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  1. This is amazing, thanks

    Comment by Joseph K — 26 Nov 2009 @ 11:51 PM

  2. Thanks, David! Will be checking this out as I get the chance.

    Comment by Kevin McKinney — 27 Nov 2009 @ 12:25 AM

  3. And so we give thanks.

    Comment by Sili — 27 Nov 2009 @ 12:27 AM

  4. David,
    Your book is on my shelf, just read it again. I speak for many when I say a BIG Thank You. I will make sure this gets widely distributed among my AMS friends in broadcasting.

    Comment by Dan Satterfield — 27 Nov 2009 @ 1:37 AM

  5. David, this is great. Now how about a second edition? We could use a new edition that fixes the documented bugs. C’mon Blackwell…

    Comment by DrCarbon — 27 Nov 2009 @ 1:45 AM

  6. Do you have any lectures that just talk about climate in general or are they all about C02 and warming? I see a pattern here.

    [Response: Sorry, but I’m a CO2 guy primarily rather than a climate physics guy. I have a class on global bio-geo-chemical cycles, but it had seven students in it last time, or something like that, and I think I’ll keep it unplugged. David]

    Comment by Ric — 27 Nov 2009 @ 2:05 AM

  7. David,

    That looks like an outstanding resource, but I could ask if the videos could be made available via YouTube or Vimeo, or similar services? At 270MB per lecture, they represent a substantial chunk of bandwidth for individuals to download outside a university network… Plus your servers wouldn’t get hit.

    But thanks, in any case.

    [Response: I think youtube is limited to 10 minutes or 10 mbytes or something like that. Suggestions welcome, though, about alternative venues. One possibility is that UC has a presence on something called iTunes University, but for that one needs itunes to watch them, which seemed to me like a bottleneck. David]

    Comment by Gareth — 27 Nov 2009 @ 2:47 AM

  8. Watched the first two lectures. The supplemental material is interesting. I have already read HF&C.

    The text (your book) is pretty expensive. I was thinking of getting this for the kids for Christmas. Any ideas on a cheaper outlet? Or do I just need to watch the lectures?

    Not to say it isn’t worth ever penny.


    Comment by Maverick — 27 Nov 2009 @ 2:47 AM

  9. Thank you very much.

    I have in the past pointed students to your lecture on global warming in geologic time at Fermilab, accessible from

    Distributing talks in video, powerpoint, etc is greatly appreciated.


    Comment by Halldór Björnsson — 27 Nov 2009 @ 3:39 AM

  10. Thanks David. Thirty-something years since my last undergrad lecture. It’s immensely comforting to know that so little has changed. (Even the jeans!)

    Comment by GlenFergus — 27 Nov 2009 @ 3:48 AM

  11. Thanks alot.

    I do not know if the sea level vs. temperature graph is in the lectures. I’ve written a few comments on it here.

    Comment by Aslak Grinsted — 27 Nov 2009 @ 3:58 AM

  12. Thanks so much for this. Even better that they are in quicktime so I can watch them on my iPhone on the train to work. Thanks heaps.

    Comment by Stephen Gloor (Ender) — 27 Nov 2009 @ 4:29 AM

  13. Yes, thank you – I’ll definitely check this out when I get a chance.

    Comment by Jack Kelly — 27 Nov 2009 @ 4:32 AM

  14. bevor you can not explain or messure the sensitivity of co2 there is no use to construct catastrophic climate simualations. i`m right?
    please show us the “co2 footprint”, where is it?

    so what about climate feedbacks on co2 emissions, thats all about.
    why don`t you show lindzens work? is he really always wrong?

    regards, silke from germany

    Comment by Silke — 27 Nov 2009 @ 5:52 AM

  15. Nice. Thanks.

    Comment by TA — 27 Nov 2009 @ 6:14 AM

  16. Many thanks,
    This could prove a valuable resource. I assume that as property of the University of Chicago there are restrictions on the use of these videos. Can you elucidate these for us?

    [Response: I guess if you start selling tickets they want a cut. David]

    Comment by C Robb Worthington — 27 Nov 2009 @ 6:29 AM

  17. Thanks a lot! This is a great contribution.

    Comment by Marc Macias — 27 Nov 2009 @ 6:41 AM

  18. Wow! Very generous! Loads of thanks!

    Comment by PeterPan — 27 Nov 2009 @ 7:07 AM

  19. Just one question, are there any answers anywhere to the exercises in the book? I’d just like to check that I haven’t made any silly mistakes anywhere, and it will help me to confirm that I understand what I’m doing.

    [Response: Send me an email and I can mail you a pdf file with solutions. David]

    I did have a look when I went through the book (which was a while back now), but I couldn’t find any then.

    Looking forward to re-going through it with these lectures, now.

    Comment by Adam — 27 Nov 2009 @ 7:12 AM

  20. Excellent introduction – I’m enjoying learning from them.

    Comment by Chris — 27 Nov 2009 @ 7:39 AM

  21. David, I enjoyed (if I can use that term about such a serious subject) your book The Long Thaw. I found the scientific explanation very accessible, so I’m not surprised to see your outreach to non-science majors. I will check out the lectures – have you thought about forwarding the link to the U of C economics department?

    Thanks. And as I sit eating too much pumpkin pie, thanks to all the RC contributors. As climatologists come under attack (H/T to Greenfyre) it is good to have such capable spokespersons.

    Comment by Deech56 — 27 Nov 2009 @ 7:53 AM

  22. Aslak,

    According to your argument, the sea level rise during the last interglacial (6 metres, 1-2 degrees higher global temp) would be a (more) valid analogy for the equilibrium response of sea level to temperature, right?

    [Response: Seems like a good guess, to me, yes. Sooner or later, more or less. David]

    Comment by Bart Verheggen — 27 Nov 2009 @ 8:52 AM

  23. Silke, there are about 10 separate, independent lines of evidence all showing that CO2 sensitivity is around 3 degrees per doubling, and precluding sensitivities less than 2-2.5 degrees per doubling. What is more, Lindzen’s analyses use questionable datasets and questionable techniques. This alone would be sufficient grounds for ignoring them.

    Add to this the fact that Lindzen makes arguments to naive lay audiences that he knows to be false, and one can conclude the RL stopped being a serious scientist a long time ago.

