WEBVTT - The Sunken Lands, Part 4 0:00:03.040 --> 0:00:07.040 Welcome to Stuff to Blow Your Mind, the production of iHeartRadio. 0:00:13.000 --> 0:00:14.960 Hey you welcome to Stuff to Blow your Mind. My 0:00:15.040 --> 0:00:16.160 name is Robert Lamb. 0:00:16.560 --> 0:00:19.439 And I am Joe McCormick, and we are back with 0:00:19.560 --> 0:00:22.639 the fourth and final part in our series called the 0:00:22.760 --> 0:00:27.200 Sunken Lands, about places on Earth that relatively recently used 0:00:27.240 --> 0:00:29.840 to be dry land but are now covered by water. 0:00:30.440 --> 0:00:30.720 Now. 0:00:30.760 --> 0:00:33.560 In previous parts of the series we talked about, of course, 0:00:33.680 --> 0:00:37.440 legendary lands of this sort Atlantis and other fictional or 0:00:37.479 --> 0:00:40.879 mythical sunken civilizations. And sorry to be a bummer to 0:00:40.880 --> 0:00:43.680 the many Atlantis hunters out there, but yes, it does 0:00:43.680 --> 0:00:46.080 seem like the experts on the original sources that this 0:00:46.159 --> 0:00:49.159 story comes from, namely a couple of dialogues of Plato, 0:00:49.520 --> 0:00:52.280 think that it probably is a fictional invention and not 0:00:52.360 --> 0:00:55.120 a reference to a real place that existed. But that 0:00:55.160 --> 0:00:58.480 doesn't mean that there are not lands that have been 0:00:59.080 --> 0:01:03.600 within the history of the human species submerged by water. 0:01:03.680 --> 0:01:06.080 In fact, we know of some examples of places that 0:01:06.160 --> 0:01:09.400 were both inhabited by humans and sunk under the water, 0:01:09.520 --> 0:01:12.479 not really anything like was described in the Atlantis story, 0:01:12.840 --> 0:01:15.640 but there are examples of the sunken land masses of 0:01:15.680 --> 0:01:20.160 Beringia and dogger Land, which during and briefly after the 0:01:20.280 --> 0:01:23.560 Last Ice Age formed land bridges between North America and 0:01:23.640 --> 0:01:27.800 Asia and Great Britain and continental Europe perspectively. We also 0:01:27.840 --> 0:01:31.199 talked about vanished islands in the Pacific. Some of these 0:01:31.480 --> 0:01:34.880 supposedly vanished islands are probably a result of errors in 0:01:34.920 --> 0:01:39.680 their original reporting, but others are places that probably actually 0:01:39.720 --> 0:01:42.880 did vanish or sink beneath the water due to cataclysmic 0:01:42.959 --> 0:01:47.360 seismic activity. We also talked about atolls, how they're formed, 0:01:47.640 --> 0:01:51.640 and where their central islands went. There was a hypothesis 0:01:51.680 --> 0:01:53.800 that Darwin had about this going all the way back 0:01:53.800 --> 0:01:57.000 to his voyage on the Beagle. There are new ideas 0:01:57.280 --> 0:02:01.960 related to karsification and the dissolution of carbonate rock or 0:02:02.040 --> 0:02:05.080 limestone when it's exposed over the surface of the sea, 0:02:05.360 --> 0:02:09.160 dissolution by rain water, and then also finally, in the 0:02:09.240 --> 0:02:13.399 last episode, we talked about places that have been flooded 0:02:13.520 --> 0:02:17.400 by damming, the damming of freshwater resources, damming rivers and 0:02:17.440 --> 0:02:21.280 streams to end up submerging areas that used to be 0:02:21.320 --> 0:02:23.560 exposed land now under lakes. 0:02:24.880 --> 0:02:26.880 Now A quick note on just the idea of sunken 0:02:26.919 --> 0:02:29.800 islands and sunken lands. We had a listener ask about 0:02:29.800 --> 0:02:31.760 this and discord. So I want to just briefly point 0:02:31.800 --> 0:02:34.840 out that, especially in our discussion of atolls in the 0:02:34.880 --> 0:02:38.760 last episode, the terms sunk in or to sink may 0:02:38.840 --> 0:02:41.720 ultimately be too simplistic for these discussions because they're all 0:02:41.840 --> 0:02:45.200 very based on the human perspective of what's going on. 0:02:45.680 --> 0:02:48.320 And in any case, we're talking about situations that may 0:02:48.480 --> 0:02:51.360 entail both rising and lowering sea levels, as well as 0:02:51.440 --> 0:02:55.320 land that is pushed up and or created by volcanic, organic, 0:02:55.400 --> 0:02:59.320 or seismic