WEBVTT 00:00:00.000 --> 00:00:03.299 Welcome to Meteorology Matters. What if we told 00:00:03.299 --> 00:00:06.240 you that humanity's really profound influence 00:00:06.240 --> 00:00:09.660 on Earth's climate? You know, the very air around 00:00:09.660 --> 00:00:12.279 us might have been detectable much, much earlier 00:00:12.279 --> 00:00:14.599 than we previously imagined. Yeah, we're talking 00:00:14.599 --> 00:00:17.280 about a time when, like, horse -drawn carriages 00:00:17.280 --> 00:00:19.399 were still the main way to get around. Exactly. 00:00:19.719 --> 00:00:21.960 Long before gas -powered cars were even a common 00:00:21.960 --> 00:00:25.379 sight. It's a revelation that genuinely shifts 00:00:25.379 --> 00:00:27.879 our understanding of climate history and, well, 00:00:28.039 --> 00:00:30.780 our long -term impact. Today, we're embarking 00:00:30.780 --> 00:00:33.659 on a truly captivating journey, sort of a scientific... 00:00:33.659 --> 00:00:36.619 thought experiment really, to explore precisely 00:00:36.619 --> 00:00:39.500 when the human impact on our atmosphere became, 00:00:39.500 --> 00:00:42.439 you know, undeniably discernible. It really challenges 00:00:42.439 --> 00:00:44.420 so many assumptions about the timeline, doesn't 00:00:44.420 --> 00:00:47.020 it? It does, pushing that moment of clear detection 00:00:47.020 --> 00:00:49.380 back over a century. That's right. Our mission 00:00:49.380 --> 00:00:52.359 in this Meteorology Matters exploration is to 00:00:52.359 --> 00:00:55.259 unravel how scientists kind of peering back through 00:00:55.259 --> 00:00:59.200 time, but using today's advanced tools and sophisticated 00:00:59.200 --> 00:01:02.119 climate models have pinpointed a precise moment. 00:01:02.240 --> 00:01:04.040 A moment when a human fingerprint would have 00:01:04.040 --> 00:01:07.540 emerged. Exactly. In the atmospheric temperature 00:01:07.540 --> 00:01:10.260 record. And this isn't just, you know, a historical 00:01:10.260 --> 00:01:13.640 curiosity for scientists. It fundamentally reshapes 00:01:13.640 --> 00:01:16.760 our understanding of humanity's longstanding 00:01:16.760 --> 00:01:19.900 and often overlooked connection to global atmospheric 00:01:19.900 --> 00:01:22.969 changes. It really makes you consider just how 00:01:22.969 --> 00:01:26.090 long we've truly been altering our planet on 00:01:26.090 --> 00:01:29.689 a planetary scale. It really does. So, if we're 00:01:29.689 --> 00:01:32.510 tracing this impact, where do we even begin? 00:01:33.150 --> 00:01:35.989 Where do we see the earliest scientific glimmers 00:01:35.989 --> 00:01:38.390 of understanding how our atmosphere actually 00:01:38.390 --> 00:01:40.370 works? Yeah, what was the foundation? Right. 00:01:40.530 --> 00:01:42.909 What set all this in motion long before anyone 00:01:42.909 --> 00:01:45.730 even thought of a carbon footprint? That's a 00:01:45.730 --> 00:01:47.750 great place to start because the groundwork was 00:01:47.750 --> 00:01:51.329 laid surprisingly early. Picture the mid -19th 00:01:51.329 --> 00:01:54.629 century, a time of incredible scientific curiosity 00:01:54.629 --> 00:01:57.549 discovery. Even while the Industrial Revolution 00:01:57.549 --> 00:02:00.730 was rapidly expanding, a handful of visionary 00:02:00.730 --> 00:02:03.489 scientists were quietly unraveling the fundamental 00:02:03.489 --> 00:02:06.010 physics of Earth's atmosphere. And who were these 00:02:06.010 --> 00:02:08.389 pioneers? What did they actually uncover? Well, 00:02:08.669 --> 00:02:10.469 the absolute foundation of our understanding 00:02:10.469 --> 00:02:13.849 of the greenhouse effect comes from the late 00:02:13.849 --> 00:02:18.449 1850s, early 1860s. This is when two really brilliant 00:02:18.449 --> 00:02:21.590 individuals Eunice Foote and John Tyndall, working 00:02:21.590 --> 00:02:24.689 independently, mind you, conducted these pivotal 00:02:24.689 --> 00:02:27.250 experimental discoveries. Ah, Foote and Tyndall. 00:02:27.389 --> 00:02:30.789 Yes. They were the first to really demonstrate 00:02:30.789 --> 00:02:32.949 the heat -trapping properties of carbon dioxide 00:02:32.949 --> 00:02:35.270 and other greenhouse gases, too. How did they 00:02:35.270 --> 00:02:37.650 even do that back then? Well, you can imagine 00:02:37.650 --> 00:02:40.229 they're labs. They'd fill these glass tubes with 00:02:40.229 --> 00:02:43.310 different gases, right? Then expose them to sunlight, 00:02:43.810 --> 00:02:46.189 measuring how much heat each gas absorbs. Simple 00:02:46.189 --> 00:02:49.159 but clever. Very. And Foote, who's actually a 00:02:49.159 --> 00:02:51.379 self -taught scientist and a women's rights advocate, 00:02:51.680 --> 00:02:54.080 she even hypothesized that an increase in atmospheric 00:02:54.080 --> 00:02:56.759 CO2 would lead to a warmer planet. Wow, back 00:02:56.759 --> 00:02:59.180 then. Absolutely, predicting something remarkable 00:02:59.180 --> 00:03:02.099 for her time. Tyndall later confirmed and expanded 00:03:02.099 --> 00:03:04.580 on her work, adding critical detail about the 00:03:04.580 --> 00:03:06.860 specific wavelengths of heat that CO2 absorbed. 00:03:07.020 --> 00:03:09.560 So these are like the seminal moments. Definitely. 00:03:10.020 --> 00:03:12.699 Essentially identifying the very mechanism that 00:03:12.699 --> 00:03:15.000 allows our planet to stay warm enough for life, 00:03:15.280 --> 00:03:17.879 but also critically how it could be altered. 00:03:18.360 --> 00:03:20.419 So they showed certain gases act like a blanket, 00:03:20.780 --> 00:03:24.080 trapping heat. But did anyone before them have 00:03:24.080 --> 00:03:26.620 inklings of this? Was the idea totally new? Good 00:03:26.620 --> 00:03:29.479 question. No, not entirely new. But the experimental 00:03:29.479 --> 00:03:32.150 proof was. Earlier thinkers, like the French 00:03:32.150 --> 00:03:34.789 mathematician Jean -Baptiste Fourier back in 00:03:34.789 --> 00:03:37.830 the 1820s, had already proposed that the Earth's 00:03:37.830 --> 00:03:40.330 atmosphere played a crucial role in keeping it 00:03:40.330 --> 00:03:42.409 warm. He compared it to a greenhouse, right? 00:03:42.590 --> 00:03:45.150 Or a hotbox. Exactly. Then Claude Pouillet in 00:03:45.150 --> 00:03:48.050 the 1830s refined these ideas, and even earlier, 00:03:48.229 --> 00:03:50.590 the Swiss naturalist Horace -Benedict de Saussure, 00:03:50.810 --> 00:03:53.210 like 1700s, he did experiments with something 00:03:53.210 --> 00:03:56.400 called a heliothermometer. What now? Heliothermometer. 00:03:56.620 --> 00:03:59.020 Basically an insulated black box designed to 00:03:59.020 --> 00:04:01.740 trap solar radiation. So it hinted at how the 00:04:01.740 --> 00:04:04.099 atmosphere might work. Okay, so the theory was 00:04:04.099 --> 00:04:06.199 kind of brewing. The theoretical stage was set, 00:04:06.199 --> 00:04:08.560 yeah. But it was the meticulous experimental 00:04:08.560 --> 00:04:11.099 work of foot and Tyndall that really solidified 00:04:11.099 --> 00:04:13.460 the understanding of specific gases as the heat 00:04:13.460 --> 00:04:16.699 trappers. Got it. And this brings us to a name 00:04:16.699 --> 00:04:22.750 many might recognize. Svante? Arrhenius. Ah yes, 00:04:23.029 --> 00:04:25.430 Arrhenius. What was his big contribution to this? 00:04:25.810 --> 00:04:28.910 Arrhenius, a brilliant Swedish chemist, came 00:04:28.910 --> 00:04:31.970 along in the late 1800s building directly on 00:04:31.970 --> 00:04:36.000 foot and Tyndall's work. And he made what was, 00:04:36.000 --> 00:04:38.259 for its time, just an utterly astounding and 00:04:38.259 --> 00:04:40.459 prescient prediction. OK. He was one of the first 00:04:40.459 --> 00:04:42.620 to really recognize that the burning of fossil 00:04:42.620 --> 00:04:45.060 fuels, mostly coal, back then during that big 00:04:45.060 --> 00:04:47.279 industrial push, was increasing the amount of 00:04:47.279 --> 00:04:48.860 carbon dioxide in the atmosphere. Right, that 00:04:48.860 --> 00:04:51.079 makes sense. But he didn't stop there. He went 00:04:51.079 --> 00:04:53.920 a remarkable step further. He actually calculated, 00:04:54.120 --> 00:04:56.579 estimated, that a doubling of atmospheric carbon 00:04:56.579 --> 00:04:59.060 dioxide could lead to a surface temperature increase 00:04:59.060 --> 00:05:01.759 of around 4 degrees Celsius. Wait, hold on. 4 00:05:01.759 --> 00:05:04.699 degrees Celsius, it sounds... uncannily familiar, 00:05:04.819 --> 00:05:07.160 isn't that close to modern estimates for climate 00:05:07.160 --> 00:05:09.519 sensitivity? Bingo. He figured that out over 00:05:09.519 --> 00:05:11.660 a century ago. Precisely. It was a profoundly 00:05:11.660 --> 00:05:14.279 insightful calculation based on the best available 00:05:14.279 --> 00:05:16.879 physics and observations of his time. Made more 00:05:16.879 --> 00:05:18.920 than a century ago. He wasn't just guessing. 