All language subtitles for BBC How Earth Made Us EP04 Fire (2010) English

Our planet has immense power...

...and yet that's rarely mentioned
in our history books.

I'm here to change that.

I'm looking at four ways the power
of the planet has shaped our history.

The deep Earth that provided the raw
materials for our conquest of the planet.

Wind...that has influenced
the rise and fall of empires.

Water.

Look at that!

Our struggle to control it has defined
the character of civilisations.

But this week I'm looking at fire.

It's deadly,

yet it's also the driving force
behind human progress.

But our dependence on fire has meant
that events deep in the Earth's past

have changed the course of history.

The vibrate is a low-air alarm.

It'll let you know when you've got
a quarter of a tank of oxygen.

- When you hear that, you need to get out.
- Get out. OK.

I'm preparing
to undergo an experience that,

on the face of it,
is absolutely terrifying.

These stickers are to measure the
temperature it reaches inside the suit.

These will tell you how hot
you're actually getting inside the suit.

- So how hot does it go up to?
- 130 degrees Fahrenheit.

- That goes over your head.
- Mm-hm.

OK. I'm fine.

My suit is eight layers thick,

its visor specially tempered,
gold-plated glass.

And I've got my own air supply.

This is what it takes
to survive just a few seconds...

...inside the heart of a fire.

The temperature around me
is 1, 600 degrees Celsius.

For all its danger,
fire is compelling -

almost hypnotic.

Oh, my gosh!

Argh! Argh!

Get his gloves. Get his gloves off.

- Come on out. Go on! Go on!
- Argh! Oh!

That was scary, right at the end.

That was scary.

No, no, no.
I feel my arms burning, though. Ha-hargh!

I'll move them around.

Ah! That...

...that is not a place
where humans should be.

But when you're going through and you see
the flames licking up in front of you,

just the raw energy of it
is absolutely entrancing.

But I'm burning.

I mean, actually, my elbow,
my hand... Argh-ha-ha!

...is burning.

I think I should get this off, actually.

The paradox of fire
is that it's lethal,

and yet we depend on it completely.

Fire generates our electricity.

It drives our machines.

We use it every day.

But the history
of our relationship with fire

reveals how the Earth
has exerted enormous power

over the fate of peoples and nations.

It's strange to think
that for 90% of Earth's history,

there simply was no fire.

Ours was a barren planet
of dust and rock.

There was nothing to burn.

Not until relatively recently,

about 400 million years ago,

did fire first appear.

The key to this transformation...

...vegetation.

The first land plants
had just appeared...

...and they provided fuel for fire.

But plants did something else as well.

Every kid likes to climb trees,

and the great thing about being grown up
is the trees...

they just get bigger, and the ways
to get up them just get fancier.

Vegetation supplied
a second crucial ingredient for fire.

You can see how
up here in the forest canopy.

Going on all around me is
a chemical reaction - photosynthesis.

It's happening in here, in the leaves.

And what the photosynthesis
is producing as a waste product

is an essential ingredient for fire...

oxygen.

Flames cannot burn unless at least 13%
of the atmosphere is oxygen.

But the Earth's early atmosphere
had almost none.

Photosynthesising plants used sunlight
to convert carbon dioxide into energy...

...and in the process released oxygen.

By around 400 million years ago,

this process had raised the level
of oxygen in the atmosphere

to that critical 13%.

Now there was only one more thing
needed for fire to start.

A spark.

Starting fire
was actually the easy bit.

Lightning storms have raged on Earth

for almost its entire history.

30,000 bolts of lightning
hit the ground every hour.

For hundreds of millions of years,

wildfires were controlled
only by the forces of nature.

They started spontaneously,

spread freely...

...and only stopped
when they ran out of fuel

or the rains came.

But then something changed.

We came along.

Around 1.5 millions years ago,

early humans learnt
how to control fire.

Our distant ancestors
probably first captured fire

by grabbing a burning stick
from a wildfire and keeping it nourished,

fanning the flames to keep it alight.

It was the beginning of a relationship
that would transform the planet...

and us.

In that sense,
fire is the human signature.

It gave us immense power
over our world.

Cooking greatly expanded
the range of foods available to us.

It gave us warmth and light...

...and protection
against hungry predators.

It allowed us to quickly clear
large areas of land.

Fire was the weapon
that began our conquest of the planet.

