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quote: Originally posted by Roger58:
you would surely want to participate in an effort to illustrate this
I don't see any usefulness in your sheet of glass analogy, I think it is actually just confusing you. quote: For anything NOT to be perfect (or as close to perfect as it is possible), there must be an idea of what that perfection is
Not true - I can know that I don't enjoy my job without knowing what job would be perfect for me. In climate terms, the optimum would be a climate that never changes but in a dynamic system like the earth that is (as far as we know) impossible. There is no CO2 level that you could magically change to today and not have the climate continue to change. quote: It strikes me that the whole CO2/climate change debate is lacking that measure at the moment and this is why it is so chaotic and attracts so much scepticism.
Because anti-scientists like yourself are unable to deal with this level of doubt and uncertainty. Unfortunately that's life - there are no certainties. quote: what scientists would create if they could build an earth for modern man, where CO2 would be exactly that determined as optimal
This is utterly meaningless! What does man care about CO2 levels? We don't photosynthesise! We care about crop yields, water supplies, diseases, flooding, usable land, ecosystems, erosion, hurricanes, skiing, tigers etc. What makes you think you can pick a level of CO2 and say that will be ideal? |
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quote: Originally posted by MindCrime:
]This is utterly meaningless! What does man care about CO2 levels? We don't photosynthesise! We care about crop yields, water supplies, diseases, flooding, usable land, ecosystems, erosion, hurricanes, skiing, tigers etc.
What makes you think you can pick a level of CO2 and say that will be ideal?
And cuddly Polar Bears - sorry ! |
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That reminds me, I think it was Seskinreay who came up with the blankets experiment? I think that was a more useful analogy - and if someone could put it on a more quantitative level it might be very useful indeed.
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quote: Originally posted by MindCrime:
That reminds me, I think it was Seskinreay who came up with the blankets experiment? I think that was a more useful analogy - and if someone could put it on a more quantitative level it might be very useful indeed.
Would be good if they could. Ironically it is the pro AGW scientific community, that is putting up such a good case for AGW, that I am relying on to prove or disprove the counter arguments (by looking hard at the possible counter balances to AGW). I assume some counter balances may not have kicked in yet - don't ask me what - I don't know. I believe Bjorn Lomborg started out as a pro AGW lobbyist but changed his mind after getting his students to perform just such a trick. |
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Mindcrime,
What do you need putting at a quantitative level?
The greenhouse effect? The enhanced greenhouse effect?
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quote: Originally posted by MindCrime:
What makes you think you can pick a level of CO2 and say that will be ideal?
I think it's possible for a snap-shot (ie a moment in time). I'm not concerned with what happens after that moment. Just the level of CO2 at that moment as determined by scientists to be ideal for a climate where "the human race can continue to generate the greatest good for humanity". Surely that simple figure can't be so difficult for you to state MindCrime? |
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quote: I think it's possible for a snap-shot (ie a moment in time). I'm not concerned with what happens after that moment. Just the level of CO2 at that moment as determined by scientists to be ideal for a climate where "the human race can continue to generate the greatest good for humanity".
Surely that simple figure can't be so difficult for you to state MindCrime?
OK. I will suggest that the ideal level is the figure that we had around the middle of the 20th Century. This level reduces the risks of another "little ice age" in the northern hemisphere, but does not produce warming much beyond current natural regional variability. The figure we have now is far too high, as even if we stop emissions tomorrow, temperatures will continue to rise another 0.5 degrees leading to strong downside risks. |
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quote: Originally posted by Steve_M:
even if we stop emissions tomorrow, temperatures will continue to rise another 0.5 degrees leading to strong downside risks.
Good. I'll be able to wear the short sleeve shirts I bought last summer. |
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quote: Originally posted by podbod:
What do you need putting at a quantitative level?
