• It was probably the constant decrease in carbon dioxide in the atmosphere - due to the development of life - that by stocking large quantities of organic matter in the form of limestone, coal or petroleum, regulated the climate (the 'Gala hypothesis' from the English ecologist, James Lovelock).

• Most of this energy comes from the burning of fossil fuels, such as oil, coal and gas, which release carbon dioxide, the main greenhouse gas, into the atmosphere.

• Under mitigation policies, coal, possibly oil and gas, and certain energy-intensive sectors, such as steel production, are most likely to suffer an economic disadvantage.