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Once there was a world
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not so very different
from our own.
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There were occasional
natural catastrophes,
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massive volcanic eruptions
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and, every once in a while,
an asteroid would come
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barreling out of the blue
to do some damage.
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But for the first
billion years or so,
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it would've seemed
like a paradise.
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This is what we think
the planet Venus
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might have looked like when
our solar system was young.
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Then things started
to go horribly wrong.
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Sync and corrections by n17t01
www.addic7ed.com
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The planet Venus,
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which once
may have seemed like a heaven,
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turned into a kind of hell.
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The difference between the two
can be a delicate balance,
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far more delicate
than you might imagine.
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Once things began to unravel,
there was no way back.
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This is what Venus,
our nearest planetary neighbor,
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looks like today.
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Venus's oceans are long gone.
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The surface is hotter
than a broiling oven,
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hot enough to melt lead.
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Why? You might think
it's because Venus
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is 30% closer to the Sun
than the Earth is,
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but that's not the reason.
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Venus is completely
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covered by clouds
of sulfuric acid that keep
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almost all the sunlight
from reaching the surface.
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That ought to make Venus
much colder than the Earth.
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So why is Venus scorching hot?
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It's because
the small amount of sunlight
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that trickles in through
the clouds to reach the surface
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can't get back out again.
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The flow of energy is blocked
by a dense atmosphere
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of carbon dioxide.
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That carbon dioxide gas--
or CO2 for short--
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acts like a smothering blanket
to keep the heat in.
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No one is burning coal
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or driving
big gas-guzzlers on Venus.
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Nature can destroy
an environment
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without any help
from intelligent life.
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Venus is in the grip
of a runaway greenhouse effect.
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Why does it look like
we're inside a bowl?
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It's due to the intense
atmospheric pressure.
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That's the wreck of Venera 13.
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In 1982, the scientists
and engineers
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of what was then
the Soviet Union
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successfully landed
this spacecraft on Venus.
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They managed
to keep it refrigerated
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for over two hours,
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so it could photograph
its surroundings...
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and transmit the images
back to Earth
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before the onboard electronics
were fried.
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Venus and Earth started out
with about the same amount
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of carbon, but the two worlds
were propelled
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along radically different paths,
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and carbon was the decisive
element in both stories.
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On Venus, it's almost all
in the form of gas--
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carbon dioxide--
in the atmosphere.
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Most of the carbon on Earth
has been stored for eons
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in solid vaults
of carbonate rock,
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like this one,
part of a chain that forms
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the celebrated
White Cliffs of Dover,
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right on the English Channel.
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What titan built
this wonder of the world?
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A creature a thousand times
smaller than a pinhead.
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Trillions of them.
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One-celled algae.
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Volcanoes supply carbon dioxide
to the atmosphere,
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and the oceans slowly absorb it.
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Working over the course
of millions of years,
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the microscopic algae harvested
the carbon dioxide
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and turned it
into these tiny shells.
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They accumulated
in thick deposits of chalk,
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or limestone,
on the ocean floor.
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Later, the restless Earth
pushed up the seafloor
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and carved out
these massive cliffs.
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Other marine creatures
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took in carbon dioxide
to build enormous coral reefs.
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And the oceans converted
dissolved CO2 into limestone
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even without any help from life.
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As a result, only a trace amount
was left as a gas
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in Earth's atmosphere.
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Not even three-hundredths
of one percent.
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Think of it--
fewer than three molecules
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out of every ten thousand.
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And yet, it makes
the critical difference
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between a barren wasteland
and a garden of life on Earth.
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With no CO2 at all,
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the Earth would be frozen.
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And with twice as many,
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we're still talking
about only six molecules
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out of ten thousand.
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Things would get
uncomfortably hot
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and cause us
some serious problems...
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but never as hot as Venus;
not even close.
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That planet lost
its ocean to space
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billions of years ago.
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Without an ocean,
it had no way to capture CO2
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from the atmosphere
and store it as a mineral.
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The CO2 from erupting volcanoes
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just continued to build up.
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Today, that atmosphere
is 90 times heavier than ours.
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Almost all of it is
heat-trapping carbon dioxide.
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That's why Venus is
such a ferocious inferno
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so hostile to life.
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The Earth,
in stunning contrast,
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is alive.
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It breathes...
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but very slowly.
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A single breath
takes a whole year.
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The forests contain
most of Earth's life,
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and most forests
are in the Northern Hemisphere.
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When spring comes to the north,
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the forests inhale
carbon dioxide from the air
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and grow,
turning the land green.
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The amount of CO2
in the atmosphere goes down.
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When fall comes and the plants
drop their leaves, they decay,
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exhaling the carbon dioxide
back into the atmosphere.
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The same thing happens
in the Southern Hemisphere
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at the opposite time
of the year.
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But the Southern Hemisphere
is mostly ocean.
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So it's the forests of the north
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that control the annual changes
in the global CO2.
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The Earth has been
breathing like this
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for tens of millions of years.
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But nobody noticed until 1958,
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when an oceanographer
named Charles David Keeling
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devised a way
to accurately measure
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the amount of carbon dioxide
in the atmosphere.
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Keeling discovered the Earth's
exquisite respiration.
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But he also discovered
something shocking--
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a rapid rise,
unprecedented in human history,
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in the overall level of CO2,
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one that has continued
ever since.
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It's a striking departure from
the CO2 levels that prevailed
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during the rise of agriculture
and civilization.
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In fact, the Earth has seen
nothing like it
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for three million years.
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How can we be so sure?
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The evidence is written
in water.
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The Earth keeps
a detailed diary
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written in the snows
of yesteryear.
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Climate scientists
have drilled ice cores
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from the depths of glaciers
in Greenland and Antarctica.
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The ice layers have ancient air
trapped inside them.
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We can read the unbroken record
of Earth's atmosphere
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that extends back over
the last 800,000 years.
