WEBVTT 00:00:11.360 --> 00:00:16.879 lost in the fog of a cosmic storm floating on 00:00:16.879 --> 00:00:21.120 whimsical wavelengths is the norm dancing through 00:00:21.120 --> 00:00:27.379 the stars chasing spectrums of light riding the 00:00:27.379 --> 00:00:32.390 waves that are just out It's solo time. Time 00:00:32.390 --> 00:00:34.750 to tackle a particular topic that is difficult 00:00:34.750 --> 00:00:37.969 to explore as an interview. And I have enough 00:00:37.969 --> 00:00:40.689 background to go down this rabbit hole solo style. 00:00:41.469 --> 00:00:45.350 Volcanoes and climate. But it's also the last 00:00:45.350 --> 00:00:48.490 episode of the season. So let's do some cleanup. 00:00:48.890 --> 00:00:53.490 Season two was amazing. Learning the craft. Growing 00:00:53.490 --> 00:00:57.130 as a podcaster, learning search engine optimization, 00:00:57.429 --> 00:00:59.929 social media, and getting better at science communication. 00:01:00.789 --> 00:01:03.310 Not to mention building networks and the wonderful 00:01:03.310 --> 00:01:05.790 guests. I've learned so much from them, and I 00:01:05.790 --> 00:01:09.269 hope so that you have as well. They're the real 00:01:09.269 --> 00:01:14.109 stars of the show. It is their work that is presented 00:01:14.109 --> 00:01:17.670 here. I wanted an outlet when I started this 00:01:17.670 --> 00:01:22.079 to explore science. Learn new things. and have 00:01:22.079 --> 00:01:25.640 new avenues to view the natural world. To be 00:01:25.640 --> 00:01:28.019 honest, this process of making whimsical wavelengths 00:01:28.019 --> 00:01:30.400 is harder than I expected, but at the same time 00:01:30.400 --> 00:01:33.920 rewarding. I even won an award for podcast of 00:01:33.920 --> 00:01:35.719 the year in the science category from the American 00:01:35.719 --> 00:01:41.359 Writing Awards and PopCom conference in Indianapolis 00:01:41.359 --> 00:01:44.900 as well in science and technology. In the many 00:01:44.900 --> 00:01:46.840 seasons to come, I hope to continue to grow, 00:01:46.959 --> 00:01:49.319 learn new things, get better at making engaging 00:01:49.319 --> 00:01:53.640 deep -dive science content, maybe add a few new 00:01:53.640 --> 00:01:56.340 tools, and perhaps find new ways to grow the 00:01:56.340 --> 00:02:01.519 podcast. That process involves you as the listener. 00:02:02.219 --> 00:02:05.780 We've had one podcast episode that was completely 00:02:05.780 --> 00:02:10.479 spawned by a suggestion. Perhaps there will be 00:02:10.479 --> 00:02:13.330 many more. Once there's enough of a community 00:02:13.330 --> 00:02:16.050 surrounding the show, perhaps an Ask Me Anything 00:02:16.050 --> 00:02:18.870 episode? I don't know. The point is that the 00:02:18.870 --> 00:02:23.590 show will continue to evolve. So there will be 00:02:23.590 --> 00:02:27.449 three Encore episodes to get through the rest 00:02:27.449 --> 00:02:31.530 of summer. And come mid -September, Season 3 00:02:31.530 --> 00:02:35.569 will start. The current peg or date for that 00:02:35.569 --> 00:02:40.900 is September 14th. Hopefully I can stick to that 00:02:40.900 --> 00:02:44.280 as long as real life doesn't get too much in 00:02:44.280 --> 00:02:47.159 the way. But I'm pretty sure we should be able 00:02:47.159 --> 00:02:50.900 to make that September 14th to be that seasonal 00:02:50.900 --> 00:02:55.139 tradition for whimsical wavelengths. Today, though, 00:02:55.219 --> 00:02:57.240 I wanted to look at one of the many climate myths 00:02:57.240 --> 00:03:00.680 that is thrown out there by those who don't like 00:03:00.680 --> 00:03:06.039 data. People who want to believe something. is 00:03:06.039 --> 00:03:09.479 false because it's against their ideology. Well, 00:03:09.560 --> 00:03:15.500 actually, I'm not entirely sure why people believe 00:03:15.500 --> 00:03:17.900 this, especially because it can be disproven. 00:03:18.840 --> 00:03:21.620 In this episode, we'll do just that, and we'll 00:03:21.620 --> 00:03:23.539 learn a little bit about volcanology and climate 00:03:23.539 --> 00:03:27.900 along the way. The claim that we are dealing 00:03:27.900 --> 00:03:30.860 with today, which we know is scientifically false, 00:03:31.020 --> 00:03:36.530 volcanoes emit... more carbon dioxide than humans 00:03:36.530 --> 00:03:41.370 do. That is a complete and utter false statement. 00:03:41.629 --> 00:03:45.610 Volcanoes emit way less than what we humans do. 00:03:46.069 --> 00:03:47.750 Now where to start with this? I guess I should 00:03:47.750 --> 00:03:52.229 state a USGS scientist, Dr. Terry Gerlach, detailed 00:03:52.229 --> 00:03:57.370 this in stark detail in his 2011 paper. And to 00:03:57.370 --> 00:04:03.110 be frank, this episode follows much of his paper. 00:04:03.879 --> 00:04:08.159 And we'll probably be returning to his conclusions 00:04:08.159 --> 00:04:12.080 several times throughout the paper. If not explicitly, 00:04:12.460 --> 00:04:17.300 but then implicitly. So, let's begin with volcanoes 00:04:17.300 --> 00:04:21.000 emit gas. And that gas can basically fumigate 00:04:21.000 --> 00:04:24.519 the area downwind. A caustic mix of gases. The 00:04:24.519 --> 00:04:27.639 three most important volatiles or gases in magma 00:04:27.639 --> 00:04:31.600 are water, carbon dioxide, and sulfur dioxide. 00:04:31.759 --> 00:04:36.399 In that order. There are other trace gases like 00:04:36.399 --> 00:04:39.500 hydrogen fluoride, hydrogen chloride, but they're 00:04:39.500 --> 00:04:42.160 at much smaller amounts, and we'll leave those 00:04:42.160 --> 00:04:45.600 aside, as they don't affect the whole calculation 00:04:45.600 --> 00:04:48.379 of trying to figure out how much carbon dioxide 00:04:48.379 --> 00:04:54.579 is degassed by volcanoes worldwide. So to look 00:04:54.579 --> 00:04:58.560 at how we know volcanoes have a smaller footprint 00:04:58.560 --> 00:05:01.720 or factor when it comes to greenhouse gases than 00:05:01.720 --> 00:05:04.560 human emissions, we need to understand several 00:05:04.560 --> 00:05:08.240 things. First, how much carbon dioxide should 00:05:08.240 --> 00:05:11.899 be in the magma? How much magma is degassed each 00:05:11.899 --> 00:05:17.139 year? And thirdly, how much do humans emit? So 00:05:17.139 --> 00:05:20.319 let's start with one. How much carbon dioxide 00:05:20.319 --> 00:05:23.529 should be in the magma? Well, how much gas in 00:05:23.529 --> 00:05:26.670 total? Like, the total number of volatiles. The 00:05:26.670 --> 00:05:28.509 logic goes, if we can estimate the amount of 00:05:28.509 --> 00:05:31.689 gas in the magma, then all we need to do is figure 00:05:31.689 --> 00:05:34.810 out how much degas is every year on average, 00:05:34.930 --> 00:05:36.990 and we'll have a good estimate of the number. 00:05:37.850 --> 00:05:41.850 There's a lot of nuance in all of this data and 00:05:41.850 --> 00:05:44.410 numbers, which will hopefully become apparent. 