kirtley,

      Thank you for referring me to the Grist post, which I had not read before. Yes, Mr. Roberts accurately captures the inherent difficulties in trying to create causal distinctions between different parts of one atmosphere. The point I was making can best be outlined in his article by quoting his steroid example: 

      "When the public asks, “Did climate change cause this?” they are asking a confused question. It’s like asking, “Did steroids cause the home run Barry Bonds hit on May 12, 2006?” There’s no way to know whether Bonds would have hit the home run without steroids. But who cares? Steroids mean more home runs. That’s what matters."

      I just wish Mr. Roberts had gone on to say that while "climate change" is  a compilation or measure of the severity and frequency of weather episodes, it is greenhouse gases in the atmosphere that are causing it to change. It is best to say that increased greenhouse gases mean more extreme weather events. That's what matters.

4655. nigelj at 06:26 AM on 10 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      There are some people that suggest that saying "climate change is causing changes in the severity of the weather" is a misnomer, because climate change is in fact changes in the severity of the weather (eg: more intense or frequent droughts or storms).

      They say we should really say that global warming or increasing greenhouse gas concentrations are causing changes in the weather. I think its all a bit pedantic. I don't think anyone is really confused as to what is causing changes in the weather. OPOF's comment seems more pertinent.

4656. One Planet Only Forever at 09:56 AM on 9 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      As a civil/structural engineer I have a different perspective regarding the debate about the merits of attribution analysis of extreme weather.

      Civil designs, especially water run-off collection systems, and structures need to be designed to withstand 'weather extremes'. The rapid changes of weather extremes due to human action causing global warming and resulting climate change is critically important work.

      It is inevitable that more frequent and more severe extreme events will be attributed to the human impacts. We have to hope that our designed systems are designed to perform successfully under the more extreme conditions, and fix already built stuff that isn't up to the challenge because it wasn't anticipated to need to be.

      The science that anticipates the attribution of more extreme weather impacts is critical to the success/survival of what we build.

4657. David Kirtley at 01:37 AM on 9 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      If I can butt in, hopefully without adding more confusion, I think what wilddouglascounty is saying is something that Dave Roberts said 10 years ago in a Grist post about the "semantic debate" involved whenever the issue of climate change attribution comes up. He even uses the example of steroids in baseball causing more home runs. I think this paragraph probably sums up wilddouglascounty's viewpoint:

      There is no division, in the physical world, between “climate change storms” and “non-climate change storms.” Climate change is not an exogenous force acting on the atmosphere. There is only the atmosphere, changing. Everything that happens in a changed atmosphere is “caused” by the atmosphere, even if it’s within the range of historical variability. Climate change is just the term we use to describe those changes.

      Wilddouglascounty, please correct me if I am putting words in your mouth.

4658. wilddouglascounty at 05:46 AM on 8 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      I posted earlier, but it did not show up, so am briefly posting one more time: In a nutshell, I have no objections whatsoever with any of the terms: climate, climate change and Anthropogenic Global Warming. I fully support them as valid concepts and useful measures of the impacts that have resulted from increasing the amount of greenhouse gases residing in our atmosphere.

      My one and only point is that those composite measures are statistical abstractions that measure the impact of greenhouse gases, and there is a tendency to reify them by saying that the measures are causing the observed changes, when it in actuality is the greenhouse gas composition of the atmosphere that is the causal force. So for clarity's sake it is much better to refer to greenhouse gases as the reason that a storm event is more severe and occurring more frequently, not the tool of measurement, i.e. "climate change."  If you want to attribute the increased frequency and increased amount of energy, I think it is worth pointing to the fact that there has been an increase of 47% in the composite greenhouse gas index since 1990 (AGGI index increasing to 1.47 since 1990) as the cause for the observed phenonenon.  I hope this clarifies this once and for all, but feel free to agree/disagree/clarify as you see fit.

4659. MA Rodger at 06:11 AM on 7 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      wilddouglascounty @8,

      This interchange becomes perplexing.

      I expressed the situation as I saw it @7 saying "I feel you are still attempting to paper over the idea that extreme weather will be worse under AGW and that will bring with it serious problems for humanity," believing you were happy that AGW resulted from increased GHGs in the atmosphere but that you had objection to the "statistical abstration" involved with the assessment of AGWs influence on extreme weather events.

      But @8 you say I am wrong in this interpretation of your position.

      It appears now that you are attempting to paper over the concept of "climate change" or AGW as you want the term "climate change" replaced by the rather lengthy phrase "a 40% increase in CO2 in the atmosphere or whatever mix of all greenhouse gases you want to choose." You even @8 describe "climate change" as being a"statistical construct we've created to monitor the impact of greenhouse gases" while @4 it is "climate"  you describe as being "a statistical abstraction."

      So is it simply use of the terms "climate change" and "AGW" or even use of the term "climate" you are objecting to? And I would find an affirmative response "perplexing" given your opening line @1 and your final line @8.

4660. BaerbelW at 19:18 PM on 6 January 2022
      The Conspiracy Theory Handbook: Downloads and translations
      

      The Conspiracy Theory Handbook is now also available in Swedish as the 14th translation!

4661. wilddouglascounty at 08:19 AM on 6 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      MA Rodger,

      Thanks so much for voicing your concerns, which I can assure you are completely unfounded.  You say you feel that I am attempting to paper over the idea that extreme weather will be worse with AGW and cause increasing problems for humanity, but your concerns are completely unfounded. Nowhere do I imply this and I'm sorry you draw this conclusion from my stating and restating that my concern is that people are being inaccurate by saying that the statistical construct we've created to monitor the impact of greenhouse gases, i.e. "climate change" is CAUSING the observed changes (more severe, frequent extreme weather events, sea level rise, acidification, etc.). It is the greenhouse gases that are CAUSING the climate to change, the rising sea levels, the acidification, etc. Climate change is merely a constructed indicator that we use to communicate the impact of increased greenhouse gases in the atmosphere (and oceans, for acidification's sake). The only way to reduce and reverse AGW is to reduce the greenhouse gases being emitted to a level that the carbon sinks on our planet can absorb in order to return to an equilibrium that results in a climate we have become accustomed to.

      In other words, when talking about attribution, instead of saying that a drought's severity is increased X percent due to climate change, I would like to see folks say that the drought's severity is increased X percent due to a 40% increase in CO2 in the atmosphere or whatever mix of all greenhouse gases you want to choose.

4662. MA Rodger at 23:51 PM on 5 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      wilddouglascounty @4,
      Thank you for the added clarity but I feel you are still attempting to paper over the idea that extreme weather will be worse under AGW and that will bring with it serious problems for humanity. (Of course, the sporting analogy breaks down here.)

      You appear to be saying that the science should restrict itself to study of the physics of "the roll of greenhouse gases in changing the atmospheric chemistry and its heat retention properties." You say "science should be focusing more on the physical impact of greenhouse gases than on what fraction of an event can be attributed to climate change."

