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One of the world's largest airships is taking a team of scientists

and explorers on a unique expedition.

A voyage deep into one of the most mysterious and precious

environments on earth.

The atmosphere.

It's in every breath you take.

It is a home to life...

..and it makes the weather.

So, we have this dynamic bubble of air, constantly moving, constantly

changing and that's what we're here with Cloud Lab to explore.

This quest is taking the team coast to coast across America.

So far, they have experienced the powerful weather systems of

the Southern coast.

You can feel the energy in the air around you.

It's absolutely fantastic.

Now, they are heading across a different kind of landscape -

the deserts of the west to the Pacific Ocean,

to explore three key themes.

Oh, wow!

Life - they will investigate the relationship between life and the

layers of the atmosphere right up to the death-zone of high altitude.

We've got every reason to think that there is life up there.

And the more interesting question, I guess, is how much is there

and what's it up to?

Climate - they will experience the surprising way in which the

atmosphere can transform the ocean...

Another giant-sized animal. This whole place is like super-sized.

..and human impact -

the ways in which we, ourselves, are changing the atmosphere.

We've hard evidence that human beings are creating

their own weather.

Checks for take-off then, please.

INAUDIBLE RADIO CHAT

The Cloud Lab Team are setting out on the second half

of their epic voyage, heading west across the United States.

From Texas, they will journey from airfield to airfield through

the arid west before concluding the expedition on the Pacific coast.

But as they meet the desert, there's a dramatic change in the airship's behaviour.

Expedition leader, Felicity Aston, wants to know what's causing it.

What's happening with the movement?

We've suddenly started making really steep climbs and sharp descents.

We've just started getting some thermals now.

So we are getting these rising bubbles of air from the surface.

When we fly into it, it lifts the nose up then as we continue

it lifts the whole body up, and then as we move further it lifts the tail up

so we've got a correcting motion that pushes us back down again.

It's really quite steep. We're pointing to the sky one minute,

and then down at the floor the next.

It can get quite extreme at times, yes.

You get used to it. Really? Like sea-sickness? Yes.

You all right? Yeah.

Despite the discomfort, it's the airship's ability to fly with the

currents of air that allows the team to pursue one of their key themes -

the relationship between life and the atmosphere.

They want to know how conditions change through the different layers

of the atmosphere and how that impacts upon the life found there.

So, Felicity and atmospheric chemist, Dr Jim McQuade,

are fishing for life in the layer of air that is the most dynamic

and closest to the earth. It's called the boundary layer.

We've got two - we've got two different ones.

By flying through this layer, they hope to shed light on one particular family of creatures...

He's pretty gorgeous.

..insects.

Whilst we're familiar with the lives of insects close to the

earth's surface, some have another, little known existence higher up

in the atmosphere.

The team are going to try and discover whether they get

blown here accidentally or are they exploiting atmospheric

conditions found in its different layers?

Elsewhere, another Cloud Lab team member

is targeting a different layer of the atmosphere

and another kind of life.

Microbiologist Dr Chris Van Tulleken is setting out

to find living bacteria in the high altitude death zone.

And the microscope I want to do last, just because it is so dusty.

He's brought in a specialist researcher, Noelle Bryan, to help him.

I need to get a sample of sky that's ten times higher than the samples

we've got before. So we're going up to almost 30,000 feet from...

you know, the cloud samples were from about 1,000 and 3,000 feet

so we want to find out if there are bacteria up there

and that's what Noelle is very, very expert at.

With this experiment, Chris is hoping to build upon some remarkable findings of his.

Earlier in the expedition, he discovered that the skies are alive.

We've got evidence here that we've got bacteria in clouds

and that's right at the cutting edge of science.

Chris not only detected bacteria in clouds, he revealed that

they played a significant role in making rain. Now, he's looking

for life beyond the clouds, upwards of 10,000 feet

to a layer of the atmosphere called the free troposphere.

Far away from the influence of the earth's surface,

the free troposphere is cold, desolate and bone dry.

Even for bacteria, this is an extreme environment.

Every time you look for a place where nothing should be able

to survive, there's always a microbe that can take it,

so that's what we are looking for.

Who is the hardiest, who is the toughest?

Who can take the desiccation, the low pressure,

the increased UV radiation?

