Arctic Methane Spike Startles Scientists
Arctic permafrost leaking methane at record levels, figures show
The Guardian (U.K.), Jan. 14, 2010
Experts
say methane emissions from the Arctic have risen by almost one-third in
just five years, and that sharply rising temperatures are to blame
Scientists
have recorded a massive spike in the amount of a powerful greenhouse
gas seeping from Arctic permafrost, in a discovery that highlights the
risks of a dangerous climate tipping point.
The
discovery follows a string of reports from the region in recent years
that previously frozen boggy soils are melting and releasing methane in
greater quantities. Such Arctic soils currently lock away billions of
tonnes of methane, a far more potent greenhouse gas than carbon
dioxide, leading some scientists to describe melting permafrost as a
ticking time bomb that could overwhelm efforts to tackle climate change.
They
fear the warming caused by increased methane emissions will itself
release yet more methane and lock the region into a destructive cycle
that forces temperatures to rise faster than predicted.
Paul
Palmer, a scientist at Edinburgh University who worked on the new
study, said: "High latitude wetlands are currently only a small source
of methane but for these emissions to increase by a third in just five
years is very significant. It shows that even a relatively small amount
of warming can cause a large increase in the amount of methane
emissions."
Global
warming is occuring twice as fast in the Arctic than anywhere else on
Earth. Some regions have already warmed by 2.5C, and temperatures there
are projected to increase by more than 10C by 2100 if carbon emissions
continue to rise at current rates.
Palmer
said: "This study does not show the Arctic has passed a tipping point,
but it should open people's eyes. It shows there is a positive feedback
and that higher temperatures bring higher emissions and faster warming."
The
change in the Arctic is enough to explain a recent increase in global
methane levels in the atmosphere, he said. Global levels have risen
steadily since 2007, after a decade or so holding steady.
The new study, published in the journal Science,
shows that methane emissions from the Arctic increased by 31% from
2003-07. The increase represents about 1m extra tonnes of methane each
year. Palmer cautioned that the five-year increase was too short to
call a definitive trend.
The
findings are part of a wider study of methane emissions from global
wetlands, such as paddy fields, marshes and bogs. To identify where
methane was released, the researchers combined methane levels in the
atmosphere with surface temperature changes. They did not measure
methane emissions directly, but used satellite measurements of
variations in groundwater depth, which alter the way bacteria break
down organic matter to release or consume methane.
They
found that just over half of all methane emissions came from the
tropics, with some 20m tonnes released from the Amazon river basin each
year, and 26m tonnes from the Congo basin. Rice paddy fields across
China and south and south-east Asia produced just under one-third of
global methane, some 33m tonnes. Just 2% of global methane comes from
Arctic latitudes, the study found, though the region showed the largest
increases. The 31% rise in methane emissions there from 2003-07 was
enough to help lift the global average increase to 7%.
Palmer
said: "Our study reinforces the idea that satellites can pinpoint
changes in the amount of greenhouse gases emitted from a particular
place on earth. This opens the door to quantifying greenhouse gas
emissions made from a variety of natural and man-made sources."
Palmer
said it was a "disgrace" that so few satellites were launched to
monitor levels of greenhouse gases such as carbon dioxide and methane.
He said it was unclear whether the team would be able to continue the
methane monitoring in future. The pair of satellites used to analyse
water, known as Grace, are already over their expected mission life
time, while a European version launched last year, called Goce, is
scheduled to fly for less than two years.
The
new study follows repeated warnings that even modest levels of global
warming could trigger huge increases in methane release from
permafrost. Phillipe Ciais, a researcher with the Laboratory for
Climate Sciences and the Environment in Gif-sur-Yvette, France, told a
scientific meeting in Copenhagen last March that billions of tonnes
could be released by just a 2C average global rise.
guardian.co.uk © Guardian News and Media Limited 2010
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