    Comment by Ray Ladbury — 27 Nov 2009 @ 9:03 AM

  24. Bart, (22)

    In short: Yes i think that the Last Interglacial (LIG) is a better analogy than the Eocene. But i realize that for each interglacial the Milankovitch forcing was slightly different. For example during the LIG there was a much stronger spring-summer forcing at high latitudes (otto-bliesner science 2006). The CAPE project shows that high latitude were warmer than present. Even so some modelling suggest that perhaps global average temperatures may have been colder (e.g. otto-bliesner) – although not all modelling agree with this (e.g. Kubatzki et al. 2000). That is why i think it is necessary to look at several interglacials as Rohling et al. does.

    Comment by Aslak Grinsted — 27 Nov 2009 @ 9:58 AM

  25. 1). Thanks for the videos. I’ve had the physics to understand the arguments, but it’s extra fun to see this explained for non-scientists. And for non-scientists, extra important so they can learn this stuff, too.

    2). Belt? Fewer things in your shirt pockets? Better fitting shirts? If you’re going to be on video, we need to spiff you up :)

    3). How many chalk boards ARE there in that sliding-thingy?

    [Response: Four, I think, and they go so high that there’s a little metal hook on a rod to retrieve them. We have lofty aspirations at Chicago. Burned out light bulbs, though, too; sorry about that. David]

    Comment by FurryCatHerder — 27 Nov 2009 @ 10:13 AM

  26. Amazing. Really generous of you, David.

    Comment by Alexandre — 27 Nov 2009 @ 10:23 AM

  27. Thank you for this. Looking forward to seeing it.

    I think youtube is limited to 10 minutes or 10 mbytes or something like that. Suggestions welcome, though, about alternative venues.

    Vimeo, at, allows large files/long videos, and is by the way a great community, well used by graphic designers, video artists and the like. They could indeed use the inspiration.

    Comment by Martin Snoer Raascohu — 27 Nov 2009 @ 10:41 AM

  28. In my opinion this should be accessible through Itunes U.

    Comment by Tom Pesch — 27 Nov 2009 @ 10:49 AM

  29. This is so unselfish and generous of you, thank you very much!!! I’m seeing now the intro lecture :]

    Comment by Luis Vega — 27 Nov 2009 @ 11:42 AM

  30. Numbering check: does it go to 11?
    The lecture numbers (both on the individual pages and the filenames)
    jump from 10 to 12:
    Chapter 6 Wind, Currents, and Heat — Lecture 10
    Chapter 7 Ice and Water Vapor Feedbacks — Lecture 12

    [Response: Lecture 11 is the Six Degrees lecture that goes with chapter 12 of my book on the forecast. I pulled it out of order in the class so they could read Six Degrees for the midterm and Hot Flat and Crowded for the final, instead of two books all at once at the end. David]

    Comment by Hank Roberts — 27 Nov 2009 @ 12:01 PM

  31. David, thank you for making your lectures available. I am a (non-environmental) economist and I found them useful in trying to gain a better understanding of the physical science of climate change.

    I was happy to see that your policy discussion in the last lecture gets the notion of “externalities” correct—I am regularly amazed at the frequency at which I encounter the incorrect and lazy notion that “externality” means “things economists ignore because they’re external to the economy.”

    However, the discussion goes a bit off the rails at that point, as the remainder of the lecture is based on the ideas of the journalist (not economist) Thomas Friedman, which seems inappropriate, and there are number of wince-worthy claims apparently attributable to Friedman (who I have never read, I should note).

    If I may make a small suggestion, I would scrap that discussion and replace it with a brief overview of efforts to integrate GCM models with macroeconomic models, such as the Stern report or Bill Nordhaus’s work. Talking about this multidisciplinary work would be a nice way unify the policy discussion with the previous lectures.

    Best, CA.

    Comment by Chris Auld — 27 Nov 2009 @ 12:10 PM

  32. Thanks David. I’m checking some of them out now. I noticed Chapter 6 is lecture 10 and the first one from Chapter 7 is lecture 12. Is there a lecture 11?

    Comment by jerryg — 27 Nov 2009 @ 1:41 PM

  33. Many Thanks for this, it is good to have an “easy” course to which I can direct people when asked questions, esp. as I find having to kill the same “zombie” memes over and over to be very tiring. Keep up the good work and thanks again both to you and to your colleagues here for persevering even in the face of contemptible smear tactics.

    Comment by Konstantin — 27 Nov 2009 @ 2:21 PM

  34. Just checked Vimeo as well. Probably your best bet.
    Vimeo Plus seems to have a 1GB limit per file but costs $59.95 dollars per year.
    Not sure what the limit is for the free basic package, but I assume compression would bring the file size down. So the basic account might do.

    Comment by Paul UK — 27 Nov 2009 @ 3:17 PM

  35. This is great David, and I like how you start with basics, stuff that most of us probably would know, but it produces a narrative that allows the extra stuff to sink in. The fact that you’re approaching it initially from a physical perspective (rather than just showing graphs about warming) is also fascinating, since it allows people to understand just how greenhouse gases operate. It becomes, from what I’ve seen so far (first three lectures) an argument about basic physics, so if someone were to contest the observed AGW data, one need only remind people of the physics at the lowest level. I’ve been chastised before for generalizing and reducing arguments, of course, but that is my favorite part of science. To get down to the nitty gritty of why things operate the way they do. Thanks very much for sharing this.

    Comment by Josh Cryer — 27 Nov 2009 @ 3:21 PM

  36. To be able to post longer videos to Youtube, you can apply for the Partner status here: Let me know if you hit a snag.

    Comment by Simon I — 27 Nov 2009 @ 3:29 PM

  37. jerryg, Lecture 11 is Chapter 12, “Six Degrees”

    Comment by Grant — 27 Nov 2009 @ 3:53 PM

  38. Fantastic resource, the net was invented for this kind of knowledge sharing. Many thanks.

    Comment by Tom Corby — 27 Nov 2009 @ 3:55 PM

  39. Re: Grant

    Thanks, noticed David’s response to Hank and the filename when I got there. Time to pick up a few books now.