00:05:19.360 --> 00:05:21.720 He was using scientific principles to anticipate 00:05:21.720 --> 00:05:24.800 a key aspect of climate change with incredible 00:05:24.800 --> 00:05:28.189 foresight. He understood the mechanism and even 00:05:28.189 --> 00:05:31.290 estimated its magnitude long before anyone could 00:05:31.290 --> 00:05:33.810 have imagined the scale of fossil fuel use we 00:05:33.810 --> 00:05:36.389 see today. That's incredible. So the theory was 00:05:36.389 --> 00:05:39.009 there, the understanding of how CO2 warms the 00:05:39.009 --> 00:05:42.269 planet was emerging. But to actually detect a 00:05:42.269 --> 00:05:45.750 human influence, you need data, right? Observations. 00:05:45.750 --> 00:05:47.529 What was happening on that front? You're right. 00:05:47.589 --> 00:05:49.589 Theory needs proof, needs observation. And in 00:05:49.589 --> 00:05:51.670 parallel with this developing theoretical understanding, 00:05:52.149 --> 00:05:54.769 the practical data needed to identify these human 00:05:54.769 --> 00:05:58.170 fingerprints was kind of slowly but surely accumulating. 00:05:58.689 --> 00:06:01.649 By the 1860s, systematic daily measurements of 00:06:01.649 --> 00:06:04.029 surface temperature had begun, mostly in urban 00:06:04.029 --> 00:06:06.189 areas across Europe and North America. So like 00:06:06.189 --> 00:06:08.649 weather station data. Pretty much. This provided 00:06:08.649 --> 00:06:10.730 a foundational record of localized temperature 00:06:10.730 --> 00:06:13.509 changes, establishing a baseline of sorts. But 00:06:13.509 --> 00:06:15.430 surface measurements alone, that wouldn't give 00:06:15.430 --> 00:06:17.550 you the full atmospheric picture, would it? You 00:06:17.550 --> 00:06:21.319 need to go higher up. Exactly. To truly understand 00:06:21.319 --> 00:06:24.579 global climate and the vertical structure of 00:06:24.579 --> 00:06:26.620 temperature, scientists needed to look beyond 00:06:26.620 --> 00:06:28.540 the surface. They needed to venture into what 00:06:28.540 --> 00:06:31.100 they called the free atmosphere. The air masses 00:06:31.100 --> 00:06:34.060 above the ground. Right. And that was a significant 00:06:34.060 --> 00:06:37.000 challenge for the technology of the time. However, 00:06:37.279 --> 00:06:40.680 pioneering efforts started in 1892. A French 00:06:40.680 --> 00:06:44.290 physicist, Gustave Hermite, And a journalist, 00:06:44.649 --> 00:06:47.209 Georges Besançon, launched some of the first 00:06:47.209 --> 00:06:50.149 unpiloted weather balloons. Unpiloted balloons 00:06:50.149 --> 00:06:53.290 in 1892. Yep. And they weren't just balloons. 00:06:53.750 --> 00:06:56.529 They carried these compact devices designed to 00:06:56.529 --> 00:06:58.589 measure temperature and pressure high above the 00:06:58.589 --> 00:07:00.970 ground. That's amazing. Just sending stuff up 00:07:00.970 --> 00:07:03.589 and hoping for the best. Kind of. It's incredible 00:07:03.589 --> 00:07:05.930 to think of them just sending up balloons, completely 00:07:05.930 --> 00:07:08.370 unaware they were laying the groundwork for discovering 00:07:08.370 --> 00:07:11.579 an entirely new atmospheric layer. What a leap 00:07:11.579 --> 00:07:13.759 of faith and ingenuity. So they were essentially 00:07:13.759 --> 00:07:15.560 sending up little weather stations on a string 00:07:15.560 --> 00:07:18.759 almost. Precisely. And their work paved the way 00:07:18.759 --> 00:07:21.839 for more systematic balloon -based measurements 00:07:21.839 --> 00:07:25.759 toward the end of the 1800s, notably by Léon 00:07:25.759 --> 00:07:28.680 Tesserin de Borde in France and Richard Assmann 00:07:28.680 --> 00:07:31.540 in Germany. Okay, more systematic efforts. Yeah, 00:07:31.560 --> 00:07:34.560 they used balloons made of paper, silk, rubber, 00:07:35.240 --> 00:07:37.800 constantly refining their techniques. And what 00:07:37.800 --> 00:07:40.029 they discovered was truly groundbreaking. What 00:07:40.029 --> 00:07:42.269 was it? They found that temperature didn't just 00:07:42.269 --> 00:07:44.170 keep dropping the higher you went, which was 00:07:44.170 --> 00:07:45.829 the common belief. Great, colder, higher up. 00:07:46.110 --> 00:07:48.689 Instead, they observed a distinct layer above 00:07:48.689 --> 00:07:51.670 roughly 11 to 14 kilometers, where the temperature 00:07:51.670 --> 00:07:54.410 either stabilized or even increased with height. 00:07:54.569 --> 00:07:57.230 Increased. That's counterintuitive. Totally unexpected. 00:07:57.629 --> 00:07:59.730 And that finding marked nothing less than the 00:07:59.730 --> 00:08:02.509 discovery of the stratosphere. a whole new layer 00:08:02.509 --> 00:08:05.490 of our atmosphere. Wow. The stratosphere, that's 00:08:05.490 --> 00:08:08.189 a huge discovery. How did that early balloon 00:08:08.189 --> 00:08:11.170 tech evolve into what we use today? Well, these 00:08:11.170 --> 00:08:13.329 early experiments, where they often had to recover 00:08:13.329 --> 00:08:15.350 the instruments manually. Right, flying the balloon. 00:08:15.509 --> 00:08:18.209 Yeah. They rapidly led to the development of 00:08:18.209 --> 00:08:21.829 what we now call radiosons. That was a massive 00:08:21.829 --> 00:08:24.970 technological leap. Radiosons, okay. Imagine 00:08:24.970 --> 00:08:28.129 a small weather balloon carrying a compact instrument 00:08:28.129 --> 00:08:31.019 package. Maybe the size of a shoebox, measuring 00:08:31.019 --> 00:08:34.259 temperature, pressure, humidity. But crucially, 00:08:34.659 --> 00:08:37.720 unlike the earlier ones, radio suns could transmit 00:08:37.720 --> 00:08:40.080 these measurements directly down to ground stations 00:08:40.080 --> 00:08:43.700 via radio. Ah, real -time data. Exactly, real 00:08:43.700 --> 00:08:45.960 -time data from much higher altitudes as they 00:08:45.960 --> 00:08:48.940 went up. It revolutionized atmospheric observation. 00:08:49.129 --> 00:08:52.309 Now, truly global records of free atmosphere 00:08:52.309 --> 00:08:54.230 temperature didn't really kick in until around 00:08:54.230 --> 00:08:57.529 1946, or maybe more broadly with the International 00:08:57.529 --> 00:09:01.179 Geophysical Year in 1958. IGY 58, right. But 00:09:01.179 --> 00:09:04.039 statistical reconstructions using historical 00:09:04.039 --> 00:09:06.779 upper air and surface data can even extend back 00:09:06.779 --> 00:09:09.360 as early as 1918. So the observational network 00:09:09.360 --> 00:09:11.320 was definitely growing. OK, so we're getting 00:09:11.320 --> 00:09:13.440 temperature data from higher up. What about the 00:09:13.440 --> 00:09:15.159 historical chemical record? How did they know 00:09:15.159 --> 00:09:17.740 what CO2 levels were actually like way back then 00:09:17.740 --> 00:09:20.539 before Arrhenius? That's where Earth itself acts 00:09:20.539 --> 00:09:23.480 as a kind of historical archive. Oh, so. The 00:09:23.480 --> 00:09:25.519 vast ice sheets of Antarctica and Greenland. 00:09:25.940 --> 00:09:28.039 These ice cores act like frozen time capsules. 00:09:28.159 --> 00:09:31.000 Right, the ice cores. As snow falls in compacts 00:09:31.000 --> 00:09:33.720 over millennia, it traps tiny bubbles of ancient 00:09:33.720 --> 00:09:36.679 air. Scientists can drill down, extract these 00:09:36.679 --> 00:09:39.019 cores, sometimes hundreds or thousands of meters 00:09:39.019 --> 00:09:41.659 deep, and analyze the air trapped in those bubbles. 00:09:41.879 --> 00:09:44.159 A direct sample of past air. A direct sample 00:09:44.159 --> 00:09:47.059 of Earth's past atmosphere. They've revealed 00:09:47.059 --> 00:09:49.820 precise historical signals of carbon dioxide, 00:09:50.039 --> 00:09:53.240 methane, other greenhouse gases, going back hundreds 00:09:53.240 --> 00:09:55.620 of thousands of years, way before the Industrial 00:09:55.620 --> 00:09:58.759 Revolution. So what did they show for the period 00:09:58.759 --> 00:10:01.120 we're talking about, the late 1800s? From those 00:10:01.120 --> 00:10:05.120 cores, we know that between 1860 and 1899, atmospheric 00:10:05.120 --> 00:10:07.720 carbon dioxide was growing at a rate of approximately 00:10:07.720 --> 00:10:10.399 2 .5 parts per million by volume per decade. 00:10:10.519 --> 00:10:13.100 Okay, so a measurable increase even then. A measurable 00:10:13.100 --> 00:10:16.059 increase. So you had the theoretical understanding 00:10:16.059 --> 00:10:18.340 from Arrhenius, the developing observational 00:10:18.340 --> 00:10:20.659 methods for the atmosphere, and now, thanks to 00:10:20.659 --> 00:10:23.720 ice cores, a detailed historical chemical record. 