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Comments 9801 to 9850:

9801. Human 2932847 at 17:37 PM on 4 September 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      I don't see much sign of controversy , though, apart from here.

9802. DrivingBy at 13:00 PM on 4 September 2019
      2019 SkS Weekly Climate Change & Global Warming News Roundup #35
      

      @William

      1. "I seem to remember that Florida is where the well off; those that made their money ignoring climate change, have retired to."

      2. ""Sea level rise and monster storms couldn't happen to a more deserving people.""

      It appears you have never been to, much less lived in Florida. 

       People who saved and are able to afford a pleasant retirement did not do so by "ignoring climate change", they did so by a dozen different means. Some made retirement nest eggs from saving 7% every year from age 23, some had public sector retirement at age 55, then continue working in some other capacity while collecting a generous pension.  Some were the person who opened the town's best roti-roll joint and then 3 satellites, some developed an app that took off. Some were in  government or other forms of organized crime. 

      What they have in common is that they wasted no time being gloating over bad things happening to people more successful than themselves. 

9803. Bob Loblaw at 10:56 AM on 4 September 2019
      CO2 effect is saturated
      

      GwsB:

      You have received a rather negative reaction, because you have made some pretty strong claims based on some faulty reasoning. Regulars here can be pretty impatient with such proclamations from newcomers.

      Let me try to explain where your error lies. To begin, thanks for making it clear just what you think "CO2 effect is saturated" means - often people that make that argument are less than clear. You have based your argument on the (correct) observation that very little IR radiation can travel directly from the surface to space.

      The part where your argument breaks down is actually hinted at in your post. You state that IR radiation absorbed in the atmosphere can be re-radiated - sometimes up, sometimes down. Eventually, that energy will be emitted to space, but it is delayed. Let us look at the implications of that.

      Radiation absorption is a logarithmic function, expressed by Beer's Law. If  a certain thickness of the atmosphere can absorb 10% of the IR radiation,and transmit 90%, then the amount passing directly through is 0.9 of the original value. The next layer (same properties) then transmits 90% of 90%, or 09.*0.9=0.81. The third layer will allow 0.9³ = 0.729, and so on.

      The figure below shows that decline. It also shows the same result for a case where each layer transmits 95%, instead of 90%. The layer-by-layer sequence for 0.95 is 0.95, 0.95², 0.95³ etc. Note the following:

      • After 200 layers, both curves show essentially zero transmission, fitting your "saturated" argument.
      • In the middle, however, the two curves are clearly not the same.For a coefficient of 0.9, it takes almost 23 layers to reduce transmission to 0.1. For a coefficient of 0.95, it takes almost 46 layers. (Yes, the doubling of the distance is an exact mathematical result of Beer's Law, and the per-layer doubling of absorption from 0.05 to 0.1.)

      The "saturation" argument fails to include that intermediate difference, and that is where it goes very, very wrong. This difference in how much IR radiation is transmitted how far is essential to understanding the greenhouse effect. Adding CO2 has a neglible effect on how much IR radiation can pass directly from the surface to space in a single step, Adding CO2 does affect how far IR radiation gets in a single step, and this affects how many steps it will take before it can finally reach high enough in the atmosphere to escape to space.

       

      

       

      You can see this in the figure I provide, if you read it from right to left - i.e., think of the right as the surface, and the left as space. IR radiation emitted upward (to the left) at layer 10 has a 39% chance of escaping to space for a coefficient of 0.9, but a 63% chance for a coefficient of 0.95.

      (Note: the values and layers in the diagram are purely illustrative. Radiation transfer in the atmosphere needs to be calculated at many different wavelengths, not a single number as shown above. The general principle is correct, though.)

      As CO2 or other greenhouse gases increase, the IR lost to space originates at a higher altitude, where the atmosphere is colder. This means less IR lost to space, until the atmosphere can warm to compensate.

      An analogy for your "saturation" argument would be a foggy night, where you can't see the building two blocks away, but you can see a building one block away. From the perspective of the distant building, visibility is "saturated" - no light from the distant building is reaching your eye. Does this mean that adding more fog has no effect? No, because additional fog will eventually make it impossible to see the building that is only one block away.

      Proper examiniation of the effects of adding CO2 to the atmosphere requires that the effects throughout the atmosphere be included, not just the direct transmission from the surface to space in a single step. And the calculation that include all those effects show clearly that adding CO2 leads to surface and tropospheric warming.

9804. william5331 at 06:00 AM on 4 September 2019
      2019 SkS Weekly Climate Change & Global Warming News Roundup #35
      

      I seem to remember that Florida is where the well off; those that made their money ignoring climate change, have retired to.  Sea level rise and monster storms couldn't happen to a more deserving people. A nice twist is that the poorer people live on an inland ridge while the rich, retired are right down on the beach.

9805. Eclectic at 01:33 AM on 4 September 2019
      CO2 effect is saturated
      

      GwsB @525 ,

      you have completely failed to understand the CO2 (and H2O) mechanism of "greenhouse".

      Before you embarrass yourself by making further comments about CO2 saturation, please read & think about Dana's OP, and check out RealClimate & other information above. 

      Moderator Response:

      [PS] Please watch tone.

9806. MA Rodger at 01:25 AM on 4 September 2019
      CO2 effect is saturated
      

      GwsB @525,

      You ask if that Wiki graph you show @525 is misleading. It certainly is!!

      That Wiki graph simply shows the chance of a photon travelling vertically through today's atmosphere without a particular species of GHG absorbing it en route. It shows nothing of how many such photons would be travelling at each wavelength or even in what direction. The CO2 absorption band at 2.7μm is stopping solar radiation coming in from the sun not IR going out. The CO2 absorption band at 4.3μm sits in the gap between incoming solar radiation and outgoing IR - there are effectively no photons to be absorbed so it has no relevance to climate. And the inability of a photon to travel un-absorbed by GHGs out through the atmosphere does not prevent the mechanisms of the greenhouse effect from gaining strength through additonal levels of GHG. And I should add that the Wiki page you took the graph from provides a woeful attempt to describe the mechanisms of the GH effect.

      You say "The basic physics is simple: A photon of light at a wavelength of 14 μm [15μm] is passed from one CO2 molecule to the next performing a kind of random walk until it exits the atmosphere. There are two exits, outer space and the earth. Saturation means that a photon starting from the earth has very little chance of exiting to outer space." The effect of this 'saturation' is solely that there will be a random walk as all photons will be absopbed. This does not of itself make the chances of IR resulting from that absorption exiting into space small.

      Interestingly, you cite Zhong & Haig (2013) 'The greenhouse effect and carbon dioxide' yet you fail to acknowledge the finding of that paper which is "We conclude that as the concentration of CO2 in the Earth’s atmosphere continues to rise there will be no saturation in its absorption of radiation and thus there can be no complacency with regards to its potential to further warm the climate."

      Instead you set out contradictory conclusions of your own - "The total negative impact is almost cancelled by the positive impact around 15 μm."

      The GH-effect works because the emission & re-emission of IR from the atmosphere containing GHGs will only occur at those same wavebands which subject to are absorption. But the rate of re-emission is set by air temperature. As the temperature drops through the troposphere, the point where emissions will get out into space through the thinner upper atmosphere; that point in the troposphere will be colder. Thus the GHG at that higher altitude will re-emit less IR because it is colder. The more the GHG in the atmosphere, the higher the altitude and the bit of troposphere which emits into space and thus the less IR is emited.