    Comment by jerryg — 27 Nov 2009 @ 4:35 PM

  40. Re #24: Aslak, could you explain why you think interglacials are a better analogy for the present than the Pliocene? The Eocene was more or less a different planet, but things don’t seem to have changed much in the last 3 million years other than the drawdown in CO2. Do we have much confidence that the scope and speed of the near-future response to increased CO2 forcing won’t be quite different from the changes in Milankovitch forcing that drove the interglacials?

    Comment by Steve Bloom — 27 Nov 2009 @ 5:12 PM

  41. David, an off-the-wall question (haven’t started studying yet).

    Has anyone run a climate model of, say, the last 3 million years but hypothetically changing the rate at which any of the orbital forcing changes? I’m wasn’t sure whether that’s imaginable, but I did come across a few suggestions, e.g.
    The Geological Society of America Special Paper 452 2009 Evidence for a change
    in Milankovitch forcing caused by extraterrestrial events at Massignano, Italy,
    Eocene-Oligocene boundary

    Mostly thinking for teaching purposes that as Gavin pointed out recently, we’re burning carbon at maybe 150x the rate at which it was naturally cycled. What happens with hypothetically running any other forcing that much faster than it has in the past?

    [Response: Funny thing is that many of the climate responses in the past were abrupt, even though the orbital forcing and the CO2 forcing were changing slowly. Another funny thought that may interest you is that it is actually the moon that stabilizes the orbit of the Earth, in particular the obliquity. Mars is thought to tip all the way over, because it’s moons don’t have the angular momentum that ours does. David]

    Comment by Hank Roberts — 27 Nov 2009 @ 6:25 PM

  42. Re “The Geological Society of America Special Paper 452 2009 Evidence for a change in Milankovitch forcing caused by extraterrestrial events at Massignano, Italy, Eocene-Oligocene boundary”

    Haven’t read it yet, but I’m thinking there’d have to be a massive massive massive massive massive crater somewhere on the Moon or …

    Comment by Patrick 027 — 27 Nov 2009 @ 8:07 PM

  43. Do you ever allow critical posts?

    Comment by Ric — 27 Nov 2009 @ 8:37 PM

  44. wtf?

    [Response: A rewrite of McKitrick and Michaels (2007) no? Still not right though. Interesting factoid, the MSU data correlates more strongly to the socioeconomic factors than the surface station data does. – gavin]

    Comment by Hank Roberts — 27 Nov 2009 @ 11:34 PM

  45. Thanks David. I downloaded some this a.m. using the download button, but this evening all I’m getting is the video with no external links or buttons (I can still download them using a Firefox add-on but otherwise I’d not be able to do it).

    [Response: I got some help from my son yesterday afternoon setting them up to come up in a browser window and begin playing while they’re still downloading. Are they not playing for you, or is the issue saving them…? What browser are you using? David]

    I also ordered your book today…it is the least I can do to thank you (plus I get myself a new book–a win-win situation :-)

    Comment by Ken — 28 Nov 2009 @ 12:33 AM

  46. Fine material, thanks; I’ve recommended the book (and the Long Thaw) to many people, and I’m about a third of the way through the videos. It isn’t slick, just a slice of normal teaching, but that is actually quite valuable, as it gives insights into plausible pacing, amount of material coverable per lecture, and typical questions, items not always obvious when reading a book.

    But, please say a bit more about this course (and the book), which may be of general interest, and for me, to help calibrate my continuing efforts to refine this knowledge scale to help categorize material to help people learn. I think this would fit K3 there, with Long Thaw as something to read at K0 and get them towards K2.

    I understand this is a course for non-science majors @ U of Chicago. But, can you tell us more:

    a) Is this a required course for all majors, or just some?

    b) What are the formal prerequisites?

    c) What year would students normally take it?

    d) Is it viewed by students as easy, reasonable, or really tough?
    (Obviously, students want to seem to take it, but that’s orthogonal.)

    Anyway, say anything else that’s useful in characterizing the audience for this.

    Thanks! (and I hope I’ve helped sell a few of your books).

    [Response: Every student has to take a few physical science classes to graduate, and this is one option. Not much by way of prerequisites. They are supposed to deal with these “core” classes as freshmen and sophmores, but often they put it off until third or fourth year. Science majors get their science credits taking their major classes, so these in my class are majoring in non-science topics. The students work hard to do some of the exercises, the ones that seem like math story problems, but I think overall the class is viewed as an easy way out. There’s a “why are you here” i-clicker question at the beginning of lecture5, and the winner was “easy science credit”. But I tell myself that’s because I explain things clearly, a good thing. David]

    Comment by John Mashey — 28 Nov 2009 @ 12:35 AM

  47. Hi Gavin,

    Slightly off topic for this thread, but can you help me with the following email fragment:

    This is apparently Trenberth to MacCraken on why Lindzen et al. 2001 (“Iris hypothesis”) must be wrong (990718506.txt):

    “3) Finally, I refer you to chapter 7 of IPCC which is a more balanced assessment. Lindzen was a coauthor of that with me and others. Lindzen wrote 7.2.1 and the same figure 1 in the BAMS article was included as 7.1 in chapter 7 along with similar ones from models, showing that these things are fully simulated in good models, although better with higher resolution. Anyway, his arguments were fully considered in chapter 7 and you can read it to see the result. The whole of 7.2.1, including and was put together originally by Lindzen, Pierrehumbert and Le Treut, but basically the final version was rewritten by me to provide better balance. Pierrehumbert is an agnostic of sorts: disbelieves everything including models but seems to have faith in simple theories. Le Treut was sound on the modeling. I did not change the substance of what they prepared, I did reshape it and polish and it ended up in a form they accepted.

    Note at the end it clearly states: “the balance of evidence favours a positive clear sky water vapour feedback of the magnitude comparable to that found in the simulations.”

    Can you or obviously even better Raypierre himself clarify the likely context of this remark? Specifically I refer to the sentence, “Pierrehumbert is an agnostic of sorts: disbelieves everything including models but seems to have faith in simple theories.”

    * In what sense is Trenberth likely to have considered Pierrehumbert an “argnostic”? It’s obviously not the existence of God; is it the sign of the clear sky water vapour feedback that Pierrehumbert is said here to be “agnostic” on here?

