Question

In the absence of greenhouse effect, what would be the mean temperature of the earth?

Answer 1

Greenhouse gases in the air, mainly carbon dioxide, methane, and water vapour, trap radiation from the sun and act as a thermal blanket around the planet. Without the greenhouse effect, the average temperature of the earth could drop down to as low as $$-18^oC$$ and be covered in ice. Life as we know would not be able to survive.