• Because CO2 is chemically inert in the atmosphere and of rather uniform concentration, natural changes in atmospheric CO2 concentration depend only on the global sum of the photosynthesis, respiration, and air-sea flows.

• In addition, natural aerosols (e.g., sea salt, dust and emissions leading to the production of sulphate and carbon aerosols) are projected to increase as a result of changes in climate.

• Natural greenhouse gases include water vapour or moisture, carbon dioxide, methane, nitrous oxide and even ozone, which is more commonly associated with the ozone layer and ultraviolet radiation.

• In addition, natural ecosystems have cultural, religious, aesthetic and intrinsic existence values.

• Economic growth consumes natural resources and produces waste.

• If the effects of all greenhouse gases other than water vapour were ignored, the natural greenhouse effect would be about 60-70 % of observed values, compared to about 25 % if only CO2 were present.