    * The models he is said to “disbelieve” here are the best coupled A/OGCM models (acknowledging this written in 2001); is that correct?

    * What are the “simple theories” that Pierrehumbert apparently does or did at the time have faith in?

    * Has his view changed since then; if so why?


    [Response: This would have been written even earlier – 1999 or 2000. And ten years is a long time for people’s view to adapt. Maybe Ray would like to give a history of his thinking on this at some point. I’ll ask him. – gavin]

    Comment by Alex Harvey — 28 Nov 2009 @ 2:22 AM

  48. Suggestion: Lecture 8, questions at end.
    (This is a minor nit):

    1) Exponential economic growth … certainly seems assumed by many economists. But that also assumes either that resources are infinite, or that resources are irrelevant to the economy.
    Personally, I think ex-physicist Robert Ayres and colleague Benamin Warr have a fairly compelling model in The Economic Growth Engine: How Energy and Work Drive Material Prosperity, i.e., a big chunk of economic growth depends on work = energy*efficiency. If that’s true, then a big chunk of the last century’s growth comes from one-time exponential growth in use of fossil fuels, which isn’t going to continue forever, even without CO2 regulation, given Peak Oil. Put another way, the typical econ models around global warming assume that the world is 6-15X richer in 2100. There is room for doubt.

    2) Regarding popcorn, I’d expect that to be better described as a sigmoid (logistic) curve, i.e., typical of effects within a constrained population. It’s slightly weird to have an exponential curve compared to a Gaussian, rather than a sigmoid, i.e., so that one was comparing total population versus total population.

    Anyway, this does seem like a good place to expose students to idea that exponentials and sigmoids look the same at the beginning, but assuming exponentials go forever may not go on forever, but can run into limits, and one had better know where they are. Moore’s Law is one like that. Moore’s law *used* to work in CMOS both for transistors/die and CPU clock rate, and it will still work a while longer for the former, but it pretty much stopped a while ago for the latter. That’s why we get all these multicore microprocessors, but little improvement in clock rates.

    Comment by John Mashey — 28 Nov 2009 @ 2:45 AM

  49. Ken #45

    I found myself in exactly the same situation. Which add-on do I need to download the remaining videos?

    [Response: SInce my sysadmin son is still asleep, I switched back to the original server system, where the videos just download directly, leaving the user to figure out how to open them. The new system I set up yesterday plays during download in Safari and Firefox, but in IE it doesn’t seem to work. Maybe that’s the problem you’re having? If you’d be a bit more specific it would be helpful. David]

    [Response: I added some codage that is supposed to make IE embed the video file properly, and changed the names of the files to .mp4 instead of .m4v. Streaming works in Safari and Firefox, but I can’t get anything to work on the old windows laptop I have here. Feedback or technical suggestions welcome. David]

    Comment by Alexandre — 28 Nov 2009 @ 7:48 AM

  50. Amazing mistake spotted and not one of students noticed immediately.

    Lecture 8. Its not 285ppm. Its 385 ppm. Mistake that the students should know!!!

    [Response: Call the New York Times! Obviously global warming is a fraud! (joke). Dunno why I said 285, that’s the preanthropogenic value. David]

    Comment by Richard Mike — 28 Nov 2009 @ 8:03 AM

  51. Many thanks Professor Archer. I was just wondering what to do next having just finished a part time degree in environmental studies and this lecture appears. Have only scanned a few of the lectures so far but will definitely work my way through the whole course.

    I would also like to thank you, the realclimate team and all those in the scientific profession that have put up with so much c**p over the years yet have kept plugging away to make sure we all understand and take responsibility for the effects we are having on our planet.

    Comment by Roly — 28 Nov 2009 @ 8:59 AM

  52. David:

    I have been working my way through your book and videos for about a month now. They are the absolutely the best resource I have found in my climate change learning curve experience.

    I particularly like how you start with the simple
    Bare Earth model,work your way through the layer model up to on-line Modtran helps me to understand climate modeling more than anything I have read.

    As an engineer,I tend to learn by working with the numbers. You have helped me and I’m sure many others grasp the computational aspects.

    Thanks for a job extremely well done. I like your videos “as is”, please don’t “spiff” them up.

    Comment by D Kelly O'Day — 28 Nov 2009 @ 9:00 AM

  53. David,

    Yesterday I downloaded 10 of the videos, and I intended to download the rest today. But now I can only watch them directly (no download, even after your recent change). Ken mentioned some Firefox add-on that would make it possible…

    [Response: Oh, I see the issue; embedding makes it harder to save them. I’ll work on it, meanwhile back to the original interface. David]

    Comment by Alexandre — 28 Nov 2009 @ 9:29 AM

  54. It is very easy to download them

    Just use this url

    And replace XX with the number of the lecture.

    Comment by Richard Mike — 28 Nov 2009 @ 10:25 AM

  55. Ric asks, “Do you ever allow critical posts?”

    Well, since this is a site about climate science, and over 90% of climate scientists think the consensus model is largely correct insofar as anthropogenic climate change goes, that poses a challenge.

    I mean, since most denialist arguments don’t get more sophisticated than tin-foil-hat-and-black-helicopter conspiracy theories and “Al-Gore-is-fat” pejoratives, there’s not a whole lot for a scientist to pick from.

    Comment by Ray Ladbury — 28 Nov 2009 @ 10:50 AM

  56. It is working normally again. Thank you for the prompt response, David. I’ll be teaching first-year ecology in January and I want to have a more relevant climate section. When you have the rest of the lectures posted I’ll greedily come back for them too. Thank you again for these lectures. This is very generous of you.

    Btw, I was using Firefox 3.5.5 running on Windows 7.

    Richard Mike @54: thanks for the tip. I’ve downloaded all available lectures now.

    Alexandre: The add-on is Download Helper

    and then I have Video Converter which you add-on to the add-on. It allows you to convert the video to the format of your choice.

    I use it to grab science clips from youtube and then insert into the middle of my powerpoint lectures. Download Helper does place a see-through icon in the upper left corner of the screen after you’ve downloaded, but I don’t find it objectionable. It is free—and you can pay for an upgrade which doesn’t have the icon.

