Following the spectacle and theatre of COP 28, I thought it might be a good idea to remind ourselves of the rationale behind the targets upon which its deliberations were founded. After all, we all thought we knew that a two degree Celsius increase in temperature would spell disaster. Now we all presume to know that one and a half degrees will do the trick. But what exactly is the strength of the science behind the determination of such thresholds?

The COP 28 delegates will tell you that they don’t care anymore, because this is a matter of settled science, and that is all you need to know. Short shrift would be given to any suggestion that there is still debate to be had concerning the scientific basis. As for any suggestion that the specification of the targets was actually a political manoeuvre … well, that is to laugh. Except it’s true, and I’m not even joking.

That values ascribed to safety targets owe more to politics than science should not strike you as controversial, but I am prepared to bet that it will, at least where climate change safety targets are concerned. This is because, whereas safety professionals are quite aware of the arbitrariness that often accompanies the quantification of targets, climate policy-makers wouldn’t dream of conceding an inch on the mantra of ‘following the science’. For them, two degrees increase doesn’t just provide a simply understood framework within which to work, it represents a consensus arrived at by thousands of scientists objectively beavering away in the way that scientists always do. It’s as if the 40 mph speed limit that suddenly appeared on your commute to work was the result of endless studies of accident statistics, combined with consideration of the local road conditions as related to accident causation, rather than an arbitrary gesture in response to a general road safety campaign (which is actually the much more likely scenario). I’m sure a set of consultants would have been employed to validate the choice of speed limit, but rest assured that their recommendations were provided only to help push through the ‘correct’ policy. Speaking as a former traffic control systems safety analyst, I have to hope that you can just take my word that this is how these things generally go down.

But climate science is different, I hear you say. Well, let us look at the evidence for that. What exactly is the history behind the setting of the current climate change speed limit?

It’s politics, stupid

It is generally accepted that the first person to mention a two degree Celsius limit was Nobel economist William Nordhaus, back in the 1970s. As he put it:

“As a first approximation, it seems reasonable to argue that the climatic effects of carbon dioxide should be kept within the normal range of long-term climatic variation. According to most sources the range of variation between distinct climatic regimes is in the order of ±5°C, and at the present time the global climate is at the high end of this range. If there were global temperatures more than 2° or 3° above the current average temperature, this would take the climate outside of the range of observations which have been made over the last several hundred thousand years.”

The first thing to note here is the range of uncertainty, i.e. ‘2° or 3°’. The second is how weak the argument is for this ‘first approximation’. It doesn’t involve a detailed scientific assessment of the impacts of warming, it merely makes the ‘reasonable’ assumption that we might not wish to invite an unfamiliar scenario. As such, it is essentially precautionary in its nature. Furthermore, no data or citations were offered at the time by Nordhaus to back up his claims regarding the Earth’s temperature record.

Be that as it may, there were many who were later willing to back Nordhaus’s intuitions. In particular, the WMO/ICSU/UNEP Advisory Group on Greenhouse Gases produced a report in 1990 that re-iterated the significance of a 2° limit (the lower of the two figures proposed by Nordhaus), this time by arguing for the likelihood of non-linear, catastrophic impacts beyond that threshold. The baton was also picked up by the German Advisory Council for Global Change (WBGU) in the 1990s. It was the WBGU, under chairman Hans Joachim Schellnhuber, that convinced Angela Merkel of the 2°C target, thereby starting a political process that ultimately led to the adoption of the 2°C target by organisations such as the G8, the Major Economies Forum, and the Conference of the Parties held in 2010 in Copenhagen. It was also largely through the exhortations of Schellnhuber (a member of the Club of Rome advocating for a ‘move towards more equitable economic, financial, and socio-political models’) that the target was later to be reduced to 1.5°C. Again, such arguments were ostensibly motivated by the desire to avoid tipping points that could not be proven but were deemed sufficiently plausible to invoke the precautionary principle.