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In all that time,
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the amount of carbon dioxide
in the air never rose
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above three-hundredths
of one percent.
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That is, until the turn
of the 20th century.
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And it's been going up steadily
and rapidly ever since.
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It's now more than 40% higher
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than before
the Industrial Revolution.
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By burning coal, oil and gas,
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our civilization
is exhaling carbon dioxide
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much faster
than Earth can absorb it.
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So CO2 is building up
in the atmosphere.
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The planet is heating up.
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Every warm object radiates
a kind of light
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we can't see
with the naked eye--
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thermal infrared light.
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We all glow with invisible heat
radiation, even in the dark.
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This is what the Earth
looks like in the infrared.
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You're seeing the planet's
own body heat.
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Incoming light
from the Sun hits the surface.
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The Earth absorbs much
of that energy,
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which heats the planet up
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and makes the surface glow
in infrared light.
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But the carbon dioxide
in the atmosphere
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absorbs most of that outgoing
heat radiation,
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sending much of it
right back to the surface.
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This makes the planet
even warmer.
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That's all there is
to the greenhouse effect.
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It's basic physics,
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just bookkeeping
of the energy flow.
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There's nothing
controversial about it.
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If we didn't have any carbon
dioxide in our atmosphere,
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the Earth would just be
a great big snowball,
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and we wouldn't be here.
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So, a little greenhouse effect
is a good thing.
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But a big one can destabilize
the climate
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and wreck our way of life.
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All right... but how do we know
that we're the problem?
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Maybe the Earth itself is
causing the rise in CO2.
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Maybe it has nothing to do
with the coal and oil we burn.
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Maybe it's those
damn volcanoes.
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Every few years, Mount Etna,
in Sicily, blows its stack.
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Each big eruption sends millions
of tons of CO2
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into the atmosphere.
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Now, combine that
with the output
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of all the other volcanic
activity on the planet.
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Let's take the largest
scientific estimate--
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about 500 million tons
of volcanic CO2
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entering the atmosphere
ever year.
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Sounds like a lot, right?
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But that's not even two percent
of the 30 billion tons of CO2
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that our civilization
is cranking out every year.
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And, funny thing,
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the measured increase in CO2
in the atmosphere
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00:13:20,718 --> 00:13:24,554
tallies with the known amount
we're dumping there
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by burning coal, oil and gas.
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00:13:28,593 --> 00:13:31,661
Volcanic CO2 has
a distinct signature--
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00:13:31,696 --> 00:13:33,330
it's slightly heavier
than the kind produced
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by burning fossil fuels.
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We can tell the difference
between the two
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when we examine them
at the atomic level.
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It's clear that
the increased CO2 in the air
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is not from volcanoes.
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00:13:45,143 --> 00:13:48,445
What's more, the observed
warming is as much as predicted
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00:13:48,479 --> 00:13:50,580
from the measured increase
in carbon dioxide.
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00:13:50,615 --> 00:13:52,516
It's a pretty tight case.
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00:13:52,550 --> 00:13:55,052
Our fingerprints
are all over this one.
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00:13:55,086 --> 00:13:59,456
How much is 30 billion tons
of CO2 per year?
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If you compressed it
into solid form,
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00:14:01,959 --> 00:14:04,061
it would occupy
about the same volume
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00:14:04,095 --> 00:14:06,430
as the White Cliffs of Dover.
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00:14:06,464 --> 00:14:10,867
And we're adding that much CO2
to the air every year,
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00:14:10,902 --> 00:14:13,437
relentlessly, year after year.
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00:14:13,471 --> 00:14:16,640
Unlucky for us,
the main waste product
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00:14:16,674 --> 00:14:20,077
of our civilization
is not just any substance.
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00:14:20,111 --> 00:14:23,613
It happens to be the chief
climate-regulating gas
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00:14:23,648 --> 00:14:26,560
of our global thermostat,
year in, year out.
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00:14:28,354 --> 00:14:30,689
Too bad CO2 is an invisible gas.
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00:14:30,723 --> 00:14:32,857
Maybe if we could see it...
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00:14:34,360 --> 00:14:36,528
If our eyes were sensitive
to CO2--
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00:14:36,562 --> 00:14:39,531
and perhaps there are
such beings in the cosmos--
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if we could see all
that carbon dioxide,
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00:14:43,035 --> 00:14:46,037
then we would overcome
the denial
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00:14:46,072 --> 00:14:49,641
and grasp the magnitude of
our impact on the atmosphere.
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But the evidence
that the world is getting warmer
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is all around us.
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00:15:09,063 --> 00:15:12,132
For starters, let's just
check the thermometers.
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00:15:12,166 --> 00:15:14,134
Weather stations
around the world
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00:15:14,168 --> 00:15:16,102
have been keeping
reliable temperature records
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00:15:16,137 --> 00:15:17,804
since the 1880s,
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00:15:17,838 --> 00:15:20,940
and NASA has used the data
to compile a map
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00:15:20,975 --> 00:15:22,642
tracking
the average temperatures
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00:15:22,677 --> 00:15:24,644
around the world through time.
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Yellow means
warmer temperatures
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00:15:27,748 --> 00:15:31,718
than the average,
for any region in the 1880s.
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00:15:31,752 --> 00:15:34,988
Orange means hot.
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00:15:36,490 --> 00:15:39,793
And red means hotter.
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00:15:39,827 --> 00:15:42,996
The world is warmer than it was
in the 19th century.
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00:15:46,067 --> 00:15:50,737
Back then, at the greatest fair
the world has ever seen,
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00:15:50,771 --> 00:15:55,375
a forgotten genius demonstrated
the solution to this problem.
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00:15:55,409 --> 00:15:56,843
Come with me.
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00:16:04,336 --> 00:16:05,937
Once there was a world
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00:16:05,971 --> 00:16:08,807
that was not too hot
and not too cold.