    Comment by Ken — 28 Nov 2009 @ 11:53 AM

  57. These would go well on iTunes U, format is right and size is typic al for them. Remove this post if redundant.

    Comment by J Pat Valentik — 28 Nov 2009 @ 2:56 PM

  58. Hey David,

    Your book is a ray of sanity ! I’ve been reading it on the “Tube” Underground (metro) trains in London, and it puts calm and serenity (and a touch of humour) into my journey. I have been recommending it to students of Climate Change, anyone who feels that John Houghton’s book doesn’t go deep enough in explanation of the basic physical processes.

    Question about your book : I keep thinking, “I’ve read this before”, but I can’t have. I did read a book (that I’ve forgotten the title of) when I studied Physics in the early 1980s, which presented Global Warming theory in roughly the same sequence. Have you any idea what that book could have been ?

    Had trouble downloading the lectures…but I’m getting some of it…would prefer YouTube or Vimeo or Flash segments…

    [Response: The concept of the layer model I took from a write-up that grad students at Harvard, including my colleague Jon Abbatt, wrote up for some class. But I don’t think I stole any text, that would be bad I understand…. David]

    Comment by jo abbess — 28 Nov 2009 @ 8:50 PM

  59. Would you mind if I posted a link to these on some Maryland homeschool mailing lists? They look like an excellent resource for high school aged kids. (They should be able to follow lectures intended for nonmajors.)

    [Response: of course not. David]

    Comment by Tamara Griesel — 28 Nov 2009 @ 9:28 PM

  60. Great set of lectures! I’m not sure it is for non-science majors (maybe lower level science majors, I’m not sure how much people who just want some quick science credits need to know about quantum physics) but this set of lectures is a great compliment to the book. I’ve had some good time to allow my roommate to watch the videos and help clear up things for him that were a little confusing, and it also gave me neat ideas for how to present information in the future.

    I’m still not sure about this whole “layer model” version of the greenhouse effect which I gather is a major theme in your lectures and book. I’ve seen it presented in your book (Dennis Hartmann follows this approach somewhat). Maybe someday someone will convince me that the greenhouse effect operates remotely anything like that, but aside from some minor stuff, this is a terrific resource. Definitely should be popularized where possible.

    [Response: I find the layer model a good place to start, and then we spend probably twice as much time pointing out its shortcomings (lack of convection, non-black behavior of greenhouse gases, etc) as we took learning the model itself. It’s also good for the class because the students can do math with it. I remember a feeling of revelation when I first read about the layer model in the Harvard lab manual I mention above, when I was prepping to teach this class with Ray Pierrehumbert many years ago. “Traps the outgoing IR and keeps the Earth warm”, the explanation you get in newspapers etc, didn’t really gel for me. David]

    Comment by Chris Colose — 28 Nov 2009 @ 10:41 PM

  61. Hi, I’m a documentary editor. I would like to re-emphasize the option of iTunes U as an *additional* outlet and here is why:

    1.) Every single owner of an iPod or iPhone on the planet has it, in addition to other users who use it as a music organizer. Millions and millions of people.

    2.) Watching the lectures on iPods and iPhones while commuting, traveling, during lunch at work. (And Apple TVs, to a lesser extent)

    3.) iTunes U already has a reputation as a destination for people looking for lectures on this subject.

    Good luck!

    -Christopher S. Johnson

    [Response: Thanks, I’m working on it. David]

    Comment by Christopher S. Johnson — 29 Nov 2009 @ 12:05 PM

  62. Here IE7 on XP still wants to:

    ‘….run the following add-on: ‘Microsoft (R) HTML Viewer’ from ‘Microsoft Corporation’. If you trust the website ………’

    not being sure that your site had not been interfered with (after all we know that ‘they who cannot be named’ like to fight dirty) I avoided doing so although a link Download appears and allows download access via Save as.

    I note that file type extension has changed between lectures 9 (lecture9.m4v) and 10 (lecture10.mp4).

    [Response: Actually I renamed all of them .mp4 because I was told that .m4v is an Apple thing. David]

    For those who get this far and wonder what happened to lecture 11 it is under Chapter 12 Six Degrees.

    Firefox just gets started and then seems to stall.

    Although I see from a pingtracer that my ISP has high latency on some nodes and I guess your server is under pressure right now, hence the slower download speeds today.

    Thank you very much for this David. Excellent stuff to point ‘those who cannot be named’ at. Although I doubt this will stop them from nay saying.

    I will order both of your books to add to my growing collection which includes Schmidt, Houghton, Burroughs, Lynas, Balog, Flannery, Barry & Chorley (Atmosphere, Weather and Climate) which is old but still useful, and books on Oceanography. My interest in the natural world also informs.

    Comment by Lionel A Smith — 29 Nov 2009 @ 12:19 PM

  63. I’m to Lecture 7. Are you entertaining questions about the material?

    [Response: Fire away. David]

    Comment by HankHenry — 29 Nov 2009 @ 2:35 PM

  64. @Steve Bloom (40):
    The Pliocene can probably still be used as a reasonable analogy. However,
    the further back in time you go the worse the proxies perform. For that reason i think that the more recent interglacial data are much preferred. I quite simply doubt the accuracy of the proxies on those time scales. A quick google gave me this quote: “Geologic estimates of maximum Pliocene sea level thus range from +5 to +40 m relative to present, with +25 m typically used by the modeling community.”. So, even if you would know the temperature of the pliocene to be +2.5degC, then you will be left with an uncertainty of 2-16 m/degC. Note, this is actually more consistent with the 4-8m/degC than the 20m/degC. Ofcourse in reality the confidence interval will be even greater.

    The plots from Rohling et al. and David Archer shows temperature against relative sea level. The idea is that this shows the an approximation to the long-term equilibrium relationship. So, they do not show sea level rise for the next century (=near-term). This will largely be determined by how fast the system approaches the equilibrium. I have examined a wide range of response times (Grinsted et al. 2009) and have found that predicted sea level rise in 2100 is largely independent of the response time. The models are primarily constrained by the observed sea level over the 20th century.

    The Archer&Rohling graphs are showing a relationship between sea level and temperature (i.e. not radiative forcing). The source of the temperature anomaly is of secondary importance. But you are right that it is a concern whether the temperature anomaly induced by GHG forcing will be so much different from what has been seen before, that the relationship breaks down.

