Doubling down?

I wrote a post a little while ago commenting on a Sabine Hossenfelder video suggesting that she was now worried about climate change because the Equilibrium Climate Sensitivity (ECS) could be much higher than most estimates have suggested. I wasn’t too taken with Sabine’s arguments, and there were others who were also somewhat critical.

Sabine has since posted a response to the various reactions. I think this response is rather unfortunate and doesn’t really engage with the criticisms of her earlier video. She suggests that Andrew Dessler and Zeke Hausfather have lost touch with reality because they say:

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 might be a bit flippant, but I think they’re probably just being realistic. Whatever the ECS, the goal will be to rapidly decarbonise our societies and the rate at which we do so will probably be determined more by societal and political factors than by whether the ECS is 3^oC or 5^oC.

Sabine then goes on to criticise those who highlight that there are many lines of evidence and that we shouldn’t focus too much on individual studies. Sabine argues that she is making a different point and suggests that climate scientists are suffering from confirmation bias. The high-ECS ‘hot’ models have already been used in IPCC reports and arguing now that they should use climate sensitivity to screen out models implies an unjustified bias against the possibility that the ECS could actually be as high as these models suggest.

Essentially, once we’ve started collecting data and doing some analysis, we shouldn’t then change how the data is used, or modify the analysis, simply because the results aren’t consistent with previous expectations. However, this isn’t quite that simple. This is an ensemble of models that are developed to try and understand the physical climate system.

We can look at how well these models compare with observations. The ‘hot’ models tend to have poor agreement with historical temperatures and struggle to reproduce the last glacial maximum. If we select models based on their transient climate response (TCR) they do a better job of matching observations. So, the argument that we should screen models isn’t simply because they have a higher ECS than might be expected.

Of course, Sabine is correct that we can’t actually rule out high ECS values. The latest IPCC report says that the “best estimate of ECS is 3°C, the likely range is 2.5°C to 4°C, and the very likely range is 2°C to 5°C”. This certainly doesn’t rule out an ECS between 4^oC and 5^oC and doesn’t even entirely rule out values of 5^oC and above, even if it suggests these are very unlikely.

Given that the highest risk is from the low-probability high-impact events, it seems entirely reasonable to be particularly concerned about the possibility that the ECS is something like 5^oC, or higher. None of the information presented by climate scientists has ever really suggested that people shouldn’t do so. However, in general, the broader societal response has not been focussed on this possibility. I doubt that this is going to change anytime soon, and it’s certainly not because climate scientists have failed to highlight the potential risks associated with global warming and climate change.

Is the ECS very high?

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 2.5^oC to 4.5^oC with a best estimate of 3^oC. A recent paper assessing Earth’s climate sensitivity using multiple lines of evidence suggested that the likely ECS range is 2.6^oC to 3.9^oC and is bounded by 2.0^oC and 5.7^oC. 

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 5^oC). 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 4.8^oC ± 1.2^oC.

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 2^oC and 4.5^oC with a best estimate around 3^oC. 

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.

How to Cavil Like Cranks

§1. Thesis. Hard to tell when Climateball scuffles kick off. Players often seem surprised to get caught in the middle of them. In one comment they exchange ideas, in the next they trade insults. This common dynamic repels some and drives otters. Both reactions create a feedback loop that explains comment sections in particular and social media in general:

Monty Python’s famous Argument Clinic. In our story, Pat is on the left, and Pat* is on the right.

§2. Antithesis. The following episode started at Roy’s, with an invitation to go debate the Arctic at Tony’s. I asked how much was on the line; my counteroffer was declined; with no incentive on either side, it stalled. Until I drop a note to put a laudatio from our favorite Lord into perspective. A flying monkey (Mr. Nice !) throws food at me, a plain skirmish springs, and Pat interposes himself to lure me with his pet bait.

Pat keeps poking me. I let it slide, until he turns to outrage porn. After that, I have enough:

Here’s the deal. Suppose I only reply to you using phrases you yourself used on that page:

https://pubpeer.com/publications/391B1C150212A84C6051D7A2A7F119

Will that suffice to be civil to you?

Cheers.

Then reality turns into art. Pat tries to land more jabs; I counter as promised. All of my responses to him after that point are his own uppercuts from that PubPeer page. A sample of Pat vs Pat*:

(PAT) You undermine any respect for your intellectual integrity by displaying an adamantine ignorance.

(PAT*) Your resistance to grasping any of this is understandable in a pragmatic sense.

(PAT) Willard scores another vacuous goal.

