1 00:00:01,920 --> 00:00:04,590 Have you ever heard that something called the ozone layer 2 00:00:04,590 --> 00:00:07,530 is thinning? Or that your aerosol hairspray is what's 3 00:00:07,530 --> 00:00:11,220 causing it? Or that it leads to more severe sunburns and UV 4 00:00:11,220 --> 00:00:15,000 rays? This is referring to the ozone hole. But what exactly 5 00:00:15,000 --> 00:00:22,170 does it all mean? Welcome to ozone 101. The ozone holes 6 00:00:22,170 --> 00:00:25,440 proper name is actually the Antarctic ozone hole because 7 00:00:25,440 --> 00:00:29,190 when it forms it forms over Antarctica. But before we get 8 00:00:29,190 --> 00:00:33,210 into what that is, let's first talk about what ozone itself is. 9 00:00:33,960 --> 00:00:38,820 Ozone is a gas comprised of three oxygen atoms, about 90% of 10 00:00:38,820 --> 00:00:42,060 the Earth's ozone exists in the stratosphere, the layer of the 11 00:00:42,060 --> 00:00:45,330 atmosphere that extends from eight to about 30 miles above 12 00:00:45,330 --> 00:00:48,600 the earth's surface. In fact, the stratosphere is often 13 00:00:48,600 --> 00:00:52,860 referred to as the ozone layer. Ozone acts as a sunscreen around 14 00:00:52,860 --> 00:00:56,910 the Earth filtering out harmful ultraviolet radiation or UV 15 00:00:56,910 --> 00:01:00,780 rays, which are mainly absorbed in the stratosphere. Without an 16 00:01:00,780 --> 00:01:04,860 ozone layer, UV radiation would sterilize the Earth with a 17 00:01:04,860 --> 00:01:07,830 damaged but still present ozone layer, there will be more 18 00:01:07,830 --> 00:01:12,180 sunburns, more skin cancer cases increased cases of eye damage 19 00:01:12,210 --> 00:01:15,390 the wilting and loss of trees and plants and significantly 20 00:01:15,390 --> 00:01:19,290 lessened crop yields. Suffice it to say ozone is pretty important 21 00:01:19,290 --> 00:01:23,970 for the planet. So what causes the ozone hole? There are 22 00:01:23,970 --> 00:01:27,390 several major factors that together lead to the destruction 23 00:01:27,420 --> 00:01:32,130 of ozone, thus creating the ozone hole. Those factors are 24 00:01:32,370 --> 00:01:37,350 one very strong winds around the South Pole, or the polar vortex 25 00:01:37,710 --> 00:01:42,780 to the sun's rays, three chlorine and bromine compounds 26 00:01:42,780 --> 00:01:47,520 from ozone depleting substances, and for cold temperatures below 27 00:01:47,520 --> 00:01:51,630 negative 109 degrees Fahrenheit in the stratosphere, which form 28 00:01:51,630 --> 00:01:56,460 a specific kind of cloud polar stratospheric clouds. The polar 29 00:01:56,460 --> 00:01:59,580 vortex forms in the southern hemisphere stratospheric during 30 00:01:59,580 --> 00:02:03,060 the winter as temperatures drop. And when sunlight returns to 31 00:02:03,060 --> 00:02:06,180 Antarctica and late winter and early spring, temperatures are 32 00:02:06,180 --> 00:02:09,660 still cold enough to form polar stratospheric clouds. And now 33 00:02:09,660 --> 00:02:13,470 there's also sunlight. Chemical reactions take place on the 34 00:02:13,470 --> 00:02:17,010 cloud particle surfaces, converting unreactive forms of 35 00:02:17,010 --> 00:02:21,510 chlorine and bromine into reactive chemicals. The vortex 36 00:02:21,510 --> 00:02:25,020 acts as a sort of container confining the contents of the 37 00:02:25,020 --> 00:02:28,440 Antarctic stratosphere within its bounds allowing the reactive 38 00:02:28,440 --> 00:02:31,950 chlorine and bromine compounds to destroy ozone molecules. 39 00:02:32,310 --> 00:02:36,000 That's when depletion can occur on a large scale with the 40 00:02:36,000 --> 00:02:39,090 presence of sunlight. The reactive chlorine and bromine 41 00:02:39,090 --> 00:02:42,750 compounds produced during winter begin to deplete ozone molecules 42 00:02:42,750 --> 00:02:46,920 by stealing one of their oxygen atoms leaving just oxygen gas or 43 00:02:46,920 --> 00:02:51,000 otoo. In its wake. As long as a polar stratospheric clouds are 44 00:02:51,000 --> 00:02:54,900 present, these reactions will occur over and over again until 45 00:02:54,900 --> 00:02:58,650 the ozone is nearly gone. This forms what we call the ozone 46 00:02:58,650 --> 00:03:02,610 hole. But that's really a misnomer. It's actually more of 47 00:03:02,610 --> 00:03:07,080 a thin layer. In mid to late spring, the vortex begins to 48 00:03:07,080 --> 00:03:10,770 break up and the polar air depleted of ozone is mixed back 49 00:03:10,770 --> 00:03:15,000 into the rest of the Southern Hemisphere. The ozone hole is 50 00:03:15,000 --> 00:03:19,470 gone. Ozone depletion has still occurred. It's just no longer 51 00:03:19,470 --> 00:03:23,010 all concentrated in one small area. It spread around the 52 00:03:23,010 --> 00:03:27,060 atmosphere. So why is the ozone hole bigger and longer lasting 53 00:03:27,060 --> 00:03:31,350 and certain years? Well, it all comes down to weather, just like 54 00:03:31,350 --> 00:03:33,930 some winters are colder and longer than others on the 55 00:03:33,930 --> 00:03:36,870 Earth's surface. The same goes for weather in the stratosphere. 