The most important and climate active naturally occurring GHGs are: Water vapour (H20), carbon dioxide (C02), nitrous oxide (N20), methane (CH4), and ozone (03). There are also manmade GHGs that also contribute to global warming.38 The most important contributor to global warming through the greenhouse effect is made by C02 followed in descending order by methane, chlorofluorocarbons (CFCs), ozone and nitrous oxide.39 With time, and especially over the past 50 years or so, rising concentrations of GHGs in the atmosphere have increased the level of absorption of the outgoing radiation. This has led to more heat being trapped in the atmosphere and consequently, in an increase in the average temperature of the earth's surface.