0:00:11 > 0:00:15Snow is the most beguiling feature of our British weather.
0:00:15 > 0:00:23It's the only meteorological element which changes the appearance of what we look out on, totally.
0:00:25 > 0:00:27It makes children of us all.
0:00:29 > 0:00:31A white Christmas is what we dream of.
0:00:38 > 0:00:42# Oh the weather outside is frightful
0:00:42 > 0:00:45# But the fire is so delightful
0:00:45 > 0:00:48# Since we've no place to go
0:00:48 > 0:00:51# Let it snow, Let it snow, let it snow. #
0:00:51 > 0:00:56But beyond snow's magic lies a complex and intriguing material.
0:00:56 > 0:01:01Scientists have looked deep into the microscopic world of the snow crystal.
0:01:01 > 0:01:04They found a larger world revealed.
0:01:04 > 0:01:10I can hold a piece of ice which has been un-melted since it fell thousands of years ago.
0:01:10 > 0:01:15Not only that, but I can tell you what year it fell,
0:01:15 > 0:01:19I can tell you whether the climate that year was colder or warmer that usual.
0:01:19 > 0:01:20I find that incredible.
0:01:22 > 0:01:26We are learning to predict snow, even to make it.
0:01:26 > 0:01:29Yet, for all our understanding,
0:01:29 > 0:01:33why does a small amount of snow still bring Britain to its knees?
0:01:45 > 0:01:51The snowflake is one of nature's most beautiful and tantalising creations.
0:01:56 > 0:01:59But beauty can sometimes be deceptive.
0:01:59 > 0:02:05As Britain found out when it started to snow on the 7th February, 1991.
0:02:10 > 0:02:14There was something different about this particular snow.
0:02:14 > 0:02:19It caused chaos and a new phrase entered the British vocabulary,
0:02:19 > 0:02:21"the wrong type of snow".
0:02:21 > 0:02:23- ARCHIVE:- Heavy snowfalls and bitter cold,
0:02:23 > 0:02:28temperatures down to minus 11 Centigrade have already been recorded
0:02:28 > 0:02:30on the south coast at Bournemouth.
0:02:30 > 0:02:33At five this morning it was colder there than in Moscow.
0:02:33 > 0:02:35As British Rail discovered,
0:02:35 > 0:02:42snow that falls at polar temperatures of more than minus ten has strange properties.
0:02:42 > 0:02:48'We were prepared for normal snow but we weren't prepared for this stuff, it caught us completely on the hop.
0:02:48 > 0:02:51'Reports came into my office that the trains were failing,'
0:02:52 > 0:02:55and I was getting this from all the depots.
0:02:55 > 0:02:58Everyone was saying, "we're getting trains limping in".
0:02:58 > 0:03:01Train services began to collapse.
0:03:05 > 0:03:07ARCHIVE: Rail schedules have been severely disrupted.
0:03:07 > 0:03:11- ARCHIVE:- British Rail say they've abandoned their scheduled timetables.
0:03:11 > 0:03:15They never seem to be prepared for it. Two snowflakes and everything goes wrong.
0:03:15 > 0:03:19Automatic doors began to jam, air brakes failed,
0:03:19 > 0:03:24but British Rail's Achilles heel was the trains' electric engines.
0:03:24 > 0:03:27We were losing motors at a great rate.
0:03:27 > 0:03:33Several hundred motors went in a matter of days,
0:03:33 > 0:03:37trains were limping in, sadly damaged.
0:03:37 > 0:03:42- ARCHIVE:- London's mainline rail stations are mostly closed or running skeleton services.
0:03:42 > 0:03:47A spokesman there said, "British Rail is in a mess."
0:03:47 > 0:03:48With the rail system crippled,
0:03:48 > 0:03:52British Rail's response to the London Evening Standard
0:03:52 > 0:03:55became one of the most famous excuses of all time.
0:03:55 > 0:03:59We've had this fascinating situation with the new snowflake
0:03:59 > 0:04:04and stopped the whole of British Rail and they'd never heard of this type before.
0:04:04 > 0:04:08I thought it was one of the great public relations exercises of this century.
0:04:10 > 0:04:14So was Jeffrey Archer right to be sceptical, or could British Rail
0:04:14 > 0:04:17really have fallen victim to "the wrong type of snow"?
0:04:19 > 0:04:26The answer lies in the work of a Japanese scientist, Ukichiro Nakaya.
0:04:28 > 0:04:32In the 1930s, in a remote mountain research hut,
0:04:32 > 0:04:38Nakaya, a scientist at the University of Hokkaido, began his remarkable work.
0:04:40 > 0:04:46This footage has been released by his family to be shown for the first time on British television.
0:04:47 > 0:04:53Nakaya wanted to discover the atmospheric conditions that grew snow crystals in the clouds.
0:04:53 > 0:04:57To do this, he needed to try and create snow in the lab.
0:04:57 > 0:04:59This was thought impossible.
0:05:06 > 0:05:12Nakaya built a cloud chamber in which he could adjust temperature, air pressure and humidity.
0:05:12 > 0:05:17His aim was to mimic the conditions found in snow-producing clouds.
0:05:20 > 0:05:25After three years, he had a breakthrough.
0:05:25 > 0:05:27This is Nakaya's own footage.
0:05:27 > 0:05:33On the tip of a fine rabbit hair, he grew the first ever artificial snowflake.
0:05:50 > 0:05:54He discovered that by finely adjusting the humidity and temperature,
0:05:54 > 0:05:59he could create snow crystals with a huge array of shapes and type,
0:05:59 > 0:06:01just like those found in nature.
0:06:10 > 0:06:16There wasn't just the classic star-shaped crystals you see on a Christmas card.
0:06:20 > 0:06:25At minus ten and low humidity, he grew simple hexagonal plates.
0:06:25 > 0:06:31Dropping the temperature further to minus 25, he grew column-shaped crystals.
0:06:31 > 0:06:35Nakaya went on to discover hundreds of different types of snow.
0:06:46 > 0:06:52Nakaya's legacy was to compile the first ever classification of snow.
0:06:55 > 0:06:59More importantly, because of his pioneering work,
0:06:59 > 0:07:05we can now understand the conditions within clouds from the shape of a snow crystal.
0:07:07 > 0:07:13So, back in 1991, as British Rail battled the polar weather,
0:07:13 > 0:07:20can Nakaya's classification of the different types of snow give us an explanation of what happened?
0:07:20 > 0:07:24Simply looking back at these charts from February '91,
0:07:24 > 0:07:26you can see that with such cold air over us,
0:07:26 > 0:07:28the snowflakes would have been that much smaller,
0:07:28 > 0:07:31and you wouldn't get the big, fluffy, goose feather-type
0:07:31 > 0:07:33snowflakes we often see in this country.
