Thin Ice

5259429165_3dd1831718_oI finally got around to watching Thin Ice – thanks Rachel. I sometimes struggle to get around to watching things that are factual, because I’m inherently lazy and it feels that it will take some actual effort. This, however, was extremely good and I enjoyed it much more than I thought I would. I found the beginning quite emotional, as it showed people arriving in the Antarctic and commenting on how it was a life changing experience. It’s something I did myself just over 20 years ago, and it is indeed a remarkable experience. I did once ponder if such experiences do influence how we perceive issues like climate change; there are some remarkable, and important, places on this planet that – in my view – have intrinsic value. Maybe being more directly aware of this influences how we assess the risks associated with climate change.

I won’t say much about Thin Ice. It was a mixture of the presenter (Simon Lamb) discussing climate science, and interviews with scientists. Ray Pierrehumbert did a great job of explaining the basics of the greenhouse effect. Myles Allen pointed out (as is my view too) that, as a physicist, it was pretty obvious that increasing atmospheric greenhouse gas concentrations would cause warming. Maybe this kind of comment is where the “science is settled” meme comes from, but it is essentially true; we might not have complete understanding of the details, but the basics are pretty settled. It discusses the different surface temperature datasets and how they all suggest essentially the same basic picture. It touches on Climategate (I won’t give away whether it concluded that it was a storm in a teacup, or not 🙂 ). It discusses climate change in the past, and what might happen in the future.

It really is – in my view – worth watching. It was even possible to support it, but that seems to have finished (you can even find Rachel’s name there). You can still stream it, download it (as I’ve just done this), or buy the DVD. I’d certainly recommend watching it if you haven’t yet done so.

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42 Responses to Thin Ice

  1. tallbloke says:

    “as a physicist, it was pretty obvious that increasing atmospheric greenhouse gas concentrations would cause warming.”

    How much have atmospheric greenhouse gases concentrations increased by, including water vapour?

  2. Rachel M says:

    I’m glad you liked it. This is my favourite climate science documentary. Some of the others have that Hollywood drama feel to them which I don’t feel is right for a climate science documentary. This one feels genuine and includes some great interviews and scenery.

  3. I watched the film a year or so back and I agree it was very good and well worth watching.

    But the thing I picked up on in your post, aTTP, was what you say about visiting places that have a profound effect: “there are some remarkable, and important, places on this planet that – in my view – have intrinsic value”. I very much agree with this. Over many years I was fortunate to undertake a project that took me to many places round the planet that certainly influenced how I “perceived issues like climate change”. To pick four images that spring instantly to my mind…

    1) Approaching Mumbai and looking down on the city from the ‘plane window as we started to descend into the clearly-visible bank of smog.
    2) Walking from the deadly silence of an oil palm plantation in Borneo, towards and into the cacophony that was the neighbouring, full-of-life, tropical rain forest.
    3) Walking down a street in Sao Paulo and looking down into a canalised river bed that flowed, rubbish-choked, between the houses before it entered the sea. The sweet-putrid smell comes right back to me as I write this.
    4) Having driven for about 4 hours along dirt roads into the Cerrado of Northern Brazil; eventually stopping at a newly-created, 200 hectare field of tomatoes, where an ancient diesel lorry engine on a home-made skid, surrounded by dozens of oil drums, pumped water up a 6 inch pipe from a ditch into the channels that irrigated the field.

    I guess these images tend to be all rather negative when compared with the pristine whiteness of Antarctica (which I’ve never visited), but they were all fundamental to me losing what I now see was my state of denial over climate change.

  4. tall,
    Atmospheric CO2 has increased by 40% since pre-industrial times, as you probably well know. If you think I’m to start a debate about feedbacks with someone who appears to dispute the basics of the greenhouse effect, then you’re sorely mistaken.

    Yes, a good point. When it started, I did wonder if it was going to come across as a bit amateurish, but it really did get a nice balance between being professionally done, yet quite genuine.

    Indeed, I guess there are places that amaze us in a very positive sense, and places that make us aware of the damage that we can actually do to the natural environment.

  5. tallbloke says:

    Well the modellers haven’t got around to coupling convection and radiation properly in their models yet, so there’s a lot of reason to question the quality of their output.

    The ‘basics’ might work in a lab OK, but the free atmosphere is another question. Speaking of questions, how about an answer to the one I asked, instead of the answer to one you know the answer to?

