“You have a very leaky system,” study co-author
Colm Sweeney, a NOAA atmospheric scientist,
said this week.
The six cities spewed nearly 937,000 tons of
methane (850,000 metric tons), which is more
than twice what the U.S. Environmental Protection
Agency estimates, according to the study in the
journal Geophysical Research Letters.
Methane comes from different places, not just
natural gas, and that’s where the study found
the biggest change from what the government
had previously thought.
The EPA’s estimates had figured much of the
methane coming out of the five cities spewed
from landfills and wetlands, not natural gas for
home use. But the airplane monitors, which
could differentiate between landfill gas and
natural gas based on other chemicals that come
out, found that 88% of the methane was natural
gas, except in Providence.
So scientists calculated that nine times as
much natural gas was being released as EPA
had estimated.
Previous studies had looked at individual cities
using different methods. This study is the first to
give a comprehensive look over a large area.
Cornell University’s Robert Howarth, who wasn’t
part of the study, praised it, saying it “shows the
problem is widespread.”
Methane traps about 30 times more heat than
carbon dioxide, but doesn’t last nearly as long.
By showing that leaks are a big issue, the study
“represents a huge opportunity to get some
early gains on controlling greenhouse gas
emissions,” Sweeney said.