0:00:11 > 0:00:16One of the world's largest airships is taking a team of scientists
0:00:16 > 0:00:19and explorers on a unique expedition.
0:00:22 > 0:00:28A voyage deep into one of the most mysterious and precious
0:00:28 > 0:00:30environments on earth.
0:00:35 > 0:00:37The atmosphere.
0:00:39 > 0:00:41It's in every breath you take.
0:00:43 > 0:00:45It is a home to life...
0:00:49 > 0:00:51..and it makes the weather.
0:00:52 > 0:00:58So, we have this dynamic bubble of air, constantly moving, constantly
0:00:58 > 0:01:02changing and that's what we're here with Cloud Lab to explore.
0:01:04 > 0:01:11This quest is taking the team coast to coast across America.
0:01:11 > 0:01:15So far, they have experienced the powerful weather systems of
0:01:15 > 0:01:16the Southern coast.
0:01:17 > 0:01:20You can feel the energy in the air around you.
0:01:20 > 0:01:22It's absolutely fantastic.
0:01:24 > 0:01:29Now, they are heading across a different kind of landscape -
0:01:29 > 0:01:33the deserts of the west to the Pacific Ocean,
0:01:34 > 0:01:37to explore three key themes.
0:01:37 > 0:01:39Oh, wow!
0:01:39 > 0:01:43Life - they will investigate the relationship between life and the
0:01:43 > 0:01:48layers of the atmosphere right up to the death-zone of high altitude.
0:01:49 > 0:01:52We've got every reason to think that there is life up there.
0:01:52 > 0:01:56And the more interesting question, I guess, is how much is there
0:01:56 > 0:01:57and what's it up to?
0:01:59 > 0:02:03Climate - they will experience the surprising way in which the
0:02:03 > 0:02:05atmosphere can transform the ocean...
0:02:08 > 0:02:13Another giant-sized animal. This whole place is like super-sized.
0:02:16 > 0:02:18..and human impact -
0:02:18 > 0:02:24the ways in which we, ourselves, are changing the atmosphere.
0:02:24 > 0:02:27We've hard evidence that human beings are creating
0:02:27 > 0:02:29their own weather.
0:02:40 > 0:02:42Checks for take-off then, please.
0:02:42 > 0:02:45INAUDIBLE RADIO CHAT
0:02:55 > 0:02:58The Cloud Lab Team are setting out on the second half
0:02:58 > 0:03:03of their epic voyage, heading west across the United States.
0:03:07 > 0:03:10From Texas, they will journey from airfield to airfield through
0:03:10 > 0:03:17the arid west before concluding the expedition on the Pacific coast.
0:03:24 > 0:03:30But as they meet the desert, there's a dramatic change in the airship's behaviour.
0:03:30 > 0:03:34Expedition leader, Felicity Aston, wants to know what's causing it.
0:03:38 > 0:03:40What's happening with the movement?
0:03:40 > 0:03:44We've suddenly started making really steep climbs and sharp descents.
0:03:44 > 0:03:46We've just started getting some thermals now.
0:03:46 > 0:03:49So we are getting these rising bubbles of air from the surface.
0:03:49 > 0:03:52When we fly into it, it lifts the nose up then as we continue
0:03:52 > 0:03:56it lifts the whole body up, and then as we move further it lifts the tail up
0:03:56 > 0:03:59so we've got a correcting motion that pushes us back down again.
0:03:59 > 0:04:02It's really quite steep. We're pointing to the sky one minute,
0:04:02 > 0:04:04and then down at the floor the next.
0:04:04 > 0:04:06It can get quite extreme at times, yes.
0:04:06 > 0:04:10- You get used to it. - Really? Like sea-sickness?- Yes.
0:04:13 > 0:04:17- You all right?- Yeah.
0:04:20 > 0:04:24Despite the discomfort, it's the airship's ability to fly with the
0:04:24 > 0:04:28currents of air that allows the team to pursue one of their key themes -
0:04:30 > 0:04:33the relationship between life and the atmosphere.
0:04:37 > 0:04:41They want to know how conditions change through the different layers
0:04:41 > 0:04:44of the atmosphere and how that impacts upon the life found there.
0:04:46 > 0:04:50So, Felicity and atmospheric chemist, Dr Jim McQuade,
0:04:50 > 0:04:53are fishing for life in the layer of air that is the most dynamic
0:04:53 > 0:04:57and closest to the earth. It's called the boundary layer.
0:04:57 > 0:05:00We've got two - we've got two different ones.
0:05:03 > 0:05:09By flying through this layer, they hope to shed light on one particular family of creatures...
0:05:09 > 0:05:11He's pretty gorgeous.
0:05:12 > 0:05:13..insects.
0:05:16 > 0:05:19Whilst we're familiar with the lives of insects close to the
0:05:19 > 0:05:24earth's surface, some have another, little known existence higher up
0:05:24 > 0:05:26in the atmosphere.
0:05:28 > 0:05:31The team are going to try and discover whether they get
0:05:31 > 0:05:35blown here accidentally or are they exploiting atmospheric
0:05:35 > 0:05:38conditions found in its different layers?
0:05:50 > 0:05:52Elsewhere, another Cloud Lab team member
0:05:52 > 0:05:55is targeting a different layer of the atmosphere
0:05:55 > 0:05:56and another kind of life.
0:05:58 > 0:06:02Microbiologist Dr Chris Van Tulleken is setting out
0:06:02 > 0:06:07to find living bacteria in the high altitude death zone.
0:06:07 > 0:06:12And the microscope I want to do last, just because it is so dusty.
0:06:12 > 0:06:16He's brought in a specialist researcher, Noelle Bryan, to help him.
0:06:18 > 0:06:25I need to get a sample of sky that's ten times higher than the samples
0:06:25 > 0:06:30we've got before. So we're going up to almost 30,000 feet from...
0:06:30 > 0:06:34you know, the cloud samples were from about 1,000 and 3,000 feet
0:06:34 > 0:06:36so we want to find out if there are bacteria up there
0:06:36 > 0:06:39and that's what Noelle is very, very expert at.
0:06:44 > 0:06:49With this experiment, Chris is hoping to build upon some remarkable findings of his.
0:06:53 > 0:06:57Earlier in the expedition, he discovered that the skies are alive.
0:06:57 > 0:07:02We've got evidence here that we've got bacteria in clouds
0:07:02 > 0:07:05and that's right at the cutting edge of science.
