[man] We have signs of very great changes occurring on the planet.
[man 2] Everything happened so fast.
[man 3] There's creeks drying up that have never dried up in my lifetime.
[man 4] We've got a forest here that's already at the edge.
[woman] We're going into uncharted territory.
[narrator] 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 ifwe don't?
The temperature is rising.
Each degree is critical.
[various voices] Just one degree...
- One degree warmer... - Two degrees...
- Threshold is about three degrees... - Three to four degrees ofwarming...
You're starting to look at four degrees...
Three degrees, four degrees, five degrees...
Six degrees is almost unimaginable.
[narrator] 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
to calculate what it means for our future.
The predictions are alarming.
In four decades, glaciers in the Himalayas,
the source ofwater 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.
We're on the brink of one degree warmer,
hotter than it's been in thousands of years.
A temperature rise between 1 and 11 degrees Fahrenheit
is possible over the next century.
Each degree means a radically different future.
In some parts of the world, the first signs of global warming
may be arriving with a vengeance.
In Australia, bushfires are a natural part of the ecosystem,
especially in drought years.
But climate change may be pushing conditions
from bad to worse.
Australia's east coast is a tinderbox.
In the winter of 2001, more than 900 fires encircled Sydney.
They called it black Christmas.
[siren]
Now after a decade of drought, the danger is growing.
[man] This year we had fires in Victoria that were very intense.
We fought them for months and months.
It is scary, and the more the bush dries out,
we're getting fires happen in areas we never had them before.
[man] Once the intensity of that fire is so high that it's in the treetops,
no amount of water is enough
to actually cool the fire down enough to put it out.
[narrator] Current data show the average global temperature
has already risen 1.5 degrees Fahrenheit.
Victoria, Australia's second most populous state,
is in the grip of one of the worst bushfire seasons in recorded history.
For many, these fires are a warning,
a wake-up call about what climate change can do.
[man] Less than a degree of warming is what we've so far experienced.
And that is enough to transform Australia,
which was already the driest continent on Earth,
into a land mass which has lost so much of its water
that they're currently experiencing the worst drought for 1,000 years.
[narrator] That drought has driven the fires out of the bush
and into the front yards of thousands ofAustralians.
[man] Get in. Get in, mate.
Weather reports are now a matter of life or death.
[man] What's happening?
Got a fire five kilometers away.
We just want to know what to do.
[narrator] If the wind shifts, families have to act fast.
[woman] The fire engine's coming now, so what I'm going to have to do
is get all the kids together and come to your place.
I'm a bit upset because Rob really wants to stay.
[narrator] In some Sydney neighborhoods, it's an awful choice:
Stay and fight the fire
or leave and hope your home will be there when you return.
I'm gonna have to call you back. It's a bit of fluster. OK. See ya, Mum.
A house is a house. If we lost it, we lost it,
but you know, if you lose a loved one...
It was our first house, we just bought it,
so he was going to do everything he could to save it.
[man] My wife left with the most important things
and it was up to me to make sure
that it was going to all be there when she come back.
Bye, hero.
I'll call you from your mom's.
You take it easy.
No worries. You get out of here. I'll see you later.
See you.
[narrator] Bushfires are already bad.
Climate scientists predict in the next three decades, they'll get worse.
And it doesn't end there.
[man] 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.
[narrator] National Geographic author Mark Lynas
spent years compiling data from climate models
to understand how each degree ofwarming
could threaten the planet.
[Lynas] 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.
[narrator] 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.
[Lynas] 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,
18,000 years ago when the ice sheets themselves
advanced to just the edge of Oxford,
and in places the ice cap was more than a mile thick.
[narrator] 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 ofwater 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 miniscule, but as the amount of CO2 rises,
so does the average temperature all over the planet.
[man] 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.
[man] 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.
[narrator] Selecting the right scenario means lowering CO2 emissions.
Experts agree it won't be an easy fix,
but there's reason for hope.
Some potential solutions are already in place,
many others still on the drawing board.
How will we respond?
What will the planet look like if it's warmer by one degree,
two degrees, three degrees or more?
Are we willing to take that risk?
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.
[Lynas] At one degree additional warming to today,
we're likely to see the emergence of new deserts
in the western half of the United States.
