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2351. piotr at 04:23 AM on 10 May 2023
      CO2 is not the only driver of climate
      

      Let me just say thanks a lot at first for your effort to explain. Give me some time to respond. Its very pleasend not to get downed with dumb comments and instead get lot of effort.

2352. Charlie_Brown at 01:46 AM on 10 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Thank you, Philippe.

      I want to make two edits to emphasize a key point about the external energy of the sun and to clarify G&T's assumption about being radiatively balanced.  Try this.

      Insert after “… requires adding external energy, electricity, to make it work. The sun is the external source of energy to increase or to maintain the Earth’s temperature given the external energy loss to cold outer space. There is no violation of the 2nd law.”

      Replace: “… incorrect description of global warming. They assume that the radiant energy input from the sun is equal to the radiant heat loss to space and the system is “radiatively balanced”. That would be true for the greenhouse effect before the industrial revolution but increasing greenhouse gases (GHG) upsets the balance and causes global warming..”

      With: “... incorrect description of global warming as well as the Earth as a cyclic device in perpetuum. They ignore the energy flows from external hot reservoir of the sun and to the cold reservoir of space by stating that the heat transfer between the Earth’s surface and the stratosphere is “radiatively balanced.”"

2353. Philippe Chantreau at 01:01 AM on 10 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      It is getting better. That latest one is pretty good, especially the analysis of G&T's trick, which is nothing more than a sophisticated straw man.

2354. Eclectic at 09:13 AM on 9 May 2023
      CO2 is not the only driver of climate
      

      Piotr @73 ,

      another puzzle is your comment about "thousand parameters" [unquote] which you mention in your third paragraph.   I would very much care to learn what these parameters  are.   (Personally, I would struggle to nominate more than a dozen relevant parameters.)

      Are you repeating the words of some non-scientist . . . or are you being very loose with your language ?   It is desirable to be accurate & precise - not loose & hyperbolical - when discussing climate.  Otherwise, you are wasting your time and are confusing yourself.

2355. Bob Loblaw at 08:12 AM on 9 May 2023
      CO2 is not the only driver of climate
      

      Another source of temperature reconstructions is the IPCC sixth assessment report. The following figure is from the Summary For Policy Makers. Full scale image is available at this link. The grey shading represents the uncertainty. Nothing even comes close to piotr's claim of a "decrease up to 1.5°C".

      

2356. Bob Loblaw at 07:54 AM on 9 May 2023
      CO2 is not the only driver of climate
      

      piotr @ 73:

      I am not sure what your "not directly" statement refers to. I presume that the Martin Mlynczak quote is the one in comment 69. To put it simply, the thermosphere and the earth's surface respond to solar radiation in very different ways. You can read about the thermosphere on Wikipedia. Note that the thermosphere is at very high altitudes (>80km), and its temperature structure is the result of the absorption of UV radiation. It also has very low density, so even though average kinetic energy is high ("temperature") it does not hold a lot of heat. It is not strongly linked to the surface, which is heated by the absorption of solar radiation over the full spectrum.

      This paper by Lean, Beer, and Bradley (1995) shows in figure 2 that variations in total solar irradiance are much less than for the UV range (in %).

      

      To use the 4W/m² drop in that figure, you need to first reduce it by a factor of 4 (area of a sphere vs. area of a circle), and then adjust for global albedo (0.3), giving an overall forcing of only about 0.7 W/m². Sustained over only a period of about 50 years, this is not going to have a major cooling effect on its own.

      You say that "it noticeabl[y]e cooled large parts of the no[r]thern hemisphere", which I presume is a claim with respect to surface temperature responding to these solar variations. You then throw in volcanic effects. You seem to grossly overestimate those solar effects, though - with no references to any supporting information. If you look at this SkS post, the first figure shows that reconstructed global temperatures for that period are much smaller than your claimed "decrease up to 1.5°C".

      

       

      In your second paragraph, you start talking about "The past 10.000 years where up and downs in global mean temperature like +/- 2°C for dozen decades, even for nearly 2000 years - as we can reconstruct with little data-points." This starts to wander into the last glacial period, where Milankovitch cycles start to play a role. You are mixing together a lot of different forcing mechanisms, as if they are all equivalent in some fashion.

      You then start into urban heat island effects, and finish off with a couple of paragraphs that represent an argument from incredulity. If you actually want to learn something about temperature reconstructions from proxies, Wikipedia has a decent article on this, too. The Wikipedia page also has a graph that shows even less variation in temperature than the one above:

      

       

      The numbers you are throwing around in your "just imagine" scenarios seem to be ones that you have a lot of confidence in. The problem is that they also appear to disagree with broad swaths of the scientific literature. You appear to be claiming that science is unsure of what happened in the past - but you are. It seems highly unlikely that you are correct.

      If you want to have any credibility here, you are going to have to provide references to the numbers you post. This is not a site where you will be permitted to post a lot of unsubstantiated opinion. As you are a new user here, I strongly suggest that you read the Comments Policy.

2357. nigelj at 06:14 AM on 9 May 2023
      Climate communications: Laura Helmuth and Susan Hassol talk about language
      

      I accept the terms climate change and global warming were always both used in the scientific literature. However this discussion page is about popular use of terms.  In New Zealand the media used the word global warming for some years after the climate problem became known, and  then the term climate change became the dominant  term used. My understanding is its the same in other countries.

2358. Eclectic at 05:51 AM on 9 May 2023
      CO2 is not the only driver of climate
      

      Piotr @73 ,

      Wind & ocean currents move heat energy around the planet - and so there is a considerable "averaging" effect on global temperatures.  Even today, you do not need thousands of observation stations in order to assess changes in global temperature.  Analysis shows that less than 100 stations are needed (if well-distributed, of course) to give a closely accurate picture of conditions.

      A so-called Grand Solar Minimum is not actually very grand ~ studies such as Feulner & Rahmstorf, 2010  and Anet et al., 2013  indicate that a GSM produces a global cooling of around 0.3 degreesC.  (Other studies indicate slightly smaller changes.)    And this is because our Sun is a very stable star, with a very stable output of radiation.   Very little variation.

      Even the Little Ice Age was not spectacularly cold  ~  a global cooling around 0.5 degreesC   . . . which had been helped along by a number of cold winters from volcanic eruptions.

      There have been periods of decades of marked cooling in the neighborhood of Greenland earlier in the Holocene, as a result in temporary changes in ocean currents.   But these had little effect on average global temperature (the planet is big, and there is a vast amount of tropical ocean).   The one exception is the millennium of strong cooling (the "Younger Dryas" ) about 12,000 years ago  ~ and this was a one-off event produced by the single event of melt/discharge of the Laurentide Ice Sheet situated in Canada.

      Piotr, you seem to have a wrong idea about earlier warm periods (of the Holocene) such as the so-called Minoan / Roman / Medieval Warm Period  ~ these were only very slight changes, around 0.3 degreesC or smaller.  These were only tiny "blips" on the general slow cooling from the Holocene Maximum temperature (slow cooling owing to the Milankovitch Cycle).

      Possibly you have been misled by reports based on Arctic region temperature estimates (the Arctic shows bigger swings than the average global temperature).

