"In 1972, a group of eminent scientists sat down to write a letter to the President of the United States." "They were frightened." "The Earth's climate seemed to be going haywire." "They worried that war, pestilence and famine were on the way." "For the first time, climate change had become a hot political topic." "The letter warned the President he had to prepare not for global warming, but for the complete opposite - a new ice age." "Yup, 36 years ago, a lot of leading scientists really thought that an ice age was just around the corner." "And yet today, they're all apparently convinced that global warming is the big threat." "But if scientists were so wrong back then, how can we be sure they've got it right today?" "In this series, I'm going to explore some simple, big questions." "How do we know the climate is warming up?" "How do we know humans are causing it?" "And how do we know what's going to happen next?" "As the story of global warming has unfolded, we've learnt of the very nature of scientific truth and about how that has been falsified, manipulated, twisted, and even bought." "manipulated, twisted, and even bought." "As close to scientific fraud as you can get." "This is the story of how science discovered global warming..." ".. perhaps the greatest challenge we've ever faced." "Whoa!" "Yes!" "That was a bumpy landing!" "This is me, lain Stewart, geologist, and lecturer at Plymouth University." "Oh, look!" "Little crystals." "Oh, we don't want to know." "But I'm also a husband and a dad, so I've got a professional and a personal interest in global warming." "That there, that's limestone..." "I don't care!" ".. that there's a sandstone." "I don't care!" "And that is..." "You don't care." "Whoa, watch it." "You know, the kids tease me that geology is just boring old rocks, but what they don't get - well, not yet at least - is that it's really about how the planet works." "is that it's really about how the planet works." "is that it's really about how the planet works." "I don't think you can be interested in that, and not be worried about what kind of future they're in for." "I'm used to studying how the planet changes over millions of years " "I'm used to studying how the planet changes over millions of years - the gradual wearing down of cliffs by the sea, the remorseless drift of the continents, the slow building of mountains." "The idea that something is happening that could fundamentally change the planet within my kids' lifetime is extraordinary and actually quite frightening." "But there's another reason why I'm fascinated by the scientific discovery of global warming." "It's a story where many of the key developments fit into my own lifetime." "It begins back in 1970s, when I was just a little kid." "The way I remember, pretty well everything was depressing in the '70s." "The haircuts were dodgy, the films were mostly disaster movies..." ".. and Britain was in a state of near anarchy." "Everything was falling apart." "Including the planet." "Earth was running out of resources, acid rain was killing the lakes and forests..." ".. overpopulation was going to lead to mass starvation." "This was a time of ecological doom mongering on an epic scale." "'Harriett, look at this." "'Just about everyone we know is a polluter!" "'" "If you asked me now what the chances are of civilisation reaching the turn of the century, I'd have to say 1 or 2% if we're lucky." "And there was one more scare story " "The threat of a new ice age." "In 1974, this major BBC documentary explored the conviction of some scientists that ice was on the march." "Besides the risk of somewhat cooler weather in the decades ahead, there's the ever-present threat of a big freeze." "there's the ever-present threat of a big freeze." "'We should be preparing ourselves for a long period of colder seasons. '" "'Already the Russians are building ice breakers as fast as they can. '" "'Will a new ice age claim our lands and bury our northern cities?" "'" "Unless we learn otherwise, it would be prudent to suppose that the next ice age could begin to bite at any time." "It didn't turn out quite like that, did it?" "The world didn't end." "You have to say in the 1970s, the environmentalists were wide of the mark on quite a few counts." "When it comes to the question of the next ice age," "When it comes to the question of the next ice age, even the scientists got it wrong." "But that doesn't mean to say that the science was bad." "For years, climate scientists had been doing what scientists do... .. Gathering data, collating it, analysing it." "And they'd noticed something." "The planet was cooling down." "In the 1960s, Britain shivered as a succession of bitter winters followed one after another." "followed one after another." "A barrier of snow on one main road defied even the snow ploughs." "Squads of workmen had to tackle it the hard way." "It wasn't just Britain." "Scientists had linked together weather reports from around the world, and it seemed clear" "Britain's cold winters were part of a global trend." "And there was a theory to