      Of course, as the graphics in Zhong & Haig show, that mechanism will go into reverse as the altitude becomes high enough to reach the stratosphere. In the stratosphere, temperature rises with altitude and so the more GHG the greater the IR emissions into space. This is the mechanism which you mention being apparent in their Fig5b which you say results in the increasing GH-effect being "almost cancelled." However, the extra GHG effect of CO2, although reduced with increasing CO2 concentrations in the well-konwn logathithmic relationship, does not peak even if the 15μm band is taken in isolation. It keeps on increasing. And at CO2 levels above 2500ppm(v), the 15μm band is boosted by a compound absorption band at 10μm.

      The climate forcing of CO2 does not hit an upper limit. In the words of Zong & Haig (2013), "as the concentration of CO2 in the Earth’s atmosphere continues to rise, there will be no saturation in its absorption of radiation."

9807. Philippe Chantreau at 23:26 PM on 3 September 2019
      CO2 effect is saturated
      

      GwsB "the wings have little effect"

      That is false.

      The links at the bottom of this page to RC's saturated gassy arguments threads explains it, as well as other sources.

9808. GwsB at 19:49 PM on 3 September 2019
      CO2 effect is saturated
      

      In the discussion about the effect of CO2 on the climate there are certain images which may be said to incorporate the essential part of the arguments. Such iconic graphs are the driving force in changing one's view of the world. A good example is the sun with the planets rotating around it. This stopped all phantasies about what happens at the edge of the (flat) earth. This iconic image made it possible to sail Westward in 1492 in order to reach India.

      For CO2 the iconic image is the rippled increasing graph of the CO2 concentration as measured at Mauna Loa from 1960 onwards, sometimes extended over the past thousand years by observations from tree rings and ice cores to obtain the "hockey stick". For the influence of CO2 on climate the iconic graph is given in Wikipedia https://en.wikipedia.org/wiki/Greenhouse_effect (last updated 23 August 2019)

      Caption: "Atmospheric gases only absorb some wavelengths of energy but are transparent to others. The absorption patterns of water vapor (blue peaks) and carbon dioxide (pink peaks) overlap in some wavelengths. Carbon dioxide is not as strong a greenhouse gas as water vapor, but it absorbs energy in longer wavelengths (12–15 micrometers) that water vapor does not, partially closing the "window" through which heat radiated by the surface would normally escape to space."

      The graph shows that the effect of water vapour, H2O, is much greater than the effect of CO2. It also shows the saturation of the absorption due to CO2. The first argument (about water vapour) is valid. We can't do anything about the concentration of H2O though, except perhaps by increasing the temperature. So we will just have to accept this effect. The second argument (about saturation) is also valid. The absorption at wavelength 4 - 4.4 μm is 100% over most of the region, and so too at 12-15 μm. In comparison with H2O the peaks of CO2 are very steep and the wings have little effect. It is only the thin peaks at 2 μm and at 4.9 μm which will grow significantly if the concentration of CO2 is increased.

      The basic physics is simple: A photon of light at a wavelength of 14 μm is passed from one CO2 molecule to the next performing a kind of random walk until it exits the atmosphere. There are two exits, outer space and the earth. Saturation means that a photon starting from the earth has very little chance of exiting to outer space. It is almost certain to exit the atmosphere to the earth, where like shortwave radiation it will be re-emitted at a different wavelength. Even if the new wavelength with probability a half lies in an absorption band of CO2 or H2O, this only means a stay of execution. In the end the photon will escape to outer space through one of the long wave gaps in our atmosphere.

      The graph in Figure 2 in Zhong & Haigh (2013) is perhaps more precise, but the vertical scale runs over twelve orders of magnitude, (twelve orders of magnitude is from one mm to a million km, or from one gram to a Megaton). The result of this scale is that I am not able to comprehend the significance of the graph. Figure 5b, bottom, gives the difference between the radiative flux for the present level of CO2 (389 ppmv) and a level increased by a factor 32 (12500 ppmv). The total negative impact is almost cancelled by the positive impact around 15 μm. This impression is reinforced by Figure 6a where the graph is practically horizontal beyond 400 ppmv. In Figure 6b we see an increase in the slope beyond ten thousand ppmv. In that graph the horizontal axis is logarithmic and runs up to a million ppmv, which is a pure CO2 atmosphere. These results are based on models and therefore should be taken with a pinch of salt.

      The conclusion is: The direct impact on the temperature of the earth of the increase in CO2 from the present level of around 400 ppmv is relatively small. This is due to saturation at the bands where CO2 absorbs long wave radiation.

      Is the graph above misleading? It is described as "(Illustration adapted from Robert Rohde.)". Clicking on Robert Rohde results in the message: www.globalwarmingart.com refused to connect.
      If anyone knows a better graph I would be very happy to obtain a link.

      There is a nice course on climate denial presented by the University of Queensland https://courses.edx.org/courses/course-v1:UQx+Denial101x+1T2019/course/ The course is free of charge and contains a huge amount of good information on climate change. Unfortunately the course does not address the topic of the absorption of CO2 at specific wavelengths. Neither does the basic rebuttal by dana 1981.

      The near saturation of CO2 at present levels makes it difficult to convince people to vote for a cut in CO2 emissions or for a tax on such emissions.

      Moderator Response:

      [RH] Your image was breaking the page formatting. I can add it back in but it needs to be smaller than 450 px wide, which for that image was going to render it unreadable.

9809. nigelj at 17:38 PM on 3 September 2019
      2019 SkS Weekly Climate Change & Global Warming News Roundup #35
      

      Hurricane Dorian is another slow moving Hurricane thus potentially being more damaging. Slow moving hurricanes are associated with climate change and dump more rain.

9810. nigelj at 07:20 AM on 3 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      OPOF @20

      "The 'high meat and fat diets' are often promoted as weight loss diets. The science indicates that people on such diets should be carefully monitored by medical professionals to ensure "

      Yes and I have generally promoted the same. The low carbs high meat and fat diets might make sense as a temporary thing to loose weight, but not as a permanent diet. People should eventually transition back to a sensible sort of balanced diet like the Mediterranean diet.

      The trouble is the low carbs high meat and high fat diets are being promoted as a permanent thing, certainly by at least some experts and many of the people who have tried them. I see this all over the internet. I had to loose weight last year hence my interest.

      This creates an awful mixed message for society where one group are saying reduce meat consumption and eat more plants (carbs) for the sake of the planet, and other groups are saying eat high meat low carb diets.  The health authorities need to give a much more resolved, consistent and clear message.

      Of course the problems of eating too many calories especially if they are mostly white carbs are well known. I would not advocate that. The answer looks like its about balance and keeping total calorie intake moderate within healthy guidlelines, and keeping the white carbs component of this sensible as well. Asians and Italians eat like this and do not have big diabetes or heart disease issues.

      And it has to be said that its not even that clear that such high meat diets loose more weight than other diets in the long run, however if someone is diabetic then a high meat low carbs diet does become pretty imperative.

      "The key is understanding that the high meat consumption diets liked by people who grew up being impressed by people who could afford to eat large amounts..."

