Using the logarithmic mean of your range of about 3 kg of CO2 per day, and the fact that the average car emits about 0.2 kg of CO2 per km, this means that a typical day of Gemini coding produces about the same amount of CO2 as a 15 km (~9 mile) round-trip commute by car.

You can't average it like that because it's not an evenly random distribution. (And a place has to be very high in renewables, like on the order of 95%, before the emissions aren't dominated by the fossil component.) I don't know what the average datacenter uses for electricity source or region