Quotes: 2005, 77 cubic miles of ice from Greenland and Antarctica melted into the sea- The Retreat is getting faster. If the present meltdown continues unchecked, our planet will turn into something unrecognizable.
From: Cosmic- Space Documentaries channel- Are We Heading For Planetary Meltdown?
Transcript here for readers writers and researchers
The overwhelming power of nature. Floods, storms, rising sea levels. 0:12 Climate change is already altering the face of our planet. Freak weather is no longer out of the 0:18 ordinary. It's becoming the norm. [Music] 0:24 Our planet's ice is melting, and that changes everything. 0:30 Seas will rise, cities could be submerged, and millions may die. 0:37 There won't be any area near the coast that won't be hit hard. 0:43 It's inevitable that we're going to lose everything at the coast. 0:48 Now, we separate fact from fiction to discover the real science behind climate 0:54 change and the melting ice caps. [Music] 1:13 Global warming. It's a term we hear all the time. But behind the familiar words 1:19 is a frightening reality. Our planet is warming up and the effect on Earth's ice 1:24 caps is catastrophic. As temperatures go up, the ice is melting. Sea levels are 1:30 beginning to rise. Around the world, ocean levels are increasing twice as fast as they were 150 years ago. In 1:39 2005, 77 cubic miles of ice from Greenland and Antarctica melted into the 1:45 sea. For comparison, the city of Los Angeles uses about 1 cubic mile of fresh 1:51 water per year. This is global meltdown. In 2001, scientists predicted that sea 1:59 levels would rise by 3 ft by the end of the century. That's a big rise, enough 2:04 to affect more than 100 million people worldwide. But now, researchers like Bill Maguire, 2:11 professor of geohhazards, worry that the predictions might be wrong. The official 2:17 scenarios for sea level rise, if you like to call them that, were published in 2001 and they were based on research 2:23 that was undertaken in in the years running up to that. So they are completely out of date now. 2:29 Even conservative estimates predicted that over the next 60 years, rising seas 2:34 would destroy a quarter of all the houses within 500 ft of America's coast. 2:40 Recent research paints a more disturbing picture. Sea levels could rise as much as 20 ft 2:47 by the end of the century. It's a bleak, even terrifying vision. But this is what 2:52 scientists believe meown could do to us all. To understand what will happen when the 2:59 ice melts, scientists need to study the processes driving the meltdown. Advanced 3:04 modern technologies can reveal our planet's ancient history. By studying how things have changed in the past, 3:11 they hope to predict our future. Sea level rise is nothing new. We know that 3:16 in the ancient past, sea levels have been both higher and lower than they are today. It's a natural cycle driven by 3:23 the melting and freezing of the polar ice caps throughout Earth's 4 and 1/2 billion year history. When the ice caps 3:30 melt, they release water into the ocean. When they freeze, they take it out again. 3:37 Earth's climate alternates. There are ice ages when the temperature drops and the ice caps freeze and expand. And 3:44 there are interglacial periods when the ice caps melt and release water back into the oceans. The cause of the cycle 3:51 is the Earth's rotation around the Sun. Earth's orbit around the Sun varies in a 3:57 number of complex ways. The most important is that it changes shape. It's 4:02 not always a circle. Through a cycle lasting about 100,000 years, the orbit 4:08 goes from being almost round to being stretched into an oval shape, then back again. 4:16 In the more elliptical orbit, we travel millions of miles further away from the sun. Less sunlight reaches the Earth and 4:23 an ice age is born. Right now, our orbit is circular, not 4:29 elliptical, and we are in a warmer interglacial period. But something is wrong. The ice is 4:36 melting too fast. One of the places where that melting is running out of control 4:43 is Greenland. Greenland covering an area of 836,000 4:51 square miles with ice of an average thickness of nearly 1 and a half miles. 4:58 Greenland contains 600,000 cubic miles of ice. and it's melting. 5:06 Professor Conrad Stefen's job at the University of Colorado is to figure out what's wrong with the glaciers before 5:13 it's too late. We came first here on the Greenland ice sheet in 1990 where we set up a 5:20 permanent camp on the ice and the main objective was to measure the climate. 5:28 Each year, Stefan trekks across Greenland, checking his remote weather stations. 