The claims you promote are without any scientific background, here's why:
The concentration of 500 ppm now would make all ice on Earth disappear, whereas 400 million years ago there would be needed 3000 ppm (note three thousand, ten times more than it was before we stat high-rate burning) to achieve the same, as, among other effects, the solar constant was 4% lower then:
Now consider this: during the last 800,000 years CO2 concentration oscillated between 200 and 300 ppm. The humanity pushed it to 400 ppm in around 100 years, and the 500 ppm is the point of no ice on the Earth.
> The claims you promote are without any scientific background, here's why
None of this addresses the actual issues I was raising.
> The concentration of 500 ppm now would make all ice on Earth disappear
According to the hypothesis given in the paper you link to. But it's a hypothesis, not a fact. One obvious omission in the paper is treatment of other forcings besides CO2 and solar. Also, all of the data is proxy data, and the solar forcing is not even based on data but on an assumed linear rate of increase in the solar constant.
> None of this addresses the actual issues I was raising.
Just when somebody closes the eyes and screams at the same time "I don't see anything." It was exactly on the subject: when you claim that millions of years ago the concentration was higher, we even know that the state of the Earth wasn't comparable. Not to mention that humans didn't exist.
The concentration of 500 ppm now would make all ice on Earth disappear, whereas 400 million years ago there would be needed 3000 ppm (note three thousand, ten times more than it was before we stat high-rate burning) to achieve the same, as, among other effects, the solar constant was 4% lower then:
http://droyer.web.wesleyan.edu/PhanCO2(GCA).pdf
Now consider this: during the last 800,000 years CO2 concentration oscillated between 200 and 300 ppm. The humanity pushed it to 400 ppm in around 100 years, and the 500 ppm is the point of no ice on the Earth.