Humans are wimps. We have a small temperature range.

We have a very defined set of environmental conditions

that we can survive.

Perhaps not all humans are wimps.

The free troposphere is far beyond the flight ceiling of the airship,

so Chris and Noelle have enlisted

the services of former paratrooper, Andy Torbet.

The idea is that I'm going to jump

out of a plane at about 26,000 feet and parachute

all the way back down to earth, collecting samples as I go.

The experiment will involve Andy attempting a highly technical jump

called a High Altitude High Opening, or HAHO.

It's usually the preserve of elite, special forces.

There's a lot of problems with sky diving from

26,000 feet so people don't do it.

One. The air is so thin, it's very, very hard to get stable.

You need to get stable within 3-5 seconds in order to open your chute.

If you open your parachute any longer than sort of 5 seconds,

you pick up so much speed again because the air is

so thin that when you open you get what's called a hard opening

and that actually has enough force to break your spine.

Bearing in mind that when I open my parachute at

26,000 feet it's going to be minus 28, minus 30

so it's going to be bloody cold as well.

And the air is so thin, there's so little oxygen,

if you don't have an oxygen supply, like a mask on,

you're going to suffocate and die within about a minute.

So it's a fairly hostile environment.

Very little is known about life at the altitudes Andy is

reaching for but as we look for life beyond our planet, finding what

can survive earth's extreme habitats is taking on new significance.

It also requires a novel, scientific approach.

The principle is presumably going to be, Andy flies up.

He's got a petri dish or a growth medium dish.

He opens the lid.

Then closes the lid before he hits the ground and there's our sample.

But presumably it's a bit more complicated than that.

The idea is the same.

We're going to have a device that goes up.

It's going to open.

We're going to catch a sample, close the doors and bring it back down.

Only, instead of one surface of a Petri dish,

with these plastic rods we're able to have 40 different surfaces.

So, it's sealed. He goes up, opens it,

the air goes over and then before he hits 10,000 feet, closes.

Seal it back up.

And that's our sample.

Then we bring it back here and we can work out what it is.

And then we can do all sorts of different things.

A lot now depends on what Andy can achieve.

Over the coming days, he'll put the finishing touches

to weeks of preparation,

working with ex-special forces skydive master, Dane Kenny.

Two minutes.

Dane will supervise Andy as he jumps from increasingly high altitudes.

Acclimatising to the changing nature of the atmosphere.

Cloud Lab biologist, Dr Sarah Beynon, has joined the expedition

to further the survey of insect life.

What time is it now? Seven...

For Sarah, it's yielding some surprising insights into

exactly which insects are found in the boundary layer,

and at what altitude.

Bear with me. So, that's a flea beetle.

And I haven't seen any data of these being found at altitude before.

We had no idea that these insects were up there.

A lot of what we do know relies on radar which tells us

what's up there in terms of the abundance but we have no idea

what makes that up so tiny insects like this,

we can't tell what species of insect are up there.

So it's only through deploying something like this

that we have any idea of what is flying at those altitudes.

Now, Sarah wants to seek out evidence for one particular relationship

between insect and atmospheric condition.

So I have a spare net, so I'll put that one in.

OK, thank you.

Can you record the altitude, as well please Jim, and the time?

What time is it now?

Uh, 7:03. OK.

The aim is to roam the vastness of the sky to intercept

a noctuid moth, one of a family of different species.

To do so, they must first wait for nightfall and a radical

transformation of the atmosphere called the nocturnal inversion.

How high are we now? Er, Nine hundred feet.

Nine hundred feet? Yeah.

As the sun goes down, the air that sits above the earth cools

more rapidly than the air at high altitude and that can create

fast-moving streams of air.

Noctuid moths are believed to use this nocturnal inversion to migrate

as far as 600 miles in a single night

by selecting the most favourable air streams...

..but rarely have they been caught in the process.

Sarah aims to change all that.

The moths at this time of night should be making their way

up into the higher airspace to migrate.

So we should catch them on their journey upwards. Yeah.

The airship's sensitivity to atmospheric conditions

pays dividends as it drifts with the air currents.

All they can do now is sit, wait and hope

that the moths are on their way.

Ooh a moth!

No kidding! No there really is a moth, where did it go?