2359. Charlie_Brown at 03:30 AM on 9 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      My next attempt.  I hope this is getting better.  I changed the first part quite a bit to emphasize that the key problem with G&T, often overlooked, is their assumption that the input solar and output IR radiation are balanced (see Fig 32).  I think these are worthwhile revisions.  The structure seems fact-myth-fallacy-fact because I wanted to begin by separating the 1st & 2nd laws, but bring back the 1st law facts to seal the deal.  Please feel free to edit and use the input as you deem suitable.

       

      The 1st law of thermodynamics is conservation of energy. The 2nd law describes limitations on how energy can be used in forms of heat and work. It is difficult to express without introducing the concept of entropy - a state of disorder that is hard to understand. Instead, the 2nd law can be expressed practically in the form of statements and corollaries. One translation of the Clausius statement is: “It is impossible to operate a cyclic device in such a manner that the sole effect external to the device is the transfer of heat from one heat reservoir to another at a higher temperature” (Wark, Thermodynamics, 4th ed., 1983). A key phrase is “sole effect external to the device.” A cyclic device can be a heat engine and the classic example is a refrigerator that requires adding external energy, electricity, to make it work. Gerlich & Tscheuschner’s paper describes modern global warming theory as a perpetual heat engine that transfers heat from the cold stratosphere and the warm surface. That would violate the 2nd law, but that is an incorrect description of global warming. They assume that the radiant energy input from the sun is equal to the radiant heat loss to space and the system is “radiatively balanced”. That would be true for the greenhouse effect before the industrial revolution but increasing greenhouse gases (GHG) upsets the balance and causes global warming.
      Some take the myth even further to claim that thermal radiation cannot transfer energy from a cold body to a warmer one. Gerlich & Tscheuschner steer the discussion into distraction by emphasizing the technical distinction between heat and energy. Consider two walls facing each other. All objects above absolute zero radiate energy. The warm wall radiates more energy toward the cold wall, but the cold wall still radiates some energy toward the warm wall. The debate amounts to whether it is energy or heat that moves towards the warm wall.

      Conservation of energy for any defined system is:
      Input = Output + Accumulation
      The global system can be defined as from the Earth’s surface to the top of the atmosphere. The input to the global system is the sun. The surface temperature is regulated by balancing heat input from the sun with heat loss from the top of the atmosphere toward space. When balanced, accumulation is zero. There are three output energy pathways: 1) Infrared (IR) radiation from the surface at wavelengths that are transmitted directly to outer space (the transparent range). 2) IR radiation from GHG in the colder atmosphere at wavelengths that are emitted by GHG, and 3) solar energy reflected by clouds and the surface. As the concentration of CO2 increases, energy output to space (path 2) is reduced. This upsets the global energy balance. Energy accumulates and the surface temperature rises. As the surface temperature rises, energy output from the surface through the transparent range (path 1) increases until the balance is restored. This is how global warming works.

2360. piotr at 03:11 AM on 9 May 2023
      CO2 is not the only driver of climate
      

      @Bob Loblaw

      Not directly. I was just wondering on Nasa's Martin Mlynczak statement to Grand solar minimum "and will not cause noticeable cooling at the surface". Yeah, not globally, except the overall temperatures may decrease a bit in statistics too. But it noticeable cooled large parts of the nothern hemisphere, like big vulcanic eruptions can cause for few years and did in even the last 150 years too -> global mean temperatures decrease up to 1.5°C, besides some areals warmed then too.

      So what is Martin Mlynczak talking about? The past 10.000 years where up and downs in global mean temperature like +/- 2°C for dozen decades, even for nearly 2000 years - as we can reconstruct with little data-points.

      Overall my main questions is the concerning how plausible is the reconstruction of earthly temperatures over thousands of years just with indirect data besides modern technology with thousend parameters, stations around the globe and on every time (even in grown urban places, which totally heat up just being sealed ground and overcrowded for decades). modern observation for like 30 years am totally cool with, but the rest is a large extrapolation of indirect measurement and got "worse" at we strife further away in time.

      Just imagen if we would have high technology measurements like today in for example 6000 BC to 5500 BC, then we would see global warming for at least 0,5 - 0,8 °C over aproxx 1-200years similar like today and we knew that for some areas or changing habitats like sahara desert, but not excessive like modern data amount. btw. its also stated there were same co2 ppm levels as pre-industrial times.

      i think its "fascinating" to have data from million years ago, when no modern human lived and we think to "know" how life was back then, globally, just by knowing some single fragments and feeding supercomputers with, which try hart to simulate complex features like climate or even local weather to be back then. Im a big fan of astronomy since my child days and read about the fist extrasolar-findings back in the days. but thats much more extreme, as we can never proof for real, even if its pretty possible to conclude a habital place somewhere on a planet just by reconstruction of the atmosphere, despite being back in time maybe million years ago. its hilarious to say "we found a possible earthlike planet!".

2361. Bob Loblaw at 00:20 AM on 9 May 2023
      Climate communications: Laura Helmuth and Susan Hassol talk about language
      

      You can read more about the "they changed the name..." myth on this SkS page.

2362. John Mason at 00:00 AM on 9 May 2023
      Climate communications: Laura Helmuth and Susan Hassol talk about language
      

      I don't think it is accurate to state that "global warming became climate change" without noting that the two terms were used interchangeably over many years - for example the landmark Plass paper in 1955 was titled, "The Carbon Dioxide Theory of Climatic Change".

2363. nigelj at 18:04 PM on 8 May 2023
      Climate communications: Laura Helmuth and Susan Hassol talk about language
      

      Excellent video.

      I have an old  book titled "Asimovs Guide to Science" 1987 edition Penguin Books, 880 pages that cover every branch of science and in surprising detail for one volume. The man is a genius. Its all beautifully written in a public friendly style. The writting does have a lot of jargon but its explained and he just has this smooth easy to grasp style of writing, all beautifully well structured and organised and easy to follow.

      There are no equations in the main text but some apendicies at the back include some maths of the key issues. Once you put equations in the body of the text you pretty much alienate most of the general public and Asimov understood this. The more equations and maths the worse it gets. I recall a book publisher discussing the issue of equations and the dismal affect this has on sales of a book. Sadly to say, because an equation explains something that requires a lot of words to explain.

      However I have some reservations about the suggestions in the video on terminology:

      Global warming became climate change and the denialists used that to accuse scientists of changing the story for nefarious purposes. The denialists were wrong on every level but mud sticks. Now we hand them more ammunition by calling it "climate disruption: I really dislike changes in terminology unless its really necessary.

      Postive feedback is the scientific term. Yes it makes it sound like a good thing but is using different terminology like self reinforcing cycle  the right response to the problem? Why not just define postive feedback  in brackets as "a self reinforcing cycle that amplifies the warming process" (or whatever process is being discussed ). Generally I think definitions in brackets is best. It only needs to be done once in an article. If every science writer comes up with their own terms as substitutes for jargon, it will just confuse the public even more.

      Heat trapping pollution is not a great term. There was controversy about whether carbon dioxide is a pollutant as such, started of course by the denialists. There is a good argument that carbon dioxide is a pollutant but why hand the denialists ammunition? The public generally understand pollution to be something added to the atmosphere that directly affects health or degrades the environment and this is the typical dictionary definition. CO2 acts more indirectly.Heat trapping gases would be better terminology (the video did suggest that as another option).

