What is CO₂?

Carbon dioxide is made up of two oxygen atoms paired with a single carbon atom, chemically represented as CO₂. Occurring naturally in its gaseous form, it is essential to life on earth because of its central role in the carbon cycle - a series of complex chemical processes that govern the metabolism of every organism on the planet. Put simply, living organisms release CO₂ during respiration and terrestrial plants and marine phytoplankton use it for photosynthesis, then it returns to animals through food intake and digestion. The average concentration of CO₂ in our atmosphere is 0.04%. Another of its crucial roles is to create the greenhouse effect, a natural process that traps a portion of the sun's heat on the surface of our planet, ensuring that temperatures are suitable to life, as happens in greenhouses during the winter. Without CO₂, the earth's surface would be much colder and there would be no vegetation at all. 

However, as CO₂ levels rise, the greenhouse effect also becomes more intense, leading to an increase in global average temperatures, which in turn affects climate patterns.

This happens because all fossil fuels contain carbon that was absorbed by living organisms millions of years ago. When these fuels are burned, carbon is released back into the atmosphere as carbon dioxide, upsetting in the space of a few decades a balance that had taken millennia to achieve. Apart from its impact on the climate, CO₂ is an inert, odourless and colourless gas. It is neither flammable nor explosive, which makes it suitable for applications such as fire extinguishers. Other common uses of CO₂ include the decaffeination of coffee, the production of dry ice and, of course, the preparation of carbonated drinks.