00:05:44.829 --> 00:05:47.980 A common theme in... the volcano episodes here 00:05:47.980 --> 00:05:51.699 on Whimsical Wavelengths, is that magma or lava 00:05:51.699 --> 00:05:56.720 is not a simple liquid. Today we will bypass 00:05:56.720 --> 00:06:01.180 the rheology or how magma and lava flows and 00:06:01.180 --> 00:06:05.459 moves to look more at the chemistry. Because 00:06:05.459 --> 00:06:09.519 this is not like, say, water from the tap. There 00:06:09.519 --> 00:06:12.519 are many different chemical constituencies in 00:06:12.519 --> 00:06:16.620 magma, the biggest of which is... sulfur dioxide, 00:06:17.079 --> 00:06:21.199 taking up just less than half, so 50%, all the 00:06:21.199 --> 00:06:27.579 way up to 75 % of the weight of magma. Gases 00:06:27.579 --> 00:06:29.920 or volatiles make up somewhere between 1 and 00:06:29.920 --> 00:06:31.920 7 weight percent, depending on the environment. 00:06:32.199 --> 00:06:34.860 And we'll kind of dive into that in just a minute 00:06:34.860 --> 00:06:41.339 or two. So, how do we know that, you ask? Well... 00:06:41.639 --> 00:06:44.579 This is the why I wanted to do this episode, 00:06:44.680 --> 00:06:48.459 to explain how we get to the conclusion. It isn't 00:06:48.459 --> 00:06:50.680 built in a vacuum or a black box. It's based 00:06:50.680 --> 00:06:53.639 on a series of real -world discoveries and advancements 00:06:53.639 --> 00:06:57.500 that were completely unrelated to climate change 00:06:57.500 --> 00:07:01.240 or climate science. It really was all about the 00:07:01.240 --> 00:07:05.300 volcanoes. For this first rung of the ladder 00:07:05.300 --> 00:07:07.939 that gets us towards the final conclusion, let's 00:07:07.939 --> 00:07:10.220 continue with the geochemistry of the rocks and 00:07:10.220 --> 00:07:14.389 then... melt inclusion geochemistry. So we can 00:07:14.389 --> 00:07:17.589 get whole rock geochemistry grinding up the rock 00:07:17.589 --> 00:07:20.209 into a powder and then running it through an 00:07:20.209 --> 00:07:24.930 x -ray fluorescent spectrometer. Basically, we 00:07:24.930 --> 00:07:26.889 hit it with wavelengths. You can think of the 00:07:26.889 --> 00:07:29.930 result here of what the magma chemistry would 00:07:29.930 --> 00:07:33.629 be if the rock was melted. For volcanic rocks, 00:07:33.850 --> 00:07:37.300 would it be the actual magma chemistry? The answer 00:07:37.300 --> 00:07:39.079 is no. Without getting into the weeds about how 00:07:39.079 --> 00:07:40.939 magmas change and evolve as they move towards 00:07:40.939 --> 00:07:44.899 the surface, what is really missing is the volatiles. 00:07:45.160 --> 00:07:48.759 The gas. Like a pop bottle that you shook. When 00:07:48.759 --> 00:07:51.959 the magma gets close enough to the surface, it 00:07:51.959 --> 00:07:54.439 is like the lid is unscrewed and gas is released. 00:07:55.680 --> 00:07:58.660 Because the pressure dropped. The material after 00:07:58.660 --> 00:08:01.339 an eruption has much less gas in it. It came 00:08:01.339 --> 00:08:03.639 out of solution and was carried away in the wind. 00:08:04.360 --> 00:08:06.579 I think I did a pretty good job back at the beginning 00:08:06.579 --> 00:08:10.300 of this season, Season 2, Episode 1, when discussing 00:08:10.300 --> 00:08:13.660 Messiah Volcano with this topic. So if you want 00:08:13.660 --> 00:08:16.279 a deep dive with respect to volcanic behavior, 00:08:16.620 --> 00:08:20.720 revisit that episode. Unfortunately, magma is 00:08:20.720 --> 00:08:23.519 much more complicated than a bottle of soda. 00:08:24.639 --> 00:08:27.699 Soda, we only need to worry about water, pressure, 00:08:27.860 --> 00:08:30.920 and carbon dioxide. Magma has lots of different 00:08:30.920 --> 00:08:33.360 chemical constituencies and volatiles, and it 00:08:33.360 --> 00:08:36.919 changes. As far as volatiles or gas, they all 00:08:36.919 --> 00:08:39.679 have different solubilities as well. So that's 00:08:39.679 --> 00:08:42.019 the ability of a particular substance to stay 00:08:42.019 --> 00:08:45.460 in solution inside a liquid. Sulfur dioxide, 00:08:45.720 --> 00:08:47.720 for instance, comes out of solution quite late. 00:08:48.039 --> 00:08:51.580 If you detect sulfur dioxide, you know magma 00:08:51.580 --> 00:08:54.279 is close to the surface. Carbon dioxide, on the 00:08:54.279 --> 00:08:56.899 other hand, is less soluble. Not too long ago, 00:08:56.919 --> 00:08:59.080 we looked at carbon dioxide flux with Gaetano 00:08:59.080 --> 00:09:02.779 in episode 18 for Kilauea and its deep magmatic 00:09:02.779 --> 00:09:06.970 system. And in Kilauea, the carbon dioxide starts 00:09:06.970 --> 00:09:09.529 to exolve and come out of solution around 35 00:09:09.529 --> 00:09:14.549 kilometers beneath the Earth's surface. And that's 00:09:14.549 --> 00:09:17.710 deep. For today, and this topic, showing humans 00:09:17.710 --> 00:09:19.909 are releasing more carbon dioxide than volcanoes, 00:09:20.350 --> 00:09:23.629 this is a bit of a wrinkle. It's a lot easier 00:09:23.629 --> 00:09:27.149 to monitor sulfur dioxide degassing. It happens 00:09:27.149 --> 00:09:29.309 when everything is quite close to the surface, 00:09:29.350 --> 00:09:32.899 so carbon dioxide... We need to dig a little 00:09:32.899 --> 00:09:36.320 bit more. Remember, I have already divided this 00:09:36.320 --> 00:09:38.340 episode into three, and this first part is all 00:09:38.340 --> 00:09:41.419 about how much carbon dioxide should be in the 00:09:41.419 --> 00:09:45.200 magma. I actually should have phrased it, how 00:09:45.200 --> 00:09:50.080 much is in the magma, and how much gets degassed. 00:09:50.500 --> 00:09:53.580 So, to get that number, we need a time capsule. 00:09:53.679 --> 00:09:57.379 We need to find magma before it ever had a chance 00:09:57.379 --> 00:10:02.929 to pop the top, or... get out close to the surface 00:10:02.929 --> 00:10:07.350 and lose its gas. In volcanology, we look for 00:10:07.350 --> 00:10:11.169 what we call primitive magmas. I've already alluded 00:10:11.169 --> 00:10:14.269 to this, sort of. As magma travels through the 00:10:14.269 --> 00:10:17.870 crust and cools and changes, different crystals 00:10:17.870 --> 00:10:21.610 form and change the concentration of what's left 00:10:21.610 --> 00:10:24.210 in the melt. Basically, all magma that erupts 00:10:24.210 --> 00:10:27.049 onto the surface has changed somewhat on its 00:10:27.049 --> 00:10:30.539 journey. A primitive melt rises quickly from 00:10:30.539 --> 00:10:32.799 the mantle without significant changes to its 00:10:32.799 --> 00:10:35.080 chemistry. The reason why these primitive melts 00:10:35.080 --> 00:10:37.860 are so valuable is we can use them to understand 00:10:37.860 --> 00:10:41.580 the original chemistries of the magma. And