From Texas in the south right up to the Canadian border
is in danger of becoming new hyper-arid areas
where really no crops can be grown at all.
[narrator] In western Nebraska, ranchers depend on spring rains
that aren't very dependable these days.
Cattleman Bruce Whoeler needs 4,000 gallons ofwater every day
for his herd to survive.
[Whoeler] We've been hauling water here for about 20, 25 days,
and sometimes twice a day.
Looks like another dry tank.
[narrator] After seven years of drought,
reservoirs are at their lowest in a century.
Just keeping his herd alive is a daily struggle.
[Whoeler] The animals go without water, they die just like anybody else.
[narrator] It's so dry here now, none of the pastures have enough grass
to last the long, hot summer.
The whoeler family is constantly moving cattle.
[Whoeler] When I was growing up, it was a lot greener, more water.
There's creeks dried up that never dried up in my lifetime.
I know even in my dad's lifetime,
there's creeks that he said he'd never seen dry up,
and they're dried up now.
[narrator] Ranchers like the Whoelers live in synch with the weather,
and rely on its patterns,
knowledge that's been passed down through their families
over six generations.
[woman] That gave us a little bit of a benefit
when we wanted to start up our own operation
as young married people ourselves.
[narrator] But past generations of experience that helped them thrive here
may not be enough in a warming world.
[Whoeler] I think it is just a trend that we're going through,
I hope it is, anyway.
It'd be very difficult to keep ranching
because a lot of this country's ungrazable, unusable for cattle
if we don't have water.
And if it turned into a desert-type of climate,
wouldn't be cattle here.
[narrator] Warming ofjust one degree
could turn some ofAmerica's most fertile ranchland
into desert... again.
6,000 years ago, 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 inches below the surface.
All it took was one or two degrees warmer
and the moisture disappeared.
The 1930s gave us a glimpse
ofjust how fragile the land can be.
[Lynas] So think of a repeat of the dust bowl situation
and multiply it by about 20.
This could devastate a huge part of the western United States.
[narrator] But a shift of only about one degree
could transform cattle country into a wasteland
of searing heat and relentless drought.
For now, the sands under this shallow soil are stable.
But for how long?
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.
[Lynas] 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.
[narrator] 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...
[narrator] 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.
Middleton is planting another crop
that's astonishing for England, again made possible by climate change:
Olive trees from Tuscany.
[Middleton] Olives will love it here.
Temperature in the summer will be that of the Mediterranean,
so they will enjoy it and we will enjoy the olives later.
[narrator] None of this would have been possible only a short time ago.
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.
[man] If you had asked us, 10 or 20 years ago,
what would be the impact of one or two degrees additional warming,
we would say, "Well, probably we can live with that."
[narrator] NASA climate scientist James Hansen
was one of the first to sound the alarm about global warming.
The threat has only escalated as he's struggled to be heard.
[Hansen] What we realize now
is that we're getting so close to tipping points
that we're gonna have to stabilize atmospheric CO2.
[narrator] Studying climates in the past has given Hansen a window
onto the dangers posed by global warming.
[Hansen] In the last million years it's never been more
than one degree Celsius warmer than it is now.
What we're doing now with the human-made greenhouse gases
is an order of magnitude larger,
and it's being introduced very rapidly.
[narrator] 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.
But the chemistry of burning fossilized remains
of prehistoric plants and animals is inescapable:
Carbon dioxide.
These three fuels combined are the single largest source
of CO2 emissions pouring into the atmosphere.
They've enhanced the quality of life for generations.
It's hard to imagine getting along without them.
Product by product, it may not seem like a lot,
to make one pair of sunglasses or light one sign.
But the carbon impact of everything we do adds up.
[man] I got to wondering...
...what's the carbon impact of something like a cheeseburger?
Americans, all 300 million of us,
eat an average of three cheeseburgers every week.
And so that's like 150 cheeseburgers
for each one of us every year.
That's billions of cheeseburgers in the United States alone every year.
[narrator] Among the scientists and other experts
investigating climate change,
Jamais Cascio has staked out a unique territory.
[Cascio] I had to be able to calculate the numbers,
calculate the actual solid numerical quantitative footprint
of a cheeseburger.
