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  • [Trace]Gotta get ready.

  • That hole in the ozone layer you know that's some serious stuff.

  • [Julian] Hey that's not a thing anymore [Trace] WHAT?

  • IT'S GONE?!

  • Howdy chlorofriendocarbons, you've found your way to DNews, thanks for that!

  • Welcome!

  • I'm Trace.

  • If you are a Millennial, you've probably spent your whole life hearing about the "hole" in

  • the ozone layer.

  • Before you can understand the hole, though, you gotta know what the ozone layer is.

  • The ozone layer isn't really its own thing, instead 90 percent ozone floats around the

  • stratosphere: about 6 to 30 miles above our heads.

  • Ozone is three oxygen atoms linked together1,3, Oh-three.

  • When in the stratosphere, ozone absorbs harmful UV-B radiation, protecting us and other life

  • here on the ground (in the troposphere).

  • In the late 19th and early 20th centuries, people were just beginning to harness the

  • power of refrigeration using toxic gasses like ammonia, methyl chloride, and sulfur

  • dioxide.

  • In 1928, an enterprising inventor at General Motors created a non-toxic chemical for refrigeration

  • called CFC -- chlorofluorocarbon.

  • It was patented as Freon by DuPont, and sold in air conditioners, fridges, bug sprays,

  • spray paints, hair conditioners, and healthcare products.

  • At it's peak companies were making a million metric tons of CFCs every year.

  • Then, in a 1974 study in Nature found this great nontoxic refrigerant was wreaking havoc

  • on the atmospheric ozone layer.

  • Sure, at sea level, CFCs are nontoxic and safe for humans, but if they get into the

  • upper atmosphere, they're subject to photodissociation: where UV radiation breaks a Chlorine atom

  • off the CFC!

  • If that free chlorine finds a molecule of ozone (O-three) it will react with it, destroying

  • the ozone by ripping off one of its oxygen atoms to make Chlorine Monoxide, leaving regular

  • old O2, or oxygen, in its wake.

  • Then the Chlorine Monoxide gets hit by UV and broke up againso it has to find another

  • O3 molecule to stabilize itand the cycle repeats itself.

  • It's bad.

  • In 1977, we were studying the ozone layer and it was fine.

  • By 1981, there were hints something was amiss.

  • Then in 1984, scientists suddenly registered a giant hole in the ozone layer.

  • They published their findings and in 1987, the Montreal Protocol was signed, beginning

  • the phasing out CFCs shortly thereafter.

  • Meanwhile even though the house was clearly on fire, Du Pont and other companies insisted

  • everything was fineand fought tooth and nail to keep CFCs legal.

  • But they finally relented after scientific evidence became indisputable.

  • A looming environmental disaster that pitted corporations against the scientific community

  • where have I heard that before?

  • Though CFCs can hide in the atmosphere for 40 to 150 years, without the emission of new

  • CFCs, eventually that free chlorine cycle will stop.

  • If the chlorine runs into some methane up there, it would break it up forming hydrogen

  • chloride which is stable enough to rain down to Earth.

  • In 2015, about 30 years after the Protocol was signed, the ozone hole reached the largest

  • size EVER.

  • But since that peak (due mostly to volcanic eruptions that sprew bromine, another Ozone

  • depleting gas), scientists have finally started to see the ozone layer repair itself!

  • A study published in Science this year found the hole had decreased in size from the year

  • 2000, and most of that decrease was specifically because of the Montreal Protocol!!

  • International Policy, for the win!

  • Without the chlorine wafting up into the stratosphere, ozone was able to form naturally -- when UV

  • light breaks up regular old oxygen from O2 into O3.

  • Without the chlorine to mess it up, this process could restart!

  • It can still be messed up by volcanic eruptions, but overall without our meddling, the ozone

  • layer may someday be back to normal!

  • Based on this new study, the Ozone layer might be back to 1980 levels by 2040!

  • You can actually see how the Ozone layer is doing right now, on NASA's website!

  • We'll put the link in the description for you.

  • Of course, this is science, so we can't have all happy endings.

  • We still need AC and fridges, and the replacement gas, HFCs, are a potent greenhouse gas.

  • So now, global warming is a concern.

  • Sigh.

  • We can never win.

  • But hey, at least that thing we fought for as kids is getting better, right?

  • But...why is there air in the first place?

[Trace]Gotta get ready.


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B2 中高級 美國腔

臭氧層(What Ever Happened To The Hole In The Ozone Layer?)

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    joey joey 發佈於 2021 年 04 月 13 日