      So AGW should be understood soley as, what, causing an increase in average global surface temperature of a degree or so, or more? Or perhaps even global averages are too statistical to have any meaning in the real world where AGW can even result in regional cooling. And sea level rise too. That may seen a solid physics thing but outside a few amphidromic points it is still dwarfed by the tidal range and requires weather to drive tidal surges.

      Weather is a series of events and climate is a measure of what weather events can be expected. The science of climatology attempts to unravel the whats and the whys of weather stuff that together comprise climate. If climate changes so will the weather we can expect.
      Yet you appear to be wanting to ignore the impacts of AGW, of say, 100-year events happening every year (on average) and even unprecidented 10,000-year events potentially now happening because it is not CO2 that directly causes these events as they are caused more correctly due to the effect of the atmospheric warming resulting from higher CO2 concentrations which in turn cause, say, on average deeper cyclones at higher latitudes which in turn occasionally drives far greater volumes of atmospheric H2O to suddenly rain-out over places where it will cause flash flooding that destroys buildings and forests and communities that have been happily standing for centuries and which would be a complete disaster if there happens to be an 'r' in the month; all of which is a "statistical abstration" which we shouldn't be bothering ourselves with.

4663. Bob Loblaw at 07:24 AM on 5 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      The way I think of it is that a "weather event" is not really a single item. A heat wave is a higher-than-something temperature, and it carries with it an area of coverage and a length of time. It can be unusual or unexpected if it exceeds previous high temperatures, or if it covers a larger area than normal, or lasts longer than normal.

      And "normal" itself has a geographical characteristic - temperatures that are normal in one place (and one time of year) may not be "normal" in another location or time of year.

      All components of that "heat wave" may be subject to the effects of a globally warmer climate. "Attribution" needs to look at all aspects of that "event", and assess the probability that it would have happened in a climate that has not warmed.

      For a simpler example, what about flooding? Let's say that a region has planned and built for river flooding up to 10 m above normal water levels. This has protected the region for decades, but then under a warmer climate there is heavier rainfall, and an 11 m flood overtops the protection and the region is flooded.

      We can ask, "which metre of flood water caused the protection to fail? There are several possible answers, all of which could be argued with at least some success:

      • The obvious answer is "all of them". Take away any single metre of flood water, and we're back to only 10m and the protection works.
      • The next obvious answer is "the last one". The first 10m did not cause a problem, it was only the last one.
      • The first problem with this answer is that you then have to ask "which factor caused that last metre of flood water?". Which means needing to determine the source of all of the metres of flood, from the first to the last. Which gets you back to "what caused 11 m of flooding?"
      • The second problem with that answer is that the last metre would not have overtopped the protection if any the previous 10 metres of flood had not already happened. Why should it get the blame?
      • So, finally, we get to another possible answer: the flood was caused by the 1 metre of flood water that was never there before. It does not matter if it was the first metre during that event, somewhere in the middle of the event, or the last metre added to the flood water during that event. In the past, there was one factor that was not present, and all the other factors that have been around for ages never managed to exceed 10 m. The problem was caused when the new kid on the block added another metre of flood water to the mix.

      So, in this case, I think we can safely say that the 11 m flood was the result of climate change (precipitation in the thought experiment). But we still need to accept that something unusual might have happened without climate change, so the attribution is done on the basis of probabilities. We're 99% sure that the flood would not have happened if it were not for climate change.

      ...and I think that an essential part of the climate change message is pointing out that we are already seeing the effects. It is not a feature of the imagined future - it is now.

4664. nigelj at 05:10 AM on 5 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      I think I see the point wilddouglas country is making about attribution studies. Its something I have also wondered about. The term attribition is defined in online dictionaries as "the action of regarding something as being caused by a person or thing." However climate attribution studies do not really say that specific weather events are caused by a warming climate. They typically find that the event is exceedingly unlikely to have happened but for climate change. Not questioning this finding, but the term attribution just doesn't seem accurate. Climate influence studies would be more accurate.

4665. BaerbelW at 03:37 AM on 5 January 2022
      2021 SkS Weekly Climate Change & Global Warming News Roundup #53
      

      CelesteRosemary @ 1 & Jonas @2

      Thanks for your feedback! Putting together the weekly summary doesn't take long so my question was just to satisfy my curiosity and not to find reasons to discontinue posting it.

      As our SkS page on Facebook is public and as our posts there are shared publicly, they can be read without an acount (or being logged in).

4666. wilddouglascounty at 02:54 AM on 5 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      Phillipe, MA Roger,

      Sorry for not being more clear: what I am saying is that just as the conversation in athletics is about how steroid use impacts the batting average/number of sixes, instead of focusing on the nonsensical statement that that last hit can be attributed to an increased batting average, science should be focusing more on the physical impact of greenhouse gases than on what fraction of an event can be attributed to "climate change."

      Climate is a statistical abstraction that can be summarized in all kinds of ways, whereas the roll of greenhouse gases in changing the atmospheric chemistry and its heat retention properties is a physical process that can be addressed by science. In other words "climate change" does not CAUSE more extreme weather events: a changed atmospheric chemistry does, and climate indicators are proof of those impacts CAUSED by greenhouse gases. Hope this helps.

4667. MA Rodger at 19:33 PM on 4 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      wilddouglascounty @1,

      I'm not familiar enough with the game of baseball to discuss a "last individual baseball hit" but if this were the game of cricket, the analogy of an increased incidence of extreme weather would perhaps be analogous to a batsman hitting more sixes which would be a contribution to an overall increase in the steroid-taking batsman's batting average, the overall increase being analogous to the changing climate.

      So in the analogy we can see the batting average increasing with the steroid-taking and we can see within that performance, the rise in the number of almost-sixes, the rise in actual sixes and the times now in which the ball sails clean out of the stadium. A statisitcal assessment can thus be made.

      Note that your posed question "Did the increased batting average cause the (baseball) player to hit that ball further, or was it the steroids?" was answered by you within your analogy as you say "Now it is the steroids which caused the change, just as a jump in the amount of greenhouses in the atmosphere has caused an increase in extreme weather events that cumulatively changes the climate, right?"

4668. Jonas at 10:30 AM on 4 January 2022
      2021 SkS Weekly Climate Change & Global Warming News Roundup #53
      

      Happy new year Baerbel and whole SkS Team.

      I usually (partially) read 7-10 of the linked articles but I also profit from the headlines (I would read more if I were not already reading too much stuff; for the research list, the fraction I read is much smaller and the overview thing more important: I am a lay person and research articles often are hard or completely undigestable ..).

      I don't have an FB account, but I just checked that I can read there (was that different in the past?). I now hate FB even more since a member of my familiy became victim of corona misinformation on FB, but I will go there and check SkS there if posting the links here is too much effort.

      Thanks for all you do. I remember how glad I was, when I found this website, way back in  .. 2008? (don't remember ..): I can't count how often I passed and still pass the link to SkS, just recently to two colleagues.