0:07:33 > 0:07:36Primarily because the air was just so dry.
0:07:40 > 0:07:45As Nakaya has shown us, when the temperature is minus ten with low humidity,
0:07:45 > 0:07:50the snow that forms is very fine plate crystals.
0:07:51 > 0:07:54This is more like snow called "diamond dust"
0:07:54 > 0:07:56found at the North Pole.
0:07:59 > 0:08:04These crystals find their way though the smallest of gaps.
0:08:04 > 0:08:06Combined with the high winds from Scandinavia,
0:08:06 > 0:08:10it was like sand-blasting British Rail's rolling stock.
0:08:12 > 0:08:18Trains are driven along by large electric motors which we call traction motors.
0:08:18 > 0:08:22And they are in here between the wheels.
0:08:22 > 0:08:26To keep them cool, cooling air is fed down a duct,
0:08:26 > 0:08:32the air is drawn into the locomotive through the vents up at roof level.
0:08:32 > 0:08:38And unfortunately, on this occasion, as well as air came snow.
0:08:38 > 0:08:42And the snow, when it got into the traction motor, melted,
0:08:42 > 0:08:44turned to water.
0:08:44 > 0:08:48And water with high voltage electricity means trouble.
0:08:48 > 0:08:52There was a big bang and we'd lost the traction motor.
0:08:52 > 0:08:54The failure rate was enormous,
0:08:54 > 0:08:59and basically, it caused the railway network to almost collapse.
0:09:01 > 0:09:08The particular snow that we had that year was quite different, and I hope I never see it again.
0:09:08 > 0:09:13So it really was the wrong type of snow that crippled British Rail.
0:09:13 > 0:09:18An extremely rare occurrence in this country.
0:09:18 > 0:09:23It's thanks to Nakaya's classification that we can identify the culprit.
0:09:23 > 0:09:25Tiny plate crystals.
0:09:39 > 0:09:45Long before Nakaya's discoveries, it was the gods that took the blame for all kinds of snow.
0:09:46 > 0:09:51In ancient Scotland, they believed that snow was brought by the Cailleach,
0:09:51 > 0:09:53a blue winter hag.
0:09:55 > 0:10:00This queen of winter personified the elemental powers of nature.
0:10:00 > 0:10:05The Ancient Greeks, before myth gave way to science,
0:10:05 > 0:10:08had their own snow god, and he had a bad reputation.
0:10:08 > 0:10:12The Greeks thought that all things in nature in 1000 BC
0:10:12 > 0:10:16were caused by the gods fighting amongst themselves.
0:10:16 > 0:10:19Mount Olympus was like the lodging house of a dysfunctional family.
0:10:19 > 0:10:26And they would have blamed all the worst conditions of weather and cold upon one god, Kraikas.
0:10:26 > 0:10:32His name meant evil, he was the son of Boreas, the son of the north wind.
0:10:32 > 0:10:39And Kraikas, of course, was often seen flying through the air and in his hands he would have a shield
0:10:39 > 0:10:44and it would be full of hailstones and he'd chuck these at the world with tremendous force
0:10:44 > 0:10:49to bring hail and storms and cold and snow
0:10:49 > 0:10:54and lock the world down below into a freezing, freezing paralysis.
0:11:05 > 0:11:09Not all Greeks looked to the gods for an explanation of snowfall.
0:11:09 > 0:11:13This was a time during the dawn of geometry and science,
0:11:13 > 0:11:18and one man, Epicurus, came up with his own ingenious theory.
0:11:18 > 0:11:24Epicurus believed that in the clouds there were pores, symmetrical little pores rather like a sieve,
0:11:24 > 0:11:28and if you have the water which he thought formed in the clouds
0:11:28 > 0:11:35being forced through the grater and freezing on the way down,
0:11:35 > 0:11:41you will end up having a lovely covering of snow on the ground.
0:11:41 > 0:11:44And it's not a bad idea, is it?
0:11:47 > 0:11:51Epicurus may have been wildly wrong about how snow forms,
0:11:51 > 0:11:54but he was right to focus on how it falls.
0:11:59 > 0:12:02Remarkably, as snow descends,
0:12:02 > 0:12:06it captures the chemistry of the atmosphere.
0:12:07 > 0:12:11In polar regions, it freezes and forms layers.
0:12:11 > 0:12:15These layers can survive for hundreds of thousands of years.
0:12:17 > 0:12:23This frozen snow gives scientists an extraordinary glimpse into the past.
0:12:23 > 0:12:30Since the birth of man, snow has been keeping a diary of climate change and human events.
0:12:41 > 0:12:47The eruption of volcanoes, the industrial revolution,
0:12:47 > 0:12:50each has been recorded by snow.
0:12:50 > 0:12:53So as snow falls through the atmosphere, it actually catches
0:12:53 > 0:12:55quite a lot of what's floating around in the air.
0:12:55 > 0:12:58So, for example, we can see sulphuric acid from big volcanoes,
0:12:58 > 0:13:00you can see lead from leaded petrol,
0:13:00 > 0:13:03you can see climate change, you can see temperature.
0:13:03 > 0:13:07So what we do is we go to the polar regions, we drill down into the ice.
0:13:07 > 0:13:09Because the ice is built up year on year,
0:13:09 > 0:13:13as we drill deeper in to the ice, effectively, we're drilling into the past.
0:13:13 > 0:13:16So my job is to excavate that ice from the polar ice sheets,
0:13:16 > 0:13:18bring it back to the lab,
0:13:18 > 0:13:23and work out what's been happening to the climate and the atmosphere over many thousands of years.
0:13:44 > 0:13:47Well, I can go into the cold room and I can hold a piece of ice
0:13:47 > 0:13:50which has been unmelted since it fell thousands of years ago.
0:13:50 > 0:13:54Not only that, but I can tell you how old it is, I can tell you what year it fell,
0:13:54 > 0:13:57I can tell you that year if it was colder or warmer than usual,
0:13:57 > 0:14:01I can tell you what levels of carbon dioxide was in the atmosphere.
0:14:01 > 0:14:05All of this from a tube of ice which hasn't melted in thousands of years.
0:14:05 > 0:14:07I find that incredible.
0:14:09 > 0:14:15The way snow records the temperature is in the change of the chemistry of the water itself.
0:14:15 > 0:14:18Now, what we do is we look at the oxygen in the water,
0:14:18 > 0:14:21and we get two different types of oxygen.
0:14:21 > 0:14:23One we call Oxygen 16 and one we call Oxygen 18.
0:14:23 > 0:14:28And the ratio of those two types of oxygen changes with temperature.
0:14:28 > 0:14:31So broadly speaking, the warmer the climate,
0:14:31 > 0:14:33the more we see of the oxygen 18,
0:14:33 > 0:14:36and the colder the climate, the less we see of the oxygen 18.
