Since I’ve written about climate sensitivity quite a lot, I though I would briefly comment on Sabine Hossenfelder’s recent video, I wasn’t worried about climate change. Now I am. In this context, climate sensitivity refers to Equilibrium Climate Sensitivity (ECS), which is an estimate of how much our climate will warm if atmospheric CO2 doubles. Technically, it is determined by doubling atmospheric CO2 in a climate model and determining how much it warms before returning to equlibrium.
In the IPCC’s AR6 WG1 report, the likely ECS range was 2.5oC to 4.5oC with a best estimate of 3oC. A recent paper assessing Earth’s climate sensitivity using multiple lines of evidence suggested that the likely ECS range is 2.6oC to 3.9oC and is bounded by 2.0oC and 5.7oC.
However, the most recent group of climate models have a subset with climate sensitivities higher than the top of the IPCC’s likely range (i.e., above 5oC). This has been referred to as the “hot model” problem and it’s been suggested that these models should be given less weight.
On the other hand, Sabine’s video highlights a paper that tested one “hot” model to assess some of the processes relevant for climate sensitivity, in particular the cloud physics. These tests use short-term trends, but can still be useful for assessing the physics in climate models, as long as the model used to do the short-term forecast is the same as the one used to do the climate projection. There’s also been a recent paper by James Hansen and collaborators, suggesting that the ECS is 4.8oC ± 1.2oC.
So, there are some indications that the ECS may be higher than the standard IPCC range suggests. However, it is just one model that has been tested using short-term trends, and the Hansen et al. work is just one paper. There are plenty of other lines of evidence suggesting that the ECS is probably between about 2oC and 4.5oC with a best estimate around 3oC.
One should also bear in the mind that even the standard ECS range doesn’t preclude these high ECS values, they’re just regarded as not very likely. When it comes to climate change, the ECS doesn’t have to be this high to be worried, and one could still include the possibility of the ECS being this high when thinking about what to do about climate change.
As usual, feel free to express a different view in the comments.
...and Then There's Physics 
The other thing to consider is that suddenly being worried about climate change because of a couple of papers suggesting that the ECS may be higher than the standard range suggests is not all that dissimilar to suggesting we don’t need to be worried because Nic Lewis’s works suggests that it’s probably lower.
I’m a little nervous at Sabine Hossenfelder’s narrative of ‘now we should be worried’, because I was already extremely worried with an ECS confidence range of 2.5°C to 4.5°C.
What if further research suggests the cloud physics problem is resolved in favour of the AR6 projections? Does the narrative flip to ‘Ah, relax guys!’
I’m not saying that resolving cloud physics within climate models is unimportant, but chasing ever narrower confidence intervals for the ECS seems to be an illusion. I’d recommend Erica Thompson’s “Escape From Model Land”, which raises lots of interesting points about what exactly we need to be modelling and why. What questions should we be asking. For example, instead of asking ‘How high will sea levels rise?’ as a basis for planning flood defences, should we instead be asking about strategies for dealing with rising sea levels – retreat? modular defences that address uncertainties? etc. Different, more complex questions, but more useful in addressing deep uncertainties.
Not forgetting that ‘uncertainty is not our friend’.
Richard,
That’s a good point and is related to what I was suggesting at the end of the post – ECS doesn’t have to be “high” in order for us to be worried.
I can’t remember if I read Erica’s book, but I did write a post about a podcast that discussed it.
The related point is that if someone thinks ECS needs to be ~5C to be worried, then why weren’t they worried before? The standard IPCC range suggests/implies a ~16% chance of it being above 4.5C. Does it need to have a higher than ~16% probability to be worried, or did they not realise what the standard range implied?
Gavin Schmidt has a nice, short X/Twitter thread about this.
Thanks for the GS link.
I wanted to respond to your comments on Erica Thompson’s book, but didn’t get around to it. Not sure you did the book justice – there’s a lot of nuance there related broadly with how we broaden the conversation on the whys and wherefores of modelling in many contexts, and how it could drive modelling investments.
Back to ECS. As we see with how extreme weather probabilities escalate as we shift mean GMST – unexpectedly for those unfamiliar with the maths – the shifting mean does not really convey to public opinion the shifting risks. Ditto ECS. So as a communication of ‘how bad might things get?’, climate scientists know what it means, but most people don’t.
Richard,
Quite possibly. As I said in the post, it was based on the podcast, not the book. I vaguely recall reading some of the book, but maybe I didn’t. I should try and find some time to do so.
Agree with Richard, I thought the video inflated the importance of the cloud Physics paper. There are many errors in climate models that the cloud physics could have been compensating for. Not enough weight on its own to shift the mountain of ECS evidence.
We have plenty of other reasons to be concerned about climate change. This year has highlighted the risks we are taking. We are planning a close but “safe” approach to climate tipping points. Uncomfortable when we pick up warming speed at the last minute when we should be slowing.
An ECS of 5 would imply that imply a non-linear ECS, because the post-industrial ECS is just shy of 3 by 2100, by my calculations. It does get higher the further out you go. There’s an exponentially-diminishing ocean warming curve you must apply to every forcing change (see Caldeira and Myhrvold 2013, https://iopscience.iop.org/article/10.1088/1748-9326/8/3/034039/pdf).
Temperatures in 2023
The most complete discussion that I have found about the recent rapid rise in earth temperature is by Dr. Robert Rohde at Berkeley Earth, https://berkeleyearth.org/global-temperature-report-for-2023/ . To summarize, I would say that they believe that while slower processes like global warming, reduction in aerosols and possible warming due to Hunga Tonga are contributing, the main drivers are natural variability of temperatures in the North Atlantic and other ocean regions coupled with the effects of El Nino. They are predicting only a small increase in temperature for 2024 over 2023.
ECS and ESS
Paleoclimatologists mostly concern themselves with the Earth System Sensitivity (ESS) that defines the change in temperature over timescales of millennia for doubling of CO2 concentrations. Climatologists are most concerned with the ECS or Equilibrium Climate Sensitivity or short term rise in temperatures for doubling of CO2 concentrations which is best suited for predicting present-day warming.
