Only Connect

You may have heard of the cumulative temperature increases plateauing between 1998 and 2013. “But Da Paws” was all the rage around 2012 in the Contrarian Matrix – recall for instance when David Rose became Judy’s megaphone. Then it subsided:

2016 was the second year in a row where global temperaturewas more than 1°C above pre-industrial levels*

[…]

2014, 2015 and 2016 all saw record global temperatures. 2017 is on track to be one of the top three warmest years on record.

You’d think Da Paws dead, but no  – Javier currently argues at Tony’s that the planet is no longer warming. At Judy’s, BobD tried to reason with him (and a bit more) using statistics. I submit it is both overkill and not enough for ClimateBall – we need to connect this kind of analysis with the little things we do in every day life.

Say you cook an egg. You fire the pan at medium, as you don’t want to lose time. Then, because you know how to cook an eggs, you reduce the heat. (Cookbooks usually talk about lowering heat.) Would you say that your pan isn’t warming? Not really.

Or say I bought some stock that gave me a 1% dividend last quarter. The market fluctuates and now it only gives me a 0.25% dividend this quarter. Does it mean I’m losing capital? No way.

Finally, suppose we all drive electric vehicles and want to save battery life. One way is to preserve our velocity. So we make our rides as smooth as possible. On deserted intersections, we might indulge in rolled stops:

 

Could we then truly say that our vehicle <em>stops</em>? Try to argue your case to the policeman who just caught you. Good luck with that.

For Javier’s argument to hit home, it seems to me that he would need to imply that eggs are not cooking at low heat, that low profits empty our portfolios, or that slowing down makes us drive us backwards. Something is amiss, yet the concept of cooling looks fine. It served scientists well so far. One way to see Javier’s trick is to ask – “Da Paws” is Da Paws of what?  Once we clarify what exactly is cooling, the trick loses most of its bite.

Javier suggests that the warming increase of the surface temperatures has been “cooling down” since 2016 and this undermines AGW. Coincidentally, he defines warming as a “positive rate of temperature change over time,” an acceleration. Not exactly the same as a long-term rise in the average temperature of the Earth’s climate system, isn’t it?

This concept of cooling down also deserves due diligence.  To cool down is a series of exercises after an intense physical activity, like hockey:

Athletes don’t immediately stop while cooling down – they keep moving at a lower rate to “recirculate fatigue byproducts” as this muscular trainer words it in the above tutorial.

This short conceptual analysis should convince you that Da Paws can be countered using simpler means than statistical hypothesis testing. In any case, transposing dry stuff into real life terms looks like a good way to connect with those who find statistical inference hard. After all, science is not a substitute for common sense, but an extension of it.

You, fellow ClimateBall player, can surely find more a intuitive way to illustrate the wrongness of Javier’s take. Practice makes perfect. I’ve omitted a most startling error.

 

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School strike for climate

This sign made me laugh (it might be a generation thing). Credit: this tweet.

I thought I would try to briefly write about today’s school strike for climate. I mostly think this is a really good thing. I don’t think we should be relying on school children. I don’t think that school children should be sacrificising their education to send this kind of message. However, a few days off school is unlikely to do much harm, and it certainly seems to be sending a pretty strong message, and is being noticed. It’s also illustrates how something that starts small, can snowball and have a substantial impact.

One unfortunate side-effect (in my case at least) of engaging in the rough and tumble of the online climate debate is that it can leave you feeling somewhat jaded, and a little battered. Even though I think the school strike for climate is a good thing, I do find it hard to get too enthusiastic. I’m also well aware that it’s easy to say that we should be getting emissions to ~zero, but much harder to decide how we should do so, and even harder to actually do so. There are many factors to consider. Climate change could clearly have severely negative impacts if we don’t start doing something to reduce emissions soon. On the other hand, we also have to be aware that people could also suffer if we aren’t careful about how we go about reducing emissions. It’s not simple, or easy.

However, putting all that to one side, school children are telling us that we should take this issue seriously. I agree.

