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An Inconvenient Truth
root wrote in :
snip point 1 Are you saying that we are all doomed if the atmospheric CO2 levels double? Is that the foundation of the entire global warming warming scare? We can see the effect using the MODTRAN atmospheric model: http://geosci.uchicago.edu/~archer/c...radiation.html Doubling the current level of CO2 from 375 ppm to 750 ppm would cause a temperature rise in the tropics of 0.83K and a lesser amount at latitudes away from the equator. The effect of atmospheric absorbtion goes as the log of the concentration of the greenhouse gases. The log rises very steeply at first but levels off. We are on the leveled off part. If instead of doubling the CO2 we were to cut it in half we would go back to the real ice age where glaciers covered all of Canada. snip point 2 It seems clear to me it is the dynamics of the ocean plankton that is responsible for the reasonable balance between the sources and sinks of CO2. The ocean has been able to handle an atmospheric CO2 level 10 times the present [http://www.grida.no/climate/ipcc_tar/wg1/107.htm] so there seems little to fear for a mere doubling. snip point 3 I would welcome a citation for a useful IPCC report. What I have seen is careful bookkeeping of atmosperic sources that I cannot relate to a model which fits the ice core records. It isn't a coincidence that sources and sinks are in relative balance historically. That is the effect of the process. Man is a newcomer to the picture and our effect has not been incorporated into the dynamic. point 1 I am not saying that we are all doomed if atmospheric CO2 levels at all. What I did say was that most reasonable scientists take doubling of atmospheric CO2 to be the level at which no amount of remediation will stave off adverse climatic impacts on the biosphere. This is not a subtle distinction and if you want to continue this conversation, do not put words in my mouth. The biosphere in total is remarkably robust and I simply do not think mankind has the ability to "kill the planet," even under the worst case scenario of humans triggering a runaway greenhouse catastrophe which vaporize the oceans. Somewhere, some microbe will survive even that. I do think that humans won't like living in a world where atmospheric CO2 has been doubled very much, if only because of the extra-virulent poison ivy. (http://tinyurl.com/j4cyt) You do understand what MODTRAN is right? It's not a climatic simulation but a radiative transfer model. That is a huge huge difference. MODTRAN gives the change in the radiative balance due to the greenhouse gas forcing, it does not estimate climatic effects. As near as I can tell that implementation of MODTRAN has some really simply parameterizations of clouds and aerosols. Estimating the global temperature rise from a simple calculation like that, that only does the radiative balance, is not worth discussing rationally no matter how sophisticated the radiative transfer model. The climatic response to that change in radiative forcing will be nonlinear, and assuming there is a one-to-one response between the change in radiative forcing and global average temperature increase is silly (but I will admit that if you are trying to impress people you think don't know what you are talking, it about sounds really convincing). The IPCC report you linked to for Point 2 also makes the point that atmospheric CO2 levels do not trigger ice ages. So your assertion that reducing CO2 to half of the pre-industrial level would glaciate Canada is as silly as using MODTRAN as a climate model. Point 2 It is interesting to note that those epochs of high CO2 are all contemporaneous with mass extinctions. The higher events 400,000,000 million years ago correlate nicely with the Ordovician and Cambrian extinctions. Admittedly, that could be just coincidence or the point is completely tangential (unless you happen to be a trilobyte or a theropod). However, the most recent time CO2 was over 1000 ppm or so was 65,000,000 years ago or so. The flora and fauna were somewhat different then and even assuming that they came through without any effect (ignoring of course the mass extinction at the K-T boundary) does not necessarily imply modern day flora and fauna will not be adversely impacted. This is especially true since we know that corals and some phytoplankton are already starting to show signs of acid stress. The ocean CO2 inorganic chemistry system can handle a *lot* of atmospheric CO2, especially on timescales of 1000s of years. There is so much limestone around available to neutralize excess CO2 that in the long term no amount of burning of fossil fuel will make a dent in the ocean pH. However, I don't think we really want to wait around for 5,000 years while the ocean and atmosphere sort this out. Again, this relation between near-term adverse effects and long-term return to what we know as the real chemical equilibrium is a subtle distinction, but then anthropogenic-induced climate change is a subject of subtlety. Because of this difference in temporal scales, it is easy to construct half-right models that purport to show there is no problem. point 3 I can't tell what you are talking about. It seems like you are agreeing with my proposition that man's affect on the natural global CO2 cycle may be important. But then again, maybe you aren't. Beats the hell out of me. -- Bill Asher |
