We need to,
they will give you.
This
is our planet.
It contains an astonishing variety
of landscapes
and climates.
Since life began
around 4,000
million years ago,
it has gone through
extraordinary changes and its climate
and in the space that their on it.
But no,
it seems that our planet is being transformed
not by natural events
the by the actions of.
One species
mankind.
You know I belong to the most
they spared and dominant species and I more
or less.
We live on 27 years ago I presented
life on Earth.
A series of traces
the evolution of life
from its very beginnings.
I set out to find them film
representative species
of the whole animal kingdom
in all it's marvelous and wonderful for us.
In the final program
I dealt with the arrival of human beings.
Still a recent event in the history of our planet.
There is no scientific evidence whatsoever.
The suppose indeed that
man will stay on earth should be any longer
than that
of the dinosaurs,
but although
denying a special place in the world,
maybe
becoming a modest.
The fact remains that man has an unprecedented control
over the world
and everything in it.
And so
whether he likes it or not.
What happens next.
It is very largely
up to him.
Up to us.
Indeed,
at the time I spoke those words.
I had no idea that we have been the
might have unleashed forces
that in the
hotel in the climate of fear.
Good.
The destruction of towns and cities
in the southern United States
be linked
to the collapse of glasses
in green.
If
going people
but is the stuff floating around
if out there.
Might drought
in the Amazon
that killed thousands of fish
be connected to the intensity of forest fires
in Australia.
And are these events related
to one of Europe's hottest ever
farmers.
Which led to the death of 27,000 people.
In every part of the world.
New climatic extremes are now being the court.
Our weather
is in turmoil.
During the last 50 years
I've been lucky enough to spend my time traveling
around the world
looking at its wonders
and its spenders
during a time of course,
I've seen many changes
some good
many bad
but it's only in the last decade
that I've come
to think about the question
as to whether or not
what I or anybody else has been doing
could have contributed to the change
in the climate
of the planet.
It is undoubtedly taking place.
In recent years,
scientists have been collaborating
on one of the most urgent and ambitious endeavors in our history.
They're trying to understand the unprecedented changes in our time
. And they're linking those changes
to the rising temperatures that they're measuring
had thousands of weather stations around the world.
So,
how much
have global temperatures
well
by just over
nought-point 6 of one degree Celsius.
Since 1900
how can such a seemingly small rise
create so much havoc
with the planet's climate.
Well,
that figure
nought-point 6 degrees
is only an average
while some places have cooled a little
some
like the Arctic
has warmed
by up to 3 degrees.
The frozen surface of the sea creates a highly specialized
environment.
And an extraordinary range of animals
have evolved to live both above and below the ice.
But the Arctic is now melting so fast
that the whole intricate web of wildlife
is under 3.
And no species is more at risk
than the animals at the top of the food chain,
the polar bears.
The turn of the year,
that is when females give birth to
raise their cut.
By this time
mothers will not have eaten for many months,
and yet they now have extra mouths to feed.
Their main prey are seals
but they can only hunt
before the ice melts,
but it does that
they must come ashore
with all the reserves only to raise their cubs.
And on land.
There are no
to hunt.
Now
because the ice is melting earlier each year
mothers are going hungry
and the less able to provide for their Cup.
In Hudson's Bay
Dr.
Nick to London
sets out each spring
to track down the polar
bears
and check on their health.
They been there.
I've been working on that all of us here in the Churchill area
since the early 1980s over the last 25 years
and we're looking at the population
ecology of polar bears in relation to tie not of change
is population is the most
studied population anywhere in the world.
By tracking the Bears with such regularity
Miquelon
and his team
have discovered that their numbers have declined
by nearly a quarter
since he first started stuck.
First he needs to find the best.
He then
tranquilized system so that he can check their body weight
to assess their health.
The team has to work quickly to make their checks on their family
before the mother wakes up.
24 and a half pounds
for Cobb one
fun
on larger bears
we take the weight and their length and weak calculate what we
call a body-body condition index.
It's essentially the weight of the bear divided by its length
Square
and it gives us a means to compare bears
between years over years
what condition there and when the come ashore and we found that
over the past 25
years or so low that the condition of these bears us declining.
Cobb 2 straight line leg zero 6-9.
Here we've got a female with a trip letter.
It's a very rare sight to find triplets.
In the fall time
one of the Cubs is
a runt of the litter and it's not likely to survive.
20 years ago.
It wasn't all that uncommon to find triplets.
In the fall.