00:10:23.799 --> 00:10:26.549 The pieces were starting to come together. By 00:10:26.549 --> 00:10:29.350 the late 1800s, early 1900s, the picture was 00:10:29.350 --> 00:10:33.090 emerging. Burning fossil fuels released CO2. 00:10:33.110 --> 00:10:35.669 CO2 enhanced the greenhouse effect that would 00:10:35.669 --> 00:10:38.490 warm the surface. And the ability to measure 00:10:38.490 --> 00:10:40.950 atmospheric temperatures was advancing fast. 00:10:41.690 --> 00:10:44.389 But, and this seems like a big but, there was 00:10:44.389 --> 00:10:46.250 still a crucial missing piece, wasn't there? 00:10:46.389 --> 00:10:48.009 Something preventing them from getting the full 00:10:48.009 --> 00:10:50.070 picture. You've hit on the critical point. Yes. 00:10:50.360 --> 00:10:53.799 They knew broadly that CO2 would warm the surface, 00:10:53.799 --> 00:10:56.000 but they didn't yet have a clear understanding 00:10:56.000 --> 00:10:59.399 of exactly how these elevated CO2 levels would 00:10:59.399 --> 00:11:01.700 specifically change the vertical structure of 00:11:01.700 --> 00:11:03.559 atmospheric temperature. Meaning? Meaning they 00:11:03.559 --> 00:11:05.899 didn't fully grasp the distinct and different 00:11:05.899 --> 00:11:08.779 effects on the stratosphere versus the troposphere, 00:11:09.120 --> 00:11:11.039 that lowest layer where we live where weather 00:11:11.039 --> 00:11:13.419 happens. Ah, the cooling versus warming pattern. 00:11:13.720 --> 00:11:16.080 Precisely. That critical understanding that detailed 00:11:16.080 --> 00:11:17.879 modeling works that could show those precise 00:11:17.879 --> 00:11:20.830 vertical changes wouldn't become a until much, 00:11:20.889 --> 00:11:23.269 much later, specifically with groundbreaking 00:11:23.269 --> 00:11:26.009 modeling work published in the 1960s. Wow, the 00:11:26.009 --> 00:11:29.470 1960s, that's a significant gap. A huge gap between 00:11:29.470 --> 00:11:32.450 the initial theory and the ability to detect 00:11:32.450 --> 00:11:35.029 the specific pattern, the unique fingerprint 00:11:35.029 --> 00:11:38.450 of human influence. And that missing piece, that 00:11:38.450 --> 00:11:41.110 later development of sophisticated climate models, 00:11:41.610 --> 00:11:43.929 brings us right to the core of this fascinating 00:11:43.929 --> 00:11:46.570 research we're discussing. The central question 00:11:46.570 --> 00:11:49.149 the scientists posed was, well, it was truly 00:11:49.149 --> 00:11:51.970 audacious, wasn't it? It really was. When could 00:11:51.970 --> 00:11:54.590 scientists first have definitively known that 00:11:54.590 --> 00:11:57.110 fossil fuel burning was significantly altering 00:11:57.110 --> 00:12:00.210 the global climate if they had access to today's 00:12:00.210 --> 00:12:02.610 advanced tools and models? Yeah, the big what 00:12:02.610 --> 00:12:05.230 if. And this contrasts sharply with a lot of 00:12:05.230 --> 00:12:06.970 previous studies, right? which mostly looked 00:12:06.970 --> 00:12:09.769 at surface temperature changes or maybe paleoclimate 00:12:09.769 --> 00:12:12.230 reconstructions. Exactly. Those often suggested 00:12:12.230 --> 00:12:15.269 a later detection time for human influence, sometimes 00:12:15.269 --> 00:12:17.570 well into the 20th century. But this study took 00:12:17.570 --> 00:12:20.009 a different angle. What's unique about this particular 00:12:20.009 --> 00:12:23.409 research and why it's so compelling is its deliberate 00:12:23.409 --> 00:12:26.149 focus on the stratosphere. Why the stratosphere? 00:12:26.450 --> 00:12:28.950 Because that upper layer of the atmosphere is 00:12:28.950 --> 00:12:31.889 expected to show a remarkably large human -caused 00:12:31.889 --> 00:12:34.570 signal with very distinct patterns of change. 00:12:34.960 --> 00:12:38.220 Think of it this way. The stratosphere is like 00:12:38.220 --> 00:12:42.240 a quiet room. A small sound in a quiet room would 00:12:42.240 --> 00:12:44.779 be much easier to hear than in a noisy concert 00:12:44.779 --> 00:12:47.000 hall, right? Right. The concert hall being the 00:12:47.000 --> 00:12:49.539 troposphere. Pretty much. The troposphere has 00:12:49.539 --> 00:12:53.139 much more natural variability, more noise. So 00:12:53.139 --> 00:12:55.460 the stratosphere makes the signal potentially 00:12:55.460 --> 00:12:58.879 much clearer, easier to detect, especially early 00:12:58.879 --> 00:13:01.500 on. It's a strategic move to find the earliest 00:13:01.500 --> 00:13:03.840 possible evidence of our impact. So if we're 00:13:03.840 --> 00:13:06.480 going back in time, hypothetically, with today's 00:13:06.480 --> 00:13:10.019 tech, how did they actually construct this scenario? 00:13:10.179 --> 00:13:11.559 It sounds like something out of science fiction, 00:13:11.700 --> 00:13:13.960 this Gdankin world. It's an ingenious approach, 00:13:14.159 --> 00:13:16.179 this Gdankin world, a thought experiment world. 00:13:16.299 --> 00:13:19.139 To answer the big question, the researchers constructed 00:13:19.139 --> 00:13:21.419 this simulated scenario with some key assumptions. 00:13:21.519 --> 00:13:23.919 OK, what were they? First, they assumed that 00:13:23.919 --> 00:13:26.159 global monitoring of atmospheric temperature 00:13:26.159 --> 00:13:28.940 with the kind of accuracy we achieve today could 00:13:28.940 --> 00:13:32.409 have existed as early as 1860. Wow. So imagine 00:13:32.409 --> 00:13:35.570 super accurate sensors everywhere back in 1860. 00:13:35.830 --> 00:13:38.470 Exactly. A network of highly advanced radiosondes 00:13:38.470 --> 00:13:41.450 or even early satellite -like instruments beaming 00:13:41.450 --> 00:13:44.590 back perfectly accurate data from every corner 00:13:44.590 --> 00:13:47.909 of the globe right from 1860. That's a huge what 00:13:47.909 --> 00:13:51.750 if. What else do they assume about these futuristic 00:13:51.750 --> 00:13:54.029 historical instruments? They went further. Second, 00:13:54.240 --> 00:13:56.559 They assumed that any instruments available back 00:13:56.559 --> 00:13:59.080 then in this hypothetical world would have had 00:13:59.080 --> 00:14:02.500 the same incredible accuracy as today's satellite 00:14:02.500 --> 00:14:04.940 -borne microwave radiometers. The really precise 00:14:04.940 --> 00:14:07.000 ones we use now. Yeah, these sensors measure 00:14:07.000 --> 00:14:09.700 microwave radiation emitted by oxygen molecules, 00:14:10.200 --> 00:14:12.159 allowing for very accurate temperature profiling. 00:14:12.379 --> 00:14:15.600 So this assumption just eliminates any technological 00:14:15.600 --> 00:14:18.159 limitations of the past. It lets them isolate 00:14:18.159 --> 00:14:20.620 just the climate signal itself. And the input 00:14:20.620 --> 00:14:23.879 data for their models, the CO2 levels and stuff. 00:14:24.159 --> 00:14:26.519 Third, they ensured that the climate model simulations 00:14:26.519 --> 00:14:29.179 they used for this historical analysis had access 00:14:29.179 --> 00:14:31.740 to completely reliable estimates of carbon dioxide 00:14:31.740 --> 00:14:34.340 changes. Using the ice core data and direct measurements 00:14:34.340 --> 00:14:36.980 we talked about? Exactly. Drawn from those ice 00:14:36.980 --> 00:14:39.379 core records, and later direct air measurements, 00:14:40.019 --> 00:14:42.000 providing the models with a perfectly accurate 00:14:42.000 --> 00:14:45.360 historical precedent, forcing the driver of the 00:14:45.360 --> 00:14:48.480 change. So armed with this idealized historical 00:14:48.480 --> 00:14:52.120 data and today's super accurate tools, what were 00:14:52.120 --> 00:14:54.059 they actually hoping to achieve with this thought 00:14:54.059 --> 00:14:56.679 experiment? What were the goals? This experiment 00:14:56.679 --> 00:14:59.799 had dual ambitious goals. Primarily, it aimed 00:14:59.799 --> 00:15:02.360 to estimate the detection times of human -caused 00:15:02.360 --> 00:15:04.779 temperature fingerprints across different atmospheric 00:15:04.779 --> 00:15:07.179 layers, stratosphere, troposphere, and across 00:15:07.179 --> 00:15:09.879 various geographical regions. Okay, so when and 00:15:09.879 --> 00:15:11.899 where could it have been detected? Right, but 00:15:11.899 --> 00:15:14.340 it also aimed to understand how those detection 00:15:14.340 --> 00:15:16.919 times would vary based on different choices of 00:15:16.919 --> 00:15:19.360 the assumed start date for this hypothetical 00:15:19.360 --> 00:15:22.879 monitoring. So starting in 1860 versus, say, 00:15:23.159 --> 00:15:25.419 1900. Exactly. They explored a wide range of 00:15:25.419 --> 00:15:28.120 start dates from that initial point in 1860 all 00:15:28.120 --> 00:15:31.779 the way up to 1986. Why 1986? That's when truly 00:15:31.779 --> 00:15:34.519 global satellite records of atmospheric temperature 00:15:34.519 --> 00:15:37.899 change actually began in the real world. So this 00:15:37.899 --> 00:15:40.320 allowed them to see not just when a signal could 00:15:40.320 --> 00:15:43.480 be detected, but how that detection time itself 00:15:43.480 --> 00:15:45.720 shifts depending on when you start observing. 