0:07:05 > 0:07:10Chris not only detected bacteria in clouds, he revealed that
0:07:10 > 0:07:14they played a significant role in making rain. Now, he's looking
0:07:14 > 0:07:18for life beyond the clouds, upwards of 10,000 feet
0:07:18 > 0:07:22to a layer of the atmosphere called the free troposphere.
0:07:24 > 0:07:26Far away from the influence of the earth's surface,
0:07:26 > 0:07:30the free troposphere is cold, desolate and bone dry.
0:07:34 > 0:07:37Even for bacteria, this is an extreme environment.
0:07:42 > 0:07:46Every time you look for a place where nothing should be able
0:07:46 > 0:07:50to survive, there's always a microbe that can take it,
0:07:50 > 0:07:53so that's what we are looking for.
0:07:53 > 0:07:55Who is the hardiest, who is the toughest?
0:07:55 > 0:07:59Who can take the desiccation, the low pressure,
0:07:59 > 0:08:01the increased UV radiation?
0:08:01 > 0:08:06Humans are wimps. We have a small temperature range.
0:08:06 > 0:08:10We have a very defined set of environmental conditions
0:08:10 > 0:08:11that we can survive.
0:08:15 > 0:08:18Perhaps not all humans are wimps.
0:08:18 > 0:08:24The free troposphere is far beyond the flight ceiling of the airship,
0:08:24 > 0:08:26so Chris and Noelle have enlisted
0:08:26 > 0:08:28the services of former paratrooper, Andy Torbet.
0:08:35 > 0:08:37The idea is that I'm going to jump
0:08:37 > 0:08:42out of a plane at about 26,000 feet and parachute
0:08:42 > 0:08:45all the way back down to earth, collecting samples as I go.
0:08:49 > 0:08:53The experiment will involve Andy attempting a highly technical jump
0:08:53 > 0:08:56called a High Altitude High Opening, or HAHO.
0:08:56 > 0:09:00It's usually the preserve of elite, special forces.
0:09:01 > 0:09:04There's a lot of problems with sky diving from
0:09:04 > 0:09:0626,000 feet so people don't do it.
0:09:06 > 0:09:09One. The air is so thin, it's very, very hard to get stable.
0:09:12 > 0:09:16You need to get stable within 3-5 seconds in order to open your chute.
0:09:16 > 0:09:18If you open your parachute any longer than sort of 5 seconds,
0:09:18 > 0:09:20you pick up so much speed again because the air is
0:09:20 > 0:09:24so thin that when you open you get what's called a hard opening
0:09:24 > 0:09:29and that actually has enough force to break your spine.
0:09:29 > 0:09:31Bearing in mind that when I open my parachute at
0:09:31 > 0:09:3526,000 feet it's going to be minus 28, minus 30
0:09:35 > 0:09:38so it's going to be bloody cold as well.
0:09:38 > 0:09:41And the air is so thin, there's so little oxygen,
0:09:41 > 0:09:43if you don't have an oxygen supply, like a mask on,
0:09:43 > 0:09:46you're going to suffocate and die within about a minute.
0:09:46 > 0:09:48So it's a fairly hostile environment.
0:09:53 > 0:09:56Very little is known about life at the altitudes Andy is
0:09:56 > 0:10:03reaching for but as we look for life beyond our planet, finding what
0:10:03 > 0:10:09can survive earth's extreme habitats is taking on new significance.
0:10:09 > 0:10:12It also requires a novel, scientific approach.
0:10:17 > 0:10:20The principle is presumably going to be, Andy flies up.
0:10:20 > 0:10:23He's got a petri dish or a growth medium dish.
0:10:23 > 0:10:25He opens the lid.
0:10:25 > 0:10:29Then closes the lid before he hits the ground and there's our sample.
0:10:29 > 0:10:32But presumably it's a bit more complicated than that.
0:10:32 > 0:10:34The idea is the same.
0:10:34 > 0:10:36We're going to have a device that goes up.
0:10:36 > 0:10:38It's going to open.
0:10:38 > 0:10:41We're going to catch a sample, close the doors and bring it back down.
0:10:41 > 0:10:44Only, instead of one surface of a Petri dish,
0:10:44 > 0:10:47with these plastic rods we're able to have 40 different surfaces.
0:10:47 > 0:10:52So, it's sealed. He goes up, opens it,
0:10:52 > 0:10:57the air goes over and then before he hits 10,000 feet, closes.
0:10:57 > 0:10:59Seal it back up.
0:10:59 > 0:11:00And that's our sample.
0:11:00 > 0:11:02Then we bring it back here and we can work out what it is.
0:11:02 > 0:11:05And then we can do all sorts of different things.
0:11:08 > 0:11:10A lot now depends on what Andy can achieve.
0:11:11 > 0:11:14Over the coming days, he'll put the finishing touches
0:11:14 > 0:11:17to weeks of preparation,
0:11:17 > 0:11:21working with ex-special forces skydive master, Dane Kenny.
0:11:22 > 0:11:24Two minutes.
0:11:25 > 0:11:30Dane will supervise Andy as he jumps from increasingly high altitudes.
0:11:30 > 0:11:33Acclimatising to the changing nature of the atmosphere.
0:11:57 > 0:12:01Cloud Lab biologist, Dr Sarah Beynon, has joined the expedition
0:12:01 > 0:12:05to further the survey of insect life.
0:12:05 > 0:12:07- What time is it now?- Seven...
0:12:07 > 0:12:10For Sarah, it's yielding some surprising insights into
0:12:10 > 0:12:14exactly which insects are found in the boundary layer,
0:12:14 > 0:12:15and at what altitude.
0:12:18 > 0:12:21Bear with me. So, that's a flea beetle.
0:12:21 > 0:12:26And I haven't seen any data of these being found at altitude before.
0:12:26 > 0:12:30We had no idea that these insects were up there.
0:12:30 > 0:12:34A lot of what we do know relies on radar which tells us
0:12:34 > 0:12:38what's up there in terms of the abundance but we have no idea
0:12:38 > 0:12:41what makes that up so tiny insects like this,
0:12:41 > 0:12:44we can't tell what species of insect are up there.
0:12:44 > 0:12:46So it's only through deploying something like this
0:12:46 > 0:12:51that we have any idea of what is flying at those altitudes.
0:12:55 > 0:13:00Now, Sarah wants to seek out evidence for one particular relationship
0:13:00 > 0:13:03between insect and atmospheric condition.
0:13:06 > 0:13:09So I have a spare net, so I'll put that one in.
0:13:09 > 0:13:12OK, thank you.
0:13:12 > 0:13:15Can you record the altitude, as well please Jim, and the time?
0:13:15 > 0:13:16What time is it now?
