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Are Humans Delaying the Next Ice Age? · The Last Observer: Science and Beyond

• 0:00
  Speaker 1: You know, when you think about it, for basically all
• 0:02
  Speaker 1: of our modern history, our collective environmental anxieties has pointed
• 0:07
  Speaker 1: in one very specific.
• 0:08
  Speaker 2: Direction, right towards the heat.
• 0:10
  Speaker 1: Exactly, we worry about heat. I mean, we worry about
• 0:13
  Speaker 1: crippling grouts, drying up reservoirs, relentless floods, overwhelming coastlines, and
• 0:20
  Speaker 1: you know the cascading agricultural failures that follow when crop
• 0:24
  Speaker 1: belts just bake under a stagnant sun.
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  Speaker 3: Yeah, and those are, to be clear, very real, very
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  Speaker 3: present concerns.
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  Speaker 1: Oh totally. But there is this massive blind spot in
• 0:33
  Speaker 1: our cultural imagination. And I want to flip that entirely
• 0:36
  Speaker 1: on its head today because what if you looked at
• 0:39
  Speaker 1: the four and a half billion year paleoclimate record and
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  Speaker 1: realize that the ground beneath your feet is technically overdue
• 0:45
  Speaker 1: for a freeze.
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  Speaker 2: It's jarring thought, right.
• 0:47
  Speaker 1: The reality is Earth's default state is not the balmy,
• 0:50
  Speaker 1: predictable climate we built our entire civilization upon. So we
• 0:54
  Speaker 1: are going to get right into the mechanics of planetary
• 0:56
  Speaker 1: climate history to find out exactly how a global.
• 1:00
  Speaker 3: Takes hold, which is fascinating considering the modeling being done
• 1:03
  Speaker 3: right now.
• 1:03
  Speaker 1: Yeah, and why this highly contrarian question is being run
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  Speaker 1: on supercomputers as we speak. Could the mechanics of an
• 1:10
  Speaker 1: ice age begin to assert themselves sooner than anyone anticipates.
• 1:14
  Speaker 3: It really forces a complete recalibration of how we perceive
• 1:17
  Speaker 3: our environment because human intuition is just incredibly poorly equipped
• 1:24
  Speaker 3: to understand geological time.
• 1:25
  Speaker 1: Yeah, we think in terms of what a human life
• 1:28
  Speaker 1: span exactly.
• 1:29
  Speaker 3: We operate on timescales of decades or maybe centuries if
• 1:33
  Speaker 3: we are thinking generationally. But when you actually look at
• 1:36
  Speaker 3: the isotopic records locked in sediment cores in ancient ice,
• 1:39
  Speaker 3: you realize that a scenario where massive glaciers actively spread
• 1:44
  Speaker 3: across continents, that isn't science fiction.
• 1:46
  Speaker 1: It's just the Earth doing its thing.
• 1:47
  Speaker 3: It is the rhythmic, mechanical heartbeat of this planet. To
• 1:51
  Speaker 3: even begin grasping this, we have to recognize that the
• 1:53
  Speaker 3: relatively stable climate of the last twelve thousand years is
• 1:57
  Speaker 3: statistically speaking, a total a noma.
• 2:00
  Speaker 1: I want to start right there, but basically tearing down
• 2:03
  Speaker 1: this baseline illusion we all share because most of us
• 2:05
  Speaker 1: walk around assuming the Earth's climate is this permanent.
• 2:08
  Speaker 2: Fixture, right, static bactrum.
• 2:10
  Speaker 1: Yeah, like we have a cold winter, a brutally hot summer,
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  Speaker 1: maybe a shift over a few decades, but the overarching
• 2:17
  Speaker 1: system feels locked in. It's like looking at a single
• 2:20
  Speaker 1: paused frame of a two hour movie and assuming none
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  Speaker 1: of the characters ever.
• 2:24
  Speaker 3: Moved, which is an entirely false premise. The Earth has
• 2:27
  Speaker 3: never maintained a permanent climate, never never. The planetary system
• 2:31
  Speaker 3: essentially oscillates between two primary thermodynamic states. You have green
• 2:36
  Speaker 3: health periods where the planet is largely devoid of permanent ice,
• 2:41
  Speaker 3: and ice house periods where massive ice sheets dominate the
• 2:44
  Speaker 3: higher latitudes. And right now, we're right now, our entire
• 2:48
  Speaker 3: cultural memory is contained within a microscopic slice of a
• 2:52
  Speaker 3: larger ice house fluctuation.
• 2:53
  Speaker 1: Okay, so really ground that in reality. Let's look at
• 2:55
  Speaker 1: the extremes, because if you try to picture a deep
• 2:58
  Speaker 1: greenhouse period, you just have to throw the current map
• 3:02
  Speaker 1: out the window, completely out the window. Like if you
• 3:04
  Speaker 1: traveled to the Antarctic Circle during the Eocene epoch, which
• 3:07
  Speaker 1: was roughly fifty million years ago, you wouldn't be packing
• 3:11
  Speaker 1: a parka to survive on a barren, frozen wasteland, No,
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  Speaker 1: not at all.
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  Speaker 2: You'd probably want a light jacket.
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  Speaker 1: Paleoclimatologists have literally pulled fossilized leaves, pollen, and wood from
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  Speaker 1: sediment cores drilled deep into the Antarctic sea floor.
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  Speaker 2: It's wild.
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  Speaker 1: You would have been walking through lush, temperate rainforests, I mean,
• 3:29
  Speaker 1: palm trees near the Arctic Dinosaurs wandering through Antarctic vegetation.
• 3:34
  Speaker 3: And you know, a lot of people assume that's because
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  Speaker 3: the continents were in vastly different positions relative to the Sun.
• 3:40
  Speaker 3: But Antarctica was already positioned near the south pole during
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  Speaker 3: that greenhouse phase.
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  Speaker 1: Wait, really, it was already at the bottom of the world.
• 3:47
  Speaker 3: Yes, the difference was entirely atmospheric and oceanic heat distribution.
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  Speaker 3: The planet was just incredibly efficient at moving heat to
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  Speaker 3: the pulse.
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  Speaker 1: Okay, wow, but the pendulum always swings back.
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  Speaker 2: It always does.
• 3:59
  Speaker 3: During the found depths of an ice house period, those
• 4:02
  Speaker 3: tropical conditions are violently erased. I mean, you don't just
• 4:06
  Speaker 3: lose the polar forests. You get ice sheets miles thick,
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  Speaker 3: blanketing North America, plunging deep into the midwestern United States,
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  Speaker 3: and suffocating massive expanses of Europe and Asia.
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  Speaker 1: Which brings us to the most jarring realization. If Earth's
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  Speaker 1: history is defined by these massive swings between hothouse and
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  Speaker 1: ice house, we have to locate ourselves on that pendulum.
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  Speaker 2: Right where are we now?
• 4:31
  Speaker 1: Yeah? Where exactly do we sit right now? Because look,
• 4:35
  Speaker 1: looking out the window in July, it feels incredibly warm.
• 4:38
  Speaker 1: But the strict geological definition tells a completely different story.
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  Speaker 3: It does based on the fundamental definitions used in paleoclimatology,
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  Speaker 3: Earth is currently in an.
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  Speaker 2: Ice age, right Okay?
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  Speaker 1: Wait, I have to stop you there, because that feels
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  Speaker 1: like a semantic technicality that ignores reality. If I'm sitting
• 4:55
  Speaker 1: on a beach in Florida getting a sunburn, in what
• 4:58
  Speaker 1: possible sense am I vacationing in the middle of an
• 5:00
  Speaker 1: ice age?
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  Speaker 3: Well, you are looking at local, temporary weather, whereas geology
• 5:05
  Speaker 3: looks at global ice volume.