      Utopian greetings,
      Jonas

4669. Philippe Chantreau at 08:00 AM on 4 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      WDC, you're splitting hair.

      It is a little ironic, since another, even more intense, winter heatwave has just hit Western Europe again.

       

      A warming climate is predicted to lead to an increased frequency of extreme weather events. The climate is warming, and an increased frequency of extreme weather events is observed.

      Going into the subtleties of: "this event was x times more likely to reach the extent that it did in a warming climate, but can not definitely be said to have done so because of it," may have merit, but is beyond the comprehension of the vast majority of the general public, who have no concept about differential probabilities. They can hardly even wrap their mind around probabilities at all, and are stunted in their quantitative thinking in general, as has been showed by the recent waves of denial and incomprehension associated with the pandemic. 

      Meanwhile, there is this: https://www.ncdc.noaa.gov/billions/time-series

4670. supak at 05:15 AM on 4 January 2022
      Patrick Michaels: Cato's Climate Expert Has History Of Getting It Wrong
      

      Pat has officially lost this bet. He is ignoring me. He owes the Climate Scientist Legal Defense Fund $250.

4671. CelesteRosemary at 03:59 AM on 4 January 2022
      2021 SkS Weekly Climate Change & Global Warming News Roundup #53
      

      I appreciate the weekly summary blog posts because I don't go on FB often, and this post gives me a chance to see the articles of interest I may have missed during the week. I checked out 5 articles on this recent post.

4672. wilddouglascounty at 01:01 AM on 4 January 2022
      How weather forecasts can spark a new kind of extreme-event attribution
      

      Isn't attribution of individual extreme weather events more of a psychological pursuit than actual science?  I mean, climate is an aggregated construct that is not unlike a baseball batting average, i.e. a statistical cumulative creation designed not to predict weather, but to evaluate what past activities show us and to tease out trends, correct?  For a baseball player, if he starts injecting steroids into his body, all things being equal, his batting average or the number of homeruns may jump.

      Now it is the steroids which caused the change, just as a jump in the amount of greenhouses in the atmosphere has caused an increase in extreme weather events that cumulatively changes the climate, right? But it seems to me that just as it is questionable science to try to tease out how much those steroids added to that last individual baseball hit compared to that player hitting that ball before he started taking steroids, the same pursuit with individual extreme weather events seems to be confusing the cumulative indicator with the observed data point. In other words, did the increased batting average cause the baseball player to hit that ball further, or was it the steroids?  To conflate the two is a psychological pursuit, not a scientific one in my mind.

4673. Eclectic at 10:12 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      My apologies, BL  ~ I should have allowed more response time than 24 hours (and perhaps moreso in a holiday period).

      My concern was that the readers (other than myself) might be unaware of the relevant context of CD's thinking.   Yes, we should focus on the precise point of argument put forward by any protagonist at all, however unphysical their background ideas.

4674. Eclectic at 08:55 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      Thank you, Bob Loblaw @11

      CD = Climate Detective . . . well now, who da thunk   ;-)

      But it is now more than 24 hours since the presumed bloggy author has posted here at SkS.   Likely he has sailed away . . . or quite possibly sunk (considering how you delivered some heavy hits below his waterline).

      To save SkS readers from wasting their time on the Climate Detective's blogsite, I will give a quick thumbnail sketch of the blog's contents.   The author's blog contents range from: some technically correct stuff . . . to some definitely incorrect stuff . . . through to some quite bizarre stuff.

      Much of the author's content has a mildly Wattsupian flavor . . . such as the cherrypicking of temperature charts for times and regions which are intended to demonstrate the wrongness of mainstream climate science & of all the national scientific bodies.   That sort of thing  ~ rather Wattsupian, but with a soft-pedal on the International Conspiracy Theories.

      Then there was a slightly political take on the recent International Climate Conference in the UK  ~ and the disastrous immorality of cutting out the consumption of petroleum oil.   # "we [the rich West] will devastate the economies of many [Third World] oil producers."    (Such callous disregard . . . cataclysmic impact . . . etcetera.)    But # "alternative strategy . . . getting the producers to cut supply by 5% per year . . . result . . . global economic collapse."

      ~  An interesting demonstration of Motivated Reasoning.  Binary thinking - only two future possibilities in that direction: Catastrophe A  or Catastrophe B .   Third or fourth possibilities are not conceivable.  (Such is the effect of emotional bias on the intelligent mind - and there is no doubt that the author has an above-average I.Q. )

      Elsewhere, the author raises the flag of Chaos, and becomes almost mystical:   "[the AGW] that climate scientists think they are measuring is probably all just low frequency noise resulting from the random fluctuations of a chaotic non-linear system."    And more: "this is because the fluctuations are actually the result of dynamic effects that played out long ago but which are only now becoming visible."   (Not even the good Dr J. Curry rises to such elevation of the Butterfly Effect.)

      And more (after plotting certain noisy graphs) ~  With a grand sweep of a mathematical wand, the author abolishes the multi-millennial swing from glaciation to deglaciation; abolishes Milanovitch cycles; abolishes solar variability . . . CO2 variations . . . volcanic aerosols . . . etcetera.

      Apparently it is all a result of chaos mathematics and fractal geometry and self-similarity in nature.   By this time, the author has disappeared down a fractal rabbit hole, into his own microcosmic concepts.   He has failed to recognize that his ideas are unphysical.

      Moderator Response:

      [BL] Although I usually hesitate to step in as moderator when I am participating in a discussion, in this case I am also the author of the blog post and all this discussion of what someone may have on their own web site is really getting off topic.

      Please restrict your comments on CD's views of climate expressed on his own web site to the items that CD links to in support of his statements here.

      As for CD's response time - it's the holidays. Lighten up.

       

4675. Bob Loblaw at 07:54 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      I encountered the Manabe and Strickler/Wetherald papers as a grad student in the 1980s, when they were still fairly new.

      The Manabe and Wetherald paper is also part of The Warming Papers.

      I often find that older papers cover more of the basics than you find in newer papers. Newer papers do not repeat the well-established science, and often tend to assume certain knowledge on the part of the informed reader. This is also true of the IPCC reports - for the basics, I often suggest reading the first one from 1990.

4676. Charlie_Brown at 06:39 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      Bob @ 10, 14, 15

      Good posts.  Thanks for the references to Manabe.  Both of these articles and also Modtran are referenced in the justification and scientific background for the Nobel Prize in Physics 2021.  

      Sorry for the re-post to CD.  I am new to this site and fumbled the submit button.

      Moderator Response:

      [BL] I deleted the duplicate copy...

4677. Bob Loblaw at 04:23 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      As a further comment on upper atmosphere IR transfer, two of the early key papers in this field were:

      Manabe and Strickler, 1964

      Manabe and Wetherald, 1967

      A key finding of this work is stratospheric cooling in response to increased CO₂, shown clearly in figure 16 from the second paper.

