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Post by steve on Jul 31, 2009 14:54:30 GMT
Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good.
I am guessing that you are looking at the changes during the ice age cycles. Perhaps your correspondent over-simplified the explanation. The cause of the timing of the ice age cycles is probably the Milankovitch cycles - slight variations in the earth's orbit and axis over time.
These wobbles do not affect the total amount of sunlight received by the earth, but they affect where and when it is received.
It is thought that these changes allow either a slight build-up or reduction in the size of the ice caps. The change in ice coverage changes the earth's albedo and acts as a positive feedback to increase or reduce the amount of ice more by reflecting more or less sunlight away. The related temperature changes appear to have an effect on CO2 levels. The CO2 levels act as a further positive feedback.
The extremes of the ice age cycles cannot be explained by albedo changes alone. The changes in CO2 are a possible partial explanation for the extremity of the cycles.
Currently, the changing levels of CO2 in the atmosphere are driven mainly by fossil fuel emissions and have little to do with past temperatures.
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Post by sigurdur on Jul 31, 2009 15:13:38 GMT
Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good. I am guessing that you are looking at the changes during the ice age cycles. Perhaps your correspondent over-simplified the explanation. The cause of the timing of the ice age cycles is probably the Milankovitch cycles - slight variations in the earth's orbit and axis over time. These wobbles do not affect the total amount of sunlight received by the earth, but they affect where and when it is received. It is thought that these changes allow either a slight build-up or reduction in the size of the ice caps. The change in ice coverage changes the earth's albedo and acts as a positive feedback to increase or reduce the amount of ice more by reflecting more or less sunlight away. The related temperature changes appear to have an effect on CO2 levels. The CO2 levels act as a further positive feedback. The extremes of the ice age cycles cannot be explained by albedo changes alone. The changes in CO2 are a possible partial explanation for the extremity of the cycles. Currently, the changing levels of CO2 in the atmosphere are driven mainly by fossil fuel emissions and have little to do with past temperatures. Steve: In another thread on this forum titled what is the fossil fuel contribution to co2, it was established that it is 16% using the last data available. Your statement that the co2 in the atmosphere are driven mainly by fossil fuel emissions is just flat out wrong. You are much to smart as evidenced by your posts to have said that, so I would think it is an error in typing on your part. |
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Post by william on Jul 31, 2009 15:29:56 GMT
Contrary to urban legend CO2 levels do not correlate with planetary temperature. There are periods of millions of years when CO2 levels are high and the planet is cold and periods when CO2 levels are low and the planet is warm. It appears based on the data that the CO2 greenhouse saturates and that there is strong negative feedback where the amount of low level planetary clouds increases or decreases to regulate planetary temperature so that significant changes in CO2 levels does not cause a significant change in planetary temperature. The cloud regulation mechanism is biased up or down by the level of galactic cosmic rays which create cloud forming ions. As the atmosphere over the ocean is ion poor, cloud nuclei has difficulty forming. Ion mediated nuclei is a factor 10 more effective hence there is significantly more clouds when GCR levels are high. GCR is a factor of 10 times higher when the solar system passes through the spiral arms of the galaxy. The past ice epochs (we are currently in the interglacial period of a ice epoch) correlate with increased GCR (determined by isotope analysis of meteoroids). Atmospheric carbon dioxide levels for the last 500 million years www.pnas.org/content/99/7/4167.fullUsing a variety of sedimentological criteria, Frakes et al. (18) have concluded that Earth’s climate has cycled several times between warm and cool modes for roughly the last 600 My. Recent work by Veizer et al. (28), based on measurements of oxygen isotopes in calcite and aragonite shells, appears to confirm the existence of these long-period (_135 My) climatic fluctuations. Changes in CO2 levels are usually assumed to be among the dominant mechanisms driving such long-term climate change (29). Superficially, this observation would seem to imply that pCO2 does not exert dominant control on Earth’s climate at time scales greater than about 10 My. A wealth of evidence, however, suggests that pCO2 exerts at least some control [see Crowley and Berner (30) for a recent review]. Fig. 4 cannot by itself refute this assumption. Instead, it simply shows that the ‘‘null hypothesis’’ that pCO2 and climate are unrelated cannot be rejected on the basis of this evidence alone. www.nature.com/uidfinder/10.1038/nature01087Despite these successes in linking variations in greenhouse gas concentrations to climate change in the geologic past, the oxygen isotope palaeotemperature record from 600 Myr ago to the present displays notable intervals for which inferred temperatures and pCO2 levels are not correlated1. One of these occurred during the early to middle Miocene (about 17 Myr ago), a time well established as a warm interval (relative to today), but with proxy evidence for low atmospheric pCO2 (ref. 2). Moreover, whereas climate models predict tropical warming in response to elevated pCO2, geologic data — in particularly the oxygen isotope record — indicate muted warming or even cooling at low latitudes while higher latitudes warm (the ‘cool tropics paradox’10–11). |
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Post by radiant on Jul 31, 2009 15:33:28 GMT
Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good. I am guessing that you are looking at the changes during the ice age cycles. Perhaps your correspondent over-simplified the explanation. The cause of the timing of the ice age cycles is probably the Milankovitch cycles - slight variations in the earth's orbit and axis over time. These wobbles do not affect the total amount of sunlight received by the earth, but they affect where and when it is received. It is thought that these changes allow either a slight build-up or reduction in the size of the ice caps. The change in ice coverage changes the earth's albedo and acts as a positive feedback to increase or reduce the amount of ice more by reflecting more or less sunlight away. The related temperature changes appear to have an effect on CO2 levels. The CO2 levels act as a further positive feedback. The extremes of the ice age cycles cannot be explained by albedo changes alone. The changes in CO2 are a possible partial explanation for the extremity of the cycles. Currently, the changing levels of CO2 in the atmosphere are driven mainly by fossil fuel emissions and have little to do with past temperatures. I note you say: The related temperature changes appear to have an effect on CO2 levels. The CO2 levels act as a further positive feedback.I wonder from where you get that information because you say to me: Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good.