explain why the Earth was cooling." "And there was a theory to explain why the Earth was cooling." "Because this was the era of King Coal." "Throughout the 1950s and '60s, the world economy boomed." "Power stations poured smoke into the air." "And before global warming came along, burning fossil fuel was responsible for a very different climate-scare story..." ".. Global cooling." "A drop in temperature large enough to cause a new ice age." "But how could pollution lead to cooling?" "The theory was simple." "Smoke from power station chimneys formed a layer of sooty particles" "Smoke from power station chimneys formed a layer of sooty particles" "Smoke from power station chimneys formed a layer of sooty particles in the atmosphere." "These particles blocked some of the sun's rays from reaching the Earth, leading to a slightly dimmer, and therefore cooler, planet." "It seemed to make perfect sense." "Some of the brightest young scientists of the day signed up to the new theory." "One of them was Steve Schneider." "In a famous paper in 1971, he said that global temperatures could decrease by over three degrees." "And he pointed out that if this happened, it could be enough to trigger a new ice age." "It all seemed to fit together." "The climate was cooling, and there was a theory to explain why." "But it didn't last." "There's a saying in science, along the lines of," ""There's nothing so sad as a beautiful theory destroyed by an ugly fact. "" "And in 1976, along came an ugly fact." "The summer of 1976 broke all records." "MUSIC: "Heat Wave" by Linda Ronstadt" "'Blazing heat and woodland fires 'have destroyed hundreds of acres of Surrey in the last two days. '" "'If water isn't saved in the home, jobs will be affected. '" "At it happens, I remember the summer of 1976 really well." "I was 12 and I was on a family holiday to Llandudno." "And I remember it for two reasons." "One was that my brother got pooed on by a seagull." "Still makes me chuckle!" "But the second was, it was just so damn hot!" "And not just here." "Across the world, 30 years of cooling came to an abrupt end." "The planet began to warm up." "And as the warming trend strengthened, it became clear that the science behind the ice-age theory was flawed." "For the scientists who had been associated with the coming ice age, it was a chastening experience." "Well, nobody likes to be wrong, But remember, I never said," ""I predict that we're gonna induce an ice age. "" "What I said was, "Under these assumptions, this is what you get. "" "Other scientists say that could trigger an ice age." "You know, it's easy to criticise Schneider, but to me, there was nothing wrong in what he did." "This is how science works." "You've got a theory, you look for evidence, if the evidence doesn't fit, you change the theory." "The ice-age theory was based on what was known at the time." "When new data came in, Schneider changed his mind." "With cooling off the agenda, the question now was very different." "Why was the planet warming up?" "For many years, a group of scientists had been working on an alternative theory about what was happening to the climate." "Now, their time had come." "The roots of this alternative theory lay with an obsessional genius by the name of Dave Keeling." "If the scientific discovery of global warming has a hero, then Keeling is probably it." "MUSIC: "California Dreamin'" by The Mamas And The Papas" "In 1956, a young Dave Keeling arrived here, at San Diego's premier academic institution - the Scripps Institution of Oceanography." "Keeling had a simple desire - to be outside." "Preferably in wild and beautiful places." "It's not unlike the reason that I took up geology." "The difference is that unlike me," "Keeling turned into a genuine, scientific hero." "As a kid, Keeling put together a lovingly crafted scrapbook of photographs from around the world that inspired him." "Now, as a researcher, he looked for a way to combine his love of science with his love of the outdoors." "And in the late 1950s, he found it." "He would focus on a problem that scientists were just beginning to worry about - measuring the level of carbon dioxide in the atmosphere." "Studying carbon-dioxide levels in the atmosphere had little to commend itself to an ambitious, young scientist." "But Keeling didn't care." "He got the chance to throw his sleeping bag in the back of the car and take off to all these amazing locations, all in the name of scientific research." "So off he went, visiting all sorts of wonderful places, all in an apparently obscure quest to measure carbon-dioxide levels in the atmosphere." "It may not have attracted much attention at the time, but Keeling's project turned out to be one of the most important pieces of scientific research ever conducted." "Keeling died in 2005, but today his son Ralph continues his work." "Keeling died in 2005, but today his son Ralph continues his work." "So how did Keeling senior measure carbon dioxide?" "This is a hollow, glass sphere wrapped in tape, this snaky thing is a valve for opening or closing." "It's like a stop