      

      You will find many detailed explanations of this effect across the 'net, but one aspect of it is that adding CO₂ also increases the emissivity, which means you get greater IR emission at the same temperature. In the stratosphere, where IR is easily lost to space, this increase in emissivity means that the earth-atmosphere system can emit the same IR to space at a cooler temperature. In the stratosphere, the Plancks' Law emission response to increased CO₂ is stronger than the Beer-Lambert Law absorption response.

      Moderator Response:

      [BL] 2022-08-06 image link fixed

4678. Bob Loblaw at 04:10 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      charlie_brown @ 12:

      Your use of the phrase "saturation" (even though you put it in scare quotes) with respect to the broadening of the absorption wings, etc., is one of the few contexts where "saturation" makes sense.

      Most of the "arguments" made that claim the CO2 effect is "saturated" (as I linked to in the original post)  seem to look at the overall transmission after a long path length, and "saturated" does not make sense in that context.

      The question of the degree of resolution of spectral radiation calculations is a valid one. To run a GCM at many points and many time steps, you can't do a full high-resolution radiative transfer model. (Well, you couldn't 40 years ago. Computer horsepower is greater now - I'm not sure what is included in current GCMs.) You can, however, use a lower resolution model and test it against the high-resolution models to make sure it is getting the important bits right. Of course, the high-resolution models are ultimately validated against measurements.

4679. Charlie_Brown at 03:10 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      CD,

      While Beer’s Law is valid, using it to track the fate of radiant energy by wavelength leaving the surface is problematic. In the lower atmosphere, the 14-16 micron band reaches 100% absorptance within only about 100 meters. With re-emission, half up and half down, it doesn’t take many kilometers before the absorption band is depleted. However, radiant energy emitted from CO2 depends only its presence and its temperature. It does not depend on the path or number of absorption/re-emission exchanges. The temperature profile for radiant emission in the troposphere is determined by the lapse rate. Conduction between molecules keeps CO2 at the same temperature as the atmosphere.
      IR that makes its way back to the surface is not the way to determine the effect of a change in CO2 on surface temperature. The surface temperature results from the overall global energy balance. It is much easier to consider the radiant heat loss to space as it is the only output energy stream for the balance. In the range for CO2, the principles of Beer’s Law determine that the uppermost emitting layer for that range is in the tropopause and lower stratosphere, which is cold at 217 K. For the US Standard atmosphere, the tropopause lies between 10-20 km. The available path length is very long. At an altitude of 20 km, the pressure is about 5% of 1 atmosphere, so 100% absorptance can be reached in about 2000 . Despite the low pressure, there are sufficient molecules in the path for CO2 to have a significant effect on radiant heat loss.

      As CO2 in the cold tropopause increases, the absorption lines extend and the absorption band widens, reducing the heat loss to space. To return the energy balance to steady state, the reduced heat loss must be compensated by increased energy radiating through transparent wavelengths. This can only be accomplished by increasing the temperature of the source, which is the Earth’s surface. The effect on the IR spectrum of the Earth-atmosphere system as viewed from space will be a decrease of energy flux in the wavelength bands that are absorbed by GHG and an increase of flux through wavelengths that are transparent to IR. This effect is described in detail Brindley, H. E., and R. J. Bantges, “The Spectral Signature of Recent Climate Change,” Current Climate Change Reports, 2 (3), pp. 112–126 (Sept. 2016).

4680. Charlie_Brown at 03:09 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      Bob @ #7

      Thank you for providing the graph for HITRAN data. The point that I wanted to make is that increasing CO2 increases the individual high resolution absorption lines in the wings. That is why the effect of CO2 is not “saturated,” but is diminishing with increasing CO2. Moderate transmission programs use algorithms to simplify the detailed line-by-line calculations into an absorption band. Essentially, it is an approach to average the lines within an absorption band, which makes the calculations easier. With this approach, increasing CO2 increases the width of the band, effectively by increasing the inclusion of small lines at the end of the wings.

      I have used the version of MODTRAN hosted by the University of Chicago quite a bit, and I find it to be an excellent tool for understanding atmospheric radiation. It is similar to the free demo version from Spectral Sciences, Inc  Fortunately, it makes all of the calculations, including Beer’s Law, molar density, temperature, pressure, etc., for you. There is no need to do a lot of math on your own. It is easy to run several cases and plot the Upward IR Heat Flux as a function of increasing CO2. The upward IR heat flux is the energy lost to space. It becomes apparent that the diminishing effect is logarithmic. Because it is an atmospheric radiation model and not an energy balance model, it is a little bit trickier to resolve the overall heat balance to determine the effect on surface temperature, but it can be done. The surface temperature is an input with a default value of 299.7 K for a tropical atmospheric profile and 288.2K for the 1976 U.S Std atmosphere. One can adjust the surface temperature manually, then use trial-and-error to find a surface temperature that causes the overall global energy balance to be closed. This means the upward IR heat flux needs to be constant, since the only other factor in the balance is solar energy in. The logarithmic diminishing effect of increasing CO2 is the same.

4681. Bob Loblaw at 02:26 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      Eclectic:

      I think that CD = Climate Detective, so you may have a tough ride ahead trying to convince CD that something on his web site is not worth linking to.

4682. Bob Loblaw at 02:25 AM on 2 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      CD @ 8:

      Well, on your own web site, equation 88.1 is stated to describe the situation when the atmosphere is in "thermal equilibrium".  (I assume you mean that temperature is not changing with time, rather than the atmosphere is isothermal.)  You also claim that this implies an equality between absorbed radiation and emitted radiation. You are wrong, in more ways than one.

      1. Conservation of energy applies to all forms of energy. Much of the energy in the atmosphere comes from thermal transfer between the surface (hot) and the air (cooler), and this energy flux extends throughout the troposphere. Additional energy is moved from the surface to the atmosphere as latent heat (evaporation at the surface, condensation in the atmosphere). This is not a "secondary issue".
      2. The atmosphere is also absorbing some solar radiation, but it is not emitting any radiation at all at those wavelengths. That energy needs to be dissipated  by other means - either moved away from where it was absorbed by convection, or emitted as IR radiation at completely different wavelengths. There is no equality between absorbed solar and emitted solar - at any height.
      3. All radiation energy absorbed in the atmosphere will be shared with all gases at that height (both GH and non-GH gases) by molecular collision. The emission at that height is not dictated by the absorption, but by Planck's Law, which includes temperature and emissivity. Since temperature is affected by all energy fluxes, not just radiation, you cannot assume that other energy fluxes are "secondary" or that radiation absorbed = radiation emitted.
      4. "Conservation of energy" applies to the total of all gases. Since all gases share thermal energy through collisions, the emission of IR radiation by any single GH gas requires that the temperature of that gas be determined in combination with all other gases. The emitted IR at any height will be the sum of the Planck's Law emissions for all individual gases, and this process does not at all resemble "scattering" or "transmission".
      5. The absorption of IR radiation at any height is a combination of the absorption of upwelling IR and the absorption of downwelling IR. In an atmosphere with a temperature gradient these will not be equal - in the tropsphere, where temperature decreases with height, upwelling IR is larger than downwelling. The emission will be equal up and down, though, so we immediately see that treating the change in IR radiation as a "transmission/scattering" issue leads to the absurd result that your "scattering" process leads to a case where "scattering" causes more downward IR than is received.

