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The Ice core data was famously used to by Al Gore in his documentary "An inconvenient truth" to imply a relation between cause effect relation between CO2 and Temperature. This paper and others suggest that CO2 lags Temperature by 800 years and is used to debunk the cause effect relation between CO2 and temprature suggested by the theory of man made global warming due to green house gases. The lagging is explained by the expelling of CO2 from the Ocean due to increase in temprature.

I would like a clarification on the suggestion that Paleoclimatic evidence implies that CO2 and temperature are related by a cause effect relation. Why is there contradictory consensus on what the Ice Core data means? Does the Ice Core data imply a cause effect relation between CO2 and temperature?

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    $\begingroup$ @CountTo10 Believe it or not I am trying to get help from this site and policy has been been annoying to me. I don't know how you guys see this entire episode called "too broad". It has only been detrimental to my learning. And this is a completely different question, which I am forced to ask because of policy restrictions. $\endgroup$ – Prathyush Nov 2 '16 at 17:37
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    $\begingroup$ Would Earth Science be a better home for this question? $\endgroup$ – Qmechanic Nov 2 '16 at 19:40
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    $\begingroup$ If you actually want answers and are not just trolling, then the IPCC Fifth Assessment Report & references therein is a good description of the state of knowledge in 2014-2015. $\endgroup$ – tfb Nov 2 '16 at 20:00
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    $\begingroup$ @Prathyush Then read them, don't repeatedly ask variants on the same question here. There is copious information out there, relatively little of it behind paywalls: read it. $\endgroup$ – tfb Nov 2 '16 at 20:31
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    $\begingroup$ @Prathyush One thing which you can see immediately from the Nature article you mention is that (proxy) temperature went up by about 4K from 22,000 to 10,000 years ago: so about $3.3\times 10^{-4}\mathrm{K}/\mathrm{y}$. In the last 200 years it has risen by about 1.5K: about $7.5\times 10^{-3}\mathrm{K}/\mathrm{y}$. The rate of change is higher by a factor of a little over 20. Treating these as if they were the same is like treating an English Electric Lightning as if it was a Sopwith Camel: they have common features, but they are not the same. xkcd puts it well. $\endgroup$ – tfb Nov 3 '16 at 1:36
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To say that there is a "contradictory consensus", or lack of consensus is inaccurate. There is nothing that 100% of people (even scientists) agree upon, but man's role in global climate change is pretty close.enter image description here

Still, your question is completely valid. The simple answer is that a single, hand-picked (note: with a specific goal in mind) cite of data is not enough to decipher a correlation. There is also nothing showing that a correlation analysis was performed... it looks like they're just claiming this 800yr lag based on eye-balling a single plot. Looking at data from the last hundred years or so (which is far, far more accurate) clearly shows that there is no such 800yr delay; for example:

enter image description here

or this (note very different data sets),

enter image description here

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  • $\begingroup$ I am interested in examining key scientific arguments trying to explain the lag(While being consitant with the theory of man made global warming) to develop my own understanding of the subject.(So consensus the word consensus was used to mean contrary viewpoint in this context). You answer does not directly address the question posed. $\endgroup$ – Prathyush Nov 3 '16 at 10:42
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    $\begingroup$ @Prathyush I have tried to explain that the source you cited provides no solid evidence for a lag at all. If something is still unclear, please specify. $\endgroup$ – DilithiumMatrix Nov 3 '16 at 13:28
  • $\begingroup$ There is a lag and it is well established in the literature. See science.sciencemag.org/content/299/5613/1728 I am only looking for reasons why it could be explained consistent with theory of man made global warming. $\endgroup$ – Prathyush Nov 3 '16 at 13:43
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    $\begingroup$ @Prathyush It is not well-established. There may be a lag, and you would expect a lag in cases where temperature change (typically very slow rates of change) is not driven by CO2 changes but by other factors, but the uncertainties in the data are really large, which is why the paper you mention is so covered in caveats. $\endgroup$ – tfb Nov 3 '16 at 23:51
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    $\begingroup$ @Prathyush It is not, sorry. You don't know this, but I work on climate, and it just is not. $\endgroup$ – tfb Nov 4 '16 at 14:31
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CO2 can increase the earth's temperature due to the greenhouse effect (blocking the reflection of IR radiation), but the inverse is also true. I.e. when temperatures rise, more CO2 (for example from the ocean) will be released in the atmosphere. There is thus a positive feedback between temperature increase and CO2 emission, both causing each other.

Fortunately, this process will eventually reach a stable equilibrium. This means that if we emit a certain amount of previously stored CO2 in the atmosphere, the temperature will slightly increase, causing more CO2 to be emitted from e.g. the oceans, which in turn causes a slightly further increase in temperature, etc. Eventually, this will reach an equilibrium where both the temperature and the amount of CO2 in the atmosphere will have increased by a certain amount.

Paleoclimatic Ice Core data shows us that when temperatures rose in the past due to changes in the sun's activity or changes in the earth's orbit around the sun, CO2 levels have risen as well. Since a rise in CO2 levels leads again to an increase in temperature, these changes in CO2 levels throughout history have helped us to precisely model the feedback between a rise in temperature and an increase in CO2 levels.

Some people incorrectly use this 'increase in temperature causes increase in CO2 levels' argument to argue global warming is not man-made. It is however, important to realize that both cause each other. In addition, there are various kinds of evidence supporting that the recent increase of CO2 in the atmosphere over the past 50-100 years has been initially caused by humans burning fossil fuels (e.g. this can be seen from the fraction of C14 isotopes in the atmosphere) and is not caused by an initial rise in temperature. It will however have a rise in global temperature (and a further rise in CO2 levels) as its consequence.

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