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So are you saying that there is no historic evidence that CO2 has any effect on temperature at all?
Thanks for the input guys. This is something I really wanted to learn about, so while I was waiting I did some (lots) of research and wrote this article on the XXX. Any comments would be appreciated, either here or on the article Thanks again for the input.
What is more, further back in past there are examples of warmings triggered by rises in greenhouse gases, such as the Palaeo-Eocene Thermal Maximum 55 millions years ago (see Climate myths: It's been far warmer in the past, what's the big deal?).
Finally, if higher temperatures lead to more CO2 and more CO2 leads to higher temperatures, why doesn't this positive feedback lead to a runaway greenhouse effect? There are various limiting factors that kick in, the most important being that infrared radiation emitted by Earth increases exponentially with temperature, so as long as some infrared can escape from the atmosphere, at some point heat loss catches up with heat retention."
Test the first link I gave, that will give extensive information on 'time lags' and CO2. Don't miss the comments, they are often very good, both sides
As for the first quote, well it's a quote but I tend to agree to it too. A lot of people studying geology and Earth’s history says the same. At the Permian-Triassic extinction event . (Around 280 to 230 million years ago) and at the Paleocene-Eocene Thermal Maximum (63-40 millions years ago), the beginning of what life we know today, this 'Greenhouse scenario' seems to have happened twice already.
This is something I really wanted to learn about, so while I was waiting I did some (lots) of research and wrote this article on the XXX
By increasing the amount of greenhouse gasses (H2O, CH4, CO2, O3, etc.), the atmospheres ability to retain heat is enhanced, which helps warm the earth to some degree.
As of now, we pump CO2 into the atmosphere in very large quantities, which is going to have some effect on temperature. The real debate is how much radiative forcing does CO2 provide compared to natural forcings.
Im not in the "modern warming in entirely anthropogenic" camp. In fact, my personal belief is that natural effects are playing a very large role in current climate, but any chemist or physicist will tell you that though CO2 is not the most efficient GHG, it will still provide more radiative heating as its concentrations increase
Therein lies the conundrum. We *KNOW* through physics and chemistry that CO2 has radiative effects and is a GHG, but there is no research (that Ive ever read or heard of anyway) that states X amount of CO2 should provide Y amount of warming. It is an unknown quantity, as far as I can tell.For now, we can qualitatively say that CO2 traps heat in the atmosphere, and that higher concentrations will trap more heat (though there is evidence that this a logarithmic trend rather than a linear one), but there is no quantitative answer as to how much.
Quote from: jason_85 on 05/03/2010 08:44:27So are you saying that there is no historic evidence that CO2 has any effect on temperature at all?No, what Im saying is that we know that CO2 has an effect on temperature, but we dont know with any certainty the magnitude of that effect.
This confuse me somewhat. "No, I do not doubt that CO2 is a contributor to current and past climate, but I do believe that much more research is needed to determine what is natural and what is anthropogenic."
Ice cores provide evidence for variation in greenhouse gas concentrations over the past 800,000 years. Both CO2 and CH4 vary between glacial and interglacial phases, and concentrations of these gases correlate strongly with temperature. Before the ice core record, direct measurements do not exist.
Okay, what I found confusing was you saying, if I got you correctly, that it's not anthropogenic (man made). Looking at the ice cores the increase seems very well correlated to our industrial revolution?How else would you like to define those increases in ppm?They seem very well correlated to me?If you agree on CO2 being able to 'drive' a Global warming as it increases it seems to me that the question only might be what started it, right?
You are basing it on a preliminary one paper here, very interesting, but still with large uncertainties, as they themselves conlude.
Do you have a simple correlation to show me over those relations, and its time scheme naturally. Without a similar time scenario it will be very hard to draw any conclusions towards if we can compare any of it with what's happening today. But it will even so give a new twist to what we think we know, if proven correct.
This map by D. Peteet shows the possible distribution of Younger Dryas cooling around the world.
Around half of the warming seems to have occurred in the space of a single span of 15 years, according to the latest detailed analyses of the Greenland ice core record (Taylor et al. 1997).
I did however post a link to lecture to the Geology Society (of London)about the PETM in the geology forum. I think it neatly addressess the question of why higher temperatures in the past may not be related to CO2, whereas the PETM was, which makes the PETM (and its consequences) all the more interesting to study.