cock." "It is in fact a stop cock." "The flask is evacuated in the lab, so all the air that's in it is sucked out of it." "So it's a vacuum?" "It's a vacuum in here right now." "And then one simply ships this or carries it to a location where one wants to get an air sample, and you hold it up and you expose it to the atmosphere." "Now the tricky bit, the only really tricky bit is to make sure you don't contaminate it, either by having something nearby like a car or your own breath, so attention has to be given to obtaining a clean sample." "Of course, air coming out of your mouth could get in there." "So do you just not breathe in?" "Yeah." "Shall I show you how it works?" "Does it take long?" "No, no, it's quite simple." "You simply face into the wind, hold your breath..." "HISSING" "So there we have the sample." "I heard it." "I can tell it's full." "But it turned out getting the sample of air was the easy bit." "Much trickier was working out how much carbon dioxide was in there." "Others had tried to do it before, but their figures differed wildly." "The key to Keeling's success was his obsessive attention to detail." "This was a man who kept logs of all his phone calls throughout his life." "Even as a young boy, he kept a meticulous record of his watering rota in the family garden." "Now he brought all his obsessive analytical zeal to the problem of how much carbon dioxide was inside his flasks of air." "He abandoned the hills, and moved into a lab." "And rather magically, it turns out his equipment is still here." "This is pretty much the exact apparatus that Keeling used to extract carbon dioxide and to measure its concentration in the atmosphere." "It may look like a museum piece, but this works." "In fact, all the modern instruments that measure carbon dioxide are calibrated or standardised with this." "In 1958, Keeling's complicated network of glass tubes delivered the first truly accurate measure of how much carbon dioxide was in the atmosphere." "It was a technical triumph." "But Keeling wasn't satisfied." "more and more carbon dioxide into the atmosphere - from cars, power stations, into the atmosphere - from cars, power stations, factories and aircraft." "He wondered if this meant that the level of carbon dioxide in the air would change over time." "The only way to find out was to keep doing his measurements, year after year." "Not everyone could see the point." "Over the years, there were many attempts to cut his funding." "But Keeling battled on." "He saw the value of keeping it going because it was documenting" "He saw the value of keeping it going because it was documenting an essential phenomenon of the time." "Creating a baseline against which you compare other processes." "Right." "If he hadn't stuck with it we wouldn't have that record." "And I don't think the rest of the community appreciated as well as he did that this was going to be something people would look back to and say, "Wow, that was important"." "So he already had a vision of people like us talking about him 50 years on." "I think he was really playing to an audience a generation or two later." "In that sense, he was out of his time." "What Keeling's dogged persistence led to was one of the most iconic images in the whole global warming debate - a graph." "And this is what Keeling produced." "His measurements started in 1958 at 315 parts per million carbon dioxide in the atmosphere." "And the first thing you notice is the rise and fall each year which is the seasonal variation in carbon dioxide." "Even in these early years, you can spot a rising trend, but you only get a true picture of the power of this graph when you track the changes through the decades." "when you track the changes through the decades." "Here, today - 2008, we're at 386 parts per million." "This relentless year-on-year rise in carbon dioxide is the one undisputed piece of evidence in the whole global warming debate." "It meant that nobody could argue with one simple statement - the human race has steadily increased the amount carbon dioxide in the air." "The significance of Keeling's discovery is simple, because carbon dioxide is a remarkable gas." "I can show you how carbon dioxide affects the Earth's climate using this heat-sensitive camera which is purring away here, a candle, this glass tube, which is hooked up" "to this rather large canister of carbon-dioxide gas." "Now, if I light the candle you'll see that on the monitor the camera picks up the flame perfectly, look at that, the hottest bits are glowing white." "Now watch what happens when I turn on the carbon dioxide." "Just keep your eye on the flame." "The gas is invisible so you don't see it filling the tube." "But as it comes in you should see the candle start to disappear." "There it goes." "Look at that." "What's happening is that the carbon dioxide in the tube is effectively trapping the heat." "The candle's warmth no longer reaches the camera." "Instead it's absorbed by the carbon dioxide inside the tube." "That's exactly how carbon dioxide works in the atmosphere." "It traps heat, preventing