0:13:16 > 0:13:19- Uh, 7:03.- OK.
0:13:26 > 0:13:29The aim is to roam the vastness of the sky to intercept
0:13:29 > 0:13:32a noctuid moth, one of a family of different species.
0:13:36 > 0:13:40To do so, they must first wait for nightfall and a radical
0:13:40 > 0:13:44transformation of the atmosphere called the nocturnal inversion.
0:13:45 > 0:13:49- How high are we now? - Er, Nine hundred feet.
0:13:49 > 0:13:50- Nine hundred feet? - Yeah.
0:13:56 > 0:14:00As the sun goes down, the air that sits above the earth cools
0:14:00 > 0:14:04more rapidly than the air at high altitude and that can create
0:14:04 > 0:14:05fast-moving streams of air.
0:14:10 > 0:14:15Noctuid moths are believed to use this nocturnal inversion to migrate
0:14:15 > 0:14:18as far as 600 miles in a single night
0:14:18 > 0:14:21by selecting the most favourable air streams...
0:14:23 > 0:14:27..but rarely have they been caught in the process.
0:14:27 > 0:14:29Sarah aims to change all that.
0:14:33 > 0:14:36The moths at this time of night should be making their way
0:14:36 > 0:14:40up into the higher airspace to migrate.
0:14:40 > 0:14:43- So we should catch them on their journey upwards.- Yeah.
0:14:46 > 0:14:50The airship's sensitivity to atmospheric conditions
0:14:50 > 0:14:53pays dividends as it drifts with the air currents.
0:14:57 > 0:15:00All they can do now is sit, wait and hope
0:15:00 > 0:15:04that the moths are on their way.
0:15:14 > 0:15:17Ooh a moth!
0:15:17 > 0:15:21- No kidding!- No there really is a moth, where did it go?
0:15:21 > 0:15:24Hang on. OK, lights? I haven't got my net with me.
0:15:24 > 0:15:27Shine a light somewhere and keep it there, to keep the moth to it.
0:15:27 > 0:15:29A moth has flown in through the window.
0:15:29 > 0:15:31I need to get a net, OK, thank you.
0:15:35 > 0:15:37Oh, it's here, it's here!
0:15:37 > 0:15:41- Whoa, whoa - gosh, where's it gone?- There.
0:15:44 > 0:15:47OK, could you grab the killing cloth please?
0:15:47 > 0:15:50We've found a moth!
0:15:50 > 0:15:52The net isn't collecting them, but it's just
0:15:52 > 0:15:57flown in at 500 feet above the ground, which means they're here!
0:15:57 > 0:16:00OK, we need to be careful as I need to know what species it is.
0:16:00 > 0:16:02I think what we'll do is just shove the whole net in
0:16:02 > 0:16:05to be on the safe side. Awesome!
0:16:07 > 0:16:11Teamwork! Excellent!
0:16:13 > 0:16:15PILOT: Ready for landing, OK?
0:16:18 > 0:16:23Sarah will need to get the moth under better light to identify it.
0:16:23 > 0:16:28Only then can she be sure if it's one of the migrating noctuid species
0:16:28 > 0:16:30taking advantage of the night-time air.
0:16:36 > 0:16:39For the airship's 15-strong ground support team,
0:16:39 > 0:16:41the night has just begun.
0:16:41 > 0:16:45After several weeks of flying, the airship has been venting helium
0:16:45 > 0:16:49in order to adjust to different altitudes. Now it needs topping up.
0:16:49 > 0:16:53Well, this is the second rack here we've probably got at least two more.
0:16:53 > 0:16:57We've been here about an hour so far so maybe another couple of hours.
0:16:57 > 0:17:02Taking care of the airship all the time - it needs constant attention.
0:17:02 > 0:17:04It's a very demanding mistress.
0:17:13 > 0:17:17Sarah is drawing together the haul of insects from the survey.
0:17:17 > 0:17:20Already, she's discerning a difference between the insects that
0:17:20 > 0:17:23travel by day and those that travel by night,
0:17:23 > 0:17:25including the one that flew into the airship.
0:17:27 > 0:17:31In the daytime, most of the insects we caught were small,
0:17:31 > 0:17:32like this leaf beetle
0:17:33 > 0:17:36and these insects would have been carried up by the
0:17:36 > 0:17:41turbulent daytime air and would have been at the mercy of the winds.
0:17:41 > 0:17:45Whereas at night-time, everything started to get a bit more
0:17:45 > 0:17:49interesting and every single time we flew at night,
0:17:49 > 0:17:52we caught migratory, noctuid moths.
0:17:52 > 0:17:57We've got a fall armyworm moth here
0:17:57 > 0:18:01and these moths, they migrate northwards in the spring
0:18:01 > 0:18:04and summer to make the most of the agricultural crops that are
0:18:04 > 0:18:09growing and they decimate crops such as corn and cotton and then they
0:18:09 > 0:18:14migrate...well, we think they migrate southwards again in the fall.
0:18:17 > 0:18:21But we know very, very little about this fall migration
0:18:21 > 0:18:26so any individuals we find in the fall is really, really useful.
0:18:29 > 0:18:34The study demonstrates how insects exploit the varying conditions
0:18:34 > 0:18:37of the sky at different altitudes and times of day.
0:18:40 > 0:18:44Other research suggests that insects exploit the dynamic nature
0:18:44 > 0:18:48of the boundary layer on a vast scale.
0:18:48 > 0:18:51So, in a 1km square patch of countryside surveyed over the course
0:18:51 > 0:18:57of a summer month, as many as 3 billion insects pass overhead.
0:19:03 > 0:19:06The question remains, how much life exists
0:19:06 > 0:19:09beyond here in the higher atmosphere?
0:19:11 > 0:19:14- Is that tight? - Yeah, that's tight.
0:19:14 > 0:19:18It's a question Andy hopes to soon help answer by undertaking
0:19:18 > 0:19:24the HAHO jump. At more than 26,000 feet,
0:19:24 > 0:19:26it will be the highest he's attempted yet.
0:19:27 > 0:19:32Remember, the priority is safe parachuting.
0:19:32 > 0:19:34So I know this is very important,
0:19:34 > 0:19:37but we can't do that if you've got an issue with the parachute.
0:19:37 > 0:19:40- Happy?- Happy.- Good.
0:19:40 > 0:19:45- Right, let's get out there. - Look at that.
0:19:45 > 0:19:48Steady as a rock but I shoot with this hand.
0:19:51 > 0:19:53You'll be fine, mate.