• 5:07
  Speaker 1: Okay, but still an ice age.
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  Speaker 3: An ice age isn't defined by the entire globe being.
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  Speaker 2: Covered in frost.
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  Speaker 3: The scientific threshold is actually quite specific. It's simply a
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  Speaker 3: period in Earth's history where permanent, extensive ice sheets exist
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  Speaker 3: on at least one of the planet's poles.
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  Speaker 1: Oh and because we have massive ice sheets sitting on
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  Speaker 1: top of Antarctica in Greenland precisely.
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  Speaker 3: The mere existence of those permanent polar ice caps means
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  Speaker 3: we are deep inside the Quaternary ice age.
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  Speaker 1: It's a binary thing. You either have permanent ice on
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  Speaker 1: a pole or you.
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  Speaker 3: Don't, exactly, and this isn't a new development either. The
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  Speaker 3: Quaternary ice Age began roughly two point six million years ago.
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  Speaker 1: Two point six million years Yeah.
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  Speaker 3: It was driven by the closing of the Isthmus of Panama,
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  Speaker 3: which rerouted global ocean currents and basically allowed ice to
• 5:54
  Speaker 3: aggressively accumulate in the northern hemisphere. So we are two
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  Speaker 3: and a half million years into this freeze.
• 5:59
  Speaker 1: Okay, So why are they're glaciers parked in my backyard
• 6:01
  Speaker 1: in North America right now? If we are in the
• 6:03
  Speaker 1: ice age, why is the ice mostly confined to the
• 6:06
  Speaker 1: extreme poles.
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  Speaker 3: Because an ice age isn't a monolithic block of cold.
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  Speaker 3: It's not static.
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  Speaker 2: The client breathe. Yeah.
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  Speaker 3: Within this two point six million year overarching ice age,
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  Speaker 3: you have long brutal periods or the ice advances.
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  Speaker 2: Those are your glacial periods, and.
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  Speaker 3: Then you have shorter temporary intervals where the planet warms
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  Speaker 3: slightly and the ice retreats back to the poles. These
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  Speaker 3: are the interglacial periods.
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  Speaker 1: And the current warm interval. Our little window of mild
• 6:32
  Speaker 1: weather is called the Holocene.
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  Speaker 3: Yes, the Holocene interglacial, and it began a mere eleven
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  Speaker 3: seven hundred years ago, immediately following the retreat of the
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  Speaker 3: last major glacial advance.
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  Speaker 1: See. It really reframes all of human history when you
• 6:46
  Speaker 1: think about it. Every single thing we consider to be
• 6:49
  Speaker 1: human civilization. I mean the invention of agriculture, the wheel,
• 6:53
  Speaker 1: the construction of the pyramids, the Industrial Revolution, the advent
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  Speaker 1: of nuclear physics, the Internet. Literally all of it took
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  Speaker 1: place within this inc rdibly brief eleven seven hundred year window.
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  Speaker 2: It's a blip.
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  Speaker 1: We basically won the cosmic lottery. We built a global
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  Speaker 1: civilization during a temporary planetary thaw, and then just convinced
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  Speaker 1: ourselves that the thaw was permanent.
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  Speaker 3: It is a textbook case of shifting baseline syndrome. Because
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  Speaker 3: all recorded human history exists within the Holocene. Our infrastructural
• 7:21
  Speaker 3: and agricultural systems are hyper optimized for a climate that
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  Speaker 3: is geologically speaking, highly anomalous. We have built our megacities
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  Speaker 3: on coastlines that are completely temporary, assuming the sea level
• 7:33
  Speaker 3: and the ice volume are static. But the geologic record
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  Speaker 3: proves how radically unstable this system is.
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  Speaker 1: And we know this from what oceanic fossils.
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  Speaker 3: Yeah, specifically the isotopic signatures left in the fossilized shells
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  Speaker 3: of microscopic ocean creatures called benthic FORMINIFRA. They show us
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  Speaker 3: just how wildly the ice volume fluctuates.
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  Speaker 1: I want to look closely at that instability. Let's rewind
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  Speaker 1: the clock back just twenty thousand years to the period
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  Speaker 1: immediately proceeds our little Holocene window.
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  Speaker 3: The last glacial maximum.
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  Speaker 1: Yes, the last glacial maximum, because I want listeners to
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  Speaker 1: really look out their window and try to visualize this.
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  Speaker 3: The last glacial maximum represents the peak of the last
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  Speaker 3: brutal deep freeze. And you have to understand the ice
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  Speaker 3: didn't just sit politely at the poles. The Laurent's Hide
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  Speaker 3: ice sheet, for example, aggressively expanded outward, marching down across
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  Speaker 3: North America.
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  Speaker 1: And we are not talking about like heavy snowfall or
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  Speaker 1: a few tough winters. The sheer physical volume of this
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  Speaker 1: ice is hard to wrap your mind around. Over modern
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  Speaker 1: day cities like Montreal, Boston, and Chicago, the ice was
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  Speaker 1: upwards of three kilometers.
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  Speaker 3: Thick, roughly two miles two miles.
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  Speaker 1: That is a solid wall of ice taller than the
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  Speaker 1: tallest skyscrapers in the world, just grinding over the neighborhood.
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  Speaker 3: And the physical mechanics of that ice are devastating. I mean,
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  Speaker 3: we know its exact extent, not from guesswork, but from
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  Speaker 3: the physical scars that left behind on the Earth.
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  Speaker 1: Like it carved up the ground.
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  Speaker 3: Glaciers act like planetary bulldozers. As a two mile thick
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  Speaker 3: sheet of ice grinds forward, it plucks up massive boulders,
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  Speaker 3: dragging them for hundreds of miles and scouring these deep
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  Speaker 3: striations into the continental bedrock.
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  Speaker 1: It just crushes everything.
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  Speaker 3: Literally everything, And when the ice finally melts, it leaves
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  Speaker 3: behind terminal moraines.
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  Speaker 1: Which are what exactly.
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  Speaker 3: There are these massive ridges of debris and rock that
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  Speaker 3: mark the exact maximum boundary of the glaciers advance like
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  Speaker 3: a debris wall. Long Island, New York, for example, is
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  Speaker 3: essentially a giant terminal moraine left behind by the Laurentide
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  Speaker 3: ice sheet.
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  Speaker 1: Wait, really, Long Island is just glacier garbage.
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  Speaker 3: Basically, Yes, it's a pile of rubble pushed there by
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  Speaker 3: two miles of ice.
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  Speaker 1: That is insane. Now think about this logically. If you
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  Speaker 1: have a two mile thick block of ice covering half
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  Speaker 1: of North America and similar sheets covering Scandinavia and Siberia,
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  Speaker 1: all of that water has to come from somewhere.
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  Speaker 2: Right, It's a closed planetary.
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  Speaker 1: System, So you are taking liquid out of the oceans
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  Speaker 1: and essentially stacking it on the continents.
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  Speaker 3: Which triggers a dramatic drop in global sea levels. During
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  Speaker 3: the last glacial maximum, because so much of the Earth's
• 10:05
  Speaker 3: available water was locked up in these continental glaciers, the
• 10:08
  Speaker 3: oceans were incredibly depleted. Global sea levels dropped by approximately
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  Speaker 3: one hundred and twenty meters.
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  Speaker 1: One hundred and twenty meters, that's nearly four hundred feet
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  Speaker 1: lower than where our modern coastlines sit today. Except but
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  Speaker 1: how do paleoclimatologists even measure a sea level drop of
• 10:24
  Speaker 1: four hundred feet from twenty thousand years ago? Like, the
• 10:27
  Speaker 1: water is gone. So what proxy tells you exactly where
• 10:29
  Speaker 1: the beach used to be?
