4.12 The Greenhouse Effect

4.12 recall that water vapour, carbon dioxide, nitrous oxide, methane and CFC's are greenhouse gases

This diagram explains the effect very well:

(a) is the UV light from the sun (short wavelength with high energy) 

(b) + (h) show that 50% is reflected back out into deep space (by things like clouds)

(c) represents absorption on the earth's surface, where the UV light is converted into Infra-red 
(d) shows the Infra-red (longer wavelength) being emitted back out
(e) some of this is lost out to space as heat
(f) shows the greenhouse gases (water vapour, CO₂, CH₄, etc.)

(g) The I.R. light hits the greenhouse gas and absorbs it, but then re-emits it but re-distributes it, with some of the I.R. heading back to earth

The Hypothesis of The Enhanced Greenhouse effect is that if we emit more Carbon dioxide and Methane they will absorb more of the escaping infra-red radiation and emit it back to earth, raising the temperature higher. and eventually causing Climate change.

CFC's (chlorofluorocarbon's)

 have an effect on the ozone layer (O₃)

CCl₃F à sunlight à CL₂F^- + CL^-
CL^- catalyses the breakdown of O₃ to O₂, O₃ is better at absorbing UV light than O₂ so we are basically removing the protection.