[narrator] The carbon footprint means all the energy
that was consumed every step of the way
for each of a cheeseburger's component parts.
[Cascio] When you look at the feedstock to feed the cattle,
growing the lettuce,
growing the wheat that gets transformed into the bun,
and milking the cattle, processing the milk into cheese,
processing the cattle into beef,
trucking all that stuff around, keeping it cold, it turns out each burger
has a pretty significant carbon footprint of its own.
[narrator] Carbon dioxide isn't the only greenhouse gas
that's produced in the end.
[Cascio] But then it struck me.
There's another critical part
of the overall greenhouse gas footprint
that I wasn't including: methane,
methane from cattle.
Well, the FDA calls it very politely
"enteric fermentation."
It's what comes out of the cow.
And methane, as it turns out, is the equivalent
of at least 23 units of carbon dioxide.
[narrator] Add it all up, all those cheeseburgers,
and all that CO2,
and you've got a very big number.
Pretty close to 200 million metric tons,
200 million metric tons of carbon dioxide equivalent
just from cheeseburgers in the United States.
[narrator] Cascio has calculated
that there are even more greenhouse gas emissions
every year from cheeseburgers
than from all the SUVs in the United States.
[Cascio] This is just one kind of food.
Think about all of the enormous variety of things
that we purchase, we consume.
And you realize that it's these everyday activities
that are really the critical aspect of human activity
leading to global warming.
[narrator] Even at the lower end of the climate forecast,
there could be fundamental changes in the way the planet functions.
If the temperature rises beyond plus-one degree,
it could threaten nature's delicate balance,
from the bottom of the oceans,
to the world's highest peaks.
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 offood 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.
[Lynas] At two degrees of warming,
the impacts in the marine ecosystem are going to be much more severe.
We're likely to lose the vast majority of the world's tropical coral reefs.
[narrator] It's a problem that's keeping Ove Hoegh-Guldberg up
late into the night.
[Hoegh-Guldberg] To some, it might seem almost incredible
that we could change something as vast as the ocean.
I mean, the Pacific Ocean, I mean,
if you just take that huge bowl of water,
how could we change it?
[narrator] A marine biologist at the university of Queensland in Australia,
Ove is tracking changes in coral reefs.
[Hoegh-Guldberg] They're acting a bit like a canary in the coal mine.
Miners used to take a bird with them.
When the bird got sick they knew to withdraw
because there was gas building up in the mine.
Well, coral reefs, you know,
a beautiful, bio-diverse part of the Earth,
the fact that that's disappearing should have all of us worried,
just like the canary in the coal mine.
[narrator] Located on the great barrier reef,
along the northeast coast ofAustralia,
his lab is on the front lines in the war against climate change.
Recently, the great barrier reef suffered two massive bleaching events.
When waters warmed past the corals' tolerance
of 86 degrees Fahrenheit,
they began expelling the algae they need to survive.
Large sections of the reef died.
[Hoegh-Guldberg] When you jump off a boat and you see a bleaching event,
it really comes home to you, the scale of the changes that are going on.
What would happen if we woke up one morning
and one in every five trees in our favorite forests
had just disappeared?
Well, that's what's been happening in coral reefs.
[narrator] More than a million species live, feed and breed around reefs.
They need the reef.
They literally can't live without it.
Another recent trend in the oceans,
far beyond coral reefs, is even more dangerous.
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 a fraction of an inch.
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.
[Lynas] 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.
[narrator] 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 130 feet per day,
melting into the sea twice as fast as a decade ago.
In just two days, the amount of ice breaking off the glacier
contains enough water
for the New York metropolitan area for one year.
[Hansen] One of the greatest concerns about what will happen
if the planet continues to get warmer
is the stability of the ice sheets.
And the danger is that the ice sheet
could begin to collapse very rapidly.
[narrator] 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 ofwealth 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.
[Holm] So, what I do, I drive around and look after the dogs.
There's snow melting up in the mountains, you know,
and suddenly the dog's place is filled up with water,
and they don't have any place to lay down.
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.
[narrator] These animals were once in peak physical condition.
They served a vital purpose in their owners' lives.
[man] 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.
[narrator] 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.
