Latest / Talking Science / The Carbon Cycle

Transcript

The Carbon Cycle · Talking Science

0:00
Wherever you are right now and whatever you're
0:02
doing, I actually want to invite you to do something
0:04
really simple. Just, you know, take a slow, deep
0:07
breath in. Like a real intentional breath. Yeah,
0:10
exactly. Hold it for just a second. No, just
0:12
let it out. It feels good to just pause for a
0:15
moment, right? But here is a completely mind
0:20
-bending fact from the research we're diving
0:21
into today. Oh, this part is wild. It really
0:24
is. The carbon dioxide you just exhaled, it contains
0:27
carbon atoms that have been on this unbelievable
0:31
journey. Like those exact atoms might have once
0:34
been circulating inside a dinosaur. Right. Or
0:37
they might have been dissolved in some prehistoric
0:39
sea millions of years ago. Yeah. Or locked tightly
0:42
inside, you know, the crushing weight of a limestone
0:45
cliff or even burped out of a glowing magma chamber.
0:49
It's just. It's crazy to think about. It is because
0:52
they're constantly on the move, right? And they're
0:54
going to go on to completely new places long
0:56
after you and I are done with them. Carbon is
0:58
fundamentally the great traveler of the Earth
1:00
system. It never just stays put. No, never. It's
1:04
forever circulating between the air, the deep
1:05
oceans, living things, and the rocks beneath
1:09
our feet. And that endless circulation is really
1:11
the core mission of this deep dive today. We're
1:15
looking at the carbon cycle. We're taking the
1:17
sources we have and using them to, well, sort
1:19
of shift how we all understand climate change.
1:22
Yeah, getting away from the typical framing.
1:24
Exactly. Moving away from the overwhelming buzzwords,
1:27
the political noise, the doom and gloom, and
1:30
just looking at this through the lens of a highly
1:32
logical story about stocks and flows. Which I
1:36
love because it really is just a mechanical story.
1:38
It's about... Where stuff is stored on our planet
1:40
and how fast it moves around. Right. And we're
1:42
taking this at a warm, unhurried pace today.
1:45
You do not need a science degree for this, I
1:47
promise. Just, you know, your natural curiosity.
1:50
Because understanding this cycle like how it
1:53
physically functions, it explains both how the
1:56
Earth has managed to stay comfortably livable.
1:58
for billions of years and exactly why our current
2:01
situation is so precarious. Yeah, it grounds
2:05
the whole thing. So if carbon and moving everywhere
2:07
and building everything, we should probably establish
2:09
why it's so special in the first place. That's
2:11
a great place to start. When I was going through
2:13
the source material, I kept picturing carbon
2:15
as like the ultimate versatile Lego block. You
2:19
know, the ones, the classic bricks that just
2:21
seem to connect to absolutely everything nature
2:24
wants to build. That's yeah. If we connect this
2:26
to the bigger picture of biology. That Lego analogy
2:29
actually holds up perfectly. And it's all because
2:32
of carbon's unique chemical superpower. Which
2:35
is what exactly? Well, a single carbon atom naturally
2:38
forms four strong bonds. And because it has those
2:42
four distinct connection points, it can link
2:44
up into endless complex chains, branches, rings,
2:48
you name it. So it's basically the scaffolding.
2:50
Exactly. Every single protein in your body. Every
2:53
strand of your DNA, the membranes of your cells,
2:56
they all require a carbon scaffold to exist.
3:00
Life is essentially just the process of constantly
3:03
assembling these carbon blocks into living tissue
3:05
and then taking them apart again. Taking them
3:07
apart again, right? It's the physical scaffolding
3:10
of the living world. But the sources point out
3:13
it doesn't just hang out in living things, right?
3:15
No, not at all. The Earth has these massive...
3:18
storage vaults i think the scientific term they
3:20
use is reservoirs where carbon is kept when it
3:23
isn't busy being part of a plant or an animal
3:26
And there are four main ones. Right, four big
3:28
vaults. You've got carbon floating in the atmosphere
3:31
as carbon dioxide gas. You've got a massive amount
3:33
dissolved in the ocean. You've got the land,
3:36
which is all the forests, grasslands, and crucially
3:39
the dirt and decaying plant matter. And then
3:42
you have the rocks. And the sheer scale of that
3:45
fourth vault, the rocks, it is genuinely difficult
3:48
to wrap your head around. It is the absolute
3:50
biggest store of carbon by far. Like, how big
3:53
are we talking? We're talking about vast expanses
3:55
of limestone, sedimentary rocks, the deep earth.
