All language subtitles for Cosmos S01E12 The World Set Free (1080p x265 10bit)

Once there was a world

not so very different
from our own.

There were occasional
natural catastrophes,

massive volcanic eruptions

and, every once in a while,
an asteroid would come

barreling out of the blue
to do some damage.

But for the first
billion years or so,

it would've seemed
like a paradise.

This is what we think
the planet Venus

might have looked like when
our solar system was young.

Then things started
to go horribly wrong.

"The World Set Free"

The planet Venus,

which once
may have seemed like a heaven,

turned into a kind of hell.

The difference between the two
can be a delicate balance,

far more delicate
than you might imagine.

Once things began to unravel,
there was no way back.

This is what Venus,
our nearest planetary neighbor,

looks like today.

Venus's oceans are long gone.

The surface is hotter
than a broiling oven,

hot enough to melt lead.

Why? You might think
it's because Venus

is 30% closer to the Sun
than the Earth is,

but that's not the reason.

Venus is completely

covered by clouds
of sulfuric acid that keep

almost all the sunlight
from reaching the surface.

That ought to make Venus
much colder than the Earth.

So why is Venus scorching hot?

It's because
the small amount of sunlight

that trickles in through
the clouds to reach the surface

can't get back out again.

The flow of energy is blocked
by a dense atmosphere

of carbon dioxide.

That carbon dioxide gas--
or CO2 for short--

acts like a smothering blanket
to keep the heat in.

No one is burning coal

or driving
big gas-guzzlers on Venus.

Nature can destroy
an environment

without any help
from intelligent life.

Venus is in the grip
of a runaway greenhouse effect.

Why does it look like
we're inside a bowl?

It's due to the intense
atmospheric pressure.

That's the wreck of Venera 13.

In 1982, the scientists
and engineers

of what was then
the Soviet Union

successfully landed
this spacecraft on Venus.

They managed
to keep it refrigerated

for over two hours,

so it could photograph
its surroundings...

and transmit the images
back to Earth

before the onboard electronics
were fried.

Venus and Earth started out
with about the same amount

of carbon, but the two worlds
were propelled

along radically different paths,

and carbon was the decisive
element in both stories.

On Venus, it's almost all
in the form of gas--

carbon dioxide--
in the atmosphere.

Most of the carbon on Earth
has been stored for eons

in solid vaults
of carbonate rock,

like this one,
part of a chain that forms

the celebrated
White Cliffs of Dover,

right on the English Channel.

What titan built
this wonder of the world?

A creature a thousand times
smaller than a pinhead.

Trillions of them.

One-celled algae.

Volcanoes supply carbon dioxide
to the atmosphere,

and the oceans slowly absorb it.

Working over the course
of millions of years,

the microscopic algae harvested
the carbon dioxide

and turned it
into these tiny shells.

They accumulated
in thick deposits of chalk,

or limestone,
on the ocean floor.

Later, the restless Earth
pushed up the seafloor

and carved out
these massive cliffs.

Other marine creatures

took in carbon dioxide
to build enormous coral reefs.

And the oceans converted
dissolved CO2 into limestone

even without any help from life.

As a result, only a trace amount
was left as a gas

in Earth's atmosphere.

Not even three-hundredths
of one percent.

Think of it--
fewer than three molecules

out of every ten thousand.

And yet, it makes
the critical difference

between a barren wasteland
and a garden of life on Earth.

With no CO2 at all,

the Earth would be frozen.

And with twice as many,

we're still talking
about only six molecules

out of ten thousand.

Things would get
uncomfortably hot

and cause us
some serious problems...

but never as hot as Venus;
not even close.

That planet lost
its ocean to space

billions of years ago.

Without an ocean,
it had no way to capture CO2

from the atmosphere
and store it as a mineral.

The CO2 from erupting volcanoes

just continued to build up.

Today, that atmosphere
is 90 times heavier than ours.