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  Speaker 3: Well, it requires looking for biological markers that are highly
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  Speaker 3: sensitive to water depth, and one of the best indicators
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  Speaker 3: is a specific species of coral called acroporapalmata, commonly known
• 10:42
  Speaker 3: as Elkorn coral. This coral requires intense sunlight to survive,
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  Speaker 3: which means it only grows in the uppermost few meters
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  Speaker 3: of the ocean surface, right at the wave.
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  Speaker 1: Break, right where the surfits.
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  Speaker 2: Yeah.
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  Speaker 3: So, by drilling deep into the seabed off the coast
• 10:55
  Speaker 3: of Barbados, geologists found fossilized reefs of this exact core,
• 11:00
  Speaker 3: seating one hundred and twenty meters below the modern ocean surface.
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  Speaker 1: Oh wow, So they found the ancient surf line way down.
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  Speaker 3: Deep precisely, and by radiocarbon dating those fossils they could
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  Speaker 3: map the precise timeline of the sea level drop.
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  Speaker 1: That one hundred and twenty meters drop completely redrew the
• 11:15
  Speaker 1: map of the Earth. I mean, it's the reason why
• 11:17
  Speaker 1: early human migration was even possible.
• 11:19
  Speaker 3: Right, because the coastlines expanded massively.
• 11:22
  Speaker 1: Yeah. With the oceans that low, massive tracks of the
• 11:26
  Speaker 1: continental shelf were exposed as dry land. Britain was not
• 11:30
  Speaker 1: an island, it was a peninsula connected to mainland Europe
• 11:33
  Speaker 1: across this grassy plain called Doggerland.
• 11:36
  Speaker 3: And crucially it exposed Beringia.
• 11:38
  Speaker 1: The land bridge.
• 11:40
  Speaker 3: Yes, the massive land bridge connecting Siberia to Alaska. And
• 11:44
  Speaker 3: it's important visualized this correctly. This wasn't some narrow, icy causeway.
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  Speaker 3: It was a vast dry step tundra ecosystem spanning hundreds
• 11:53
  Speaker 3: of miles.
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  Speaker 1: It was just a massive continent connecting the two exactly.
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  Speaker 3: It allowed nomadic human populations to literally walk from a
• 12:00
  Speaker 3: into the Americas, hunting megafauna along the way. The entire
• 12:03
  Speaker 3: geographical foundation of human history was dictated by the mechanics
• 12:07
  Speaker 3: of that frozen world.
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  Speaker 1: So we have established the sheer, violent scale of a
• 12:11
  Speaker 1: glacial maximum. The obvious question that follows is the mechanism, right,
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  Speaker 1: what triggers it? Yeah, what possesses the planet to suddenly
• 12:18
  Speaker 1: pull that icy blanket up to its chin? Like what
• 12:21
  Speaker 1: breaks the interglacial warmth?
• 12:23
  Speaker 3: Well, it is not a sudden, singular trauma to the system.
• 12:27
  Speaker 3: It's not like a switch being flipped. Cyclical ice ages
• 12:29
  Speaker 3: are born from orbital mechanics, and I understand this. We
• 12:32
  Speaker 3: really have to look at the work of Milutin Milankovitch.
• 12:36
  Speaker 3: He was a Serbian mathematician and astronomer who fundamentally changed
• 12:41
  Speaker 3: how we understand planetary climate in the early.
• 12:43
  Speaker 1: Twentieth century, and Malakavich's personal story is actually incredible. I mean,
• 12:47
  Speaker 1: he didn't figure this out using supercomputers or satellite telemetry.
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  Speaker 1: He developed this overarching theory while he was a prisoner
• 12:54
  Speaker 1: of war during World War One.
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  Speaker 3: He did He was interned in Budapest during the war,
• 12:59
  Speaker 3: but he was eventually granted access to the library of
• 13:02
  Speaker 3: the Hungarian Academy of Sciences.
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  Speaker 1: That's lucky, very so.
• 13:05
  Speaker 3: Over years of captivity, using nothing but paper, pencil and
• 13:09
  Speaker 3: complex spherical trigonometry, he meticulously calculated the varying amounts of
• 13:14
  Speaker 3: solar radiation hitting different latitudes of the Earth over hundreds
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  Speaker 3: of thousands of years.
• 13:19
  Speaker 1: Just doing planetary math by.
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  Speaker 3: Hand exactly, and he hypothesized that long term climate is
• 13:25
  Speaker 3: governed by three distinct, overlapping astronomical cycles. We now call
• 13:29
  Speaker 3: them the Malankovitch cycles.
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  Speaker 1: Let's break down the physical physics of these three cycles,
• 13:33
  Speaker 1: because this is where it gets really interesting. The first
• 13:36
  Speaker 1: one is eccentricity, and this deals with the actual shape
• 13:40
  Speaker 1: of Earth's orbit around the Sun.
• 13:42
  Speaker 3: Correct So we tend to visualize Earth's orbit as a
• 13:45
  Speaker 3: perfect circle, you know, like a classroom model, but it
• 13:48
  Speaker 3: is actually somewhat valuable over a primary cycle of roughly
• 13:52
  Speaker 3: one hundred thousand years. The gravitational tug of the massive
• 13:55
  Speaker 3: gas giants in our solar system, specifically Jupiter and saturn A,
• 14:00
  Speaker 3: physically pull on the Earth.
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  Speaker 1: Like gravity's stretching us out.
• 14:03
  Speaker 3: Yeah, this gravitational interference causes our orbit to stretch, shifting
• 14:08
  Speaker 3: from nearly circular to slightly elliptical, and then slowly relaxing
• 14:12
  Speaker 3: back again.
• 14:12
  Speaker 1: So when the orbit is more elliptical, like an oval,
• 14:15
  Speaker 1: the Earth's physical distance from the Sun varies far more dramatically.
• 14:19
  Speaker 1: Throughout the course of a single year. You have a
• 14:21
  Speaker 1: point where we are much closer to the Sun and
• 14:23
  Speaker 1: a point where we are much further.
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  Speaker 3: Away exactly, and this shift in eccentricity alters the total
• 14:29
  Speaker 3: distribution of solar energy if we call insulation that the
• 14:32
  Speaker 3: Earth receives. When the orbit is highly elliptical, the intensity
• 14:36
  Speaker 3: of sunlight hitting the planet fluctuates significantly depending on where
• 14:39
  Speaker 3: we are in that orbital past.
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  Speaker 1: Okay, got it. Cycle two is obliquity or axial tilt.
• 14:45
  Speaker 1: The Earth spins on a tilted axis, which is what
• 14:48
  Speaker 1: gives us our seasons. Currently, we are tilted at about
• 14:51
  Speaker 1: twenty three point four degrees right but that tilt isn't
• 14:53
  Speaker 1: fixed over a forty one thousand year cycle. It nods
• 14:56
  Speaker 1: back and forth between twenty two point one degrees and
• 14:58
  Speaker 1: twenty four point five degreesrez it does now logically, my
• 15:02
  Speaker 1: instinct is that if the Earth tilts further away from
• 15:04
  Speaker 1: the sun in the winter, you get a much more
• 15:06
  Speaker 1: brutal extreme winter, and that causes an ice age. But
• 15:10
  Speaker 1: the science says the exact opposite, a smaller tilt is
• 15:12
  Speaker 1: actually the trigger. Why let's unpack that counterintuitive logic.
• 15:16
  Speaker 3: It is an incredibly counterintuitive mechanism. I completely agree, but
• 15:19
  Speaker 3: it goes to the very heart of how glaciation begins.
