Resources for a sustainable future

23/5/2008 BBC Higher atmospheric levels of the greenhouse gas methane noted last year are probably related to emissions from wetlands, especially around the Arctic.  Scientists have found indications that extra amounts of the gas in the Arctic region are of biological origin.
Global levels of methane had been roughly stable for almost a decade.
Rising levels in the Arctic could mean that some of the methane stored away in
permafrost is being released, which would have major climatic implications.
The gas is about 25 times more potent than carbon dioxide as a greenhouse gas,
though it survives for a shorter time in the atmosphere before being broken down
by natural chemical processes.
Northern lights
Indications that methane levels might be rising after almost a decade of
stability came last month, when the US National Oceanic and Atmospheric
Administration (Noaa) released a preliminary analysis of readings taken at
monitoring stations worldwide.
Noaa suggested that 2007 had seen a global rise of about 0.5%.
Some stations around the Arctic showed rises of more than double that amount.
One is the station at Mount Zeppelin in Svalbard, north of Scandinavia.
In addition to the long-term monitoring carried out there by Norway and Sweden,
a British team has recently started gathering samples and analysing them in a
way that could reveal where the methane is coming from.
Methane produced by bacteria contains a high proportion of molecules with the
lighter form (isotope) of carbon, carbon-12, rather than the heavier form,
carbon-13.
      I think 2007 is probably down to wetland emissions
      Ed Dlugokencky, Noaa

“Anything where bacteria form methane, you get depletion in C-13 because
methanogens (the bacteria) preferentially use C-12,” said Rebecca Fisher from
Royal Holloway, University of London, who has been running the Svalbard
experiments.
“The results we have so far imply a predominantly biogenic source,” she told BBC
News.
The researchers also match methane levels with wind direction, so they can see
where the gas is being produced. This analysis also implies a source in the
Arctic regions, rather than one further afield such as the additional output
from Asia’s rapid industrialisation.
Warm and wet
Ed Dlugokencky, the scientist at Noaa’s Earth System Research Laboratory (ESRL)
who collates and analyses data from atmospheric monitoring stations, agrees that
the 2007 rise has a biological cause.
“We’re pretty sure it’s not biomass burning; and I think 2007 is probably down
to wetland emissions,” he said.
“In boreal regions it was warmer and wetter than usual, and microbes there
produce methane faster at higher temperatures.”
Dr Dlugokencky also suggested that the drastic reduction in summer sea ice
around the Arctic between 2006 and 2007 could have increased release of methane
from seawater into the atmosphere.
A further possibility is that the gas is being released in increasing amounts
from permafrost as temperatures rise.
Researchers will be keeping a close eye on this year’s data which will indicate
whether 2007 was just a blip or the beginning of a sustained rise.
Methane concentrations had been more or less stable since about 1999 following
years of rapid increases, with industrial reform in the former Soviet bloc,
changes to rice farming methods and the capture of methane from landfill sites
all contributing to the levelling off.
In the recent past, concentrations have risen during El Nino events, whereas the
world is currently amid the opposite climatic pattern, La Nina.
Solid evidence
An upturn in methane concentrations emissions could have significant
implications for the Earth’s climatic future.
A sustained release from Arctic regions or tropical wetlands could drive a
feedback mechanism, whereby higher temperatures liberate more of the greenhouse
gas which in turn forces temperatures still higher.
A particularly pertinent question is whether methane is being released from
hydrates on the ocean floor.
These solids are formed from water and methane under high pressure, and may
begin to give off methane as water temperatures rise.
The amount of the gas held in oceanic hydrates is thought to be larger than the
Earth’s remaining reserves of natural gas.
In collaboration with other British institutions, Dr Fisher’s team will begin
work this summer sampling water near hydrate deposits to look for indications of
gas emerging.