Some pollutants, including soot, nitrates and sulfates from fossil-fuel burning, coat the planet in a fine, aerosol haze. Scientists say too many particles floating around can reflect sunlight, impair crop production in certain places and contribute to cooler temperatures in some places. Conversely, diesel soot and carbon dioxide are powerful greenhouse gases. They shroud the planet like a blanket, preventing heat from escaping Earth and increasing world temperatures. Cleaning up global smog will not be easy.
Blame falls on industrial and developing nations alike.
Although the United States has some of the world's most stringent pollution control laws, those controls do not apply abroad. International cooperation, similar to the agreement between Canada and the United States to reduce acid rain emissions, will be required. Michael Kenny, executive officer for the California Air Resources Board, said one strategy is to seek international standards for vehicles and power plants. He said multinational corporations that manufacture those and other products need to take a leadership role. Environmental groups and other nongovernmental organizations also need to address the matter.