Climate scepticism in the UK

I came across a book called Climate Change Scepticism: A transnational ecocritical analysis, by Greg Garrard, Axel Goodbody, George Handley, and Stéphanie Posthumus. The reason I found it interesting is that it includes a chapter on Climate Scepticism in the UK. I did, however, also find it rather an odd analysis.

The chapter about the UK included quite a lot of history, going back to the late 1800s, and included discussions of Margaret Thatcher and Tony Blair. The discussion of more recent climate scepticism focused on Jeremy Clarkson and James Delingpole, who purvey hyperbolic satire with a recognisably British cultural pedigree. It mentions Nigel Lawson and Matt Ridley, but without mentioning the Global Warming Policy Foundation. The Global Warming Policy Foundation does get mentioned in the next chapter, which seems to suggest that it’s based on the United States. It discusses a number of people I’ve never heard of, which seems odd given that I’ve spent a number of years discussing this topic myself (maybe I’m ill-informed). There’s no mention of Andrew Montford, despite him having written quite an influential book.

However, maybe what I found most strange was the choice of language, especially given that the book is written by scholars of literature and culture. The introduction has a section on why the term denier is inflammatory because of its association with the Holocaust. It even says

Popular Technology’s website (for some reason) has collected a whole webpage of journalists and environmentalists drawing on the analogy in different ways and asks why the Jewish Anti-Defamation League has not objected

Maybe I misunderstand the inclusion of for some reason, but it seems to suggest that this is an odd inclusion for Popular Technology’s website. I don’t see why. Popular Technology is a website run by someone who promotes all sorts of contrarian narratives. It also includes various pages that expose information about other people who comment publicly about climate change. It’s the site that finally outed me, when I was still writing pseudonymously. I don’t know if there was a stage when Popular Technology was a more credible site than it is now, but I’ve only ever known it as a website that disputes anthropogenic global warming (AGW).

Because the authors of the book seem to object to the use of denier, they use climate sceptic when referring to those who either dispute AGW itself, or dispute its importance. The problem, though, is that they then use warmist, or alarmist, when referring to those who do not dispute AGW. Essentially, they use quite a positive term to describe those who are dismissive of AGW, while using rather pejorative terms to describe those who are not. Whether intentional, or not, they end up seeming sympathetic to climate “sceptics” and rather critical of those who are not “sceptical” of climate science. This rather brings into question their claim that they’re reading climate scepticism agnostically.

I wasn’t quite sure how to end this, so I started reading the book’s Conclusion. This seems to confirm that the authors have at least some sympathy for climate “sceptics”. It doesn’t quite buy into some of the standard “sceptic” narratives, but it certainly seems to think they have some merit, or are worth considering. Overall, I’m not entirely sure of the point of the book. They seem to suggest that they’ve modelled some kind of depolarization. I’m not entirely sure how, but maybe they’re suggesting that the overall narrative should aim to be more inclusive, and should avoid saying things that make climate “sceptics” seem excluded. My own view is that it would be better if climate “sceptics” stopped promoting nonsensical narratives, but maybe that’s just me.

Common ground?

Judith Curry testified before the US House of Representatives. You can read her evidence and post. In a follow up post Judith suggests that there is some common ground that we can build on. I’m not really convinced that there is. I’ll try to explain why here.

For starters, Judith’s evidence starts with the claim that

…, there is considerable disagreement about the most consequential issues: whether the recent warming has been dominated by human causes versus natural variability

This is simply not true. A vast majority of relevant experts accept that human factors are the dominant cause of recent warming. As an aside, I would still like to better understand what those who dislike consensus messaging think we should do to address such claims.

The bit I wanted to highlight, though, was the following

[o]verreaction to a possible catastrophic threat may cause more harm than benefits and introduce new systemic risks, which are difficult to foresee for a wicked problem.

Firstly, I don’t agree that this is really a wicked problem. At least, not in the sense that we don’t know what needs to be done (get emissions to zero). It’s probably true that if we overreact, then we could do more harm than good. However, few who argue that we should be reducing emissions are suggesting that we should do so in a way that produces catastrophic economic damages.

