If there was no CO2 in the earth’s atmosphere the temperature

If there was no CO₂ in the earth’s atmosphere the temperature of earth’s surface would be

1. higher than the present form environmental issues
2. less than the present
3. the same
4. dependent on the amount of oxygen in the atmosphere from environmental issues

CO₂ is a green house gas which traps the solar radiation i.e. heats up the earth’s atmosphere.