0:00:02 > 0:00:05Heat drives our weather.
0:00:05 > 0:00:09From the rage of a tropical storm,
0:00:09 > 0:00:11the blinding heat of the desert,
0:00:11 > 0:00:14to the violence of a summer sky.
0:00:14 > 0:00:18I'm Donal MacIntyre and I'm about to take a journey with heat...
0:00:20 > 0:00:23..from the equator to the Poles
0:00:23 > 0:00:28to see for myself the awesome power it can unleash around the world.
0:00:31 > 0:00:35From its birth in the tropics, through the perfect summer,
0:00:35 > 0:00:42into a hotter world, one which could turn the weather of the future into a nightmare.
0:00:43 > 0:00:45This is Wild Weather.
0:01:14 > 0:01:21Have you ever wondered what's the power behind the weather, what makes it tick?
0:01:24 > 0:01:30In just a few moments' time, we're going to see the true source of all weather.
0:01:35 > 0:01:40And this is it - the sun, the fuse that lights the weather.
0:01:44 > 0:01:48It's over a 100 times bigger than the earth.
0:01:48 > 0:01:54Every second, it releases enough energy to power the USA for 9 million years.
0:01:54 > 0:02:01It also takes one million years for the heat at its core to reach the surface.
0:02:01 > 0:02:06Once it does, it makes its journey here in just 8½ minutes.
0:02:06 > 0:02:10A journey that ends in a blaze of glory every single day.
0:02:24 > 0:02:30All that blinding heat and light is blasted out through space towards us.
0:02:37 > 0:02:40As it homes in on our little planet,
0:02:40 > 0:02:46it's at its most intense heading for the steaming jungles of the tropics.
0:02:47 > 0:02:50The sun's rays hit the equator.
0:02:50 > 0:02:55It's the start of heat's epic journey around the planet.
0:02:55 > 0:02:59But to find out what it does to the weather down here,
0:02:59 > 0:03:04I'm heading to where the sun's energy is most intense.
0:03:05 > 0:03:12Trapped beneath the jungle canopy, all that heat creates one of the most extreme environments there is.
0:03:12 > 0:03:17So to find out what all that heat does to the weather,
0:03:17 > 0:03:22I'm going to spend 24 hours in the jungles of Belize.
0:03:24 > 0:03:30If you're in the jungle, and you don't know what you're doing, like me,
0:03:30 > 0:03:33you're already this close to death.
0:03:33 > 0:03:35This is Sergeant Bob McCloud,
0:03:35 > 0:03:39an expert in jungle survival, and a very handy man to know.
0:03:39 > 0:03:45- Hello. Morning. - You're looking after me.- I sure am. - That's a heavy responsibility.
0:03:45 > 0:03:52- I mean, one second it's torrential rain, the next second it's a sauna. - Yeah, you're constantly wet.
0:03:52 > 0:03:56And it'll go from one extreme to another in such a short time.
0:03:56 > 0:04:02- Hypothermia and dehydration in one day?- Yeah.- That's crazy. - Follow me, I'll show you.
0:04:04 > 0:04:08For most of the year, the sun lies directly overhead,
0:04:08 > 0:04:15so there are no conventional seasons here, just hot and wet, then a little less wet.
0:04:15 > 0:04:19Even the daily weather is delightfully predictable.
0:04:19 > 0:04:26There are clear skies in the morning, showers in the afternoon, clear skies again in the evening.
0:04:26 > 0:04:28It's a weatherman's dream.
0:04:28 > 0:04:32The one wild card in all this predictability
0:04:32 > 0:04:38is the vast amount of energy constantly being built up in all this heat and humidity.
0:04:40 > 0:04:44It's all that energy that makes this place as cloudy as it is.
0:04:44 > 0:04:47The heat warms the land,
0:04:47 > 0:04:52rainwater evaporates from the vast amount of vegetation and rises.
0:04:54 > 0:04:59The water vapour condenses into tiny droplets that create huge clouds.
0:04:59 > 0:05:04The droplets collide, growing larger until gravity pulls them down again.
0:05:13 > 0:05:17The weather here is in a continuous cycle fuelled by heat.
0:05:17 > 0:05:24And whether you're in the water or on the river bank, it doesn't make a whole lot of difference
0:05:24 > 0:05:29because everything is permanently soaked.
0:05:29 > 0:05:33- Everything's wet, wet, wet.- That's the big problem in the jungle.
0:05:33 > 0:05:40It doesn't matter whether it's hot or actually raining like it is here, everything ends up wet.
0:05:40 > 0:05:45The only way round it is having a dry set of kit and a wet set of kit,
0:05:45 > 0:05:52and tonight, make sure you get into your dry kit, so you have 12 hours where your body can recuperate.
0:05:52 > 0:05:59- In the morning, you've got to get into your wet gear?- Yes. If you don't, then things will start to rot.
0:05:59 > 0:06:03Your boots and your clothing will go and your skin will start to rot away.
0:06:03 > 0:06:07You can end up with crotch rot and foot rot.
0:06:07 > 0:06:14Bob has spent the last five years training the British Army how to deal with life in this kind of heat.
0:06:14 > 0:06:16God, I'm knackered.
0:06:16 > 0:06:22As I struggle through the jungle, my body produces yet more heat.
0:06:22 > 0:06:29My blood carries that heat away from the muscles and is cooled when it finally reaches the skin.
0:06:29 > 0:06:33Out here that's never enough, so we sweat.
0:06:33 > 0:06:39One drop of sweat can cool a litre of blood as it evaporates off the skin's surface.
0:06:41 > 0:06:43Keep going. Get up there.