      Look at the graphs provided by the MODTRAN web site I mentioned previously. It defaults to "looking down" - i.e., upwelling IR. Choose altitudes of 2, 5, 10 km etc and see how the IR flux decreases as height increases.

      Now, repeat with the "looking up" option (downwelling IR). See how the fluxes increase as altitude decreases - i.e., as the IR radiation continues in the downward direction, more and more IR radiation is added to the stream. You cannot interpret this as "scattering with transmission <1". If your theory of the mathematics is correct, this increasing IR radiation requires a transmission coefficient that exceeds 1.

      Your mathematics are not correct. They assume things that are not true (absorption = emission, non-radiative energy fluxes are not important).

      If you follow the link to Schwarzschild’s equation, you will see that it has independent terms for absoprtion and emission - terms that cover the Beer-Lambert absorption and the Planck emission. This is the correct way to do it.

      You started your comments here with the statement that the Beer-Lambert Law does not apply. The argument that you have presented appears to implicitly suggest that Planck's Law also does not apply. You have invented your own theory of radiation transfer, and it has some serious problems.

4683. Eclectic at 12:51 PM on 1 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      CD @ #8 and prior :

      Best if you avoid the blogsite you have linked to [ClimateScienceInvestigations blogspot by "Climate Detective"].

      It is one of those sad blogsites where much is correct, but much is wrong.

      Rather like the famous "Curate's Egg"  ~  where parts of it are quite good, but parts of the egg are rotten.

      The "good" parts can never compensate for the bad parts.

4684. CD at 07:54 AM on 1 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      @6 Bob Loblaw

      Ok, perhaps saying the Beer-Lambert Law was not applicable was a bit strong. But my point is that relying on it, and it alone, gives the wrong answer for the amount of radiation that is transmitted through the gas. More importantly it underestimates the transmission for large thicknesses of gas as my original comment (@5) states, and so underestimates the impact of any large increases in the CO₂ concentration.

      As for the idea that my "concept of transmission" leads to a transmissivity > 1, the equations 88.8 and 88.14 set out here clear demonstrate otherwise. It is also true from the equations set out in the link that the reflected radiation flux I_d is always less than that upward IR flux I_u at all altitudes x.

      Finally, before claiming that energy transfers from CO₂ to non-GHG molecules (and back again) invalidate my analysis, I suggest you look again at the principle of detailed balance. In thermal equilibrium, what goes in must come out, otherwise you start to violate the 1st & 2nd laws of thermodynamics. Yes there are complicating factors such as convection and direct heating of the atmosphere from the Sun, but these are secondary issues.

      I am aware that the atmosphere is a complicated body, but that does not mean it cannot be largely understood by considering idealized models in the first instance. That is how modellers approach the problem. The Beer-Lambert Law is one such idealized model.

4685. Bob Loblaw at 06:55 AM on 1 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      charlie_brown:

      The image from figure 1 of the SpectralCalc document you link to would be this one:

      

       

      This diagram clearly shows the high level of variation with wavelength. Radiation transfer codes vary in their spectral resolution. You mention HITRAN. There is also a web site here that lets you work with an older lower-resolution model: MODTRAN. You can select different temperature profiles, change gas concentrations, cloud cover, etc., and choose looking up or down at selected altitudes.

      All of the equations discussed - Beer-Lambert Law, Schwarzschild equation, etc. - are most properly applied to spectral radiation where properties such as absorption coefficients are highly variable with wavelength. For solids and liquids, some ranges of wavelengths can be treated as having proprties that are fairly constant. That is a Bad Idea (tm) for gases though.

      The "cylinders" in the blog post diagrams and discussion are theoretical ones: the walls are perfectly transparent and do nothing to impede any sort of energy transfer. In the real world, the equations are differential ones. Keeping things simple usualy means not doing Calculus, though.

      Introductory meteorology courses love talking about "parcels of air" (e.g. for explaining atmospheric instability), but of course the atmosphere is made up of continuous flows of air, not small balloons of air. Likewise, radiation does not work with distinct cylinders of air, but with air as a continuous medium. Your "shells" are an infinite number of identical stacks of columns, side by side.

4686. Bob Loblaw at 06:14 AM on 1 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      CD:

      You are making some pretty strong assertions for someone that has clearly not read the entire post and comments in detail.

      As is stated at the end of the original post, "For IR radiation, the earth and atmosphere are also doing the reverse of absorption – thermal energy is being transformed into photons, resulting in the emission of IR radiation in all directions." This is also discussed in more detail in the comments by charlie_brown and myself. You are not introducing any concept that has not already been mentioned. The post acknowledges that there are additional concepts that are needed for the full picture.

      It may be a matter of semantics, but you are wrong in saying that the Beer-Lambert Law "is not applicable here". It is only part of the story, but is is clearly applicable to the absorption part of the story.

      Where you go wrong is in claiming that the process of re-emission "looks like scattering". It most certainly does not. Scattering results in changing the direction of travel of radiation - but the radiation is still the same wavelength as the incident radiation, and each photon carries the same energy it had before it was scattered. You cannot create new radiation travelling in a new direction at a new wavelength through scattering, and scattering will not create new radiative energy. Emission does create new radiation.

      For absorption/re-emission, the emitted IR radiation will not necessarily be at the same wavelength as any radiation what was absorbed. The absorbed radiation energy  is not immediately emitted as new IR radiation - it virtually always gets lost by the GHG molecule to other molecules (including non-GHG ones). There is a good description of this over at Eli's. The energy that appears as emitted IR radiation does not need to come from the absorption of radiation - it almost always comes from collisions with other molecules that can get their energy from anywhere.

      As a result, any emitted IR radiation is dependent on two factors:

      1. The number of all GHG molecules present that can pick up thermal energy through collisions with other molecules. The emitted IR radiation may not be coming from CO₂, and its wavelength will depend on the emission spectra of that other GHG molecule.
      2. The temperature of the surrounding air. This controls the overall availability of thermal energy to drive IR emission. If the atmosphere is very cold, IR emissions will be less than if the air is very warm.

      As mentioned in comment #2, Schwarzschild’s equation covers the case where an atmosphere is both absorbing and re-emitting, and the net change in IR radiation with height is dependent on the temperature gradient.

      One thing you have correct: IR radiation is equal in all directions, and in this sense it resembles scattered light (which occurs in all directions, but is not exacly equal in all directions), but that is the only similarity.

      A key aspect of the dependence of net IR radiation on the temperature gradient is that upward IR fluxes normally decrease with increasing height, while downward IR fluxes normally increase as you go lower in the atmosphere. If we applied your concept of "transmission" to the downward flux, we would have transmissivity >1, This makes no sense.