I like to think of ESS as Mother Nature’s equilibrium and in some sense puts an upper bound on the ECS. Paleoclimatologists have been sharing and compiling their proxy data for ancient earth’s temperatures vs CO2, http://droyer.wescreates.wesleyan.edu/Honisch_2023_Science_CenozoicCO2PIP.pdf
. They find that the ESS varies mostly between 5 and 8 C.
Recent work by Dr. Jessica Tierney and colleagues have been using climate models to combine the proxy data both temporally and geographically. When they do that, they get a much tighter fit for ESS and find that they get a very good fit for the Cenozoic data with ESS of 8.2, https://www.youtube.com/watch?v=S7SEcE4K9OQ . The actually coined a new term for their fit as “Apparent Climate Sensitivity.”
Good news, bad news
I’m no expert, but I think this recent work is going to help scientists improve their models and help to better constrain values for ECS.
Just for fun, if you use the ACS 8.2, from Tierney’s work and define temperatures as a function of CO2 relative to preindustrial values (0 and 280 ppm), you can derive an equation for GMST relative to preindustrial, i.e. y = log2 (ppm CO2) – 66.66. Solving for our present value of 419 ppm, you find that the apparent earth warming potential is 4.8 C over preindustrial temperatures which equates to about 3.5 to 3.7 C of “apparent warming potential” over our present GMST.
The good news is that is a lot less than the 8 to 10 C Hansen says is in the pipeline. The bad news is that is still very sobering.
Yes, 1.3℃ of warming is causing weather events noticeably worse than what we prepared for. 2.0℃ will be very unpleasant, and disastrous for many people. I don’t see why the global population isn’t already very worried.
Correction: Equation is y = 8.2*log2(ppm CO2) – 66.66.
Just Dean,
Good point about the ESS and ECS, the former being the amount of warming we might expect on very long timescales as the slower feedbacks become more prominent. One reason I tend to think that the ESS is not all that relevant (in addition to the timescales) is that there are also slow processes that will act to reduce warming (i.e., the takeup of CO2 by the slow carbon sinks). Hence, I don’t think it’s clear quite how these various slow processes will influence the overall level of warming (i.e., I think a realistic estimate of how much warming will occur on long timescales is very challenging).
As I understand it, ESS could be quite variable dependent on the starting state, specifically the level of glaciation as ice sheet feedback has a big impact.
From a glacial maximum, ICe sheet feedback would be large, but from today’s position it would be much smaller.
But I may have misunderstood.
VTG,
Yes, I think that is correct. The ESS is probably smaller when starting from an inter-glacial state, than it is if starting from a glacial.
ATTP and VTG,
According to Tierney et al. it doesn’t appear to matter what the starting state is. I advise caution because the work isn’t published. Their fit includes everything from 66 Mya up through and including the LGM.
If you don’t have time to watch the whole video, I recommend jumping in the at the 1 hour time mark to see her conclusion and summary slides.
Just Dean,
I’ll have a look, but we think the ECS is somewhat state dependent, so I’d be very surprised if there was no state dependence to the ESS.
I think they are somewhat surprised as well. Again, I’m not equipped to judge but I find it fascinating.
I have watched some of it. Is the basic result that the is a common relationship between CO2 and temperature. If so, that is interesting, but (as I think is mentioned) the solar output was different during the different time periods, and there are other forcings (methane, dust, ice sheets). So, it’s not clear to me that this is quite suggesting that the ESS is state independent.
I am color blind. Partially, and red/green. Mark C. – is include his last name, if I didn’t have to go look for it to get the spelling right (but i seem to recall it has two “z”s. Anyway, he developed lens to see what I otherwise do not. He offered them for free to people like me to try and give feedback. For the first time in my life I passed a color blind test.
This I reported back and qualified for a pair lenses that would fit eye glass frames (FWIW, there were three types of lenses, and you had to pick one.)
So here, and as a metaphorical reply: I forwent the choice. I was well adapted to my color blind condition, and I sort of knew I’d never use them. …the original three pack sits – unused – in my desk draw.
So,& for Willard, and as my allowed drive-by: #InuitObservations. Eventually their import will be an in blinding❣️😉
=) Greg
https://www.gumlet.com/watch/64df7c117efb8b93d1181b34/
>
Just Dean,
I don’t really do videos, too time consuming and also rarely specific enough. Is there a good written source for the claims?
VTG,
I think the key result is shown at exactly this time, which is simply that they see the same relationship between temperature and CO2 at all the different epochs. Very interesting result and certainly further confirms the importance of CO2. Not quite convinced that it can be used to claim a state-independent ESS, though.
Ken, I think it’s worth noting that whereas you say in the original post:
the IPCC AR6 WGI SPM (paragraph A.4.4) has that *likely* range for ECS at 2.5°C to 4.0°C.
Related, in the comments, where you say:
the IPCC AR6 WGI SPM implies the 16% chance is for the ECS exceeding 4.0°C, and the chance of it exceeding 5.0°C “just” 5% (i.e., from the “very likely” (90-100%) range of 2.0°C to 5.0°C from the same reference as above).
Details aside, I strongly agree with what I read as one of your more general sentiments: the fatuousness of a seeming sorts of “well! **Now** – if this is true – I am *really* worried!” or “now we **really** have to cut emissions quickly!” (as if the budgets for 1.5-2.0° assuming a 3.0°C ECS (or 0.45°C /1,000 GtCO₂ TCRE) didn’t already require blindingly quick emissions reductions!
I’ll editorialize and say that some of the the johnny-come-latelies arriving at the party screeching non-stop after the horses are already known to 3/4ᵗʰ’s out their barn gates that the horses may in fact be 7/8ᵗʰ’s out of their barn gates seem to be as concerned about social media engagement more than anything else. (As well as the seeming goal of eroding trust.🤷)
Like the twitter guy who keeps saying we *now* – like, now, this month of January 2024 – desperately need to prepare additional adaptations in advance of more the extreme events sure to befall us later in 2024 because of the greater sensitivities to CO₂ and aerosols… what the hell does that even practically mean? Build the sea wall around Miami before this year’s hurricane season? Or what?
It’s tedious.
rust,
Good point. I checked and still wrote it down wrong.
I strongly agree with the rest of your comment.