Hang on. OK, lights? I haven't got my net with me.

Shine a light somewhere and keep it there, to keep the moth to it.

A moth has flown in through the window.

I need to get a net, OK, thank you.

Oh, it's here, it's here!

Whoa, whoa - gosh, where's it gone? There.

OK, could you grab the killing cloth please?

We've found a moth!

The net isn't collecting them, but it's just

flown in at 500 feet above the ground, which means they're here!

OK, we need to be careful as I need to know what species it is.

I think what we'll do is just shove the whole net in

to be on the safe side. Awesome!

Teamwork! Excellent!

PILOT: Ready for landing, OK?

Sarah will need to get the moth under better light to identify it.

Only then can she be sure if it's one of the migrating noctuid species

taking advantage of the night-time air.

For the airship's 15-strong ground support team,

the night has just begun.

After several weeks of flying, the airship has been venting helium

in order to adjust to different altitudes. Now it needs topping up.

Well, this is the second rack here we've probably got at least two more.

We've been here about an hour so far so maybe another couple of hours.

Taking care of the airship all the time - it needs constant attention.

It's a very demanding mistress.

Sarah is drawing together the haul of insects from the survey.

Already, she's discerning a difference between the insects that

travel by day and those that travel by night,

including the one that flew into the airship.

In the daytime, most of the insects we caught were small,

like this leaf beetle

and these insects would have been carried up by the

turbulent daytime air and would have been at the mercy of the winds.

Whereas at night-time, everything started to get a bit more

interesting and every single time we flew at night,

we caught migratory, noctuid moths.

We've got a fall armyworm moth here

and these moths, they migrate northwards in the spring

and summer to make the most of the agricultural crops that are

growing and they decimate crops such as corn and cotton and then they

migrate...well, we think they migrate southwards again in the fall.

But we know very, very little about this fall migration

so any individuals we find in the fall is really, really useful.

The study demonstrates how insects exploit the varying conditions

of the sky at different altitudes and times of day.

Other research suggests that insects exploit the dynamic nature

of the boundary layer on a vast scale.

So, in a 1km square patch of countryside surveyed over the course

of a summer month, as many as 3 billion insects pass overhead.

The question remains, how much life exists

beyond here in the higher atmosphere?

Is that tight? Yeah, that's tight.

It's a question Andy hopes to soon help answer by undertaking

the HAHO jump. At more than 26,000 feet,

it will be the highest he's attempted yet.

Remember, the priority is safe parachuting.

So I know this is very important,

but we can't do that if you've got an issue with the parachute.

Happy? Happy. Good.

Right, let's get out there. Look at that.

Steady as a rock but I shoot with this hand.

You'll be fine, mate.

Andy will have just one attempt to get the precious air sample,

and with it, a chance of finding microbial life.

The weather is closing in and safe conditions

are unlikely to return for days.

Before going to altitude,

the entire team must flood their lungs with pure oxygen.

If not, there's a risk that the nitrogen in their blood

could form bubbles, leading to the bends.

Without this and other precautions against

the sub-freezing temperatures and desperately dry air,

Andy would be dead within seconds.

It raises the question of how ANY life, even bacteria,

can survive extreme altitudes.

The answer could lie in another form of microscopic life,

one that has an extraordinary adaptation to aridity.

These are things called tardigrades or water bears

and they are unusual because they're extremely small and they can

survive complete desiccation, so complete drying out and this is

a desiccated, a dried out tardigrade here magnified on the microscope.

They are in a state of almost suspended animation.

The chemical processes that drive life are at a virtual standstill.

But it takes just a few drops of water to re-animate it.

When you run water over it, you see the chemical reactions start

happening again, absorbing the water and is now very obviously alive.

And it's gone from chemically dead, chemically totally inert, to now

being, you know, obviously quite an adorable little living thing.

It's got little legs and kind of a little face there.

Whilst the transformation is plain to see,

the secret to the tardigrade's survival is what's happening within.

We think that the way the tardigrades survive those

environments is by being able to tolerate the DNA

and protein damage that comes from being terribly dried out.

What they have is very, very good DNA repair mechanisms.

Chris believes that bacteria at high altitude

may use these same repair mechanisms to withstand the aridity.