  6. tall,
    Two things. As should be obvious, I’m not going to waste my time discussing this with someone who appears to dispute the greenhouse effect. Also, I’ve just seen your comment on the article on which we’re both commenting elsewhere. If you think it is acceptable to say such things, you can stay at the kind of sites that encourage that, and stay away from here.

  7. Ethan Allen says:


    “seen your comment on the article on which we’re both commenting elsewhere”
    Any further hints as to where elsewhere is?

  8. MieScatter says:

    The greenhouse effect, and the fact that it strengthens with increasing CO2 is an observed fact*, see Feldman et al. (2015) and Harries et al. (2001). The radiative transfer models do amazingly well, showing that radiative physics is a theory that makes excellent predictios (Tjemkes et al., 2003).

    Greenhouse effect denial is beyond ridiculous, and while sceintists were busy pushing our understanding and explaining the incredibly complex spectra we measure, greenhouse effect deniers have pushed nothing but sophistry.

    *or as close as we can get to a fact in science

  9. tallbloke says:

    You have cause and effect backwards. The radiation levels are primarily the outcome, not the cause of atmospheric temperature. Astrophysicists have known for decades that surface temperature is primarily a function of atmospheric mass, not its composition. That’s why the temperature profile of the Venusian atmosphere at the same pressures is the same as Earth’s, allowing for the difference in solar distance.

  10. Ethan Allen says:


    Well that was really rather depressing. As I thought it might involve a REAL discussion of climate models. That particular blog post is a good one wrt the usual ‘flatline’ suspects, but that discussion with the usual ‘flatline’ suspects not so much, if fact, that part is bog dead boring.

    We now return you to your regular scheduled program.

  11. tall,
    That’s your last comment on this topic. I’m not having you spread your scientific nonsense here.

    Astrophysicists have known for decades that surface temperature is primarily a function of atmospheric mass, not its composition.

    No, they have not. Surface pressure depends on mass. Temperature does not. Temperature depends on pressure and density. If there were no greenhouse effect, but there was still an atmosphere, the pressure at the surface would stay the same, but the temperature would be set by basic energy balance. Also, not that I like appeals to authority, do you know who I am?

  12. MieScatter,
    Indeed. Since the topic has been brought up, I’ll go a bit further. The enhancement in CO2 alone would explain about half of the observed warming. However, our best estimate for anthropogenic warming is slightly more than all since 1950. Hence something is probably amplifying CO2 warming, and feedbacks are likely positive. The dominant feedback is water vapour. Also, it turns out that it is extremely difficult to construct a scenario where more than half of the warming since 1950 was not anthropogenic. One simple reason is that for there to be an extended period of natural warming would require physical processes that are essentially the same as those that act as feedbacks to anthropogenic warming. It’s not really logically consistent to argue that these processes operate when the underlying warming is natural, but do not operate when it’s anthropogenic.

  13. Ethan,
    Indeed. There’s probably a reason why many don’t bother engaging below the line on those kind of articles.

  14. tallbloke says:

    N. Madhusudhan1 and S. Seager1,2
    Published 2009 November 17 • © 2009. The American Astronomical Society. All rights reserved. • The Astrophysical Journal, Volume 707, Number 1

  15. @tallbloke: “Astrophysicists have known for decades that…”

    I’ll say it because I know aTTP likes to hide his light under a bushel: you’re making a fool of yourself, patronising a professor of astrophysics.

  16. BBD says:

    Part of the art of clowning is to get the audience to anticipate the pratfalls.

  17. Marco says:

    “Astrophysicists have known for decades that…”
    Astrophysicists such as James Hansen and Carl Sagan, perhaps?

  18. tall,
    You really should read things properly. That paper is NOT saying what you seem to be suggesting. The abstract alone says

    we have developed a parametric pressure-temperature (P -T ) profile coupled with line-by-line radiative transfer, hydrostatic equilibrium, and energy balance, along with prescriptions for non-equilibrium molecular composition and energy redistribution.

    The energy balance section says

    In the context of our 1D atmosphere, the constraint of energy balance means that the wavelength integrated emergent flux at the top of the planetary atmosphere matches the wavelength integrated incident stellar flux, after accounting for the Bond albedo (AB) and possible redistribution of energy onto the night side (fr).

