20120327_HZ

Source: BBC2 Horizon

URL: N/A

Date: 27/03/2012

Event: Global Weirding

Credit: BBC2

People:

• Helen Chivers: Meteorologist, Met Office
• Jason Dunion: Meteorologist, University of Miami and NOAA
• Professor Kerry Emanuel: Meteorologist, Massachusetts Institute of Technology
• Matt Farmer: Farmer
• Pieter Figdor: Architect
• Daniel Goedbloed: Engineer
• David Harewood: Narrator
• Professor Katharine Hayhoe: Climate scientist, Texas Tech University
• Professor Mike Lockwood: Physicist, University of Reading
• Ron Roberts: Chief meteorologist, KAMC TV station
• Dr Adam Scaife: Meteorologist, Met Office Hadley Centre
• Tamsin Waley-Cohen: Violinist

[Thunder, lightning, ominous music.]

Narrator: Something strange is happening to our weather. It seems to be getting more extreme.

[Scene of traffic on icy road.]

Newsreader: It could be a record-breaking cold night...

Narrator: Britain recently shivered through two back-to-back record-breaking cold winters.

[Scenes of flooding.]

Narrator: Last year, Scotland splashed through its wettest year on record. Yet, earlier in the year, parts of eastern England had their driest spring ever. But the UK's not alone. Records are being broken all over the planet.

[More scenes of flooding and a raging dust storm.]

Newsreader: I have never ever seen anything like this before...

[Scenes of hurricanes.]

Narrator: Storms appear to be getting bigger.

Kerry Emanuel: Hurricane power has more than doubled between the decade of the '80s and this past decade.

Narrator: The weather's been getting so weird that, in some places, record-breaking rain has been followed by record-breaking drought.

Ron Roberts: We've never had this kind of steep oscillations go from one year to the next.

Narrator: Some scientists are calling it "global weirding."

Katharine Hayhoe: Events that used to be very random and extreme are becoming much more frequent. And more severe. We're going to be living in a different world than the one we grew up in.

[Scenes of fluffy white clouds.]

Narrator: Our weather is hypnotically beautiful. It's constantly changing, famously difficult to predict. But why does it seem to be getting weirder? The world's leading weather scientists are trying to understand what's happening. It's part of a global investigation. Because however local your weather feels, it's just a small part of what plays out across the planet as a whole. It may seem obvious, but one of the places scientists are trying to get to grips with global extremes is in one of the most extreme weather events on Earth.

[A large aeroplane is preparing to take off.]

Narrator: And there's no bigger weather event than a hurricane.

[A man in a blue jumpsuit is walking across the airstrip.]

Narrator: And that's where people like Jason Dunion come in. He's a hurricane scientist, who's turned in his white coat for a blue jumpsuit, and left the lab to work at the MacDill Air Force base in Tampa, Florida. Because Jason and his colleagues fly these aircraft into the middle of the weather madness. It's the best way to work out what really makes hurricanes tick.

[Scene of plane flying into a storm.]

Jason Dunion: You can't get everything you need to know about a hurricane by just looking at it from, say, satellites, or, say a buoy [?] that might be measuring the storm. So we've actually got to fly into that storm to get a better sense of what's going on, whether we're dropping instruments into it or using our radars to really get a nice three-dimensional picture of what's going on. You really can't do that in any other way.

Narrator: But carrying out complicated scientific experiments in the middle of a hurricane creates its own set of unique problems.

Jason Dunion: You're coming in at, say,10,000 feet and you're passing through outer rain bands, and you're starting to get jostled around a bit in the plane. Then you go through the eye wall, so that's that doughnut around the eye of the storm, that's really tense, and you're getting tossed around pretty good. And you can lose a few hundred feet of altitude in a few seconds. Pop through that eye wall, and it's incredible. You're in what looks like a football stadium. The biggest one you've ever seen, but it can be ten, twenty, thirty miles across. And it's very still, a very surreal spot in the storm, after what you've gone through. And you know this is a beast. But of course you're only through half the storm, and you're still halfway through to go.