Finding live specimens will go a long way to suggesting as much.

That now depends on what happens when Andy meets

the vanishingly thin air.

If Andy can't get stable, he'll have to free-fall to where the air is dense enough to slow his descent.

God, he's got a lot to think about.

It's much, much more skilful than I thought it was.

Andy's botched the exit and is struggling to get stable.

Despite the poor exit, Andy managed to open his parachute within

the vital first few seconds.

Now, he has to gather the sample.

The box must be closed at 10,000 feet.

If not, he will expose the sample to the lower atmosphere

where life can more easily exist.

There he is.

The reason I get Andy to do this is because he's a much better

microbiologist than I am a sky diver.

Andy appears to have pulled off the job.

But there's one thing the team haven't foreseen

that jeopardises the entire experiment.

Oooh!

Now, the sample is at risk of contamination.

You all right, mate? How you doing?

It was a good landing.

What I wasn't expecting is my feet were dead.

I had no blood in my feet. They were numb, really?

Your shoes are freezing cold. Because I've been

sitting in this harness 20 minutes,

my legs were completely numb and they just gave way on me.

Well, never mind that, let's make this safe.

Good. Right I'm going to get this to the lab. OK, mate, no dramas.

The sense of relief is just... It was weird.

You don't notice the kind of the amount of stress or pressure

that's on your shoulders that's built up over the last three months

until it's taken away.

And suddenly you're like... It's gone, we've actually done it.

There's an element of kind of disbelief we've actually

pulled this off.

I got to jump the HAHO

and I managed to pull it off without seriously

injuring myself or killing myself, so, er... It was really good.

No-one's ever done it like this before.

But you know, if you work out how much of the air up there we've

passed over the rods, we should get something sticking and all we want

to see is that there's something up there, you know it's... One

or two bugs and we can amplify them, grow them, work out what they are.

It's a lovely thought isn't it, this,

got a little bit of troposphere in here.

It's really nice.

Noelle! Is this it?

That is it.

Did you think we were going to get this, honestly?

No.

Andy's slow descent through more than 16,000 feet

of high-altitude air has given Chris and Noelle the best chance

of finding microbial life.

It will require forensic precision to ensure it wasn't in vain.

It's worth explaining that while we do this, sterile air is

flowing from this all over this surface so that no bugs can get in.

So even if a piece of hair falls off Noelle's head,

it won't land on the sample.

This is what I do all day virtually every day in London.

And I think it puts a lot of people off doing science

because it seems super mundane but it isn't.

This is where we... This is where we get the answers.

The best bit is not the skydiving.

The best bit is the answers.

Now we want to have a look at it on the microscope.

And in order to look at it, we're going to stain it with another dye.

We're going to stain it with this stuff which stains nucleic acid

so, things like DNA. Again, only life has nucleic acid, so it'll

stain that and then we'll be able to see the objects more clearly.

Once the sample is stained,

any cells will reflect back the light emitted from the microscope,

showing up as tiny glimmers of green.

There you go. You see...

You think there's going to be nothing there don't you,

you're just looking in to blackness and then -

what I was hoping to see and what I can see - is every

once in a while you move the microscope and that's what you see.

You just get that little beacon of a green dot.

Just a little green glow.

And each of those little green dots - those are cells.

The amazing thing is it's one thing

seeing the DNA glowing in the right size and shape of a bacteria

but the fact that it's alive, that is a really peculiar thing.

To find dead bacteria up there yeah, maybe.

To find living stuff up there is such a harsh environment.

No oxygen, its freezing cold, low pressure,

high winds, you know, no water. No water.

Amazing.

The experiment joins a growing band of scientific research into life high in the atmosphere.

The picture that is emerging is that life is far more robust than ever imagined.

And that opens up all sorts of possibilities

for the prospects for life

in other extreme environments beyond our planet.

PILOT SPEAKS OVER RADIO

The airship is heading to the desert city of Phoenix, Arizona.

What's drawing the team here is another of their key themes,

the way in which we, ourselves,

can change the way the atmosphere behaves.

Earlier in the expedition, Felicity and atmospheric chemist,

Dr Jim McQuade, uncovered the surprising link

between pollution, clouds and extreme weather.

So what we're saying is that by cleaning

up our atmosphere, we've allowed there to be more hurricanes.