5:34 These beam data via satellite to his computers at Colorado. The news isn't 5:40 good, and it's getting worse. Since 1990, the average winter 5:46 temperatures in Greenland have risen by 46.4° F. The Greenland ice sheet loses 275 5:54 billion gallons of water every 40 hours as icebergs crash into the Atlantic. 10 6:01 years ago, the melting rate was just a third of this. 6:08 At Yakob's Haven in western Greenland, scientists have tracked the movement of this glacier's edge since records began 6:15 in 1850. Over the past 150 years, the edge has 6:20 retreated 37 mi. That's bad. But what's worse is that the retreat is getting 6:27 faster. The glacier is now disappearing twice as fast as it was 5 years ago. 6:36 Every day, this glacia pushes icebergs into the ocean that is sufficient to 6:43 give fresh water used for the town of New York for one year. 6:48 Almost all the glaciers in Greenland that are south of the Arctic Circle have speeded up their discharges into the 6:54 ocean. Glacier melting is nothing unusual. Their edges melt all the time, but 7:01 normally the ice they lose at the edges is balanced by the amount of snow that falls on top. The snow compacts into new 7:09 ice. So the glacier grows in the higher regions and melts at the edge. 7:14 Scientists call this mass balance. Glaciers gain as much ice as they lose. 7:21 This natural balance keeps the ice cap stable and sea level rise in check. 7:26 For the past 10,000 years, that's how it's been. Our ice caps have been stable. But now, the balance is off. The 7:35 edges of Greenland's glaciers are melting faster than the rest can grow. 7:41 Greenland's losing 20% more mass than it gains from new snowfall each year. 7:51 If this continues as the balance shows, we are losing more mass. And this is 7:57 what we actually discovered. This is happening right now. We are losing currently about 50 cubic 8:03 miles. Can this be sustained? No. If it continues like this, Greenland ice sheet 8:10 will lose mass every year by a certain amount and the sea level will rise. 8:17 To get a detailed study of what was going on, NASA installed a global positioning system to monitor the 8:24 elevation of the glaciers and track their loss of volume. What they discovered blew them away. Glaciers were 8:32 melting faster than ever before. They were literally sliding into the 8:38 sea. 8:45 Over the last few years when we had the extreme warm temperature, the ice sheet actually accelerated not only 10 20% but 8:53 50 80%. In the summer of 1985, the glacier was 8:59 moving toward the sea at just over 4 m per year. By the summer of 2003, it was nearly 8 m 9:07 per year. It was clear that the process was 9:13 accelerating. The glaciers were moving faster toward the sea. 9:19 The reason was simple physics and the effect of meltwater. 9:25 If you place a block of ice on a dry surface, the ice will move very slowly or not at all. 9:33 [Music] But once the ice starts to melt, water 9:38 gets between the ice and the surface, lubricating it. The ice is able to move 9:44 much faster. [Music] This is exactly what was happening in 9:50 Greenland. Warmer average temperatures were causing the top and edges of the glaciers to 9:56 melt. Large pools of melt water formed on the surface. But glaciers have huge 10:02 cracks and channels within them. The melt water drained down through these cracks to collect beneath the glacier. 10:10 Here it lubricated the junction between the glacier and the earth, reducing the 10:15 friction holding it in place and causing it to slide ever faster toward the sea. 10:21 This is very bad news. If Greenland melts completely, it will 10:27 release enough water to raise all the world's oceans by 23 ft. Until recently, 10:34 scientists thought that was as bad as it could get. They were wrong. Greenland 10:39 holds a lot of ice. But this isn't the only ice on the planet. 10:45 Here, there are half a million cubic miles of ice. But Antarctica, the huge 10:51 continent capping the Earth's south pole, holds 11 times more. 10:57 Scientists used to think that was no problem. The vast Antarctic ice sheets had a mass balance that worked. 11:06 Antarctica is huge, mountainous, and cold. It should guarantee enough 11:11 snowfall at the glaciers heads to balance out the melting at their bases. 11:17 That's the theory. And that's how it's been for the last 10,000 years. Then in 11:22 2002 came evidence that the balance had changed. In just 3 weeks, a 1250 square 11:30 mile chunk broke away and vanished. There is now little doubt. The Antarctic 11:38 meltdown has begun. 