The global temperature has increased in recent time, as has the atmospheric
concentration Of CO2, CH, and other gases. However, most of the temperatur
e increase occurred before the anthropogenic release Of CO2 became a potent
ially important factor. Greenhouse gases cause a warming of the world becau
se these gas molecules absorb outgoing long-wave radiation and therefore le
ss radiation will be lost to space (1). The effect of an increased atmosphe
ric concentration of greenhouse gases is not known; theoretically, the effe
ct is nonlinear and decreases with increasing concentration (2). Changes in
solar irradiation also have an impact on the global climate although the m
agnitude of this impact is still unclear. The relevance,and weight of some
of the arguments used in support of the theory that the climate is highly s
ensitive to greenhouse gases, in particular to CO2, are questioned here.