NASA Sees Definitive Evidence of the Montreal Protocol's Success

Narration: Dr. Susan Strahan

Transcript:

1 00:00:00,010 --> 00:00:04,200 The Montreal Protocol has been a great success at banning 2 00:00:04,200 --> 00:00:08,270 the production of ozone-depleting substances. 3 00:00:08,270 --> 00:00:12,380 And we know this because we've been measuring those substances at the Earth's surface since 4 00:00:12,380 --> 00:00:16,520 the 1980s or even before, in some cases. So before the Montreal Protocol, 5 00:00:16,520 --> 00:00:20,700 ozone-depleting substances at the surface were going up rapidly. 6 00:00:20,700 --> 00:00:24,910 Once the Protocol was signed and the regulations went into effect, 7 00:00:24,910 --> 00:00:29,090 we saw at the surface, levels of ozone-depleting substances going down. 8 00:00:29,090 --> 00:00:33,460 And so that's great. But those substances have to 9 00:00:33,460 --> 00:00:37,630 get high up into the stratosphere before they can destroy ozone, and they have to break down 10 00:00:37,630 --> 00:00:41,810 high up in the stratosphere, and the chlorine that gets released from the chlorofluorocarbons 11 00:00:41,810 --> 00:00:45,990 that's what actually destroys ozone. What we haven't had up until 12 00:00:45,990 --> 00:00:50,170 now is any measurement inside the Antarctic ozone hole 13 00:00:50,170 --> 00:00:54,220 that the chlorine levels there is actually going down. What I've shown 14 00:00:54,220 --> 00:00:58,300 is that if you're very careful about when you measure 15 00:00:58,300 --> 00:01:02,340 hydrogen chloride, that's HCl, in the atmosphere, and you measure it over time, 16 00:01:02,340 --> 00:01:06,390 you can see that HCl, so that reactive chlorine that destroys 17 00:01:06,390 --> 00:01:10,460 ozone, those levels are actually going down inside the Antarctic 18 00:01:10,460 --> 00:01:14,580 ozone hole. So that's great, so that's part of saying, 19 00:01:14,580 --> 00:01:18,760 "Hey, the ozone hole's recovering, it's getting smaller and it's because of declining chlorine." 20 00:01:18,760 --> 00:01:22,930 But the other part is to also look at how much ozone depletion 21 00:01:22,930 --> 00:01:27,110 is going on at the same time, because ozone levels can vary 22 00:01:27,110 --> 00:01:31,290 for a lot of different reasons, mostly because of temperature. If one year it's warm, 23 00:01:31,290 --> 00:01:35,330 you don't have as much ozone depletion. One year's really cold, you have more ozone depletion. 24 00:01:35,330 --> 00:01:39,430 So it makes it really hard to see the signal that the atmosphere's showing 25 00:01:39,430 --> 00:01:43,610 us, is the ozone hole really recovering? So what we did 26 00:01:43,610 --> 00:01:47,640 in this study, we were able to look at ozone changes during 27 00:01:47,640 --> 00:01:51,830 a period of time, in the winter, when most of that ozone change 28 00:01:51,830 --> 00:01:56,010 is coming just from chemical changes, so that temperatures aren't really affecting it very much. 29 00:01:56,010 --> 00:02:00,050 And we're able to do this because of measurements from the NASA Aura 30 00:02:00,050 --> 00:02:04,170 instrument called the Microwave Limb Sounder, so what we've seen by using the MLS 31 00:02:04,170 --> 00:02:08,330 data is that ozone depletion has declined. 32 00:02:08,330 --> 00:02:12,510 It does vary a lot still, but it declines and it's declining 33 00:02:12,510 --> 00:02:16,690 sort of in step with the chlorine changes, and so that's what we're 34 00:02:16,690 --> 00:02:20,880 excited about, is that we see, for the first time, chlorine levels are definitely 35 00:02:20,880 --> 00:02:24,930 going down, and ozone levels are responding to it. 36 00:02:24,930 --> 00:02:28,367