WEBVTT 00:00:00.817--> 00:00:02.682 The voice of the water. 00:00:03.619--> 00:00:07.603 Sea level rise explained and understood. 00:00:09.761--> 00:00:18.209 Thinking of Holland I see slow streams slowly through infinite lowlands. 00:00:19.026--> 00:00:25.943 In 1936 Hendrik Marsman published his poem Reminder to Holland. 00:00:26.357--> 00:00:28.920 The most beautiful thing I think is the final rule. 00:00:29.372--> 00:00:39.092 In all regions, the voice of the water with its eternal disasters is feared and heard 00:00:40.120--> 00:00:46.367 I asked the engineers of Rijkswaterstaat how much sea level rise the Netherlands might have 00:00:46.499--> 00:00:54.612 Before it becomes uninhabitable here and the answer was The sky is the limit. 00:00:55.716--> 00:00:58.382 I had to think about the tower of Babylon. 00:00:58.994--> 00:01:02.819 So we can feel safe behind our dikes 00:01:03.477--> 00:01:08.296 But at the same time realize that it can go wrong once. 00:01:08.971--> 00:01:16.931 The Flood and the ark of Noah, the watershot of '53. 00:01:18.177--> 00:01:29.502 In the flood the word sounds sinful and I was therefore not surprised that the EO just broke the series Breaking the dikes. 00:01:30.252--> 00:01:36.077 Because I appreciate a nice disaster movie at the time I went to sleep well. 00:01:36.704--> 00:01:43.894 Great was the disappointment when I realized that the series was made from the point of view of human interest 00:01:43.965--> 00:01:47.713 And the disaster itself got little attention. 00:01:48.108--> 00:01:51.043 I watched it after a couple of minutes. 00:01:52.567--> 00:01:56.921 The engineer of Rijkswaterstaat was also critical of the series. 00:01:57.305--> 00:02:01.770 A storm that occurs once in the ten thousand years 00:02:01.873--> 00:02:12.147 Had broken the dikes just in a place that was strengthened by Rijkswaterstaat and made breakthrough free. 00:02:13.504--> 00:02:18.790 In Southampton I work with Ivan Haigh on flood risks. 00:02:18.854--> 00:02:28.221 And Ivan estimated that only 6% of the extreme high water levels coincide with an extreme storm. 00:02:29.023--> 00:02:35.745 When the dikes break, this happens due to a storm that occurs in the 600 years 00:02:36.110--> 00:02:40.356 But in the 10,000 years coincides with spring tide. 00:02:41.030--> 00:02:46.627 You must look at another part of the probability distribution of wind climatology 00:02:46.652--> 00:02:50.529 To estimate future risks on high water. 00:02:52.881--> 00:02:57.568 And those risks are increasing rapidly as the sea level rises. 00:02:58.155--> 00:03:06.736 What is still a high tide that occurs once in the 100 years takes place once every 100 years. 00:03:07.601--> 00:03:14.653 And in some countries like the United Kingdom, the future seems to have come true. 00:03:14.899--> 00:03:20.132 In the winter of 2013/14 and 2015/16 00:03:20.441--> 00:03:28.146 There was a "conveyor belt or storms battering the coasts of Britain" 00:03:28.337--> 00:03:33.194 As the BBC's weaver has said beautifully. 00:03:35.908--> 00:03:39.016 In the Netherlands we have better deal with our business. 00:03:39.445--> 00:03:46.040 We are the only country in the world with a national health care system. 00:03:47.873--> 00:03:54.065 We had to laugh at home when Prime Minister Cameron announced in 2016 00:03:54.239--> 00:04:01.962 To invest millions to avoid flooding like in the past winters in the future. 00:04:03.120--> 00:04:05.599 That had to be billions of course. 00:04:06.265--> 00:04:12.115 What England needed was a Delta Commissioner with a Deltaplan. 00:04:13.488--> 00:04:19.026 Last year I visited the Seventh National Delta Congress. 00:04:20.066--> 00:04:27.796 The left front leg on which this chair stands is the connection between science and policy 00:04:28.146--> 00:04:30.494 And hence I was in Apeldoorn that day. 00:04:31.169--> 00:04:36.386 The motto of the conference was Together on price. 00:04:37.401--> 00:04:46.055 And I heard the beauty say that we want to make the Netherlands water-resistant and climate-proof 00:04:46.529--> 00:04:51.666 And I thought Oh and for how long? 00:04:53.508--> 00:04:58.667 Even if we can stop global warming today 00:04:59.278--> 00:05:03.088 The sea level continues to rise for a few thousand years. 00:05:04.889--> 00:05:08.952 That science also tries to find its way to the policy. 00:05:09.293--> 00:05:18.341 There we have the National Knowledge and Innovation program for Water and Climate in the Netherlands. 00:05:18.990--> 00:05:21.915 I was talking to a dike dig. 00:05:22.751--> 00:05:28.081 The dike grave did not believe in climate change. 00:05:28.890--> 00:05:34.269 He suggested that there was no acceleration of sea level rise for our coast. 00:05:34.825--> 00:05:43.920 Since 1865, the sea level has increased steadily and only by 20 cm. 00:05:45.593--> 00:05:53.779 I gave it equally equally, but I answered, on average, that acceleration is true. 00:05:54.668--> 00:05:59.813 In some places, the sea level rises much harder than in other places. 