Almost all of it is
heat-trapping carbon dioxide.

That's why Venus is
such a ferocious inferno

so hostile to life.

The Earth,
in stunning contrast,

is alive.

It breathes...

but very slowly.

A single breath
takes a whole year.

The forests contain
most of Earth's life,

and most forests
are in the Northern Hemisphere.

When spring comes to the north,

the forests inhale
carbon dioxide from the air

and grow,
turning the land green.

The amount of CO2
in the atmosphere goes down.

When fall comes and the plants
drop their leaves, they decay,

exhaling the carbon dioxide
back into the atmosphere.

The same thing happens
in the Southern Hemisphere

at the opposite time
of the year.

But the Southern Hemisphere
is mostly ocean.

So it's the forests of the north

that control the annual changes
in the global CO2.

The Earth has been
breathing like this

for tens of millions of years.

But nobody noticed until 1958,

when an oceanographer
named Charles David Keeling

devised a way
to accurately measure

the amount of carbon dioxide
in the atmosphere.

Keeling discovered the Earth's
exquisite respiration.

But he also discovered
something shocking--

a rapid rise,
unprecedented in human history,

in the overall level of CO2,

one that has continued
ever since.

It's a striking departure from
the CO2 levels that prevailed

during the rise of agriculture
and civilization.

In fact, the Earth has seen
nothing like it

for three million years.

How can we be so sure?

The evidence is written
in water.

The Earth keeps
a detailed diary

written in the snows
of yesteryear.

Climate scientists
have drilled ice cores

from the depths of glaciers
in Greenland and Antarctica.

The ice layers have ancient air
trapped inside them.

We can read the unbroken record
of Earth's atmosphere

that extends back over
the last 800,000 years.

In all that time,

the amount of carbon dioxide
in the air never rose

above three-hundredths
of one percent.

That is, until the turn
of the 20th century.

And it's been going up steadily
and rapidly ever since.

It's now more than 40% higher

than before
the Industrial Revolution.

By burning coal, oil and gas,

our civilization
is exhaling carbon dioxide

much faster
than Earth can absorb it.

So CO2 is building up
in the atmosphere.

The planet is heating up.

Every warm object radiates
a kind of light

we can't see
with the naked eye--

thermal infrared light.

We all glow with invisible heat
radiation, even in the dark.

This is what the Earth
looks like in the infrared.

You're seeing the planet's
own body heat.

Incoming light
from the Sun hits the surface.

The Earth absorbs much
of that energy,

which heats the planet up

and makes the surface glow
in infrared light.

But the carbon dioxide
in the atmosphere

absorbs most of that outgoing
heat radiation,

sending much of it
right back to the surface.

This makes the planet
even warmer.

That's all there is
to the greenhouse effect.

It's basic physics,

just bookkeeping
of the energy flow.

There's nothing
controversial about it.

If we didn't have any carbon
dioxide in our atmosphere,

the Earth would just be
a great big snowball,

and we wouldn't be here.

So, a little greenhouse effect
is a good thing.

But a big one can destabilize
the climate

and wreck our way of life.

All right... but how do we know
that we're the problem?

Maybe the Earth itself is
causing the rise in CO2.

Maybe it has nothing to do
with the coal and oil we burn.

Maybe it's those
damn volcanoes.

Every few years, Mount Etna,
in Sicily, blows its stack.

Each big eruption sends millions
of tons of CO2

into the atmosphere.

Now, combine that
with the output

of all the other volcanic
activity on the planet.

Let's take the largest
scientific estimate--

about 500 million tons
of volcanic CO2

entering the atmosphere
ever year.

Sounds like a lot, right?

But that's not even two percent
of the 30 billion tons of CO2

that our civilization
is cranking out every year.

And, funny thing,

the measured increase in CO2
in the atmosphere

tallies with the known amount
we're dumping there

by burning coal, oil and gas.

Volcanic CO2 has
a distinct signature--

it's slightly heavier
than the kind produced

by burning fossil fuels.

