METHANE AND OTHER
So far, we have concentrated on C02 as the main greenhouse gas for a couple of reasons. The first reason is that it is something we can do something about, and the second is that production of C02 is going to grow rapidly as the world gets richer and people consume more energy. We would be remiss if we just stopped there, though, because there are a few other things going on that we should study. C02 is just one of the Big Six gases cited by the Kyoto Protocol. While C02 accounts for 60% of the problem, the other gases are actually much more toxic; thankfully, the level of emissions of these gases is minute in comparison with C02.
Of the Big Six, three are naturally occurring greenhouse gases. These include C02, methane (CH4) and nitrous oxide (NOx). The other three are man-made gases: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6).
Most of the emissions of C02 can be laid down clearly to a simple cause and effect relationship: we burn and we create gas. This is not the entire cause of C02 emissions, though. About one-quarter of the C02 enters the atmosphere through land use change, and a further 3% can be accounted for by cement production.