forces, and land that lowers sometimes beneath water 0:02:59.400 --> 0:03:04.720 level due to erosion, seismic forces, etc. So just in 0:03:04.760 --> 0:03:07.040 all cases, just keep in mind that, yeah, sunk in 0:03:07.240 --> 0:03:11.440 sinking maybe doesn't fully capture the picture of what's going on. 0:03:12.000 --> 0:03:14.680 Well. Actually, as luck would have it, I do want 0:03:14.720 --> 0:03:19.119 to get to one example of actual sinking of lands 0:03:19.880 --> 0:03:23.440 in just a bit here. So in the background of 0:03:23.639 --> 0:03:27.880 discussing these historical cases of landscapes covered by rising seas, 0:03:28.560 --> 0:03:31.000 there is the knowledge that most of us have now 0:03:31.160 --> 0:03:35.440 that relatively rapid increases in sea level are happening right 0:03:35.480 --> 0:03:39.040 now and will continue in the coming decades due to 0:03:39.320 --> 0:03:42.120 climate change, due to the warming of the seas the 0:03:42.160 --> 0:03:46.400 melting of glaciers. Sea level changes have happened on Earth before, 0:03:46.480 --> 0:03:49.520 but one thing that's different now is how much of 0:03:49.600 --> 0:03:54.640 the physical infrastructure and culture of modern human civilization was 0:03:54.720 --> 0:03:57.480 designed on the assumption of current sea levels staying where 0:03:57.520 --> 0:04:01.160 they are. Whole cities, whole countries even are threatened by 0:04:01.280 --> 0:04:05.120 rising waters because they have been built without those rising 0:04:05.160 --> 0:04:06.080 waters in mind. 0:04:06.600 --> 0:04:08.600 Yeah, some of the very places we've discussed, at least 0:04:08.640 --> 0:04:12.560 in passing in these episodes, like the Maldives, are greatly 0:04:12.600 --> 0:04:14.840 threatened by these rising sea waters. 0:04:15.240 --> 0:04:18.320 Yes, absolutely, But of course this applies to coastal settlements 0:04:18.360 --> 0:04:21.600 all over the world, on every continent on Earth, though 0:04:22.120 --> 0:04:25.599 though in different ways. Not every coastal settlement will be 0:04:25.600 --> 0:04:27.080 affected the same, and I want to get to some 0:04:27.120 --> 0:04:30.400 of that variance in just a bit here. But as 0:04:30.400 --> 0:04:33.719 a baseline, I thought we should look at how much 0:04:33.960 --> 0:04:37.120 are sea levels expected to rise in the next century 0:04:37.200 --> 0:04:40.320 or so. That depends on a number of variables, but 0:04:40.680 --> 0:04:43.479 I was looking at the most recent ipc SA report, 0:04:43.560 --> 0:04:47.000 which had put together a series of estimates. First of all, 0:04:47.040 --> 0:04:49.120 they look at the question of what is happening to 0:04:49.279 --> 0:04:52.760 global mean sea level right now, what has already happened 0:04:53.800 --> 0:04:57.200 in the traceable recent past, whatever happens in the future. 0:04:57.240 --> 0:04:59.440 One thing we know for certain is that the sea 0:04:59.520 --> 0:05:03.080 level is already rising and has already risen, and the 0:05:03.200 --> 0:05:07.240 rate at which it rises will very likely accelerate in 0:05:07.320 --> 0:05:10.839 the future. Based on our best measurements averaged over different 0:05:10.920 --> 0:05:13.520 time periods, we can see that sea levels have risen 0:05:13.760 --> 0:05:18.159 over over the past century, and the basically the more 0:05:18.320 --> 0:05:20.760 recent the chunk of time you look at, is the 0:05:20.800 --> 0:05:24.520 faster they're rising. So the IPCC report points out that 0:05:24.839 --> 0:05:28.240 sea levels rose about one point four millimeters per year 0:05:28.560 --> 0:05:30.600 if you look at the time period nineteen oh one 0:05:30.680 --> 0:05:34.160 to nineteen ninety If you shift more recently and look 0:05:34.160 --> 0:05:37.520 at nineteen seventy to twenty fifteen, it's two point one 0:05:37.600 --> 0:05:40.640 millimeters per year. If you just look at nineteen ninety 0:05:40.680 --> 0:05:44.479 three to twenty fifteen, it's three point two millimeters per year. 0:05:44.800 --> 0:05:46.680 If you just look at two thousand and six to 0:05:46.720 --> 0:05:50.720 twenty fifteen, it's three point six millimeters per year. So 0:05:50.920 --> 0:05:53.360 the later the period of the last century you look at, 0:05:53.400 --> 0:05:56.600 the more it is rising per year. Now you might 0:05:56.680 --> 0:05:59.800 reasonably wonder how do you actually measure sea level down 0:05:59.800 --> 0:06:02.440 to the millimeter? Like the top of the water is 0:06:02.480 --> 0:06:05.760 always moving, so that's a reasonable question. What methods do 0:06:05.839 --> 0:06:08.719 you have to know that the average level of the 0:06:08.760 --> 0:06:12.200 sea is rising. There are a couple of major metrics 0:06:12.240 --> 0:06:15.839 here cited, and I didn't fully know how these worked beforehand, 0:06:15.880 --> 0:06:19.600 so I thought this was interesting. One method used is 0:06:19.920 --> 0:06:24.599 tide gauges. These systems have been used in some form 0:06:24.760 --> 0:06:27.360 to record sea levels for hundreds of years, or at 0:06:27.400 --> 0:06:29.640 least going back I think to the early eighteen hundreds, 0:06:29.839 --> 0:06:33.200 though now they've changed form to incorporate different types of 0:06:33.240 --> 0:06:38.320 sensors and computers and other modern components, but they still 0:06:38.320 --> 0:06:41.239 have some things in common. So the old method here 0:06:41.800 --> 0:06:45.040 was that they would use a device called a stilling well, 0:06:45.160 --> 0:06:47.880 and this was basically a pipe about a foot wide 0:06:48.360 --> 0:06:51.680 that would be plunged down into the water from a 0:06:51.720 --> 0:06:55.000 place called a tide station, essentially a house built out 0:06:55.000 --> 0:06:58.080 on a dock, and this pipe would still the water 0:06:58.320 --> 0:07:02.000 around a floating device. The float would be suspended down 0:07:02.160 --> 0:07:05.039 into the well by a wire, and then that wire 0:07:05.080 --> 0:07:08.080 would be attached at the other end to a recording device, 0:07:08.120 --> 0:07:11.000 which might be something like a pin that would mark 0:07:11.080 --> 0:07:15.040 the water level automatically on a paper strip. So the 0:07:15.040 --> 0:07:17.280 float floats on the top of the water. As the 0:07:17.280 --> 0:07:20.240 water rises, the pin moves and marks that level on 0:07:20.520 --> 0:07:22.840 the paper strip. As the water goes down, the pin 0:07:23.000 --> 0:07:26.440 moves again, and then these marks were analyzed and averaged 0:07:26.480 --> 0:07:29.440 together to form a picture of the tidal variance and 0:07:29.600 --> 0:07:33.400 the average sea level over time. This method changed so 0:07:33.440 --> 0:07:36.560 that the data could be fed directly into computers and 0:07:36.920 --> 0:07:39.880 these tide stations also they had measuring staffs as well. 0:07:39.920 --> 0:07:43.160 You've probably seen things like this somewhere around the coast before, 0:07:43.520 --> 0:07:45.440 where it's just like a stick poking out of the water. 0:07:45.480 --> 0:07:47.760 It's basically a ruler, you know, It's got height markings 0:07:47.760 --> 0:07:51.240 on them, and then the operators could visually observe the 0:07:51.280 --> 0:07:54.640 staff and compare that to the mechanical readings from the 0:07:54.640 --> 0:07:58.200 float device. Now, tide gauges still exist and they still 0:07:58.240 --> 0:08:01.040 make readings, but they've got new system new types of 0:08:01.080 --> 0:08:05.040 sensors today to get their readings from. Modern tide gauges 0:08:05.280 --> 0:08:09.120 tend to use acoustic sounding tubes instead of a float 0:08:10.120 --> 0:08:13.679 and distilling well, so the acoustic sounding tube will admit 0:08:14.000 --> 0:08:16.880 will emit a sound wave from a fixed height and 0:08:16.920 --> 0:08:19.360 then wait for it to bounce off of the water's 0:08:19.360 --> 0:08:22.520 surface and come back. And the time to return of 0:08:22.560 --> 0:08:24.560 the signal allows you to calculate the height of the 0:08:24.600 --> 0:08:27.880 water across the tidal variants. So you can put in 0:08:27.960 --> 0:08:32.160 place these tide gauges in coastal environments all around the 0:08:32.160 --> 0:08:35.160 world and average them out to try to get some 0:08:35.440 --> 0:08:39.559 information about what the global sea levels are doing all 0:08:39.600 --> 0:08:42.280 around the world. And if you look at that information, 0:08:42.480 --> 0:08:45.200 it shows yes, indeed the sea levels have been rising. 