We can tell the difference
between the two

when we examine them
at the atomic level.

It's clear that
the increased CO2 in the air

is not from volcanoes.

What's more, the observed
warming is as much as predicted

from the measured increase
in carbon dioxide.

It's a pretty tight case.

Our fingerprints
are all over this one.

How much is 30 billion tons
of CO2 per year?

If you compressed it
into solid form,

it would occupy
about the same volume

as the White Cliffs of Dover.

And we're adding that much CO2
to the air every year,

relentlessly, year after year.

Unlucky for us,
the main waste product

of our civilization
is not just any substance.

It happens to be the chief
climate-regulating gas

of our global thermostat,
year in, year out.

Too bad CO2 is an invisible gas.

Maybe if we could see it...

If our eyes were sensitive
to CO2--

and perhaps there are
such beings in the cosmos--

if we could see all
that carbon dioxide,

then we would overcome
the denial

and grasp the magnitude of
our impact on the atmosphere.

But the evidence
that the world is getting warmer

is all around us.

For starters, let's just
check the thermometers.

Weather stations
around the world

have been keeping
reliable temperature records

since the 1880s,

and NASA has used the data
to compile a map

tracking
the average temperatures

around the world through time.

Yellow means
warmer temperatures

than the average,
for any region in the 1880s.

Orange means hot.

And red means hotter.

The world is warmer than it was
in the 19th century.

Back then, at the greatest fair
the world has ever seen,

a forgotten genius demonstrated
the solution to this problem.

Come with me.

Once there was a world

that was not too hot
and not too cold.

It was just right.

Then there came a time
when the life it sustained

began to notice
our lovely planet was changing.

And it's not
as if we didn't see it coming.

As far back as 1896,

the Swedish scientist
Svante Arrhenius

calculated
that doubling the amount

of CO2 in the atmosphere
would melt the Arctic ice.

In the 1930s, the American
physicist EO Hulburt,

at the Naval
Research Laboratory,

confirmed that result.

So far, it was still
just theoretical.

But then, the English engineer
Guy Callendar

assembled the evidence to show

that both the CO2 and
the average global temperature

were actually increasing.

Even now, man may be unwittingly
changing the world's climate

through the waste products
of his civilization.

Due to our release,
through factories

and automobiles every year,
of more than

six billion tons
of carbon dioxide,

which helps air absorb heat
from the Sun,

our atmosphere seems
to be getting warmer.

This is bad?

Well, it's been calculated,
a few degrees rise

in the Earth's temperature

would melt the polar ice caps.

In 1960,
Carl Sagan's PhD thesis

included the first calculation

of the runaway
greenhouse effect on Venus.

This was part
of a career-long interest

in the atmospheres of
the planets, including our own.

In the original Cosmos series,
in 1980, Carl Sagan warned...

We are releasing vast
quantities of carbon dioxide,

increasing
the greenhouse effect.

It may not take much

to destabilize
the Earth's climate,

to convert this heaven,
our only home in the cosmos,

into a kind of hell.

Since Carl spoke those words,

we've burdened the atmosphere
of our world with an additional

400 billion tons
of carbon dioxide.

If we don't change our ways,

what will the planet be like
in our children's future?

Based on scientific
projections,

if we just keep
on doing business as usual,

our kids are in
for a rough ride.

Killer heat waves,
record droughts,

rising sea levels,
mass extinction of species.

We inherited a bountiful world

made possible
by a relatively stable climate.

Agriculture
and civilization flourished

for thousands of years.

And now, our carelessness and
greed put all of that at risk.

Okay, so if we scientists
are so good

at making these dire, long-term
predictions about the climate,

how come we're so lousy
about predicting the weather?

Besides, this year, we had
a colder winter in my town.

For all us scientists know,

we could be in
for global cooling.

Here's the difference
between weather and climate...