it from escaping into space, and warms the atmosphere in the process." "The more carbon dioxide there is in the air, the more heat is trapped." "This is the greenhouse effect." "As the temperatures rose in the 1970s," "Keeling's carbon dioxide graph seemed to provide the perfect explanation." "But what of the cooling period in the 1950s and '60s?" "It turned out that for a while the cooling effect of soot from smokestack chimneys had cancelled out the warming caused by carbon dioxide." "But that didn't last long." "The relentless rise in carbon dioxide soon took over as the dominant factor." "So now, scientists focused on a different possibility" " not a new ice age, but the complete opposite... .. Global warming." "The abrupt change didn't go unnoticed." "At the highest levels of the American government, officials pondered whether global warming was the new threat." "They turned for advice to the elite special forces of the scientific world - a secret, shadowy organisation known as Jason." "Every year, an elite bunch of scientists gather in this building in a desirable suburb of San Diego." "They've been meeting for more than 50 years." "But these are no ordinary scientists." "These are the Jasons." "A select group chosen for their intellectual brilliance" "A select group chosen for their intellectual brilliance and their patriotism." "Their mission - to provide secret advice to the American government on matters scientific." "'A few hundred miles apart, fallout patterns can overlap... '" "Most of what they do today, and have always done, is to do with defence." "'Tests on army's Nike Zeus continued in the last year... '" "But in 1978, they were asked to investigate the growing evidence for global warming." "the growing evidence for global warming." "One Jason remarked that it made a bit of a change - instead of finding ways to destroy the world, now they were being asked to save it." "In the 1970s, being a Jason was just about the best job going in American science." "Every summer, the Jasons all moved out to San Diego to devote six whole weeks to working with the other Jasons." "They were paid so much that they could rent a house by the beach, so their kids could spend the summers gambolling in the waves, looked after by their wives, whilst their menfolk got on with saving the world." "Or destroying it, depending on the year." "Then in the evenings, the husbands would join their families to recharge their batteries." "The fact is, it was less James Bond and more like Club Med." "It's the kind of science I'd like to get into!" "So it was that in 1978 the Jasons got to work on global warming." "There was one potential problem." "Few of them knew anything about climate." "The Jasons decided to build their own computer model of the global climate system." "They called it, "The Jason Model Of The World. "" "They didn't lack confidence, those boys." "Not everyone was amused." "Bona fide climate scientists grumbled that a bunch of amateurs were trespassing on their territory." "The Jasons ignored them." "And what came out of it was a report." "And even though it's yellowed with age, it's quite remarkable." "What's most impressive is that it makes predictions." "That's what science is all about, trying to test out your theories." "And with the benefit of hindsight, the Jason report got it pretty well spot on." "Here, for example, right at the start " "CO2 concentrations in the atmosphere expected to double by 2035." "Well, the models today suggest maybe 2050." "Well, the models today suggest maybe 2050." "Then over here, it talks about temperature rises of 2-3 degrees by the end of the 21st century." "That's pretty much what the predictions are today." "And they suggested that polar regions would warm by more than the average, perhaps by as much as much as 10 or 12 degrees." "by more than the average, perhaps by as much as much as 10 or 12 degrees." "Again, close to current thinking." "You know, for a 30-year-old document, this isn't half bad." "But back in the '70s, the Jason Report was explosive stuff." "So the American Government commissioned another one, this time by climate scientists." "this time by climate scientists." "And it came up with very similar conclusions." "Clearly, something needed to be done." "But then something happened that always confuses scientific issues." "Politics got in the way." "Well, there's never been a more humbling moment in my life." "In 1980, a new President arrived at the White House." "Ronald Reagan was pro business and unashamedly pro America." "Ronald Reagan was pro business and unashamedly pro America." "I aim to try and tap that great American spirit." "He knew that the US was already in the environmental dog house because of acid rain." "And if global warming turned into a major problem, there was only going to be one bad guy." "The US was by far the biggest producer of greenhouse gases in the world." "If the President wasn't careful, global warming could become a stick to beat America with." "So Reagan commissioned a third report about global warming." "The man