0:08:45.280 --> 0:08:48.840 They've been rising over the last century along the lines 0:08:48.840 --> 0:08:51.840 of the measurements I mentioned a minute ago. But if 0:08:51.880 --> 0:08:54.240 you're able, you'd also want to compare that data to 0:08:54.320 --> 0:08:56.560 other sources of information to make sure you're getting the 0:08:56.559 --> 0:09:00.600 most accurate possible average. So there is another method is used, 0:09:01.040 --> 0:09:05.239 and that is altimetry. This is the use of satellite 0:09:05.320 --> 0:09:08.720 based tools called radar altimeters to measure the height of 0:09:08.760 --> 0:09:11.920 the sea. Basically, you can know the altitude of a 0:09:11.960 --> 0:09:14.640 satellite with a high degree of precision. You can track 0:09:14.679 --> 0:09:19.280 that with instruments like laser range rangefinders, like you bounce 0:09:19.280 --> 0:09:21.959 a laser off the satellite, so you can tell pretty 0:09:22.000 --> 0:09:25.840 much exactly how high it is. And then with that 0:09:26.000 --> 0:09:29.080 information in mind, you can use a satellite to send 0:09:29.120 --> 0:09:33.680 out a microwave pulse toward the Earth. That pulse bounces 0:09:33.720 --> 0:09:36.000 off of the surface of the ocean and then bounces 0:09:36.080 --> 0:09:39.720 back to the satellite and hits a return sensor, and 0:09:39.760 --> 0:09:42.960 then the satellite measures the time of the round trip 0:09:43.160 --> 0:09:47.080 between the emitter and the surface of the ocean to 0:09:47.160 --> 0:09:50.040 get a very precise measurement of the distance between the 0:09:50.040 --> 0:09:53.199 satellite and the water, which, again in combination with the 0:09:53.240 --> 0:09:56.400 precisely known altitude of the satellite, can be used to 0:09:56.440 --> 0:09:59.040 measure the level of the sea. And of course radar 0:09:59.120 --> 0:10:02.080 altimetry can be used to measure average sea level changes 0:10:02.120 --> 0:10:04.520 over time and get global averages and stuff, but it 0:10:04.559 --> 0:10:07.600 can be also used I thought this was interesting to 0:10:07.679 --> 0:10:12.240 measure variations in the height of the water around the 0:10:12.240 --> 0:10:15.760 world at the same time. So a kind of crazy 0:10:15.800 --> 0:10:18.760 thing about the ocean is that it is not at 0:10:18.800 --> 0:10:21.800 the same height everywhere on Earth all the time. That 0:10:22.360 --> 0:10:25.800 seems counterintuitive because you think of water and a container 0:10:25.880 --> 0:10:28.560 like a bowl or something eventually finding you know, finding 0:10:28.600 --> 0:10:31.559 its own level. It kind of levels out. But across 0:10:31.600 --> 0:10:35.400 the world's oceans there are peaks and valleys that arise 0:10:35.440 --> 0:10:38.880 in certain places at certain times, and so one example 0:10:38.920 --> 0:10:41.480 we're all familiar with is the tide. You know, the 0:10:41.520 --> 0:10:44.840 tide is caused mainly by gravity, by the gravitational influence 0:10:44.880 --> 0:10:47.560 of the moon, but also the Sun. But there are 0:10:47.600 --> 0:10:51.439 other factors that can cause local and sometimes temporary high 0:10:51.440 --> 0:10:54.319 and low altitudes of seawater as well. I was reading 0:10:54.320 --> 0:10:58.160 a report from NASA Earth Observatory about this and it 0:10:58.280 --> 0:11:01.600 mentioned friction caused by wind on the surface of the water, 0:11:01.720 --> 0:11:04.360 So like wind sort of dragging the water around and 0:11:04.400 --> 0:11:07.480 piling it up in certain places. I guess that's a 0:11:07.520 --> 0:11:09.680 crude way of describing it, but that is sort of 0:11:09.679 --> 0:11:14.240 what happens. There are also Coriolis effects and ocean currents, 0:11:14.760 --> 0:11:18.880 and there are also effects of variations in atmospheric pressure, 0:11:18.960 --> 0:11:21.960 so you know, the atmosphere pushing the surface of the 0:11:22.000 --> 0:11:24.680 water down in regions where the pressure is high and 0:11:24.720 --> 0:11:28.560 so forth. And we can measure these altitude variations across 0:11:28.559 --> 0:11:32.360 the ocean with the help of satellite based radar altimetry. 