Fire was so central to our survival,

perhaps it's no surprise that it was
worshipped by some early civilisations.

In the Middle East, one of the oldest
religions in the world, Zoroastrianism,

grew up around the worship of fire.

For the Zoroastrians,
the flame itself was sacred.

Humans have always
been drawn to fire.

Flames have long been a symbol
of a spirit far greater than ourselves -

almost a divine presence.

To this day, the eternal flame
is still a potent symbol

for the world's great religions.

But the greatest landmark in our use
of fire came about 6,000 years ago.

The breakthrough centred
on an extraordinary element - carbon.

This is carbon in its purest form...

...diamond.

This particular stone is 25 carats

and apparently it's worth £3.3 million.

It's absolutely beautiful.

Diamonds are made under
extreme pressures and temperatures

deep in the Earth.

I've always loved the idea
that the ultimate in glitz

was to adorn ourselves
in tiny pieces of the Earth's interior.

Geological bling.

But there are other forms of carbon that
are far more valuable to us than this...

...because carbon is the basis
for all life on Earth.

And it's the key ingredient in fire.

And once again,
it depends on photosynthesis.

Plants use the sun's energy

to extract carbon from carbon dioxide
in the atmosphere,

and use it to create their living tissue.

It is this carbon that burns in a fire,

releasing the energy that originally came
from the sun as heat.

The more carbon-rich a fuel is,
the more heat it produces.

Normal wood fires burn
at about 700 degrees Celsius.

But 6,000 years ago, our ancestors
discovered the trick of burning wood

in a low-oxygen environment.

It only partially burns,

but in doing so it creates
a much purer, carbon-rich fuel...

...charcoal.

And that can burn
at 1,100 degrees Celsius...

...hot enough
to melt metal out of rock.

The invention of metal smelting,
culminating in the use of iron,

was one of the most critical
turning points in human history.

The age of metals had begun.

Our mastery of metal gave us tools...

...money

and weapons.

It was the foundation
on which human progress was built.

So much so that by the Middle Ages,

the production of charcoal
for iron smelting was a major industry.

But there was an inevitable problem.

People began to run out of wood.

In prehistoric times,

Britain had been
almost completely covered in forest,

but by the end of the 16th century,

90% of the ancient woodland had gone.

In London, which was growing fast,

the shortage of accessible wood
meant that the price rocketed.

Around the growing cities
of Europe and Asia,

similar fuel shortages developed.

In fact, the end of the 16th century

was the world's first great energy crisis.

In many societies,
the demand for energy

had reached the limits
of what photosynthesis could provide.

A new source of carbon was needed.

And the planet had a solution.

The answer to the energy shortage
started out in cold, wet places...

...like here in Oregon,
in the western United States.

This looks like a perfectly ordinary -

if very beautiful - lake,
but these waters hold a secret.

Because down there is a lost world...
and a very cold one.

Melting glaciers keep the water clear.

Ghostly shapes
appear in the distance...

...standing like sentinels.

But this is not their natural home.

These are 3,000-year-old tree trunks...

...the remains of a drowned forest.

They were submerged when lava
from a nearby volcano dammed this valley

and created the lake.

These trees are completely waterlogged,
but they're actually

the crucial first stage
in an extraordinary transformation.

Because the trees are under water,
there is no oxygen to help rot them away.

Instead, they're preserved,
and eventually buried in mud

at the bottom of the lake...

...the start of a long transformation
which turns wood

into something very different.

Oh!

That was incredible.

It's absolutely freezing, though.

The thing is, today,
there are precious few places

where whole forests die
and get preserved,

but 300 million years ago, this was
happening right across the globe.

It was just a lot warmer then!

300 million years ago,
trees dominated the planet.

Many of these forests
were in lowland swamps.

So when the trees died,
they fell into the water.

In fact, so many carbon-rich trees
were buried

that this period in the Earth's history

is known as the Carboniferous -

the Age of Carbon.

Eventually, these drowned trees
would be squeezed and cooked

deep inside the Earth and turned
into something new and different.

Coal.

Coal was to change our relationship
with fire in a fundamental way.

Instead of burning carbon
from the present, coal gave us access

to a huge new source of carbon
from the Earth's past.

Coal was, in essence,
an immense store of fossilised sunshine.

But coal wasn't evenly distributed
across the Earth,

and this meant
that from the 17th century onwards,

the planet began to play a new
and crucial role in human history.

