Latest / Talking Science / Climate Change – The Physics Behind It

Transcript

Climate Change – The Physics Behind It · Talking Science

0:00
You know, it's wild to think about, but 10 ,000
0:02
years of human civilization, agriculture, modern
0:07
infrastructure, all of it exists in this highly
0:10
delicate temperature window. Oh, absolutely.
0:12
It's an incredibly narrow band. Right. And the
0:14
difference between this comfortable, familiar
0:16
world we live in right now and a world where
0:18
cities like New York are buried under, I mean,
0:20
a full kilometer of solid ice, it's just five
0:24
degrees. Yeah, just five degrees globally. That
0:27
is the... The razor -thin thermal margin separating
0:31
the world we know today from the depths of a
0:34
deep ice age. It really puts the scale of our
0:36
planet into perspective immediately. And it makes
0:39
me think about the simple analogy from the material
0:41
we're looking at today. When you put a kettle
0:44
on a stove and turn on the burner, you don't
0:46
stand there debating whether the water is going
0:48
to get hot. No, of course not. You don't argue
0:50
about the kettle's political affiliation or its
0:52
ulterior motives. You just accept that heat is
0:55
being applied and the water is going to boil.
0:57
Exactly. Because the laws of thermodynamics,
0:59
they operate completely independently of our
1:01
opinions. Heat moves, energy balances, and physical
1:05
systems respond, regardless of how any of us
1:08
feel about it. Which brings us to our mission
1:10
for this deep dive. Today, we are taking a phrase
1:13
that is arguably the most politically loaded,
1:16
emotionally charged phrase of our time climate
1:19
change. And we are looking at today's source
1:21
material to completely strip all that politics
1:24
away. Right. Taking a totally impartial look
1:26
at the text. We're going to dive into the underlying
1:28
19th century physics of the whole thing. The
1:32
author describes this underlying science as being,
1:34
quote, settled, unglamorous and about as controversial
1:37
as the boiling point of water. I love that phrasing.
1:41
We will be exploring the pure mechanics of our
1:43
planet. We'll look at how the Earth stays warm,
1:45
what alters that delicate energy balance, and
1:48
crucially, exactly how scientists actually know
1:51
what they claim to know based on the source.
1:53
And if you are listening to this right now, you
1:55
don't need a background in science to follow
1:57
along. We are just going to trace the logic step
1:59
by step. Yeah, assume absolutely no prior science
2:02
background. We're breaking it all down. So I
2:04
invite you to just relax, put aside the shouting
2:07
matches you might see on the evening news, and
2:10
just follow this trail of basic physics and forensic
2:14
chemistry with us. Let's start with a foundational
2:17
premise from the text. Why is the Earth the temperature
2:21
it is in the first place? Well, it all comes
2:23
down to a cosmic energy budget. A balance sheet,
2:27
essentially. The sun pours massive amounts of
2:30
energy onto our planet every single day. Right,
2:32
a constant stream of energy. Yeah, and because
2:35
the sun is burning at such an incredibly high
2:37
temperature, that energy arrives across the vacuum
2:39
of space primarily as short wavelength visible
2:42
light. Okay, so the Earth absorbs that incoming
2:44
energy and as a result it warms up. But the Earth
2:47
isn't just a sponge, right? It's also a radiator.
2:50
Exactly. It has to send energy back out into
2:52
cold space. If it didn't, it would just get hotter
2:54
and hotter until... it literally vaporized which
2:57
would be bad very bad but because the earth is
2:59
much much cooler than the sun it radiates that
3:02
energy in a totally different form it sends it
3:04
back out as infrared radiation Let's define that
3:07
real quick, just to be sure we're all on the
3:08
same page. Infrared is just invisible, longer
3:11
wavelength light, right? Yeah, exactly. You can't
3:14
see it, but you can physically feel it as heat.
