The relevance of this demonstration is that the public is told that fossil fuel combustion is increasing the CO2 content of the atmosphere, but it is difficult for many to understand how human activity could conceivably change the atmospheric composition. If it is recognized that CO2 is only about 0.04% of the atmosphere, it should help the public understand that human activity has been able to increase the CO2 by a quantity approaching 40%, Because the atmospheric CO2 content is low, the current annual production of CO2 of 31.5 gigatonnes from combustion amounts to about 1% of the CO2 content of the atmosphere (total of about 3,000 gigatonnes of CO2) Not all