  19. In fact, if I understand the Madhusudhan & Seager paper properly, they’re simply assuming a Pressure-Temperature profile. They’re not assuming that the actual Pressure and Temperature values are known a-priori; simply that the profile is known. The actual values are determined via radiative transfer, hydrostatic equilibrium, and energy balance. This is simply to save computational time and because it appears to match more complex calculations quite well. This should also be fairly obvious from Figure 2, which shows that the shape of the P-T profiles are similar, but the actual values are not the same.

  20. Richard says:

    ATTP – Back to your post … Thin Ice, funnily enough I also saw it for the first time yesterday. We had a Climate Awareness Day in our small town and a showing of the film was held as part of the day’s programme (we actually had an ad hoc cross-party group organising the day – left, right and centre – we are that kind of town where politics does not trump logic and science). I found it moving for different reasons. It really humanised the scientists themselves, in a number of cases people dedicating half their lifetimes to look at one piece of the jigsaw of our planetary system – whether plankton in the souther oceans or those studying the chemical records of ice cores; and so on. I liked the scientist (I did not catch her name) who said how much she enjoyed being there on the boat helping to collect the data and that sense of dedication and integrity ran through all the different disciplines. The film did do some exposition of the science but the stars were the scientists themselves. A million miles of course from the caricatures promulgated by those who poor their ill-informed vitriol into trollosphere. I would recommend not merely viewing it, but organising an event in a local hall or wherever to show the film and follow-up with a Q&A.

  21. Richard says:

    P.S. Thanks Rachel for recommending it. I got there in the end!

  22. izen says:

    ‘Thin Ice’ is a very well made example of the type of documentary that is intended to communicate ‘abstract scientific knowledge’ to people who are more interested in other people and what they do than graphs or numbers.

    It is difficult not to enjoy the moment of schadenfreude as TB first invokes the authority of ‘astrophysicists’ to make a false assertion, and when warned this might not be the appropriate venue to pull that trick, doubles down with a cite of a paper that fails to back his claim.

    But then any claims about the science made by TB are not intended to be convincing to anyone who knows the subject. They only serve as dubious rationalisations for rejecting a body of scientific knowledge by those that know less science but share the ideological view that AGW is a purely political conspiracy.

    Thin ice might even confirm them in their suspicion that scientists clearly enjoy their time spending the taxpayers money doing expensive things to find out stuff that provides no wealth or profit for anyone. Research that uses up money that could be spent getting coal to children in Africa…

  23. hmmm … thanks for the reminder. I supported it too, but was left off the list, no big deal. But I should indeed watch it, though it appears to cover an all too common cast of characters. My word of the day is corruption.

  24. MieScatter says:

    That’s it. I just looked through the paper and well played Tallbloke, I think you Poed me!

    But for non-satirical greenhouse effect deniers, that paper and the physics behind it is a good example against their case. It parameterises the standard energy balance and radiative transfer type results from which the basic understanding of the greenhouse effect comes.

    Of course, greenhouse effect denial is so ridiculous that a paper like that should be unnecessary. There are three main facts I see that they seem incapable of ever addressing. You ask about any of these things and their interest immediately shoots off.

    1) If the greenhouse effect is fake, we know that about 65 W m-2 of sunlight reaches Venus’ surface and 16.5 kW m-2 is emitted as thermal infrared due to its temperature. What happens to all that extra heat to prevent it from escaping, or does greenhouse effect denial get to break energy conservation as well?

    2) The theoretical dry adiabatic lapse rate in _temperature_ is set by gravity and the gas’ properties. But what sets the pressure profile? Show the calculations (hint, PV=nRT and T is related to energy balance)

    3) Observed spectra contain hundreds or thousands of bands, meaning a lot of information needs to be explained. Standard physics does it brilliantly. Make a predictive model of observed spectra without the greenhouse effect.

    These 3 fundamental questions simply haven’t been answered by greenhouse effect deniers, and for years they have refused to. This tells you what you need to know.

  25. That’s it. I just looked through the paper and well played Tallbloke, I think you Poed me!

    Hmmm, I wish.

  26. verytallguy says:


    I’m not sure why point 2 is paticularly relevant. The pressure at the surface is simply set by the mass of the atmosphere; it must be sufficient to support the weight of the atmosphere.

    The way I’ve come to conceptualise the greenhouse effect is that the height of the top of the atmosphere, the effective radiating surface, is set by the level of radiating gases, or “greenhouse gases”(GHGs) as they’ve come to be known.

    The temperature of this surface stays constant as GHGs increase, to maintain radiative energy balance.

