Very clear. Each of us who hopes to influence those around us should study these videos. It is hard to see how naysayers can dispute the science which is presented here. It is clear that these aren’t subtle matters which reasonable people can differ about.
Comment by Stephen Curran — 21 Dec 2012 @ 11:12 AM
Excellent videos. But in the second, he seems fixated on the 2 degrees of warming ahead….even though he explicitly calls it a political number not a scientific one. There is not much mentioned of 3, 4 or 5 degree possibility. However, a video submitted question: Is there a limit to warming? http://www.youtube.com/watch?v=ay5l96jZgA8 to Potsdam Institute for Climate Impact Research says the limit is unknown. And beyond 2100, that 7,8, 12 degrees C is all possible.
The notion that a painless transition to a global economy that is not too unlike the current one, using renewable energies seems highly optimistic. I wonder if this notion has been scientifically tested in any way? It seems that there is very little science done on environmental impacts of various levels of different types of renewable energy, of the availability and cost of resources needed to harness that energy and of the utility for our economies of the type of energy that renewables provide. Further to that, if all of these questions were satisfactorily answered, what would be the impact of continuing business as usual, only with different energy sources? It is not only the use of fossil fuels that has caused environmental degradation. Lastly, of course, is whether the political limit of 2 degrees makes scientific sense at all. If we are experiencing more extreme weather events (and other environmental stresses) more often, with less than 1 degree of warming, would 1.95 degrees, say, really result in a fairly stable and liveable world?
Re- Comment by Tony Weddle — 22 Dec 2012 @ 4:53 AM
Your concerns have been discussed extensively in the academic literature. You can find it if you use Google Scholar in order to eliminate the opinionated blogosphere from an internet search. Pay very close attention to the added features of this search engine to get the most from it. http://scholar.google.com/schhp?tab=vs&hl=en
“It is not only the use of fossil fuels that has caused environmental degradation.”
No, but it’s surprising, when you think about it, how many of the many facets of environmental degradation do in fact have a strong link to the use of fossil fuels. They’ve been sort of a ‘force multiplier,’ it seems to me.
That’s not to say, of course, that if you just got rid of FF use we’d be living in Utopia.
Most excellent lectures. Very useful. Very good. Very Strong.
Comment by Vendicar Decaruan — 22 Dec 2012 @ 9:25 PM
I am one of those who do not use a computer capable of running the adobe viewer although this computer can view any current video format. If html5 is used or a video is downloadable I’m on it. I can view your World in Transition interview but not the above lectures. At least I get to read your books.
Thank you for the Virtual Academy. I understand the rate of increase of atmospheric C02 is around 1.9 parts per million per year. So the rate of increase in ppm is a small number. But in round petagrams of carbon it is equivalent to a large number. What is the equivalent rate of increase in round metric tons of carbon per year? Thank you.
Yes, we have already heard on our mainstream media here in australia that acheiving the magic 2Deg threshold is now virtually impossible and that we shouldn’t be surprised to end up at the 4-5deg mark in the not too distant future. I listened to both lectures; being a climate scientist he lent a lot of cred to the presentation. It was interesting the graph of temp vs sea level rise. You can appreciate the problem we have at present having created this 40% rise in CO2 almost overnight..very very unnatural! So that the temp/sea level graph are now simultanously tracking each other. He didn’t mention either the thawing permafrost and methane hyrates in the ocean bed that as the ocean unstoppably warms will progressively get released in a more or less exponential fashion. He still rather naively (to me at least) stated that there is still a window of time at which to address CC. The arctic will be ice free in summer within 5-6 years, progressing rapidly to all the remaining 9 months of the year as the arctic ocean continues to warm. Greenland ice albedo is now in full swing, we have reached a tipping point now that ensures all the land ice will disappear probably well before the next couple of millenia. Prof. Ramsdorf still believes we have time???.
Comment by Lawrence Coleman — 23 Dec 2012 @ 1:29 AM
This is the clearest scientific explanation of Global Warming and its devastating expected impacts I have seen to date. Well done Stefan. Keep up the good work. Climate scientists are the unspoken heroes of our age.
