Maria Gilardin: TUC Radio, San Francisco. Time of useful consciousness. Dangers of climate change: global warming in the Antarctic. [Sounds in the background] This is the sound of ice-berg calving, brash ice melting, and the trilling of leopard seals, recorded on the West Antarctic peninsula [End of sounds]. While the earth as a whole has warmed by an average of half a degree Celsius, since the industrial age, the Antarctic, Siberia, and Alaska have shown much stronger regional warming. Temperatures rose on average by 2.5 degrees Celsius, five times more than the rest of the world. The British Antarctic Survey has done research in the Antarctic for almost 60 years. They predicted in 1998 that warming in the Antarctic peninsula would put several ice-shelves at risk. That same year the Wilkins ice-shelf collapsed. Only three years earlier, in 1995, Larsen A had broken off. The warning of the British Antarctic Survey was dramatically realized in 2002, when 500 billion tons of ice from the Larsen B ice-shelf broke into thousands of ice-bergs. Soil sediments from that ice-shelf showed that Larsen B had been intact for 20,000 years, since the peak of the last ice-age. The accelerated melting in the Antarctic is of global importance. The enormous ice-sheets and glaciers hold 90% of the worlds fresh water. If all of it melted, the global mean sea level would rise by 52 meters. Also, the circumpolar ocean current around the Antarctic is driving all the great ocean currents of the world, influencing climate for all continents way up into the northern hemisphere. Chris Rapley, the director of the British Antarctic Survey, gave one of three opening speeches at the Symposium on Climate Change held at the Hadley Centre in Exeter, England, in February of 2005. He presented the most recent survey of glaciers on the antarctic peninsula and warned that the disintegration of ice-shelves might contribute to the accelerated melting of these glaciers. Of 224 glaciers, 87% are now in retreat because of the warming in the Antarctic. I reached professor Rapley in his office at the British Antarctic Survey in May of 2005 . Trained as an astronomer, he headed the international geosphere/biosphere program at the Royal Swedish Academy of Sciences in Stockholm before coming to the British Antarctic Survey. Here is Chris Rapley.
Chris Rapley: I started out life in astronomy years ago, so I always start my lectures with that beautiful Apollo 17 image of the earth, that full disk image with it tilted back so you can see the Antarctic. There's several points worth making. First of all, there it is, it's finite, there it sits in its inky blackness. The second thing is, it is all interconnected, the atmosphere, the ocean, the ice, the land, the biology, the human societies; all interconnected, and it is the most complicated and complex object in the universe that we know of. There are lots of other exotic objects in the universe, but none of them has all of that. None of them has the physics, the chemistry, the geology, the biology, and the anthropology if you like. Figuring out how it works is the Big One from the point of view of complexity science, it's not an easy subject and given the processes on it from the microscopic to the planetary scale and processes that run back over 4.5 billion years down to milliseconds; they are all relevant, one way or another. It's not surprising that it's quite a struggle to make progress with it. On the other hand, we have made enormous progress in understanding bits and pieces of how it works, and what we know already is a bit worrying, because not just carbon-dioxide emissions, it's the fact that humans have transformed more than half of the land surface, and that changes the way moisture is exchanged between soils and the atmosphere. We've doubled the amount of nitrogen that *** through agricultural use of fertilizers that we totally changed the nitrogen cycle worldwide. Of course we completely transformed the carbon cycle by the carbon emissions. We've paved over significant amounts of the planet. We've shifted alien species, shifted species from one part of the planet to another. We've changed the habit, we are destroying biodiversity. All of these things are intricately connected, so there's no way other than by being a sort of flat-earth ostrich that you can imagine that humans could do these things and there couldn't be consequences on a finite planet which provides us with our food, our fresh air, our fresh water, our energy, and our shelter. It's like being in a life-support machine and saying: "Hmm, I don't know what this lever does over here but I think I'll pull that, and I think I'll unplug this, and that box doesn't look very important, I think I'll jettison that", it's not very sensible. Sorry, got my on my high horse.
MG: Why is the Antarctic so important for global climate? Can you comment on that?
