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Comments 1351 to 1400:

  1. 2021 SkS Weekly Climate Change & Global Warming News Roundup #6

    There is strong evidence climate change is an existential threat to various plant and animal species with up to 50% of species under threat, according to a David Attenborough documentary I was watching last night. Past mass extinction events are strongly associated with climate change. Its not clear to me why climate change would literally lead to extinction of the human race, even in tropical regions. Im not aware of any published science saying this. It is clear it could lead to sharply increased mortality with plenty of studies suggesting this. It is clear it could cause collapse of modern civilisation, but that is not extinction.

    The trouble is by just saying "existential threat" or "extinction level event" this is rather general and vague, and  young people might assume it means the human race. No wonder they get anxious. Children need to be told a more accurate and nuanced picture.

  2. Increasing CO2 has little to no effect

    MA Rogers... Thanks for that further clarification. One thing that I always wonder is, what would the temperature structure of the planet be without GHG's? Setting aside the fact that we'd have a snowball earth, what would a pure nitrogen-oxygen atmosphere do? There would certainly be some conduction from the surface and convection off of that.  I have a hard time working out the results. I'm sure someone has modeled this. I've just never heard what the results were. Perhaps understanding this would help people to better understand why trace gases have such an important effect.

  3. Increasing CO2 has little to no effect

    Rob Honeycutt @418,
    I don't think it is entirely correct to say the 0.041% CO2 warms up the rest of the atmosphere. It is the result of the GH-effect that provides the warming and that encompasses far more than the IR absorbed by CO2. As well as absorbing IR, the CO2 also emits IR. And as only GHGs do this, the prospect of an atmosphere with GHGs absent takes a bit of mental grappling.

    But if there is CO2, within the 15 microns wave band.....
    I would describe the CO2 as providing two things. First a fog that prevents the 15 micron wave band of IR from travelling very far, this by absorbing the IR. Imagine a candle in a thick fog. A few metres away and there is no sign of it. The thicker the CO2 fog the shorter the distance.
    But there is the flip-side of this fog. The CO2 fog, as well as absorbing IR is also glowing, emitting IR. And because it is the fog itself that is glowing, the intensity of the glow is dependent on the temperature and not on the CO2 concentration. In the atmosphere, the lapse rate will thus give maximum glow close to the surface with the glow diminishing with altitude. The surface itself acts pretty-much as a mirror, reflecting back the 15 micron glow except being on average a little warmer than the surface air, it will glow a bit brighter.
    The diminishing brightness with altitude will also mean a net flow of upward energy and when the quantity of CO2 above gets so thin to allow the IR to shoot off into space, the downward flux starts to faulter and that causes an evolution of the net upward energy flux, creating the one out into space which is dependent on the temperature of the atmosphere at that altitude emitting into space.

    The effective size of a 0.041% CO2 concentration may also be worth a few words because, as Scaddenp @419 says, Avogadro's number is impressively large and that does make a bit of a nonsense of the “But it's only 0.041%!!” argument. I have (more correctly “had”) a couple of visualisations which hopefully shows how Avogadro's number makes a nonsense of such an argument and they might be worth setting out here for the thread.

  4. Veganism is the best way to reduce carbon emissions

    Sorry, Klemet, but the link you provided doesn't address the question I asked, and specifically doesn't address any IPCC statement to the same effect. I found the FAO statement regarding 14.5%, though.

    One of my problems with all this is that the high end calculation for animal agriculture are assuming full supply chain. A large portion of those emissions are going to be surface/air transportation, buildings, and other industrial processes which are separated out in other GHG sector analyses, and are genuinely a different topic. 

    The other issue I have is that, you still have to replace the nutritional value of whatever is removed from that provided by animal agriculture. 

    In discussions of this topic I always have to point out that I've been a vegetarian for, now, 40 years. While I don't disagree that consuming less meat is more healthy and better for the environment, I do get annoyed when the science on this topic gets misused.

  5. Veganism is the best way to reduce carbon emissions

    Thanks @Klemet I'm indeed not saying that global veganism is the single best way to achieve climate goal, or that everyone should go vegan before anything else. As previously stated I'm just saying that this whole article is in inadequacy with current scientific litterature on the subject, which might jeopardize the credibility of your website to anyone knowing a little on the subject

    I made a very complete commentary adressing specific points on your article and correcting them or rebutting them, I'm surprised not to have an answer for any of the specific things I've mentionned. I cannot waste more time chasing a goal post you're constantly moving. I've made a detailled comment about everything's that's wrong in your article and because you've made the pro-truth pledge I expected somehow to have a substantive debate about those point. If you don't want to pin point to  what we agree on and what you disagree with in my comment responding to the article, I don't know what's the point of submitting such a comment in the first place.

    I have provided you with many reference, a whole bibliography on the subject is here for you to dig on the subject in support of the point I'm only making because science says so.