      Yes absolutely. Adults only need 60 grams of protein a day which is not very much, and it can come from meat or plants. High meat consumption is indeed more about habit and displays of status. However some meat in the diet seems fine to me in moderation, and another reason is because much of our land only really suits cattle grazing and can't be easily converted to crops. 

      Finally humans evolved as omnivores, ie we eat quite a varied diet with a bit of everything, and it's also important to enjoy our food. I'm reluctant to change this towards extreme sorts of diets, unless theres very solid science based evidence.

9811. One Planet Only Forever at 01:38 AM on 3 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      nigelj@19,

      The 'high meat and fat diets' are often promoted as weight loss diets.

      The science indicates that people on such diets should be carefully monitored by medical professionals to ensure that their health is not compromised by the strict temporary diet. In some cases, just a minor 'cheat' on the diet can cause major harm to internal organs because the body systems are not in an adaptive state that is able to respond to the 'cheat'. And the person on such a diet still has to learn how to eat a healthy diverse diet that will not return them to the condition they tried to correct.

      The key is understanding that the high meat consumption diets liked by people who grew up being impressed by people who could afford to eat large amounts of meat are not healthy (and the protein from 4 oz of meat is all that a body will process from a meal). And that 'perception of superiority of eating lots of meat' is an unsustainable impression (just as the impressions of over-sized, over-powered personal transportation or housing is unsustainable).

      There is a massive variety of healthier reduced meat diets that can be enjoyed that maximize the use of locally sustainably grown products (including appropriately limited amounts of locally produced meats). And those diets, combined with adding activity like walking and biking rather than 'powered transport' will result in sustainable healthier weight loss, it will just take longer than the 'crash diets'.

      Improving awareness and understanding is hard to do in societies that are flooded with misleading advertising that harmfully develops easily impressed people who want what they develop a liking for 'quicker, easier, and cheaper', people who declare that they cannot and will not give up something they have developed a liking for.

9812. nigelj at 07:05 AM on 2 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      Driving By @14 was perhaps a bit snarky, but does raise a very interesting and pertinent  issue on diet. Dietary advice is indeed  very contradictory, with seemingly well qualified people promoting diets that are low in meat and fat consumption, like the Mediterranean diet, and vegean diets (no meat) and others promoting high meat and fat diets like Atkins, Ketosis, and the Paleo Diet (technically a high fat diet but people will achieve this with higher meat consumption).

      People must be utterly confused, and plenty express this on websites.

      The high meat diets are in total contradiction to advice to reduce meat consumption for the good of the planet.

      Personally I think moderately low meat mediterranean diet makes the most sense all things considered. Italians and Greeks apparently have good health and longevity. Humans are omnivores.

      While meat is an inefficient use of resources, many grasslands grazed by cattle dont really suit crop production, so this suggests to me the only practical answer is moderately low meat diet.

9813. nigelj at 06:41 AM on 2 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      I want to clarify my point @10. I was responding briefly to wjohnallen @7 who it seemed to me made an odd sort of statement namely " it turns out that a cow consumes more CO2 than it belches out as CH4 (on a CO2eq basis at a GWP of 25).Who knew that ruminants on grass pastures are carbon negative? " That seems an impossibility as I explained. Tell me why I would be wrong.

      However I accept there is good evidence that cows can managed to encourage higher rates of grass growth and thus more sequestration of atmospheric carbon by that grass and its products of decomposition in the soil. I've said this before. This seems like a different issue to wjohnallen's point. This would make cows carbon negative, although its not all that clear to me just how carbon negative they would be.

      I think science of the methane cycle was being confused with mitigation by enhanced soil sinks.

9814. One Planet Only Forever at 04:31 AM on 2 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      For the benefit of those who choose not to read the 1972 Stockholm Conference report, it includes the following in its opening statements:

      "3. Man has constantly to sum up experience and go on discovering, inventing, creating and advancing. In our time, man’s capability to transform his surroundings, if used wisely, can bring to all peoples the benefits of development and the opportunity to enhance the quality of life. Wrongly or heedlessly applied, the same power can do incalculable harm to human beings and the human environment. We see around us growing evidence of man-made harm in many regions of the earth: dangerous levels of pollution in water, air, earth and living beings; major and undesirable disturbances to the ecological balance of the biosphere; destruction and depletion of irreplaceable resources; and gross deficiences (sic), harmful to the physical, mental and social health of man, in the man-made environment, particularly in the living and working environment."

      That was understood by Global Leadership 47 years ago. How about today? What has been learned by many of the Winners of competition for personal benefit, popularity and profit? They appear to have learned how to fight against improving awareness and understanding, including influence on the stories that get told and believed, and abusing their power to 'bake correction resistance into the systems (including laws and their enforcement) that they can influence' (william's steady point that the people Paying the Piper powerfully influence the actions of Leadership).

9815. One Planet Only Forever at 02:07 AM on 2 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      Note to all:

      At the end of my comment@15 (the end of the quote from the 1987 UN Commission Report "Our Common Future") the likes of today's Greta Thunberg come to mind - don't they.

      What has changed in the past 30 years? The youth today are becoming more noticed, and are more violently attacked (through dismissive condescending statements and the trigger of anger in the general population to threaten them) by unjustified Winners in the Status Quo.

      Also note the increased amount of generic unjustified attacks on "The UN" and "Global Government".

      History is tragically full of cases where things had to get unbearably worse before attempts are made to correct and recover from the harmful developments. And History is full of examples of powerful beneficiaries of harmful development harmfully resisting understood required corrections (including efforts to limit improving awareness and understanding in the general population). That is a tragic history of Human Development that needs to be Sustainably Corrected to Limit the Damage Done and Increase the rate of Sustainable Improvement of the Future of Humanity.

      Children should not have to be the ones who are 'pointing that out'. Perceived Winners who do not very publicly and very powerfully support such children are undeserving of their Status.

9816. One Planet Only Forever at 01:43 AM on 2 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      DriveBy@14,

      There is little justification for such a snarky attack on the very challenging pursuits of an integrated understanding of all of the considerations related to sustainably feeding the entire global population. It is a far more complex issue than climate science and the related required corrections of developed human activity (which, by the way, also impact the food issue).

      I will start by stating that 'Green' needs to be replaced by 'Sustainable Development'. And that, like Climate Action, the improvement of awareness and understanding can be crippled by a lack of interest by Leadership (the winners in the Status Quo) in developing and acting responsibly on that improving understanding. The main barrier to action by leadership is the vested interests of Leadership in defending the Status Quo which includes rigging institutions and laws in favour of the Status Quo, to the detriment of pursuits of Sustainable Development. Many developed popular and profitable actions, sources of status in the Status Quo, cannot be continued if Sustainable Development is the Objective.

      Please read the UN-ESA 2012 "Back to Our Common Future Project - Summary for Policymakers" and then investigate the globally agreed 2015 Sustainable Development Goals that need to be achieved by 2030 and be improved on.

      There are better solutions than Soylent Green. They are the development of Governance of all human actions by things like Sustainable Institutions and Cultures, everything governed by the Combined Governing Objectives of 'Helping the less fortunate' and 'Doing no harm to Others, especially the future generations of Others - the largest group, almost infinite, therefore a group that is deserving of the most consideration'.

