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The never-ending RCP8.5 debate

Posted on 27 December 2019 by , ATTP

This is a re-post from ATTP

I think my New Year’s resolution is going to be to not talk about RCP8.5. However, I think I will briefly summarise the state of the never-ending debate. I thought we’d reached a bit of a breakthough when Zeke Hausfather and Justin Ritchie posted an article suggesting that [a] 3C world is now “Business as Usual”, but it seems to have degenerated once more. David Wallace-Wells also has a follow up article pointing out that our climate future doesn’t look as bad as it once looked. If you’re interested, Pietro Monticone has a summary of the state of the debate.

The basic idea is that current emission projections (from the International Energy Agency) suggest that emissions won’t rise much between now and 2040. If you then make some reasonable assumptions and project these to 2100, you find that we will probably follow something close to an RCP6 pathway which will probably lead to warming of between 1.9oC and 4.4oC, with a best estimate of around 3oC. In other words, current policy suggests that business-as-usual is closer to RCP6, than to RCP8.5 (which has often been regarded as a business-as-usual pathway).

So, the basic message seems to be that we’re heading towards a world where the climate impacts might not be as apocalyptic as they could have been. Good news, in some sense. However, there are a great many uncertainties associated with these projections. Even though we may be heading towards a 3oC world, we can’t rule out that we’ll still end up in a >4oC world.

This is where I have some problems. Some are interpreting this as suggesting that we’ve essentially limited warming to ~3oC, which completely ignores all the uncertainties associated with these projections. Similarly, some are arguing that we should pay no attention to studies that use RCP8.5, which completely ignores that we still can’t rule out levels of warming typically associated with RCP8.5 (>4oC, for example). From a climate modelling perspective, RCP8.5 is simply a concentration/forcing pathway. Even if it’s now higher than is likely along business-as-usual pathway, it is still a useful pathway for investigating the higher levels of warming that are still possible.

I think it is good that we may have ruled out some of the worst case impacts, but we’re still potentially heading for a world that has warmed by more than 3oC (potentially even 4o – 5oC). Also, despite the confidence of some energy analysts, we have still yet to peak global emissions. A number of quite high-profile climate scientists (Richard Betts and Ken Caldeira) are still pointing out that given the uncertainties associated with socio-economic projections, and potential carbon cycle feedbacks, we really can’t yet completely rule out an RCP8.5 concentration pathway.

I do think it’s become very unlikely that we will follow such a high concentration pathway, but I also think that this current narrative has been poorly framed, and that some will use it to argue that we don’t really need to do much more about climate change. I do worry that in 10 years time we’ll be having a similar discussion – “yes, emissions may have continued rising through the 2020s, but – trust us – they’re just about to peak”. I hope I’m wrong.

Links:
A 3C world is now “Business as Usual” – Breakthrough Institute article by Zeke Hausfather and Justin Ritchie.
We’re Getting a Clearer Picture of the Climate Future — and It’s Not as Bad as It Once Looked – Article by David Wallace Wells.
RCP8.5 issues & comments – summary by Pietro Monticone.

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Comments 1 to 50 out of 76:

  1. "In other words, current policy suggests that business-as-usual is closer to RCP6, than to RCP8.5 (which has often been regarded as a business-as-usual pathway)."

    Gut reaction. I can't see how you can take policies which have not even been properly implemented yet, and no significant change in global emissions, and start talking about a new business as usual. The terms don't belong in the same sentence, not yet by a long way.

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  2. nigelj,

    I agree that it is incorrect to be impressed by appearances that things are getting better.

    Only a portion of the problem-population (the higher consuming and higher impacting people), has cared to limit how harmful they are. And only a portion of that portion try to be helpful about reducing climate impacts.

    As long as there is a significant portion of the population wanting to be high impacting people able to 'believe what they want with the power to get away with doing as they please' the problem is not on a pathway to a solution.

    Humanity will only be able to be declared to have started on the pathway to a sustainable future that can be sustainably improved when the number of powerful people caring to be helpful, and rejecting any thoughts that there is a way to justify being harmful to Others, is large enough to govern and limit the behaviour of their uncaring harmful peers. Even then, vigilance will be required to ensure that the harmful uncaring people do not get a resurgence of popularity and profitability.

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  3. Skeptical Science offers a helpful guide to RCP basics and more, in this pdf:

    The Beginner's Guide to Representative Concentration Pathways

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  4. Time is running out and you dare talking that our climate future wouldn’t "look as bad as it once looked". Meanwhile, a decade of ice, ocean and atmospheric studies found systems nearing dangerous tipping points!

    => Climate Science Discoveries of the Decade: New Risks Scientists Warned About in the 2010s

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  5. Perhaps it would be worthwhile to challenge the "Monktons" of the world with this thought.  https://mtkass.blogspot.com/2010/10/forget-climate-change.html  They don't have to believe that the climate is changing or that we are  causing it or that it would be  bad.  They would have to support the very measures that would address the problem or reveal their real motivation and real backers.

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  6.  It is strange, history has repeated itself. It was reputed to be a little boy who was the only person to say "The King is as naked as the day he was born".

    Now its a little girl, this time most of the world hav'nt noticed that we are in a desperate situation, only the ones who cannot say anything because they do not have the means and are taking the brunt of it.

    Is it too late? have we gone beyond the threshold that everybody is talking about, beyond the tipping point? This is an equally dangerous situation because people are saying," Well there is nothing I can do about it so lets go on as normal".

    All I can say is from what I see the increase in world temperature graphs are generally a hypabola, if it goes on and if the world population goes on doubleing every twenty years, far from having a problem at the end of the century, its going to be in less than 5 years.

    Take a simple thing like boiling a kettle, I first empty a kettle, then as I put water back in with the tap running at fast, count to four for 1 person, eight for two ect. That way I am only boiling as much water as required.

    Simple but if everybody did it we could do away with a number of nuke reactors. Getting people to do it is a different matter, everybody has their reason not to do it. 

    Then there is shear greed and people not wanting to lower what they concider their standards.

    Then there is the industrys telling people to buy 4X4 cars or electric cars, they all want to sell more and more but what they are selling does nothing to save the world.

    I feel there is no hope because nobody is going to listen anyway.

    I think if there is going to be a change it will have  to be a massive revolution of some kind to have any effect.

    Tell me if you think I am wrong.

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  7. Human emissions are only one part of the problem: natural emissions and natural sinks are the other important parts. The Keeling curve (plot of monthly CO2 concentrations) is the best indicator of how we're doing, and it's still accelerating upwards (Ralph Keeling himself uses the words "accelerating upwards").

    I will gain hope not when our emissions stabilize, but when the Keeling Curve stabilizes.

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  8. The big picture context of ATTP’s OP and this discussion thread is encapsulated in the following…

    But keep in mind that scientists are reluctant, for professional reasons, to go far beyond the immediate data in formal publication. Moreover, organizations like the United Nations, including even its Intergovernmental Panel on Climate Change, are so dominated by economists’ concerns and bent by political considerations that extraneous noise obscures the scientific signal.

    Prominent climate scientist Hans Joachim Schellnhuber, director emeritus of Germany’s Potsdam Institute for Climate Impact Research, argues that, in these circumstances “a trend towards ‘erring on the side of least drama’ has emerged” and “when the issue is the survival of civilization is at stake, conventional means of analysis may become useless.”

    Exploring this argument, policy analysts David Spratt and Ian Dunlop conclude, “Climate policymaking for years has been cognitively dissonant, ‘a flagrant violation of reality.’ So it is unsurprising that there is a lack of understanding amongst the public and elites of the full measure of the climate challenge.”

    Yes, the Climate Crisis May Wipe out Six Billion People by William E Reese*, The Tyee, Sep 18, 2019

    *William E. Rees is professor emeritus of human ecology and ecological economics at the University of British Columbia.

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  9. John@8. Nice summary of the problem. Thanks.

    I would prefer that we message to people that we must, absolutely must stabilize the Keeling Curve. If people follow the Keeling Curve, rather than emissions curves, they will have a much better idea of what to expect. 