Weather is what the atmosphere
does in the short term--

hour to hour, day to day.

Weather is chaotic,
which means that even

a microscopic disturbance can
lead to large-scale changes.

That's why those ten-day
weather forecasts are useless.

A butterfly flaps its wings
in Bali, and six weeks later,

your outdoor wedding
in Maine is ruined.

Climate is the long-term average

of the weather,
over a number of years.

It's shaped by global forces
that alter the energy balance

in the atmosphere,
such as changes in the Sun,

the tilt of the Earth's axis,

the amount of sunlight
the Earth reflects back to space

and the concentration
of greenhouse gases in the air.

A change in any of them
affects the climate

in ways
that are broadly predictable.

My friend's meandering

represents
the short-term fluctuations--

that's weather.

It's almost impossible
to predict

what'll attract
his interest next,

but not hard to know what the
range of his meandering will be,

because I'm holding him
on a leash.

We can't
observe climate directly--

all we see is the weather--

but the average weather,
over the course of years,

reveals a pattern.

I represent
that long-term trend,

which is climate.

Keep your eye on the man,
not the dog.

Weather is hard to predict,
like my friend here,

but climate is predictable.

Climate has changed many times
in the long history of the Earth

but always in response
to a global force.

The strongest force driving
climate change right now

is the increasing CO2 from
the burning of fossil fuels,

which is trapping more heat
from the Sun.

All that additional energy
has to go somewhere.

Some of it warms the air.

Most of it ends up
in the oceans.

All over the world,
the oceans are getting warmer.

It's most obvious
in the Arctic Ocean

and the lands that surround it.

Okay, so we're losing
the summer sea ice

in a place
where hardly anyone ever goes.

What do I care if there's
no ice around the North Pole?

Ice is the brightest
natural surface on the Earth,

and open ocean water
is the darkest.

Ice reflects incoming sunlight
back to space.

Water absorbs sunlight

and gets warmer,
which melts even more ice,

which exposes
still more ocean surface

to absorb even more sunlight.

This is what we call
a positive feedback loop.

It's one of many natural
mechanisms that magnify

any warming caused
by CO2 alone.

We're at Drew Point, Alaska,

on the edge of the Arctic Ocean.

When I was born, the
shoreline was a mile farther out,

and it was breaking off at a
rate of about 20 feet per year.

Now...

it's being eaten away
at about 50 feet per year.

The Arctic Ocean is warming

and at an increasing rate.

So it's ice-free
during more of the year.

That leaves the shore here

more exposed to erosion
from storms,

which are also getting
more powerful,

another effect
of climate change.

The northern reaches of Alaska,
Siberia and Canada

are mostly permafrost,

ground that has been frozen
year-round for millennia.

It contains lots
of organic matter,

old leaves and roots
from plants

that grew thousands
of years ago.

Because the Arctic regions
are warming faster

than anywhere else on Earth,

the permafrost is thawing

and its contents are rotting,

just like when you unplug
the freezer.

The thawing permafrost
is releasing carbon dioxide

and methane, an even more
potent greenhouse gas,

into the atmosphere.

This is making things
even warmer,

another example of a positive
feedback mechanism.

The world's permafrost stores
enough carbon

to more than double the CO2
in the atmosphere.

At the rate we're going,

global warming
could release most of it

by the end of the century.

We might be tipping the climate
past a point of no return

into an unpredictable slide.

Okay, the air, the water

and the land
are all getting warmer,

so global warming
is really happening.

But maybe it's not our fault.

Maybe it's just nature.

Maybe it's the Sun.

No, it's not the Sun.

We've been monitoring the Sun
very closely for decades,

and the solar energy output
hasn't changed.

What's more, the Earth
is warming more at night

than in daytime,

and more in winter
than in summer.

That's exactly what we expect
from greenhouse warming,

but the opposite of what
increased solar output

would cause.

It's now clear beyond
any reasonable doubt

that we are changing
the climate.