0:19:55 > 0:19:59Andy will have just one attempt to get the precious air sample,
0:19:59 > 0:20:02and with it, a chance of finding microbial life.
0:20:08 > 0:20:11The weather is closing in and safe conditions
0:20:11 > 0:20:13are unlikely to return for days.
0:20:16 > 0:20:18Before going to altitude,
0:20:18 > 0:20:21the entire team must flood their lungs with pure oxygen.
0:20:23 > 0:20:26If not, there's a risk that the nitrogen in their blood
0:20:26 > 0:20:28could form bubbles, leading to the bends.
0:20:33 > 0:20:35Without this and other precautions against
0:20:35 > 0:20:39the sub-freezing temperatures and desperately dry air,
0:20:39 > 0:20:41Andy would be dead within seconds.
0:20:47 > 0:20:51It raises the question of how ANY life, even bacteria,
0:20:51 > 0:20:53can survive extreme altitudes.
0:21:01 > 0:21:04The answer could lie in another form of microscopic life,
0:21:06 > 0:21:09one that has an extraordinary adaptation to aridity.
0:21:12 > 0:21:16These are things called tardigrades or water bears
0:21:16 > 0:21:20and they are unusual because they're extremely small and they can
0:21:20 > 0:21:25survive complete desiccation, so complete drying out and this is
0:21:25 > 0:21:30a desiccated, a dried out tardigrade here magnified on the microscope.
0:21:30 > 0:21:33They are in a state of almost suspended animation.
0:21:35 > 0:21:39The chemical processes that drive life are at a virtual standstill.
0:21:43 > 0:21:47But it takes just a few drops of water to re-animate it.
0:21:49 > 0:21:53When you run water over it, you see the chemical reactions start
0:21:53 > 0:22:01happening again, absorbing the water and is now very obviously alive.
0:22:01 > 0:22:07And it's gone from chemically dead, chemically totally inert, to now
0:22:07 > 0:22:11being, you know, obviously quite an adorable little living thing.
0:22:11 > 0:22:14It's got little legs and kind of a little face there.
0:22:17 > 0:22:20Whilst the transformation is plain to see,
0:22:20 > 0:22:25the secret to the tardigrade's survival is what's happening within.
0:22:25 > 0:22:28We think that the way the tardigrades survive those
0:22:28 > 0:22:31environments is by being able to tolerate the DNA
0:22:31 > 0:22:35and protein damage that comes from being terribly dried out.
0:22:35 > 0:22:39What they have is very, very good DNA repair mechanisms.
0:22:44 > 0:22:47Chris believes that bacteria at high altitude
0:22:47 > 0:22:51may use these same repair mechanisms to withstand the aridity.
0:22:55 > 0:22:58Finding live specimens will go a long way to suggesting as much.
0:23:02 > 0:23:05That now depends on what happens when Andy meets
0:23:05 > 0:23:07the vanishingly thin air.
0:23:33 > 0:23:39If Andy can't get stable, he'll have to free-fall to where the air is dense enough to slow his descent.
0:23:54 > 0:23:56God, he's got a lot to think about.
0:23:57 > 0:24:00It's much, much more skilful than I thought it was.
0:24:39 > 0:24:42Andy's botched the exit and is struggling to get stable.
0:25:15 > 0:25:18Despite the poor exit, Andy managed to open his parachute within
0:25:18 > 0:25:20the vital first few seconds.
0:25:22 > 0:25:24Now, he has to gather the sample.
0:25:55 > 0:25:58The box must be closed at 10,000 feet.
0:25:59 > 0:26:03If not, he will expose the sample to the lower atmosphere
0:26:03 > 0:26:05where life can more easily exist.
0:26:30 > 0:26:32There he is.
0:26:32 > 0:26:35The reason I get Andy to do this is because he's a much better
0:26:35 > 0:26:38microbiologist than I am a sky diver.
0:26:40 > 0:26:43Andy appears to have pulled off the job.
0:26:46 > 0:26:49But there's one thing the team haven't foreseen
0:26:49 > 0:26:52that jeopardises the entire experiment.
0:26:54 > 0:26:55Oooh!
0:26:57 > 0:27:01Now, the sample is at risk of contamination.
0:27:01 > 0:27:03You all right, mate? How you doing?
0:27:03 > 0:27:05It was a good landing.
0:27:05 > 0:27:07What I wasn't expecting is my feet were dead.
0:27:07 > 0:27:11- I had no blood in my feet. - They were numb, really?
0:27:12 > 0:27:15- Your shoes are freezing cold. - Because I've been
0:27:15 > 0:27:16sitting in this harness 20 minutes,
0:27:16 > 0:27:20my legs were completely numb and they just gave way on me.
0:27:20 > 0:27:23Well, never mind that, let's make this safe.
0:27:27 > 0:27:30- Good. Right I'm going to get this to the lab.- OK, mate, no dramas.
0:27:33 > 0:27:36The sense of relief is just... It was weird.
0:27:36 > 0:27:39You don't notice the kind of the amount of stress or pressure
0:27:39 > 0:27:42that's on your shoulders that's built up over the last three months
0:27:42 > 0:27:44until it's taken away.
0:27:44 > 0:27:47And suddenly you're like... It's gone, we've actually done it.
0:27:47 > 0:27:51There's an element of kind of disbelief we've actually
0:27:51 > 0:27:52pulled this off.
0:27:52 > 0:27:53I got to jump the HAHO
0:27:53 > 0:27:56and I managed to pull it off without seriously
0:27:56 > 0:28:02injuring myself or killing myself, so, er... It was really good.
0:28:02 > 0:28:04No-one's ever done it like this before.
0:28:06 > 0:28:09But you know, if you work out how much of the air up there we've
0:28:09 > 0:28:14passed over the rods, we should get something sticking and all we want
0:28:14 > 0:28:17to see is that there's something up there, you know it's... One
0:28:17 > 0:28:21or two bugs and we can amplify them, grow them, work out what they are.
0:28:21 > 0:28:24It's a lovely thought isn't it, this,
0:28:24 > 0:28:27got a little bit of troposphere in here.
0:28:27 > 0:28:29It's really nice.
0:28:30 > 0:28:33- Noelle!- Is this it?
0:28:33 > 0:28:35That is it.
0:28:35 > 0:28:37Did you think we were going to get this, honestly?
0:28:37 > 0:28:39No.
0:28:41 > 0:28:44Andy's slow descent through more than 16,000 feet
0:28:44 > 0:28:47of high-altitude air has given Chris and Noelle the best chance
0:28:47 > 0:28:51of finding microbial life.