11:44 The present Antarctic ice sheet accounts for 90% of Earth's total ice volume and 11:50 70% of its fresh water. It holds enough water to raise global sea level between 11:57 150 and 200 ft if completely melted. Until recently, we thought it was 12:03 stable. But new satellite imaging technology is revolutionizing our understanding of our planet's vast ice 12:10 caps and is teaching us that our world is not as stable as it seems. 12:17 From hundreds of miles above the ice wastess of Antarctica, satellite data shows us something we thought was 12:23 impossible. We believed the Antarctic ice was completely secure. 12:29 But new research shows that it's breaking apart. Professor Eric Reno from NASA's Jet 12:35 Propulsion Laboratory uses satellites to monitor the movement of glaciers of Antarctica with inch perfect accuracy. 12:43 The senior people in my community when they were going to the field in Antarctica in the 50s or 60s didn't even 12:49 know where the glaciers were. In 2002, the new satellite surveys 12:55 dramatically proved their worth. This is, or rather was, Larsson B, an 13:04 ice sheet covering, 1250 square miles. It sat here for the last 10,000 years. 13:12 Then over a period of 3 weeks in early 2002, satellites watched as it 13:18 completely vanished. Melt water was again the culprit. But instead of lubricating the glacier, 13:24 speeding its passage toward the sea like in Greenland, this time it literally 13:30 split the ice shelf apart. Again, it was simple physics. When water 13:37 freezes, its volume expands by 9%. Place a sealed glass bottle inside a 13:43 freezer. It will shatter because of the pressure of the expanding frozen water 13:48 inside. In Antarctica, it was this expansion that was doing the damage. 13:56 Air temperatures in Antarctica are increasing three times faster than anywhere else in the world. 14:03 This increase in temperature melts the surface and edge of the glaciers. Melt 14:08 water builds up and then seeps down into cracks and crevices inside the glacier 14:14 or ice sheet. But unlike the Greenland glaciers, these cracks don't go all the 14:19 way down to the rock below. Because it can't drain away, the melt water builds 14:25 up within the cracks, freezes, and then expands. The crevices are forced apart, and the 14:32 glacier breaks up and slips into the sea. And as a result, we saw a large 14:38 fraction of LS and B literally explode in 3 weeks from a series of very warm 14:44 summers. It's quite an amazing event because this ice shaft had been around for 10,000 years. 14:50 Larsson B's disappearance triggered an even bigger problem. Now, the landbased 14:56 glaciers damned up behind it had nothing to prevent them from flowing down into the sea and melting. 15:05 These glaciers over here are sped up by a factor eight. They flow eight times faster now than prior to uh the collapse 15:11 of Larsson B. The ice sheets are also being attacked from below. Over the last 15:17 50 years, the temperature of the sea around Antarctica has risen by over a degree. This warmer water circulates 15:25 under the ice at the edge of the glacier and into cavities deep beneath the surface. 15:32 Water conducts heat 25 times more efficiently than air. 15:37 The warmer water melts the base of the ice sheet at a rate of 162 ft a year. 15:44 As their foundations melt, the glaciers ice breaks off and floats out into the 15:49 ocean. The combination of these two processes, the cracking and the deep ice 15:55 melting is breaking up the sea ice. The huge western Antarctic ice pack is 16:01 becoming more and more unstable. RNO has calculated that the Antarctic 16:07 currently dumps 26 cubic miles of ice into the ocean each year. Antarctica 16:12 holds uh enough ice to raise sea level by about 150 ft. We don't know how long 16:18 ago it started to get warmer, but it's too warm for the ice shelves to survive and the glaciers are accelerating. 16:25 As recently as 2001, scientists predicted the Antarctic ice sheets would 16:31 remain stable throughout this century. Thanks to these astonishing images, we 16:37 now know the truth. Antarctica is a disaster in the making. 16:43 As an observer, I say, well, you should not panic and run to the hills. But what we're seeing happening in the ice sheets 16:50 today is is a serious concern. If the present meltdown continues unchecked, 16:56 our planet will turn into something unrecognizable. Already, the average temperature is 17:02 hotter than it has been for a thousand years. It's getting warmer at a faster rate than ever. Many scientists believe 17:10 that it's due to man-made climate change, but some point to the Earth's natural rhythms. The only way to 17:18 discover what's going on is to study Earth's past climate. 17:23 During the 80s and 90s, an international team of scientists went to the poles 17:29 where the history of Earth's climate is preserved in the ice. 17:36 Richard Alli was part of that team. Today, he's one of the world's leading glaciologists. 