00:15:45.870 --> 00:15:48.230 Fascinating. And central to this whole thing, 00:15:48.389 --> 00:15:50.429 you mentioned a technique called fingerprinting. 00:15:50.570 --> 00:15:52.750 Can you explain that a bit more? How do you fingerprint 00:15:52.750 --> 00:15:55.690 a human climate signal? Yeah, the fingerprinting 00:15:55.690 --> 00:15:57.970 method is really the cornerstone here. It's a 00:15:57.970 --> 00:16:00.590 powerful statistical technique used in climate 00:16:00.590 --> 00:16:03.909 science. Its job is to distinguish human -caused 00:16:03.909 --> 00:16:07.139 climate effects from natural variations. Like 00:16:07.139 --> 00:16:09.860 picking out one voice in a noisy crowd. That's 00:16:09.860 --> 00:16:12.460 a great analogy. Fingerprinting looks for unique 00:16:12.460 --> 00:16:14.980 patterns, like the distinctive sound of a human 00:16:14.980 --> 00:16:17.200 -caused climate signal amidst the background 00:16:17.200 --> 00:16:19.480 noise of natural climate variability. And the 00:16:19.480 --> 00:16:21.159 climate system has a lot of natural noise, right? 00:16:21.259 --> 00:16:23.879 El Nino, volcanoes. Exactly. El Nino, volcanic 00:16:23.879 --> 00:16:26.419 eruptions, solar cycles. This system is inherently 00:16:26.419 --> 00:16:29.700 noisy. So you need a robust way to confidently 00:16:29.700 --> 00:16:31.679 say, OK, this pattern we're seeing isn't just 00:16:31.679 --> 00:16:34.169 natural noise. This is us. So they're looking 00:16:34.169 --> 00:16:36.690 for a specific signature, a specific pattern. 00:16:36.909 --> 00:16:39.870 Precisely. Specifically, this method searches 00:16:39.870 --> 00:16:43.929 for particular model predicted patterns of atmospheric 00:16:43.929 --> 00:16:46.269 temperature change that are characteristic of 00:16:46.269 --> 00:16:48.590 combined human and natural influences. And for 00:16:48.590 --> 00:16:51.210 the human fingerprint, that pattern is? It's 00:16:51.210 --> 00:16:53.809 very distinct, characterized by stratospheric 00:16:53.809 --> 00:16:56.649 cooling and simultaneously tropospheric warming. 00:16:56.809 --> 00:16:59.690 Ah, that vertical structure again. Exactly. It's 00:16:59.690 --> 00:17:01.909 not just a uniform change across the whole atmosphere. 00:17:02.049 --> 00:17:04.950 Yeah. It's a specific vertically differentiated 00:17:04.950 --> 00:17:07.809 structure of warming and cooling that models 00:17:07.809 --> 00:17:10.190 predict our emissions would cause. It's like 00:17:10.190 --> 00:17:12.890 a unique barcode for human influence. And how 00:17:12.890 --> 00:17:15.650 do they know when that signal, that barcode, 00:17:15.910 --> 00:17:17.910 is strong enough to be considered a definitive 00:17:17.910 --> 00:17:20.869 detection, not just a random blip? Good question. 00:17:21.049 --> 00:17:23.190 The confidence in detection relied heavily on 00:17:23.190 --> 00:17:25.849 what scientists call signal -to -noise ratios. 00:17:25.970 --> 00:17:28.589 Okay. Think of our crowded room analogy again. 00:17:29.109 --> 00:17:31.069 If the specific voice you're listening for is 00:17:31.069 --> 00:17:33.490 barely audible, the signal -to -noise ratio is 00:17:33.490 --> 00:17:36.549 low. If the voice gets much louder, or the background 00:17:36.549 --> 00:17:39.390 chatter quiets down, the ratio improves. Makes 00:17:39.390 --> 00:17:41.769 sense. For detection to be considered robust 00:17:41.769 --> 00:17:45.009 in this research, the human -caused signal had 00:17:45.009 --> 00:17:48.390 to be significantly larger than the natural background 00:17:48.390 --> 00:17:51.450 variability. Specifically, the signal -to -noise 00:17:51.450 --> 00:17:54.009 ratio had to remain above a 1 % significance 00:17:54.009 --> 00:17:57.109 level for a sustained period. 1 % significance? 00:17:57.109 --> 00:17:59.670 That sounds pretty strict. It is. It means there's 00:17:59.670 --> 00:18:02.349 less than a 1 % chance that the observed pattern 00:18:02.349 --> 00:18:05.769 is just due to random chance or natural fluctuation. 00:18:06.289 --> 00:18:08.490 It's a very high bar for certainty. Okay, here's 00:18:08.490 --> 00:18:11.529 where it gets truly fascinating. the results 00:18:11.529 --> 00:18:14.609 of this hypothetical experiment, they were absolutely 00:18:14.609 --> 00:18:17.190 startling, weren't they? Especially for the stratosphere. 00:18:17.420 --> 00:18:20.839 So what did this thought experiment, this Kadankan 00:18:20.839 --> 00:18:24.079 world, reveal first? The headline finding, the 00:18:24.079 --> 00:18:26.779 one that really makes you pause, was that a human 00:18:26.779 --> 00:18:29.380 -caused stratospheric cooling signal could have 00:18:29.380 --> 00:18:31.440 been confidently identified by approximately 00:18:31.440 --> 00:18:35.059 1885. 1885. Let that sink in. That's a century 00:18:35.059 --> 00:18:36.960 before many people even started talking about 00:18:36.960 --> 00:18:39.220 climate change seriously. Before cars were common, 00:18:39.400 --> 00:18:41.579 before widespread electricity. How is that even 00:18:41.579 --> 00:18:43.900 possible? It's astonishing, isn't it? That's 00:18:43.900 --> 00:18:47.619 just 25 years after the hypothetical 1860 monitoring 00:18:47.619 --> 00:18:50.960 start date. Just 25 years? And what's more, even 00:18:50.960 --> 00:18:53.420 if this hypothetical monitoring in 1860 hadn't 00:18:53.420 --> 00:18:57.240 been global, say we only had high quality stratospheric 00:18:57.240 --> 00:18:59.200 temperature measurements in a limited region 00:18:59.200 --> 00:19:01.920 like northern hemisphere mid -latitudes, detection 00:19:01.920 --> 00:19:05.640 was still feasible by 1894, yearly 34 years after 00:19:05.640 --> 00:19:08.460 the assumed start. Why that region specifically? 00:19:08.500 --> 00:19:10.779 That region, the northern hemisphere mid -latitudes, 00:19:11.200 --> 00:19:13.680 actually aided early detection because it generally 00:19:13.680 --> 00:19:15.759 exhibits lower natural temperature variability 00:19:15.759 --> 00:19:18.599 in the stratosphere compared to, say, the more 00:19:18.599 --> 00:19:21.140 dynamic polar regions. Ah, so it was a quieter 00:19:21.140 --> 00:19:23.599 place to listen for the signal. Exactly. Made 00:19:23.599 --> 00:19:25.640 it easier to spot the emerging human signal. 00:19:25.960 --> 00:19:29.319 And the scale of the emissions back then compared 00:19:29.319 --> 00:19:31.440 to now, it must have been minuscule. Precisely. 00:19:31.559 --> 00:19:34.079 What makes this even more profound is the scale 00:19:34.079 --> 00:19:36.940 of the change at this early stage. The decadal 00:19:36.940 --> 00:19:39.759 increase in atmospheric CO2 between 1860 and 00:19:39.759 --> 00:19:42.579 1899 was roughly 10 parts per million total. 00:19:42.960 --> 00:19:45.960 OK, 10 ppm over about 40 years. Right. Compare 00:19:45.960 --> 00:19:48.539 that to the first 25 years of the 21st century, 00:19:48.940 --> 00:19:53.299 2020 -25, where CO2 levels shot up by about 50 00:19:53.299 --> 00:19:56.000 parts per million. Wow. So the increase in the 00:19:56.000 --> 00:19:59.240 late 1800s was a factor of nine smaller than 00:19:59.240 --> 00:20:02.500 what we've seen recently. Yet the signal was 00:20:02.500 --> 00:20:04.480 apparently clear enough to be detected in the 00:20:04.480 --> 00:20:07.180 stratosphere, hypothetically. So why the stratosphere 00:20:07.180 --> 00:20:10.319 first? What makes that specific layer so sensitive 00:20:10.319 --> 00:20:13.019 to our emissions, and why does it show this cooling 00:20:13.019 --> 00:20:15.460 signature? It seems backward. Yeah, it seems 00:20:15.460 --> 00:20:17.819 counterintuitive, but there are compelling physical 00:20:17.819 --> 00:20:21.130 reasons. First, as we touched on, anthropogenic 00:20:21.130 --> 00:20:24.150 increases in CO2 lead to a very pronounced cooling 00:20:24.150 --> 00:20:26.329 of the mid to upper stratosphere. Right. Unlike 00:20:26.329 --> 00:20:28.349 the troposphere, which warms. Exactly. Think 00:20:28.349 --> 00:20:30.710 of it this way. CO2 in the troposphere acts like 00:20:30.710 --> 00:20:33.049 a blanket, trapping outgoing heat from the Earth's 00:20:33.049 --> 00:20:35.869 surface. But in the stratosphere, the increasing 00:20:35.869 --> 00:20:38.390 CO2 means more heat is radiated away from the 00:20:38.390 --> 00:20:40.690 stratosphere, directly out into space. So it 00:20:40.690 --> 00:20:43.549 becomes a better radiator at that altitude. Precisely. 