3:58
And, you know, this also includes fossil fuels,
4:01
coal, oil, gas, which are really just ancient
4:05
carbon -based life that geological pressure has
4:07
turned to stone over millions of years. Yeah,
4:10
well over 99 % of all the carbon on Earth is
4:13
locked away in that rocky vault. Over 99%. Okay,
4:16
let's unpack this for a second. Because if nearly
4:19
all the world's carbon is buried underground
4:21
or... dissolved in the deep ocean, the atmosphere
4:24
is actually one of the smallest vaults for carbon.
4:27
Yes. Relatively speaking, it's tiny. When I read
4:30
that, it totally threw me. I mean, why is the
4:33
smallest vault the one we hear about the most
4:35
in the news? Well, ironically, because it's the
4:37
smallest, it's also the most vulnerable. Think
4:40
of it like a very small glass of water. If you
4:44
drop a spoonful of salt into that tiny glass,
4:47
it drastically changes the chemistry of the water
4:49
instantly. Right. It's undrinkable. Right, yeah.
4:52
But if you drop that exact same spoonful of salt
4:54
into an Olympic -sized swimming pool, the change
4:57
is entirely unnoticeable. Oh, I see. Yeah. Because
5:01
the atmospheric vault is comparatively tiny,
5:03
any extra carbon we add to it changes its overall
5:06
makeup, and specifically its ability to trap
5:09
solar heat very quickly and very noticeably.
5:12
Small vault, highly sensitive to extra deposits.
5:15
That makes perfect sense. So we know where it
5:17
lives, the air, the ocean, the land, and the
5:20
rocks. But the really fascinating part of the
5:23
sources is how carbon physically moves between
5:27
these vaults. Flows. Exactly, the flows. It splits
5:31
this movement into two main loops that run at
5:33
completely different speeds. Let's look at the
5:35
biological fast lane first, because this is the
5:38
loop we interact with every single day. Right.
5:40
The one that keeps us alive. Yeah. To use an
5:41
analogy, the fast loop is kind of like the Earth's
5:44
daily operating budget. Every living thing on
5:46
the planet is constantly borrowing and returning
5:49
carbon just to stay alive, turning it over in
5:52
a matter of years or decades. And the primary
5:55
engine driving those deposits from the air into
5:57
living things is photosynthesis. Right. Which
6:00
we all learned about in school. We all know the
6:01
term from grade school. Yeah. But in the context
6:04
of this cycle, it's not just plants making food.
6:08
It is the actual physical mechanism. dragging
6:11
carbon gas out of the sky and turning it into
6:14
solid matter. It's crazy to picture it that way.
6:17
It really is. A tree isn't really growing from
6:19
the ground up. It's pulling carbon dioxide out
6:21
of the air, using sunlight to strip the carbon
6:24
atoms away, and literally building its wood and
6:27
leaves out of thin air. Basically a materialization
6:30
trick. And then the withdrawal happens, right?
6:33
Animals, including us. eat those plants, essentially
6:37
consuming that trapped carbon, and we breathe
6:39
a portion of it right back out into the air as
6:41
carbon dioxide. Exactly. And when things die,
6:44
decomposers in the soil break them down and release
6:47
the rest of the carbon back into the sky. So
6:50
it's the daily operating budget in action, through
6:53
photosynthesis, out through respiration and decay.
6:56
Yeah, and that biological engine is running in
6:58
the ocean, too, on a massive scale. Carbon dioxide
7:00
physically dissolves into seawater at the surface.
