抗击洪水:谁打?

Over the past 40 years, the exact cause of the death of the dinosaurs has beenhotly debated. Some favour the theory that a massive meteor hit the Earth and changed the climate, while others argue that a sequence of huge volcanic eruptions also contributed to the mass extinction. Research this week from Leeds University has poured cold water on the latter theory, suggesting that the impacts of these volcanoes would have been relatively small. Georgia Mills spoke to lead researcher Anja Schmidt to find out how they investigated a mystery 60 million years old...

Anja - I'm running climate models and, what I did is, I gathered all the information we have about this volcanism that happened 65-66 million years ago. So we needed to know, how long were these eruptions, how much volcanic gases were emitted and then once we had all this information, we put that in a very sophisticated computer model, and then we could simulate what these omissions would do to the environment, but also to climate.

Georgia - And what did you find out when you ran these simulations?

Anja - Some researchers, previously, actually suggested that, because of these volcanic eruptions, temperatures on earth would drop really drastically and they call this a so called "volcanic winter". Just imagine, really, really cold surface temperatures. But what we find actually when running this climate model with all the information we gathered, we find that temperatures didn't drop that drastically. So the situation wasn't as grim as previously suggested by some scientists. So with our work, we actually find that because there is a drop in temperature, but it would probably be okay for most animals and plants, so they would have been able to cope with these temperature changes.

Georgia - Why would a volcano erupting cause a drop in temperature in the first place?

Anja - So, volcanos emit a lot of gases, and one of the most prominent gases is sulphur dioxide and, once sulphur dioxide is in the atmosphere, it actually gets chemically converted to form very, very small particles - you can't see them with your bare eye. But these particles, they basically reduce the amount of energy that comes down to the surface from the Sun. So less energy reaches the surface and, therefore, you end up with the cooling of the Earth's surface. We're really sure that depending on how long this eruption lasted. So if they lasted, for example, a decade we find that the surface temperatures returned back to normal very quickly, within a couple of decades. So, as quickly as 50 years, for example, and that's just a normal process. Basically there's a big kick to the Earth's system because of these volcanic emissions and these particles in the atmosphere, so they reduce the energy but, all of these particles eventually fall out of the atmosphere, and the Earth's temperatures can basically return back to normal.

Georgia - Is it just the cooling temperatures that volcanos could have impacted?

安雅——没有。事实上,一些科学家thought about the fact that, following a volcanic eruption, the atmosphere gets very, very acidic and you get what we call "acid rain." Acidic rain can actually damage vegetation, so we also assess this in our model, and what we actually find is rather surprising. We find that in some parts of the world, vegetation would indeed have died off because of the acid rain but, this effect, we don't see it on a global scale. So we can't explain a global scale mass extinction with acid rain due to volcanism.

Georgia - In your paper you mentioned that this simulation would be accurate provided that climate feedback systems, so the way the climate worked in the past, was the same as it is today. Do we have any reason to suspect that it was the same?

安雅,我们不确定,因为我们是真正的y talking about many million years ago. So we had to make this assumption, that was the best assumption we could make at the time, but it could well be that the climate feedbacks would actually be very different in ancient times, but we still don't know. So that's another area of research, to understand climate feedbacks. So how does the climate react to a volcanic forcing, as we call it, so if the system is kicked by a big volcanic eruption - how does it react?

Georgia - Why should we care what killed the dinosaurs that happened 60 million years ago? It's probably not going to happen again. Why research this?

Anja - So, I think one thing is dinosaurs are really, really fascinating. Young and old are fascinated by creatures that are not around anymore. They were really, really powerful; they also looked a bit weird didn't they with their head gear, some had really nice colours and even feathers, and I think it's fascinating and they were so powerful and we still don't understand what actually killed them. So that's one reason to study that, and in terms of volcanic eruptions, I think it's very important to understand what volcanic eruptions can do to climate and the environment because, for sure, there may be another eruption in our lifetime. Completely different than the eruption I was talking about in my study, but you may also know that now people are talking about ways to mitigate global warming, and one of these is called geoengineering. So people propose to put in tiny particles into the atmosphere; very similar to what we have after a volcanic eruption. So my work can also help to understand the consequences of doing this kind of geoengineering.

One hundred years ago, on the 25th of November, Albert Einstein presentedhis theory of general relativity to the world. This theory fundamentally changed aspects of physics that hadn't altered since Isaac Newton first came up with them, hundreds of years earlier. Over night, Einstein became a celebrity - in fact the first scientific celebrity. Connie Orbach has been hearing how, beginning with a whistlestop tour, thanks to the UK's Science and Technology Facilities Council and David Tenant, of what general relativity is all about...