Narrator: The hurricane chasers produce mountains of data from every flight. And one of the things they've discovered is that hurricanes pulse at night. More significantly, they've also recorded an increase in the number of Category Five storms, the most extreme and powerful hurricanes.

Jason Dunion: If you look at the history, we've seen many Category Fives over the years. We certainly have better tracking capabilities right now, so we can actually see Category Fives that maybe happen in the middle of the ocean that we would have missed, hundreds or, say, fifty years ago. Certainly there have been more major hurricanes in recent years, and we're trying to understand exactly why that's happening. But - we have to keep an eye on those. Because those are the storms that can cause all the damage.

Narrator: So Jason and his fellow hurricane chasers are recording more Category Five storms. And this is a development that scientists are really starting to grapple with.

[Scene of a windswept beach.]

Narrator: North Atlantic hurricanes only account for 11% of the world's tropical cyclones. But Professor Kerry Emanuel, one of the world's leading hurricane experts, has started to see something of a pattern, in his own backyard.

Kerry Emanuel: This last decade was the worst in the record books. 2005 was an especially bad year - we had a record number of hurricanes, so many that they ran out of letters of the alphabet and had to go to the Greek alphabet.

Narrator: Professor Emanuel is trying to figure out why this might be happening. One crucial factor is the mechanism that's at the core of what makes them work in the first place. Hurricanes are driven by heat. In fact, they're quite simply massive heat engines. They effectively transfer warmth from the ocean, and into the atmosphere. As all of that heat drifts upwards, it gets whipped into huge, hurricane-force winds. But this is a process we all have personal experience of.

Kerry Emanuel: When people go outside, and one of the main reasons that we feel cool is water is evaporating from our skin. And when water evaporates from us, it chills us. And that energy doesn't disappear, it goes into the atmosphere. By the same token, when water evaporates from the oceans, it takes heat out of the oceans and puts it into the atmosphere.

Narrator: Hurricanes are so powerful, because the heat energy being transferred from the ocean to the atmosphere is unimaginably huge. They take heat from hundreds of thousands of square miles of ocean, and the average hurricane turns that into three trillion watts of kinetic energy. The equivalent of a ten megaton nuclear bomb exploding about every twenty minutes. Because they are driven by heat, hurricanes are sensitive to any changes in the temperature of the Atlantic Ocean. And that's recently been on the rise.

Kerry Emanuel: Part of this increase in hurricane power from the '80s to recent times is related to sea surface temperature. The reason is that as the temperature goes up, this thermal disequilibrium between the ocean and the atmosphere also goes up. And it goes up at a rate that would increase the wind speed of hurricanes maybe 7% for every 1 degree C, but we've seen a lot more than 7% for half a degree. So we're trying to understand that.

Narrator: But he's not just interested in what's happened in the past. He's trying to get a sense of what the future might be, if ocean temperatures continue to rise.

Kerry Emanuel [drawing in the sand, with a stick]: If we look at the distribution of hurricanes in the present climate, with weak storms over on this side, and strong storms over on this side, what we see is lots of weak events, and as you go to stronger events, the numbers decline until you get to a speed limit - which, in today's climate is about 200 miles per hour. Now after the climate warms, the distribution's expected to look more like this, with actually fewer weak storms up here, but more strong storms. And we expect that that speed limit will go up to something like 220 miles per hour.

Narrator: But the weirding of hurricanes doesn't stop there. Professor Emanuel believes that in the future we can expect to see hurricanes in parts of the world that have never seen them before. He calls these "black swan events".

Kerry Emanuel: I'm somebody who spends a lot of time modelling hurricanes in the current climate, and in future climates, and when we do that, we begin to see hurricanes that haven't happened yet in history, if you will, but they could happen, on physical grounds. We like to call those "black swan events", the particularly bad ones. So this is something that worries me in particular, because there are places around the world that are at great risk from hurricanes, some of which don't know they're at great risk from hurricanes.

