All language subtitles for CF1677744E93213A02BCFAC299CEAC65_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 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.

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 on board 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 1 percent.

Think of it, fewer than three molecules
out of every 10,000.

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 10, 000...

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 the forests of the north that control
the annual changes in 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 3 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 1 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 percent higher
than before the Industrial Revolution.

By burning coal, oil and gas...

our civilization is exhaling carbon dioxide
much faster than the 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 could destabilize
the climate and wreck our way of life.

All right,
but how do we know 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 damned volcanoes.

Every few years, Mt. 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 percent
of the 30 billion tons of CO2...

that our civilization
is cranking out every year.

And, funny thing, the measured increase
of 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 the 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 average temperatures
around the world through time.

Yellows mean warmer temperatures than
the average for any region in the 1880s.

Orange means hot.

And reds means hotter.

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

Back then, at the greatest fair
the world had 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 1930's,
the American physicist E.O. Hulbert...

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 6 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.

And 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 those 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.

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 the 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 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.

Ha-ha-ha! 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.

Thirty-five 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.

It's 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,
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 1 percent of their power...

we'd have enough energy
to run our civilization.

And more solar energy falls
on the 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 3 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 2000 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 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 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...

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.