00:06:01.321--> 00:06:07.490 He watched me infidelity. That can not be true, he cast off 00:06:08.030--> 00:06:16.530 If you are middle of waves and tides, the sea level is the same everywhere and indignant, he walked away. 00:06:18.434--> 00:06:23.255 The dike grave sees the world sea as a waste dump. 00:06:24.811--> 00:06:29.604 That wastewater fits a flat motionless earth. 00:06:30.620--> 00:06:36.429 And while there are still surprisingly many people in the belief that the earth is a flat disk, 00:06:36.818--> 00:06:40.628 I assume we can skip that step here. 00:06:42.318--> 00:06:47.549 Even with a spherical earth, we can imagine that the sea level is flat. 00:06:48.748--> 00:06:53.843 Now a spherical surface. Only the earth is no sphere. 00:06:54.803--> 00:07:00.843 We can imagine more complex geometries that fit even better with the shape of the earth 00:07:01.375--> 00:07:05.994 But the earth knows mountains, valleys filled with oceans 00:07:06.370--> 00:07:13.965 Lighter and heavier rock that is inhomogeneously distributed over the surface and deep below it. 00:07:14.620--> 00:07:19.949 In all cases gravity determines the shape of the sea level. 00:07:20.838--> 00:07:28.584 And the gravity on earth varies from place to place, depending on whether more or less mass is below the surface. 00:07:29.560--> 00:07:35.343 If you travel from Barcelona to Istanbul, you are about 100 meters down 00:07:35.369--> 00:07:39.865 And climb back one hundred meters to the center of the earth. 00:07:41.603--> 00:07:49.560 If you move the Himalayas to Germany, Amsterdam is tens of meters underwater 00:07:49.877--> 00:07:54.155 Only because of the increased gravity that pulls up the sea level. 00:07:55.544--> 00:08:00.730 Using satellites, we can determine the shape of the sea level at a sea at rest. 00:08:01.151--> 00:08:07.556 We call that shape the geoid and nowhere is the geoid level. 00:08:08.418--> 00:08:11.727 He looks like a wrinkled potato. 00:08:13.823--> 00:08:18.108 Also, the sea level is almost unrelated to the geoid. 00:08:19.156--> 00:08:23.415 We have not yet processed the influence of flow and rotation. 00:08:24.195--> 00:08:27.782 And I can illustrate the effect of the two with a teacup. 00:08:28.774--> 00:08:33.044 Sprinkling with a spoon creates a whirl. 00:08:34.426--> 00:08:39.914 The mirror is the lowest in the middle and the highest at the edge. 00:08:40.533--> 00:08:43.400 The revolving tea is pushed out by the 00:08:43.400--> 00:08:47.669 Centrifugal force but can not escape the head. 00:08:48.066--> 00:08:53.407 There must be an opposing force pushing the tea in again. 00:08:54.216--> 00:09:02.146 The pressure difference between the edge and the center of the cup, or the difference in the mirror. 00:09:03.575--> 00:09:09.122 On a revolving earth, the Coriolis force takes over the role of centrifugal force 00:09:09.853--> 00:09:12.506 Both depend on the flow rate. 00:09:13.059--> 00:09:18.519 If the flow becomes stronger, the pressure difference in the liquid must also be increased. 00:09:20.058--> 00:09:24.050 This is reflected in height differences in the sea surface. 00:09:24.670--> 00:09:30.183 Lines of equal sea level are the isobars on a weather map. 00:09:30.437--> 00:09:38.091 Flow and wind flow parallel to those lines and where they are close to each other, the flow is strong, 00:09:38.416--> 00:09:42.250 Where they are far apart, the flow is weak 00:09:43.090--> 00:09:50.110 A low sea level corresponds to a low pressure range and the same applies to high. 00:09:50.580--> 00:09:57.603 The pressure differences arise due to differences in temperature and salt content in the water, 00:09:58.103--> 00:10:03.258 Caused by variations in wind and heat and moisture exchange with the atmosphere. 00:10:05.200--> 00:10:09.580 There are also differences between Corilis power and centrifugal force. 00:10:10.411--> 00:10:18.139 The ocean has hollow and convex vertebrae depending on the direction of rotation and the hemisphere in which we are. 00:10:18.893--> 00:10:30.022 A chart of the sea level trend over the past few years shows that in many places the trend was greater than the world average trend of 3 mm per year. 00:10:30.920--> 00:10:34.878 And that in other places the trend was even negative. 00:10:35.385--> 00:10:44.722 Locally, over a period of less than a century, the trend is mainly determined by fluctuations in wind precipitation and temperature. 00:10:45.341--> 00:10:52.680 The map of recent years is a reflection of the effect of the negative phase of El Niño 00:10:55.524--> 00:11:01.625 An El Niño at the beginning and a La Niña at the end of the measurement period 00:11:01.880--> 00:11:07.819 With warm water and high sea levels in the western Pacific and Indian Ocean 00:11:08.116--> 00:11:13.184 Cold water and low sea levels in the eastern Pacific Ocean. 