[Sistall] 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.
[narrator] When Finn was growing up, this was their winter hunting ground,
solid ice for more than half the year.
[Sistall] Everything happened so fast.
It's so visible.
You don't have to be a scientist to determine what's happening.
[narrator] With each passing season, Finn watches as traditions
locked in the ice melt away.
[Sistall] 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.
[narrator] 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 leads the team
that has to dig out every spring.
Lately, he's found areas of the glacier
that hadn't melted in thousands of years,
covered in water every summer.
[Steffens] I checked the weather station. Guess what?
- What? - It's not getting colder.
Why not?
We have record temperatures again in early January.
[narrator] Some experts predict two degrees ofwarming
could be enough to dismantle the glacier completely,
but that would take thousands of years.
Steffens suspects we could reach a tipping point
much more rapidly,
within the next 50 years,
when melting would become unstoppable.
To find out, he must venture even further out across the ice sheet.
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.
[Steffens] 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.
[narrator] In 1992,
3.5 miles of glacier was slipping into the sea
and disappearing.
Ten years later, that number more than doubled
to 7.8 miles 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.
[man] Fifty meters.
Sixty meters.
- Seventy meters. - [man 2] Seventy meters.
[narrator] 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 three or four feet over the next century.
The consequences could be catastrophic.
[Lynas] 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.
[narrator] Many scientists focus on two degrees ofwarming
as the tipping point
that will fundamentally change how we live on this planet.
We are very close to the slippery slope right now.
Some scientists already say
it's probably too late to save the Arctic.
I don't agree with that, but I do think we're very close
to going to a situation
where we would have no ice in the Arctic in the warm season.
[narrator] 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.
Many solutions already available could, in combination,
avoid the plus-two-degree tipping point.
They add up quickly.
From switching to fluorescent light bulbs,
to increasing the efficiency of the world's coal power plants
byjust 20 percent.
Together, solutions like these can have an enormous impact
before we start making irreversible changes
to the Earth's primary climate control systems.
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.
[Lynas] In a three-degree-warmer world,
these kinds of summer heat waves will be the norm.
So an extremely hot summer by this point
will bring the kinds of temperatures into central Europe
that you now experience in the Middle East and in northern Africa.
[narrator] 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.
[speaking French]
[translated] Never before would I have thought it possible
that one could die of heatstroke
at the beginning of the third millennium in Paris.
It was a terrible awakening.
[siren]
[narrator] Emergency room doctors were the first to realize
something was terribly wrong.
[man speaking French]
[translated] Around the six, seven, eight ofAugust
we started getting red-flag warnings.
The patients arrived and died from heat.
This was not a pathology we used to be faced with.
[narrator] Emergency room 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 ofAugust 10
is between 2,500 and 3,000.
[narrator] 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.
[man speaking French]
[translated] In Paris, the roofs are made of tin.
Inside the houses became a real oven.
[narrator] The death toll would top 30,000 across Europe.
In France alone, over 14,000 died in just a few weeks.
[Pelloux speaking French]
[translated] The heat wave of 2003
was probably the first huge catastrophe
due to global warming that affected a rich country,
a rich country that thought itself to be protected from everything.
Well, that was wrong.
[narrator] If global warming increases to three degrees,
it won't be the end of all life in Paris.
But the character of this great city could be changed forever
when extreme summer heat waves start coming every summer.
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.
Philippe Ciais, a carbon-cycle scientist,
noticed unusually high levels of CO2
in satellite images of Paris.
[Ciais] We saw a large release of atmospheric carbon dioxide to the air
from the vegetation.
The trees were not able to take CO2 like they normally do.
But they were emitting, releasing CO2, outgasing CO2 to the atmosphere.
[narrator] 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.
Massive super-computers factor in millions ofweather variables
to project the impact of global warming
all over the planet.
Trying to peer decades into the future
keeps climate modelers at their desks overtime.
Tea and coffee?
[narrator] 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.
[man] 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.
[narrator] The climate model produces an ominous prediction:
Three degrees ofwarming
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.
[Betts] When you see predictions of potentially enormous changes,
and you think, it's a different world
that our children are going to see, you can't help but be affected by it.
It takes someone coming from the outside saying,
"You're talking about the death of the Amazon."
