Climate Change and Renewable Energy

Climate Change, ancient ice, carbon capture and storage and wave power...
21 January 2007
Presented by Chris Smith, Helen Scales


Figure 2: Drilling ice cores in Antarctica.


Following this week's crazy weather Dr Chris and Dr Helen have a look at Climate Change. Eric Wolff from the British Antarctic Survey tells us what secrets about our climate are locked away in ancient ice, Jon Gibbins from Imperial College tells us about ways we can store all that excess carbon dioxide underground, and Ali talks to Alison Hill from the British Wind Energy Association and Max Carcas from Ocean Power Delivery about wind energy and wave energy. Derek Thorne, Dave Ansell and Ali Webb try to discover how much power we could generate by hooking the country's gyms to the electricity grid.

In this episode

Solar Powered Bikinis

You've heard of solar powered boats, solar powered cars, and even solar powered handbags have had their share of the limelight, but now it's the turn of the solar bikini and solar bathing shorts. New York University's Andrew Schneider unveiled his beach-friendly solution to a flat iPod and warm beer at the Interactive Telecommunications Program show. It consists of a standard bikini retrofitted with photovoltaic cells stitched together with conductive thread. It pumps out 6.5 volts and terminates in a USB socket for connecting to an iPod. The male version, which is dubbed the iDrink, apparently has a much greater surface area of solar cells and can produce up to 1.5A of current, enough to power a miniature can-cosy peltier cooling device, which is capable of keeping your beer cold. Cool as it sounds, at the moment it's not clear whether wearers will actually be able to take a dip in their new beachwear, or whether the combination of electricity and sensitive parts of the anatomy could prove painful...

Wierd Creatures

Ever heard a bumblebee bat, a Bactrian camel or a long-eared jerboa? Maybe not - these are two of the top ten weird creatures that the Zoological Society of London or ZSL have chosen to try and protect under their new Edge of existence programme - with Edge standing for "Evolutionarily Distinct and Globally Threatened" species. The project focuses on animals that not only need immediate conservation action to prevent them from going extinct but they are also strange and distinct with not many close relatives - species that are truly one of a kind. In order to work out how evolutionarily distinct all the different mammal species are in the world, scientists at ZSL, as well as the University of Virginia in the US and Imperial College in London, created a super-tree of all the mammal species. It's just like a human family tree and maps out how all the mammals are related to each other. For a species to have a higher score for evolutionary distinctiveness they need to have fewer close relatives and represent a whole branch of the tree rather than just a twig. The idea is that these unusual and often little known species are especially important since once they have disappeared there will be nothing similar left on the planet. They then combined these evolutionary distinctiveness or ED scores with score for how globally endangered each species is, based on the IUCN Red List of threatened species, which is the most comprehensive assessment of how endangered species are - giving an over all Edge Score for every mammal. They found 564 Edge species, which are those with higher than average ED scores as well as being threatened with extinction. Of these, they short listed a top ten of the most endangered Edge species which will be the first to benefit from the initiative. These include Attenborough's long-beaked echidna, which was named after Sir David Attenborough and is also known as the spiny anteater. It looks a bit like a large pale coloured hedgehog with a long nose and it lives in the rainforests of Papua New Guinea and is only known from one dead specimen found in 1961. Now a team of scientists will be in search of these elusive creatures and trying to work out how best to help protect their habitat which is being destroyed by mining and farming. If you want to find out more about these unique animals visit the ZSLs website at They also work to support young scientists in the countries where these mammals occur, to equip them with the necessary skills to continue monitoring and protecting their country's unique Edge species into the future.

Golden Eggs

Scientists have found a way to make chickens lay the pharmaceutical equivalent of a golden egg. Helen Sang and her team, from Scotland's Roslin Institute, used a virus to genetically alter chickens so that they could produce eggs containing drugs. In two different examples the team linked the genes for human interferon beta, or a melanoma-attacking antibody called miR24, to the chicken gene sequences that control the production of ovalbumin, the protein that makes up egg white. The idea was to use the genetic signals that control the production of egg white to make sure that the drug only ended up in the egg. The team then inserted these genetic 'constructs' into an equine infectious anaemia virus (EIAV) from which all of the harmful viral genes had been removed. The modified virus was then injected into a fertilised egg, where it added the new genes to the chick developing inside. The resulting chicken then laid eggs containing the new drug, and also passed the ability to do so onto its offspring. A study of the bird's tissues also confirmed that, as the team had hoped, only the oviduct, which produces eggs, was making the drug.