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00:16:08,841 --> 00:16:11,309
It was just right.
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00:16:11,414 --> 00:16:15,017
Then there came a time
when the life it sustained
254
00:16:15,051 --> 00:16:19,388
began to notice
our lovely planet was changing.
255
00:16:19,422 --> 00:16:24,092
And it's not
as if we didn't see it coming.
256
00:16:26,697 --> 00:16:29,833
As far back as 1896,
257
00:16:29,867 --> 00:16:32,736
the Swedish scientist
Svante Arrhenius
258
00:16:32,770 --> 00:16:35,138
calculated
that doubling the amount
259
00:16:35,172 --> 00:16:38,942
of CO2 in the atmosphere
would melt the Arctic ice.
260
00:16:41,345 --> 00:16:44,881
In the 1930s, the American
physicist EO Hulburt,
261
00:16:44,915 --> 00:16:46,816
at the Naval
Research Laboratory,
262
00:16:46,851 --> 00:16:48,651
confirmed that result.
263
00:16:48,686 --> 00:16:51,588
So far, it was still
just theoretical.
264
00:16:53,891 --> 00:16:57,093
But then, the English engineer
Guy Callendar
265
00:16:57,128 --> 00:16:59,229
assembled the evidence to show
266
00:16:59,263 --> 00:17:02,499
that both the CO2 and
the average global temperature
267
00:17:02,533 --> 00:17:05,001
were actually increasing.
268
00:17:05,036 --> 00:17:09,372
Even now, man may be unwittingly
changing the world's climate
269
00:17:09,407 --> 00:17:11,675
through the waste products
of his civilization.
270
00:17:11,709 --> 00:17:13,677
Due to our release,
through factories
271
00:17:13,711 --> 00:17:16,379
and automobiles every year,
of more than
272
00:17:16,414 --> 00:17:18,682
six billion tons
of carbon dioxide,
273
00:17:18,716 --> 00:17:21,117
which helps air absorb heat
from the Sun,
274
00:17:21,152 --> 00:17:23,887
our atmosphere seems
to be getting warmer.
275
00:17:23,921 --> 00:17:25,755
This is bad?
276
00:17:25,790 --> 00:17:28,458
Well, it's been calculated,
a few degrees rise
277
00:17:28,492 --> 00:17:29,759
in the Earth's temperature
278
00:17:29,794 --> 00:17:32,562
would melt the polar ice caps.
279
00:17:37,601 --> 00:17:41,438
In 1960,
Carl Sagan's PhD thesis
280
00:17:41,472 --> 00:17:43,306
included the first calculation
281
00:17:43,341 --> 00:17:45,942
of the runaway
greenhouse effect on Venus.
282
00:17:45,977 --> 00:17:47,811
This was part
of a career-long interest
283
00:17:47,845 --> 00:17:50,947
in the atmospheres of
the planets, including our own.
284
00:17:50,982 --> 00:17:55,118
In the original Cosmos series,
in 1980, Carl Sagan warned...
285
00:17:55,152 --> 00:17:57,454
We are releasing vast
quantities of carbon dioxide,
286
00:17:57,488 --> 00:18:00,323
increasing
the greenhouse effect.
287
00:18:00,358 --> 00:18:02,058
It may not take much
288
00:18:02,093 --> 00:18:04,461
to destabilize
the Earth's climate,
289
00:18:04,495 --> 00:18:07,931
to convert this heaven,
our only home in the cosmos,
290
00:18:07,965 --> 00:18:09,966
into a kind of hell.
291
00:18:15,240 --> 00:18:17,442
Since Carl spoke those words,
292
00:18:17,476 --> 00:18:20,545
we've burdened the atmosphere
of our world with an additional
293
00:18:20,579 --> 00:18:25,049
400 billion tons
of carbon dioxide.
294
00:18:25,084 --> 00:18:26,951
If we don't change our ways,
295
00:18:26,985 --> 00:18:29,721
what will the planet be like
in our children's future?
296
00:18:29,755 --> 00:18:33,057
Based on scientific
projections,
297
00:18:33,092 --> 00:18:35,927
if we just keep
on doing business as usual,
298
00:18:35,961 --> 00:18:38,329
our kids are in
for a rough ride.
299
00:18:38,363 --> 00:18:41,466
Killer heat waves,
record droughts,
300
00:18:41,500 --> 00:18:45,303
rising sea levels,
mass extinction of species.
301
00:18:45,337 --> 00:18:47,805
We inherited a bountiful world
302
00:18:47,840 --> 00:18:50,975
made possible
by a relatively stable climate.
303
00:18:51,009 --> 00:18:53,344
Agriculture
and civilization flourished
304
00:18:53,378 --> 00:18:55,313
for thousands of years.
305
00:18:55,347 --> 00:19:01,552
And now, our carelessness and
greed put all of that at risk.
306
00:19:03,021 --> 00:19:05,189
Okay, so if we scientists
are so good
307
00:19:05,224 --> 00:19:08,192
at making these dire, long-term
predictions about the climate,
308
00:19:08,227 --> 00:19:11,095
how come we're so lousy
about predicting the weather?
309
00:19:11,130 --> 00:19:14,966
Besides, this year, we had
a colder winter in my town.
310
00:19:15,000 --> 00:19:16,934
For all us scientists know,
311
00:19:16,969 --> 00:19:18,836
we could be in
for global cooling.
312
00:19:18,871 --> 00:19:21,773
Here's the difference
between weather and climate...
313
00:19:21,807 --> 00:19:25,009
Weather is what the atmosphere
does in the short term--
314
00:19:25,044 --> 00:19:27,145
hour to hour, day to day.
315
00:19:27,179 --> 00:19:29,814
Weather is chaotic,
which means that even
316
00:19:29,848 --> 00:19:32,817
a microscopic disturbance can
lead to large-scale changes.