for 00:10:41.580 --> 00:10:44.659 this topic, we can get close to the original 00:10:44.659 --> 00:10:48.600 concentrations of carbon dioxide because of melt 00:10:48.600 --> 00:10:51.879 inclusions. Imagine a crystal, usually olive 00:10:51.879 --> 00:10:54.590 ink, growing deep underground. As it grows, it 00:10:54.590 --> 00:10:58.169 occasionally traps a tiny droplet of the surrounding 00:10:58.169 --> 00:11:01.710 liquid magma inside its structure. Because that 00:11:01.710 --> 00:11:04.509 olivine crystal is incredibly strong, it acts 00:11:04.509 --> 00:11:08.309 like a microscopic pressure vesicle. It keeps 00:11:08.309 --> 00:11:11.409 that little drop of magma under the same intense 00:11:11.409 --> 00:11:15.649 pressure it felt many kilometers or miles below 00:11:15.649 --> 00:11:18.929 the surface, preventing the volatiles like carbon 00:11:18.929 --> 00:11:21.889 dioxide from escaping. But even these little 00:11:21.889 --> 00:11:25.200 time capsules... Kind of a bubble problem. As 00:11:25.200 --> 00:11:28.299 magma is erupted, it cools. The liquid inside 00:11:28.299 --> 00:11:30.980 that little time capsule of a crystal shrinks 00:11:30.980 --> 00:11:35.080 and a tiny vapor bubble forms. Because carbon 00:11:35.080 --> 00:11:41.019 dioxide is so unhappy or incompatible or insoluble 00:11:41.019 --> 00:11:43.820 in the liquid, almost all of it, sometimes up 00:11:43.820 --> 00:11:47.240 to 90%, comes out of solution into that tiny 00:11:47.240 --> 00:11:49.659 little bubble. And quite frankly, for a long 00:11:49.659 --> 00:11:51.940 time, we were underestimating volcanic carbon 00:11:51.940 --> 00:11:55.139 dioxide. that comes from these volcanoes because 00:11:55.139 --> 00:11:58.019 we're only measuring the carbon dioxide in the 00:11:58.019 --> 00:11:59.919 glass in the melt inclusion and ignoring the 00:11:59.919 --> 00:12:03.820 bubble. Today we use Raman spectroscopy, basically 00:12:03.820 --> 00:12:05.720 hitting that bubble with a laser, I mean wavelengths, 00:12:05.919 --> 00:12:09.799 to measure the density or concentration of the 00:12:09.799 --> 00:12:13.440 gas inside. By adding the gas in the bubble back 00:12:13.440 --> 00:12:17.960 into the gas in the glass, we get a truer concentration, 00:12:18.460 --> 00:12:22.080 original concentration of carbon dioxide. when 00:12:22.080 --> 00:12:24.740 that magma was entrapped by the olivine crystal 00:12:24.740 --> 00:12:28.539 it is important to note that this must still 00:12:28.539 --> 00:12:32.159 be treated as a minimum as carbon dioxide could 00:12:32.159 --> 00:12:35.659 have degassed before it was captured from the 00:12:35.659 --> 00:12:39.580 melt one would think that primitive melts something 00:12:39.580 --> 00:12:42.139 that can go from the mantle to the earth's surface 00:12:42.139 --> 00:12:45.820 relatively quickly with very little changes are 00:12:45.820 --> 00:12:52.129 rare so what happens when we can't find good 00:12:52.129 --> 00:12:55.730 primitive melt inclusions. Well, now we have 00:12:55.730 --> 00:12:58.429 to use different techniques, like the geochemical 00:12:58.429 --> 00:13:01.289 buddy system. We look at the ratio of carbon 00:13:01.289 --> 00:13:03.870 dioxide to elements that behave similarly but 00:13:03.870 --> 00:13:07.990 don't turn into a gas, like niobium, Nb on the 00:13:07.990 --> 00:13:11.669 periodic table, or barium. In the mantle, the 00:13:11.669 --> 00:13:15.809 ratio of carbon dioxide to niobium is fairly 00:13:15.809 --> 00:13:20.230 consistent and constant. Since niobium doesn't 00:13:20.639 --> 00:13:24.139 degas when the pressure drops, we can measure 00:13:24.139 --> 00:13:28.059 the niobium in an erupted rock and use that mantle 00:13:28.059 --> 00:13:31.200 ratio to calculate exactly how much carbon dioxide 00:13:31.200 --> 00:13:34.220 should have been there before the eruption started. 00:13:34.759 --> 00:13:39.700 Okay, we can also do this with hydrogen -3 ratios 00:13:39.700 --> 00:13:44.779 as well, but we need to really make sure we understand 00:13:44.779 --> 00:13:48.220 something because the steps to back out carbon 00:13:48.750 --> 00:13:51.950 Dioxide concentration of magma only really works 00:13:51.950 --> 00:13:55.250 in your typical basaltic systems. Think mid -ocean 00:13:55.250 --> 00:13:57.769 ridges like the Atlantic Ridge or the Nazca Ridge 00:13:57.769 --> 00:14:01.470 or ocean island basalts, like hotspots, so Hawaii, 00:14:01.610 --> 00:14:04.529 Galapagos Island, Piton Franais. And when we 00:14:04.529 --> 00:14:07.289 apply these methods to primitive basaltic magmas 00:14:07.289 --> 00:14:11.070 globally, we find mid -ocean ridge basalts come 00:14:11.070 --> 00:14:17.730 up between 0 .05 and 0 .25%. carbon dioxide. 00:14:17.830 --> 00:14:20.389 And for hot spots, like Hawaii, somewhere between 00:14:20.389 --> 00:14:26.110 0 .5 and 1 .5 weight percent CO2. It might sound 00:14:26.110 --> 00:14:28.110 like a lot, but when you do the math on how much 00:14:28.110 --> 00:14:30.049 magma actually reaches the surface each year, 00:14:30.169 --> 00:14:33.529 don't worry, we'll get there. But let's go back 00:14:33.529 --> 00:14:36.330 to subduction zones, because subduction zones 00:14:36.330 --> 00:14:38.870 are a lot trickier. First, getting primitive 00:14:38.870 --> 00:14:41.169 melt inclusions are basically never found, because 00:14:41.169 --> 00:14:44.909 the chemistry is so different due to the way 00:14:45.700 --> 00:14:50.279 melting is caused. In mid -Atlantic ridge or 00:14:50.279 --> 00:14:53.919 ocean island hot spots like Hawaii, it's primarily 00:14:53.919 --> 00:14:57.120 due to depressurization. Either as you split 00:14:57.120 --> 00:14:59.100 the rocks apart, you lower the pressure and you 00:14:59.100 --> 00:15:02.159 cause melting, or in the case of a hot mantle 00:15:02.159 --> 00:15:04.440 plume, not only do you have the increase of heat, 00:15:04.519 --> 00:15:08.220 but you also are moving hot material up towards 00:15:08.220 --> 00:15:11.360 the surface through the plume and depressurizing 00:15:11.360 --> 00:15:15.309 and causing some melting. However, for... Subduction 00:15:15.309 --> 00:15:17.950 zones, it's the addition of volatiles, namely 00:15:17.950 --> 00:15:21.509 water. So, a quick refresher. Subduction is where 00:15:21.509 --> 00:15:25.570 one ocean plate is pulled under another. The 00:15:25.570 --> 00:15:27.830 subducting plate is carrying a lot of water, 00:15:27.950 --> 00:15:30.649 locked up into the minerals as well as just into 00:15:30.649 --> 00:15:34.690 sediments and the like. When the plate is plunged 00:15:34.690 --> 00:15:37.730 beneath the other, it gets pushed into the hot 00:15:37.730 --> 00:15:41.269 mantle below. It's heated up and put under incredible 00:15:41.269 --> 00:15:43.309 amounts of pressure, the lithostatic pressure. 