he chose to lead it was Bill Nierenberg." "Nierenberg was the perfect choice." "He'd made his name working on the Manhattan Project, developing America's atom bomb." "He went on to run the famous Scripps Institution... '..." "Dr William Nierenberg, director of the institution. '" ".. where he'd built up the Climate Research Division." "And he was a Jason." "No-one could question Nierenberg's scientific credentials, or his academic integrity." "It was a fine choice by the President." "Like Reagan, he was a fervent believer in the free market." "Nierenberg called in lots of experts, did his research, and produced a report that spookily enough chimed pretty much completely with the President's beliefs." "Nierenberg accepted that some warming was likely." "But he argued that any warming that came our way would happen slowly, so society would have plenty of time to adapt." "Human ingenuity would see us through." "There was nothing to fear, and certainly no need to act to reduce emissions of carbon dioxide." "It was just what Reagan wanted to hear." "A presidential aide reputedly asked a leading climate scientist," ""How long before global warming becomes a major problem?"" "The considered reply, "40 years. "" "The aide quipped, "Get back to me in 39."" "Global warming was duly kicked into the long grass." "And at this stage, in the early '80s, it was easy to sympathise with Nierenberg's view." "Global warming was still just a prediction, and the science was in its infancy, so no-one could be sure how big a problem it was going to be." "And all around there was evidence from history that a changing climate was really nothing to be frightened of anyway." "After all, it's something humans have always had to cope with." "You only have to drive out to the edge of the Californian desert" "You only have to drive out to the edge of the Californian desert to find clear evidence that climate varies naturally." "I'm standing on the edge of an ancient waterfall." "It might be dry barren rock now, but thousands of years ago a roaring torrent of water cascaded its way through here, carving out this massive ravine." "But that water has long since gone." "It's difficult to imagine what it must have been like when the water was in full flow, but I certainly couldn't have stood here." "The normally jagged rock has been smoothed to a polish, and those potholes there have been churned out by the turbulent water" "This is a fossilised river." "But it's not just a geological relic." "There is plenty of evidence here to back up Nierenberg's case." "I bring my students here, not just to show them the river-sculpted rocks, but for something else equally intriguing." "The clues are all around, like these small flakes of dark volcanic glass" "called obsidian that Native Americans used to fashion arrowheads and spear points." "And art like this over here carved into the rock, looks like an elk or a deer of some kind." "It's all evidence that a large community lived and worked around the river here." "If you stay here long enough you can just imagine them chipping away in the veil of the spray and roar of the falls." "DISTANT CHATTER AND LAUGHTER" "Then the climate must have changed, the river stopped, and the people moved on." "It's this process of natural climate change which lay at the heart of Bill Nierenberg's case." "Humans have lived with climate change for thousands of years." "All that's changed is how we cope." "The key is adaptation." "In the past when the rains went, so did the people." "In the past when the rains went, so did the people." "Today, we can do much better than that." "Today, we can do much better than that." "The Hoover Dam was built in the 1930s to tame the mighty Colorado river." "If you ever wanted a symbol of what human ingenuity and sheer bloody mindedness can achieve, then this is it." "Mind you, it's a bit unnerving to think that behind this concrete wall is a hundred miles of lake." "to think that behind this concrete wall is a hundred miles of lake." "Lake Mead has helped the Western United States conquer the cycle of drought and flood that used to afflict this desert region." "It's a powerful symbol of our ability to ride out climate change." "Especially when you realise that today, the lake is in the 8th year of a major drought." "As you'd expect, the lake level has dropped." "You can see a band of light-coloured rock that's been exposed as the water has fallen." "It's only when you get into these narrow canyons that you get a sense of just how far the water has fallen." "This light-coloured rock here is what was once covered by the water and it stretches up for about a hundred feet." "It's like a giant bathtub ring." "But so far at least, the Hoover Dam has done its job." "Despite the drought, Las Vegas and the other desert cities of the American West are doing just fine." "You know, the lake level is always yo-yoing up and down." "In the 1980s it reached its during the 1950s and 1960s the level was way down here." "But even in those really bad droughts, the lake never ran out of water." "For 70 years, Lake