Top down:
World carbon emission: 8 billion ton (32 billion CO2)
Transportation share: 33%
World vehicle population: ~800 million
Each vehicle: 3.3 ton per year
Carbon emission per day per vehicle: 9 Kg (35 Kg CO2)
Bottom up:
Assuming your daily milage: 30 mile
Gasoline comsumed: ~1.5 Gallon
Carbon emission per day for your car: 3.5 Kg (13.5 Kg CO2)