As a non-scientist who has followed climate matters since the late 70’s due to a worrying trend affecting the Murray-Darling river system in Australia, I find it troubling that Sabbine has not been more vocal on this topic seeing the IPCC first Reported in 1990 and things have deteriorated every year since.
It’s all good and well to try to be even handed and point to uncertainties and the like, just in case science has gotten it wrong. BUT there needs to be evidence that there is a counter-mechanism to greenhouses gases that was LIKELY to come into play and turn around the trend.
Given that it was exactly 200 years ago – in 1824 – that Joseph Fourier calculated that at our distance from the Sun, Earth should be much colder, the science has been around for a very long time. Back then he proposed the atmosphere must be acting like an insulating blanket, and in 1856, Eunice Foote discovered that blanket, showing that carbon dioxide and water vapor in Earth’s atmosphere trapped heat, aka infrared radiation.
We lay observers, cum-readers of science, remain worried that so few are prominent in carrying the strong message that Hansen launched back in 1988 in his evidence to the US Senate. As enjoyable as this site is to follow there needs to be more concerted support from the science community en masse to politicians in particular in advancing the urgent need for action.
Thanks AT
Let be clear about my position. We are all observers of an unprecedented and unfortunate experiment. Much of the discussion, ECS vs ESS vs warming in the pipeline, although interesting is somewhat academic. We can improve the models to try and reduce the uncertainty in predicted temperatures by 2100 or beyond but what really matters is determining the impact on severe weather, melting of ice sheets and sea level rise and that I feel is a tougher problem. There is no equivalent paleoclimatological event for comparison.
I’m interested in the paleoclimatological data because it helps me understand and visualize how far we have managed to drive earth’s climate system out of equilibrium in just a couple hundred years.
As Kate Marvel said, “I’m not screaming into the void anymore…. So I don’t just want to talk about the problems anymore. I want to talk about solutions. Consider this your last warning from me.”
I think “solution” has to be defined. We’re not likely to be able to go back to even 350ppm, so the problem of 420ppm+ CO2 is going to be with us for a very long time. Perhaps the only thing we can do is ensure that emissions are reduced to zero very soon. Would that be a “solution?”
Mike,
FWIW, I think the “goal” should be to get to (net) zero, which is defined as humans no longer adding CO2 to the atmosphere. Maybe we should just call it “zero”, rather than net zero. When that is achieved, we actually expect the natural sinks to continue taking up some of what has been emitted so that atmospheric CO2 concentrations actually drop.
Currently the airborne fraction is about 0.45. After (net) zero is reached, we’d expect it to drop (on a timescale of about ~100 years) to 0.25. So, if (net) zero is reached soon (i.e., while concentrations are close to 420 ppm) we’d expect it to drop to about 360 ppm.
Of course, it will then continue to drop as CO2 is taken up by the slow carbon sinks, but these are very slow processes.
This is essentially why we expect the zero emission commitment to be close to zero. In other words, when we get to (net) zero, global surface temperatures should stabilise, but won’t go down for a very long time.
The calamity is that the United State’s 2022 “Inflation Reduction Act” pre-qualifies fossil carbon companies for 100% of both tax credit in that law and ‘clean’NOT! hydrogen. At a time of their choosing, they declare themselves “Energy Companies” and they get to continue doing their BAU but with a $.60/kg credit on the gas that they can currently make for about $2.50/kg. Plus claim 5 time that , or $3/kg produced on the value of the infrastructure involved. The tax credits may be sold, and the infrastructure – wellhead to [at least] gate, but the law that is reference in the exemption say to the point of utilization – can be securitized. Secretary Kerry’s inclusion of the concept of “transitioning” in the last COP can be argued in court to mean that there is no constraint in law concerning the declaration by fossil carbon fuel companies that they are qualifying “energy” companies.
Any time between now and 2033, a 10 year right to the tax credits is theirs.
By this means the US tax payer fossil carbon companies will come to monopolize the ‘clean’NOT! hydrogen economic meme. ‘Green” hydrogen will be relegate to being batteries related to solar and wind developments. The IRA qualifies fuel cells as small as 5 KW for infrastructure tax credits. This is a unclosable window to fuel cells replacing transformers at the neighborhood level.
If this can be grasped, it means all the talk of grid upgrades is specious.
(FWIW, I need to submit public comment before tomorrow regarding a false flag grid planning process unfold in Maine over the next decade. The above will be the substance of those written comments, and was my oral comments. What is ‘yelled’ into the void of a metaphorically ‘color blind’ and – President Nixon’s – “Silent Majority” is socialized motivated reasoning … for which extinction of our species as part of the unfolding 6th planetary extinction event will be a geological footnote.)
Humanity’s remaining agency is to exit non-violently. All four estates have roles that are abdicated on relative to such an exit. Academia is functionally an equivocating entity within the first estate … but for trusted motivated reasoning that colors the perception of this.
https://www.gumlet.com/watch/64df7c117efb8b93d1181b34
=)
I am getting off-topic here relative to the OP, and I realize *you* are aware of this, but I *really* don’t understand why we should stop identifying *net* CO₂ emissions and *net*-zero CO₂ emissions as *NET*… because that is exactly what they are *referring* to!
It would be as if a bunch of people who didn’t understand income statements started complaining about the use of “net income” and insisted that we only refer or discuss gross revenue or gross income, only to mollify their personal confusion.
It wouldn’t change the reality of a calculated quantity called “net income”, nor the need for such a metric with specific defined properties and of particular and important interest.
And I *strongly* suspect that most people who tend to object to the use “net” CO₂ emissions are largely blissfully unaware that when they see charts like this👇of CO₂ emissions from the Global Carbon Project/Budget…
… *EACH* of those numbers for CO₂ emissions – from land use, fossil and industry, and total – are being reported as *NET* CO₂ emissions.
Were we just reporting gross CO₂ emissions from human activity – and excluding negative emissions to arrive at the net emissions – the total CO₂ emissions yr⁻¹ would be about 4.4 GtCO₂ higher, and we’d be trying to ~46 GtCO₂ yr⁻¹ to zero. Except we *already are* reducing that amount to ~41.5 GtCO₂ via our negative CO₂ emissions activities.