00:20:43.829 --> 00:20:45.910 It becomes a more efficient radiator of energy 00:20:45.910 --> 00:20:48.289 from that altitude. Okay, so it's like the CO2 00:20:48.289 --> 00:20:50.630 is acting as a window for heat to escape from 00:20:50.630 --> 00:20:52.430 that specific layer. That's a good way to put 00:20:52.430 --> 00:20:55.150 it. Second, the pattern of this human -caused 00:20:55.150 --> 00:20:58.230 cooling is remarkably distinct. It differs markedly 00:20:58.230 --> 00:21:00.170 from the patterns of natural variability, making 00:21:00.170 --> 00:21:03.109 it easier to pick out. The unique barcode. Right. 00:21:03.630 --> 00:21:06.329 Third, this CO2 -induced stratospheric cooling 00:21:06.329 --> 00:21:08.789 actually amplifies with increasing height. It 00:21:08.789 --> 00:21:10.690 gets even stronger the higher you go into the 00:21:10.690 --> 00:21:12.410 stratosphere. How much cooling are we talking 00:21:12.410 --> 00:21:15.430 about? Over the entire simulated period. From 00:21:15.430 --> 00:21:19.950 1860 to 2024, the multi -model average global 00:21:19.950 --> 00:21:22.470 mean stratosphere cooling ranged from about 1 00:21:22.470 --> 00:21:25.150 .1 degrees Celsius in the lower stratosphere 00:21:25.150 --> 00:21:28.410 to a significant 6 .0 degrees Celsius in the 00:21:28.410 --> 00:21:30.750 upper stratosphere. Six degrees. That's a huge 00:21:30.750 --> 00:21:33.470 temperature shift over time. It is. And the primary 00:21:33.470 --> 00:21:35.930 mechanisms for this cooling involve that increased 00:21:35.930 --> 00:21:38.849 longwave emissivity from CO2 radiating more heat 00:21:38.849 --> 00:21:41.869 away and also ozone losses, particularly later 00:21:41.869 --> 00:21:44.869 in the 20th century. Ozone absorbs solar radiation, 00:21:45.089 --> 00:21:47.470 so less ozone means less absorption, leading 00:21:47.470 --> 00:21:50.309 to further cooling. So multiple factors reinforcing 00:21:50.309 --> 00:21:53.809 that cooling signal. Yes. It's a very clear, 00:21:54.029 --> 00:21:56.210 strong signature that doesn't get easily ground 00:21:56.210 --> 00:21:58.789 out by natural noise, especially compared to 00:21:58.789 --> 00:22:01.250 the troposphere. Okay, so while the stratosphere 00:22:01.250 --> 00:22:04.990 provided this early striking signal, the troposphere... 00:22:04.960 --> 00:22:07.380 the layer closer to home where weather happens 00:22:07.380 --> 00:22:10.299 told a different story. What did the models reveal 00:22:10.299 --> 00:22:12.740 about temperature trends down there? Right, down 00:22:12.740 --> 00:22:15.400 below it's different. Unlike the stratosphere, 00:22:15.819 --> 00:22:17.940 the two tropospheric layers looked at the lower 00:22:17.940 --> 00:22:21.039 and the total troposphere have consistently warmed 00:22:21.039 --> 00:22:23.940 in both the satellite data we have and in the 00:22:23.940 --> 00:22:26.220 climate models. Which is what we generally associate 00:22:26.220 --> 00:22:28.240 with global warming. Exactly. That's the warming 00:22:28.240 --> 00:22:30.339 we feel on the surface, the warming that impacts 00:22:30.339 --> 00:22:32.920 our daily lives. The multimodal average warming 00:22:32.920 --> 00:22:36.299 simulated from 1860 to 2024 for these layers 00:22:36.299 --> 00:22:40.319 was about 1 .2 to 1 .3 degrees Celsius. OK, so 00:22:40.319 --> 00:22:43.349 it was warming down there, too. But. Why wasn't 00:22:43.349 --> 00:22:45.730 the human signal detectable as early as in the 00:22:45.730 --> 00:22:47.309 stratosphere? If it was warming, shouldn't that 00:22:47.309 --> 00:22:50.269 be obvious? Ah, that's the crucial distinction. 00:22:50.630 --> 00:22:54.210 Despite this warming, robust, anthropogenic fingerprint 00:22:54.210 --> 00:22:57.230 identification in the troposphere was not feasible 00:22:57.230 --> 00:23:00.869 with an 1860 monitoring start date and only 40 00:23:00.869 --> 00:23:03.750 years of hypothetical data. Not feasible. Why 00:23:03.750 --> 00:23:06.390 not? The human signal simply wasn't strong enough 00:23:06.390 --> 00:23:09.289 yet to clearly stand out from the natural background 00:23:09.289 --> 00:23:12.109 variability in that layer. The noise was too 00:23:11.980 --> 00:23:14.519 high relative to the signal. So when did it become 00:23:14.519 --> 00:23:16.619 clear in the troposphere according to the models? 00:23:17.059 --> 00:23:19.160 Consistent detection of human fingerprints in 00:23:19.160 --> 00:23:21.640 tropospheric temperature only occurred for assumed 00:23:21.640 --> 00:23:25.779 monitoring start dates on or after 1960. 1960, 00:23:26.000 --> 00:23:28.920 that's a significant delay compared to the 1885 00:23:28.920 --> 00:23:31.539 potential in the stratosphere. A very significant 00:23:31.539 --> 00:23:34.000 delay. So the noisy concert hall analogy really 00:23:34.000 --> 00:23:36.099 holds true here then. The human signal, the warming 00:23:36.099 --> 00:23:38.079 was there, but it was just harder to pick out 00:23:38.079 --> 00:23:40.480 from all the other sounds. Exactly. And the reason 00:23:40.480 --> 00:23:42.980 for this delay is multifaceted. Firstly, as we 00:23:42.980 --> 00:23:45.299 said, the global mean anthropogenic signals are 00:23:45.299 --> 00:23:47.519 generally smaller in magnitude in the troposphere 00:23:47.519 --> 00:23:49.740 compared to the dramatic cooling in the stratosphere. 00:23:49.799 --> 00:23:52.809 OK, smaller signal. Secondly, And this is critical 00:23:52.809 --> 00:23:55.390 for the fingerprinting method. The signal patterns 00:23:55.390 --> 00:23:58.710 from human influence and the noise patterns from 00:23:58.710 --> 00:24:01.930 natural variability are more similar in the troposphere. 00:24:02.069 --> 00:24:04.549 Ah, so they look more alike. Yes, they tend to 00:24:04.549 --> 00:24:07.589 blend more, making it inherently harder to distinguish 00:24:07.589 --> 00:24:10.309 the human influence from natural ups and downs 00:24:10.309 --> 00:24:13.369 early on. Okay. Any other factors? Furthermore, 00:24:13.549 --> 00:24:16.250 the rate of warming in the troposphere only saw 00:24:16.250 --> 00:24:18.450 a really significant increase after approximately 00:24:18.450 --> 00:24:22.450 1980. Why after 1980? This acceleration was partly 00:24:22.450 --> 00:24:25.170 due to controls introduced on anthropogenic sulfur 00:24:25.170 --> 00:24:27.950 emissions, mainly in the late 1970s and early 00:24:27.950 --> 00:24:31.529 80s. Think acid rain regulations. Right, sulfur 00:24:31.529 --> 00:24:34.509 pollution. Prior to those controls, sulfate aerosols 00:24:34.509 --> 00:24:37.049 from human industrial activity actually had a 00:24:37.049 --> 00:24:38.930 damping cooling effect on the troposphere. They 00:24:38.930 --> 00:24:40.970 reflected sunlight. So they were masking some 00:24:40.970 --> 00:24:43.730 of the greenhouse warming. Effectively, yes. 00:24:43.869 --> 00:24:45.690 They were masking some of the underlying warming 00:24:45.690 --> 00:24:48.980 trend from greenhouse gases. Once those aerosols 00:24:48.980 --> 00:24:51.539 were reduced, the greenhouse gas warming signal 00:24:51.539 --> 00:24:54.359 became much more apparent and accelerated. So, 00:24:54.799 --> 00:24:56.880 natural forces and even other human pollutants 00:24:56.880 --> 00:24:59.759 can act as a kind of cloak, temporarily obscuring 00:24:59.759 --> 00:25:02.490 the main CO2 signal. Let's talk more about that 00:25:02.490 --> 00:25:04.710 natural variability. It's not just CO2 driving 00:25:04.710 --> 00:25:07.829 things. How does something like a massive volcanic 00:25:07.829 --> 00:25:11.349 eruption impact this detection process? Volcanoes 00:25:11.349 --> 00:25:15.069 are indeed powerful short -term disruptors. Large 00:25:15.069 --> 00:25:19.250 explosive eruptions think Krakatoa in 1883, Pinatubo 00:25:19.250 --> 00:25:24.019 in 1991. A gum. Right. Those inject vast amounts 00:25:24.019 --> 00:25:26.680 of sulfur dioxide high into the stratosphere. 00:25:27.160 --> 00:25:30.019 This SO2 converts into tiny sulfate aerosols 00:25:30.019 --> 00:25:31.799 that reflect sunlight. Okay, and these cause 00:25:31.799 --> 00:25:34.740 temperature changes. Oh yes. Very distinct short 00:25:34.740 --> 00:25:36.759 -term signals. How do they affect the stratosphere 00:25:36.759 --> 00:25:39.720 specifically? We know CO2 cools it. Right. Volcanoes 00:25:39.720 --> 00:25:42.240 do the opposite, temporarily. In the stratosphere, 00:25:42.380 --> 00:25:44.220 especially the lower stratosphere, where most 00:25:44.220 --> 00:25:46.519 of the volcanic aerosol hangs out, these eruptions 00:25:46.519 --> 00:25:49.059 cause a temporary warming signal. Warming? Why 00:25:49.059 --> 00:25:51.470 warming there? The aerosols absorb some radiation 00:25:51.470 --> 00:25:53.890 at that altitude. This warming typically lasts 00:25:53.890 --> 00:25:56.349 one to three years. So it's the exact converse 00:25:56.349 --> 00:25:59.069 of the long -term cooling signal from CO2. So 00:25:59.069 --> 00:26:03.150 a volcano could temporarily cancel out or mask 00:26:03.150 --> 00:26:05.809 the human cooling signal there. Exactly. It can 00:26:05.809 --> 00:26:07.690 temporarily counteract the human fingerprint 00:26:07.690 --> 00:26:10.069 in the stratosphere, making it harder to spot, 00:26:10.509 --> 00:26:12.769 like someone briefly turning up background noise. 