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Post by nautonnier on Dec 17, 2009 22:28:14 GMT
And all the preceding argument is on the false premise that CO2 has been steadily rising since 1750.
Everyone should step back and check the assumptions
* CO2 is NOT at an unprecedented level. It was as high if not higher in 1850
* Temperatures are NOT at unprecedented levels they have been as high in the MWP and Roman optimum
AGW would appear to be a hypothesis that has been based on false assumptions obfuscated by 'the team'. Until these assumptions have been shown to have validity proceeding any further is a nugatory exercise.
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Post by hunter on Dec 17, 2009 22:47:54 GMT
nautonnier could you please review the evidence and sources for the assertion that CO2 is largely unchanged over the past ~100+ years? I am a definite skeptic, but I am puzzled as to how we can burn as much carbon based fuel as we do and NOT increase CO2 ppm in the atmosphere. What is the evidence for this static level? What is the explanation for where the CO2 went? thanks, hunter
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Post by sigurdur on Dec 17, 2009 22:59:41 GMT
Hunter: Do a search for co2 levels in the near past. There have been two papers published this year that show that the Keeling curve is pure and utter baloney.
I don't remember exactly where, but by searching you should find them. co2 level in the early 1800's was 420 ppm. That is a proven fact.
The oceans do a great job of absorbing co2. That is where most of it goes, and also, the earth in this past 30 year warming phase has increased bio mass by approx 12%.
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Post by hunter on Dec 17, 2009 23:04:29 GMT
sigurdur, I appreciate the challenge. However, I hope that nautonnier will be more specific and well documented in his claim. This is a game changing assertion,and it should be well documented.
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Post by icefisher on Dec 18, 2009 0:25:04 GMT
Both gases have influence. The point is a lot of the radiation emitted near the surface is reabsorbed. Adding more greenhouse gases near the surface doesn't make much difference. Hence some sceptics crude suggestion that spitting on the ground won't make a bit of difference. When you get up to 5km or so, the atmosphere is thinner and there is less water vapour, so a proportion of the radiation emitted goes into space (so cooling the earth). Increasing the levels of greenhouse gas *here* therefore has an impact. The impact is to raise the height in the atmosphere from which radiation escapes to space by a bit. Because the height is raised, the emissions are coming from a colder location. Because the emissions are coming from a colder location, Stefan-Boltzmann tells us that the emissions will be less. Because the emissions are less, the earth is out of radiation balance and may tend to absorb more than it emits until the atmosphere readjusts due to the effects of the radiation imbalance. More first order approximations: based on a lapse rate of about 6C per 1000 metres, raising CO2 from 280-560 ppm would need to raise this effective emitting layer by about 150 metres - not a great deal given that at 5km or so the relative importance of CO2 is quite high due to the lack of water vapour. You are leaving out some important issues Steve. You are saying in effect that the average emission layer height will rise somewhere between 3 and 4 percent by adding only something less than 3 hundredths of a percent of gases to the atmosphere. Looking at satellite data (albiet an amateurs look) If anything the lapse rate seems to have increased rather than decreased as you suggest here.
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Post by glc on Dec 18, 2009 9:34:09 GMT
You are leaving out some important issues Steve. You are saying in effect that the average emission layer height will rise somewhere between 3 and 4 percent by adding only something less than 3 hundredths of a percent of gases to the atmosphere.
He's not saying that - at least I think he's not saying that. The relative increase of CO2 is more like 35%. CO2 does have a strong influence on the height at which radiation is finally emitted to space. We can see this in earth's emission spectra. It is likely, therefore, that the addition of more CO2 to the atmosphere will increase the average height at which radiation is emitted. Steve's explanation as to how this will disturb the 'incoming/outgoing energy balance' is correct, i.e. the earth should get warmer.
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Post by steve on Dec 18, 2009 9:44:57 GMT
nautonnier could you please review the evidence and sources for the assertion that CO2 is largely unchanged over the past ~100+ years? I am a definite skeptic, but I am puzzled as to how we can burn as much carbon based fuel as we do and NOT increase CO2 ppm in the atmosphere. What is the evidence for this static level? What is the explanation for where the CO2 went? thanks, hunter Hunter, I have asked these eminently sensible questions before. Perhaps you will have a better chance of getting answers.
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Post by steve on Dec 18, 2009 9:59:14 GMT
It has a general application to bodies that are not black bodies. Since we are comparing similar things, using it to obtain a first order assessment is reasonable, unless you have substantive reasons for suggesting it is not.
