> the sun was about 20% dimmer back then According to wikipedia[1], the Sun increases in brightness steadily about 1% every 100M years, yet we had CO2 levels 1

> the sun was about 20% dimmer back then According to wikipedia[1], the Sun increases in brightness steadily about 1% every 100M years, yet we had CO2 levels 10 times higher than now about 500M years ago. [1] https://en.wikipedia.org/wiki/Solar_luminosity https://en.wikipedia.org/wiki/Solar_luminosity