1 00:00:02,040 --> 00:00:07,240 Speaker 1: Welcome to brain stuff from how stuff Works a brain stuff, 2 00:00:07,240 --> 00:00:10,240 Speaker 1: I'm Christian Sager. When the ancient Romans arrived at the 3 00:00:10,280 --> 00:00:13,239 Speaker 1: Caspian Sea a couple of thousand years ago, they thought 4 00:00:13,320 --> 00:00:16,520 Speaker 1: they'd arrived at an ocean. That's because the water they 5 00:00:16,600 --> 00:00:23,880 Speaker 1: encountered was salty. Nestled amongst modern day Russia, Kazakhstan, Turkmenistan, Azerbaijan, 6 00:00:24,280 --> 00:00:29,760 Speaker 1: and Iran, the Caspian Sea actually is the world's largest lake. 7 00:00:30,320 --> 00:00:35,160 Speaker 1: For comparison, Lake Superior is the world's largest freshwater lake, 8 00:00:35,360 --> 00:00:38,720 Speaker 1: with the surface area of thirty one thousand, seven hundred 9 00:00:38,960 --> 00:00:43,040 Speaker 1: square miles or eighty two thousand, one hundred square kilometers. 10 00:00:43,400 --> 00:00:48,000 Speaker 1: The Caspian Sea occupies a space significantly larger, at a 11 00:00:48,120 --> 00:00:51,680 Speaker 1: hundred and forty three thousand, two hundred square miles or 12 00:00:52,080 --> 00:00:56,000 Speaker 1: three hundred and seventy one thousand square kilometers for a 13 00:00:56,120 --> 00:01:00,520 Speaker 1: US reference, that's like comparing the sizes of Maryland and Montana. 14 00:01:01,240 --> 00:01:05,000 Speaker 1: The Caspian seas waters are brackish, about a third as 15 00:01:05,040 --> 00:01:09,200 Speaker 1: salty as most ocean water. Because the water finds its 16 00:01:09,240 --> 00:01:12,039 Speaker 1: way into it from about a hundred and thirty different 17 00:01:12,080 --> 00:01:16,560 Speaker 1: freshwater sources. It has no outlet. If water is going 18 00:01:16,600 --> 00:01:19,200 Speaker 1: to escape the Caspian Sea, it's got to do it 19 00:01:19,360 --> 00:01:22,920 Speaker 1: through evaporation. So it's strange that the water level of 20 00:01:22,959 --> 00:01:25,720 Speaker 1: the Caspian Sea has been steadily dropping for the past 21 00:01:25,800 --> 00:01:29,800 Speaker 1: couple of decades. Between nineteen six and two thousand and fifteen, 22 00:01:30,120 --> 00:01:33,839 Speaker 1: the sea has drawn down about three inches or seven 23 00:01:33,880 --> 00:01:38,000 Speaker 1: centimeters per year. That's about five ft or one point 24 00:01:38,080 --> 00:01:41,680 Speaker 1: five meters total. This is not the first time water 25 00:01:41,800 --> 00:01:45,320 Speaker 1: levels in the Caspian have dramatically dropped. Over the course 26 00:01:45,319 --> 00:01:49,480 Speaker 1: of the twenty century. Changes in agricultural practices in its basin, 27 00:01:49,800 --> 00:01:52,560 Speaker 1: as well as industry in damming in the Vulgar River, 28 00:01:52,720 --> 00:01:55,360 Speaker 1: which accounts for eighty percent of the inflow of water, 29 00:01:55,800 --> 00:01:58,760 Speaker 1: all of it pulled the seed down the three feet 30 00:01:59,080 --> 00:02:02,080 Speaker 1: or one me or below what it is today by 31 00:02:02,080 --> 00:02:06,080 Speaker 1: the late nineteen seventies. But a new study published in 32 00:02:06,240 --> 00:02:11,080 Speaker 1: Geophysical Research Letters finds that the Caspian seas current shrinking 33 00:02:11,520 --> 00:02:15,600 Speaker 1: is due to the water simply evaporating away, driven by 34 00:02:15,639 --> 00:02:20,320 Speaker 1: increasing average atmospheric temperatures. The researchers found that between the 35 00:02:20,360 --> 00:02:24,280 Speaker 1: two time frames they studied the years between nineteen seventy 36 00:02:24,320 --> 00:02:29,560 Speaker 1: nine and nine, and then again between nine and fifteen, 37 00:02:30,120 --> 00:02:34,720 Speaker 1: the average yearly air temperatures directly above the sea rose 38 00:02:34,880 --> 00:02:40,680 Speaker 1: by about one point eight degrees fahrenheit or one degree celsius. Now. 39 00:02:40,880 --> 00:02:44,680 Speaker 1: Co author Clark Wilson said, what really controls the sea 40 00:02:44,720 --> 00:02:47,520 Speaker 1: going up and down over long periods of time is 41 00:02:47,680 --> 00:02:52,840 Speaker 1: most likely evaporation, which is almost completely dominated by temperature. 42 00:02:53,360 --> 00:02:56,800 Speaker 1: This study is the first to provide convincing evidence that 43 00:02:56,880 --> 00:03:01,000 Speaker 1: the Caspian Seas water levels are changing due to evaporation 44 00:03:01,360 --> 00:03:04,840 Speaker 1: and a changing climate, rather than things like changes in 45 00:03:04,960 --> 00:03:09,959 Speaker 1: river discharge or rainfall. If the trend continues, evaporation will 46 00:03:09,960 --> 00:03:13,280 Speaker 1: have the biggest impact on the shallowest parts of the 47 00:03:13,320 --> 00:03:16,440 Speaker 1: sea first. Much of the water at the sea's northern tip, 48 00:03:16,480 --> 00:03:20,240 Speaker 1: for instance, is only about sixteen feet or five meters deep. 49 00:03:20,600 --> 00:03:24,919 Speaker 1: At this rate of evaporation, that portion will disappear within 50 00:03:25,080 --> 00:03:29,640 Speaker 1: seventy five years. Cities currently located on the shore would 51 00:03:29,680 --> 00:03:33,720 Speaker 1: quite quickly become landlocked as waters recede, and many of 52 00:03:33,760 --> 00:03:38,440 Speaker 1: these population centers derive significant economic value from the sea, 53 00:03:38,800 --> 00:03:43,840 Speaker 1: from tourism to fishing to shipping. Additionally, the Caspian Sea 54 00:03:43,960 --> 00:03:47,520 Speaker 1: is home to some pretty crazy ancient animals that would 55 00:03:47,560 --> 00:03:50,880 Speaker 1: be out of a home if the sea disappeared. The 56 00:03:50,960 --> 00:03:54,960 Speaker 1: Caspian was part of the Teta's Ocean about three hundred 57 00:03:55,000 --> 00:03:58,760 Speaker 1: million years ago. Relatives of some of those species remain, 58 00:03:59,000 --> 00:04:06,480 Speaker 1: including a whopping of the world's caviare producing and endangered sturgeon. 59 00:04:12,000 --> 00:04:16,400 Speaker 1: Today's episode was written by Jesslyn Shields, produced by Dylan Fagan, 60 00:04:16,720 --> 00:04:19,760 Speaker 1: and For more on this and other topics, please visit 61 00:04:19,839 --> 00:04:31,919 Speaker 1: us at how stup works dot com.