David - At 26, he figured out nothing less than a new theory of space and time. It led to a nifty way of simplifying physics by treating space and time as one thing - spacetime. But Albert was just warming up. He wasn't happy with Isaac Newton's mysterious force of gravity. Naturally he started work on his own theory and sure enough, he cracked it.

Mass causes space time to curve. The natural motion of thing is to follow the simplest path through space time but, since objects with mass curve space time, stuff moves towards the most massive object - that's what you feel as gravity. It's warped space and time that's keeping your feet on the ground.

Connie - So that general relativity - a theory to end all theories. But how did Einstein himself become so famous. I caught up with Professor Gerry Gilmore at Cambridge University's Institute of Astronomy to find out...

Gerry - We're going down to this end of the building which is where the Director used to live and going into the room that used to be the Director's sitting room where the great people would have worked, and there's a whole string of famous people lived in this half of the building. The one that's particularly relevant for this current centenary is Sir Arthur Eddington, who in 1919, showed that light is bent by the sun in just exactly the way that Einstein's general relativity, which is 100 years old today, predicted. That was the event - the public announcement of that - which was in November, 1919 was what made Einstein famous. That's when Einstein appeared on the front page of the New York Times and London Times and became a celebrity. That was the beginning of scientific celebrity and it changed our view of scientists completely.

康妮-早期的男友…

Gerry - Absolutely.

Connie - An A-lister indeed. And if you ask many people today, Einstein will still be on their dream dinner party list. Let's go back 100 years to find out how it all came about...

Gerry - Okay, so this was, of course, right in the middle of the darkest days of the First World War but, in spite of that, mathematical physics in Germany was advancing at a spectacularly fast rate, so there were several people racing towards what became general relativity - Einstein got there first - but none of this was known in the West. The only connection between German science and the outside world was via The Netherlands - a neutral country at the time - they were communicating both with Einstein and with Eddington and so the people in Leiden realised the importance of what Einstein was doing and sent the work to England to be published by Eddington. Eddington also independently realised the enormous value of this and further developed the work himself, and took it upon himself to market and explain relativity to Western scientists. And so he wrote books and articles which were hugely popular, hugely influential. Whereas Einstein's own work marketing the theory didn't actually appear in English until the 1920s, so Eddington had already done it.

Connie - Since then, we're now a 100 years on from that this theory still stands.

Gerry - That's right, yes. It turns out that general relativity has been tested to astonishing precision and every single test we've done of it over the last 100 years, it turns out to be dead right. It's truly remarkable. So the whole subject of black holes and space, all these wonderful things we take for granted, X-ray astronomy, massive exotic events, quasars; these are all extreme version of general realistic phenomena, none of which happened under Newton. And every single day we astronomers are studying things that just exactly follow general relativity. So we know it's accurate because the description of the solar system around us to much better than one part in a million.

Connie - Einstein's theory has inspired scores of scientists with his work but, beyond that, he has also become a figure of popular culture in literature, art and, on this centenary, also in music and Sam Genders has written a song to commemorate the anniversary with his band, Diagrams. I got in touch with Sam to see what inspired him...

Sam - He was obviously a really interesting person and came up with these incredible ideas and, for me, there's something so inspiring about the fact that so much, so much of the work he did just came from pure maths and thought experiments. And so much science is done through technology these days that I find that really exciting.

Connie - The bending of space and time is something which can quite easily be kind of turned into music in a way. It's got quite a romantic element to it...

Sam - Yes, it's sort of metaphorically ripe for kind of slightly ambiguous lyrics that could be about science, or could be about relationships. Einstein himself was a, as far as relationships went, especially romantic ones, was a fairly complicated human being and so, within the song, there are sort of these threads of relationship and playing on the words a little bit of general relativity about how we do all see things from certain different perspectives. So yes, it inspired me anyway.

Connie - Sam joins the pile of people inspired by Einstein - science's first A-lister, but he couldn't have got there alone. Work on relativity made him a great scientist, but Sir Arthur Eddington made him famous..,

Gerry - Yes, Eddington deliberately made Einstein a superstar. It was part of a conscious programme, for a small number of people lead by Eddington, to try and rebuild scientific connections between Germany and the rest of the world after the war. But Einstein was all over the front page of the New York Times and the front page of the London times - a world shaken by a new theory; Newton wrong; the stars are not where they ought to be - all this sort of stuff, and so this started the cult of celebrity science.

To avoid catastrophic flooding, planners also need to know where it is likely tooccur. To get this glimpse into the future, researchers like New Castle University hydrologist Liz Lewis use physical and computer model simulations. Sam Mahaffey went to see their newest piece of kit, an augmented reality sandpit, but first took a look around the facility.

