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How has the increase in global CO2 been attributed to an anthropogenic cause?

It would seem to me that this could be definitively determined on the basis of placing gas spectrometers on the exhausts of a stratified random sample of exhaust pipes: (a) Motor vehicles, (b) Aircraft (c) smoke stacks of factories. et cetera. Has this been done or are we just guessing?

There is a very great answer show below that essentially says from:
(a) The known GHG emissions of the fossil fuels
(b) The known fossil fuel consumption for last year
(c) The known increase in atmospheric GHG last year
we can use simple arithmetic to determine how much of this emission has an anthropogenic cause.

Because the ocean is such a powerful GHG sink, I would expect that the above process might account for more than 100% of the increase of atmospheric GHG.

I am still trying to find the data to quantify the above

The EPA relied on the IPCC assessment:
Human activities are responsible for almost all of the increase in greenhouse gases in the atmosphere over the last 150 years.1 https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions

  1. IPCC (2007). Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis.

This graph shows all CO2 emissions and how much goes into the atmosphere, thus proving that humans cause much more than all of the increase of CO2 in the atmosphere.

https://www.carbonbrief.org/what-global-co2-emissions-2016-mean-climate-change

https://www.carbonbrief.org/wp-content/uploads/2016/11/GlobalCarbonBudget_3.png

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There are multiple ways of determining this, but the simplest, which doesn't require any high-tech monitoring devices on exhaust pipes and the like, is simply to determine how much fossil fuel (coal, oil, &c) is mined each year. This economic data is readily available from for instance the CIA World Factbook: https://www.cia.gov/library/publications/the-world-factbook/

From this, you do a bit of simple chemistry, e.g. every 12 tons of coal burned produces 44 tons of CO2. Compare the amount produced with the measured increase in CO2, and you'll find they match. QED

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    $\begingroup$ A more complete answer would include the measurement of the changing proportions of carbon isotopes, since we can tell that the increasing proportion of CO2 is largely driven by burning long-buried fossil fuels. $\endgroup$ – jeffronicus Apr 8 at 20:55
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    $\begingroup$ This answer is weak beacuse it is a one-relation-only answer. While I agree with your thesis, there is a lot of people that can deny this answer by showing that, for example, there are many natural phenomena that release CO2 in the atmosphere. The answer to this question needs to be a list of demonstrations, or another form od container of multiple yet coordinate scientific thesis (a report, for example, or a cause effect graph) $\endgroup$ – Tms91 Apr 8 at 21:47
  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – gerrit Apr 10 at 9:37
  • $\begingroup$ @Tms91: The "multiple processes" idea doesn't hold, because (quite apart from the fact that no such process has ever been discovered) if there was some other process that released anywhere near the same amount of CO2 as fossil fuel burning, then the amount of CO2 in the atmosphere would be much higher. Duh! $\endgroup$ – jamesqf Apr 11 at 17:26
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    $\begingroup$ @Tms91 Other processes aren't important at all. Since the increase in atmospheric CO2 matches carbon burned the only way other sources would matter is if you could somehow show all the burned carbon didn't end up in the atmosphere, which is impossible. $\endgroup$ – Turksarama Apr 14 at 1:41
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The question is too generic to be specifically answered in few lines.
The answer to this question is the history of climate change science itself.

You can find a good essay here:

Historical Overview of Climate Change Science

But to understand it, you probably need to start from here:

Understanding and Attributing Climate Change

IMHO even in these essays you won't find a quick and short answer to your answer.
These whole essays represent a part of the answer to your question.

Also note that climate change is not just linked to gases emissions, but to anthropic-induced changes in the natural carbon cycles. This means that also land use change (intensive agriculture, intensive farming, deforestation) is responsible for climate change, even if "there is no chimney".

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  • $\begingroup$ The original answer proves that the original question was sufficiently specific. $\endgroup$ – polcott Apr 8 at 21:48
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    $\begingroup$ No, it is not. The fact that the reports I linked show many ways the scientists used to demonstrate that the increase in global CO2 has anthropogenic cause, shows that there are several answers to the question. Also, IMHO jamesqf answer is weak. I explained why in comments. $\endgroup$ – Tms91 Apr 8 at 21:58
  • $\begingroup$ @Tms91 is correct. It's possible for two numbers to be equal and still not be related. The answer assumes there are no other changes in the production or consumption of CO2. $\endgroup$ – user967 Apr 8 at 23:23
  • $\begingroup$ @BarryCarter "find evidence that CO2 increases in sync with fossil fuel usage." That is reasonable. $\endgroup$ – polcott Apr 9 at 18:34
  • $\begingroup$ Let us continue this discussion in chat. $\endgroup$ – user967 Apr 9 at 18:35

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