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#2
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An Inconvenient Truth
William Asher wrote:
point 1 I am not saying that we are all doomed if atmospheric CO2 levels at all. What I did say was that most reasonable scientists take doubling of atmospheric CO2 to be the level at which no amount of remediation will stave off adverse climatic impacts on the biosphere. This is not a subtle distinction and if you want to continue this conversation, do not put words in my mouth. Asking what you mean is not putting words in your mouth. You do understand what MODTRAN is right? It's not a climatic simulation but a radiative transfer model. Of course I understand that, and I never represented MODTRAN as anything else. it does not estimate climatic effects. It is the pure physics of the atmosphere and the radiation passing through it. As near as I can tell that implementation of MODTRAN has some really simply parameterizations of clouds and aerosols. In fact most of my uses have had "no cloud cover". What the UChicago site offers is several types of clouds in addition. Estimating the global temperature rise from a simple calculation like that, that only does the radiative balance, is not worth discussing rationally no matter how sophisticated the radiative transfer model. The climatic response to that change in radiative forcing will be nonlinear, and assuming there is a one-to-one response between the change in radiative forcing and global average temperature increase is silly (but I will admit that if you are trying to impress people you think don't know what you are talking, it about sounds really convincing). One starts with the physics, from that point is becomes less and less science. When an atmospheric effect suggests a surface temperature change less than 0.1K, say, it is pretty hard to get excited, but people do. The IPCC report you linked to for Point 2 also makes the point that atmospheric CO2 levels do not trigger ice ages. So your assertion that reducing CO2 to half of the pre-industrial level would glaciate Canada is as silly as using MODTRAN as a climate model. Overall there has to be global balance between the solar input and the re-radiation from the earth. If the CO2 level were halved the absorbtion of the atmosphere would be reduced, the radiation from the earth would be increased, and the earth would cool. That is physics. Now, using silly MODTRAN we find that if the CO2 level were halved the temperature in the tropics would fall by 17K. As shown on the ice core site: http://carto.eu.org/article2481.html the temperature change from the present to the last major ice age is about 10K. Whether or not that means a new ice age, wouldn't you agree that the consequence of halving the CO2 would be worse than doubling the CO2? Point 2 It is interesting to note that those epochs of high CO2 are all contemporaneous with mass extinctions. The higher events 400,000,000 million years ago correlate nicely with the Ordovician and Cambrian extinctions. Admittedly, that could be just coincidence or the point is completely tangential (unless you happen to be a trilobyte or a theropod). However, the most recent time CO2 was over 1000 ppm or so was 65,000,000 years ago or so. The flora and fauna were somewhat different then and even assuming that they came through without any effect (ignoring of course the mass extinction at the K-T boundary) does not necessarily imply modern day flora and fauna will not be adversely impacted. This is especially true since we know that corals and some phytoplankton are already starting to show signs of acid stress. The ocean CO2 inorganic chemistry system can handle a *lot* of atmospheric CO2, especially on timescales of 1000s of years. There is so much limestone around available to neutralize excess CO2 that in the long term no amount of burning of fossil fuel will make a dent in the ocean pH. However, I don't think we really want to wait around for 5,000 years while the ocean and atmosphere sort this out. Again, this relation between near-term adverse effects and long-term return to what we know as the real chemical equilibrium is a subtle distinction, but then anthropogenic-induced climate change is a subject of subtlety. Because of this difference in temporal scales, it is easy to construct half-right models that purport to show there is no problem. Step back and look at what you have said and tell me how much of that is science and how much is speculation? point 3 I can't tell what you are talking about. It seems like you are agreeing with my proposition that man's affect on the natural global CO2 cycle may be important. But then again, maybe you aren't. Beats the hell out of me. I am a scientist (physicist) and have no dog in this fight. I am trying to sort out the arguments for myself. |
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