We have signs of very great
changes occurring on the planet.
Everything happened so fast.
There's creeks drying up that
have never dried up in my lifetime.
We've got a forest here
that's already at the edge.
We're going
into uncharted territory.
Our planet
is at a crossroads.
Global warming isn't out of control,
but it soon could be.
The warning signs are all around us.
This is the challenge
of climate change.
What can we do about global warming?
What will happen
to the Earth if we don't?
The temperature is rising.
Each degree is critical.
Just one degree...
- One degree warmer...
- Two degrees...
- Threshold is about three degrees...
- Three to four degrees of warming...
You're starting
to look at four degrees...
Three degrees,
four degrees, five degrees...
Six degrees is almost unimaginable.
Imagine the 21st century,
if global warming accelerates.
Where does the next super-storm hit,
the next scorching heat wave,
the next catastrophe,
as the world warms degree by degree?
The debate has ended.
Scientists around the globe
agree we now live
in a world warmer by almost
one full degree Celsius.
Tracking the Earth's vital signs
is an armada.
Thousands of ships at sea.
Tens of thousands of stations on land.
Satellites monitoring from space.
Scientists feed the data into
the most advanced computer models
The predictions are alarming.
In four decades,
glaciers in the Himalayas,
the source of water
for millions, could be gone.
Within 50 years,
Greenland's melting ice sheet
could be unstoppable.
By the end of this century,
the Amazon rainforest,
home to half
the world's biodiversity,
could wither to an arid savannah.
A temperature rise between
is possible over the next century.
Each degree means
a radically different future.
Global warming doesn't just mean
the slow increase
in average temperatures.
It completely changes the way
the Earth's system operates,
which is why we can see droughts
in one place, floods in another,
or even a succession of drought
and flood in the same location.
National Geographic
author Mark Lynas
spent years compiling data
from climate models
to understand how each
degree of warming
could threaten the planet.
It's difficult
for people to visualize
the future impacts of global warming.
It's something I really
wanted to try and do,
to help people visualize the reality,
because it isn't actually intuitive
that the emissions
from your car exhaust
are going to be melting a glacier
in the Himalayas in 50 years' time.
While experts estimate
the average temperature
could rise up to six degrees Celsius,
or nearly 11 degrees Fahrenheit,
over the next 100 years,
the future isn't set in stone.
Even a small shift
in the Earth's temperature,
just six degrees,
can have extreme consequences.
Six degrees shift
from one day to the next
is the sort of thing that we expect
with normal weather fluctuations.
If it's six degrees hotter tomorrow,
I might just be wearing some shorts.
Six degrees in terms of a global
average change, six degrees colder,
is the difference between now
and the last ice age,
when the ice sheets themselves
advanced to just
the edge of Oxford,
and in places the ice cap
was more than a mile thick.
Just six degrees of cooling
transformed the Earth into an ice age.
Imagine it six degrees hotter.
The very earliest changes would
start high above the Earth.
The atmosphere
is our buffer zone
between the planet's surface
and outer space.
A small percentage
are the greenhouse gases,
a cocktail of water vapor,
carbon dioxide, methane,
nitrous oxide and ozone.
They are like a dome over the planet,
retaining just enough
of the sun's reflected energy
to maintain temperatures
that support life.
As the amounts of those gases increase,
they trap more heat
and can radically affect
the climate all over the planet.
For the last 250 years,
greenhouse emissions have soared
as we find more and more ways
to use more and more energy.
CO2 is the hidden price we pay.
Carbon dioxide rises
into the atmosphere
from the energy that powers
all our modern conveniences.
It's literally in the air we breathe.
There are now 383 carbon dioxide
molecules out of every million.
It seems minuscule,
but as the amount of CO2 rises,
so does the average temperature
all over the planet.
Doubling of CO2 is
a guarantee for global disaster.
The dangerous level
is about 450 parts per million,
and we're already up to 383.
Additional global warming
of one or two degrees Celsius
is a very big deal.
All we're doing is saying
what we think our best estimate is,
what will happen if we carry on
at the rate we're going.
