The New Scientist has an excellent summary of one of the melting Arctic, which is one of the greatest non-linear accelerators of climate change. As the sea ice vanishes, the permafrost melts, which contains over 1000 gigatons of organic carbon. This carbon will be converted to methane by microbes and released to the atmosphere. We need to seriously consider ways to save the Arctic sea ice from completely melting, which may not be possible with emissions reductions alone.
"The danger is that if too much methane is released, the world will get
hotter no matter how drastically we slash our greenhouse gas emissions.
Recent studies suggest that emissions from melting permafrost could be
far greater than once thought. And, although it is too early to be
sure, some suspect this scenario is already starting to unfold: after
remaining static for the past decade, methane levels have begun to rise
again, and the source could be Arctic permafrost.
"No one knows for sure how much carbon is locked away in permafrost, but it seems there is much more than we thought. An international study headed by Edward Schuur of the University of Florida last year doubled
previous estimates of the carbon content of permafrost to about 1600
billion tonnes - roughly a third of all the carbon in the world's soils
and twice as much as is in the atmosphere.
estimates that 100 billion tonnes of this carbon could be released by
thawing this century, based on standard scenarios. If that all emerged
in the form of methane, it would have a warming effect equivalent to
270 years of carbon dioxide emissions at current levels. "It's a kind
of slow-motion time bomb," he says.