      There can be a vast diversity of ways to live Sustainably (not just the food part - all of the SDGs being achieved and improved on). But they will struggle to be Developed and Sustained if they have to compete for popularity or profitability with unSustainable and Harmful alternatives. That is a Key Understanding. And it was expressed well in the 1987 document "Our Common Future" which was developed by collaboration of global expertise based on the global agreement that in order for Humanity to have a future improved awareness and understanding must govern global leadership (established by the 1972 Stockholm Conference with the Report from that conference here). The following is one of Key Understandings expressed in 1987 (about the time that resistance to correction by powerful Status Quo people on a bunch of fronts can be seen to be ramping up):

      "25. Many present efforts to guard and maintain human progress, to meet human needs, and to realize human ambitions are simply unsustainable - in both the rich and poor nations. They draw too heavily, too quickly, on already overdrawn environmental resource accounts to be affordable far into the future without bankrupting those accounts. They may show profit on the balance sheets of our generation, but our children will inherit the losses. We borrow environmental capital from future generations with no intention or prospect of repaying. They may damn us for our spendthrift ways, but they can never collect on our debt to them. We act as we do because we can get away with it: future generations do not vote; they have no political or financial power; they cannot challenge our decisions.
      26. But the results of the present profligacy are rapidly closing the options for future generations. Most of today's decision makers will be dead before the planet feels; the heavier effects of acid precipitation, global warming, ozone depletion, or widespread desertification and species loss. Most of the young voters of today will still be alive. In the Commission's hearings it was the young, those who have the most to lose, who were the harshest critics of the planet's present management."

9817. DrivingBy at 14:00 PM on 1 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      Eat this, no eat that, no, eat the first this that was stated. 

      May I in modesty propose that the only true way for people to eat Green is Soylent. 

9818. Human 2932847 at 05:53 AM on 1 September 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Thank you for going to this effort for me, I'll follow through and read up on what has been presented, and hope that it is useful for others too.

9819. nigelj at 05:51 AM on 1 September 2019
      IPCC's land report showed we're entering an era of damage control
      

      Red baron @11

      "Remove the cow and other ruminents and that grassland environment loses its sink properties. Plow it to produce plant crops instead of meat, and it becomes a net source for both CO2 and CH4."

      Please stop lecturing me and implying I said things I didnt say. I made no reference in my comment @10 to the relationship between cows and soil carbon sinks. You are completely mistaken about what I said, again.

      Moderator, I'm tired of Red Barons repeated false accusations against me comments, aggressive attitude, and strawman statements.

9820. MA Rodger at 04:23 AM on 1 September 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Human 2932847 @20,

      Regarding Seager et al (2002), I think you were looking in the very short list within the 2007 weblog you linked-to @6 (& its associated presentation slide show). I failed to consider this list as I was not expecting a publication to precede the weblog/presentation. I was expecting such publication afterwards and was thus faced with a list over 200 papers long to trawl through.

      Regarding a high number of citations, do note that the last publication I can see with Seager as co-author addressing directly the AMOC is Delworth et al (2008) mentioned @12 and that does not cite Seager et al (2002), that being a rather strong message. (And ditto Hurrell et al 2010 which also considers the Atlantic MOC with Seager as co-author.)

      And of the four papers citating Seager et al (2002) which I mentioned @19, two of them did not accept the controversial aspect of Seager et al (2002) and the other two did make mention of the controversy but were in truth far from supportive. So can it be "really so controversial if 313 people cite it?"  Yes it can indeed!

      "If it's really been supeceded then that's what I really want to know."  Even as no-more-than a controversial alternative, there is no indication within post-2015 literature that it now hasn't been.

9821. Human 2932847 at 22:57 PM on 31 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Seager et al (2002) was easy enough to find, being in the reference list. I agree that having multiple authors isn't a guarantee of correctness, but it is a guarantee of multiple authorship, for sure, which was my point. Is it really so controversial if 313 people cite it ?

      My point about changing the Columbia website is more a question - if it's so bad, and it's purpose is probably educational, then why is it still there ? I thought this might indicate it's merit in the eyes of academics, and widespread dissemination of the idea to students.

      If it's really been supeceded then that's what I really want to know.

9822. MA Rodger at 21:32 PM on 31 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Human 2932847,
      You ask that you "don't want to get bogged down in lonesomeness and reputations of the scientists" so let us ignore the denier K-K Tung.

      You have done well tracking down Seager et al (2002) 'Is the Gulf Stream responsible for Europe's mild winters?'. Note that multiple authors is not a mark of good findings. A more normal gauge of the importance of a paper (but again not always a mark of good findings) is the reported number of citations and Seager et al (2002) has gained a healthy 313.

      The findings of the paper are accepted in part (the cause of the E-W Atlantic temperature differential & the AMOC's impact on Arctic ice edge) but the controversial finding (the AMOC is not significant in warming W Europe) has had a remarkably long life (eg Buckley & Marsall 2015, Palter 2015) given the only up-date is Seager (2006) 'The Source of Europe’s Mild Climate:- The notion that the Gulf Stream is responsible for keeping Europe anomalously warm turns out to be a myth' which is more an opinion piece that a research paper.

      Generally, as Seager (2006) sets out, most ignore this controversial finding (eg Wood et al 2003, Rahmstorf 2003), is last paper saying:-

      "To what extent do Europe’s mild winters depend on the transport of heat by the Gulf Stream and North Atlantic Current? Simulations in which the ocean’s heat transport is switched off consistently show a large winter cooling over the northern Atlantic and adjacent landareas, reaching several degrees in inland Europe, up to 10ºC over Greenland and even exceeding 20ºC over the Nordic seas. This heat transport warms the climate on both sides of the Atlantic, and is therefore not the main reason that Europe is warmer than Newfoundland — this phenomenon is mainly due to the prevailing winds in the two regions. But ocean currents do make the northern Atlantic much warmer than at comparable latitudes in the northern Pacific."

      Generally, the controversial finding has been left behind, including by Richard Seager. But as it is a part of the science, it should not be purged from the records (perhaps the suggestion @15).

9823. Human 2932847 at 17:03 PM on 31 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      I don't know anything about why Chen and Tung are supposed to be bad - I'd never heard of them. And Seager has co-authors signing off on his papers, I count five co-authors on, "Is the Gulf Stream responsible for Europe's mild winters?", why don't these count ?
      It may be a personal quirk, but if I'm told that someone should be ignored because they're on their own I just start to root for the underdog, which may be counterproductive to the resonable aim of eliminating unreliable outliers from consideration.
      I don't want to get bogged down in lonesomeness and reputations of the scientists, please.

9824. nigelj at 16:41 PM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      RedBaron @11

      You just aren't making any sense, and I'm sick and tired of your personal attacks, hectoring attitude, and false accusations.

      "This has been explained to you multiple times. I am not sure why you keep making stuff up without references that sounds good to you, but it is nothing more than sloganeering."

      I haven't made stuff up. I said "However the methane from cattle breaks down into CO2 and is mostly absorbed by natural sinks, so cattle are largely carbon neutral as far as I can see. The exception is where there is huge overstocking, and over grazing." This is non controversial accepted science and it doesnt need a bibliography.