They're now hoping that Cloud Lab will enable them

to get to the bottom of another question

about our impact on the atmosphere -

can cities make their own weather?

So, I've been looking at historical data

and you can see that Phoenix, in the last 100 years, has gone

from being a really small, agricultural settlement into a large, urban city.

In the same period of time, there has been a distinct

change in the amount of rainfall in the city.

There are areas of Phoenix that have had up to

a 12% increase in the amount of rainfall which is really significant

and it looks like there might be a correlation between the two.

So, we want to see

if we can unravel how the city might be creating its own weather.

It's difficult to imagine that a single city could interfere

with a process that unfolds on such a grand scale as the weather.

The rain that falls here has followed the same cycle for millennia.

Every summer, warm, moist air is swept up from the oceans

to the South. As this air meets the hot desert,

variations in the landscape drive pockets of air upwards as thermals

where the moisture cools, condenses and ultimately falls

in sudden downpours of rain.

Where this rain occurs should be fairly random...

..but something appears to be concentrating it upon the city.

To see why, Felicity is going to start by surveying temperatures in Phoenix and the surrounding desert.

I took several readings of the surface temperature and I was

getting between 37 and 38 degrees centigrade.

So, it's pretty hot down there,

it's soaking up all the heat from the sun.

For the city to be concentrating rainfall, it needs to be

hotter than the desert, driving extra thermal activity.

Meanwhile, Jim is surveying another factor that could be increasing rain - humidity.

A hygrometer gives an on-the-spot reading of how much water vapour

is being carried in the air.

The dry bulb was 24.5, giving

a relative humidity of 26%.

So, the air's very dry here, which is actually the definition of a desert.

It's nothing to do with temperature.

It's how dry it is,

so that's why Antarctica can be classified as a desert.

Unsurprisingly, in the desert, there's plenty of heat but no water.

But what really matters is how this picture compares with the city.

OK, another measurement next to an orange tree

and a lemon tree in someone's front garden.

It's not like back in Leeds - got an apple tree.

45% relative humidity.

It's very obvious that there's a lot more water available to be

evaporating into the atmosphere just from manicured lawns.

There are lots of sprinklers down here.

Increased humidity is a consequence of the millions of gallons of water

diverted to the city from the surrounding rivers.

I'm getting a real variety in surface temperatures.

So, if I take a reading from the road or a car park, it's pretty much the

same surface temperature as in the desert, but if I point the camera

at a garden or a swimming pool or a roof top, then it's a lot less.

So, on average, the surface temperature here will overall

be a lot less than the desert.

The city is more humid and a little cooler than the surrounding desert.

Despite these differences, there's no evidence

for the increased thermal activity that can explain the rainfall.

As the day wears on, that picture soon changes.

See, look, look, look, look! See the city...

Yeah. .it's hotter than the desert.

OK, yeah, you can see definitely the boundary.

So that's the desert cooling down

and that's the hot city.

That's a really nice example of it.

Whilst the natural landscape has quickly cooled,

the camera reveals the city to have remained warm.

They've identified an effect called the urban heat island.

Earlier today we measured the ground temperature of the suburbs to

be 24, 25 degrees, and see I'm measuring 23, 22.

I mean, it's still as hot as

when we measured it in the middle of the day.

The city's surfaces are continuing to radiate the energy of the sun

they absorbed earlier in the day.

The question is whether the urban heat island is generating thermals.

If it is, they should be able to detect

an increase in temperature at altitude from the airship.

So, I've just had a look the temperature

and this is the temperature going down and that's going down simply

because the sun's going down, you know, we're turning the heater off.

So, this is the temperature over the desert

and this is the temperature over the city.

Oh, wow, so this is where we hit the city? Yeah. OK, this is us...

this is the temperature over the desert and then

we hit the city limits and the temperature quite clearly goes up.

It's not a huge increase, you know, no more than half a degree,

but you can't argue with that. That's a definite.

Despite the difference in temperature being small, it's critical.

It's enough for us to know that the

air above the city is warmer.

So we've got this big parcel of warm air sitting over the city.

It makes a lot of logical sense that that air is going to start rising and

that's going to start convection and the consequence of that is weather.

