—
Permafrost covering almost a quarter of the northern hemisphere contains 1,700
gigatonnes of carbon, twice that currently in the atmosphere, and could
significantly amplify global warming should thawing accelerate as expected,
according to a new report released November 27 by the UN Environment Programme
(UNEP).
Warming
permafrost can also radically change ecosystems and cause costly
infrastructural damage due to increasingly unstable ground, the report says.
Policy Implications of Warming Permafrost seeks to highlight the potential
hazards of carbon dioxide and methane emissions from warming permafrost, which
have not thus far been included in climate-prediction modelling. The science on
the potential impacts of warming permafrost has only begun to enter the
mainstream in the last few years, and as a truly "emerging issue"
could not have been included in climate change modelling to date.
The
report recommends a special IPCC assessment on permafrost and the creation of
national monitoring networks and adaptation plans as key steps to deal with
potential impacts of this significant source of emissions, which may become a
major factor in global warming."Permafrost is one of the keys to the
planet's future because it contains large stores of frozen organic matter that,
if thawed and released into the atmosphere, would amplify current global
warming and propel us to a warmer world," said UN Under-Secretary General
and UNEP Executive Director Achim Steiner.
"Its
potential impact on the climate, ecosystems and infrastructure has been
neglected for too long," he added. "This report seeks to communicate
to climate-treaty negotiators, policy makers and the general public the
implications of continuing to ignore the challenges of warming
permafrost."Most of the current permafrost formed during or since the last
ice age and extends to depths of more than 700 meters in parts of northern
Siberia and Canada. Permafrost consists of an active layer of up to two metres
in thickness, which thaws each summer and refreezes each winter, and the
permanently frozen soil beneath.
Should
the active layer increase in thickness due to warming, huge quantities of
organic matter stored in the frozen soil would begin to thaw and decay,
releasing large amounts of CO₂ and
methane into the atmosphere. Once this process begins, it will operate in a
feedback loop known as the permafrost carbon feedback, which has the effect of
increasing surface temperatures and thus accelerating the further warming of
permafrost -- a process that would be irreversible on human timescales.
Arctic
and alpine air temperatures are expected to increase at roughly twice the
global rate, and climate projections indicate substantial loss of permafrost by
2100. A global temperature increase of 3°C means a 6°C increase in the Arctic,
resulting in an irreversible loss of anywhere between 30 to 85 per cent of
near-surface permafrost.
Warming
permafrost could emit 43 to 135 gigatonnes of carbon dioxide equivalent by 2100
and 246 to 415 gigatonnes by 2200. Emissions could start within the next few
decades and continue for several centuries. Permafrost emissions could
ultimately account for up to 39 per cent of total emissions, and the report's lead
author warned that this must be factored in to the treaty to address global
climate change expected to replace the Kyoto Protocol.
"The
release of carbon dioxide and methane from warming permafrost is irreversible:
once the organic matter thaws and decays away, there is no way to put it back
into the permafrost," said lead author Kevin Schaefer, from the University
of Colorado's National Snow and Ice Data Center."Anthropogenic emissions'
targets in the climate change treaty need to account for these emissions or we
risk overshooting the 2°C maximum warming target," he added.
Most
of the recent climate projections are biased on the low side relative to global temperature
because the models do not at this time include the permafrost carbon feedback,
the report says. Consequently, targets for anthropogenic greenhouse gas
emissions based on these climate projections would be biased high.
Ecosystems
and Infrastructure under Threat
Warming
permafrost also brings negative consequences in terms of ecosystem and infrastructure
damage.
The
dominant ecosystems in permafrost regions are boreal forests to the south and
tundra to the north. Permafrost is impermeable to water, so rain and melt water
pool on the surface -- forming innumerable lakes and wetlands which are used by
migratory birds as summer breeding grounds.
For further information
visit: http://www.sciencedaily.com/releases/2012/11/121127094250.htm
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