CR: Yes, it's often forgotten that we have this huge continent sitting in the normal map projection at the bottom end of the earth, that it is the fifth largest continent. It's the highest, coldest, windiest, and ironically driest continent, because all the water that's down there is frozen. It contains a huge amount of ice. It contains over 90% of the worlds fresh water frozen-up there. Of course it's a much smaller percentage of the total water because the oceans are salty. What's really important is that if you melted all of that ice it would raise global mean sea level by 52 meters, which would have a huge impact globally. From the point of view of today, this bog dome of ice, it's up to four kilometers thick, has an absolutely dominant effect on the atmospheric circulation of the southern hemisphere, and the cold water that is generated around the Antarctic chills about 40% of the worlds ocean, that's like a refrigerator for the worlds oceans. It has a big impact on the ocean currents that circulate all over the world, and we know that ocean currents are really important from the climatic point of view. If we just consider Europe for a start; Europe is about 5 to 10 degrees warmer than it should be at its latitude, because so much heat is drawn northwards by the Gulf-stream, and we believe that all of these currents are interconnected, so changes down in the Antarctic can affect even the way currents far in the north, like the Gulf-stream, works. It's a, what can we call it, a key cog in the machinery of the climate system.
MG: Let's go to more recent developments, and remember when the Larsen A broke off. Quite a few people got worried and others said: "well, that's normal, it keeps happening", but then in 1998 the Wilkins broke off and 2002 Larsen B. What do you make of these ice-shelf disintegrations?
CR: This is a really interesting story, and worth just saying a couple of things first. The first thing to understand is that snowfall accumulates ice on the continent, and it's like porridge I suppose: it slowly flows under its own weight towards the coast guided into streams of flow by the mountains that it's flowing over, sometimes very deep under the ice. It ultimately reaches the coast, and around the Antarctic about 80% of the coastline is fringed by thick floating ice. This isn't frozen ocean, this is not chilled air that is just frozen on the surface of the ocean, that's called sea-ice and it's a huge area of that around the Antarctic which froze and shrink each year, but this is stuff that is extruded, it's flowed off the continent, it's floating, it's maybe anywhere between a kilometer and hundred meters thick. It flows outwards at anything up to a kilometer or so per year, and ultimately big bits break off the end of it as icebergs, and they float away off into the ocean. It's perfectly normal for this cycle of snowfall, accumulating on the continent, flow, and then loss of icebergs off these ice-shelves. What's different in the Antarctic peninsula is that there's been a very very strong regional warming there. We now that from our measurements over 40 years that temperatures have gone up there at about five times the rate that temperatures have gone up elsewhere on the planet, on average. 2.5 degrees there, as opposed to about half a degree, the global average. Interesting that the two other areas that are real rapidly warming spots, hot-spots, are in Siberia and Alaska.
MG: Excuse me, I actually don't understand it. It's so well cooled, why should it be warming?
CR: It's a feedback system. In any complicated connected system there are links, you do one thing and it has consequences. In the polar regions there are some strong positive feedbacks. Let's just take some ice on some dark rocks. Ice and snow is white, so when it's sunny the sun light gets reflected away. Most of the heat that is coming in from the sun just hits the surface, because it's white it bounces off and away it goes. If you blowtorch an area of that snow to reveal black rock, then the rocks absorb the heat and will melt more ice which will absorb heat and it will melt more ice and so on. You get this positive feedback. Let's just deal with the peninsula, because there are a couple of really important points about that. We've just had this paper, Alison Cook paper, published. It got a lot of interest about the 224 glaciers that she has studied using 40 years worth of airborne and satellite data. Whereas forty years ago pretty much all of them were just slowly extending, almost certainly because of the warming (I don't think there's any doubt about it) 87% of them are now in retreat. You probably wouldn't expect too much else, but it is a dramatic demonstration, a confirmation if you like, that this warming is regional, and that it's important, it's significant. I mean it has knock-on effect on how far penguins colonize to breed and so on. It's having ecosystem impacts, but things fluctuate all the time, so perhaps that's not so important. What is interesting is that associated with this, there has been the collapse of the ice-shelves that you were talking about, the Larsen A, the Larsen B, the Wordie and so on. Quite a lot of ice-shelves have gone. What we see happening is where the summer melting can extend to is critical, as that line has moved south where you get significant summer melt-water ponding on top of the ice-shelves, that