00:11:14.881--> 00:11:23.308 Some statisticians believe that the best model for predicting sea levels in the future is to extrapolate the current trend. 00:11:24.340--> 00:11:30.044 Applied to these data we would expect a growing La Niña 00:11:30.322--> 00:11:38.369 Ultimately ocean currents of tens of kilometers per hour and tsunamis destroying the coasts of the world. 00:11:39.749--> 00:11:44.213 But past performance does not guarantee the future. 00:11:44.649--> 00:11:53.820 The patterns on a trend card are predominantly determined by fluctuations that change in their opposite years. 00:11:54.922--> 00:11:57.099 What does this mean for the Netherlands now? 00:11:58.272--> 00:12:03.510 Over the last 20 years, the sea level for our coast has risen below average 00:12:04.889--> 00:12:10.027 But in the middle of the North Atlantic, stronger than average. 00:12:11.466--> 00:12:20.429 In the west of Ireland, a huge swirl runs around the ocean and the North Sea is on the edge of that vertebra. 00:12:21.546--> 00:12:31.407 Like the tea cup, it means that the sea level in the North Sea is high and in the middle of the vertebra. 00:12:32.340--> 00:12:37.805 But the sea level in the North Sea and those in the middle of the vertebra whip a little up and down 00:12:38.282--> 00:12:42.557 As the vertebra turns slower or faster. 00:12:44.303--> 00:12:49.485 And the vertebra turns faster when the water in the middle becomes colder and vice versa. 00:12:50.249--> 00:12:55.762 For the last 20 years the vertebra was relatively hot and weak 00:12:56.129--> 00:13:00.167 But now it seems to hit cold and strong. 00:13:00.901--> 00:13:07.676 I therefore predict an additional strong sea level rise on the Dutch coast for the next 20 years. 00:13:09.774--> 00:13:18.095 Regional sea change is the right front leg on which this chair stands. 00:13:18.696--> 00:13:28.115 Together with and especially by colleague Dewi Le Bars, we have set up a model for the European coast at the KNMI 00:13:28.693--> 00:13:37.854 And the agreement between the monthly average sea level variations in the model and in the observations is incredibly good. 00:13:39.185--> 00:13:43.900 I hope we can make predictions and projections in the future soon. 00:13:46.428--> 00:13:52.777 The third and fourth leg of this chair have to do with the ice-cream of Antarctica. 00:13:52.857--> 00:13:57.790 But I can only explain the third leg if I showed something of the fourth leg. 00:13:59.734--> 00:14:06.953 I start with the temperature spiral designed by Ed Hawkins of Reading University. 00:14:07.588--> 00:14:16.007 It shows the temperature deviation per month over the period 1850-1900 per month. 00:14:17.618--> 00:14:22.232 Last year we passed the 1.4 degree, 00:14:23.930--> 00:14:28.856 Which places the agreements of the Paris climate agreement in a certain context. 00:14:29.634--> 00:14:40.645 Geological observations show that the relationship between sea level and temperature rise for a climate that seems to be about 6 meters or a degree today 00:14:41.756--> 00:14:48.758 We already have 1.4 and only 30 cm sea level rise. 00:14:49.219--> 00:14:50.219 What's up with that? 00:14:51.805--> 00:15:01.299 The sea level rise in recent years is mainly due to the expansion of warmer water and the melting of small glaciers. 00:15:01.632--> 00:15:08.887 The extra meters that are still in the vessel come from the ice caps and respond with delay 00:15:11.451--> 00:15:17.815 Until recently, we thought that the reaction time of ice cream was over a thousand years. 00:15:18.442--> 00:15:21.458 But the ice caps appear to respond much faster 00:15:21.894--> 00:15:28.146 In many places ice caps are surrounded by ice shelves 00:15:28.313--> 00:15:34.678 Floating ice sheets stabbing the ice cream like supporting a cathedral. 00:15:35.860--> 00:15:43.946 In the transition between ice cream and ice sheet, land ice is in contact with sea water. 00:15:44.669--> 00:15:47.395 And water conducts heat much better than air 00:15:48.069--> 00:15:53.458 And melt from below is the biggest threat to Antarctica. 00:15:55.109--> 00:16:01.462 But where comes that warm water with -1 degree celsius 00:16:01.487--> 00:16:06.650 Still as hot as compared to ice melting water actually? 00:16:07.515--> 00:16:11.373 This brings me to the left hind leg of this chair. 00:16:11.786--> 00:16:19.726 That hot water comes from the north but how it gets under the floating ice sheets is a mystery. 00:16:21.456--> 00:16:27.844 The flow follows lines of constant sea level and thus circles around Antarctica. 00:16:29.043--> 00:16:35.893 That hot water should be brought to the Antarctica perpendicular to the flow. 00:16:37.551--> 00:16:40.037 How does that work? 00:16:41.916--> 00:16:50.561 The wind pumps that bring warmer water as a sub stream from the warm Gulf Stream to the Southern Ocean 00:16:50.922--> 00:16:53.713 About 1000 km from the coast 00:16:54.287--> 00:16:58.590 But most of the water is driven back to the north by the wind. 00:16:59.946--> 00:17:05.293 Many mechanisms have been devised to explain how part of that water comes to the ice creams 00:17:06.325--> 00:17:10.814 But in our climate models, those processes do not work. 00:17:11.625--> 00:17:17.355 There is a heat front on the continental slope of Antarctica 00:17:17.972--> 00:17:21.650 And the warm water stays neatly behind the front. 