It is estimated that the average temperature on Earth is 16 degrees celsius.

This average temperature is determined by a delicate balance produced between the solar energy received by the Earth and the this same energy being reflected back into space.

Greenhouse gases (water vapour, carbon dioxide, ozone, methane and nitrous oxide) are crucial for providing a blanket effect that ultimately keeps the Eath warmer by retaining and sendng back into the atmosphere part of sun's long-wave radiation thus keeping the Earth's temperature warmer.