About 5% of the bears.
We caught more females with cubs had triplets.
We're seeing triplets born in the spring,
but we're not
one or more of those cubs is not making it through the fall.
We're seeing reductions in Cup survival,
things of that nature,
all related to climb out of form.
The ice is now melting
3 weeks earlier
each year.
That means that there is 3 weeks less feeding time for pregnant
mother.
Once they come ashore in the sea ice melts
the bears are forced to fast for anywhere from 4 months for most
parents up to 8 months for a female such
this
here.
Who would have come ashore last summer
and it's not hard to see all meal since last July.
If the current warming trend continues
the future
looks bleak
for polar bears.
It's not just that sea level.
Is melting at Sutton alarming rate.
The global temperature rise is also being felt much higher up.
Mountain glasses
all over the planet
also now.
The mountain ranges of Patagonia
rundown
towards a sudden tip of South America.
This is the,
in the northern
Patagonian Ice Field
it starts almost 2.5 thousand meters above sea level.
This remote part of Patagonia
is one of the coldest places on earth outside the poll nobody.
JC allergist Dr. Stephen Harmison
has been working in locations like the meth
for 20 years
he's been studying how they've changed over that time.
The Patagonian Ice Field,
the most dynamic ice fields on Earth.
To understand climate change in the southern hemisphere.
We need to go to places like this.
He gives a very good record of climate change over the whole range
of time to go.
The ground I'm standing on
that last year,
the net glass.
It was here in about the 1870s and by about 19 the 1930s
it will be treated to this
shoreline the lake shoreline
and since then,
since 1930s of courses
retreated another
2.5 to 3 kilometers perhaps 2 miles
back up this valley.
We were hearing Martin 88
is this the whole night was completely covered with icebergs.
All.
Some fake MySpace
we hardly get our boats in the ice front
and yet that's will go on that landscape is completely changed now
. Russia's
give us a very
visual record of climate change and and the they should be no
doubt the climate change is happening.
If we look at what glasses and doing all around the world,
not just these ones on the north Patagonian Ice Field but glasses
everywhere.
They're all in recession pretty well
and and that gives us a very visual record what exactly is going
on in most one.
The rate of that class Immelt
is now accelerating.
In southern Greenland.
The amount of ice flowing into the sea
has doubled in the last 10 years.
This
is slowly but steadily
causing sea levels to rise.
8,000 miles away.
The inhabitants of the tiny Pacific islands
of Tuvalu
are already facing the realities of an invading sea.
As temperatures rise so do those of the sea,
causing oceans to expand
and that
coupled with the dresser melt
means that sea levels will rise even higher.
Earlier this year
tides rose to their highest level ever known
flooding the homes of the islanders.
They have been troubled by this problem
for the last few decades,
but according to
Diana semi
it's getting progressively worse.
Most of the people now experiencing this high tide is much higher
than
it
hasn't
won and.
If next year is going to happen like this and much higher than
this year
then
I don't think there's any future for him to.
Through Mario Silva
is now 2 values
disaster coordinator.
The
prediction for tomorrow.
The highest,
but now
looking at this time.
Boats
he flooded.
And so,
so it's them
all their properties is they have been cowed
tour
guide binning in all those would be
damaged by this.
See what I.
You can see that
our rubbish everywhere
and you're you seeing that
the kids swimming
and those
waste area,
I think
a big
health problem for kids
and especially his
people thing these houses and.
Very worried
flood
they have
at
door
climbing outside
inside,
but the flow this company here.
Yes.
All my
really.
PC
fear well you here
only
here and at times,
calling them but now this year as they
really
high time
inside the house.
This is the first time
I think to
to move out because and freight.
I don't
know placed move.
But on the islands where the highest point is less than 5 meters
above sea level.
There is nowhere else to go.
There are already plans
for some of the population
to be evacuated
to New Zealand.
But
warming seas
don't only mean
rising seas.
They have other implications,
too.
In August 2005
Hurricane Katrina struck the coastline of Louisiana,
Mississippi.
Wasn't the high sea temperatures that many Katrina so intense.
A typical hurricane,
an atmospheric disturbance over Africa
but it's here in the Gulf of Mexico
that they grow to their full destructive power.
How you can expert Greg Holland
has been investigating what fueled Katrina's force.
The process requires that the oceans be warmer than about 26
degrees Celsius.
The tropical
to get the hurricane started and
Jordanian
from the surface high up into the atmosphere
and what this means
the ocean heat energy
is used to fuel the development of the immensely powerful winds
and it is so powerful,
he could run the entire electric grid of the United States for
several weeks.