    The rate of change of temperature to the surface, the “lapse rate” is governed by convection, not affected by radiative properties.

    Thus with more distance from surface to top of the atmosphere, there is a larger temperature difference. As temperature at the top remains constant, so the temperature at the surface must rise.

    There are several gross assumptions in this, but I think it’s a reasonable first order description.

  27. dikranmarsupial says:

    Thought experiment: Consider a planet like the Earth, but in inter-galactic space, so far from the nearest star that incoming LW radiation is negligible. If the surface temperature actually did depend on atmospheric mass, then the surface temperature would be set by the mass of the atmosphere, and hence would radiate IR energy out into space indefinitely without cooling. We have just broken the laws of thermodynamics.

  28. pbjamm says:

    If Tallbloke is a Poe then he is playing a VERY long con. I tried to have a reasoned conversation with him about 6 years ago and it was no more fruitful than the one here or that ATTP linked to.

  29. mt says:

    +1 to Thin Ice and humanizing scientists in general

  30. MieScatter says:


    I think point 2) is useful because you need to include the energy balance to get the pressure profile. The bottom boundary is set by the weight of the atmosphere, but the profile of pressure is affected by greenhouse gases. Ignoring complications due to ozone, you add CO2 to a simple atmosphere and the surface-air system warms. Warmer gases expand, so the pressure lapse rate becomes smaller. The expanded gases increase the distance between the surface and the equilibrium emission layer in the atmosphere, so for a constant temperature lapse rate the difference in temperature between the emission altitude and the surface is now higher – a stronger greenhouse effect.

    This seems to me to be one way of understanding the greenhouse effect, but while I’ve seen greenhouse effect deniers gleeful over the physics of the temperature lapse rate, they never seem to discuss the pressure lapse rate. Because if you admit that energy is conserved and that warmer gases expand then greenhouse effect denial falls apart.

  31. MieScatter,
    Except that, roughly, the dry adiabatic temperature profile (lapse rate) is largely independent of the composition. So, if you think in terms of the GHGs setting an effective emission height, then the surface temperature is simply set by this effective emission height, and the (temperature) lapse rate – working down from this height to the surface.

  32. MieScatter says:


    I think of it in terms of optical depth. The emission level is at a given optical depth: adding GHGs reduces the physical distance from TOA to this level. So immediately you get the GHE boost you expect since there’s more physical distance from the emission level to the surface. If I understand you properly, that’s the first component of the greenhouse effect…

    But there’s another component. Imagine you change the emission altitude as above, the atmosphere near the surface is now warmer than it was before. It therefore expands, pushing the equilibrium emission altitude even higher than you’d expect from the first step. The temperature lapse rate doesn’t need to change, but the pressure lapse rate does.

    It seems obvious to me if you consider starting from extreme cases, but please point out if I missed something here.

  33. Ahh, okay, you’re saying (I think) that the change in the pressure profile itself changes the effective emissions height. Is that right? I tend to simply fold that all into the first step and simply point out that an increase in GHGs increases the effective emission height and hence – given then approximately constant lapse rate – increases the temperature at the surface.

  34. To put it differently – I think. The equation of state is

    P = \dfrac{\rho}{m} k T.

    Therefore if the surface temperature goes up, the fact the the pressure at the surface is set by the mass of the atmosphere, the density goes down slightly, and the scale height (the distance over which the density will drop by 1/e) also increases. Hence the GHGs are moved to a slightly higher altitude, which then influences the optical depth and also increases the effective emission height. At least, I think that’s right.

  35. MieScatter says:


    Yeah, it looks like we’re on the same page now. It’s a translation between optical depth height, pressure height and physical height that can cause confusion. So my original point follows from what you said there: energy balance ultimately affects the pressure scale height. If you deny the greenhouse effect then you can’t get the energy balance right, so you can’t work out the pressure profile. This might explain why I’ve never seen a greenhouse effect denier try to calculate pressure profiles.

  36. MieScatter,
    I’ve never really seen them try to calculate anything 🙂

  37. Christopher Winter says:

    Thanks for mentioning this documentary. I’ll have to look it up. I wonder it it owes anything to Mark Bowen’s book of the same name. Probably not, I’m guessing.

    Allow me to put in a good word for another documentary. it’s not about climate change, but about the green energy techniques that can help us alleviate climate change impacts.

  38. Victor Petri says:

    Intrinsic value doesn’t depend on one’s views by definition.

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