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THE GUARDIAN : NAFEEZ AHMED - 2013 - 5 - AUG
Seven facts you need to know about the Arctic methane timebomb
catastrophic methane danger ignore robust science in favour of outdated mythology of climate safety
THE GUARDIAN : NAFEEZ AHMED - 2013 - 5 - AUG
Seven facts you need to know about the Arctic methane timebomb
catastrophic methane danger ignore robust science in favour of outdated mythology of climate safety
Debate over the plausibility of a catastrophic
release of methane in coming decades due to thawing Arctic permafrost has
escalated after a new Nature paper warned that exactly this scenario
could trigger costs equivalent to the annual GDP of the global economy.
Scientists of different persuasions remain
fundamentally divided over whether such a scenario is even plausible. Carolyn
Rupple of the US Geological Survey (USGS) Gas Hydrates Project told NBC News the scenario is "nearly
impossible." Ed Dlugokencky, a research scientist at the National Oceanic
and Atmospheric Administration's (NOAA) said there has been "no detectable
change in Arctic methane emissions over the past two decades." NASA's
Gavin Schmidt said that ice core records from previously warm Arctic periods
show no indication of such a scenario having ever occurred.
Methane hydrate expert Prof David Archer reiterated
that "the mechanisms for release operate on time scales of centuries and
longer." These arguments were finally distilled in a lengthy, seemingly
compelling essay posted on Skeptical Science last Thursday, concluding with
utter finality:
"There is no evidence that
methane will run out of control and initiate any sudden, catastrophic effects."
But none of the scientists rejecting the plausibility of the scenario are experts in the Arctic, specifically the East Siberia Arctic Shelf (ESAS). In contrast, an emerging consensus among ESAS specialists based on continuing fieldwork is highlighting a real danger of unprecedented quantities of methane venting due to thawing permafrost.
But none of the scientists rejecting the plausibility of the scenario are experts in the Arctic, specifically the East Siberia Arctic Shelf (ESAS). In contrast, an emerging consensus among ESAS specialists based on continuing fieldwork is highlighting a real danger of unprecedented quantities of methane venting due to thawing permafrost.
So
who's right? What are these Arctic specialists saying? Are their claims of a
potentially catastrophic methane release plausible at all? I took a dive into
the scientific literature to find out.
What
I discovered was that Skeptical Science's unusually skewered analysis was
extremely selective, and focused almost exclusively on the narrow arguments of
scientists out of touch with cutting edge developments in the Arctic. Here's
what you need to know.
1. The 50 Gigatonne decadal methane pulse scenario
was posited by four Arctic specialists, and is considered plausible by Met
Office scientists
The
authors of the controversial new Nature paper on costs of Arctic warming didn't just pull
their decadal methane catastrophe scenario out of thin air. The scenario
was first postulated in 2008 by Dr Natalie
Shakhova of the University of Alaska Fairbanks, Dr Igor Semiletov from the
Pacific Oceanological Institute at the Russian Academy of Sciences, and two
other Russian experts.Their
paper noted that while seabed permafrost underlying most of the ESAS was
previously believed to act as an "impermeable lid preventing methane
escape," new data showing "extreme methane supersaturation of surface
water, implying high sea-to-air fluxes" challenged this assumption. Data
showed:
"Extremely high concentrations
of methane (up to 8 ppm) in the atmospheric layer above the sea surface along
with anomalously high concentrations of dissolved methane in the water column
(up to 560 nM, or 12000% of super saturation)."
One
source of these emissions "may be highly potential and extremely mobile
shallow methane hydrates, whose stability zone is seabed permafrost-related and
could be disturbed upon permafrost development, degradation, and thawing."
Even if the methane hydrates are deep, fissures, taliks and other soft spots
create heat pathways from the seabed which warms
quickly due to shallow depths. Various mechanisms for such processes have been
elaborated in detail.