    Comment by Aslak Grinsted — 30 Nov 2009 @ 6:42 AM

  65. Mr. Archer, it seems kind of silly to ask this, but it’s something that occurred to me so I will. What’s the situation for light (or radiation) that penetrates the ocean? Is there such a thing as a greenhouse liquid? If not why wouldn’t there be since both air and seawater are transparent, radiation must penetrate them in a similar way and radiate back upward through seawater just as radiation from the surface radiates upward.

    #2 I may be rushing ahead but I don’t see a time element in the Stefan-Boltzman formula. Since experience of a what a day is like tells us that heat “builds” during a day it would seem to me that the T^4 factor could have a bearing on how hot a planet gets based on the length of the day on the planet. My question is, would a quickly spinning planet be expected to have a different average temp than a slowly spinning one because the changing heat of a day pulsed more rapidly on a planet with short days?

    Comment by HankHenry — 30 Nov 2009 @ 7:29 AM

  66. An interesting series of lectures – thanks for posting!

    As I understand it, without the AGW/CO2 we would naturally be heading into the next ice age due to the Milankovich cycle
    – with currently a slight -ve net forcing
    – so how quickly would the entry into the next ice-age occur?
    – and what sort of CO2 levels would be needed to balance the -ve forcing effects of the Milankovich cycle?
    – and is managing the CO2 level a realistic way to ensure a balanced climate?

    [Response: I wrote a paper on this, downloadable from my website (A Movable Trigger, G^3 2005), and also discussed in The Long Thaw. We came to the conclusion that burning all the coal could keep the Earth in an interglacial state for half a million years, until the end of not this time period of near-circular orbit, but the next one, 400 kyr from now. David]

    Comment by Phil M — 30 Nov 2009 @ 8:53 AM

  67. HankHenry, Not silly at all. First, let’s remember what a greenhouse gas is–namely a gas that absorbs a portion of the spectrum in the infrared. This means it will also radiate in the infrared. Because we’re talking about a gas, we’re talking about a system that is very quantized (that is, individual molecules, that interact with each other only weakly), so the absorption features tend to be lines. In a liquid, the intermolecular interactions are a lot stronger, so the lines broaden out, and the liquid tends to absorb much more of the spectrum. So, the water will tend to heat up in the sunlight, unlike the gas in the atmosphere, which tends to remain cool. And if it doesn’t absorb it, it will either transmit it or reflect it. For this reason, we tend to look at water as having an albedo and to be radiating with a certain temperature. I don’t know if this helps, but basically, water gets treated like the rest of the surface of Earth, which absorbs sunlight (visible) and radiates in the IR.

    [Response: There’s the added twist that sunlight that is absorbed in the subsurface ocean may not affect the sea surface temperature; when this effect is included it makes a difference particularly in the equatorial oceans. David]

    Comment by Ray Ladbury — 30 Nov 2009 @ 9:23 AM

  68. I thank you for this.

    Having made my way through Lecture 5, I’m getting the sense that a niggling question that I have won’t be addressed (quite possibly this is because it is too obvious to warrant such. Nonetheless…): Why does the energy into the system balance exactly with the energy leaving, at least on a timescale which makes any calculations of temperature at any given moment meaningful?

    For example, your first model calculates what turns out to be the temperature of the skin given solar constant L; but your assumptions of radius and albedo seem (to my perhaps befuddled mind) to ignore a gigantic pool of molten rock, which is to say that the Earth has a temperature already.

    [Response: The energy fluxes don’t have to balance at all times and places, which we talk about in Chapter 6, about heat fluxes and seasons. The leftover heat from the Earth, however, is a negligible part of the energy balance. So on a long enough time average and averaged globally, the heat fluxes do have to balance just by conservation of energy. David]

    I personally find that analogies generally confuse me more than elsewise (I much prefer to think of the “pane of glass” as an idealized atmosphere, for example, as this seems both more accurate and less confusing), but your analogy of the “sink” as containing the earth’s energy is an apt one. My above issue translates well to this way of expressing the point. No matter when, during the span of radius R and albedo a, we start to utilize the equation balancing energy in and energy out, there will have been water in the sink already. Does this not matter? A related issue is the assumption that there exists a water level which will result in this balance, and the instantaneousness of any rebalancing.

    [Response: It doesn’t have to get there instantaneously, it just gets there eventually. ]

    Perhaps these are issues which are best left as assumptions for the level of exposition (and my ability to understand it), but if we are going to address it later anyway, I would prefer to do it sooner rather than later.

    I will continue watching these regardless of whether you have the time or patience to reply, so I don’t want this to seem like a demand (one which I hope you would feel no compunction ignoring even so). Thank you again. If you can see it, feel free to email any material to which you cannot link in a response.

    Comment by jhm — 30 Nov 2009 @ 10:46 AM

  69. David – thanks – I’m only upto Chapter 7 in the lectures (lecture 10/12)
    – so it was just a random question
    – I’ll read the pdf & carry on with the lectures in due course…

    Comment by Phil M — 30 Nov 2009 @ 12:25 PM

  70. HankHenry,

    Concerning a rotating body, this also depends on the properties of the planet as well. Venus, for example, has a relatively slow rotation rate but its atmosphere does not heat or cool rapidly since it is so sluggish, and so the diurnal temperature range (DTR) is quite small. Mercury, on the other hand, has a substantially large DTR which presents a large problem for simple global scale models like “S (1-albedo) = 4sigma*(T^4)” since the T^4 is not a linear relationship.

    Comment by Chris Colose — 30 Nov 2009 @ 2:53 PM

  71. Thanks and congratulations for the lectures.
    Is there a possibility to post them in audio format (.mp3) so to learn while driving (or this will be too… dangerous)

    [Response: I’ve posted audio files at*.mp3 where * is 1 2 3 … 23. I’m working on getting them plus the video files onto itunes U, also. David]

    Comment by Panos Giannopoulos — 30 Nov 2009 @ 4:41 PM

  72. Thank all who answered my questions. I am sure things will clarify themselves as I proceed. One thing I reminded myself of is that the earth radiates at all times of the day in all directions. I also reminded myself that liquid water qualifies as what is referred to as “condensed matter” in the lectures.