I would not wish to give the idea that there was no science behind the proposal of the 2°C target, or indeed its subsequent reduction to 1.5°C. However, it would be naïve to suggest that the values chosen arose from any detailed calculations corroborated by multiple groups of scientists working independently. The history of the limit owes a lot more to the scientific hand-waving of small but influential bodies who have furnished their political overlords with suitably rounded numbers that can function as a focal point in the climate policy arena. In that respect, the analogy with traffic speed limits is most apt. The science might suggest a speed limit of 37 mph, and even that different limits apply for differently experienced drivers. It is fortunate, however, that speed limits are not set by scientists but set by politicians who understand that focal points are important for success, and simplicity is important for focal points. Richard Betts of the Met Office puts it this way:

“The level of danger at any particular speed depends on many factors… It would be too complicated and unworkable to set individual speed limits for individual circumstances taking into account all these factors, so clear and simple general speed limits are set using judgement and experience to try to get an overall balance between advantages and disadvantages of higher speeds for the community of road users as a whole.”

So 40 mph it is for everyone. Similarly, 1.5°C is chosen not so much for its scientific accuracy but for its political expediency. After all, it is supposed to equate to an acceptable level of risk, and questions of acceptability are political rather than scientific.

Build it and they will come

And that would be the end of my story were it not for one more important detail. If 1.5°C is just a number plucked out of the air because it sets a good target, then why is it that so many scientific studies have subsequently appeared to verify its critical importance? How come that a figure that arose from years of intuitions, guesses and vaguely applied scientific insights has proven to be bang on the money, according to the current crop of peer-reviewed articles published in prestigious journals.

To understand this apparent coincidence, one has to appreciate just how a politically established focal point serves to guide the direction taken by scientific study. Furthermore, one has to drop the naïve view, often expressed, that the scientific method and the competitive nature of the scientific enterprise ensure that any suspect propositions will be challenged and ultimately overturned. The main problem with this naïve view is that it ignores the social feedback that occurs once a particular view has gained dominance. In an ideal world, such dominance should not interfere with the objectivity of decisions taken, but in the real world there are positive feedbacks that tend to reinforce popularity at the expense of veracity. Put another way, once an authoritative position has been established, credence can no longer be purely evidence-driven. One example of this phenomenon is the Matthew Effect as it applies to the establishment of a dominance of citations for particular researchers. Unfortunately, however, because science is a social undertaking, such feedbacks are a lot more pervasive than citation bias alone might suggest, since they also bear upon the popularity of research undertaken, methods adopted, the conclusions to be drawn and the chances of gaining publication. None of the above are free decisions to be undertaken, since they will all be marshalled by a guiding social hand that reinforces with agency that has no need of conspiracy.

Occasionally, though rarely, the reality of social feedback within the scientific domain will be highlighted by those who operate within it. The message is rarely welcomed, however, since it undermines the whole idea that scientific authority can always be trusted to inform political decision-making. The suggestion that science has a propensity to provide politically correct answers does not go down well with those who have been brought up to believe in an unchallengeable scientific integrity. And so the social sanctions for those who speak out can be severe, as exemplified by the recent experience of climate scientist Patrick T. Brown when he detailed how these mechanisms operate within climate science. To him there is no surprise that research vindicating the 1.5°C target hugely dominates within the prestigious journals, any more than I wasn’t surprised to see safety analyses that conveniently validated traffic speed limits that had been the result of politically taken decisions.

But does any of it matter?

One of the most interesting features of limits and targets is the alacrity with which they are set and the facility with which they are ignored. There are laws of physics that should be borne in mind when determining whether a proposed action or current situation can be deemed sufficiently safe. But the law that states ‘thou shalt not exceed 1.5°C warming’ is of quite a different stripe. It was readily conceived with the minimum of required science, and has been subsequently ‘validated’ with more science than can be decently applied. Since COP 15, such limits have been treated with a dread reverence that looks increasingly melodramatic when one considers how much reality and rhetoric have diverged. It is no wonder, therefore, that each successive COP declaration has been heralded with unprecedented hope, only to be reviewed with unprecedented despair. I guess there is only so much one can achieve by setting limits when everyone knows that they are just symbolic focal points.

