The question whether human activities seriously affect climate is asked with increasing voice these days. Quite
understandable since the climate appears to be out of control with the significant global temperature increases
already seen during the last three decades and with still heavier temperature increases to come in the future ac-
cording to prognoses, among others, in the recent comprehensive IPCC reports [1]. However, the most recent
climate data [2], show global temperature development levelling off or even turning negative since 2001 in con-
trast to the anticipated course related to the steady increases in the concentration in the atmosphere of
green-house gasses, primarily carbon dioxide and methane