So what you can do is to lay out
a number of possible pictures
of the future
and hope people will select
the right one.
If the world warms
by one degree,
the Arctic is ice-free
for half the year,
opening the legendary
northwest passage for ships.
Tens of thousands of homes
around the Bay of Bengal are flooding.
Hurricanes begin hitting
the South Atlantic.
Severe droughts in the western U.S.
Cause shortages
in global grain and meat markets.
This could be our world
plus-one degree.
Warming of just one degree
could turn some of America's
most fertile ranchland
into desert... again.
much of the American west
was part of a vast desert
dominating the continent.
A minor shift in the Earth's orbit
caused the summer sun
to warm slightly,
just enough to radically
transform this entire region.
Only a very thin layer of topsoil
covers the desert sand that still lurks
just centimeters below the surface.
As we race toward a planet
warmer by one degree,
the global warming scorecard
lists both losers and winners.
While the western U.S.
is dry and thirsty,
England is enjoying
an agricultural makeover.
Fortunes will be made and lost,
if global weather patterns rearrange
where different crops can be grown.
The winters, which used
to be hard in this country,
are getting much milder
so in some sense, that's a good thing.
That's not counterbalanced
by the devastation
which is affecting
other parts of the world.
Right now, England
is in the right place at the right time
for one of the world's most fragile
and most valuable crops.
You can't have it too hot for grapes,
because you realize
in the Champagne region...
When David Middleton
first planted Champagne-style grapes,
neighbors thought he'd gone mad.
But as wine producing regions
in France are getting hotter,
the climate for growing grapes
is migrating across the English Channel.
The idea of a fine English wine
is no longer a joke.
Now there are more
than 400 vineyards in Britain.
The Earth's average temperature
has always fluctuated.
And a variable climate isn't unusual.
It's the pace of climate change
today that's unprecedented.
The planet has experienced
climate change before.
But it usually plays out over
thousands or millions of years.
Now global warming
is measured in decades,
even years.
It means scores of species
won't be able to keep up.
Warming at this speed could send
us into uncharted territory,
like nothing we've experienced
in the history of life on Earth.
Global warming started
with our insatiable appetite for energy.
Every switch we flip, every plug,
every button we push
to turn something on,
inevitably leads back
to a place like this.
Nearly 90 percent of the world's energy
starts as a fossil fuel:
Coal, oil, natural gas.
These three fuels combined
are the single largest source
of CO2 emissions pouring
into the atmosphere.
If the world warms by two degrees,
some changes to the biosphere
are no longer gradual.
Greenland's glaciers are disappearing.
So much ice has melted,
polar bears struggle to survive.
Insects migrate
in strange new directions.
As a temperate climate
moves north in the U.S.,
pine beetles kill off
the white bark forests,
a grizzly bear's key source
of food in the fall.
New forests take root
in Canada's melting tundra.
The Pacific islands
of Tuvalu are lost
beneath the rising tides
of global warming.
This could be our world
plus-two degrees.
At two degrees of warming,
the impacts in the marine ecosystem
are going to be much more severe.
The oceans are the planet's
largest "carbon sink,"
nature's primary mechanism
for absorbing CO2
out of the atmosphere.
But lately there are indications
these systems are breaking down.
Under normal conditions,
tiny sea creatures like forams
and coccolithophores
absorb carbon out of the water
and use it to build
their shells and skeletons.
But there is a tipping point,
when too much CO2 in the oceans
turns the water
increasingly acidic.
Acidification dissolves
the creatures' shells and skeletons
and prevents them from absorbing
more CO2 out of the water
to build new ones.
Some of these tiny animals
at the bottom of the food chain
measure only one millimeter.
But the fate of all sea creatures,
of all shapes and sizes,
larger and larger,
hangs in the balance.
Alter the ocean's chemistry,
and nature's primary mechanism
for controlling the climate
begins to break down.
You lose a coral reef,
you lose perhaps 500,000 species.
You lose those little coccolithophores,
these little algae,
and you start to lose things
that are very important
to life on this planet.
We're losing some of the most vital
elements of the way the world works.
