National Geographic: Six Degrees Could Change the World Page #3

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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.

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