HEH. 

Reductions in industrial emissions
in many countries, along with the use of particulate filters for car
exhausts and smoke stacks, seem to have reduced the amount of dirt in
the atmosphere and made the sky more transparent.

That
sounds like very good news. But the researchers say that more solar
energy arriving on the ground will also make the surface warmer, and
this may add to the problems of global warming. More sunlight will also
have knock-on effects on cloud cover, winds, rainfall and air
temperature that are difficult to predict. 

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