0:11:32.760 --> 0:11:35.720 As just one example of the variance in the height 0:11:35.800 --> 0:11:39.720 of the oceans around the world. According to NASA, the 0:11:39.800 --> 0:11:43.560 sea level in the Pacific Ocean is generally higher than 0:11:43.600 --> 0:11:47.600 the Atlantic Ocean, roughly twenty centimeters or about eight inches higher. 0:11:48.040 --> 0:11:51.600 How is that possible, Well, the volume of seawater is 0:11:51.640 --> 0:11:55.840 not static. Changes in the temperature and salinity of seawater 0:11:56.280 --> 0:12:01.600 affect its density, so warmer water generally is less dense, 0:12:01.760 --> 0:12:05.320 it takes up more space per unit of mass. The 0:12:05.360 --> 0:12:09.200 Pacific is on average warmer, so its volume is greater, 0:12:09.360 --> 0:12:12.840 and thus Pacific sea levels are higher, and other factors 0:12:12.840 --> 0:12:16.400 contribute like this as well. This kind of variation is 0:12:16.440 --> 0:12:20.280 actually acknowledged in the IPCC report where they say, quote 0:12:20.280 --> 0:12:24.439 sea level rise is not globally uniform and varies regionally. 0:12:24.679 --> 0:12:29.040 Thermal expansion, ocean dynamics, and land ice loss contributions will 0:12:29.080 --> 0:12:33.320 generate regional departures of about plus or minus thirty percent 0:12:33.559 --> 0:12:38.319 around the global means sea level rise, and those regional 0:12:38.400 --> 0:12:41.080 variations in changes in sea level I want to come 0:12:41.120 --> 0:12:42.160 back to that in a minute. 0:12:42.640 --> 0:12:42.880 Now. 0:12:42.920 --> 0:12:45.680 Of course, we all know the main cause of the 0:12:45.760 --> 0:12:49.320 current warming that is driving sea level rise is, of 0:12:49.360 --> 0:12:54.160 course what the IPCC report calls anthropogenic forcing. This means 0:12:54.400 --> 0:12:58.360 results of human activity, primarily the changing of the composition 0:12:58.440 --> 0:13:01.800 of the atmosphere it to trap more heat This is 0:13:01.920 --> 0:13:06.000 the famous greenhouse effect. Putting more things like carbon methane 0:13:06.040 --> 0:13:11.520 into the atmosphere increases the heat trapping potency of the atmosphere. 0:13:11.520 --> 0:13:24.400 It traps more heat the earth worms. So we know 0:13:24.520 --> 0:13:27.959 sea levels have been rising and they will continue to rise, 0:13:28.600 --> 0:13:33.040 but how much and how fast they rise is highly 0:13:33.160 --> 0:13:36.559 variable from our current point of view. So there are 0:13:36.559 --> 0:13:40.080 some estimates based on current data. According to the IPCC 0:13:40.280 --> 0:13:44.520 predictions relative to the mean sea level in the period 0:13:44.520 --> 0:13:47.040 from nineteen eighty six to two thousand and five, they 0:13:47.080 --> 0:13:51.080 predict that the global mean sea level will rise probably 0:13:51.120 --> 0:13:54.000 somewhere between zero point four to three meters or about 0:13:54.000 --> 0:13:57.440 one point four feet to zero point eight four meters, 0:13:57.679 --> 0:14:00.280 which is about two point eight feet, by the year 0:14:00.280 --> 0:14:03.520 twenty one hundred, and then due to a cascade of factors, 0:14:03.520 --> 0:14:06.400 sea levels will continued to rise for centuries after that, 0:14:06.480 --> 0:14:10.719 and we'll probably stay higher for thousands of hyears. Now, 0:14:10.760 --> 0:14:14.240 I wouldn't hang on those exact numbers too much because 0:14:14.440 --> 0:14:18.120 those are estimates. There are also averages of estimates, and 0:14:18.200 --> 0:14:20.840 I've seen other reports with different estimates, especially at the 0:14:20.920 --> 0:14:23.400 high end of like how bad could it possibly get 0:14:23.440 --> 0:14:27.240 if we just keep increasing more and more greenhouse gas emissions. 