(PAT*) Never have I ever encountered such incompetence so often repeated.

(PAT) Dodge as you might, falsification hurts doesn’t it Willard. Tough.

(PAT*) You provided no objective criticism.

(PAT) How would you know?

(PAT*) Your entire attack was baseless.

(PAT) The attacks on my paper are base. Your comments are vacuous.

(PAT*) That’s your logic, Pat. It produces utter nonsense.

(PAT) Oracular dismissal. The only stick in the alarmist armamentum.

(PAT*) Insistent repetition of fatuous criticisms does not make them correct, Pat.

You get the idea. If not, the Argument Clinic does not end there: Pat is still arguing with himself as we speak. I still have enough ammunition for a while, but I might stop after this report {1}. Confer to Pat’s interactions at PubPeer’s for more, especially with Dikran.

* * *

§3. Synthesis. Cranks cavil because it helps them. Take Pat: when he insults, either he gets ignored or he gets a response. Stonewalling him proves him right; responding in kind galvanizes him. Something like perpetual motion powers his eristic machine.

Which is why commenters like bdgwx or Nick are Pat’s kryptonite: they follow his shadowboxing while remaining impervious to his chest beating. Only with the ad nauseam can he save face. Since there are diminishing returns in trying to make him mind his units, he will eventually declare victory. How could he lose? Just like other contrarians, he can’t.

So why cavil with contrarians? I see only two good reasons: intellectual curiosity, and artistic beauty. Our host may have reached his own limit as to what he can get out of contrarians. Unless cranks they step up their game, I might soon reach mine too.

{1} I did not.

RCP4.5/SSP2-4.5

I messed up something on Twitter so, of course, I now have to write a blog post. There seems to be this narrative developing that we’re either tracking well below RCP4.5/SSP2-4.5, or that it’s now a plausible high-end pathway, and I was trying to point out that we might want to be a little a cautious about making such claims. I managed to mess up the cumulative emissions from this pathway, but I think my general point still mostly stands.

In case people don’t know, the RCPs are Representative Concentration Pathways that present a set of possible future atmospheric greenhouse gas concentration pathways, ranging from very high (RCP8.5) to very low (RCP2.6). These have now be largely been replaced by a set of scenarios that combine Shared Socioeconomic Pathways (SSPs) with Representative Concentration Pathways, SSP2-4.5 being a middle of the road socio-economic pathway in which social, economic and technologicl trends do not differ much from historical patterns, combined with an RCP4.5 concentration pathway. You can find more detailed descriptions in this Carbon Brief article.

Thanks to a number of people on Twitter (Paul Skeoch, Chris Parker and Zeke Hausfather) I now know the correct cumulative emissions for these different pathways. As shown in the Figure on the right, SSP2-4.5 has cumulative emissions between 2020 and 2100 of about 2700 GtCO₂. For context, this is very similar to what has been been emitted to date (~2500 GtCO₂), so SSP2-4.5 essentially implies doubling emissions by 2100.

Similarly, emissions today are just over 40 GtCO₂ per year, so SSP2-4.5 has average emissions for the rest of the century that are about 80% of current emissions. Something to bear in mind is that there is some uncertainty in associating emissions with concentrations, and earth system feedbacks could act as an additional source. Hence, we could emit less and still follow an SSP2-4.5-like pathway.

Of course, we’d like to do much better than something like SSP2-4.5. There are policies that have been, and will continue to be, implemented that will reduce emissions, at least relative to what they might have been. We are developing and implementing alternative energy sources. People are also changing their behaviours so as to reduce their personal carbon footprints. However, to claim that we’re doing better than something like SSP2-4.5, when emissions have yet to peak, seems a bit premature. Similarly, implying that it’s now a plausible high-end, or worst case, scenario when continuing with current emissions would exceed it, also seems somewhat over-optimistic.

To me, this is a situation where there are multiple positions that can be held at the same time. There can be what we’d like to happen, what will probably happen given where we are today, what could happen if we do more in the future, but also what might happen if something goes wrong and things don’t work as expected.

In a sense, this is quite a tricky situation. In my view, it is important to be optimistic and to both hope, and try, to do better than we might think is currently possible. At the same time, it’s also important to be aware of what could go wrong and the potential impact of that scenario. It would be nice to think that something like SSP2-4.5 is now a plausible high-end scenario, but it just seems slightly over-optimistic. On the other hand, if emissions do indeed peak in 2023, then this may become a more reasonable inference.

What does net-zero actually mean?

