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  • [♪ INTRO]

  • Carbon dioxide isn't just a greenhouse gas,

  • warming the planet by trapping heat in the atmosphere.

  • According to the US National Oceanic and Atmospheric Administration,

  • one third of our estimated CO2 emissions end up in the ocean.

  • This leads to ocean acidification, which is harmful to marine life.

  • But ocean acidification might also trigger another phenomenon:

  • stronger lightning strikes.

  • Bet you didn't see that one coming.

  • On the one hand, the ocean absorbing CO2 might seem like a good thing

  • because there's less of it in the atmosphere to warm the planet.

  • But on the other hand, CO2 that dissolves in the ocean becomes carbonic acid.

  • And the more CO2 the ocean absorbs, the more acidic the water becomes.

  • This is bad news for corals and other shell-forming marine organisms,

  • because they make their shells from minerals like calcium carbonate,

  • which dissolve in acidic water.

  • But that's not the only effect decreasing the pH of the ocean might have.

  • We think of pH as a measure of acidity, and that's true.

  • But on a molecular scale,

  • pH is actually a measure of the concentration of hydrogen ions in a solution.

  • The more hydrogen ions, the more acidic the solution is.

  • In the case of CO2, the carbonic acid splits apart into positively charged hydrogen ions

  • and negatively charged bicarbonate.

  • The presence of those charged ions means the solution can also carry an electrical charge.

  • A higher acidity, or a lower number on the pH scale,

  • means more hydrogen ions in the solution, and more potential to conduct electricity.

  • And that's a big deal, because the ocean is getting more acidic.

  • Due to climate change, seawater has experienced a 0.1 unit drop in pH.

  • Which seems tiny, but the pH scale is logarithmic.

  • A pH of 6 is ten times more acidic than a pH of 7.

  • So that change of 0.1 in the oceans corresponds to a 30% increase in acidity!

  • So if climate change is potentially affecting the electrical conductivity of the ocean,

  • could it affect lightning?

  • This led a group of scientists to look into the idea,

  • publishing two papers on the subject in 2020.

  • Surprisingly, we don't know a lot about what happens when lightning hits the ocean,

  • even less than we know about lightning strikes in general,

  • because almost all lightning strikes happen on land.

  • For something so big, covering nearly two-thirds of the Earth,

  • oceans are only struck by about 10% of all the lightning that occurs.

  • We used to assume that all surfaces act as perfect conductors,

  • whether that surface is rocks, soil, or water.

  • But while this assumption makes it easier to do calculations,

  • it probably doesn't reflect reality perfectly.

  • In fact, models show that when lightning does hit the ocean,

  • it could be more intense than on land, probably because salt water is a better conductor.

  • So to test whether lightning could intensify as the ocean acidifies,

  • the researchers carried out a simple experiment.

  • They filled a beaker with seawater and placed two electrodes in the water,

  • about two centimeters apart.

  • Then they ran power through the electrodes, forming sparks between them.

  • Next, they changed the seawater's pH in two different ways.

  • First, they added hydrochloric acid directly to the water.

  • This is a good way to change the pH of the solution,

  • but it doesn't reflect the real-world process of ocean acidification very well.

  • Second, they decreased the pH by bubbling carbon dioxide into the water,

  • which is pretty close to how ocean acidification actually works.

  • And they found that as the water got more acidic, the spark's intensity did increase.

  • The bubbling technique, which most closely replicates ocean acidification,

  • made the spark twice as intense as the other method.

  • That means ocean acidification could be making lightning stronger.

  • In fact, the researchers claim that if ocean pH keeps decreasing

  • according to the worst case predictions, where CO2 emissions keep increasing unchecked,

  • the intensity of ocean lightning strikes could increase by 30% by the end of this century.

  • This is a definite concern for ships, oil rigs, and other ocean infrastructure.

  • All of these structures already have some form of lightning protection.

  • But if lightning does get more intense with climate change,

  • these protections might need an upgrade.

  • But it isn't just human-made structures that might be affected.

  • Lightning strikes aren't just shocking; they're also loud.

  • So if lightning strikes are getting stronger, animals that use sound to navigate,

  • like whales and dolphins, might have a harder time.

  • But maybe we shouldn't worry too much yet.

  • Some researchers caution that while this study's method does what it's supposed to do,

  • measuring a spark in a beaker of water might not be directly applicable to storms over the ocean.

  • Lightning produces very large sparks, up to several hundred meters long.

  • Sparks this big might behave very differently from small sparks

  • generated in a controlled environment like a laboratory.

  • Lightning is also a hundred times more intense than the sparks these researchers produced.

  • So, comparing the two is a bit of a stretch.

  • But these studies are laying the groundwork for future experiments.

  • Which hopefully will spark more research.

  • Thanks for watching this episode of SciShow.

  • Before you go, I just want to remind you that time is running out to grab

  • SciShow Space's Pin of the Month for June!

  • It's this charming little drawing of Surveyor 1,

  • the probe that heralded the Apollo missions to the Moon.

  • And you can only pre-order it until midnight, June 30th.

  • After that, we'll stop taking any more orders and start working on the next pin.

  • You can check it out at the link in the description,

  • and stay tuned for next month's pin, too!

  • [♪ OUTRO]

[♪ INTRO]

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Can Climate Change Make Lightning… Supercharged?

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    joey joey に公開 2021 年 06 月 30 日
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