Carbon dioxide, even in minute quantities, causes almost two-thirds of man-made global warming. Man-made emissions have upset the Earth’s delicate natural balance. Natural ‘sinks’ can no longer cope so rising carbon dioxide levels cause global warming.

It is true that carbon dioxide exists in small quantities in the atmosphere, about 387 parts per million, or 0.04%, by volume at the present time. Other gases such as nitrogen and oxygen exist in far greater amounts but they are not greenhouse gases and so do not contribute to global warming. Carbon dioxide is just one of several greenhouse gases (methane and nitrous oxide are others) that exist in small amounts in the atmosphere. Greenhouse gases, because of their particular molecular structure, contribute to the greenhouse effect by trapping heat in the atmosphere. However it is important to recognise that the total warming effect of a greenhouse gas is due to a combination of its abundance, its molecular structure and its lifetime in the atmosphere (greenhouse gases eventually disappear, unless replenished, because they react with other gases or, in the case of carbon dioxide, are removed by living organisms or by dissolving in water). It so happens that carbon dioxide comes out ahead of all other greenhouse gases when these three factors are considered and accounts for about two-thirds of the global warming caused by greenhouse gases that have been emitted by mankind. Normally carbon dioxide is absorbed by natural ‘sinks’, such as tiny organisms living in the surface waters of the oceans and the vegetation in tropical forests, however the recent and continuing relentless increase in atmospheric carbon dioxide, plus the destruction of tropical forests, means that the natural equilibrium of the Earth’s system has been upset. The sinks can no longer cope with the amounts of carbon dioxide being added to the atmosphere and so the atmosphere is warming.