What scientists and policy makers are concerned about is an accelerated global warming due to the immission into the atmosphere of large quantities of "greenhouse gases", most notably CO2, CH4, and CFC.
Svante Arrhenius, winner of the Nobel Prize in Chemistry, 100 years ago predicted that the pollution introduced by rapid industralization would cause a warming of the Earth. He predicted that the temperature would increase by a few degrees for a doubling of the concentration of CO2 in the atmosphere as a result of fossil and forest burning.
The amount of carbon dioxide has indeed increasd over the years. Samples taken at Manua Loa (Hawaii) and from drilling into ice sheets, have shown an increase of CO2 by 25-30% in the last century. Please click here to see the data. This increase has tracked the increase of the average temperature on Earth, about 0.5 C in the last century.
1. It is not yet clear how much of this CO2 is retained in the atmosphere and how much is exchanged with the oceans. It is without doubt, however, that CO2 concentration in air has increased since the first part of 1800s. In the previous 1,000 year, CO2 changed by less than 5%.
2. CO2 concentration changes seasonally, higher in the fall, lower in the spring. This is due to the change of foliage cover, mostly in the northern hemisphere.
Methane concentration in the atmosphere has increased because of:
CFC (Chlorofluorocarbons) concentration increased because of its use in electronic industry (to clean computer boards) and in refrigeration systems. The production of CFC is now regulated worldwide, while phasing to alternative fluids is taking place.This page was produced by Gianfranco Vidali