00:15:43.980 --> 00:15:45.620 because of all that weight of the rock above 00:15:45.620 --> 00:15:49.179 you. This causes the water to be released and 00:15:49.179 --> 00:15:52.279 rise into the mantle above the subducting plate. 00:15:53.100 --> 00:15:55.799 Adding water to the hot mantle reduces its melting 00:15:55.799 --> 00:15:59.000 point and causes it to partially melt. The resulting 00:15:59.000 --> 00:16:03.360 chemistry from this process is also different. 00:16:03.759 --> 00:16:07.120 That is an important point. There will be material 00:16:07.120 --> 00:16:10.500 in the subducting plate or slab that will leave 00:16:10.500 --> 00:16:14.880 with the water and other volatiles. What? because 00:16:14.880 --> 00:16:18.600 those elements are extremely soluble in the released 00:16:18.600 --> 00:16:22.440 fluids or volatiles from the slab. One of the 00:16:22.440 --> 00:16:24.840 knock -on effects of this is increasing the oxidation 00:16:24.840 --> 00:16:26.940 of the melt. I'll throw out a term here as a 00:16:26.940 --> 00:16:28.840 bookmark if you want to go further on your own. 00:16:29.559 --> 00:16:33.379 Oxygen fugacity. The fluids change how the melt 00:16:33.379 --> 00:16:36.240 behaves and what crystals or minerals are stable. 00:16:37.220 --> 00:16:41.659 For our story here, we care about titanium oxide 00:16:41.659 --> 00:16:46.139 or rutile. It is this mineral that gives niobium 00:16:46.139 --> 00:16:49.379 a way out of the melt. It can substitute into 00:16:49.379 --> 00:16:51.940 the crystal structure, meaning we cannot treat 00:16:51.940 --> 00:16:54.580 it as a geochemical buddy to carbon dioxide like 00:16:54.580 --> 00:16:58.220 we can for the basaltic systems. It can also 00:16:58.220 --> 00:17:01.259 add carbon dioxide. See, the subducting slab 00:17:01.259 --> 00:17:04.079 is carrying more than just water, as we are potentially 00:17:04.079 --> 00:17:07.079 adding significant carbon dioxide from the slab 00:17:07.079 --> 00:17:11.079 volatiles. So, we need to go back to the slab. 00:17:11.660 --> 00:17:13.940 As volatiles are expelled, it carries with it 00:17:13.940 --> 00:17:17.579 large ion lithophile elements like barium and 00:17:17.579 --> 00:17:20.119 strontium. Well, yes, these are present in the 00:17:20.119 --> 00:17:23.039 mantle as well. They're only in really quite 00:17:23.039 --> 00:17:26.680 small quantities in comparison to the slab fluids. 00:17:26.759 --> 00:17:30.259 The resulting melt here, though, from this process 00:17:30.259 --> 00:17:32.859 of adding volatiles and melting the mantle is 00:17:32.859 --> 00:17:35.700 then significantly enriched in these elements. 00:17:36.319 --> 00:17:40.240 So you can treat the concentration of strontium 00:17:40.240 --> 00:17:44.059 or... Barium has a proxy for the slab component 00:17:44.059 --> 00:17:46.900 of the volatiles. I went back and forth about 00:17:46.900 --> 00:17:48.960 the best way to explain this. The more simple 00:17:48.960 --> 00:17:52.880 case is when the mantle melting due to depressurization 00:17:52.880 --> 00:17:57.140 and heat. Nubidium and things like helium -3 00:17:57.140 --> 00:18:01.400 ratios work. As described, we can fairly accurately 00:18:01.400 --> 00:18:03.880 peg the primitive carbon dioxide and check it 00:18:03.880 --> 00:18:07.319 via melt inclusions. This slab component of adding 00:18:07.319 --> 00:18:11.339 volatiles and changing chemistry? I think I need 00:18:11.339 --> 00:18:15.480 a two -step explanation. So I'm going to leave 00:18:15.480 --> 00:18:17.559 the slab discussion behind for just a moment. 00:18:17.720 --> 00:18:21.319 Let's look at the volatiles themselves. Active 00:18:21.319 --> 00:18:24.099 volcanoes are degassing carbon dioxide and others 00:18:24.099 --> 00:18:27.079 like sulfur. In fact, sulfur stays locked up 00:18:27.079 --> 00:18:28.819 in the magma until it's quite close to surface. 00:18:29.140 --> 00:18:32.160 The resulting gases are also easy to detect in 00:18:32.160 --> 00:18:36.019 volcanic plumes using wavelengths. A little further 00:18:36.019 --> 00:18:39.279 into this quick aside. Similar to what is done 00:18:39.279 --> 00:18:41.619 in astronomy studying nebula and other planets 00:18:41.619 --> 00:18:46.000 to observe what gases are at present, spectrums, 00:18:46.000 --> 00:18:49.380 absorption lines. Each gas will absorb different 00:18:49.380 --> 00:18:51.940 wavelengths, and if we know the original spectra 00:18:51.940 --> 00:18:53.980 of the light source, we can back -calculate what 00:18:53.980 --> 00:18:57.480 the material was in between. We volcanologists 00:18:57.480 --> 00:19:00.279 use the same principle. We use a light source, 00:19:00.519 --> 00:19:03.099 usually the sun, but sometimes we can use a lamp, 00:19:03.200 --> 00:19:06.650 and we look at... parts of the spectrum that 00:19:06.650 --> 00:19:09.390 are absorbed between whatever we're using to 00:19:09.390 --> 00:19:12.210 measure and the light source. And typically, 00:19:12.390 --> 00:19:14.809 we're looking at what spectrums were absorbed 00:19:14.809 --> 00:19:18.450 by the volcanic plume to back out the concentration 00:19:18.450 --> 00:19:22.430 of things like sulfur. And then integrate across 00:19:22.430 --> 00:19:25.190 the whole plume, like say you're driving a car 00:19:25.190 --> 00:19:28.069 or flying a helicopter underneath the plume looking 00:19:28.069 --> 00:19:31.130 up into the sun, we can have a total emission 00:19:31.130 --> 00:19:35.380 per unit time for sulfur. Okay, back on track. 00:19:35.500 --> 00:19:37.839 Sulfur only degasses after the magma is quite 00:19:37.839 --> 00:19:40.359 close to surface. We can get measurements from 00:19:40.359 --> 00:19:42.559 the ground and from satellite -based instruments 00:19:42.559 --> 00:19:47.140 on the total sulfur emission rates. Now, we can 00:19:47.140 --> 00:19:50.480 play a game of ratios. Assuming one can find 00:19:50.480 --> 00:19:54.720 a hot primary fumarole on the volcano, that is. 00:19:55.180 --> 00:19:58.539 Because that hot primary fumarole, using it, 00:19:58.579 --> 00:20:01.099 we can get a sample of the volatile breakdown. 00:20:01.819 --> 00:20:03.660 of what's coming through the magma system at 00:20:03.660 --> 00:20:07.019 the time. We use what is called a Gigenbach bottle. 00:20:07.720 --> 00:20:10.180 Named after Werner Gigenbach who first introduced 00:20:10.180 --> 00:20:12.140 them. The bottle essentially has a vacuum in 00:20:12.140 --> 00:20:15.039 it using hoses that are shoved into the fumarole. 00:20:15.240 --> 00:20:17.900 They have to be hoses that are going to withstand 00:20:17.900 --> 00:20:20.519 that kind of temperature. The valve is opened 00:20:20.519 --> 00:20:22.799 and the vacuum provides the force to suck up 00:20:22.799 --> 00:20:25.859 the escaping gas from the fumarole. This gas 00:20:25.859 --> 00:20:28.599 is sampled carefully to represent what is coming 00:20:28.599 --> 00:20:31.329 out of the volcano. which can be taken back to 00:20:31.329 --> 00:20:34.349 a lab and analyzed for its chemical constituents. 