0:14:40 > 0:14:44When scientists studied temperature records from ice cores in Greenland,
0:14:44 > 0:14:48they noticed something unusual had happened 700 years ago.
0:14:51 > 0:14:56The planet's temperature started to drop steadily,
0:14:56 > 0:15:01and by the 16th century, the average temperature in Britain had fallen by half a degree.
0:15:01 > 0:15:04Half a degree temperature change doesn't sound like an awful lot,
0:15:04 > 0:15:08but it's enough to shift the winter temperatures significantly colder,
0:15:08 > 0:15:13so we would have more snow, more frost, perhaps rivers freezing over.
0:15:14 > 0:15:18It's not yet clear what caused this half-a-degree drop.
0:15:18 > 0:15:23But we do know it has led to a period known as "the Little Ice Age".
0:15:23 > 0:15:27The impact on Britain was devastating.
0:15:28 > 0:15:34The coldest period was the 300 years between 1550 and 1850.
0:15:37 > 0:15:42In Scotland, cod fishing failed as fish migrated south.
0:15:43 > 0:15:49Bitter winters reduced the growing seasons for farmers by as much as two months.
0:15:51 > 0:15:53Crops failed.
0:15:53 > 0:15:56The result was malnutrition and famine
0:15:56 > 0:16:01which aggravated the plague and the influenza epidemic of 1557.
0:16:03 > 0:16:06Many rooms wouldn't even have had fireplaces,
0:16:06 > 0:16:11and you would have had people locked in by the cold for months and months on end.
0:16:19 > 0:16:23The Little Ice Age caused the River Thames to freeze over.
0:16:23 > 0:16:27Lively Frost Fairs were staged on the ice.
0:16:27 > 0:16:31This new frozen territory quickly became a lawless zone
0:16:31 > 0:16:34outside the control of the authorities.
0:16:36 > 0:16:40You had stalls, you had oxen being roasted on the ice,
0:16:40 > 0:16:43you had drink being sold outside the normal legal limit,
0:16:43 > 0:16:50you have all sorts of people flocking in for illicit trading and fun and games.
0:16:50 > 0:16:55When you read even the poems and the plays and the songs of this period,
0:16:55 > 0:16:58there's a whole sense of the depths of winter.
0:16:58 > 0:17:04And one particular song I know, each strain ends with all of the jollities you get at Christmas,
0:17:04 > 0:17:07"to keep the hard winter away".
0:17:07 > 0:17:11So every strain ends "To keep the hard winter away, mm-mm."
0:17:11 > 0:17:15And gives you a sense of how bitter winters were in those days.
0:17:20 > 0:17:26The regular snowfalls of the Little Ice Age prompted one of Britain's greatest scientific minds
0:17:26 > 0:17:28to explore the structure of snow.
0:17:30 > 0:17:34This was made possible thanks to an amazing new invention.
0:17:36 > 0:17:43The revolutionary instrument which would lead to huge advances in science was the microscope.
0:17:43 > 0:17:45The scientist, Robert Hooke.
0:17:48 > 0:17:53In the mid-17th century, Hooke was one of a small group of visionaries
0:17:53 > 0:17:56pushing the boundaries of experimental science.
0:17:56 > 0:17:59To understand Robert Hooke's work with the microscope,
0:17:59 > 0:18:03you have to first look at the invention of the telescope, 60 years before.
0:18:03 > 0:18:07Galileo had first shown, along with an Englishman called Thomas Harriot,
0:18:07 > 0:18:13that when you use the newly-invented Dutch spyglass or telescope, the universe looks utterly different.
0:18:13 > 0:18:17And this is the first device to, what I call, break the perception barrier.
0:18:17 > 0:18:22To go beyond the naked eye and show what instrumentation can do for refining the human senses.
0:18:22 > 0:18:28The microscope was invented in the early 17th century, around the same time as the telescope,
0:18:28 > 0:18:33but for decades the microscope had been mainly used as a toy.
0:18:33 > 0:18:37Robert Hooke's genius was to recognise it as a research tool.
0:18:37 > 0:18:41What the microscope does is enable you to see a realm
0:18:41 > 0:18:44as vast and as intricate and as beautiful in the minute
0:18:44 > 0:18:51as what Galileo and Harriot saw in the heavens with a telescope.
0:18:51 > 0:18:56Hooke began to draw everything in this new world revealed by the microscope.
0:18:56 > 0:19:02In January 1665, he published his great work, Micrographia.
0:19:02 > 0:19:07The book transformed our perception of the natural world.
0:19:15 > 0:19:18People were amazed that there was such a wonder
0:19:18 > 0:19:21in the world beyond vision shown by lenses.
0:19:23 > 0:19:30To study snow under the microscope, Hooke had to work in a rooftop gazebo at freezing temperatures.
0:19:33 > 0:19:38Allan Chapman has reconstructed Hooke's research technique.
0:19:38 > 0:19:42He mentions at first noticing snowflakes on a black hat
0:19:42 > 0:19:48or on a black cloak and being struck by their beautiful geometry.
0:19:49 > 0:19:56He then suggests that he would take a candle and a large vessel of water,
0:19:56 > 0:20:00brine, with a very high power to bend and focus light.
0:20:00 > 0:20:05He'd then adjust the candle so it produced a focus of light,
0:20:05 > 0:20:12and he'd then adjust it until there was a brilliant illumination falling on the snowflake.
0:20:29 > 0:20:33Hooke's drawings revealed that all snowflakes had six sides.
0:20:33 > 0:20:38He saw it as divine, it was part of God's plan that ran through the whole of the natural world.
0:20:41 > 0:20:45With the microscopes of the time, Hooke couldn't get close enough
0:20:45 > 0:20:50to understand the scientific explanation for the six-sided crystals.
0:20:50 > 0:20:53And this extraordinary thing about the crystal aspect of it.
0:20:53 > 0:20:55The six, why is it six?
0:20:55 > 0:20:59We don't really know as children or even as non-scientific adults.
0:20:59 > 0:21:01It's just a magical fact.
0:21:01 > 0:21:05But there's this common element of the sixy-ness of it.
0:21:05 > 0:21:10Even by 1885, when an American, Wilson Bentley,
0:21:10 > 0:21:13combined the microscope and the newly-invented camera
0:21:13 > 0:21:16to photograph snowflakes for the first time,
0:21:16 > 0:21:19he was no closer to solving the riddle of the six sides.
0:21:26 > 0:21:30The answer lay in delving deeper into the snowflake.
0:21:30 > 0:21:34Then, in 1929, the breakthrough arrived.
0:21:38 > 0:21:42A new scientific technique called X-ray crystallography
0:21:42 > 0:21:47would allow scientists to peer into the very molecular fabric of snow.
