| Forum Home | ||||
| PC World Chat | ||||
| Thread ID: 140464 | 2015-10-16 19:47:00 | Global Warming | jayal (1291) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 1410072 | 2015-10-24 07:03:00 | I agree - playing with the numbers for atmospheric CO2 is a good idea. You argue that 400ppm is a very low ratio, and in absolute terms I would agree. But I want to look at the figures in a different way, using some very rough calculations that are not exact but should show the order of magnitude of the effects we argue about. The density of air at "standard conditions" is about 1.2kg/m^3 (thats per cubic meter - I haven't figured out how to do superscripts here). At 400ppm of CO2, that corresponds to about 0.2 micrograms of carbon per cc, with the carbon in the form of CO2 gas molecules. Plug in Avogadro's Number and you get near enough to 10^16 CO2 molecules per cc of air. The very small number we started with no looks a bit bigger. Now my calculation gets very hairy indeed and any physical chemist will wince, but the point remains valid. The bond length of the CO2 molecule is of the order of a couple of Angstrom units, and for my purpose I will treat it as a radius. So the geometric cross-section area of one molecule is of the order of 13x10^-16 cm^2. Now, if we project all the CO2 molecules in 1 cc (10^16) against on face of the 1cm cube, we see that their areas will overlap. This means that a ray passing through the cube is almost guaranteed to intercept at least one CO2 molecule, and that's for only 1cm path length - we have kilometres available. Replace the ray by a photon of thermal radiation with a wavelength corresponding to an absorption band in CO2. The photon has a good probability of being absorbed (remember that the oxygen & nitrogen are pretty well invisible to such a photon). It gives its energy to the molecule, which then begins vibrating and/or rotating. The CO2 may re-emit the photon, which can set off in any direction, or, more likely the CO2 will collide with another gas molecule, almost certainly nitrogen or oxygen. The result is like what happens when you toss a pingpong ball into a rotating fan - it comes out faster than it went in. The excitation energy of the CO2 molecule is transferred into kinetic energy of the colliding molecule and it bangs into neighbouring molecule, passing on some of its energy. But this increase in kinetic energy of the gas molecules is simply what we call heat. A chemist might say that CO2 acts as a catalyst to convert radiant energy into heat. The amount of energy involved in a single event like this is minuscule, but we have a huge number of molecules available. OK, B.M., I've left enough wriggle room here for you to find all sorts of objections (I don't doubt your ingenuity), but I just want to show that because a number looks small, it doesn't mean it's insignificant. Oh, yes, your comment about 0.8 degrees rise in 135 years is a red herring - the accelerated rise dates from the mid-20th century. Rising and falling 20C in a day - oh, come now, you know better than that. Excellent, at last a mathematician! But while I’m absorbing and considering your post, could you please pop back to post 67 and confirm or deny what old Ivar Giaver concluded from Llam Samson’s puzzle? Thanks. :) (It's bugging me) |
B.M. (505) | ||
| 1410073 | 2015-10-25 04:43:00 | Excellent, at last a mathematician! But while I’m absorbing and considering your post, could you please pop back to post 67 and confirm or deny what old Ivar Giaver concluded from Llam Samson’s puzzle? Thanks. :) (It's bugging me) Damn. I put together a reply, took too long, the system logged me out and I lost everything I wrote. I'll try again shortly - sorry about that. |
Jayess64 (8703) | ||
| 1410074 | 2015-10-25 06:19:00 | Exxon Researched Climate Change in 1977: www.youtube.com |
zqwerty (97) | ||
| 1410075 | 2015-10-25 09:45:00 | Excellent, at last a mathematician! But while I’m absorbing and considering your post, could you please pop back to post 67 and confirm or deny what old Ivar Giaver concluded from Llam Samson’s puzzle? Thanks. :) (It's bugging me) Ivar Giaever shared the 1973 Nobel Prize with John Bardeen and Brian Josephson for work in solid state physics. Nobels are not handed out lightly and we can take it that Giaever deserved his award. But being an expert in one area does not make you right everywhere else, and Giaever's somewhat rambling address last July gives the impression of someone who is rather out of his depth. He starts by saying that when he first heard of global warming he spent a day on Google and was horrified by what he found. Near the end of his talk he describes a demonstration of how a single match burnt in room "the size of a large living room" produces the same CO2 concentration as all the worlds motor vehicles in one year. The point of this is not at all clear, but it looked like a fun exercise. I took a match from a box we have in the house and measured it. It was 43mm x 2mm x 2mm, so it has a volume of 0.172cc. The next thing was to weigh it, but kitchen scales aren't much good for something this small, so I dropped it in a glass of water. It floated (of course), but the top surface barely broke the surface of the water, so I took the density as 1gm/cc, giving a weight of 0.17gm. Now I needed the proportion of carbon in wood, and as far as I can find it appears to be pretty close to 50% by weight. So I have about 0.1gm of carbon - one decimal place is enough here. Our friend's room is 20ft x 20ft x 10ft which I calculate as 1.1x10^8cc. I assume that burning the match converts all the carbon to CO2 gas. Each CO2 molecule contains just 1 carbon atom, so multiply the carbon weight by Avogadro's number and divide by 12 to get the number of atoms and hence the number of CO2 molecules. I get 5.0x10^21 molecules. To get the concentration of CO2 in the room, divide the number of molecules by the room volume, which gives 4.6x10^13 molecules/cc. The original question was, how many matches must be burnt in the room to get the same CO2 concentration as produced by driving cars for one year. More interesting is to find how many matches are required produce the same concentration as in the atmosphere. In my previous post I got