0:28:51 > 0:28:55It will require forensic precision to ensure it wasn't in vain.
0:28:55 > 0:28:59It's worth explaining that while we do this, sterile air is
0:28:59 > 0:29:06flowing from this all over this surface so that no bugs can get in.
0:29:06 > 0:29:09So even if a piece of hair falls off Noelle's head,
0:29:09 > 0:29:11it won't land on the sample.
0:29:21 > 0:29:26This is what I do all day virtually every day in London.
0:29:26 > 0:29:29And I think it puts a lot of people off doing science
0:29:29 > 0:29:32because it seems super mundane but it isn't.
0:29:32 > 0:29:37This is where we... This is where we get the answers.
0:29:37 > 0:29:39The best bit is not the skydiving.
0:29:39 > 0:29:42The best bit is the answers.
0:29:42 > 0:29:46Now we want to have a look at it on the microscope.
0:29:46 > 0:29:51And in order to look at it, we're going to stain it with another dye.
0:29:51 > 0:29:55We're going to stain it with this stuff which stains nucleic acid
0:29:55 > 0:30:00so, things like DNA. Again, only life has nucleic acid, so it'll
0:30:00 > 0:30:04stain that and then we'll be able to see the objects more clearly.
0:30:06 > 0:30:08Once the sample is stained,
0:30:08 > 0:30:13any cells will reflect back the light emitted from the microscope,
0:30:13 > 0:30:15showing up as tiny glimmers of green.
0:30:17 > 0:30:18There you go. You see...
0:30:18 > 0:30:21You think there's going to be nothing there don't you,
0:30:21 > 0:30:24you're just looking in to blackness and then -
0:30:24 > 0:30:28what I was hoping to see and what I can see - is every
0:30:28 > 0:30:31once in a while you move the microscope and that's what you see.
0:30:31 > 0:30:34You just get that little beacon of a green dot.
0:30:34 > 0:30:36Just a little green glow.
0:30:36 > 0:30:39And each of those little green dots - those are cells.
0:30:39 > 0:30:41The amazing thing is it's one thing
0:30:41 > 0:30:45seeing the DNA glowing in the right size and shape of a bacteria
0:30:45 > 0:30:49but the fact that it's alive, that is a really peculiar thing.
0:30:49 > 0:30:52To find dead bacteria up there yeah, maybe.
0:30:52 > 0:30:55To find living stuff up there is such a harsh environment.
0:30:55 > 0:30:58No oxygen, its freezing cold, low pressure,
0:30:58 > 0:31:02- high winds, you know, no water. - No water.
0:31:02 > 0:31:04Amazing.
0:31:07 > 0:31:13The experiment joins a growing band of scientific research into life high in the atmosphere.
0:31:17 > 0:31:22The picture that is emerging is that life is far more robust than ever imagined.
0:31:27 > 0:31:29And that opens up all sorts of possibilities
0:31:29 > 0:31:31for the prospects for life
0:31:31 > 0:31:34in other extreme environments beyond our planet.
0:31:47 > 0:31:52PILOT SPEAKS OVER RADIO
0:32:11 > 0:32:15The airship is heading to the desert city of Phoenix, Arizona.
0:32:21 > 0:32:25What's drawing the team here is another of their key themes,
0:32:27 > 0:32:29the way in which we, ourselves,
0:32:29 > 0:32:32can change the way the atmosphere behaves.
0:32:37 > 0:32:41Earlier in the expedition, Felicity and atmospheric chemist,
0:32:41 > 0:32:44Dr Jim McQuade, uncovered the surprising link
0:32:44 > 0:32:49between pollution, clouds and extreme weather.
0:32:51 > 0:32:54So what we're saying is that by cleaning
0:32:54 > 0:32:59up our atmosphere, we've allowed there to be more hurricanes.
0:33:05 > 0:33:07They're now hoping that Cloud Lab will enable them
0:33:07 > 0:33:10to get to the bottom of another question
0:33:10 > 0:33:12about our impact on the atmosphere -
0:33:12 > 0:33:15can cities make their own weather?
0:33:17 > 0:33:20So, I've been looking at historical data
0:33:20 > 0:33:24and you can see that Phoenix, in the last 100 years, has gone
0:33:24 > 0:33:30from being a really small, agricultural settlement into a large, urban city.
0:33:30 > 0:33:33In the same period of time, there has been a distinct
0:33:33 > 0:33:36change in the amount of rainfall in the city.
0:33:37 > 0:33:40There are areas of Phoenix that have had up to
0:33:40 > 0:33:46a 12% increase in the amount of rainfall which is really significant
0:33:46 > 0:33:49and it looks like there might be a correlation between the two.
0:33:49 > 0:33:50So, we want to see
0:33:50 > 0:33:54if we can unravel how the city might be creating its own weather.
0:33:59 > 0:34:03It's difficult to imagine that a single city could interfere
0:34:03 > 0:34:07with a process that unfolds on such a grand scale as the weather.
0:34:10 > 0:34:14The rain that falls here has followed the same cycle for millennia.
0:34:16 > 0:34:20Every summer, warm, moist air is swept up from the oceans
0:34:20 > 0:34:26to the South. As this air meets the hot desert,
0:34:26 > 0:34:32variations in the landscape drive pockets of air upwards as thermals
0:34:32 > 0:34:39where the moisture cools, condenses and ultimately falls
0:34:39 > 0:34:41in sudden downpours of rain.
0:34:47 > 0:34:51Where this rain occurs should be fairly random...
0:34:57 > 0:35:01..but something appears to be concentrating it upon the city.
0:35:07 > 0:35:13To see why, Felicity is going to start by surveying temperatures in Phoenix and the surrounding desert.
0:35:19 > 0:35:22I took several readings of the surface temperature and I was
0:35:22 > 0:35:28getting between 37 and 38 degrees centigrade.
0:35:28 > 0:35:29So, it's pretty hot down there,
0:35:29 > 0:35:32it's soaking up all the heat from the sun.
0:35:36 > 0:35:40For the city to be concentrating rainfall, it needs to be
0:35:40 > 0:35:43hotter than the desert, driving extra thermal activity.
0:35:52 > 0:35:58Meanwhile, Jim is surveying another factor that could be increasing rain - humidity.
0:35:59 > 0:36:04A hygrometer gives an on-the-spot reading of how much water vapour
0:36:04 > 0:36:07is being carried in the air.
0:36:07 > 0:36:10The dry bulb was 24.5, giving
0:36:10 > 0:36:13a relative humidity of 26%.