7:03
Like carbonation in a soda. It's the exact same
7:06
mechanism as gas dissolving into a liquid to
7:08
make a fizzy drink, yeah. And once the carbon
7:11
is in the water, tiny marine plants called phytoplankton,
7:14
which are essentially just microscopic algae,
7:17
they photosynthesize just like trees do. They
7:20
pull that dissolved carbon in to build their
7:21
cells. Which brings up a massive favor the ocean
7:24
is doing for us. The source material highlights
7:27
that the ocean acts like a giant sponge, and
7:31
it has already absorbed roughly a quarter to
7:33
a third of all the extra carbon dioxide humans
7:35
have emitted. It's an incredible buffer, yeah.
7:38
Without the ocean soaking that up, the atmospheric
7:40
vault would be much more crowded, and the warming
7:43
we're experiencing would be significantly worse.
7:47
And I have to push back on the panic I hear around
7:49
this sometimes. Sure, go ahead. If the ocean
7:51
is absorbing a third of our emissions and saving
7:54
us from a hotter atmosphere, isn't that a win?
7:56
Like, why are marine biologists so worried about
7:59
the oceans taking on more carbon? That's a really
8:02
fair question. But the problem is that this atmospheric
8:05
favor comes with a very steep, hidden biological
8:08
bill. The cost is a process called ocean acidification.
8:12
Okay, I've heard that term. What does it actually
8:14
mean? When we look at the actual chemistry, the
8:16
how of it, when carbon dioxide dissolves in seawater,
8:20
it doesn't just sit there inertly. It reacts
8:22
with the water molecules to form something called
8:24
carbonic acid. So we're physically changing the
8:27
pH level of the ocean. We are. The ocean is now
8:30
about 30 % more acidic than it was before the
8:32
industrial era. Wow, 30 %? Yeah, it's a huge
8:35
shift. And here is why that matters to the ecosystem.
8:38
That carbonic acid essentially hunts down and
8:42
binds with carbonate ions in the water. It hoards
8:45
them. And carbonate is important. It's crucial.
8:49
Carbonate is the exact building block that corals,
8:52
oysters, and countless tiny marine creatures
8:56
desperately need to build their shells and skeletons.
8:58
Oh, wow. So it's stripping the water of their
9:01
construction materials. It sounds like osteoporosis
9:03
for the ocean. That's an incredibly accurate
9:05
way to picture it, actually. They have to expend
9:08
significantly more energy just to maintain their
9:11
shells, let alone grow new ones. That's terrifying.
9:14
And since these tiny shelled creatures form the
9:16
very base of the marine food web, weakening them
9:19
threatens the entire ecosystem built on top of
9:21
them. The daily operating budget of the fast
9:24
loop gets completely thrown into chaos when the
9:26
ocean absorbs too much too quickly. So the daily
9:29
budget is highly active but incredibly fragile
9:31
when the balance gets thrown off. Which brings
9:33
us to the second loop. Right. Yes, the slow loop.
9:36
If the fast loop is the daily operating budget,
9:39
The geological slow loop is Earth's deeply locked
9:42
retirement vault. And here's where it gets really
9:45
interesting. This slow loop operates over millions
9:48
of years. It's a completely different timescale.
9:50
Yeah. And looking at the sources, getting carbon
9:53
out of the sky and into solid rock involves two
9:56
massive slow motion physical processes. It does.
10:00
And it actually starts with some of those same
10:01
marine creatures we just talked about. When phytoplankton
10:04
and those tiny shelled organisms die. They sink.
10:08
Just drifting down. Exactly. Billions of tiny
10:11
carbon -based shells fall to the very bottom
10:13
of the seafloor like this slow, eternal snowstorm.
10:17
Over unimaginable stretches of time, that sediment
10:20
piles up, gets crushed by the weight of the ocean,
10:22
and is compressed into limestone. And that physically
10:25
locks it away. Right. That physical process takes
10:28
carbon completely out of the biological fast
10:31
cycle and locks it away in the stone vault for
10:33
millions of years. And there's a terrestrial
10:35
version of this locking mechanism, too, which
10:37
completely blew my mind. Chemical weathering.
10:39
Oh, yeah. Weathering is fascinating. I always
10:42
thought rain just eroded rocks by washing dirt
10:44
away, but it's actually scrubbing carbon out
10:47
of the sky. As raindrops fall, they act like
10:50
tiny sponges, soaking up atmospheric carbon dioxide.