00:17:23.334--> 00:17:33.630 An important process that can not reproduce climate models is the formation of vertebrates of 1 to 10 km in diameter 00:17:33.930--> 00:17:36.804 Which mix the hot water across the front. 00:17:37.854--> 00:17:42.680 With a model of the Antarctic Slope Front 00:17:42.680--> 00:17:47.628 10x as fine as the finest climate model, 00:17:48.121--> 00:17:55.083 We simulate vertebrae that mix warm and cold water, but it does not prove enough. 00:17:55.551--> 00:17:58.857 Other processes must also play a role 00:17:59.571--> 00:18:04.012 Katabatic winds pouring down the icecream 00:18:04.170--> 00:18:12.132 And to cause a north-south flow in the ocean not properly solved in climate models. 00:18:12.646--> 00:18:17.979 Mixing of tides not even included in climate models. 00:18:18.631--> 00:18:24.390 Deep canyons in the seabed that can lead the hot water under the front. 00:18:25.122--> 00:18:33.058 Those canyons are everywhere but because the seabed can hardly be mapped under the floating ice sheets 00:18:33.244--> 00:18:37.784 Are they not present in our database of the seabed. 00:18:40.861--> 00:18:47.037 Also, we are interested in temperature fluctuations in the water of the ice cream 00:18:48.078--> 00:18:55.212 Is that water so hot due to the greenhouse effect or there are also natural variations 00:18:56.524--> 00:19:07.469 Many models show a 50 to 100 year fluctuation between seawater temperature around Antarctica and in the North Atlantic Ocean. 00:19:08.607--> 00:19:15.497 In the ocean model of Utrecht University, this fluctuation is controlled by processes in the Southern Ocean. 00:19:16.397--> 00:19:19.330 There is the outlet for the swing. 00:19:19.633--> 00:19:29.292 However, in the KNMI climate model, this fluctuation is controlled by North Atlantic processes and sales take place in the north. 00:19:31.135--> 00:19:40.322 These fluctuations are so slow that the observations can not yet give an indication of where the sales take place. 00:19:42.658--> 00:19:55.009 The fluctuation in temperature of the water near the coast that is in direct contact with the ice caps is about a 10th degree. 00:19:56.076--> 00:20:13.133 10, which seems at first sight nothing but 0.1 degree difference in sea water temperature in the deep southern ocean can completely change the face of the world. 00:20:16.650--> 00:20:22.315 The right back leg of the chair is the instability of the Antarctic Ice Cream. 00:20:24.308--> 00:20:34.157 If you move the Himalayas to Germany, only by changing the gravitational force of Amsterdam will be tens of meters under water. 00:20:36.168--> 00:20:45.402 If we change the mountain of stone in ice in our thought experiment that slowly begins to melt 00:20:46.478--> 00:20:49.745 Then Amsterdam is slowly dry 00:20:50.521--> 00:20:54.568 Because the gravity decreases on the ground and the geoid drops down 00:20:55.459--> 00:21:01.271 While the sea level in the rest of the world must rise due to all the melting water that comes with it. 00:21:02.991--> 00:21:10.288 The turnaround between bags and ascents is 2500l km away. 00:21:11.619--> 00:21:18.824 For this reason, we do not mind much in the Netherlands from melting the Greenlandic icecream 00:21:19.432--> 00:21:22.251 But of Antarctica all the more 00:21:24.773--> 00:21:37.581 Last year, the scientific world was frightened by a US study with a ice cream model incorporating two new processes that had been overlooked until now 00:21:38.225--> 00:21:47.052 And which could increase the rate of sea level rise to 6 cm per year in the beginning of the next century. 00:21:48.710--> 00:21:56.408 The Wadden Sea is already disappearing if the sea level rise rises more than 1 to 2 cm per year 00:21:57.004--> 00:22:01.528 In this scenario in the second half of this century. 00:22:03.115--> 00:22:04.831 What are these new processes? 00:22:07.106--> 00:22:18.473 I start with a process that can simulate all ice cream models today but which have not yet been taken into account in the last IPCC report. 00:22:19.593--> 00:22:25.213 Marine Ice Sheet Instability MISI 00:22:26.536--> 00:22:34.841 If the sea water gets under the floating ice sheets, it also melts more land ice. 00:22:36.341--> 00:22:47.125 The point where floating ice hits the ground and land ice becomes the grounding, line then moves inland. 00:22:49.092--> 00:22:58.352 In places where the bottom is down, the amount of ice above the grounding line increases in that case. 00:22:59.843--> 00:23:03.057 And this is the case in West Antarctica. 