Patrick Brown has a nice post that illustrates a key point. It’s already clear that there are economic (and other) benefits to emitting less than we otherwise could. Of course, this doesn’t tell us how much less we should emit, but it does tell us that some kind of optimal pathway involves some level of emission reductions.

However, if you want to see an actual estimate of an optimal pathway, you can consider a recent paper by the winner of the 2018 Nobel Memorial Prize in Economics. As I discussed in this post, I don’t really think that this is some kind of definitive optimal pathway; I think there are too many factors that can’t be properly incorporated into these models, and it doesn’t even rule out warming above 4K. However, apart from this still potentially leading to substantial warming by 2100, this is not all that relevant to what I’m trying to get at here.

Credit: Nordhaus (2016)

Consider the emission pathway associated with Nordhaus’s optimal pathway (Figure on right). Bear in mind that this is an optimal pathway that is expected to lead to about 3.5K of warming by 2100, with an uncertainty of about 0.9K (i.e., it doesn’t rule out warming by more than 4.5K). Yet, even this optimal pathway still has emissions increasing slowly for a couple of decades, peaking around 2040, and then reducing towards zero.

So, even an optimal pathway that potentially leads to quite substantial warming would still require starting to decouple emission increases from economic growth very soon, peaking emissions in ~20 years, followed by substantial emission reductions. It’s hard to see how this could happen without some kind of explicit intervention (a combination of a carbon tax, investment in innovation, and incentivising some changes in behaviour). I don’t think that no regrets policies, that essentially everyone is happy with, is going to be sufficient.

It’s hard to see how there can be common ground if some don’t even seem to accept the basis for the discussion. We can certainly argue about how to reduce emissions, when to start reducing emissions, and how fast to reduce them. It’s hard to do so with those who argue that

[a]ttempting to use carbon dioxide as a control knob to regulate climate on decadal to century timescales is arguably futile.

A giant impact outside our Solar System

I’ve come down to listen to a General Interest seminar about climate change given by retired physics professor, but I’ve discovered it’s next week. I’ll have to wait to find out if it satisfies the stereotype. Since there is no point in going back up to my office before my next meeting, I thought I would mention a paper of ours that has got quite a lot of press coverage.

The paper is about Kepler-107, an exoplanetary system already known to host 4 planets. We collected a lot of high-precision spectra which allowed us to determine the radial velocity of the host star and, consequently, estimate the masses of the planets. The observations were made using an instrument on the Telescopio Nazionale Galileo, a telescope operated by the Italian National Institute for Astrophysics (INAF), researchers from which led the paper. I did an extra radial velocity analysis and carried out some dynamical simulations to test the stability of the planetary system.

The figure shows one frame from the middle of a hydrodynamical simulation of a high-speed head-on collision between two 10 Earth-mass planets. The temperature range of the material is represented by four colours grey, orange, yellow and red, where grey is the coolest and red is the hottest. Such collisions eject a large amount of the silicate mantle material leaving a high-iron content, high-density remnant planet similar to the observed characteristics of Kepler-107c. (Credit: Zoe M. Leinhardt and Thomas Denman, University of Bristol)

The reason that this is an interesting system is that the two inner planets (Kepler-107b and Kepler-107c) have very similar radii, but very different masses. Kepler-107c is more than twice the mass of Kepler-107b. If Kepler-107c were the innermost planet, then you could explain this through it being born in an environment that is heavily bathed in radiation from the central star. Since it orbits beyond Kepler-107b, this explanation seems implausible. What is most likely is that Kepler-107c underwent some kind of giant impact that stripped part of the mantle, leaving behind a dense (probably iron) core that now makes up 70% of its mass. Kepler-107b, on the other hand, has a composition more like that of the Earth, with the core making up around 30% of its mass.

There is evidence for giant impacts in our Solar System; we think that the Moon formed through a collision between the Earth and a Mars-sized body. However, we think this is the first convincing evidence for a giant planetary impact occuring outside our Solar System.