24 Comments

  1. The politically motivated ‘science’ behind 1.5C critically depends upon the following:

    1. The assumption that beyond 1.5C, extreme weather gets even worse and that changes in the ocean/atmosphere/cryosphere may become irreversible, i.e. ‘tipping points’ may be passed.
    2. The notion of a fixed ‘carbon budget’ which, if exceeded, will heat the world beyond 1.5C.

    The first has no sound scientific basis whatsoever. The second is belied by the fact that the 1.5C carbon budget in AR5 (2013) was much less than the subsequent updated SR15 (2018) carbon budget, meaning that the ‘settled science’ changed quite radically in just 5 years!

    Liked by 1 person

  2. Physics deniers are responsible for FLOP 28:

    “No doubt there will be lots of cheer and back-slapping… but the physics will not care,” said Kevin Anderson, a professor of energy and climate change at the University of Manchester.

    Humanity has between five and eight years of emissions at the current level before blowing through the “carbon budget” required to hold long term warming to the 1.5 degrees Celsius needed to avert the worst impacts of long term planetary heating, he said.

    I’m not sure if he’s quoting the AR5 or SR15 carbon budget. Neither is Physics I suspect.

    Oh no! Because of FLOP 28, millions are going to find themselves on the ‘climate frontline’ and many will DIE! The oil barons and the physics deniers have sent them up over the trenches.

    Friederike Otto, a climatologist and leader in the field of assessing the role of climate change on specific extreme weather events, was equally damning.

    “It’s hailed as a compromise, but we need to be very clear what has been compromised,” said Otto, who lectures at The Grantham Institute for Climate Change. “The short-term financial interest of a few have again won over the health, lives and livelihoods of most people living on this planet.”

    “With every vague verb, every empty promise in the final text, millions more people will enter the frontline of climate change and many will die.”

    https://phys.org/news/2023-12-weak-tea-climate-scientists-cop28.html

    Liked by 1 person

  3. Jaime,

    The reaction of the scientists is predictable. They want the world to know that the limits are scientifically determined and so cannot be trifled with. But there is no scientific formula that could possibly generate the limits. For that you need to introduce politics into the equation. There is a disingenuousness to the assertions being made by the likes of Mann and Otto. They either don’t understand how safety targets work, or they hope that none of their audience does.

    Liked by 1 person

  4. It’s remarkable how Friederike Otto’s observation that ‘The short-term financial interest of a few have again won over the health, lives and livelihoods of most people living on this planet‘ is almost the precise opposite of the truth: the refusal to phase out fossil fuels means that the health, lives and livelihoods of most people living on this planet have again won over the short-term financial interest of a few. Brendan O’Neill puts it well HERE .

    Liked by 4 people

  5. John,

    It’s interesting that this starts with William Nordhaus, who is an economist. I have just read Thomas Piketty’s magnus opus, “Capital in the twenty first century”, and this includes a section on climate change:

    The Stern Report… calculated that the potential damage to the environment by the end of the century could amount, in some scenarios, to dozens of points of global GDP per year. Among economists, the controversy surrounding the report hinged mainly on the question of the rate at which future damage to the environment should be discounted. Nicholas Stern… argued for a relatively low discount rate, approximately the same as the growth rate (1-1.5 percent a year). With that assumption, present generations weigh future damage very heavily in their own calculations. William Nordhaus… argued that one ought to choose a discount rate closer to the average return on capital (4-4.5 percent a year), a choice that makes future disasters seem much less worrisome. In other words, even if everyone agrees about the cost of future disasters (despite the obvious uncertainties), they can reach different conclusions. For Stern, the loss of global wellbeing is so great that it justifies spending at least 5 points of global GDP a year right now to attempt to mitigate climate change in the future. For Nordhaus, such a large expenditure would be entirely unreasonable, because future generations will be richer and more productive than we are. They will find a way to cope, even if it means consuming less, which will in any case be less costly from the standpoint of universal wellbeing than making the kind of effort Stern envisions. So in the end, all of these expert calculations come down to a stark difference of opinion.

    I think that says it all, really.