seems to be crucial in damaging the fabric and the strength of the ice-shelves which leaves them vulnerable then to dramatic collapse. What some of the people here at BAS found a few years ago is that in the ocean sediments underneath those ice-shelves there's evidence that 3-5,000 years ago the northern one had disintegrated and been absent for some time. What we learned from that is that the climate system is perfectly capable of fluctuating in that region without any human beings being around driving cars or emitting carbon-dioxide, and those ice-shelves collapsed but they reformed again. What we find now is that that progression further south has reached a point where the ice-shelves that have collapsed more recently, the Larsen B, the sediments from those, and this is worked by some US researchers, show that those ice-shelves have been intact at least over that period back to the peak of the last ice-age, 20,000 years ago. This warming has now reached ice-shelves that previous fluctuations haven't reached, and that begins to ring alarm bells, because it implies that that really is something to do with humans, rather than just another fluctuation. The fact that it's happened so quickly is also evidence that it's unusual. That actually isn't the thing that really worries me. There's a guy called Mercer in '78 who wrote a seminal paper on the potential for the West Antarctic ice-sheets collapse, I'll come back to that in a minute. In his paper he said: "If we begin to see progressive collapse of ice-shelves in the peninsula, what would be really interesting is to see whether the glaciers that are feeding them accelerate, because if they do the loss of those ice-shelves is important for the future of global mean sea level, because more ice will be pouring into the ocean and that means that it won't be an equilibrium situation where you got a balance between water accumulating on the continent of the Antarctic and then sliding into the sea and maintaining sea level, but you'll have more sliding off and so that will cause sea level to rise". That's exactly what we've seen over the last decades using satellite imagery and satellite lasers. A mixture of European and US satellite data. That's the peninsula story. Mercer was talking about the West Antarctic ice-sheet which has got a 5 meter sea level equivalent. The reason he was concerned about that was that it sits on rocks that is well below sea level. Anything up to a couple of kilometers below sea level. He pointed out that if that starts to melt and slide, there's huge water pressure at its base, so the ocean might penetrate underneath, lubricating its slippage and that might cause a rapid collapse. He wasn't very clear what he meant by rapid, but hundreds of years maybe thousands of years, he was a bit vague. The East Antarctic ice-sheet, by the way most of it sits on rocks above sea level, so it's not susceptible to that sliding mechanism. Anyway, what the satellite data show us is that an area of the West Antarctic ice-sheet, Pine Island, Thwaithes, and Smith Glacier area in the Amundsen sea in (Baymon?) is discharging large quantities of ice, about 250 cubic kilometers a year, which is equivalent to about 0.24mm of global mean sea level rise per year, which is sort of significant: about 15% of the sea level rise that we measure overall. It's the idea that the loss of the fringing ice-shelves that lead to this sort of acceleration of that that means that I think we have to worry a lot more about what's going on there. The new evidence of significant loss from this area of the West Antarctic ice-sheet coupled with the knowledge now that when you lose ice-shelves it does cause sea and high streams and glaciers to accelerate means that I think we've got to reevaluate the whole thing. We need to go and make measurements of it, close at hand and from space, to reassure ourselves one way or another whether it is a danger.
MG: I think quite a few people are familiar with the part of the ocean circulation that's called the Gulf-stream, but is it true that these enormous ocean streams are sort of linked to each other?
CR: There's a very famous US scientist called Wally Broecker. He came up with the phrase: the ocean conveyor belt, 10-15 years ago, maybe a bit longer. You can draw a very neat little diagram on a global map that shows how cold water that's generated down in the Antarctic sinks to the bottom of the ocean and it draws water down from the tropic which then links into all three major ocean basins: Pacific, Atlantic, and Indian. You can see how all of these currents link together. Actually, the truth of the matter is just a little bit more subtle than that, because the oceans are full of circular eddies, just like that atmospheres has weather systems in it. So more of the energy in the motion of the water in the ocean is in a sort of circular spinning motion, than in just being translated along like a conveyor belt. What we're really talking about is the net effects of all of these turbulent motions. There is no doubt that the net effect is to carry the heat, salt, and water around the world in a continuous stream, and the fact that the Antarctic is so important in generating these very cold streams of water, that is has an effect world-wide.
MG: How can global warming around the Antarctic affect this very delicately balanced system of circulation?