- Science Update - Backpacks and Chairs

Chelsea and Bob look at a new bungee backpack and how you should sit in a chair

Science Update - Backpacks and Chairs
with NULL

Chelsea - Whether you're a hiker, a paramedic, or a third grader, a heavy backpack can be a real pain. Now, University of Pennsylvania muscle physiologist Larry Rome has designed an ergonomic pack that can lighten the load and potentially prevent injuries. It's rigged with a springy, stretchy bungee cord, which allows the load to glide up and down on a frame as you walk. That eliminates the exertion of lifting the pack a few inches every time you take a step.

Larry Rome (University of Pennsylvania): The bungee cord stretches so the load stays at the same height with respect to the ground. If the load doesn't move with respect to the ground, then it doesn't have to be accelerated, and there's no accelerative force.

Chelsea - That may sound trivial, but Rome says these peak forces can double or even triple a pack's load while you're walking or running. In contrast, the bungee pack's effective load stays very close to its actual weight.

Bob - Thanks Chelsea. If you sit for a living, the common wisdom that you should sit up straight could be wrong. This according to Asim Bashir, a musculoskeletal radiologist at the university of Alberta in Canada. He and his colleagues used a new full body MRI scanner to study various sitting positions.

Asim - Sitting up bolt straight, 90 degrees with your back straight and your legs parallel to the floor increases the amount of pressure in your lower back discs, adds strain on your ligaments and muscles, and also causes squashing of the discs when you're in that position.

Bob - They found that it's much better to recline slightly with your knees well below your hips, creating a wide angle between your thighs and torso. That's hard to do in most office chairs, but Bashir says putting a wedge shaped cushion under your back and raising the seat height can help. Unfortunately they found that slouching, which is what most of us do, is still not smart.

- Climate Change and Ice Cores

Eric Wolff has been studying the ancient atmosphere trapped in an ice core, and how it affects our understanding of the environment.

Climate Change and Ice Cores
with Dr Eric Wolff from the British Antarctic Survey

Air bubbles in an ice core
Figure 1: Air bubbles fixed in ice. These can tell us how gas concentrations have changed over thousands of years.

Chris - A lot of people say that all the severe weather must be evidence for climate change. On the other hand you've got people saying that the earth has always had natural cycles and this is just one of them. Which camp are your feet planted in and what's the evidence?

Eric - Clearly an individual bad day or good day doesn't tell you anything, you do get extremes. So you need to look at what happens over a long period. But I think that the arguments about whether global warming is real hinge on four aspects. The first one is the physics that tells us to expect that when we get more carbon dioxide in the atmosphere it should get warmer. The second one is whether carbon dioxide has actually increased in the atmosphere, and that's what I'm best at because that's what we can see from ice cores. The third one is whether in the past that's caused climate change. And we can see in the ice cores that at least every time carbon dioxide's changed in the past, then it has warmed. So there's no counter evidence. And the fourth one is, is it warming today? Which is actually the hardest one to do because we don't have much detailed evidence about what the climate was in the past. And in a way it's the least relevant one because if we think the physics tells us that it's going to warm, and if we find out that in the past it's always warmed, then the fact that we can't quite see it yet doesn't matter. People often want to know if it's warmer now and it is but that's the hardest one to be sure about.

Chris - How are you using ice to work out what's been going on in the past?

Eric - The Antarctic ice sheet is up to about 3 miles or 4.5 kilometres thick at the thickest part. And if you drill into it you're effectively drilling into snowfalls that go back over hundreds of thousands of years. The oldest core that we've worked on is 800,000 years old. So we drill out a cylinder of ice 10cm in diameter but 3km long,

Chris - Do you do it in an environmentally friendly way?

Eric - We do it in as environmentally friendly a way as possible. But I'm afraid there's no getting away from the fact that going to the Antarctic is not actually an environmentally friendly thing to do by itself but hopefully you'll think the benefit was worth it. So we drill this cylinder of ice and in the ice is lots of evidence about what the climate was like in the past; how much snowfall there was in the past, what the temperature was and perhaps most crucially, we have little bubbles in the ice. The snow compacts to form solid ice with air bubbles trapped in it. You can then crack open these bubbles, put them into a chemical analyser, and find out literally what the proportion of carbon dioxide to nitrogen and oxygen and all the other parts of the air.