Roger Pielke Jr had a recent guest post on his substack by Tom Wigley called Net-Zero Does Not Mean What You Think it Does. The post concluded that CO₂ emissions do not need to be eliminated to meet the Paris targets and that uptake by the natural sinks means that CO₂ emissions can remain positive for a very long time. I was slightly surprised, since this didn’t seem consistent with our current understanding, but it was based on some slightly older work and I thought it may not be quite up-to-date with our current understanding.

However, I’ve since watched some of a recording of a debate between Roger Pielke Jr and Steve Koonin on “Is net zero by 2050 both achievable and necessary to address climate change?” The first question you reasonably might ask is why they would arrange a debate on this topic between these two speakers, but that isn’t the point of this post. In the recording Roger explains what net zero is and suggests that it’s the point at which emissions are balanced by the natural sinks (oceans and biosphere) and, hence, that net zero requires emission reductions of about 80%, rather than 100%.

This is simply wrong. It’s very clear that net-zero means that anthropogenic emissions are zero, with any residual positive emissions balanced by negative emissions that lead to essentially permanent geological storage, hence the “net”. The latest IPCC report says explicitly:

Net zero CO₂ emissions: Net zero carbon dioxide (CO₂) emissions are achieved when anthropogenic CO₂ emissions are balanced globally by anthropogenic CO₂ removals over a specified period.

The scientific under-pinnings of net-zero go back to papers published in about 2008 (e.g., Matthews & Caldeira 2008) demonstrating that when anthropogenic emissions go to zero, global average surface temperatures would soon stabilise. The reason for this is that we currently have a planetary energy imbalance that – all else being equal – would lead to continued warming so as to return the system to energy balance. When anthropogenic emissions go to zero, the natural sinks continue to take up some of what has been emitted so that atmospheric CO₂ concentrations go down in such a way as to compensate for this unrealised warming.

Of course there are uncertainties (there could be some additional warming, or even some cooling) and there are other slower feedbacks that are not considered (carbon released from the permafrost, for example). However, the best estimate today is still that, on multi-decadel timescales, the zero-emission commitment is close to zero.

Roger’s definition of net-zero would lead to stabilised atmospheric CO₂ concentrations, rather than stabilised global surface temperatures. Given that the system is not yet in energy balance, stabilising concentrations would lead to continued warming. Since atmospheric CO₂ concentrations are already 420 ppm, even if we could achieve ~80% reductions in emissions by 2040, we’d probably have concentrations of ~440 ppm. If you calculate the equilibrium warming for such an atmospheric CO₂ concentration, assuming an ECS of 3^oC, it’s about 2^oC. So, Roger’s definition of net-zero is essentially committing us to at least 2^oC of warming. Also, if emissions don’t eventually go to zero, concentrations would start rising again, and warming would resume.

So, to clarify, net-zero does not mean that positive anthropogenic emissions are balanced by uptake by the natural sinks so that emissions just need to be reduced by ~80%, it means reducing anthropogenic emissions by 100% with any positive anthropogenic emissions being balanced by “permanent” anthropogenic negative emissions.

You might be surprised that someone could engage in a high-profile debate about net-zero without properly understanding what the term means and the scientific understanding that underpins the term. Of course, if you’re a long-standing veteran of the public climate debate, this is entirely expected. Evidence would suggest that Roger doesn’t regard being properly informed about a topic as being a pre-requesite for making confident assertions about the topic.

Conversations

Stoat, who I do still sometimes read, had a recent post about the state of the blogging game. Some resonated with me, which I why I thought I would write this post. It does feel that the “blogging game” has clearly changed quite a lot. It really doesn’t feel nearly as active as it once was and there isn’t the same kind of back-and-forth that used to take place.

In my case, I think I’ve tried to stick to writing about topics that I find interesting, and have mostly tried to stay in some kind of lane; topics for which physics, or being in academia, might provide some relevant expertise. Of course, I haven’t always done so. It would be boring if one never went outside one’s comfort zone, but I think I mostly drift back. I also don’t really write this blog expecting anyone else to take it seriously; it can be both nice, but also somewhat stressful, when people do.

I’ve been writing this blog for just over 10 years, and one obvious issue is that it’s difficult to remain enthusiastic if you feel that you’re mostly just repeating yourself. Nothing fundamentally wrong with this, but not particularly interesting, both for the writer and the reader. I could try to explore different topics, but I don’t really have the time, or the energy, to become informed enough to write about them. I’m also not really trying to be heard, and I have enough going on without worrying about how active, or popular, the blog is.