Narrator: It seems scarcely credible, but one of the places he thinks could be hit by a hurricane is here in Dubai, in the Persian Gulf.

Kerry Emanuel: The Persian Gulf is a body of water that gets very hot in summer. Really hot, and the hot water runs very deep, as well. To our knowledge, in the limited history of the region, there hasn't been a hurricane there. There may have been one in the distant past, that wasn't recorded. But our models tell us that there could be a hurricane there - maybe rare, but if a hurricane ever happened there, it could get very, very intense - even today, it could get winds of over 200 miles per hour. And it worries us because we see a lot of building going on there, with no thought that there might be a risk from hurricanes.

Narrator: One of the important things about the weather is that small changes in temperature, that we hardly notice, can whip up storms we can't avoid. But how are these small changes having an impact on weather events in other parts of the world? This is West Texas, where they're very comfortable with extremes. Big cars, big hats and big farms aren't the exception but the norm. But this isn't normal. [Scene of dusty ground with a few plants.] These fields should be white, covered in blooming cotton. But all that's blowing in the wind is dust. Matt Farmer has been growing cotton here for most of his life, and he's been looking in desperation for any sign of rain.

Matt Farmer: I'm 51 years old and was raised not far from the farm we're sitting on right now, and I've never seen it - I've seen it be dry, but I've never seen it be dry for this amount, this length of time, you know. Never have seen anything like this at all.

Narrator: And it just keeps getting worse. [Scenes of raging dust storm.] Matt recorded this raging dust storm on his camera phone.

Matt Farmer: Just a reminder of how dry we are, and the condition that our land is in.

Narrator: This dust storm was so huge it made the local news, 55 miles away.

Newsreader: Look at this incredible video, folks. I have never ever seen anything like this before

Matt Farmer: This is where we live and what we're in for, until we get some moisture. And it's going to take - it's going to take a pretty significant rain event, you know - we need, we need moisture and we need a bunch of it, to where we can do something to this land.

Narrator: It's now officially the worst drought on record, here. It's fast becoming like the dust bowl of the 1930s, which forced thousands of people off their land.

Ron Roberts [at work in TV studio]: - take a look, the storm system is departing, and live-pinpoint Doppler [?] radar, we're using live -

Narrator: Local weatherman Ron Roberts, who's been working at KAMC for over 30 years, hasn't been able to forecast rain for nearly all of 2011.

Ron Roberts: - moving towards North Texas, and what does all that blue mean? Well, that's a freeze warning -

Ron Roberts [interviewed]: We are seeing an incredible drought. This is the worst drought in climate history for this region. Only four inches of precipitation, and the worst drought before this - eight inches - about 70 years ago. That should give you a pretty good idea of just how severe this drought is. We've never ever had a drought like this.

Narrator: It's yet another example of a weather record being broken. Doesn't make forecasting the weather any easier.

Ron Roberts: Actually, I think this is one of the toughest year's forecast, because it is a drought and everybody wants the drought to end. When's it going to rain? When's it going to rain? And there's more pressure during a drought, there's more pressure to know what they need to do.

Narrator: The stakes couldn't be higher. Trying to get to the bottom of this is one of the world's leading climate scientists. Professor Katharine Hayhoe has a more than academic interest in figuring out what's happening here. She lives and works in West Texas.

Katharine Hayhoe: What we are seeing, what we are experiencing ourselves, where we live, in our day-to-day lives, is changes in the average conditions that we're used to. And one of the first things we're seeing is changes in our extremes. We're seeing global weirding.

Narrator: "Global weirding" is a phrase she helped to popularise. And one of the clues to the weirding of the West Texas weather lies right under her feet.

Katharine Hayhoe [sitting in a field with a handful of soil]: What you've got here is you've got some West Texas dirt. And this is good dirt, even though it's blowing away like sand. It's just very, very dry. Right now, we're below - 99% below average, right now. We're so far below average, we can't even measure how dry it is.