      "The cow properly managed is part of an ecosystem that is a very large net sink for BOTH CO2 and CH4."

      I didn't say or imply  it wasn't a net sink for both CO2 and methane.

      "Running out of Time | Documentary on Holistic Management" 

      I support regenerative farming in general terms, but I do question some of the huge claims made by yourself and the regenerative community as to how much CO2 grasslands can sequester because it doesn't square up with the published research taken as a whole, and I make no apologies for that. More research is needed. Nick Palmer has raised similar points.

       

9825. RedBaron at 14:38 PM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      @10 Nigel,

      This has been explained to you multiple times. I am not sure why you keep making stuff up without references that sounds good to you, but it is nothing more than sloganeering.

      The cow properly managed is part of an ecosystem that is a very large net sink for BOTH CO2 and CH4.

      Cenozoic Expansion of Grasslands and Climatic Cooling
      Gregory J. Retallack

      "Unidirectional, stepwise, long‐term climatic cooling, drying, and climatic instability may have been driven not by tectonic forcing but by the coevolution of grasses and grazers."

      Remove the cow and other ruminents and that grassland environment loses its sink properties. Plow it to produce plant crops instead of meat, and it becomes a net source for both CO2 and CH4.

      So no. You are wrong, again... for the upteenth time. Not sure why you keep getting a pass from moderation for just making stuff up, not science based, not referenced, but please stop.

      I have had to repeat this to you an a few others so many times that I have made set answers with full references.

      What reaction can you do to remove methane?

      Can we reverse global warming?

      The bottom line is that adding animals and plants cools the planet, while destroying plants and animals is currently warming the planet. You have it exactly backwards.

      Maybe this video will help you understand better.

      Running out of Time | Documentary on Holistic Management

      Moderator Response:

      [DB] "you keep making stuff up without references"

      In order to provide a positive stimulus to the conversation, it would be best if you were to provide examples of such claims.  Simply asserting the claims of another are sloganeering without providing supportive examples is itself sloganeering.  Note that the emphasis of this forum is peer-reviewed literature published in credible journals, something that videos fall far short of.

      Inflammatory rhetoric snipped.

       

9826. nigelj at 12:25 PM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      wjohnallen @7

      " it turns out that a cow consumes more CO2 than it belches out as CH4 (on a CO2eq basis at a GWP of 25).Who knew that ruminants on grass pastures are carbon negative? "

      Yes a cow consumes slightly more carbon than it releases, because some of that carbon is building body mass, but in the greater scheme of things it does not make ruminants carbon negative, because the cow eventually dies and the carcass rots and the carbon is released back to the atmosphere, or the cow is eaten by humans but the carbon still ends up back in the atmosphere one way or the other, eventually.

      However the methane from cattle breaks down into CO2 and is mostly absorbed by natural sinks, so cattle are largely carbon neutral as far as I can see. The exception is where there is huge overstocking, and over grazing. Reducing meat consumption is therefore an absolute reduction in carbon emissions.

9827. wjohnallen at 12:18 PM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      @Evan #8

      You are right that the determination of the GWP for biogenic methane accounts for the fact that it is a short lived gas (compared to CO2).  That assesses its warming impact and in terms of emissions accounting (to the IPCC), that conversion to CO2eq equates to it remaining in the atmosphere for as long as CO2 does.  We do not often see it used, but fossil methane has a GWP100 of 33 (from memory), compared to the most recent figure for biogenic methane of 28. This difference in accounting reflects the fact that fossil methane is a new-to-the-atmosphere ghg, unlike biogenic methane which is part of the short-term carbon cycle.  

      All that accounting aside, the point still remains that in terms of warming impact, once CH4 degrades (to CO2, H20,...) its warming impact also degrades but nowhere is that accounted for. Each molecule of CH4 is accounted for as if it remained in the atmosphere. So, if atmospheric biogenic CH4 concentrations are not increqsing, then biogenic CH4 sources are not adding to global warming to any significant extent.

9828. Evan at 10:25 AM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      wjohnallen@7

      But the second thing missed by many is that the IPCC report regime, counts each molecule of CH4 as if it is in the atmosphere forever.

      My understanding is that a GWP (global warming potential) of 25 for methane accounts for the fact that it does not remain in the atmosphere forever. Or am I missing something?

9829. nigelj at 08:19 AM on 31 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Human 2932847 @15, 

      "I don't think it matters whether Seager is alone in his views or his papers are ten years old, he seems a perfectly sane and competent scientist, not a fringe flake or paid shill."

      I agree Seager doesn't come across as a fringe flake or some sort of closet climate denialist, and his article you linked to seems ok, but it does matter that he is alone in his view. This doesn't mean hes wrong, but it does mean we need to be rather cautious, a point made by MAR rather clearly I would say with his example of Chen and Tung. 

      The little detail that stood out to me is western europe is much milder in climate than canada on the same latitude line, and this not well explained by the atmospheric heat transport, or oceans giving up heat in winter, but is easily explained by the gulf stream, so a slowing gulf stream would seem fairly large implications for Europe.

9830. wjohnallen at 07:50 AM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      A couple of things about meat missed by many:

      One is that the grass a ruminant eats, regrows and as it does so, CO2 is taken out of the atmosphere.  Based on the numbers used to report emissions to the IPCC (CH4 emissions factor (Kg CH4/animal/year), animal weight (Kg), feed energy requirements (MJ E/day)) and data from the dairy industry (energy content of pasture grasses (MJ/Kg DM) and feed consumed (Kg DM/day)), it turns out that a cow consumes more CO2 than it belches out as CH4 (on a CO2eq basis at a GWP of 25).

      Who knew that ruminants on grass pastures are carbon negative?  

      Further, of the global average emissions factor for beef on the plate (26.6 KG CO2e/Kg meat), other on-farm processes plus the beef supply chain adds more emissions than the animal does.  If CAFO operations were eliminated, then the average beef emissions factor would come down and beef would then be seen as a carbon neutral protein source. 

      Those who want animal agriculture to be the cause of our climate problem will rush on to say that CH4 is a more potent ghg than CO2.  They are right of course, it is.  

      But the second thing missed by many is that the IPCC report regime, counts each molecule of CH4 as if it is in the atmosphere forever.  Of course it is not - because natural processes remove it from the atmosphere over time.  Which means that if biogenic methane emissions did not exceed withdrawals, then biogenic methane makes little contribution to global warming (not none, just not as much as the ghhg accounting system makes out).

      But who cares about these facts when pointing the finger at agriculture means that we humans do not have to address the prime drivers of global warming - the mining and burning of fossil CO2 and CH4, plus, and more importantly, the harvesting of nature's carbon sinks (forests).

9831. NoctambulantJoycean at 07:24 AM on 31 August 2019
      Models are unreliable
      

      @rupisnark 1151

      Christy's offers his usual distortions that he's been giving for decades. His core argument is that climate models exaggerate bulk tropospheric warming, especially in the topics, and this results from climate models over-estimating climate sensitivity (over-estimating CO2-induced warming). His conclusion is wrong, and the discrepancies he points out are primarily not due to model error, but instead primarily due to errors in inputted forcings for the models, along with internal variability and observational uncertainty (ex: Christy showing tropospheric warming estimates contaminated by stratospheric cooling). So the models aren't greatly over-estimating climate sensitivity.