    I'm not for scaring people needlessly, but I assume that anybody reading SkepticalScience.com is already in the elite class of people trying to make a difference and would prefer to know the truth. Stabilizing emissions will not stabilize the Keeling Curve. Not even close.

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  10. "Yes, the Climate Crisis May Wipe out Six Billion People"

    There is without doubt compelling evidence the the IPCC are conservative in their conclusions, and climate change could kill huge numbers of people, but this number of 6 billion is off the scale, and looks like it needs a little bit of healthy scepticim. It's just that we can't call ourselves educated people with some healthy proper scepticism, if we just accept any old claims at face value. I'm not an expert and happy to be told if I'm wrong somewhere below.

    This claim of 6 billion people being wiped out appears based mainly on a 4 degree world where huge areas of the world become deserts (from their map). But deserts aren't caused primarily by heat but by low rainfall. My understanding is the subtropical deserts either side of the equator are caused by the equatorial hadley cell, and thus high pressure air forcing down high altitude low pressure air with its low levels of moisture, and this low pressure air also a tendency to heat up the ground more than normal, so the combination that creates deserts. Deserts have other causes like air flow over mountains but again this is a thing not hugely affected by climate change.

    It's hard to see why climate change would push these circulation patterns so far north and south to so hugely expanding the deserts. According to Hadley cells on wikipedia climate scientists think the hadly cell would expand this century by 2 degrees of latitude, so not very much. And overall climate change increases the atmospheres absolute humidity and rainfall.

    That said, there will clearly be more deserts not less, and the tropics are going to get really hot, and heatwaves will become a deadly serious problem for survival and agricultural production will be affected, and temperate zones will have their own problems. Mortality will increase, a lot.

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  11. NOAA recently posted this animated data. It’s a good graphic to share because it grabs people’s attention. Even those who are familiar with the data, find it is dramatic and convincing. “History of atmospheric carbon dioxide from 800,000 years ago until January, 2019.”  www.esrl.noaa.gov/gmd/ccgg/trends/history.html

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  12. Nigelj,

    William Reese is an acknowledged expert commenting on the carrying capacity of the Earth.  He quotes at least 6 other experts to support the claim of 6 billion deaths.  Your unsupported word is not a strong argument against multiple experts opinions.

    The point of Reese's essay is that public discussion is completely centered on the best case.  Bad cases are dismissed without evidence.  A worst case of 6 billion deaths is as likely as 10 billion healthy people in 2100.  He is addressing your attitude exactly.

    A large fraction of the best farmland worldwide will be covered with only 2 meters of sea level.  600 million people displaced with no new farmland available.  That is only damage from sea level rise. Possible downsides are very large.  The precautionary principle indicates we must seriously consider these scenarios.

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  13. michael sweet@12

    You're playing into the hands of those mirror images of denialists, the doomists.

    Reese's spin depends on Earth getting to at least 4°C+ and the article in which he makes the 6 billion speculation is full of the 'usual suspects' - Roger Hallam, Kevin Anderson and the various Potsdam Institute for Climate Impact Research people.

    These people are the inheritors of the mantle of Paul R Ehrlich, who severely damaged the credibility of 'sustainability' science in the 1970s with his predictions (made in 1968) that in "the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now"

    When assessing the likelihood of things happening ONLY the peer reviewed science should be looked at. Nothing else. If the various risks to society are being assessed, then and only then, should all the rest of the speculative projections be taken into account for likelihood. The two separate things should not be blurred in the minds of the public as they are being done today by various public facing individuals

    Here is what highly credible and well known climate scientists said:

    "UC Davis research scientist Amber Kerr dismisses Hallam outright. The idea that six billion people are doomed to die by 2100 “is simply not correct. No mainstream prediction indicates anywhere near this level of climate-change-induced human mortality, for any reason.”

    Similarly, Ken Caldeira, senior scientist, Carnegie Institution, points out:

    "There is no analysis of likely climate damage that has been published in the quality peer-reviewed literature that would indicate that there is any substantial likelihood that climate change could cause the starvation of six billion people by the end of this century"

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  14. Nick@13. I don't want to get into the discussion of whether 6 billion people will or won't die by 2100. Even 1/10th of that would be disasterous.

    Peer-reviewed research is typically 5 years out of date, due to the time delay between research, analysis, submission, review, and publication.

    How many times have you heard reputable climate scientists say "Things are proceeding more rapidly now than we thought 5 years ago."?

    Models still fail to explain why the arctic is warming as fast as it is. I've watched enough videos of reputable scientists to know that they routinely say they don't know how things will unfold and how fast.

    Peer reviewed means the research is well documented and well reviewed by peers. Reputable scientists are having a very difficult time keeping up with the pace of climate change and making projections. This should make all of us skeptical of any arguments we read, whether apocolyptic or arguments meant to put our minds at ease.

    Can we agree on the message that until CO2 concentrations stabilize we are in trouble?

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  15. "How many times have you heard reputable climate scientists say "Things are proceeding more rapidly now than we thought 5 years ago?"

    Quite a few. Those remarks get publicised whereas the majority saying  'things are proceeding at about the rate we thought' or even ' some aspects' are proceeding slower than we thought' get less publicity. That's the point. Within the peer reviewed literature one will find all of those - don't cherry pick what you think supports your stance.  Also, bear in mind that apart from the literature, climate sceintist are in constant communication with each other on Twitter etc keeping each other up to date with the latest findings. When such as Ken Caldeira says the 6 billion scaremongering is crap you should listen.

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  16. Nick@15. Thanks for your balanced comments. Personally I don't care about the dramatic "6 billion people will die by ..." arguments, because there are so many factors beyond science that will affect the course of human civilization, and which we cannot guess nor control.

    The point I am trying to express is that I think there is too much optimism being generated by focusing on emissions scenarios. I am all for being optimistic, but not if it causes us to let down our guard. I am trying to hone my arguments for non-technical people, who will not be following the technical discussions at any level, and the message I like to provide to them is to watch the Keeling Curve, because in one curve we have all natural and human effects reflected in one plot. The message is to make your response and preparations on the basis of what the Keeling Curve is doing. To me that is realistic and rational preparation. Getting optimistic about targets set in Paris or elsewhere is not responsible planning. It is more wishful thinking.

    So whether RCP8.5 or RCP6 is more indicative of business-as-usual is somewhat of a moot point. Either one spells big problems. I appreciate ATTP's article and clarifying current thinking and research, because it is good to keep up to date with the latest research and where we're headed.

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  17. michael sweet @12, you can't argue every issue by pointing to what an expert or two said and leaving it at that. Sometimes experts are dead wrong. You are using the "argument from authority fallacy," and also doing exactly what the denialists do when the point at a couple of denialist experts.

    Reese argument is that 6 billion would die this century. The worst case is 2 metres sea level rise this century, but obviously that would only develop much later this century. Its simply not logical to conclude this would so devastate farmland to cause 6 billion deaths this century. I do not need to do calculations to see what is self evident.

    6 billion might die 'eventually'. That would have been a more defensible argument.

    You have not addressed the point I made about deserts. Instead you have shifted the goal posts to sea level rise. But nobody is telling me Im wrong about the deserts issue. I do not need to publish a paper on something that straightforward. I did support my comments with a reference to what the research says about changes in the Hadley cells.

    Nobody advocates the precautionary principle more than me, but coming up with more and more extreme scenarios simply because we can't definitively rule them out is a process that has no end point, so next week it will be complete human extinction by 2100, then by 2050 etc, and this may just alienate the public and feed the denialists as others point out above. We already have enough sensibly based extreme case scary scenarios with wide support in the scientific community to use as communication tools, without having to go further into things that are wildly speculative.

    Or put it this way, speculation is valuable for obvious reasons, and I do respect Reeses views and courage, but his views do not stand the test so shouldn't become the received wisdom and be put in front of the public too much.

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  18. Regarding 2 metres per century sea level rise. Although this is possible to me,  its not going to happen within a couple of years. It will still be a decades to centuries process, so if it causes food shortgages inland forests will be felled to supply extra land. Duh!  But it will obviously wreck good farmland and lead to massive deforestation and infrastructure damage. The costs will be horrendous.