00:23:05.041--> 00:23:15.939 Now the outflow from land ice to drift ice is proportional to the thickness of the ice layer above the grounding line. 00:23:17.324--> 00:23:25.893 So as the bottom slopes down and the grounding line starts moving inland 00:23:26.678--> 00:23:34.372 Increases the flow of land ice to drift ice, which causes land ice to lose more mass 00:23:34.690--> 00:23:44.968 Increasing the grounding line further inland, increasing the flow of land ice to drift ice, etc. 00:23:47.189--> 00:23:54.914 This self-strengthening process is initiated when a so-called tipping point or tilt point is passed. 00:23:56.175--> 00:24:06.760 Recently it has been proven that this is happening at the Pine Island glacier in the Amundsen Sea at Antartica and probably in a few more places. 00:24:08.380--> 00:24:18.017 The process is only very difficult to demonstrate, but it has been successful with drilling through the ice sheet into the seabed. 00:24:18.705--> 00:24:22.912 It was concluded that an El Niño had initiated the process 00:24:23.580--> 00:24:30.670 And that the process continued only after the seawater had cooled down when the El Niño was over. 00:24:31.984--> 00:24:36.832 You have that variation of a 0.1 degree still in mind. 00:24:38.516--> 00:24:43.869 The plate was found to lose 500 m thick but 20 m per year. 00:24:46.109--> 00:24:51.133 The Antarctic icecream rattles bump off. 00:24:52.350--> 00:24:59.043 The two most northerly ice sheets Larsen A and Larsen B, 00:24:59.140--> 00:25:04.989 Something east of the Antarctic Peninsula has now collapsed. 00:25:06.126--> 00:25:12.321 After the disappearance of those ice sheets, the outflow of land ice to the sea increased by a factor of five 00:25:14.861--> 00:25:23.123 The disintegration of a floating ice sheet is caused by the fact that hot air melts and cracks leave behind 00:25:23.480--> 00:25:27.598 Soaking the water down and eroding the ice. 00:25:28.604--> 00:25:36.017 The technical term for this is hydrofracturing and the warmer it gets the more often it occurs. 00:25:36.996--> 00:25:39.796 Two Americans added theConto and Pollard 00:25:41.590--> 00:25:47.670 This process accelerated enormously to their ice-cream model and the demolition of Antarctica. 00:25:49.443--> 00:25:57.596 Other scientists have argued that this process would not occur on the more southern ice sheets this century 00:25:57.869--> 00:26:00.612 Because it's too cold and remains for the time being. 00:26:02.182--> 00:26:06.344 But satellite imagery proves the opposite. 00:26:06.732--> 00:26:13.544 Melting plants are found everywhere, even in East Antarctica where nobody thought they would be sitting. 00:26:15.378--> 00:26:25.494 Last week there was an article that estimated that more than 1000 X is present on the ice sheets and on the edge of the iceberg so much melting water 00:26:25.767--> 00:26:30.407 As calculated by the best regional climate model of Antarctica. 00:26:31.466--> 00:26:37.901 The underestimation in the model we understand, but the factor with which is gigantic. 00:26:38.491--> 00:26:40.747 What is going on? 00:26:43.978--> 00:26:47.489 As we see, new cracks arise in various places. 00:26:47.636--> 00:26:59.258 At Larsen C is currently developing a hundred kilometers long and hundreds of meters wide crack that threatens to break the record. 00:27:00.470--> 00:27:09.291 The plate breaks out ever more and yesterday it became known that the front of the crack is only 13 km from the coast. 00:27:10.527--> 00:27:22.022 A warning has been issued to all ships in the vicinity that breaks down a huge ice sheet within a few weeks, resulting in huge waves. 00:27:22.521--> 00:27:31.092 Whether this is the forerunner of Larsen C's complete breakdown is still unclear, but it does not look good. 00:27:32.890--> 00:27:36.898 Also, the ice sheets appear to tear down from the bottom. 00:27:37.374--> 00:27:41.955 These basal gaps are sometimes hundreds of feet deep. 00:27:42.771--> 00:27:47.528 A process that was not included in the American icecream model. 00:27:50.567--> 00:27:59.529 A second controversial process in their new model is Ice Cliff Instability ICI 00:28:00.855--> 00:28:05.762 Above the grounding line, land ice cream is floating in a floating ice sheet 00:28:06.651--> 00:28:11.851 But when the ice sheet breaks up, a cliff rises above the grounding line. 00:28:13.000--> 00:28:17.439 And too high a cliff falls under its own weight. 00:28:18.947--> 00:28:22.756 On land landslides on cliffs are universal. 00:28:24.148--> 00:28:30.106 The equivalent ice shift is accompanied by much larger chunks 00:28:30.616--> 00:28:36.024 But the process is the same and has been observed on the large ice caps in a few places. 00:28:38.269--> 00:28:43.370 The critical height for ICI is 80 m above sea level. 00:28:45.080--> 00:28:49.971 DeConto and Pollard have estimated how quickly this process breaks down a icecream. 