0:06:43 > 0:06:50It's the process of evaporation that cools you down, but it's not working here.
0:06:50 > 0:06:56The hotter I get, the faster my heart beats and the tireder I feel.
0:06:56 > 0:06:59Go on, keep moving. Get up there.
0:07:01 > 0:07:06I'm soaked in sweat, but the air is so damp that it can't evaporate.
0:07:06 > 0:07:09Stop moaning and keep going.
0:07:09 > 0:07:13I'm a dangerous man with a weapon like this.
0:07:13 > 0:07:15You're being a bit of a cowboy there.
0:07:15 > 0:07:20- Am I?- Even using your machete, there's a technique to it.- Yeah?
0:07:20 > 0:07:22This is crazy terrain.
0:07:23 > 0:07:31But it is what every kid trained for, aged six and seven, hacking through the jungle.
0:07:31 > 0:07:35I'm just doing it a little late in life.
0:07:38 > 0:07:42As the day wears on, it gets hotter and hotter.
0:07:42 > 0:07:49More and more moisture fills the air until it becomes saturated with water.
0:07:49 > 0:07:55Finally, it reaches a point where your sweat literally can't evaporate into the air any more.
0:07:55 > 0:08:00I'm pouring sweat, but it's not doing me any good.
0:08:01 > 0:08:04You can't see heat or humidity,
0:08:04 > 0:08:10but to appreciate it, all you've got to do is imagine closing your bathroom door,
0:08:10 > 0:08:16knocking the central heating up to full blast, turning the hot taps on
0:08:16 > 0:08:19and leaving it on for a couple of hours.
0:08:19 > 0:08:22That gives you a sense of it.
0:08:22 > 0:08:26- Give us a break, Bob.- Breaks are for losers. Come on, keep moving.
0:08:30 > 0:08:35Fortunately, this kind of weather is rare outside the jungle.
0:08:35 > 0:08:42But occasionally it reaches out beyond the tropics and, when it does, the results can be lethal.
0:08:44 > 0:08:49In 1995, tropical weather descended on Chicago.
0:08:50 > 0:08:55Even in a modern city like this, it brought chaos and death.
0:08:56 > 0:09:00July, and the temperatures were already soaring
0:09:00 > 0:09:04when heavy rains drenched the great plains outside the city.
0:09:06 > 0:09:10The air mass above these fields became hot and steamy.
0:09:12 > 0:09:16Days later, things took a turn for the worse.
0:09:17 > 0:09:24A mass of warm, moisture-laden air from the Gulf of Mexico forced its way north.
0:09:29 > 0:09:36The 2.8 million inhabitants of Chicago were about to experience the extremes of tropical weather.
0:09:38 > 0:09:43That's when it really hit you, and you sat back and said, my gosh!
0:09:43 > 0:09:47700 people died because of this event.
0:09:50 > 0:09:53Weathermen stationed in the Midwest
0:09:53 > 0:09:55realised something was wrong.
0:09:55 > 0:09:59We're taking a look at temperatures well over 100 degrees,
0:09:59 > 0:10:03widespread, not just one or two places.
0:10:06 > 0:10:11High pressure produced hours of uninterrupted sunshine
0:10:11 > 0:10:18and as the moist air from Mexico arrived in the area, levels of humidity shot up to 90%.
0:10:19 > 0:10:26This mass of sweltering tropical air was then blown over Chicago by south-westerly winds.
0:10:29 > 0:10:34It sat over the city like a steaming wet blanket.
0:10:38 > 0:10:44Day two - heat wave. The city is an oven. All over Chicago, an invisible enemy takes hold.
0:10:44 > 0:10:47It was like, you know,
0:10:47 > 0:10:50hitting a brick wall.
0:10:51 > 0:10:56It just totally surrounded you, like walking into a blanket.
0:10:56 > 0:11:02You could put your bathing suit on and be in the water, and it would still be hot.
0:11:02 > 0:11:06It affected the sound, too, when you walked out.
0:11:09 > 0:11:14For Gabby Kuhn, this freak tropical weather made life difficult,
0:11:14 > 0:11:18but for Mabel, her elderly neighbour, it was deadly.
0:11:19 > 0:11:24It was about the second day of the heat wave, Mabel had done fine,
0:11:24 > 0:11:27we had set up fans in the house.
0:11:27 > 0:11:32She sat in this seat and we put a fan that would blow on her face.
0:11:32 > 0:11:40The next day - normally she called me around two in the afternoon when she got up - and she didn't call.
0:11:41 > 0:11:46Day three, the story's the same all over the city.
0:11:46 > 0:11:50The emergency services are going into free fall.
0:11:50 > 0:11:52And she's not alert or oriented?
0:11:52 > 0:11:57The city's emergency warnings have failed to reach those most at risk.
0:11:57 > 0:12:04As the heat increases, the emergency centre is swamped with thousands of calls for help.
0:12:10 > 0:12:14Back in the suburbs, Gabby still hadn't heard from Mabel.
0:12:14 > 0:12:20I said to my daughter, I think I need to go and check on Mabel.
0:12:20 > 0:12:27She usually calls between two and three in the afternoon. I called her and she didn't answer.
0:12:27 > 0:12:32I tried a couple of times, so I thought I should come over.
0:12:32 > 0:12:38I came in and when I walked into the house I found her, and she was laying right here,
0:12:38 > 0:12:42in between the dining room and the bathroom.
0:12:42 > 0:12:49Apparently she tried to get into the washroom and didn't make it, and collapsed here on the floor.
0:12:49 > 0:12:55The ironic thing is that this is my house right here, and it's probably three feet or a metre away.