Chris - So it's like a time capsule going back over hundreds of thousands of years. How far back can you wind that clock?

Eric - Well so far we've gone back 800,000 years. I think there is older ice around in the Antarctic, and we'd like to look at it but that's as old as we've found so far.

Drilling an Ice Core
Figure 2: Drilling ice cores in Antarctica.

Chris - What do those 800,000 years tell you?

Eric - Well in that time we know that the earth has gone through roughly 8 ice ages. When I say that I mean that there was ice covering northern Europe and northern America. In Britain that's as far south as Norfolk at times, or even a little bit further. It was also colder over the entire globe including Antarctica. And what we've found is that every time it was colder, there was less carbon dioxide in the atmosphere. Every time it was a little bit warmer like it has been for the last 10,000 years, there's a bit more carbon dioxide in the atmosphere, but never anything like the amount that there has been over the last few decades.

Chris - How much has it changed recently?

Eric - Well let me give you some numbers. In the last 800,000 years, carbon dioxide's always ranged between 180 ppm (parts per million) in the cold periods up to 300 ppm in the very warmest times. And at the moment, it's 380 ppm. So that's already 30% higher than it's ever been. And the only possible explanation for that is human activity. There's other evidence too. We can look at the isotopic structure of the carbon and it looks like stuff that's come from fossil fuels rather than from natural systems. Also we know how much stuff we're putting into the atmosphere and all the calculations work. We're contributing to the increase.

Chris - Whilst you can demonstrate that there's lots of carbon dioxide in the atmosphere that doesn't actually mean that that's causing the warming does it? Because there's lots of other things that can be a greater greenhouse-provoking agent than carbon dioxide. Water for example, and methane are much stronger green house gases.

Eric - Yes the biggest greenhouse gas is water vapour. But we don't have any control over that, the water vapour just acts as a feedback in this system. It's the carbon dioxide that we can actually do something about. Methane, although more effective is at lower concentration. But that's also double, now, from the concentration it's ever been in the last 650,000 years. There's no comfort to be had from talking about other gases. The carbon dioxide is actually increasing very fast, about 50 times faster than any time we can see in the historical record. But you're right to ask how do we know that that's what's causing the change. We can see in the past that every time we came out of an ice age the CO2 increased. If the CO2 increased in the past and the climate didn't change then we would have a cause to question if we know what we're talking about. But the fact that it did, although not proof for, is not negative proof, which is what we want. What people have done for the last 100 years is run climate models that understand the physics of the system. And if they put in things like volcanic eruptions which cause a cooling, or changes in solar activity, then they can reproduce more or less what happened in the first half of the 20th century. But only by adding in carbon dioxide can they reproduce what's happened in the second half of the 20th century.

Chris - So that's the nail in the coffin for carbon dioxide. You mentioned earlier you found a number of ice ages and warm cycles. Given that humans have only been knocking around for 6 million years, how do you account for that?

Eric - There are certainly natural cycles in the climate and nobody's claiming that all climate change is man made. And in a certain way it almost doesn't matter whether the change is man made or natural. If we were coming out of an ice age you might be living in a village in what's now the English Channel. The fact is that all climate change is pretty bad for people. What people have done in the past is to move to places that suit their lifestyle better. Unfortunately now we have a very crowded planet and there's really nowhere for people to move to. So we're going to have to deal with this in a different way.

Big Bend Power Station

- Carbon Capture and Storage

One way of reducing the build up of Carbon Doxide is to just hide it underground. We look at carbon capture.

Carbon Capture and Storage
with Professor Jon Gibbins, Imperial College

Chris - We've heard from Eric Wolff that carbon dioxide's the culprit, well what are we going to do with it? Jon Gibbins is here with us from Imperial College in London. So you reckon the answer is that we don't dump the carbon dioxide in the atmosphere in the first place, we've got to put it somewhere.

Jon - The big problem is the fossil carbon that was locked up hundreds of millions of years ago that's getting into the atmosphere at a much higher rate than we can take. What we're trying to achieve to mitigate the risk of climate change is quite interesting. We talk a lot about the rate of emissions, but not so much about cumulative emissions. We're looking at being able to put about 500 billion tonnes of carbon into the atmosphere and still have a reasonable risk of avoiding dangerous climate change. But there's probably ten times as much carbon as that in fossil fuels.