I do somewhat miss the conversations that I used to have more of, either here, on other blogs, or on X/Twitter. Maybe it is still possible to have them, but it does feel as though it’s much more difficult to have nuanced discussions about complex topics. Many of the vocal people on social media seem to be mostly trying to broadcast their views, rather than putting out ideas that they’re happy to have challenged (even if they say otherwise). I’m also not a fan of intemperate exchanges. I typically regret being uncharitable, even if the other party might have deserved it, and just can’t be bothered starting discussions that aren’t likely to go well.

Overall, it’s been a mostly interesting experience writing the blog and it doesn’t really bother me that the “blogging game” has changed. I’ve learned a lot and I have mostly enjoyed the conversations that I have had. Change is probably inevitable and expecting things to stay the same is probably unrealistic. That doesn’t mean that I don’t think that the public discourse couldn’t be better, but I don’t really think that complaining about it on blogs will make much difference.

Staggering!

There are climate scientists all over social media highlighting how staggering September 2023’s global surface temperature anomaly has been. It’s about 1.75^oC above the pre-industrial reference period. This is in addition to Antarctic sea ice also “dropping off a cliff” in 2023.

This could all just be internal variability on top of an anthropogenically-driven trend. A strong El Niño is developing and there are potential reductions in anthropogenic aerosol emissions. Both of these could, for example, have contributed to the unusual increase September 2023’s unusually large increase in global surface temperature anomaly.

However, this does illustrate a concern I have always had about climate change. We do have a pretty good understanding of the climate system, both from recent observations, paleo-climatology, and very sophisticated climate models. However, we are perturbing a complex, non-linear system in a way that is reasonably unprecedented. Even though we might have a good understanding of how it’s likely to respond, it could still respond in unexpected ways.

Of course, what we’re seeing now doesn’t necessarily indicate that we’re seeing responses that are outside what we’d expect, but they are still rather surprising and not exactly comforting.

Of course, none of this really changes what should probably be done. Stopping anthropogenically-driven climate change is going to require getting anthropogenic emissions to (net) zero, and dealing with the impacts that we can’t, or probably won’t, avoid is going to require developing resilience and reducing vulnerabilities. We just shouldn’t ignore that the climate can respond to anthopogenic forcings in ways that, even if not completely imexpected, are still surprising.

Scientifically intriguing?

Last week, Judith Curry had a guest post about causality and climate. I was initially a little confused, because I thought it was about a paper published in Proceedings of the Royal Society A, that I’d discussed in an earlier post. However, even though this paper was mentioned in the post, the post is actually about a more recent paper that uses the same method and draws the same conclusion.

The Proceedings of the Royal Society A paper applied a stochastic approach to causality to a number of case studies, including looking at [a]tmospheric temperature and carbon dioxide concentration. The newer paper focusses only on the relationship between atmospheric temperature and concentration of carbon dioxide. The key results are:

changes in CO₂ concentration cannot be a cause of temperature changes.

and

All evidence resulting from the analyses of the longest available modern time series of atmospheric concentration of [CO₂] at Mauna Loa, Hawaii, along with that of globally averaged  T, suggests a unidirectional, potentially causal link with  T as the cause and [CO₂] as the effect.

In other words, the claim is that the increase in atmospheric CO₂ is driven by increasing temperatures, and that this increase in atmospheric CO₂ is not the cause of the increase in temperature.

As most of the regulars here will know, this is clearly nonsense. It’s virtually certain that the recent increase in atmospheric CO₂ is driven by anthropogenic emissions. There are multiple lines of evidence that support this conclusion. It’s also unequivocal that human influences have warmed the atmosphere, ocean and land.

When the Proceedings of the Royal Society A paper came out last year, I emailed the editor to point out that they’d published a paper with a rather nonsensical result. I didn’t get a response. However, I was cc’d into a response to someone else who had also complained. This response was, unfortunately, rather dismissive and somewhat insulting.

The response said that the criticism had been discussed with the board member and subject editor who handled the paper. According to them, the criticism misinterpreted what was in the paper and was not well-founded. Apparently, the result was scientifically intriguing and would be of interest to many of their readers.

The latter may be true. However, a paper suggesting that the recent rise in atmospheric CO₂ is not due to anthropogenic emissions and that this rise in atmospheric CO₂ is not the cause of global warming is not scientifically intriguing, it’s simply wrong. The board member and subject editor is either being disingenuous, or understands this so poorly, they probably should not be a subject editor for the journal.