Narrator: As the soil becomes drier and drier, the drought gets worse and worse. And that gets amplified because there's no moisture left in the soil to evaporate into rain. But the weird thing about the weather in West Texas is that the year before they had this record-breaking drought, these bone-dry fields were awash in rain. So much rain that it broke all records. Two record-breaking years, back to back, is unheard-of in this part of the world.

Ron Roberts [at work in TV studio]: - concerned about, is that the dew points are going to be a little bit higher, the cloud cover's -

Ron Roberts [interviewed]: We have 100 years of climate history in Lubbock. And in these 100 years, we've never had this kind of steep oscillations go from one year to the next. So something, obviously, is impacting our natural variabilities that we have every year.

Narrator: Over the years, the weather here naturally swings between wet and dry. But the swing has never been this extreme, rewriting the record books in the space of 12 months. So how can it be recording-breaking wet and dry at virtually the same time?

Katharine Hayhoe: Our planet has warmed by almost 1 degree Celsius over the last 100 years. A tiny change in temperature - how could that make a difference? That temperature change, in and of itself, makes no difference at all to our lives. It makes a huge difference to what we're used to.

Narrator: The weather here has all the hallmarks of global weirding. It may not rain as often, or as regularly, which makes droughts possible. But when it does rain, it's heavier and more intense.

[Scenes of thunder and lightning.]

Katharine Hayhoe: One of the changes we've seen is that the average humidity of our planet has increased by 4%. Warmer air holds more water vapour. And so, on average, our atmosphere is 4% more humid than it used to be, 30 or 40 years ago. What does this mean for us in West Texas? Our humidity's what - 10%, probably. So we don't feel that so much here, but what happens is there's more water vapour in the atmosphere. So when storms come through, there's more water for them to pick up and dump.

[Scene of a tractor crossing a field, with lots of wind turbines in the background.]

Narrator: It's these storms - or lack of them - that trigger the extreme dry and wet weather in West Texas. In the future, scientists expect this pattern of drought and flooding to be played out across the planet. But it's the small change in average temperature that's behind the predicted increase in some extreme weather events. And scientists believe it's all a question of balance. As the Earth struggles for climate stability, the weather begins to get extreme and weird.

Katharine Hayhoe: Our planet's a really complex place. And so, as we increase the temperature of our planet, we are changing the dynamics of our atmosphere. We are changing the way our weather systems move across the country. We are changing the - our subtropical zones are expanding, our dry areas of the world are actually growing. So we're changing how water gets distributed around our planet. Places already dry are getting drier. Places that are already wet are getting wetter. And our extremes are getting stronger in both directions.

Narrator: Whether this warming is natural, or man-made - as the vast majority of scientists believe - it's triggering global changes. And they are expected to play out in Britain. This year's government report on climate change risk says we are likely to see more flooding, on the one hand, and longer drier spells, on the other. The record-breaking rains in Scotland last year and the worst spring drought ever in parts of eastern England could be a taste of things to come. But the intriguing question is the effect it might have been having on our winters.

[Scenes of snow-covered countryside, followed by scenes of traffic on icy roads.]

Narrator: As Christmas 2009 approached, Britain started to shiver.

Newsreader: It could be a record-breaking cold night...

Narrator: The cold went on, day after day. It was the coldest winter for 30 years. Just a year later, records were being broken again. December 2010 was the coldest for over 100 years. The weather was so brutal that Heathrow Airport was closed at one of the busiest times of the year. But how was this possible, if the world was supposed to be getting warmer, not colder? The British weather is so complicated, and has so many variables, that scientists believe that really understanding what was going on was well nigh impossible. But that didn't deter the weather experts at the Met Office.

Adam Scaife: The view in my research group is that we shouldn't give up on this, because there are these key pieces of this puzzle, very intriguing connections that may be predictable. And it's our job to squeeze as much predictability out of the climate system as we can, so that we can advise people about the possibility of impending extremes.