      Perhaps these are nit picks. Clearly the writer is correct that the scientific jargon often creates the wrong impression with the public. But the simple answer is just define it in brackets in plain language where possible, or as a footnote, as opposed to dreaming up completely new terms and using those.

2364. Bob Loblaw at 11:20 AM on 8 May 2023
      CO2 is not the only driver of climate
      

      piotr @ 70:

      You ask what might have caused the Maunder Minimum. First, you should think about exactly what the Maunder Minimum was: a period of low sunspot numbers. Wikipedia has a good article, and they include this figure:

      

       

      Technically, "what caused the Maunder Minimum?" is a question of astrophysics, not climatology. But what you are probably wanting to ask is "what caused the xxxxx?, where xxxxx is something that you feel is correlated with the Maunder Minimum. Reduced solar irradiance? Lower temperatures? The Little Ice Age?

      So, this means that you are looking at something where the Maunder Minimum is an indirect/proxy indicator of some potential climate factor. You do realize that we do not have direct evidence that the Maunder Minimum caused a specific decrease in solar irradiance? You do realize that many of the observations indicating cooler temperatures - such as ice on the Thames -are local, and not global? The Little Ice Age appears to be related to a number of factors. You can read about it a bit more in this post.

      Understanding of past climates is based on things like vegetation, sediments, etc. A lot of those have automatic time-averaging (trees don't grow in a year) and spatial averaging (sediments and pollen  get carried in to lakes from large watersheds). The analysis of past climates includes a wide variety of proxy indicators. You can read more about it on this post.

      In short, you need to be more specific in explaining what you do understand, and what questions you have.

       

2365. Eclectic at 10:20 AM on 8 May 2023
      CO2 is not the only driver of climate
      

      Piotr @70 ,

      Think about it this way  ~  causes and effects.

      In this universe, if you see an effect, there must be a cause (and with enough study, you can find that cause - which may be a single cause, or a combination of causes).

      Past studies (by experts) have shown broad changes in climate - not measured in tenths of a degree as per modern thermometers, but in broad assessments of indirect indications of climate average temperatures / sea level changes / vegetation changes / and so on.  From this, it is evident that the climate changes when there is a causative change (a change in solar output, or in atmospheric CO2 levels, or in reflective "albedo" from global ice coverage, or in stratospheric aerosol particles from major volcanic eruptions).

      All these jig-saw pieces fit together nicely, to give the scientists (and us) a good understanding of how climate "works".

      Beware of non-scientists who say that "stuff just happens"  [excuse the American expression].   They seem to wish to believe that the past century or two of very rapid global warming is somehow not caused by the obvious causes.  And that it came for no identifiable reason.  They seem to wish to believe that the modern warming "just happened for no cause"  (sometimes expressed in the meaningless phrase "it is just a rebound from the Little Ice Age").

      (The Little Ice Age had its own causes - frequent major volcanism plus episodes of reduction in solar output.)

      Or they say that the modern rapid warming must instead be caused by "long-term changes/oscillations in ocean currents" ~ which actually does not make scientific sense (if they bothered to think it through).

      Piotr, there are definitely some people who do not wish to think.

2366. piotr at 06:09 AM on 8 May 2023
      CO2 is not the only driver of climate
      

      Greetings. @Daniel Bailey

      ""Observations have shown that solar flare activity on the surface of the Sun is in the quiet phase of its continuing 11-year cycle. This causes cooling of the thermosphere—a layer of the atmosphere that starts 65 miles above the surface—and will not cause noticeable cooling at the surface""

      - so how could happen the Maunder Minimum, when the baltic sea and the thames were frozen then?

      Btw. Im still curious on early indirect data measures. We use satelites and probably thousand of observation-stations everywhere, even in already urban densed areals where its hotter due to soil sealing/buildings etc. than decades ago.

      but how precise can data be when hundreds or even thousand of years ago, where we usually collect data from drilling cores from ice, dendro analysis etc.?  the modeled graphs showing co2 concentration or temperatures from early periods of the neogene era for example could never be scaled that detailed like modern oberservations, so how do we could know other than extrapolate or try to forecast on this "rough" data? just saying the data of the past century heavily fluctuates with different natural events as we have a lot of different parameters and thousend of different stations to check. but few hundred years ago there are some marks here and there for months or years, not thousends a day - you know what i mean?

      so anyway do we have a chance to differentiate natural occuring warming of the past few decades from self-induced co2 with this methology?

      I just think we cannot use modern nanotechnolgy to understand stone-age tools were used, or maybe better metaphor: collecting a bunch of single bones from an ancient creature is no evidence to know how it moved or hunted, even we know a lot of biomechanics today and may let us classify the biological type/race etc.

      hope its understandable, as im no native speaker obviously :)

2367. John Mason at 20:01 PM on 7 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Also note that when each rebuttal page is updated with these, it will retain the fact-myth-fallacy structure we've used all along.

2368. John Mason at 12:51 PM on 7 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Going in way over most people's heads, Charlie. Introduce, introduce!

2369. Charlie_Brown at 08:09 AM on 7 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Here is my next attempt for the At-A-Glance section.  It is 356 words.  I will start by copying the "Myth" from the top of the main page.  That saves trying to paraphrase it in the discussion.  

      "The atmospheric greenhouse effect, an idea that many authors trace back to the traditional works of Fourier 1824, Tyndall 1861, and Arrhenius 1896, and which is still supported in global climatology, essentially describes a fictitious mechanism, in which a planetary atmosphere acts as a heat pump driven by an environment that is radiatively interacting with but radiatively equilibrated to the atmospheric system. According to the second law of thermodynamics such a planetary machine can never exist." (Gerhard Gerlich)

      The Clausius statement of the 2nd law of thermodynamics is: “It is impossible to operate a cyclic device in such a manner that the sole effect external to the device is the transfer of heat from one heat reservoir to another at a higher temperature” (Wark, Thermodynamics, 4th ed., 1983). The myth claims that back radiation or downward infrared (IR) radiation emitted by greenhouse gases (GHG) is the mechanism that increases the temperature of the Earth’s surface. Since that would not be possible according to the 2nd law, the myth concludes that global warming is false. However, the myth overlooks the fact that the sun is the external energy source that drives global warming and outer space is the external cold reservoir. The sole external effect is transferring heat from the hot sun to cold outer space. If heat loss to space is reduced, the planet will get warmer. Some take the myth even further to claim that thermal radiation cannot transfer energy from a cold body to a warmer one. Consider two walls facing each other and that all objects above absolute zero radiate energy. The warm wall radiates more energy toward the cold wall, but the cold wall will still radiate some energy toward the warm wall.

      The 1st law of thermodynamics is conservation of energy – input = output + accumulation. The global system can be defined as from the Earth’s surface to the top of the atmosphere. The input to the global system is the sun. The surface temperature is regulated by balancing heat input from the sun with heat loss from the top of the atmosphere toward space. There are three output energy pathways: 1) infrared (IR) radiation at wavelengths that are transmitted from the surface directly to outer space (the transparent range). 2) IR radiation at wavelengths that are emitted by GHG in the cold atmosphere, and 3) solar energy reflected by clouds and the surface. As the concentration of GHG increases, energy output to space (path 2) is reduced. This upsets the global energy balance. Energy accumulates and the surface temperature rises. As the surface temperature rises, energy output from the surface through the transparent range (path 1) increases until the balance is restored. This is how global warming works.