00:28:51.060--> 00:28:56.960 If you take that process along, you can not really lose hell in their model 00:28:58.411--> 00:29:04.670 Many scientists find that ICI is still not known enough to model it 00:29:05.010--> 00:29:12.551 And that the two gentlemen were out of sensation; A publication in the journal Nature. 00:29:13.527--> 00:29:14.793 Undoubtedly true. 00:29:15.590--> 00:29:26.317 But the Americans dispel that their estimation is still on the conservative side and that without this process the geological sea level variations are not imitated. 00:29:27.474--> 00:29:30.674 The last word has not yet been said. 00:29:32.599--> 00:29:39.814 Their new projections of the sea level rise for the end 2100l amount to more than 1 m 00:29:40.087--> 00:29:45.665 Only through Antarctica and even 6m in 2200. 00:29:46.878--> 00:29:50.620 It is a worst case scenario 00:29:50.915--> 00:29:56.516 CO2 emissions are not reduced for 2200 but still 00:29:57.435--> 00:30:02.243 And for the Netherlands another 20% Because of the gravity effect. 00:30:04.749--> 00:30:14.769 If you also charge the other processes, the probability distribution for the total sea level rise according to the IPCC scenario 00:30:15.166--> 00:30:20.146 And the worst case scenario of the account and pollard totally different. 00:30:20.990--> 00:30:25.475 They are both valid within the limits of their own assumptions. 00:30:26.019--> 00:30:32.907 But at the same time they close each other and how to connect those two does not know anyone yet. 00:30:36.717--> 00:30:44.681 In a policy hackathon where a group of employees tries to crack a policy issue 00:30:45.554--> 00:30:59.079 More than 20 employees from Deltares considered the consequences of extreme sea level rises and the possible measures to limit the impact on the Netherlands. 00:30:59.498--> 00:31:04.124 They confirmed the image of the Rijkswaterstaat engineers 00:31:04.306--> 00:31:12.775 That there are no fundamental technical barriers that also prevent adequate coastal defense. 00:31:14.464--> 00:31:19.952 But there is a price tag. About 500 billion. 00:31:20.768--> 00:31:26.555 And the accompanying measures will make the Netherlands a totally different country 00:31:27.371--> 00:31:31.156 Dunes and beaches migrate inland. 00:31:31.873--> 00:31:37.590 The upward pressure on groundwater begins to burst the coating on which we live and work. 00:31:37.995--> 00:31:45.015 Groundwater. The drop of altitude difference between Lobith and the sea, 00:31:45.174--> 00:31:49.658 Requires huge pumps to get rid of the Rhine. 00:31:50.816--> 00:31:56.155 The river drain must pass through the IJssel and the Gelderse valley to the IJsselmeer. 00:31:56.980--> 00:32:04.789 Higher dikes become proportionally wider and quadratic more expensive, ports and farmland disappear. 00:32:05.980--> 00:32:12.093 And with the current rate of dive replacement, we need to think ahead for 125 years. 00:32:12.411--> 00:32:17.532 And now taking into account the sea level rise in the mid-century century. 00:32:19.881--> 00:32:24.261 If we take that all for granted, there are three options left: 00:32:24.658--> 00:32:29.245 A walled fort of the Netherlands with huge pumps, 00:32:30.150--> 00:32:34.326 Or extremely deep rivers with ever higher dikes, 00:32:35.374--> 00:32:41.610 Or let the low-lying areas run with a few cities on terriers. 00:32:43.856--> 00:32:52.220 It seems science fiction, but the discussion that the Netherlands has to go must actually start today. 00:32:54.320--> 00:33:00.958 With Bangladesh, Suriname and Guyana we belong to the 4 countries 00:33:01.132--> 00:33:06.651 Whose population, if we make the switch to renewable energy in 2100, 00:33:06.746--> 00:33:11.190 To live below 75% below sea level. 00:33:12.166--> 00:33:24.429 And not only the Randstad but about 30 mega cities with more than 10 million inhabitants will become uninhabitable without extremely expensive measures. 00:33:31.386--> 00:33:39.807 The question for science is: how quickly and how much is the risk of these kinds of scenarios. 00:33:42.434--> 00:33:47.490 But when I last introduced a colleague, the accounts of the Account and Pollard in our 00:33:47.490--> 00:33:51.042 To study their own icecream models was the response: 00:33:53.756--> 00:33:58.908 I do not currently feel like testing Antarctic disaster scenarios. 00:34:01.606--> 00:34:08.262 Was I an evil prostitute? Someone who swallows in calamity and misery? 00:34:09.493--> 00:34:13.951 Does the right rear leg of this chair stand on ice-cream? 00:34:16.991--> 00:34:23.248 In an interview following his Bible for unbelievers 00:34:23.720--> 00:34:30.163 Author Guus Kuijer said that prophets are the worst battle people are in the Bible 00:34:31.575--> 00:34:34.809 Prophets believe to have the truth in mind 00:34:35.174--> 00:34:40.548 And close others or kill them if they do not add to that truth. 00:34:41.445--> 00:34:44.420 The true heroes of the Bible are people who are the 00:34:44.420--> 00:34:50.074 Truth not to be in charge but to seek the truth. 