[narrator] Summer 2005.
The Amazon River.
Extreme heat teams with the driest conditions anyone can remember.
It's the perfect drought.
Few can recall a time
on the mightiest river in the world,
when its tributaries ran dry, not low,
dirt dry.
[Lynas] 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.
[narrator] First drought, then fire.
In the aftermath of summer 2005,
over a thousand square miles of the rainforest burn.
In the upper Xingu Park, the Kisedje tribe
is on the front lines as the battle escalates.
A fierce warrior tribe, they now face an invisible new enemy,
one that could destroy their forest.
[chanting]
The Kisedje men prepare for the struggle with a war dance, for strength,
passed down from their ancestors.
In the past, they have fought to defend their land
against commercial agriculture and deforestation.
But this opponent is elusive.
It comes armed with deadly drought and fire.
Chief Kuiussi already notices changes.
[speaking Kisedje language]
[translated] We used to be able to look at the stars,
at the Milky Way,
and know exactly when the rains would come for planting.
But we cannot see any reliable pattern anymore.
They do not come.
[narrator] The Kisedje rely on the river, the rains, and the forest,
for their survival.
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.
[man] For every tree that we lose, we're making one more incremental step
towards a scenario of drought and fire in the region.
[narrator] 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.
[Nepstad] 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.
[narrator] 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.
[Nepstad] 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.
[narrator] A world warmer by three degrees
could finally tip the balance on runaway global warming.
Nothing in our past prepares us for these extreme conditions,
a time when the rare 100-year storm
becomes a common event.
In a world warmer by three degrees,
climate change could be manifest
in the most violent weather humans have ever experienced.
[Hansen] People don't yet realize
the changes that we're talking about
could really lead to a different planet.
[narrator] 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.
There's evidence for this in the past.
Back in the Pliocene, for example,
when it was about three degrees warmer than it is now,
the whole ocean circulation pattern in the Pacific was different,
and there was essentially a permanent El Nino.
[narrator] 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.
[narrator] scientists are still investigating a connection
between global warming and hurricane strength.
Lately they have seen more violent storms.
Hurricanes are rated on a scale of one to five.
One study concludes, in the last 30 years,
there have been twice as many severe storms.
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 175 miles per hour.
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 ofwater into Mayfield's neighborhood.
His father stays to protect the family home.
His body won't be found for weeks.
[Mayfield] When someone has lost their high school,
theirjunior 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.
[narrator] Two years later, much of New Orleans still feels temporary.
The wreckage is still overwhelming.
The recovery, still unfolding.
It's impossible to directly link Katrina to global warming.
The process that forms hurricanes is too complex.
But many in New Orleans want to know if more Katrinas,
or worse, are in their future.
[Mayfield] After seeing what hurricane Katrina has done
and what it's continuing to do today,
you would think people would at least want to start to get serious
about figuring out this global warming deal
and what that really means and what they can do.
[narrator] In 2005, Katrina seemed like the storm of the century.
But if the planet warms by three degrees,
we could be in for a new generation of super-storm.
[Lynas] In a world which is warmer, the hurricanes will have
a lot more energy to drive them.
So the most powerful hurricanes
which we currently see in today's climate are category five.
We could see hurricanes
which are half or more category higher, category-six storms.
[narrator] Imagine it's decades later.
New Orleans is looking down the barrel of an unprecedented mega-storm,
the first category-six storm to threaten the rebuilt city.
What if Katrina is only a hint
at the magnitude of destruction climate change could cause?
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 offresh 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.
[narrator] 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.
If Ganges is not there, then it will not be an India,
it will be a desert in the world.
[narrator] climate scientists predict India could be one of the countries
where the impact of global warming takes its greatest toll.
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 offresh 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.
[man, translated] We used to have eight to 15 feet of snow
in a single night.
Now you barely get one and a half to two feet ofsnow
during the entire season.
The Ganges River will become a desert,
and all you will see in her place is a dirty creek.
Not a thing of beauty.
[narrator] 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.
[Sundaranand, translated] 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.
[narrator] 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.
Literally following in the swami's footsteps
is a new generation of climbers,
lured by the pilgrimage to the glacial ice cave
that gives the Ganges its life.