0:12:59 > 0:13:03And I didn't see her. I often think about that.
0:13:06 > 0:13:09Is the patient conscious and breathing?
0:13:09 > 0:13:13By Saturday, 165 people lay dying all over Chicago.
0:13:13 > 0:13:18Many would not be discovered for days. By then it would be too late.
0:13:18 > 0:13:23Help is on the way over there. You watch for the ambulance, right.
0:13:24 > 0:13:29When it really hit us, we started watching television ourselves,
0:13:29 > 0:13:37and seeing that they were starting to have pictures of the morgues and the bodies were starting to pile up.
0:13:37 > 0:13:39It was a shock.
0:13:39 > 0:13:45Mabel was one of the first 20 to die in the city of heat-related...
0:13:47 > 0:13:50..and then there were more.
0:13:50 > 0:13:54Day four. Hospitals all over the city are at breaking point.
0:13:54 > 0:13:59It started on a Thursday and it continued to build Friday.
0:14:02 > 0:14:07By Saturday, we started having such a huge influx of patients
0:14:07 > 0:14:13that where we used to have one cubicle, we'd now have 3A, 3B, 3C, 4A, 4B, 4C.
0:14:13 > 0:14:19The death toll rose dramatically. Most victims were the elderly or impoverished,
0:14:19 > 0:14:26whose bodies found it more difficult to cope with the extreme temperature conditions.
0:14:26 > 0:14:31Firstly, the body's temperature rises to dangerous levels,
0:14:31 > 0:14:34bringing about a state of confusion.
0:14:34 > 0:14:41In this state of mind, we're less likely to seek shelter or the aid of a cooling fan.
0:14:41 > 0:14:45As the body dehydrates, we slip into coma.
0:14:45 > 0:14:50In these super-heated conditions, our internal structure changes.
0:14:50 > 0:14:56Our blood loses its ability to clot, leading to a cruel and bizarre fate.
0:14:58 > 0:15:02Blood oozes... from almost any orifice,
0:15:02 > 0:15:08out of your nose, and your mouth and your rect...your bottom, from your stomach,
0:15:08 > 0:15:12anywhere in your body, and people just die from that.
0:15:14 > 0:15:19Day five. By the time all the victims had been discovered
0:15:19 > 0:15:23the heat wave had already left Chicago.
0:15:26 > 0:15:29It's just unbelievable
0:15:29 > 0:15:34that so many people can die so quickly, just from the weather.
0:15:35 > 0:15:38It was an awful week.
0:15:44 > 0:15:51In the end, the tropical heat wave had claimed 525 victims in under a week.
0:15:53 > 0:16:00The city and its people were simply not prepared for the intense jungle weather that invaded their lives.
0:16:04 > 0:16:11With only 12 hours left in the jungle, I'm about to experience night-time weather in the tropics.
0:16:12 > 0:16:15As the heat of the day subsides,
0:16:15 > 0:16:21all the moisture hanging in the air means nightfall can bring heavy rain or worse.
0:16:21 > 0:16:26Bob and I are making sure we're ready for anything.
0:16:26 > 0:16:28Have you bought the duvets?
0:16:28 > 0:16:33I'm afraid not, not out here. We do have sleeping bags.
0:16:33 > 0:16:40Where's my little Coke? And a little kind of mini-bar and a phone here for room service.
0:16:40 > 0:16:44- The creature comforts, eh?- Plenty of creatures, no comforts here. Ah!
0:16:44 > 0:16:48You're looking at a good 12 hours of darkness,
0:16:48 > 0:16:52and we wouldn't move during the night because of how thick the jungle is.
0:16:52 > 0:16:57From stopping, you'll probably get a good 12 hours' kip.
0:16:57 > 0:16:59Any Maltesers, chocolates, Pringles?
0:16:59 > 0:17:02I've got some noodles.
0:17:02 > 0:17:04Yeah.
0:17:04 > 0:17:07I can't remember where I left my machete.
0:17:11 > 0:17:16As night falls, a stormier kind of weather takes hold.
0:17:16 > 0:17:23After 12 hours of sunshine, when hot, humid air releases massive amounts of energy,
0:17:23 > 0:17:25this is the result.
0:17:28 > 0:17:31THUNDER CRASHES
0:17:32 > 0:17:37A big storm can dump several inches of rain in a night,
0:17:37 > 0:17:40equal in power to an atomic bomb.
0:17:40 > 0:17:45They can also reduce the jungle to matchwood.
0:18:13 > 0:18:15RAIN BATTERS DOWN
0:18:15 > 0:18:23I know there aren't supposed to be seasons in the jungle, but this certainly feels like winter to me.
0:18:27 > 0:18:31It's about 7 o'clock in the morning,
0:18:31 > 0:18:34it's raining outside, it's cold,
0:18:34 > 0:18:36I've had an awful sleep.
0:18:36 > 0:18:39And I'd just like to say
0:18:39 > 0:18:43that communing with nature in the jungle
0:18:43 > 0:18:45isn't all...
0:18:45 > 0:18:48it's set up to be.
0:19:05 > 0:19:07(Oh, God!)
0:19:07 > 0:19:09Sorry.
0:19:11 > 0:19:14- Disaster, Bob.- I did warn you.
0:19:18 > 0:19:23At least the spiders that were in them have now gone, or drowned.
0:19:24 > 0:19:30DONAL LAUGHS The main thing is to learn something.
0:19:30 > 0:19:37I thought the tropics, where the sun's energy is at its most intense, would be the hottest place on earth.
0:19:37 > 0:19:43But I'm wrong. I'm about to get out of the frying pan and get into the fire.