      If you want an introduction to this subject, then I recommend reading "A response to the “Data or Dogma?” hearing", "Fact sheet for “Causes of differences between model and satellite tropospheric warming rates”", along with the papers with the following DOI numbers: 10.1175/JCLI-D-16-0333.1 ; 10.1038/NGEO2973 ; 10.1002/2017GL073798

      Here is a list of some of the problems:

      1) If bulk tropospheric warming was muted relative to surface warming, especially in the tropics, then that would be a sign of a muted negative lapse rate feedback. That would increase climate sensitivity, not decrease it, contrary to what Christy claims. And there's plenty of evidence of a multi-decadal, positive water vapor feedback.
      2) If Christy's position was right, then we'd expect to see a strong model vs. observational analyses discrepancy pre-1999. But we don't. We instead see it post-1999, as one would predict if the issues were with errors in inputted forcings over that period, not over-estimated climate sensitivity.
      3) The models don't greatly exaggerate temperature responses to volcanic eruptions in the way one would expect if Christy were right about over-estimated climate sensitivity.
      4) A number of papers showed that errors in inputted forcings largely explained residual post-1999 differences between surface analyses vs. models; that would also imply a contribution to post-1999 bulk tropospheric discrepancies as well.
      5) Christy has a decades-long history of too hastily jumping to model error as an explanation, when the actual explanation was something else. This includes the notorious case in which he claimed models over-estimated satellite-based bulk tropospheric warming, when actually Christy screwed up the sign of the diurnal drift correction for his UAH satellite-based analysis.

      There are other problems with Christy's position, but I think that list should be enough to get you started.

      Moderator Response:

      [DB] Hot-linked reports and DOI's.

9832. william5331 at 07:04 AM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      Technically, these problems are pretty easy to solve.  It is the political will and the fact that Who Pays the Piper Calls the Tune which is the core problem.  Politicians will do the bidding of whoever finances them.  But leaving that aside, no solution to the food problems will succeed without affordable contraception in the hands of women.  To paraphrase Richare Dawkins,  "If ever there is an increase in food production, population will rise until the original state of misery has been re-established".  The much vaunted green revolution of the 60's is a case in point with an extimated increased population of 700m people as a result.  With every increase in population we push Gaia, with her free provision of air, water, genes, fiber etc. into an ever smaller corner.

9833. marilia16805 at 03:04 AM on 31 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      I have downloaded the summary and the controversial chart wasn't there. Nor was any mention to vegan or other (also controversial) diets. It seems to me that most dietary concerns focus on food waste rather than radical changes on macronutrient sources.

      I can't see how to reconcile concerns with poverty-derived macronutrient malnutrition and radical recommendations such as vegan diets (extremely expensive to meet protein demands). I cound't find one single economic projection of shifts to veganism (and I suspect it is impossible to model that).

      Moderator Response:

      [DB] The graphic in question is Figure 5.12 from Chapter 5 from the full report, and is found on page 766.  The full legend:

      "Figure 5.12 Technical mitigation potential of changing diets by 2050 according to a range of scenarios examined in the literature. Estimates are technical potential only, and include additional effects of carbon sequestration from land-sparing. Data without error bars are from one study only."

9834. Daniel Bailey at 01:15 AM on 31 August 2019
      It's the sun
      

      "Can 'the sun' account for as much as 10%?"

      That depends upon where you demarcate your start and end periods.

      Scientists have quantified the warming caused by human activities since preindustrial times and compared that to natural temperature forcings.

      Changes in the sun's output falling on the Earth from 1750-2011 are about 0.05 Watts/meter squared.

      By comparison, human activities from 1750-2011 warm the Earth by about 2.83 Watts/meter squared (AR5, WG1, Chapter 8, section 8.3.2, p. 676).

      What this means is that the warming driven by the GHGs coming from the human burning of fossil fuels since 1750 is over 50 times greater than the slight extra warming coming from the Sun itself over that same time interval.

      

9835. Human 2932847 at 01:05 AM on 31 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Looking at Ka-Kat Tung's stuff online, he doesn't seem to be denying AGW, and it's not obvious why he's unreliable - certainly not to a layman such as I. He might be, he might not, I don't know.

9836. Human 2932847 at 00:46 AM on 31 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Thank you again for taking the time to help me. If I may say, though, I don't think it matters whether Seager is alone in his views or his papers are ten years old, he seems a perfectly sane and competent scientist, not a fringe flake or paid shill. So his academic minority status doesn't seem a problem to me. He also seems to draw his conclusions from other's work and has several co-authors. So I don't know why you say it's only his opinion.
      Anyway, thanks for showing me the plurality of views, which may give an updated refutation of Seager's points, and you probably know what the predominant views are in the field of things AMOC so I'll stay open minded.
      If it's out of date, maybe Columbia should look at updating it's website ?

9837. Nick Palmer at 22:38 PM on 30 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      RedBaron @2
      
      While broadly sympathetic to the 'regenerative agriculture' solution to sequestrating our carbon emissions, I have to say, having a fair amount of experience interacting with exponents in the field that they really have to up their game and PROVE their beguiling assertions with properly conducted independent peer reviewed trials published in reputable journals.
      
      'Leading light' figures such as Gabe Brown, Elaine Ingham, Allan Savory, Christine Jones et al need to reduce the 'gee wiz' anecdotes and supply published hard data on request, instead of just hand waving. I look forward to these other figures doing the sort of scientific evaluation work that Dr David C Johnson of NMU is doing to establish the veracity of claims. In the meantime, there are plenty of extreme 'soil regeneration cowboys' who've just done correspondence courses out there making ridiculously overhyped unproven assertions and muddying the waters.

9838. MA Rodger at 20:30 PM on 30 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Human 2934527 @13,
      The understanding that a weaker AMOC cools lands bordering the N Atlantic is pretty-much accepted by all. There are exceptions. one being Richard Seager from a decade ago. I would suggest his position back then was fuelled by the work from a few years earlier enumerating the poleward energy fluxes. From his presentation slide 12 (linked @12) “First hint that this may all be myth comes from using observations to estimate atmosphere and ocean heat transports.“ This basically shows that above 40N only a tenth of the north-bound energy is via the oceans, a finding that has pretty-much stood the test of time. Thus from Schmitt (2018) 'The Ocean's Role in Climate'  its Fig 3:-
      
      
      Being an ocean-based account, |Schmitt (2018) splits the atmosphere fluxes into dry and wet, but the proportion of the total within the ocean is small beyond 40N, not much more than 10 percent.
      And that 'not much more than 10 percent' is almost all the AMOC which operates on a rather small bit of the planet so its influence over that bit of planet is quite large. (The number often given to the AMOC energy flux is ~0.4PW. Today's climate forcing due to AGW is [3.1Wm^-2 x 510M sq km=] 1.6PW acting over the entire world.) So I would suggest that Seager was barking up the wrong tree in his 2007 presentation & his modelling was presumably somehow flawed in concept.

      What has been of interest to the science of recent years is getting the strength of the AMOC & its present rate of decline, of interest because AGW models suggest it will decline under AGW and this will cool the N Atlantic borderlands. The science is now starting to get results on the decline. (See for instance this RealClimate post from this January.)
      