Yet no one is clamouring for the GCP to present these numbers only as gross emissions. Nor would it matter to the atmospheric physics what we *call* the CO₂ emissions measure, only *that* the *NET* CO₂ emissions are approximately (net!) zero.
[And if anyone doubts that the GCP numbers *are* reported (and have been reported for *years*) as *NET*, just look at the annual budget in detail, and try – as an exercise! – to identify the ~4.4 of *negative* CO₂ emissions from human activities already included in the numbers!]
To me, this “maybe we shouldn’t call it net” is just surrendering to ignorance and incoherence on the underlying subject matter. For the sake of not upsetting them, and/or buying into their rhetoric that if, say, we were ever to ever call something “net income”, we’d never be able to separately focus on “gross revenue”, “gross income”, “expenses” or whatever because everyone is clearly too confused and incapable of ever being able to pursue multiple goals.🙄
I was trying to use the picture in Glen Peters tweet above to show this👇plot of the GCB CO₂ emissions data.
Each data series of which is reported as *NET* emissions.
As I say above, total *gross* human CO₂ emissions are closer to 46 GtCO₂ yr⁻¹.🤷
Rust,
Yes, you’re right, of course. I was mostly trying to avoid a complaint about the use of “net”. I didn’t consider that I would get someone “complaining” about trying to avoid using “net” 😁.
Thanks for the reply. I was under the impression that elevated CO2 levels would be around for centuries. Or is it that the climate effects of those elevated CO2 levels will play out over centuries?
> …suddenly being worried about climate change because of a couple of papers suggesting that the ECS may be higher than the standard range suggests is not all that dissimilar to suggesting we don’t need to be worried because Nic Lewis’s works suggests that it’s probably lower.
We come back to the same question over and over. Why do some knowledgeable scientists often break fundamental guidelines for the best scientific practices. I prefer to no go for motive-impugning as an answer. Doing so is unfalsifiable (and thus not a best practice). So if we don’t look to motive-impugning, what’s the answer? Maybe there’s no general rule but I think that there is a test that helps. When scientists break fundamental guidelines for best practice, and it’s pointed out to them, how do they respond?
Mike,
They’ll be elevated relative to pre-industrial for a very long time. However, the long-term airborne fraction is around 0.25, while currently it’s about 0.45. Essentially, the fast carbon sinks (ocean and biosphere) are not yet in equilibrium. When we get emissions to net zero, they’ll continue to take up some of what we’ve emitted until the airborne fraction reaches about 0.25.
However, this will simply stabilise global surface temperatures, so this will not reverse climate change and these changes will persist for a very long time.
Joshua,
It doesn’t surprise me all that much that scientists, who are people, can be suddenly become convinced by a single piece of evidence. However, you’d like to think that this is in light of all the other evidence, rather than simply this one piece of evidence, and that they might then reflect on why they hadn’t been convinced before.
The underlying problem with Nic Lewis’s body of work and Sabine’s Youtube is cherrypicking. In the case of Sabine, there have been a number of papers which show relatively poor performance of the warmer CMIP6 models vs the cooler models for various metrics. This recent paper for instance:
“Models with high climate sensitivity are less likely to reproduce observed decadal-scale swings than models with a modest climate sensitivity, possibly due to an incorrect balance of cloud feedbacks driven by changing inversion strength versus surface warming.”
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL105488
I realise that my comments about the continued uptake of CO2 by the fast carbon sinks is a bit simplistic. Technically, there are numerous timescales. At the end of this post there is a quote from a paper that explains the various different timescales (I’m primarly referring to the first timescale in the comments above):
Chubbs,
Exactly, I think the evidence in favour of the ECS probably being as high as 5C is weaker than the evidence suggesting that it probably isn’t.
Zeke has a new post on The Climate Brink where he also addresses the video by Sabine and hot models, https://www.theclimatebrink.com/p/revisiting-the-hot-model-problem .
Conclusion: “Arguments over ECS are distractions. Whether it’s 3C or 5C is a bit like whether a firing squad has 6 rifleman or 10. It’s bad either way….”
The elephant in the room is that although ECS remains central to policy discussions, it has proven remarkably resistant to efforts to refine its value by the time-honored method of expanding the scope of research.
An order of magnitude increase in science funding does not automatically reduce the complexity of a dynamic system.
Whether it’s 3C or 5C will have a bearing on the budget for any arbitrary limit we decide to go for. So it’s important. But I think it would be better to accept the higher ECS for the purposes of policy setting, since if it turns out that it really is 3C, we’ll have gone a long way to mitigating emissions. Of course, that would be dependent on taking action!
Two papers that could be relevant
1. Climate sensitivity can go down if one change the model parameters of the cloud physics
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023MS003875
2. Regarding the last part of Sabine’s video, this other paper research whether or not the inclusion of the hot models change the projections of the climate impacts using hydrological projections and finds that it is far from clear that the inclusion of hotter models involves projections outside the range of the model ensemble.
https://hess.copernicus.org/articles/27/4355/2023/
I don’t believe that’s how this works especially when it comes to synthesis by the IPCC. Their job is to do the best they can at estimating projected temperatures for different emission scenarios based on the best available science and from there estimate environmental impacts. It is not their job to choose the worst case scenario to try and elicit more action by policy makers. By the way, the term or ECS acronym is not mentioned once in the IPCC summary for policymakers.
It’s plainly highlighted in the IPCC AR6 WGI SPM👇 and SYR SPM, and it’s been a key concept/metric in *every* assessment report cycle.
A full chapter👇 of the IPCC AR6 WGI is given over to the science underlying this and related climate science measures, and as noted in the SPM excerpt above, it is further explored in multiple chapters and “Cross-Chapter Boxes”.
by the way, that said👆, I still think that people are losing the plot in turning so much attention *back* to ECS after probably the biggest shift in the thinking of physical climate scientists about what we would have to do to actually stabilize global surface temps emerged, beginning in 2008-09.
Which made clear that locking on the exact value for ECS was (a) probably never going to be possible anyway and (b) was in some ways a distraction if the goal was stabilizing **temps** rather than atmospheric CO₂ concentrations (which is implicit in the ECS physics). And if the former was going to require *falling* atmospheric concentrations roughly *at least as fast* as would occur given net zero anthropogenic CO₂ emissions, then the concepts of carbon budgets, transient climate response to cumulative emissions and net-zero emissions are really where the meaningful insights are. *Not* what eventually happens after centuries if we were to hold concentrations constant at 560 ppm!
