Spiegel: The 1970s were a hazy time: Cars ran on sulfur-rich gasoline, power plants and heavy industry burned sulfur-rich coal. Europe lay under a blanket of fumes filled with sulphate particles. Acid rain brought the particles back to earth, ravaging the continent’s forests. That was then. The situation today is considerably different. Auto emissions are low in sulfur, power plants only run with smoke filters and acid rain is no longer an issue. But the success of efforts to restore Europe’s …