Key Points
Enhanced acidity (average pH < 5.0)
A product of industrial air pollution
Problems in regions downwind
Sulfate aerosol conceals greenhouse warming
Reduction facilitated by SO2 emissions trading
- Established in U.S. by Clean Air Act 1990
- Enables stricter standards than command and control approach
- Presumes effective monitoring of actual emissions
- Prototype for international allowance trading of CO2