The first place to benefit
was a small, north-European island...

Britain.

Britain was lucky.

It had an abundance of coal,

much of which could be easily collected
from the surface.

From the beginning
of the 17th century,

burning coal began to replace wood
in homes and workshops.

It was the beginning of a transition

that would end up changing Britain
and the world.

To see how, I'm heading to
the Forest of Dean, in Gloucestershire.

It didn't take long for all that
easy-to-get-at coal to be used up,

so the miners were forced
to tunnel into the Earth,

chasing the coal seams underground,

and down there they had a problem.

But it was a problem which, it turned out,

would unleash
the Industrial Revolution.

In the process,
mining condemned millions

to a dusty, dirty, existence
as men and even children

were sent underground.

This mine is the nearest I can get

to experiencing
what early coal mining was like.

It's owned by Robin Morgan,
who's spent all his life mining.

Is it falling down?

No, I'm just putting this one back up.
This is a new one I'm putting in here.

So there we go.

That's right - drop him down there
in that hole, like that.

The first mine I ever went down,

- I was only 13 years of age.
- Oh!

My two brothers had their own mine.

They used to drop me
down a shaft 100 foot deep

in a 40-gallon drum
with two hooks in the side

on a hand winch.

So where's the coal? That's what
I'm looking forward to seeing.

Well, the coal seam
is actually on in there.

- I can take you on into the seam.
- Yeah, please.

- Keep your head down here.
- Yeah, OK.

Just like the early miners,
Robin hacks out the coal by hand.

Robin, do you think I could have a go?

You can have a go, by all means, Iain.
But there's not much room up here.

All right.

Ah, dear, dear!

I thought coal was supposed to be soft!

Swing the pick instead ofjust tapping it.

You've got to pull the pick right back

and swing it right into those two-inch
layers, and they will prise off there.

Oh!

My arms hurt. How do you do it, Robin?

You get used to it over the years,
you know.

I mean to say,
you've only been up there five minutes.

I know! I have!

- You will gradually get used to it.
- And you've been...

I like rocks all right, but...

spending 12 hours a day
smashing lumps out of them...

- Well, that coal isn't as hard as rocks.
- No.

As you are performing at the moment,
I definitely wouldn't give you a job,

because the rate you're getting that off,
you would not survive.

But in the 17th and 18th centuries,

the problem for Britain's miners

was more fundamental
than a lack of muscle power.

The trouble was,
the deeper they tunnelled,

the more likely they were
to encounter a major obstacle.

Water, and plenty of it.

300 years ago, when miners first followed
the coal seams underground,

this was a problem they faced,

and solving this problem was the key
to our industrial transformation.

Once the miners got down
to the water table, their tunnels flooded

and the coal became inaccessible.

It was impossible to pump
the water out by hand.

A technological solution
was desperately needed...

...and in the early 18th century,
engineers came up with one.

The steam engine.

It was designed specifically
to pump water out of mines,

but it soon found other uses.

Within decades, the combined power
of steam and coal became the force

behind an extraordinary,
integrated economy.

Coal fuelled the blast furnaces
which smelted steel.

The steel was turned
into trains and ships,

powered by steam engines of course,
which in turn burnt more coal.

Today, we know this transformation
in our use of fire

as the Industrial Revolution.

You know, being down here
really focuses your mind.

Britain owes a tremendous amount

to that distant geological age
when trees ruled the world.

Think of the Industrial Revolution

as the rise of carboniferous capitalism.

But the planet was fickle
with its favours.

Britain was given huge reserves of coal

and the geography to exploit it.

Not everywhere was so lucky.

There was another country

blessed by the planet
with huge reserves of coal.

In the 17th century,

it too was poised on the edge
of an industrial revolution,

but its story
played out rather differently.

That country

was China.

By this time, China had been moulded
into a vast empire.

It was rich
and technologically advanced.

China seemed perfectly positioned
to exploit its coal reserves.

There was one problem.

China's coal reserves
may have been massive,

but they were a long way
from the country's cities on the coast.

However, running straight
from the coalfields to the sea

was the mighty Yellow River.

So, in theory,

transporting the coal to the market
should have been possible.

This is Qikou, a beautiful old town
on the Yellow River.

It's right in the heart of coal country.

If coal was to be carried
downstream to the coast,

it would have to pass through here.

Hello. How are you?