      "Transmission" is not a useful concept when the air can create new IR radiation and add it to the stream. It is a concept that only applies to IR radiation that originates elsewhere and is passing through the air. And that is exacly what the Beer-Lambert Law describes.

      I have briefly looked at the URL you provided. It suffers from the same basic errors: confusing re-emission with scattering, and treating the addition of emitted IR to the upward stream as if it is a "transmission" question. It is not.

      Proper radiation transfer theory and the effects in the atmosphere take into account all energy fluxes, and properly account for the process of absorbing IR radiation, transforming it into thermal energy contained in all gases, possibly moving it through convection, and then re-emitting that energy as IR radiation (by all GH gases).

4687. CD at 02:10 AM on 1 January 2022
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      An interesting article, but I have to disagree with the main point: The Beer-Lambert law is not applicable here.

      The Beer-Lambert law applies to attenuation or absorption. But in the case of the interaction of IR radiation with CO₂ we also have re-emission. That, after all, is how we get downwelling radiation and hence the Greenhouse Effect.

      The principle of detailed balance dictates that in thermal equilibrium the re-emission must reverse the absorption process, so the combined process looks like scattering. And the maths of scattering is different to that of attenuation.

      The big difference is that the transmission coefficient is no longer exponentially dependent on layer thickness, x, as e^-kx, but instead has a reciprocal dependence of the form 1/(1+ax). For an explanation see here.

      The net result is that the transmission tends to zero much more slowly as x increases than it would with just attenuation. In practical terms it is a small point because the transmission is still less than 2%. But what it does mean is that the temperature rise with increasing CO₂ is greater (but still small).

4688. Charlie_Brown at 10:24 AM on 28 December 2021
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      The figure that I wanted to show is very similar to Figure 1 from this document from SpectralCalc.com Calculating Gas Spectra.
      The diminishing effect of increasing CO2 is due to the increasing absorptance (decreasing transmittance since a = 1 – t) of the absorption lines on the “wings” or “shoulders” of the spectrum between 14 to 16 microns (wavenumbers 625 to 714 cm-1). The major peak at 15 microns (668 cm-100) reaches an absorptance of 1.0 with increasing path length or increasing CO2 first, then the other peaks follow with further increases.

      The graph can be replicated or plotted for other concentrations and conditions using the Gas Cell Simulator in the free demo version of SpectralCalc.com. The gas cell is the same as the cylinder in the previous discussions, but as used for the graph, it illustrates the strength of each absorption line. The transmittance is different for each wavelength.  The free version is limited to wave numbers.  This is another way to interface with the HITRAN line-by-line database.

4689. Charlie_Brown at 04:36 AM on 28 December 2021
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      Bob, thank you for your prompt and detailed reply to my reply. I enjoy technical discussions on the details of the warming mechanism and find few willing to engage at this level. I also think that it is important to have a solid understanding of the concepts to counter claims made by deniers, which often are based on a kernel of truth with explanations that are badly distorted. The concepts are complex, but they can be simplified. One does not have to be a climate scientist expert, university professor, or math whiz to work through them. I am a retired chemical engineer who took some radiation heat transfer courses in college, and have developed most of my thinking about global warming over the last 2 years.

      Regarding measurements of attenuation by CO2 in a cylinder, the photons that are absorbed by a CO2 molecule are re-emitted, most likely toward the wall where they will be absorbed and converted to thermal energy. The energy will not be re-emitted from the walls at the same wavelength as emitted by CO2. It is unlikely that they will travel in a straight line and be measured at the end of the cylinder. Beer’s Law of attenuation describes the fate of the photons that are emitted from a source until they strike a target, not what happens with re-emitted photons. This is why I like to describe the atmosphere as layers of shells that have no sidewalls. Multiple stacked cylinders with adjacent, transparent walls is the same thing.

      Regarding re-emission, it took me a long time to think through the problem of attenuation of surface IR through layers of the atmosphere and trying to figure out how many layers it would take as half of absorbed/emitted energy does up and half goes down. Finally, I realized that it is unnecessary to start at the surface and think about re-emission, convection, conduction, evaporation and condensation. Global warming is the result of the overall system energy balance, which is simply:
      Solar energy in = IR emitted to space from the uppermost emitting layer for each IR wavelength + Accumulation
      In the 13-17 micron range, Beer’s Law explains that the uppermost emitting layer is the lower stratosphere for many wavelength peaks emitted by 400 ppm CO2. The uppermost emitting layer for other GHG depends on their molecular density. For water vapor, the uppermost emitting layer is the troposphere, where the temperature is warmer than the bottom of the stratosphere. At wavelengths transparent to GHG, the emitting surface is the earth’s surface. It doesn’t matter how many layers, or cylinders, of 1% or of 90% attenuation are stacked in the lower atmosphere. Again, radiant energy lost to space depends only on the uppermost emitting layer. Where there are CO2 molecules, photons will be emitted at an intensity related to the temperature. There does not need to be conservation of photons from those emitted from the surface. Any imbalance in the photon count will be manifested as thermal energy changes, including by conduction to adjacent non-GHG molecules.

      The link that you provided to Schwarzschild’s equation provides excellent descriptions of the essential role of the lapse rate, as well as attenuation. If I am not expressing my thoughts clearly enough, I recommend reading the sections on “Origins of the greenhouse effect,” “Saturation,” and “Applications to climate science” in that linked Wikipedia article.

4690. Bob Loblaw at 02:19 AM on 28 December 2021
      It's albedo
      

      blaisct @ 106:

      Although it has been almost two weeks since your post, and others have commented, I wish to respond to one statement you have in your opening paragraph. You state:

      My understanding has been expanded to include: AGHs hotter temperature will reduce humidity and thus reduce cloud cover, expose more earth surface to the sun thus reduce earths albedo; therefor, albedo vs time for AGHs may not be flat.

      The "hotter temperatures will reduce humidity" does not follow. If air temperature increases and absolute humidity does not change, then yes, relative humidity will decrease, but we have no a priori reason to expect this to be the case.

      I suggest that you review the use of differnt terms for "humidity", which can get quite confusing at times. Wikipedia has a decent page covering this.

      A warmer atmosphere is expected to increase evaporation, which will add water vapour to the atmosphere. This cannot go on indefinitely, and globally we expect a new equilibriium where increased evaporation is matched by increased precipitation. At this new equilibrium, we expect global absolute humidity to be higher, and global relative humidity to be roughly the same as now.

      Spatial variation will almost certainly be different, and exactly how cloud cover will respond has uncertainties, but it is not as simple as you describe.

      Usually, the incorrect assumption you will see in the comments here goes along the lines of "more evaporation = more cloud". This is also far too simplistic. The balance between temprature, evaporation, cloud formation, and precipitation is a complex and delicate one.