  6. Veganism is the best way to reduce carbon emissions

    Lots of interesting stuff written here. I’ll try to join it :

    @Rob Honeycutt : If I remember correctly, the IPCC base their figures and tables in their Special Report on Climate Change and Land (Chapter 5 : Food Security) on the numbers derived from the FAO and over studies like the one of Poore and Nemecek (2018) in Science. Latest FAO numbers I’ve seen puts animal agriculture as responsible for 14.5% of GHGs emissions, so I’d say that Guilhem is in the right there. I might be wrong, though.

    @Eclectic : I agree with what you say, except that I don’t think that Guilhem wrote that making the vegan diet mainstream will be enough to save the world, or that’s it’s even the our best option. From what I read, Guilhem wrote that this article doesn’t sound on point with current science, and even kind of “strawman-ish” on some aspects, which I agree with. Plus, concerning the idea of achieving a worldwilde vegan of vegetarian diet, what evidence do we have that it is such a crazy idea ? Indeed, surveys seem to show that between 2014 and 2017, the number of vegans rose by 600% in the US, reaching almost 20 million people; and that’s not considering the fact that environmental considerations is only one argument for veganism, and often not the most compelling for people from what I’ve read.

    But I think that we might be missing the point here, which is that this article might need some revision. I completly agree with its premice (i.e. veganism is not the best option to reduce GHGs emissions at the individual levels), but some of the things written seem very odd or downright wrong, as Guilhem pointed out.

    • Concerning people’s willigness to change their diet (section 2), I don’t think that the fact that people are currently willing or unwilling to give up on animal products like meat and dairy does not refute the argument that this could be the #1 option to reduce individual carbon emissions (i.e. the subject of the article and PETA's quote). And while data exist on people unwilingness to go vegan, I deem it important to complete it with recent demographic data on veganism to get the complexity of the question, as it reveals veganism as one of the biggest trends in western societies.
    • Concerning increased waste in vegan diets (section 3), it is something that I have never seen so far in the main reviews that we have today, such as the one from Poore and Nemecek who does talk about waste. Does this argument hold if we take into account the quantities that are produced (e.g. if less meat and dairy is produced and bought than fruit and vegetables, isn’t it normal that less waste is associated with them) ? What of taking into account the fact that a great quantity of food resources (mainly cereals) are produced to feed livestock, which could associate their waste with meat and dairy ? What proof do we have that a switch to a vegan diet would increase the consumption of fruits and vegetables (as dairy and meat are often replaced by vegans with proteins sources such as soy products) ?
    • Concerning GHGs emissions due to transportation (section 3), everything I’ve read on this subject says that transportation is really not the main issue when talking about GHGs emissions. As summarized by the I4CE, or stated in Weber and Matthews (2008) (for the USA), Whyne and Nicholas (2017) (for comparison between plant-based diet and “local” diet), or Sandström et al. (2018) (for Europe), transportation is but a very small part (around 10% on average) of GHGs emissions for food products, and meat and dairy are always the foods associated with the biggest GHGs emissions. Knowing that, why focusing on tropical food exclusively, like is done in the paragraph (omitting the fact that it could be a very interesting option for people in the tropics themselves) ? And what of the impact of food for livestock that is grown in other countries, such as the soy often produced in brazil to feed cattle in europe or the USA ? Also, why focusing on food transported by plane when it seems to represent only a very small percentage of the food we produce, as Guilhem pointed out ?
    • Concerning the capacity to shift management practices of livestock to reduce GHGs emission, I don’t think that there currently is credible evidence of strategies of extensive management that can make animal produces much better for GHGs emissions. In fact, there are studies that seem to show that extensive management could be even worse, as hinted in Clark and Tilman (2017) or Hayek and Garret (2018). That said, how does one article (the one by Zomer from 2017 that is quoted) equals to enough evidence enough for what is proposed here, when current litterature suggest overwise ? Especially when recent research seem to temper the expectation of possible offtest of animal agriculture by soil sequestration, as with the article of Godde et al. (2020) that indicates that “any sequestration is time-limited, reversible, and at a global level outweighed by emissions from grazing systems”. The Food Climate Research Network also has a nice report on the issue, that synthetize most of what has be researched to date on the issue.
    • As Guilhem pointed out, the focus on the article of Kim et al. (2019) in section 4 seems a bit strange. The paragraph implies that a flexitarian diet is better than a vegetarian (not vegan) diet. But the article clearly states that a full vegan diet is the best in 97% of the countries studied; even better that the flexitarian diet that is mentionned. Why not mentionning this fact ? Why suddendly switching the focus on a vegetarian diet in a post talking about vegan diets, when the article that is quoted does talk about vegan diets ? And why not mentionning the majority of the recent litterature that do indicate a vegan diet as the best diet to reduce GHGs emissions, such as Poore and Nemceck (2018), the Lancet EAT study, or even the chapter 5 of the report of the IPCC “Climate change and land” ? It’s just so weird to me; but maybe I’m missing something. I don’t think that Dana (the author) is the type of person to do misinformation, so I’ll do my best to keep my mind open on that.

