What they mean are “carbon dioxide emissions” and a “carbon dioxide footprint”.

This is not merely an academic point but is part of the way the language of the debate is distorted to bolster concerns about possible human-caused climate change. Ignoring oxygen atoms and calling CO2 ‘carbon’ is like ignoring the oxygen in water (H2O) and calling it ‘hydrogen’. Most of the public would regard such a communications trick as ridiculous. Imagine getting a hydrogen tax bill, only to be told later that was water tax.

Such deceptions do serve a purpose, however: to frighten the public into CO2 cuts. Using such phrases as “harmful carbon emissions” encourages people to think of the gas as ‘dirty’, like graphite or soot. Referring to CO2 by its proper name only would help people remember that it is an invisible gas essential to plant photosynthesis and so all life.