0:36:13 > 0:36:18So, the air's very dry here, which is actually the definition of a desert.
0:36:18 > 0:36:20It's nothing to do with temperature.
0:36:20 > 0:36:21It's how dry it is,
0:36:21 > 0:36:24so that's why Antarctica can be classified as a desert.
0:36:27 > 0:36:32Unsurprisingly, in the desert, there's plenty of heat but no water.
0:36:35 > 0:36:40But what really matters is how this picture compares with the city.
0:36:50 > 0:36:53OK, another measurement next to an orange tree
0:36:53 > 0:36:56and a lemon tree in someone's front garden.
0:36:57 > 0:37:00It's not like back in Leeds - got an apple tree.
0:37:06 > 0:37:0945% relative humidity.
0:37:10 > 0:37:14It's very obvious that there's a lot more water available to be
0:37:14 > 0:37:18evaporating into the atmosphere just from manicured lawns.
0:37:18 > 0:37:20There are lots of sprinklers down here.
0:37:32 > 0:37:36Increased humidity is a consequence of the millions of gallons of water
0:37:36 > 0:37:39diverted to the city from the surrounding rivers.
0:37:42 > 0:37:45I'm getting a real variety in surface temperatures.
0:37:45 > 0:37:51So, if I take a reading from the road or a car park, it's pretty much the
0:37:51 > 0:37:56same surface temperature as in the desert, but if I point the camera
0:37:56 > 0:38:02at a garden or a swimming pool or a roof top, then it's a lot less.
0:38:02 > 0:38:07So, on average, the surface temperature here will overall
0:38:07 > 0:38:09be a lot less than the desert.
0:38:14 > 0:38:19The city is more humid and a little cooler than the surrounding desert.
0:38:19 > 0:38:22Despite these differences, there's no evidence
0:38:22 > 0:38:25for the increased thermal activity that can explain the rainfall.
0:38:38 > 0:38:41As the day wears on, that picture soon changes.
0:38:48 > 0:38:52See, look, look, look, look! See the city...
0:38:52 > 0:38:54- Yeah. - .it's hotter than the desert.
0:38:54 > 0:38:58OK, yeah, you can see definitely the boundary.
0:38:58 > 0:39:00So that's the desert cooling down
0:39:00 > 0:39:02and that's the hot city.
0:39:02 > 0:39:04That's a really nice example of it.
0:39:09 > 0:39:11Whilst the natural landscape has quickly cooled,
0:39:11 > 0:39:14the camera reveals the city to have remained warm.
0:39:18 > 0:39:21They've identified an effect called the urban heat island.
0:39:26 > 0:39:29Earlier today we measured the ground temperature of the suburbs to
0:39:29 > 0:39:35be 24, 25 degrees, and see I'm measuring 23, 22.
0:39:35 > 0:39:36I mean, it's still as hot as
0:39:36 > 0:39:39when we measured it in the middle of the day.
0:39:41 > 0:39:44The city's surfaces are continuing to radiate the energy of the sun
0:39:44 > 0:39:46they absorbed earlier in the day.
0:39:49 > 0:39:53The question is whether the urban heat island is generating thermals.
0:39:55 > 0:39:58If it is, they should be able to detect
0:39:58 > 0:40:01an increase in temperature at altitude from the airship.
0:40:03 > 0:40:06So, I've just had a look the temperature
0:40:06 > 0:40:09and this is the temperature going down and that's going down simply
0:40:09 > 0:40:12because the sun's going down, you know, we're turning the heater off.
0:40:12 > 0:40:15So, this is the temperature over the desert
0:40:15 > 0:40:18and this is the temperature over the city.
0:40:18 > 0:40:22- Oh, wow, so this is where we hit the city?- Yeah.- OK, this is us...
0:40:22 > 0:40:24this is the temperature over the desert and then
0:40:24 > 0:40:28we hit the city limits and the temperature quite clearly goes up.
0:40:28 > 0:40:33It's not a huge increase, you know, no more than half a degree,
0:40:33 > 0:40:35but you can't argue with that. That's a definite.
0:40:38 > 0:40:42Despite the difference in temperature being small, it's critical.
0:40:44 > 0:40:46It's enough for us to know that the
0:40:46 > 0:40:48air above the city is warmer.
0:40:48 > 0:40:53So we've got this big parcel of warm air sitting over the city.
0:40:55 > 0:40:58It makes a lot of logical sense that that air is going to start rising and
0:40:58 > 0:41:03that's going to start convection and the consequence of that is weather.
0:41:07 > 0:41:10So the increased rainfall in Phoenix could be caused
0:41:10 > 0:41:12by the urban heat island effect.
0:41:14 > 0:41:18It generates thermals over the city that force air upward where it
0:41:18 > 0:41:20begins to cool.
0:41:20 > 0:41:23That, in turn, can cause the vapour to condense
0:41:23 > 0:41:27and form rain concentrated here upon Phoenix.
0:41:30 > 0:41:31So, we've found
0:41:31 > 0:41:35the connection we were looking for, between cities, and the increased
0:41:35 > 0:41:40rainfall that Phoenix has been experiencing in the last 100 years.
0:41:40 > 0:41:43And the really exciting thing about that is that we've hard
0:41:43 > 0:41:47evidence that human beings are creating their own weather.
0:41:52 > 0:41:56It's a finding that threatens to have far-reaching consequences.
0:41:57 > 0:42:02Our world is increasingly urban and much of that urban expansion
0:42:02 > 0:42:06is taking place in sparsely populated arid regions...
0:42:06 > 0:42:08..with unknown consequences.
0:42:20 > 0:42:23If you take an area of desert and build a city on it,
0:42:23 > 0:42:27then that city is going to be much warmer than the desert it's replaced.
0:42:27 > 0:42:30And it's going to have an overall warming effect.
0:42:31 > 0:42:36So if you multiply that by all the cities being built in desert
0:42:36 > 0:42:42areas, all this turning from desert land into green agricultural,
0:42:42 > 0:42:46irrigated land, then it leaves another little hanging question,
0:42:46 > 0:42:50whether this is having a much larger global effect on our climate.
0:43:03 > 0:43:07The airship has reached the western edge of the desert.
0:43:07 > 0:43:09Beyond here lies their destination...
0:43:15 > 0:43:20..the mighty Pacific, where the team want to conduct their final
0:43:20 > 0:43:21set of studies.
0:43:23 > 0:43:28An exploration of how the prevailing onshore Pacific wind shapes
0:43:28 > 0:43:31the wildlife of the entire Californian coastline.
0:43:34 > 0:43:37And that includes the life below the ocean surface.