Chris - So in other words there's a time bomb sitting beneath the surface of the earth just waiting to go off if we unleash it. How do we get around the problem, because we need energy don't we?

Jon - we do, but the amount of energy we need is quite variable. I think you can get quite fixated on saying we'll give people as much energy as they want. If we just think about CO2, we could say if we didn't have the fossil fuels there, we wouldn't have a problem. We wouldn't have quite so much energy but we'd adjust. But the big thing to say is that if you're going to use fossil fuels, you have to use them in an environmentally responsible way. And ultimately that means capturing the CO2. One of the things we do worry about, and I worry about quite a lot, is that if you leave them there and don't use them. For example if you use wind energy which we've just heard about, effectively you're saying you've left some fossil fuel in the ground by using that wind power. But for that to do any good, we have to not use it for the next 3000 years.

Chris - So what you're advocating is that if we have a coal power station opening in China, and every single week they're opening a new one. What you're saying is that in China and everywhere, we need to have some way of making sure that the CO2 is not going into the atmosphere. How do we do that?

Jon - There's essentially three ways. One way is to capture the CO2 that's coming out of the chimney, scrub it out with a solvent that absorbs it, then release it as a concentrated gas, compress it till it's liquid and then put it underground. Another way is to burn the coal with oxygen so you just get a reaction that makes carbon dioxide directly and you clean it up a bit, and put that underground. A third way is to gassify coal, turn it into a fuel gas in which the carbon exists as carbon monoxide, and then instead of reacting the CO with oxygen to make CO2, react it with water vapour to make hydrogen. Then separate out the carbon dioxide and put that underground.

Chris - How much energy does it take to clean up the CO2 coming off a coal fired power station? And therefore how much more coal will you have to burn to make up the amount of energy you're sinking into these clean up mechanisms?

Jon - We have probably 10 times as much coal as we can safely put in the atmosphere. You have to recalibrate your thinking.

Chris - But are we flogging a dead horse? Should we say just don't burn these fuels and sink the money into not producing it in the first place?

Jon - If you think you can get the Chinese to follow along with that, go and tell them. I think you've got a lot more chance of asking people to modify the way they're operating, by a relatively small amount, burning perhaps 20 percent more coal. It's basically carrying on with life as usual but not putting CO2 in the atmosphere. As an example: if we were talking about dealing with the carbon dioxide from oil, costing say $50 a tonne to deal with it, that would add the equivalent of $20 to a barrel of oil. You wouldn't notice it.

Chris - What's the state of the technology that's dealing with this? Are we in a position to make this a reality?

Jon - We are certainly in a position to make it a reality. We're not in a position to roll it out on all new power plants overnight. We're talking about developing some big technology. Power plants have to be reliable, they need to run for a long time. We need to learn how to do it, and actually what's very important, is how to get the first plants built. The EU just announced it wants to have up to 12 plants with Carbon capture and storage running in Europe by 2015. But what they don't say is when the first one of those is going to be built. We're just debating in the UK at the moment how to fund one or two plants with carbon capture and storage that will be flagship projects for the world.

Wind Turbine

- Renewable Energy

Ali looks into wind energy, both onshore and offshore along with the new technology of wave power.

Renewable Energy
with Alison Hill, British Wind Energy Association, and Max Carcas, Ocean Power Delivery

Alicia Webb spoke with the British Wind Energy Association's Alison Hill and Max Carcas from Ocean Power Delivery about alternative energy sources...

Ali - Wind energy was in the news late last year when the government approved a massive new offshore wind farm to be built just where the Thames empties into the sea. It's called the London Array and it's going to have about three hundred turbines generating 1000 megawatts of clean electricity. That one wind farm will generate half as much energy as is currently operational in the whole of the UK, and enough to power about a quarter of the homes in greater London. I asked the British Wind Energy Association's Alison Hill all about it.

Alison - The London Array offshore wind farm has certainly attracted a lot of attention. This is going to be the biggest offshore wind farm in the world by about a factor of 5. The UK is very firmly at the forefront of adopting the whole climate change issue and taking measures to secure future energy supplies and wind farms are a good way of doing this.

Ali - Are there any environmental costs to putting a huge wind farm in the Thames Estuary?

