Placing atmospheric CO2 in perspective

Atmospheric carbon dioxide, which amounts to 320 parts per million (ppm) by volume, rather than being a pollutant, is essentially a thread of life woven through the globe on which we live. In the past century alone, the amount of CO2 in the atmosphere has increased by 40 ppm, with levels increasing at a current rate of about 0.75 × 1010 tonnes per year. Fortunately, man can tolerate CO2 levels many times present concentrations, and plant life actually grows better at increased CO2 levels. What does cause concern is the effect that atmospheric CO2 has on the earth's climate. It appears that the 40-ppm increase over the last century may have contributed to a global temperature increase of the order of 0.2 K. Since 1940, however, the global atmospheric temperature has been decreasing-an indication that other factors (such as atmospheric dust) are of much greater importance in determining the overall heat balance of the world.