0:19:43 > 0:19:47I'm heading to the hottest place on earth.
0:19:47 > 0:19:54From the heart of the tropics, all that warm air rises, dumping its rain as it goes.
0:19:54 > 0:20:00At around nine miles high, at the edge of the troposphere, it can rise no further,
0:20:00 > 0:20:05so it begins to head both north and south of the equator.
0:20:05 > 0:20:12About 1500 miles later, at about 20 degrees latitude, the air begins to sink back down to earth,
0:20:12 > 0:20:15warming as it drops.
0:20:16 > 0:20:22Where it falls, it creates two strips of arid land that circle the globe.
0:20:22 > 0:20:27That's where you'll find the great deserts of the world.
0:20:29 > 0:20:33And the greatest of them all is the Sahara.
0:20:33 > 0:20:41Having left all that wet heat in the jungle, I am about to find out what dry heat does to the weather.
0:20:52 > 0:20:57The air above me is so warm that water cannot condense into rain,
0:20:57 > 0:21:02so it hangs there, trapped, above the very places that need it most.
0:21:02 > 0:21:09Just look around me at the results. Theoretically, there's more moisture in the sky above me now
0:21:09 > 0:21:13than over the skies of Britain and yet it's completely clear.
0:21:13 > 0:21:17This desert only gets three inches of rain every year.
0:21:17 > 0:21:21Even when it does rain, the sun's rays are so intense
0:21:21 > 0:21:25that it evaporates 200 times the amount that falls.
0:21:25 > 0:21:28So, this is what we're left with.
0:21:40 > 0:21:42The sun cooks the desert rocks,
0:21:42 > 0:21:48causing the minerals to expand so much that the rocks eventually shatter.
0:21:49 > 0:21:54Over thousands of years, powerful desert winds grind them all to sand.
0:21:56 > 0:22:03The Sahara covers an area of over 3 million square miles, almost as big as the USA.
0:22:04 > 0:22:06It's also record-breakingly hot.
0:22:07 > 0:22:12In 1922, the highest air temperature ever recorded was taken here,
0:22:12 > 0:22:18a staggering 58 degrees Celsius, 136.4 degrees Fahrenheit.
0:22:21 > 0:22:27Just one of these dunes is made up of thousands of tons of sand.
0:22:27 > 0:22:34All those tiny grains go to make up our most romantic and enduring image of the world's deserts...
0:22:36 > 0:22:41..endlessly driven by the winds, like some half-frozen ocean.
0:22:45 > 0:22:48This is an amazing place.
0:22:48 > 0:22:52The vast stillness is completely overwhelming.
0:22:52 > 0:22:57It's timeless. There's a real sense that nothing here has ever changed.
0:22:57 > 0:22:59But that's an illusion.
0:22:59 > 0:23:04Beneath this ocean of sand lies an incredible secret.
0:23:05 > 0:23:08In 1981, 140 miles above my head,
0:23:08 > 0:23:15the space shuttle Columbia looked down upon this desert and took a hi-tech snapshot.
0:23:16 > 0:23:21What they saw took them completely by surprise.
0:23:21 > 0:23:25Instead of a flat and barren expanse of sand,
0:23:25 > 0:23:30the infrared revealed mountains and river valleys underneath.
0:23:30 > 0:23:36That picture revealed a hidden world only a few metres beneath my feet.
0:23:47 > 0:23:51As they saw through the layers of sand,
0:23:51 > 0:23:58they where amazed to discover that, 35 million years ago, the Sahara was once a great fertile savannah
0:23:58 > 0:24:01with rivers and lush meadows.
0:24:04 > 0:24:11Over time, small changes in the global climate meant that life simply withered and died.
0:24:13 > 0:24:20We like to think of the desert as timeless, but in fact it is constantly changing.
0:24:22 > 0:24:27Here in the dry heat of the desert my journey continues,
0:24:27 > 0:24:33this time to see if I can survive the highest temperatures on the planet.
0:24:33 > 0:24:37Instead of the sunbathing and camel treks I'd hoped for,
0:24:37 > 0:24:43I have to face a tougher test, so I'm practising for the most gruelling marathon on earth.
0:24:47 > 0:24:54I've come here to run in the toughest race in the world, the infamous Marathon Of The Sands.
0:24:54 > 0:25:01Seven days through some of the hottest and most hostile environments on the planet.
0:25:10 > 0:25:16If you really want to experience the very worst the desert weather can throw at you,
0:25:16 > 0:25:21this is the one event that promises to hit you with everything.
0:25:21 > 0:25:27Cutting desert winds, killer dehydration, blinding dust and the unbearable searing heat.
0:25:27 > 0:25:31Earlier on, it seemed like a very good idea.
0:25:33 > 0:25:36STARTER COUNTS DOWN
0:25:49 > 0:25:56Unlike in the jungle, all this hot, dry air literally sucks the water out of you,
0:25:56 > 0:26:01so I've been told to carry and drink at least nine litres per day.
0:26:01 > 0:26:06And when it really heats up, I'll be losing a litre an hour.
0:26:20 > 0:26:24This is the really tough part. I can hardly move.
0:26:36 > 0:26:42I haven't been running for too long, but already I can feel myself sweating all over.
0:26:42 > 0:26:48You can't really see it, because the sun's evaporating it straight from my skin, but if you do this,
0:26:48 > 0:26:52you can taste the salt and the sweat.
0:26:52 > 0:26:58And the more I sweat, the more salt I lose. In a full day, I can lose about three teaspoonfuls.
0:26:58 > 0:27:03That could be really dangerous. It could give me severe muscle cramps.