317
00:19:32,851 --> 00:19:35,686
That's why those ten-day
weather forecasts are useless.
318
00:19:35,721 --> 00:19:40,191
A butterfly flaps its wings
in Bali, and six weeks later,
319
00:19:40,225 --> 00:19:42,827
your outdoor wedding
in Maine is ruined.
320
00:19:42,861 --> 00:19:44,829
Climate is the long-term average
321
00:19:44,863 --> 00:19:47,031
of the weather,
over a number of years.
322
00:19:47,066 --> 00:19:49,667
It's shaped by global forces
that alter the energy balance
323
00:19:49,702 --> 00:19:52,737
in the atmosphere,
such as changes in the Sun,
324
00:19:52,771 --> 00:19:54,405
the tilt of the Earth's axis,
325
00:19:54,440 --> 00:19:57,208
the amount of sunlight
the Earth reflects back to space
326
00:19:57,242 --> 00:20:00,478
and the concentration
of greenhouse gases in the air.
327
00:20:00,512 --> 00:20:02,814
A change in any of them
affects the climate
328
00:20:02,848 --> 00:20:05,416
in ways
that are broadly predictable.
329
00:20:05,451 --> 00:20:07,385
My friend's meandering
330
00:20:07,419 --> 00:20:09,520
represents
the short-term fluctuations--
331
00:20:09,555 --> 00:20:12,156
that's weather.
332
00:20:12,191 --> 00:20:13,725
It's almost impossible
to predict
333
00:20:13,759 --> 00:20:15,560
what'll attract
his interest next,
334
00:20:15,594 --> 00:20:18,663
but not hard to know what the
range of his meandering will be,
335
00:20:18,697 --> 00:20:21,432
because I'm holding him
on a leash.
336
00:20:23,135 --> 00:20:25,603
We can't
observe climate directly--
337
00:20:25,637 --> 00:20:27,438
all we see is the weather--
338
00:20:27,473 --> 00:20:29,440
but the average weather,
over the course of years,
339
00:20:29,475 --> 00:20:31,109
reveals a pattern.
340
00:20:31,143 --> 00:20:33,544
I represent
that long-term trend,
341
00:20:33,579 --> 00:20:35,713
which is climate.
342
00:20:35,748 --> 00:20:39,617
Keep your eye on the man,
not the dog.
343
00:20:42,287 --> 00:20:44,589
Weather is hard to predict,
like my friend here,
344
00:20:44,623 --> 00:20:47,191
but climate is predictable.
345
00:20:47,226 --> 00:20:50,261
Climate has changed many times
in the long history of the Earth
346
00:20:50,295 --> 00:20:52,930
but always in response
to a global force.
347
00:20:52,965 --> 00:20:56,267
The strongest force driving
climate change right now
348
00:20:56,301 --> 00:20:59,270
is the increasing CO2 from
the burning of fossil fuels,
349
00:20:59,304 --> 00:21:01,606
which is trapping more heat
from the Sun.
350
00:21:01,640 --> 00:21:04,442
All that additional energy
has to go somewhere.
351
00:21:04,476 --> 00:21:06,277
Some of it warms the air.
352
00:21:06,311 --> 00:21:08,379
Most of it ends up
in the oceans.
353
00:21:08,414 --> 00:21:12,650
All over the world,
the oceans are getting warmer.
354
00:21:12,685 --> 00:21:15,086
It's most obvious
in the Arctic Ocean
355
00:21:15,120 --> 00:21:17,989
and the lands that surround it.
356
00:21:20,592 --> 00:21:23,561
Okay, so we're losing
the summer sea ice
357
00:21:23,595 --> 00:21:27,165
in a place
where hardly anyone ever goes.
358
00:21:27,199 --> 00:21:30,802
What do I care if there's
no ice around the North Pole?
359
00:21:39,945 --> 00:21:42,914
Ice is the brightest
natural surface on the Earth,
360
00:21:42,948 --> 00:21:45,850
and open ocean water
is the darkest.
361
00:21:45,884 --> 00:21:49,454
Ice reflects incoming sunlight
back to space.
362
00:21:49,488 --> 00:21:51,522
Water absorbs sunlight
363
00:21:51,557 --> 00:21:54,859
and gets warmer,
which melts even more ice,
364
00:21:54,893 --> 00:21:58,129
which exposes
still more ocean surface
365
00:21:58,163 --> 00:22:00,131
to absorb even more sunlight.
366
00:22:00,165 --> 00:22:03,601
This is what we call
a positive feedback loop.
367
00:22:03,636 --> 00:22:07,372
It's one of many natural
mechanisms that magnify
368
00:22:07,406 --> 00:22:10,508
any warming caused
by CO2 alone.
369
00:22:10,542 --> 00:22:12,777
We're at Drew Point, Alaska,
370
00:22:12,811 --> 00:22:17,715
on the edge of the Arctic Ocean.
371
00:22:27,831 --> 00:22:31,700
When I was born, the
shoreline was a mile farther out,
372
00:22:31,735 --> 00:22:35,738
and it was breaking off at a
rate of about 20 feet per year.
373
00:22:35,772 --> 00:22:37,740
Now...
374
00:22:37,774 --> 00:22:41,911
it's being eaten away
at about 50 feet per year.
375
00:22:41,945 --> 00:22:43,913
The Arctic Ocean is warming
376
00:22:43,947 --> 00:22:46,282
and at an increasing rate.
377
00:22:46,316 --> 00:22:49,385
So it's ice-free
during more of the year.
378
00:22:49,419 --> 00:22:51,387
That leaves the shore here
379
00:22:51,421 --> 00:22:53,923
more exposed to erosion
from storms,
380
00:22:53,957 --> 00:22:56,258
which are also getting
more powerful,
381
00:22:56,293 --> 00:22:59,461
another effect
of climate change.