Narrator: There are a number of clues to unravelling this mystery. They lie buried away in the Arctic, in the long history of the Sun and possibly the contents of this case. [Scene of a violin case being opened.] This is a Stradivarius violin. They are the most expensive violins in the world. And they're worth so much because they have a unique sound.

Tamsin Waley-Cohen: They have an incredible singing quality, and also an incredible depth and richness. And I think they reach closer than any other instrument to being like the human voice, which touches people.

Narrator: The body of this violin has a remarkable connection to the weather. Stradivarius violins are defined, in part, by the exceptionally fine-grained wood they're made from. This violin was made in 1721, nearly 300 years ago, and the comparison with the grain of a 20th-century tree is startling. Intrigued, scientists in America have conducted a series of tests, which seem to suggest that the unique sound of the Stradivarius is down, in some ways, to the fine-grained wood they're made from.

Tamsin Waley-Cohen: I think that's extremely interesting, that's fascinating. I've heard about the quality of the wood, of course, but not particularly the closeness of the grain, but it absolutely does make sense in a lot of the violins from around this period - the Golden Period of Stradivarius - have this very tight grain.

Narrator: Whatever the truth about why the Stradivarius sounds so beautiful, the fact is: trees grow slowly in the cold. So the closer the grain, the colder it was. The fine grain on this instrument is evidence that the climate of the time was freakishly cold. But what caused this bout of extreme winters 300 years ago? And could the same thing be responsible for the record-breaking winters of the last few years in Britain?

[Scenes of Mike Lockwood in a boat on the Thames.]

Narrator: Solar scientist Mike Lockwood went looking for clues in the most obvious place - the Sun. The Sun's energy exerts the most important influence on the Earth's climate. It defines the seasons, creates weather patterns and drives the ocean's currents. And it's what was happening to the Sun 300 years ago that's brought him to the river Thames and the crucible of British science.

Mike Lockwood: We're just coming up to Greenwich on the river here. Greenwich is a really important place in the history of science - it was the first ever purpose-built laboratory and it was built to solve the longitude problem. But they did other things as well. They were really, really useful - they observed the Sun. They made a great sequence of data that's been incredibly useful for understanding the Sun.

Narrator: Hidden away in the dusty archives that were tantalising clues that would help Mike understand what was happening to our nearest star. Because 300 years ago men of science were carefully observing the face of the Sun. The records show that they were mystified by something they hadn't seen before - the Sun's spots, which they had known about for years, seemed to have unexpectedly vanished.

Mike Lockwood: Initially it was thought this was just because people weren't looking properly, at that time. But then, as more and more observers' records were found, it became quite clear that no: that wasn't the case, that there just weren't spots there. There were people who carried on looking for sunspots for 50 years, despite the fact they hardly ever appeared. And those records are now valuable because they tell us about the state of the Sun just 300 years ago.

Narrator: Sunspots are important because scientists now know that they can affect the British climate. The Sun's spots - shown here in white - come and go on an 11-year cycle. When there are no spots, when solar activity is low, there is a reduction in the amount of ultraviolet light hitting the Earth. Low solar activity has the potential to disrupt the jet stream and the flow of warm air over Britain, allowing the wind to blow cold winter air from the east.

Mike Lockwood: Our work suggests that, statistically, if you have this low solar activity, you will get more of these cold winters. And it seems to be a phenomenon that's very much prevalent in Europe, but not really so significant anywhere else.

Narrator: But 300 years ago, the Sun's spots didn't just vanish for a few years in the 11-year cycle. They disappeared for two generations. The impact on Britain's winter weather was recorded by 17th-century weathermen all over the country. This period coincided with a series of exceptionally cold winters in Britain. The Thames froze over and frost fairs were held on the river. The period from 1650 to 1700 has become known as the Little Ice Age. In fact, the coldest winter ever recorded was in 1683-84.

Mike Lockwood: It's interesting to see the care with which things were recorded, but also the rather colourful language that people used, that we don't actually use nowadays, sort of - "profound cold", and things like that, is the sort of wording that we can't use in a modern scientific paper, but actually means quite a lot.