I am guessing that you are looking at the changes during the ice age cycles. Perhaps your correspondent over-simplified the explanation.If you can show me that C02 and temperature rises happen at the same time throughout history or show me that they only dont happen in unusual circumstances then please do so. It is not something i have ever heard of before in all my 3 weeks of investigation ;D |
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Post by zer0th on Jul 31, 2009 15:33:32 GMT
Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good. The Andean-Saharan ice-age at ~5,000ppm (to name but one), mammal's initial evolution at ~2,000ppm, monkeys at ~600ppm... and the sky is about to fall at 385ppm. Cognitive dissonance? |
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Post by steve on Jul 31, 2009 15:43:30 GMT
Currently, the changing levels of CO2 in the atmosphere are driven mainly by fossil fuel emissions and have little to do with past temperatures. Steve: In another thread on this forum titled what is the fossil fuel contribution to co2, it was established that it is 16% using the last data available. Your statement that the co2 in the atmosphere are driven mainly by fossil fuel emissions is just flat out wrong. You are much to smart as evidenced by your posts to have said that, so I would think it is an error in typing on your part. I phrased the sentence with you in mind! Please reread it. The "base" CO2 level is approx 270ppm. The current level is about 390ppm. Most of the 120ppm rise and the ongoing "changing levels of CO2" is due to fossil fuel burning. |
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Post by radiant on Jul 31, 2009 15:52:45 GMT
Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good. The Andean-Saharan ice-age at ~5,000ppm (to name but one), mammal's initial evolution at ~2,000ppm, monkeys at ~600ppm... and the sky is about to fall at 385ppm. Cognitive dissonance? Sounds interesting. Do you have some links for these concentrations please? |
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Post by zer0th on Jul 31, 2009 15:58:49 GMT
Sounds interesting. Do you have some links for these concentrations please? The following *used* to be part of wikipedia's main entry on CO2, I guess it became an embarrassment. Unless you prefer models to actual measurements, it's the Royer compilation you want. AFAIK, the text is fair and reasonable. en.wikipedia.org/wiki/File:Phanerozoic_Carbon_Dioxide.png |
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Post by sigurdur on Jul 31, 2009 16:02:00 GMT
Steve: In another thread on this forum titled what is the fossil fuel contribution to co2, it was established that it is 16% using the last data available. Your statement that the co2 in the atmosphere are driven mainly by fossil fuel emissions is just flat out wrong. You are much to smart as evidenced by your posts to have said that, so I would think it is an error in typing on your part. I phrased the sentence with you in mind! Please reread it. The "base" CO2 level is approx 270ppm. The current level is about 390ppm. Most of the 120ppm rise and the ongoing "changing levels of CO2" is due to fossil fuel burning. Thanks for thinking of me, but land use changes add much more co2 than fossil fuel burning, so the 120ppm rise is mostly from land use change verses fossil fuel burning. And even that 120 ppm is not a significant change on a geo scale timeline. |
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Post by steve on Jul 31, 2009 16:26:36 GMT
Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good. The Andean-Saharan ice-age at ~5,000ppm (to name but one), mammal's initial evolution at ~2,000ppm, monkeys at ~600ppm... and the sky is about to fall at 385ppm. Cognitive dissonance? Cognitive dissonance can be resolved by thinking through the alternatives. CO2 is not the only influence on climate. For example, if ice can build up sufficiently it takes a lot of CO2 warming to overcome the fact that the ice reflects away a lot of sunlight. The sun gets brighter with age. At the time of the last "snowball earth" it was less strong, so higher levels of CO2 then would not be inconsistent with a cooler planet. For example, a 5% reduction in strength would be balanced by CO2 levels of 2500ppm based on a forcing of 3.7W/m^2 for a doubling of CO2. Also the planet was quite different with the continents in a different place, and different plants. One paper I read recently (unfortunately I can't find the link at the moment) looked at silicate weathering rates which is a function of both CO2 levels and temperature. If the weathering rate is high, then it is due to high temperatures or high CO2 levels. If it is low, it is due to low CO2 levels or low temperatures. Making reasonable estimates of upper temperature ranges gives a lower bound on the effect of CO2 on temperature which was about 1.5C for a doubling of CO2. |