17:42 To Ally, ice cores are like time machines. They let him reconstruct climate changes from Earth's distant 17:49 past. If you go to Greenland or Antarctica or a mountain glacier and you you drill 17:54 into it and you pull up a stick of ice and you look at the ice, the first thing you'll see is that it will have layers 18:00 and you can go summer, winter, summer, winter, summer, winter, tell how much it snowed, um tell how old it is. 18:08 Ice is a treasure trove of information. The layers not only tell us the ice's 18:14 age, they also preserve dust from volcanoes and sand from drought periods. 18:21 They can even tell us what the weather was like. And so there's anything in the 18:26 atmosphere is there and you can measure it, including the atmosphere. How much CO2, how much methane, what were the 18:32 greenhouse gases doing. The concentration of different isotopes of oxygen in the ice cores can tell us how 18:40 temperature fluctuated in the past. Plot ancient temperatures against ancient levels of carbon dioxide from the ice 18:47 cores and the cause of our present crisis becomes crystal clear. 18:53 The charts show two things. First, CO2 levels are directly related to temperature. 19:00 Second, today they are rising fast. Carbon dioxide is one of the main 19:06 greenhouse gases. These gases trap heat radiating out from the Earth's surface. 19:11 The heat stays in the atmosphere instead of traveling out into space. The result 19:17 is global warming. So, carbon dioxide is rising in the 19:24 atmosphere. Now, what will that do? We're pretty sure it means it's going to get warmer. Okay. And here's one piece 19:30 of evidence for that. We are looking in blue at temperature in Antarctica and then in red at carbon dioxide in the 19:37 atmosphere from 440,000 years ago up to today. In blue, we see 19:44 the great ice age cycle of temperature. It was warm and cold and warm and cold and warm and cold and warm and cold and 19:49 warm, which is linked to features of Earth's orbit. things that tip the pole. So, it gets more sunshine, wiggles in 19:56 the orbit, changes in the shape of the orbit, and the beautiful pacing that one sees as the features of the orbit. Now, 20:03 what's weird about that is that Antarctica's summers were getting a lot 20:08 of sunshine when it was cold. And that's been really hard to explain. Why do you get more sun and less warmth? And the 20:16 answer is in the carbon dioxide. When it was cold in Antarctica, carbon dioxide was low. When it was warm in 20:22 Antarctica, carbon dioxide was high. So, as we see carbon dioxide rising, we expect warming. 20:29 The link between carbon dioxide and temperature is ancient. But today, there's a difference. The present surge 20:36 in carbon dioxide isn't just due to natural processes. It's also due to us. 20:43 1850, the industrial revolution turns on and we start to see CO2 going up. We're 20:49 burning fossil fuels. We're cutting a lot of trees. CO2 is rising and it's still going up and we're burning and we're right there. And the change that's 20:55 happened is very real. It's very clear. We know where it came from. We know what happened. There's no question that we've 21:02 changed the atmosphere. These are possible futures. Will the economy grow 21:07 like crazy? Will the economy tank? Will we clean up? Will we not clean up? All 21:12 of these projections show that the change that's coming is very big compared to the change that's happened. 21:20 All of them are still going up as they cross the year 2100. The world does not end in the year 2100. And so we have 21:27 made a difference. We're going to make a bigger one. If we do nothing to reduce emissions, carbon dioxide levels could 21:34 rise by an average of 30% over the next 50 years. This could result in an 21:39 average temperature increase of almost 10° F. If this trend continues unabated, 21:45 by the end of the 21st century, our planet will see higher temperatures than at any time for the last million years. 21:56 As our planet becomes more crowded and polluted, understanding the forces that are driving climate change becomes ever 22:03 more important. Until recently, no one knew how soon Earth would reach meltdown. Now, new 22:10 evidence from organisms that died many thousands of years ago suggests it may be sooner than we thought. 