    So in the end, I'd suggest the following revisions :

    • To delete section 2 (“Are people willing to change their diets for the environment?”) , or to add it as an afterthought rather than a main argument; but I think that more data should be added to it to present the problem more globally.
    • To delete section 3 (“Problems with the vegan diet”), or to precise aspects concerning waste and add some more evidence-based environmental problems with the vegan diet.
    • To delete section 4 (“Vegan vs. Vegetarian vs. meat diets”), or to improve references to Kim et al. (2019) and add references to recent meta-analysis and reviews on the subject.
    • To make the article simpler and shorter, focusing on the ideas develloped by Wynes and Nicholas (2017), which I think are much more easy to understand and justify : veganism is not the best way to reduce our GHGs emissions simply because options like not having a child or ditching planes are more effective. However, while doing so, I think that credit should be given to vegan diets that it can have some other good effects on the environment than GHGs emission reduction (as stated in Poore and Nemececk 2018), as is done in section 5. The idea could be that instead of saying how "bad" a vegan diet can be as the article does right now (which I think is hard to argue with the current litterature), it would be easier to justify how good the other options are (having less children, not taking the plane, etc.). I think that this would keep the original intent, why not sounding like a hit-piece on the movie Cowspiracy (which I do not endorse).
  7. Increasing CO2 has little to no effect

    4% seems like a small no. but easy to forget that Avogadro's number is very large - there are a lot of molecules. Beside the sheer no. of photos per meter square per second, the other intuition to help guide understanding is how far on average will a photon travel on average before encountering a molecule of CO2. I suspect people that think 4% is a small no. will imagine that it easy for a photon to escape whereas the mean path length is more like a few meters.

  8. A Climate Bet Impossible to Lose

    Bob... I actually made that graph for Stephen Lewandowski for use on twitter. I guess Gavin picked it up from there.

  9. A Climate Bet Impossible to Lose

    RealClimate has a new post up about a number of climate bets of this sort. They have a graph very similar to Rob's first graph above, and link back to this post as one of the bets.

  10. Increasing CO2 has little to no effect

    I was just thinking more about this question coming from devcarr. It seems like a very common logical track that people take. How can one CO2 molecule possibly heat up 2500 other atmospheric molecules? 

    The mechanism of collisional transfer is fairly complex (per Eli's piece) for a non-scientist. Maybe the more simple answer is in regards to the relative number of IR photons and molecular collisions constantly taking place. 

    For one radiatively active greenhouse gas molecule to heat up 2500 other radiatively transparent gas molecules is quite easy, when you think of it in terms of the many millions (billions?) of IR photons hitting those GHG's every... second? millisecond? I'm not sure what the right number is.

    People get stuck on the proportion of CO2 in atmosphere and forget the proportion of IR interacting with the CO2.

  11. Increasing CO2 has little to no effect

    Thanks Bob! (Apologies. I forgot to check my link after posting.)

  12. Increasing CO2 has little to no effect

    Tom's link to "Eli Rabbet explained" seems to lead nowhere, but Eli has a full explanation on his blog:

    The short story is as MA Rodger explained.

  13. Increasing CO2 has little to no effect

    devcarr: Pro scientist Eli Rabbett explained the details, and summarized "a quick estimate that only one out of 100,000 CO2 molecules excited into the (0,10,0) by collision or absorbing a photon, will emit." The vast majority either hang on to the energy or lose it by collision.

    Moderator Response:

    [TD] Fixed broken link.

  14. Increasing CO2 has little to no effect

    devcarr @411,

    The molecules of the atmosphere are in collision with each other at timescales measured in microseconds. The time for an excited CO2 molecule to use the excitement to emit an IR photon averages thousands of times longer. Thus the chances of an excited CO2 molecule being given time to emit an IR photon is very small. Effectively, this means pretty-much all the IR energy that bombards atmospheric gas and is absorbed by CO2 is transfered to the general atmospheric gas molecules as thermal energy.

    But the large number of molecular collisions suffered by CO2, as well as robbing them of almost all incidents of them in an excited state before they can emit IR, also imparts this same excited state into many many more CO2 molecules. And it is this enlarged population of excited CO2 molecules that provides the CO2 molecules for a few of them with the chance to emit an IR photon.

    This should make sense as it is the temperature of the gas, and thus the level of inter-molecular collisions, that determines the level of IR being emitted by the gas. And conversely, it is thus not the level of bombardment of IR photons that determines the level of IR being emitted from the gas.

  15. Increasing CO2 has little to no effect

    Thanks, Rob Honeycutt..

    Somehow the entire atmosphere is warming up, not just the GHG. A thermometer measures the nitrogen and oxygen just as much as the CO2 and water. You can't say the infrared radiation is warming the atmosphere if it only warms the GHG. I am asking how the heat transfers from the hot GHG to the cooler gases, which are 99.9% or more. I presume you are correct that some is transferred through collisions (conductance). I would like more details about how that happens, and how such a small fraction can heat up all the other gases so quickly.

  16. A Climate Bet Impossible to Lose

    If there is another round please let me know. I do would suggest to have a neutral party collect the money in advance. I do not expect these people to be less Trumpian in 10 years, if anything moral values in these groups are on a steep decline.