0:21:48 > 0:21:53What they found was the frozen H2O water molecules in snow,
0:21:53 > 0:21:57arranged in a perfect six-sided hexagon.
0:21:58 > 0:22:02The snow crystal grows at the six corners of this hexagon
0:22:02 > 0:22:07and that's why the snow flake always has six sides.
0:22:07 > 0:22:10I think we are mesmerised by snow crystals
0:22:10 > 0:22:13because they remind us of the infinite beauty of nature.
0:22:13 > 0:22:15It's like looking down a kaleidoscope as a kid,
0:22:15 > 0:22:17the shape infinitely changes.
0:22:17 > 0:22:21It reminds us that even when things are cold and wet and horrible,
0:22:21 > 0:22:25there's still beauty there in a kind of geometric way.
0:22:29 > 0:22:33As snow falls to earth, it grows into a huge array of shapes.
0:22:33 > 0:22:38It's these shape that determine how different layers of snow bind together.
0:22:42 > 0:22:44These are needle crystals.
0:22:44 > 0:22:51Under the right conditions, these thin hexagonal columns can produce an unstable snow pack.
0:22:51 > 0:22:53What's known as a weak layer.
0:22:57 > 0:23:02In the Alps, they dig into the snow to check for weak layers.
0:23:02 > 0:23:08If a cross section of snow slides apart, it reveals the danger of an avalanche.
0:23:14 > 0:23:18It's a perfect demonstration that there's a weak layer there.
0:23:18 > 0:23:22This footage from the Alps shows that when a weak layer fails,
0:23:22 > 0:23:25it can trigger a slab avalanche.
0:23:42 > 0:23:44These skiers were lucky.
0:23:44 > 0:23:46They survived.
0:23:46 > 0:23:51In 1999, 31 people died in the Austrian town of Galtur
0:23:51 > 0:23:54from another type of avalanche.
0:23:54 > 0:24:00Massive snowfalls built up into giant drift cornices which suddenly collapsed.
0:24:08 > 0:24:13This kind of avalanche kills dozens of people every year in the European Alps,
0:24:13 > 0:24:15and even occasionally in Scotland.
0:24:23 > 0:24:30But you would not expect one in the sleepy, picture-postcard town of Lewes,
0:24:30 > 0:24:31in southern England.
0:24:33 > 0:24:41Yet, in 1836, this was the location of the deadliest avalanche in British history.
0:24:57 > 0:25:01This is the plaque that remembers the people that died.
0:25:01 > 0:25:04And William and Jane and Mary,
0:25:04 > 0:25:08just children and old men that were dying in this terrible accident.
0:25:15 > 0:25:19This was a time way before official meteorological records.
0:25:19 > 0:25:23So the only way we have any idea of the extreme weather
0:25:23 > 0:25:27that led up to the disaster on December 27th 1836
0:25:27 > 0:25:33is thanks to a private diary held in the Met Office archives.
0:25:33 > 0:25:37Looking at these diaries, you see that overall it was a pretty average month,
0:25:37 > 0:25:40until we got towards the end of the month, towards Christmas itself,
0:25:40 > 0:25:45where it looks like there was an awful lot of snow in a short space of time, and those drift heights,
0:25:45 > 0:25:48anything up to 30 or 50 feet in some parts of the country.
0:25:48 > 0:25:52I mean, depths of 50 feet, if you imagine that walking along the pavement
0:25:52 > 0:25:58and you think how a house is, that's a pretty high snowdrift to be having to deal with.
0:26:02 > 0:26:05Although snow of this depth can be a problem,
0:26:05 > 0:26:10the real danger was the direction of a blizzard from the north east.
0:26:10 > 0:26:15This whisked thousands of tonnes of snow across the South Downs.
0:26:15 > 0:26:20When it reached the top of the cliffs, 300 feet above Lewes,
0:26:20 > 0:26:25it accumulated into a large snowdrift overhanging the town.
0:26:29 > 0:26:34Up where the Snowdrop Inn is now, there would have been a row of seven cottages called Bolters Row.
0:26:35 > 0:26:38They were for the very poorest people living in Lewes.
0:26:38 > 0:26:40They were very densely populated.
0:26:40 > 0:26:44We know there were 40 people living there,
0:26:44 > 0:26:46and 11 children in one household alone.
0:26:47 > 0:26:52We're not used to large amounts of snow down here and I'm sure the children were enjoying it,
0:26:52 > 0:26:57I suspect people were admiring the snow coming over the cliff, thinking how wonderful it looked.
0:26:58 > 0:27:01One man, though, a local publican, was worried about the snow.
0:27:01 > 0:27:04There'd been cracks discovered in it the day before.
0:27:04 > 0:27:07And he decided to climb up and see how bad the danger was.
0:27:10 > 0:27:15And as he got up there, he saw more and more cracks appear and the avalanche happened there and then.
0:27:15 > 0:27:20He was running back down to warn people and as he ran the snow came down beside him.
0:27:22 > 0:27:27The avalanche hit with so much force that when it reached the row of houses,
0:27:27 > 0:27:29they exploded.
0:27:35 > 0:27:40There was enormous devastation there. The cottages were torn to pieces.
0:27:53 > 0:27:57It was a scene of total destruction.
0:27:57 > 0:28:02Surprisingly, several women and children were dug out alive.
0:28:02 > 0:28:07Tragically, five adults and three children were killed.
0:28:09 > 0:28:14It is just terrifying just to think of them trapped under that snow.
0:28:20 > 0:28:24In the churchyard there's a mass grave, but it's completely unmarked.
0:28:24 > 0:28:29This is the only memory, kind of memorial stone for these people.
0:28:31 > 0:28:35And I know there was a baby that was taken out of here alive.
0:28:35 > 0:28:40And I've actually had the descendant of that baby, who's been in this church.
0:28:43 > 0:28:46So how do we know if the heavy snowfall
0:28:46 > 0:28:50that caused an avalanche in the south of England will happen again?
0:28:50 > 0:28:57Without records, we have no patterns and no way of knowing what to predict and what to prepare for.
0:29:03 > 0:29:09In Britain, it's thanks to just one man that we have any official record of snowfall at all.
0:29:09 > 0:29:14His name was Leo Claude Wallace Bonacina.
0:29:14 > 0:29:21He was so obsessed with snow that his friends nicknamed him "the Abominable Snowman".
0:29:21 > 0:29:27Leo Bonacina was a typical late Victorian, eccentric gentleman.
0:29:27 > 0:29:35His main interest was weather and especially snow, and in a cold winter, he'd tramp around London
0:29:35 > 0:29:37from Hampstead Heath to Richmond Park,
0:29:37 > 0:29:41measuring the snow depth in different parts of the capital.
0:29:41 > 0:29:48By going though private diaries, old newspaper reports and railway company logs,
0:29:48 > 0:29:51along with his own up-to-date measurements,
0:29:51 > 0:29:57Bonacina spent a lifetime piecing together a record of snowfall in Britain.