Just watched the first lecture. Overall it was very clear, and I liked the way there was no concession to denialism alternatives. Tone was “we know” rather than “we think” or even “we are almost certain”.
The only area which I believe could have been improved was the segment on C02 effects; how the 0.7C – 0.9C predicted increase was derived.
Steve thanks for the suggestion of Google Scholar. I don’t have subscriptions that allow me to see the text of any hits I came up with though it does seem that science has addressed real world limits of renewables a little more extensively than I thought, though I still couldn’t find (looking at abstracts for the first few pages of hits since 2007) recent science that more than skims the issues. I recall a paper one or two years ago that showed environmental impacts would limit wind power but I’ve seen little for other energy sources.
Kevin, it’s true that fossil fuels have multiplied environmental degradation. This is why the decline of fossil fuels would almost certainly result in a lessening of environmental degradation but partly because that decline would entail a different way of living anyway. A reduction in fossil fuel usage means a decline in standards of living (though not, necessarily, quality of life).
Patrick, I’m not sure which particular aspect of my comment you’re trying to address with your multiple links to other comments.
In the real world, economic growth can’t go on for ever. This is a key realisation because most societies today are based on the opposite assumption and I think most scientists make the same assumption when commenting on supposed solutions to our problems. There will not always be a way to keep hold of what we have or maintain a way of life that is intrinsically unsustainable.
@17 Thank you. I’m learning my P-T-Gs. The page I was on is really about the difference between land and ocean surfaces, impacts of drought on the natural sink effect, etc. And I see that the ppm series is alarming enough without calculating in tons.
Thank you to Stefan and to everyone who helped to make the videos available. The concepts in the second video are very helpful on heat waves, drought, fires, floods, and sea-level rise–because that’s what’s in the news, and it’s not going to stop anytime soon.
For those who want to get just as little more in depth into the science, but not beyond college freshman level, David Archer, University of Chicago, has made his intro class lectures available online at http://forecast.uchicago.edu/lectures.html. His book, Understanding the Forecast, and these lectures cover the same material. (If you get the book, get the 2nd edition, the first edition has some difficulties which I suspect are fixed.)
at least in respect to differences in the world at different temperature changes. My take is that 1.95 C would not be very different from 2.0 C, unless that happens to be right near some tipping point. A large worry is that we don’t know where these tipping points are, though we are fairly certain they exist.
There is more than enough fossil carbon in the ground to drive us past 6 degrees of warming. That much warming (and likely less) pretty much means a crash in human population. Beyond the crash, it starts to matter less what would happen under continued BAU for two reasons: There won’t be many people left, and BAU will be at an end anyway. I’m not sure what possible economic price would not be worth paying to avoid that future.
The elegance of a good climate presentation is invaluable to us all. It shows the robustness and strong stature of this science.
About Greenland point of no return with respect to it melting continuously. The 3 km height mentioned is in fact much lower on its sides , exactly where the greatest melting and calving occurs. Need to point out that moulins seem to exist there, where 1000 meter heights can be close to 0 C at times in the dead of winter.
The warmer air warms the ice by conduction, additionally water going down from top moulins may also warm the sides from within, twinned with warmer lower troposphere surrounding the lower levels, the combination may increase the melting rate more than expected.
Re- Comment by Tony Weddle — 25 Dec 2012 @ 4:29 PM
Tony, I don’t have access to a university library anymore so that publisher paywalls are very annoying for me as well. However, Scholar is a tool that requires some work to learn so don’t give up. You had many questions and they should be broken down into separate searches. For example, from the first two sentences of your 22 Dec 2012 @ 4:53 AM post I decided on “renewable energy future” (without the quotes) for an initial search term and got the following- http://scholar.google.com/scholar?hl=en&q=renewable+energy+future&btnG=&as_sdt=1%2C5
The first hit- “A realizable renewable….” has a full text PDF provided by a university. Look for this. This paper is a little old, but notice that you can refine your search by clicking “Related articles” or looking at the “Cited by” link to see newer research that had a reason to cite the paper.