the atmospheric concentration corresponding to 400ppm to be 10^16 molecules/cc. So the answer to the question is 10^16 divided by 4.6x10^13, which my calculator shows to be 220 matches. Of course, it depends on the size of the matches. The real question is, so what? The issue here is not burning matches in sealed rooms, but how much atmospheric CO2 will cause a significant increase in the temperature of the atmosphere. With no CO2 the earth is unliveable; just under 300ppm gives the conditions under which human society evolved and to which it has adapted, and that adaptation has taken place over thousands of years. Above 400ppm those conditions will change in a number of ways, some of which can be predicted and others can't. That is where the debate should be focussed, not on whether CO2 can cause warming - it can. Not on whether the CO2 concentration is rising - it is. Not on whether the temperature of the atmosphere and oceans is rising - it is. |
Jayess64 (8703) | ||
| 1410076 | 2015-10-25 19:30:00 | Ivar Giaever shared the 1973 Nobel Prize with John Bardeen and Brian Josephson for work in solid state physics. Nobels are not handed out lightly and we can take it that Giaever deserved his award. But being an expert in one area does not make you right everywhere else, and Giaever's somewhat rambling address last July gives the impression of someone who is rather out of his depth. He starts by saying that when he first heard of global warming he spent a day on Google and was horrified by what he found. Near the end of his talk he describes a demonstration of how a single match burnt in room "the size of a large living room" produces the same CO2 concentration as all the worlds motor vehicles in one year. The point of this is not at all clear, but it looked like a fun exercise. I took a match from a box we have in the house and measured it. It was 43mm x 2mm x 2mm, so it has a volume of 0.172cc. The next thing was to weigh it, but kitchen scales aren't much good for something this small, so I dropped it in a glass of water. It floated (of course), but the top surface barely broke the surface of the water, so I took the density as 1gm/cc, giving a weight of 0.17gm. Now I needed the proportion of carbon in wood, and as far as I can find it appears to be pretty close to 50% by weight. So I have about 0.1gm of carbon - one decimal place is enough here. Our friend's room is 20ft x 20ft x 10ft which I calculate as 1.1x10^8cc. I assume that burning the match converts all the carbon to CO2 gas. Each CO2 molecule contains just 1 carbon atom, so multiply the carbon weight by Avogadro's number and divide by 12 to get the number of atoms and hence the number of CO2 molecules. I get 5.0x10^21 molecules. To get the concentration of CO2 in the room, divide the number of molecules by the room volume, which gives 4.6x10^13 molecules/cc. The original question was, how many matches must be burnt in the room to get the same CO2 concentration as produced by driving cars for one year. More interesting is to find how many matches are required produce the same concentration as in the atmosphere. In my previous post I got the atmospheric concentration corresponding to 400ppm to be 10^16 molecules/cc. So the answer to the question is 10^16 divided by 4.6x10^13, which my calculator shows to be 220 matches. Of course, it depends on the size of the matches. The real question is, so what? The issue here is not burning matches in sealed rooms, but how much atmospheric CO2 will cause a significant increase in the temperature of the atmosphere. With no CO2 the earth is unliveable; just under 300ppm gives the conditions under which human society evolved and to which it has adapted, and that adaptation has taken place over thousands of years. Above 400ppm those conditions will change in a number of ways, some of which can be predicted and others can't. That is where the debate should be focussed, not on whether CO2 can cause warming - it can. Not on whether the CO2 concentration is rising - it is. Not on whether the temperature of the atmosphere and oceans is rising - it is. Not according to the ostriches they think nothing is changing and so we should do nothing. |
gary67 (56) | ||
| 1410077 | 2015-10-25 20:50:00 | Exxon Researched Climate Change in 1977: www.youtube.com Another interesting bit of propaganda of which there is no shortage on the Internet. However, this lot fell at the first fence with their Introduction. “Exxron Researched Climate Change in 1977”. Well the problem with that is the term “Climate Change” didn’t come about until post November 2009 when Climategate was exposed and Global Warming found to be a figment of the imagination. It seems the Spin Doctors figured “Global Warming” was out and “Climate Change” couldn’t be denied. 6789 What they didn’t count on was that even the average person realised the climate was changing and had been for millions of years, so it got treated by many as a non-event, which appears to be the case. However, not to be outdone the Alarmists then pushed for another name change, this time to “Global Climate Disruption” but that hasn’t really caught on yet. So it looks to me like the story of The Farmer and his Dog. “I’ve changed the damn dogs name three times and it still can’t round up stock”. :) |
B.M. (505) | ||
| 1410078 | 2015-10-25 20:55:00 | B.M., you dismiss the work of Michael Mann, Professor of Meteorology at Penn State University in you forum signature. Have you read any of his work on global warming? | rumpty (2863) | ||
| 1410079 | 2015-10-25 21:06:00 | Not according to the ostriches they think nothing is changing and so we should do nothing. What Ostriches? Are they to be found HERE (http://www.brooksanctuary.org/) |
B.M. (505) | ||
| 1410080 | 2015-10-25 21:11:00 | B.M., you dismiss the work of Michael Mann, Professor of Meteorology at Penn State University in you forum signature. Have you read any of his work on global warming? Yes, and found he manufactures faulty Hockey Sticks. :) |
B.M. (505) | ||
| 1410081 | 2015-10-25 21:44:00 | Plant more trees turn the world back into a forest problem mostly resolved Apart from having to live in a tree !! |
Cicero (40) | ||
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | |||||