Mr Li is 76 years old, and he's been
navigating these waters since he was 11.

His son runs a local ferry service.

The water looks very calm.

Very still - the water.

Cos I get seasick.

Can I get on? OK.

The Li family
are going to take me down the river

in a traditional, flat-bottomed boat -
a design used for generations.

This is the route

that coal from China's coalfields
would have had to travel.

It's like a nice, relaxing row
down the Thames.

But just downstream from Qikou
is an obstacle.

Mr Li and his friends,
who boast an average age of 75,

are the last people
who know how to ride these rapids.

These rapids are only here because
the channel of the Yellow River

gets constricted between these boulders
over here and this hard rock here.

It's literally caught
between a rock and a hard place.

It means it's really choppy.

And it would be even harder to get through
if we were laden down with coal.

Well, we made it!
Just a couple of hairy moments, but...

Mind you, it wasn't the worst set
of rapids in the world,

but it makes you realise that if you're
taking a bulky cargo like coal down here,

then either it or us are going to end up
in the drink, at the bottom of the river.

This is only the start.

Downstream, there are many more rapids.

And just to add to the difficulties,
the only way to get the boat

back upriver is sheer manpower.

What these rapids meant was

that you could transport goods downstream
as far as Qikou over there,

but it was impossible to take it further.

For cargo boats,
these rapids were the end of the line.

So the only way to get the coal to market
was to carry it overland to the coast...

...1,000 kilometres away.

But its price doubled
every 40 kilometres.

The geography of the Yellow River
ensured

that coal could never be shipped
directly to the big coastal markets,

and that meant that the empire
was effectively cut off

from the vast reserves that could have
completely transformed it.

The British invented the steam engine
to overcome

the barrier posed by flooded mines.

But the Chinese failed
to find a similar solution

to their geographical problems.

It was one of those moments

when human factors interacted

with the opportunities
the planet had to offer.

While Britain was forging
an industrial revolution,

the Chinese were building
these enormous gardens at Chengde.

They were designed to celebrate
the size and diversity of the empire.

There was a miniature replica
of the Yellow River...

...a smaller version of the Great Wall...

and even a copy
of the Dalai Lama's palace in Tibet.

These gardens symbolised
China's preoccupation

with managing its vast territory.

It was such a high priority

that rather than focusing
on technological innovation,

the brightest minds
were sucked into running the empire.

Not until the middle
of the 20th century

did China build extensive road
and rail systems into its heartland

and start its own
industrial revolution.

Ironically, China is now the biggest user
and producer of coal in the world.

China's rulers
might not have found a way

to solve their fuel crisis 300 years ago,
but its people had a go.

They came up with a brilliant invention,
which today is known across the world.

Until the 16th century,
Chinese cuisine was renowned

for its delicious stews, which took
loads of time and loads of wood to cook.

So in an era of growing wood shortage,

a radical new approach was needed,
and this was it -

the wok.

It's funny to think that
a crippling wood famine gave us

one of the most famous cuisines
in the world - the Chinese stir-fry.

The story of coal shows how the planet

played a crucial role
in transforming the fate of nations

at the time
of the Industrial Revolution.

It turned fire into the energy
that fuelled human progress.

And yet that was only the beginning.

Today, the planet's stores
of ancient carbon

have an even greater impact
on our world.

That impact hinges
on another type of buried carbon.

To see how it's formed,

I've come to an amazing cave
on an island off southern Iran.

- Do this one up nice and tight.
- Cheers.

- Is it straight down?
- Yeah.

There's a little bit of a lip
and then it goes straight down,

and then it opens out wide
and you just drop into space.

The last drop, 10-15 metres,
you're in space.

I just looked. Oh, my God!

I have to abseil 50 metres
to enter the cave system.

Inside is evidence that reveals

where this other store of ancient carbon
comes from and how it's made.

That is just plain weird.

Look at those colours!

I'm heading for some caverns
that are even deeper underground.

Phew!

Oh!

This...has got to be the toughest

and scariest cave climb I've ever done.

There's 100 metres
of solid rock above me,

but it's going to be worth it,

because ahead is one of the most
unusual cave systems in the world.

Most caves are made from solid rock.

This cavern is different.

Oh, wow, look at these!

These are stalactites.

They're the weirdest ones
I've ever seen.