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Post by glc on Dec 18, 2009 10:03:55 GMT
Hunter: Do a search for co2 levels in the near past. There have been two papers published this year that show that the Keeling curve is pure and utter baloney.
I don't remember exactly where, but by searching you should find them. co2 level in the early 1800's was 420 ppm. That is a proven fact.
This is not a "proven fact". You are no doubt referring to the Beck study which, to take one example, shows CO2 levels at 481 ppm in 1827 and at 385 ppm in 1829, i.e. a drop of nearly 100 ppm in just 2 years. The problem with these studies is that the readings are clearly not taken at the same time or from the same location.
If you were to measure the CO2 concentration in London or New York, say, you might find it's as high as 450 or 500 ppm. What's more it could be higher on a Friday than it is on a Sunday.
The big advantage in using remote measuring sites like Mauna Loa and Barrow (Alaska) is that the gas is "well mixed" in the atmosphere. The readings from these sites are not affected by the local conditions.
The Beck 'measurements' may be accurate but they are irrelevant. The problem for the sceptics is that arguments such as these can be easily knocked back by the warmers. It's like all the solar guff it eventually results in a loss of credibility.
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Post by steve on Dec 18, 2009 10:05:35 GMT
You are leaving out some important issues Steve. You are saying in effect that the average emission layer height will rise somewhere between 3 and 4 percent by adding only something less than 3 hundredths of a percent of gases to the atmosphere.He's not saying that - at least I think he's not saying that. The relative increase of CO2 is more like 35%. CO2 does have a strong influence on the height at which radiation is finally emitted to space. We can see this in earth's emission spectra. It is likely, therefore, that the addition of more CO2 to the atmosphere will increase the average height at which radiation is emitted. Steve's explanation as to how this will disturb the 'incoming/outgoing energy balance' is correct, i.e. the earth should get warmer. GLC. I guess I am saying that! Icefisher is going onto "How can CO2 be important when it is only 0.03% of the atmosphere". To which I usually say "Fight it out with the people who believe that the absorption from CO2 is saturated, and therefore adding any more can't make a difference". I'll sit in the middle and state, as you do, that basic spectroscopy gives us an answer that is neither of the two opposite extreme positions.
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Post by steve on Dec 18, 2009 10:10:18 GMT
I get the impression that with the advent of climategate, sceptics think they can now get away with anything. Meanwhile we have evidence that the raw. unadulterated, unhomogonized temperature data gives pretty much the same global warming trend as the adjusted data. And the data from the "quality" surfacestation sites gives pretty much the same US trend as the analysed data for the whole network. So the science gets stronger and the scepticism gets more careless.
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Post by trbixler on Dec 18, 2009 10:20:41 GMT
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Post by steve on Dec 18, 2009 10:28:03 GMT
Foolish to assume it will be important without further analysing the issue. Models are perturbation experiments, so if the rise is generally even over time, the results remain as valid (or invalid) as before. Compare the trends at different latitudes, and you will see they are almost identical. Eg. cdiac.ornl.gov/trends/co2/
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Post by icefisher on Dec 18, 2009 11:00:39 GMT
Seeing as how both GLC and Steve are denying what Steve said I will start with what Steve said: The impact is to raise the height in the atmosphere from which radiation escapes to space by a bit. Because the height is raised, the emissions are coming from a colder location. Because the emissions are coming from a colder location, Stefan-Boltzmann tells us that the emissions will be less. Because the emissions are less, the earth is out of radiation balance and may tend to absorb more than it emits until the atmosphere readjusts due to the effects of the radiation imbalance. More first order approximations: based on a lapse rate of about 6C per 1000 metres, raising CO2 from 280-560 ppm would need to raise this effective emitting layer by about 150 metres - not a great deal given that at 5km or so the relative importance of CO2 is quite high due to the lack of water vapour. So Steve said the effective emitting layer goes up by 150 meters. If one looks at the satellite data you find about an average 255k temperature layer at about 4,000 meters. So 150 meters is 3.75%. Now Steve said we will add 280 parts per million of CO2 to the atmosphere which works out to about 2.8 hundredths of one percent additional gas to the atmosphere. I said: "You are leaving out some important issues Steve. You are saying in effect that the average emission layer height will rise somewhere between 3 and 4 percent by adding only something less than 3 hundredths of a percent of gases to the atmosphere.
