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Are the levels of natural (before the industrial revolution) levels of CO2 and ppm known? Also as a related question, should the "natural" levels be considered before the industrial revolution or before the start of the deforestation 8000 years ago?

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  • $\begingroup$ for the last 500000 years the CO2 level have been from 180-280 ppm we are at 410 ppm now i do not think this is safe. $\endgroup$ – trond hansen Feb 8 at 13:14
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    $\begingroup$ The absolute level is only one side of the coin, you also have to look at how fast the change happens, if the ecosphere as a whole can adapt to the changes $\endgroup$ – Erik Feb 8 at 13:37
  • $\begingroup$ 400 ppm CO2 is truly too low. CO2 in no way jose can possibly warm this planet! Mars has 95% CO2 atmosphere and that percentage is not helping Mar's atmosphere to warm. Yet Venus? 97% CO2...both planets lost the life and their oceans and the lighter gases got ripped off to be replaced by the CO2 that couldn't stay in sequestration because life and oceans were gone...thus almost 100 percent CO2. On both planets, one cold and one hot. Mankind is not MAKING more CO2 we are releasing CO2 from sequestration or storage a bit earlier. There is no global warming happening!! We are in a GSM... $\endgroup$ – stormy Feb 20 at 3:01
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There is no such thing as a single "natural" level of $CO_2$: In Earth's history, there have been levels much higher and much lower than currently, and they are all natural.

What we should consider instead is what levels of $CO_2$ are compatible with the mild and stable climate that humanity has enjoyed for the last few millennia, or conversely, which levels will upset the climatic equilibrium and send Earth into a completely new climatic regime.

The means to measure atmospheric $CO_2$ concentrations were invented during the industrial revolution, so we don't have direct records before that. However, we can reconstruct past $CO_2$ concentrations using proxies such as the analysis of air bubbles trapped deep within the ice in Antarctica.

Ice cores were drilled up to ~600 meters deep between 1987 to 1993 at Law Dome (Antarctica), allowing the reconstruction of $CO_2$ concentrations from the last millennium, and it looks like this:

enter image description here

Where the darker blue at the end corresponds to the direct instrumental record (source).

Later, another ice core from Vostok station in Antarctica was drilled to a depth of more than 3.6 km, allowing the reconstruction of atmospheric $CO_2$ concentration during the last 400,000 years, and it looks like this:

enter image description here

(Figure source)

The data from Law Dome and that of modern records at Mauna Loa, Hawaii are also displayed on the end for comparison.

More ice cores have been drilled after Vostok, and all of them tell more or less the same story.

So we know that atmospheric $CO_2$ concentrations now are much higher than at any other time since we invented agriculture. And the people that think they know how the atmosphere works run models and say that current levels will significantly upset the climate as we know it. On the other hand, the people who don't know how the atmosphere works (like me), should just stop producing so much $CO_2$, because we don't ourselves know what the effects could be, and at the same time, we rely on the climate to stay nice and stable to keep your flourishing society alive.

To address the last bit of the question, to transform 1 PPM by volume of atmospheric $CO_2$ into a GigaTon of Carbon you just have to multiply by 2.13. So the pre-industrial base level during the last millennia of 280 PPM is equivalent to ~596 GtC or 2,187 Gt of $CO_2$ (multiply again by 44/12, the ratio of $CO_2$ mass to C mass).

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  • $\begingroup$ This graph looks suspiciously like a HOCKEY stick Camilo! $\endgroup$ – stormy Feb 14 at 23:51
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    $\begingroup$ @stormy And what that is supposed to mean? I don't get it. $\endgroup$ – Camilo Rada Feb 15 at 3:25
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    $\begingroup$ @stormy I'm a Chilean glaciologist that doesn't work for any government. The data I showed here have been extracted by colleagues from Antarctic ice cores, I know some of them personally. Answers like the one you posted should be backed with references: big proofs for big claims. As me, there thousands of scientist that devote all their time to questions like this and that have found outstanding evidence to show that most of what you said in your answer is wrong, as well as many of John Casey claims. If you rather believing that all of us are conspiring against you, there is nothing I can do. $\endgroup$ – Camilo Rada Feb 15 at 22:05
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    $\begingroup$ @Camilorada...I've got to give you the name of this incredible geologist up here in the Pacific Northwest. I just know you will love his lectures! Free on the internet! Even non geologists LOVE learning from him! A real, black board teacher. He has nothing to do with warming, just geology! The PNW is such an amazing, geologically vigorous area with a powerful historic past. Look up Nick Zentner from Central Washington University. You will LOVE his lectures! Another super duper dude for human biology is Robert Sapolsky of Stanford University! Incredible FREE lectures! $\endgroup$ – stormy Feb 18 at 23:51
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    $\begingroup$ @CamiloRada this is an ongoing project right now beyondepica.eu/about it should provide good data about the last one and a half million years. $\endgroup$ – trond hansen Mar 12 at 13:21

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