3:17
Like, think about standing near a dark asphalt
3:20
road at dusk on a summer evening. That heat radiating
3:24
off the pavement, that's infrared. Oh, that's
3:27
a perfect example. So for the planet's overall
3:29
temperature to hold steady over thousands of
3:32
years, the energy coming in is visible sunlight.
3:35
has to perfectly match the energy going out as
3:38
infrared heat. OK, let's unpack this, because
3:40
this is where the atmosphere comes into play.
3:42
And it acts like a very specific kind of filter,
3:45
doesn't it? It does. See, the atmosphere is completely
3:47
transparent to incoming sunlight. The visible
3:50
light sails right through the air and hits the
3:51
ground. But when that infrared heat tries to
3:54
leave, the atmosphere suddenly isn't transparent
3:57
anymore. Right. Certain gases in our air are
3:59
invisible to the short wavelength visible light
4:02
coming in, but they act like a brick wall to
4:04
the long wavelength infrared radiation trying
4:06
to get out. They catch it. Yeah, they absorb
4:08
that outgoing heat and re -emit it in all directions,
4:11
bouncing a huge portion of it right back down
4:14
toward the Earth's surface. I pictured this while
4:16
reading the notes, and I think it helps. Imagine
4:19
throwing a tiny, hard golf ball at a chain -link
4:22
fence. That golf ball is the incoming visible
4:25
sunlight. It passes right through the holes in
4:28
the fence and hits the ground. Makes sense. But
4:31
when the Earth tries to throw the energy back
4:33
into space, the energy is transformed. It's no
4:36
longer a tiny golf ball. It's a giant inflated
4:40
beach ball. I like this. When you throw that
4:42
giant beach ball at the exact same chain link
4:45
fence, it gets intercepted. It bounces off the
4:48
metal links and it comes right back at you. That
4:50
is a great visual. And that intercepted heat,
4:52
the bouncing back of the beach ball. That is
4:55
the greenhouse effect. Which the source points
4:57
out is actually a good thing. Oh, it's a critical
4:59
thing. It often gets lost in the noise. But the
5:01
greenhouse effect is a fundamental necessity
5:03
for life. Without that chain link fence intercepting
5:07
the heat, the Earth's average temperature would
5:09
be roughly minus 18 degrees Celsius. Wow. Minus
5:13
18. Yeah, we would be living on a frozen, totally
5:15
uninhabitable ball of ice. The planet actually
5:18
has to warm up more than it otherwise would just
5:20
to build up enough infrared pressure for enough
5:23
of it to finally escape into space and balance
5:26
the books. So the existence of the greenhouse
5:28
effect is what keeps us alive. The problem isn't
5:31
the blanket itself. The problem is that we are
5:33
adding more metal to the chain link fence, basically
5:36
making the hole smaller and smaller. Exactly.
5:39
We're turning the dial up, which forces us to
5:41
look really closely at the specific gases in
5:44
the atmosphere that are doing this trapping.
5:46
And this was a surprising fact from the source
5:48
for me. Our atmosphere is overwhelmingly made
5:51
of just two gases, right? Right. Roughly 78 %
5:53
nitrogen and 21 % oxygen. Together, that's 99
5:57
% of the air we breathe. And neither of those
6:00
absorbs infrared heat at all. Not even a little
6:02
bit. The visible light sails past them, and the
6:05
infrared heat sails past them, too. So the only
6:07
gases that matter for this whole energy budget
6:10
are the quote -unquote trace? Gases? Yeah, things
6:13
like water vapor, carbon dioxide, methane, and
6:16
nitrous oxide. But I got hung up on a statistic
6:18
here. The source says carbon dioxide makes up
6:21
only about 400 parts per million of the atmosphere.
6:24
That's right. That is 0 .04%, just a tiny fraction.
6:29
My first thought was, how can something that
6:31
small actually do anything? How can a fraction
6:34
of a fraction of a percent of a gas control an
6:36
entire planetary system? It's a super common
6:39
question, and it comes down to molecular structure
6:42
and resonance. Molecules of nitrogen and oxygen
6:46
are simple, tightly bound pairs of atoms. They
6:49
just don't react to infrared waves. But the trace
6:51
gases are different. Very different. Molecules
6:54
of trace gases, like carbon dioxide, are physically
6:57
built in a way that allows them to flex, bend,
7:00
and vibrate at the exact frequencies of infrared
7:02
light. So they're like tuned to it. Exactly.