0:27:03 > 0:27:10And because salt's essential for brain function, it can leave me disorientated and confused.
0:27:10 > 0:27:12No change there, then.
0:27:15 > 0:27:22The desert heat can play tricks on you at the best of times. Without water, these tricks can be lethal.
0:27:22 > 0:27:27The temperature on the ground here can get close to boiling point.
0:27:27 > 0:27:32It's only about 9am, but already the heat is vicious.
0:27:32 > 0:27:38I can feel my head throbbing and tightening as the sun takes its toll.
0:27:38 > 0:27:45But if I do this, that's when the heat really hits you. Down here it's 50% hotter than at eye level.
0:27:45 > 0:27:50The temperature difference creates strange, sometimes deadly effects.
0:27:53 > 0:27:56We've all heard the stories.
0:27:56 > 0:28:00You're lost, you've used your last drop of water.
0:28:07 > 0:28:15And just as it looks like it's all over, you see a lake shimmering on the horizon.
0:28:15 > 0:28:22In the distance you see the water you've been so desperately searching for,
0:28:22 > 0:28:26but however fast you run towards it, it never gets any closer.
0:28:29 > 0:28:36Desert mirages occur because of the temperature differences between here...
0:28:36 > 0:28:40and here. It cools by nearly 20 degrees in less than two metres.
0:28:42 > 0:28:47That incredibly hot layer near the ground can behave just like a lens.
0:28:47 > 0:28:53Like the lens in your spectacles, it can refract, actually bend the light.
0:28:53 > 0:28:59When I look out there towards the horizon, I can't see a cool lake of water.
0:28:59 > 0:29:05What I'm actually seeing is the sky refracted, so it appears to be lying on the ground.
0:29:05 > 0:29:08A cruel trick indeed.
0:29:50 > 0:29:53Oh, what monster designed that race?
0:29:55 > 0:29:59Every time you sink in the sand and it's blistering with the sun.
0:29:59 > 0:30:06And there's dust in your ears and your eyes, burning your throat, and it's like, oh... It's a killer.
0:30:13 > 0:30:19But at the end of the day, the desert has another trick of the light up its sleeve.
0:30:19 > 0:30:24There's one kind of mirage you can see out here just about every day.
0:30:24 > 0:30:30The sun I'm looking at has actually already set. It's exactly the same effect as the lake mirage.
0:30:30 > 0:30:36This optical illusion gives us two minutes of extra light at the end of the day.
0:30:56 > 0:31:01Out here, you can drive for days without seeing any signs of life whatsoever.
0:31:01 > 0:31:07And if that's not worrying enough, the desert also has some special weather treats in store
0:31:07 > 0:31:12for those foolish enough to venture into its dusty heart.
0:31:15 > 0:31:21Here in the desert, there is a menace as old as the wind that turns day to night in an instant.
0:31:21 > 0:31:27The heat rising from the desert floor mixes with the powerful easterly winds,
0:31:27 > 0:31:32creating a vicious turbulence that whips the sand up and blasts it into the air.
0:31:32 > 0:31:35It's called a haboob.
0:31:38 > 0:31:43When the wind really gets going and you're in its way, it can be very nasty indeed.
0:32:04 > 0:32:08Sometimes it can look like the whole desert is on the move.
0:32:08 > 0:32:11The sight can be truly apocalyptic.
0:32:14 > 0:32:20It happened in Melbourne, Australia, in February 1983,
0:32:20 > 0:32:25when a massive cold front gathered to the north of the city.
0:32:25 > 0:32:29As it flowed south, a thunderstorm grew along its leading edge
0:32:29 > 0:32:36causing a downdraught that kicked up the dust beneath it and drove it forward like a vast, red wave.
0:32:36 > 0:32:38As it swept into town,
0:32:38 > 0:32:45this huge wall of dust blotted out the sun in an instant and it brought the city to a standstill.
0:32:48 > 0:32:51The cloud was 320 metres thick
0:32:51 > 0:32:56and dumped over 1,000 tons of sand in an hour.
0:33:02 > 0:33:05From miles above the Sahara,
0:33:05 > 0:33:10we can see clouds of incredibly fine sand that dwarf even Melbourne's experience.
0:33:10 > 0:33:13When the wind and the sun get going,
0:33:13 > 0:33:17the clouds they create can be truly global.
0:33:28 > 0:33:32Some of them can be the size of Europe.
0:33:32 > 0:33:36Caught up in the winds that blow west across the Atlantic,
0:33:36 > 0:33:43these fine sands are carried as far as the Caribbean, where they help top up the perfect beach.
0:33:43 > 0:33:48From the mountains of Morocco to the palm trees of the Caribbean,
0:33:48 > 0:33:53these enormous dust clouds travel 4,500 miles,
0:33:53 > 0:34:00bringing about 90 million tons of the Sahara here to the Caribbean every single year.
0:34:00 > 0:34:03That's an awful lot of beach.
0:34:05 > 0:34:10My journey has finally arrived in the kind of heat we all love.
0:34:10 > 0:34:15A friendly sun, a cooling dip - it all makes for a holiday mood.
0:34:16 > 0:34:22The sun's rays boost our levels of serotonin, a brain chemical that makes us feel good.
0:34:24 > 0:34:28But this sense of wellbeing can be deceptive.
0:34:28 > 0:34:33It's easy to forget, as we cover ourselves in sun cream,
0:34:33 > 0:34:38the price we pay to soak up those precious rays.
0:34:38 > 0:34:42This feels great. Lying here is deeply relaxing.
0:34:42 > 0:34:47I'm getting a good dose of vitamin D from the sun's rays.