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  19. While we're on the topic of sea level rise, Richard Alley is on record as saying sea level rise could be more than 15ft this century. Not saying it will be, but saying it could be.

    I think the readers of SkS will acknowledge that Richard Alley is one of the most respected voices on this topic, and he is also not given to exaggerations. I feel it is pointless to predict how many people would be affected with that level of sea level rise, but needless to say it would throw the world into chaos. Here is the link.

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  20. I spoke with Alley at the AGU this year.  He indicated as much because of coming research showing that the ongoing melting of the ice sheets and thinning of the glacial tongues in Antarctica is causing the surrounding ocean to have a freshwater lens on the top. 

    Why this matters is becuase the upwelling warm water at depth can no longer reach the surface and instead is being redirected like a "blowtorch" at the base of the adjacent ice sheets. 

    Because the models treat the ice sheet like a "white painted rock" (the models do not feature coupled, dynamic interconnections between the ice, atmosphere and the sea) they therefore miss a great deal of the interplay driving the acceleration of ice mass losses there.

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  21. Nigelj,

    You appear to be arguing that your opinion is more  valuable on any topic than experts in the topic that you deem "dead wrong".  On this board you need to post links to support your wild claims.

    For example sea level rise.  So far you have provided no support for your claims that 2 meters of sea level rise this century is "worst case" or will take "decades to centuries".  Evan has provided a link that shows actual scientists think 15 feet is possible (although not the most probable event). 

    If you had followed sea level rise over the past 15 years you would be aware that long ago James Hansen projected 5 meters of sea level rise to protest the IPCC projection that around 0.4 meters was the highest likely.  He was roundly criticized for that projection by people like you.  Fast forward to 2016 and 18 coauthors backed a 5 meter top projection .  The Richard Alley link above shows their argument convinced some other scientists.  Read the background before you make wild claims.

    In the USA currently 8 feet (2.4 meters) of rise by 2100 is recommended for engineering purposes.  Two meters is so 2014!!

    Your claim that 2 meters sea level rise is a worst case analysis is false and your repeating it without any support is sloganeering which is against the posting policy here at SkS.  Your unsupported, uninformed opinion is not a valid scientific argument.

    This is a perfect example of what William Reese was arguing against.  I do not think 6 billion people will die by 2100, but there are legitimate scientists who do support that claim.  They are left out of the discussion.  How can we come to proper conclusions of what path we should choose if we leave out the worst projections because we do not like them?

    You say "[William Reese's] views do not stand the test" but you provide only your opinion to test his against.  You must provide data to support your wild claims.

    I switched to sea level rise because I think it supports Reese's argument better.  I have provided data to support my claim of 2 meters sea level rise (actually a possible 5 meter rise which would be much worse).  If 600 million people are displaced by sea level alone, along with destruction of prime, irreplaceable farmland, it is not much of a strech to see billions threatened by all of AGW's effects.

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  22. Nick Palmer:

    You quote William Reese's article's references to Ken Calderia and Amber Reese to argue against him.  He is arguing that extreme views need to be considered.  The example of sea level discussed above is a perfect example where 15 years ago scientists argued that Hansen's 5 meter projection should not be considered because it was too extreme.  Today 5 meters is accepted as a possibility (hopefully a slim possibility).  It will not make the IPCC report because the rules for the IPCC mean all estimates are low balled.

    I note that Caulderia qualifies his comment as "quality" peer reviewed.  Presumably he does not consider 5 meters of sea level rise a possibility because he deems the journal Atmospheric Chemistry and Physics as not "quality" enough.  Daniel Bailey's report of his discussion with Alley is very bad news.  Hansen has long argued that a fresh water lens could focus heat on the ice sheet.

    The example of sea level alone suffices to demonstrate that billions are at risk.  We must all work as hard as we can to prevent these disasters from occuring.  Leaving out the high end projections while keeping in denier low balls means nothing ends up getting done.

    From where I sit, I hear that projections of how much it would heat up have been accurate.  Projections of the effect of that heat have often overestimated the amount of heat needed to cause destructive changes.  Who predicted widespread wildfires, massive coral bleaching, killer heatwaves and dramatically increased storms at only 1.2C warming?

    I have a strong recollection from around 2005 I wondered it I would live long enough to see dramatic effects from AGW before I died of old age (I was born in 1958 so I was about 50 years old, I expect to live to 85 years old).  I am now 61 and see dramatic effects all around me.  These effects were not described in the IPCC reports in 2005.

    10 years ago deniers taunted scientists with descriptions of CAGW (catastrophic AGW).  Scientists bent over backwards to say they were not making catastrophic projections.  Today catastrophy is in everyones mouth: fires, storms, sea level rise, coral bleaching, forrest death, farm failures.  Deniers never mention CAGW anymore.  Changes have exceeded expectations.

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  23. michael sweet @21

    "You appear to be arguing that your opinion is more valuable on any topic than experts in the topic that you deem "dead wrong". On this board you need to post links to support your wild claims."

    I did supply a reference to the wikipedia article on Hadley Cells, which in turn quoted:

    Xiao-Wei Quan; Henry F. Diaz; Martin P. Hoerling (2004). "Changes in the Tropical Hadley Cell since 1950".

    Dian J. Seidel; Qian Fu; William J. Randel; Thomas J. Reichler (2007). "Widening of the tropical belt in a changing climate". Nature Geoscience.

    I try to provide as many references as I can in the time I have, and I think I do quite well on the whole, and I wont be doing more.

    "For example sea level rise. So far you have provided no support for your claims that 2 meters of sea level rise this century is "worst case" or will take "decades to centuries". Evan has provided a link that shows actual scientists think 15 feet is possible (although not the most probable event). "

    I admit I didn't provide a reference for two metres. Yes you are right there are a few scientists predicting far more than two metres sea level rise per century. I forgot that. However its somewhat beside the point I was making, and the thinking of the wider communiry seems to be converging on 2-3 metres per century as a plausible worst case scenario, and that was in my mind, for example here:

    phys.org/news/2019-05-metre-sea-plausible.html

    Its absurd to suggest we could ramp up from current rates of sea level rise to 2 metres in the space of a couple of years, even Hansen didn't claim that. It misses the point anyway. My point was  that there will at least be some time to adapt regarding finding more farm land. It will be harder to adapt  in terms of physical infrastructure

    Yes the IPCC worst case of 1 metre sea level rise looks far too conservative, a "keep everyone happy" sort of estimate and very frustrating. I've thought for ages that 2 metres / century is a very distinct possibility and needs to be in fornt of the public. I think I'm entitled to my opinion. There is good evidence in the paleo climate record for 2 metres per century at around  2 degrees of warming so nobody has to model anything, its a matter of historic record. But when people with a science degree start waving thier arms and saying 5 metres is possible by the end of this century,  and that half the world could become a desert I wonder if thats plausible and helpful.

    "Fast forward to 2016 and 18 coauthors backed a 5 meter top projection "
    You are just doing the same thing again. Emphasising the extreme estimate from a small group of scientists, while criticising denialists who do the same. Nothing has happened in the real world to date to suggest 5 metres this century is possible. The very recent trends in the Antarctic and Greenland suggest 2 metres is possible from what I have read.

    "This is a perfect example of what William Reese was arguing against. I do not think 6 billion people will die by 2100, but there are legitimate scientists who do support that claim. They are left out of the discussion. How can we come to proper conclusions of what path we should choose if we leave out the worst projections because we do not like them?"

    They have not been left out of the discussion, because we are discussing them right now! Not that my opinion counts for much.

    "You say "[William Reese's] views do not stand the test" but you provide only your opinion to test his against. You must provide data to support your wild claims."

    I've provided some data that Reeses claims on vast areas of deserts are nonsensical, as mentioned above. That was my main point and appeared to be his main point. I concede I provided no reference when I mentioned sea level rise (:

    "If 600 million people are displaced by sea level alone, along with destruction of prime, irreplaceable farmland, it is not much of a strech to see billions threatened by all of AGW's effects."

