Scientists just pointed out how the Earth itself could undermine a Paris climate agreement

December 10, 2015 12:07 pm

Secretary of State John Kerry delivers his remarks at the Caring for
Climate Forum during the COP21 the World
Conference in Paris. Photo / Getty Images

With only days left, tensions are rising as countries race to
resolve outstanding differences and forge an agreement that – hopefully –
will set the planet on a path to avoiding the worst consequences of
climate change.
The goal is an agreement that would set the world
on a path to limit warming to below 2 degrees Celsius, or perhaps even
1.5 degrees Celsius, above pre-industrial levels. But at a
conference here at the Le Bourget conference centre, scientists pointed
out a factor that could make hitting these targets quite a lot harder.
It’s called permafrost.
the planet warms, this frozen northern soil is going to continue to
thaw – and as it thaws, it’s going to release carbon dioxide and methane
into the air.

A lot of it, it turns out. Potentially enough to really
throw off the carbon budgets that have been calculated in order to
determine the maximum emissions that we can release and still have a
good chance of keeping warming to 2 C or below it.
In particular,
Susan Natali of the Woods Hole Research Centre explained that with a
very high level of warming, permafrost emissions this century could be
quite large indeed.
Natali used numbers from the 2013 report of the
United Nations’ Intergovernmental Panel on Climate Change, which found
that humans can only emit about 275 more gigatons, or billion tons, of
carbon (about 1000 gigatons of carbon dioxide, which has a greater
molecular weight) to have a greater than 66 per cent chance of limiting
warming to 2 C.
But out of that limited budget, she said,
permafrost emissions could take up some 150 of those gigatons (or about
550 gigatons of carbon dioxide).
“That’s on par with current US
rates of emission,” Natali said, which are about 1.4 gigatons of carbon
per year. “So we’re talking about another emitting region that’s
currently not included in our emissions scenarios.”
even though they’re not considered to be strong enough, the current
national pledges to limit global warming appear to have taken the world
off a truly high emissions path. These pledges, or “intended nationally
determined contributions,” could potentially limit warming to 2.7 C,
according to the United Nations.
But in an interview, Natali and
her Woods Hole colleague and fellow permafrost expert Max Holmes
explained that even for lower warming scenarios like this, permafrost
could emit 50 gigatons of carbon (or about 180 gigatons of carbon
dioxide) in this century.
This is because under lower warming
scenarios, only about 30 per cent, rather than about 70 per cent, of
surface layer permafrost is expected to thaw.
Another 50 gigatons
out of a 275 gigaton carbon budget – or, another 180 gigatons out of a
1000 gigaton carbon dioxide budget – would significantly constrain how
much the world could emit and still have a strong chance of keeping
warming below 2 C.
And Natali and Holmes also noted that
permafrost emissions don’t end at 2100 – they are expected to continue
after that and even get worse. “Most of the release will happen after
2100,” said Natali.
That’s a big problem because the global
carbon budget is fixed, and after it is exceeded there can be zero
further emissions. Because carbon dioxide lasts so long in the
atmosphere, you don’t get to start with a fresh budget in the next
century. So permafrost emissions beyond 2100 would also have to be taken
into account, and would restrict the budget even further.
is a potential carbon bomb because over thousands of years, dead plant
life has been slowly swallowed up by the soil but has not decomposed.
Plants pull carbon out of the atmosphere as they grow, but release it
again when they die and decompose. As permafrost warms and thaws,
microbes will have more ability to break down the plant life it
contains, which is what will trigger a steady stream of emissions.
just like you put celery in your freezer and then you turn your freezer
into a refrigerator, and it starts to rot,” says Woods Hole’s Max

Skip to toolbar
shared on