This is an archive of a discussion that was originally in the Open Physics and Astronomy forum of the vU3A
at 1:07 pm on Feb 17, 2010
It should be possible, in theory at least, to set up a ring of satellites circling the equator, to cut off enough sunlight to cancel global warming and stop the icebergs from melting.
at 10:21 pm on Feb 17, 2010
I do not think that grandiose high tech solutions are a sensible approach. The real solution will only come with living with the changes, moving steadily to a sustainable lifestyle which avoids the use of fossil fuels, accepting globally the real problem, which is overpopulation and working hard to solve in a humane way. If we fail to do this evolution will step in and do it in a way that may destroy most of our society after which we may have to spend a thousand years trying to rebuild it with far fewer resources. Look at the history of the natives on Easter Island to see a frightening example of what will happen.
at 8:39 pm on Feb 19, 2010
In the short term of 100 years or so we have to do much more than is proposed for cutting the production of carbon dioxide. The melting of icebergs is already taking place and if things are left with only the proposed reduction in carbon dioxide production, the low-lying countries are going to be inundated. If you do not want to partially shield us from the sun, then we must find some way of removing carbon dioxide from the atmosphere – planting lots of trees would help. To stop further production of carbon dioxide the immediate solution is the use of electricity produced from uranium. The problem of radioactive waste could possibly be solved by loading it into rockets and shooting them into the sun. Ultimately the scientists will no doubt find a way of controlling the hydrogen nuclear reaction to produce heat and hence electricity.
at 8:48 pm on Feb 19, 2010
I agree with your predictions of climate change but we will have to live with them. It will take great patience and forbearing to avoid major wars. We will have to use our scarce resources to develop our lifestyle rather than spend great time, efforts and fuel in putting stuff into space. I say this honestly as a great space enthusiast. If I thought that doing it could be worthwhile I would agree with you but it would not make much difference in the requirement that we live with a sustainable population in a sustainable way. These are problems enough.
at 3:57 pm on Mar 3, 2010
Ian, what do you make of this? It’s taken from a letter by a certain James Farquhar CChem FRSC in the NEWS magazine of the Royal Society of Chemistry. “…….A study of the properties of carbon dioxide, and in particular it’s infra red spectrum, certainly suggests that an increase in the concentration of this gas in the world’s atmosphere will result in an increase in temperature. Carbon dioxide concentrations are undoubtedly increasing…..and so the qualitative statement, that this will raise the temperature, is correct.
It is when the scientists attempt to define a quantitative relationship between the two parameters that the theory breaks down. Actual measurements of world temperatures and the measurement of temperatures in distant locations out into our solar system and far from the earth’s influence, confirm that natural changes in radiation from the sun are overwhelmingly greater than any change resulting from carbon dioxide, which is probably infinitesimal. That is why ice and snow can and are increasing in the polar regions in spite of increases in atmospheric carbon dioxide…….”
It will be interesting to see if there are any replies to this in next month’s issue.
at 12:09 am on Mar 4, 2010
I personally see these arguments as largely pointless and motivated mostly by greed and commercial interests and aimed at discrediting the bulk of the scientific evidence. I therefore ignore them.
at 2:57 pm on Mar 4, 2010
I have for some time vaguely wondered whether the narrow absorption bands of CO2 in relation to the broad black body radiation at room temperature would prevent it from having a marked effect on global warming. This article has prompted me to look on the internet. There are of course many references. The following (http://www.nov55.com/ntyg.html) gives the absorption spectrum of CO2 and the emission spectrum of black body radiation at room temperature. Without spending a lot of time looking at all the evidence, I think I shall have to keep an open mind.
at 10:07 pm on Mar 4, 2010
Please bear in mind if you are a climate change skeptic that there is absolutely no reason why the bulk of the scientific community would wish to be alarmist about the prospects but there are very many good reasons why established industries with a big involvement in climate change effects would wish to discredit the evidence. My personal experience of selling innovation into industry throughout my entire working life is that they are totally averse to change and will go to ANY lengths to prevent it until the situation has become totally unavoidable. I KID YOU NOT!!!
at 8:25 am on Mar 5, 2010
What is the ' broad black body radiation'?
at 11:08 am on Mar 5, 2010
Sorry Kate. I should have said "broad spectrum of black body radiation".
at 1:11 pm on Mar 5, 2010
Kate, here in more detail is what I was referring to. All solid bodies emit heat (and also light if they are hot enough), the amount depending on the temperature. Black bodies emit the most. The spectrum of the emission is very broad, covering a very wide range of wavelengths. In contrast, the absorption of carbon dioxide gas occurs only in three narrow bands of wavelengths, and thus the proportion of the heat from the earth that can be absorbed by the carbon dioxide is limited, no matter how much carbon dioxide is present in the atmosphere. This does not mean that there can be no global warming from carbon dioxide, but simply that this is one factor limiting it.
at 7:24 pm on Mar 5, 2010
Thanks Allen, but what is a 'black body'?
at 11:53 pm on Mar 5, 2010
Kate, if the end of a poker were covered with soot, it would be a « black body », and if it were hot it would emit more heat than any other colour, e.g. a shiny yellow poker, at the same temperature.
at 12:00 am on Mar 7, 2010
Black body radiation. A back body is just a way of describing something that is a perfect radiator at the temperature. the opposite would be a perfect mirror which just reflects all the energy falling on it.
