Completely irrelevant. Humans cannot survive in the conditions of the Cambrian. Merely going back to the Cambrian is enough to ensure our extinction. No one car

Completely irrelevant. Humans cannot survive in the conditions of the Cambrian. Merely going back to the Cambrian is enough to ensure our extinction. No one cares that the CO2 levels were higher then. What matters is that we will all be dead if we go anywhere near those levels.