Swans on ice

I was out walking in the Pentlands Hills yesterday. They’re quite close to where I live and I particularly like it when there’s snow on the ground. Rather embarassingly, I’ve been aiming to go over one of the higher hills, which by most standards is still not very high. A couple of weeks ago, I turned back down too soon. Yesterday, I thought I’d gone over it, but when I got home I realised I’d turned down too soon again. At least it gives me an excuse to go out again.

The hills ring a reservoir which, yesterday, was mostly covered in ice. There were some swans sitting on the snow-covered ice, with the shadow of the hills running right behind them. It produced a rather surreal effect, which I tried to capture. I’m not sure I did it justice, but I quite like the photograph anyway.

The Hawkmoth Effect

I’ve been down to the University of Warwick to give a seminar, and was reading Eric Winsberg’s book on the train. Eric was interviewed by Willard for the previous post and his book is about Philosophy and Climate Science. I’m finding the book very good, and very accessible, but then it does say a lot of things I agree with, so I would say that 🙂

What I wanted to mention was the book’s discussion about something called the Hawkmoth Effect, about which it is actually quite criticial. I’ve come across it before, but have never quite understood what it referred to. I may still not quite understand it, but I think it’s not something that is necessarily all that well-defined. It seems to have first appeared in Erica Thompson’s PhD thesis, the relevant chapter of which I’ve just read.

The Hawkmoth Effect is named so as to complement the Butterfly effect and refers to structural instability of complex systems. The idea being that, in complex dynamical systems,

[y]ou can be arbitrarily close to the correct equations, but still not be close to the correct solution.

Having read the thesis chapter that discusses this, it seems to be regarded as a combination of models being unable to incorporate all the necessarily physics, and non-linear effects potentially coupling to produce unexpected outcomes (Tipping points, for example).

So, this seems like a combination of non-linear systems being chaotic (related, at least, to the Butterly Effect) and George Box’s all models are wrong, but some are useful. We know that computational models are not prefect representations of reality. They’re approximations that are typically used to try to understand how a system evolves, and how it responds to various changes. It’s probably impossible for complex models to produce results that are arbitrarily close to reality, but this is not really what computational modellers expect.

It’s, of course, possible that something is missing that could have a big impact on the outcome. It’s, of course, also possible that non-linearities might tip the system into a completely unexpected state. It’s clearly worth considering all these possibilities, and I certainly agree with this aspect of the motivation behind the Hawkmoth Effect. I just don’t see that the Hawkmoth Effect is in the same kind of category as the Butterfly effect.

The Butterfly Effect is essentially the idea that some systems are very sensitive to initial condition. This chaotic nature of some non-linear, deterministic systems is a well-defined property of these systems. I don’t see how the Hawkmoth Effect is similarly well-defined. It seems to be mainly a suggestion that we should be careful of trusting the results of complex simulations too much. However, one should also bear in mind that physical models are typically based on equations that describe well-understood conservation laws. This means that you can often sanity check the output from complex models using much simpler implementations of these conservation laws; typically you don’t simply evolve the complex models and assume that the output is right.

I do think that there is merit to being more aware of the limitations of complex numerical models. I also think that people who develop, and use, computational simulations should be clear about where they have confidence in the model and where they think the model has limitations. However, I do think this is often considered and discussed, even if it isn’t always easy to define. Maybe this is essentially the motivation behind the Hawkmoth Effect concept, but I’m just not convinced that it’s really all that well-defined, or that you can describe the complexities of computational modelling with a simple term like the Hawkmoth Effect. Of course, I may mis-understand what’s being presented. If so, I’m happy to be corrected.

Links:
Philosophy and Climate Science – Eric Winsberg’s book, which you should read if you want a more detailed critique of the Hawkmoth Effect.
Modelling North Atlantic storms in a changing climate – Erica Thompson’s PhD thesis which – I think – first presents the Hawkmoth Effect.
An antidote for hawkmoths: on the prevalence of structural chaos in non-linear modeling – A link to Nabergall, Navas & Winsberg (2019), Eric’s recent paper on the Hawkmoth Effect.