0:14:27.680 --> 0:14:30.280 But the important thing to note is that the high 0:14:30.360 --> 0:14:33.800 and low end projections here are dependent on the variable 0:14:33.800 --> 0:14:37.560 of human activity. So if we continue increasing the concentration 0:14:37.600 --> 0:14:41.160 of greenhouse gases in the atmosphere, we're somewhat closer to 0:14:41.200 --> 0:14:44.080 the top end of that range, and the low end 0:14:44.200 --> 0:14:48.240 is feasible if we drastically reduce greenhouse gas output and 0:14:48.320 --> 0:14:51.040 factor in some kind of negative emissions as well, such 0:14:51.040 --> 0:14:55.640 as massive natural or artificial carbon sequestration, and natural carbon 0:14:55.680 --> 0:15:00.600 sequestration would be trapping carbon in things like plants, forests. 0:15:01.720 --> 0:15:04.320 Yeah, so as is. I've heard a lot of experts 0:15:04.320 --> 0:15:08.600 say it's not that there isn't room for optimism in 0:15:08.640 --> 0:15:14.120 all of this, but the optimism does not come without action, Right, 0:15:14.600 --> 0:15:19.000 there are definite steps that need to be taken. We 0:15:19.040 --> 0:15:21.240 can't just be like, ah, it might be, it might 0:15:21.240 --> 0:15:22.840 be okay, maybe it's just gonna be the lower We'll 0:15:22.880 --> 0:15:24.400 just we'll roll the dice and see, like that's not 0:15:24.800 --> 0:15:25.920 how it's going to work out. 0:15:26.440 --> 0:15:29.560 Yeah, that's exactly right. The lower end of the prediction 0:15:29.760 --> 0:15:32.920 range there is based on an assumption of action. If 0:15:32.960 --> 0:15:37.840 humanity does something to massively reduce the contribution to global 0:15:37.840 --> 0:15:42.240 warming through greenhouse gases, So in that case, yes, we 0:15:42.280 --> 0:15:44.920 could limit it to the lower levels of sea level rise. 0:15:45.000 --> 0:15:48.160 But to be clear, some amount of sea level rise 0:15:48.160 --> 0:15:52.320 at this point has already happened and is basically locked in. 0:15:52.640 --> 0:15:56.360 The question is how much worse will it get? And 0:15:56.480 --> 0:15:59.120 that outcome is clearly dependent to a large extent on 0:15:59.200 --> 0:16:02.720 what we do. But in most plausible scenarios we can 0:16:02.800 --> 0:16:07.360 expect somewhere between something like one and three feet of 0:16:07.480 --> 0:16:10.840 global sea level rise by the end of this century. 0:16:11.680 --> 0:16:13.800 Now I mentioned there are other estimates I've come across. 0:16:13.800 --> 0:16:17.320 Some of these are specifically focused on like certain countries 0:16:17.480 --> 0:16:21.840 or regions, or might might be drawing on some emphasizing 0:16:21.840 --> 0:16:24.480 different data sources or something. But another estimate I came 0:16:24.520 --> 0:16:27.440 across was a twenty twenty two joint report by NASA, 0:16:27.880 --> 0:16:31.080 the NOAA, and several other federal agencies of the US 0:16:31.200 --> 0:16:34.520 government called Global and Regional Sea Level Rise Scenarios for 0:16:34.560 --> 0:16:37.520 the United States. This was an update to a previous 0:16:37.560 --> 0:16:41.720 report from twenty seventeen, and this report quote concludes that 0:16:41.840 --> 0:16:44.880 sea level along US coast lines will rise ten to 0:16:44.960 --> 0:16:48.840 twelve inches or twenty five to thirty centimeters on average 0:16:49.000 --> 0:16:53.600 above today's levels by twenty fifty, so that's predicting roughly 0:16:53.640 --> 0:16:56.080 a foot of increase by the middle of the century. 0:16:56.600 --> 0:16:59.520 Also on the more dire end, this one was predicting 0:17:00.560 --> 0:17:04.200 much higher levels of sea level rise at the basically 0:17:04.240 --> 0:17:07.040 at the letter rip scenario. It's just like do nothing 0:17:07.119 --> 0:17:09.840 scenario by the end of this century. If you want 0:17:09.840 --> 0:17:12.399 to experiment with the findings of this report, it actually 0:17:12.440 --> 0:17:15.159 has an online mapping tool you can look up you 0:17:15.200 --> 0:17:18.520 and mess around with yourself, called the Interagency Sea Level 0:17:18.640 --> 0:17:21.960 Rise Scenario Tool. You can google that and mess with 0:17:22.000 --> 0:17:25.080 it yourself if you want. Now, there are a couple 0:17:25.080 --> 0:17:28.800 of major contributors to the actual physical causes of sea 0:17:28.880 --> 0:17:31.360 level rise due to a warming climate. One of them 0:17:31.480 --> 0:17:35.800 is melting ice, melting glaciers and ice sheets. We've already 0:17:35.800 --> 0:17:38.200 talked about the role of melting ice in the sea 0:17:38.280 --> 0:17:41.000 level increases at the end of the Pleistocene, which were 0:17:41.040 --> 0:17:45.879 responsible for inundating Doggerland and Beringia, But there's still a 0:17:45.880 --> 0:17:49.320 lot of ice on Earth left to melt. Another important 0:17:49.320 --> 0:17:52.840 cause of sea level rise is the thermal expansion of water. 