National Geographic : 2016 Oct
PHOTO: CREDIT HERE UNITED STATES CHINA TAIWAN HAWAII (U.S.) ALASKA (U.S .) ASIA NORTH AMERICA EQUATOR North Pole PACIF ICOCEAN N ORTH30°120°E150° 180° 150°120°W 60°N SUBTROPICAL JET STREAM U.S. CHINA 30° 150°E 180° 150°W 60°N EQUATOR North Pole TAIWAN Reductions in the U.S. During China’s boom, American regulations led to a 21 percent reduction of nitrogen oxide emis- sions in the western U.S. These reductions were partly offset by transpacific pollution. SURFACE LAYER OZONE Local geography and atmo- spheric conditions dictate where surface ozone travels. Surface ozone can move, but the majority produced in China remains as smog in East Asia. FREE-TROPOSPHERIC OZONE The burning of fossil fuels creates nitrogen oxides and carbon monoxide, which combine in the presence of sun- light to form ozone. Attempts to reduce ozone in one region can be offset by the effects of global circulation.