4691. Bob Loblaw at 01:57 AM on 28 December 2021
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      Charlie Brown:

      Yes, your discussion touches on some of “the complexity of radiation transfer in the atmosphere” that I dismissed in a single paragraph at the end of the blog post. The blog post was only intended as a counter to the “CO₂ exists in small concentrations” misinterpretation of the Beer-Lambert law, and leaves a whole host of other fundamental principles in atmospheric radiation transfer to the imagination of the reader.

      You refer to several issues that deserve more discussion – issues that take entire university courses or textbooks to cover. You mention at least four specifics I’d like to elaborate on:

      • re-emission of IR radiation
      • the three-dimensional aspect of the atmosphere
      • the vertical structure of the atmosphere
      • the concept of “saturation”

       

      With regard to re-emission, the amount of IR radiation leaving the cylinder is the sum of what was transmitted through the cylinder plus the amount that was emitted within the cylinder (and manages to leave before being re-absorbed within the cylinder). With regard to the emitted IR:

      • Any CO₂ that absorbs energy will lose it by collision with other molecules, so chances are that it will be a different gas that is emitting, which means it might be at a different wavelength. Thus, to look at the whole situation we need to consider all the greenhouse gases in combination.
      • The emissions of IR radiation will depend on the temperature of the gases within the cylinder, which will depend on the balance of all energy fluxes, not just radiation.
      • Just as adding CO₂ increases the absorbance within the cylinder, adding CO₂ increases the overall emissivity within the cylinder, so more IR can be emitted at the same temperature.
      • The emission of IR happens in all directions, as you state, which means that only half of the emitted radiation can be said to be continuing in the same direction as any IR radiation that entered the cylinder (figure 4).

       

      You mention IR lost through the side walls of the cylinder. There is also IR gained through the side walls, coming from adjacent cylinders that are behaving the same way as the one in figure 4. If the adjacent cylinders are identical, then each cylinder will be gaining and losing identical IR radiation amounts through the sides, so the net effect is zero.

      Can we say the same things about the IR transfers between cylinders in the vertical stack of cylinders (figure 4b)? No, and there is a very important reason why. The net effect between adjacent cylinders (side by side, or top over bottom) depends on the temperature within each. If the temperatures are equal, the net IR transfer effect will be zero – but if they are not equal, there will be a net transfer from the warmer one to the cooler one. In the horizontal direction, temperature gradients are very small, so it is reasonable to ignore that direction. Vertically ,however, we see strong temperature gradients – the environmental lapse rate averages 6.5 C°/km. So, the top cylinder tends to be colder than the bottom cylinder, and the net IR transfer is upward.

      So, we get to think in terms of up/down fluxes of IR radiation, and need to consider the thermal stratification of the atmosphere, as you mention. The up/down aspect has a formal label: the two-stream approximation. The extension of the use of the Beer-Lambert Law to include the emissions of IR radiation and the net IR flux along a temperature gradient also has formal solutions, one of which is called Schwarzschild’s equation.

      Of course, the vertical temperature structure of the atmosphere is not purely due to radiation, so we can’t model it purely using radiation theory. Weather and climate models need to include convection, etc. - anything that transfers energy.

      We also can’t leave the 3-d atmosphere discussion without mentioning clouds. Although gases in the atmosphere have absorption/emission characteristics that are highly dependent on wavelength, clouds (either as liquid or solid/ice) are essentially black bodies. In the same way that the two-stream approximation treats radiation transfer as either up or down, we can begin to cover cloud effects by dividing the atmosphere into a clear sky portion and a cloudy portion. Clouds have layers, too, and three-dimensional characteristics of clouds become quite complex, but the clear/cloudy categorization is place to start.

      Lastly, you discuss saturation. I tend to dislike the use of that term, because it seems to mean so many different things to different people. One of the issues not mentioned in the blog post is pressure broadening, where overall increases in atmospheric pressure reduce the absorbance coefficient of the greenhouse gases such as CO₂. This leads to a “law of diminishing returns” as CO₂ concentrations increase, but we are far from running out of space on that one.

      You use “saturation” in the context of IR radiation leaving the surface and escaping to space – and point out that nearly all the IR escaping to space is lost from the upper atmosphere. This is correct, and one way of looking at this is to ask “how many times will IR emitted from the surface be absorbed and re-emitted before the energy reaches the upper atmosphere and can finally be lost to space?” Even now, the probability that surface-emitted IR escapes directly to space is very small – but if adding CO₂ increases the number of absorb/re-emit cycles from two to four, to eight to sixteen, etc., there is a reduction in the efficiency of transfer of energy from the surface to space.

      For each absorb/emit cycle, only half gets emitted upwards. The half that emits downwards must go through at least one more absorb/emit cycle to get moving upwards again – and it only has a 50% chance that the next absorb/emit cycle will get it going in that direction. If it emits downward again, then it needs another absorb/emit cycle – with only a 50% chance again that it will emit in the upward direction. Adding more and more CO2 will always increase the number of absorb/emit cycles involved, but there is a law of diminishing returns here, too, which leads to the closing paragraph of yours where doubling CO₂ from 200 to 400, or 400 to 800 ppm will have the same warming effect. Remember that convection is involved in that warming response, too – as radiation transfer becomes less efficient, convection takes a more dominant role (and it is already important).

4692. MA Rodger at 22:49 PM on 27 December 2021
      Was Greenland really green in the past?
      

      dpc @33,

      The original name for Greenland was Inuit Nunaat meaning 'country of human beings'. So perhaps there was once a burgeoning population living there. Or perhaps such names are poor descriptors which would be why, apparently, "people often say that Iceland and Greenland should switch names since Iceland is green and Greenland is so icy."

4693. dpc21240 at 16:56 PM on 27 December 2021
      Was Greenland really green in the past?
      

      I was just looking around for some discussion around the topic of origin of the name Greenland and it's striking to me that people uncritically use the

       

      "Because," said he, "men will desire much the more to go there if the land has a good name."

       

      as any argument. It's a huge jump to conclusions.

       

      If a company releases a product named "ecofleebus" trying to market it as a very ecological fleebus how can one hop to conclusion that this fleebus has no ecological design aspects to it at all? Quite the opposite - for marketing to work, it has to be very believable. Marketing is more about exagerating, over-selling, etc. and rarely about calling black color white.

       

      Men will desire to go somewhere if it has an appealing name. No duh. Doesn't mean such appealing name is complete lie.

       

      So while it's still a huge guesswork, I think it's far more likely to assume that Greenland was "green enough" to try to "(over-)sell it".

4694. Charlie_Brown at 11:07 AM on 27 December 2021
      From the eMail Bag: the Beer-Lambert Law and CO2 Concentrations
      

      This is an excellent description of Beer’s Law. The distinction between concentration (ppm or molecules per million molecules) and molar density (molecules per cubic meter) is very good. However, the described application to the atmosphere has a few shortcomings that leave an incomplete description of the effect of saturation. The description does not account for re-emission, nor the multiple absorption lines for CO2 of different intensities. It also does not describe the role of temperature stratification in the atmosphere.  The conclusion does allude to some of these issues.