0:17:53.160 --> 0:17:54.960 Remember what I was talking about a minute ago, with 0:17:55.000 --> 0:17:57.439 the difference in the height of the Pacific Ocean versus 0:17:57.440 --> 0:18:00.760 the Atlantic Ocean. One factor there being that the Pacific 0:18:00.840 --> 0:18:04.760 Ocean waters on average are warmer. This stacks on top 0:18:04.840 --> 0:18:07.399 of the melting, but as water heats up, it becomes 0:18:07.520 --> 0:18:10.880 less dense and takes up more space. Warmer water takes 0:18:10.920 --> 0:18:14.200 up more space per unit of mass, so warmer oceans 0:18:14.280 --> 0:18:18.600 will be taller. And the thermal expansion of water plays 0:18:18.600 --> 0:18:22.560 a role already in a number of different phenomena that 0:18:22.600 --> 0:18:25.320 happened within the ocean, for example in the in the 0:18:25.359 --> 0:18:28.960 creation of ocean currents and in stratification of water levels 0:18:29.040 --> 0:18:32.000 within the ocean. Like warmer water floats on top of 0:18:32.080 --> 0:18:36.800 colder water, but anyway, as the Earth warms, the water 0:18:37.080 --> 0:18:40.320 thermally expands also, so that contributes to the sea level 0:18:40.320 --> 0:18:43.639 being higher. Now, what does this actually mean for the 0:18:43.720 --> 0:18:47.520 everyday life of people living in low lying coastal areas 0:18:47.640 --> 0:18:51.639 of planet Earth. I think one thing people sometimes like, 0:18:51.640 --> 0:18:53.639 if you haven't read much about this, you might have 0:18:53.680 --> 0:18:57.760 trouble imagining the form exactly this will take. Like you're 0:18:57.800 --> 0:19:01.040 just imagining the sea rising in a kind of static way, 0:19:01.200 --> 0:19:03.920 Like you know, it's either dry land or it's underwater. 0:19:04.000 --> 0:19:07.400 What's in between? There actually is something in between, which 0:19:07.480 --> 0:19:12.800 is frequent flooding. The way many people will probably experience 0:19:13.000 --> 0:19:16.639 sea level rise at first is an increase in the 0:19:16.680 --> 0:19:21.040 frequency and destructiveness of extreme weather events that are dependent 0:19:21.080 --> 0:19:23.720 on sea level for the amount of damage they cause. 0:19:24.280 --> 0:19:26.600 So a person who lives in a low lying coastal 0:19:26.600 --> 0:19:30.919 city will start dealing with storm related floods on a 0:19:31.000 --> 0:19:33.520 more and more frequent basis. What used to be a 0:19:33.600 --> 0:19:37.200 once in a century flood will become a regular occurrence, 0:19:37.400 --> 0:19:40.280 until at some point the flooding becomes so common that 0:19:40.320 --> 0:19:44.439 people may start to simply consider a place uninhabitable. And 0:19:44.640 --> 0:19:48.359 this happens before that place is more or less permanently underwater, 0:19:48.720 --> 0:19:51.720 But that eventually happens too. Of course, this kind of 0:19:51.760 --> 0:19:55.679 flooding and water encroachment, it comes with all kinds of 0:19:55.720 --> 0:20:00.680 consequences of massive economic damage, destruction of property, destruction of life, livelihoods, 0:20:01.000 --> 0:20:04.080 displacement of people, and all of the downstream effects of that. 0:20:05.240 --> 0:20:08.240 But another factor people might not think about are the 0:20:08.280 --> 0:20:13.080 effects of the ingress of salt water into places with 0:20:13.200 --> 0:20:16.920 freshwater resources, like into river deltas and so forth. Of course, 0:20:17.000 --> 0:20:19.840 this can have negative effects on habitats and wildlife, but 0:20:19.920 --> 0:20:23.080 also on agriculture and groundwater and all that. You don't 0:20:23.080 --> 0:20:25.639 want to salt your earth. But to come back to 