0:29:57 > 0:30:03He produced a catalogue of exactly what snow conditions were like
0:30:03 > 0:30:08over the UK as a whole in every year from 1875
0:30:08 > 0:30:11until his death in 1975.
0:30:11 > 0:30:14In other words very, very nearly 100 years of records.
0:30:15 > 0:30:21And Bonacina's records reveal a surprising pattern in British snowfall.
0:30:21 > 0:30:28We seem to think that a typical British winter will inevitably bring snowfall, little or much,
0:30:28 > 0:30:32but Bonacina's records actually show that a snowy winter
0:30:32 > 0:30:35is actually quite a rare animal in the British Isles.
0:30:35 > 0:30:37They don't happen all that often.
0:30:37 > 0:30:40There have been many periods in the past where we have had
0:30:40 > 0:30:43three or four winters without very much snow at all.
0:30:43 > 0:30:47But then, along comes a really good snowy winter
0:30:47 > 0:30:49just to remind us that it can happen.
0:31:03 > 0:31:08The winter of all winters was in 1963.
0:31:08 > 0:31:12The unprecedented Arctic conditions would break all the records.
0:31:12 > 0:31:14The sea froze over.
0:31:15 > 0:31:2095,000 miles of roads became snowbound.
0:31:20 > 0:31:26Milk froze, water pipes cracked and fresh water had to be rationed.
0:31:26 > 0:31:29NEWSREEL: Tanks were set up in the street, but even they froze up.
0:31:29 > 0:31:34And you needed hot water to thaw out the tap, before you could get cold water to make hot water with.
0:31:34 > 0:31:38This was the coldest winter for centuries,
0:31:38 > 0:31:41in fact, the coldest since the bitter winters of the Little Ice Age.
0:31:41 > 0:31:45It was in this blizzard that three people died battling against the snow
0:31:45 > 0:31:49and two more were suffocated in a snowbound car.
0:31:53 > 0:31:57Hundreds of towns and villages were cut off.
0:31:57 > 0:32:02For some, the only way to survive was to walk miles in the snow.
0:32:02 > 0:32:05Others had to be carried to safety.
0:32:15 > 0:32:20By mid-January, food supplies were dangerously low all across the country.
0:32:22 > 0:32:27Farmers struggled to harvest their crops and feed their livestock.
0:32:27 > 0:32:32If they couldn't reach the animals, they would die.
0:32:35 > 0:32:40On the Isle of Wight, Christine Broom was a 16-year-old farm worker.
0:32:45 > 0:32:51She'd been in charge of cattle that were now stranded on a farm six miles from her home.
0:32:52 > 0:32:57The only way to get to the livestock was to walk through the deep snow.
0:33:02 > 0:33:08This is the first time Christine has re-traced her steps for 50 years.
0:33:08 > 0:33:14Once I'd started walking, I realised that it was absolutely horrendous.
0:33:14 > 0:33:20There were drifts of 10, 15 feet deep and you couldn't see any houses,
0:33:20 > 0:33:23a lot of the telegraph poles, you only saw the top of them,
0:33:23 > 0:33:26you actually trod on the roofs of cars.
0:33:26 > 0:33:32Unusually still, you didn't see anyone, you didn't see any animals or any people at all.
0:33:32 > 0:33:34It just seemed to be me walking,
0:33:34 > 0:33:36and it was just like a wilderness of snow.
0:33:36 > 0:33:39It was very quiet, quite haunting, really.
0:33:45 > 0:33:51A journey that on a sunny summer's day takes just over 60 minutes, took Christine six hours.
0:33:51 > 0:33:54She then had several more hours of farm work.
0:33:54 > 0:34:00The snow was right nearly to the top of the barn here and everything was just covered in snow.
0:34:00 > 0:34:04It was really hard work to get the feed to the cattle and get the cattle milked.
0:34:04 > 0:34:09And when I'd finished at five o'clock I had to trudge all the way home,
0:34:09 > 0:34:12and it was another six hours until I got back to Lake.
0:34:12 > 0:34:14And it was really hard work.
0:34:17 > 0:34:23After this 12-hour round trip, Christine had to do it all again the next morning.
0:34:23 > 0:34:28Remarkably, she kept this up for six long weeks.
0:34:28 > 0:34:31The winter of '62-'63 was really, really bad.
0:34:31 > 0:34:37It was the coldest over the UK as whole since 1740.
0:34:37 > 0:34:44The first snow fell in Scotland on Christmas Day and over England and Wales on Boxing Day.
0:34:44 > 0:34:50And over most of England and Wales, the snow stayed on the ground until the beginning of March.
0:34:50 > 0:34:53In other words, something like 70 consecutive days.
0:34:55 > 0:34:57It was the longest cold spell on record.
0:35:00 > 0:35:04The British adapted quickly to the new conditions.
0:35:04 > 0:35:10# Snow, snow, snow, snow, snow
0:35:10 > 0:35:16# It won't be long before we'll all be there with snow
0:35:16 > 0:35:19# Snow, snow
0:35:19 > 0:35:24# I wanna wash my hands, my face and hair with snow
0:35:27 > 0:35:29# Snow
0:35:29 > 0:35:34# I want to clear a path and lift a spade of snow
0:35:34 > 0:35:37# Snow, oh... #
0:35:37 > 0:35:40I could see the adults were worried about it, they were kind of frowning
0:35:40 > 0:35:43and thinking the world was coming to an end.
0:35:43 > 0:35:47We'd just had the Cuban missile crisis, the Cold War was going on and we were frozen solid.
0:35:47 > 0:35:52But for the kids it was fantastic, we'd go out sledging for three or four days on the run.
0:35:52 > 0:35:55In fact my mum said to me, "This might never end, you know".
0:35:58 > 0:36:00Ian's mum was almost right.
0:36:00 > 0:36:05The arctic winter gripped Britain for nearly three months.
0:36:05 > 0:36:12The reasons for this phenomenon lay in the unusual meteorological conditions over the British Isles.
0:36:12 > 0:36:15What happens in a typical British winter
0:36:15 > 0:36:18is that you have low pressure in the Iceland region,
0:36:18 > 0:36:22and high pressure around the Azores,
0:36:22 > 0:36:26and between the two, you have south-westerly winds blowing from the Atlantic
0:36:26 > 0:36:28across the British Isles,
0:36:28 > 0:36:34and that gives typical British winter weather of rain and wind and temperatures above freezing.
0:36:34 > 0:36:37What happened in '63 was that everything was reversed.
0:36:37 > 0:36:43On December 21st, this Siberian anti-cyclone started to move in our direction.
