It is true that some individual molecules of CO2 will remain in the atmosphere for thousands of years statistically speaking . But this is not the right way of looking at fossil fuel contribution.
Of course it is exactly the way to look at the fossil fuel contribution.
"Some individual molecules", amounting to 20% plus of all "individual molecules" introduced into the atmosphere by any form, are not completely removed by uptake from the oceans etc and remain in the air for hundreds of years.
In the meantime, more and more "individual molecules" (gigatons of them each year) are being pumped into the atmosphere of which 20% plus will again, and again, expand the time additional CO2 remains in the atmosphere again - for many many hundreds of years.
And then, as CO2 exchange does not result in a net draw down anyway, the time needed for further reaction to take place (CaCO3-rocks etc) means many thousands of years of lifetime for the atmosphere to recover its original concentration levels anyway, never mind the time needed after being artificially loaded with CO2.
Again let me emphasize that Anthro CO2 is so tiny compared to natural sourcing and sinking that even a very slight change in the natural balance will render any Anthro contribution from fossil fuel burning completely not only undetectable, but insignificant.
You have already agreed it is accepted as true how by the application of basic scientific principles... the observed variations trace constituents of CO2 in the atmosphere would greatly influence the heat budget of the Earth.
We've done this already. CO2 whether anthro or natural makes no difference. It is still CO2 and it will greatly amplify the warming effect.
Now you're saying it doesn't because the contribution is
undetectable, it isn't ,( I've already said why), and
insignificant ( it isn't, that basic chemistry you agree is true - says different).
No direct measurement of the Anthro contribution is possible.* It has to be estimated from calculation. The amount that CO2 goes up (this we can measure directly but with considerable scatter as to place and time) is assumed to be all coming from fossil fuels.
Sophisticated scientific techniques involving C13/C12 ratio observation provide accurate direct measurement and differentiates between nearly a couple dozen gases including anthro CO2 emissions. There is no assumption that all CO2 is coming from fossil fuel.
It is only your
assumption that is
assuming it is
assumed.
Rather than argue with you, I invite you to study this review article and then follow up by reading key papers which are cited at the end.
Carbon isotopes characterize rapid changes in atmospheric carbon dioxide during the last deglaciation
Thanks for those piezoe but you don't need to shout them and quite honestly, without reading more than you posted, the comment... "it is not just fossil fuel use that changes CO2 isotope mix.." makes the reading frankly beside the point.
The distinction is indeed made and the statement... ".. it is not just fossil fuel use that changes CO2 isotope mix, but temperature as well!!!" ... is surely no more than a truism.
By assuming an extremely long half life for CO2 added to the atmosphere, which actually never made logical sense in light of the many gigatons of annual natural sourcing and sinking
...while all the time Ignoring the logical sense of many gigatons of annual fossil fuel being burned and artificially introduced into the atmosphere. Plus deforestation to counter the natural balance , plus ocean acidification to unbalance it all further again on an ever increasing scale. That logical sense!
__________
* I have never been able to explain this to anyone who did not have training and experience in experimental science. Theoretical mathematicians, for example, sometimes have of trouble with this, believe it or not! It's because the concept of significant digits never enters their world. The problem of significant digits, and therefore the problem of differences in relative magnitudes, is a problem unique to the experimental sciences.
Ah! the old "scientists don't understand science... but I do!" argument.
You gotta ask yourself what exactly drives you towards preferring smoke and mirrors on this subject in preference to basic scientific principle. Because
that sure ain't making logical sense.