    Arm waving and speculation. I agree billions would be threatened, but being threatened is not the same as being killed. Some precision is importrant, is it not?

    I'm applying the mission statement of this website. "Scepticalscience". Are you?

    I was born in 1958 as well.

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  24. Nigelj@23

    I don't want to nitpick too much, but I'm sure you're aware that during the last deglaciation that an increase of 1 ppm/100 years was enough to drive sea level up 5m/century for about 3-4 centuries (i.e., meltwater pulse 1A). We are now driving up CO2 at 1 ppm/5 months. It seems to me that 5m/century is very much in line with the paleo record given how hard we're pushing the climate.

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  25. Evan @24, and I dont want to nitpick either, but meltwater pulse 1a happened during a period with vast ice sheets over much of the planet so its not directly comparible with todays conditions. Two metres makes more sense to me.

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  26. Not a climate scientist, my background is in managing technology risk, but I'd observe from parallels in the issues:

    1. Deciding what's the worst 'credible' risk scenario is invariably contentious because it drives policy debate and usually also has an associated high degree of uncertainty. However you do need to bound it otherwise you start dealing with risk that is effectively infinite. 

    2. Using a worst possible scenario that is not credible is generally counter-productive due to the so called anchoring cognitive bias. Once you've stated it becomes very hard to argue people away from this scenario (just ask the nuclear safety community) when you figure out that it's not going to be that bad. 

    3. Retaining RCP 8.5 because it addresses/covers as yet undetermined uncertainties in the physical models about carbon feedbacks is not (I think) a good practice. Better to explicate those uncertainties in the physical model and explore their effects there.

    4. If there's uncertainty about the worst credible RCP scenario then model it as a family with associated epistemic degrees of belief and run a monte carlo simulation on them. 

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  27. With all of this reassuring discussion, please remember that CO2 concentrations continue to accelerate upwards. Not just increase, but accelerate.

    It is difficult to emphasize how far we are from any kind of optimistic projections. Even if we bound the worst-case scenario to RP6 as a more rationale approach to risk management (I am not making fun of your very well-stated arguments MattSq), that is still an unimaginable future.

    Let's make our New-Year's resolutions for each of us to continue rapidly cutting our carbon emissions.

    Happy New Year and hoping for a brighter tomorrow.

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  28. Alley said '"we don't have the - pound on the table - this is the published refereed literature - that says this rate, but they have not done the worst case scenario." (15-20ft).
    He does say that would be the worst case and suggests the probability is low but not zero.
    This is a good scientist speaking. Bear in mind that Reece's article said this  "But on Aug. 15, in a memorable session of the BBC’s HardTalk, Hallam irritated multiple cultural nerves by claiming, on the basis of “hard science,” that six billion people will die as a result of climate change in coming decades."

    Nowwhere does he point out the deceit or delusion in Hallam's words inherent in "will" and that is the problem when figures like Reece over represent the chances of low probabilit events happening. This 'fear porn' is very counter-productive to getting the public on side nad it give enormous quantities of easy 'ammunition' to the denialist movement so those who exaggerate and mislead should not be praised or given airtime but should instead be castigated.

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  29. Nigelj,

    At 17 you claimed:

    "you can't argue every issue by pointing to what an expert or two said and leaving it at that. Sometimes experts are dead wrong. You are using the "argument from authority fallacy," and also doing exactly what the denialists do when the point at a couple of denialist experts."

    at 23 you said"

    "You are just doing the same thing again. Emphasising the extreme estimate from a small group of scientists, while criticising denialists who do the same. Nothing has happened in the real world to date to suggest 5 metres this century is possible. The very recent trends in the Antarctic and Greenland suggest 2 metres is possible from what I have read."

    At 23 you posted a link to a press release.  The actual paper is here.  It is clear you have not read it.  It states that the consensus of experts is a long tail of very high sea level rise just as described in the paper I cited with 18 authors, not "an expert or two".  It is not my problem if you are uninformed about the subject we are discussing.  You must withdraw your suggestion that I have cherry picked my citations.

    We started this discussion because at 17 you claimed 2 meters was an extreme estimate of sea level and at 23 you say:

    "I admit I didn't provide a reference for two metres. Yes you are right there are a few scientists predicting far more than two metres sea level rise per century. I forgot that. However its somewhat beside the point I was making, and the thinking of the wider communiry seems to be converging on 2-3 metres per century as a plausible worst case scenario"

    Your paper actually supports my posts: 2 meters is a high estimate but within 95%  estimates of high sea level rise and 5 meters is within the long tail.  You did not read the paper.  The paper also states that the consensus of experts has significantly increased since 2013.  For sea level rise the consensus always increases every 5-10 years.

    In 18 you said:

    "Regarding 2 metres per century sea level rise. Although this is possible to me, its not going to happen within a couple of years. It will still be a decades to centuries process, so if it causes food shortgages inland forests will be felled to supply extra land. Duh!"

    Farmers raise crops on all the good land.  Only poor land is allowed to go to trees.  Virtually all farmable land is already occupied by a farmer.  Your gross insensivity to farmers on good, delta land being forced to move to cities is disgusting.  Lost good land is not replaced by poor land in the mountains or melted permafrost.  All the estimates I used were for 2100.  You refer to multiple time periods so it is unclear what you mean.  It is clear that you are not up to date on the amount and consequences of sea level rise.

    You do not advance the conversation if you criticize my posts without reading your own citations.

    You should not comment strongly on subjects you are not up to date on.  Duh!  If you wonder why land does not exist to replace delta land ask a question.   I did not comment on dessertification because I do not follow that topic.   I note that your references on Hadley cells are over 10 years old and only indirectly relate to dessertification.  Did you read them?  You have not cited a reference that directly supports your claims there either.  The fires currently in Australia indicate to me that dessertification is expanding rapidly and you were incorrect (although I am not current on dessertification).

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  30. Nick Palmer:

    The IPCC AR5 Executive Summary  gives an expected sea level rise of 65 cm by 2100 for BAU.  Media reports often claimed a range of 26-82 cm by 2100.  This range was only an 83% expectation.  Most scientific papers give 95% confidence intervals which increase the top end to 180cm.  Is the public really served by low balling problems this way?

    The rules for the IPCC reports were written by fossil fuel lawers.  The summaries reflect the lowest end of possible problems.

    Lowballing problems as you suggest has not motivated anyone to take action in the past 30 years.  Extinction Rebellion has organized numerous rallies world wide since it was formed.  I attended my first rally a month ago and Extinction Rebellion helped organize it.  Low balling has not achieved anything.  Where is data to support your claim that low balling problems gets more people to take action?  This is simply opinion.  Peoples opinions differ.  

    In the end I think people only respond when they see disaster actually occur that affects them.  The fires in Australia, California and Europe (gigantic wildfires were not predicted by scientists for 2019) will change more minds than any scienttific discussions.  Extraordinary heat waves (not predicted) are convincing.  Dead trees in my neighborhood are convincing.

    I do not support frightening people with 15 feet (Alley actually mentioned 30-40 feet as a maximum in his talk, listen to it again), but having 65 cm in the Executive summary, which is the most you expect people to read, is not accurate.

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  31. Michael - it's getting tedious hearing your defence of extremist views. Yo just repeatedly used then term 'lowballing' which shows you do not have a good grasp of the science. The figures from the IPCC represent MIDBALLING, being the most likely figures.  Lowballing would be using the figures, again least likely, at the other end of the probability graph.

    If you havent seen the clear evidence from psychology that overstating risks not only turns people off, but reduces the credibility of the 'consensus' middle ground of science in the publics' eye then you need to read a bit wider.

    Most people, if they have memories, have seen extremist science predictions - or rather how the media report such predictions - fail before. The textbook example is that of Paul R. Ehrlich who famously, in 1968 wrote a book and the original edition of The Population Bomb began with this statement: "The battle to feed all of humanity is over. In the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date nothing can prevent a substantial increase in the world death rate ..."[20] Ehrlich argued that the human population was too great, and that while the extent of disaster could be mitigated, humanity could not prevent severe famines, the spread of disease, social unrest, and other negative consequences of overpopulation."

