- At least 15% of the Northern Hemisphere
has permafrost underneath it.
Technically, that's ground that's been frozen
for at least two years, but much of it has been frozen
for millennia and it stores a staggering amount
of carbon locked safely away in the soil,
as long as it stays below 32 degrees.
I don't think viewers
of this channel will be surprised to learn
that it's already begun thawing due to global warming.
But new research shows that,
with just a little bit more warming,
a tipping point could be reached, causing a sudden
and widespread change to this frozen ground.
- So around about 1500 gigatons
of carbon locked in this permafrost that becomes available
for release when it thaws.
That's actually about two and a half times
the amount that humanity has emitted so far.
- This is one of the first major climate tipping points
that human emissions could trigger.
And it's a feedback loop where global warming
releases carbon, which speeds up warming.
So what does this mean for our planet's climate?
And are any efforts to slow global warming totally doomed
if this carbon bomb is triggered?
In this episode of Weathered, we're talking
to the scientists behind this new research who
actually have a pretty good answer to that question.
So watch till the end to find out.
And if you appreciate this kind
of science-based climate content, hit like and subscribe.
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Back in 2008,
Tim Lenton published a groundbreaking paper
outlining nine climate tipping points that,
once triggered, could be irreversible,
leading to the collapse of many important earth systems
and contributing significantly to global warming.
At that time, other scientists were skeptical,
but now sadly, his work has become highly respected.
Back then, permafrost didn't make the list.
So we were very interested to read
Dr. David Armstrong McKay's New Research, which finds
that a permafrost abrupt thaw could be triggered,
even if we meet the most aggressive targets
of the Paris Agreement.
That would suddenly make a lot
of carbon available to be released as carbon dioxide,
as well as methane, which is some 85 times more potent
of a greenhouse gas than CO2
over its first 20 years in the atmosphere.
Because permafrost is deep underground,
it's hard to measure, but we know
that a gradual thaw of permafrost is already happening.
- When we try to to quantify it, this change
in permafrost extent, you just look for where on the globe
do we still have a temperature below zero degrees
in the ground.
- And they found that since 1997, in fact,
this permafrost extent has decreased
by two and a half percent.
Much of this ground that remains
below zero degrees has been frozen since the last ice age,
keeping dormant all of the tiny microbes that break
down organic matter and release greenhouse gases.
It's almost all in latitudes far north where
it's warming four times faster than the global average.
And when it thaws,
those little microbes start quickly digesting carbon
into either CO2 if they're dry, or methane,
if they're under water.
It's a process called "soil respiration."
Dr. David Armstrong McKay's new paper breaks
down permafrost tipping points into two stages.
The first and most likely is the abrupt thaw.
- This is something a bit newer that's been
researched recently.
This is not in most climate models and this is that the,
you can get all these localized tipping point starting.
- David outlined three related examples for us.
The first is landslides known as slumps or thaw slumps.
- So you can imagine these more steeper slopes
that have permafrost underneath them.
If you are melting some
of the the ice blocks that are in them,
you can get little slumps happening
and that can turn into landslides, effectively.
And that gouges out large amounts of land that leads
to all of the carbon exposed to be degraded and rot
and release greenhouse gases as well.
- And there are several hundreds
of thousands of these thaw slumps across the Arctic.
It's a really huge number.
You find them in North America,
you find them all across Siberia.
- The ground subsiding as permafrost
thaws can also lead to the second local tipping point,
known as Thermokarst Lakes.
- It starts off with a little bit
of slumping that forms a lake
above it and effectively it keeps on spreading outwards
as this lake forms.
The lake forming accelerates
and amplifies the decay of permafrost underneath it.
So effectively, each Thermokarst Lake is kind of
like a little tipping point in action.
These sort of features like slumping
and Thermokarst Lakes can make deeper carbon
more available more quickly than
if you're just thawing gradually from the top down.
And that's something that can really amplify emissions.
- And the third example of a localized tipping point came
as a real surprise to scientists and everyone, really.
- So maybe you have heard about these craters
in Siberia, really in a lot in the news.
And that's from this really old methane in the ground.
Yeah, so that's a kind of trapped beneath the permafrost.
And some researchers, they think it's due
to the thawing permafrost
that hot summers triggered the the release.
- Since they became newsworthy back in 2014,
at least 17 of these craters have been found.
And there are even reports of locals
in Siberia hearing loud explosions before finding new ones.
Many scientists now agree that these craters were caused
by a sudden release of a pocket of methane that was capped
and held underground by permafrost.
As it thaws, the structure weakens
and the methane can cause a bulge on the surface
until it explodes, leaving behind large, mysterious craters
and exposing lots of deep carbon that will thaw even more.