2370. John Mason at 00:46 AM on 7 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      NigelJ #28 - yes it is a complex challenge achieving balance in this business. The deniers have the advantage that they can make stuff up. We cannot!

      Also, some myths are very straightforward to rebut - e.g. "it hasn't warmed since 1998". This particular one we are discussing here is something of a pig by contrast!
      
      Realclimate has improved by strides since its inception. I was working on "Further details" about the Urban Heat Island effect - a debate largely triggered by a paper by Ross McKitrick and Pat Michaels in 2004. Realcimate's response was robust but only undererstandable to someone with serious statistical training. I nevertheless linked to it but with a note to that effect.
      
      Fortunately, most of the myths on the database can be laid to rest in the At-a-glance pieces in less than 500 words, that being the ideal word limit for that class of rebuttals. Like I said, the one we are commenting on is a bit of an outlier in this respect because so much needs introducing to the layperson. But I firmly believe we need to be near-absolutely inclusive in this business - near because I accept that there are people out there who have reading difficulties, but nevertheless reaching the biggest possible audience is the aim here.

2371. nigelj at 06:43 AM on 6 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Just my two cents worth on communications style. I believe this website is well written overall and would be reasonably intelligible to the general public. It avoids complex jargon and when it uses jargon there are definitions. It has beginner and advanced sections in the myths. This is a great feature.

      In comparison realclimate.org is too technical.

      It's a very hard balance to strike. The thing is its only possible to simplify science to a certain extent before it starts to become meaningless. And science is hard and some people will never understand.

      Of course its always possible to refine and improve things. I'm just saying that theres probably not a whole lot more that can be done to communicate the science better. The real problem is people who don't want to understand or receive the message, or who don't see climate change as an urgent threat. Just writing the science differently won't solve those particular problems.

      I thought Charlie Browns original comment on radiation physics and the second law @17 was rather good, and sounded technically correct and would be reasonably intelligible to a lay person. People do undertand numbers and probably have some understanding of the terms used enough to get the right message. I liked its brevity so you wouldnt want it to get too much longer.

      I think with a little bit of refining the comment would be 100%. 

      The only real criticism I would have Is your final statement was "Nothing about this radiant energy flow violates the 2nd law of thermodynamics" It might have helped to briefly explain why and define the law. It left me sort of hanging, for want of a better word. I understood why but others may not have put two and two together.

2372. nigelj at 06:27 AM on 6 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Charlie Brown @23

      Thanks. Makes sense.

2373. Bob Loblaw at 04:14 AM on 6 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      There is a huuuge number of comments on the main post, so that's one tough slog you've made for yourself, Charlie!

      My apologies to anyone that followed the link to Eli's Green Plate Effect post, read the comments, and had their head explode. I re-read them this morning, and boy do you need a head vice for the weapons-grade idiocy from a few of the determined commenters. Same goes for the comments Charlie is reading on the main article here at SkS. Take your head vice, don't drink coffee while reading...

      I've referred to the Manabe and Wetherald paper a number of times over the years. There is a reason it's a classic. I sometimes find these older papers do a better job of covering some of the basics - stuff that won't be included in later papers because it's all old and well-established.

      The same can be said for the IPCC reports - start with number 1, if your climatology background is limited. It could be used as the basic text for an undergraduate climatology course. The newer reports leave so much of that "old ground" out, because they assume that the reader has taken (and passed) the prerequisites.

2374. Charlie_Brown at 02:56 AM on 6 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Excellent comment, Bob.  Far too many words are spent on misunderstanding technical distinctions.  Concepts need to be conveyed succinctly at understandable levels.  That requires knowing just what is being misunderstood.  Input from a non-technical person is helpful.  To understand the point of view of denialists, I have been working my way through the comments on the main aarticle for this thread.  I now understand Philippe's comment @8 above, (@1112 in the main thread.  I just saw your reference to Manabe & Wetherald @1134 which you provided to me a little while ago.  I am thinking of having another go at drafting something as input for at-a-glance. I am hopeful that I can distill and limit the 2nd law myth into something managable.  It's a tall order, but maybe my 2-cents would help.

2375. Bob Loblaw at 23:59 PM on 5 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      I think you guys are illustrating the difficulty of specialized terminology versus common usage. In day-to-day conversation, "heat" and 'energy" are almost interchangeable, but the difference is important at a technical level.

      For conduction, you are still looking at bulk properties what talking about heat flow from warm to cold. Temperature only has meaning as the average kinetic energy level of a large number of molecules. Individual molecules will be transferring energy from one to another via collision, and individual collisions can transfer energy in any physical direction. It will always be from the higher energy molecule to the lower energy molecule, but that is not dictated by the bulk properties of "hot" versus "cold". It's only when you get to the average of a large number of collisions that you can say "heat/energy goes from warm to cold"

      So, even "conduction" is a net transfer result. For radiation, if you have two plates facing each other with a vacuum between, the net radiative transfer will be from the hot plate to the cold plate - but there will be photons travelling in both directions. The photons emitted from the cold plate have no knowledge of the existence of the hot plate and its emitted energy. What individual photons do is not limited to matching the net result of many photons - just as individual molecular collisions are not limited to matching the net result of conduction.

      The "heated by..." phrasing is also ambiguous in common usage. People can imaging being "heated by" an electric blanket that is warmer than they are. A regular blanket that is cooler than the person? "Heated by" make a little less sense, but "kept warm by" is perfectly reasonable. The use of "heated by" instead of "kept warm by" isn't enough to say that a regular blanket violates the laws of thermodynamics, though.

      Likewise for IR radiation and the greenhouse effect. The surface is "heated by" back-radiation? Maybe a bit sloppy in terminology? How about "kept warmer by.."? But to make sense, you really have to get into the overall energy balance and some mathematical descriptions. The main article for this thread includes a link to an excellent post by Eli Rabbet on The Green Plate Effect. It has a loooong comments thread, but in it you can see some of the die-hard denialists at work. The extreme cases are people that claim that downward-directed IR from the atmosphere to the surface simply does not exist - usually with some "2nd Law" faulty logic involved.

      As I mentioned earlier, countering a "2nd law" argument depends hugely on exactly what flavour of "2nd law" the person is claiming. The only common element is that the person making the claim has misunderstood something - what they call "2nd law" is not actually the real 2nd law..

2376. Bob Loblaw at 23:06 PM on 5 May 2023
      CO2 is just a trace gas
      

      jgillis:

      The photos of the different blue dye concentrations in your twitter feed are illuminating. Or should I say, absorbing. Or, oh, heck - radiation terminology can be so complex....

      I also used dye to illustrate how concentration affects absorption in this "from the email bag" posting a year and a half ago. In addition to showing the effect of small concentrations, it illustrates how it is really the absolute amount of dye that is important - not the concentration.

      https://skepticalscience.com/from-email-bag-beer-lambert.html

2377. jgillis at 17:34 PM on 5 May 2023
      CO2 is just a trace gas
      

      I had this idea to pack some extra punch into the "ink" analogy.
      If you use ink to color a candle, you may in fact experimentally verify that a dark colored one melts in the sun, while a lighter one stands firm.