0:36:43 > 0:36:49But the westerly Atlantic winds that usually keep it at bay suddenly weakened,
0:36:49 > 0:36:55and the Siberian anti-cyclone moved right across to us, and by Dec 22nd,
0:36:55 > 0:37:00it had hit us, it was here and the Big Freeze had begun.
0:37:00 > 0:37:04There were several occasions, especially during February,
0:37:04 > 0:37:06when the Atlantic tried to assert itself,
0:37:06 > 0:37:11but it never got further than south-west England and Wales and Northern Ireland.
0:37:11 > 0:37:14And these regions were the battleground during February,
0:37:14 > 0:37:18between the mild Atlantic air and the cold continental air.
0:37:18 > 0:37:23And as a result, these regions got plastered with snow, time after time.
0:37:26 > 0:37:31In spite of the hardship and cold endured through the winter of 1963,
0:37:31 > 0:37:34there were always those who revelled in the snow.
0:37:44 > 0:37:50If I think of the word snow, what immediately comes to mind is I think I'm about 12 or 13
0:37:50 > 0:37:57and the park that I walk through to get to school was overnight covered in snow.
0:37:57 > 0:38:03And I remember going out with some adult studenty types who were just two doors down from where I lived,
0:38:03 > 0:38:05and we just played in it.
0:38:05 > 0:38:12So snow immediately means play to me, that that what these grown men were doing,
0:38:12 > 0:38:15and me, as a mere teenager, was doing as well.
0:38:15 > 0:38:18It's midnight and there are 6,000 people...
0:38:25 > 0:38:27We may love snow,
0:38:27 > 0:38:32but most of us have no idea of the scientific process of how snow is formed in clouds.
0:38:32 > 0:38:38It could be lots of raindrops joined together and frozen.
0:38:40 > 0:38:44I don't really know the scientific explanation at all for how snowflakes are made at all.
0:38:44 > 0:38:49They could be frozen rain, they could be something else that forms in the upper atmosphere.
0:38:50 > 0:38:56But when rain freezes, it reaches the ground as hail.
0:38:56 > 0:38:59Snow is something altogether different.
0:39:00 > 0:39:07The process that triggers the growth of snow in the clouds remained a mystery until as late as the 1920s.
0:39:07 > 0:39:11Then, scientists discovered that two vital ingredients have to
0:39:11 > 0:39:16interact in clouds at the same time for snow to be produced.
0:39:16 > 0:39:21First, a seed is needed to initiate the growth of the snow flake.
0:39:21 > 0:39:26For snowflakes to grow, you need a nucleus, an ice-forming nucleus
0:39:26 > 0:39:28to start the growth of the ice crystal.
0:39:28 > 0:39:31That's normally something like dust in the atmosphere,
0:39:31 > 0:39:36pollution from combustion, even bacteria,
0:39:36 > 0:39:42are the kinds of particles which will initiate the formation of ice in the atmosphere and the growth of snow.
0:39:43 > 0:39:48Besides a particle such as dust to seed the snow crystals,
0:39:48 > 0:39:52the second ingredient is droplets of super-cooled water.
0:39:52 > 0:39:57This is water that stays liquid below freezing.
0:39:57 > 0:40:01Most people will be surprised to know that water doesn't necessarily freeze
0:40:01 > 0:40:04at zero, which is, after all, the freezing point.
0:40:07 > 0:40:11And what we're going to do is demonstrate this with these test tubes of water.
0:40:12 > 0:40:18Doctor Saunders will cool the water to well below zero degrees
0:40:18 > 0:40:20while carefully monitoring the temperature.
0:40:22 > 0:40:25And we we'll be able to see, with any luck, whether these...
0:40:25 > 0:40:28samples do freeze at zero or not.
0:40:36 > 0:40:43As the water cools down below zero, if it remains liquid, it becomes super-cooled.
0:40:47 > 0:40:51This super-cooled water will now only freeze
0:40:51 > 0:40:56if an ice-triggering nucleus such as dust or pollen is present.
0:40:56 > 0:41:00The smaller the volume of water, as in these test tubes,
0:41:00 > 0:41:02or in water droplets,
0:41:02 > 0:41:07the less likely it is that there will be a particle which can trigger freezing.
0:41:11 > 0:41:14We've got two test tubes which are frozen and two tubes which
0:41:14 > 0:41:19are super-cooled, and they're at minus 11.5 and they're still liquid water.
0:41:24 > 0:41:29To demonstrate how a particle is needed to trigger ice growth,
0:41:29 > 0:41:32Clive adds a speck of ice to the super-cooled water
0:41:32 > 0:41:34to act as a nucleus.
0:41:38 > 0:41:40Fantastic, look at that freezing.
0:41:44 > 0:41:50A second more dramatic experiment uses a super-cooled bubble of soapy water.
0:41:50 > 0:41:54When a nucleus particle is introduced, the ice grows instantly.
0:42:13 > 0:42:17The ability of tiny nucleus particles to trigger ice growth
0:42:17 > 0:42:20is at the heart of the formation of snow.
0:42:22 > 0:42:27Like the super-cooled water in Clive's lab, high in the clouds,
0:42:27 > 0:42:32there are millions of tiny super-cooled water droplets at sub-zero temperatures.
0:42:33 > 0:42:40These droplets slowly evaporate, filling the air with an invisible vapour of water molecules.
0:42:42 > 0:42:46The vapour is carried through the cloud until the water molecules
0:42:46 > 0:42:49make contact with a nucleus particle of dust or pollen.
0:42:52 > 0:42:57As soon as this happens, tiny snow crystals form around the particle.
0:42:57 > 0:43:02These crystals rapidly grow until they fall out of the sky as snow.
0:43:07 > 0:43:12Across the UK, the snow making process in the clouds happens all the time.
0:43:12 > 0:43:17In fact, almost all British rain begins as snow.
0:43:20 > 0:43:25It's only when it's cold enough, we get our weather's most beautiful spectacle.
0:43:45 > 0:43:48Understanding the process behind the formation of snow
0:43:48 > 0:43:55means that scientists at the University of Manchester can create snow fall inside their laboratory.
0:44:02 > 0:44:06Falling out of this chamber are millions and millions of little ice crystals.
0:44:06 > 0:44:09And the hold of the cold room is full of ice crystals.
0:44:13 > 0:44:17These tiny snow crystals have only fallen a short distance through the air,
0:44:17 > 0:44:23so they haven't had enough time to grow into the larger snow needed for skiing.
0:44:23 > 0:44:26# Sleigh bells ring Are you listening
0:44:26 > 0:44:31# In the lane, snow is glistening
0:44:31 > 0:44:36# It's a beautiful sight We're happy tonight
0:44:36 > 0:44:39# Walking in a winter wonderland. #
0:44:39 > 0:44:44To create alpine ski conditions indoors, you need real snowflakes.