00:34:51.216--> 00:34:52.740 So scientists! 00:34:54.065--> 00:34:59.204 I felt restured, but still something went wrong. 00:35:00.029--> 00:35:08.256 Old prophets heard the voice of God, maybe new prophets, the voice of the water. 00:35:09.987--> 00:35:14.451 Everyone knows the song "When Jonas was in the whale" 00:35:14.974--> 00:35:22.276 With someone on the left forehead holding the right front leg to the left and right hind legs 00:35:22.625--> 00:35:28.154 A few times back and forth sling and release huppetee. 00:35:28.179--> 00:35:31.012 Jonah is my favorite pro. 00:35:32.496--> 00:35:36.866 He does not fit into the category that Guus Kuier despises. 00:35:38.532--> 00:35:46.422 Jonah came from Ninevé, a city in the low-lying delta between the Euphrates and the Tigris 00:35:47.240--> 00:35:51.652 And he was wearing a climate dynamics chair. 00:35:53.540--> 00:35:58.647 With his scenarios for sea level rise he was laughed by everyone. 00:36:00.306--> 00:36:02.521 But Jonah did not discourage it. 00:36:03.140--> 00:36:06.112 Human interest was not his thing. 00:36:06.953--> 00:36:14.153 Every day he sought the truth, and in that capacity he spoke to God. 00:36:16.312--> 00:36:19.285 But on an evil day, the roles turn around. 00:36:20.311--> 00:36:22.628 God wants to speak to Jonah. 00:36:24.226--> 00:36:30.312 He is still disappointed in humans and in Nineveh's most. 00:36:31.296--> 00:36:36.517 As a punishment for sin, God intends to undermine the city with a flood. 00:36:38.279--> 00:36:44.719 Jonah gets forty days to turn off the disaster and convert the people. 00:36:46.981--> 00:36:51.110 That does not matter, he spits against. 00:36:51.689--> 00:36:54.379 I'm not taken seriously by anyone. 00:36:56.657--> 00:37:00.017 You are doing your best, but God answers. 00:37:00.597--> 00:37:05.030 And, reluctantly, Jonah begins a public hearing 00:37:05.530--> 00:37:08.697 And pulls with his powerpoint from hall to hall. 00:37:09.499--> 00:37:12.821 But everywhere he is run away. 00:37:15.258--> 00:37:23.139 On the fortieth day he installs himself on the Utrechtse Heuvelrug where he has a good view of the delta. 00:37:24.258--> 00:37:32.620 He's going to sit well for it, because Jonah knows how to appreciate a great disaster movie. 00:37:34.770--> 00:37:40.726 But at sunset there is still nothing happening and indignant, he tests the familiar number. 00:37:41.662--> 00:37:44.637 You basted me completely. 00:37:44.693--> 00:37:51.168 7 meter sea rise you promised me and I have not seen a centimeter of it yet. 00:37:54.057--> 00:37:58.181 The people have repented to answer God. 00:37:58.927--> 00:38:02.957 They have signed an agreement in Paris. 00:38:03.902--> 00:38:11.764 A declaration of intent to limit the world average temperature rise to 1.5 degree. 00:38:12.900--> 00:38:14.973 And you believe that? 00:38:15.664--> 00:38:17.694 We are already at 1.4! 00:38:17.948--> 00:38:22.937 How do you think they are going to do that, asks Jonah disbelief. 00:38:24.897--> 00:38:31.235 That is still being sought, God says, but the first step has been taken. 00:38:31.553--> 00:38:39.359 Yes, yes, the road to hell is paved with good intentions, Jonah opposes 00:38:41.812--> 00:38:45.383 There I know everything about answer God. 00:38:46.208--> 00:38:51.213 But Nineve's people deserve a second chance. 00:38:53.157--> 00:38:54.223 Jonah is furious. 00:38:55.053--> 00:38:59.630 Immediately he checks the number of the National Oceanography Center 00:38:59.876--> 00:39:03.476 With the question of whether they still have a chair. 00:39:04.027--> 00:39:05.427 That is the case. 00:39:06.470--> 00:39:09.497 And the next day he goes to Southampton. 00:39:11.550--> 00:39:18.723 That night is the storm that breaks the dikes once in 10,000 years. 00:39:20.056--> 00:39:22.819 But in the middle of the night the storm is moving its course. 00:39:22.987--> 00:39:25.541 Jonah is awakened by the captain. 00:39:26.097--> 00:39:31.274 I have never seen such a sea and you are an oceanographer, says the captain 00:39:31.989--> 00:39:33.989 Tell me how to get out of here. 00:39:36.555--> 00:39:38.089 Jonah shakes his head. 00:39:39.333--> 00:39:45.354 This is the perfect storm he answers. There is no way out. 00:39:45.870--> 00:39:52.930 You're just unlucky to take me on board because the storm has hit me. 00:39:54.216--> 00:39:59.558 Some sailors who listened to the conversation think that there is indeed a way out. 00:40:00.875--> 00:40:08.483 The first takes Jonah to the left forehead, the second at the right forehead, and so forth. 00:40:09.014--> 00:40:10.749 Jonah goes overboard. 00:40:13.196--> 00:40:17.587 Regardless of the storm that occurs once in 10,000 years, 00:40:18.580--> 00:40:24.416 Or by global warming or that it was a pre-planned plan. 00:40:25.527--> 00:40:35.005 But a whale on the way to the Polish Sea takes the wrong exit between the Orkney and the Shetlands and swims the North Sea. 00:40:36.120--> 00:40:45.634 After Jonah has been aboard, he ends up in the mouth of the planktoneter who lovingly returns him to the coast. 