      This may be a fun experiment to educate children, but also to sway doubters that rely solely on "common sense" to form opinions.

      Described in this twitter thread.

       

2378. Charlie_Brown at 01:19 AM on 4 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Nigelj, Thanks for the question.

      You are almost correct, although I would rephrase "... the (weak) radiant heat source heats the warmer surface".  "Heats" implies raising the temperature of the warmer surface, which would be a violation of the second law.  Since the warmer surface radiates more energy away than it receives from the weak source, the temperature will drop unless there is another source of energy keeping it warm.  Rephrase it to "... the radiant heat source directs (or sends or radiates) energy to the warmer surface."

      Yes, touching surfaces changes the mode of heat transfer from radiant to conduction.  The net heat flow between the two surfaces is from warm to cold in either case, but with conduction there is no flow toward the warmer surface.

2379. nigelj at 08:53 AM on 3 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Charlie Brown

      Your comment @21  "This statement does not say that it is impossible to transfer heat from a cold body to a hot body (Look and Sauer, Thermodynamics, 1982). As stated above in the “At A Glance” description, it is “the net sum of the energy flows will be from hot to cold”."

      Makes sense. This is my understanding as follows as a lay person. Its probably naive. If you shine a weak radiant heat source at a warmer surface than the source then surely the radiant heat source heats the warmer surface? I mean the radiant heat isnt going to bounce off the warmer molecules.  But over time the warm surface will loose its  total energy to a colder surface somewhere so the second law isn't violated. 

      If however you had a warm and colder sufaces physically touching each other so you have conduction, then heat flow would be from warmer to colder.

      Am I right or wrong?

2380. Charlie_Brown at 08:04 AM on 3 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Clearly countering a highly technical argument using non-technical explanations poses a difficult problem. I don’t think that I am capable of meeting the objective of simplifying this to the level necessary for the non-technical reader. As stated above, the Gerlich & Tscheuschner paper contains many technical errors and distractions. Primarily, they misrepresent the technical basis of the greenhouse effect and then criticize the erroneous description. In particular, they criticize the use of thermal conductivity when thermal conduction has nothing to do with the greenhouse effect. They also spend a lot of time criticizing the radiative explanation. This becomes a problem for non-technical people because they have trouble figuring out which scientist to believe. Interestingly, G&T argue that there are many examples of consensus scientists being wrong, but make no mention that individual contrarians, such are themselves, might be the ones who are wrong.

      The first law of thermodynamics, conservation of energy, is relatively easy to understand. The second law is much more difficult. In its shortest oversimplified form, it says that entropy increases, which doesn’t mean much to most people. It has the Kelvin-Planck and Clausius statements and several corollaries, which are helpful concepts. The Clausius statement is: “No process is possible whose sole result is the removal of heat from a reservoir at one temperature and the absorption of an equal quantity of heat by a reservoir at a higher temperature.” This statement does not say that it is impossible to transfer heat from a cold body to a hot body (Look and Sauer, Thermodynamics, 1982). As stated above in the “At A Glance” description, it is “the net sum of the energy flows will be from hot to cold”.

      G&T oversimplifies the Clausius statement to:
      “– Heat cannot move itself from a cooler body into a warmer one.
      – A heat transfer from a cooler body into a warmer one cannot happen without compensation.”

      G&T continue their argument by addressing and discounting potential criticisms of their paper. They quote climatologist Stefan Rahmstorf, who has it right, then proceed to reject Rahmstorf with some undefined nonsense about the distinction between heat and energy.

      G&T quotes Rahmstorf: “Some ‘sceptics’ state that the greenhouse effect cannot work since (according tothe second law of thermodynamics) no radiative energy can be transferred from a colder body (the atmosphere) to a warmer one (the surface). However, the second law is not violated by the greenhouse effect, of course, since, during the radiative exchange, in both directions the net energy flows from the warmth to the cold.”

      Then G&T counters: “Rahmstorf’s reference to the second law of thermodynamics is plainly wrong. The second law is a statement about heat, not about energy. Furthermore, the author introduces an obscure notion of “net energy flow”. The relevant quantity is the “net heat flow”, which, of course, is the sum of the upward and the downward heat flow within a fixed system, here the atmospheric system. It is inadmissible to apply the second law for the upward and downward heat separately redefining the thermodynamic system on the fly.”

      Unfortunately it is G&T who are plainly wrong, even after very clear and accurate explanations are provided for them.  How can it be resolved  when two scientists are called "plainly wrong" when both should be knowledgeable on the technical issues? 

      Maybe an example would help.  Consider two walls of different temperature facing each other, perhaps as a large radiant heating panel in a room. The net flow of radiant heat will be from the hot wall to the cold wall. All objects above absolute zero radiate energy (heat), so the cold wall must be radiating heat in the direction of the hot wall. Raise the temperature of the cold wall to warm, so now the flow of energy from the warm wall is increased and the net flow of heat is reduced. One can go to the extreme of making the temperatures equal and the net heat flow will be zero, but both walls will be radiating.

2381. One Planet Only Forever at 03:08 AM on 2 May 2023
      Why the food system is the next frontier in climate action
      

      Evan @6,

      I briefly reviewed the 2014 Research Article you pointed/linked to (note it is almost 10 years old). I would update my previous comments to add that human actions causing increased N2O in the nitrogen cycle are to be considered the same way I refer to impacts on the carbon cycle. And I would add that there are other good reasons for more aggressive reduction of nitrogen cycle impacts than climate change (refer to Planetary Boundaries).

      I will also clarify that reducing methane emissions from rice is still an opportunity for reducing the peak level of ghg impacts even if that methane could be considered to be ‘part of the natural carbon cycle (an action that does not increase the amount of carbon in the carbon cycle the way that burning fossil fuels or leaks of methane from fossil fuel operations or permafrost melting do).

      More specifically, the report’s evaluated floor level of non-CO2 emissions from food production and consumption (Global total 7 GtCO2e/year by 2050 with more if population continues to grow beyond 2050 and also influenced by 'potential changes of attitudes towards being less harmful') appears to be based on the perceived willingness of the UK population, at the time the report was prepared, to learn and be less harmful consumers. And the evaluated UK willingness is extended globally with all people expected to want develop to live in ways comparable to the less harmful ways that the UK population was evaluated to be willing to live.

      The following is a quote from the “Options and barriers to mitigating food system non-CO2 emissions - Agriculture” section of the Research Article:

      “For both N2O and CH4, socioeconomic and environmental circumstances dictate the extent to which changed agricultural technologies and practices can deliver cuts in emissions at a systems level. Stakeholders suggested that important factors influencing uptake of mitigation options affecting the UK revolve around cost, dominant practices, the aging farming community and attitudes of ‘young farmers’, existing infrastructure, cultural norms, changing climate as well as a feedback linked to levels and patterns of consumption.”