0:34:47 > 0:34:51But, as the hours tick by, it's a very different story.
0:34:53 > 0:34:56Sunburn!
0:34:56 > 0:35:02Beneath the surface of my skin, only half that vicious ultraviolet light from the sun is getting through.
0:35:03 > 0:35:08But even so, it's destroying the skin cells nearest the surface.
0:35:08 > 0:35:16My skin reddens as blood flow increases, carrying nutrients and oxygen to repair the damage.
0:35:16 > 0:35:21The longer I spend in the sun, the more permanent the damage becomes.
0:35:23 > 0:35:27Like me, the planet also has a protective skin.
0:35:27 > 0:35:33The atmosphere above us stops half of the sun's lethal rays,
0:35:33 > 0:35:37which are absorbed or reflected back into space
0:35:37 > 0:35:42by clouds, particles in the air and atmospheric gases.
0:35:42 > 0:35:47Without the atmosphere, life wouldn't be possible.
0:35:51 > 0:35:57But the skies that shield us from these harmful rays also contain their own deadly energy.
0:35:57 > 0:36:01It's one of summer's biggest killers - lightning.
0:36:05 > 0:36:07Viewed from space,
0:36:07 > 0:36:12NASA cameras captured these amazing images of our electric skies.
0:36:12 > 0:36:14Right at this very moment,
0:36:14 > 0:36:19there are almost 1,800 thunderstorms taking place around the planet.
0:36:19 > 0:36:25On average, lighting strikes the earth about a hundred times a second.
0:36:28 > 0:36:33When the lightning hit me, it was like nothing I could have imagined.
0:36:33 > 0:36:38I felt like someone had thrown a hand grenade in my face.
0:36:41 > 0:36:46To get as close as I could to being struck by lightning,
0:36:46 > 0:36:52I went to see Mike Alexander at the Theatre of Electricity in Boston.
0:36:53 > 0:36:58- Well, Mike, this is your very own lightning machine.- That's right.
0:36:58 > 0:37:03It's a Van de Graaff generator. It was invented here in Boston.
0:37:03 > 0:37:09It works in a very simple way. It stores a lot of extra negative charge on the top of those two spheres,
0:37:09 > 0:37:15- till there's enough charge up there to make about 1.5 million volts. - That can do a lot of damage.
0:37:15 > 0:37:20Well, everyone's safe out here, but inside this cage, it can get a little bit dangerous.
0:37:20 > 0:37:26Your hair stands on end, you get a bluish glow off your nose, you feel a shock whenever you touch anything.
0:37:26 > 0:37:28The scientists tell me
0:37:28 > 0:37:35that if you were hit by one of those lightning bolts, you would probably live. But I haven't tried that yet.
0:37:38 > 0:37:44They say that you will feel your hair stand up on your arms or your skin tingle. I didn't.
0:37:44 > 0:37:47I felt this enormous blast.
0:37:49 > 0:37:53This enormous, white light blinded me
0:37:53 > 0:37:59and I felt the electricity going through my body. That's the last thing I felt,
0:37:59 > 0:38:05because, at that point, it picked me up and threw me at the concrete and knocked me out.
0:38:05 > 0:38:07Would you like to come in?
0:38:08 > 0:38:14While the machine is working, this is the safest place to be - surrounded by metal.
0:38:14 > 0:38:19It seems that all this metal is the most unsafe it could possibly be.
0:38:19 > 0:38:25Yeah, it goes against your common sense, but if you're completely surrounded by metal, you're safe.
0:38:25 > 0:38:30- The lightning can't get in to where you are.- If you're in a thunderstorm and in a car,
0:38:30 > 0:38:36- does that mean that's a safe place to be?- It is, surprisingly enough. It has nothing to do with the tyres.
0:38:36 > 0:38:41The metal surrounding you protects you. But it has to be a METAL car. A fibreglass car is no protection.
0:38:41 > 0:38:47- What about rubber soles, Wellington boots, lightning all around you? - It would probably keep your feet dry,
0:38:47 > 0:38:53- but it won't stop a lightning bolt from hitting you.- You've just buried another old wives' tale. Terrible!
0:38:53 > 0:38:57You feel a bit like it's God's booth up here, lightning at command.
0:38:57 > 0:39:04Yeah, it's great, isn't it? You feel like the guy in the Wizard Of Oz behind the curtain.
0:39:04 > 0:39:09And they say lightning never strikes twice.
0:39:09 > 0:39:12Not so for Linda Cooper.
0:39:13 > 0:39:18I answered the telephone. It was my daughter. She wanted her dad.
0:39:18 > 0:39:24About the time she said, "Is Dad...?" lightning struck the telephone.
0:39:24 > 0:39:26I had the receiver up to my face.
0:39:26 > 0:39:32I could feel the electricity going into my face. I dropped the phone and screamed.
0:39:35 > 0:39:40And I said, "It got me again." I cannot believe that it got me again.
0:39:40 > 0:39:44The pain was nothing like the first time.
0:39:44 > 0:39:50The first time was like being hit by a truck, the second time like a moped. But the fear!
0:39:50 > 0:39:57I had just come back from years of studying, years of trying to get my health back, my strength back.
0:39:57 > 0:40:03And here it got me again. I thought it was going to steal all that away from me.
0:40:04 > 0:40:09To the naked eye, lightning always looks like it comes from the sky.
0:40:09 > 0:40:11But that's only half the story.
0:40:11 > 0:40:16What you can't see is that the big flash is shooting up from the ground
0:40:16 > 0:40:21into the clouds in one ten-thousandth of a second.
0:40:21 > 0:40:26At 30,000 degrees Celsius, the bolt superheats the air around it,
0:40:26 > 0:40:29making it literally explode...