The Sun isn't the problem.

But it is the solution,

and we've known this
for a long time,

much longer
than you might think.

Paris, September 1878.

The Eiffel Tower won't be built
for years to come.

Witness one
of the most glorious spectacles

the world has ever seen.

The magnificent head
of the Statue of Liberty

has just been completed.

Thousands of exhibitors
from around the planet

covered 66 acres of Paris

with their inventions
and goods.

Edison's first public
demonstration of the lightbulb

will not take place
for another year.

There's no such thing
as electrical appliances.

People don't flick switches
and press buttons.

It's a hand-cranked,
horse-drawn world.

That's the guy we came to see,

the one
with the crazy moustache.

He's a math teacher
named Augustin Mouchot.

Remember, it's 1878.

This is a world
lit mostly by gaslight.

The automobile
is still years away.

But Mouchot, here,
is dazzling the crowd

with his solar power
concentrator.

The Sun belongs to all of us!

Even though it is 150 million
kilometers away from us,

feel its awesome power!

My invention concentrates
the free energy of the Sun

and converts it
into mechanical motion.

It can power any kind
of machine.

It can produce electricity
or run a printing press

or make ice on a hot day.

Et voilà !

Think of it,

sunlight converted into ice.

You see, my friends,
what wonders we can work

if we harness
the bounteous energy of the Sun.

The world will someday
run out of coal,

but the magnificent Sun
will always be there for us.

Mouchot took home the gold medal
from the fair.

But the price of coal tumbled,

becoming so cheap that there was
no interest in solar energy.

Besides,
no one understood, back then,

what the true cost was
of burning fossil fuel.

Mouchot's research funding
was cut off.

35 years later, in the early
years of the 20th century,

another door opened
to an alternative future.

It happened in Egypt,
on the banks of the Nile.

Memo to future time travelers...

this would be
an excellent entry point

for averting climate change.

Egypt, 1913.

That's Frank Shuman
of Philadelphia.

He's only had
three years of schooling,

but his genius for innovation
more than makes up for that.

Before he was 30, Shuman
had invented safety glass.

Its use in automobiles and
skylights saved countless lives

and made him a very rich man,

rich enough
to pursue his real passion,

solar energy.

Shuman led the team
that designed and built

an array
of solar energy concentrators.

It could power a steam engine.

Shuman is hoping
to use the Sun's power

to irrigate the desert

and turn it green.

The official inauguration

of Shuman's solar power plant,
in 1913,

was a dazzling success.

He had invented a practical way
to tap the Sun's energy

on an industrial scale,

making solar energy
even cheaper than coal.

The British
and German governments

both offered Shuman
generous funding

to develop his invention.

It was the ideal source
of abundant power

in tropical regions,

where imported coal
was prohibitively expensive.

But Shuman was dreaming
even bigger.

In a letter
to Scientific American,

he calculated
that his solar power plants,

if deployed in an area
of the Sahara Desert

only 150 miles on a side,
could supply as much power

as consumed by all
the industries of the world.

But it was not to be.

The market for a liquid
fossil fuel, petroleum,

was exploding for shipping,

home heating,
and cars and trucks.

Oil was abundant,
cheaper even than coal,

and much easier to get
out of the ground and process.

It took 100 men a week
to fuel a ship with coal,

but with oil,
one man could do the job

in a single day.

A year after Shuman's
triumph in the desert,

World War I broke out.

His solar collectors
were recycled into weapons.

Frank Shuman's dream
of a solar-powered civilization

would have to wait
another century

before it was reborn.

There's another inexhaustible
source of clean energy

for the world.

The winds themselves
are solar powered,

because our star drives
the winds and the waves.

Unlike solar collectors,

wind farms take up
very little land,

and none at all, if offshore,

where the winds are strongest.

If we could tap even
one percent of their power,

we'd have enough energy
to run our civilization.

And more solar energy
falls on Earth in one hour

than all the energy
our civilization consumes

in an entire year.