CR: I'm not sure I'll completely accept that it's very delicately balanced, it might be. I think we don't know, although there are ever-improving computer models of the ocean and the atmosphere, and indeed the coupled ocean and atmosphere. The extent to which, for example, the Gulf-stream might cut itself off and paradoxically through global warming plunge Europe into a slightly colder phase, the two things would would more or less compensate in some of the models. The extent to which the ocean is vulnerable to that isn't really well-sorted out yet. Nevertheless, it's absolutely clear that in the past the earth has had different climate patterns. We know that there's been a whole series over the last 30 million years of ice-age cycles, warm periods and cold periods. During the cold periods the ocean circulation and atmospheric circulation was very different to the pattern that we have today. What we're about is that there's evidence in previous cold periods that the whole pattern of ocean and atmospheric circulation could suddenly shift into a different pattern; it's called a regime-shift. There's evidence that this could happen under those circumstances very quickly in periods of less than 10 years, higher resolution than we can actually resolve in the ice-cores and sediments that we get this data from. What we don't know is whether the climate system in a warm period, which is what we're in now, is as vulnerable. The so called Holocene, it has last ten thousand years, has been unusually stable and indeed people argue that because it's being stable that it's allowed human society and agriculture and technology and all of those things to develop. It's been a sort of benign period. Whether or not we're pushing the limit so that we might lose that stability we don't know.MG: I did ask this Steve already, because as a lay-person one is really impressed by these amazing libraries of ice-cores. They do show this very sort of even up-and-down of heating and cooling over time, but don't the ice-cores show by the analysis of the embedded air that we have added two of the ingredients in larger numbers than ever before?
CR: Oh yes. These climate skeptics are very much on to this at present. They call it the hockey-stick diagram, and they claim that various ways in which the past temperature of the planet have been estimated from what they call proxy measures from carbon in tree rings or thickness in tree rings and a variety of other ways, and the way that those data have been connected to the recent 150 years of actual temperature record data is flawed. The temperature stuff... I don't believe that anyway. I think there's been some very careful analysis that show that the global mean temperature really has gone up by about 0.6 degrees over the last 100 years, and mainly over the last 40 years. The thing that the climate skeptics kind of duck-and-weave about and don't address is the fact that we have bubbles of gas in these ice-corse which we know to be anything up to 900,000 years old, that's the oldest ice that's been extracted so far. We've had ice-cores going back 450,000 years for some time now, and have very analyzed the carbon-dioxide and methane contents of the gas in those bubbles, and there's just no question that the carbon-dioxide contents of the atmosphere has increased by 37% since the industrial revolution. If it continues to rise at this rate, and the projections are not very reassuring, then we will at least double and possibly go even further than that. This will be not only the largest rise but also the fastest rise, certainly over the last million years and arguably over the last 30 million years or even 100 million years. That short of shock to the earth system is bound to have consequences. You can argue like mad about how severe they'll be and what will it do to me and my backyard, but you can't do that sort of thing to this incredibly complicated and interconnected system and not have it react, particularly when you've more than doubled the amount of methane in the atmosphere over the same period. You asked me early on, why is the Antarctic important in climate research. It is important firstly because it is, as I say, a key cog in the machinery, but it is an absolute treasure-trove of information about how the planet has behaved in the pasted, how the climate system has behaved in the past. When you combine that information with information from other ice-corse in Greenland and ocean sediments and lake sediments, all of which are sort of detective story, it's like a forensic investigation. When you put all that information together then you can build up a picture that shows that humans are really doing things to the planet that we ought to worry about.
MG: That was a conversation with professor Chris Rapley, director of the British Antarctic Survey. The British Antarctic Survey is based in Cambridge, England. It has for almost 60 years undertaken the majority of Britain's scientific research on and around the Antarctic. This is part two of a six-part program on climate change, based on a conference held in February of 2005 at the Hadley Centre in Exeter, England. The aim of the conference was to encourage an international scientific debate on the long-term implications of climate change. 200 of the world's leading climate scientists issued the most urgent warning to date, that dangerous climate change is taking place and that time is running out. The sounds of ice-bergs calving and breaking, and leopard-seals trilling were recorded by Douglas Quinn on the West Antarctic Peninsula. In the next program you will hear from Jason Lowe on the role of sea-level rise and the Greenland ice-sheet. You can find out more about this series on the dangers of climate change on TUC Radio's web site www.tucradio.org, look under newest programs. You can get information how to order a copy of the complete one hour program with Stephen Schneider and the director of the British Antarctic Survey by calling us. TUC Radio is free to all radio stations, your tape or CD order is the only support we receive and helps us stay on the air. Call us toll-free anytime at 877-TUCTAPE for information on how to order. You can get your tape or CD by mail, or credit card, by phone, or on the web. Our toll-free phone-number 877-TUCTAPE translates into 18778828273 . "Time of useful consciousness" is an aeronautical term, the time between the beginning of oxygen deficiency and the loss of consciousness, time for the pilot to save the plane. My name is Maria Gilardin. Thank you for listening, give us a call.
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