So the increased rainfall in Phoenix could be caused

by the urban heat island effect.

It generates thermals over the city that force air upward where it

begins to cool.

That, in turn, can cause the vapour to condense

and form rain concentrated here upon Phoenix.

So, we've found

the connection we were looking for, between cities, and the increased

rainfall that Phoenix has been experiencing in the last 100 years.

And the really exciting thing about that is that we've hard

evidence that human beings are creating their own weather.

It's a finding that threatens to have far-reaching consequences.

Our world is increasingly urban and much of that urban expansion

is taking place in sparsely populated arid regions...

..with unknown consequences.

If you take an area of desert and build a city on it,

then that city is going to be much warmer than the desert it's replaced.

And it's going to have an overall warming effect.

So if you multiply that by all the cities being built in desert

areas, all this turning from desert land into green agricultural,

irrigated land, then it leaves another little hanging question,

whether this is having a much larger global effect on our climate.

The airship has reached the western edge of the desert.

Beyond here lies their destination...

..the mighty Pacific, where the team want to conduct their final

set of studies.

An exploration of how the prevailing onshore Pacific wind shapes

the wildlife of the entire Californian coastline.

And that includes the life below the ocean surface.

But first, the airship will have to overcome the Pacific wind.

We're so close to the end of our journey that we can

almost smell the Pacific Ocean.

But there's one last obstacle. These mountains behind me.

There's only one pass through these mountains for miles in either direction.

It's called Banning Pass and it's a bit of a problem for the airship

because it's so narrow. All the winds are funnelled through.

And the winds come from the west towards us so it's going to be flying

into the winds and if there's too much wind, it could take hours, days.

Perhaps we could even be waiting for a week

until conditions are just right.

Even if the wind is blowing a gentle breeze on the far

side of the pass, by the time it reaches the entrance

the funnelling effect can accelerate it to gale force.

We seem to be hitting a lot of turbulence.

The wind is gusting and coming down the valley here.

There's two big mountain ranges coming together to give us

just this one little gap down the middle, so it's much rougher air now.

So you are really having to fight to keep it level?

It's a continuous fight

but at the moment we're making slow progress.

OK, so what's our ground speed at the minute?

About five knots. Five knots? 6mph.

It's very bizarre. We are in this unseen jet stream of air.

So these engines are going fast enough to propel us at 30-40 knots,

but unfortunately the wind's coming in the opposite direction

at 30-35 knots, so we're only making only 2 or 3 knots ground speed.

We've barely moved at all. About two miles in the last hour.

Co-pilot: It's actually getting worse right at the moment.

We've actually stopped.

I don't think we're going to be going through today.

The vast wind farm here one of the largest in Southern California

is testament to the winds near-constant presence.

We're definitely starting to move forward.

Back there we were not,

now we are definitely moving forward a wee bit.

CO-PILOT: Yeah, there we go. We are going it a little bit here.

Despite Felicity's worst fears it seems as though they have

chosen the right day to make their move.

Sarah has gone ahead of the airship to experience the power of the

onshore Pacific wind for herself.

We are going to do a little bit of scratching here,

when we are close to the cliff edge.

And scratching is doing what?

Well, when we are very close to the edge of the cliff... Like this?

Yeah. Scratching is our term.

This is where the most lift is, close to the cliff edge.

Sarah and Kirk are being carried on a type of air

movement known as ridge lift.

As the onshore wind hits the cliff, it is diverted

and accelerated upward.

But the real reason Sarah is here is to see how this movement of air

supports life.

Home! Shanty!

Good girl.

Oh, wow! Unbelievable, huh? Oh!

So this is Shanty, who is a trained bird

and she's using the same updraught that we're using. Up!

Shanty is a Harris hawk.

A native to this region, they are so highly evolved to

fly on the movement of air from ridge lift to rising thermals

much of their flight time is spent soaring.

Wow!

You can really see her wide, fairly short wings

and that's an adaptation to soaring.

Look at her soaring up there now.

And it's great to see the sort of finger-tips of her wings that

she's using to control her flight.

It's a behaviour found throughout the family of birds called raptors

that also includes eagles and vultures, enabling them

to extend their range to vast distances.

It makes sense for them to use these up-draughts

so that they expend as little energy as possible when they are hunting.