As Allen says all material bodies in the universe emit electromagnetic radiation (this includes light and heat) dependant on the temperature that they are at. This radiation is produced by the atoms and molecules "jostling together" for very cold bodies (like the cosmic background radiation) this is at radio frequencies for room temperature bodies this is in the infra red (what we percieve as heat) for hot bodies like fires and the sun it is in the form of light and extemely hot bodies like nuclear explosions and the internals of stars this is in the form of gamma radiation.
The frequencies absorbed by carbon dioxide are those of room temperature radiation given off by the earth so it cannot escape into space whereas the energy coming in from the sun id in the form of light which is not absorbed by carbon dioxide.
this process is similar to the effect of glass in a greenhouse which lets in the light but does not let out the heat. that is why the process is called the greenhouse effect. The radiation balance of the earth is very fine and it does not require a great deal of change between input and output to have a significant change in the earth's climate. so even a small amount of change in carbon dioxide is significant and the increase in carbon dioxide in the atmosphere over the last 50 years has been quite substantial
at 11:19 am on Mar 9, 2010
Ian, I hope you don't mind if I correct the first sentence of your final paragraph. "The frequencies absorbed by carbon dioxide are only a small proportion of all those frequencies given off by the earth at room temperature"
at 7:21 pm on Mar 9, 2010
I agree that they are a long way from being the total room temperature radiation but they are a significant proportion and plenty enough to cause the greenhouse effect. There are much more effective gases than carbon dioxide (notably methane). note for any body isolated in the vacuum of space near to a significant source of radiation i.e. a star the radiative balance is a very critical temperature control.
It is interesting to note also how big an effect other minor energy sources can have on planetary temperatures notably the radioactive heating that is keeping the centre of the earth molten and the tidal friction heating up the moons of Jupiter and Saturn this latter effect was not suspected until the voyager space probes showed how hot Io was.
at 7:45 pm on Mar 9, 2010
Ian, have you thought about this? The human race is putting out enormous amounts of heat into the atmosphere compared with 150 years ago. Isn't this alone enough to produce the global warming?
at 12:46 am on Mar 10, 2010
The energy inputs of civilisation do warm up our city centres by noticeable amounts and this has been observed for more than 50 years but the total energy input is not really significant on a global scale however the combustion products and the methane outputs of increased cattle rearing do cause global warming
at 5:38 am on Mar 10, 2010
Ian, surely methane gas is produced by all animal life, including humans. Is the increase in cattle rearing not offset by the decrease in our wildlife? For example the once vast herds of bison that roamed the Earth.
at 9:48 am on Mar 10, 2010
It is not considered that they balance and cattle are particularly good at producing methane. Many vast areas that had few indigenous large grazers are now given over to large herds of cattle for human consumption.
at 9:54 am on Mar 10, 2010
If you want to look at some really well worked pages on climate study go to the U3A works page
http://u3aclimatestudy.pbworks.com/FrontPage
This really shows what can be done with a small team working to produce a study workspace using PB works.
at 7:04 pm on Mar 10, 2010
Ian, what evidence do you have for saying that in answer to my last question? I would have thought thatthe direct transfer of the heat into the atmosphere would have had a far greater effect than the narrow bands of frequencies of absorption by carbon dioxide compared with the very wide band of frequencies emitted by a black body.
at 7:47 pm on Mar 10, 2010
Watched the Horizon cosmology programme last night on Deep Flow. Think probably this is a step to far for me to grasp! It would seem that, as with much science, there is still so much to discover and understand. One of the things that intrigued me was the creating of maths equations to explain the theory. Is everything reduced to elegant but abstruse equations, only understood by few cosmic mathematicians.?
at 11:41 pm on Mar 10, 2010
Allen the absoption spectrum of carbon dioxide is not a narrow frequency line but a broad swathe of frequencues because of the many modes of vibration of the molecule
This graph shows how this fits with the thermal radiation of the earth. It effectively prevents a broad band of frequencies near the peak of energy escaping.
http://lasp.colorado.edu/~bagenal/1010/graphics/earth_ir_emission.gif
Whilst researching this I noted that a search on this topic turned up a lot of pseudo scientific pages suggesting that carbon dioxide could not contribute to global warming. These were using incorrect arguments. Have you been reading these pages? this is one of the problems of looking up stuff on the web there are a lot of very bad pages and downright lies out there and it can be very difficult to recognise genuine information from rubbish unless you have a lot of background knowledge already.