    Liked by 2 people

  6. Thanks for this John: “One of the most interesting features of limits and targets is the alacrity with which they are set and the facility with which they are ignored.”- as I found my portable dvd drive the other day, actually Robin found it. I had wanted to listen to The Art of Critical Decision Making by Michael A. Roberto (amazon.com) again and going through the meaning of alacrity hit home with this usage – “If they can, people avoid real life ‘ tests ‘ and ‘ opportunities for growth ‘ with alacrity.””

    Lecture two: Cognitive Biases brought the “real life” part of the definition into focus.

    Mark

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  7. Mark (Hodgson),

    Yes it is slightly odd that the first attempt to quantify an acceptable warming threshold should have been made by an economist rather than a climate scientist. Even so, Nordhaus himself was far from convinced with his own line of argument, saying “that the process of setting standards used in this section is deeply unsatisfactory.” Since then, a great deal of effort seems to have been made by economists to try to beef up the argument by performing various cost benefit analyses. But as your quote illustrates, getting economists to agree on the correct values for the essential parameters in their economic models is easier said than done. This can be no surprise when one considers how subjective it can be to decide how environmental damage should be accounted for. It’s a field of research that appears capable of entertaining any conceivable conclusion.

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  8. Kakatoa,

    Cognitive bias plays a major role whenever judgments are being made collectively, and it took some self-restraint on my part not to get too side-tracked in the second part of my article by discussing them at length. A lot is made regarding the wisdom of the crowd, insofar as the average for a group of people making a predictive judgement is more likely to be closer to the truth than any single individual’s prediction. However, this only works when they make their judgements independently. As soon as they start to make judgements collectively (or at least as soon as everyone gets to know what others are thinking before they make their judgement), all sorts of social factors get in the way, resulting in anything but collective wisdom. For example, Kahneman, Sibony and Sustein explain in their book ‘Noise: A Flaw in Human Judgment’ how a group’s predictions depends critically upon who offers the first opinion. Group views tend to anchor upon the initial view expressed and cascades can then develop, positively reinforcing the bias. On the basis of such arbitrariness, the same group is capable of making diametrically opposed judgements on different days. So once a 2 degree limit had been proposed and endorsed by an authoritative body, it was always going to take quite some effort to move away from that view. I actually don’t mind that an expedient value has been chosen for the threshold, but I do mind that it is presented as hard science.

    Liked by 3 people

  9. On the Nordhaus analysis and climate economists, Ross McKitrick had some choice comments within a wide-ranging interview with Tom Nelson.. For example:

    RM: When I started work in 1996 when I graduated from my PhD, there were only a couple of people who did anything to do with climate change. But like any field there’s a lot of money pumped into climate institutes and into universities to study climate change. So it’s not a standard field in the same sense as trade economics or labor economics or environmental economics would be. So a lot of people will call themselves climate economists now.

    I would guess that a lot of those climate economists don’t have a big picture approach to the field like they don’t necessarily see climate policy is embedded in the whole array of economic socioeconomic policies, where the ultimate question is what will make people better off on balance all things considered. Because you can get a lot of these young climate economists who will happily endorse Net Zero, even sign letters to the European Parliament encouraging them to pursue Net Zero.

    And all they’ve ever studied is what would get us to Net Zero faster and more effectively. But they don’t step back and ask: Is NetZero a very good Target for us to pursue and is the cure worse than the disease? And what would be a climate policy that we could confidently say would be consistent with making people better off around the world over the next 80 years, all things considered?

    There aren’t many economists that think about it in that framework. One one of them who does is William D. Nordhaus who won a Nobel Prize in 2018 for his work in climate economics. A lot of the activist crowd were jubilant, thinking finally the economists have noticed climate change. And look at William Nordhaus: He’s an advocate for carbon taxes he won the Nobel Prize. They don’t want to mention the fact that his modeling work showed that: We should do a bit of mitigation to eliminate some of the lowest value activities that generate greenhouse gas emissions, but otherwise the optimal policy is just to live with it and adapt to it. And that’s the upshot of his modeling work and it’s been a very robust result over the 20 or so years that he’s been doing this modeling work. And it convinced the profession enough that his papers are in the best journals and he won a Nobel Prize for it.