The
paper then posits the plausibility of a 50 Gigatonne (Gt) methane release
occurring abruptly "at any time." Noting that the total quantity of
carbon in the ESAS is "not less than 1,400 Gt", the authors wrote:
"Since the area of geological
disjunctives (fault zones, tectonically and seismically active areas) within
the Siberian Arctic shelf composes not less than 1-2% of the total area and
area of open taliks (area of melt through permafrost), acting as a pathway for
methane escape within the Siberian Arctic shelf reaches up to 5-10% of the
total area, we consider release of up to 50 Gt of predicted amount of hydrate
storage as highly possible for abrupt release at any time. That may cause ∼12-times increase of modern
atmospheric methane burden with consequent catastrophic greenhouse
warming."
So
the 50 Gt scenario used by the new Nature paper does not postulate the total
release of the ESAS methane hydrate reservoir, but only a tiny fraction of it.
The
scale of this scenario is roughly corroborated elsewhere. A 2010 scientific analysis led by the UK's Met Office in
Review of Geophysics recognised the plausibility of catastrophic carbon
releases from Arctic permafrost thawing of between 50-100 Gt this century, with
a 40 Gt carbon release from the Siberian Yedoma region possible over four
decades.
Shakhova
and her team have developed these findings from data derived from over 20
field expeditions from 1999 to 2011. In 2010, Shakhova et. al
published a paper in Science based on their annual
research trips which highlighted that the ESAS was a key
reservoir of methane "more than three times as large as the nearby
Siberian wetland... considered the primary Northern Hemisphere source of
atmospheric methane." Current average methane concentrations in the Arctic
are:
"about 1.85 parts per million,
the highest in 400,000 years" and "on par with previous estimates of
methane venting from the entire World Ocean."
As
the ESAS is shallow at only 50 metres, most of the methane being released is escaping into the
atmosphere rather than being absorbed into water.
The
existence of such shallow methane hydrates in permafrost - at depths as small as 20m -
was confirmed by Shakhova in the Journal of Geophysical Research. There has
been direct observation and sampling of these hydratesby Russian geologists in recent decades until now; this has also
been confirmed by US government scientists.
2. Arctic methane hydrates are becoming
increasingly unstable in the context of anthropogenic climate change and it's
impact on diminishing sea ice
The
instability of Arctic methane hydrates in relation to sea ice retreat - not predicted by
conventional models - has been increasingly recognised by experts. In
2007, a study in Eos, Transactions found that:
"Large volumes of methane in gas
hydrate form can be stored within or below the subsea permafrost, and the
stability of this gas hydrate zone is sustained by the existence of permafrost.
Degradation of subsea permafrost and the consequent destabilization of gas
hydrates could significantly if not dramatically increase the flux of methane,
a potent greenhouse gas, to the atmosphere."
In
2009, a research team of 19 scientists wrote a paper in Geophysical Research Letters documenting
how the past thirty years of a warming Arctic current due to contemporary
climate change was triggering unprecedented emissions of methane from gas
hydrate in submarine sediments beneath the seabed in the West Spitsbergen
continental margin. Prior to the new warming, these methane hydrates had
been stable at water depths as shallow as
360m. Over 250 plumes of methane gas bubbles were found rising from the seabed
due to the 1C temperature increase in the current:
"... causing the liberation of
methane from decomposing hydrate... If this process becomes widespread along
Arctic continental margins, tens of Teragrams of methane per year could be
released into the ocean."
The
Russian scientists investigating the ESAS also confirmed that the levels of
methane release they discovered were new. As Steve Connor reported in the
Independent, since 1994 Igor Semilitov:
"... has led about 10
expeditions in the Laptev Sea but during the 1990s he did not detect any elevated
levels of methane. However, since 2003 he reported a rising number of methane
'hotspots', which have now been confirmed using more sensitive
instruments."
In
2012, a Nature study mapping over 150,000
Arctic methane seeps concluded that:
"... in a warming climate,
disintegration of permafrost, glaciers and parts of the polar ice sheets could
facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere
cap."