And that's got us all concerned.
Scientists half a world away
share those concerns.
They're investigating global warming
at the climate's opposite extreme.
It took nature 150,000 years
to make the great Greenland ice sheet
that's now melting into the sea
faster than at any time in history.
As it disappears, rising oceans
will flood coastal cities
around the world.
Greenland's Jakobshavn Glacier
is the fastest moving ice field
on the planet,
more than 40 meters per day,
melting into the sea
twice as fast as a decade ago.
Rising temperatures
are transforming
one of the Earth's harshest climates,
disrupting the way people have lived
in Greenland for hundreds of years.
For as long as anyone can remember,
sled dogs have been
a symbol of wealth here
and a necessity for survival,
especially for hunting
across the winter sea ice.
When the winter ice started thinning,
dogs became an expense
most islanders couldn't afford.
In this town of 4,500 people,
there are 4,000 dogs,
with very little to do these days.
Many are starving.
Some are being put down.
Marit Holm is one of Greenland's
five veterinarians.
As she patrols the town of Ilulissat,
she sees the impact of climate change
in every sled dog
without a sled to pull.
So, what I do, I drive
around and look after the dogs.
The dogs are hungry,
so I have to be a little bit careful
not to get bitten.
And when the dogs are hungry,
they are a little bit more dangerous
to people and kids walking around.
It doesn't seem to be sick.
He's very skinny.
So I have to try to find out
who's the owner
and talk to him.
These animals were
once in peak physical condition.
They served a vital purpose
in their owners' lives.
That's a thing of the past,
and we don't see
any young people who take
some dogs and live
as a fisherman and a hunter.
Dogs have been
in Finn Sistall's family
as long as he can remember.
He finally gave up his team of 19
just in the last few years.
In the winter,
even though it was
an impossible thing to do
about 20 years ago,
most of the fishermen go out
with a boat today
instead of dogsleds.
When Finn was growing up,
this was their winter hunting ground,
solid ice for more than half the year.
Everything happened so fast.
It's so visible.
You don't have to be a scientist
to determine what's happening.
With each passing season,
Finn watches as traditions
locked in the ice melt away.
Something
interesting in this ice,
because you
can see small bubbles.
And these bubbles are older
than all living creatures in the world.
And you can listen to it.
[Popping]
Because the bubbles
are so compressed,
and when they get out,
it's like popping.
You can talk to the ice.
That's what an intrepid team
of scientists does once a year,
fly into Greenland's interior
to listen to the ice.
Swiss camp is a scientific
research installation
built directly into the glacier
to track climate change.
Dr. Konrad Steffens
has erected 23 full-service
weather stations
that take a complete range of climate
measurements every 15 seconds,
updating global warming
computer models
all over the world.
The ice sheet is very old.
It's over 150,000 years old.
If you start to remove it,
then you actually start a process
that is unknown to civilization.
We have never seen
Greenland disappearing.
Watch it, watch it, watch it.
In 1992,
was slipping into the sea
and disappearing.
Ten years later, that number
more than doubled
to 15.5 kilometers annually.
Steffens wouldn't understand
how warmer weather affects
the speed of glaciers,
until he came upon
one of the strangest
and most dangerous features
of this forbidding landscape.
Rivers of melted ice
are cascading straight down
into the glacier,
creating huge tunnels
called moulins.
The team lowers
a fiber-optic camera.
Their hypothesis:
That melt water
has cut all the way through
to the bedrock
a quarter of a mile below,
and is lubricating
the underside of the glacier,
propelling it faster
and faster into the sea.
Fifty meters.
Sixty meters.
For Steffens and his team,
it is a chilling moment.
This shaft, and many like it,
go all the way through the glacier,
revealing a whole new mechanism
for speeding
the ice sheet's disappearance.
It's melting so rapidly now,
oceans could rise
as much as a meter
over the next century.
The consequences
could be catastrophic.
The Greenland ice sheet
actually contains enough frozen water
to raise global sea levels
by about seven meters,
which is enough to flood
most of London, Bangkok,
New York, Shanghai, you name it.