22:21 Most of the time, the sea is our friend, a place to relax, to buy property. It's 22:26 estimated that within three decades, 75% of the world's population will live in 22:32 the coastal zone. A century from now, cities from Shanghai to New York could 22:38 be beneath the waves. The problem is ice. 22:45 Icebergs, mountain glaciers, the huge ice sheets of Greenland and Antarctica, 22:53 all of them are melting. If our ice melts and the coast moves way 22:59 inland, our cities will be reefs and we will not be terribly happy with that. Not all melting ice is a problem. It all 23:07 depends where the ice is. If the melting ice is already floating on the sea, it 23:13 doesn't pose a threat. There's lots of ice on the planet and only some of it raises sea level when it melts. So, 23:20 let's see what happens when we get too much heat on floating ice to start with. 23:31 The level has not raised. Melting floating ice does not raise 23:38 things. The ocean is not going to get filled up that way. But what would happen if we melted the glaciers of the 23:45 Alps, the glaciers of Antarctica, or in this case, let's call this Greenland. 23:51 What's going to happen if the heat turns on to Greenland and we start melting it? 23:56 We could even have an iceberg break off of the side of Greenland or two and fall 24:02 in. There's a couple falling in right there. And now what's going to happen when we're melting, when we're cving, 24:08 when we're putting more in. And the answer is in. If you melt 24:16 Greenland or if Greenland flows faster and starts dumping more icebergs into the ocean, it will raise sea level. 24:28 If we burn all the fossil fuels, if we raise the temperature a lot, if we we 24:33 melt Greenland, that there's going to be huge impacts on the coasts. [Music] 24:39 In 2001, a rise of 3 ft was predicted. But a new discovery suggests future 24:46 rises could be as high as 20 ft. The clues to this new threat come from a 24:52 tiny organism that lived hundreds of millions of years ago. A creature that still lives in many parts of the planet 24:59 today. Coral. 25:05 Ancient coral reefs reveal how high sea levels can rise after a meltdown. 25:12 This kind of tropical coral only grows in shallow water just beneath the sea 25:17 surface. If it is left out of water, it dies. If it is too deep in water, it 25:23 also dies. It's an excellent marker of sea level throughout history. If coral 25:29 beds are found high above present sea levels, this means that at one time the 25:34 water level must have been higher. 25:40 Dr. Jonathan Overpek and his team at the University of Arizona have been studying 25:45 ancient fossil coral reefs from 130,000 years ago. By measuring the elevation on 25:51 the coral, he can determine how high the sea level reached. 25:58 You needed to have a sea level rise uh somewhere between 13 and 20 ft, perhaps a little more higher than today. These 26:06 ancient corals show that the water level was up to 20 ft higher than today. 26:12 By studying ancient ice core data, Overpek calculates the average temperature of the Earth at the time 26:18 when the corals were alive. He's surprised by the results. The Arctic 26:23 summer temperatures causing those high sea levels 130,000 years ago were a mere 26:29 5 to 8° warmer than today. We figured, oh, by the end of this 26:35 century, that's when we'll cross this point by which we'll be warmer than it was then, and therefore we'll get all 26:41 this ice sheet melting. But lately, uh, the Arctic has been warming faster than we expected. And, uh, now it's possible 26:49 we could get that warm by the middle of this century. By comparing melt rates from today, 26:55 Overpek concluded that the western Antarctic ice sheet may have melted as well as Greenland. 27:03 And the mechanism that caused this massive meltdown is exactly the same that Eric Winon discovered happening in 27:10 the Larsson B ice sheet in western Antarctica. Just like in Larson B in 27:15 2003, the warm water of 130,000 years ago was melting the substructure of the 27:22 glaciers and ice sheets. What was happening apparently is that the ocean was warming and that was 27:28 melting underneath the ice shelves and then uh as these ice shelves uh disintegrated that allowed the ice sheet 27:36 to flow out to the ocean. That was a big surprise for us. It seems 27:42 history is repeating itself. The mechanisms that led to meltdown back 27:47 then are causing sea levels to rise again today. Scientists are worried 27:54 Earth could be heading toward a total meltdown far sooner than anyone thought. 