CO2s

CO2s is a nonstandard plural sometimes used to refer collectively to carbon dioxide and related species. It is not common in formal chemical nomenclature, where CO2 denotes the simple molecule carbon dioxide. In various contexts, CO2s may encompass carbon dioxide molecules, isotopologues such as 13CO2 and 14CO2, dissolved inorganic forms in water (carbonic acid, bicarbonate, carbonate), and other gas-phase or dissolved forms involved in the carbon cycle. The term is more likely to appear in data sets, education materials, or discussions that track multiple carbon dioxide-related species together.

Chemical characteristics of carbon dioxide include a linear molecule with two double bonds between carbon and oxygen (O=C=O). It is a colorless, odorless gas at room temperature and is sparingly soluble in water, where it forms carbonic acid and its dissociation products. In aqueous solution, carbonic acid partially dissociates to bicarbonate and carbonate, buffering pH and influencing carbonate chemistry in oceans and soils.

Natural processes produce and consume CO2s as part of the carbon cycle. Respiration, decomposition, fermentation, and combustion release CO2, while photosynthesis consumes it. The atmosphere, oceans, terrestrial ecosystems, and sediments exchange carbon, with the oceans acting as a major reservoir that absorbs substantial atmospheric CO2. Isotopic analyses of CO2s help distinguish natural from anthropogenic sources and inform climate research.

Human activities—most notably fossil fuel burning and cement production—have raised atmospheric CO2 concentrations, contributing to the greenhouse effect and climate change. Global monitoring networks, such as those at Mauna Loa and other observatories, track CO2 levels, currently around the low hundreds of parts per million and trending upward. Mitigation approaches include reducing emissions, enhancing sinks, afforestation, energy efficiency, and carbon capture and storage.