    I think you will find that although he was a top person in his field at the time he was essentially completely wrong. The inheritors of his mantle today are such as Guy McPherson, Pete Wadhams, Beckwith, Kevin Anderson, Carana, Scribbler etc who all take the far-end-of-the-probability-graph most unlikely forecasts and, in their public interviews, talk as if the least likely is pretty certain. It's just not scientifically valid to do that.

    Alley, of course, is a top notch scientist but people have to remember that he is speaking as a scientist using very precise language which unfortunately can be very prone to misintrepretation when reported on by interviewers of lesser scientific appreciation.

    Similarly the Hallam of E.R.  activist types who spout extremist definitive statements such as  "six billion people will die as a result of climate change in coming decades" need to be told to shut up because they are are seriously damaging the credibility of the actual climate science in the public arena.

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  32. Nick@31. I like your statements of caution and your presentation of the centrist view. Whereas I agree with your assessment of Guy McPherson as being on the fringe, I respect Kevin Anderson as one of the few researchers willing to call people's attention to just how serious the situation is. He is also addressing the engineering challenges to tackling the problem. Whereas I don't encourage people to listen to Guy McPherson, I do encourage people to listen to Kevin Anderson. I think he has a good message and one worth hearing.

    In addition, he is trying to walk the talk, which is also rare these days.

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  33. Nick Palmer @31 (also applicable to swampfoxh),

    Michael Sweet may not have explained in detail why it is correct to refer to IPCC reported summaries of the science as 'low-balling' how serious the problem is. However, it is true that the IPCC methodology for finalizing the wording of its reports, particularly the Executive Summary, results in 'low-balling of the negative seriousness'.

    The science continues to be clear. Human impacts beyond 1.5C warming are likely very negative for the future generations. That has not changed. Politicians who have less concern for future generations decided that a 1.5C limit was 'too hard on the current generation' and tried to say 2.0C would be OK. And some extremist economists, extreme in their lack of concern for future generations, have determined and declared that 3.0C would not only be OK, it would be a generous restriction of the harm done to future generations. They say that to be fair the warming limit could be even higher than 3.0C, depending on how much less concern for the negative future impacts (discounting of future costs) is acceptable (even though it is patently absurd to believe that it is acceptable to benefit from actions that create, or risk creating, negative impacts on Others).

    The IPCC report writing methodology is for an 'absolute consensus' to be reached among the participants in the authorship of a Report. And each science contributor has a 'political minder from their nation' influencing the way the report is worded. The 'absolute consensus' wording has to meet the desires of the political minders, but can only be pushed to the limit of scientific legitimacy. The result is reports that are pushed to the 'low-ball end' statements of what can be scientifically supported. (Based a my listening to a CBC Radio interview from long ago of a Canadian Scientist who was a participant in the process).

    That process has resulted in almost every subsequent Report 'stepping-up' its statement of 'negative consequences'. When you start from a position of 'low-balling how bad things are' it is almost certain that increased investigation will result in a 'higher low-balling of how bad things are'. Even the incredibly frightening most recent IPCC Special Reports regarding Climate Change impacts on Oceans and Land could be understating the severity of the future impacts.

    Compromising expanded awareness and improved understanding of climate science has not been helpful at all, from the perspective of the future generations. But nobody 'has to look at things that way' these days do they? - which is the real problem, especially when leaders don't have to see how unsustainable and harmful their choices actually are.

    It is correct to understand that some people will rigidly dig-in when faced with an attempt to correct something they developed a liking for believing. But some people are open to continued learning, even as they get older.

    The future of humanity requires Sustainable Development, the sooner the better, no matter how angry that makes the 'learning resistant'.

    The future will only be better without the 'learning resistant'.

    The 'learning and correction resistant' who fight against any of the pursuits of Sustainable Development corrections need to understand that their harmfulness will not be missed by Others. And their collective fading into impotent angrier irrelevance will be an improvement for global society and the future of humanity. Their lack of significant impact on Others would be a welcome improvement. I would prefer that they choose to learn to be more helpful, less harmful, and have their impacts be more welcomed and sustainably admired by Others.

    Once a person's basic needs are met, any improvement of their circumstance increases their ability to be helpful to Others. The choice is theirs to make. Hopefully more of them will resolve to become more helpful, less harmful, people.

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  34. michael sweet @29

    "you can't argue every issue by pointing to what an expert or two said and leaving it at that. Sometimes experts are dead wrong. You are using the "argument from authority fallacy," and also doing exactly what the denialists do when the point at a couple of denialist experts."

    Yes I did say this, but at that point I was referencing the claims of Reese that 6 billion people will die by 2100, not sea level rise per se. This is really Reeses opinion, its not in the peer reviewed literature as far as Im aware, its been heavily criticised by several other experts, and like Nick Plamer says theres a big difference between claiming what will happen and what might happen. Reese is feeding the denialists. It's sad if you can't see this.

    "Your paper actually supports my posts: 2 meters is a high estimate but within 95% estimates of high sea level rise and 5 meters is within the long tail. You did not read the paper. The paper also states that the consensus of experts has significantly increased since 2013. "For sea level rise the consensus always increases every 5-10 years."

    Whatever. I have already stated that I accept some published science (Hansen and others) concludes 5 metres is possible as the most extreme worst case. An incredible numbers of things have to happen for this to occur and some of the mechanisms in Hansens research are none too clear. That's the opinion of plenty of scientists. Not everyone accepts Hansens conclusions. 2-3 metres by 2100 is what is considered more reasonably possible and scares the hell out of me anyway and would be devastating. I don't know why anyone needs to wildly speculate beyond this.

    Even Hansens sea level rise predictions that New York would be underwater by date xyz have fed the denialists for decades, and the scientific community has had to do gymnastics to defend them.

    If we want to be convincing the public, and using scary predictions towards the upper end, imho we need to be focusing in on a worst case for sea level rise that is strongly backed by evidence, not the off the chart highly contested stuff at the extreme end. I have already made this point so I'm trying again. It's a subtle difference but its important.

    Nick Plalmer is right when he says "If you havent seen the clear evidence from psychology that overstating risks not only turns people off, but reduces the credibility of the 'consensus' middle ground of science in the publics' eye then you need to read a bit wider." I have done some psychology, so Im aware of this. Basically fear can motivate change, but the research finds when using extreme and scary scenarious, there has to be a solid evidence base or fear can work in the opposite direction to whats intended.

    "Farmers raise crops on all the good land. Only poor land is allowed to go to trees. Virtually all farmable land is already occupied by a farmer. Your gross insensivity to farmers on good, delta land being forced to move to cities is disgusting. Lost good land is not replaced by poor land in the mountains or melted permafrost. All the estimates I used were for 2100. You refer to multiple time periods so it is unclear what you mean. It is clear that you are not up to date on the amount and consequences of sea level rise."

    My point was sea level rise will reduce framland, and forests might be cut down to provide more farmland so its hard to see 6 billion people dying by 2100. And it seems plausible, given huge numbers of trees are being cut down in the Amazon rain forest to grow crops and for cattle (unfortunately). Obviously there could well be very increased mortality longer term given seaa level rise wont stop by 2100.

    I said nothing about farmers being forced to move to cities. I said nothing about growing trees on mountains or permafrost regions. I don't recall using multiple time periods. I only talked about 2100 or end of this century. I provided you with a reference from physics.org to some of the latest science on sea level rise.

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

    Michael Sweet @30

    "The rules for the IPCC reports were written by fossil fuel lawers."

    Where do you get that from? Not that it would suprise me.

    "Lowballing problems as you suggest has not motivated anyone to take action in the past 30 years. "

    I don't think problems have been low balled as much as you think. While the IPCC have not highlighted the possibility of multi metre sea level rise by 2100, there is a graph in their report talking about 12 degrees c by 2200 for business as usual. This is not low balling. The media has been full of scary predictions of all sorts.