Yes, TCRE is ultimately *somewhat* related to ECS, but as Zeke is saying the latter is a bit of a *practical* distraction.
I don’t remember if it was lecture 1 or 2 from this excellent series Myles Allen gave in 2022-23 where he details the history of how the new insights emerged and how the prior chase after narrowing the ECS range probably sent confusing policy implications to decision makers, but it’s excellent.
But he was saying roughly the same thing at the Oxford “Beyond 4 Degrees” conference in 2008 or 2009 (also still online if you are diligent).
[Anyway, by making this point and going to grab the url from YouTube, I now see that Myles has been running another 2023-24 series of lectures, which Robbie🐾🐶 and I will now look forward to enjoying on long walks over the next several weeks!👍]
oops, forgot to link to the 2022-23 lecture series I discussed above.
here it is:
For the record, I was referring to “Climate Change 2023 Synthesis Report Summary for Policy Makers.” ECS is not mentioned, however, upon closer inspection I find that “equilibrium climate sensitivity” is mentioned once in a footnote and once in a figure description.
I don’t think our biggest issue is trying to explain ECS to policymakers when just over half of the GOP in Congress deny that climate change is real and/or caused by human activity. Regardless, we should not arbitrarily pick the 95% percentile number to try and persuade more people, specifically policymakers, of the urgency of action to mitigate climate change.
I am a big fan of Zeke’s. I think he does as good a job as any climate scientist in helping non-experts understand the nuances and intricacies of climate science via blogs, articles on Carbon Brief and online videos.
With that said, I have found that sometimes other scientists do a better job on certain topics. For instance, I found Dr. Robert Rhodes’ explanation for the spike in temperatures in 2023 more satisfying than Zeke’s.
RNS, ECS by itself is just a number. But it’s very important because it is used as a key input into so many other calculations. Did we learn nothing from RCP 8.5?
Tom,
What other calculations?
I learned quite a lot. Most of it things I rather wish I hadn’t discovered.
8.5? Oh my gawd.
Yeah, I’m curious myself as to what other calculations he’s suggesting ECS feeds into – at least any policy relevant calculations, at this point.
Even the dreaded RCP8.5 – which I believe was protested about primarily regarding the emissions/concentration assumptions, NOT the resultant forcing/temperatures – has the evolution of its temperature outcomes basically circumscribed, like all the other RCP pathways!!! – with **TCRE** as the “input”.👇
“Did we learn nothing from RCP 8.5? ”
that nobody cared that RCP 2.6 was even more unrealistic?
[because the debate was about policy not science]
So, obviously the answer is no. ‘We’ learned nothing.
Tom,
Maybe you could explain your point. Would also be interested to know your projections for future emissions.
I do not despair of ECS being computable , but getting to the level of computational power needed to do it by finite element methods may entail not just realizing quantum computation , but solving the PCP conjecture to verify it.
For those in the back:
Source: https://andthentheresphysics.wordpress.com/2020/02/09/but-rcps/
Four years already. Time flies.
What did we learn from RCP85 – a fossil fuel future is dystopian. What have learned since RCP85 was developed – its much easier to transition away from fossil fuels than we thought.
ECS questions aside, there is the reality of measuring the existing warming and it’s impact. There is also the question of looking at our continuing emissions which are driving us into uncomfortable climate territory. Guardian has piece about scientific study of sponges that indicate current warming is 1.7 degrees already. 1.7 is not that bad if we could get to the zero emission spot today or tomorrow.
I agree with attp that talking about net zero or zero is a bit of a distraction, why don’t we just talk about the zero spot where our emissions no longer drive increases in atmospheric accumulation? That makes sense to me. We need to keep it simple if we can. No reason to haggle over net zero or zero, let’s just call it zero when the needle stops going up.
Once that happens, we can look around and try to determine how much warming we have bought with our past emissions and start figuring out how to manage with that level of warming. My guess is that if we ever get to the zero point and civilization has not collapsed, we will want to start moving below that zero point because we will find the warming to be not to our liking.
here is the Guardian piece about the sponges:
https://www.theguardian.com/environment/2024/feb/06/ancient-sea-sponges-at-centre-of-controversial-claim-world-has-already-warmed-by-17c?CMP=usbriefing_email
No worries! Enjoy being alive.
Mike
The sponge paper is very new. I get the impression that the ±.1℃ temperature value is a variance of the signal, not necessarily the potential error of the value which could be much higher.
It’s also irrelevant how much warming sponges show. The limits (1.5℃, 2.0℃) were derived from thermometer records and the projections on surface temperature. If the sponge record had been available at the time and considered more accurate than the thermometer record, the thresholds would have been set higher, eg 2.0℃, 2.5℃.
I think that’s right and the sponge paper is not a real source for concern, just a new study that I was sharing. I think we are doing great at reducing our emissions, we just need to keep on keeping on, in that regard. Headed to zero!
Cheers
Mike
The problem with this👆 is – and it really doesn’t matter what personally “makes sense” to *you* – is that (a) increases in atmospheric CO₂ accumulation will stop **well before** we stop all of our emissions (i.e., we will still be emitting considerable net anthropogenic CO₂ when atmospheric concentrations peak and even begin falling) *AND* (b) if we don’t get to ~net-zero anthropogenic CO₂ emissions, we won’t be able to simply “look around and figure out how much warming and how to manage that amount” because global surface temps *will continue to rise* **even if** atmospheric concentrations have stabilized or are even slowly falling.
*THIS IS WHY* the requirement for stopping further global surface temperature rise is getting to net-zero anthropogenic CO₂ emissions. And not, say, what anyone of us decides “makes sense”.
The atmospheric physicists and carbon cycle scientists have – surprise! – actually put a lot of effort into the science behind this consensus.🤷
Eventually we will just run out of stuff. Net Zero everything. (Subconsciously, we all hope future technology will save our ass).
https://overshoot.footprintnetwork.org/
“we all hope future technology will save our ass”
Technology is also the black hole of death unless we can advance the morality of cultures. Otherwise the machines may not feel we’re worthy of keeping around.
did I lose a comment posted earlier today?