10:54
Making the rain slightly acidic. Exactly. The
10:57
rain becomes a weak acid. And when that weak
11:00
acid rain hits certain types of rock on land,
11:03
a chemical reaction happens. It physically binds
11:06
that atmospheric carbon into a liquid mineral
11:10
state called bicarbonate. And that liquid bicarbonate
11:13
doesn't just evaporate. It washes into streams,
11:15
flows down rivers, and empties into the ocean,
11:17
dragging the sky's carbon along with it. And
11:20
then the sea creatures use it. Right. Marine
11:22
creatures use it to build those shells we mentioned,
11:24
which eventually sink to the bottom and become
11:25
limestone. Through weathering and shell formation,
11:28
the Earth is constantly slowly burying carbon
11:31
in rock. But wait, if the Earth is always locking
11:34
carbon away in this retirement vault, wouldn't
11:36
the atmosphere eventually run completely dry?
11:39
Like, wouldn't plants suffocate if all the CO2
11:41
is buried? How does the carbon escape the rock
11:43
vault and get back into the sky? Through volcanoes.
11:46
Volcanoes. Yep. Set against all this slow burial,
11:49
volcanoes are the great return mechanism. As
11:53
the Earth's tectonic plates shift and melt deep
11:55
underground, that buried limestone and carbon
11:58
-rich rock gets superheated. It melts. It melts
12:01
and the carbon is released as a gas. Then volcanoes
12:04
belterette from deep inside the Earth's crust
12:06
right back into the atmosphere. Wait, okay. If
12:09
volcanoes are constantly burping up greenhouse
12:11
gases from deep inside the Earth, how has our
12:14
planet not just turned into a boiling, lifeless
12:17
greenhouse, especially since we know the sun
12:20
has actually gotten substantially brighter and
12:22
hotter over Earth history? That is the big question.
12:25
And what's fascinating here is how these two
12:27
massive geological forces, volcanic outgassing
12:31
and rock weathering, balance each other out.
12:33
It's this slow seesaw that has governed Earth's
12:36
climate over hundreds of millions of years. It's
12:38
a balance. Yes, and it acts as a remarkably elegant,
12:41
genuinely self -regulating natural thermostat.
12:44
A thermostat. Okay, I want to trace the logic
12:47
of this, make sure I have it right. If the planet
12:49
gets too hot, say... there's a huge spike in
12:52
volcanic eruptions releasing massive amounts
12:54
of carbon dioxide. The atmosphere warms up, right?
12:57
Right. And a warmer atmosphere means more water
12:59
evaporates from the oceans. More evaporation
13:02
means heavier rainfall. And since rain is the
13:05
thing that causes chemical weathering, more rain
13:08
means the rocks are scrubbing carbon dioxide
13:10
out of the sky much faster. washing it to the
13:13
sea you're tracking it perfectly so it acts as
13:16
a break it physically pulls the heat trapping
13:19
gas out of the air cooling the planet back down
13:22
you've got it and the beauty of it is that the
13:24
feedback loop works perfectly in reverse too
13:26
how so well if the planet cools too much evaporation
13:29
drops rainfall decreases and that chemical rock
13:32
weathering slows to a crawl The Earth basically
13:35
stops pulling carbon out of the air. But the
13:36
volcanoes keep going. Exactly. The volcanoes
13:39
deep underground don't care about the weather
13:42
on the surface. They keep erupting, steadily
13:44
releasing carbon dioxide. So with the weathering
13:47
break removed, that volcanic carbon builds back
13:50
up in the atmosphere unchecked. The greenhouse
13:52
effect strengthens and it warms the freezing
13:55
planet back up. So the Earth has effectively
13:58
been sweating and shivering its way to stability
14:00
for billions of years. It's brilliant. It's just
14:04
an incredibly, incredibly slow mechanism. Very
14:06
slow. Hundreds of thousands of years. Which perfectly
14:09
sets up our current situation. If the Earth has
14:12
this built -in self -regulating thermostat, why
14:14
are we in a climate crisis right now? The source
14:17
material lays the logic out beautifully, and
14:19
it's because humans found a way to bridge the
14:21
slow geological vault and the fast biological
14:24
lane. We engineered a massive short circuit.
