What is permafrost? Q & A
- 29 Nov 2012, 12:15
- Roz Pidcock
Melting permafrost in the Arctic could push the earth towards
climate change that is "irreversible on human timescales",
according to a new report released yesterday. Here's our quick
guide to what you should know about melting permafrost.
by the United Nations Environment Programme (UNEP), says billions
of tonnes of carbon once locked up in permafrost could be released
into the atmosphere this century - accelerating global warming. But
how much might be released, and how quickly? These questions are
still being debated in the scientific community, which means that
it's sometimes hard for media coverage to strike the right
balance when discussing how significant the effect could
1. What is permafrost?
Permafrost is the name given to permanently-frozen ground in
high latitudes. Permafrost acts like a lid, locking frozen carbon
deposits deep below ground. The upper layer of permafrost thaws and
re-freezes naturally each year. As the carbon thaws, microbes
degrade it - a process that releases carbon dioxide and
As atmospheric temperatures rise
- due mainly to
human activity - heat penetrates deeper into the ground than
before. This leads to more permafrost thawing, and more carbon
being released to the atmosphere.
2. What does that have to do with climate
Scientists are concerned that carbon dioxide and methane
released into the atmosphere from permafrost will mean more global
warming. Methane is a powerful greenhouse gas - around 25 times
more effective at trapping heat than carbon dioxide over a
What's more, this additional warming can create a vicious
circle. Extra warming thaws more permafrost, leading to further
warming - and so on. Scientists call a self-reinforcing warming
cycle like this a positive feedback.
This has important consequences for limiting climate change -
it's already looking
increasingly unlikely that warming can be limited to two
degrees above pre-industrial levels - the internationally accepted
An additional source of greenhouse gases from permafrost further
reduces the chances of hitting that target.
The positive feedback from thawing permafrost amplifies
existing atmospheric warming due to human activities. Source: UNEP
report "Policy Implications of Warming Permafrost".
3. Don't scientists know about melting permafrost
Yes, scientists have already raised
concern that rising temperatures could thaw part of the vast
reservoir of frozen methane along
continental shelves and undersea
in the Arctic and, more recently, in the
But there is a lot of uncertainty about how big the global
reservoir is and how much of it is thawing, which we wrote a bit
more about here.
60 per cent of methane in the atmosphere results from human
activity, like agriculture and landfill. So far, only a small
amount is from melting permafrost. The remaining
40 per cent is released naturally from wetlands.
All of this uncertainty means that the Intergovernmental Panel
on Climate Change has been
unable to properly account for thawing permafrost in its
projections for future global warming.
4. What does the new UNEP report say?
report is a synthesis of the most up-to-date scientific
research. It says that permafrost covers a quarter of the northern
hemisphere and currently stores around
1700 billion tonnes of carbon - almost twice the amount
currently present in the atmosphere.
Between 43 and 135 billion tonnes of methane could be released
by 2100 as permafrost thaws, according to the report, and by 2200
that number could reach 246 to 415 billion tonnes. These emissions
could start now but continue for many centuries, influencing both
the short term and long term climate.
Temperatures in the high latitudes are projected to rise twice
as fast as the global average. The report warns a three degree
world, or six degrees in the Arctic, could melt 30 to 85 per cent
of near-surface permafrost. As well as affecting the climate, this
would permanently affect local hydrology, alter habitats and could
damage critical infrastructure built on melting ground.
One model projection indicates a 59% loss in near-surface
permafrost area by 2100 for the IPCC A1B scenario Source: UNEP
report "Policy Implications of Warming Permafrost".
5. Will this push the earth past a tipping
The UNEP report warns that the release of carbon from permafrost
is essentially irreversible on human timescales. Some media
coverage of the UNEP report has suggested that carbon released from
melting permafrost could
push the climate past a tipping point.
tipping point is a threshold beyond which the climate undergoes
a shift from one physical state to another, and could include
things like thawing permafrost, melting of the Greenland ice sheet
or the dieback of the Amazon rainforest.
While scientists are confident that such tipping points exist in
theory, predicting when they might occur and measuring progress
towards them cannot be done with certainty. Research is beginning
to provide a clearer picture though - a recent
study suggests that some tipping points in the climate may even
occur below two degrees of warming.
6. So what should be done about melting
To reduce some of the uncertainty on this subject, the report
recommends a special IPCC assessment into how emissions from
melting permafrost will influence global climate. Countries with
substantial permafrost should also create national networks to
adequately monitor permafrost carbon release and develop adaptation
plans to estimate the costs and risks of permafrost thaw, says the
report. All this will help scientists factor permafrost feedbacks
into future projections of the climate, as well as set emissions
targets to reduce global warming.
Methane from permafrost is likely to be an important source of
carbon emissions on timescales of hundreds or even thousands
of years, and it's important that the feedbacks are better
understood so they can be factored into climate projections. But
carbon dioxide emissions from burning fossil fuels continue to be
the biggest obstacle to stabilising global climate in the short
As Professor David Archer, expert on the impact of methane on
global climate at the University of Chicago, explained to Carbon
if the problem of excess carbon dioxide emissions is fixed, methane
is unlikely to be much of an issue.