Looking at satellite data (albiet an amateurs look) If anything the lapse rate seems to have increased rather than decreased as you suggest here." GLC said: "He's not saying that "I would suggest you reread what Steve said GLC. He is in here doing some kind of 4th grade science demonstration and you are saying he is not saying what he is saying. 150 meters from where GLC? Perhaps I got the percentage wrong, please explain.
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Post by glc on Dec 18, 2009 11:39:58 GMT
GLC. I guess I am saying that!
I suppose you are - in a way, but I was trying to point out that CO2 has an affect (at pre-industrial levels) and we have increased CO2 by a relatively larger proportion than that suggested by Icefisher.
Now with sceptic hat on.
So the science gets stronger and the scepticism gets more careless.
I disagree with the first part of this. Most of us never disputed that the earth has got warmer over the past ~150 years (a good thing too). 'Our' argument was that this warming is not particularly unusual.
1. The trend between 1915 and 1945 was 0.14 deg per decade - compared to 0.16 deg per decade over the past 30 years. i.e. there is not a statistically significant difference between the trends in the 2 periods. Lots of attempts ("detection and attribution studies") have been made to explain the warming and they have been included in 'climate models'. We now know they are wrong. The models are still using outdated solar reconstructions (Lean et al). Even Lean has conceded that her reconstructions show too much variability - particularly in the earlier years.
2. The "hide the decline trick" was fraudulent. It was done to hide a 20th century temperature decline in 2 key reconstructions, i.e. Briffa et al , Mann et al. These reconstructions showed a relatively flat MWP and LIA - contrary to hundreds of studies from all over the world which showed the MWP (and LIA) to be a real and widespread event. The fact that the reconstructions were heading in the opposite direction to observations in the post (and pre) calibration period suggests that the reconstructions are junk. Something we knew anyway (for lots of reasons). In other words, the MWP could easily be as warm if not warmer than to-day.
3. The CET (Central England Temperature) record. Although I'm generally reluctant to conclude anything on a global scale from local observations, the CET is the longest thermometer record available and, for that reason, it warrants special attention. First, a couple of points: (i) The smoothed (10 year) CET record is a pretty decent proxy for the NH surface temperature record. (ii) The CET record tracks other long term records fairly closely.
Between the 1690s and 1730s (~40 years) the CET shows a temperature increase of more than 2 degrees. As I've said above, over the last 150 years the smoothed CET record and NH record have never drifted apart by very much so I don't see any reason why there should have been a significant divergence during any previous period. I reckon it's reasonable to assume that the NH, at least, experienced a minimum 1 deg shift in temperatures in the early 18th century.
Gavin Schmidt (Realclimate) was one of the authors of a study which claimed that the temperature increase between 1680 and 1780 was ~0.3 deg. However, I'm convinced they've missed the 1730s hump (as well as the 1690s trough).
Finally, Steve, if you're from the UK you might be familiar with Iain Stewart who presented 'The Climate Wars' programme on BBC. I emailed Iain recently with some comments about the mid-20th century cooling which he, along with many other 'experts', believes was caused by industrial aerosols. I say it wasn't. The main reason being that it was only the arctic that experienced significant cooling, i.e. a non-industrialised region.
Anyway, Iain replied and forwarded me the Wild et al paper on global dimming/brightening. I'd come across the paper before but hadn't really read it. I have now and it is quite interesting. I might even start a separate thread on the subject. The main point of interest concerns Wild's tabled measurements of solar insolation forcing. Between 1960 and 1990, it seems the decrease in solar radiation at the surface was somewhere between 10 and 15 w/m2. Between 1986 and 2000 there was an increase of ~3 w/m2 (much more if you take one particular measurement).
Now remember Iain sent this to me in order to bolster his claims.
Iain appears not to know that the total CO2 forcing since ~1850 is only ~1.7 w/m2. Even if we double CO2 that only gives ~3.7 w/m2. Ok, I accept there is probably some amplification at the surface relative to the TOA forcing, but the dimming/brightening forcings are orders of magnitude larger than the CO2 forcings over the same period.
If Wild's numbers are correct, and he does use figures from other researchers, then we can only conclude that
(i) The total warming from doubling CO2 will be, at most, about twice as much the warming between 1986 and 2000. Lets go mad and call it ~0.7 deg. (ii) Most, if not all, of the warming since ~1986 is due to more sunlight reaching the surface.
I wonder if Iain would like to debate this on TV?
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