27:59 A lot of us, myself included, are really quite concerned that we might be warming the Earth past a point where these big 28:07 ice shelves and ice sheets could uh disintegrate, raising sea level in dramatic ways. We could cross that 28:13 threshold before we have a chance to even understand the process, let alone stop it. 28:19 The Earth is approaching a tipping point. A point where climate change gets so severe that it could spiral out of 28:27 control. A temperature increase of just a few degrees would have an enormous impact on 28:34 human societies and ecosystems. That will cause the warming to 28:39 accelerate to a point where the Earth cannot recover. If Overpek is right, we 28:45 are on the brink of planetary meltdown. Unless we take urgent measures to reduce greenhouse gases, we could be looking at 28:52 up to 20 ft of sea level rise. Overpek has created computer simulations 29:00 that show the effects. This image is focused on the New York 29:05 metropolitan area. So, right in the center is New York City. We can see as we move to 1 meter or 3 feet uh along 29:12 the southern margin of Long Island, you can see Fire Island would start to flood out at this and up along Connecticut and 29:18 the Meadowlands in New Jersey. A rise of 6 ft results in further 29:24 flooding of the metropolitan area of New York. As the waters reach 10 ft, large 29:30 areas of New York City would be underwater. Here is going up to 13 or 14 ft. And you 29:36 can see here a lot of red and a lot of pink. And the pink is where we've uh flooded areas that are heavily 29:42 populated. But New York at least has the advantage of some high ground. 29:48 Florida has no such luck. Most of the big populated areas of Florida are along the coast and surprise 29:55 surprise, they're impacted by sea level rise. I'll just ratchet this up to 20 30:00 ft. And you can see that the amount of area flooded in Florida could be just 30:06 devastating. [Music] 30:11 It's a bleak vision of the future. Sea level rise out of control. 30:17 2/3 of the world's population lives within 60 mi of the sea. The effects of 30:23 the coming meltdown could be catastrophic. Temperatures might be climbing slowly at the moment and sea 30:28 levels might be climbing slowly, but things are happening on the planet which are going to accelerate those things so 30:33 that we see a very rapid change. The whole system is going to tip and we're going to see catastrophically rising sea 30:39 levels, dramatically rising temperatures. The problem is that as temperatures 30:45 continue to rise, weather patterns begin to change. The Earth has many processes that keep 30:52 violent climate change in check. Even ice itself is part of the process that 30:58 keeps the earth cool. But some scientists worry that these fail safes are breaking down and planetary warming 31:06 is out of control. 31:14 The Earth is heating up. The ice caps are melting and sea levels are rising. Human industry is the cause, and that 31:23 should mean we can stop it. But recently, scientists have discovered a new problem. Global warming is damaging 31:31 one of the processes the Earth uses to regulate its temperature. Ice reflects the sun's energy back into 31:38 space, and that helps keep the Earth cool. Melt the ice, and there is less ice to 31:45 reflect the sun. More heat is absorbed into the oceans and the cooling effect 31:50 gets smaller. As more and more ice melts, more and more heat from the sun 31:56 gets through, melting more ice. It's a vicious circle. 32:02 CIS geoysicist, Professor Don Perovich, is on a mission to understand how the 32:08 interaction between sunlight and ice controls the planet's temperature. 32:14 When it's all said and done, what keeps the Earth warm is sunlight. And how much 32:20 of that sunlight is reflected is a key parameter in the global climate system. 32:25 Now, let's do a little experiment. I've got these two boards which are identical. Well, almost identical except 32:31 for one thing, and you can see what the difference is. This board is black. This board is white. The white board, the 32:38 snow covered sea ice, is the best naturally occurring reflector on Earth. The black board represents the open 32:44 ocean which absorbs most of the sunlight. So, let's just do a little experiment now. We'll measure the 32:50 temperature of these two. Got this nice little thermometer. I pointed at it and 32:56 I can see that the temperature is 26° centigrade, a little around 78° F. Look 33:03 at the blackboard. It's the same temperature because I just exposed them to sunlight. So, what we're going to do 33:09 is just take a couple minutes to see how the temperature changes between these two boards. 33:20 Okay, let's take another temperature measurement. We'll look first at the white board. 33:27 The white board still at 27° centigrade. Now, let's look at the black board. 