00:40:47.959--> 00:40:53.868 As I said to you, the whale speaks against him 00:40:54.606--> 00:40:59.547 Everyone gets a second chance at me. 00:41:02.196--> 00:41:06.992 A year ago we installed an icecream model from Antarctica in Southampton. 00:41:07.540--> 00:41:14.364 That model is driven by atmospheric fields of the model known as RACMO. 00:41:15.721--> 00:41:17.967 Almost one million numbers. 00:41:18.808--> 00:41:23.012 But for the ocean, only one parameter was available. 00:41:23.660--> 00:41:29.024 A constant seawater temperature, uniform for the whole continent. 00:41:30.778--> 00:41:39.045 That should be better, I thought, and I asked my programmer Jeff Blundell to add that parameter to time and place 00:41:39.362--> 00:41:44.385 So that the graduate student could investigate what happens when seawater warms up 00:41:44.580--> 00:41:48.151 And what if the seawater temperature also varies from year to year. 00:41:49.500--> 00:41:54.537 It turned out months of work for student and programmer to change the model code. 00:41:55.442--> 00:41:57.197 Time for Plan B. 00:41:58.594--> 00:42:10.397 We kept T (ocean) constant but left in each new run the sea water temperature with you recommends increasing it by 0.1 degree. 00:42:11.913--> 00:42:19.580 With a temperature of -1.7 below the floating ice sheets and the RACMO atmosphere today 00:42:20.064--> 00:42:24.772 The Antarctic Ice Cream is now imitated. 00:42:26.256--> 00:42:32.321 If you make that ocean temperature -1.6 you get almost the same ice cream 00:42:32.846--> 00:42:36.528 Also with -1.5 nothing is going on. 00:42:37.420--> 00:42:46.863 But at -1.4 we have more than 2 meters sea level rise for the pick and at -1.3 degrees even more than 7 meters. 00:42:48.299--> 00:42:50.777 Then there is a plateau. 00:42:51.999--> 00:42:56.201 First, the ice cream is insensitive to a temperature rise. 00:42:56.725--> 00:43:04.500 Then there is a tipping point where a change of 0.1 degree or less is enough to cause something tremendous 00:43:05.047--> 00:43:08.860 And then there is an interval where the sensitivity of the ice cream is small. 00:43:11.145--> 00:43:17.165 7 meters sea level rise means that the entire West Antarctic icecap is lost 00:43:17.617--> 00:43:20.199 By a little bit of ocean warming. 00:43:20.556--> 00:43:24.869 Without the need for further warming of the atmosphere. 00:43:26.678--> 00:43:35.371 Even the COP21 agreement can not stop the disappearance of the West Antarctic icecap. 00:43:37.562--> 00:43:45.428 But the rate of degradation depends critically on the rate at which COP21 is performed. 00:43:47.500--> 00:43:56.421 If the ocean starts to get warmer, the ice cube degradation begins at two places in the model. 00:43:57.003--> 00:44:01.663 At the Filchner-Ronne ice sheets at the ice sheets in the Amundsen Sea 00:44:02.703--> 00:44:06.458 And a little later at the ice sheet in the Ross Sea. 00:44:07.727--> 00:44:14.536 But in reality, the seawater in the Amundsen Sea is much warmer than the other ice sheets 00:44:15.280--> 00:44:18.338 And even a bit warmer than at the turning point. 00:44:19.640--> 00:44:26.095 The ice sheets there are already disappearing and are doomed. 00:44:26.706--> 00:44:32.179 But the Filchner-Ronne and Ross Zee tipping points have not yet been reached. 00:44:34.250--> 00:44:38.804 The 7 meter sea rise through Antarctica takes place in three steps 00:44:39.249--> 00:44:49.551 And between the first step of 1 meter and the third step from 2.5 to more than 7 meters lies our second chance. 00:44:50.337--> 00:44:53.969 And there's even a third chance of damage control. 00:44:55.350--> 00:44:59.565 We can greatly slow down passing those other tilt points. 00:45:00.827--> 00:45:07.917 The extra chance and the extra chance lies in the nature of the laws of nature 00:45:08.393--> 00:45:13.769 Or in the mathematics with which we describe and intend to understand nature. 00:45:14.119--> 00:45:20.750 And whether that is a coincidence, or something has been written by someone or someone may make each one a separate one. 00:45:21.120--> 00:45:30.208 But the second chance is universal because the universe is full of systems with multiple tilting points. 00:45:31.494--> 00:45:39.026 The message I want to give this afternoon to the politicians who are trying to conclude a new government agreement 00:45:39.470--> 00:45:42.750 To the policy staff of the ministry of I & M 00:45:43.260--> 00:45:52.662 And the staff of DG Water, members of the Delta Commission and your wealthy citizens with their own voice 00:45:53.249--> 00:46:00.661 In which once in the 4 years and sometimes the voice of the water may sound together 00:46:01.440--> 00:46:04.575 Is: "Grab that opportunity"! 00:46:05.384--> 00:46:11.341 Otherwise, much of this country has more history than the future. 00:46:12.619--> 00:46:13.700 I have said.