• 15:23
  Speaker 3: You are right that a greater tilt produces more extreme seasons,
• 15:26
  Speaker 3: harsher winters and blistering summers, But an ice age is
• 15:29
  Speaker 3: not triggered by a cold winter. At the extreme northern latitudes,
• 15:32
  Speaker 3: winter is going to be freezing regardless of a one
• 15:35
  Speaker 3: degree shift in tilt. Snow will inevitably fall. The critical
• 15:39
  Speaker 3: climate trigger is actually a cold summer.
• 15:41
  Speaker 1: A cold summer allows the winter snow to survive exactly when.
• 15:45
  Speaker 3: The Earth's axial tilt is smaller closer to that twenty
• 15:48
  Speaker 3: two point one degree mark. The sun just doesn't rise
• 15:51
  Speaker 3: as high in the sky during the summer. At the
• 15:53
  Speaker 3: higher latitudes, the solar radiation strikes the surface at a
• 15:57
  Speaker 3: shallower angle, spreading the energy over a large area, which
• 16:01
  Speaker 3: severely reduces its melting power.
• 16:03
  Speaker 1: So just can't burn off the snow right.
• 16:05
  Speaker 3: The summer has become too mild to fully melt the
• 16:08
  Speaker 3: massive accumulation of snow from the previous winter. Year after
• 16:11
  Speaker 3: year that surviving snow packs down, recrystallizes in defern and
• 16:16
  Speaker 3: eventually compresses into solid glacial ice.
• 16:18
  Speaker 1: That makes perfect thermodynamic sense. It's not about how much
• 16:21
  Speaker 1: snow falls, it's about how much snow survives.
• 16:23
  Speaker 2: The melt season precisely.
• 16:25
  Speaker 1: Okay. The third cycle is axial precession, which operates on
• 16:28
  Speaker 1: roughly a twenty six thousand year cycle. This is the wobble.
• 16:31
  Speaker 3: Think of a spinning top on a table. As it
• 16:34
  Speaker 3: loses momentum, the top of the axis doesn't just point
• 16:37
  Speaker 3: straight up. It slowly traces a circle.
• 16:40
  Speaker 1: In the air, like it's wobbling around.
• 16:42
  Speaker 3: Yeah, the Earth does exactly this. As it rotates, its
• 16:45
  Speaker 3: axis wobbles.
• 16:46
  Speaker 1: But if the axis is just wobbling in place, how
• 16:49
  Speaker 1: does that affect the temperature on the ground.
• 16:51
  Speaker 3: It interacts directly with the elliptical orbit we discussed in
• 16:53
  Speaker 3: the first cycle. Because our orbit isn't perfectly circular. There
• 16:57
  Speaker 3: is a point called perihelium where we are closest to
• 17:00
  Speaker 3: the Sun aphelion where we are furthest Away procession dictates
• 17:05
  Speaker 3: which way the Earth is tilted when we reach those
• 17:07
  Speaker 3: specific points. It determines whether the northern hemisphere is experiencing
• 17:12
  Speaker 3: its summer when the Earth is closest to the Sun
• 17:14
  Speaker 3: or when it's its furthest.
• 17:15
  Speaker 1: Away ah, So it dictates the contrast of the seasons.
• 17:19
  Speaker 2: Exactly.
• 17:19
  Speaker 1: If the northern hemisphere is tilted toward the Sun, having
• 17:22
  Speaker 1: summer at the exact moment the Earth is physically furthest
• 17:25
  Speaker 1: from the Sun and its elliptical orbit, you get a
• 17:28
  Speaker 1: remarkably weak cool.
• 17:29
  Speaker 3: Summer precisely, and this is where the orbital mathematics become destiny.
• 17:34
  Speaker 3: When these three massively long cycles, the one hundred thousand
• 17:38
  Speaker 3: year eccentricity, the forty one thousand year tilt, and the
• 17:41
  Speaker 3: twenty six thousand year wobble, when they all mathematically align
• 17:45
  Speaker 3: to minimize the summer insulation hitting the northern hemisphere, you
• 17:49
  Speaker 3: have the perfect celestial storm for glaciation.
• 17:52
  Speaker 1: But I want to push back on the scale here,
• 17:54
  Speaker 1: because we are talking about microscopic shifts in the angle
• 17:57
  Speaker 1: of sunlight hitting northern Canada. Does a slight dip in
• 18:01
  Speaker 1: summer sunlight translate into two miles of solid ice crushing
• 18:04
  Speaker 1: a continent. Orbital mechanics might set the table, but they
• 18:07
  Speaker 1: don't just conjure billions of tons of ice out of
• 18:10
  Speaker 1: thin air.
• 18:10
  Speaker 3: You are absolutely correct. The Malankovitch cycles are merely the
• 18:13
  Speaker 3: pacing mechanism. They provide the initial nudge. The heavy lifting
• 18:17
  Speaker 3: is done by the planet's own internal feedback loops, specifically
• 18:21
  Speaker 3: the ice albedo effect.
• 18:22
  Speaker 1: Let's get into the thermodynamics of albedo. We generally understand
• 18:26
  Speaker 1: that dark colors absorb heat and light colors reflect it,
• 18:29
  Speaker 1: but how does this operate on a planetary scale.
• 18:31
  Speaker 3: Albedo is simply a measure of the reflectiveness of a surface.
• 18:35
  Speaker 3: The oceans and dense forests they have a very low albedo.
• 18:38
  Speaker 3: They are dark, and they absorb massive amounts of incoming
• 18:41
  Speaker 3: solar radiation, trapping that energy.
• 18:43
  Speaker 1: As heat, like wearing a black shirt on a sunny day.
• 18:47
  Speaker 3: Yes, but snow and ice however, are bright white. They
• 18:50
  Speaker 3: have extremely high albedo. They act as brilliant planetary mirrors,
• 18:54
  Speaker 3: reflecting up to ninety percent of incoming solar radiation straight
• 18:58
  Speaker 3: back out into space before it can be absorbed by
• 19:00
  Speaker 3: the surface.
• 19:01
  Speaker 1: It's like wearing a white T shirt on a hot
• 19:03
  Speaker 1: summer day to stay cool, but scaled up to a
• 19:05
  Speaker 1: planetary level where the shirt just keeps growing until you freeze.
• 19:09
  Speaker 2: That's a perfect analogy.
• 19:10
  Speaker 1: So going back to our mild summer scenario, the orbital
• 19:14
  Speaker 1: mechanics give you a cool summer and a layer of
• 19:16
  Speaker 1: winter snow survives across say northern Canada.
• 19:20
  Speaker 3: Right And once that layer of snow survives, it radically
• 19:23
  Speaker 3: alters the local microclimate. Because it is highly reflective. It
• 19:27
  Speaker 3: bounces the summer sunlight away, actively preventing the ground beneath
• 19:31
  Speaker 3: it from warming up.
• 19:31
  Speaker 1: It's chilling its own bed exactly.
• 19:34
  Speaker 3: Furthermore, as the air directly above the snowpack cools, it
• 19:37
  Speaker 3: becomes dense. This creates a localized high pressure system, basically
• 19:42
  Speaker 3: a dome of heavy cold air that physically pushes away warmer,
• 19:47
  Speaker 3: moist weather systems from the south.
• 19:49
  Speaker 1: It's essentially creating its own atmospheric shield.
• 19:52
  Speaker 3: Yes, and because it has insulated itself even more, snow survives.
• 19:56
  Speaker 3: The following summer, the patch of snow becomes a permanent
• 19:59
  Speaker 3: ice field. The ice field grows into.
• 20:01
  Speaker 1: A glacier, and as it grows, the mirror gets bigger.