Normally, stalactites
are made of limestone

and they drip vertically down, but these,

if you look at them closely,

they're made of small crystals
that twist and turn.

You can check what they're made of
really easily. You just need to lick them.

Wow! Yeah... salt.

Written in the roof is a clue
to where the salt came from.

This magnificent, striped banding
is a real giveaway clue.

The layers are formed
when seawater evaporates away,

leaving behind
a thin residue of salt crystal.

This is all evidence that the salt rock

was originally laid down
in an ocean that dried up.

To create so much salt, you need
to evaporate an awful lot of seawater.

Usually, this happens in shallow seas

which get cut off
from the rest of an ocean.

Seawater then evaporates,
leaving behind a thick layer of salt.

But it's not only salt
that gets left behind

when an ocean evaporates.

Shallow seas are the most biologically
productive part of the ocean.

They're teeming with life...

...all made from carbon.

When marine creatures die,
their skeletons build up on the sea floor.

Over millions of years,
these skeletons are transformed

into a sludge of carbon and buried
under sediment and layers of salt.

One of the best places to see
what that sludge ends up looking like...

...is in the republic of Azerbaijan.

Here they call it naftalan.

It's been used as a health treatment
for thousands of years,

hailed as a cure for everything
from rheumatism to baldness.

Look at that!

That looks disgusting!

It's said that 4,000 years ago,

the Babylonians mixed this stuff with beer
and drank it as a medicine.

But there is another way
to enjoy its healing properties.

Ah...

Ugh! It's so weird!

Ah...

Ugh!

It's so clingy.

Oh, my God!

Oh...

Ah...

People have been doing what I'm doing

way back to the time of
the ancient Persians, although Lord knows

what made them get their kit off
and start to bathe in this stuff.

I must admit, when I first saw it,
it looked absolutely disgusting.

The feeling of it being warm and clingy
was horrible.

But now, after five minutes,

it still feels absolutely disgusting.

Just as well this isn't its only use.

You known, I think I can smell
someone smoking,

which is making me a bit jittery,
because...

well, because this is oil.

I'm lying in a bath of petroleum.

Ugh!

Today, we've thought
of a few more ways of using oil.

It's the ultimate source
of concentrated carbon energy.

It's more energy-rich than coal,
easier to transport,

and it's got a million different uses.

The use of oil is the pinnacle
of our mastery of fire.

Fittingly, the first country to benefit
from the exploitation of oil

was the home of naftalan...

...Azerbaijan.

For centuries, this thick,
black, oily sludge

was dug out of the ground here by hand,
on a small-scale basis.

But in the middle of the 19th century,
demand for oil really took off,

and what had been a cottage industry
turned into this.

Within 20 years,
these fields were the site

of the first great global oil boom.

From across the world,

entrepreneurs rushed to Azerbaijan
to make their fortunes.

Some succeeded so well
that their names are almost legendary.

The Shell oil company started life here,
and the Nobel brothers of Nobel prize fame

built their business empire on Azeri oil.

This place oozed money!

By the early 1900s,

Baku, the capital of Azerbaijan,

boasted more millionaires
than anywhere else on Earth.

But Azerbaijan really owed
its sudden wealth to a fluke of geology.

In the land of naftalan, oil happens to be
exceptionally close to the surface.

You can see how close at an unusual
location in the south of the country.

If you want to appreciate why this country
was the site of the first great oil boom,

you don't have to look any further
than these curious mounds.

It's not so much the mounds
that's interesting,

it's what's bubbling out of them - mud.

But not just ordinary mud.

Look what happens when I do this.

D'oh!

The reason it's flammable is
that the mud is full of natural gas,

which is formed along with the oil.

You know, these things are like
miniature volcanoes, really...

...except that rather than hot,
molten lava spewing out of the top,

it's just mud.

The thing is, you can dig into them,
and you can see

what the kind of plumbing is like inside,
which is exactly what I'm doing now.

Ah, now, look at this, look at this.

You can see it in here.

Mud is just bubbling up in this cavity,
and then there's a little vent pipe

that carries it up to the top,
where it spews out.

There were few places on Earth

where it was easier to extract oil and gas
than Azerbaijan.

But by the start of the 20th century,
demand for oil was rocketing,

and new sources had to be found.

Once again, the Earth's distant past
would play a decisive role

in meeting our needs.

The big question is why a few lucky places
ended up with huge oilfields,

but others didn't.