  17. Increasing CO2 has little to no effect

    devcarr... Each IR photon leaving the surface is interacting with more than one molecule of CO2. Each photon is being absorbed and re-emitted many times. Some of the energy is transferred to other atmospheric molecules through collisions, but often it's being re-emitted only to collide with another GHG molecule. Some of that energy ends up back at the surface. Some eventually makes its way out to space.

  18. Increasing CO2 has little to no effect

    I need some clarification about how greenhouse gases warm the atmosphere. I understand how the GHG warm up by absorbing certain infrared wavelengths. How does the other 99.9% warm? According to the National Weather Service, only 5 units of the heat comes from convective currents, presumably originating with conductance at the surface. Another 24 units comes from condensation of water vapor. 104 units comes from longwave radiation absorbed by GHG. How does the heat transfer from the small volume of GHG to the large volume of other gases? Is it conductance at the molecular level? Wouldn't this have to occur very rapidly, given the very high ratio of the two volumes? How does this affect the ability of the GHG to re-radiate in the wavelengths originally absorbed?

  19. Skeptical Science New Research for Week #3, 2021

    Thank you for all the work you put in to orgnaize these reference lists.  I am hoping that Gavin at RealClimate will comment on this paper.

  20. Skeptical Science New Research for Week #3, 2021

    Sorry, Michael, missed this until now. 

    Referring your question to better brains. :-)

  21. A Climate Bet Impossible to Lose

    Good news! This means I can bulldoze my way into Gosselin (and his merry maniacs) Notrickszone armed with this wonderful phrase:  "If the loser of the bet refuses to pay, then he will be forever regarded as a useless deadbeat loudmouth scumbag with no honour."

  22. A Climate Bet Impossible to Lose

    I often forget myself, but the first question a statistician is supposed to ask is "How was these data collected?".

    On the wildfires, Jewish Space Lasers, anyone?

  23. A Climate Bet Impossible to Lose


    Its possible that many of the remaining climate denailist scientists have narcissistic  personality disorder. This affects about 1% of the general population. People with this disorder are psychologically incapable of admitting they are wrong, or find it extremely painful to do so, and so only do so rarely. Plenty of people have something close to this disorder. The point is there will always be a few denialists just as there is still a flat earth society.

  24. We're heading into an ice age

    Recommended supplementary reading...

    Video interview of Ian Plimer at Sky News falsely claims that a new study announces an incoming ice age, partly based on an incorrect Daily Mail headline, Edited by Nikki Forrester, Article Review, Climate Feedback, Jan 20, 2021

  25. A Climate Bet Impossible to Lose

    Johnny's point about "raw data" raises an important issue. What is "raw" data? When does data processing start?

    For the satellite data, what is being measured is actually microwave emissions form the atmosphere, and it take a lot of modellig to derive "temperature" from that data. Rob's post has some good links in the "Selection of data sets" paragraphs that explain much more.

    Pretty much any environmental variable has some sort of processing that needs to be carried out. Even something as simple as the regular temperature measurements aren't that "raw":

    • In the "olden days" (and probably still at some community-based volunteer observing stations), a liquid-in-glass thermometer was used. The "raw" data is the length of liquid in a tube, and the model used to transform that into temperature involves the temperature-dependence of liquid volume.
    • Most current system measure temperture electronically, where the resistance of some material (either platinum or a semicondutor material) is measured. It is then transformed into temperature using models that relate the electrical properties of materials to temperature.

    Both of these still just give you the temperature of the thermometer, not the air, so the temperature measurement system has to try to make sure the thermometer is at air temperature, usually using a Steveson Screen or some other form of ventilated radiation screen.

    That gives you local air temperature, and then  you need to make sure that your local temperature is telling you the information you need at a regional scale. There is a good series of posts here on how temperature measurements taken for the purpose of weather observations are used to estimate global temperature changes:

    Everything in science has "models" involved at some point. Some are simple and extremely well-defined. Others are complex and involve considerably more uncertainty.

  26. A Climate Bet Impossible to Lose

    Johnny... That's a very interesting point, and one that I will absolutely remember in the future.

  27. A Climate Bet Impossible to Lose

    Speaking as a satellite systems engineer, please don't refer to that second graph as "raw data". That is already at least a "Level 1" product. Level 0 is raw data, right from the sensors. I build astrophysics instruments, so I don't know for sure that the graphed data is L1; I strongly suspect it's Level 2, which has had even more processing done to it.

    I mention this not for the sake of pedantry, but because it's worth pointing out always that any satellite numbers in Kelvins have already undergone a large amount of processing. The only numbers that come down in Kelvins are the internal temperatures of the satellite itself. (Okay, even those probably are downlinked in A/D counts, but the conversion to Kelvin is usually a simple linear calibration.)

    Anyway, I think it's worth avoiding the term "raw data" when referring to anything that's already been heavily processed based on a model, especially when there are two models whose outputs are outside each others' one-sigma error bars.