    Yet as I say the implications are lost on people including a lot of people in this climate economics field that you refer to. Who somehow think the fact that William Nordhaus got the Nobel prize in economics means we should all rush to net zero, even though his own analysis would say absolutely not. That result is not defensible and would make us incomparably worse off and be worse than doing nothing; be worse than just ignoring the climate issue altogether and pursuing economic growth.

    The whole interview is here with transcript an illustrations:

    McKitrick: Reckoning Coming for Climate Alarmists

    Liked by 4 people

  10. And I should have said thank you John for drawing our attention to the way in which political and scientific views can run away with supporting one another, often without really understanding why they are doing it or what precisely they are supporting. Of course, the IPCC is the classic example of the very dangerous interaction between science and politics.

    Liked by 2 people

  11. Mark,

    The Patrick Brown presentation that I link to in my article is the best account of the social feedback loop in science that I have yet seen. In some ways, taking the time to view that presentation is far more important than taking the time to read my article.

    Liked by 1 person

  12. Ron,

    I couldn’t comment upon what the majority of climate change economists are getting up to because it is a field that I do not follow particularly. All I can say is that Nordhaus has done a lot to promote the CBA approach and he has had a lot of detractors. I think one of the problems is that the whole point of applying the precautionary principle is to avoid the limitations of CBA as they appertain to deep uncertainty problems. Trying to model future economic scenarios, that are themselves premised upon modelled climate scenarios, seems to be layering uncertainty upon uncertainty to such an extent that it is unlikely that reliable assessments are then possible. And when you add onto that the potential for catastrophic non-linearity, it all gets far too messy. Even if we are dealing with settled science, we are certainly not dealing with settled economics.

    Getting back to the true nature of the targets, I think it is telling that when talking about Figure SPM.3 of AR6 WGII (the so-called ‘burning embers diagram’), Schellnhuber said it provided “a direct scientific way to gauge the political target of limiting global mean temperature (GMT) rise to less than 2°C”. So here we have a scientist that acknowledges the political nature of the target and looks to providing a scientific justification for it. Meanwhile, so many wish to portray it as a scientifically sound limit around which to base the politics!

    Liked by 2 people

  13. John, as you note, the eco alarmists are against any consideration of the benefits assessment to avoid the complexities. They also fail to specifiy the extreme costs of climate-fighting policies, not only in money spending, but also in the destroying peoples’ livelihoods and quality of life.

    Another example is the whole initiative to define “planetary boundaries”. Since 2009 ecologists have been promoting a schema purporting to define an array of limits beyond which we and the planet are doomed. The Stockholm Resilience Centre is the nexus of this effort and here is their latest diagram.

    The original 2009 paper in Nature suggested nine boundary conditions in the earth system that could, if crossed, result in a major disruption in (parts of) the system and a transition to a different state, which is likely to be hostile to human prosperity. For each of these planetary boundaries, one or more control variables were identified (e.g., atmospheric carbon dioxide concentration), which in turn were assigned with numerical boundary values at a “safe” distance from dangerous levels, or where applicable, “tipping points” in earth system processes

    On climate change, for instance, the boundary value proposed was 350 ppm, which had been passed long ago in the second half of the twentieth century. Regarding biodiversity, the current extinction rate is more than 100 extinct species per million species per year, whereas the suggested boundary was 10 extinctions. As for the nitrogen cycle, humans remove today approximately 121 million tons of nitrogen per year from the atmosphere, whereas a safe rate would be a maximum of 35 million tons. In these three areas, therefore, this analysis suggested that humankind had pushed the earth system past planetary boundaries and possibly dangerous levels, into a new—and unknown—world.

    It is pseudo science of course, but intended to make the great transition (or reset, or whatever) sound “sciencey.” Breakthrough Institute people have written extensively debunking it, but prior to COP28, the media reported on how we have pushed the planet beyonds its limits (shades of Club of Rome).