      A quote from the “Options and barriers to mitigating food system non-CO2 emissions - Consumption” section of the Research Article:

      “Within the UK consumption-based scenarios, the most significant dietary change considered was a 70% per capita cut in meat consumption, with the deficit replaced with rises in other food types. However, even with changes to per capita meat consumption, absolute emissions levels are driven by population growth (consistent across the scenarios) as well as growth in per capita consumption levels. Population growth per se strongly constrains N2O mitigation, as crops for consumption and for feed for livestock continue to require manure or mineral fertilizer. Barriers to changing patterns of consumption are confirmed through consumer focus group analysis: moderate changes in meat consumption (20% per capita) were considered in line with financial pressures to reduce expenditure given the context of the 2009–2012 recession, whereas a 70% reduction was perceived too substantial a change for many [Citation33].”

      That indicates that the evaluation was (likely unwittingly) biased by accepting questionable opinions like ‘the higher cost of being less harmful is a valid reason to be more harmful’ and ‘the developed popularity of eating more meat is a valid reason to not reduce meat consumption’. Note that I tried to present both of those points in a way that highlights that populist political misleading messaging significantly caused those attitudes to develop to be so influential that they compromise the evaluation and the way it is reported.

      Quote from “Discussion - Implications for cumulative GHG emissions”

      “Finding ways of reliably reducing non-CO2 emissions will become increasingly pressing as global demand for food rises. A wide range of feasible CH4 mitigation options were put forward by stakeholders, taken from the literature and quantitatively assessed during the scenario process, providing evidence for greater scope for achieving substantial CH4 mitigation than for N2O. This, coupled with the much longer lifetime of N2O compared with CH4 as well as the influence of carbon cycle feedbacks in raising the GWP of CH4 from 21 to 34, highlights the critical importance of fully exploiting CH4 mitigation potential whilst increasing the research effort towards developing agricultural systems that can minimize N2O production.”

      That indicates that if the developed research bias is corrected there could be more reduction of N2O resulting in a lower ‘floor level’.

      Quote from “Discussion - Implications for managing and mitigating CO2”

      “The focus here on non-CO2 reinforces other studies that identify the existence of an emissions floor, further emphasizing an urgent need to mitigate CO2 emissions where it is most feasible and quickest to do so. The higher the non-CO2 floor, the more rapidly CO2 emission cuts are needed within the constraints of a chosen climate target. Conversely, relying on a low or non-existent emissions floor suggests a larger CO2 budget is available, again relaxing the rates of mitigation for a chosen climate change target, delivering a more palatable but less realistic assessment of the climate change challenge.”

      This emphasizes that the learning from the report is that more rapid efforts to reduce fossil fuel use are required.

      Quotes from the “Conclusion” of the research article:

      “A continuation of absolute growth in global N2O emissions, despite assuming optimistic mitigation has, because of cumulative emissions, direct implications for how urgently and deeply to cut both CO2 and CH4 for an assumed climate target.”

      This reinforces the need for more research to reduce N2O and the need to more aggressively cut CO2 and CH4 unless new research develops viable ways to rapidly reduce N2O.

      “As energy systems become decarbonized, global non-CO2 emissions largely associated with food consumption and production will increase in the share of annually produced GHGs. Emphasizing the importance of making cuts in food-related emissions highlights an urgent need for policymakers in Annex B nations to consider not only technological and supply-side interventions, but tackle the thorny issue of levels and types of consumption. Unlike large-scale infrastructure developments, measures tackling consumption and demand have the potential to cut emissions of CO2 and non-CO2 alike in the short term and could improve the diminishing chances of remaining within the carbon budget commensurate with the 2ｰC threshold.”

      That highlights the need for policymakers to “tackle the thorny issue of levels and types of consumption” because the reports conclusion is that current over-developed populations are not as willing to be less harmful as they should be.

      A quote from the “Future perspectives” part of the research article:

      “If the challenges posed by climate change are to be overcome, at least in part, a meeting of minds to define problems can offer new, much needed insights. This is already emerging in some quarters, with an increase in interest from research funders around the food–water–energy nexus as well as a rise in the number of researchers keen to engage in genuinely interdisciplinary activity. Of course disciplinary research may, out of necessity, continue to dominate, but the emerging expertise in interdisciplinary research needs support and encouragement given the extent of the systemic and complex challenges facing society.

      "The climate change challenge becomes ever more urgent each year, with time limiting the options available for mitigating emissions to be largely those that can deliver change in the short term. Perhaps with agronomists, biologists, engineers, political and social scientists working increasingly in single units, systemic ‘solutions’ to the climate challenge can be found. Specialists in demand and consumption require the same prominence in the portfolio of research endeavour as technologists, physical scientists and engineers. Only then will resilient options be derived and ultimately implemented in a timescale befitting of the scale of change facing society.”

2382. Charlie_Brown at 14:27 PM on 1 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Eclectic@18:

      Good catch.  The conversion was my mistake.  It should be 15,000 meters (50,000 feet) for the cold layer of the atmosphere between the troposphere and the stratosphere.

2383. John Mason at 09:35 AM on 1 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Charlie #17:
      
      There you portray the dilemma in an illustrative way. Now go back through it and, critically, add an asterisk after every single word/acronym that, to your knowledge, the typical "consumer" has not meaningfully encountered before.
      
      The vast majority of folk are slightly to non-curious about global warming until one of its effects comes a-banging on their door. We have to reach them - they ARE the majority here. Deniers and activists are in contrast a small percentage at two ends of a spectrum- although I figure activists are far more populous these days but at the same time some deniers still have a disproportionare noise-allowance. But it's the everything-in-between we have to reach and explain what's happening.

2384. Eclectic at 08:00 AM on 1 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Thanks, Charlie_Brown.

      But permit me a grumble or two.   What is this 15,000 meters (25,000 feet) business of equivalence?   One, or two, typos/errors ?

      And 15-micron band broadening . . . is over-technical and of minimal relevance to the basic topic.

2385. Charlie_Brown at 00:16 AM on 1 May 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      I would like to have a go at this.

      All molecules above absolute zero vibrate and radiate energy. With each bend and stretch, the molecular internal energy state changes, which emits radiant energy. The amount and wavelength of the emitted energy depends on the temperature and the molecular structure. The sun emits energy at about 5,800 degrees Kelvin (6,000 C, 11,000 F) and a small fraction is intercepted by the Earth. Due to the high temperature, very little solar energy is emitted at wavelengths above about 5 microns. The Earth’ surface emits radiant energy at infrared wavelengths above 5 microns based the average surface temperature of about 288 Kelvin (15 C, 59 F). Part of that infrared energy between about 14 and 16 microns (the 15-micron band) is absorbed and re-emitted by CO2 in the atmosphere until it reaches an altitude of about 15,000 meters (25,000 feet) where it is emitted at a temperature of about 217 Kelvin (-56 C, -69 F) toward space, which is at absolute zero. As CO2 increases, the edges of the 15-micron band strengthen and energy loss to space is reduced. Nothing about this radiant energy flow violates the 2nd law of thermodynamics.

2386. Evan at 20:29 PM on 30 April 2023
      Why the food system is the next frontier in climate action
      

      OPOF#4, I am not any kind of expert on GHG emissions in the food cycle, but from what I've seen and read, there are baseline emissions that are difficult to eliminate, such as methane emissions due to rice cultivation. I've heard and read of 1 ton CO2e/person/year as a reasonable baseline estimate (read the Conclusions here where they refer to an emissions floor).

      nigelj#5, I don't disagree with your statements about the benefits of a vegetarian diet. My friend is a particular case in that he had cancer, and for his specific situation his doctor recommended he give up his vegetarian diet because his body needed animal protein to fight the effects of the cancer he had. So his was a special case, but it still highlights that there is not always a one-size fits all answer.