      Rather than as cylinders, the atmosphere is better described as layers of shells. One problem with the description lies in the third path for the fate of radiation in a cylinder (Quantity C): “3. Be absorbed, through interactions with the mass inside the cylinder, so that the energy in the photons is transformed from radiation energy into thermal energy. The radiation ‘is no more’ (although the energy is conserved as heat).” However, as energy absorbed by a molecule, it is re-emitted to maintain thermal equilibrium. Re-emitted energy occurs in all directions, not just in a straight line. Therefore, re-emitted energy is lost to the walls of the cylinder. Meanwhile, in the atmosphere, there are no walls and re-emitted energy is absorbed and re-emitted again elsewhere in the atmosphere. In this manner, there are multiple absorptions and re-emissions in a convoluted path with some net energy flowing upward and some downward.

      The key concept behind saturation lies in the different absorptances for each IR wavelength. Saturation occurs when the absorptance equals 1.0. The major peak at 14.98 microns is saturated first, then smaller peaks become saturated as CO2 increases. I wish that I could insert a graphic, but I haven’t figured out how to do it yet. Absorption lines can be seen using bytran, which is an open-source interface under the MIT License for the HITRAN database (Pliutau, D. and K. Roslyakov, “Bytran -|- spectral calculations for portable devices using the HITRAN database,” Earth Science Informatics, 10 (3), pp. 395-404. Feb 2017.)

      Beer’s Law as related to the atmosphere comes into play with determining the uppermost layer that limits the escape of radiant energy to space through the 13 to 17 micron window for CO2 absorption/emission of IR. This layer turns out to be the bottom of the stratosphere at an altitude of about 30 km, just above the tropopause. At this altitude and considering a path length of 1000 meters, which is a reasonable distance in the atmosphere, there are still sufficient CO2 molecules to form an emission layer for CO2. It is a little harder to see the difference in the absorption lines at 400 and 800 ppm under these conditions, but this explains the diminishing effect of saturation.

      It is common to think of radiant energy leaving the surface and trying to explain what happens as it works its way through the atmosphere. However, it is instructive to focus on the radiant energy exiting the top of the atmosphere rather than the energy leaving the surface. The lower stratosphere is the uppermost CO2 layer with sufficient molecules for an emittance of 1.0. Since absorptance equals emittance, this is the maximum emittance for that wavelength. This layer of the atmosphere is cold, so the radiance, total emitted energy, from this layer is less than the radiance emitted from the warmer surface. As the uppermost emitting layer, it becomes the limiting layer for radiant energy loss to space.

      There is a saturation effect, but it is better illustrated using an atmospheric radiation model than using Beer’s Law with a number of cylinders. Using a simplified model, it can be illustrated that increased radiant IR energy flux lost to space from doubling CO2 from 200 ppm to 400 ppm is the same as doubling CO2 from 400 ppm to 800 ppm. This forms a logarithmic curve. The warming effect due to CO2 is saturating, but it is not saturated.

      Moderator Response:

      [BL] Regular commenters here cannot directly embed images from their local computers within the code/comments that are stored on the web site's servers. Images have to be stored on some other publicly-accessible server, and then you can link to them.

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4695. Cedders at 05:43 AM on 27 December 2021
      Medieval Warm Period was warmer
      

      Thanks to Daniel Bailey for the useful update links. I wonder if these could be incorporated into the rebuttal?

      Link rot means PAGES 2K work is now best found at  https://pastglobalchanges.org

4696. Cedders at 05:35 AM on 27 December 2021
      Major PAGES 2k Network Paper Confirms the Hockey Stick
      

      A bit more link rot.  The PAGES pages disappeared from UniBe within the past year.  They can now be found at for example https://pastglobalchanges.org/about

      Also wonder if worth cross-referencing to more recent PAGES 2k work, eg Neukom et al (2019), 'No evidence for globally coherent warm and cold periods over the preindustrial Common Era', https://doi.org/10.1038/s41586-019-1401-2

4697. Anoo at 05:00 AM on 27 December 2021
      CO2 measurements are suspect
      

      Came across this post today after looking at some statistics that got stuck in my head.

      Today the total landmass area of the world is 149 million sq km.

      The total forested area of the world in 2016 was 30.7 million sq km, down from 49.8 in 1996.

      Up to at least 2013 science had stated that the Amazon rainforest, at 5.5 million sq km, the Canadian Boreal Forest, at 2.7 million sq km, and the Congolese rainforest, at 1.7 million sq km, along with the rest of the boreal zone, were all CO2 sinks. In total it comes up to over 20 million sq km, out of a total of 30.7 million.

      Now I am reading that all of these are net CO2 emitters. So up until 2013 they were sucking in CO2, now they are pumping out CO2. 

      Here's my question for all of you: Why isn't the CO2 level rising exponentially? If these combined forests were sequestering more than they were producing, but are now not able to sequester as much CO2 as they produce, this means that since 2013, with deforestation, and a loss of carbon sinks, we should have had at least a doubling of CO2, should we not have? Yet, when I look at the numbers, it would seem that the CO2 level increases are actually slowing, while emissions are increasing.

4698. sekwisniewski at 04:59 AM on 27 December 2021
      Is Nuclear Energy the Answer?
      

      The following paper provides a comprehensive assessment of the environmental footprint of the French nuclear power generation around 2010. Specifically, it compares the material throughput of once-through (UOX) and twice-through (UOX+MOX) fuel supplies. For example, it finds that both fuel supplies generate around 1.5 m³/TWh_e of HLW+ILW-LL that requires geologic disposal, but twice-through requires 3.5 times less geologic storage volume due to a smaller proportion of HLW/ILW-LL. In terms of emissions there is almost no difference - 5.29 vs 5.45 gCO₂eq/kWh_e for twice-through and once-through, respectively. (If I’m not mistaken, this paper hasn’t appeared in this long discussion yet.)

      Poinssot, Ch, et al. "Assessment of the environmental footprint of nuclear energy systems. Comparison between closed and open fuel cycles." Energy 69 (2014): 199-211.

      

      

      

4699. Mick James at 09:59 AM on 26 December 2021
      Thanksgiving advice, 2021: How to deal with climate change-denying Uncle Pete
      

      The Pentagon predictions weren't wrong: they were about what might happen were an abrupt climate change to occur (as happened 8000 years ago) rather than the gradual change currently observed and predicted.  They didn't suggest such an event was likely or imminent.  The report should be read in the same light as one outlining the consequences of, say, a nuclear war between Russia and China in 2004. 

4700. djinghis at 11:05 AM on 23 December 2021
      Why Senator Manchin Should Support Build Back Better
      

      This article is treating Manchin as though he deserves any respect even though he's obviously acting in self interest. Simply analysing his voting record on environment, and military spending should give us a clue. Re-re-re-negotiating on an already watered down bill was his plan all along – delay/obstruct and kill the bill.

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