    See https://www.annualreviews.org/doi/full/10.1146/annurev-environ-012320-080337

    My synopsis:

    Don’t Buy “Planetary Boundaries” Hype

    Liked by 4 people

  14. Ron,

    It would appear that the Stockholm Resilience Centre’s ‘Planetary Boundaries’ were invented to address a fear deficit. There is something rather alarming about the idea of going over a limit, thereby entering unknown territory or passing a point of no return. I think it’s got something to do with our preoccupation with fate and doom. That’s why the idea of passing beyond a black hole’s event horizon strikes such a chilling chord. And it’s why limits are such a powerful and ubiquitous tool when arguing for a particular policy. We need boundaries, and if there aren’t any, we have to invent them. But as your own synopsis points out, boundaries have to be well-defined and meaningful, which the majority of the Planetary Boundaries are not. The quote you provide, taken from a critique of planetary boundaries to be found in ‘Trends in Ecology and Evolution’, was particularly telling:

    “At the heart of the problem are terms such as ‘planetary boundaries’, but also ‘sustainability’, ‘health’, ‘harmony’, and others, that are emotionally appealing but rarely, if ever, defined … We must set policies and establish management for the vast tracts of land and sea that we do not protect. Fatally, those who do so often use language that does not borrow from the existing knowledge about ecosystem processes, nor readily translates its aspirations to those who study them [7].”

    Liked by 1 person

  15. One of the first places to attempt to forge links between the climate sciences and economics may have been the School of Environmental Sciences at UEA. Here the department consisted of a mix of hard and soft scientists coupled with social “scientists” : economists and political “scientists” some quiet eminent. Discussions in the staff coffee room were always erudite and diverse. Coffee and tea breaks commonly extended well past the allotted times.

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  16. Seeing as the Patrick Brown affair had been sparked by his accusations against the journal Nature, I thought it might be interesting to see what that journal has previously posted on the subject of social feedback in science. More specifically, what did it have to say, if anything, regarding the politicisation of science and the role that selective allocations of grants has to play. What I found was this series of three podcasts:

    ‘Stick to the science’: when science gets political”

    https://www.nature.com/articles/d41586-020-03067-w

    Clearly, Nature recognises the potential problem, since the following statement is made at the end of the first of the three podcasts:

    “Science would like to be independent. Scientists like the argument that they are independent of politics. And yet, insofar as their funding comes through political processes, they are fundamentally … I mean, it’s just inescapable that science and politics are intertwined. If your funding comes through the political system.”

    At this point I was wondering if Nature would then address the elephant in the room by asking whether political funding is politicising climate science in particular. And yes they do. In the second podcast we are offered the following illustration of the point:

    “For quite a while, people did not use the words ‘climate change’. The phrase that was often substituted was ‘geochemical cycling’ or ‘biogeochemical cycling’. That, you know, basically speaks to all the things that happen related to climate change without that trigger word, getting anyone’s attention. And they started doing that, because one of our congress members started digging into any grant that said climate change. So framing can sometimes be a way around studying politically hot issues without showing that that’s what you’re doing.”

    So, according to Nature, scientists daren’t mention ‘climate change’ in their grant applications because that reduces their chances of getting funding?

    My god! It turns out that the bias in Nature is so fundamentally ingrained that they don’t just want to control the narrative, but also the narrative regarding the narrative. This level of bias would be risible if it were not so depressing.

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  17. John – thanks for above link & comment.

    ““The phrase that was often substituted was ‘geochemical cycling’ or ‘biogeochemical cycling’. ……””

    If I understand that correctly, they (nature) seem to be saying to grant seekers/potential author, don’t use “climate change” in your paper, use these obscure but expert sounding words instead.

    ps – from your link above – “Transcript – Episode 1: A brief history of politics and science”
    quote –
    “Host: Nick Howe
    Nature received this comment on Facebook after we published a story about the damage Donald Trump has done to science. Why am I sharing it with you? Well, I want to know if they’re right.”

    as you say, depressing.