  28. A Climate Bet Impossible to Lose

    Interesting ...

    I can 't figure out whether climate change deniers genuinely believe that the earth is not warming. But now I am starting to believe that some of them are sincere, even though they are wrong. I think it is called "emotional investment". As they have invested years, even decades of their life defending the denier position, admitting their mistake now would be admitting they have wasted years.

    Humans are a social species. Of course, believing falsehoods is not a clever survival strategy. But being loyal to the group you belong to – sometimes by agreeing with what everyone in your group claims to be true – IS a valuable survival strategy. You have a better chance of survival in a group than on your own. But that also means that such people cannot be persuaded by logical arguments or by facts.

  29. A Climate Bet Impossible to Lose

    Leprechauns? No way. It's pirates.

    ...but a nice piece on an interesting bet, Rob. As you said, it was a pretty sure bet. I think the "coolists" were out on a Snipe Hunt looking for support for their viewpoint.

    I think your cheating was the result of using physics instead of fizzicks to predict what would happen.

    It's the kind of bet I wish we would lose, but that will take a bit of time.

  30. A Climate Bet Impossible to Lose

    Ah, luck of the Irish, I say. :-)

  31. Philippe Chantreau at 05:20 AM on 2 February 2021
    A Climate Bet Impossible to Lose

    You cheated. Ocean cycles were rebooted in the middle and then commandos of invisible leprechauns were lighting fires everywhere to heat up things. I'm pretty sure I saw it on FaceBook. It's all a hoax.

  32. Veganism is the best way to reduce carbon emissions

    Guilhem... You're going to have to show me where the IPCC makes such a statement because I'm not finding it. 

  33. Veganism is the best way to reduce carbon emissions

    Guilhem , there is much in what you say.  But essentially your line of argument fails the test of practicality & timeliness, if you are pursuing a primary goal of halting the current rapid global warming.  And I need hardly point out to you that AGW is heading toward colossal damage to the biosphere, with resultant cruelty to all animals not just the domesticated species used by omnivorous humans.

    Stabilizing the present-day climate must take precedence.  Eliminating fossil fuels is a goal reasonably possible over 30 - 50 years.  In effect : in two generations of humans.

    But achieving a Vegan or merely vegetarian diet worldwide, will take far more time than two generations.  Can I cite a scientific study to support this contention - no - but your own knowledge of human nature & history will surely admit the truth of it.   Guilhem, there is simply not the luxury of time to achieve your "Vegan ASAP" goal.   Other goals must take moral priority over your desired Vegan revolution.

    To aim simultaneously at AGW correction and Veganism, is to attach an iron ball & chain to the ankle of the Anti-AGW movement.

    Guilhem , doubtless you have many  worthy aims in this life.   But if you wish to be more successful than Napoleon was, then you had best conquer one enemy at a time.   And choose wisely your first enemy ~ and move fast, before your other enemies wake up and combine against you.

  34. Veganism is the best way to reduce carbon emissions

    Actually the 5.8% figure only account for enteric fermentation and manure management. The whole livestock sector account for 15% of GHGE (about 8Gigaton CO2) as stated by the UN, Lancet Countdown, IPCC report on land use etc (see source in the comment above) and many more reputable institutions

    I hope the rest of the message is considered valid and worth being added in a way or another (to correct the current article maybe?) as you only mention this single figure in a comment that is 5 pages long

  35. Veganism is the best way to reduce carbon emissions


    Perhaps you need to widen your scope.

    Livestock only accounts for about 5.8% of all GHG emissions. That's important, but there are many other larger sources.

  36. Climate's changed before

    It's time the scientists admit they really don't know what they are doing.

    Moderator Response:

    [TD] You must be more specific in your comments. Future comments like this one will be deleted without warning.

  37. 2021 SkS Weekly Climate Change & Global Warming News Roundup #5

    so, was Planet of Humans wrong about the fallacy of biomass and solar and wind?  They could be less carbon neutral than what they are replacing.

    Moderator Response:

    [TD] Yes, that pseudo-documentary is wrong. See this post.

  38. Veganism is the best way to reduce carbon emissions

    Hi all, I appreciate when people take time to debunk climate hoax, however I think this particular article is misleading, to say the least, and need major updates. It is both in the name of the truth in science, especially related to climate change, and the credibility of your page that I’m writing this very comprehensive exhaustive feedback on the many flaws I’ve identified.

    We know that land use and food production are major actors in climate change. The argument for veganism from an environmental perspective is oftenly that animal agriculture is a big contributor to climate change and shifting toward a plant based diet is better for the environment. Most people would agree that Veganism isn't the single best solution to climate change, and that -for instance- collective suicide might probably be better, as well as a totalitarian regime imposing a zero carbon lifestyle. From an individual perspective, a non vegan eating a single slice of pork ham a year but living car and plane free is probably doing better for the environment than a vegan doing a Bali - New-York plane round trip every year. With these arguments in mind, “veganism isn’t the best way to reduce carbon footprint” is a no brainer. That being said, it is true that some animal right activists overestimate the impact that veganism can have so I understand why you wish to clarify to them that it is not as black and white as they wish it to be. However globally the impact of animal agriculture is hugely underestimated (see for instance and by trying to debunk a very marginal argument (‘veganism is the single best way to reduce carbon footprint’), you end up downplaying the power that one have by shifting to a plant-based or even vegan diet. This kind of attitude might actually increase the total carbon footprint, or at least minimize the carbon mitigation of people’s action by discarding a sector on which people can have a huge impact which is widely unknown from the general public.