382
00:22:59,496 --> 00:23:02,464
The northern reaches of Alaska,
Siberia and Canada
383
00:23:02,499 --> 00:23:04,333
are mostly permafrost,
384
00:23:04,367 --> 00:23:07,770
ground that has been frozen
year-round for millennia.
385
00:23:07,804 --> 00:23:09,605
It contains lots
of organic matter,
386
00:23:09,639 --> 00:23:12,341
old leaves and roots
from plants
387
00:23:12,375 --> 00:23:15,511
that grew thousands
of years ago.
388
00:23:15,545 --> 00:23:17,513
Because the Arctic regions
are warming faster
389
00:23:17,547 --> 00:23:19,448
than anywhere else on Earth,
390
00:23:19,482 --> 00:23:21,517
the permafrost is thawing
391
00:23:21,551 --> 00:23:24,520
and its contents are rotting,
392
00:23:24,554 --> 00:23:27,189
just like when you unplug
the freezer.
393
00:23:30,060 --> 00:23:33,462
The thawing permafrost
is releasing carbon dioxide
394
00:23:33,496 --> 00:23:37,032
and methane, an even more
potent greenhouse gas,
395
00:23:37,067 --> 00:23:38,801
into the atmosphere.
396
00:23:38,835 --> 00:23:41,203
This is making things
even warmer,
397
00:23:41,238 --> 00:23:44,874
another example of a positive
feedback mechanism.
398
00:23:44,908 --> 00:23:47,643
The world's permafrost stores
enough carbon
399
00:23:47,677 --> 00:23:51,213
to more than double the CO2
in the atmosphere.
400
00:23:51,248 --> 00:23:52,548
At the rate we're going,
401
00:23:52,582 --> 00:23:54,150
global warming
could release most of it
402
00:23:54,184 --> 00:23:55,885
by the end of the century.
403
00:23:55,919 --> 00:23:59,321
We might be tipping the climate
past a point of no return
404
00:23:59,356 --> 00:24:01,957
into an unpredictable slide.
405
00:24:01,992 --> 00:24:04,793
Okay, the air, the water
406
00:24:04,828 --> 00:24:07,129
and the land
are all getting warmer,
407
00:24:07,164 --> 00:24:09,965
so global warming
is really happening.
408
00:24:10,000 --> 00:24:12,134
But maybe it's not our fault.
409
00:24:12,169 --> 00:24:14,203
Maybe it's just nature.
410
00:24:14,237 --> 00:24:16,272
Maybe it's the Sun.
411
00:24:17,741 --> 00:24:20,576
No, it's not the Sun.
412
00:24:21,846 --> 00:24:25,148
We've been monitoring the Sun
very closely for decades,
413
00:24:25,183 --> 00:24:28,525
and the solar energy output
hasn't changed.
414
00:24:29,021 --> 00:24:31,822
What's more, the Earth
is warming more at night
415
00:24:31,857 --> 00:24:33,991
than in daytime,
416
00:24:34,026 --> 00:24:36,827
and more in winter
than in summer.
417
00:24:36,862 --> 00:24:40,264
That's exactly what we expect
from greenhouse warming,
418
00:24:40,299 --> 00:24:42,533
but the opposite of what
increased solar output
419
00:24:42,568 --> 00:24:44,569
would cause.
420
00:24:44,605 --> 00:24:46,807
It's now clear beyond
any reasonable doubt
421
00:24:46,841 --> 00:24:49,543
that we are changing
the climate.
422
00:24:49,577 --> 00:24:51,545
The Sun isn't the problem.
423
00:24:51,579 --> 00:24:53,380
But it is the solution,
424
00:24:53,415 --> 00:24:55,582
and we've known this
for a long time,
425
00:24:55,617 --> 00:24:59,253
much longer
than you might think.
426
00:25:02,791 --> 00:25:06,327
Paris, September 1878.
427
00:25:06,361 --> 00:25:10,698
The Eiffel Tower won't be built
for years to come.
428
00:25:16,305 --> 00:25:19,107
Witness one
of the most glorious spectacles
429
00:25:19,141 --> 00:25:22,143
the world has ever seen.
430
00:25:22,178 --> 00:25:25,413
The magnificent head
of the Statue of Liberty
431
00:25:25,448 --> 00:25:27,983
has just been completed.
432
00:25:33,122 --> 00:25:36,358
Thousands of exhibitors
from around the planet
433
00:25:36,392 --> 00:25:38,594
covered 66 acres of Paris
434
00:25:38,628 --> 00:25:40,896
with their inventions
and goods.
435
00:25:40,930 --> 00:25:43,899
Edison's first public
demonstration of the lightbulb
436
00:25:43,933 --> 00:25:46,568
will not take place
for another year.
437
00:25:46,603 --> 00:25:49,471
There's no such thing
as electrical appliances.
438
00:25:49,505 --> 00:25:52,474
People don't flick switches
and press buttons.
439
00:25:52,508 --> 00:25:56,111
It's a hand-cranked,
horse-drawn world.
440
00:25:57,519 --> 00:26:00,154
That's the guy we came to see,
441
00:26:00,189 --> 00:26:02,990
the one
with the crazy moustache.
442
00:26:03,025 --> 00:26:06,027
He's a math teacher
named Augustin Mouchot.
443
00:26:06,061 --> 00:26:08,496
Remember, it's 1878.
444
00:26:08,530 --> 00:26:11,966
This is a world
lit mostly by gaslight.
445
00:26:12,000 --> 00:26:14,368
The automobile
is still years away.
446
00:26:14,403 --> 00:26:18,172
But Mouchot, here,
is dazzling the crowd
447
00:26:18,207 --> 00:26:20,141
with his solar power
concentrator.
448
00:26:22,211 --> 00:26:25,480
The Sun belongs to all of us!
449
00:26:25,514 --> 00:26:29,684
Even though it is 150 million
kilometers away from us,
450
00:26:29,718 --> 00:26:31,853
feel its awesome power!