00:26:12.990 --> 00:26:14.910 And what about down in the troposphere? We usually 00:26:14.910 --> 00:26:17.819 hear volcanoes cause cooling. Correct. Down in 00:26:17.819 --> 00:26:20.180 the troposphere, these same eruptions cause short 00:26:20.180 --> 00:26:22.660 -term cooling signals. This generally lasts a 00:26:22.660 --> 00:26:24.759 bit longer, maybe three to five years. Because 00:26:24.759 --> 00:26:26.839 the aerosols block sunlight from reaching the 00:26:26.839 --> 00:26:29.279 surface. Precisely. So what this means for our 00:26:29.279 --> 00:26:31.359 detection timeline is that volcanic activity 00:26:31.359 --> 00:26:34.200 can temporarily cause the human signal either 00:26:34.200 --> 00:26:36.539 stratospheric cooling or tropospheric warming 00:26:36.539 --> 00:26:39.500 to dip below the detection threshold. Briefly 00:26:39.500 --> 00:26:42.180 delaying recognition. Yes. For instance, the 00:26:42.180 --> 00:26:44.400 study notes that the massive Krakatoa eruption 00:26:44.400 --> 00:26:46.880 caused a noticeable dip in the signal -to -noise 00:26:46.880 --> 00:26:51.400 ratios around 1883 -1885, momentarily obscuring 00:26:51.400 --> 00:26:53.680 the human fingerprint just as it was trying to 00:26:53.680 --> 00:26:57.529 emerge in that hypothetical 1885 detection scenario. 00:26:58.170 --> 00:26:59.690 Interesting. And the troposphere cooling lasts 00:26:59.690 --> 00:27:03.730 longer? Tends to, yes. Volcanic temperature signals 00:27:03.730 --> 00:27:05.890 generally persist longer in the troposphere than 00:27:05.890 --> 00:27:08.750 the stratosphere, largely due to the huge thermal 00:27:08.750 --> 00:27:11.150 inertia of the ocean. Ah, the ocean takes longer 00:27:11.150 --> 00:27:13.789 to cool down and then warm back up. Exactly. 00:27:13.970 --> 00:27:15.789 It holds onto that volcanic chill for longer. 00:27:15.809 --> 00:27:19.130 Okay, so volcanoes are big short shocks. What 00:27:19.130 --> 00:27:22.009 other natural forces create this noise or maybe 00:27:22.009 --> 00:27:23.990 ripples in the signal? I'm thinking about the 00:27:23.990 --> 00:27:26.619 sun itself. Does solar activity play a role? 00:27:26.940 --> 00:27:29.539 Excellent point. Yes, beyond volcanoes, solar 00:27:29.539 --> 00:27:32.440 variability also plays an important role, primarily 00:27:32.440 --> 00:27:35.000 through its roughly 11 -year cycle. The sunspot 00:27:35.000 --> 00:27:38.359 cycle. Right. The total solar irradiance, or 00:27:38.359 --> 00:27:42.119 TSI, the total amount of solar energy Earth receives 00:27:42.119 --> 00:27:44.859 fluctuates slightly on this rhythm. It varies 00:27:44.859 --> 00:27:47.240 by a small percentage. And that affects temperature. 00:27:47.480 --> 00:27:50.460 It does. This fluctuation causes coherent stratospheric 00:27:50.460 --> 00:27:53.140 warming during periods of high TSI when the Sun 00:27:53.140 --> 00:27:55.880 is more active and corresponding cooling during 00:27:55.880 --> 00:27:58.920 periods of low TSI. Okay, so the Sun's activity 00:27:58.920 --> 00:28:01.200 can either help or hinder us in spotting the 00:28:01.200 --> 00:28:04.160 human CO2 signal in the stratosphere. Precisely. 00:28:04.359 --> 00:28:07.880 This natural solar forcing can either reinforce 00:28:07.880 --> 00:28:11.119 the human -caused CO2 cooling if the sun is in 00:28:11.119 --> 00:28:14.880 a cooling phase, or partially offset it if the 00:28:14.880 --> 00:28:17.640 sun is in a warming phase. Making the human signal 00:28:17.640 --> 00:28:21.119 easier or harder to detect. Exactly. It influences 00:28:21.119 --> 00:28:23.259 the strength and clarity of the human signal, 00:28:23.759 --> 00:28:26.180 especially for those early monitoring start dates 00:28:26.180 --> 00:28:28.539 when the anthropogenic signal was relatively 00:28:28.539 --> 00:28:31.019 smaller. It's like another instrument in our 00:28:31.019 --> 00:28:33.920 orchestra, either playing in harmony or slightly 00:28:33.920 --> 00:28:36.789 out of tune with our target CO2 sound. And it's 00:28:36.789 --> 00:28:39.670 not just the regular 11 -year cycle itself, is 00:28:39.670 --> 00:28:41.789 it? There are longer -term variations. That's 00:28:41.789 --> 00:28:43.970 right. It's not just the cycle. Longer term, 00:28:44.150 --> 00:28:46.410 lower frequency changes in the amplitude of this 00:28:46.410 --> 00:28:49.630 11 -year solar cycle can also cause what the 00:28:49.630 --> 00:28:52.150 researchers call ripples in the human signal 00:28:52.150 --> 00:28:54.970 strength and the detection times. Ripples, meaning? 00:28:55.089 --> 00:28:57.029 Meaning, the time required for detection doesn't 00:28:57.029 --> 00:28:59.329 always just get shorter and shorter as you start 00:28:59.329 --> 00:29:01.630 monitoring later. Sometimes, because of these 00:29:01.630 --> 00:29:03.569 solar variations, it might take slightly longer 00:29:03.569 --> 00:29:06.250 to reach detection for a later start date compared 00:29:06.250 --> 00:29:08.170 to an earlier one. Can you give an example? Sure. 00:29:08.569 --> 00:29:11.109 The study found that for a hypothetical 1920 00:29:11.109 --> 00:29:13.809 start date, It actually took a bit longer to 00:29:13.809 --> 00:29:16.069 detect the signal compared to a 1900 start tape. 00:29:16.710 --> 00:29:18.109 Part of the reason was that the period following 00:29:18.109 --> 00:29:21.529 1920 sampled larger amplitude solar cycles, meaning 00:29:21.529 --> 00:29:24.150 more pronounced solar warming periods that counteracted 00:29:24.150 --> 00:29:27.789 the CO2 cooling. Another ripple occurred for 00:29:27.789 --> 00:29:30.029 analysis periods ending near a solar maximum 00:29:30.029 --> 00:29:33.069 in the late 1930s. This caused the signal -to 00:29:33.069 --> 00:29:35.430 -noise ratios to temporarily diff below that 00:29:35.430 --> 00:29:38.269 significance threshold, thereby delaying fingerprint 00:29:38.269 --> 00:29:40.309 detection for start dates around that time. So 00:29:40.309 --> 00:29:42.789 it illustrates how these natural solar forces, 00:29:42.869 --> 00:29:44.690 even though they're smaller in magnitude over 00:29:44.690 --> 00:29:47.190 the long haul compared to greenhouse gases, can 00:29:47.190 --> 00:29:49.410 still influence the precise timing of when a 00:29:49.410 --> 00:29:51.809 human signal becomes statistically undeniable. 00:29:51.950 --> 00:29:54.230 Exactly. They add complexity to the detection 00:29:54.230 --> 00:29:57.390 timeline. Okay, so given the hypothetical nature 00:29:57.390 --> 00:30:00.069 of this Gdankin world and all these complexities 00:30:00.069 --> 00:30:03.309 with natural variability, how much confidence 00:30:03.309 --> 00:30:06.109 can we really place in these findings, especially 00:30:06.109 --> 00:30:09.049 those really early detection times like 1885? 00:30:09.660 --> 00:30:12.640 The reliability seems to hinge on how accurately 00:30:12.640 --> 00:30:16.099 the climate models estimate that natural internal 00:30:16.099 --> 00:30:18.579 variability, the noise. That's absolutely right. 00:30:18.960 --> 00:30:21.559 If the models underestimate the noise, wouldn't 00:30:21.559 --> 00:30:23.700 that make the signal look clearer earlier than 00:30:23.700 --> 00:30:25.220 it really would have been? How do we know the 00:30:25.220 --> 00:30:27.240 models are getting the noise right? That's a 00:30:27.240 --> 00:30:29.619 critical question for any modeling study like 00:30:29.619 --> 00:30:32.480 this. You have to validate the model's background 00:30:32.480 --> 00:30:35.559 variability. So how did they check? Well, for 00:30:35.559 --> 00:30:37.220 tropospheric temperature, there have been quite 00:30:37.220 --> 00:30:39.359 a few studies using multiple climate models, 00:30:39.640 --> 00:30:42.220 and they generally suggest that systematic underestimates 00:30:42.220 --> 00:30:44.819 of decadal internal variability are not a major 00:30:44.819 --> 00:30:47.799 concern. Okay. When we compare observed variability 00:30:47.799 --> 00:30:50.099 in the troposphere using our satellite data, 00:30:50.700 --> 00:30:53.400 it generally aligns quite well within the range 00:30:53.400 --> 00:30:55.619 of variability the models produce in their control 00:30:55.619 --> 00:30:58.000 runs. Control runs being simulations without 00:30:58.000 --> 00:31:00.700 human influence. Exactly. They just run the model 00:31:00.700 --> 00:31:03.039 with natural factors to see its inherent variability. 