When Nidish Shwama was a boy,
his father was an early summiter of Everest.
Since the late '70s,
he's climbed the Ganges Glacier 30 times.
[Shwama] In 1978, this place, Borgwasa,
there used to be a dense forest of silver birch.
And now there is not a single tree.
[narrator] The glacier holds millions of tons of ice,
nearly five cubic miles' worth sustains the Ganges
as it begins its descent to the Indian Ocean.
This was all glacier once,
before it started shrinking 100 feet a year.
Just a century ago,
this stone marked the edge of the ice field
that has retreated high up the mountain.
[Shwama] I am sad because I have seen this glacier.
My father has seen this glacier.
But probably maybe my children or their children
may not be able to see this,
which is the most holiest thing for we Hindus.
[narrator] If current trends continue,
the next hundred years could wreak havoc on agriculture, hydroelectric power,
transportation, mining and wildlife all along the Ganges.
At first, the melt might unleash unprecedented floods.
But then, seasonal water scarcity and famine
could strike year-round
once the glacier vanishes completely.
At the current rate of loss, it's estimated
there will be no more glaciers in the Himalayas
by the year 2035,
dramatically reducing the flow offresh water
to more than a billion people.
[Hansen] There are people depending upon this fresh water
from the glaciers.
But most of them will be gone
if we have global warming of three or four degrees Celsius.
[Lynas] That will lead to tens of millions of climate refugees
having to go and find somewhere else to live.
Pretty scary stuff.
[narrator] At plus-four degrees, different parts of the world
will face very different kinds of problems
with only one thing in common:
They will all be extreme.
At four degrees ofwarming,
sea level could be rising by three or four feet,
as the world's great coastal cities confront catastrophe.
Among them, the largest and most densely populated metropolis
in the United States.
Surrounded by water,
New York will no longer seem like an invulnerable fortress
if it's up against storm surges powered by global warming.
[man] This is federal hall here, stock exchange behind me.
We're probably at about 15 feet above sea level, Alex.
[narrator] At plus four degrees, this could be beach-front property.
[man] So now we're moving up Broadway.
[narrator] Armed with elevation maps and climate forecasts,
professor of geophysics Malcolm Bowman
and one of his graduate students
plot the course future flooding could take
through New York's financial district.
[Bowman] Could be massive flooding
in parts of New York City, parts of Manhattan, especially the lower part.
That could be the flood line
for a category-three hurricane hitting at high tide,
a direct hit on New York City.
[narrator] Even a category-two or -three storm
could submerge the financial capital of the world.
New York is supremely vulnerable, both above,
and especially, below the city streets,
where much of the city's infrastructure is below sea level.
The utilities that power New York
are all buried underground,
electric, water,
and one of the most extensive subway systems in the world.
Without them, the city would shut down.
[man] The subway system is always fighting water.
We pump almost ten million gallons of water a day
out of our subway system.
We are in many cases the lowest point of New York City,
lower than the sewer system.
[narrator] If millions of gallons ofwater are already flooding
into New York's subway system every day,
imagine the scope of the problem as ocean levels rise.
For New York City, the problem is no longer theoretical.
They have brought in one of the federal government's
most technologically advanced agencies
to assess the impact global warming may have.
This NASA team uses computer models
the same way generals calculate battle scenarios.
These are war games.
New York City versus a super-storm surge
as sea levels continue to rise.
[man] We don't necessarily notice the effects
here in a major city like New York
of, say, a one- or two-foot sea level rise every day,
but we do notice it when a storm arrives.
People's houses are gonna be flooded. They'll have to be evacuating.
[narrator] Computer simulations reveal a city
in the wrong place at the wrong time.
For a long time, disaster scenarios were based
on the catastrophic 100-year event.
In a world warmer by four degrees,
they could come every four or five years.
[Bowman] Not just talking about rising sea level.
We're talking about huge dislocations, a catastrophic scenario for humankind.
[narrator] If a mega-storm hits
on top of a major sea level rise,
it will mean destruction on an epic scale.
Parts of the city could be 25 feet under water.
One thing is clear,
unless we limit the impact of global warming,
major coastal cities will have to spend
many billions of dollars to protect themselves.