451
00:26:31,887 --> 00:26:35,857
My invention concentrates
the free energy of the Sun
452
00:26:35,891 --> 00:26:38,860
and converts it
into mechanical motion.
453
00:26:38,894 --> 00:26:41,496
It can power any kind
of machine.
454
00:26:41,530 --> 00:26:45,867
It can produce electricity
or run a printing press
455
00:26:45,901 --> 00:26:48,169
or make ice on a hot day.
456
00:26:51,340 --> 00:26:52,840
Et voilà !
457
00:27:04,019 --> 00:27:04,986
Think of it,
458
00:27:05,020 --> 00:27:07,422
sunlight converted into ice.
459
00:27:07,456 --> 00:27:10,258
You see, my friends,
what wonders we can work
460
00:27:10,292 --> 00:27:13,428
if we harness
the bounteous energy of the Sun.
461
00:27:13,462 --> 00:27:17,231
The world will someday
run out of coal,
462
00:27:17,266 --> 00:27:21,436
but the magnificent Sun
will always be there for us.
463
00:27:35,951 --> 00:27:38,419
Mouchot took home the gold medal
from the fair.
464
00:27:38,454 --> 00:27:40,254
But the price of coal tumbled,
465
00:27:40,289 --> 00:27:43,758
becoming so cheap that there was
no interest in solar energy.
466
00:27:43,792 --> 00:27:46,527
Besides,
no one understood, back then,
467
00:27:46,562 --> 00:27:49,263
what the true cost was
of burning fossil fuel.
468
00:27:49,298 --> 00:27:52,433
Mouchot's research funding
was cut off.
469
00:27:52,468 --> 00:27:56,871
35 years later, in the early
years of the 20th century,
470
00:27:56,905 --> 00:27:59,540
another door opened
to an alternative future.
471
00:27:59,575 --> 00:28:03,578
It happened in Egypt,
on the banks of the Nile.
472
00:28:13,595 --> 00:28:16,563
Memo to future time travelers...
473
00:28:16,598 --> 00:28:18,899
this would be
an excellent entry point
474
00:28:18,933 --> 00:28:22,002
for averting climate change.
475
00:28:22,037 --> 00:28:25,005
Egypt, 1913.
476
00:28:25,040 --> 00:28:28,108
That's Frank Shuman
of Philadelphia.
477
00:28:29,878 --> 00:28:32,179
He's only had
three years of schooling,
478
00:28:32,213 --> 00:28:37,184
but his genius for innovation
more than makes up for that.
479
00:28:37,218 --> 00:28:41,255
Before he was 30, Shuman
had invented safety glass.
480
00:28:41,289 --> 00:28:46,093
Its use in automobiles and
skylights saved countless lives
481
00:28:46,127 --> 00:28:48,429
and made him a very rich man,
482
00:28:48,463 --> 00:28:52,366
rich enough
to pursue his real passion,
483
00:28:52,400 --> 00:28:54,601
solar energy.
484
00:28:54,636 --> 00:28:56,870
Shuman led the team
that designed and built
485
00:28:56,905 --> 00:29:00,107
an array
of solar energy concentrators.
486
00:29:00,141 --> 00:29:03,610
It could power a steam engine.
487
00:29:03,645 --> 00:29:06,780
Shuman is hoping
to use the Sun's power
488
00:29:06,815 --> 00:29:08,382
to irrigate the desert
489
00:29:08,416 --> 00:29:10,217
and turn it green.
490
00:29:10,251 --> 00:29:11,852
The official inauguration
491
00:29:11,886 --> 00:29:14,855
of Shuman's solar power plant,
in 1913,
492
00:29:14,889 --> 00:29:16,557
was a dazzling success.
493
00:29:19,928 --> 00:29:23,630
He had invented a practical way
to tap the Sun's energy
494
00:29:23,665 --> 00:29:26,266
on an industrial scale,
495
00:29:26,301 --> 00:29:30,104
making solar energy
even cheaper than coal.
496
00:29:32,073 --> 00:29:34,541
The British
and German governments
497
00:29:34,576 --> 00:29:36,543
both offered Shuman
generous funding
498
00:29:36,578 --> 00:29:38,445
to develop his invention.
499
00:29:38,480 --> 00:29:41,482
It was the ideal source
of abundant power
500
00:29:41,516 --> 00:29:43,484
in tropical regions,
501
00:29:43,518 --> 00:29:47,321
where imported coal
was prohibitively expensive.
502
00:29:47,355 --> 00:29:51,091
But Shuman was dreaming
even bigger.
503
00:29:51,126 --> 00:29:53,494
In a letter
to Scientific American,
504
00:29:53,528 --> 00:29:56,330
he calculated
that his solar power plants,
505
00:29:56,364 --> 00:29:58,666
if deployed in an area
of the Sahara Desert
506
00:29:58,700 --> 00:30:02,736
only 150 miles on a side,
could supply as much power
507
00:30:02,771 --> 00:30:05,906
as consumed by all
the industries of the world.
508
00:30:05,940 --> 00:30:07,908
But it was not to be.
509
00:30:07,942 --> 00:30:11,011
The market for a liquid
fossil fuel, petroleum,
510
00:30:11,046 --> 00:30:12,846
was exploding for shipping,
511
00:30:12,881 --> 00:30:15,482
home heating,
and cars and trucks.
512
00:30:15,517 --> 00:30:18,152
Oil was abundant,
cheaper even than coal,
513
00:30:18,186 --> 00:30:20,956
and much easier to get
out of the ground and process.
514
00:30:21,090 --> 00:30:25,560
It took 100 men a week
to fuel a ship with coal,
515
00:30:25,595 --> 00:30:28,096
but with oil,
one man could do the job
516
00:30:28,130 --> 00:30:29,764
in a single day.
