carbon dioxide (CO2)

One of the trace gases present in the atmosphere, whose origin is both natural and due to the combustion of carbon-rich fossil fuels - such as petroleum, mineral coal, or natural gas -, the burning of biomass, as well as changes in land use and certain industrial activities. It is the main greenhouse gas of anthropogenic origin, whose atmospheric concentration has increased very markedly since the middle of the last century, in parallel with the emissions generated by our activities. By the end of the second decade of the 21st century it reaches 415 parts per million by volume. It is a colorless, odorless gas with a slightly acidic taste, which at high concentrations causes asphyxiation. It is not flammable and is soluble in water. Its atmospheric residence time ranges between 5 and 200 years. A single value cannot be established, due to the complexity of the carbon cycle, with different rates of gas absorption linked to different natural removal processes. Its chemical formula is CO₂ and it is also known as carbonic anhydride or, by the now-disused archaism, carbon bioxide. In climate change studies the concept of "carbon dioxide equivalent" is used, defined as the amount of CO₂ that would be needed to exert the same radiative forcing (warming) produced by a given greenhouse gas or a mixture of several of those gases.