Mead has kept the American West supplied with water." "For Nierenberg, this was living proof that human ingenuity could overcome the gradual creep of climate change." "Modern society, far from being ever-more vulnerable to climate change, was actually more robust than it had ever been." "So there was no need to fear climate change." "It was an optimistic message that resonated with the political times." "Nierenberg went on to set up one of the leading think tanks that would fight the whole idea of global warming and help create what became known as the sceptic movement." "The global-warming sceptics argued that the Earth's climate system was simply too vast for humans to change." "They claimed there was still very little evidence humans were causing the climate to warm up." "And they suggested that any warming that did happen was likely to be slow and therefore easy to cope with." "These ideas have remained central to the global-warming debate ever since." "But as the 1980s advanced, all three arguments came under sustained scientific attack." "all three arguments came under sustained scientific attack." "What shook the sceptics' argument was some more of those ugly facts." "And by the mid 1980s, ugly facts were piling up at an alarming rate." "Ugly fact number one would challenge the reassuring notion that climate change would be slow, and therefore easy to cope with." "It had its origins in one of the coldest and remotest places on Earth - Greenland." "More than 80% of Greenland's surface is covered in ice." "It's the largest body of ice on Earth, outside Antarctica." "Today, despite its remoteness, scientists come here from all over the world scientists come here from all over the world to study the effects of climate change on the ice." "to study the effects of climate change on the ice." "But 50 years ago, at the height of the Cold War, virtually no-one did scientific research on Greenland." "Except the American military." "The ice sheet under my feet is up to two miles deep." "50 years ago, the Americans decided the perfect place to build a military base was down there - inside the ice." "Officially they called it Camp Century because it was 100 miles from the coast, but the men who built it gave it a different name " "The City Under The Ice." "More than 200 people lived here." "It was a massive project." "Huge convoys used to grind their way from the coast up onto the ice, laden with supplies for Camp Century." "They used to call them heavy swings." "When it was finished," "Camp Century had a library, a hospital, and even a gym." "And what powered it all?" "What else but a nuclear power station?" "I know it's hard to believe, but they buried a nuclear reactor inside the ice." "Now hear this." "With all five control rods withdrawn, 6.24 inches, PM 2A went critical at 06520." "Camp Century was built to do research into fighting in cold-weather environments." "But that's not what made it famous." "Today, there's nothing left of the City Under The Ice." "They took out the nuclear reactor and abandoned the camp somewhere up there." "But what happened at Camp Century would eventually - almost by accident - lead to a scientific revolution." "It was a revolution that would challenge a scientific article of faith - the idea that climate could only change exceptionally slowly." "Because Camp Century saw the beginning of an entirely new branch of science - using samples of ancient ice to reconstruct the climate of the past." "The Greenland ice sheet is made up by year after year of snowfall." "As snow falls, it captures a record of the conditions in the atmosphere, which then gets preserved in layers of ice." "So many traces from the past are buried in the ice." "There's ash from big volcanic eruptions like Krakatoa... .. dust from Ice-Age dust storms as far away as Mongolia..." ".. and even traces of lead from smelting during the Roman Empire." "It's all blown in by the wind, carried down by the snow and buried down there." "Even more importantly, as snow falls, it captures an indirect record of the temperature at the time it was falling." "And the ice preserves this temperature information." "So scientists drilled down to retrieve long cylinders of ancient ice known as ice cores." "Now, they could use these ice cores to create a record of past temperatures." "In effect, they could travel back in time." "And in the mid 1980s, they began to realise that the old idea, that climate always changed slowly..." ".. couldn't be more wrong." "Today this freezer in Denver in the United States stores many of the ice cores that have been drilled around the world." "I don't think I've ever been as cold in my life." "The cores that are stored in these silver tubes are at minus 35C." "They're so valuable that there's back-up systems in place to make sure the freezer keeps working if there's a power cut." "Even so, the guys that work here carry bleepers 24 hours a day to tell them if there's been a power failure." "And I know you don't want to know this, but the fluid in my nostrils has just frozen up." "HE SNIFFS" "It's