00:20:35.369 --> 00:20:38.789 Now, even here there are some assumptions, like 00:20:38.789 --> 00:20:43.089 the hydrothermal system has no interaction, the 00:20:43.089 --> 00:20:46.890 degassing is linear, tapping only the magma body, 00:20:47.089 --> 00:20:50.309 and probably a few others that I'm neglecting 00:20:50.309 --> 00:20:52.420 to mention off the top of my head. There's also 00:20:52.420 --> 00:20:55.039 other ways of doing this in situ using wavelengths 00:20:55.039 --> 00:20:57.160 in a similar way to what we've already described, 00:20:57.220 --> 00:20:59.640 but they have much higher air bars as you're 00:20:59.640 --> 00:21:02.680 looking above the fumaroles or the vent, and 00:21:02.680 --> 00:21:05.200 it's all mixing within the atmosphere instead 00:21:05.200 --> 00:21:08.240 of being concentrated within the fumarole itself. 00:21:08.819 --> 00:21:12.279 Okay, so we have a ratio of carbon dioxide and 00:21:12.279 --> 00:21:17.059 sulfur. Based on this very hot, ideally primitive, 00:21:17.220 --> 00:21:19.680 it's coming straight from deep within the Earth, 00:21:19.819 --> 00:21:22.730 and... because of all that monitoring at the 00:21:22.730 --> 00:21:26.349 earth's surface we have total sulfur so now we 00:21:26.349 --> 00:21:29.630 can use a ratio to back out a total carbon dioxide 00:21:29.630 --> 00:21:34.990 but wait there's still problems sulfur doesn't 00:21:34.990 --> 00:21:37.970 fully degas from the melt after eruption some 00:21:37.970 --> 00:21:40.289 stays behind and gets locked up in the volcanic 00:21:40.289 --> 00:21:45.210 glass so the total sulfur measured via the emissions 00:21:45.210 --> 00:21:48.950 isn't the total in the magma There's also other 00:21:48.950 --> 00:21:51.930 processes that can cause sulfur to be left behind 00:21:51.930 --> 00:21:54.450 near the bottom of the magma chamber. So the 00:21:54.450 --> 00:21:56.890 air bars at this point are actually quite large. 00:21:57.509 --> 00:22:00.210 Yes, we can correct or estimate the amount that 00:22:00.210 --> 00:22:03.309 stays behind in the glass, in the rock, but those 00:22:03.309 --> 00:22:06.349 deeper processes are really out of sight. We 00:22:06.349 --> 00:22:08.650 don't really have a good way of measuring them 00:22:08.650 --> 00:22:11.230 and figuring out just how much is being scrubbed 00:22:11.230 --> 00:22:16.220 out of the system. So let's bring back. Our large 00:22:16.220 --> 00:22:19.980 ion lipophile elements. Oh, and melt inclusions 00:22:19.980 --> 00:22:24.680 too. To overcome these large bars that we have 00:22:24.680 --> 00:22:29.119 encountered so far requires two things. And some 00:22:29.119 --> 00:22:32.660 math and trend lines. First, measuring the barium 00:22:32.660 --> 00:22:35.960 and lanthium a whole bunch of times across eruptive 00:22:35.960 --> 00:22:39.579 products. Barium and lanthium elements, they're 00:22:39.579 --> 00:22:42.549 non -volatile. And stay in the melt until the 00:22:42.549 --> 00:22:45.190 very end. These ratios are locked in and shouldn't 00:22:45.190 --> 00:22:47.950 change. And the interesting thing here to note 00:22:47.950 --> 00:22:50.970 is that barium, as we've talked with strontium 00:22:50.970 --> 00:22:56.289 above, comes from the slab. And lanthium does 00:22:56.289 --> 00:23:00.009 not. It will not increase due to the volatiles. 00:23:00.390 --> 00:23:02.589 It's coming from the mantle and not the slab. 00:23:02.690 --> 00:23:06.309 So this means that increasing barium, or increasing 00:23:06.309 --> 00:23:09.230 the ratio, means increasing the slab component. 00:23:10.380 --> 00:23:12.180 It's really, really important. We're playing 00:23:12.180 --> 00:23:16.240 a geochemical sleuthing game here. Now, all we 00:23:16.240 --> 00:23:19.799 need is melt inclusions. Finding an olivine melt 00:23:19.799 --> 00:23:22.960 inclusion that we can use for the official sulfur 00:23:22.960 --> 00:23:26.859 concentration. In arc or subductive settings, 00:23:27.019 --> 00:23:31.119 this is not easy. Many volcanoes in this setting 00:23:31.119 --> 00:23:33.000 do not erupt lava with the right chemistry to 00:23:33.000 --> 00:23:36.720 form olivine. They're too, quote -unquote, evolved. 00:23:37.660 --> 00:23:40.240 which just means too much change from the primary 00:23:40.240 --> 00:23:42.599 melt or the first melt produced in the mantle. 00:23:42.880 --> 00:23:46.079 But in every arc, there are usually a few volcanoes 00:23:46.079 --> 00:23:49.799 that erupt basalt, and these elusive olivines 00:23:49.799 --> 00:23:52.799 with melt inclusions can be found. To name drop 00:23:52.799 --> 00:23:57.380 a bit more, shoulders of giants, it was geochemists 00:23:57.380 --> 00:24:03.569 like Terry Plank and Alessandro Iuppa that plotted 00:24:03.569 --> 00:24:07.130 the surface gas ratios of carbon dioxide to sulfur 00:24:07.130 --> 00:24:09.849 dioxide against the whole rock of barium and 00:24:09.849 --> 00:24:13.309 lanthium ratios of global volcanoes. They observed 00:24:13.309 --> 00:24:18.569 a striking, tight, linear correlation. The volcanoes 00:24:18.569 --> 00:24:20.710 with the strongest slab signature in their rocks 00:24:20.710 --> 00:24:24.269 constantly had the highest carbon dioxide to 00:24:24.269 --> 00:24:27.490 sulfur ratios in their gas. The slab components 00:24:27.490 --> 00:24:31.779 matter. So putting it into practice, this two 00:24:31.779 --> 00:24:34.680 -step geochemical trick or empirical relationship 00:24:34.680 --> 00:24:38.279 together. Step one, we take those rare primitive 00:24:38.279 --> 00:24:41.000 olivine melt inclusions from the anchor volcanoes, 00:24:41.240 --> 00:24:43.799 as we'll call them right here, and use them to 00:24:43.799 --> 00:24:47.759 measure the true deep sulfur concentration of 00:24:47.759 --> 00:24:50.599 the magmatic source before it hits the surface. 00:24:51.180 --> 00:24:55.329 Step two, we pair that deep volatile data with 00:24:55.329 --> 00:24:57.869 whole rock trace element chemistry specifically 00:24:57.869 --> 00:25:00.730 the ratios of barium which is going to represent 00:25:00.730 --> 00:25:04.769 the slab to lanthium which represents the mantle 00:25:04.769 --> 00:25:09.529 to act as our geochemical slab meters by plotting 00:25:09.529 --> 00:25:13.049 many of these values for an arc trend lines are 00:25:13.049 --> 00:25:16.930 built with a robust trend line we can take the 00:25:16.930 --> 00:25:20.680 ratio of barium and lanthium from any volcano 00:25:20.680 --> 00:25:23.960 or eruption within a particular arc and use the 00:25:23.960 --> 00:25:28.099 trend line to obtain the carbon dioxide total 00:25:28.099 --> 00:25:33.460 to sulfur dioxide total ratio. Now we can use 00:25:33.460 --> 00:25:36.720 the average sulfur still in the glass of erupted 00:25:36.720 --> 00:25:40.299 products because sulfur doesn't completely degas. 