'The end of communism has contributed to global warming.' This may sound like a joke but it isn't. It's called the Gorbachev effect by German scientist Graßl (in a recent issue of Geophysical Research Letters). The end of communism has done a lot for cleaner air in middle Europe (closing down of dirty industries in GDR, Poland and Chechoslovakia). As a consequence, less small dirt particles and aerosols are in the clouds and therefore more sun energy comes through.

It has been debated controversely whether more aerosols is a cooling or a warming factor but the end of communism with a quite abrupt closing down of dirty industries has provided the researchers with a real life experiment of enormous proportions. The different and differing models can be checked against the data and it seems to be clear now, more than 10 years later, that the clouds now let more sunlight through (2.8%) and that, on the balance of all factors, cleaner air contributes to global warming.

Graßl's recommendation, by the way, is not to reintroduce communism or to provide tax deduction benefits to dirty production plants, but to acknowledge that it is a very complicated field and that sensible action "has to tackle all reasons for climate change at the same time".

Wolfgang