been said that these ice cores are like having a weather station in Greenland for the last 100,000 years." "By chemically analysing the ice, it's possible to reconstruct the climate counting back through tens of thousands of years." "the climate counting back through tens of thousands of years." "In the early 1980s, most scientists believed, as this graphs shows, that the climate changed only very slowly and gradually, through the Ice Age and up to the present warm period." "But the ice cores told a completely different story." "The climate seemed to be jumping all over the place from warm to cold and back again." "What the ice revealed was hard to believe." "In the past 100,000 years, there had been literally dozens" "What's more, the changes didn't happen gradually." "In most cases, they occurred in just a few short years." "Scientists realised that they'd fundamentally misunderstood how the climate works." "Far from changing with imperceptible slowness, it was now beginning to dawn on them that the climate could change big, it could change often, and it could change fast." "You know, the discovery of abrupt climate change unleashed a previously-hidden literary talent among climate scientists - a talent for metaphor." "Climate was an angry beast, and we, it was said, were poking it with a stick." "Alternatively, climate was a flickering switch, turning on and off between hot and cold periods." "But, regardless of the metaphor you plumped for, it was clear that global warming could mean some nasty surprises." "We might wake up one day to find that global warming had triggered a sudden, massive shift in climate - like the ones revealed in the ice cores." "But in the 1980s, this idea was still controversial." "Many scientists - not just sceptics" " argued that the theory of rapid climate change was still unproven." "And the sceptics had another argument." "They said that something as vast and complicated as the global climate system was simply too big for we humans to influence." "A new discovery was about to change all that." "but from a social revolution." "After all, this was the 1980s." "I was at university, studying hard of course, and one thing I remember is it was the era of big hair." "A new age of consumerism." "The trouble was, packed within the consumer lifestyle was an environmental time bomb - aerosols." "Aerosols owed their existence to one of the unluckiest men in scientific history." "Thomas Midgley invented CFCs... .. the gases that were used in aerosols and in fridges." "Before that, he'd come up with the idea of putting lead in petrol." "The trouble was, CFCs had a terrible secret." "They appeared to be good news - inert, safe, cheap to manufacture." "But when they floated up to the top of the atmosphere, they turned into something deadly." "They destroyed a vital gas that protects us all from lethal solar rays." "They destroyed ozone." "In 1984, British scientists working in Antarctica discovered that the ozone layer that protects the planet had a huge hole in it." "Studies from space show that the hole, in blue and pink, is growing year by year, and last year, spanned the whole Antarctic continent." "The culprit is most probably chloro or fluoro carbons used in aerosols and fridges." "used in aerosols and fridges." "Faced with the rapidly growing health risks, the world acted." "Midgley's CFCs were banned, at about the same time that his other great invention, that his other great invention, lead in petrol, was also being banned." "Poor old Midgley ended up victim of his own inventive genius in one final way." "In 1944, he contracted polio." "In order to keep working, he devised a pulley and harness that would lift him out of bed." "But one day, he got tangled in the harness and was strangled by his own contraption." "Surely there's never been a more unlucky scientist." "The hole in the ozone layer proved beyond doubt that humans were capable of causing catastrophic damage to very significant parts of the atmosphere and in a very short space of time." "Another part of the sceptic's case - the idea that the atmosphere was simply too vast for us to have any serious effect on it - had crumbled." "And in the 1980s, there was one final ugly fact that challenged the sceptics' view that climate change was nothing to worry about." "'The heat wave broke 88 high temperature records across the nation since Sunday. '" "'New York City was one of 12 cities that suffered and sweltered in record high temperatures. '" "'Temperatures in some places went as high as 109 degrees. '" "Through the 1980s, the temperature of the planet kept rising, building on the warming that had first begun in the 1970s." "'The 80s have brought us the four hottest years in the last 100.'" "'At least 60 cities reported... '" "Almost every year broke records." "'Daily temperatures in the 90s, even in the hundreds. '" "The question for scientists was whether this was just a natural variation, or whether it was due to man-made emissions of carbon dioxide - the greenhouse effect." "In 1988, one man, top NASA scientist Jim Hansen, decided