I don't think it's an exaggeration
to say that the answer to that puzzle

has shaped the global geopolitics
of our age.

It's probably the most powerful way that
the Earth has influenced human history.

After Azerbaijan
faded from prominence,

the Middle East became the key
oil-producing region in the world.

It owes this good fortune
to a chain of events that began

almost 300 million years ago.

Back then, the two areas

that would one day form most
of the modern Middle East were separate,

but they were on the move.

Remarkably, as they moved,

both areas spent much of the time
submerged by shallow seas.

So layer upon layer of dead sea creatures
built up on the ocean floor.

And when, periodically,
the seas evaporated,

layers of salt were also deposited.

As the modern Middle East came together,

these layers were buried
deep inside the Earth,

where the heat and pressure turned
the dead sea creatures into oil.

But the Earth played one final role
in turning this area

into the dominant oil-producing region
in the world, and to see what it is...

...I've come to an unusual
mountain range in Iran.

The drifting continents
helped form the oil, but in most areas

the oil was buried deep in the Earth.

Too deep to be exploited.

It needed to be brought closer
to the surface,

which is where salt returns to the story.

As a geologist, I've been lucky enough

to go to a lot of places
and see a lot of rocks,

but nothing really prepares you
for what you find here.

Cos here I am, walking in the scorching
desert sun, looking down on a glacier.

But that isn't made of ice -
it's made of salt.

This whole mountainside
is covered in salt

that's oozed upwards
from deep inside the Earth...

...the remains of a long lost ocean.

You know, this is
such a surreal landscape.

What's hard to take is that virtually
everything under my feet is moving.

You can see that - look at this here.

Look at these cracks
that are opening up in the salt

as it opens up and then closes again.

And then also, here and there...
Look, there's a bit.

This was carried down the glacier
by the salt from somewhere up there.

I mean, this is exactly what ice does.

Salt is similar to ice because it's soft
and plastic, which is why it flows.

On the Earth's surface, this means it can
slide across the land like a glacier.

But even more spectacular

is the role it played underground
in the formation of oil reserves.

As the continents collided
to form the Middle East,

layers of salt and oil-rich rock strata
began to buckle upwards.

The salt made it much easier
for the rock to bend, until eventually...

...it cracked.

Now the oil could flow upwards until
it was trapped in a fold in the rock,

kept in place
by an impermeable layer above.

The salt helped the rock slide easily,

acting as a kind of lubricant,
creating huge folds called anticlines,

which were perfect for trapping oil.

And where there are oil traps,
there are generally oilfields.

If you take a look at a map
of the world's buried salt deposits, .

and overlay the major oilfields,

it's easy to see why geologists
searching for oil go looking for salt.

It takes millions of years,

and some pretty extraordinary
geological events, to create

an oil trap that we can exploit.

So it's not surprising that only
a few countries have oil beneath them.

And when they find it, there's
almost no limit to what they'll do

to get it out of the ground.

Nowhere symbolises this determination
more than this town

in the former Soviet Union.

At first glance, this looks like
your typical Eastern European town.

You've got your standard-issue
apartment blocks,

and the architecture has got
a real industrial feel to it.

It was first started in the 1940s.

It's got a football team...

...and even a mosque.

This place is called Oily Rocks,

and over 2,000 people
live and work there.

If ever there was a monument
to our obsession for oil, then this is it.

Because what you don't see
from the ground is that Oily Rocks

was built in the middle
of the Caspian Sea.

It's 50 kilometres from dry land.

Over the years, more than 600 oil wells

have been drilled from these platforms.

Today, Oily Rocks is still producing oil,
but it's past its peak.

And that about sums up
our relationship with oil more generally.

Today, we're burning it far faster
than the planet can make it.

It would take the Earth
three million years to make enough oil

forjust one year
of our consumption.

We've reached
a turning point in human history.

Every major advance in human civilisation
has been made possible

by our ability to raid the Earth

for ever more energy-rich forms of carbon.

But our love affair with burning
carbon-based fuel is coming to an end.

Carbon itself
has become the problem.

Burning it produces greenhouse gases
which are changing our climate.

And that means if human civilisation
is to continue to advance,

we will have to break the link between
progress and the burning of carbon.

Next time,
a very different planetary force...

us.

We are changing
the surface of the planet more

than all the forces of nature
put together.

But are we threatening the Earth's ability
to support human civilisation?