7:05
When that specific wavelength of heat hits them,
7:07
it's like hitting a tuning fork with a perfect
7:09
pitch. They soak up the energy. The text uses
7:11
a really great visual for this scale, too. Think
7:13
of a large glass of completely clear water. The
7:18
water represents the nitrogen and oxygen. If
7:20
you drop just two or three tiny drops of dark
7:23
concentrated ink, which represents the carbon
7:26
dioxide, into that glass, the whole volume turns
7:29
cloudy and dark almost instantly. Right. A tiny
7:31
concentration of a strong absorber has a massive
7:34
outsized effect on the whole system. So it's
7:37
about the potency of the gas, not just the volume.
7:39
Exactly. And to ground this in history, this
7:42
is some new computer modeling discovery. The
7:44
underlying physics of how carbon dioxide absorbs
7:46
infrared light was actually married with physical
7:49
laboratory equipment in the 1850s and 1860s.
7:52
Wait, really? That long ago? Yeah. Scientists
7:55
literally passed light through tubes of gas and
7:57
measured the heat difference. And the foundational
8:00
hand calculations for exactly how much the Earth
8:02
would warm if you doubled the carbon dioxide
8:04
in the air. Those were published in 1896. That
8:07
is wild. It's incredibly old, deeply solid science.
8:10
So the physics is over a century old. We know
8:13
adding these specific gases thickens the blanket.
8:16
If the math says more trace gases equal a hotter
8:19
planet, the next logical question we have to
8:22
figure out is whether we're actually adding more
8:24
of them to the sky. And we have incredibly direct
8:26
evidence for that. The text points to an observatory
8:29
sitting high up on the Mauna Loa volcano in Hawaii.
8:32
Ah, yes, the famous Keeling curve. Right. Since
8:36
1958... Scientists there have been continuously
8:39
measuring the exact concentration of carbon dioxide
8:42
in the air. And it shows a relentless upward
8:45
climb. Back in 1958, it was at about 315 parts
8:49
per million. Today, it has shot past 420. Yep,
8:54
a very clear trend. But the line itself has this
8:56
fascinating little sawtooth pattern every single
8:59
year. It's not just a straight line. That sawtooth
9:01
is amazing. It's essentially the heartbeat of
9:04
the Earth's biosphere. See, the majority of the
9:07
planet's landmass and forests are in the northern
9:09
hemisphere. So every summer, when those forests
9:12
bloom, they breathe in massive amounts of carbon
9:15
dioxide to build leaves and wood, causing the
9:18
global CO2 level to drop a tiny bit. And then
9:21
in the winter. Every winter, as the leaves fall
9:23
and decay, the forests breathe that carbon back
9:26
out and the line ticks back up. But beneath that
9:29
planetary breathing, the baseline just keeps
9:31
rising year after year. And to get a deeper historical
9:35
context, scientists go to the ice caps, right?
9:38
Right. When snow falls in places like Antarctica,
9:41
it traps microscopic bubbles of air. As that
9:44
snow gets compressed into ice over millennia,
9:46
it creates a vertical timeline of the ancient
9:49
atmosphere. A literal time capsule. Exactly.
9:51
And analyzing the air in those deep ice cores
9:54
shows that carbon dioxide levels have now shot
9:56
far above anything seen in at least the last
9:58
800 ,000 years. Wow. 800 ,000 years. And it is
10:02
wising faster than anything in that entire geological
10:05
record. Okay, so the gas traps heat, and the
10:07
gas is going up rapidly. But we still need to
10:10
prove the source. I mean, to play devil's advocate
10:13
here, how do scientists know for sure that this
10:16
massive spike in carbon dioxide is coming from
10:19
humans? Could it just be, you know, the Earth
10:21
venting carbon naturally from volcanoes or deep
10:24
ocean vents? What's fascinating here is that
10:27
scientists rely on a beautiful piece of forensic
10:29
chemistry to answer this. It all has to do with
10:33
isotopes. Let's define isotopes for the listeners.