Narrator: So why did the sunspots disappear for 50-odd years. To answer that question, Mike had to go back even further in time, back before the beginning of civilisation. And one of the best places to get that long view of the history of the Sun is in ice. He and his fellow scientists analysed ice cores, because they contain a signature of what's been happening to the Sun over thousands of years.

Mike Lockwood: We can core into them, effectively look back in time. Roughly speaking, there are 20 to 30 Grand Maxima and Grand Minima in the 9,000 years that we can look at.

Narrator: So what the ice showed was something nobody could have predicted. The Sun had a secret rhythm. As well as an 11-year time frame, it also operated on a much longer time scale - the Grand Solar Cycle, averaging every 300 years or so. And Mike Lockwood's ground-breaking research helped explain what was happening in the 17th century. Because that was the time of a Grand Solar Minimum, where UV light would be at its lowest. Not just for years, but decades. And that would create conditions to allow the wind to blow from the east, leading to frost fairs and the production of beautiful violins. But could that help explain the recent cold winters? Have we reached another Grand Solar Minimum? The answer was a convincing "no".

Mike Lockwood: We seem to be coming out of a Grand Maximum of solar activity, and we will - past experience tells us - go into a Grand Minimum. It's just a question of how soon. It could be as little as 40 years' time, it could take a couple of hundred years, but the long-term record from cosmogenic isotopes tell us that it will eventually go back at some point into a Grand Minimum again.

Narrator: So we now know for sure that it wasn't the Grand Solar Cycle that was responsible for Britain's shivering through two record-breaking cold winters on the trot. Of course, the end of the regular 11-year cycle, combined with other natural weather factors, played a part in these record-breaking winters. But some experts didn't think that was enough. Something was missing. Over the last few years, climate scientists from around the world have been trying to figure out what might have been happening. One of the leading lights of that group is Dr Adam Scaife. He and his team have been accumulating and analysing mountains of weather data. Weirdly, they believe the answer to the problem lies in the Arctic. Even weirder, they think it's the warming of the Arctic that may be holding the key. But how can it be getting warmer in the Arctic, yet colder in Britain?

Adam Scaife: If you melt the Arctic ice, you might naively think that might give warmer conditions further afield, for example over Europe. It is indeed true that when you reduce the ice, that lets lots of heat out of the ocean, and so in the Arctic you do see several degrees of warming in the lower part of the atmosphere.

Narrator: And there's little doubt that it's been getting warmer in the Arctic. In the last 10 years, the sea ice has reached record low levels. But according to the Met Office's highly sophisticated computer models, a hotter Arctic doesn't equal a warmer Britain.

Adam Scaife: That warming that's happening over the Arctic is not seen over Europe, and the reason for that is because the circulation changes, the wind changes. And it turns out that when you remove the Arctic ice, then the winds become more easterly, so the winds start to circulate from east to west around the Arctic, and south of the Arctic, and it's that that starts to dominate the response over Europe. So instead of warming in the winter, over Europe, when the ice is depleted, we get cooling, because we're dragging the air again from Siberia over northern Europe.

Narrator: They're still trying to understand the mechanism that produces this effect. But when you add this new factor to variables, like the Sun's solar cycle, what happened to our winters starts to make sense. And perhaps what's even weirder is as the world gets warmer, some bits of it can get colder.

Adam Scaife: Of course Europe, and the UK, is only one region of the globe. And there are many other regions. And when you average those up, you still see warming. So the fact that Europe is cold, and the US is cold at the same time, is balanced by the fact that Canada and the Mediterranean tend to be milder in those winters. So when you integrate up this change in the winds, the extra easterly winds, when you average it over the whole globe, it cancels out. So global warming can continue unaffected, but the regional temperatures over, say, the UK and Europe can actually go down, at least for a few years, as the globe warms up. Even though, in the end, global warming will of course win, if we continue on that trend.

Narrator: This is why, as the world gets warmer, it makes sense to talk about the weather getting weirder. It affects different parts of the planet in different ways. But every extreme weather event isn't an example of global weirding. Freak weather still happens. The difference is: in the future, there's likely to be more of it. The dice are now being loaded.

