Is climate sensitivity derived from paleoclimate studies a good indicator of future climate sensitivity?

Question

In a recent paper
http://www.nature.com/nature/journal/v463/n7280/abs/nature08769.html
a median value for positive feedback of 8 ppmv CO2 per C was deduced from paleoclimate studies. This estimate applies to an earth system minimally perturbed by human activity. Excluding the effects of greenhouse gasses, is there sufficient human modification of the ecosystem that would cause the ecosystem to behave differently in response to a rise in temperature than in the past?

Answer 1

Currently, the oceans are a CO2 sink, they are absorbing CO2 rather than giving it off. Oceans are currently a negative feedback, and this research is concluding, as I understand the abstract, that in the future they will become a positive feedback but not as strong a feedback as some models assume. This study is looking back to a time when warming preceded CO2 buildup, and thus can only be compared to a future state after the oceans are saturated and are again throwing off CO2. If the research is correct, then in a time far warmer now and with oceans far more acidic than now to the point of saturated maximum, continued warming may cause the oceans to throw back CO2 at a rate that is less catastrophic than some models suggest. Once things are horrible, they might not get worse as fast as some models say -- that's the point of this research.



I would far rather that we make some adaptations to avoid the point of ocean CO2 saturation. The point in time in the future that this research is talking about, the point that the oceans become a positive rather than negative feedback, is after some very terrible changes to the oceans themselves and to our abililty to use our lands. I don't really care if it is correct; I won't be around and I really don't want to think about it. Let's try to avoid the point of ocean saturation. I'm sure this is good reseach, but to debate whether it is accurate is helpless hand-wringing rather than positive decision-making. Let's not be so pessimistic.

Answer 2

I don't know enough to comment on the question, but can comment on the comments.



For the first time, I find myself in agreement with Jim, but Nola is just talking out of his own private volcanic eruption.



"Saturation" is too simple a concept, since we have equilibria (or systems more or less trending towards equilibria) involving solid limestone,dissolved carbonate, dissolved hydrogencarbonate (a.k.a. bicarbonate), "carbonic acid" which is simply carbon dioxide dissolved in water (I know that elementary chem textbooks say different), and CO2 in the atmosphere.



At any given temperature, the equilibrium amount of CO2 dissolved in water is proportional to pressure, as required by Henry's Law, but this solubility decreases with increasing temperature, which I think is the main reason why warming for any cause is expected to be followed by release of CO2 into the atmosphere, generating the positive feedback loop.



Most of these equilibria are established quite rapidly locally, although equilibria involving calcium carbonate can be much slower, and organisms generally rely on the oceans being supersaturated in calcium carbonate in order to build their shells.



However, because the oceans are large, diffusion, heat energy transfer, and turnover are slow (time period around 1000 years), giving long time lags.



As Einstein may or may not have said, every scientific problem should be made as simple as possible, and no simpler.

Answer 3

The way I understand the study, if the temperature rises a degree, the ocean gives off approximately 8 ppmV. Does this indicate how much human emissions of CO2 increase the temperature? No. It wouldn't. It simply tells how the ocean responds to varying temperatures. Am I missing something?

Answer 4

I read that and was going to post a question about it as it suggests that the possible amplification effect may have been dramatically overstated. I didn't because i still think that paleoclimatology is a far less exact science then is often claimed. (And, by the way, I like the way the article talks about "a refined understanding of pre-industrial anthropogenic activities". Do they mean campfires? (p. 529)).



I though the news article on p. 408 was far more interesting. I didn't know that "most of what we know about past Co2 levels . . . comes from the dust-free Antarctic ice".

Answer 5

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Answer 6

8 ppm per degree sensitivity is obviously nowhere near the ballpark. Even the most zealous AGW proponents attribute the estimated 100 ppm of anthropogenic CO2 to about half a degree of warming.



Still it wont stop believers from building a religion around it.

Answer 7

More silly religious fantasy and for the NOLA guy this is basically why smart women try to lose their virginity as early as possible so they are free from the fear of being sacrificed for some silly liberals religious fantasies.





http://en.wikipedia.org/wiki/Year_Without_a_Summer

http://en.wikipedia.org/wiki/Inquisition

http://vanallens.com/exchristian/calvin.htm





http://en.wikipedia.org/wiki/Atmosphere_of_Mars

http://en.wikipedia.org/wiki/Atmosphere_of_Venus

Answer 8

No. That's BS. You did not take into affect all the other variables.