10:35
Think of isotopes as different varieties of an
10:38
element. Carbon atoms are chemically identical
10:40
to one another in how they react, but they can
10:43
have slightly different physical weights or masses.
10:45
Right, like carbon -12, carbon -13, and carbon
10:47
-14. Exactly. Now, millions of years ago, ancient
10:51
plants absorbed carbon from the air. When those
10:53
plants died, they were buried and compressed
10:55
over eons, eventually turning into coal, oil,
10:58
and natural gas. Fossil fuels. Right. And because
11:02
of the way plants process carbon during photosynthesis,
11:04
the carbon inside them is naturally depleted
11:07
in the heavier isotopes. They prefer the lighter
11:09
carbon. They do. And more importantly, that ancient
11:12
buried carbon contains absolutely zero carbon
11:16
-14. Because carbon -14 is radioactive, right?
11:19
Yes, it's a radioactive isotope that slowly decays
11:22
over time. Because fossil fuels have been buried
11:24
underground for tens of millions of years, all
11:27
of their carbon -14 has completely decayed away.
11:30
There's none left. Oh, wow. So it's basically
11:32
dead carbon. Exactly. So as we spend the last
11:35
century and a half digging up and burning those
11:37
fossil fuels, we pump that very specific dead
11:40
carbon into the sky. And what happens when we
11:42
measure the air today? When we analyze the atmosphere
11:45
today, the overall carbon signature has shifted.
11:48
It matches the exact isotopic signature you would
11:51
expect if you were flooding the air with old,
11:53
dead plant carbon. It's lighter, and the radioactive
11:56
fraction is highly diluted. So the extra carbon
11:59
dioxide wears our fossil fuel fingerprint. It
12:02
is a chemical smoking gun. And the math of the
12:04
Earth's natural system supports this perfectly,
12:06
too. The text mentions that the amount of CO2
12:09
accumulating in the atmosphere is only about
12:11
half of what humanity actually emits. The oceans
12:14
and the land are absorbing the other half. Right.
12:17
Nature is a net sink, not a source. We are putting
12:20
it into the air faster than the planet can scrub
12:22
it out. The mechanism is proven and the chemical
12:25
fingerprint is undeniably ours. OK, so a 19th
12:30
century lab tube shows CO2 traps heat and chemical
12:34
signatures prove we're filling the atmosphere
12:36
with it. But a lab tube isn't a planet. Are we
12:40
actually seeing the Earth's thermometer respond
12:42
the way that century -old Matt predicted? We
12:46
absolutely are. Global average surface temperatures
12:48
have risen roughly 1 .2 degrees Celsius since
12:51
the late 1800s. And that's confirmed across the
12:53
board? Yes, by independent lines of evidence.
12:56
We're talking thermometers on land, sensors deep
12:58
in the sea measuring ocean heat content, shrinking
13:01
glaciers, rapidly rising sea levels, and biological
13:04
markers like the consistently earlier arrival
13:07
of spring. Here's where it gets really interesting.
13:09
An honest skeptic might look at that 1 .2 degrees
13:12
and say, well, the climate has always changed.
13:14
Ice ages have come and gone naturally long before
13:17
humans ever built a combustion engine. A very
13:19
common and fair question. Right. So how do scientists
13:22
know this specific warming isn't just a natural
13:25
cycle, like a wobble in the Earth's orbit or
13:28
the sun getting hotter? Answering that relies
13:31
on a field of science called attribution. which
13:34
is the meticulous process of isolating causes.
13:37
Scientists know that natural drivers exist. The
13:40
Earth's orbit wobbles, the sun's output fluctuates,
13:44
and massive volcanic eruptions alter the atmosphere.