0:40:29 > 0:40:33- LOUD CRASH - That's the sound of thunder.
0:40:33 > 0:40:39Some day something's going to go wrong here, somebody's going to be zapped. Let's hope it's not today!
0:40:39 > 0:40:44- It's pretty safe, though?- Yes, it's very safe. You don't have to worry.
0:40:44 > 0:40:50As long as you stay inside this metal cage, the lightning can strike just half an inch away from you
0:40:50 > 0:40:55and you're still absolutely safe. Put your finger out, you'll get a bad zap.
0:40:55 > 0:40:59I've done it a couple of times by mistake, and it hurts.
0:40:59 > 0:41:04- What's it like getting 1.5 million volts in your little finger? - It feels like being hit by a hammer.
0:41:04 > 0:41:09- Your muscles tense all of a sudden. It's not pleasant.- OK.
0:41:10 > 0:41:13You look a bit like a mad professor.
0:41:14 > 0:41:16It feels that way sometimes.
0:41:18 > 0:41:20Three, two, one...
0:41:30 > 0:41:35A bolt of lightning can be up to 30 miles long, and it's just the width of my thumb.
0:41:35 > 0:41:40It's also six times hotter than the sun, so I'm going to be very careful.
0:41:41 > 0:41:46In the real world though, the chances of being hit by lightning are pretty minimal.
0:41:46 > 0:41:51Even so, about a 1,000 people are killed and struck by lightning every year.
0:42:02 > 0:42:08There's about 1.5 million volts hitting my finger right now.
0:42:13 > 0:42:16Oh, my God. Thank God for that!
0:42:22 > 0:42:28The third time I was struck was totally different than the first two.
0:42:31 > 0:42:36I thought the storm was gone, so I got up and made jello.
0:42:36 > 0:42:41I went to wash out the cup after I'd finished making the jello.
0:42:43 > 0:42:47I put it in to the sink and turned on the water faucets.
0:42:47 > 0:42:52I didn't realise that the cold water faucet was a ground to your house.
0:43:00 > 0:43:04Lightning struck, came through the cold water faucet,
0:43:04 > 0:43:09ran up both of my arms and across my chest. I felt like I was on fire.
0:43:09 > 0:43:13This was totally different than the other two times.
0:43:13 > 0:43:21This time I felt like somebody had taken a torch and lit both of my arms. I put them inside the freezer.
0:43:21 > 0:43:26I leaned into my freezer and stayed there for I don't know how long.
0:43:39 > 0:43:42Lightning is nature's electricity.
0:43:42 > 0:43:47It's in the air, and it's going to hurt you if it hits you.
0:43:47 > 0:43:52It could kill you, but if you live, you will never be the same,
0:43:52 > 0:43:57you will never feel the same, you will never think the same.
0:43:57 > 0:43:59And I wouldn't wish that on anyone.
0:44:01 > 0:44:07In the future, the violence of our summer skies may be about to get worse.
0:44:07 > 0:44:11So the next time you're caught in a storm, consider this -
0:44:11 > 0:44:14it could be all your own fault.
0:44:17 > 0:44:20It's Friday and time to go home.
0:44:20 > 0:44:25The weather's been lovely all week and everyone's looking forward to a weekend in the sun.
0:44:27 > 0:44:33But have you ever noticed how the weather goes and messes it all up?
0:45:07 > 0:45:13You may think rain at the weekend is just bad luck,
0:45:13 > 0:45:20but scientist Randy Savini has stumbled on something really strange - WE may be the cause of it.
0:45:20 > 0:45:25My research into weekend rainfall began as a fortunate accident.
0:45:25 > 0:45:28I had been studying hurricanes
0:45:28 > 0:45:33and inadvertently ran a computer programme that classified hurricane observations by day of the week.
0:45:33 > 0:45:40When I plotted out those hurricane observations, I found a very bizarre, interesting pattern.
0:45:46 > 0:45:52He found that the strength of hurricanes seemed to differ depending on the day of the week.
0:45:52 > 0:45:56What Randy's computer told him about hurricanes
0:45:56 > 0:46:03led him to realise that the way we live and work may be directly changing the weather around us.
0:46:03 > 0:46:07It all comes down to the seven-day week.
0:46:07 > 0:46:13Given that the seven-day cycle is something that doesn't occur in nature,
0:46:13 > 0:46:19that it is only the result of man, if we see changes in weather that are occurring on a seven-day cycle,
0:46:19 > 0:46:24the assumption is that it's something that we're doing.
0:46:24 > 0:46:30To prove we are influencing the weather on a weekly basis, Randy needed more evidence.
0:46:30 > 0:46:37We went back to the archives and grabbed 20 years of data and looked at rainfall.
0:46:37 > 0:46:42Rainfall is something that's easily measured, that is measured in a lot of different locations
0:46:42 > 0:46:47and is very important to people. And for location after location,
0:46:47 > 0:46:54we found that rainfall showed the same exact cycles as we were seeing with hurricanes.
0:46:54 > 0:46:58It was a lot wetter on the weekends than it was during the week.
0:47:05 > 0:47:11Randy found that, as pollution levels built up over the course of the working week,
0:47:11 > 0:47:19from car exhausts and factories, the warm air carries these particles of pollution upwards.
0:47:20 > 0:47:25They rise high above the city and begin to seed the clouds.
0:47:25 > 0:47:31Moisture attaches to the particles, which eventually turn into water droplets.
0:47:31 > 0:47:38By the end of the week, it has all drifted out into the suburbs, bringing thunderstorms and showers.