The second item- “Ethanol for a sustainable….” is not available, but if you click the “All 20 versions” link you will find several sources that provide full text. The fourth hit has a university PDF link available.
If you can’t find a free full text article, try pasting the entire title (within quotes) into regular Google (or your favorite search engine) and you may find an advocacy or author site that has a full text download. In general, pick up search terms and author names for searching from abstracts and use the “Advanced search” form for focus. Steve
i just watched the first video. very nicely done. i liked the quotes by von Humboldt and Tyndall – i emphasize to my students just how long the climate system has been studied and continuously point out that CO2 physics is really well-understood. one thing i’m always looking for in regards to teaching material are animations. Stefan: is the animation based on the Ganopolski et al 2010 paper and shown at 8m45s in your video lecture 1 available for download? also is the animation at 30m00s (lecture 1) available for download? re: #26, thanks for the links!
Thank you very much for such an initiative, Mr Rahmstorf.
Your involvement is to be congratulated. I wish this lesson could be largely shared and hope to see again such summaries throughout the climate monitoring process.
Great videos, thanks for posting them. I’m a bit late getting to this, but I was hoping I could ask a question to see if I can get a back-of-the-envelope understanding of the beginning of the presentation. If I look at slide #6 of the first video (~5 minutes in), then I see that at the Earth’s surface and at the TOA the energy fluxes exactly balance. If that were true however, then there would be no problem — no need for further warming of the Earth’s surface since the fluxes are equal.
Since the fluxes are given to the nearest W/m2, and Stefan said that these are measured quantities, I’m going to assume that the energy imbalance — that we know has to be there — is on the order of something less than 0.5 W/m2. That is, the back radiation has to be something like <342.5 W/m2 which is then rounded to 342 in the diagram. Is this correct?
If I then apply the SB equation to the 390 W/m2 outgoing radiation, that gives me a surface temperature ~ 288 K. Not a bad result. If I then estimate how much additional warming I need to make up the 0.5 W/m2 imbalance that I am assuming, then I need an additional 0.09 K. Is this about right? Like I said, I'm interesting in a BOTE estimate, not a solution to the radiation transfer equations. Thanks!
Keep in mind that the surface budget is not just determined radiatively, but also by the evaporation and sensible heating fluxes, which also change in a new climate. More importantly, it isn’t just the surface that is adjusting its outgoing radiation to the increased CO2, but the entire troposphere, and most of that radiation is emanating from the high atmosphere. It is inconsistent to treat the surface in isolation while leaving the atmospheric state unchanged.
Thus, for a well-coupled convecting troposphere, one defines the climate sensitivity (in the absence of feedback) as 1/[d(SB)/dT] = 1/(4*sigma*T^3), where T in this case is actually the emission temperature of the planet where infrared radiation leaks out to space (analogous to the photosphere of the sun, where eventually the outer layers of the sun become optically thin to visible radiation, and allow that energy to escape to space), not the surface temperature. But the remaining heating in the pipeline is proportional to the system’s climate sensitivity, since the planet is less efficient at adjusting to radiation balance in a highly sensitivity system. In the most extreme case, you can draw a horizontal line in a plane of outgoing radiation vs. surface temperature, and you can actually have a sustained imbalance while surface temperature rises without bound.
Thanks very much for the replies. I read the Graeme Stephens paper which puts the energy imbalance at 0.6 W/m2. I find this a bit disconcerting because it is very close to my guess, which I came to merely by considering the round-off error in the video graphic.
I understand that the process is a lot more complicated then my simple calculation. However, if 0.6 W/m2 is the imbalance then to correct this imbalance, the Earth has to warm 0.1K if I take T = 288K at the ground or 0.2K if I take T = 228 (6C/km lapse rate for 10 km). If this isn’t the right answer, what is? What am I missing here?