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Let it Snow! The First Direct Measure of Cloud Seeding | SciShow News - YouTube
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[ intro ]
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If you grew up in a place where it snowed,
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you might have appreciated snow days.
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On a cold winter’s morning,
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you may have found yourself staring longingly
at a dark cloud in the distance,
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wishing it would just dump all its snow so
you could skip school and play.
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Well now, imagine that all of a sudden,
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you saw a pair of airplanes fly over those
clouds
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and release a powdery looking substance on
top of them.
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A few minutes later, it starts snowing.
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This kind of weather manipulation may sound
far-fetched,
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but it’s a real thing that’s been around
for decades.
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It’s called cloud seeding—
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though, it’s not a get-out-of-school-free
card.
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It’s been used to encourage precipitation
in dry parts of the world.
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The only problem is,
scientists haven’t been sure how well it
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actually does that.
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But a new study published this week in the
journal PNAS
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details a way to figure that out.
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Cloud seeding involves finding a supercooled
cloud of liquid—
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one where the water in the air is /already/
below freezing,
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but it hasn’t yet formed large enough ice
crystals to precipitate as snow.
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You then inject a fine mist of nucleating
materials into that cloud—
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particles that all that ready-to-freeze water
vapor can coalesce around.
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And, if all goes well,
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enough super-chilled water freezes onto those
molecules
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that they fall to the ground as snow.
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But… researchers have had basically no clue
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how well this works in practice.
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Some reports say seeding does nothing,
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while others say it increases snowfall by
50%.
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That’s because, up until now,
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researchers have had to rely on
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comparing the volumes of snowfall from regular
clouds
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to the snowfall from seeded clouds.
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And that’s not all that reliable,
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since you don’t know what the difference
between those clouds
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would have been /without/ seeding.
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You have to rely on statistics—
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and weather is hard to predict, y’know?
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So this time around,
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a team of U.S. researchers focused on separating
out seeded snow from natural snow.
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They set up snow gauges in strategic spots
underneath the planes’ flight path.
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Then, they tracked the cloud
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from the moment they seeded it with silver
iodide
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all the way until its snow fell on the ground
using radar devices on nearby mountains.
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Those let them detect when and where snow
was bunching up around those nucleating molecules.
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And if snow fell in a gauge right after the
cloud above it was hit with silver iodide,
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it was considered to be seeded snow.
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In the end, they calculated that 20 minutes
of seeding
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resulted in 67 minutes of snowfall which covered
about 900 square miles…
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in about a tenth of a millimeter of snow.
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Now, I know that doesn’t sound like much.
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But it is enough water that, when melted,
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it would fill almost 50 Olympic sized swimming
pools.
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And over three attempts,
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the team managed to produce 282 Olympic pools’
worth of precipitation from seeding.
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That’s not nothing in an area thirsty for
water.
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Most importantly, though,
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it demonstrated you can measure the effect.
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Before cloud seeding can become a common solution
for water scarcity,
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we have to figure out how well it works.
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And now that researchers have shown they more
reliably measure that,
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they can hopefully improve on the technique.
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And if nothing else,
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they’ll be able to accurately crunch the
numbers to decide whether or not it’s worth
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the effort.
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In other news,
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researchers in China have found over a thousand
tiny green algae fossils
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that are /a billion years old/,
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pushing the origin of these plants back by
some 200 million years.
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The advent of photosynthesis was kind of a
big deal on Earth,
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since it fundamentally changed the atmosphere
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and made it possible for oxygen-breathing
organisms like us to thrive.
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So, evolutionary biologists are eager to understand
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how different photosynthesizers came to be.
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Of particular interest
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are the origins of the group Viridiplantae
—
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which literally means /green plants/.
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As in, well, /all the green plants/ you can
think of.
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Trouble is, when and where different lineages
of plants began isn’t entirely clear.
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Using genetic differences and fossils,
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researchers have estimated that they diverged
from their closest cousins
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—the red algae—
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sometime between 1.6 billion
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and 720 million years ago.
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But those estimates have a ton of uncertainty
built into them,
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and scientists haven’t been able to validate
them
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since fossil evidence from that era is so
rare.
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Not only are there debates about timing,
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some think /green/ plants began as /marine/
plants,
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while others say they got their start in freshwater
lakes, rivers, or streams instead.
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So older fossils could really help nail down
when and /where/ this group evolved.
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The oldest fossils to date came from a research
mission
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to an island in the Arctic Ocean in the early
1990.
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Among the finds were fossils of what appeared
to be
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a new green plant they called Proterocladus.
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At about 700 million years old,
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it was potentially the world’s most ancient
seaweed.
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But, these fossils weren’t in amazing shape,
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so some questioned whether the seaweed really
/was/ a seaweed.
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[naan-fehn]
In this new study,
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published this week in Nature Ecology and
Evolution,
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researchers from universities in Virginia
and China
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went to the Nanfen Formation in northern China
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and found /loads/ of Proterocladus fossils.
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/Over a thousand specimens/, in fact.
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Though each was /tiny/ — only 2 millimeters
long!
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And since these fossils were much older than
the ones described in the 90s,
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they called them Proterocladus antiquus.
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The great part about finding so many of these
little fossils was that,
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with the help of high-powered microscopes,
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the team was able to get a really solid sense
of this ancient algae’s features.
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Like, that they had complex branches
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and root-like structures similar to the green
algae around today.
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And since they were found in /ocean/-derived
rocks,
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the findings help bolster the argument that
these plants arose in the sea.
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Plus, they provide firmer support to the notion
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that green plants had already split from their
redder cousins a billion years ago —
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much earlier than some of the estimates to
date.
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That also means we have probably been underestimating
their importance in marine ecosystems.
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But, the more fossils we find,
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the clearer our picture of ancient life becomes.
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Thanks for watching this episode of SciShow
News!
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We put out news episodes every week,
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so if you want to learn about more awesome
breakthroughs,
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be sure to check YouTube.com/SciShow every
Friday!
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