Alison - No technology comes without impacts. The London Array obviously has had several years worth of very detailed environmental assessment carried out. There will be consequences it is inevitable but this project has been designed as closely as possible to minimise those impacts. We just had reports published from the Danish offshore experience, which looks at 8 years worth of environmental impacts from two of their offshore wind farms which are currently the biggest in the world. And these demonstrate very clearly that wind farms do operate in harmony with the local environment.

Ali - Small wind turbines on peoples roofs are a bit less visually impacting. Do they work the same way as the large wind farms and do you think they're feasible?

Alison - The principle of generating electricity from the wind is the same, whether you do it onshore, offshore, on a roof or on a pole down the back of your garden. What you will find with these smaller domestic scale turbines is that they're not necessarily as efficient as their commercial colleagues the wind farm turbines. But studies have shown that you can see a reduction in your energy bills of up to a quarter in some cases, and possibly even more importantly; we've found that when people have small wind turbines installed, they actually become more energy aware. By seeing their meter ticking over when they generate electricity, and also ticking back when they use electricity, they become more conscious of how much they use. So they will switch lights off when they leave the room, they won't leave the TV on standby, and that actually is going to make a huge difference to reducing carbon dioxide emissions.

Ali - So putting small wind turbines up doesn't just contribute to your household electricity but also changes your attitude.

Alison - That's possibly one of the most important points to consider about micro generation technologies. They're something that we come into contact with in our daily lives and do actually change our daily routines for the better.

Ali - My last question for you today is would you, Alison Hill, live next to a wind farm?

Alison - I would love to live next to a wind farm, I really would. My parents in Scotland are just in the process of buying a new house and my mother was quite upset when they had to sell the old one because she had a beautiful view of a wind farm from her kitchen window. She said she found it most soothing while she was doing the dishes. We have lots of people in the UK that deliberately buy houses that look out over wind farms, we have farmers that use the turbines as weather markers for their projects. So yes, wind energy, I think, is a beautiful thing. I would be delighted to live next to a wind farm and there are many thousands, if not millions of people out there in the UK who agree with me.

Ali - Ok, so we've heard briefly about wind power, which is a pretty established technology that these days we're all pretty familiar with. But what's next in renewable technology? A Company in Scotland has come up with a very cool new machine, which generates electricity by floating on top of the waves, and which looks like an enormous red worm. They built the world's first commercial wave farm, which was opened at the end of October, just last year. It's off the coast of Portugal and it consists of three of these machines, each with a capacity to generate 750 kW, in total enough for a couple of thousand homes. I asked Max Carcas from Ocean Power Delivery how they work.

Max - First of all, to describe what it looks like. If you image four train carriages out at sea, that's a bit what the machine looks like in terms of it's shape and size. The machine is moored at it's nose. And what happens is it points into the direction of oncoming waves. It's free to swing and point into those waves. And waves travel down the length of the machine and in doing so each of these 'train carriages' articulates both up and down, and side to side. That movement is resisted by hydraulic rams a bit like big bicycle pumps, which pump high pressure hydraulic fluid through hydraulic motors which turn generators.

Ali - What environmental impacts could the machines have?

Max - We certainly think that our footprint is very small. We have no fluids or greases in direct contact with seawater we've got no rapidly moving pieces of equipment in the water. It's fair to say we're biased of course but we think our environmental impact is actually one of the least of any of the main power generating technologies.

Ali - What about the comparative costs?

Max - The costs at this stage are higher, but that's because the technology is relatively immature. Like with all these technologies you've got to produce something and get it out there in volume in order to drive the cost down. And what gives us tremendous hope is that our opening costs are substantially below where wind started 20 or 25 years ago and substantially below the current costs of solar photovoltaics. So all the projections are that if we can really deliver into this market then wave energy has the potential to become one of the cheapest methods of generation.

Ali - Why do you think the development of wave power is lagging so far behind the development of wind power?

Max - I think it's a mix of things. The challenges are three fold. They're technical, to make something that works reliably and can cope with the conditions, they're commercial, to find the right partners to work with, but also importantly they're political. What we're trying to do here is what any business school would tell you not to do which is come up with a new product in what is after all a commodity market. Electricity's just a commodity and what comes out of the socket, you can't really differentiate. People don't brag about wave power electricity to their friends and enthuse about the electrons being made by artisan wave power engineers off the coast of Orkney. What's really required and has always been the case in energy technology is the feeder markets that can allow these things to go forward. If we can do that we can also build a major industry. If you look at wind turbines, it employs many 10s of thousands of people worldwide but sadly not so many in the UK, because we really missed the boat on that. So let's not miss it in wave energy.

