[aperson]

It doesn't back your claim because the upper bound estimates of 2000 ppm have been refuted by more recent evidence. Our proxy records have high uncertainty that is slowly narrowing over time as we improve our paleoclimate record. The paper that I linked you to was from 2014 and was significantly cited because it refuted those overly high estimates. Modern scientific consensus in 2018 is better than modern scientific consensus in 2004 in the same way that our 5 day hurricane error cone in 2018 is as big as our 3 day hurricane error cone in 2004.

So your claim that carbon levels haven't significantly changed is bullshit because the ceiling is now twice as low as it was originally. And for the record, our current value of ~410ppm is higher than any other time during the quaternary altogether. It hasn't occurred since the mid Paleocene and by the late 21st century we could reach values that are more in line with modern estimates of the Eocene.

And of course, now that your claims are shown to be complete bullshit because someone waltzed into the thread that actually know the science, you're going to go back to your tired trope of calling modern climate science "agenda-driven" because you're a stupid man that can't admit when you're wrong.