2387. nigelj at 10:39 AM on 30 April 2023
      Why the food system is the next frontier in climate action
      

      Evan @3

      "I know a person who used to be vegetarian, but after having cancer his doctor recommended he start eating meat again."

      This statment  got my attention, having recently read about the cancer risks of high meat diets. Had a look on the internet and this came up:

      "Results from a large-scale analysis show that following a vegetarian or pescatarian (fish-eating) diet could significantly reduce the risk of developing cancer – but even limiting red and processed meat to five meals a week or less may also have a benefit...."

      "Compared with regular meat-eaters, the risk of developing any type of cancer was lower in low meat-eaters (2% less), fish-eaters (10% less), and vegetarians (14% less). This means that the absolute reduction in cancer diagnoses for vegetarians was 13 fewer per 1,000 people over ten years, in comparison to regular meat-eaters."

      www.ndph.ox.ac.uk/news/new-study-finds-lower-risks-of-cancer-for-vegetarians-pescatarians-and-low-meat-eaters#:~:text=Compared%20with%20regular%20meat%2Deaters,vegetarians%20(14%25%20less).

      The study is large, recent and significant.

      Now I'm not vegetarian or promoting vegetarianism per se. A low meat diet, especially a diet low in red meat, sounds sensible and makes for a decent reduction in emisssions. 

2388. One Planet Only Forever at 09:10 AM on 30 April 2023
      Why the food system is the next frontier in climate action
      

      Evan,

      Your question may be questionable.

      The climate change issue is primarily about human actions that are increasing ghgs in the carbon cycle (increasing the balanced state of ghgs in the atmosphere and causing other harms like increased CO2 absorption in oceans).

      That perspective helps identify and understand the differences between the variety of ghg impacts caused by human actions. Most important, it helps understand that some causes of CO2e from human food production and consumption are ‘not the concern’.

      Steady-state production of ghgs from food production and consumption is not the primary concern. That would be a sustainable carbon cycle. Food production and consumption that increases the level of ghgs, especially the use of fossil fuels, is the primary concern. An increasing population that eats less ‘higher impact food like meat or rice’ can actually result in a reduction of the steady-state level of ghgs. In addition to an increasing population having less consumption, the remaining consumption can be changed to be less harmful, like developing meat and rice production that does not cause as much ghg impact.

      Therefore, an answer to the question about the ‘per capita CO2e’ is that, due to the current developed problem of significant excess ghgs, especially CO2, already in the atmosphere, unnecessary CO2e impacts from human activity need to be ended and actions that will reduce the steady-state ghg levels in the atmosphere are required. (The peak level of ghg increase due to the historic, and continuing, lack of interest in seriously restricting harmful and unnecessary actions will undeniably be a harmfully excessive level).

      Also, the required changes of food production and consumption for the collective of human activity to be more sustainable will vary by region. Regions that currently have more people eating less than a ‘diet necessary for healthy living’ can be expected to have increasing impacts. But if such a region also has a significant amount of harmful unnecessary food consumption, due to a significant status gap in that region's society, then that region could, depending on how much harmful consumption is occurring in the region, reduce the total regional level of ghg impacts while the less fortunate in the region increase their impacts.

      PS. The titles of the two study reports linked in the last paragraph you are questioning are informative (the reports are even more informative): “A meta-analysis of projected global food demand and population at risk of hunger for the period 2010–2050” and “Future warming from global food consumption”. However, developed socioeconomic-political biases can bias what is investigated, how it is investigated, and how it is reported. That is likely a significant root cause of the populist political attacks on less biased science that establishes a requirement for significant changes of developed beliefs and actions, especially if it highlights the need for rapid changes of popular and profitable developments. It may also be why I did not see the obvious problem of harmful over-consumption being highlighted.

2389. John Mason at 01:03 AM on 29 April 2023
      EGU2023 - Highlights from the last week of April
      

      Graphs where online attendees have to turn their head on one side in order to read axis captions on their screens....

      Stefan's talk this afternoon, covering "what Exxon knew" was a must-watch. Baerbel will likely have plenty to say about it!.

2390. Bob Loblaw at 00:08 AM on 29 April 2023
      EGU2023 - Highlights from the last week of April
      

      "it's a pity that presentation skills are not taught at final year undergraduate level"

      It's a pity that they aren't taught at the graduate level, too. I saw far too many professors with nearly zero teaching skills during my academic career, and far too many scientists at conferences and meetings with nearly zero presentation skills.

      To your excellent list, add graphs with too many lines, graphs shown and removed before you can even read the axes to find out what is being displayed (and no explanation from the presenter), colours of lines or symbols that are almost indistinguishable.

      ...and modern software that makes animations, lack of contrast, etc. as "features", wher in reality theywork against clarity.

      For web sites, its as if the features epitomized at buduglydesign represent some sort of ideal, rather than something to avoid.

2391. Bob Loblaw at 23:53 PM on 28 April 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      nigelj @10:

      I'd be curious about the three versions of the 2nd law "violations" that you found. What were the key differences between them?

      I'd agree that the "energy can't flow from cold to hot" is probably the most common.

2392. Bob Loblaw at 23:51 PM on 28 April 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      I was still in public school when the significance of the term "law" was discussed in science class. The progression of confidence in scientific understanding  used to follow the path from hypothesis (untested) to theory (well-tested) to law (extremely well-tested over a long time).

      But even when I was in public school, it was explained that "law" was a traditional term and science recognized that all understanding is subject to revision as more evidence is gathered.

      We have "laws" of gravity, motion, etc that have been supplanted by the "theory" of relativity, etc. We still talk of "laws" of universal gases, thermodynamics, etc. As John says, use of this terminology is grandfathered in.

      In common use, even "theory" gets misused when a scientist would say "hypothesis". The put-down of "that's just a theory..." should have the caveat "but I'm not a scientist" attached to it.

2393. John Mason at 22:00 PM on 28 April 2023
      EGU2023 - Highlights from the last week of April
      

      My take on Friday so far: Baerbel has already covered sessions where we were both present above.

      I particularly enjoyed CL1.1.4: Deep-time climate change: insights from models and proxies. This session provided a wide-ranging series of palaeoclimate studies looking at various parts of and the whole Earth at key points in the past such as the Permo-Triassic transition, the K-T extinction and the early Cenozoic hyperthermals.

      Some topics were more familiar than others, for example looking at the selective nature of the K-T extinction interval in the oceans: the post-impact 'winter' actually had a positive effect on e.g. siliceous diatom productivity whereas the Deccan Traps large Igneous Province was mostly negative in that instance. Calcareous planktom however suffered greatly. The most though-provoking presentation, "Resilience and implications of an Antarctic monsoon during the Eocene", was something I had not looked at before. It appeasrs there were local ice-sheets even then, but unlike today the continent's periphery supported dense forest.

      It's refreshing to be with so many people to whom the key principles of climate forcings are no longer argued over but instead it's the increaingly minute details of past climates that are under investigation and being presented.