he knew the answer." "And he wanted the whole world to hear what he had to say." "His chosen forum was an American congressional inquiry." "Gentlemen, thank you very much for being here, Dr Hansen, if you'd start us off we'd appreciate it." "Mr Chairman, committee members..." "You'll have to talk right into the microphone." "These are not high-tech microphones, you have to pull it right over." "Bit of an inauspicious start." "But he warms up nicely." "I would like to draw three main conclusions." "Number one, the earth is warmer in 1988 than at any time in the history of instrumental measurements." "Number two, global warming is now large enough that we can ascribe, with a high degree of confidence, a cause-and-effect relationship to the greenhouse effect." "And number three, our computer climate simulations indicate that the greenhouse effect is already large enough to begin to affect the probability of extreme events, such as summer heat waves." "You know, you have to say this was as much political theatre as scientific evidence." "It was Hansen himself that suggested he give his evidence at the end of June, figuring that the weather would be hot." "He wasn't disappointed - they were in the middle of a heat wave." "So people were in the mood to write about global warming." "He'd also checked the press were going to be there that day, and that he was the first person giving testimony." "This man wanted to make news." "And he saved the best till last." "Altogether, this evidence represents a very strong case, in my opinion, that the greenhouse effect has been detected and it is changing our climate now." "It was pretty explosive stuff." "Essentially, what Hansen was saying was that global warming was no longer a prediction." "It was now an observation." "For the first time, a leading scientist had stepped off the fence and told the world global warming had arrived." "'All of us must begin to face up the fact that if we continue emitting 'vast quantities of greenhouse gases, we're going to face 'vast quantities of greenhouse gases, we're going to face 'a global temperature rise larger than anything experienced in human history. '" "Hansen succeeded." "Thanks to him, global warming became an overnight sensation." "'The time for action to respond to the impending warming is now. '" "Hansen later admitted that he'd weighed up the risk of being wrong against the costs of saying nothing, and decided that he had to speak out." "'Most scientists would rather not make a definitive statement." "'But the public doesn't always understand that. '" "I mean, if you say on the one hand this and on the other hand that, it makes the public think, well, we don't know enough to draw a conclusion." "And that... that can be, er, unhelpful in terms of when you do need to have policy changes." "Basically, Hansen stuck his neck out - not something that we scientists are famous for." "I don't think I'd have the nerve to do it." "favours the brave, because Hansen's testimony has stood the test of time pretty well." "Within a few months of Hansen's evidence, the United Nations had helped set up an international committee to examine global warming, the Intergovernmental Panel On Climate Change." "And politicians jumped on board too." "Margaret Thatcher became the first world leader to warn about the dangers of global warming." "The danger of global warming is as yet unseen, but real enough for us to make changes and sacrifices so that we do not live at the expense of future generations." "That prospect is a new factor in human affairs." "It's comparable in its implications to the discovery of how to split the atom." "Indeed, its results could be even more far reaching." "No generation has a freehold on this earth." "All we have is a life tenancy with a full-repairing lease." "All we have is a life tenancy with a full-repairing lease." "By the early 1990s, it looked like the scientific battle was pretty well over." "The idea that a new ice age was on the way had been comprehensively overturned." "Scientists and politicians agreed that humans were altering the climate." "And something had to be done about it." "Global warming had well and truly arrived." "And then along came the most familiar of plot twists - the backlash." "And what a backlash it was." "In the 1990s, global warming was to become the biggest scientific controversy of my lifetime." "In a way, Jim Hansen had been too successful." "His high-profile testimony galvanised all those who, for whatever reason, disagreed with taking action to prevent climate change." "'It's just not true. '" "It was the beginning of an organised fight back, driven by a band of maverick scientists..." "Global warming is not a crisis." ".. supported by powerful businesses and politicians." "And they would subject the whole idea of global warming to a new and searching critique." "Next time, the sceptics fight back!" "How a scientific consensus turned into a vicious battleground." "And how science itself was ultimately the winner." "Subtitles by Red Bee Media Ltd" "E- mail subtitling@bbc. co. uk"