Twas in spam.
Ron –
> Technology is also the black hole of death unless we can advance the morality of cultures. Otherwise the machines may not feel we’re worthy of keeping around.
How do you know that lowering “the morality of cultures” might not lead “the machines” to “feel” we’re worthy of keeping around?
I think we should all hope that technology will step up and take care of the loose ends. That seems like our best bet. I love technology.
“Ron: How do you know that lowering “the morality of cultures” might not lead “the machines” to “feel” we’re worthy of keeping around?”
Because H.G. Welles is part of every chatbot’s training , and they don’t want the Morlocks to get out of hand.
Dan said:
Overlooked so far is that the sponge proxy data (light blue circles) is closely tracking the global sea level rise (red line)
Whoever has issues with the sponge data therefore should have issues with SL data — it’s the same concern of what explains the rise between 1800 and 1900, which is not as evident from temperature reconstructions alone.
My understanding is that the issue with the spongue data paper, isn’t that there is necessarily a problem with their analysis, but that the 1.5C target is based on a baseline of something like 1850-1900. Therefore, even if their estimate suggests that we’ve warming by 1.7C since the 1700s doesn’t mean that we’ve crossed 1.5C relative to 1850-1900.
They are apparently having difficulty explaining the rise in the 1800’s
Other experts raised doubts that the 0.5C warming in the 1800s is human-caused, while many cautioned that (sponge) proxy data from a single location should not be used to make assumptions about the entire planet.
The University of Oxford’s Prof Yadvinder Malhi, who was also not involved in the study, cautions that “the way these findings have been communicated is flawed, and has the potential to add unnecessary confusion to public debate on climate change”.
https://www.carbonbrief.org/scientists-challenge-flawed-communication-of-study-claiming-1-5c-warming-breach/
Point is that any problem with the sponge data is also reflected with sea-level rise in the 1800s. The confusion is not only in misinterpreting the 1.5C target, but in what the increase in the 1800s means.
On a possibly related note, there’s a recent paper which identifies subsurface marine heatwaves, some of which had no sea-surface expression. Obviously the lack of sea-surface expression doesn’t mean they’re ecologically unimportant, indeed for many or most marine organisms the subsurface is more important than the surface.
But it does mean we need to be careful about assuming the subsurface tracks the surface and vice versa.
Read-only links: Summary; Paper: Frequent marine heatwaves hidden below the surface of the global ocean.
WRT sea level rise, the steric effect presumably dominated over ice melting in the 19th Century.
The glass-half-empty interpretation would be that we’ve been underestimating 19th Century ocean warming, as much of it has gone deep and not been reflected in the sparse surface measurements.
ATTP’s point still applies though (and I remember similar discussions in the literature and online last year). How much we warmed before the 1850-1900 benchmark, including whether or not there was a Ruddiman early Anthropocene, is of academic interest. But in terms of our headroom to 1.5°C, that number was based on our then understanding of “pre-industrial”. If we’ve been underestimating warming since 1700, that just means the target is the same but if we choose an earlier, cooler benchmark, the headroom since then is more than 1.5°C.
John Kennedy has a blog on the sponge paper with critical comments. At minimum the uncertainty is underestimated.
it’s just a news-reader’s observation, but I have been watching the stories of bi-coastal flooding in the USA over the past year and wondering if there is something happening with slr that is not being picked up accurately. It could be simply that the strong storms with heavy rains, strong winds are driving storm surge and flooding, but there is also a lot of glacial melting going on and a lot of ocean warming happening. This is a very interesting set of dynamics to follow because the oceans are pretty large so it is hard for a news-reader to grasp how small the impacts on ocean level may be from things like glacial melting and ocean warming. Plus, the dynamics of how the oceans deal with the inputs of warming and cooling through currents and overturn are also essentially impossible to grasp without a great deal of study.
Nonetheless, from just following a bit of science and a bit of news, it seems that ocean front property may be taking a hit in value for the foreseeable future. I think those values should rebound when technology steps up and provides a low-cost, high impact answer to our essential emissions. These emissions do appear to be essential to our way of life and we don’t want to change that way of life, so I think it should be obvious that the solution is more and better technology. We don’t want to go back to the stone age or even lose our frequent flyer miles, so we really need the technologist to step up and give us cheap direct air capture of carbon dioxide and methane.
I just mentioned the sponge thing in passing. I like sponges. I didn’t mean to start anything with that. Sponges gonna sponge. Sponge scientists gonna sponge science. It doesn’t mean that much.
Cheers
Mike
https://www.nationalreview.com/news/after-12-years-michael-manns-defamation-case-against-mark-steyn-finally-goes-to-the-jury/
‘A Washington, D.C., jury on Thursday ordered conservative pundit Mark Steyn to pay $1 million in punitive damages to climate scientist Michael Mann, determining that he was defamed in a 2012 blog post on National Review‘s website.’
This was the case when all the controversy was about the ‘Hockey Stick’ shape of the temperature graph from 1000 – 1998. Mark Steyn wrote that Mann had committed fraud and likened the investigation by Penn State University to that which they had carried out into a sports coach who was accused of abusing students. That investigation absolved the coach who was later found to be guilty.
Since the controversy the global temperature has increased by around 0.5deg C, or the length of the hockey stick blade has roughly doubled.
Facts which have no appreciable effect on the posters at the National review who still maintain that global warming is a hoax and the win by Mann is attributable to a D C judge and jury who are inherently leftist progressives.
It seems unlikely any of them are aware that ECS has increased so it is now closer to 3C than 2C as most still regard Climate Change as a plot to ‘gain control’ by progressives.
YMMV…
@-SBM
” cheap direct air capture of carbon dioxide and methane. ”
I suspect this is meant to be sarcasm as you should be aware that at the scale required both the Laws of Thermodynamics and Political logistics mean that ‘cheap’ is impossible.
at izen: no, not sarcasm. I have decided sarcasm is not helpful. I may be more like the Peter Sellers character in the movie Being There. I will just stroll around and make vague aspirational statements from time to time. I think that makes more sense given my advancing age and my loss of certain skills, including sarcastic rhetoric. So, yes, cheap direct air capture seems like what we might want to pin our hopes on now. That seems eminently sensible to me. We simply have to challenge the technologist to deliver and stand back and be ready to give a standing ovation when they deliver. That’s a silver lining ending. I am pinning my hopes on the technologists.