00:25:40.319 --> 00:25:43.940 So we can get that total sulfur that is being 00:25:43.940 --> 00:25:46.960 degassed and match it to what we measure on the 00:25:46.960 --> 00:25:50.829 Earth's surface. and therefore obtain a reasonable 00:25:50.829 --> 00:25:55.150 value of the carbon dioxide budget for a particular 00:25:55.150 --> 00:25:58.869 arc. Over the years, this data was collected 00:25:58.869 --> 00:26:01.509 to understand volcanoes. Primitive mountain inclusions, 00:26:01.509 --> 00:26:04.309 chemical ratios, empirical relationships, they 00:26:04.309 --> 00:26:08.430 were developed to understand volcanoes and Earth 00:26:08.430 --> 00:26:13.390 processes, not climate change. That was never 00:26:13.390 --> 00:26:17.779 the goal, but once you have it, Now you can start 00:26:17.779 --> 00:26:22.059 asking questions because it has a direct application 00:26:22.059 --> 00:26:25.359 as an input for the atmosphere. It just becomes 00:26:25.359 --> 00:26:28.059 abundantly clear. I don't want to get sidetracked 00:26:28.059 --> 00:26:31.839 into looking at aerosols and sulfate and the 00:26:31.839 --> 00:26:33.799 expected cooling that happens from explosive 00:26:33.799 --> 00:26:36.200 volcanism. Perhaps one day I'll walk through 00:26:36.200 --> 00:26:38.960 a super volcano and what an eruption would do 00:26:38.960 --> 00:26:41.720 to climate as a solo episode. The point is volcanoes 00:26:41.720 --> 00:26:45.099 can have large impacts on climate. We know looking 00:26:45.099 --> 00:26:47.140 back through geologic time, the volcanic activity 00:26:47.140 --> 00:26:49.819 was one variable changing long -term climate. 00:26:50.140 --> 00:26:52.640 And obviously in very large eruptions, it will 00:26:52.640 --> 00:26:56.240 have a punctuated short -term climate change 00:26:56.240 --> 00:27:01.480 as well due to the sulfate. So we have our volatile 00:27:01.480 --> 00:27:05.119 weight percents. So applying this analysis to 00:27:05.119 --> 00:27:07.539 mid -ocean ridges and ocean island basalts, like 00:27:07.539 --> 00:27:11.259 hotspots, like Hawaii, we get estimates of our 00:27:11.259 --> 00:27:14.420 carbon dioxide concentration. And I'm going to 00:27:14.420 --> 00:27:19.220 be giving it here is grams per kilogram of magma. 00:27:19.759 --> 00:27:23.160 So at mid -ocean ridges, we have 0 .5 to 1 .5 00:27:23.160 --> 00:27:25.839 grams per kilogram. We can have an extreme high 00:27:25.839 --> 00:27:28.359 of about 2 .5, really, for mid -ocean ridges. 00:27:28.480 --> 00:27:30.740 For ocean island basalts like Hawaii, we get 00:27:30.740 --> 00:27:34.599 5 to 15 grams per kilogram. The extreme side 00:27:34.599 --> 00:27:38.819 of this is 30 grams per kilogram. And arcs, 5 00:27:38.819 --> 00:27:42.039 to 20 grams per kilogram. In the extreme, it 00:27:42.039 --> 00:27:45.900 can be up as high as 40. Yay, numbers! Well, 00:27:45.960 --> 00:27:49.980 that is the first part. All done. Now we're on 00:27:49.980 --> 00:27:53.059 to part two. How much magma degasses each year? 00:27:53.259 --> 00:27:56.480 So we have the concentrations. There's two different 00:27:56.480 --> 00:27:59.000 games we can play here. We can calculate an average 00:27:59.000 --> 00:28:02.180 per year eruptive flux, i .e. how much is on 00:28:02.180 --> 00:28:05.640 average erupted per year in each geologic environment. 00:28:06.579 --> 00:28:10.359 Or we can try estimating via measuring... sulfur 00:28:10.359 --> 00:28:13.380 degassing flux and use ratios developed above. 00:28:14.119 --> 00:28:17.839 Here on the podcast, though, it's easier to talk 00:28:17.839 --> 00:28:20.920 and walk through the first one. So let's do that 00:28:20.920 --> 00:28:25.299 and present values for sulfur estimates. For 00:28:25.299 --> 00:28:27.460 some volcanoes, we have great constraints on 00:28:27.460 --> 00:28:31.279 eruptive output due to how active they are. The 00:28:31.279 --> 00:28:34.579 Hawaiian volcanoes, Etna, Masaya volcano as location 00:28:34.579 --> 00:28:37.950 examples. When we start to deal with broader 00:28:37.950 --> 00:28:41.490 arcs like the Cascades or the Andes, there are 00:28:41.490 --> 00:28:44.170 areas that go thousands of years between eruptions. 00:28:44.349 --> 00:28:47.250 So detailed mapping of the eruptive products 00:28:47.250 --> 00:28:51.569 and averaging over the entire arc is the game 00:28:51.569 --> 00:28:55.390 we need to play. For mid -ocean ridges, spreading 00:28:55.390 --> 00:28:58.990 rates and averaging the required output for the 00:28:58.990 --> 00:29:02.569 entire length is what we'll do. So let's take 00:29:02.569 --> 00:29:06.799 the Cascades as the first example. It has one 00:29:06.799 --> 00:29:09.319 to two eruptions per century, which works out 00:29:09.319 --> 00:29:17.900 to 0 .001 to 0 .01 kilometers cubed per year 00:29:17.900 --> 00:29:21.319 for the whole arc. Yeah, there's going to be 00:29:21.319 --> 00:29:24.240 a lot of numbers. The point is, is that it's, 00:29:24.240 --> 00:29:27.799 you know, quite a small percentage or quite a 00:29:27.799 --> 00:29:32.059 small volume in the grand scheme of things. Expanding 00:29:32.059 --> 00:29:36.700 this to a global scale, the above sea level volume 00:29:36.700 --> 00:29:42.279 of subduction arc magmas is just 1 .8 to 4 cubic 00:29:42.279 --> 00:29:45.619 kilometers per year. That's for the entire globe. 00:29:46.940 --> 00:29:50.839 What about the underwater arc volcanism? Think 00:29:50.839 --> 00:29:53.200 island arcs where the volcanoes are still below 00:29:53.200 --> 00:29:57.839 the waves. Well, for our numbers, these eruptions 00:29:57.839 --> 00:30:02.700 get fuzzier. We still only get additional half 00:30:02.700 --> 00:30:06.759 to one cubic kilometer, though, even though the 00:30:06.759 --> 00:30:09.880 air bars are slightly large. Using a maximum 00:30:09.880 --> 00:30:13.579 volume here of five cubic kilometers, that's 00:30:13.579 --> 00:30:17.240 a fair bit of magma, representing five Mount 00:30:17.240 --> 00:30:21.680 St. Helens eruptions in 1980. What about the 00:30:21.680 --> 00:30:25.039 gas? Going back to the high end of the estimates 00:30:25.039 --> 00:30:29.740 above of 20 grams per kilogram. And let's just 00:30:29.740 --> 00:30:34.380 keep it as grams per unit volume as it's much 00:30:34.380 --> 00:30:38.140 easier to estimate. We get 53 ,000 grams per 00:30:38.140 --> 00:30:43.759 meter cubed. Unit conversions arrives at 53 million 00:30:43.759 --> 00:30:47.740 metric tons of carbon dioxide per cubic kilometer 00:30:47.740 --> 00:30:52.440 of erupted material. So we have 265 million metric 00:30:52.440 --> 00:30:56.200 tons of carbon dioxide for arc volcanoes. using 00:30:56.200 --> 00:31:01.880 our high -end estimates for