What is inadvertent weather modification?
While attempts at deliberately altering the weather have met with only modest suc cess, humans have been changing local weather and perhaps global climate simply by going about their daily activities. Clouds form in the smoke plumes of factories and steel mills. Oceangoing ships leave trails of clouds extending 1,000 miles behind them as they pump billions of cloud nuclei from their smoke stacks into the marine air. Cities are warmer than their rural surroundings. There is some evidence that precipi tation is higher downwind of some cities. Visibility has dropped dramatically in many parts of the industrialized world due to the vast amounts of smoke, soot, and sulfate particles belched into the atmosphere.