• 20:04
  Speaker 3: As the glacier expands outward, the physical size of the
• 20:06
  Speaker 3: planetary mirror increases. It reflects ever larger amounts of solar
• 20:10
  Speaker 3: radiation back to space, which drops the global temperature further,
• 20:14
  Speaker 3: which allows the ice to spread faster. It is a runaway,
• 20:17
  Speaker 3: self reinforcing thermodynamic engine. The ice literally manufactures its own cold.
• 20:22
  Speaker 1: Wow. If we connect this to the bigger picture, it
• 20:25
  Speaker 1: really shows how fragile planetary equilibriums are. I mean, a
• 20:28
  Speaker 1: few degrees of summer cooling in the northern hemisphere can
• 20:30
  Speaker 1: rewrite the climate of the entire globe.
• 20:32
  Speaker 2: It is incredibly sensitive.
• 20:33
  Speaker 1: But wait, if the ice is reflecting all the sunlight
• 20:36
  Speaker 1: and cooling the planet down, why does it ever stop.
• 20:39
  Speaker 1: Why doesn't the Earth just turn into a permanent snowball.
• 20:42
  Speaker 3: That is where atmospheric chemistry steps in. The orbital cycles
• 20:46
  Speaker 3: dictate the rhythm, and the albedo effect provides the physical momentum.
• 20:50
  Speaker 3: But The ultimate volume knob for the planetary climate is
• 20:53
  Speaker 3: atmospheric greenhouse gas, primarily carbon dioxide.
• 20:57
  Speaker 1: Let's look at the historical data for CO two, because
• 21:00
  Speaker 1: this is where the mechanics get incredibly complex. How do
• 21:03
  Speaker 1: we even know what the atmosphere was doing eight hundred
• 21:06
  Speaker 1: thousand years ago during these deep glacial freezes. I mean
• 21:09
  Speaker 1: we didn't have weather stations.
• 21:10
  Speaker 2: No, we didn't.
• 21:11
  Speaker 3: We rely on direct atmospheric proxy data extracted from ice cores,
• 21:16
  Speaker 3: primarily from the Vostok Research Station in Antarctica and the
• 21:19
  Speaker 3: Epicidome Sea project.
• 21:20
  Speaker 1: How does that work?
• 21:21
  Speaker 3: When snowfalls in the extreme cold of Antarctica, it doesn't melt,
• 21:25
  Speaker 3: It piles up and slowly compresses into ice. As it compresses,
• 21:29
  Speaker 3: it traps microscopic pockets of the ambient air between the snowflakes.
• 21:32
  Speaker 1: So there are literal time capsules of the ancient atmosphere exactly.
• 21:36
  Speaker 3: Scientists drill down and extract continuous cylinders of ice that
• 21:40
  Speaker 3: are over three thousand meters long. That represents hundreds of
• 21:45
  Speaker 3: thousands of years of accumulation. Back in the laboratory, they
• 21:48
  Speaker 3: place sections of this ancient ice into vacuum chambers, crush
• 21:51
  Speaker 3: it and release the trapped air bubbles that is so cool,
• 21:54
  Speaker 3: and by running that ancient air through mass spectrometers, they
• 21:57
  Speaker 3: can directly measure the exact concentration of carbon dioxide and
• 22:01
  Speaker 3: methane that was present in the atmosphere during any given millennia.
• 22:04
  Speaker 1: What do those mass spectrometer readings tell us about the
• 22:07
  Speaker 1: relationship between CO two and the massive glaciers.
• 22:11
  Speaker 3: The correlation is absolute. During the deep glacial periods, when
• 22:14
  Speaker 3: the ice sheets are two miles thick. Over North America
• 22:17
  Speaker 3: atmosphere carbon dioxide levels naturally plummet to incredibly low baseline levels.
• 22:22
  Speaker 3: They typically hover around one hundred and eighty parts per million.
• 22:25
  Speaker 1: But where does the carbon go? It doesn't just vanish
• 22:28
  Speaker 1: from the Earth if it's not in the atmosphere acting
• 22:30
  Speaker 1: as a greenhouse blanket. Where is the planet hiding it?
• 22:33
  Speaker 3: It is sequestered in the oceans. It's driven by a
• 22:35
  Speaker 3: mechanism known as the biological pump.
• 22:37
  Speaker 1: Okay, biological pump. How does that work?
• 22:39
  Speaker 3: It's the planet cools due to the orbital shifts in
• 22:41
  Speaker 3: the albedo effect. The ocean's also cool, cold water is
• 22:46
  Speaker 3: physically capable of dissolving and holding significantly more carbon dioxide
• 22:50
  Speaker 3: than warm water, but the biology of the ocean plays
• 22:52
  Speaker 3: an even larger role.
• 22:53
  Speaker 1: Biology like fish, more.
• 22:56
  Speaker 3: Like microscopic plants. During an ice age, a massive amount
• 22:59
  Speaker 3: of water locked up in glaciers, which means global sea
• 23:03
  Speaker 3: levels drop and the climate becomes drastically drier. Deserts expand.
• 23:08
  Speaker 3: Powerful glacial winds pick up massive amounts of iron rich
• 23:10
  Speaker 3: dust from these expanding deserts and blow it out over
• 23:13
  Speaker 3: the open ocean.
• 23:14
  Speaker 1: Iron fertilization.
• 23:15
  Speaker 3: Precisely that iron dust acts as a critical fertilizer for
• 23:19
  Speaker 3: microscopic marine plants called phytoplankton. The influx of iron triggers
• 23:23
  Speaker 3: massive phytoplankton blooms across the oceans. These organisms photosynthesize, sucking
• 23:28
  Speaker 3: colossal amounts of carbon dioxide directly out of the atmosphere,
• 23:31
  Speaker 3: and then what when they die, They sink to the
• 23:33
  Speaker 3: abyssle depths of the ocean floor, locking that carbon away
• 23:36
  Speaker 3: in the deep sea.
• 23:37
  Speaker 1: From millennia, you know, the late oceanographer John Martin famously said,
• 23:41
  Speaker 1: give me half a tanker of iron, and I will
• 23:43
  Speaker 1: give you an ice age. It's incredible to think that
• 23:46
  Speaker 1: dust blowing off a dry continent can fertilize the ocean
• 23:50
  Speaker 1: so intensely that it physically strips the greenhouse blanket off
• 23:53
  Speaker 1: the planet, allowing the glaciers to surge forward.
• 23:56
  Speaker 3: It's a beautifully intricate system. And conversely, when the orbital
• 24:00
  Speaker 3: cycles slowly shift back, allowing more intense summer sunlight to
• 24:03
  Speaker 3: hit the ice sheets, the ice begins to.
• 24:05
  Speaker 1: Melt and the cycle reverses.
• 24:07
  Speaker 3: Yes, fresh water floods the oceans, changing the circulation. The
• 24:12
  Speaker 3: deep oceans eventually begin to warm and release their stored
• 24:14
  Speaker 3: CO two back into the atmosphere. This rising greenhouse gas
• 24:18
  Speaker 3: amplifies the warming, melting the ice faster and driving the
• 24:21
  Speaker 3: planet rapidly back into an interglacial hothouse.
• 24:24
  Speaker 1: So for millions of years, the Earth has been locked
• 24:27
  Speaker 1: in this elegant, if brutal dance. The orbital wobble cools
• 24:31
  Speaker 1: the summers, the snow reflects the light, The dusty ocean
• 24:33
  Speaker 1: sucked down the CO two, The ice advances, Then the
• 24:36
  Speaker 1: orbit shifts, the oceans warm, the CO two is exhaled,
• 24:39
  Speaker 1: and the ice retreats.
• 24:40
  Speaker 2: That is the natural cycle, yees.
• 24:42
  Speaker 1: But that brings us crashing into the present day because
• 24:45
  Speaker 1: we have fundamentally tampered with one of those core mechanisms.
