We don't know that increased CO2 results in increased temperature. The temperature was already increasing long before human-based CO2 was increasing.

There is evidence in the geological record that CO2 increases lagged temperature increases. There is evidence in the geological record that CO2 levels, and temperatures, were much higher than they are today.

Water vapor and the sun are the two biggest inputs into the greenhouse effect on Earth, not CO2. CO2 is infinitesimal by comparison.