13:47
And because we can measure those phenomena, we
13:49
can calculate exactly what they should be doing
13:52
to our temperature right now. Exactly. We can
13:53
test the natural variables independently of the
13:55
human ones. So what happens when we run those
13:58
calculations? The math simply doesn't support
14:01
natural warming. The orbital cycles of the Earth
14:04
are currently, if anything, slowly nudging our
14:07
planet toward a cooling phase. Oh, really? Yeah.
14:10
And the sun's energy output has been largely
14:12
flat, or even slightly down, over the exact same
14:15
period where our temperatures have risen the
14:16
fastest. What about volcanoes? Volcanoes throw
14:19
ash into the sky that blocks the sun, causing
14:21
short -term cooling blips, not decades of sustained
14:24
warming. Adding up every natural driver simply
14:27
cannot explain the warming we observe. The math
14:30
only matches reality when you add the human -made
14:33
greenhouse gases back into the models. That's
14:35
right. And the source mentions an ultimate proof
14:38
here, a literal atmospheric fingerprint. If the
14:41
sun were suddenly burning hotter and causing
14:44
global warming, the extra heat would be coming
14:46
from the outside in. The entire atmosphere from
14:49
the top down to the surface would warm up together.
14:52
But that's not what we see. Because the warming
14:55
is caused by greenhouse gases forming a blanket
14:57
near the surface, they trap the heat down low.
15:00
As a result, we observe the lower atmosphere
15:03
rapidly warming up while the upper atmosphere
15:05
is actually cooling down because that outgoing
15:08
heat is intercepted before it can reach it. That
15:10
is incredible. It is an unambiguous, undeniable
15:13
fingerprint that the warming is coming from a
15:16
blanket trapping heat from the inside, not from
15:19
a hotter sun on the outside. You really can't
15:22
fake a cooling upper atmosphere. No, you can't.
15:24
So we've established human -driven warming. But
15:28
the Earth is a complex, chaotic system. And a
15:31
little bit of warming doesn't just stop there.
15:33
It triggers other mechanisms that make it snowball,
15:36
which the source describes as self -amplifying
15:39
feedback loops. Could you explain what that means?
15:42
Sure. A feedback loop is basically a chain reaction.
15:44
A primary example involves water vapor. We established
15:48
that carbon dioxide warms the air, right? Right.
15:51
Well, warmer air physically has the capacity
15:53
to hold more moisture. The basic physics dictate
15:56
that as air temperature rises, it expands its
15:59
capacity to hold water vapor. And water vapor
16:02
is itself a potent greenhouse gas. Ah, I see.
16:05
So a little warming from CO2 causes more water
16:08
to evaporate from the oceans, raising the humidity,
16:10
trapping even more heat, and warming the air
16:12
further. Which holds more water, which traps
16:15
more heat. Exactly. It feeds itself. And the
16:17
text gives another clear, everyday example involving
16:20
ice. Yes, the albedo effect. Yeah. Bright white
16:23
ice is highly reflective. It acts like a mirror,
16:25
bouncing incoming visible light back out into
16:27
space before it can warm the Earth. But as the
16:30
planet warms, that ice melts. Right. And when
16:33
it melts, it exposes the dark blue ocean, or
16:36
the dark land underneath. Those dark surfaces
16:39
absorb light instead of reflecting it. So the
16:42
area gets hotter, melting more ice, exposing
16:44
more dark surface. And the source notes that
16:47
these feedbacks are so powerful, they roughly
16:49
double the warming that the carbon dioxide would
16:51
cause on its own. Yeah, they amplify the whole
16:53
system. So what does this all mean for you and
16:55
me? The text says we've warmed about 1 .2 degrees
16:59
Celsius. Maybe we hit 1 .5 or 2 degrees. To an
17:03
average listener, the difference between, say,
17:05
20 degrees and 22 degrees on a thermometer sounds
17:08
negligible. It's like the difference between
17:10
wearing a sweater or a T -shirt. Why should anyone
17:13
care about a tiny shift in a global average?
