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Greenhouse Gases, Carbon Dioxide and Methane, Rise Sharply in 2007

ScienceDaily

Thursday 24 April 2008

Last year alone global levels of atmospheric carbon dioxide, the primary driver
of global climate change, increased by 0.6 percent, or 19 billion tons. Additionally
methane rose by 27 million tons after nearly a decade with little or no increase.
NOAA scientists released these and other preliminary findings today as part
of an annual update to the agency’s greenhouse gas index, which tracks
data from 60 sites around the world.

The burning of coal, oil, and gas, known as fossil fuels, is the primary source
of increasing carbon dioxide emissions. Earth’s oceans, vegetation, and soils
soak up half of these emissions. The rest stays in the air for centuries or
longer. Twenty percent of the 2007 fossil fuel emissions of carbon dioxide are
expected to remain in the atmosphere for thousands of years, according to the
latest scientific assessment by the International Panel on Climate Change.

Viewed another way, last year’s carbon dioxide increase means 2.4 molecules
of the gas were added to every million molecules of air, boosting the global
concentration to nearly 385 parts per million (ppm). Pre-industrial carbon dioxide
levels hovered around 280 ppm until 1850. Human activities pushed those levels
up to 380 ppm by early 2006.

The rate of increase in carbon dioxide concentrations accelerated over recent
decades along with fossil fuel emissions. Since 2000, annual increases of two
ppm or more have been common, compared with 1.5 ppm per year in the 1980s and
less than one ppm per year during the 1960s.

Methane levels rose last year for the first time since 1998. Methane is 25
times more potent as a greenhouse gas than carbon dioxide, but there’s
far less of it in the atmosphere-about 1,800 parts per billion. When related
climate affects are taken into account, methane’s overall climate impact
is nearly half that of carbon dioxide.

Rapidly growing industrialization in Asia and rising wetland emissions in the
Arctic and tropics are the most likely causes of the recent methane increase,
said scientist Ed Dlugokencky from NOAA’s Earth System Research Laboratory.

“We’re on the lookout for the first sign of a methane release from
thawing Arctic permafrost,” said Dlugokencky. “It’s too soon
to tell whether last year’s spike in emissions includes the start of such
a trend.”

Permafrost, or permanently frozen ground, contains vast stores of carbon. Scientists
are concerned that as the Arctic continues to warm and permafrost thaws, carbon
could seep into the atmosphere in the form of methane, possibly fueling a cycle
of carbon release and temperature rise.

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Adapted from materials provided by National Oceanic And Atmospheric Adminstration.