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- [Alex] Could this 
little trailer help save

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the drought-stricken West

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by bringing more rain 
and snow to the region?

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That's what these 
engineers think.

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They've parked the 
trailer up here

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in the mountains of Colorado,

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in hopes of changing 
the weather.

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And there's dozens of 
them just like this

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in use right now.

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It might all sound 
like science fiction,

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but it's a weather 
modification technique

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called cloud seeding,

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and it was first 
done successfully

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as early as the 1940s.

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In Colorado, some ski 
towns were cloud seeding

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as far back as the '70s.

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And it's also been 
used around the globe.

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China's cloud seeding 
program reportedly had a plan

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to make clouds rain 
before they had a chance

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to float over the 
Beijing Olympic stadium.

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You can find cloud seeding from 
California to North Dakota.

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But how does cloud seeding work?

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To learn more, I've 
come to Colorado

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to see how seeding works 
up close and personal.

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The night before I arrived,

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the clouds above me were seeded.

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- We are approaching 
the location

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of our cloud seeding generator.

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- [Alex] Scott Griebling is 
a water resources engineer

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for the local water 
conservancy district.

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The locations chosen 
for these sites

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had the right elevation and 
can reach the perfect clouds.

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- Our district has come to the 
conclusion that cloud seeding

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and weather modification 
is a very safe

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and very cost effective way

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of increasing local 
water supplies.

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- [Alex] So how do 
you seed a cloud?

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- Hey, welcome to 
our remote generator.

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- [Alex] Garrett 
Cammans is president

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of a cloud seeding company

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that operates hundreds 
of cloud seeding sites.

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- And it sounds like 
you're terraforming

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or completely changing 
the climate of an area,

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but that's not how it works.

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- [Alex] Since clouds are 
basically water vapor,

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the idea is to release 
particles into the clouds

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that will attract water,

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making it easier for water 
droplets or snowflakes to form.

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They get heavier,

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and eventually fall to earth 
instead of staying in the sky.

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This Colorado team 
uses a solution

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with a chemical 
called silver iodide,

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which, when burned,

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splits into billions 
of particles per gram.

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- Ice is the perfect seeder.

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Clouds seed themselves 
with ice crystals.

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Silver iodide is 
really the closest

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and similar structure as ice,

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so that's why we are 
using silver iodide.

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- [Alex] Here, Cammans 
activates the flame.

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It contains a silver iodide 
solution mixed with propane.

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A series of tanks and 
regulators manage the pressure

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and exact flow rate of the 
silver iodide solution.

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- A typical storm 
system will only drop

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about 10% of its moisture.

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We're hoping that 
the storm system

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will drop 10 1/2 to 11 
1/2% of its moisture.

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- [Alex] Okay, but does 
cloud seeding actually work?

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- We would come out 
with research aircraft

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and with ground-based radars,

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and we would basically 
measure the atmosphere

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prior to cloud seeding 
and during cloud seeding.

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- [Alex] The landmark 
Snowie project set out

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to discover just that.

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It took a pretty 
clever approach.

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A plane flying back and 
forth dropped chemicals

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into the clouds.

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When the team studied the 
resulting precipitation,

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they found it had snowed 
in a zigzag pattern,

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matching the path of the 
seeding agent's flow.

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Could it have all 
just been a fluke?

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- We were in shock 
or in disbelief.

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And then, of course, 
we were saying,

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"Okay, we saw it one day.

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Can we repeat it?"

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- [Alex] They did 
the same experiment

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several more times.

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As the wind blew 
the seeding agent,

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the same zigzag line of 
precipitation appeared,

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which you would never see 
in a natural snowfall.

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- This is revolutionary

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because we have a 
hard time quantifying

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what really comes out 
from cloud seeding.

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- [Alex] So, at least 
in some situations,

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cloud seeding can 
increase precipitation,

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but is up against 
challenging odds.

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- Concern about 
reservoir levels.

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Over the last 43 years,

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snowpack has only been this 
low or lower seven times.

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- I'm in a creek.

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Snow is crucial to the Rockies.

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Because as it gradually 
melts, water runs downstream,

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replenishing bodies of 
water for nearby towns.

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That's why Colorado's Water 
Conservation Board partnered

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with a water conservancy 
district to share the cost

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of hiring a cloud seeding 
company to seed in the area.

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But is cloud seeding safe?

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Silver iodide has been 
used since the 19th century

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in photo development,

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and also as an 
antiseptic in medicine.

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Exposure to a large amount 
of it could even lead

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to skin and eye irritation.

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High levels of silver iodide 
in one area could be toxic

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to organisms in 
our water and soil.

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For these reasons and others,

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state cloud seeding 
efforts are reported

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to federal agencies.

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- And we wanna be conscious.

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We don't really wanna 
put a lot of silver

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into the atmosphere.

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- [Alex] Over the years,

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another big concern about 
cloud seeding has been

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that it could cause 
too much precipitation,

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such as this massive flood 
in a small town in the UK,

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which destroyed homes and 
killed more than 30 people.

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While circumstantial,

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some linked it to a nearby 
cloud seeding program.

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- Cloud seeding 
programs actually have 
to play by the rules.

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As soon as they have 
a certain snow depth,

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they stop seeding in 
order to prevent floods.

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- [Alex] Today, Cammans' 
company has hundreds

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of seeding sites,

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and across the globe,

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several other nations are 
testing the technology.

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In fact, nearly 
every meteorologist 
I spoke with told me

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to get ready, as they 
expect cloud seeding,

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once a big question mark, 
to increase in frequency.

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As for the potential 
to impact drought,

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it may be a long time

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before scientists know for sure.

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Even if widely used, 
it's still difficult

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to quantify exactly how much 
additional precipitation comes

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from seeding a cloud.

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We all know about the 
greenhouse effect,

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but how many of us 
understand why it happens?

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Our friends at Reactions uncover

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what's so unique 
about carbon dioxide

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that has allowed it to 
transform our entire planet.

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Check out the link 
in the description,

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and let them know Nova sent you.