3. Multiple scientific reviews, including one by
over 20 Arctic specialists, confirm decadal catastrophic Arctic methane release
is plausible
A
widely cited 2011 Nature review dismissed such a
catastrophic scenario as implausible because methane "gas hydrates occur
at low saturations and in sediments at such great depths below the seafloor or
onshore permafrost that they will barely be affected by [contemporary levels
of] warming over even [1,000] yr."
But
this study and others like it completely ignore the new empirical evidence on
permafrost-associated shallow water methane hydrates on the Arctic shelf.
Scientific reviews that have accounted for the empirically-observed dynamics of
permafrost-associated methane come to the opposite conclusion.
In
2007, scientists Matthew Reagan and George Moridis at the Lawrence Berkeley
National Laboratory published a paper in Geophysical Research Letters exploring
the vulnerability of methane gas hydrates. They concluded based on simulations
of different types of oceanic gas hydrate responding to seafloor temperature
changes:
"... while many deep hydrate
deposits are indeed stable under the influence of rapid seafloor temperature
variations, shallow deposits, such as those found in arctic regions or
in the Gulf of Mexico, can undergo rapid dissociation and produce
significant carbon fluxes over a period of decades."
"The time scales for
destabilization of marine hydrates are not well understood and are likely to be
very long for hydrates found in deep sediments but much shorter for
hydrates below shallow waters, such as in the Arctic Ocean... Overall,
uncertainties are large, and it is difficult to be conclusive about the time
scales and magnitudes of methane feedbacks, but significant increases
in methane emissions are likely, and catastrophic emissions cannot be ruled out... The
risk of a rapid increase in [methane] emissions is real but remains
largely unquantified."
Another
extensive scientific review of data from the ESAS gathered between 1995 and
2011 by over twenty Arctic specialists published in the Proceedings of the Russian Academy of
Sciences similarly concluded that:
"The [ESAS] is a powerful
supplier of methane to the atmosphere owing to the continued degradation of the
submarine permafrost, which causes the destruction of gas hydrates. The
emission of methane in several areas of the [ESAS] is massive to the extent that
growth in the methane concentrations in the atmosphere to values capable of
causing a considerable and even catastrophic warning on the Earth is possible."
Other
recent scientific reviews corroborate these findings.
4. Current Arctic methane levels are unprecedented
A 2011 Nature paper found that ten times
more carbon than thought is escaping via thawing coastal permafrost at the
ESAS. Although it is not yet clear whether or how the quantities of Arctic
methane are impacting on total atmospheric methane emissions, a number of
scientists argue that the increasing spikes in methane detected in the Arctic
in recent years is indeed unprecedented.
Despite NOAA scientist Dr Dlugokencky's reassurances
that current Arctic methane emission levels are nothing to be
"alarmed" about, his own data shows that Arctic methane levels were
1850 ppb in yr 2000, rising up to 1890 ppb in 2012.
Indeed,
Dr Leonid Yurganov, Senior Research Scientist at the NASA/UMBC Joint Centre for
Earth Systems Technology, and his co-scientists from NOAA and Harvard (Shawn
Xiong and Steven Wofsy) disagree with Dlugokencky. In a paper for the American Geophysical Union last
December they charted a worrying "global increase of methane" since
2007-8, with particular spikes in 2009 and 2011-12 in the northern hemisphere,
with maximum methane concentrations in the Arctic:
"IASI data for the autumn months
(October-November) clearly indicate Eurasian shelf areas of the Arctic Ocean as
a significant methane emitter. The maximal methane concentrations were found
over Kara and Laptev Seas. According to IASI data, during the last three years
in autumn time, methane over Eurasian shelf has been increased by 25 ppb, over
the N. American shelf, by 23 ppb, and over the land between 50 N and 70 N for
both Eastern and Western hemispheres, by 20 ppb."
Yurganov
et. al point out that between January 2009 and 2013, Arctic methane levels
ramped steadily higher by about 10-20 ppb on average each year. They also note
that maximum Arctic methane emissions occur annually between September and
October - coinciding with the Arctic sea ice minimum.
