Recent changes of CO total column amount over Russia.

Is CO concentration increasing, decreasing or being constant in the Northern Hemisphere? A consideration of total column CO measurements in Russia compared with similar measurements in Switzerland gives evidence that total CO had a decade-long period of stability over Europe between the mid 1980s and the mid 1990s. During a period between 1997 and 2001, annual means for four years of five were lower than annual means between 1987 and 1996. Exclusion was 1998, when record high CO total column amount has been observed. The data for the first half of 2002 confirm this depletion. The reasons for these CO changes are discussed.