[cogitator]

I think comparing human activity today against human activity 55 million years ago may not be scientifically accurate.

The main analogous factor is that the PETM is the only period in the Cenozoic where there was clearly a rapid rise in atmospheric greenhouse gases absent any other climate forcing agents. The resulting effect on global temperatures is pretty obvious.

[palmer]

The main analogous factor is that the PETM is the only period in the Cenozoic where there was clearly a rapid rise in atmospheric greenhouse gases absent any other climate forcing agents. The resulting effect on global temperatures is pretty obvious.

Warming and CO2 increases are often coincident, but it doesn't mean one causes the other. The phrase "climate forcing agents" implies a degree of certainty that would come from a testable scientific theory rather than an artifact of computer models repeatedly shown to be wrong.