33:34 the blackboard. It's increased to 48 degrees centigrade, almost 120 degrees 33:40 Fahrenheit. Now, this is a nice little experiment to do on a sunny day, but it also has ramifications for the Arctic 33:47 sea ice cover. Because what we're doing is the ice cover retreats that it's been doing for the past few decades is we're 33:54 replacing the snow covered sea ice, the best reflector, with the open ocean, the worst reflector. And as a consequence, 34:00 we've been putting a lot more heat into the Arctic system. 34:06 The measure of the reflectivity of a surface is known as its albido. 34:12 White ice has an albido of 80%. Dark sea is around 20%. 34:18 A snowball Earth would reflect 80% of solar energy back into space. An Earth 34:24 with no ice would absorb most of it. And somewhere in between, there is a tipping 34:29 point where there's not enough ice to counteract the heat being absorbed by the darker oceans. Global temperatures 34:36 will rise rapidly. The last of the ice will melt and sea levels will rise. 34:46 Perovic wants to know when our planet will reach this tipping point, when the process becomes irreversible. 34:54 74 118 118. 34:59 He's worried it could be sooner than we think. The concern is if you start to push the 35:05 system too far, if you have a sequence of warm summers, you begin to shrink the ice cover by 10, 20, 30%. Where you 35:13 reach a state where it becomes exceedingly difficult to go back. 35:18 In 1979, the perennial sea ice cover of the Arctic was approximately the same 35:23 size as the continental United States. By 2005, the equivalent of almost all 35:30 the states east of the Mississippi has been lost. It's feared this recent retreat of the 35:36 sea ice is likely to speed up so fast that all the ice cover may have gone by 35:41 2045. If you look closely at this record, you can see that this retreat's been 35:47 accelerating in the past few years. And if you look at that accelerating trend, the ice cover could be gone in as short 35:54 a time as a few decades. At present, it's not known at what point 36:00 the process becomes irreversible. The melting of all the ice cover may 36:06 already be inevitable. The destruction of the ice cover will 36:11 have an even more immediate effect. We already know that the seas are 36:18 warming. We know this will accelerate the melting of the ice sheets and push sea levels higher. But it will also have 36:25 a dramatic effect on our weather. Heat is energy and sea temperatures are 36:32 the engine that powers one of the most destructive phenomena on our planet, the 36:37 hurricane. [Music] 36:48 Hurricanes use water vapor coming off the sea surface as their power source. 36:54 As the vapor rises, it condenses into water droplets, releasing energy as heat 36:59 into the hurricane. That's what makes them grow stronger. So, as sea surface temperatures continue 37:06 to rise in the hurricane breeding grounds of the Atlantic, Gulf Coast, and Pacific, hurricanes will increase in 37:13 intensity. It's not just the power of the winds. In 37:18 a world of higher sea levels, another danger comes from the huge storm surges 37:24 the hurricanes bring with them. The duration of tropical storms and 37:29 their maximum wind speeds have increased by about 50% since the mid 1970s. 37:36 In the past decade, the world has seen the most powerful El Nino ever recorded, 37:41 the most devastating hurricane in 200 years, and in 2005, the most active and 37:47 destructive hurricane season on record. The Earth faces disaster. 37:54 Scientists predict storms will intensify. In America, cities along the East Coast 38:00 lie in the path of hurricanes. How long before one of them gets hit? 38:08 The earth is getting hotter. The ice caps are disappearing. 38:13 And the seas are getting warmer and higher. It's a recipe for disaster. 38:19 Warmer elevated seas mean more hurricanes, more storms, and more flooding. Many of our major cities will 38:26 be under threat. New Yorker and professor of geology Nick Cotch of Queens College is concerned 38:32 that powerful hurricanes hitting northern states will cause mass devastation. 38:38 People's minds are on hurricanes a lot now after Katrina, which was our first national repercussions. But people have 38:46 to understand that a northern hurricane, the type that will hit from Washington to the Canadian border, has very 38:52 different characteristics. It moves two to three times faster. And because it moves faster, the effective 38:58 winds on its right side go way up. So even though it's a category three, it might have category 5 winds on that 39:05 side. He's right to be worried. Cities like New York are vulnerable to 39:10 flooding. In December 1992, a powerful northeasterly storm gave New Yorkers a 39:17 taste of what it's like to be inundated. The destruction that it did along the 39:23 shoreline was easily equal to a low-level hurricane. 