14:27
Yeah. To understand the sheer scale of the disruption,
14:29
we have to completely redefine what fossil fuels
14:32
actually are in the context of this cycle. Right.
14:34
They aren't just fuel. No. Coal, oil, natural
14:37
gas, they aren't just fuel. Yeah. They are ancient
14:39
plants and plankton. They are concentrated pockets
14:43
of carbon that photosynthesis pulled out of the
14:46
air tens or hundreds of millions of years ago.
14:49
The slow cycle buried them. Exactly. Geology
14:51
locked them underground safely out of the daily
14:54
operating budget. And the core of the climate
14:57
problem is that in just the span of a couple
14:59
of centuries, human beings basically became the
15:02
ultimate geological force. We dug into that deeply
15:05
buried slow loop retirement vault, pulled the
15:09
carbon to the surface and burned it. We forced
15:11
it out. Yeah, by burning it, we dumped it directly
15:13
back into the atmosphere. We are taking carbon
15:16
that the slow geological cycle took millions
15:18
of years to safely remove, and we are returning
15:20
it to the sky in a planetary eye blink. It is
15:23
the ultimate short circuit. Yeah. And the real
15:25
tragedy here is that the natural thermostat,
15:27
that chemical rock weathering we discussed, it
15:29
does still respond. It is actively trying to
15:32
do its job right now. It just can't keep up.
15:34
Not even close. It operates on a timescale of
15:37
tens of thousands of years. It is far, far too
15:42
slow to counteract the massive, sudden spike
15:45
of carbon we are dumping into the fast loop in
15:48
a mere matter of decades. It's totally overwhelmed.
15:50
Right. Because there is no natural fast process
15:53
capable of mopping up this extra carbon. It just
15:56
lingers. It stays trapped in the fast loop for
15:59
centuries to millennia, overheating the air and
16:02
acidifying the sea. So what does this all mean?
16:05
When we put all these pieces of the cycle together,
16:07
it gives us a really powerful tool for reasoning
16:10
through the noise. I hear people argue all the
16:13
time, and maybe you listening have wondered this
16:15
yourself. They say carbon dioxide is completely
16:17
natural. Plants need it to survive. breathe it.
16:20
So how can it possibly be a pollutant? I hear
16:22
that all the time, too. It's a vital distinction
16:24
to make, and their premise is technically correct.
16:27
Carbon dioxide is absolutely not bad or unnatural.
16:30
It's the currency of life. We're made of it.
16:32
The entire biosphere depends on it. The crisis
16:35
we are facing is purely an issue of speed and
16:38
balance. We have knocked the cycle entirely out
16:40
of balance by physically relocating carbon from
16:43
a slow, deep store to a fast, volatile one at
16:47
a highly unnatural speed. That reframing changes
16:51
everything. It's not a poison. It's just in the
16:53
wrong place way too fast. We overloaded the daily
16:57
operating budget. And understanding exactly how
17:00
we broke the cycle gives us a perfectly clear
17:03
map for what the various climate solutions are
17:05
actually trying to achieve in terms of stocks
17:07
and flows. It demystifies the solutions entirely.
17:10
It really does. When I looked at the solutions
17:12
for the biological fast loop, things like reforesting
17:16
or promoting healthy soils made total sense.
17:18
just artificially inflating the size of the terrestrial
17:21
checking account so it can physically hold more
17:23
of the excess carbon. Right. Planting trees is
17:25
strengthening the land's ability to hold carbon
17:27
in the fast loop. But the most critical solution,
17:30
cutting our emissions and transitioning away
17:33
from fossil fuels, is simply about stopping the
17:35
short circuit at the source. Just turning it
17:37
off. Exactly. It means halting the unnatural
17:40
transfer of carbon from the rock fault to the
17:42
air. And then there's the big flashy tech solution
17:44
we hear so much about, carbon capture technologies.
