Sunshine, in the form of
ultra-violet radiation, passes through the
ozone layer on its way to the planet's surface. When it hits the ground it is converted to
infra-red radiation and reflected back into the
atmosphere, and from there into
space.
Greenhouse gases trap the infra-red radiation and reflect it back towards earth, heating the planet up. Glass performs a similar function in a greenhouse.
Greenhouse gases include :
The concentration of most of these gases in the atmosphere has increased by 25% since industrialisation began.