      One word on presentations: it's a pity that presentation skills are not taught at final year undergraduate level. I've seen talks varying from absolutely outstanding to hard-to-follow this week. The cause of the difficulty variably includes talking at breakneck speed about highly complex topics, large blocks of text in slides too long to read for their display-time and using too small a font size to even screengrab effectively. Some, by no means all people need to learn how to communicate findings more clearly (the EGU Guidelines are quite specific in this respect) and in addition, every author had a Supplementary Material folder in which to upload a more detailed file. Attention to such points would have made an aleady enjoyable event even more so!

2394. Evan at 21:38 PM on 28 April 2023
      Why the food system is the next frontier in climate action
      

      OPOF, thanks, as always, for your comments. However you slice it, ag-related emissions are a tough nut to crack. I eat primarily a plant-based diet, but during periods where I physically work hard, I have a difficult time keeping going without adding in a bit more dairy or some meat.

      I know a person who used to be vegetarian, but after having cancer his doctor recommended he start eating meat again.

      No doubt people in developed countries eat excessively and eat more meat and dairy than needed, but from my own experience I also know that the body has minimum requirements that change based on lifestyle (how hard I'm working) and current physical condition (my friend with cancer, or other conditions). No doubt in a world where we are properly feeding everyone, the GHG emissions will go up, just because properly nourishing everyone will require many to eat more and perhaps to eat more foods that are associated with higher GHG emissions.

      So I restate my last question. Do the authors have an estimate for baseline, per-capita GHG emissions (quantified in CO₂e) in a world where we do all the right things to reduce ag-related emissions and where all people are properly nourished, but not over-nourished?

2395. John Mason at 20:43 PM on 28 April 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Eclectic #13 - 'principles' would be good but I like your point about an explainer - the only issue in this case is it would lengthen the rebuttal by another paragraph! Will give it some thought once EGU is over (today's the last day).

2396. Eclectic at 19:35 PM on 28 April 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Quite so, John Mason ~  but my apologies for poorly conveying my thoughts.   I was not wishing to suggest terms like "Law" or other jargon of a technical or traditional type should be excised from the basic rebuttal . . . but rather that some sort of ultra-brief explanatory warning be used to put the earnest reader on guard against accepting "Laws" of physics (or anything else) as being more than a convenient summary (and nothing more real that that).

      The "Laws of Thermodynamics" can sound impressively authoritative ~ and I think this usage is sometimes purposely intended, to fool the layman into believing that the Denialist's objection to AGW has some validity.

      That said, I don't have a ready phrase or two which would serve.

2397. John Mason at 18:33 PM on 28 April 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Ineed, Eclectic! It's like many terms in science, including a lot of mineral names, that are "grandfathered" i.e. they are not considered to systematic or ideal but because they have such frequent use they are regarded as acceptable with caveats.

2398. One Planet Only Forever at 14:14 PM on 28 April 2023
      Why the food system is the next frontier in climate action
      

      Evan,

      I agree that the last paragraph is stated poorly. The answers to your questions may be in the two studies linked to in that paragraph:

      • “50 to 110%” contains per capita and global total values evaluated to 2050. However, a quick scan finds the following within that report: “How do the +60% to +110% figures compare to our findings? We find that under SSP2 (which, like the FAO projections, is regarded as a business-as-usual scenario), total food consumption will increase by 51%, with a 95% confidence interval of +45% to +56%. This is substantially lower than the FAO2 and Tilman et al.1 projections of 60–110%.”
      • “research suggests” has the following in its Abstract: “We find that global food consumption alone could add nearly 1 °C to warming by 2100. Seventy five percent of this warming is driven by foods that are high sources of methane (ruminant meat, dairy and rice). However, over 55% of anticipated warming can be avoided from simultaneous improvements to production practices, the universal adoption of a healthy diet and consumer- and retail-level food waste reductions.”

      So it is not clear how the last paragraph comes to be stated the way it has been stated.

      However, my criticism of the report is that it fails to mention the following fairly obvious realities:

      • Immediate significant reduction of harm done can be achieved by reducing unnecessary consumption. Few people want to discuss that ‘herd of elephants in the room’ because that would reduce perceptions of economic prosperity that are based on all the unnecessary consumption, especially the conspicuous unnecessary consumption displays of higher status – like eating more meat.
      • The current developed socioeconomic results are loaded with harmful unsustainable activities. The system aspires to ‘meet the wishes of the winners of competition for status, power, popularity and profit’ and ignore, dismiss or make excuses for the harmful systemic inequities of the developed ‘starting point’.
      • The obvious best ‘ideal’ action to aspire to is all humans being governed, self-governing preferred, to limit their harmful actions to ‘essential (necessary) needs’ and limit the harmfulness of those essential needs. That means that anything beyond ‘essential needs’ has to ‘ideally’ be strictly limited, again preferably by self-governing, to harmless actions.

      An example of the report being written from the biased perspective of a '(potentially unwitting) promoter of the harmful unsustainable status quo' is the unquestioned inclusion of the following:

      "According to the World Economic Forum, investment in plant-based protein offers the highest heat-trapping pollution savings per dollar of invested capital of any sector but remains significantly under-invested. This burgeoning industry offers a major opportunity for smart policymaking and investing."

      That promotes 'unnecessary' industrial food production, potentially with many other harms 'but the focus is restricted to the climate impact'. Local family cooperatives producing 'natural meat in ways that sequester carbon' combined with diets corrected to consume less meat would be a better solution ... but that would reduce opportunities for investors and diminish their developed perceptions of wealth ... but 'investors pursuing their maximum benefit' are not necessarily beneficial, especially if they employ populist misleading messaging to hide or excuse harm done, especially if they promote positive perceptions that some people can be tempted to hope to obtain from more harm done.

2399. Eclectic at 13:19 PM on 28 April 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      Part of the communication problem is the word "Law"  ~  a word of great historical & cultural weight (especially among the religious).

      The sight of the word Law  has a mesmerizing effect on non-critical thinkers.   Law seems something forever unquestionable and beyond discussion;  something fixed and eternally true  ~  a divine decree received directly from the Hand of God.   Instead of being just a word meaning a convenient concept in the minds of physicists.   The word is mistaken for the reality.

      Perhaps there could be room for some brief form of words, to deflate the awesomeness  of a "Law" in the discussions about GreenHouse Effect.

2400. nigelj at 13:03 PM on 28 April 2023
      At a glance - The greenhouse effect and the 2nd law of thermodynamics
      

      John Mason @7

      Thanks. I agree its useful to include general information on thermodynamics in the rebuttal. Make it a teaching session. But I just believe "at a glance" should be something reasonably short, so the full teaching session would be better in the "details" section. Seems obvious to me.

      Just to clarify. My version in ten lines is very much in my own words and structured, expressed  and ordered as I wished. I just used the realclimate resource as background information and a detailed point they made seemed very good. In other ways their account as a bit confusing.

      --------------------

      Bob Loblow @8. 

      I did a quick scan of the internet on the greenhouse effect violating the second law, because my own knowledge was sketchy. I found three versions. The one I mentioned was the most commonly expressed version I came across.

      I agree its a complicated area and does require a lengthy explanation but for me that is better in the "details"section. Or perhaps I'm being a bit OCD about how its organised!

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