00:31:03.279 --> 00:31:05.319 The fact that the model's natural variability 00:31:05.319 --> 00:31:07.960 matches what we actually observe in the troposphere 00:31:07.960 --> 00:31:10.619 gives us pretty good confidence in the tropospheric 00:31:10.619 --> 00:31:13.359 findings and detection times. OK, confidence 00:31:13.359 --> 00:31:16.779 is good for the troposphere. What about the stratosphere, 00:31:16.859 --> 00:31:18.619 though? That's where the really early detection 00:31:18.619 --> 00:31:21.240 happened. Is the confidence as high there? The 00:31:21.240 --> 00:31:23.440 stratosphere, however, presents a bit more nuance. 00:31:24.039 --> 00:31:28.059 There are simply fewer direct long -term comparisons 00:31:28.059 --> 00:31:30.420 available for stratospheric temperature variability 00:31:30.420 --> 00:31:33.779 between models and observations. Less data to 00:31:33.779 --> 00:31:36.299 compare against. Essentially, yes. We just haven't 00:31:36.299 --> 00:31:38.019 been observing the stratosphere globally for 00:31:38.019 --> 00:31:40.990 as long or as comprehensively. Now, while some 00:31:40.990 --> 00:31:43.710 studies show models sometimes have smaller variability 00:31:43.710 --> 00:31:46.130 in their control runs compared to observations. 00:31:46.390 --> 00:31:48.730 Which would support the idea of maybe detecting 00:31:48.730 --> 00:31:51.309 too early. Right. But it's also true that the 00:31:51.309 --> 00:31:53.990 observed variability, the real world noise, can 00:31:53.990 --> 00:31:56.329 sometimes be inflated by factors that aren't 00:31:56.329 --> 00:31:59.329 fully included in the standard historical simulations 00:31:59.329 --> 00:32:01.789 used for fingerprinting. Like what? For instance, 00:32:02.170 --> 00:32:05.470 specific unusual volcanic eruptions, like the 00:32:05.470 --> 00:32:09.690 huge Hungatanga event in January 2022. that injected 00:32:09.690 --> 00:32:12.589 massive amounts of water vapor into the stratosphere, 00:32:13.150 --> 00:32:15.369 causing unusual temperature effects not typically 00:32:15.369 --> 00:32:18.789 simulated. Or, there might be small mismatches 00:32:18.789 --> 00:32:20.769 in the assumed solar forcing used in the models 00:32:20.769 --> 00:32:22.990 versus what actually happened, especially in 00:32:22.990 --> 00:32:26.309 recent years after 2014. These things can make 00:32:26.309 --> 00:32:29.109 the real world appear noisier. than the models 00:32:29.109 --> 00:32:32.450 might otherwise predict based only on CO2 standard 00:32:32.450 --> 00:32:35.150 volcanoes and solar cycles. So it's complex. 00:32:35.230 --> 00:32:36.890 There might be slight underestimates of model 00:32:36.890 --> 00:32:38.950 noise, but also factors making the real world 00:32:38.950 --> 00:32:41.069 seem noisier than the model baseline. Exactly. 00:32:41.109 --> 00:32:44.009 It's a nuanced picture. So despite these nuances, 00:32:44.269 --> 00:32:46.730 how robust is the conclusion that a human fingerprint 00:32:46.730 --> 00:32:49.970 could have been detected so early back in 1885 00:32:49.970 --> 00:32:52.630 in the stratosphere? Does the uncertainty undermine 00:32:52.630 --> 00:32:55.140 that finding? That's the key question. And the 00:32:55.140 --> 00:32:57.599 answer, based on this research, is that the conclusion 00:32:57.599 --> 00:33:00.460 remains incredibly robust. How so? Even if there 00:33:00.460 --> 00:33:03.180 were some degree of underestimate of stratospheric 00:33:03.180 --> 00:33:06.099 variability in the models, the observed and modeled 00:33:06.099 --> 00:33:09.859 stratospheric cooling trends are just so substantial, 00:33:10.039 --> 00:33:13.180 so large. The signal is huge. The signal is huge. 00:33:13.900 --> 00:33:16.160 Model variability would need to be biased low 00:33:16.160 --> 00:33:19.099 by an order of magnitude, a factor of 10, to 00:33:19.099 --> 00:33:21.940 fully explain away those cooling trends as just 00:33:21.940 --> 00:33:24.660 natural variability. A factor of 10 error? That 00:33:24.660 --> 00:33:27.599 seems unlikely. Highly unlikely, based on everything 00:33:27.599 --> 00:33:29.920 we know about atmospheric physics and model performance. 00:33:30.740 --> 00:33:33.680 In fact, if you recalculate the signal -to -noise 00:33:33.680 --> 00:33:36.519 ratios using the observed variability instead 00:33:36.519 --> 00:33:39.160 of the model's internal variability, the ratios 00:33:39.160 --> 00:33:41.859 remain incredibly strong. How strong? They reach 00:33:41.859 --> 00:33:44.140 levels of certainty comparable to what scientists 00:33:44.140 --> 00:33:47.519 call five sigma in physics. That's the level 00:33:47.519 --> 00:33:49.480 often used to confirm the discovery of a new 00:33:49.480 --> 00:33:52.140 particle, like the Higgs boson. Wow. So virtually 00:33:52.140 --> 00:33:55.000 impossible for it to be just random chance. Essentially, 00:33:55.160 --> 00:33:57.200 yes. Yeah. The signal is that clear in the stratosphere. 00:33:57.400 --> 00:34:00.039 OK. And what about when global satellite records 00:34:00.039 --> 00:34:02.779 actually began in the real world around 1986? 00:34:03.400 --> 00:34:05.480 Did the signal become even clearer then across 00:34:05.480 --> 00:34:07.779 the board? Absolutely. That's another striking 00:34:07.779 --> 00:34:11.699 result. For monitoring, starting in 1986, when 00:34:11.699 --> 00:34:14.000 we actually got comprehensive global satellite 00:34:14.000 --> 00:34:17.440 data, The human fingerprint was detectable with 00:34:17.440 --> 00:34:20.559 high confidence across all atmospheric layers 00:34:20.559 --> 00:34:23.679 stratosphere and troposphere and across all geographical 00:34:23.679 --> 00:34:26.440 regions Everywhere and every single one of the 00:34:26.440 --> 00:34:29.000 32 different climate model simulations used in 00:34:29.000 --> 00:34:31.599 the study every single model run showed it every 00:34:31.599 --> 00:34:34.679 single one And this is true despite the significant 00:34:34.679 --> 00:34:37.619 counteracting effects of the 1991 Mount Pinatubo 00:34:37.619 --> 00:34:40.760 eruption, which, as we discussed, initially warmed 00:34:40.760 --> 00:34:42.619 the stratosphere and cooled the troposphere. 00:34:42.960 --> 00:34:45.179 So even with that huge volcanic disruption? Even 00:34:45.179 --> 00:34:48.139 with Pinatubo's disruption, the underlying anthropogenic 00:34:48.139 --> 00:34:51.159 signal was simply strong enough to emerge clearly 00:34:51.159 --> 00:34:54.059 through that substantial natural noise by that 00:34:54.059 --> 00:34:56.699 point. It provides overwhelming confidence in 00:34:56.699 --> 00:34:58.579 the detection methods and the strength of the 00:34:58.579 --> 00:35:00.980 human signal, especially from the 1980s onwards. 00:35:01.309 --> 00:35:03.869 The message seems clear then. The human signal, 00:35:04.110 --> 00:35:06.110 particularly in the stratosphere, is powerful, 00:35:06.489 --> 00:35:08.730 it's distinct, and it has been for a very long 00:35:08.730 --> 00:35:10.980 time. That sums it up well. This entire thought 00:35:10.980 --> 00:35:13.699 experiment provides truly compelling evidence. 00:35:14.139 --> 00:35:16.480 It suggests that with suitable high -quality 00:35:16.480 --> 00:35:19.079 temperature measurements, the kind we hypothetically 00:35:19.079 --> 00:35:22.239 gave the past a discernible human influence on 00:35:22.239 --> 00:35:24.699 global climate could have been detected way back, 00:35:24.760 --> 00:35:27.059 maybe by the end of the 19th century. And this 00:35:27.059 --> 00:35:28.980 isn't just a hypothetical could have been, is 00:35:28.980 --> 00:35:33.449 it? It underscores a profound reality. Significant 00:35:33.449 --> 00:35:36.210 human interference with Earth's climate is not 00:35:36.210 --> 00:35:38.909 some new phenomenon of the late 20th or 21st 00:35:38.909 --> 00:35:41.309 century. Not at all. It has been present and 00:35:41.309 --> 00:35:45.070 leaving its mark for over 130 years. It's a critical 00:35:45.070 --> 00:35:47.429 reframing of the timeline, isn't it? And consider 00:35:47.429 --> 00:35:50.889 the stark contrast. Those relatively small CO2 00:35:50.889 --> 00:35:53.550 increases in the late 1800s were apparently enough 00:35:53.550 --> 00:35:56.269 to leave a clear identifiable mark on the stratosphere. 