0:44:44 > 0:44:49That was the task faced by a remarkable British engineer,
0:44:49 > 0:44:54and he found a way recreate one of nature's most complex processes,
0:44:54 > 0:44:57indoors, on a massive scale.
0:45:12 > 0:45:15His name is Malcolm Clulow.
0:45:15 > 0:45:18A one-time refrigeration engineer,
0:45:18 > 0:45:23he realised that the only way to get the skis to slide properly was to produce real snow.
0:45:23 > 0:45:27Malcolm cleverly combined science and technology,
0:45:27 > 0:45:30and has made Britain the world's biggest producer of snow.
0:45:33 > 0:45:36We were approached by an English lord who owned a dry ski slope,
0:45:36 > 0:45:39and because he had a great business in the winter,
0:45:39 > 0:45:42and a bad business in the summer,
0:45:42 > 0:45:45he wanted to cover his dry ski slope with real snow.
0:45:45 > 0:45:49And I quickly found out that no-one had made snow indoors at this time.
0:45:49 > 0:45:50This was 1988.
0:45:52 > 0:45:56And it seems magic, but to me as an engineer, it's pretty simple.
0:45:56 > 0:46:02What Malcolm needed to do was recreate the conditions found in snow-producing clouds.
0:46:02 > 0:46:08First, he built a refrigerated building in which he could cool the air temperature to well below zero.
0:46:12 > 0:46:15Second, as we know from Clive's experiments,
0:46:15 > 0:46:20Malcolm introduced the two ingredients needed to create real snow.
0:46:20 > 0:46:24Thousands of super-cooled water droplets and snow forming nuclei.
0:46:27 > 0:46:30The ingredients are introduced into the cold air
0:46:30 > 0:46:34using a specially-designed snow-making machine, high up in the roof.
0:46:36 > 0:46:40First of all, our snowmakers make a cloud of these particles.
0:46:40 > 0:46:43We then open up the nozzles.
0:46:45 > 0:46:51And the nuclei get drawn in to this plume, immediately triggering the freezing process.
0:46:51 > 0:46:53And the crystals form immediately.
0:46:53 > 0:47:00The key to Malcolm's snow making success is placing the snow machines as high up in the roof as possible.
0:47:00 > 0:47:06This way the snow crystals have enough time to fall through the air, just like they do in nature.
0:47:12 > 0:47:15We're recreating nature,
0:47:15 > 0:47:17it's pure magic to make snow indoors.
0:47:21 > 0:47:24The attraction of Malcolm's snow domes,
0:47:24 > 0:47:28which he has built all over the world, is you can predict exactly when it's going to snow.
0:47:31 > 0:47:35It's not so easy for weather forecasters in Britain.
0:47:35 > 0:47:39Because our island sits at a volatile junction between major weather systems,
0:47:39 > 0:47:43predicting snow is notoriously difficult.
0:47:47 > 0:47:51Forecasting snow in the UK is one of the forecaster's biggest headaches,
0:47:51 > 0:47:56it's a headache because if you get it wrong, it tends to cause a lot of disruption
0:47:56 > 0:47:57and everyone notices.
0:47:57 > 0:48:00The road and rail networks grind to a halt, the airports too.
0:48:00 > 0:48:03It's not like making a mistake with rain.
0:48:03 > 0:48:07If the ground is covered in white and you haven't said that's what's gonna happen,
0:48:07 > 0:48:09there tends to be a pretty big enquiry.
0:48:09 > 0:48:13Towards the east, places like Eastern Europe and Scandinavia,
0:48:13 > 0:48:18they get cold winters, they know it's going to snow because the temperatures are well below freezing,
0:48:18 > 0:48:22but for us here in the UK, it's always much more marginal.
0:48:22 > 0:48:28It's Britain unique climate that leads to our snow frequently taking us by surprise.
0:48:30 > 0:48:36This is no bad thing when it comes to our love of telling stories about the weather.
0:48:44 > 0:48:47Saturday and then Sunday was the...
0:48:47 > 0:48:5031st, 31st of...
0:48:50 > 0:48:51May, yep.
0:48:51 > 0:48:53It started on 31st May.
0:48:55 > 0:48:59We were a bit younger, the last time we did this, you know.
0:48:59 > 0:49:04In 1975, Derbyshire played Lancashire at Buxton cricket ground.
0:49:04 > 0:49:10Two days into the match, June 2nd, was a day never to be forgotten.
0:49:10 > 0:49:15The annual county match was the big thing for this club.
0:49:15 > 0:49:22The lead up to this match at the end of May, very dry, good preparation of wicket.
0:49:23 > 0:49:29For Buxton, it was a great day, and it gave the whole area
0:49:29 > 0:49:35the picture of perfection for a county cricket match - sun, warmth.
0:49:35 > 0:49:40Crowds start to come in, got a big crowd, 3,000, 4,000 people on the ground.
0:49:40 > 0:49:42Happy smiling faces.
0:49:45 > 0:49:49Some good cricket played, certainly by Lancashire batting anyway.
0:49:49 > 0:49:52They put on over 400 runs.
0:49:52 > 0:49:56Britain's most famous umpire, Dickie Bird, was in charge.
0:49:56 > 0:50:00June, I would say, is one of the best months...
0:50:00 > 0:50:03of the summer for weather to play cricket in.
0:50:03 > 0:50:07- All of a sudden...- Things went dark.
0:50:12 > 0:50:16And white stuff started appearing out of the skies.
0:50:18 > 0:50:21Bits of white, and...
0:50:21 > 0:50:25nobody could believe it, it started snowing.
0:50:25 > 0:50:28All we could do was look in amazement.
0:50:30 > 0:50:31I couldn't believe it.
0:50:31 > 0:50:34I thought it was not right, this,
0:50:34 > 0:50:37Buxton was under about six inches of snow!
0:50:49 > 0:50:52I thought, I can't believe this, we're in June!
0:50:52 > 0:50:57Main reaction by the players was like big kids, I mean, snow?
0:50:57 > 0:51:02For West Indian player, Clive Lloyd, it would be a day to remember.
0:51:02 > 0:51:06Clive Lloyd had not seen snow as far as we knew.
0:51:06 > 0:51:11Clive was very, very excited and we kept saying, these are snowballs, Clive.
0:51:11 > 0:51:18He's making snowballs and they're having snowball raids out here on the middle.
0:51:19 > 0:51:25So what caused this freak event, a one-of-a-kind since records began?
0:51:25 > 0:51:29The big high pressure system which had been sitting over the UK for a few days
0:51:29 > 0:51:32shifted out into the Atlantic.
0:51:32 > 0:51:38And that opened the back door for a northerly plunge to come all the way down from the Arctic Circle,
0:51:38 > 0:51:40well within the Arctic Circle,
0:51:40 > 0:51:45from within a few hundred kilometres of the North Pole.