17:47
From a systems perspective, these machines are
17:50
essentially... human attempts to artificially
17:53
replicate the slow geological burial loop. They
17:57
are, yeah. The goal of carbon capture is to engineer
18:00
machinery that can physically pull carbon dioxide
18:03
directly out of the air and pump it permanently
18:06
underground, mimicking what chemical rock weathering
18:09
and limestone formation do naturally over millions
18:11
of years. To synthesize this, I want to use an
18:14
analogy that really crystallized it for me. It's
18:16
like living in a house that is actively flooding
18:18
because a massive underground pipe burst. Okay,
18:21
I like this. Cutting emissions is rushing down
18:23
to the basement to turn off the main water tap.
18:26
Planting trees and restoring soil is like throwing
18:28
down every towel you own to soak up the water
18:31
that's already ruining the floors. And carbon
18:33
capture technology is like trying to invent a
18:35
magical super vacuum that can instantly suck
18:38
up the water and teleport it outside. That's
18:40
a great way to visualize it. Which makes me ask,
18:42
with all the grand claims we see in the news
18:45
and from startups about carbon capture tech,
18:47
is that super vacuum actually going to save us?
18:50
This raises an important question, and the source
18:53
material is very clear about the caveats here.
18:56
While the theory of direct air capture perfectly
18:58
mimics the Earth's natural slow burial loop,
19:01
engineering it to work at the speed and sheer
19:03
mass of human emissions is incredibly difficult.
19:07
I imagine the scale is just daunting. It is.
19:10
Pulling a dispersed gas out of the atmosphere
19:12
and safely injecting it into bedrock takes staggering
19:15
amounts of energy and infrastructure. The research
19:17
suggests that this is an area where careful skepticism
19:19
about grand claims is absolutely warranted. We
19:22
can't just cross our fingers and wait. No, we
19:25
can't simply rely on blind faith in future super
19:27
vacuums to fix a massive cycle we are currently
19:30
overwhelming. It really is all about stocks and
19:33
flows. where Kargan sits, and how fast it moves.
19:37
Earth's great, elegant circulation kept the planet
19:40
livable across almost incomprehensible stretches
19:43
of time. Our challenge right now is that we reached
19:46
down into its slowest, deepest vault, and we
19:49
threw the contents into the fastest loop, quicker
19:52
than the natural thermostat can possibly adjust.
19:55
And our challenge is figuring out how to let
19:57
the Earth catch up. Exactly. Reading the carbon
20:00
cycle properly really does turn climate change
20:02
from a political slogan into something you can
20:05
physically visualize and reason about. It removes
20:08
the abstraction. It's just plumbing on a planetary
20:11
scale. Plumbing on a planetary scale. I love
20:14
that. Let's bring this all the way back to where
20:15
we started. Remember that slow, deep breath you
20:18
took at the beginning of this deep dive? Think
20:20
about where the carbon in your next exhale is
20:22
going to go. It's starting its next journey.
20:24
Into a plant on your windowsill, absorbed into
20:27
the surface of the sea. Perhaps millions of years
20:29
from now, it will be compressed into stone on
20:32
a distant ocean floor. It is on a journey that
20:34
lasts from seconds to hundreds of millions of
20:36
years. It's a beautiful thing to think about.
20:38
It really is. But I want to leave you with one
20:41
final provocative thought to chew on as you go
20:44
about your day. Look at the physical world around
20:47
you right now. Look at the plastic casing on
20:50
your computer or phone. Look at the synthetic
20:52
clothes you might be wearing. Think about the
20:55
fuel sitting in your car's gas tank. It's all
20:57
carbon. We are so used to seeing these things
21:00
simply as products we bought at a store. But
21:03
chemically, structurally, they're just carbon.
21:05
There are ancient plants and prehistoric plankton.
21:08
Next time you look at these everyday items, don't
21:11
just see a consumer product. Think of them as
21:13
temporary resting stops for ancient carbon atoms
21:15
on a billion -year journey. a layover the brief
21:18
layover they were pulled from the deep slow rock
21:21
vault and right now they are just pausing in
21:23
your life on a brief layover before they inevitably
21:25
enter the fast loop of the atmosphere if we started
21:29
viewing our everyday material world not as disposable
21:32
goods but as borrowed pieces of earth slow ancient
21:35
vault how might that fundamentally change our
21:38
relationship with the things we buy use and throw
21:40
away thanks for joining us on this deep dive
21:43
we'll catch you next time