5. The tipping point for continuous Siberian
permafrost thaw could be as low as 1.5C
New
research led by Prof Antony Vaks published this year in Scienceanalysing a 500,000 year
history of Siberian permafrost found that "global climates only slightly
warmer than today are sufficient to thaw significant regions of
permafrost." The study by eight experts found that there is a tipping
point for continuous thawing of permafrost at 1.5C which "can potentially
lead to substantial release of carbon trapped in the permafrost into the
atmosphere."
6. Arctic conditions during the Eemian interglacial
lasting from 130,000 to 115,000 years ago are a terrible analogy for today's
Arctic
Two
recent studies challenge the relevance of Arctic conditions in the Eemian
interglacial. A 2012 Geophysical Research Letters study rejects the idea that
the Arctic experienced ice free summers in the Eemian, noting that Arctic
temperatures were cooler than previously thought, with evidence
that ice sheets were more resistant - partly due to vastly different Arctic
ocean currents. Similarly, a new Nature study found that the
Greenland ice sheets experienced only modest melting in the Eemian, such that
the extensive sea level rise at the time could only be explained by melting in Antarctica. Both studies suggest
that the Arctic sea ice simply had not retreated enough to expose permafrost.
According
to Prof Paul Beckwith of the University of Ottawa Laboratory for
Paleoclimatology and Climatology, this can be explained by a number of factors:
"... the key distinction is that
the warming today is from Greenhouse gases being higher and occurs 'twenty-four
seven', namely the cooling at night is much less (diurnal variation smaller);
in the Eemian the tilt of the Earth was much greater so there was much more
seasonality, thus winters were much colder so the sea ice extent, thickness,
and thus volume could build up much more, and the summers were warmer in the
daytime, however the cooling at night was much greater than now (less
greenhouse gas [GHG], more diurnal variation); net result is that the ice was
much more durable in the Eemian. Greenland temps were higher during the
daytime, but cooled off much more during the nighttime in the lower GHG
concentration world."
7. Paleoclimate records will not necessarily
capture a large, abrupt methane pulse
Prof
Beckwith also poured (ice cold) water on the claim that we know an abrupt
methane release cannot occur, because it has never occurred before -
purportedly proven as such an event is not detected in the ice cores:
"The length of time for the
methane pulse is very important here. If most of the methane came out in a
decade, for example then within a subsequent decade or so most of the methane
will have been broken down to CO2 and H20 and also been dispersed/distributed
around the planet, away from the pulse source area in the Arctic. The CO2
produced would have been small (CO2 stayed within 180-280 ppm range). It takes
about 50 years or even more (depending on the snowfall rate and surface melt
rates) for snow at the surface to be compacted into firn that closes off the
air spaces creating the bubbles in the ice that are reservoirs of the methane
and other atmospheric gases. Because of that 50 year bubble closure time, the
large pulse of methane that was burped out of the marine sediments and
terrestrial permafrost would be long gone and not result in a detectable signal
in the ice core record. Just because the record does not capture it does not
mean that it was not produced."
These
comments are confirmed by an in-depth American
Geophysical Union study which notes that it "remains
unclear if the full magnitude of atmospheric [methane] changes are recorded in
ice cores because of diffusional smoothing of the [methane] while in the
firn" as well as "signal smoothing" caused by "atmospheric
effects."
But
studies do indicate past precedent. A 2009 Science paper argues that abrupt,
catastrophic emissions from Arctic methane clathrates including from thawing
permafrost played a key role 11,600 years ago at the end of the Younger Dryas
cold period in driving wetland emissions, generating sudden massive warming.
So what?
All
this proves that the $60 trillion price-tag for Arctic warming estimated by the
latest Nature commentary should be taken seriously, prompting further urgent
research and action on mitigation - rather than denounced on the basis of
outdated, ostrich-like objections based on literature unacquainted with the
ESAS.
Dr Nafeez Ahmed is
executive director of the Institute for Policy Research & Development and
author of A User's Guide to the Crisis of Civilisation: And How to
Save It among other books. Follow him on Twitter @nafeezahmed
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