0:20:25.720 --> 0:20:30.199 an issue I raised earlier, an interesting factor contributing to 0:20:30.320 --> 0:20:34.080 the coming inundation of coastal areas and especially coastal cities, 0:20:34.640 --> 0:20:38.399 is that not only are sea levels definitely rising around 0:20:38.400 --> 0:20:42.159 the globe and differently in different places, in some places 0:20:42.359 --> 0:20:46.439 the ground is literally sinking. The lands are not just 0:20:46.560 --> 0:20:49.639 metaphorically sunken because the water covers them, they are quite 0:20:49.680 --> 0:20:53.600 literally directly sunken. The land is going down. So you 0:20:53.720 --> 0:20:56.159 might have a coastal city that is experiencing more and 0:20:56.200 --> 0:20:59.800 more frequent flooding during storm surges as the sea grows taller, 0:20:59.840 --> 0:21:03.280 But also the ground level of the city is several 0:21:03.359 --> 0:21:07.240 millimeters lower every year, which makes the relative sea level 0:21:07.320 --> 0:21:11.800 rise even worse. Now, how is that possible? Well, there 0:21:11.800 --> 0:21:14.359 are multiple causes, but I was reading about this in 0:21:14.440 --> 0:21:17.560 a major One of the causes seems to be the 0:21:17.640 --> 0:21:23.680 extraction of ground water from underlying aquifers. Especially you're extracting 0:21:23.720 --> 0:21:27.280 it faster than those aquifers are replenished, and as the 0:21:27.280 --> 0:21:31.760 water is extracted, it creates these voids underground. These voids 0:21:31.840 --> 0:21:35.560 grow the soil gets compressed, especially if you're putting a 0:21:35.560 --> 0:21:38.000 bunch of heavy stuff on the soil, such as a 0:21:38.040 --> 0:21:40.840 city like building on top of it, and then that 0:21:41.000 --> 0:21:44.560 compressing of the ground and the compressing into the voids 0:21:44.600 --> 0:21:49.320 below essentially means the city literally starts to sink. And 0:21:49.440 --> 0:21:51.520 this is happening to cities all around the world. I 0:21:51.560 --> 0:21:56.159 was reading a really interesting article that addresses this issue. 0:21:56.280 --> 0:21:59.840 It's in Wired by Matt Simon called sea level rise 0:22:00.119 --> 0:22:05.160 be catastrophic and unequal. So this article is emphasizing again 0:22:05.200 --> 0:22:08.440 that the global means sea level rise estimates are averages. 0:22:08.560 --> 0:22:12.080 In specific places, the problem could be not as bad 0:22:12.359 --> 0:22:17.800 or much much worse. Simon writes, quote Galveston, Texas, where 0:22:17.800 --> 0:22:21.000 the land is slumping, could see almost two feet of 0:22:21.080 --> 0:22:24.960 rise by the year twenty fifty. Meanwhile, Anchorage, Alaska could 0:22:25.000 --> 0:22:28.280 see eight inches of sea level drop thanks to the 0:22:28.280 --> 0:22:32.160 fact that its land is actually rising following the departure 0:22:32.240 --> 0:22:37.520 of long gone glaciers. So why is Galveston, Texas sinking 0:22:37.600 --> 0:22:41.359 relative to the sea level, he says, Mainly, there are 0:22:41.359 --> 0:22:44.879 two causes here, and they're both related to the extraction 0:22:45.080 --> 0:22:48.679 of liquids from underground reservoirs. One is the extraction of 0:22:48.720 --> 0:22:52.600 water and the other is oil extraction of oil. And 0:22:52.680 --> 0:22:55.119 this is true in many places as a result of 0:22:55.160 --> 0:22:58.920 the combination of global sea level rise and land subsidence. 0:22:59.440 --> 0:23:01.240 Some of the areas of the world that are going 0:23:01.280 --> 0:23:04.560 to be the hardest hit by the greatest relative local 0:23:04.600 --> 0:23:07.240 sea level rise are on the Gulf Coast of the 0:23:07.320 --> 0:23:10.199 United States, the Gulf Coast, because they're suffering both of 0:23:10.200 --> 0:23:12.240 these at the same time. The land is going down 0:23:12.280 --> 0:23:15.280 and the sea is coming up. Simon in this article 0:23:15.359 --> 0:23:18.199 quotes a guy named Bob Stokes who is president of 0:23:18.280 --> 0:23:23.000 the conservation nonprofit called the Galveston Bay Foundation, and he 0:23:23.080 --> 0:23:26.120 tells a story that I thought was wild. So this 0:23:26.160 --> 0:23:29.199