00:35:56.269 --> 00:35:59.630 Right. Whereas today, our increases are far more 00:35:59.630 --> 00:36:01.989 rapid, far more extensive, and far more impactful 00:36:01.989 --> 00:36:04.710 across the entire climate system. This historical 00:36:04.710 --> 00:36:07.670 perspective really gives us pause. It forces 00:36:07.670 --> 00:36:10.789 us to recognize the long -term cumulative consequences 00:36:10.789 --> 00:36:13.369 of our industrial advancements and just how far 00:36:13.369 --> 00:36:16.349 back our planetary influence truly extends. And 00:36:16.349 --> 00:36:19.269 this leads us directly to the critical need for 00:36:19.269 --> 00:36:21.889 continued observation, especially these upper 00:36:21.889 --> 00:36:24.389 atmospheric layers that gave the earliest signals. 00:36:24.909 --> 00:36:27.429 Why is it so crucial to keep monitoring given 00:36:27.429 --> 00:36:30.889 this long history? Well, the findings powerfully 00:36:30.889 --> 00:36:34.570 emphasize the indispensable importance of continuous, 00:36:34.869 --> 00:36:37.190 high -quality monitoring of the upper atmosphere. 00:36:37.789 --> 00:36:40.389 These atmospheric temperature changes, particularly 00:36:40.389 --> 00:36:43.030 the stratosphere cooling and tropospheric warming 00:36:43.030 --> 00:36:46.130 patterns, they aren't just indicators of our 00:36:46.130 --> 00:36:49.230 current climate state. They also serve as early, 00:36:49.309 --> 00:36:52.309 sensitive signals of the success or, unfortunately, 00:36:52.730 --> 00:36:54.690 the failure of our climate mitigation efforts. 00:36:54.750 --> 00:36:57.519 A real -time report card. Exactly. A real -time 00:36:57.519 --> 00:36:59.659 report card on how our actions are impacting 00:36:59.659 --> 00:37:01.920 the planet's energy balance. It allows us to 00:37:01.920 --> 00:37:04.420 see if policy changes, technological advancements, 00:37:04.760 --> 00:37:07.340 emission reductions, are they truly making a 00:37:07.340 --> 00:37:09.199 difference in the atmosphere. And are there concerns 00:37:09.199 --> 00:37:11.739 that this vital monitoring capability might be 00:37:11.739 --> 00:37:14.710 at risk? Unfortunately, yes. There are always 00:37:14.710 --> 00:37:17.349 concerns when budget discussions happen around 00:37:17.349 --> 00:37:19.530 crucial climate satellites and vital research 00:37:19.530 --> 00:37:22.369 programs. We've seen discussions around proposals 00:37:22.369 --> 00:37:26.150 affecting major scientific agencies like the 00:37:26.150 --> 00:37:28.570 National Oceanic and Atmospheric Administration 00:37:28.570 --> 00:37:32.050 or NOAA. Right, NOAA and NASA. And the National 00:37:32.050 --> 00:37:34.849 Aeronautics and Space Administration, yes, and 00:37:34.849 --> 00:37:37.349 even the Department of Energy. Proposals that 00:37:37.400 --> 00:37:40.639 if enacted, could potentially impact this long 00:37:40.639 --> 00:37:42.920 -term monitoring capability. In what way? For 00:37:42.920 --> 00:37:44.539 instance, we've heard about potential proposals 00:37:44.539 --> 00:37:47.239 that could, say, eliminate parts of the National 00:37:47.239 --> 00:37:49.679 Oceanic and Atmospheric Administration's research 00:37:49.679 --> 00:37:52.199 division, which handles critical CO2 monitoring, 00:37:52.960 --> 00:37:54.900 or discussions about maybe cutting some climate 00:37:54.900 --> 00:37:57.420 -relevant satellite missions, or even stripping 00:37:57.420 --> 00:38:00.059 future National Oceanic and Atmospheric Administration 00:38:00.059 --> 00:38:02.519 satellites of specific climate science sensors. 00:38:02.750 --> 00:38:04.969 So essentially we're talking about potentially 00:38:04.969 --> 00:38:08.070 flying blind to some extent, reducing our ability 00:38:08.070 --> 00:38:10.670 to see these changes. That's the worry. When 00:38:10.670 --> 00:38:12.909 we lose the capability to measure and monitor 00:38:12.909 --> 00:38:14.849 how our world is changing, particularly these 00:38:14.849 --> 00:38:17.849 sensitive atmospheric indicators, it undeniably 00:38:17.849 --> 00:38:21.190 makes us all less safe. How so? It hinders our 00:38:21.190 --> 00:38:22.849 fundamental understanding of what's happening. 00:38:23.309 --> 00:38:25.489 It weakens our predictive abilities for the planet's 00:38:25.489 --> 00:38:28.510 future. And it leaves us more vulnerable to change 00:38:28.510 --> 00:38:30.650 that we can't fully anticipate or prepare for. 00:38:31.130 --> 00:38:33.130 It's like dimming the lights in a rapidly changing 00:38:33.130 --> 00:38:36.150 room. We just lose our ability to navigate effectively. 00:38:36.730 --> 00:38:39.760 And looking ahead. The projections for future 00:38:39.760 --> 00:38:42.000 changes in atmospheric temperature, say over 00:38:42.000 --> 00:38:45.119 the next 26 years to 2050, they're even larger 00:38:45.119 --> 00:38:47.320 than the changes simulated for the period from 00:38:47.320 --> 00:38:50.579 1986 to 2024 that we just discussed. That's right. 00:38:50.639 --> 00:38:52.940 The rate of change is projected to continue or 00:38:52.940 --> 00:38:55.940 even accelerate under many scenarios. So this 00:38:55.940 --> 00:38:58.219 research, showing detection was possible over 00:38:58.219 --> 00:39:01.360 a century ago, serves as a really stark reminder 00:39:01.360 --> 00:39:04.440 that humanity is now more than ever right at 00:39:04.440 --> 00:39:06.780 the threshold of what the UN Framework Convention 00:39:06.780 --> 00:39:10.179 on Climate Change calls dangerous anthropogenic 00:39:10.179 --> 00:39:12.280 interference with the climate system. Indeed. 00:39:12.559 --> 00:39:14.800 We are right there. The choices we make collectively 00:39:14.800 --> 00:39:16.639 and individually in the very near future, like 00:39:16.639 --> 00:39:18.880 this decade, will likely determine whether or 00:39:18.880 --> 00:39:21.739 not we cross that critical threshold into truly 00:39:21.739 --> 00:39:24.039 dangerous and potentially irreversible territory. 00:39:24.190 --> 00:39:26.269 It's not a problem for the distant future anymore. 00:39:26.369 --> 00:39:28.610 Not at all. It's a challenge unfolding in real 00:39:28.610 --> 00:39:31.489 time, requiring immediate attention and informed 00:39:31.489 --> 00:39:34.250 decision making based on the best possible science 00:39:34.250 --> 00:39:36.710 and observations. We've walked through a truly 00:39:36.710 --> 00:39:39.070 captivating scientific thought experiment today 00:39:39.070 --> 00:39:42.130 on meteorology matters, revealing that humanity's 00:39:42.130 --> 00:39:44.349 impact on atmospheric temperature might have 00:39:44.349 --> 00:39:47.610 been detectable over 130 years ago. It's just 00:39:47.610 --> 00:39:50.429 a powerful reminder of how long our actions have 00:39:50.429 --> 00:39:54.199 been shaping the very air around us. A long shadow. 00:39:54.579 --> 00:39:56.599 It really raises a profound question, doesn't 00:39:56.599 --> 00:40:00.179 it? If scientists back in 1885 had truly understood 00:40:00.179 --> 00:40:03.119 the full implications of what that stratospheric 00:40:03.119 --> 00:40:06.699 cooling signal meant, if they'd had today's clarity, 00:40:07.659 --> 00:40:10.079 would it have prompted human societies to follow 00:40:10.079 --> 00:40:12.960 a different path, a more sustainable one? It's 00:40:12.960 --> 00:40:15.079 impossible to know. But it's a sobering thought. 00:40:15.320 --> 00:40:17.159 And what does that tell us about our responsibility 00:40:17.159 --> 00:40:19.460 to act on the knowledge, the much clearer knowledge 00:40:19.460 --> 00:40:21.599 that we possess today? Something to think about. 00:40:21.679 --> 00:40:23.920 Now, if you're curious to learn more about the 00:40:23.920 --> 00:40:26.639 complexities of our atmosphere, the forces shaping 00:40:26.639 --> 00:40:28.780 our planet's weather, and want to keep up with 00:40:28.780 --> 00:40:31.320 current meteorology, you'll definitely want to 00:40:31.320 --> 00:40:34.019 follow our very own meteorologist, Rob Jones. 00:40:34.219 --> 00:40:36.559 He does great work. He does. You can find Rob 00:40:36.559 --> 00:40:38.880 on Instagram. Just search for meteorologist. 00:40:39.119 --> 00:40:42.940 Pretty easy to remember. On TikTok, he's TV Meteorologist, 00:40:43.400 --> 00:40:45.340 and over on YouTube, follow his channel, Rob 00:40:45.340 --> 00:40:48.139 Jones Hurricane. And you can also find the Meteorology 00:40:48.139 --> 00:40:50.619 Matters podcast playlist there for more episodes 00:40:50.619 --> 00:40:53.360 like this one. Great resources to stay informed. 00:40:53.400 --> 00:40:55.260 Definitely. Well, thank you for joining us on 00:40:55.260 --> 00:40:58.320 this exploration today. We really hope this Meteorology 00:40:58.320 --> 00:41:00.860 Matters deep dive into the historical detection 00:41:00.860 --> 00:41:05.239 of human climate influence sparks further curiosity 00:41:05.239 --> 00:41:07.920 and critical thinking for you. Until next time, 00:41:08.019 --> 00:41:08.719 keep looking up.