If Earth's climate is controlled by CO2, then why is Mars so cold in comparison to Venus? Mars is very cold (average about –60°C) and Venus is very hot (+460°C).
The density of the atmosphere on Venus is approximately $65\ \mathrm{kg/m}^3$, whereas, the density of Earth's atmosphere is $1.217\ \mathrm{kg/m}^3$ and the density of Mars's atmosphere is $0.02\ \mathrm{kg/m}^3$. Earth's atmosphere is 60 times denser than that of Mars; Venus's atmosphere is over 3000 times denser.
With such a thin atmosphere on Mars, there is little atmospheric mass to retain heat, despite the atmosphere being composed of 95.3 percent carbon dioxide.
For the last 800,000 years, Earth's ambient CO2 NEVER went up above 280 ppm average. In the last 10,000 years, we've had 20 major warming and cooling events and ambient co2 remained fairly constant.....