    First, the livestock sector accounts for 65% of the food sector GHGE while only providing 18% of the world's calories. And while most of the food fed to animal is non-edible (in dry weight), meat production is still globally inefficient (it takes about 3kg of edible dry plant to produce 1kg of meat Because the livestock sector is about 15% of all anthropogenic emissions as calculated from many LCA, notably by the FAO (, it is a huge source of potential mitigations.

    To get a first idea of what are the order of magnitude we’re talking about, governmental official French figures are as follows : An average omnivorous diet emits 2,8 tons of equivalent CO2 per year, about half of which is coming from animal products (meat, dairy and eggs). A diet with ruminant at every meal emits 6 tons of CO2 per year. A vegan diet can emit as low as 0.6 tons and is the least carbon intensive diet. To achieve Paris agreement on climate change we need an individual carbon footprint of 2 tons or less of CO2 per person per year, which is impossible to achieve on a cheese or meat-based diet. [1]. A vegan meal is, on average 0.8kg of CO2 [2], a egg-based meal is on average 2kg of CO2 [3], a cheese/pork/chicken based-meal is 5.4kg of CO2 [4] and a ruminant based meal is 25.2kg of CO2 [5]. According to the french national agency for climate transition, a vegan meal emits 2.5 to 31.5 times less CO2eq than any other meal and there is no reason that this figure should be much different in other countries. If anything, French carbon impact of animal products -especially ruminant- should be lower than in other countries such as Brazil. These kinds of figures appear nowhere in your article while they could provide useful insight to readers as to what are the best food sources to fight climate change.

    “Although veganism does have the potential to reduce GHG emissions associated with diet, it is important to consider other sectors that are also part of the problem.” → One might ask why we should consider other sectors when it is this one we are debating. This kind of “whataboutism” argument can be used to discard every policy on reducing carbon footprint.

    Insisting on what people perceive (to be feasible, to be environmentally friendly, etc.) instead of what is factually positive for the environment is misleading. If you claim to answer the complex question of limiting the worst for the climate you cannot rely on people’s opinion. I know just as much as you that major societal and individual change are required to achieve climate goals and prevent the worst scenario. Claiming that veganism isn’t good because some people really want to eat meat as a main argument is unbelievable on a website such as yours and by trying to debunk such a minor myth in our society (PETA's claim), you perpetuate more dangerous myths (such that grass fed ruminants are carbon friendly). Because the myth that does currently more damage is that local, organic, grass fed animal are better for the environment you should reverse the debunking and show that actually, intensive exported plant food are way more carbon friendly (and that “organic” isn’t really doing much, except increasing the demand for land by decreasing the productivity)

    When you’re pointing at non-vegan related issues such as food waste to dismiss the major changes that could be brought, you’re obscuring the debate further. When we talk about change, we have to think about counterfactual scenarios: the question is not ‘is veganism with a lot of fruit imported by plane wasted good?’ but ‘is veganism good, all things else being equal ?’. Otherwise it might sound like a strawman.

    On the Kim et al. (2019) paper, I don’t know how you manage to distort the results that much in the process of trying to make veganism look bad. The paper is clear: the vegan diet is the less carbon intensive in all country studied (97% to be correct), only the low-food-chain diet is slightly above, but not statistically significantly different, from vegan diet*. The argument you make about vegetarianism has not his place here if you want to discuss Veganism. What the paper is saying is that it’s better to be ⅔ vegan than 100% vegetarian because dairy products have a massive impact so it doesn’t compensate for the ⅓ of omnivorism remaining. Therefore, your conclusion “there are arguments that a flexitarian diet with moderate amounts of meat is better than a vegetarian diet that cuts out meat completely, showing that stopping meat intake completely does not necessarily reduce dietary GHG emissions and cannot be assumed to do so in a vegan diet.” is a fallacious non-sequitur : vegan diet is better than both flexitarian and vegetarian diet (as shown by the very study you’re citing) because it eliminate both meat AND dairy which both are very carbon intensive. I can’t believe you haven’t seen that and I really wish I was able to assume you’ve made an honest mistake but I barely can. Such mistakes, always in the disadvantage of veganism, and repeated, seriously undermine the ideological neutrality of the author on these questions.
    (*Please note that the low food chain diet is a diet where 90% of animal proteins are replaced with pulses, so we could say it’s a 90% vegan diet. That’s why it’s not statistically significantly different from vegan diet).