• 24:48
  Speaker 3: We have profoundly altered the atmosphere chemistry. For the last
• 24:52
  Speaker 3: eight hundred thousand years, atmospheric CO two fluctuated between one
• 24:56
  Speaker 3: hundred and eighty parts per million during deep freezes and
• 24:59
  Speaker 3: about two hundred eighty parts per million during warm interglacials. Today,
• 25:04
  Speaker 3: primarily due to the combustion of fossil fuels, atmospheric CO
• 25:07
  Speaker 3: two has exceeded four hundred and twenty parts per million.
• 25:10
  Speaker 1: So what does this all mean for us?
• 25:12
  Speaker 2: Right now?
• 25:12
  Speaker 1: Are we effectively breaking a multimillion year old cycle? I mean,
• 25:17
  Speaker 1: if the celestial clock is ticking toward a freeze, but
• 25:19
  Speaker 1: the atmosphere is wrapped in an unnaturally thick carbon blanket,
• 25:23
  Speaker 1: which force wins.
• 25:24
  Speaker 3: This is one of the most intense areas of debate
• 25:26
  Speaker 3: in kaleoclimatology right now. When you run the current orbital
• 25:29
  Speaker 3: parameters through complex Earth system models like the climber two
• 25:33
  Speaker 3: model used by researchers at the Postdam Institute, the data
• 25:36
  Speaker 3: suggests a fascinating irony. Okay, without anthropogenic green half gas emissions,
• 25:41
  Speaker 3: the natural orbital configuration suggests Earth should have already been
• 25:44
  Speaker 3: on a slow downward slope toward the next glaciation.
• 25:47
  Speaker 1: Wait, let me make sure I am understanding this. If
• 25:50
  Speaker 1: the Industrial Revolution never happened, if we never pumped giga
• 25:54
  Speaker 1: tons of carbon into the sky, humanity would currently be
• 25:57
  Speaker 1: facing the onset of a new ica.
• 26:00
  Speaker 3: Yes, this raises an important question about cause and effect.
• 26:04
  Speaker 3: The slow, inexorable march of the glaciers would likely have
• 26:07
  Speaker 3: begun the orbital alignment was favoring a cooling trend. However,
• 26:12
  Speaker 3: the sheer volume of heat trapped by four hundred and
• 26:14
  Speaker 3: twenty parts per million of CO two is actively overpowering
• 26:17
  Speaker 3: the orbital mechanics.
• 26:19
  Speaker 1: It sounds almost like a sci fi plot. Did humanity
• 26:21
  Speaker 1: accidentally engineer a shield against a natural ice age by
• 26:24
  Speaker 1: causing global warming? I mean, how do scientists even balance
• 26:27
  Speaker 1: the immediate risks of warming against the distant risks of freezing.
• 26:31
  Speaker 3: You have to separate the intent from the mechanics and
• 26:33
  Speaker 3: look closely at the timescales. We did not carefully engineer
• 26:36
  Speaker 3: a planetary thermostat to stave off glaciation. We recklessly dumped
• 26:40
  Speaker 3: carbon into the atmosphere, triggering a completely different crisis. A
• 26:44
  Speaker 3: natural transition into a glacial period takes tens of thousands
• 26:48
  Speaker 3: of years. It's a creeping, multigenerational challenge. Anthropogenic global warming
• 26:53
  Speaker 3: is happening on a scale of decades. We have traded
• 26:56
  Speaker 3: a distant, slow moving geological hazard for an immediate, hyper
• 27:01
  Speaker 3: accelerated climate shock.
• 27:02
  Speaker 1: But regarding the glaciers, what do the models say about
• 27:05
  Speaker 1: the delay? How long does that four hundred and twenty
• 27:07
  Speaker 1: ppm carbon blanket hold the iceback?
• 27:10
  Speaker 3: Some models suggest the onset of the next major glaciation
• 27:13
  Speaker 3: has been delayed by fifty thousand years. Other more aggressive
• 27:16
  Speaker 3: models suggest that because co two lingers in the atmosphere
• 27:20
  Speaker 3: for such an incredibly long time, the next glaciation might
• 27:22
  Speaker 3: be delayed by one hundred thousand years or more. We
• 27:25
  Speaker 3: have essentially skipped an entire beat of the Malankovitch cycle.
• 27:28
  Speaker 1: Wow, so we don't have to worry about two miles
• 27:30
  Speaker 1: of ice over Chicago anytime soon. The primary overarching threat
• 27:33
  Speaker 1: is global warming. But does a warming globe mean a
• 27:36
  Speaker 1: uniform warming experience for everyone or could we still see isolated,
• 27:40
  Speaker 1: severe regional freezes while the rest of the planet bakes.
• 27:43
  Speaker 3: That is a critical distinction, and it highlights why global
• 27:46
  Speaker 3: warming can be a slightly deceptive term. The global average
• 27:49
  Speaker 3: temperature is rising, but that rising heat aggressively disrupts oceanic
• 27:54
  Speaker 3: and atmospheric circulation.
• 27:55
  Speaker 1: Patterns, which can cause regional chaos.
• 27:58
  Speaker 3: Precisely, a disrupted the climate system can trigger sudden, severe,
• 28:02
  Speaker 3: localized cooling events. The prime suspect for this kind of
• 28:05
  Speaker 3: wild card scenario is the.
• 28:07
  Speaker 1: AMOC, the Atlantic Meridional Overturning circulation. Most people just refer
• 28:13
  Speaker 1: to it as the Gulf Stream, though the Gulf Stream
• 28:15
  Speaker 1: is technically just one surface component of it, right correct.
• 28:18
  Speaker 3: The AMOC is a massive, incredibly powerful system of ocean
• 28:23
  Speaker 3: currents that operates like a global conveyor belt. It's driven
• 28:26
  Speaker 3: by differences in temperature and salinity, what we call thermohaline circulation.
• 28:31
  Speaker 1: Explain the physics of that engine. How does salt drive
• 28:33
  Speaker 1: an ocean current?
• 28:35
  Speaker 3: It starts in the tropics. The equatorial sun beats down
• 28:37
  Speaker 3: on the ocean, heating the water and causing massive evaporation.
• 28:41
  Speaker 3: When the water evaporates, it leaves the salt behind, making
• 28:43
  Speaker 3: the surface water incredibly salty and dense.
• 28:46
  Speaker 1: Okay, so it gets heavy.
• 28:47
  Speaker 3: Yes, This warm salty water is pulled northward by wind
• 28:51
  Speaker 3: currents traveling up the eastern coast of North America and
• 28:55
  Speaker 3: across the Atlantic toward northwestern Europe, and.
• 28:57
  Speaker 1: As it travels north it carries massive amounts of tropical
• 29:00
  Speaker 1: heat with it, like a radiator.
• 29:02
  Speaker 3: Fluid colossal amounts of heat. It is the primary reason
• 29:05
  Speaker 3: why cities like London and Paris, which share a latitude
• 29:08
  Speaker 3: with frigid regions in Canada, have relatively mild winters. The
• 29:12
  Speaker 3: ocean is literally venting tropical heat into the European atmosphere,
• 29:16
  Speaker 3: but as the water reaches the North Atlantic near Greenland
• 29:19
  Speaker 3: and Iceland, it begins to cool down rapidly in the Arctic.
• 29:22
  Speaker 1: Air, and cold water is denser than warm water.
• 29:25
  Speaker 3: Exactly, you now have water that is both very cold
• 29:28
  Speaker 3: and very salty, making it extremely dense and heavy. Because
• 29:32
  Speaker 3: it is so heavy, millions of cubic meters of this
• 29:35
  Speaker 3: water physically sinc to the abyssle depths of the ocean.
• 29:38
  Speaker 1: It just drops.