Various kinds offlood barriers
are already on the drawing board,
including colossal sea gates
that can be opened and closed when a storm surge hits.
New York would have to build three massive sea gates:
One around the Verrazano-Narrows Bridge,
blocking the entrance to the harbor.
Another behind Staten Island.
And a third blocking the entrance to Long Island Sound.
Anticipating a storm surge,
massively powerful hydraulic engines
rotate gates weighing thousands of tons,
30 feet out of the water into a vertical position.
These sea barriers on the Thames
cost Great Britain more than a billion dollars,
but they're protecting London from sea surges
more and more frequently every year.
At least major industrial nations
have the option of mega-engineering projects,
with the technology to protect themselves
and the resources to pay for it.
It's likely to be a very different story
in poorer countries, that haven't contributed nearly as much
of the greenhouse gases causing their disasters.
[man] Can you dike this entire planet? No, you can't.
And I think that's what we really need to be worried about.
[narrator] Dr. Rajendra Pauchari
chairs the Nobel-prize-winning panel on climate control.
I'm worried all the time
at the direction that the world has taken in this...
In this day and age, which is not sustainable.
[narrator] At the upper limits, plus-five and six degrees,
the effects of climate change are much more difficult to predict.
Beyond that, genuine disaster scenarios
could become a reality.
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.
[Lynas] I think in a world which is much warmer than now,
five degrees, it's going to be inconceivable
that human civilization can withstand
that kind of a climatic shock.
[siren]
[narrator] Now we enter the twilight zone of climate change,
a nightmare vision of life on Earth.
Perhaps most frightening of all is
how much we can't know.
Traditional social systems would break down.
[Pauchari] It's the poor everywhere that are going to suffer,
because if you take the example of, say, Hurricane Katrina,
which I'm not saying was necessarily caused
by human-induced climate change,
who were the worst sufferers in the city of New Orleans?
The poorest of the poor, they were just left behind.
[narrator] The best way to survive the catastrophe
of a hotter planet is to prevent it from happening in the first place.
Failing that, we may be confronting
far more difficult choices.
[man] The survivor of the future is mobile.
Mobility is the key. You've got to be able to get from place to place.
If you think that you can hunker down in one area, you're wrong.
[narrator] Aton Edwards travels around the country
offering personal preparedness training
designed to survive disasters like the chaos of a climate meltdown.
Katrina was our lesson.
But Katrina was a lesson that's going to be repeated again.
[narrator] Edwards is convinced survival is just a matter
of planning ahead and a little ingenuity.
His gadgets are low-tech but effective.
In New York City, because there are many windows and doors
that you've got to move through, a critical tool would be a mini pry bar.
I carry mine with me all the time.
[narrator] It's not likely we'll reach plus-five degrees in our lifetime,
but Edwards has prepared everything he and his family might need, just in case.
[Edwards] And what we have here is what I call an urban nomad bag.
That means you're going to basically have a bag that is your home.
So you need everything that you have in your home in the bag.
[narrator] If the worst should happen,
Edwards is ready to become a new age hunter-gatherer,
carrying what he needs on his back,
living off the resources he finds along the way.
[Edwards] A first aid kit. These are toiletries.
You can put five gallons of water in this.
Regular old ramen noodles.
Old military mess kit.
This is a six-person tent.
People don't think that you can actually have... carry your home with you.
There is no more permanence. They should remove the word "permanence"
from the dictionary at this point. It's the death of permanence.
It's all about mobility.
[Lynas] 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.
[narrator] 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.
[Lynas] 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.
[narrator] Six degrees ofwarming 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.
Two degrees hotter puts us on the brink
of runaway global warming,
when it could dramatically disrupt how we live our lives.
[Lynas] The scientific reality seems to be that we have to,
if at all possible, peak global emissions
within the next ten years, by 2015.
And this, of course, is an extremely tight timetable.
We're talking about turning around the energy supply
for most of humanity within the space of a decade.
[narrator] 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.
More than half the electricity in the United States
goes into buildings in one form or another.
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.
[man] 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.
[narrator] ForAmory Lovins, solutions start with efficiency,
reducing the use of energy that produces CO2 emissions.