I mean actually putting numbers to the analogy - being able to say doubling the current level of CO2 is like adding one blanket to a pile of N blankets. I think that would be a meaningful analogy (still a bit misleading as being 1C warmer in bed is not as serious as the world being 1C warmer). |
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Roger 58 quote: To get back to our 1m sq glass analogy Son of Mulder. I like this analogy for for CO2 and if I can understand it, it could be a good way of presenting the AGW case to a world as confused by the complexities of the science as I am.
The aim of the analogy I introduced was purely to demonstrate that even a seemingly small quantity (280 ppm) can have a massive effect when spread through something the size of the atmosphere. It was in reply to Philliper's statement quote: I do not believe that a few hundred ppm of CO2 is significant at all
and was intended to show something extreme was possible from such a small concentration in a situation similar to the atmosphere. Introducing different glass translucency could be used but it means the audience needs to understand translucency. You could consider using net curtains as an example (starting to sound a bit Monty Python). Several thicknesses of those will keep out a lot of light. But I'd argue that if someone is struggling with this type of analogy they just aren't going to understand the subtleties of feedbacks etc where the real puzzle of the magnitude of AGW exists. |
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quote: Originally posted by Son of Mulder:
The aim of the analogy I introduced was purely to demonstrate that even a seemingly small quantity (280 ppm) can have a massive effect when spread through something the size of the atmosphere. It was in reply to Philliper's statement
I'm just asking for a benchmark. An optimum level of CO2, expressed in ppm, in which "the human race can continue to generate the greatest good for humanity". The 'Warmers' are very keen to shout about excess CO2 levels and link to thousands of pieces of 'evidence' to prove this... but when asked 'what should it be then, at any one time?' they keep squirming out of giving a straightforward an answer. I agree that "even a seemingly small quantity (280 ppm) can have a massive effect when spread through something the size of the atmosphere", but that effect is a NEGATIVE one - moving BACKWARDS from the suggested optimum of 310 ppm, and NOT the POSITIVE one that the 'Warm-Faithful' claim to be in a state of alarm about - which moves FORWARD from the optimum. It's clear to see why the whole AGW debate is in such a state of intellectual chaos, is constructed around wishy-washy quasi-religious 'belief' and attracts a healthy dose of well-deserved scepticism and ridicule. Lots of preaching from the pulpit about what is WRONG... but not even a single murmur about the RIGHT it is measured by. |
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Let's say CO2 is 250 ppm. That means one out of every 4,000 molecules is CO2. I am not impressed.
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Right, a few things people need to know about CO2.
Firstly, it is a weak greenhouse gas in terms of global warming potential (GWP) which is why it is used as the baseline for measuring GWP.
GWP is based on warming potential over a 100 years as different gases have different lifespans in the atmosphere. CO2 can remain in the atmosphere for anywhere between 200-400 years.
In terms of contribution to the Greenhouse effect, it is the 2nd largest contributor after water vapour. Water vapour contributes 95% and CO2 3.2% of the Greenhouse Effect. The other greenhouse gases (GHGs) make up the remaining 1.8%.
CO2 ability to absorb infra-red radiation is temperature dependant. A warmer atmosphere means increased absorption among the inefficient bandwidth of CO2. There are only three small efficient points where CO2 absorbs infra-red radiation and these bandwidths are saturated. Hence in an Ice Age, it doesn't matter how much CO2 is in the atmosphere, it cannot have a significant effect due to the temperature levels.
The IPCC gives a forcing from a doubling of CO2 of 3.7watts/m2. Excluding feedbacks, this amounts to a temperature increase of 0.6C. To generate a further 0.6C rise, CO2 needs to double again.
For illustration: current levels of CO2 in the atmosphere is 380ppm. A doubling of CO2 to 760ppm generates a 0.6C rise. You then need to double again to 1,520ppm to generate a further 0.6C.
Based on the current trends of CO2 increases, we won't get to 500ppm until the early 22nd century.
