Carbon dioxide equivalent (CDE) and equivalent carbon dioxide (CO 2e and CO 2eq) are two related but distinct measures for estimating how much global warming a given type and amount of greenhouse gas may cause, using the functionally equivalent amount or concentration of carbon dioxide (CO 2) as the reference. CO 2e calculations depend on the time-scale chosen, typically 100 years but occasionally 20 years or less.[1][2] They also depend on assumptions about the amount of time a given pollutant will remain in the atmosphere, which rely on other assumptions such as the amount of natural carbon sequestration that will occur in the future.