[Scene of Katharine Hayhoe in her car, with furry dice over the dashboard.]

Katharine Hayhoe: Dice are a great way to picture what climate change is doing to our world. We always have a chance of rolling that six, whether it's extreme heat or record-setting rainfall, or even the longest drought on record, that could always happen naturally. What climate change is doing now, is one by one, it's taking those sixes, those weather extremes, and adding a few more to the dice. So that now our chances of a record-breaking heat wave are twice what they used to be. Our chances of record-setting rainfall events have increased, relative to the last 50 years. We'll never know for sure if that six that we rolled, that extreme weather event, is the natural one or the climate change one. But we do know that the chances of rolling those sixes are increasing.

Narrator: More extreme weather appears to be the new normal. So what, if anything, can we do about it? One strategy is on display here, in Holland. But it's not exactly visible. Half the country lies below sea level, which makes it vulnerable to weather extremes. Not surprisingly, they've come up with a few clever solutions to the problem. [Scene of underground car park.] This car park in the city of Rotterdam might look like any ordinary car park. But hidden away in the bowels of the building is an unusual approach to dealing with the consequences of weather weirding. There's nothing to advertise where it is. Access is through this nondescript door. Inside it looks like a series of interlinked concrete bunkers. This man has created something that's dark, cold and utterly functional.

Daniel Goedbloed: Well, what we saw in the last year was that we had an increased amount of heavy rainfall events. And with these heavy rainfall events, actually the centre of the city has water problems.

Narrator: If the weather gets weird in the streets above, it can be dealt with at the press of a button that pulls a plug in the sewer system and the excess floodwater is siphoned off down here. For Daniel Hoedbloed, the man who designed and built these bunkers, they're an essential element in the city's defence against the new weather extremes.

Daniel Goedbloed: We had streets flooding, we had basements flooding, and we had canals coming up and, more or less, overflowing. So what we did is we literally calculated how much extra storage we needed in the city centre, just to face this problem of extra rainwater.

Narrator: This space is big enough to deal with 10 million litres of water, enough to cope with the worst flood in a century. The whole project cost 11 million euros, about 10 million pounds. But for Daniel, and Rotterdam, that's a small price to pay for the level of protection it brings.

Daniel Goedbloed: The rainfall events are going to increase. There are going to be more heavy showers, so over a year we're going to have less rainfall, but it's going to come at us in shorter amounts of time, so really in heavier rain showers. So we're going to have to deal with this rainwater in this short amount of time. And then you can just let it flow here quickly, and store it.

Narrator: After the flood, the stored water can be released back into the sewer system, and the tanks can be flushed and cleaned, ready to deal with the worst of the weather patterns of the future. But Rotterdam's adapting to a wetter future in even more ingenious ways. They're so concerned about flooding, that they're making plans not just to continue living by the water, they actually think it's possible to live on it. [Scene of geodesic domes near some water at night.] This futuristic-looking building is floating in the city's docklands area.

Pieter Figdor: It's a pilot, and a sort of showcase to show to the people floating construction, and floating living and working, is possible, it's really stable, and I think in Rotterdam, at the heart of the city, there's an opportunity to make new city parts with a nice way of living and working possibilities.

Narrator: Most of the world's biggest cities are built near water, and the Dutch think their plan to fill this whole dockland area with a raft of these types of buildings could be a blueprint for urban living in the future.

Pieter Figdor: We are now planning, in this harbour, a new floating community. And the city has announced a competition for international architects to think about this new floating community, and it could be a sort of new Venice.

Narrator: That's all well and good for small rich countries like Holland, who can afford to built the infrastructure to cope with a future of weather extremes. However, there is another solution, that's more about brain than brawn. An example of that strategy had its finest hour when the future of the world was also in the balance. In a quiet corner of the Met Office library hangs a map, probably the most famous weather map in the world. It's the forecast for D-Day. And it played a critical role in the outcome of the Second World War.