Many scientists focus
on two degrees of warming
as the tipping point
that will fundamentally change
how we live on this planet.
This could be
where global warming
becomes a runaway train.
Warming accelerates
the loss of polar ice.
The loss of ice
accelerates warming.
More water from melting ice
absorbs more of the sun's heat,
melting the ice sheet
and heating the planet even faster.
The warmer it gets,
the faster it gets warmer.
That's when global warming
becomes a chain reaction
we can't easily predict.
If a rise of two degrees
doesn't push the planet
to the tipping point,
many scientists predict
three degrees will.
If the world warms by three degrees,
the Arctic is ice-free all summer.
The Amazon rainforest is drying out.
Snowcaps on the Alps
all but disappear.
El Nino's extreme weather
patterns become the status quo.
The Mediterranean and parts of Europe
wither in searing summer heat.
This could be our world
plus three degrees.
The summer of 2003
may have opened a window
onto life in a world
that's three degrees warmer.
All across Europe,
an unrelenting heat wave
developed into a natural disaster.
Paris tends to empty in the summer.
Many elderly stay behind.
Nobody could have anticipated
the danger they'd be in.
[Siren]
Emergency room
doctors were the first to realize
something was terribly wrong.
Doctor Patrick Pelloux
quickly realizes
the heat wave is turning
into a catastrophe.
[Speaking French]
[Translated] You had
such a heat wave,
comparable to a flame-thrower
igniting an entire area.
The number of people who died
on the night of August 10
is between 2,500 and 3,000.
The city's
distinctive metal roofs
were designed for an earlier era:
To protect against winter chill.
Now rising temperatures have
turned them against the Parisians.
The death toll
would top 30,000 across Europe.
In France alone, over 14,000
died in just a few weeks.
During the heat wave of 2003,
another little-noticed phenomenon
among Europe's trees
and plants was unfolding,
a kind of vegetation backlash.
Photosynthesis
was breaking down.
Under normal conditions,
plants and trees
are a first-line of defense
against greenhouse gases,
absorbing CO2,
then converting it into oxygen
and releasing it
back into the atmosphere.
But in the extreme heat that summer,
some plants retained oxygen,
releasing CO2
into the atmosphere instead.
What happens to the biosphere
if one of the planet's
most important mechanisms
for converting CO2 into oxygen
stops working on a regular basis?
Possible answers are emerging
here at England's Hadley Centre,
one of the world's foremost facilities
for forecasting where
our climate could be headed.
Trying to peer decades into the future
keeps climate modelers
at their desks overtime.
Tea and coffee?
One of their
toughest challenges
is calculating the effect
of plus-three-degree warming
on the Amazon rainforest,
where 20 percent
of the world's oxygen is produced.
We wanted to know
how climate change in the future
would affect tropical rainforests
and in particular the Amazon
because it is such an iconic region,
important both environmentally,
ecologically and economically.
The climate model
produces an ominous prediction:
Three degrees of warming
could trigger
a catastrophic feedback loop,
accelerating global warming even more,
possibly reducing one
of the wettest places on Earth
into a patchwork of arid savannah.
It takes someone coming
from the outside saying,
"What do you know what that means?
You're talking about
the death of the Amazon."
Summer 2005.
The Amazon River.
Extreme heat teams with the driest
conditions anyone can remember.
Few can recall a time
on the mightiest river in the world,
when its tributaries ran dry, not low,
dirt dry.
In 2005, we saw
a situation in the Amazon
which was just incredible.
It was completely off the scale.
The Brazilian army actually
had to fly by helicopter
huge quantities of water up
the dried-up Amazon tributaries
in order to stop people dying of thirst
in villages which are normally
on the edge of this enormous river.
First drought, then fire.
In the aftermath of summer 2005,
over 2500 square kilometers
of the rainforest burn.
Trees help generate 50 percent
of the water for rainfall in the Amazon.
As more forest is lost,
the very source of the Amazon's
rainfall diminishes.
For every tree that we lose,
we're making one more incremental step
towards a scenario of drought
and fire in the region.