      As for the future the jury is still out as to how much the AMOC will slow, with some evidence still in play that it could actually collapse under AGW. Thus Lui et al (2017) 'Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate'. which modelled a 2xCO2 world.
      And the overwhelming view is that slowing of the AMOC does lead to cooling of the European Atlantic coastal regions. A figure obtained for a RealClimate post from the researches of Lui et al is captioned:-
      
      Temperature change in the winter months (DJF), 300 years after CO2 doubling in the experiment. Due to the almost completely extinct Atlantic flow, the northern Atlantic region has cooled significantly. Source: Wei Liu, with permission.

      Of course, the dangers of relying on a single paper can be demonstrated by the paper Chen & Tung (2018) 'Global surface warming enhanced by weak Atlantic overturning circulation'. One of its two authors is Ka-Kat Tung who is happy to beat the denialist drum and, as I can testify, a very unreliable source of AGW research. So folk should take what Chen & Tung (2018) says with an oceanful of salt.

9839. Postkey at 17:54 PM on 30 August 2019
      It's the sun
      

      Can 'the sun' account for as much as 10%?

      “Gavin A. Schmidt, head of the Goddard Institute for Space Studies in Manhattan, a NASA division that studies climate change, said that the sun had probably accounted for no more than 10 percent of recent global warming and that greenhouse gases produced by human activity explained most of it.”

      www.nytimes.com/2015/02/22/us/ties-to-corporate-cash-for-climate-change-researcher-Wei-Hock-Soon.html

9840. Human 2932847 at 07:07 AM on 30 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      @MA Roger

      Thanks for your comments and points of order. I'm still not really seeing why the slowdown of the AMOC would be a cooling problem as everything I've read from Seager (granting the oddity you noted) indicates a continuity of warming due to AGW, doesn't it ?

      What's the crux of disagreement between people who think cooling would be a problem, and people who don't ? Is it just factoring in Greenland melt ?

9841. Evan at 01:07 AM on 30 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      Thanks for the article John.

      We live in an age of large-scale distrust of government and organizations. The IPCC is saying that we can stay below 1.5C if we all sacrifice and do herculean things to modify the way we farm, eat, produce energy, ...

      Meanwhile we've hit 415 ppm CO2 (more or less) and CO2 is accelerating upwards (just take a look at your favorite form of the Keeling curve). Using a climate sensitivity of 3C/doubling CO2, 415 ppm CO2 means we have already locked in 1.5C warming, unless we can drop atmospheric CO2 to below 400 ppm. That requires either that the optimistic science reports are all correct (unlikely), or that everyone on Earth pulls together to do the right things and that a lot of the scientific reports are correct (still unlikely).

      CO2 is not just increasing, it is accelerating upwards. Do we have a realistic chance of doing any more than stopping the upward acceleration of CO2 by 2030?

      Assuming that the responsible people of the Earth respond during the 2020's by sacrificing and doing as much as they can, how will they feel when we blow by 1.5C? Will trust in the IPCC begin to erode along with trust in all other government organizations?

      We need to do all of the things these reports say, we need to remake the energy and food system. I get that and agree.

      But perhaps we need to motivate people by simply saying that we need to stabilize climate ASAP. That there is no time to waste, because severe effects are upon us and will continue to worsen until we stabilize CO2, without citing specific levels. There is no realistic hope of staying below 1.5C, so telling people we can do that can only lead to distrust and anger when we blow by it.

9842. MA Rodger at 19:40 PM on 29 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Human 2932547 @11,

      You are mistaken by the authorship you attribute to your citation which appears to be the same article that you linked-to @6 - 'Climate mythology:The Gulf Stream, European climate and Abrupt Change' This has no multiple authorship, just Richard Seager of the Lamont-Doherty Earth Observatory, Columbia University. nigelj @7 rightly describes it as a "one person's view."
      Note the link on the webpage to a presentation by Seager which gives a better understanding of his argument and the modelling it is based on. (Both this presentation & the article appear to be over a decade old.) The presentation sets out the following conclusion:-

      "Conclusion: The climate system is so rich, complex, and still not well understood that the current emphasis on the limited impacts of the Gulf Stream and North Atlantic Ocean circulation is a serious distraction of effort and resources when many regions of theworld face a truly worrying future, even in the near-term." [original emboldening]

      Your comment @9 (& repeated @11) concerning the article linked by nigelj @7 is perhaps overhasty. You brand the article as irrelevant because we are concerned with interglacial condiditons and the article concerened glacial conditions which could be fundamentally different. But do note the final lines of that article which runs with an 'on the other hand' rider, the ending:-

      But [Jerry] McManus [of Columbia University] says that studies looking deeper into the ice ages have found that the 1500-year climate oscillations tend not to be nearly as strong during interglacial periods. “It would suggest that this kind of thing isn’t so likely to happen today,” he says. On the other hand, he adds, “In most interglacials, Greenland didn’t melt … and Greenland is currently melting.”

      The only work Seager has had published directly** concerning the AMOC appears to be Delworth et al (2008) 'The Potential for Abrupt Change in the Atlantic Meridional Overturning Circulation'. Interestingly this skates over the warmth brought to northern latitudes by the AMOC.
      Delworth et al (2008) does concur that there is measurable cooling resulting from a weaker AMOC but that the reduced strength of the AMOC will be small enough through the 21st century that this cooling will probably do no more than reduce the rate of AGW warming. "Even with the projected moderate AMOC weakening, it is still very likely that on multidecadal to century time scales a warming trend will occur over most of the European region downstream of the North Atlantic Current in response to increasing greenhouse gases, as well as over North America."
      So it is a little strange that later in considering the impact of a collapsed AMOC, they write:-

      "Although our current understanding suggests it is very unlikely that the AMOC will collapse in the 21st century, the potential consequences of such an event could be severe. These would likely include sea level rise around the North Atlantic of up to 80 centimeters (in addition to what would be expected from broad-scale warming of the global ocean and changes in land-based ice sheets due to rising CO2), changes in atmospheric circulation conditions that influence hurricane activity, a southward shift of tropical rainfall belts with resulting agricultural impacts, and disruptions to marine ecosystems."

      So not one mention of temperature effects, or importantly, no mention of there being minimal temperature effects.
      ** Seager & Battist (2007) considers abrupt climate change and its causes which includes the AMOC.

       

9843. RedBaron at 17:54 PM on 29 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      There is a huge problem with this graph, and in fact this whole article. This demand side mitigation idea presumes that we can't change agriculture to sustainable systems. 

      The report states with high confidence that balanced diets featuring plant-based and sustainably produced animal-sourced food “present major opportunities for adaptation and mitigation while generating significant co-benefits in terms of human health”. 1

      This so called "demand side mitigation" is extremely misleading. We already know how to change agriculture from a net emissions source into a net sink. That flips everything on that graph upside down and those demand side actions most beneficial become the least beneficial. More importantly though, it is impossible for that graph to actually happen in a world where all excess arable ground not needed for food production is instead used to make biofuels. Any relatively tiny changes that diet might make are immediately absorbed by increased commodity biofuel production, which has a vastly larger footprint.