volatiles that last 00:31:01.880 --> 00:31:05.259 part is important so far the numbers being used 00:31:05.259 --> 00:31:08.500 here are near the maximum for volume and co2 00:31:08.500 --> 00:31:11.880 concentration using minimum numbers drops that 00:31:11.880 --> 00:31:19.480 value by a factor of 10. now ocean island basalts 00:31:19.480 --> 00:31:22.539 best estimates based on the data is two cubic 00:31:22.539 --> 00:31:26.470 kilometers going back to our carbon dioxide flux 00:31:26.470 --> 00:31:30.230 and again choosing the maximum 15 grams per kilogram 00:31:30.230 --> 00:31:33.029 of magma and again using the same unit conversions 00:31:33.029 --> 00:31:38.869 arrives with 81 million metric tons of carbon 00:31:38.869 --> 00:31:44.630 dioxide finally mid -ocean ridges where plates 00:31:44.630 --> 00:31:47.869 are pulling apart this gets a bit problematic 00:31:47.869 --> 00:31:51.210 first and foremost most of these eruptions occur 00:31:51.210 --> 00:31:55.369 deep beneath the ocean CO2 erupted there doesn't 00:31:55.369 --> 00:31:58.269 degas to the atmosphere. There are chemical reactions 00:31:58.269 --> 00:32:01.150 and the like that will bind it earlier, but for 00:32:01.150 --> 00:32:03.450 this exercise, we're just going to keep it simple. 00:32:03.549 --> 00:32:06.730 Based on observations and models, ridges erupt 00:32:06.730 --> 00:32:11.049 3 to 4 .5 cubic kilometers of magma. They intrude 00:32:11.049 --> 00:32:13.470 or stuff magma beneath the crust at a rate of 00:32:13.470 --> 00:32:17.880 18 to 21 cubic kilometers a year. Adding it together 00:32:17.880 --> 00:32:20.079 and taking the maximum and ignoring the fact 00:32:20.079 --> 00:32:22.220 that essentially zero would directly interact 00:32:22.220 --> 00:32:25.700 with the atmosphere, we get 26 cubic kilometers 00:32:25.700 --> 00:32:30.619 of magma being erupted or emplaced. Again, going 00:32:30.619 --> 00:32:33.160 back to the concentration for the mid -ocean 00:32:33.160 --> 00:32:37.460 ridges, we get 1 .5 grams per kilogram. And then 00:32:37.460 --> 00:32:39.960 running the same unit conversions arrives at 00:32:39.960 --> 00:32:44.220 105 million metric tons of carbon dioxide. Adding 00:32:44.220 --> 00:32:50.460 all of these together. 105, 81, and 265. For 00:32:50.460 --> 00:32:54.000 the mid -ocean ridges, the ocean island basalts, 00:32:54.119 --> 00:32:59.539 and the arcs across all of the world, we get 00:32:59.539 --> 00:33:03.900 a grand total of 451 .3 million metric tons of 00:33:03.900 --> 00:33:08.140 carbon dioxide degassed per year. So given, throughout 00:33:08.140 --> 00:33:11.700 this, I've chosen values near the max every single 00:33:11.700 --> 00:33:17.039 time. The real number will be smaller. In fact, 00:33:17.039 --> 00:33:18.700 let's look at those published values that take 00:33:18.700 --> 00:33:21.440 a longer view, breaking it down more granularly 00:33:21.440 --> 00:33:23.720 instead of just taking the values near max like 00:33:23.720 --> 00:33:26.900 I did here, doing a lot more estimates, if you 00:33:26.900 --> 00:33:31.480 will. The maximum published value is 440 million 00:33:31.480 --> 00:33:35.619 metric tons. The minimum is 130 million. The 00:33:35.619 --> 00:33:38.079 value from the paper I introduced at the very 00:33:38.079 --> 00:33:41.940 beginning, the 2011 seminal paper by USGS scientist 00:33:41.940 --> 00:33:46.569 Dr. Terry Gerlach, arrived at 260. metric tons 00:33:46.569 --> 00:33:50.410 as the best value. So my more simple method based 00:33:50.410 --> 00:33:53.329 on estimates of global magma flux is very close. 00:33:53.730 --> 00:33:57.470 Not super rigorous. I chose to do something different 00:33:57.470 --> 00:34:00.349 than just reproduce Dr. Garalex to show that 00:34:00.349 --> 00:34:03.789 the same conclusion can be arrived at using different 00:34:03.789 --> 00:34:07.309 measurements. This is important. This is how 00:34:07.309 --> 00:34:10.829 we test science. This isn't just... I am taking 00:34:10.829 --> 00:34:14.090 somebody else's numbers and reproducing the exact 00:34:14.090 --> 00:34:16.829 same thing in the paper. Oh no, I took numbers 00:34:16.829 --> 00:34:20.690 that represent the globe instead of what Dr. 00:34:20.789 --> 00:34:22.610 Terry Gerlach did, which was a bit more granular 00:34:22.610 --> 00:34:25.849 and a lot more accurate, given the numbers that 00:34:25.849 --> 00:34:29.690 he had at the time that he published. I tested 00:34:29.690 --> 00:34:34.190 the same hypothesis and got basically the same 00:34:34.190 --> 00:34:38.940 result. So we have the number 451 metric. Million 00:34:38.940 --> 00:34:40.619 metric tons. And we're going to keep going with 00:34:40.619 --> 00:34:44.139 this number. A true maximum. So, step one and 00:34:44.139 --> 00:34:49.260 step two are done. We have a value for the volcanoes 00:34:49.260 --> 00:34:53.119 of the world. Now for the human emissions part. 00:34:53.460 --> 00:34:56.760 The final part. We don't need to play a game 00:34:56.760 --> 00:34:59.699 of melt inclusions and eruptive output. The methodology 00:34:59.699 --> 00:35:03.460 is very different. I will go into some of it 00:35:03.460 --> 00:35:05.980 here, but... It's all published by organizations 00:35:05.980 --> 00:35:08.920 like the Intergovernmental Panel on Climate Change, 00:35:09.099 --> 00:35:15.500 IPCC, the International Energy Agency, IEA, and 00:35:15.500 --> 00:35:19.380 the Global Carbon Project. If you have in -depth 00:35:19.380 --> 00:35:22.940 questions, send the show an email, or better 00:35:22.940 --> 00:35:27.099 yet, jump into the source material. You don't 00:35:27.099 --> 00:35:29.619 have to just take my word for it. That's why 00:35:29.619 --> 00:35:32.800 we publish things as scientists. That's why if 00:35:32.800 --> 00:35:36.409 you... Know enough and willing to take the time, 00:35:36.489 --> 00:35:39.230 you can go derive it all from the first principles 00:35:39.230 --> 00:35:42.269 and follow the same rubric that is set out in 00:35:42.269 --> 00:35:45.809 these publications. So let's start with fossil 00:35:45.809 --> 00:35:48.670 fuel. The organizations that I just mentioned 00:35:48.670 --> 00:35:50.869 above estimate fossil fuel numbers from values 00:35:50.869 --> 00:35:54.369 that are produced independently by legally binding 00:35:54.369 --> 00:35:57.570 international trade data, customs ledgers and 00:35:57.570 --> 00:36:01.099 national energy taxation registers. It's not 00:36:01.099 --> 00:36:03.360 scientists trying to estimate something through 00:36:03.360 --> 00:36:06.699 proxies. These numbers are accurate because of 00:36:06.699 --> 00:36:09.099 the requirements of modern reporting. Scientists 00:36:09.099 --> 00:36:13.480 just get to use the data. So using the type of 00:36:13.480 --> 00:36:17.039 fuel being sold and what it will produce when 00:36:17.039 --> 00:36:20.820 burned, we can account for nearly 90 % of human 00:36:20.820 --> 00:36:25.349 emissions. There are, of course, non -fossil 00:36:25.349 --> 00:36:28.630 fuel sources as well for carbon dioxide, and 00:36:28.630 --> 00:36:30.349 those are a bit harder to pin down. Generally, 00:36:30.369 --> 00:36:33.869 we're talking about cement. If this is a surprise, 00:36:34.090 --> 00:36:36.369 it's because you don't know how it's made. We 00:36:36.369 --> 00:36:42.190 take limestone, calcium carbon oxygen 3, that's 00:36:42.190 --> 00:36:44.690 what limestone is, and heat it to get calcium 00:36:44.690 --> 00:36:48.789 oxide. What's missing when you get calcium oxide 00:36:48.789 --> 00:36:54.849 from CaCO3? Carbon dioxide. It also takes a whole 00:36:54.849 --> 00:36:56.610 lot of heat to get limestone to break down like 00:36:56.610 --> 00:37:01.050 that. The heat? Yeah, often we almost always 00:37:01.050 --> 00:37:03.949 use fossil fuels. I don't want to get into the 00:37:03.949 --> 00:37:07.190 weeds here, but we're looking at about 8 % of 00:37:07.190 --> 00:37:10.190 human emissions. New technology could bring that 00:37:10.190 --> 00:37:13.190 number way down. Building materials move slow 00:37:13.190 --> 00:37:16.389 because of regulations. Regulations are very, 00:37:16.409 --> 00:37:18.210 very important. I live in an earthquake zone. 00:37:19.070 --> 00:37:21.449 I wish I could speed up the testing and adoption 00:37:21.449 --> 00:37:24.929 of these technologies, though. The last bucket 00:37:24.929 --> 00:37:27.269 of human emissions is land use, deforestation, 00:37:27.690 --> 00:37:32.050 soil degradation. We can model this and make 00:37:32.050 --> 00:37:34.289 measurements, but the data here is a bit fuzzy. 00:37:35.170 --> 00:37:40.289 Then again, it is a very small factor than the 00:37:40.289 --> 00:37:42.989 first two. We're looking around, you know, somewhere 00:37:42.989 --> 00:37:48.170 in the realm of 2%. Breaking down. Fossil fuels 00:37:48.170 --> 00:37:53.989 emissions clock in around 33 .3 billion metric 00:37:53.989 --> 00:37:59.230 tons, leaving all the rest at 4 .7 billion metric 00:37:59.230 --> 00:38:02.230 tons of carbon dioxide. Remember the volcanoes, 00:38:02.449 --> 00:38:06.730 our number? 451 million metric tons, or if we 00:38:06.730 --> 00:38:09.409 want to make it the same so we can compare it, 00:38:09.510 --> 00:38:19.010 we're looking at 0 .45 billion tons. Just 1 .2 00:38:19.010 --> 00:38:25.150 % of what we humans produce. So where does that 00:38:25.150 --> 00:38:28.349 leave us? We've gone from the microscope pressure 00:38:28.349 --> 00:38:32.449 vessel of an olivine crystal to the massive plate 00:38:32.449 --> 00:38:35.190 tectonic reality of subduction zones. We've looked 00:38:35.190 --> 00:38:37.670 at the bubble problem, played the geochemical 00:38:37.670 --> 00:38:39.909 buddy system, and mapped out all the trend lines 00:38:39.909 --> 00:38:46.829 of global arcs. After all that math, all the 00:38:46.829 --> 00:38:49.130 sifting through the gas ratios, the trace elements, 00:38:49.250 --> 00:38:52.309 we arrive at the bottom line. Yeah, volcanoes 00:38:52.309 --> 00:38:56.449 emit carbon dioxide. Sure. They are, you could 00:38:56.449 --> 00:38:58.269 argue, the heartbeat of the planet's natural 00:38:58.269 --> 00:39:00.789 degassing. They are definitely one knob in the 00:39:00.789 --> 00:39:03.889 whole climate system that the Earth just does 00:39:03.889 --> 00:39:07.210 without us. But when you look at the total global 00:39:07.210 --> 00:39:10.170 budget, the contribution from human industrial 00:39:10.170 --> 00:39:14.699 activity is just different. It's... orders of 00:39:14.699 --> 00:39:16.940 magnitude larger. The idea that volcanoes are 00:39:16.940 --> 00:39:19.619 out emitting humans just doesn't hold up. The 00:39:19.619 --> 00:39:25.139 data doesn't support it. I hate to say that it's 00:39:25.139 --> 00:39:27.719 a myth because there's not much truth to it other 00:39:27.719 --> 00:39:31.099 than volcanoes do emit carbon dioxide. And I 00:39:31.099 --> 00:39:32.900 don't really understand the reaching for straws 00:39:32.900 --> 00:39:34.639 to protect a viewpoint that falls apart when 00:39:34.639 --> 00:39:37.909 we just look at the data. I hope this episode 00:39:37.909 --> 00:39:39.869 gave you a bit of a window into how we actually 00:39:39.869 --> 00:39:42.690 know what we know. Science isn't a black box 00:39:42.690 --> 00:39:48.010 or a magical guess. So often it's a painstaking 00:39:48.010 --> 00:39:50.650 process of cross -referencing different things 00:39:50.650 --> 00:39:53.630 like bubbles, isotopes, and ratios to build a 00:39:53.630 --> 00:39:56.230 clearer picture of reality. It's messy. It's 00:39:56.230 --> 00:39:58.829 full of error bars. And sometimes it takes a 00:39:58.829 --> 00:40:01.409 decade just to get one measurement right. But 00:40:01.409 --> 00:40:06.269 it's how we move from I think to we know. So... 00:40:06.639 --> 00:40:10.880 We know that humans emit way more carbon dioxide 00:40:10.880 --> 00:40:16.219 than volcanoes. Okay, so this wraps up season 00:40:16.219 --> 00:40:18.219 two of Whimsical Wavelengths, a science podcast. 00:40:18.559 --> 00:40:20.699 And as I've already mentioned, it's been a wild 00:40:20.699 --> 00:40:22.960 ride. I hope you've enjoyed peeling back the 00:40:22.960 --> 00:40:26.300 curtain on how we make science as much as I have 00:40:26.300 --> 00:40:29.320 for this final episode. To reiterate, I'm taking 00:40:29.320 --> 00:40:32.340 a break for the rest of summer, planning to be 00:40:32.340 --> 00:40:35.480 back on September 14th. Encore editions will 00:40:35.480 --> 00:40:39.940 fill the gap to keep the feed fresh. It's also 00:40:39.940 --> 00:40:42.079 a time to re -listen to some of my favorites 00:40:42.079 --> 00:40:45.900 in the back catalog. So hopefully life doesn't 00:40:45.900 --> 00:40:47.780 throw a wrench into everything I've planned for 00:40:47.780 --> 00:40:49.840 the start of season three. And if it does, I'll 00:40:49.840 --> 00:40:51.880 do my best to communicate about it should it 00:40:51.880 --> 00:40:55.880 be delayed. Remember, leave a rating and a review 00:40:55.880 --> 00:40:59.059 in your podcast app. Tell a friend about it. 00:41:00.019 --> 00:41:05.590 This is literally the best way to... Spread whimsical 00:41:05.590 --> 00:41:07.489 wavelengths and get it into other people's ears. 00:41:08.210 --> 00:41:11.590 So much is planned for season three. Well, I'm 00:41:11.590 --> 00:41:15.650 Dr. Jeffrey Zirk. I'm signing out. And I should 00:41:15.650 --> 00:41:19.829 be back in your feeds with new episodes starting 00:41:19.829 --> 00:41:37.000 September 14th. We have stories painting the 00:41:37.000 --> 00:41:44.199 sky Swaying to rhythms as the galaxies fly by 00:42:08.230 --> 00:42:08.710 J.