• 29:38
  Speaker 2: Yes.
• 29:39
  Speaker 3: This mechanism is called North Atlantic deep water formation. As
• 29:43
  Speaker 3: this massive volume of water sinks, it creates a void
• 29:47
  Speaker 3: at the surface which physically pulls more warm, salty water
• 29:51
  Speaker 3: up from the tropics to replace it. The sinking is
• 29:54
  Speaker 3: the engine that drives the entire global conveyor belt.
• 29:57
  Speaker 1: It's like the heating vents in a house, If the
• 30:00
  Speaker 1: duct to one specific room gets blocked, that room freezes,
• 30:03
  Speaker 1: even if the furnace in the basement is running hotter
• 30:05
  Speaker 1: than ever.
• 30:05
  Speaker 2: That's a very aft way to look at it.
• 30:07
  Speaker 1: So what happens when the globe warms up and the
• 30:09
  Speaker 1: massive ice sheet covering Greenlands starts melting rapidly?
• 30:12
  Speaker 3: Glacial meltwater is entirely fresh water with zero salt content.
• 30:16
  Speaker 3: Fresh water is significantly lighter and less dense than salty
• 30:19
  Speaker 3: ocean water. As hundreds of billions of tons of fresh
• 30:23
  Speaker 3: glacial meltwater pour into the North Atlantic, it dilutes the
• 30:26
  Speaker 3: surface salinity.
• 30:27
  Speaker 1: The water isn't salty enough to sink anymore.
• 30:29
  Speaker 3: Pre Silightly, the water becomes too buoyant, it stops sinking
• 30:32
  Speaker 3: to the abyss, and if the sinking stops, the pump breaks,
• 30:36
  Speaker 3: the northward pull of the Gulf stream stalls.
• 30:38
  Speaker 1: What are the models showing right now is is a
• 30:40
  Speaker 1: theoretical worry or are we see active disruption? Because if
• 30:45
  Speaker 1: you shut off the heat vent to Europe the consequences
• 30:48
  Speaker 1: are immediate.
• 30:49
  Speaker 3: Supercomputer models are highly focused on this.
• 30:52
  Speaker 2: Right now.
• 30:52
  Speaker 3: We are observing early warning signals, statistical losses of resilience
• 30:56
  Speaker 3: in the current that suggest the AMOC is weakening and
• 31:00
  Speaker 3: could potentially reach a tipping point where it collapses entirely.
• 31:03
  Speaker 3: And if it collapses, if the AMC shuts down, the
• 31:06
  Speaker 3: transport of equatorial heat stalls. Consequently, parts of northwestern Europe
• 31:11
  Speaker 3: could plunge into severe localized cooling, dropping by several degrees
• 31:15
  Speaker 3: celsius in a matter of decades, drastically altering their agricultural capacity,
• 31:20
  Speaker 3: even as the global average temperature continues to rise.
• 31:23
  Speaker 1: That perfectly illustrates how chaotic the system is. You could
• 31:26
  Speaker 1: have London freezing while the equator burns. But we've talked
• 31:29
  Speaker 1: about orbital mechanics and ocean currents, which are planetary systems.
• 31:32
  Speaker 1: What about subter abrupt climate forcings from outside the system.
• 31:35
  Speaker 1: Volcanoes and asteroids.
• 31:37
  Speaker 3: Both can induce sudden, dramatic cooling, but the mechanics and
• 31:41
  Speaker 3: the duration are completely different from a cyclical ice age.
• 31:45
  Speaker 3: When a massive stratovolcano erupts, it injects millions of tons
• 31:49
  Speaker 3: of sulfur rich aerosols high into the stratosphere, far above
• 31:53
  Speaker 3: the weather systems where rain could wash.
• 31:55
  Speaker 1: Them out, and those aerosols act like a chemical mirror exactly.
• 31:59
  Speaker 3: They form a hazy shite yield that reflects incoming sunlight
• 32:01
  Speaker 3: away from the Earth. The eruption of Mount Pinatubo in
• 32:05
  Speaker 3: the Philippines in nineteen ninety one is a perfectly documented example.
• 32:09
  Speaker 3: It threw twenty million tons of sulfur dioxide into the stratosphere. Wow,
• 32:13
  Speaker 3: that single eruption reflected enough sunlight to drop the average
• 32:16
  Speaker 3: global temperature by roughly zero point five degrees celsius for
• 32:20
  Speaker 3: about two years.
• 32:21
  Speaker 1: Half a degree globally is massive. But that shill only
• 32:23
  Speaker 1: lasted for a couple of years. The aerosols eventually disperse
• 32:26
  Speaker 1: and settle out of the atmosphere. Volcano is going to
• 32:29
  Speaker 1: trigger one hundred thousand.
• 32:30
  Speaker 3: Year deep freeze, right, It's temporary.
• 32:32
  Speaker 1: But what if the particulate matter blocking the sun isn't
• 32:35
  Speaker 1: sulfur from a volcano, but millions of tons of vaporized
• 32:39
  Speaker 1: rock and sit from an asteroid impact.
• 32:41
  Speaker 3: An asteroid impact of sufficient scale, such as the Chisaluv
• 32:44
  Speaker 3: impact sixty six million years ago, operates on an apocalyptic scale.
• 32:49
  Speaker 3: The kinetic energy of the impact vaporizes the crust, throwing
• 32:53
  Speaker 3: colossal amounts of dust, soot from global wildfires and sulfur
• 32:57
  Speaker 3: into the upper atmosphere. The sunlight wouldn't just be slightly dimmed,
• 33:00
  Speaker 3: it would be catastrophically blocked.
• 33:02
  Speaker 1: Out for years the ultimate impact winter.
• 33:04
  Speaker 3: Yes, in an impact winter, the sudden total lack of
• 33:08
  Speaker 3: sunlight causes photosynthesis to collapse almost globally. The foundational level
• 33:13
  Speaker 3: of the food chain dies off, and marine interrestrial ecosystems
• 33:16
  Speaker 3: experience mass extinction.
• 33:18
  Speaker 1: But again, this is a sudden, violently acute trauma to
• 33:21
  Speaker 1: the system.
• 33:21
  Speaker 3: Exactly, the temperatures drop precipitously, but once the atmosphere eventually clears,
• 33:25
  Speaker 3: the orbital mechanics in greenhouse gases reassert control. It is
• 33:29
  Speaker 3: fundamentally different from the slow, agonizing, permanent baseline shift of
• 33:33
  Speaker 3: a Milankovitch cycle glaciation.
• 33:35
  Speaker 1: Let's pull all of this together and look at the
• 33:38
  Speaker 1: human element, whether it happens thousands of years from now
• 33:41
  Speaker 1: due to the slow grind of the orbital wobble, or
• 33:44
  Speaker 1: whether we trigger a localized freeze by breaking the amoc
• 33:48
  Speaker 1: ocean currents. I want to game out the scenario what
• 33:52
  Speaker 1: actually happens to a modernized, highly populated global civilization if
• 33:56
  Speaker 1: the ice returns. Let's talk about surviving the un thing.
• 34:00
  Speaker 3: If a major glaciation eventually returned, the socioeconomic and geopolitical
• 34:06
  Speaker 3: consequences for modern civilization would be profound, cascading, and largely
• 34:10
  Speaker 3: insurmountable without massive loss of life and a total restructuring
• 34:14
  Speaker 3: of human society.
• 34:15
  Speaker 1: It's that bad.
• 34:16
  Speaker 3: The very first pillar to fall would be the global
• 34:19
  Speaker 3: food supply.
• 34:20
  Speaker 1: Because our agricultural zones are rigidly defined by the Holocene climate.