Ecologist Daniel Nepstad
has been studying the Amazon
for over 25 years
and sees global warming
and deforestation
pushing the region
toward a tipping point.
We think that maybe
as early as 20 years from now,
we're gonna see what we call
positive feedbacks kick in,
these vicious cycles of drought
leading to fire,
leading to more drought.
And that's much sooner, of course,
than the climate models
are giving us.
In the extreme conditions
of a world warmer by three degrees,
losing much of the Amazon
could cause the re-release
of hundreds of millions of tons
of stored carbon,
perhaps intensifying
global warming another degree.
If we get
to 30 years from now,
and the Amazon is brushland,
I think I would look back
and say
we had a chance to save one
of the world's great treasures.
A place that's intimidating in
its vastness and its complexity.
And it's so grand in scale that
it really is reaching its influence
around the entire planet.
Everyone in the world
in some way is tied
to this ecosystem.
And I think, in looking back,
I'd say we had a chance
and we blew it.
Humanity had a chance.
In a world warmer by three degrees,
climate change could be manifest
in the most violent weather
humans have ever experienced.
As the oceans
get hotter and hotter,
a new global climate pattern emerges
mirroring the violent weather
anomaly we call El Nino.
But in a three-degree world,
those extreme conditions
could become the status quo.
Normally the trade winds
drive warm ocean currents
toward the western Pacific,
leaving cold, nutrient-rich waters
along the coast of South America.
El Nino turns that system
upside down.
The first signs are wild
fluctuations in air pressure.
The trade winds weaken
and completely change direction.
Warm water spreads east
across the Pacific.
Torrential rains and flooding
strike coastal South America.
Indonesian rainforests
and Australian farmland
experience extreme drought conditions.
And many climate models include
another troubling forecast:
Continued warming could turbo-charge
a new generation of super-storms.
In a world which
is three degrees warmer,
there's going to be a lot more
energy in the world's oceans
to drive hurricanes.
And hurricanes derive their rocket fuel
from the warming of the ocean.
scientists are still
investigating a connection
between global warming
and hurricane strength.
The summer of 2005 would bring
dramatic new evidence.
In late August,
a hurricane hunter aircraft
is dispatched over the Gulf of Mexico.
A colossal storm is building
and tracking straight
for the city of New Orleans.
Anyone left there has only
one word in mind: Katrina.
By Sunday, August 28th,
Katrina's winds reach
Thermal imagery along the storm track
reveals Katrina's clout.
Orange and red indicate
the sea temperature has risen
to 82 degrees Fahrenheit,
a full degree higher than normal.
Dropping pressure within the eye wall
is the fourth lowest ever recorded
for an Atlantic storm.
It revs Katrina even more.
When Hurricane Katrina makes
landfall in New Orleans,
it unleashes a terrible fury.
Within six hours, the storm
is on its way out of the city.
But the destruction of
New Orleans only gets worse,
transforming the natural disaster
into a national tragedy.
Jazz trumpeter Irvin Mayfield
grew up in New Orleans.
The storm surge and a breach
at the London Avenue canal
sent eight feet of water
into Mayfield's neighborhood.
His father stays
to protect the family home.
His body won't be found for weeks.
When someone
has lost their high school,
their junior high school,
elementary school,
their pictures, their video tapes,
their clothes, their friend's house,
their friend's mother's house,
barber shop,
the place they had their first kiss,
when you lose all that,
and some people lost loved ones.
When you have all
of that come together, it's...
You can't imagine the type of tragedy,
a city-wide catastrophe,
not even rivaled
by September 11th.
It's impossible to directly link
Katrina to global warming.
The process that forms
hurricanes is too complex.
But if the planet warms
by three degrees,
we could be in for a new generation
of super-storm.
If the Earth reaches
plus-three degrees,
over the next 40 or 50 years,
the planet's basic life-support systems
could begin to break down.
But beyond three degrees,
the science of global warming
becomes more and more speculative
and more and more frightening.
If the world warms by four degrees,
oceans rise, overtaking
heavily populated deltas,
home to a billion people.