Exactly. And the raptors own motto, like any good predator,

is the maximum amount of reward for the least amount of effort.

So if they can stay up without putting much energy into it,

that's great.

Here she comes again. Goodness me.

Good girl!

Hang on, it's the Pacific, it's the sea!

You should have your bikini on, we should be there in swimming trunks!

We've made it.

This is the ocean, we've made it. Fantastic!

So, Atlantic to Pacific.

It's not quite journeys' end.

The team have chosen this particular destination to explore

a surprising relationship between life and the Pacific wind.

What's that there!? Ah, yes!

What is it then go on? A Blue Whale.

Is it really? Really.

I've never seen a Blue Whale before. Look at that. Wow!

Hang on, there's more than one. There's two of them.

These are just the first indications of what they have come to see

because the wind can make habitats in the ocean too.

This is Monterey Bay, California.

Beneath its gleaming surface is a uniquely fertile eco system...

..that makes this one of the most biodiverse habitats in the earth's oceans.

There you go, there you go. There's two more of them right there.

The charismatic megafauna. Charismatic megafauna.

Chris and Andy have joined local marine biologist,

Steve Lonhart, to understand how this rich environment is

created by the wind.

If you can imagine the wind which is coming from

the northwest, so kind of over our shoulder, moving in this direction.

As it moves that way,

it actually just pushes the warm waters of the surface off,

and then you get this really cool nutrient rich water that's coming

up from the bottom, right where we are, right here, coming up from

the bottom and that's sort of like...you can think of it like fertiliser.

Meaning dead sea lions, dead kelp,

anything that dies, birds, all falls to the bottom?

Falls to the bottom,

and it is broken down into all its little constituent members,

that eventually just dissolve into the water.

When the water comes up, its clear, which allows things like kelp

and seaweeds, to do what they do which is photosynthesise.

Just like plants on land nitrogen,

carbon, building blocks of life.

And instead of those things being in the air and the soil,

they're dissolved in the water. That's right.

Then you have a forest, not on land,

it's actually on the shore.

To see the result of this process in its full majesty you have to

look beneath the surface...

..and to the unique environment that it creates.

The forest of giant kelp.

Not only does the kelp benefit from the nutrients drawn

up from the depths,

it is also bathed in the energy of the sun, allowing it to

reach 175 feet in height.

Ah, so these are the giant kelp.

You see the little bubbles?

Awesome, and that's what holds the giant kelp up.

Chris, this is Andy. Go ahead. Over.

Every square inch of this entire system all the rocks,

the nooks, the crannies - are all teeming with life.

There's not a square inch that's left bare and barren.

There's life everywhere. Outstanding again.

How does this compare with other dives you've done?

This whole place is like a normal sort of temperate

reef but just much, much, much bigger.

Everything has been super-sized.

It's huge.

It seems like all the life

down there is scaled-up enormously because of this nutrient-rich water.

I've just seen the biggest anemone I've ever

seen in my life. It's huge.

I've never seen an anemone that I would consider a man-eater,

but if there ever was one, this is it.

This is probably the best sight so far. I'm coming up.

I'm rising up the trunks of these huge, giant kelp.

Whilst this may be a very special environment, it also

vividly demonstrates the power of the atmosphere to reach into every

corner of the planet and make it a place for life.

For me, it really provides an insight into just how complex the atmosphere is.

It's not just something that we breathe and that produces

weather, it has the ability to shape the landscape underneath it.

It plays a huge part in forming the environments in which we all live.

Reaching the Pacific brings to an end what has been an extraordinary

and unique adventure.

This epic journey coast to coast

has enabled the team to experience the atmosphere as never before.

That's the one I want! That one!

They've explored the extraordinary processes that generate weather...

20 million. So, that small cloud weighed four tonnes? Yes.

That's incredible. It is.

..they've seen some of the many ways that life - at every scale

from microscopic bacteria...

Now we are sucking in the cloud.

..to more familiar species exploit each level of the atmosphere...

Good luck, little one.

These waterfronts, they are vital for movement,

not just on a small scale, but on a global scale.

..and they've revealed the often complex mechanisms by which

we, ourselves, are shaping this realm.

Cheers, everyone! Cheers, guys.

Cheers! To the Pacific!