    "I do not support frightening people with 15 feet (Alley actually mentioned 30-40 feet as a maximum in his talk, listen to it again), but having 65 cm in the Executive summary, which is the most you expect people to read, is not accurate."

    This seems in total contradiction to all your previous rhetoric!

    My position is this and it always has been and I've said it 100 times: The IPCC understate things in the executive summary and are too cautious. The possibility of 2 metre sea level rise should be mentioned, or something like that, because theres good evidence its a reasonable possibility. But making truly extreme claims like 6 metres sea level rise and 6 billion people dead within one hundred years feeds is on shaky ground, and feeds the denialists and could be counter productive.

    I think we might be more on the same page than you think.

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  35. Nick Palmer at 31:

    Thank you for a post completely lacking in citations so I do not need to go read them. 

    Long time readers ar Ske[ptical Science might remember a drawing from a scientist (sorry I do not remember the scientists name) which had a large gaussian curve labeled "Scientific Opinion" on one side.  At the far right of the gaussian curve was a line labeled "IPCC position.  About 10% of the curve was to theleft of the IPCC line.   Much further to the left, past the point of no problems,  was a line labeled Denier scientists.  In the middle of the IPCC line and the denier line was a line labeled "news reports splitting the middle".  The news reports line was far to the left of the end of scientific opinion. (If anyone has a link to this drawing please post it below, I have not been able to find it).

    The point of the graph was that, exactly as OPOF describes, the IPCC report determines the point where a consensus of scientists agrees "the damage must be higher than this".  That means the average of scientific opinion is much more damage than reported by the IPCC.  The lowest 10-15% of scientific opinion determines where the line is drawn.  Your description of the IPCC linne as the midpoint of scientific opinion is simply incorrect (I note that you have provided no citations to support your claim).

    I support my claim with this reference to  a RealClimate post. (the data discussed is referenced to a peer reviewed paper at RealClimate).  The graph below shows the data from IPCC AR5 and the results of a survey of 90 sea level rise experts.

    sea level graph

    In the IPCC report the data was only quoted from the 17-83%.  Standard data in scientific reports is to the 95%.  Thus for RPC 8.5, the I(PCC reported a maximum expected rise of just under 1 meter.  The 95% opinion of the experts was just over 1.5 meters.  

    I call the IPCC claim of under 1 meter low balling.

    Just for giggles let us look at a recently published survey of experts:  

    "We find that a global total SLR exceeding 2 m by 2100 lies within the 90% uncertainty bounds for a high emission scenario." my emphasis

    Your position is that I should only say sea level will rise 0.95 meters when expert opinion says there is as much as 10% chance of over 2 meters if we go BAU??  If I am responsible for building an airport I am expected to anticipate it will last 100 years with 95% certainty.  That would be well over 2 meters.

    According to this RealClimate post, Jason Box, a glaciologist who studies this issue, has said:

    "There was controversy after AR4 that sea level rise estimates were too low. Now, we have the same problem for AR5 [that they are still too low]."

    Stefan states:

    "One statement that I do not find convincing is the IPCC’s claim that “it is likely that similarly high rates [as during the past two decades] occurred between 1920 and 1950.” I think this claim is not well supported by the evidence. In fact, a statement like “it is likely that recent high rates of SLR are unprecedented since instrumental measurements began” would be more justified."

    At 27:40 of the video linked above Dr. Alley says:

    "The IPCC is way on the optomistic side fo what is possible [for this issue and many others]"

    He does not mention 30-40 feet but does say "could be bigger than this [15-20 feet]. they have not done a worst case study"

    Prominent scientists complain repeatedly that the IPCC is lowballing the numbers.  I think it is acceptable for me to do the same.  Can you provide something besides ":this what Nick Palmer thinks" to support your position.

    I have not been called a doomer before.  Thinking about it, I note that low balling it for 30 years as you advocate has not gotten anything done.  Perhaps Hallem of ER will do better with his approach.

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  36. Nigelj,

    We basically agree.  I do not like being called a cherry picker.  I responded to some of your issues in the post above.

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  37. Reviewing my post at 35 I confused the graph with another I reviewed.  The light lines on the graph show the 90% confidence interval and not the 95% confidence interval.  95% confidence is much higher.

    Nigelj: the graph shows the consensus 90% confidence in 2013 was 1.5 meters.  The quote indicates that "global total SLR exceeding 2 m by 2100 lies within the 90% uncertainty bounds" [in 2019].  The consensus 90% value BAU increased over 0.5 meters from 2013-2019. 

    It is difficult for amateurs like us to keep track of what is going on.  Tamino has good posts on sea level rise.  RealClimate has a good post every so often.  This year had a lot of bad news on sea level rise.  Hopefully next year will be better.

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  38. Michael Sweet. You still seem to have a problem understanding that "theres a big difference between claiming what will happen and what might happen".

    You quote a blizzard of figures but you don't seem to have understood the original post - about R.C.P 8.5. All of the shock horror predictions that the Hallam's of this world tell people are going to happen, and the low probability 'highball' IPCC projections too, are dependent on what is increasingly seen as an unrealistically high increase in future emissions by the very same scientists whose work is used to formulate the projections of the consequences of the 'what ifs' that are the RCPs.

    You may not know but the author of this article - ATTP - is Ken Rice, a highly respected figure in the field and I have been in communication with him (and other noted and noteworthy climate scientists) over some years, so I have the advantage over you of not just knowing what the 'boiled down' IPCC reports say, but also what the scientists behind the scientific papers that are considered by the IPCC say. They're not fond of extremist alarmist and doomers...

    Skepticalscience is not an alarmist or doomer site (despite what denialists say on a daily basis...) and anyone giving any sympathy or support to the 'fear porn' rhetoric of the likes of Hallam is probelmatical to keeping intact the integrity of the site as a repository of objective reliable scientific knowledge.

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  39. Another fact and reference free post from Nick Palmer disparaging me.

    Let us review the conversation.

    At 12 I entered the conversation.  I supported William Reese's article advocating allowing people to discuss high danger possibilities of AGW.  Currently only low ball projections are publicly discussed.

    At 13 you entered calling me a doomer for supporting discussing high danger, low probability issues.  You criticize Reese and others who worry about the long, very fat tail of probabilities.  You provide no data to support your claims.  You quote Reese to support your argument.

    At 15 you claim without data that "the majority [of scientists are] saying 'things are proceeding at about the rate we thought'.  You claim without suppport that Cauderia says 6 billion dead is scaremongering crap.

    At 22 I use the example of gross underestimates of sea level rise in the IPCC reports to support my claims.  I point out that Hansen was roundly criticized for his estimates of 5 meters rise 15 years ago.  You would have completely censored him.  I point out that 5 meters rise is now standard in the fat tail of possibilities.  I point out that 600 million people are currently at risk from 2 meters of sea level rise alone (currently at risk, an estimated 800 million at risk by 2100).  Here is the paper describing this risk, it was widely discussed several weeks ago.  Previous estimates understated the problem by a factor of three.

    I then list more 4 examples of underprediction.  It would be easy for me to list many more.

    At 28 you describe Alleys talk.  You complain about Hallam using the word "will" while Alley only says the probability is low.  (According to DB the probability has increased significantly since Alley was recorded).  You ignore your previous complaints about underprediction and shift the goalposts to a single word Hallam said.  You complain about people who discuss worst case scenieros and imply that I discuss worst case scenieros.

    At 30 I detail IPCC lowballing of sea level rise with references.  I point out that the IPCC numbers are very low ball numbers, far below the scientific norm.  I state I believe most people will only respond after problems directly affect them.  I state I do not use numbers from the end of the fat tail but support others using what they think is appropriate.

    At 31you insult me for supporting extremist views, although that is not my position.  You change the goal posts to describe how best to affect public opinion.  You state your opinion of the best way to address the public without any citations to support your reasons.

    At 35 I detail my claim about IPCC lowballing scientific estimates with detailed citations.  I show 2 meters was a reasonable choice, within the 90% percentile.  I prove the IPCC AR5 lowballed sea level rise.  I provide numerous quotes of scientists complaining about IPCC lowballing.  I state that I see no reason to think lowballing issues will get more people to take action than describing extreme problems.  I point out that lowballing has had no effect for the past 30 years.

