CO2d

CO2d is a term used in several contexts to denote a derivative or rate related to carbon dioxide, but it does not have a single, universal definition. Its precise meaning depends on the discipline and source.

In climate science and environmental modeling, CO2d is sometimes used as shorthand for the time derivative of atmospheric CO2 concentration, commonly written as dCO2/dt. In this usage, CO2d represents how quickly CO2 levels are changing over time and is derived from time-series measurements or model outputs. It is distinct from CO2 concentration itself, and from transport properties such as diffusion coefficients.

In data management or sensor software, CO2d may appear as a variable name or label for the differential value calculated from successive CO2 observations (for example, a first difference between measurements). When used in this way, explicit definitions are provided in accompanying documentation or code comments.

Other uses are possible in project codes, publications, or educational materials. Because CO2d is not standardized across disciplines, readers should consult the source to understand the intended definition in that context. See also CO2, dCO2/dt, atmospheric CO2 data, carbon cycle, and diffusion coefficient.