17:16
It's a great question because our brains just
17:18
aren't wired to think globally. A global average
17:20
is a, quote, vast, sluggish quantity. Right.
17:24
It takes a lot to move it. Enormous energy. To
17:27
move the average temperature of the entire atmosphere
17:29
in all the oceans of the Earth by even a single
17:31
degree requires a truly incomprehensible amount
17:34
of thermal energy. We go back to that ice age
17:37
comparison from the beginning. The five degrees.
17:39
Yeah. Just five degrees separated our modern,
17:43
comfortable world from a kilometer of ice crushing
17:45
what is now Canada and Europe. A degree or two
17:49
of warming isn't about a mildly warmer Tuesday
17:51
afternoon. It is a fundamental shift in the baseline
17:54
operating conditions of the planet. The text
17:57
uses the analogy of loading the dice. Exactly.
17:59
It loads the dice for extreme events. Because
18:02
a warmer baseline means there is vastly more
18:05
thermal energy and moisture pumping through the
18:07
entire weather system. When you load the dice,
18:09
a heat wave reaches higher peaks than it ever
18:12
could before. Right. And a drought bites harder
18:14
and lasts longer because the hotter air evaporates
18:17
more moisture from the soil. And conversely,
18:19
because that hot air is holding all that extra
18:21
water vapor, when it finally does rain, the heaviest
18:24
downpours become significantly heavier, leading
18:27
to catastrophic floods. Exactly. The source specifically
18:30
points to Australia to illustrate why these loaded
18:33
dice matter so deeply. It's a continent already
18:36
naturally hot, dry, and prone to massive bushfires
18:39
and devastating floods. So if you shift the baseline
18:42
even a little bit in a place like that... The
18:44
extremes get magnified to a point where human
18:47
infrastructure just struggles to cope. The consequence
18:51
isn't a slow, gentle warming. It's an escalation
18:54
of volatility. Looking back at the trail of evidence
18:57
we've followed today, the narrative from this
18:59
source is incredibly clear. Heat -trapping gases
19:03
keep us alive. We are adding them to the atmosphere
19:05
faster than at any time in the deep geological
19:08
record. Forensic chemistry using isotopes proves
19:12
without a doubt that the extra gas belongs to
19:14
us. Yep. The planet is warming precisely as 19th
19:18
century physics dictated it would. And those
19:21
feedback loops are doubling the effect. And this
19:23
brings us to a crucial distinction the author
19:25
makes, and it's a great way to summarize all
19:26
this, separating the physics from the policy.
19:29
Right, because we are strictly looking at the
19:31
source material objectively here. Exactly. We
19:33
can debate all day long about what humanity should
19:36
actually do about this. The economic costs of
19:38
transitioning to green energy, the tradeoffs
19:41
of different technologies, the fairness of it
19:43
all, how fast we need to move. Those are real,
19:45
highly valid debates that society must have.
19:48
But the underlying physics is not up for debate.
19:51
No, it's not. The basic mechanics were worked
19:53
out with glass tubes, laboratory equipment, and
19:57
handwritten calculations more than a century
19:59
ago. Everything we have measured since confirms
20:02
it. It's not a matter of opinion. It's just heat
20:05
and where it goes. The evidence is written in
20:08
the ice, in the oceans, and in the air itself.
20:11
Absolutely. Well, to wrap up this deep dive,
20:14
I want to leave you with a final thought to mull
20:16
over. The next time you walk outside and look
20:19
up at a clear blue sky, think about that invisible
20:22
boundary high above you. That place where the
20:25
lower atmosphere is trapping heat and warming
20:27
up while the upper atmosphere is quietly cooling
20:30
down in the dark. It's kind of haunting when
20:32
you picture it. It really is. It is not just
20:34
a weather pattern. It is a literal physical signature
20:36
of human history written right into the air.
20:39
Which makes you wonder, what other invisible
20:42
fingerprints might we be leaving on the world
20:44
without even realizing it?