• During the 20th century, the Earth 's average surface temperature rose by around 0.6 ° C.

• This "natural greenhouse effect" is an important phenomenon to biological life on Earth.

• The Earth has an atmosphere, consisting mostly of nitrogen (78 % ), oxygen (21 % ) and a number of greenhouse gases, which affect the balance of light and ultraviolet energy coming from the Sun and heat energy leaving the Earth, the global energy balance.