    Like

  18. A copy of my comment on ‘The UK’s Net Zero Policy – An Update’, as it is relevant on this post too:

    Ross McKitrick has an excellent post at Climate etc. on the use of Total Least Squares statistical regression method used to estimate the ‘fingerprint’ of GHGs on global warming. Again, we see that Al Jaber was right when he said there’s “no science” behind the claim that we need to phase out fossil fuels to limit global warming to 1.5C.

    “One of them, after noting that statisticians and econometricians don’t like TLS, added:

    “it seems to me that the target audience of the paper are practitioners using TLS quite uncritically for climatological applications. How large is this community and how influential are conclusions drawn on the basis of TLS, say in the scientific debate concerning attribution?”

    In my reply I did my best to explain its influence on the climatology field. I didn’t add, but could have, that 20 years’ worth of applications of TLS are ultimately what brought 100,000 bigwigs to Dubai for COP28 to demand the phaseout of the world’s best energy sources based on estimates of the role of anthropogenic forcings on the climate that are likely heavily overstated. Based on the political impact and economic consequences of its application, TLS is one of the most influential statistical methodologies in the world, despite experts viewing it as highly unreliable compared to readily available alternatives like IV.”

    In particular, on the subject of the ‘settled science carbon budget’ for 1.5C:

    “Among other things, since TLS-estimated coefficients are plugged into carbon budget models, this will result in a carbon budget being biased too small.

    TLS-derived signal coefficients yield systematically underestimated carbon budgets.”

    Climate attribution method overstates “fingerprints” of external forcing

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  19. Jaime – thanks for the link – Ross McKitrick has an excellent post at Climate etc.

    interesting post/read, then I read some comments below which detract/have no input into the post sadly.

    Like

  20. Having said the above – found this comment interesting –

    “Morgan Wright | December 19, 2023 at 5:46 am
    Let me raise my hand and comment about ocean acidification.

    Currently, when calcium carbonate settles on the ocean floor at depths lower than the lysocline and CCD, it is dissolved. The high CO2 content on the ocean floor at great depth dissolves CaCO3, and releases CO2 back into the atmosphere. For the past 250 million years, CO2 has been decreasing linearly (roughly), such that it would hit the zero point in about 50 million years. This is due to limestone deposits above the lysocline. When atmospheric CO2 gets lower, the depth of the CCD decreases, and when it gets low enough, the CCD reaches the bottom of the ocean, and limestone would start collecting there. When the lysocline reaches the bottom of ocean, CO2 levels there would be too low to dissolve calcium carbonate at all, and limestone would collect there in large amounts. This would cause more CO2 to be taken out of the air, and the jig is up for CO2 in the atmosphere. Sooner or later, around 50 million years from now, CO2 drops to zero and all life ends. The CO2 has been decreasing for 250 million years, but once the lysocline is gone, the rate at which it decreases would rise quickly until it reaches zero, and all life on earth would end forever. The best thing humans have ever done is put CO2 back in the air where it belongs. If humans had not arrived and started burning fossil fuels, life on earth would have been doomed. So yes, I’m a climate doomer.”

    Maybe Alan can comment on that!!!

    Liked by 1 person

  21. df, I always thought that the action of acids on limestones was to release carbon dioxide, not sequester it. Ancient limestones record fluctuating CO2, not a monotonic change so much of this communication I would class as garbage

    Like

  22. Alan – Thanks for your reply, great to have your input/insights on above comment.

    did a bit digging on “lysocline and CCD” since it was new to me & found this link –
    https://geo.libretexts.org/Bookshelves/Oceanography/Oceanography_(Hill)/03%3A_Sediments_-_the_Memory_of_the_Ocean

    A bit brief but a useful overview & found this fact/statement interesting –

    “At the CCD the rate of supply of calcite equals the rate of dissolution, and no more calcite is deposited below this depth. In the Pacific, this depth is about 4,5000 below the surface; in the Atlantic, it is about 6,000 m deep. This dramatic variation is due to differences in ocean chemistry. The Pacific has a lower pH and is colder than the Atlantic, so its lysocline and CCD are higher in the water column because the solubility of calcite increases in these conditions”

    You learn something everyday, wonder if it wins a pub quiz for me 🙂

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