    The vegan diet doesn’t lead to a higher consumption of fruit: because vegan doesn’t eat meat, cheese and eggs which are the main source of protein, fat and calories, we should expect vegan to eat protein and fat sources instead such as legumes, beans and nuts or oil. Increasing fruit consumption is within the nutritional guidelines of every country which have one. For these reasons, the whole paragraph appears as a non-sequitur. At best, the argument is very weak and it is on you to show that the eventual additional portion of fruit due to veganism (and not due to healthier lifestyle as vegans also usually have healthier lifestyle, but uniquely due to veganism, which its very existence is one of your unproven assumption) will increase carbon emission so much that it will cancel out the 8Gigaton of CO2 mitigation from quitting animal agriculture. I think because of the assumption it relies on, both the waste and plane-transported food fruits are not a valid argument

    Speaking about the food waste, which is another issue a priori unrelated to and independent from veganism, there’s a paper titled “The opportunity cost of animal based diets exceeds all food losses” []. The title is pretty straightforward: in the US, after adjusting for various nutrient density, the adoption of a vegan diet could feed 300 millions more people while the total elimination of all waste along the whole food production line (which is impossible) could only feed 100 millions more people. Once again, just like the “Vegetarian vs. vegan” paragraph, I don’t understand how you can try to use an unrelated issue to make veganism look bad but still fail.

    As a reminder, the biggest meta-study on food impact shows that only 0.16% of the food on the planet is transported by plane []. It is questionable to mention it only here, when talking about veganism. The main impact of the vast majority of food is on-farm emission, as shown by the same meta-study on 38000 farm in 119 countries [] eating 100% local would only reduce emission by 5-10% whereas eating vegan can divide by several time the carbon footprint of diet.

    The argument of carbon sequestration by grazing livestock, a favorite of the industry, have been proven wrong for a long time, as the methane and nitrous oxide emission from ruminant far exceed the best sequestration possible. See for instance this review of the literature (and note the discrepancy between figure from the academic domain and claim from outsider unpublished in journal such as Savory) []. Also, wild ruminants could do the same job and it would be vegan, as grazing pasture doesn’t require either killing nor exploiting them. Many wild ruminants still exist, preceded humanity and very likely will still exist if humanity disappears.

    You might want to update the carbon impact of a vegan diet because Scarborough and Berners-Lee are not really in agreement with current research. Current research from Poore and Nemecek [], of the BMJ paper by Springmann [] show that a vegan diet emits several times less (>50% less) CO2 than conventional diet. The official French figure show that a vegan diet can emit 4 times less CO2 than the current diet. You might as well check out the IPCC report on land use showing that a vegan diet could prevent the emission of 8 Gigaton of equivalent CO2 per year, showing a massive reduction (roughly 20% of all current anthropogenic emission A recent Science paper also showed that shifting toward a plant-based diet (EAT Lancet which is about 70% less white meat and 95% less red meat than current French diet) and other food change are mandatory to reach climate agreement []. The Kim paper of 2019 you’ve cited above shows a global reduction of 70% GHGE (why did you choose to not mention it ?). In the light of these various paper, it seems strange that you choose to show only to moderate-impact paper.

    The latest Lancet Countdown report shows that animal agriculture emits about 55% of the carbon footprint of food production (including the feed) while providing only 18% of the world's calories. What is really shocking to me is that 95% of the animal farming carbon footprint comes from ruminants which represent a tiny minority of the number of animals killed and meat consumed. How can you suggest that eating lamb or beef is sustainable in any way ? For an outsider it looks like you’ve internalized the rhetorics of the industry and are really detached from the reality of the current research. []

    The occurrence of cowspiracy appears as you have something against this movie and seems to alter your neutrality. There are ways to criticize some element of cowspiracy (such as the Goodland paper and the 51% figure) without making such a poor quality argument against veganism as a whole.

    I would like to add few points that you have eluded about the impact a vegan diet can have: it can do much more to the planet than just ‘reducing GHG emissions associated with diet’. It can, for instance, lower potential health crises by reducing zoonotic emergence risk (70% of new diseases are zoonotic Land which are not used could be left to the wild, and with the natural reforestation of pasture we could sequester up to 700 Gigatons of CO2, making the climate goal of +1.5°C by 2100 feasible at 66% as shown by this Nature Sustainability article of 2020 []. In countries where the meat consumption is high, it could drastically reduce the disease burden and total mortality, according to this BMJ paper, it could reduce total mortality of several tenth of % []. Note that this article also explored the carbon impact and showed a vegan diet emit globally 80% less CO2 than what we are currently doing (and is of course the least carbon intensive of all diet studied)

    I hope I have achieved to make you realise how this page may sound to an outsider who knows the figure, and I have provided you with many up-to-date research sources.

    Please make an impartial page to properly inform about the climate impact of food and the huge potential of plant based, vegetarian but especially vegan diet to mitigate climate crisis. As you’re part of the Pro-Truth Pledge i’m sure you will take this matter seriously. I would be more than happy to help to write something about it if you want, or to answer any of your questions.