0:43:42 > 0:43:46But first, the airship will have to overcome the Pacific wind.
0:43:49 > 0:43:52We're so close to the end of our journey that we can
0:43:52 > 0:43:54almost smell the Pacific Ocean.
0:43:54 > 0:43:58But there's one last obstacle. These mountains behind me.
0:43:58 > 0:44:02There's only one pass through these mountains for miles in either direction.
0:44:02 > 0:44:06It's called Banning Pass and it's a bit of a problem for the airship
0:44:06 > 0:44:09because it's so narrow. All the winds are funnelled through.
0:44:09 > 0:44:14And the winds come from the west towards us so it's going to be flying
0:44:14 > 0:44:20into the winds and if there's too much wind, it could take hours, days.
0:44:20 > 0:44:22Perhaps we could even be waiting for a week
0:44:22 > 0:44:24until conditions are just right.
0:44:29 > 0:44:31Even if the wind is blowing a gentle breeze on the far
0:44:31 > 0:44:35side of the pass, by the time it reaches the entrance
0:44:35 > 0:44:38the funnelling effect can accelerate it to gale force.
0:44:48 > 0:44:51We seem to be hitting a lot of turbulence.
0:44:51 > 0:44:53The wind is gusting and coming down the valley here.
0:44:53 > 0:44:56There's two big mountain ranges coming together to give us
0:44:56 > 0:45:00just this one little gap down the middle, so it's much rougher air now.
0:45:00 > 0:45:02So you are really having to fight to keep it level?
0:45:02 > 0:45:03It's a continuous fight
0:45:03 > 0:45:06but at the moment we're making slow progress.
0:45:06 > 0:45:08OK, so what's our ground speed at the minute?
0:45:08 > 0:45:11- About five knots. - Five knots? 6mph.
0:45:14 > 0:45:19It's very bizarre. We are in this unseen jet stream of air.
0:45:19 > 0:45:24So these engines are going fast enough to propel us at 30-40 knots,
0:45:24 > 0:45:27but unfortunately the wind's coming in the opposite direction
0:45:27 > 0:45:32at 30-35 knots, so we're only making only 2 or 3 knots ground speed.
0:45:32 > 0:45:37We've barely moved at all. About two miles in the last hour.
0:45:37 > 0:45:41- Co-pilot:- It's actually getting worse right at the moment.
0:45:41 > 0:45:44We've actually stopped.
0:45:49 > 0:45:52I don't think we're going to be going through today.
0:45:58 > 0:46:02The vast wind farm here one of the largest in Southern California
0:46:02 > 0:46:05is testament to the winds near-constant presence.
0:46:11 > 0:46:14We're definitely starting to move forward.
0:46:14 > 0:46:15Back there we were not,
0:46:15 > 0:46:17now we are definitely moving forward a wee bit.
0:46:17 > 0:46:20- CO-PILOT:- Yeah, there we go. We are going it a little bit here.
0:46:22 > 0:46:26Despite Felicity's worst fears it seems as though they have
0:46:26 > 0:46:28chosen the right day to make their move.
0:46:50 > 0:46:54Sarah has gone ahead of the airship to experience the power of the
0:46:54 > 0:46:56onshore Pacific wind for herself.
0:46:56 > 0:46:59We are going to do a little bit of scratching here,
0:46:59 > 0:47:01when we are close to the cliff edge.
0:47:01 > 0:47:03And scratching is doing what?
0:47:03 > 0:47:07- Well, when we are very close to the edge of the cliff...- Like this?
0:47:07 > 0:47:09Yeah. Scratching is our term.
0:47:11 > 0:47:16This is where the most lift is, close to the cliff edge.
0:47:18 > 0:47:21Sarah and Kirk are being carried on a type of air
0:47:21 > 0:47:23movement known as ridge lift.
0:47:25 > 0:47:28As the onshore wind hits the cliff, it is diverted
0:47:28 > 0:47:30and accelerated upward.
0:47:31 > 0:47:35But the real reason Sarah is here is to see how this movement of air
0:47:35 > 0:47:37supports life.
0:47:37 > 0:47:39Home! Shanty!
0:47:41 > 0:47:43Good girl.
0:47:46 > 0:47:50- Oh, wow!- Unbelievable, huh?- Oh!
0:47:50 > 0:47:53So this is Shanty, who is a trained bird
0:47:53 > 0:47:57- and she's using the same updraught that we're using.- Up!
0:48:01 > 0:48:04Shanty is a Harris hawk.
0:48:06 > 0:48:09A native to this region, they are so highly evolved to
0:48:09 > 0:48:13fly on the movement of air from ridge lift to rising thermals
0:48:13 > 0:48:15much of their flight time is spent soaring.
0:48:18 > 0:48:20Wow!
0:48:20 > 0:48:25You can really see her wide, fairly short wings
0:48:25 > 0:48:27and that's an adaptation to soaring.
0:48:27 > 0:48:29Look at her soaring up there now.
0:48:29 > 0:48:32And it's great to see the sort of finger-tips of her wings that
0:48:32 > 0:48:36she's using to control her flight.
0:48:36 > 0:48:41It's a behaviour found throughout the family of birds called raptors
0:48:41 > 0:48:44that also includes eagles and vultures, enabling them
0:48:44 > 0:48:50to extend their range to vast distances.
0:48:50 > 0:48:52It makes sense for them to use these up-draughts
0:48:52 > 0:48:56so that they expend as little energy as possible when they are hunting.
0:48:56 > 0:49:00Exactly. And the raptors own motto, like any good predator,
0:49:00 > 0:49:03is the maximum amount of reward for the least amount of effort.
0:49:03 > 0:49:08So if they can stay up without putting much energy into it,
0:49:08 > 0:49:10that's great.
0:49:10 > 0:49:14- Here she comes again. - Goodness me.
0:49:14 > 0:49:15Good girl!
0:49:43 > 0:49:45Hang on, it's the Pacific, it's the sea!
0:49:45 > 0:49:48You should have your bikini on, we should be there in swimming trunks!
0:49:48 > 0:49:51We've made it.
0:49:51 > 0:49:54- This is the ocean, we've made it. - Fantastic!
0:49:54 > 0:49:58So, Atlantic to Pacific.
0:50:00 > 0:50:04It's not quite journeys' end.
0:50:04 > 0:50:08The team have chosen this particular destination to explore
0:50:08 > 0:50:12a surprising relationship between life and the Pacific wind.
0:50:14 > 0:50:17- What's that there!? - Ah, yes!