It’s one thing for a paper like this to slip through. Peer review isn’t perfect and clearly papers that aren’t very good do get published. It’s another thing, however, to double-down when people point out the problem. Today, it is virtually certain that the increase in atmospheric CO₂ is due to anthropogenic emissions, and that this increase is driving global warming. A paper using a purely statistical causal method is not going to overthrow these extremely well-established results.

It’s one thing to see a paper making these claims appear in an MDPI journal, but you’d hope that the Royal Society would have higher standards for their journals. In my view, rather than regarding the results in the paper as being scientifically intriguing, the Royal Society should really be embarassed that this paper was published in the first place.

Scientific Shenanigans

An anonymous stan of Junior challenged me to opine on a recent Climateball episode. While thinking about what to say in response, another kerfuffle emerged. So allow me to explain why outrage porn over scientific shenanigans leaves me cold in general.

On the one hand, it is trivial to produce. The scientific publishing industry sucks. Like every other for-profit plateform, it suffers from enshittification. Peer review more than sucks. The sheer volume of online communication has turned knowledge dissemination into write-only devices. Too much work and no play makes everybody dull.

On the other hand, it is self-perpetuating. Contrarians bathe in pathos. They lay down concerns in couch fainting venues or showboated on soapboxes every…freaking…hour..of…every…day. Nothing will ever stop their shrieks for they can’t lose. Dealing with them may appeal to many, me included, but very little ever gets done while doing so. Better contrarians would help. We need some.

On a third hand, it is easy to game. Lobbying happens {1}. In a free society, honest brokers have the right to grieve on their personal blogs and to delete years of comments. They have the right to complain on their department’s blog, in their Forbes columns, in their government testimonies on behalf of the Republican party. They even have the right to monetize all these scientific shenanigans {2}.

These judgments stand on robust facts. Our predicament may not be fair, but it is good enough for me. As someone who embraces crappiness, who believes that science has always been political, and who chose a side in the eternal fight in the virtual world between snark and smarm, I might be biased.

I see no reason to defend big journals; Axel Springer has its share of controversies. I see no reason to defend academia either; BTI has its share of careerists too. More generally, I see no reason to criticize the idea of speaking truth to power. That being said, management rights escape pundits’ remits and legal matters should be turned over to lawyers, or at least those who really have agency over the situation.

* * *

Don’t get me wrong: I ain’t no stoic. Public outrage can help make things better. On the margin, they kinda do. And as Kate Marvel observes, the Climateball nexus changed:

At around 49:00, Kate shows how to express anger positively, and a bit after 52:00 she attests that contrarians are starting to accept that climate changes and that we need to do something about it.

Overall, troglodytes’ tropes seem to have improved since Bill Buckley Jr.

Nevertheless, the point of getting angry is to get even, not to spend one’s day yelling at clouds or to rage about kids on lawns. Properly channeled, reactance increases motivation. Exacerbated by outrage porn, it induces reactionary politics and may lead to conspiracy ideation. Hence why there ought not be no crying in Climateball {3}. A little antagonism gets our juices flowing, a little too much spills blood.

More scientific shenanigans will no doubt emerge. The outrage porn industry will continue to prosper. The tears of the world are a constant quantity. The same is true for the laugh.

Meanwhile, cryptominers receive millions to stop mining during a heatwave in Texas.

* * *

{1} Thanks. Russell coined the phrase in a recent thread.

{2} Enigma. Junior calls his newsletter The Honest Broker. An Honest Broker should not be in the scientific shenanigans business. Does it mean he is committing the moral sin of stealth advocacy?

{3} Disclaimer. The information contained on this post shall not be understood or construed as any kind of advice. It is not intended to reform scientific practice. It is not substitute for norms tailored to facts and circumstances or situation of specific research field. I have done my best to ensure that the information provided &c.

The Bad Boy of Science

I realise that this was mentioned in the comments of my previous post, but I thought I would just advertise that I spent a bit of time last Friday chatting with Sam Gregson, who runs the Bad Boy of Science youtube channel. The topic was, unsurprisingly, the furor over Patrick Brown’s claims that he had to satisfy a particular narrative in order to get his paper published in Nature and the video is at the end of this post.

It was arranged at relatively short notice and we did it in one sitting, as I had to get to a farewell for someone who was retiring and then to a barbecue for our new PhD students. I’ve listened back to most of it and I didn’t think I made any howlers, but there are a couple of places where I might have phrased things slightly differently had I had a bit more time to think.