If we could harness
a tiny fraction

of the available
solar and wind power,

we could supply
all our energy needs forever,

and without adding
any carbon to the atmosphere.

It's not too late.

There's a future
worth fighting for.

How do I know?

Every one of us comes
from a long line of survivors.

Our species is nothing
if not adaptive.

It was only because
our ancestors learned

to think long-term,
and act accordingly,

that we're here at all.

We've had our backs
to the wall before,

and we came through
to scale new heights.

In fact, the most mythic
human accomplishments of all

came out of our darkest hour.

Once there was a world

rigged with 60,000
hair-triggered nuclear weapons.

The combatants were

the two most powerful
countries on Earth,

and they were locked
in a deadly embrace,

each vowing that
they would rather see

everything we love destroyed

than submit
to the will of the other.

When I was three years old,

the largest man-made
explosion of all time

was detonated
by the Soviet Union.

That terror has subsided,
to be replaced by new fears.

The danger that the 2,000
largest cities on Earth

would be reduced to rubble
in the space of an afternoon

is no longer one of them.

The nuclear rivalry
between the United States

and the Soviet Union

had another by-product.

The Apollo missions to the Moon
were an extension

of the arms race
that raged between them.

Sending people
to orbit the Earth

or go to the Moon
requires big, reliable,

powerful rockets--
precisely the same technology

you need to carry
a nuclear warhead

halfway around the planet

to destroy your enemy's
largest cities.

I believe that this nation

should commit itself
to achieving the goal,

before this decade is out,
of landing a man on the Moon

and returning him safely
to the Earth.

President Kennedy's 1961 speech

electrified the nation,

and it contained much
that was remarkably prophetic--

but not a word about
a scientific objective

for going to the Moon.

No questions
about the Moon's origin

or the hope of bringing back
samples to analyze.

No, the Apollo missions
were conceived

as a demonstration
of the superior power

and precision
of our strategic missiles.

But a funny thing
happened to us

on our way to the Moon.

We looked homeward...

and discovered another world--

our own.

For the first time,
we inhabitants of Earth

could step back
and see it as it really is--

one world, indivisible,

and kind of small
in the cosmic context.

Whatever the reason we first
mustered the enormous resources

required
for the Apollo program,

however mired it was
in Cold War nationalism

and the instruments of death,

the inescapable recognition
of the unity

and fragility of the Earth

is its clear
and luminous dividend,

the unexpected gift of Apollo.

A project conceived
in deadly competition

made us recognize
our community.

What titan built
this wonder of the world?

It was the Ifugao people
of the Philippines,

working with not much more
than their hands.

About 10,000 years ago,
our ancestors all over the world

took advantage of another form
of climate change,

the gentler climate of the
intermission in the ice age--

they invented agriculture.

They gave up
the ceaseless wandering,

hunting and gathering
that had been their way of life

for a million years or so,

to settle down and produce food.

They found a way to harvest

ten to a hundred times
more solar energy

than the environment naturally
provided for their ancestors.

People all over the world
made the difficult transition

from nomadic cultures
to agricultural ones

that used solar energy
more efficiently.

It gave rise to civilization.

We stand on the shoulders
of those who did the hard work

that such a fundamental
transformation required.

Now... it's our turn.

Once there was a world...

If life ever existed on Venus,
it would have had no chance

to avert the hellish destiny
of this world.

This runaway greenhouse effect
was unstoppable.

Once...

there was a world...

ours.

And that world is now.

There are no scientific
or technological obstacles

to protecting our world

and the precious life
that it supports.

It all depends...

on what we truly value...

and if we can summon
the will to act.

But why, some say, the Moon?

Why choose this as our goal?

And they may well ask,

why climb the highest mountain?

We choose to go to the Moon...

we choose to go to the Moon...

...we choose to go to the Moon
in this decade

and do the other things,

not because they are easy,
but because they are hard.