[Lovins] Once people understand
that climate protection puts money in your pocket
because you don't have to buy fuel,
political resistance is going to melt faster than glaciers.
Do you see that little red light in the corner?
[narrator] Lovins is a sort of New-Age meter reader,
hell-bent on killing wasted watts.
[woman] If you have all kinds of appliances,
your TV, your VCR, your DVD, et cetera,
that have that little light on...
[woman] Yes.
[woman 2] ...they're using electricity. It's called "vampire loads."
[Lovins] 109 watts.
Almost 60 bucks a year, just sitting there, turned off.
[narrator] If every household in the U.S. killed offwasted vampire loads,
we could eliminate at least 18 coal-fired power plants.
Lovins doesn'tjust talk the talk.
He lives in a house he designed without a furnace,
in Aspen, Colorado,
where temperatures in winter routinely drop below zero Fahrenheit.
[Lovins] 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.
[narrator] 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.
[Lovins] 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.
[narrator] 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.
Nowhere is the problem of emissions from transportation
more urgent than in developing countries,
especially China.
Rising affluence has paved the way
to many of the perks of middle-class life,
like owning a car.
The numbers are staggering.
So are the emissions.
Fourteen thousand new cars hit the road every day.
[Lynas] I don't think we can turn around to the Chinese
and say, "I'm sorry, we need to save the future of the planet."
The rich countries have to take the lead,
and we have to cut our emissions in a much more dramatic sense
in order to allow some room for growth in the poorer countries.
[narrator] 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 15 miles per gallon to 30
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.
[Cascio] We have an arsenal of solutions already.
It's 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
to get away from the fossil fuel economy.
[narrator] They look like some giant robot army,
marching across the landscape.
Wind power and windmills date back thousands of years.
With today's technology,
one wind turbine can power about 300 homes.
They're a 100 percent clean and renewable resource.
But wind power is no panacea.
[man] The fuel is free, but the maintenance is not free,
and we're seeing a lot of problems with the units.
[narrator] And, of course, nature controls the on-off switch.
On a global level, it would take
more than two million wind turbines
to replace coal power plants worldwide.
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.
These are still the early days of climate change.
The longer we wait to do something about global warming,
the harder it will be to solve,
requiring more science, more money,
and more global cooperation.
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.
[man] 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.
[narrator] It won't be easy.
With the volatile gases involved,
engineers can't work directly on the reactor's core.
They depend on a new generation of robot,
some of the smartest and most skillful ever invented,
to work in such extreme conditions.
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
or a solar mirror which is going to reflect enough of the sun's rays
to keep us tolerably cool.
The reality is that we have to deal with what we've got,
and have to do it within ten years.
[narrator] With or without us, the biosphere has always done
an excellentjob of cleaning up after itself.
The planet has both the resources and the experience
to deal with global warming.
It's done it before.
Global heating also spiked during the Cretaceous Era,
between 144 and 65 million years ago.
It is the age of dinosaurs.
The climate is changing radically, but slowly,
over millions of years,
giving many species a fighting chance to adapt over time.
A period of extreme volcanic activity
floods the atmosphere with six times the CO2,
sending the average global temperature skyrocketing.
It takes millions of years,
but nature scrubs all that extra CO2 out of the atmosphere.
It's absorbed through natural carbon sinks
in the oceans and plants,
and buried deep in the Earth.
Then, over millions of years more, it's fossilized.
Billions of tons of carbon
infused with the power of the sun
were buried throughout the Earth's history.
Those fossils sunk deep underground,
producing enormous reserves of coal and crude oil.
That's where the CO2 nightmare ended for the Cretaceous Period
and ours began.
It's the final irony of global warming.
The very same carbon that was scrubbed out of the atmosphere so long ago
is now being pumped back into the air
every time we burn those fossil fuels.
And it's warming the planet all over again.
Humans come along, we dig the stuff up,
we find it's an incredibly valuable energy resource,
and without thinking about it, we burn it
and return this carbon back to the atmosphere in less than a century.
[narrator] In effect, we're reproducing
the extreme conditions of the cretaceous era.
Only this time, at breakneck speeds,
so quickly that most species won't have a chance to adapt
and survive.
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:
Theyjust don't know,
and they hope we'll never find out.