at 11:47 pm on Mar 10, 2010
Rosemary. I too watched this programme and found it quite interesting if a bit glib, big on wow factor and thin on clear explanations (in common with many science programmes nowadays)
It is very true that precise mathematical modelling of all science processes is essential nowadays and it is frequently absolutely amazing how precise this modelling is. The deviations that are causing concern are frequently very small in the general picture of things but this is how discoveries are made. Most people just do not realise how precisely many of these things are understood.
at 12:03 am on Mar 11, 2010
Ian, I beg to differ. The graph does not show the CO2 absorption fitting the thermal radiationfrom the earth. The line is the emision from a black body at earth temperature, the earth emission is the dark broad area, and the sharp peak is one of the absorption bands of CO2.
at 12:50 am on Mar 11, 2010
Sorry Ian, I think I had misread the graph. It seems to indicate that CO2 absorbs strongly at about 20 - 25% of the wavelengths.
at 2:47 pm on Mar 11, 2010
Ian, the absorption spectrum of co2 shown in this reference (http:/www.nov55.com/ntyg.html) is more like the one I remembered. It would mean that the co2 in the atmosphere has already absorbed all it can, which would be about 8% of black body radiation.
at 11:58 pm on Mar 11, 2010
The reference you are quoting is one of those top level sites that I quoted above that uses bad reasoning and is NOT a valid argument. This is not true. The infra red spectrum of a multi atomic gas has many elements in it some of which are very weak and the spectrum absorption is NOT saturated at all. Increases in carbon dioxide WILL result in increases in the retention of energy. Also a I said above the temperature of the earth is very sensitive to this parameter. You are being captured by the forces that are trying to deny a process that has been proved by physics and calibrated by previous changes of carbon dioxide and global temperature measurements
at 11:17 am on Mar 12, 2010
Nonsense Ian. Co2 has three vibrational modes.
at 3:18 pm on Mar 12, 2010
Ian, I should have said "when the co2 has absorbed all it can". I am prepared to look at ALL the evidence and judge which makes sense. The possibility of global warming does not necessarily have to rely on the absorption of co2 itself. For example, has anyone looked into the possibility of carbonic acid formation in a moist atmosphere?
at 12:09 am on Mar 13, 2010
You are missing the point. multi atomic atoms have various vibrational and rotational modes of oscillation but within these modes there can be very many discrete quantum energy levels with different probabilities of excitation. so the absorption pattern is very complex and almost continuous.
I agree that one should look at all the evidence. to my mind the strongest is the correlation between general global temperatures as measured by isotope ratios and the carbon dioxide levels in fossil atmosphere samples.
carbonic acid is just carbon dioxide dissolved in water. What is significant about this? it would be bound to occur.
at 8:33 am on Mar 13, 2010
Interesting discussion - but you lost me some days ago,,,,,,,,!
at 10:37 am on Mar 13, 2010
Allen can we step back from this detailed discussion for a moment. Could you give me a brief statement of your background thinking on the subject of man made and natural climate change and explain to me why you appear to be searching hard to prove the main stream scientific opinion incorrect.
Simply stated my opinions are as follows:
1. A complex society tends to require stable conditions for its successful operation and these are currently based on heavy fossil fuel usage
2. Natural climate change occurs and it is essential that a long lived complex society is capable of accommodating these changes.
3. There is a strong correlation between global temperature and the quantity of carbon dioxide in the atmosphere over millions of years.
4 There are good scientific reasons related to infra red absorption why this should be.
5. Mankind's use of fossil fuels has increased the level of carbon dioxide in the atmosphere by a significant amount in our lifetimes.
6. fossil fuels are a limited resource and mankind will have to eventually stop using them.
Conclusion it is essential for mankind to develop resilience to climate change and develop a non fossil fuel dependant society of a sustainable population density.
Failure to do this through agreement will result in warfare and a serious degradation of this planet's resources and the long term damage to human society. this will mean that the next cycle of human development will have to contend with a severely damaged planet.
We already have an example of this process having taken place on the earth in an isolated population on Easter Island
at 11:32 am on Mar 13, 2010
Until we started discussing it I had accepted the generally held conclusion that global warming is due to co2 absorption. It's only now, since we started discussing it that I am not so sure. I agree that there is global warming but I am not convinced of the cause. I cannot agree with your point no.4 without derailed study of ALL the relevant measurements.
at 3:16 pm on Mar 14, 2010
Ian, here is another paper that presents good arguments that further emission of CO2 would have little effect on global warming:
http://brneurosci.org/co2.html
at 6:48 pm on Mar 14, 2010
That is a substantial article and will take some reading and I have not the time available at the moment. The general opinion on global warming has been that carbon dioxide is a big player and I have been aware of this since I was a teenager long before it was considered significant. It will take a lot of convincing for me to accept the argument of one person in particular one who does not give me his background interests and support.
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