0:47:46 > 0:47:52So the ironic twist is that we work all through the week
0:47:52 > 0:47:55to be able to enjoy a weekend barbecue,
0:47:55 > 0:47:59and our midweek activities are going to rain out our barbecue.
0:48:14 > 0:48:19But it's not just our cities we are affecting.
0:48:19 > 0:48:25It seems that the whole planet is warming up. The next stage of my journey is to Hawaii,
0:48:25 > 0:48:32and if this can tell us anything, it will be that a big change is just around the corner.
0:48:41 > 0:48:46I'm on my way to find the cleanest air on the planet,
0:48:46 > 0:48:52and when I get there, I'm going to show you something that changed the world.
0:48:53 > 0:48:57When it comes to the fate of the weather,
0:48:57 > 0:49:02it's the most important scientific device of the last 100 years.
0:49:04 > 0:49:07And it's just over there.
0:49:12 > 0:49:14Just a second.
0:49:18 > 0:49:20It's over here.
0:49:28 > 0:49:30Hang on a minute.
0:49:32 > 0:49:35I'll just try and find the lights.
0:49:37 > 0:49:40Yes, this is it. You guessed it.
0:49:40 > 0:49:45You're looking at the Ultramat III, the machine that changed the world.
0:49:48 > 0:49:52The reason the Ultramat III is so important
0:49:52 > 0:50:00is because up here at 14,200 feet in the middle of the Pacific is the purest air on earth,
0:50:00 > 0:50:05so it's the best place to detect any changes in the global atmosphere.
0:50:06 > 0:50:11The Ultramat III sniffed out a big change.
0:50:11 > 0:50:17The recent burning of fossil fuels has put more carbon dioxide gas into the air
0:50:17 > 0:50:21than at any other time in the last 20 million years.
0:50:21 > 0:50:26The gas acts like a greenhouse, letting the sun's energy into the atmosphere
0:50:26 > 0:50:31but preventing it leaking back into space.
0:50:31 > 0:50:36So it heats up - 0.6 degrees Celsius in the last 150 years.
0:50:36 > 0:50:40A tiny amount, but we are already seeing the effects.
0:50:43 > 0:50:48One of the biggest concerns is how these changes will affect the oceans.
0:50:48 > 0:50:55This small rise in global temperature is warming the sea, causing the water to expand.
0:50:55 > 0:51:01Even a fraction of a degree could mean that the sea level will rise by as much as a metre.
0:51:03 > 0:51:07Research by NASA's Goddard Space Institute
0:51:07 > 0:51:14has already produced a glimpse of the future for New York's 20 million inhabitants.
0:51:14 > 0:51:17In the next 100 years,
0:51:17 > 0:51:22there could be as much as 42 inches of higher seas surrounding Manhattan and New York.
0:51:22 > 0:51:27In the most catastrophic case, Manhattan turns into two islands.
0:51:37 > 0:51:39Combined with higher sea levels,
0:51:39 > 0:51:44even an ordinary storm will have drastic consequences for cities by the sea.
0:51:44 > 0:51:50'This just in. City Hall has issued an urgent flood warning.
0:51:50 > 0:51:55'A major storm surge is expected to swamp areas from the Battery to the Midtown area.
0:51:55 > 0:52:00'The Mayor's office is advising the immediate evacuation of basements...'
0:52:08 > 0:52:14The subterranean basements of New York flood about once every 100 years.
0:52:14 > 0:52:22But the research suggests that in the future this could happen once every TEN years.
0:53:13 > 0:53:16But it's not just New York.
0:53:16 > 0:53:20Every city by the sea faces the same future.
0:53:23 > 0:53:29As the world heats up and the oceans expand, the sea level will rise.
0:53:29 > 0:53:33Around the world other low coastlines,
0:53:34 > 0:53:39like those around Bangladesh or Mozambique, face an even more uncertain future.
0:53:51 > 0:53:54In London, the Thames will rise.
0:53:56 > 0:54:01And already we can see the effects on our coastline.
0:54:03 > 0:54:09Further inland, the future will bring more rain and more floods.
0:54:11 > 0:54:16It's wet, it's flooded and it's cold.
0:54:16 > 0:54:18It's also the future.
0:54:18 > 0:54:24This is Britain tomorrow - wetter, stormier and altogether under water.
0:54:34 > 0:54:40Back in the clear, clean mountain air of Hawaii,
0:54:40 > 0:54:44where we first realised that big change was on the way,
0:54:44 > 0:54:50the Ultramat III is still quietly counting the cost of our effect on the weather.
0:54:50 > 0:54:55Which is why this little machine is so important.
0:54:55 > 0:55:02There are many theories about what the weather will be like over the next 50, 100 or 200 years' time.
0:55:02 > 0:55:07One thing's for sure, a warmer climate means wilder weather.
0:55:07 > 0:55:12The question we all have to ask is what kind of world do we want?
0:55:12 > 0:55:16Because to a certain extent, each of us holds that in our own hands.
0:55:16 > 0:55:21Every time you flick a switch, you affect the future.
0:55:25 > 0:55:29We've already seen the changes around us.
0:55:29 > 0:55:34All we can do is learn to cope, whatever those changes bring.
0:55:34 > 0:55:37My journey is at an end.
0:55:37 > 0:55:43I've been blasted, roasted and soaked by the invisible forces that drive our weather.
0:55:43 > 0:55:50It's been a wild ride, and in the future it may be about to get even wilder.
0:57:09 > 0:57:14Subtitles by Dorothy Moore and Audrey Flynn BBC Broadcast 2002
0:57:14 > 0:57:17E-mail us at subtitling@bbc.co.uk