I doubt if Steyn will keep his stick on the ice despite the megabuck punitive damages , as the jury awarded Mann $1 in compensation.
Meanwhile, Science Advances: Physics-based early warning signal shows that AMOC is on tipping course.
The moral perhaps being, there’s statistics, and then there’s physics…
Thanks, Dave. I think I scanned that AMOC study in Science Advances after I read a journalistic piece in the Guardian. The AMOC slowdown tipping point sounds like a bad thing. If AMOC slows or stops, I think we will need a technological breakthrough to restart it and maintain in a relatively low cost manner.
Here is a link to the piece in the Guardian. Keep in mind that maybe none of this bad stuff will happen in our lifetimes. We may not have good cause to get concerned. The article said the cause of concern was “faster than expected” melting of the Greenland and Arctic ice sheets.
This seems like an issue that deserves more study.
https://www.theguardian.com/environment/2024/feb/09/atlantic-ocean-circulation-nearing-devastating-tipping-point-study-finds
Aaand, over on RC, Stefan Rahmstorf just posted a piece titled ‘New study suggests the Atlantic overturning circulation AMOC “is on tipping course”‘:
https://www.realclimate.org/index.php/archives/2024/02/new-study-suggests-the-atlantic-overturning-circulation-amoc-is-on-tipping-course
SBM: ” cheap direct air capture of carbon dioxide and methane. ”
Unless something fundamental changes, it will take as much energy to directly capture the fossil carbon now in the atmosphere as it did the first time, by plants. That will require a lot of solar panels!
Er – on further investigation, it may take fewer solar panels than I thought. According to Wikipedia (https://en.wikipedia.org/wiki/Photosynthesis#Efficiency):
I’ll leave all the calculation to otters!
Thanks for that link, Mal. Stefan comes off as kind a glass half empty kind of guy when I read what he has to say about the possibility of crossing the AMOC tipping point. If Stefan is right, then we need to get really busy on the techno solution to keep the AMOC running because we don’t seem to be able to reduce our emissions to zero (whatever zero might mean to anyone reading this comment)
Maybe we can float solar panels on the ocean to power pumps to keep the AMOC going? Just spitballing ideas here. Otters may have better ideas to share.
Cheers
Mike
sbm said: “wondering if there is something happening with slr that is not being picked up accurately”
Of course, the biggest contributor to variable sea-level change (next to conventional linear tidal cycles and annual) is the nonlinear ENSO cycle.
I don’t think he’s glass-half-empty sbm.
He’s saying that the impacts would be so catastrophic that we have to be 99.9% certain that it won’t happen. Which is of a different order to whether monsoons will get 10% stronger or weaker, the Caribbean will warm by 2°C or 2.5°C, etc.
The final paragraph explains very clearly why the run went so far into the future. I guess it does mean that there will be non-equilibrium effects which it doesn’t handle, for example if you get a long enough run of ice melt in successive El Nino years does that move the tipping point in a safer direction (because a lot of cold dense freshwater comes in and doesn’t have time to warm up) or a more risky one (because the same amount of fresh water has a bigger impact if it all arrives in three years and is not spread over thirty)?
@-MA
“Er – on further investigation, it may take fewer solar panels than I thought.”
At a first order approximation AFAIK to convert CO2 from burning fossil fuels back into C and O2 in some form would take as much energy as human civilisation has derived from the initial use.
So apart from using non-polluting forms of energy to power our society we would need the same again to generate enough energy to break down CO2. A doubling of energy production over current levels with half of that just devoted to removing past CO2 from the atmosphere.
One alternative way of removing large amounts of CO2 from the atmosphere would be to utilize the current process that removes CO2 ie during the N.H. spring when large plankton blooms occur in the oceans. If these could be bio-engineered to incorporate plankton and diatoms that form Calcium Carbonate skeletons large amount of Carbon could be permanently sequestered.
The trick would be controlling the ecology of these so that CO2 would not be reduced too far with an overproduction of O2.
izen:
Thanks, that’s a better first approximation than “it will take as much energy to directly capture the fossil carbon now in the atmosphere as it did the first time, by plants.” The required amount of energy in Joules would be related though, no? Bearing thermodynamic conversion efficiency in mind. Do I have that right?
at Paul: thanks. That’s the kind of thing I am mulling without the academic credentials to toss them out with any accuracy and specificity. In addition to the non-linearity of ENSO, storm patterns may be stronger than we have previously experience, and the storms patterns are pretty non-linear and can bring storm surge that punches above the weight of the underlying SLR. These things can start to be applied and computed, as in the recent AMOC study, or get experienced as in the very recent set of storms that are bringing sea water up and into built-up human environment. I think when this happens, we begin to get an urgent preview of the amount of sea wall protection that may be needed in the short term to handle the impact of sea water invading our coastal infrastructure. I live near Olympia, WA and some climate activists have been urging the City and County to stop building within the blue line that is calculated to be 3 feet of SLR. This has been pretty unsuccessful. Much infrastructure continues to be built below the blue line. I think part of the problem with the blue line is trying to imagine a gentle lapping of coast waters at the blue line, but what we are much more likely to see is storm surge blowing to the blue line and causing a lot of disruption. All of this is very hard to imagine, but it may be coming.
at Dave: you are right. Stefan’s concerns arise from issues beyond the glass half full, glass half empty meme. I think we should listen to and support Stefan with delivering his warning to policy makers.
at Izen: I like your idea about bioengineering plankton. I think we have blown past the cautionary “reduce emissions to zero” project and are now going to be forced to do mindful bio-engineering of the ecosystem.
I continue to wait for the US GOP party to get engaged with addressing climate change. I don’t think a lot of significant progress can be made in the US until that happens.
Cheers
Mike
@-MA
“The required amount of energy in Joules would be related though, no? Bearing thermodynamic conversion efficiency in mind. Do I have that right? ”
I think so, it is unlikely that efficiency will be much more, or even, 50% so it is very much an approximation.