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Post by poitsplace on Jul 31, 2009 18:21:14 GMT
The sun gets brighter with age. At the time of the last "snowball earth" it was less strong, so higher levels of CO2 then would not be inconsistent with a cooler planet. For example, a 5% reduction in strength would be balanced by CO2 levels of 2500ppm based on a forcing of 3.7W/m^2 for a doubling of CO2. Also the planet was quite different with the continents in a different place, and different plants. 5% lower would be about 14 watts. It should take over 7000ppm to offset a 5% change. However, when you start looking at the actual math...to suggest CO2 was responsible for the recovery of a snowball earth event (as many do) is utterly ridiculous...even taking into account the fact that a snowball event is the ONLY time when CO2 actually starts to dominate climate (as opposed to water vapor), But as long as there's water vapor in the troposphere CO2 has no way to significantly affect the temperature anyway. The water vapor, being far more abundant than CO2, lighter than air and capable producing its own, powerful convection currents...short circuits across the gradient that CO2 would create. The earth is essentially covered in an adaptive heat-pipe. Try to force a more pronounced gradient and more water vapor moves up to compensate. The water vapor caries immense amounts of energy in the form of latent heat but simultaneously deprives CO2 of energy by sidelining some of the energy emitted by CO2 into water vapor's own spectrum. |
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Post by icefisher on Jul 31, 2009 20:02:03 GMT
The Andean-Saharan ice-age at ~5,000ppm (to name but one), mammal's initial evolution at ~2,000ppm, monkeys at ~600ppm... and the sky is about to fall at 385ppm. Cognitive dissonance? Hmmm, wonder how much warmer it was when the naked ape evolved? |
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Post by sigurdur on Jul 31, 2009 21:25:20 GMT
The Andean-Saharan ice-age at ~5,000ppm (to name but one), mammal's initial evolution at ~2,000ppm, monkeys at ~600ppm... and the sky is about to fall at 385ppm. Cognitive dissonance? Sounds interesting. Do you have some links for these concentrations please? Radiant: Look under what is man's fossil fuel co2 contribution. Wylie did an excellent job of explaining the load there. |
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Post by steve on Aug 2, 2009 9:59:27 GMT
The sun gets brighter with age. At the time of the last "snowball earth" it was less strong, so higher levels of CO2 then would not be inconsistent with a cooler planet. For example, a 5% reduction in strength would be balanced by CO2 levels of 2500ppm based on a forcing of 3.7W/m^2 for a doubling of CO2. Also the planet was quite different with the continents in a different place, and different plants. 5% lower would be about 14 watts. It should take over 7000ppm to offset a 5% change. However, when you start looking at the actual math...to suggest CO2 was responsible for the recovery of a snowball earth event (as many do) is utterly ridiculous...even taking into account the fact that a snowball event is the ONLY time when CO2 actually starts to dominate climate (as opposed to water vapor), But as long as there's water vapor in the troposphere CO2 has no way to significantly affect the temperature anyway. The water vapor, being far more abundant than CO2, lighter than air and capable producing its own, powerful convection currents...short circuits across the gradient that CO2 would create. The earth is essentially covered in an adaptive heat-pipe. Try to force a more pronounced gradient and more water vapor moves up to compensate. The water vapor caries immense amounts of energy in the form of latent heat but simultaneously deprives CO2 of energy by sidelining some of the energy emitted by CO2 into water vapor's own spectrum. But the water vapour levels are roughly determined by the weather. The driver of the water vapour levels are the things that affect the weather and climate such as the sun, albedo, greenhouse gas levels, area of open water. Your last sentence is beginning to sound like a pseudoscientific mantra. "The good energy in the crystals works to destroy the bad energy emanating from the cancer cells" sort of stuff. |
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Post by icefisher on Aug 2, 2009 18:03:14 GMT
Over most of geological history, the evidence for a correlation between CO2 changes and temperature changes is quite good. The extremes of the ice age cycles cannot be explained by albedo changes alone. Why? If you claim multiple degrees effect for 4 watts of forcing at TOA how can you not allow 10 or 12 degrees for the some 100 watt difference you can get out of clouds? Calculations please! |
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