• 34:23
  Speaker 3: Exactly, modern agriculture is a highly optimized, fragile system. Take
• 34:27
  Speaker 3: the North American wheat belt stretching for the US Midwest
• 34:30
  Speaker 3: up into the Canadian prairies. Under glacial advance, that entire
• 34:34
  Speaker 3: region wouldn't just experience shorter growing seasons, it would eventually
• 34:37
  Speaker 3: be buried under miles of ice, or at best transformed
• 34:40
  Speaker 3: into barren frozen permafrost.
• 34:42
  Speaker 1: And the same goes for other bread baskets.
• 34:44
  Speaker 3: The same applies to the agricultural heartlands of Northern Europe, Russia,
• 34:48
  Speaker 3: and northern China.
• 34:49
  Speaker 1: So you are instantly wiping out the regions that produce
• 34:51
  Speaker 1: the vast majority of the world's caloric intake. You have
• 34:54
  Speaker 1: billions of people living in areas that are suddenly incapable
• 34:57
  Speaker 1: of producing food and physically uninhabitable due to the cold.
• 35:01
  Speaker 1: The immediate result has to be mass migration.
• 35:04
  Speaker 3: Mass migration on a scale that defies current logistical modeling.
• 35:09
  Speaker 3: As the ice sheets expand southward and the permafrost line deacons,
• 35:13
  Speaker 3: massive populations would be forced to evacuate toward the warmer
• 35:17
  Speaker 3: increasingly crowded latitudes near the equator.
• 35:19
  Speaker 1: And the equator doesn't have an infinite carrying capacity.
• 35:22
  Speaker 3: Precisely, you would be attempting to compress the population of
• 35:25
  Speaker 3: the northern hemisphere into a drastically shrinking livable zone. The
• 35:30
  Speaker 3: geopolitical choke points would become zones of intense conflict. Imagine
• 35:35
  Speaker 3: hundreds of millions of people attempting to cross the Mediterranean
• 35:38
  Speaker 3: or migrating down through the Darien Gap in Central America.
• 35:41
  Speaker 1: The equatorial regions would just become hyper dense megacities, straining
• 35:44
  Speaker 1: local water and soil resources beyond their breaking points. Absolutely,
• 35:48
  Speaker 1: and it's not just a matter of people walking south.
• 35:51
  Speaker 1: Think about the infrastructure we struggle with supply chain logistics.
• 35:54
  Speaker 1: When a major city gets three days of heavy snow
• 35:57
  Speaker 1: in the highway freezes, the grocery store shelves go empty
• 36:00
  Speaker 1: in forty eight hours. Imagine trying to relocate the industrial base,
• 36:05
  Speaker 1: the energy grids, and the agricultural output of the entire
• 36:08
  Speaker 1: northern hemisphere. Can technology actually out engineer two miles of ice?
• 36:13
  Speaker 3: The energy demands alone would be staggering. Every city that
• 36:16
  Speaker 3: wasn't immediately crushed by the advancing ice would face a
• 36:19
  Speaker 3: drastically colder reality. The global demand for heating was a skyrocket, right,
• 36:24
  Speaker 3: and because solar radiation would be heavily impacted by the
• 36:27
  Speaker 3: changing albedo and shifting cloud cover, and hydro electric dams
• 36:31
  Speaker 3: in the north would freeze solid, the strain on whatever
• 36:33
  Speaker 3: nuclear or fossil fuel power grids remained operational would be catastrophic.
• 36:38
  Speaker 1: I sometimes hear the argument that we would just out
• 36:40
  Speaker 1: engineer it. Our ancestors survive the last ice age with
• 36:43
  Speaker 1: animal skins and fire. We have nuclear power, advanced material science,
• 36:47
  Speaker 1: and indoor hydroponic agriculture. Couldn't we just build massive, heated
• 36:51
  Speaker 1: and closed cities and write it out.
• 36:53
  Speaker 3: It is an appealing techno optimist vision, but it ignores
• 36:56
  Speaker 3: the fundamental constraints of resources and social stability. We certainly
• 37:01
  Speaker 3: have the technical knowledge to build a sealed, nuclear powered biosphere,
• 37:05
  Speaker 3: but building one that can sustain billions of people requires
• 37:09
  Speaker 3: unbroken global supply chains, massive resource extraction, and unprecedented geopolitical cooperation,
• 37:15
  Speaker 3: which you wouldn't have Right in a scenario where nations
• 37:18
  Speaker 3: are abandoning their sovereign territory to the ice and fighting
• 37:21
  Speaker 3: for scraps of arable land at the equator, the global
• 37:24
  Speaker 3: economic system that enables high tech engineering would almost certainly collapse.
• 37:29
  Speaker 3: Technology requires stability. A glaciation event is the ultimate destabilizer.
• 37:34
  Speaker 1: So where does this leave us We set out to
• 37:36
  Speaker 1: dismantle the illusion of a permanently stable Earth, and looking
• 37:39
  Speaker 1: at the mechanics of the orbital wobbles, the albedo feedback loops,
• 37:42
  Speaker 1: and the fragile oceanic pumps, I think it's impossible to
• 37:45
  Speaker 1: look at the ground the same way again.
• 37:47
  Speaker 3: The history of Earth teaches a remarkably humbling lesson in impermanence.
• 37:52
  Speaker 3: No single environmental state lasts forever. The coastlines we have
• 37:56
  Speaker 3: meticulously mapped and built upon will inevitably move, the temperate
• 38:01
  Speaker 3: forest will eventually vanish, and the ice will eventually advance,
• 38:04
  Speaker 3: just as surely as it will one day retreat again.
• 38:07
  Speaker 1: The Earth is just a restless, dynamic engine.
• 38:09
  Speaker 3: Yes, and human civilization is just a temporary passenger operating
• 38:14
  Speaker 3: in a brief, remarkably calm window of weather. The goal
• 38:17
  Speaker 3: isn't just to predict the next shift, but to build
• 38:20
  Speaker 3: a civilization capable of adapting to a planet that is
• 38:23
  Speaker 3: perpetually in motion.
• 38:24
  Speaker 1: But because we have intervened, the immediate future is dictated
• 38:27
  Speaker 1: by heat, not ice.
• 38:29
  Speaker 2: Exactly.
• 38:30
  Speaker 3: Understanding these incredibly deep, long term natural cycles doesn't diminish
• 38:34
  Speaker 3: the threat of current anthropogenic warming. It actually highlights how
• 38:37
  Speaker 3: aggressively we have perturbed the system. It allows scientists to
• 38:41
  Speaker 3: distinguish between long term background rhythms and the violent short
• 38:44
  Speaker 3: term variability we are actively causing today.
• 38:47
  Speaker 1: Which brings me to a final thought, something to really
• 38:49
  Speaker 1: chew on as we look toward deep time. We've learned
• 38:52
  Speaker 1: today that human emissions have likely and entirely accidentally delayed
• 38:56
  Speaker 1: the next ice age by tens of thousands of years.
• 39:00
  Speaker 1: But think about the incredibly distant future. If we eventually
• 39:03
  Speaker 1: master our carbon output and stabilize the atmosphere, what happens
• 39:07
  Speaker 1: when the Melankovitch cycles eventually demand freeze? Will our distant
• 39:11
  Speaker 1: descendants one day use artificial greenhouse gases intentionally to fight
• 39:15
  Speaker 1: off the orbital shifts and keep the ice at bay.
• 39:18
  Speaker 1: Are we destined to become the permanent, conscious thermostat of
• 39:21
  Speaker 1: the Earth. Something to think about the next time you
• 39:23
  Speaker 1: look up at the night sky and realize the planet
• 39:25
  Speaker 1: is constantly in motion. Keep wondering and we'll catch you
• 39:28
  Speaker 1: next time.