56 00:03:37,350 --> 00:03:41,550 If the Antarctic stratosphere stays cold, the polar vortex and 57 00:03:41,550 --> 00:03:45,660 the ozone hole within it will persist. And in years with cold 58 00:03:45,660 --> 00:03:48,840 springtime temperatures, the polar vortex and the ozone hole 59 00:03:48,840 --> 00:03:49,620 are large. 60 00:03:50,880 --> 00:03:54,810 Make no mistake, ozone depletion is not a natural thing. It stems 61 00:03:54,810 --> 00:03:56,910 from human emissions of chemicals called 62 00:03:56,910 --> 00:04:03,060 chlorofluorocarbons or CFCs. In the early 1900s refrigerators 63 00:04:03,060 --> 00:04:07,050 use toxic gases like ammonia and methyl chloride as refrigerants. 64 00:04:07,110 --> 00:04:10,440 Unfortunately, this led to fatalities as the toxic gases 65 00:04:10,440 --> 00:04:14,550 leaked out of the appliances. So the search began for a non toxic 66 00:04:14,580 --> 00:04:17,700 and non flammable chemical that can be used as a refrigerant. 67 00:04:17,850 --> 00:04:22,620 Thus the CFC was born. There are many types of CFCs but the two 68 00:04:22,620 --> 00:04:28,980 most common are CFC 11 and CFC 12. In the 1930s, the production 69 00:04:28,980 --> 00:04:34,140 and consumption of CFCs began to skyrocket. By the early 1980s, 70 00:04:34,170 --> 00:04:38,610 over 300 million pounds of CFC 11 alone were being released 71 00:04:38,610 --> 00:04:43,680 into the atmosphere each year. Then, in 1985, British 72 00:04:43,680 --> 00:04:46,560 researcher Joe Farman and his colleagues published their 73 00:04:46,560 --> 00:04:50,730 research on large seasonal ozone losses over Antarctica. Thanks 74 00:04:50,730 --> 00:04:53,670 to the combined efforts of the quick acting science community 75 00:04:53,700 --> 00:04:57,780 industry and policymakers the Montreal Protocol was signed in 76 00:04:57,780 --> 00:05:02,790 1987, restricting the production and consumption of CFCs. Every 77 00:05:02,790 --> 00:05:06,780 nation on earth has now signed the Montreal Protocol. So for 78 00:05:06,780 --> 00:05:09,960 the record, your hairspray and aerosol deodorant hasn't been 79 00:05:09,960 --> 00:05:14,610 harming ozone since these laws went into effect in the 80s. But 80 00:05:14,610 --> 00:05:19,230 why do we still see an ozone hole today? First CFCs have 81 00:05:19,230 --> 00:05:23,010 lifetimes of 50 to 100 plus years and it will take some time 82 00:05:23,010 --> 00:05:26,220 for the concentration of CFCs in the atmosphere to drastically 83 00:05:26,220 --> 00:05:30,330 decline. Second, there are still CFCs being released into the 84 00:05:30,330 --> 00:05:34,650 atmosphere today. For example, as an old refrigerator or air 85 00:05:34,650 --> 00:05:38,400 conditioning unit deteriorates in a landfill, the CFCs within 86 00:05:38,430 --> 00:05:42,930 are slowly released. From the time a CFC is released into the 87 00:05:42,930 --> 00:05:46,410 air, it takes about five years for its impact to be felt over 88 00:05:46,410 --> 00:05:50,760 Antarctica, where depletion will occur. The CFCs emitted at the 89 00:05:50,760 --> 00:05:55,170 surface eventually rise into the tropical stratosphere. The ozone 90 00:05:55,170 --> 00:05:59,070 in the stratosphere blocks most of the sun's UV radiation, so 91 00:05:59,070 --> 00:06:02,520 the CFCs have to rise above most of the ozone layer before 92 00:06:02,520 --> 00:06:06,540 sunlight can then break them down. Once they get high enough 93 00:06:06,570 --> 00:06:09,540 solar radiation releases the chlorine most of which 94 00:06:09,570 --> 00:06:13,350 eventually goes into ozone, say forms like hydrochloric acid and 95 00:06:13,350 --> 00:06:16,680 chlorine nitrate. When these compounds make their way to 96 00:06:16,680 --> 00:06:20,220 Antarctica, those chemical reactions start up. And if 97 00:06:20,220 --> 00:06:23,430 you're wondering why Antarctica these reactions are unique to 98 00:06:23,430 --> 00:06:26,340 the polar regions, because of their extreme low temperatures, 99 00:06:26,370 --> 00:06:30,270 and presence of polar stratospheric clouds, one 100 00:06:30,270 --> 00:06:34,680 chlorine atom can destroy 1000s of ozone molecules, and millions 101 00:06:34,710 --> 00:06:39,000 of tons of CFCs were pumped into the atmosphere from the 1920s 102 00:06:39,030 --> 00:06:44,250 through the early 1990s. As CFC concentrations in the atmosphere 103 00:06:44,250 --> 00:06:47,820 continue to decline, the ozone hole is expected to gradually 104 00:06:47,820 --> 00:06:51,090 become less severe, and scientists expect the Antarctic 105 00:06:51,090 --> 00:06:54,930 ozone to recover back to healthy levels around the year 2070.