0:51:45 > 0:51:491975 was really a once-in-a-lifetime event.
0:51:53 > 0:51:58You can see the ground now, it's lashing it down with rain, it's under water.
0:51:58 > 0:52:01You would expect that in our English summers.
0:52:01 > 0:52:08But no way would you expect six inches of snow...in June!
0:52:08 > 0:52:14And notice boards outside the ground, saying no play today because of snow.
0:52:17 > 0:52:22It's a surprise to see snow in June, but there is one day in the year
0:52:22 > 0:52:25when all of Britain hopes it will snow.
0:52:25 > 0:52:27Christmas Day.
0:52:27 > 0:52:32The image of somehow the peace and quietness of Christmas time under a thick blanket of snow,
0:52:32 > 0:52:35that is probably my enduring favourite image of snow.
0:52:46 > 0:52:51The dream of a white Christmas is woven into the British culture.
0:52:51 > 0:52:53But where did it all begin?
0:52:53 > 0:52:551815,
0:52:57 > 0:53:00the eruption of the volcano Tambora.
0:53:05 > 0:53:10This massive volcanic explosion, along with the impressionable mind of a young boy,
0:53:10 > 0:53:15would result in a book that still fuels our passion for a White Christmas.
0:53:15 > 0:53:19"And they stood in the city streets on Christmas morning,
0:53:19 > 0:53:21"where, for the weather was severe,
0:53:21 > 0:53:25"the people made a rough, but brisk and not unpleasant kind of music
0:53:25 > 0:53:31"in scraping the snow from the pavement in front of their dwellings and from the tops of their houses.
0:53:31 > 0:53:36"Whence it was mad delight to the boys to see it come plumping down
0:53:36 > 0:53:43"into the road below and splitting into artificial little snowstorms."
0:53:43 > 0:53:47The book was called A Christmas Carol, by Charles Dickens.
0:53:47 > 0:53:52We can say as a shortcut that Dickens invented the idea of a white Christmas.
0:53:52 > 0:53:55It's a little bit of a shortcut, because I don't think,
0:53:55 > 0:53:58no matter how great a writer is, we can actually say he invented it.
0:53:58 > 0:54:01But what we've done is construct this lovely story,
0:54:01 > 0:54:05this myth, if you like, on the back of A Christmas Carol.
0:54:12 > 0:54:17We can tell what happened during Charles Dickens' childhood from the chemistry of ice cores.
0:54:17 > 0:54:22His boyhood encounters with snow would shape the writing of A Christmas Carol.
0:54:22 > 0:54:27Dickens managed to be born in quite an interesting period as far as climate was concerned.
0:54:27 > 0:54:32If we look at the Antarctic ice cores, we can see a huge sulphuric acid spike in 1815.
0:54:34 > 0:54:42This increase in atmospheric sulphur indicates the eruption of the Indonesian volcano, Tambora.
0:54:42 > 0:54:45The largest eruption in recorded history.
0:54:47 > 0:54:52It put an enormous amount of material into the atmosphere, and that blocked out some of the sunlight,
0:54:52 > 0:54:56causing the atmosphere to cool and therefore the climate cooled.
0:54:56 > 0:55:02And, in fact, the year following Tambora in 1816 is generally known as the year without a summer.
0:55:02 > 0:55:06So in his boyhood, I would have expected him to see quite a lot of very snowy winters.
0:55:06 > 0:55:10Every Christmas, I think, would have been a snowy one for him.
0:55:10 > 0:55:16In fact, Dickens saw six white Christmases in the first ten years of his life.
0:55:16 > 0:55:22Since then, his classic story has helped fuel our yearning for the white Christmas dream.
0:55:24 > 0:55:29# It's the most wonderful time of the year
0:55:30 > 0:55:35# With the kids jingle belling And everyone telling you
0:55:35 > 0:55:37# Be of good cheer... #
0:55:37 > 0:55:43We even part with large amounts of money every year at the bookies wishing for snow on December 25th.
0:55:46 > 0:55:51But in the UK, what exactly constitutes an official white Christmas?
0:55:51 > 0:55:56The definition of white Christmas, it can actually on the day not look entirely different to this,
0:55:56 > 0:55:59because the definition is pretty much driven by the bookies,
0:55:59 > 0:56:03and it actually comes down to just one flake of snow falling
0:56:03 > 0:56:07between midnight on Christmas Day and midnight on Boxing Day.
0:56:07 > 0:56:09And that one flake of snow can melt on its way down
0:56:09 > 0:56:14before it touches the ground so it doesn't mean lying snow, it just means snow has been observed.
0:56:14 > 0:56:19# I'm dreaming
0:56:19 > 0:56:24# Of a white Christmas... #
0:56:26 > 0:56:31Unlike the six White Christmases Dickens saw before he was ten,
0:56:31 > 0:56:35in London there have only been six in the last 50 years,
0:56:35 > 0:56:38and they are becoming increasingly rare.
0:56:38 > 0:56:42How many here have seen a white Christmas?
0:56:42 > 0:56:44No.
0:56:45 > 0:56:50The most alarming indication that the British white Christmas may become a thing of the past
0:56:50 > 0:56:56comes from scientific evidence within the polar snow cores.
0:56:56 > 0:57:01I think if we look at the cores we're collecting in the Antarctic and see the levels of carbon dioxide
0:57:01 > 0:57:03and how intimately they are related to temperature
0:57:03 > 0:57:08and the fact that carbon dioxide is still rising in the atmosphere relentlessly,
0:57:08 > 0:57:11and it's going to continue rising for the next 50 to 100 years.
0:57:11 > 0:57:15I think it's absolutely certain that temperature will continue to rise.
0:57:15 > 0:57:19It may well be that we never go back to the white Christmases that I remember from my youth.
0:57:19 > 0:57:24It's quite a though, isn't it, that with global warming, for children in this country,
0:57:24 > 0:57:29the only way they are going to experience snow is either through its Disneyfication
0:57:29 > 0:57:31or through travel.
0:57:31 > 0:57:34So you'll always be a snow tourist.
0:57:34 > 0:57:39So you won't see your back yard turned into this snowscape.
0:57:39 > 0:57:43We're going away to see the snow or we're going to the movies to see the snow.
0:57:43 > 0:57:44How peculiar.
0:57:51 > 0:57:54Snowy winters in Britain
0:57:54 > 0:57:56are becoming much less frequent.
0:57:59 > 0:58:03Yet, because of the meteorological conditions over the British Isles,
0:58:03 > 0:58:07we will always remain vulnerable to a freak winter
0:58:07 > 0:58:11that brings polar temperatures when we least expect it.
0:58:46 > 0:58:49Subtitles by Red Bee Media Ltd
0:58:49 > 0:58:52E-mail subtitling@bbc.co.uk