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.
The report, 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
more effective at trapping heat than carbon dioxide over
a 100-year cycle.
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.