Based on the geological record, CO2 concentration levels have responded to climate temperature changes. A good illustration is the previous interglacial period (the Eemien) which shows CO2 concentrations rising a few hundred years after temperature rises and also falling in concentration a few hundred years after the return to an Ice Age. This suggests that CO2 has a small effect on temperature changes and that positive feedback is small.
(one interesting piece of evidence is that sea levels in the Eemien interglacial were 6m higher than they are today)
Hope this helps.
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quote: Right, a few things people need to know about CO2.
In terms of contribution to the Greenhouse effect, it is the 2nd largest contributor after water vapour. Water vapour contributes 95% and CO2 3.2% of the Greenhouse Effect. The other greenhouse gases (GHGs) make up the remaining 1.8%.
Your 95% statement doesn't make any sense. If you removed all the CO2 from the atmosphere, the amount of heat absorbed by the atmosphere goes down 9%. If you remove all the water vapour, it goes down about 36%. So you are underestimating the proportionate effect of CO2. quote: CO2 ability to absorb infra-red radiation is temperature dependant. A warmer atmosphere means increased absorption among the inefficient bandwidth of CO2. There are only three small efficient points where CO2 absorbs infra-red radiation and these bandwidths are saturated.
Sources on this info would be useful. From a physics perspective I can understand that they will be dependent on temperature in Kelvin (so not much different over the temperature ranges of the atmosphere). An absorption band may be saturated in its middle, but bands have width (a probability distribution), so increasing concentration will increase the absorption at frequencies around the centre of the band. quote: The IPCC gives a forcing from a doubling of CO2 of 3.7watts/m2. Excluding feedbacks, this amounts to a temperature increase of 0.6C. To generate a further 0.6C rise, CO2 needs to double again.
In the ideal state, a forcing of 3.7W/m2 gives a temperature rise of 1K, not 0.6K. Including feedbacks from water vapour etc. will double this or more. The earth is still catching up from the additional CO2 because the ocean takes a long time to warm up. So current observed surface warming of 0.6C or so is not a correct reflection of the warming that will be caused just by the current 30% increase in CO2. More realistically, an extra 0.5K warming is expected from current levels. With regard to the Eemian, the question should be what was the climate of Greenland and Antarctica like then as compared with now, since it is the icesheets from these that would related to such a sea-level difference. I don't know much about the Eemian (yet). |
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Not had a look back at this discussion for a while, and note that there was some discussion based on my suggested optimum of around 310ppm.
The rationale behind this was that the 'pre-industrial' levels at 280ppm were the levels at the end of the mid 19C (relatively) cool period, and that 'natural' variation suggests that levels in (naturally) warm periods go up to 310-320ppm (based on ice core data, leaf stomata suggest somewhat higher values).
Marginally warmer climates are generally advantageous compared with cooler ones (Roman vs Dark Ages for example), so I sugegsted 310ppm as a value associated (by this reckoning) with a sort of pleasantly warm climate.
Of course all this is based on the assumption that the climate sensitivity to CO2 is relatively high, and on non-existent technology that would allow geo-engineering of CO2 levels without any significant changes to any other climatic parameters.
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quote: Originally posted by Dr Ian B:
Roman vs Dark Ages
I realise that you haven't got much choice as data is sparse, but that judgement is rather Euro-centric. |
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MindCrime
Accepted.
The same (to an even higher degree) can be said for the various proxy and multi-proxy studies that have been used to 'prove' that we are warmer now than for any time in the last 1300 years.
The NAS review of Mann et al. 1998 + 1999 decided it was a reasonable conclusion that our current climate is warmer than for the last 400 years, but that the uncertainties increase back in time reduce the reliability of the data beyond this.
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quote: The NAS review of Mann et al. 1998 + 1999 decided it was a reasonable conclusion that our current climate is warmer than for the last 400 years, but that the uncertainties increase back in time reduce the reliability of the data beyond this.
