I video-taped and posted all the lectures from my Global Warming class this quarter. The class is part of our core science curriculum for non-science majors at the University of Chicago, and interest has been strong enough that the class has kind of taken over my teaching life. The lectures are based on my textbook, Understanding the Forecast, written for the class a few years ago. The students found it useful, I think, to be able to skip lectures and watch them later, but mostly I taped them for y’all, thinking someone might them useful. cheers, David.
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.
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.
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]
It is very easy to download them
Just use this url
http://mindonline.uchicago.edu/media/psd/geophys/PHSC_13400_fall2009/lectureXX.m4v
And replace XX with the number of the lecture.
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.
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 http://www.downloadhelper.net/install.php
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.
http://www.downloadhelper.net/conversion-manual.php
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.
These would go well on iTunes U, format is right and size is typic al for them. Remove this post if redundant.
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]
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]
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]
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]
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.
I’m to Lecture 7. Are you entertaining questions about the material?
[Response: Fire away. David]
@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.
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?
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]
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]
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.
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…
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.
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)
thanks
Panos
[Response: I’ve posted audio files at http://geosci.uchicago.edu/~archer/audio/lecture*.mp3 where * is 1 2 3 … 23. I’m working on getting them plus the video files onto itunes U, also. David]
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.
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.
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.
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.
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.
http://www.physicalgeography.net/fundamentals/7l.html
It would go a long way toward convincing people on the legitimacy of models.
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.
I wonder if you would care to add this link to your Climate Diagnosis post —
http://agwobserver.wordpress.com/2009/11/28/the-copenhagen-diagnosis-references/
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.
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?
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.
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: http://climateprediction.net/board/index.php and the News here: http://climateprediction.net/board/viewtopic.php?f=36&p=86647#p86647.
Thank you for making this course available.
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]
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?
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.
My Safari browser tried opening 8 files, with .mp4 extensions.
It always displayed nothing but the text gibberish.
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!)
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.
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.
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.
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]
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?
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?
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.
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 http://www.sciencedaily.com/releases/2009/09/090917191609.htm . 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.