Sam - I'm meeting Liz in theNovak Hydraulics Labat Newcastle University. It's a long, high-ceilinged room full of pipes, pumps, and huge tanks of water running from one end to the other. The noise you can hear is the sound of water gushing into a big open top channel right in the middle of the room. I asked Liz why it's so difficult to predict where floods are going to hit?

Liz - In some ways it's very easy because we know how water flows - water flows downhill and it pools when it can't get out, but there are lots of other compounding factors such as, the drains might be blocked and the ground's already wet. Somewhere might have flood defences in place already but they might not have been opened or shut at the right time and there's a big human element of it. So it might happen in the night when roads getting flooded isn't so bad, but it might happen at rush hour which means you get lots of traffic jams so knowing where the water's going to go is one thing, but its knowing how that's going to affect our transport networks and our distribution networks.

Sam - How do scientists and engineers do this?

Liz - There are lots of things to think about and we do it with models. We have physical models like you can hear in the background, and we also have computer models which lets us run thousands of simulations of something happening and have a look at a whole range of outputs.

山姆-当我想到一个模型,我想到我looking at right now. Which is this sort of scaled down river with water flowing through it; there is sand and gravel that's like the river bed. How useful are these kinds of physical models?

Liz - These models are very useful, but we probably don't use them like you would think, so we don't build a physical model city. Instead what we've got here is kind of a segment of a river bed and we use it for understanding how water flows. We look at how the water will move the sand and the gravel around, so looking at sediment transport. So we use it more to understand the processes which we can then build into our computational models.

Sam - These computational models sound really complicated but Liz promised to show me something that would explain it all and it gave us chance to get away from the noisy lab... I'm in a dimly lit room but in front of me is a big box of sand and projected onto the sand is a map with contours and some little Lego pieces in the corner - don't know what we're going to do with those. Liz, what am I looking at here?

Liz - So this is the department's augmented reality sandbox. What we've got set up here is a kind of a metre square sandbox, full of sand and above it we've got a projector and we also have an X-Box Connect, which is a 3D camera, so that can sense the surface of the sand. And so what that does is the camera senses the surface of the sand, that feeds down into the computer that's at the bottom and that projects back on to it these contours, which is the topography, which the model uses to figure where to route the water.

Sam - What does this sand correspond to?

Liz - So, what we're doing with the sand is basically building hills and a valley, so we can make a nice flat catchment like you'd find in Cambridge on the Fens, or we can build a really steep sided catchment like you'd find in Scotland and we can use that to demonstrate how water's going to flow in these different environments. Shall we have a go?

Sam - Yes, lets.

Liz - What we're going to do now is build some mountains.

Sam - Okay. So Liz is gouging out a big valley into the sand.

Liz - The map that's projected onto the surface of the sand has changed completely now the contours are in a completely different place.

Sam - You can kind of see that it's looking like some hills now.

Liz - At the bottom of this valley and where the river widens out, we've got this kind of flood plain now - so a of flat bit, and this is historically where towns and villages were built along next to a river. So what we are going to do is put our lego houses and build a mini city at the bottom of this valley to see what happens when different amounts of rain occur and to see where it's going to get flooded.

Sam - So this is what the lego's for. We're going to build a model village. Okay, so now we've got our topography and we've got a little village at the bottom. Please can we make it rain..

Liz - Yes, so we make it rain by holding our hands above the surface and, again, the 3D camera is sensing that my hand's there and so what it does is it simulates water directly underneath where my hand is. So I've put it over the top of the catchment - so this is kind of at the very top of the valley where it's steepest, and we can see that this digital simulated water is flowing really quickly down the sides, and really quickly down the river, and the water's swooshing up the sides and completely devastating the little lego town that we built.

Sam - It looks like an aerial view of what you might see during a flood. As you hover your hand over, rainfall is collecting on the ground, just flowing downhill straight towards our lego houses. Behind this sandbox presumably there's lots of computery things going on that's working out what's downhill and what will affect where the water goes?

Liz - That's right. So, there is a computational model behind this which is using proper hydraulic equations to route the water. So that basically means it knows the shape and size of the channel and it knows how much water has been simulated.

Sam - What kind of uses do you have for these computer models?

Liz - There are lots of reasons that we build models. Firstly to understand where might flood; to understand how big the flood is going to be; to understand what it's likely to impact. So is it going to flood near our hospital or is it going to flood near our supermarket. And then lastly, the really important thing is what can we do to prevent flooding. So what we can do now in this sample box; we can put a little lego wall in here, and we can empty all the water out and then we can create another storm and this time, when the water flows down the sides and it gets towards the city, it doesn't enter the city because we've built this big flood defence.