With more warming, they could become more common.
But when will all of these small local tipping
points hit a more significant threshold?
- So a key piece of evidence here is
that in one of the previous warm interglacials,
the amount of permafrost thaw really expanded
by around about 1.5 degrees of warming to expand
over a much wider area than was seen before.
In other interglacials.
And 1.5 degrees really does mean that there's quite a lot
of permafrost thaw expanding over a larger area.
So that's why we assign that as being what we
call a regional impact climate tipping element.
Because even though it's not one coherent tipping element,
it still affects a really large area
and it does have a impact on the whole system, as well,
because of the amplification of the emissions
from permafrost and really has a substantial global impact
as a result.
- We've already warmed the planet more
than 1.1 degrees Celsius.
So 1.5 degrees could come quickly.
In fact, a number of studies show
that we could cross the 1.5 degrees sometime
during the 2030s, and unfortunately that number falls well
within the Paris Agreement goals,
which aim to keep warming under two degrees.
But as we've covered in a previous episode, we're currently
on track for around 2.6 degrees of total warming.
Still, how bad is this tipping point?
- If you add it all up, it looks a bit
like 10% amplification of global warming from human causes.
So it's big, but it's not dominant.
It's more of a gradual chronic leak that we're
triggering that will just make it that much harder to try
and actually get global warming to stop and halt
preferably at the 1.5 degree level.
- So that's mixed news.
From a climate perspective,
we definitely don't want 10% more warming
outside of our control.
Thankfully those emissions happen over a century or more,
but there's another far more dire tipping point
that could be crossed
if we overshoot the Paris Agreement targets
by around one full degree Celsius.
- So there are some regions where permafrost
is a lot deeper.
The Yedoma region, it covers parts
of Eastern Siberia and far east Russia
and also goes into Alaska and Northern Canada, as well.
And it's really deep deposits left
from one of the previous ice ages, basically,
and it's very rich in carbon.
- The large amount of carbon found
in Yedoma permafrost, about 2% by mass,
is the result of abundant vegetation
and animals like wooly mammoths that populated the region
during the last ice age,
which began around 2 million years ago.
Over time, this material became frozen in the permafrost,
preventing its decomposition
and preserving the organic carbon within it.
And in addition to this carbon dense soil
and millions of wooly mammoth tusks
the Yedoma is also filled with deep ice deposits.
- The ice is important cause that's part of why
you get abrupt thaw affecting these areas so badly.
Cause if you melt some of these big ice occlusions
and ice layers, suddenly the whole landscape
can just sort of slump, it can collapse
under itself because it's losing mass from that ice melt.
And that means that you can suddenly expose a lot
of deeper carbon quite quickly,
and the more carbon is being exposed
and the more carbon is degrading simultaneously
the more warmth that's gonna release.
- And David and his team believe that the thaw
of this Yedoma permafrost could begin at
around three degrees of warming
and becomes more likely at four degrees.
- So that's where the possibility
of this self-sustaining permafrost thaw
which is sometimes referred to as compost bomb instability.
The idea being it's like a compost heap
that generates its own heat
and keeps its, it's effectively kind of
like a reaction going to itself.
- This compost bomb instability is the result
of what is known as compost warming reaction,
which is a process that occurs naturally when
organic matter breaks down and decomposes.
As this matter breaks down, it can act as fuel
for microorganisms leading to an increase in temperature.
As the temperature increases, the decomposing activity
of the microorganisms also increases, leading
to further release of heat.
This process creates a positive feedback loop
where warming leads to further decomposition, which leads
to more warming, which leads to, well, you get the idea.
- And the same thing might be possible
with permafrost where there's enough
of this carbon together.
So that could happen in some of the these Yedoma regions.
- One bit of good news here is
that the Yedoma tends to be found very far north.
- Luckily they're some of the colder regions
and that's why you tend to need a higher warming
level to potentially trigger those.
- So would this tipping point be truly catastrophic
for the climate?
Well, David stressed that he
and his team aren't sure if or when it will happen,
but he found that a collapse of the Yedoma and
similar permafrost formations could increase atmospheric CO2
by up to 60 parts per million over 50 years.
We're currently at about 420 parts per million
and 350 is considered safe.
That on top of the four degrees of warming it
would take to trigger the thaw could mean catastrophe.
Thankfully, that level
of warming is likely a long way into the future
and we do have time to reduce emissions before it hits.
But what do you think?
Will we keep warming low enough to avoid either
of the permafrost tipping points we discussed here?
And how many wooly mammoth tusks will we find if we don't?
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