TED SCHUUR: If we think about climate change, most of society
is focused on fossil fuel combustion.
But what humans release on an annual basis
is just one part of the carbon cycle.
Carbon dioxide concentrations also go up and down
because of the actions of plant photosynthesis
taking carbon out of the air, and then
respiration by all living things releasing carbon back
to the air.
So as humans continue to release fossil fuels
into the atmosphere, it's critical to know
what these natural ecosystems are going to do in the future.
Are they going to play a role like they do today,
balancing the carbon cycle?
Or in the future, might these systems
release more carbon to the atmosphere,
which will increase future warming?
SCOTT GOETZ: Alaska, in many ways,
is at the forefront of climate change because
of the dramatic temperature changes
that have been seen here.
And it is an indicator of changes
that are taking place across the whole high northern latitudes.
The Boreal forest extends from Siberia, Northern Asia,
and it stretches all across Southern Canada
all the way up to Alaska, where it's primarily
concentrated in the interior that's dominated
by evergreen conifers.
But there is also a significant deciduous component
of aspen and birch.
My particular interest in Boreal forest
is how the forests are changing and what the feedbacks are
to climate, how much the warming and drying
in these high northern latitudes has changed the fire regime
and how it's changed what grows back after the fire.
MAN: 57 watts per meter squared.
SCOTT GOETZ: We estimate how much
light is absorbed by the trees, because that
drives photosynthesis.
And we also measure the carbon dioxide fluxes through time.
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We see quite dramatic changes in the amount of area
that burns every year, the intensity or severity
of burning.
Most of the big fire years have been in the past 10 years,
with the biggest by far being 2004, 2005, and then 2009.
Changes in burn severity mean that we
see this greater deciduous component of the forest coming
back, out-competing this conifer forest that was there before.
And that feeds back to the climate system
in a number of different ways.
Deciduous forests grow much faster.
They're more productive.
So they take up a lot of carbon through productivity.
Whereas a confier forest grows slowly,
incrementally through time.
Another way the forest feeds back to climate
is how they reflect light.
So a dark conifer forest is absorbing a lot of energy
and warming the surface, whereas the deciduous forest is
much more reflective and actually reflects light back
to the atmosphere.
So if we see this regime shift to more deciduous species,
that suggests that we're not only taking more carbon out
of the atmosphere, but the forests are also
reflecting more light back.
And those would both tend to mitigate
the impacts of climate change.
But I think much of that mitigation
could be dwarfed by the carbon that
has been stored here over centuries in permafrost soil.
As that thaws, it could release an enormous amount of carbon
into the atmosphere.
And in the past, that's been referred to as the carbon bomb.
TED SCHUUR: We're inside a permafrost tunnel
that was drilled in the 1960s.
And what we're looking at are plant roots that grew here
probably 10,000 years ago.
And these roots, they look alive.
But really, they've been frozen since that time, trapped
in the permafrost.
Permafrost is permanently frozen ground
that contains carbon, the remains of plants and animals
that have accumulated over thousands of years.
What's exciting about permafrost is that deep in the soil
is the outer space of ecosystems.
We tend to think of an ecosystem where plants
are growing at the surface.
But with permafrost ground, we're
finding that this carbon pool extends down tens of meters.
But it's also frozen in place, so it's protected
by its current climate.
What we're seeing in this core, this dark brown color,
is pockets of organic carbon.
This is exactly a type of pool that we would call
vulnerable to climate change.
Right now, we have twice as much carbon
stored frozen in permafrost soils
than there is currently in the atmosphere.
In a warmer world, as the ground thaws,
that carbon may end up as a big release of carbon
to the atmosphere and increase future warming.
So the ultimate question that we have
is once permafrost thaws, what's the impact on the ecosystem
carbon cycle, and how does that feed back to climate change.
This site is an experiment that we set up
to actually warm up the permafrost ourselves.
Each one of these boxes, as it closes,
it encompasses a small atmosphere.
And we're measuring the movement of carbon dioxide
in and out of the ecosystem.
The first one is 55.
To get the perspective of this exchange of carbon,
we need to make these measurements
during the day and the night, during all seasons of the year,
to come up with this annual movement of carbon
between the ecosystems and the atmosphere.
Currently, we have computer models that
predict the future climate.
But these models have nothing in them
in regards to permafrost carbon.
So we're working to integrate the variables we measure here
about permafrost into these models.
SCOTT GOETZ: The changes that we're seeing in Alaska
are not like anything we've seen,
certainly in our lifetimes.
So in some ways, it's exciting as a scientist
to be able to study it.
But at the same time, it's a bit worrisome.
TED SCHUUR: The pace of climate change
is much faster than we ever have seen in the recorded past.
So what that means is there's a lot more uncertainty about what
the outcome will be.
Everyone wants to predict the future, which
we know is impossible.
But we use our scientific analysis and computer models
to get a better understanding of future climate.