    At 38 you shift goalposts again and state that I do not differentiate between what will happen and what might happen, although I have clearly shown that 2 meters is around the 90th percentile of probability for a high emission model.  You then shift the goal posts again to discuss RCP 8.5, which I have not discussed at all.  You claim that you do not need to cite data since you have discussed this issue with scientists and your recollection of the discussion is enough.

    None of us know what will happen after tomorrow.  All projections have to be taken with that caveat.  In the full video that we discussed above of Dr Alley he shows the entire curve and states emphatically that we must take strong action to ensure the end of the fat tail [15-20 feet] does not happen. (watch the video yourself to find this). 

    I think lowballing problems as you advocate is bad policy.  I try to discuss problems near the 90% area.  Hallam goes further up the tail.  That reflects on Hallam, not me.  People here in Tampa think 0.5 meters by 2100 is the top estimate of sea level rise because the IPCC numbers are so low.  That is a disservice to the public and keeps people from taking action.

    You have been deliberately offensive.  You keep shifting the goal posts when I give examples that you are incorrect.  You have not provided a single reference to support your claims.

    Moderators: Nick Palmer is sloganeering and deliberately insulting other posters.  Please ask him to provide references to support his wild claims and stop insulting me.

    I found this reference by Oreskes, Oppenheimer and Jamieson:

    Scientists Have Been Underestimating the Pace
    of Climate Change
     (description of book)

    The problem of underestimating problems is much more complicated than I described and much more widespread.

    I think your suggestion that we should all lowball the problems of AGW is a bad idea.  It has failed for 30 years.  In the next 10 we will see if Hallam's efforts are helpful or harmful.  He can hardly do worse than the last 30 years of lowballing.  In the past year Extinction Rebellion has gotten more attention for AGW action than traditional sources you advocate.

    I note that Michael Mann is making much stronger public statements than he used to.  Australia, your country is burning – dangerous climate change is here with you now

     

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  40. This article is very relevant. We are seeing the very worst of our scientific predictions come to pass in these bushfires. Note particularly the discussion on the next IPCC report, and the suggestion it will include a section on abrupt climate change. There's a link to the main topics to be included in the report. 

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  41. Michael Sweet. Whether you realise it or not, you argue in exactly the same way as denialists do, only in an alarmist mirror fashion. Clearly you are going to continue with your long ill-thought out posts chock full of incorrect assertions and characterisations and I wonder if the moderators need to slow you down a bit. I'll just point out an example of your style: M.S. wrote "I supported William Reese's article advocating allowing people to discuss high danger possibilities of AGW. Currently only low ball projections are publicly discussed"

    It is absolutely untrue that only lowball projections are publicly discussed - you just made that up.

    M.S also wrote: "You claim without suppport that Cauderia says 6 billion dead is scaremongering crap" Firstly, it is Caldeira actually...
    This was extraordinarily easy to check - yet M.S didn't... - again, his aggressive denier/alarmist style shows because he appears to believe that if one don't know of something, that it doesn't exist. Try looking again at the 'Reece article' linked to in the comment#8. In it is this: "Similarly, Ken Caldeira, senior scientist, Carnegie Institution, points out, “There is no analysis of likely climate damage that has been published in the quality peer-reviewed literature that would indicate that there is any substantial likelihood that climate change could cause the starvation of six billion people by the end of this century.”"

    Which rather proves my point about Caldeira's views and demolishes his insinuation and it also strongly suggests that M.S. didnt read or properly understand the words in the article he referenced!. Only reading headlines or cherry picking articles is a classic denialist/alarmist trait

    There is a point which M.S, is fundamentally not getting, which I have addressed several times already - incorrigibly ignoring or failing to understand repeated points is also classic denialist/alarmist think. That is starkly illustrated in his fallacious statement: "You ignore your previous complaints about underprediction and shift the goalposts to a single word Hallam said. You complain about people who discuss worst case scenieros and imply that I discuss worst case scenieros"

    The point is that those who campaign and pontificate using 'fear porn' and say worst case low probability things WILL happen, like Hallam, are simply wrong. Get it? WRONG.... They are also highly irresponsible because they give massive amounts of ammunition to the denialist propagandists, who use it to confuse and mislead the public about what the sensible peer-reviewed science says. No scientist worth his salt would support that nonsense, indeed they get angered by it.  BTW Michael Mann wouldn't approve of Sweet's postion either! It is the implied certainty in the words of Hallam and his ilk that is dangeously misleading.

    I did not 'complain' about people who discuss worst case scenarios at all, all those scenarios are covered in the science and often in restrained magazine articles. It is legitimate to mention low probability outcomes as part of a full risk assesment process. It is not legitimate to tell the public that 'we're all going to die in X years'. Again, I say it is absolute nonsense to say that the very low probablity, worst case scenarios which depend not only on nothing at all being done to fix things but that fossil fuel use, particularly coal, will massively increase in future, which is the R.C.P 8.5 pathway which is next to being abandoned as a possible future, are not being mentioned publicly. However, it's true that climate scientists and policy makers are not 'hyping' them, like the dangerously stupid and irresponsible Hallam's of this world tend to do, for very good psychologcal reasons. Such risks may even be mentioned in the public arena more if only the reporters, fired up by the irresponsible doomers, extremists and alarmists, who create a journalistic hunger for headline worthy quotes about 'worst cases' happening and  make them interview as if those were firm, almost inevitable, predictions, didn't need to be corrected so often by real scientists when interviewed.

    Those types I do, and did, complain about are those who misrepresent the science and the possibilities to be as scary as they can possibly make them out to be in order to plug their cause or their ideology or whatever motivates them. NigelJ, who is probably one of the most regular commenters here, and who knows his stuff, has already confirmed that trying to scare the public with over the top hype to try and stampede them towards a policy, desired by the scarey pontificator, does not work and is actually counterproductive. People like Michael Sweet seem either unaware of this or ignore it

    As Sweet clearly can't acknowledge that others can know stuff he is unaware of, shown by his denier like demands that everything anyone says that he doesn't like be ' proved' - MS: "You provide no data to support your claims", here's a few links that support what I and NigelJ wrote about hyping fear and its countreproductive nature.

     Fear won't do it- Promoting Positive engagement With Climate Change Through Iconic and Visual Representations

    'Loss-Framed Arguments Can Stifle Political Activism' Adam Seth Levine (a1) and Reuben Kline (a2)

    'How Hope and Doubt Affect Climate Change Mobilization Jennifer R. Marlon1*, Brittany Bloodhart2, Matthew T. Ballew1, Justin Rolfe-Redding3, Connie Roser-Renouf3, Anthony Leiserowitz1 and Edward Maibach3

    https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1751-9020.2008.00188.x

    'Fear-Based Climate Appeals Can Be Counterproductive'
    https://psmag.com/environment/fear-based-climate-appeals-can-be-counterproductive

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    Moderator Response:

    [DB]  Let's tone things down and take a higher road. For reference, Michael Sweet is a member of the Skeptical Science author team.

    Ad hominems and inflammatory snipped.

  42. Nick Palmer:

    Reading Nigelj's link, Dr. Joelle Gergis, one of the lead authors of AR6, says:

    "I can assure you that the planetary situation is extremely dire.

    It’s no exaggeration to say my work as scientist now keeps me up at night."...

    "The scientific community is acknowledging this by including new sections on abrupt climate change throughout key areas of the upcoming IPCC report. We now consider these “low probability, high impact” scenarios an increasingly critical part of our work."

    It appears that the IPCC scientists agree with me.  

    I have provided extensive references to support my claims that previous IPCC reports were low ball.  Naomi Oreskes et al show IPCC reports are low ball.  You have provided nothing to support your claim that "The figures from the IPCC represent MIDBALLING, being the most likely figures."  Changing the goal posts again and claiming scientific reports already contain extreme results is simply false.  Provide references to an IPCC summary for policy makers that contains references to the fat tail.