517
00:30:29,799 --> 00:30:33,602
A year after Shuman's
triumph in the desert,
518
00:30:33,636 --> 00:30:35,377
World War I broke out.
519
00:30:35,471 --> 00:30:39,157
His solar collectors
were recycled into weapons.
520
00:30:39,243 --> 00:30:42,177
Frank Shuman's dream
of a solar-powered civilization
521
00:30:42,312 --> 00:30:44,819
would have to wait
another century
522
00:30:45,154 --> 00:30:46,846
before it was reborn.
523
00:30:47,921 --> 00:30:50,322
There's another inexhaustible
source of clean energy
524
00:30:50,356 --> 00:30:52,357
for the world.
525
00:30:54,027 --> 00:30:57,096
The winds themselves
are solar powered,
526
00:30:57,130 --> 00:31:01,500
because our star drives
the winds and the waves.
527
00:31:01,534 --> 00:31:03,268
Unlike solar collectors,
528
00:31:03,303 --> 00:31:06,438
wind farms take up
very little land,
529
00:31:06,473 --> 00:31:08,741
and none at all, if offshore,
530
00:31:08,775 --> 00:31:11,777
where the winds are strongest.
531
00:31:11,811 --> 00:31:14,646
If we could tap even
one percent of their power,
532
00:31:14,681 --> 00:31:18,817
we'd have enough energy
to run our civilization.
533
00:31:30,899 --> 00:31:34,201
And more solar energy
falls on Earth in one hour
534
00:31:34,236 --> 00:31:36,837
than all the energy
our civilization consumes
535
00:31:36,872 --> 00:31:38,706
in an entire year.
536
00:31:38,740 --> 00:31:40,508
If we could harness
a tiny fraction
537
00:31:40,542 --> 00:31:42,643
of the available
solar and wind power,
538
00:31:42,677 --> 00:31:45,813
we could supply
all our energy needs forever,
539
00:31:45,847 --> 00:31:49,050
and without adding
any carbon to the atmosphere.
540
00:31:57,427 --> 00:31:59,561
It's not too late.
541
00:31:59,596 --> 00:32:01,663
There's a future
worth fighting for.
542
00:32:01,698 --> 00:32:03,332
How do I know?
543
00:32:03,366 --> 00:32:06,702
Every one of us comes
from a long line of survivors.
544
00:32:06,736 --> 00:32:10,339
Our species is nothing
if not adaptive.
545
00:32:10,373 --> 00:32:12,875
It was only because
our ancestors learned
546
00:32:12,909 --> 00:32:14,683
to think long-term,
and act accordingly,
547
00:32:14,776 --> 00:32:16,540
that we're here at all.
548
00:32:16,614 --> 00:32:18,682
We've had our backs
to the wall before,
549
00:32:18,716 --> 00:32:21,818
and we came through
to scale new heights.
550
00:32:21,852 --> 00:32:25,355
In fact, the most mythic
human accomplishments of all
551
00:32:25,389 --> 00:32:28,124
came out of our darkest hour.
552
00:32:37,529 --> 00:32:39,196
Once there was a world
553
00:32:39,231 --> 00:32:43,701
rigged with 60,000
hair-triggered nuclear weapons.
554
00:32:43,735 --> 00:32:45,336
The combatants were
555
00:32:45,370 --> 00:32:48,005
the two most powerful
countries on Earth,
556
00:32:48,040 --> 00:32:50,174
and they were locked
in a deadly embrace,
557
00:32:50,208 --> 00:32:52,777
each vowing that
they would rather see
558
00:32:52,811 --> 00:32:54,679
everything we love destroyed
559
00:32:54,713 --> 00:32:57,248
than submit
to the will of the other.
560
00:32:57,285 --> 00:32:59,252
When I was three years old,
561
00:32:59,287 --> 00:33:01,822
the largest man-made
explosion of all time
562
00:33:01,856 --> 00:33:05,292
was detonated
by the Soviet Union.
563
00:33:08,430 --> 00:33:11,566
That terror has subsided,
to be replaced by new fears.
564
00:33:11,600 --> 00:33:14,302
The danger that the 2,000
largest cities on Earth
565
00:33:14,336 --> 00:33:17,371
would be reduced to rubble
in the space of an afternoon
566
00:33:17,406 --> 00:33:20,374
is no longer one of them.
567
00:33:20,409 --> 00:33:23,044
The nuclear rivalry
between the United States
568
00:33:23,078 --> 00:33:24,078
and the Soviet Union
569
00:33:24,112 --> 00:33:28,382
had another by-product.
570
00:33:28,417 --> 00:33:31,486
The Apollo missions to the Moon
were an extension
571
00:33:31,520 --> 00:33:35,223
of the arms race
that raged between them.
572
00:33:35,257 --> 00:33:37,325
Sending people
to orbit the Earth
573
00:33:37,359 --> 00:33:40,394
or go to the Moon
requires big, reliable,
574
00:33:40,429 --> 00:33:43,798
powerful rockets--
precisely the same technology
575
00:33:43,832 --> 00:33:46,567
you need to carry
a nuclear warhead
576
00:33:46,602 --> 00:33:48,136
halfway around the planet
577
00:33:48,170 --> 00:33:52,306
to destroy your enemy's
largest cities.
578
00:33:53,310 --> 00:33:55,111
I believe that this nation
579
00:33:55,146 --> 00:33:58,314
should commit itself
to achieving the goal,
580
00:33:58,349 --> 00:34:02,152
before this decade is out,
of landing a man on the Moon
581
00:34:02,186 --> 00:34:05,588
and returning him safely
to the Earth.
582
00:34:05,623 --> 00:34:08,358
President Kennedy's 1961 speech
583
00:34:08,392 --> 00:34:10,693
electrified the nation,
584
00:34:10,728 --> 00:34:14,097
and it contained much
that was remarkably prophetic--
585
00:34:14,131 --> 00:34:16,599
but not a word about
a scientific objective
586
00:34:16,634 --> 00:34:18,601
for going to the Moon.