Bangladesh, washed away.
Egypt, inundated.
Venice, submerged.
Glaciers disappear, shutting off
the flow of fresh water
to billions more.
Northern Canada becomes
one of the planet's most
bountiful agricultural zones,
while a beach in Scandinavia
could be the next St. Tropez.
The entire west Antarctic
ice sheet could collapse,
sending sea levels rising even further.
This could be our world
plus four degrees.
At four degrees, we really
do begin to see a planet
which is completely unrecognizable
from the one we know today.
We would see the possible drying up
of some of the most important
rivers in the world,
and this will endanger the survival
of tens and even hundreds
of millions of people.
if the planet
is ever four degrees warmer,
one of its great rivers
will be self-destructing,
at both ends,
from a high mountain glacier
to the Indian Ocean.
Locals call it "Mother Ganges,"
the holiest river in India,
perhaps in all the world.
Millions of devout pilgrims
gather each year
in a mass ritual to celebrate
the river's birthday,
when it is said,
the Goddess Ganga came to Earth
to save her people from drought.
Himalayan rivers
are the wellspring of life
for over a billion people
in China, Nepal and India.
Unless we begin to slow global warming,
in fewer than four decades,
the Ganges could be a river
fighting for its very life.
The battle will be fought here
in the vast crystalline ice fields
of the Himalayan glaciers,
the planet's largest store
of fresh water
outside of the polar ice caps.
Himalayan glaciers are receding,
the fastest of any in the world.
Few have ventured here,
to the headwaters of the Ganges,
as often as one man.
Swami Sundaranand,
an 80-year-old holy man known
as the "swami who clicks,"
has been photographing
the glaciers above the Ganges
for 50 years.
The first photo I took
of the glacier was in 1956.
After 1962, I started to worry
about the changes I was seeing
in the glacier.
I went to this glacier on foot in 1965,
to the base of Meru Peak.
When I went back after 15 years,
the glacier had vanished.
When I saw the glacier receding,
I became very worried
and started crying.
If the holy Ganges is not
in existence in the future,
the entire world will seem
like it has become an orphan.
The swami's trove of icescapes
documents 50 years of change
to this magnificent glacier.
Now NASA satellite imagery
confirms the rate of loss.
Side by side, the high
and low-tech images
tell a similar story,
one that spells danger for the future.
This was all glacier once,
before it started shrinking
Just a century ago,
this stone marked the edge
of the ice field
that has retreated
high up the mountain.
If the world warms five degrees,
two massive uninhabitable zones
spread into once-temperate regions
of the northern
and southern hemispheres.
Snow-pack and aquifers
that feed the world's great cities,
Los Angeles, Cairo, Lima, Bombay,
are drying out.
Climate refugees number
in the hundreds of millions.
This could be our world
plus-five degrees.
If we allow global warming
to take off that far,
I really see a situation where we have
conflict across vast areas of the globe
as the people who remain
and the people who survive
fight it out with each other for what
remains of the world's resources.
And it can get even worse.
If the world warms
by six degrees,
from a distance, the oceans
may appear bright blue.
But they are marine wastelands.
Deserts march across continents
like conquering armies.
Natural disasters
become common events.
Some of the world's great cities
are flooded and abandoned.
This could be our world
plus six degrees.
Warmings of six degrees over longer
time periods have been associated
with some of the most devastating mass
extinctions which have ever taken place.
It's fair to assume that
if temperatures soar by six degrees
within less than a century
that we're going to face nothing
less than a global wipeout.
Six degrees of warming has
been called "the doomsday scenario."
Our lives would never be the same again.
But it's not all doom and gloom, yet.
Most experts believe we can
awaken from the nightmare.
Right now, the average temperature
has only risen 0.8 degrees Celsius.
But we don't have much time.
We're talking about turning
around the energy supply
for most of humanity
within the space of a decade.
For anyone looking for solutions,
there's no place like home.
This is the Cohen residence,
a pleasant three-bedroom
in Snowmass, Colorado.
But lurking beneath the surface,
an energy-eating monster.