    Changing the goal posts to RCP8.5 again is not helpful.

    Take your complaints about having to provide references to WUWT.

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  43. Guys, its getting very testosterone charged, and remember we are supposed to be on the same team.

    This is my take:

    I think the problem is this: I agree with MS, the IPCC have definitely lowballed things, certainly on sea level rise. Maybe not on temperatures. But a few scientists and media people have highballed things to the maximum as NP alludes to. Its created decades of confusion on who to listen to.

    This is why I suggest we need a solid middle ground. We need to focus on scenarios that are extreme and low probability, but evidence based ones, not ones at the truly ridiculous end of the spectrum. The hand waving stuff.

    I have lost count of the number of times I've seen Hansens New York will be underwater by 1928 quote. Its provided denialists ammunition for decades, its so easy to shoot down. The general public read this stuff and it hands them an excuse to dismiss the whole climate issue. Now before you attack me, I'm well aware Hansen has been quoted out of context, and it was based on a very high emissions scenario, but explaining all this has us on the back foot. I'm hoping you see the point.

    The Paris commitments along with actual coal reserves and deployment of wind power etc look like they kill the very most extreme scenarious dead, although they by no means kill dangerous scenarios dead. The trouble is the commitments are not bedded in enough to be sure. Am I missing something?

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  44. Nigel@43, yes, we need to tone things down.

    At the risk of sounding like a broken record, the Keeling curve is accelerating upwards. Not only is it a tall order to stabilize CO2 concentrations, but at some point the dynamics of the Keeling curve move out of our control, and no amount of climate negotiations, nor wind mills, nor solar panels are likely to help us reverse course.

    We really don't need dire scenarios to know that we are out of time to take serious, drastic action. Soon our plans will mean very little. We may become climate passengers.

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  45. Evan @44, in a word, yes. A guy called Mike over at Reaclimate.org posts a lot of weekly, monthly and yearly data on MLO CO2 levels. I've thought much of this is a bit to short term to mean much, but I'm beginning to think he's the only guy with his eye firmly fixed on the ball, for want to a better description.

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  46. Sorry if I went outside the forum rules. While I was writing #41 I was simultaneously taking on a very tricky, very agressive denialist/sceptic and I probably slipped into the mindset I use when taking on such types, which I have found extremely effective - not at convincing them (which is very hard) but it is one of the best techniques I have discovered for  drawing out into the open, where the audience can see them, 'what lies beneath' - the underlying motivations that make such types so incorrigible. Call into question their rationality or intelligence and 9 times out of ten they will come back with stuff attacking one's own position which reveals that they are mostly hard line right wingers scared of left wing solutions,  a smattering of evangelicals who believe God so loves us that he has designed Earth with hidden negative feedbacks which will prevent us doing anything much, or (rare these days) hard line left wingers who believe climate science was faked up  so the West can deny energy and development to the Third World.

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  47. While the 'robust' discussion on the damage that would be wrought by a BAU future appears to have abated, I'm not surprised such discussion can become 'robust'. I think you need to keep firmly on mind what BAU is, on what it will cause climate-wise and also how quickly, if the consequences of BAU are to be discussed. And I would stick to temperature as a gauge of 'what it will cause.' SLR is too much of a long-term thing. According to IPCC AR5, even at +1.5ºC we are due 4 metres of SLR, evenyually.

    As for what increased global temperatutre will bring, I note an article in the UK's Daily Mail that presents an interesting extreme, although there was already one critique of XR's Roger Hallam that made a similar claim. The Mail quotes a report from pension company Aviva saying:=

    Aviva warns that the world is on track to warm by more than 3C by 2100 – double the 1.5C limit that was set in the 2016 Paris Agreement.

    The fund manager estimates that warming on this scale would wipe £10trillion off the value of global stock markets.

    The cost would rise to around £33trillion if temperatures rise by 6C. 'While the likelihood of that much warming is low, the results would be catastrophic,' the report said.

    This mixing of the £33trillion cost (that is 30% of global share values) with it being 'catastrophic' does raise the question of 'catastrophic to whom?' It is perhaps pension-fund managers and presumably not the global population as a whole.

    I note a similar conclusion on financial terms was given by Ken Caldeira when criticising Hallam:-

    Climate damage has been discussed extensively in various IPCC reports and in the peer-reviewed academic literature. Estimates of climate change damage for this century, in business-as-usual scenarios, are typically in the range of a few percent of global GDP to tens-of-percent of GDP for the most extreme damage functions in the most extreme scenarios. There is no analysis of likely climate damage that has been published in the quality peer-reviewed literature that would indicate that there is any substantial likelihood that climate change could cause the starvation of 6 billion people by the end of this century.

    So for those who are saying that +3.0ºC would leave 90% of the global economy functioning happily and that even +6.0ºC would still leaving two-thirds in tact; for such folk, the idea of +4.0ºC causing six billion deaths will take some explaining.

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  48. Nick Palmer @46, my experience of online denialists is similar, and they do indeed fall into those three groups. You could add another very small group of apolitical scientific cranks with massive dunning kruger (Victor over at RC). As my Dad used to say "it takes all sorts to make a world". 

    Dealing with politically motivated denialists frustrates me. Hard to know whether to delve into the politics, or just stick with the science, and  let their politics be on show for people to see their motives and reach their own conclusions. However one thing is for sure, we have to try to win over as many people on the right of politics as possible, and violently attacking their world view won't do that. Discussion needs to be subtle and more upbeat. But you know that.

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  49. nigelj@48 wrote "and violently attacking their world view won't do that. Discussion needs to be subtle and more upbeat"

    I said I found my methods very effective because what I aim to do is draw out and lay bare in front of any watching audience 'what lies beneath' the apparently sincere 'sceptical' views. Most of the audience/readers don't know that these denialist memes have been debunked a thousand times, so all they see is one 'sciency sounding' argument versus another nand most are not sophiscated or knowledgable enough to make a value judgement as to whose views are more credible. That is why, IMHO, the SKS method of countering pseudoscience with science is not the bese way of getting through to the great mass of the ordinary public.

    By all means 'innoculate' the public with 'stickier' facts but if one can publicly rip off the mask of a right or left wing propagandist (or evangelical) and show that they are spreading misleading partial truths and constructed deceit to sway the minds of the public towards their chosen ideology, I believe it has a more fundamental positive effect. People don't like it when they are being lied to by fanatics. So yes, I use what some might call ad hominems to achieve this. I particulary use them when arguing on Tony Heller's videos!

    BTW, I hate to say it, but I've found in my mission to 'tell it straight' that because I sometimes take on alarmists who exaggerate the science or dangers as well as denialists, that those who argue using the 'worst that could happen' (on steroids) possibilities are actually more resistant to rational argument and correction than out and out climate science deniers.

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  50. Nick Palmer @49

    I strongly agree its important to bring the denialists politics and ideologies out in the open, and I use every trick in the book to try to do that, including being quite blunt with them at times. I'm very polite here because this website is strictly moderated, but I'm blunter elsewhere.
    However I mostly try to stop short of ad hominems where possible, because I feel we loose the moral high ground and sympathy of fence sitters in the middle of the debate. Plus I'm not really the name calling type.

    However whats appropriate does depend on the context, and I'm not saying you are wrong especially if it works for you. Just mentioning my approach.

    Its frustrating, as a lot of these politically motivated denialists work for lobby groups, and rule number one with lobby groups is to not discuss personal information and political leanings. I find sometimes you have to prod them quite hard! But their politics usually comes out in the end with a stream of slogans and buzzwords.

    While I struggle with certain political ideologies, I tend to avoid attacking them head on and vilifying them, because it alienates people, and just doesnt work. But I'm very critical of specific political policy and data claims and I'm happy to tell people they are spreading ignorance!

    Alarmists who exaggerate the science are very frustrating, and do more harm than good, like the mirror image of the hard core denialists. There are a couple over at realclimate.org and I've battled with them, politely. They get real nasty and call me names and label me a denialist or luke warmer. Some of these guys look like they have personality issues, dunning kruger, etcetera. They mean well, but that's about the best I can say.

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