587
00:34:18,636 --> 00:34:20,870
No questions
about the Moon's origin
588
00:34:20,905 --> 00:34:24,007
or the hope of bringing back
samples to analyze.
589
00:34:24,041 --> 00:34:26,876
No, the Apollo missions
were conceived
590
00:34:26,911 --> 00:34:29,279
as a demonstration
of the superior power
591
00:34:29,313 --> 00:34:32,315
and precision
of our strategic missiles.
592
00:34:32,349 --> 00:34:34,651
But a funny thing
happened to us
593
00:34:34,685 --> 00:34:37,887
on our way to the Moon.
594
00:34:38,222 --> 00:34:40,490
We looked homeward...
595
00:34:40,524 --> 00:34:42,663
and discovered another world--
596
00:34:42,694 --> 00:34:44,328
our own.
597
00:34:44,362 --> 00:34:47,664
For the first time,
we inhabitants of Earth
598
00:34:47,699 --> 00:34:50,827
could step back
and see it as it really is--
599
00:34:50,870 --> 00:34:53,438
one world, indivisible,
600
00:34:53,472 --> 00:34:56,541
and kind of small
in the cosmic context.
601
00:34:58,078 --> 00:35:01,013
Whatever the reason we first
mustered the enormous resources
602
00:35:01,048 --> 00:35:03,449
required
for the Apollo program,
603
00:35:03,483 --> 00:35:06,285
however mired it was
in Cold War nationalism
604
00:35:06,319 --> 00:35:08,354
and the instruments of death,
605
00:35:08,388 --> 00:35:11,357
the inescapable recognition
of the unity
606
00:35:11,391 --> 00:35:13,359
and fragility of the Earth
607
00:35:13,393 --> 00:35:15,895
is its clear
and luminous dividend,
608
00:35:15,929 --> 00:35:18,364
the unexpected gift of Apollo.
609
00:35:18,398 --> 00:35:21,567
A project conceived
in deadly competition
610
00:35:21,601 --> 00:35:24,904
made us recognize
our community.
611
00:35:35,082 --> 00:35:38,751
What titan built
this wonder of the world?
612
00:35:39,854 --> 00:35:42,856
It was the Ifugao people
of the Philippines,
613
00:35:42,890 --> 00:35:46,126
working with not much more
than their hands.
614
00:35:46,160 --> 00:35:50,797
About 10,000 years ago,
our ancestors all over the world
615
00:35:50,831 --> 00:35:54,367
took advantage of another form
of climate change,
616
00:35:54,402 --> 00:35:58,638
the gentler climate of the
intermission in the ice age--
617
00:35:58,673 --> 00:36:02,208
they invented agriculture.
618
00:36:02,243 --> 00:36:04,377
They gave up
the ceaseless wandering,
619
00:36:04,412 --> 00:36:07,681
hunting and gathering
that had been their way of life
620
00:36:07,715 --> 00:36:09,683
for a million years or so,
621
00:36:09,717 --> 00:36:13,320
to settle down and produce food.
622
00:36:13,321 --> 00:36:15,830
They found a way to harvest
623
00:36:15,841 --> 00:36:18,740
ten to a hundred times
more solar energy
624
00:36:18,744 --> 00:36:23,515
than the environment naturally
provided for their ancestors.
625
00:36:23,549 --> 00:36:27,052
People all over the world
made the difficult transition
626
00:36:27,086 --> 00:36:30,355
from nomadic cultures
to agricultural ones
627
00:36:30,389 --> 00:36:33,591
that used solar energy
more efficiently.
628
00:36:33,626 --> 00:36:37,228
It gave rise to civilization.
629
00:36:37,263 --> 00:36:40,799
We stand on the shoulders
of those who did the hard work
630
00:36:40,833 --> 00:36:44,402
that such a fundamental
transformation required.
631
00:36:44,437 --> 00:36:47,806
Now... it's our turn.
632
00:36:52,678 --> 00:36:55,246
Once there was a world...
633
00:37:00,086 --> 00:37:03,988
If life ever existed on Venus,
it would have had no chance
634
00:37:04,023 --> 00:37:07,625
to avert the hellish destiny
of this world.
635
00:37:09,261 --> 00:37:12,897
This runaway greenhouse effect
was unstoppable.
636
00:37:22,278 --> 00:37:24,012
Once...
637
00:37:24,046 --> 00:37:26,247
there was a world...
638
00:37:28,250 --> 00:37:30,385
ours.
639
00:37:30,419 --> 00:37:33,054
And that world is now.
640
00:37:33,089 --> 00:37:35,557
There are no scientific
or technological obstacles
641
00:37:35,591 --> 00:37:37,425
to protecting our world
642
00:37:37,460 --> 00:37:40,895
and the precious life
that it supports.
643
00:37:40,930 --> 00:37:42,797
It all depends...
644
00:37:42,832 --> 00:37:45,800
on what we truly value...
645
00:37:45,835 --> 00:37:49,471
and if we can summon
the will to act.
646
00:38:37,115 --> 00:38:39,283
But why, some say, the Moon?
647
00:38:39,317 --> 00:38:42,453
Why choose this as our goal?
648
00:38:42,487 --> 00:38:44,588
And they may well ask,
649
00:38:44,623 --> 00:38:47,091
why climb the highest mountain?
650
00:38:47,125 --> 00:38:50,361
We choose to go to the Moon...
651
00:38:50,395 --> 00:38:52,463
we choose to go to the Moon...
652
00:38:58,037 --> 00:39:00,572
...we choose to go to the Moon
in this decade
653
00:39:00,607 --> 00:39:02,441
and do the other things,
654
00:39:02,475 --> 00:39:06,111
not because they are easy,
but because they are hard.
655
00:39:20,292 --> 00:39:25,394
Sync and corrections by n17t01
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