You seem to be implying that this criticised Mann et al. But it is in reasonable agreement with Mann et al's 1999 paper. In the conclusion they state: quote: Although NH reconstructions prior to about AD1400 exhibit expanded uncertainies, several important conclusions are possible, notwithstanding certain caveats. While warmth early in the millennium approaches mean 20th century levels, the late 20th century still appears anomalous: the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium. More widespread high-resolution data...are needed before confident conclusions can be reached...
(their italics) |
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quote: Originally posted by Lost in Kate Winslet:
Right, a few things people need to know about CO2.
Firstly, it is a weak greenhouse gas in terms of global warming potential (GWP) which is why it is used as the baseline for measuring GWP.
GWP is based on warming potential over a 100 years as different gases have different lifespans in the atmosphere. CO2 can remain in the atmosphere for anywhere between 200-400 years.
In terms of contribution to the Greenhouse effect, it is the 2nd largest contributor after water vapour. Water vapour contributes 95% and CO2 3.2% of the Greenhouse Effect. The other greenhouse gases (GHGs) make up the remaining 1.8%.
CO2 ability to absorb infra-red radiation is temperature dependant. A warmer atmosphere means increased absorption among the inefficient bandwidth of CO2. There are only three small efficient points where CO2 absorbs infra-red radiation and these bandwidths are saturated. Hence in an Ice Age, it doesn't matter how much CO2 is in the atmosphere, it cannot have a significant effect due to the temperature levels.
The IPCC gives a forcing from a doubling of CO2 of 3.7watts/m2. Excluding feedbacks, this amounts to a temperature increase of 0.6C. To generate a further 0.6C rise, CO2 needs to double again.
For illustration: current levels of CO2 in the atmosphere is 380ppm. A doubling of CO2 to 760ppm generates a 0.6C rise. You then need to double again to 1,520ppm to generate a further 0.6C.
Based on the current trends of CO2 increases, we won't get to 500ppm until the early 22nd century.
Based on the geological record, CO2 concentration levels have responded to climate temperature changes. A good illustration is the previous interglacial period (the Eemien) which shows CO2 concentrations rising a few hundred years after temperature rises and also falling in concentration a few hundred years after the return to an Ice Age. This suggests that CO2 has a small effect on temperature changes and that positive feedback is small.
(one interesting piece of evidence is that sea levels in the Eemien interglacial were 6m higher than they are today)
Hope this helps.
It helps a lot. Thank You. These facts, logical as they are, are seldom heard and if heard, the subject changed. |
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Lost in Kate Winslet quote: The IPCC gives a forcing from a doubling of CO2 of 3.7watts/m2. Excluding feedbacks, this amounts to a temperature increase of 0.6C. To generate a further 0.6C rise,
Looks a good summary of facts. Just out of interest if feedbacks are included what is the additional rise in temperature and Infrared emission? |
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quote: Originally posted by Son of Mulder: Lost in Kate Winslet quote: The IPCC gives a forcing from a doubling of CO2 of 3.7watts/m2. Excluding feedbacks, this amounts to a temperature increase of 0.6C. To generate a further 0.6C rise,
Looks a good summary of facts. Just out of interest if feedbacks are included what is the additional rise in temperature and Infrared emission?
Well this is where we get into speculation. The geological record suggests a positive feedback of 1.3K (1C) temperature rise but the IPCC scenarios range from 1.1C to 6.5C. What exactly do you mean by infra-red radiation emission? |
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Lost in Kate Winslet quote: What exactly do you mean by infra-red radiation emission?
It was an early in the morning brain storm I meant additional rise in forcing. |
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quote: The IPCC gives a forcing from a doubling of CO2 of 3.7watts/m2. Excluding feedbacks, this amounts to a temperature increase of 0.6C. To generate a further 0.6C rise,
LKW, where do you get this 0.6K figure, because it is obviously wrong from a basic physics level. quote: It helps a lot. Thank You. These facts, logical as they are, are seldom heard and if heard, the subject changed.
Phlipper, I've commented on this as I think much of it | |