      If you actually want to make any demand side impact at all, you must stop raising commodity grains for biofuels, and stop clearing forest for palm plantations. The forests need replanted, and the arable land in grains replanted into grasslands. Eliminate the over demand for these commodity crops and return agriculture to feeding people.

      It's Time to Rethink America's Corn System - Scientific American

      Only a tiny fraction of corn grown in the U.S. directly feeds the nation’s people, and much of that is from high-fructose corn syrup

      according to a recent study published in the Proceedings of the National Academy of Sciences, roughly 1.3 million acres of grassland and prairie were converted to corn and other uses in the western Corn Belt between 2006 and 2011, presenting a threat to the waterways, wetlands and species that reside there.

      Then when we do that, use regenerative practices instead of industrialised practices and in net we turn that 23% net source into a net sink potentially as much as 50-100% depending on how much degraded land we restore. But to restore that land we MUST use animal husbandry. This is why one sided reports like this are so misleading and actually harmful biased reporting making mitigation even harder.

      “The number one public enemy is the cow. But the number one tool that can save mankind is the cow. We need every cow we can get back out on the range. It is almost criminal to have them in feedlots which are inhumane, antisocial, and environmentally and economically unsound.” Allan Savory

      Just to give someone an idea of scale. The above 1.3 million acres recently cleared prairies mainly to produce biofuels is 1/2 the total acreage in the whole country in vegetable production. (2.62 million acres) and according to the USDA in 2019 the total area in corn is 91.7 million acres, up 3% from 2018. In other words, in a single year roughly equivalent to the entire acreage in vegetable production was offset by just corn and with the exception of HFCS, it did not feed anyone! About 1/2 goes into the gas tanks and about 1/2 into CAFOs.

      That land needs replanted into prairies and prairies need animals on them That's your problem and your solution. The suggested demand solution given in this article (and to be fair others too) is bordering on ridiculous and absolutely NOT what the UN climate-change report said or implied.

      "If all farmland was a net sink rather than a net source for CO2, atmospheric CO2 levels would fall at the same time as farm productivity and watershed function improved. This would solve the vast majority of our food production, environmental and human health ‘problems’." Dr. Christine Jones

9844. Human 2932847 at 16:33 PM on 29 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Hmm, well, that's Columbia university Earth Institute saying the effect of the Gulf Stream is way overestimated. If you disagree you could email and chew it over with them.

      I would have thought that ice caps over Europe (and America) affect a lot of things like wind, ocean currents, albedo etc. There would be no North Sea or Baltic. Your link says that there was huge amounts of fresh water released from the American ice cap, more than from Greenland, but that wouldn't be available now. There would be different solar insolation - what else ? It just seems like a very different context to the current one.

      They say

      The determinants of North Atlantic regional climates
      We showed that there are three processes that need to be evaluated:

      • The ocean absorbs heat in summer and releases it in winter. Regions that are downwind of oceans in winter will have mild climates. This process does not require ocean currents or ocean heat transport.
      • The atmosphere moves heat poleward and warm climates where the heat converges. In additions, the waviness in the atmospheric flow creates warm climates where the air flows poleward and cold climates where it flows equatorward.
      • The ocean moves heat poleward and will warm climates where it releases heat and the atmosphere picks it up and moves it onto land.

      I don't know anything about the middle one - but the first and third points must be affected by ice cap conditions over sea and land - of which there was more in the past.

9845. One Planet Only Forever at 14:24 PM on 29 August 2019
      2019 SkS Weekly Climate Change & Global Warming Digest #34
      

      Comments 3 through 6 on "2019 SkS Weekly Climate Change & Global Warming News Roundup #34" directly relate to this Story of the Week.

      One thing to add to  the many concerns that are presented in these two posts and their related comments (or present more directly) is the reduction of biodiversity due to human impacts reducing Rainforest extents.

      Researchers in Rainforsts are constantly discovering lifeforms that have never before been documented. That makes it likely that, unlike the likes of DoDos and Passenger Pigeons, there are almost certain to be losses of unkown biodiversity. And that could mean losses of lifeforms with potential for human benefit. Those opportunities for human benefit will never be known to have been lost forever. And that loss will have happened because a portion of current day humanity had developed powerful desires for "other interests and priorities" and allowed those interests and desires to compromise the environment and biodiversity to the detriment of the future of humanity.

      As the full Story of the Week concludes: "The fires in the Amazon remind us this is not just a crime against nature but a crime against humanity."

9846. One Planet Only Forever at 13:48 PM on 29 August 2019
      2019 SkS Weekly Climate Change & Global Warming Digest #34
      

      A question/suggestion and a correction regarding the presentation of the Story of the Week.

      I read the full article linked at the bottom of the part that was extracted and presented here. Is there a way to be clear that only an extract of the full story is being presented here? Could the link be provided at the top rather than at the end of the extract?

      I also just noticed that the Big W at the start of the full article did not get picked up at the start of the exctract.

      Moderator Response:

      [JH] Beginning with this week's edition of the Weekly Digest, I will  embed a link to the full article in the initial title of the article appearing immediately after the heading, "Story of the Week". I will also add text at the end of the article indicating that what is presented above is only an excerpt of the complete article — typically the introductory paragraphs. I'll incorporate both changes into "Editor's Choice" article of the Weekly News Roundup. Thank you for the suggestions.  

      The missing "Big W" has been inserted. Thanks for catching and pointing out this glitch.  

9847. nigelj at 13:02 PM on 29 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      Human 2932847 @9, maybe there is other reseach I dont know, but plenty of research suggests the slowing gulf strean brings cool conditions to Europe, see my comment at 1 and the links.

      I dont see why it matters that the gulf stream slowdown happened during an ice age which is just a cold period. The gulf stream slowed down and the ice age deepened further, thats the point apparent in the article. If slowing cools things then, why wouldn't it do the same now? I can't see a reason. 

      In addition, its non controversial that the gulf stream originates in the warm oceans off africa where the trade winds blow this water north ultimately, influenced by the coriolis effect and the thermohaline circulation. Its hard for me to see why slowing this down wouldn't cool the northern atlantic.

      I guess its a question of how much and what other influnces there are, and I agree its all not 100% certain. The research you quote has to be right to the extent that warm air does travel north due to the basic global circulation system and global warming is affecting this pattern as well. But it looks like the conventional view is quite strong that a slowing gulf stream could cause a cooler climate in the north to some extent.

9848. John Hartz at 04:47 AM on 29 August 2019
      IPCC's land report showed we're entering an era of damage control
      

      Recommended supplemental reading:

      What Does '12 Years to Act on Climate Change' (Now 11 Years) Really Mean? by Bob Berwyn, InsideClimate News, Aug 27, 2019

9849. Human 2932847 at 19:02 PM on 28 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      The sciencemag article describes conditions during glacial times, not the interglacial in which we are now. Presumably, conditions where quite different, and Europe was already ice-bound. The climate change referenced in the article wasn't the change from an interglacial into a glacial - day after tomorrow style - but variations in an already glacial kind of environment. So I don't know how much that work tells us about our current situation, I'd like to know more.

9850. Human 2932847 at 18:51 PM on 28 August 2019
      The North Atlantic ocean current, which warms northern Europe, may be slowing
      

      nigelj @7

      Well, being on his own doesn't make him wrong, and he draws on several other's work so I assume there is a body of work about this.

      thanks for link

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