Methane levels to rise and add to Global Warming
Pastor Dale Morgan
Methane levels to rise and add to Global Warming*
Ian Sample, science correspondent
Thursday September 28, 2006
The Guardian
Scientists have uncovered evidence that levels of the greenhouse gas
methane will rise sharply in the next few years, warming the planet
faster than previously expected. The new data from an international team
of scientists has revealed that while methane levels began to level off
in the 1990s, emissions from human activity started to climb again
before the end of the last century.
Phillipe Bousquet at the Laboratory of Sciences of Climate and the
Environment in Paris joined scientists from the US, Australia, the
Netherlands and South Africa to examine methane levels in the atmosphere
from the early 1980s using a network of 68 ground-based tracking
stations around the world. The upturn in man-made emissions was masked
by a drop in the methane released naturally from wetlands, by unusually
dry weather.
Writing in the journal Nature today, the scientists raise fears that
inevitably wetter weather will return the wetlands to their normal state
in the next three to five years, boosting the amount of methane in the
atmosphere by 10m tonnes a year. Although methane levels are 200 times
lower than the most widespread greenhouse gas, carbon dioxide, molecule
for molecule, it is 20 times more effective at retaining heat in the
atmosphere.
They discovered that methane levels fell from nearly 12 parts per
billion in the 1980s to four parts per billion in the 1990s. But their
calculations show that the slowing of emissions was only partly to do
with strict limits imposed on industry. Since 1999, levels of methane
from human activity have been rising in Asia, consistent with a surge in
coal usage in China.
"The bad news is that the slowdown in global methane emissions in the
past few decades was only temporary," said Jos Lelieveld, director of
the Max Planck Institute for Chemistry in Mainz, Germany.