- What is the difference between good and bad fats?

What's the difference between good fats and bad fats, and are good fats actually good for you or just not as bad?

What is the difference between good and bad fats?

If you look at the way people eat and the length of time they live in the Mediterranean, this gives rise to a thing called the Mediterranean paradox, or the French paradox. People there seem to live a lot longer than they ought to because they eat very fatty food. But the fats that they do eat are of a certain type, things like olive oil. Olive oil is very rich in a type of fat called mono-unsaturated. When we talk about fats we talk about long chains of carbon atoms linked together. You can either have one bond between one carbon atom and the next, or sometimes you can have a double bond. And if you have lots of single bonds between them, then that's saturated fat, and it's bad for you. And the reason it's bad for you is that all the carbon chains can get very close together and stack up very neatly. This forms a very solid block of fat. It's not very chemically exciting and it clogs your arteries up. If you have things like olive oil, they have a double bond, which gives the chain a kink. So when you try to press oil molecules together they don't stack up very neatly. They don't form a solid block of lard, they're much more chemically exciting and this is why they're better for you.

- How did CFCs get to the poles?

Jet streams flow laterally due to centripetal forces. If CFC gases caused the hole in the ozone layer over the poles, how did those CFCs ...

How did CFCs get to the poles?

CFCs are actually everywhere in the atmosphere and not just over the poles. But over the poles where the CFCs are coldest, you get ice particles, which allow the ozone depleting reactions to occur. So it's not that the CFC concentrations are different, it's just what happens to them. Because Antarctica is completely isolated and surrounded by ocean, you get a whirlpool effect in the atmosphere there which has a concentrating effect. The depleted ozone therefore stays put rather than mixing in with the rest of the atmosphere.

- Why do insects legs fold when they die?

How is it that when an insect such as a ladybird dies, it folds it's 6 legs up under itself. Why does it do that and what's the underlyin...

Why do insects legs fold when they die?

I imagine it's something to do with the weight of the wing cases of the ladybird, that weigh it down and cause it to collapse, and also something to do with the muscle structure. When they die they relax and the tendons and things must retract the legs. When insects die there is also an element of drying, and dried things tend to shrink a bit and contract and go into their most compact shape

- Could volcano ash relate to global warming?

I've heard that the eruption of Krakatoa causes massive cooling in the atmosphere and these effects are diminishing. Could this be a cont...

Could volcano ash relate to global warming?

The particles that go into the atmosphere from volcanoes do cause cooling but it only tends to last for a couple of years before the particles all drop out again back to the background level. You'd have to have really big volcanoes going off all the time into the upper atmosphere to really have an effect like that.

- How do volcano and industry pollution compare?

With so many active volcanoes around the world how does the pollution from industry over the last 150 years compare with the number of th...

How do volcano and industry pollution compare?

We do actually have our own volcanic effect because industry also puts sulfate aerosols a little bit like a volcano into the atmosphere and that is actually helping to keep us a little bit cooler than we would be otherwise. And so that's actually a concern. When we stop burning dirty coal, which produces sulfur dioxide we'll actually make things a bit worse for a while before they get better.

- Is the southern hemisphere cooling?

A lot of smart people think global warming is just part of a natural trend that humans have very little influence on. One person points o...

Is the southern hemisphere cooling?

'm afraid I can't even give you comfort there. Although parts of the Antarctic haven't shown a very strong warming yet, maybe because they're so isolated from the rest of the atmosphere, the Antarctic Peninsula for example, has been warming very fast. It's one of the places that has been warming the most rapidly. We now think that probably is related to global warming. We weren't really sure before because despite what you may think, we Scientists are cautious people. So the rest of the Antarctic hasn't yet shown a very strong cooling but the models suggest that it will. It is actually true that the ice sheets under warming probably will get thicker at first because what happens is around the edges where it's warmest, it will start to melt. But in the centre the temperature is nowhere near that, so it won't start to melt in the centre and you get a little bit more snowfall when it's warmer so that does make it a little bit thicker in the centre. Unfortunately all the predictions are that what happens at the edges wins.


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