    Comment by HankHenry — 30 Nov 2009 @ 11:01 PM

  73. The claim that the Earths’ atmosphere adds 33 degrees to the temperature of the Earth is based on the fact that calculating the temperature, without an atmosphere, gives a temperature 33 degerees below the observed value. The assumption is made that this gap of 33 degrees is due to the greenhouse effect of the atmosphere. However, when I try to calculate the surface temperature of the moon or Mercury I get the wrong answer and there is no atmosphere to blame the discepancy on. Whats going on here? Why should we use a model for Earth when it doesn’t work for bodies with longer rotation periods? The model appears to ignore th flux into the ground during day and out of it during the night.

    Comment by Michael Chisnall — 1 Dec 2009 @ 2:27 AM

  74. David, thanks a lot that is an awesome research and thanks for keeping the videos, It is definitely so much help. Please do let us know what add on is needed to download the remaining videos.

    Comment by dsi r4 — 1 Dec 2009 @ 2:30 AM

  75. HankHenry,

    Yes, a slowly spinning planet is hotter than a fast-spinning one, at least on the day side. I’m not sure how the average works out.

    The sunlight falling on a planet is

    pi R^2 S (1 – A)

    where R is the planet’s radius
    S is the Solar constant, and
    A is the planet’s albedo.

    The IR radiated by a planet, which in the long run must equal the input, is

    4 pi R^2

    Where Fe is the IR luminosity at the top of the atmosphere — Fe = sigma Te^4 where sigma is the Stefan Boltzmann constant and Te the radiative equilibrium temperature. Solving for Te,

    Te = [S (1 – A) / (4 sigma)] ^ 0.25

    For Earth, S = 1366.1 watts per square meter, A = 0.306, and sigma is 5.6704 x 10^-8 W/m^2/K^4, so Te works out at 254 K.

    But if Earth rotates slowly, it effectively radiates only from the dayside — from 2 pi R^2 instead of the 4 pi R^2 you’d expect from a sphere. So the equation becomes:

    Te = [S (1 – A) / (2 sigma)] ^ 0.25

    And Te becomes 302 K, higher by 48 K. But, of course, that’s for the day side.

    The equation for the temperature of the night side of a slowly-rotating planet is left as an exercise for the reader. Hint — it’s a function of elapsed time.

    Comment by Barton Paul Levenson — 1 Dec 2009 @ 7:03 AM

  76. I wonder if there are any models that attempt to match a typical day at such and such a location and at such and such a time of the year. It would be a great test of a model if you could show it matching peak temperatures after noon in the way a real typical day happens.

    It would go a long way toward convincing people on the legitimacy of models.

    Comment by HankHenry — 1 Dec 2009 @ 12:12 PM

  77. Whoops! I got that wrong. That would apply only to a tidally locked planet that kept one face always toward its sun. A slowly rotating planet would bring more warm land under the night sky from the day side, continuously, providing more energy to radiate away. Some equilibrium would be reached (on average). And I imagine the nightside temperature would be highest near one (new, dusk) terminator and lowest near the other (old, dawn) terminator.

    Comment by Barton Paul Levenson — 1 Dec 2009 @ 12:37 PM

  78. I wonder if you would care to add this link to your Climate Diagnosis post —
    The Copenhagen Diagnosis references
    Posted by Ari Jokimäki on November 28, 2009
    This is a linklist to the abstracts and full texts of the papers referenced in The Copenhagen Diagnosis, an update to the IPCC AR4.

    Comment by dz alexander — 1 Dec 2009 @ 1:32 PM

  79. Thank you SO much Dr. Archer for these videos! I can’t wait to start watching them. As an environmental studies/biology major with a strong passion for this subject, I wish my small university would offer a course along these lines!

    Although I’ve been able to download the videos, it appears that the links on your page are not working.

    Any advice?

    Comment by Cameron Holland — 1 Dec 2009 @ 6:52 PM

  80. Thanks a lot, I will take a look. I am teaching a non-majors course as well, but want to start a majors level class. This will be a good resource.

    Comment by Jeff Johansen — 2 Dec 2009 @ 11:23 AM

  81. Dr Archer, I’m a moderator on the ClimatePrediction distributed computing forums and hope you don’t mind that I’ve posted a link to your lectures in the forum News and Announcements section. If you want to look at what I said, the home page is here: and the News here:

    Thank you for making this course available.

    Comment by Maureen Vilar — 2 Dec 2009 @ 11:34 PM

  82. Thanks for your reply (68), I’ve progressed to lecture 10 (or so) where you do address my earlier question.

    If I’m allowed a follow up, another confusion for me was when you introduced the idea of a frequency of light needing to equal the frequency of a particular vibration in a CO2 molecule. I was with you until you specified a specific n/cm and left it at that. At this point I couldn’t understand how only one frequency of vibrations were allowed. Later, you produced a chart with a ‘v’ shaped trough around n, and said that the size of this trough can get bigger or smaller when CO2 concentrations change, which seems to justify my earlier assumption that the n frequency is simply the one to which that mode of CO2 vibration is most sensitive. I suggest that this be made more explicit in the lecture earlier.

    [Response: Yeah, I guess I was thinking of an oscillator that had a particular frequency, determined by the weights and springs. David]

    My question is: does the range of frequency have a limit (i.e., is there an asymptote separating the ‘v’ from the atmospheric window), or could a sufficient combination of CO2 and temperature crowd out the window?

    [Response: I’ll bet there’s no atmospheric window on Venus, but there the CO2 has condensed into a supercritical fluid. I don’t think the climate ever becomes insensitive to further increases in CO2, to Venus conditions and beyond. David]

    Comment by jhm — 3 Dec 2009 @ 8:44 AM

  83. In downloading the lectures, I’ve encountered a computer oddity: my browser (Safari) insists on opening/downloading each lecture as a text file (.txt). Of course, it then looks like gibberish, since it’s really an mp4.

    I can work around this by manually deleting the superfluous .txt suffix so that it once again has just the correct suffix (.mp4), so it’s not a huge deal. But there may be interested folks who are more put off than I am.

    Any ideas what’s causing this glitch, and how to rectify it more elegantly?