39:28 Winds at one point reached hurricane level. The worst hit area was the coast of Long 39:34 Island where houses were literally dragged into the sea. It was an immensely powerful uh event 39:42 that did tremendous damage along our shorelines. Downtown Manhattan was underwater. 39:52 Flood water shorted out the entire New York City subway system. 39:58 All our subways and and and highways and railroads have what we call choke 40:03 points. Points where they reach low levels and those choke points were 40:09 flooded and there was massive dislocation. [Music] 40:18 LaGuardia airport closed. Parts of Manhattan lay under 4 ft of 40:23 water and wave height reached 24 ft at the shore. But this was simply a bad 40:30 storm. Cotch fears that with sea levels rising, 40:37 a strong northerly hurricane could flood much of New York. 40:42 [Music] The New York, New Jersey metropolitan 40:48 area is one of the most dangerous places to be in a northeast or a hurricane for 40:54 a simple reason. The problem is geography. Long Island 40:59 and the New Jersey shoreline create a right angle. If a hurricane approaches New York, the counterclockwise winds 41:07 would force a hump of water into that coastal right angle. You can't push water into a right angle 41:13 without it rising. As the water is forced into the narrowing gap, it rises fast. 41:20 We're talking about a storm surge rise at the Statue of Liberty of 22 ft and 28 41:26 ft in Jamaica Bay. This massive wall of water would breach the coastline and race into the city. 41:34 The last strong hurricane to strike New York was in 1938, causing 600 deaths and 41:41 $5.4 billion of damage in today's money. But as sea levels rise and hurricanes 41:48 increase in intensity, it's only a matter of time before New York is struck by a big storm. 41:56 No burrow would be untouched. Hundreds of square miles would be 42:01 flooded. New York would cease to function. 42:06 There is no service in the city at this time. 42:12 John F. Kennedy Airport and Battery Park would be under 10 ft of water. The 42:17 subway would be flooded and hundreds of buildings severely damaged. 42:24 Rebuilding would cost hundreds of billions of dollars. 42:30 Parts of the greater New York City metropolitan area. presently home to more than 20 million people would be 42:36 forced to evacuate. It would be a catastrophe on an unimaginable scale. 42:44 Global meltdown. It's a bleak vision of the future. But scientists believe it is 42:50 inevitable unless we act. Our world is changing beyond recognition. And we 42:55 humans are making it worse. The ice caps are melting and sea levels are creeping 43:00 higher and higher. Worse, it appears that we are moving ever closer to a tipping point beyond 43:07 which we can't stop it happening. But there is hope. Some scientists believe that if we act now, we might just stop 43:14 the meltdown before it's too late. Let me show you something really cool. This 43:20 is the history of lead concentration and snow falling in Greenland. And in 1750, 43:26 we're starting to use a lot of lead in the industrial revolution for batteries and paints and so on. And we see the the 43:33 lead that we're using showing up in in spreading around the globe, showing up in Greenland, and we start putting it in 43:39 more things. We start putting it in gasoline to make our cars work. Then we had the Great Depression, we had World 43:44 War II, and the economy goes down the tubes. And then we get really serious about putting lead in gasoline and 43:50 running our motorc cars around. And then we said no. We said, "Hey, too much lead 43:56 in our cities, too much lead in paint and gasoline is making us stupid. It's making us sick. It's bad for us. We have 44:03 to clean this up." And we did. We got the lead out. And 44:09 it's really it's really beautiful that this worked. And so what one sees is that we humans really can mess things 44:15 up. We can foul our nest. And when we decide we want to, we really can clean 44:21 it up. [Music] We stopped pumping lead into the 44:27 atmosphere and the atmosphere changed. Could we do the same with carbon dioxide? By investing in renewable 44:34 energy sources like wind and solar power and cutting greenhouse gas emissions, we 44:40 could perhaps begin to clean up the atmosphere. Maybe we can avoid pushing the climate past the point of no return. 44:48 It's going to be hard. [Music] But the consequences of failure are 44:55 truly terrifying. If we fail, tomorrow may bring an unrecognizable world of 45:01 social and economic chaos, human tragedy on an appalling scale. 45:08 Or if we act, it may bring little change at all. The choice is ours. 45:19 [Music]
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