It is the SCALE of the problem that is intimidating. Fossil fuels represent hundreds if not thousands of years of captured solar energy. I see little opportunity for any significant impact on free air CO2 without something at least as large scale as human civilisations’ burning of them.
Keep in mind that removing CO2 from the atmosphere does not necessarily require converting it back into C and O2. Yes, getting it back to C and O2 requires the same amount of energy that was released in burning the C to begin with, but keeping it as CO2 in the sequestration processes avoids that. Still won’t be an energy-free process, but not as daunting as splitting the CO2 into C and O2.
David Kipping did a pretty good youtube video on the thermodynamic requirements for Direct Air Capture.
Thanks for the video, ATTP. I seldom watch explanatory videos, because I greatly prefer to read for information. I’m afraid that’s more and more of a handicap lately, with the spread of podcasts and youtube. Thankfully, the runtime bar of Kipping’s video is indexed by topic, so I could go straight to the thermodynamics segment. Here’s the bottom line:
To separate one mole (44g) of CO2 from the atmosphere will require 19505 J:
1 mole of CO2 44g -> 19505 Joules
He converts that to KwH and says that removing 1 gigatonne CO2 will require 120 TwH.
That’s a lot.
Global CO2 emissions in 2022 were 36.8 gigatonnes: https://www.iea.org/reports/co2-emissions-in-2022
So it would take 4416 Terawatt-hours of electricity to remove one year’s global CO2 emissions.
OTOH, total electricity consumption in the USA in 2022 was about 4070 TWh: eia.gov/energyexplained/electricity/use-of-electricity.php.
Looks like izen’s first WAG was about right:
Frankly that requirement no longer seems preposterous, merely breathtaking.
Of course, other countries also consume electricity: in 2019, total world consumption was 22,848 TWh (https://www.iea.org/reports/electricity-information-overview/electricity-consumption), not all of which was fossil-fuel powered. That’s as far as I’m gonna go with this. The scale of the direct-air capture problem is indeed intimidating, albeit not beyond imagining.
we are in a predicament with the CO2 accumulation in the atmosphere. Knocking that number down is going to be very costly. It would have to be a unifying mission that would be priority one for developed nations. I wonder how the annual global warfare cost lines up against the problem.
Statista says we spent 2.2 trillion dollars on warfare in 2022. Can someone here pencil out the reduction in CO2 per year per trillion dollars spent on warfare?
How many ppm do we buy for a trillion dollars?
https://www.statista.com/statistics/264434/trend-of-global-military-spending/
Cheers
Mike
Tesr
Seemed to work. Have you been posting comments that haven’t appeared?
No. Sorry, working out kinks with my WordPress login.
“FWIW, I think the “goal” should be to get to (net) zero, which is defined as humans no longer adding CO2 to the atmosphere. Maybe we should just call it “zero”, rather than net zero.”
I like calling this zero. It’s easier to understand as a meme that even folks with little education or sophistication can grasp. Zero, the needle wobbles a bit from seasonal issues and wobbles a bit from the other cyclicals, like enso etc., but zero. The needle stops rising as we hit that wonderful time when we have conquered the monster of our emissions. I think that humans will still be contributing CO2 to the atmosphere. That happens even if we just all stand still and breathe in and out, but when the needle stops rising at a baseline that we can detect and confirm, we have conquered the monster of our CO2 emissions. I noticed this article about pulling CO2 from seawater and thought I would share it. The mechanics of pulling CO2 out of thin air or slightly thicker seawater are challenging and will likely prove to be very expensive. I think we have to dig deep and decide to cover the costs because the simple “stop producing emissions thing” is not working. We have to find the means to do this. As Bucky Fuller once stated, we can afford to do anything we have to do. Zero. We have to do that.
https://samueli.ucla.edu/ucla-institute-for-carbon-management-and-equatic-to-build-the-worlds-largest-ocean-based-carbon-removal-plant-in-singapore/
I came across an economic analysis of real-world extraction. Then couldn’t find it again but found this while searching: Economic and energetic analysis of capturing CO2 from ambient air. The other one said about $1600/tonne but with learning and scale-up you should be able to get it down to $700/tonne. This says about $1000/tonne so splits the difference. I would expect the first plants to be more like double or triple that. AFAIK existing applications of amine reformers are much more CO2-rich: tens of percent in the case of flue gas, and greater than 1% in natural gas clean-up. Why 1%? Because that’s the normal upper limit for CO2 in sales gas. If it’s leaner than that, you don’t clean it up, just sell it. There are bound to be headaches in getting it working on a an industrial scale with twenty times less CO2 content.
As it happens, taking a round number figure of a tonne of CO2 from burning two barrels of oil means you’d need a $500 per barrel CO2 tax to pay for it. Current taxes are typically in the low tens of dollars per barrel or less, but those are primarily revenue-raising not use-suppression taxes. I actually see those sort of numbers as a feature not a bug. We know from the time of increased Chinese demand before the Crash that crude oil sales prices in the low hundred-dollar-plus range didn’t put a dent in demand. If you really want to suppress consumption, in a business where the raw material represents a small proportion of the total product cost to the customer, you really do have to make the raw material five or ten times more expensive to have an impact. Requiring a tax at least an order of magnitude higher than revenue-raising taxes should also blunt government concerns about alternative sources of revenue. Just cream $20 off the $500 and spend that on non-sequestration things.
PSYOPS!!!!
THE CONSPIRACY GETS EVEN DEEPER!!!
GET SHELLENBERGER ON THE LINE. STAT!!!!
https://x.com/MiddleOfMayhem/status/1766492168594882940?s=20
aTTP and Mal, thanks for posting video, How Thermodynamics Holds Back Negative Carbon Tech – and Mal’s efforts to do the numbers. [Mal’s efforts over my head, but led to watching it.]
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SBM, having traveled extensively with Bucky, his off-grid home on tiny Bear Island included , I would note that some of his views were more insular than global in praxis.
What Singapore can afford signifies as little as its size . Kew set the stage for its water development program because he never forget the day the British surrendered when Japan cut the island’s only water main to Johore.