It's predicted that climate-driven extreme weather events, such as flooding, aregoing to become more common and more severe around the globe. The big question is what can we do about it? How are we going to protect ourselves into the future? Dr Ilan Kelman, a researcher for Risk and Disaster Reduction at the Institute for Global Health at UCL, spoke to Kat Arney about how we can reduce the risk...

IIan - The first thing that we can do is actually learn from our past. So, flooding has always happened and humans have been dealing with it for 10,000 years, sometimes better, sometimes worse. So, let's look at what went wrong, what went right, and try and implement that. We can do that at the very small level, at the household level, so people can make decisions in their open properties to use flood resistant finishes, flood resistant materials. But there's much wider issues in terms of planning, urban governance, dealing with people's streets, houses, infrastructures, and that means planning, living with rivers, living with coasts. A flood plain is called that for a reason...

Kat - That's the bit that floods?

IIlan - That's the bit that floods. It has a job to do, so maybe we should think about the way we live, how we live, where we live, and let the flood plain do its job.

Kat,所以where are some parts of the world that are doing this well, that are coping with flooding and flood plains?

IIan - Well, I grew up in Toronto, Canada and I always enjoyed the ravine system which was wonderful recreational pathways, wildlife, cycling, walking. Then when I got into this as a profession I realised, in fact, it came from flooding. So 1954, a devastating hurricane went through Toronto - Hurricane Hazel. It killed about 83 people and, in response, the government said "well, we're going to let the ravines, the rivers be flood plains, which is what they are meant to be being beside a river." So they designated it to be green areas, greenways, recreational pathways and building is now forbidden there.

Kat - Now, as the global population does increase though, building is encroaching on flood plains. I've lived in East London which is basically a swamp and they are building all kinds of things right next to the river. And is this risky, not just in London but in other parts of the world? Should we just not be building there at all? Can it be possible to build safely in these areas?

IIan - Wherever we build there is going to be some risks. Therefore, we have to ensure that we have the knowledge and work with the people in the areas to determine what risks they do want; what risks they don't want. If we avoided all flood plains in all of the risky areas we wouldn't be able to build anywhere. That's where we decide - well maybe at the local level, maybe at the household level. What we have to do is accept that some houses, some buildings are going to be flooded at times but, construct them in such a way that it's easy to wash them out, clean them afterwards and then go back and live there.

Kat - And presumably tell people to store stuff in waterproof boxes?

IIan - Well, part of it is ensuring there are not valuables on the ground floor; part of it ensuring we do have an adequate warning system; part of it is people knowing they are in the flood plain and therefore being able to respond and react when warnings are issued.

Kat - Tell me a bit more about some of the kinds of strategies that we can use to enable us to build on flood plains because, for example, just building urbanisation increases the risk of flooding. Are there ways, for example, planning or housing could help to mitigate some of those risks.

IIan - This is a lot of the challenge that people do need a place to live, we do need the infrastructure. As soon as you pave something over that increases run off but there are ways to reduce that so we can use, for example porous material on the roads. That means it will rain on the road and go straight through, rather than necessarily giving driveways, rather than necessarily paving over front gardens. It would be possible to keep them as plants. And also, a lot of it is simply the layout and the planning to ensure that when it does rain the water does go into the river, and that the river has a capacity to take that water rather than bursting it's banks.

Kat - Is there a risk of kind of over-engineering this? How often would these kind of events happen? Would it make it worth it in financial terms to build all this kind of stuff in?

IIan——好吧,当然目前在的地方the UK, we are over-engineering anyway and a lot of the over-engineering is an attempt to separate people from the water. That makes a lot of sense, no-one wants to be flooded. It does keep us dry. On the other hand then, when it does rain and as the rainfall patterns change, when flooding happens it seems unusual - people are not ready for it. So, what we have to do is actually work with people, and ourselves to try and determine what balance are we seeking. How often will we accept being flooded or do we want to completely separate ourselves from the water, recognising that maybe every 50 years, maybe every 100 years, there's going to be a massive flood. There's no quick fix, there's not silver bullet. We simply need to recognise there's a whole variety of solutions we can take and it really depends on how much we are going to accept being flooded, to what degree, and how frequently.

Kat - And we've just heard from Claire earlier about the vulnerability of developing countries that are poorer. How can they cope with these kinds of risks?

IIan - Everyone, whether they are in Myanmar as Claire mentioned, whether they are in East London where you live, everyone has some form of knowledge but, they also have gaps in their knowledge. That's where it's not about going in and bestowing our wonderful aid and wonderful ideas on these poor people, it's actually about ensuring we work with the people, we use their knowledge, recognise what they don't know and work together to avoid the risk of flooding.