    Thank you for your considerations,

  39. Philippe Chantreau at 06:20 AM on 31 January 2021
    Refining the remaining 1.5C ‘carbon budget’

    We're already pretty much a one degree and nowhere near equilibrium for current CO2 levels. The probability that warming would not exceed 1.5 degrees is likely lower than what is outlined in this article. The probability that emissions will stabilize by 2050 to levels that will allow for the atmospheric fraction to stop increasing is close enough to zero to be negligible. We should prepare for 2 degrees as minimum. The 2050 and after generations are going to have an interesting world to live in...

  40. One Planet Only Forever at 09:05 AM on 30 January 2021
    Case study - identifying myths and fallacies in Climate Science (Mis)Information Briefs

    Bob Loblaw @4,

    When I got my MBA decades ago the professor of the Marketing course prefaced the course by telling us how the science of marketing could be abused to fool people, but that we were to avoid trying to benefit from the tactic because it would only temporarily be successful.

    Tragically, misleading marketing only being able to temporarily succeed has been all that is needed by Political Parties inclined to cheat that way, success on election day (or the short period of election days).

    More tragically, there continues to be a lack of effective measures to discourage or penalize misleading political marketing.

    Social Democracy (pursuing truer democracy through the correction of developed injustice and inequity) and the international pursuit of constantly improved understanding of how to reduce harm and be more helpful to Others, especially to help future generations are important parts of the solution. Those guiding principles are the basis of Agenda 21 and the Sustainable Development Goals which focus on limiting the harm done by fossil fuel use because limiting the harm of climate change makes it easier to achieve almost every other SDG objective.

  41. Case study - identifying myths and fallacies in Climate Science (Mis)Information Briefs

    BaerbelW @3, yes I have read it thanks. I have posted a link to it in a response to someone over on the Realclimate website. 

  42. Philippe Chantreau at 05:05 AM on 30 January 2021
    2021 SkS Weekly Climate Change & Global Warming Digest #4

    Thanks for the links, the Nature review is very interesting.

  43. Case study - identifying myths and fallacies in Climate Science (Mis)Information Briefs

    "Winning the argument" also has a lot in common with "making the sale".

    There is an entire industry out there whose sole purpose is to convince people that they need something they previously didn't know they needed. And probably things they don't actually need.

    The psychological tricks used in the marketing business are being applied in the political arena, and in general by anyone wanting to shape public opinion. For sales, there are "Truth in advertising" regulations and possibilities of criminal prosecution (at least in Canada, where I live), but that doesn't apply to so much of our social discourse.

    A "well-informed public" is our best protection, but too much is done to make sure the public is not well-informed.

    The mantra of this dishonesty is "you can fool all of the people some of the time, and you can fool some of the people all of the time, and that's enough."

  44. Case study - identifying myths and fallacies in Climate Science (Mis)Information Briefs

    nigelj @ 2

    I really hope that John Cook's Cranky Uncle game can help with this general and widespread issue! Have you seen the Teachers' Guide he published yesterday?

  45. Case study - identifying myths and fallacies in Climate Science (Mis)Information Briefs

    The reason these misinformation campaigns that use logical fallacies manage to fool so many people might be as simple as logic not being taught in school. It wasn't taught when I went to school in the 1970s and 1980s, but by pure chance I stumbled across a book on logic and fallacies when quite young. However there is probably more to it. Many people just dont think terribly logically.

    Some people use logical fallacies as a matter of course, because to them its all about winning the argument by fair means or foul. It becomes ingrained in them.

  46. 2021 SkS Weekly Climate Change & Global Warming Digest #4

    Boava et al (2021) is also the focus of:

    Climate crisis: world is at its hottest for at least 12,000 years – study by Damian Carrington, Environment, The Guardian, Jan 27, 2021

  47. 2021 SkS Weekly Climate Change & Global Warming Digest #4

    Nature has a review of the Bova article, here.

  48. 2021 SkS Weekly Climate Change & Global Warming Digest #4

    Phillippe Chantreau @1,

    Bova et al (2021) 'Seasonal origin of the thermal maxima at the Holocene and the last interglacial' certainly looks to have made some interesting and important findings but as you say it is paywalled. There is a graphic attached to this Rutgers press release which is perhaps a little clearer than the thumb-nails attached to the paywalled paper.

  49. Philippe Chantreau at 05:03 AM on 29 January 2021
    2021 SkS Weekly Climate Change & Global Warming Digest #4

    Suggestion for upcoming digest: Seasonal origin of the thermal maxima at the Holocene and the last interglacial

    Unfortunately behind paywall, but seems to elucidate a discrepancy between data and modeling in paleoclimate.

  50. The SCIARA Project – Interactive Time Travel into the Climate Future

    @doug_bostrom, thank you for the kind exchange. I very much appreciate it.

    Recruitment is wide open, and every particpant needs to go through some socio-demographic screening.

    Otherwise we could never select representative samples or measure representativity in the first place.

    Of course, we will make sure that this data and the behavioural data from the experiments cannot be connected to individual user accounts by simply stealing our database. ;-)

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