Many homes waste
more energy than they use.
[Teapot whistling]
A team of eco-detectives is
investigating the Cohen house
for crimes against the climate.
This innocent-looking thing
here, when it is on,
eats a whole lot of money.
When I feel this much cold
on the outside of the freezer,
I know that the insulation
is really not as thick
as we would like.
Oh, what have we here?
Climate change is a problem
we don't need to have,
and it's cheaper not to.
For Amory Lovins,
solutions start with efficiency,
reducing the use of energy
that produces CO2 emissions.
Do you see that little red light
in the corner?
If you have all kinds
of appliances,
your TV, your VCR, your DVD, et cetera,
that have that little light on...
Yes.
... they're using electricity.
It's called '"vampire loads."
Almost 60 bucks a year,
just sitting there, turned off.
Lovins doesn't just talk the talk.
He lives in a house he designed
without a furnace,
in Aspen, Colorado,
where temperatures in winter
routinely drop below -17 Celsius.
We're at 7,100 feet here.
It can go to -47 F.
You can get frost any day of the year,
and we can get 39 days
of continuous mid-winter cloud.
Lovins' house is a mix
of high-technology
and homespun common sense.
Solar units on the roof
produce more electricity
than the house uses.
The entire house runs
on just 120 watts,
slightly more than a single light bulb.
Energy efficiency
is the biggest, fastest, cheapest way
to solve the climate problem,
to save money
and to make a safer, richer,
fairer, cooler world.
Next to our homes,
the second largest source
of emissions we're responsible for
is parked right outside.
Cars produce nearly 20 percent
of global greenhouse gases.
To keep warming below
the critical two-degree threshold,
we need to cut seven billion tons
of greenhouse gas emissions every year.
Doubling the average
fuel efficiency of all cars
from 25 kilometers per gallon to 50
would save one billion tons.
But we would still need
to cut billions more
from our carbon footprint
to stay on the safe side
of plus-two degrees.
We have an arsenal
of solutions already.
It's going to be solar, wind,
going to be solar, wind,
and it's going to be tidal power
and thermal power.
All of these different things
working together
actually give us a pretty good ability
t0 get away from
the fossil fuel economy.
The ultimate answer may be
just over the horizon.
But the problem continues to grow.
With each passing year,
we consume more energy.
The future will test
the best minds in science.
An international team
of Physicists in England
is already started, attempting the
mother of all technological solutions:
Nuclear fusion.
They're building a fusion reactor
modeled on the single best power plant
in the solar system,
the sun.
Harnessing that same power could mean
a virtually limitless
and self-sustaining source of energy
without producing
any greenhouse gases.
This energy
lights up the universe,
powers most of the stars
in the universe.
So, what we're trying to do here
is to replicate
the same process on Earth
and use this amount of energy
to produce electricity.
It won't be easy.
The core of the reactor will be
nearly 10 times hotter than the sun.
A powerful magnetic field
contains the super-hot plasma
and prevents it from melting
through the reactor's walls.
Even if it works,
and there's no guarantee,
the reactor won't produce
commercial electricity
for at least another 30 years.
As ambitious as it may be,
fusion may appear
relatively down-to-Earth.
Imagine outer space filled
with a cosmic fleet of mirrors.
One current research project
estimates that one million mirrors,
each about three feet across,
could block out enough of the sun's heat
to lower the Earth's temperature.
It's no good sitting around
hoping that someone's going to invent
some fantastical new source
of free energy
The reality is that we have
to deal with what we've got,
and have to do it within ten years.
The world's appetite for energy
remains voracious.
Our carbon footprint is staggering.
As global warming escalates,
it also accelerates.
At some point, climate change
could take on a life of its own,
and global warming would
become a runaway train.
The only question is,
now that we know about it,
what are we going to do?
Even the worst-case scenarios
of six degrees
won't mean the end
of all life on Earth.
But the planet after
extreme global warming
would be radically different
from the life we know today.
How bad could it get?
At that point, the best minds
on Earth agree on two things:
They just don't know,
and they hope we'll never find out.