Chinese Smog Clouding US Skies,
Condensed by Native Village
Since the 1980s, surface ozone levels in the U.S. have
decreased by 30%. That drop is due to
stronger environmental regulations. But
scientists puzzled over why ozone levels in
the free troposphere -- two to five
miles above sea level -- increased 14% from 1995
points to air pollution from Asia as a major
cause. The study tracked smog from Asian
nations like China as it drifted over the
Pacific Ocean towards the U.S.
"We studied a broad range of ozone levels
that we could track coming from Asia," said
Owen R. Cooper from the University of Colorado. "And we know
that, though the Chinese government has just
started to measure ozone levels there, the
gas has been increasing in China over the
past 10 years."
Cooper studied the drifting ozone in
springtime when the jet stream transports
the most pollution across the Pacific. Spring ozone
levels have risen 29% in the U.S.
Cooper is not sure how much ozone comes from
Asia but said the amount doubles when the jet stream passes over
southern and eastern Asia.
we still don't know is how much of the ozone
from Asia is coming down to the earth's
surface and affecting health in the United
States," Cooper said.
Along with other "greenhouse
gases" like as carbon dioxide and
methane, ozone contributes to global