0:50:17 > 0:50:19- What is it then go on?- A Blue Whale.
0:50:19 > 0:50:20- Is it really?- Really.
0:50:20 > 0:50:25- I've never seen a Blue Whale before. Look at that.- Wow!
0:50:25 > 0:50:30- Hang on, there's more than one. - There's two of them.
0:50:30 > 0:50:35These are just the first indications of what they have come to see
0:50:35 > 0:50:38because the wind can make habitats in the ocean too.
0:50:45 > 0:50:48This is Monterey Bay, California.
0:50:51 > 0:50:55Beneath its gleaming surface is a uniquely fertile eco system...
0:50:58 > 0:51:02..that makes this one of the most biodiverse habitats in the earth's oceans.
0:51:22 > 0:51:25- There you go, there you go.- There's two more of them right there.
0:51:25 > 0:51:29- The charismatic megafauna. - Charismatic megafauna.
0:51:29 > 0:51:33Chris and Andy have joined local marine biologist,
0:51:33 > 0:51:37Steve Lonhart, to understand how this rich environment is
0:51:37 > 0:51:39created by the wind.
0:51:41 > 0:51:43If you can imagine the wind which is coming from
0:51:43 > 0:51:47the northwest, so kind of over our shoulder, moving in this direction.
0:51:47 > 0:51:50As it moves that way,
0:51:50 > 0:51:54it actually just pushes the warm waters of the surface off,
0:51:54 > 0:51:57and then you get this really cool nutrient rich water that's coming
0:51:57 > 0:51:59up from the bottom, right where we are, right here, coming up from
0:51:59 > 0:52:03the bottom and that's sort of like...you can think of it like fertiliser.
0:52:03 > 0:52:06Meaning dead sea lions, dead kelp,
0:52:06 > 0:52:09anything that dies, birds, all falls to the bottom?
0:52:09 > 0:52:11Falls to the bottom,
0:52:11 > 0:52:15and it is broken down into all its little constituent members,
0:52:15 > 0:52:18that eventually just dissolve into the water.
0:52:18 > 0:52:22When the water comes up, its clear, which allows things like kelp
0:52:22 > 0:52:26and seaweeds, to do what they do which is photosynthesise.
0:52:26 > 0:52:28Just like plants on land nitrogen,
0:52:28 > 0:52:30carbon, building blocks of life.
0:52:30 > 0:52:33And instead of those things being in the air and the soil,
0:52:33 > 0:52:35- they're dissolved in the water. - That's right.
0:52:35 > 0:52:37Then you have a forest, not on land,
0:52:37 > 0:52:39it's actually on the shore.
0:52:43 > 0:52:47To see the result of this process in its full majesty you have to
0:52:47 > 0:52:49look beneath the surface...
0:52:50 > 0:52:53..and to the unique environment that it creates.
0:53:07 > 0:53:09The forest of giant kelp.
0:53:12 > 0:53:15Not only does the kelp benefit from the nutrients drawn
0:53:15 > 0:53:17up from the depths,
0:53:17 > 0:53:21it is also bathed in the energy of the sun, allowing it to
0:53:21 > 0:53:24reach 175 feet in height.
0:53:29 > 0:53:33Ah, so these are the giant kelp.
0:53:37 > 0:53:40You see the little bubbles?
0:53:40 > 0:53:43Awesome, and that's what holds the giant kelp up.
0:53:52 > 0:53:58- Chris, this is Andy. - Go ahead. Over.
0:53:58 > 0:54:05Every square inch of this entire system all the rocks,
0:54:05 > 0:54:09the nooks, the crannies - are all teeming with life.
0:54:09 > 0:54:14There's not a square inch that's left bare and barren.
0:54:14 > 0:54:22There's life everywhere. Outstanding again.
0:54:24 > 0:54:29How does this compare with other dives you've done?
0:54:29 > 0:54:33This whole place is like a normal sort of temperate
0:54:33 > 0:54:38reef but just much, much, much bigger.
0:54:38 > 0:54:40Everything has been super-sized.
0:54:44 > 0:54:45It's huge.
0:54:47 > 0:54:48It seems like all the life
0:54:48 > 0:54:54down there is scaled-up enormously because of this nutrient-rich water.
0:54:57 > 0:55:01I've just seen the biggest anemone I've ever
0:55:01 > 0:55:06seen in my life. It's huge.
0:55:06 > 0:55:11I've never seen an anemone that I would consider a man-eater,
0:55:11 > 0:55:14but if there ever was one, this is it.
0:55:17 > 0:55:21This is probably the best sight so far. I'm coming up.
0:55:21 > 0:55:26I'm rising up the trunks of these huge, giant kelp.
0:55:31 > 0:55:35Whilst this may be a very special environment, it also
0:55:35 > 0:55:40vividly demonstrates the power of the atmosphere to reach into every
0:55:40 > 0:55:44corner of the planet and make it a place for life.
0:55:50 > 0:55:56For me, it really provides an insight into just how complex the atmosphere is.
0:55:56 > 0:55:59It's not just something that we breathe and that produces
0:55:59 > 0:56:04weather, it has the ability to shape the landscape underneath it.
0:56:04 > 0:56:08It plays a huge part in forming the environments in which we all live.
0:56:14 > 0:56:18Reaching the Pacific brings to an end what has been an extraordinary
0:56:18 > 0:56:20and unique adventure.
0:56:22 > 0:56:25This epic journey coast to coast
0:56:25 > 0:56:29has enabled the team to experience the atmosphere as never before.
0:56:29 > 0:56:33That's the one I want! That one!
0:56:33 > 0:56:39They've explored the extraordinary processes that generate weather...
0:56:39 > 0:56:43- 20 million.- So, that small cloud weighed four tonnes?- Yes.
0:56:43 > 0:56:46- That's incredible.- It is.
0:56:46 > 0:56:50..they've seen some of the many ways that life - at every scale
0:56:50 > 0:56:53from microscopic bacteria...
0:56:54 > 0:56:57Now we are sucking in the cloud.
0:56:58 > 0:57:03..to more familiar species exploit each level of the atmosphere...
0:57:05 > 0:57:06Good luck, little one.
0:57:06 > 0:57:09These waterfronts, they are vital for movement,
0:57:09 > 0:57:12not just on a small scale, but on a global scale.
0:57:22 > 0:57:25..and they've revealed the often complex mechanisms by which
0:57:25 > 0:57:29we, ourselves, are shaping this realm.
0:57:54 > 0:57:56- Cheers, everyone!- Cheers, guys.
0:57:56 > 0:58:00- Cheers! - To the Pacific!