    Comment by Kevin McKinney — 3 Dec 2009 @ 10:13 AM

  84. Kevin McKinney says:
    3 December 2009 at 10:13 AM
    In downloading the lectures, I’ve encountered a computer oddity: my browser (Safari) insists on opening/downloading each lecture as a text file (.txt). Of course, it then looks like gibberish, since it’s really an mp4.

    I can work around this by manually deleting the superfluous .txt suffix so that it once again has just the correct suffix (.mp4), so it’s not a huge deal. But there may be interested folks who are more put off than I am.

    You need to load a Quicktime plugin which will then open a .mp4 file using QT automatically.

    Comment by Phil. Felton — 3 Dec 2009 @ 11:08 AM

  85. My Safari browser tried opening 8 files, with .mp4 extensions.

    It always displayed nothing but the text gibberish.

    Comment by J. Althauser — 4 Dec 2009 @ 10:16 PM

  86. J. Althauser, download them instead of opening them; then you can change the suffix as I described.

    Or try Phil’s approach, which sounds good. (And thanks for that, Phil–I’d already done the files the hard way when I first saw your message, but I appreciate the thought!) I’m thinking you’d need to open the files from QuickTime, not from the browser, but since I didn’t try it, I’m obviously no authority.

    Re the spring-and-weight oscillator simile mentioned in the inline to #82, the issue reminds me of the acoustics of resonators: the CO2 can be thought of as ‘tuned.’ Musical instruments make use of the acoustical analog to this phenomonon in a number of ways–for example, the sitar and the viola d’amore both have sympathetic strings that are not played directly, but which “ring” in response to the frequencies of other strings.

    Like the CO2 case, musical resonators usually have some “wiggle room” in the frequency match–as in that “v-shaped curve” mentioned. (That is sometimes to the discomfort of listeners in musical applications!)

    Comment by Kevin McKinney — 5 Dec 2009 @ 12:38 AM

  87. David,
    I just finished your firstlecture on heat and light and got a liitle confused toward the end on the 150,000 watts per recees.

    My understanding was 1 Kcal equals 1000 scientific calories so 3.8 Kcal equals 3800 scientific calories times, so 4.2 joules times 3800 scientific calories equals 15,960 converted to 15,960 watts. Where did I go wrong?

    It’s been quite a while since I studied at university. I started paying attention after the CRU story and I’m trying to learn. I live down here in the deep south, basically enemy country to logic and reason. Thank you very much for posting these lectures. Just curious how much does it cost a student to take your class up there? Thank you very much.

    Comment by Conrad Easley — 5 Dec 2009 @ 2:19 PM

  88. David,

    I went back and see were I made my mistake. I multiplied by 3.8 Kcal instead of 38 Kcal which equals 38000 scientific calories times 4.2 joules gives me 159,600 converted to watts per second which equals 159,600 watts which is still different than your 150,000 watts answer. I don’t see where I went wrong? I don’t mean to be a nuisance, I just want to make sure I understand the fundamentals before I proceed. Thank you very much.

    Comment by Conrad Easley — 5 Dec 2009 @ 2:39 PM

  89. Here is a suggestion.

    Every Christmas at the Royal Institution in the UK, someone is chosen to do the ‘Christmas Lectures’ for an audience of children. They were first presented by Faraday in 1825 and they have continued ever since.
    These days they are televised, they used to be on BBC, but they are now on chan Five over the Christmas holiday.

    I wonder if these lectures could be simplified and presented with demonstrations as a series of these Christmas Lectures. In the past they have presented complex subjects to children. David you seem to be be very good at presenting the information.

    It would be a very good way of getting the science across to a wider audience.

    Comment by Paul UK — 5 Dec 2009 @ 5:44 PM

  90. What does the existence of the urban heat island effect tell us about the completeness and adequacy of greenhouse gas models of heating of the atmosphere?

    [Response: Nothing. They are different processes. – gavin]

    Comment by HankHenry — 6 Dec 2009 @ 12:52 AM

  91. Dr Archer, still working on your video – who knows I may end up getting your book. I wonder if you have a reaction to the paper in this month’s Geology magazine about the response of sea organisms to elevated CO2. Unhappily I don’t have access to the original article. The researcher Anne Cohen expresses surprise (in press accounts) but to me it seems quite the expected result if one thinks of it as a fertilization of carbonate producing creatures. This could be good news in terms of the carbon cycle – but of course one wouldn’t argue it’s all good news as this would not just be environmental fertilization but probably a quite differential fertilization of the oceanic biome. My question in terms of models, which is a good part of what we are doing in this thread, is whether the models, as they now exist, are refined enough to have factors such as this possible fertilization of carbon sequestration included? Would the possible numbers involved be big enough to need to be accounted for?

    Comment by HankHenry — 7 Dec 2009 @ 11:34 AM

  92. Can’t remember which video/lecture this is, but am I right in thinking that based on the phase diagram of water vapour, when the atmospheric temperature increases, the pressure at which 100% humidity occurs increases. This means that in order for clouds/rain to form, the pressure has to be greater.

    What effect does this have on weather, winds etc?

    Comment by Paul UK — 8 Dec 2009 @ 9:52 AM

  93. David:
    Very nice. Thank you for sharing this. When I first downloaded the lectures there were additional links for the workbook and Python scripts for the programs used in the labs. As of today I no longer see the workbook or Python script links. Were these deleted intentionally or by accident? I would really like to see how a couple of these scripts work as it looks like a very good open source resource.

    Comment by steve n — 9 Dec 2009 @ 3:50 PM

  94. Dr. Archer, I am still thinking about your lectures. Thank you for your offering. An interesting comparison to make is between the earth which has an atmosphere and the moon which doesn’t. The thing that doesn’t immediately occur to the new student is that on earth we generally speak of air temperatures and take pains to measure temperatures out of direct sunlight while on the moon there is no air temperature – since there is no atmosphere. I also found an interesting article about temperature on the moon at ScienceDaily . Of particular interest was paragraphs 9 and 10 indicating there is what might be called regional climate on the moon due to differences in the heat capacity, etc. of rock.

    Comment by HankHenry — 18 Dec 2009 @ 8:38 AM

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