All language subtitles for 55C12C557CCFFA9712A6484DE79317D8_eng

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 have 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 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

percent 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.

Thus, it cannot hit Earth.

It can't 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 for 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 different.

The 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.

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 ninety 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.

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, but 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
limit.

It's 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.

Alright, 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 every year.

Sounds like a lot, right?

But that's not even 2% 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?

Rested 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,
if 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 E.

O.

Hilbert at the Naval Research Laboratory
confirmed that result.

So far, it was still just theoretical.

But then, the English engineer Guy
Callender 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 Ph.D.

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 the 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 10-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, 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
will 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.

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 things we can do.

There are 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 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

light bulb 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 mustache.

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 voila!

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 Schumann 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, Schumann 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.

Schumann led the
team that designed and

built an array of solar
energy concentrators.

It could power a steam engine.

Schumann is hoping to use the sun's power
to irrigate the desert and turn it green.

The official inauguration
of Schumann'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

Schumann generous funding
to develop his invention.

It was the ideal source of
abundant power in tropical

regions where imported coal
was prohibitively expensive.

But Schumann 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, 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 Schumann's triumph in the
desert, World War I broke out.

His solar collectors were recycled into
weapons.

Frank Schumann'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
1% 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 byproduct.

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 weapon.

You need a 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 at 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.

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 10 to 100
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.

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.

We choose to go to the moon.

We choose to go to the moon.