Helen Chivers: The weather forecast might well have won the war. They were trying to predict, within a window of a few days where you could have the right amount of Moon, the right tides, as to whether the weather would be just flat enough for the landings to take place. Now the forecast was for this ridge of high pressure here [pointing to the map] to move in across the western part of the Channel. And as you can see from the chart here, it probably hadn't got quite as far in as was expected, so conditions weren't perfect by any means, but they knew that if they didn't go at the beginning of June, they'd have to wait another month.

[Newsreel footage from D-Day landings.]

Narrator: If this forecast was wrong, the consequences could have been catastrophic. So it's no exaggeration to say that the D-Day weather forecast didn't just help to change the course of history, it also saved countless lives. And getting an accurate, reliable forecast is vital in our new weather future, because the hope is: prediction will lead to protection.

Helen Chivers: The point of the weather forecast, when you get down to the nitty-gritty, is getting the extreme weather events - the heavy rainfall, the high temperatures, the forecasts for those - absolutely spot-on, so people can get correct warnings in the right time scales, so that they can take precautions to save themselves if they need to.

Narrator: And the one thing weather forecasters have managed to improve, over the years, is the accuracy of the forecast. The five-day forecast is now as accurate as the one-day forecast was, 30 years ago. That could be vital, in a future predicted to be dominated by extreme weather events. The technological development that's driven the improved accuracy in the forecast floats thousands of miles above us - satellites.

Helen Chivers: We've got so much more information because of all the satellites that are up there. And we know that you need to know what's going on globally, to get a good forecast of what's going to happen in the UK and around the world for the next five days. You can't do it without global coverage, and satellites have given us that global coverage.

Narrator: Satellites provide huge amounts of information about the world's most extreme weather events. But making sense of them requires one of these. [Scenes of computer banks with flashing lights.] This is the Met Office's computer behemoth. It only came online three years ago, and it can do a hundred trillion calculations a second. That's the equivalent of a hundred thousand PCs, and it makes it one of the biggest number-crunchers in the world.

Helen Chivers: We need that power. Partly because we've got millions of observations coming into the super computer every day. But it's also trying to calculate what the weather's going to be like on that grid, all the way around the globe, up to five days ahead and beyond, because we use the same model that we do our day-to-day forecasts on, for our climate forecasts, that go hundreds of years into the future.

Narrator: And that computing power could be a vital weapon in the coming struggle with global weather extremes, allowing the Met Office to develop new kinds of weather forecasts.

Adam Scaife: The big new idea in climate science is not just to look at the distant future, 100 years ahead. Of course, that's very important - it tells us what road we're on. But in the near term, on planning time scales, years or months ahead, when people are making real decisions, then the big thing is to increase the skill of the forecast on those time scales. Maybe give some warning, weeks or months ahead, of impending extremes, perhaps even unprecedented extremes. That's what we're really trying to do with this.

Narrator: The new science of weather extremes highlights the profound links between our climate and the way we live. It also underlines just how vulnerable our civilisation is.

Kerry Emanuel: We're playing a kind of dangerous game with the climate. The last seven or eight thousand years has been a remarkably stable climate, very unusual in the last two million years of Earth's climate history. And it was during that time that human civilisation developed. So I think we should be clear about something, that climate change, whether it's natural or whether we're doing it, is no danger to the planet. The planet will be fine, the planet has gone through much worse. The danger is to us. Our civilisation developed in a very unusually stable climate, and it's very well adapted to that climate. And when you change it, and again whether that change is natural or man-made, it's going to cause dislocations and problems.

Narrator: However we choose to deal with global weather extremes, be it protection or prediction, one thing is clear - the world has changed.

Katharine Hayhoe: The past is no longer a guide to the future. Our climate - the average conditions that we grew up with - is not the same now as it was 30 years ago. Events that used to be very random and extreme are becoming much more frequent. And more severe. We're going to be living in a different world than the one we grew up in. And we have to adapt to those changes.