Really destructive winds are in the region.
Just outside the eye of the hurricane
and this is how strong they shred the surface of the ocean into a
morass of sea and spray
to become so think
that the Mitchell becomes impossible to tell a difference between
air and water.
And the one the tropical oceans,
the more destructive the hurricane can out.
When Harry can Katrina breached the levees of New Orleans
sea temperatures in the Gulf of Mexico and the Atlantic were the
highest ever recorded.
In the United States.
The intensity and sheer destructiveness of the Heineken
became the turning point
in the debate about global warming.
Although scientists
will not say that one particular had can is caused by climate
change.
Many are now making the connection between global warming
rising sea temperatures and the increasing strength of Vatican.
2005 it was the worst season
ever recorded.
And Greg Holland
is one of those who believes
that worse is yet to come.
As you can see there's a massive rebuilding program underway,
but unfortunately this stretch of coast song
will certainly be revisited by hurricanes,
like a trainer
and because of global climate change
we going to be more intense
more destructive
and possibly more frequent.
It's a grim warning
but is global warming of the changes we're now seeing
really
a new phenomenon
in the Earth's history.
These days,
when we talk of climate change,
we tend
to mean changes
that we ourselves have brought about,
but of course the climate of the Earth
has always been changing,
either because of some great,
cosmic event
like a collision with a meteorite
or else because of some more slower
gradual change
in the amount of energy that the Earth receives
from the sun.
The
reborn rearguard.
It's the sun
that provides our planet with warmth and light.
Why
when
you know.
Not the amount amenities
that the Earth receives from the sun
there.
You know.
In cycles of tense and often hundreds of thousands of years
the earth
tilts and changes it orbits around the sun
and with each cycle
the patterns of light energy playing on the
changes.
These natural changes
have contributed
to dramatic shift in my client
in the time of the dinosaurs.
It was much warmer than it is now.
He would have found dinosaurs
roaming in forests,
close to the north and south poles.
70 million years after that
much of our Paris was freezing.
It's become locked in a cycle of success if ice
ages.
If the city of New York had existed 160.
Thousand years ago
it would have.
Been on the edge of an ice pack some 2 kilometers high
and yet global temperatures were only 4 degrees lower than they
are today.
30 thousand years later,
the same city
would have been under 5 meters of water
yet global temperatures were less than 2 degrees warmer.
This see-sawing in the Earth's climate
was driven by natural forces
long before mankind
appear.
But there's another
powerful influence on our climate.
If we have to take into account
among the
many glasses that make up the air we breathe,
there is one
that is particularly important
carbon dioxide
it
traps the sun's energy
and so keeps a panic.
Greenhouse gases like carbon dioxide
act as a blanket around the earth
prevent in the sun's energy from reflecting back into space.
Left.
It's called the greenhouse effect and it prevented the planet from
freezing
since the earth began
without
the global temperature would be minus 19
subsidies.
On the face fit
carbon dioxide seems to be a good thing
it stops our planet from freezing and so sustains life on Earth
and without it,
no plant could grow because they need carbon to build their
tissues.
Leaves absorb the gas from the atmosphere
through their pores.
They then break down on the carbon dioxide molecules
released the oxygen
and retain the Cup.
Over hundreds of millions of years
the great forests
so much carbon dioxide.
Out of the atmosphere
that they
reduce the greenhouse effect and cool the planet down.
When the trees died.
They were buried
and overtime
crushed and compressed
with the carbon still within
in the ages that followed.
These layers are slowly buried
beneath the earth's surface.
At this open cast coal mine in China,
you can descend for 500m
through layer upon layer of rock
representing 10s of millions of years.
Right at the bottom,
a layer
of what was once would and leaves
and is now
coal and.
It's an ideal place
for Professor Bob Spicer
to studies appliances
influence the climate.
All that time ago.
These leaves
blast saw the light of day.
Some 50 million years ago
when they were
on the trees
taking in carbon dioxide and using the energy of the sun
the fix that carbon
into
their tissues and leaves and twigs and the like.
Now the original
had a
cooling effect on the atmosphere because they were
taking carbon dioxide out
and where we
Burnley
the call
on the carbon.
That's nice one,
and put it back into the atmosphere.
Today
we have the opposite effect we warm up the atmosphere.
Now
all the coal is being carried up to the surface
to be burned in the power station,
which provides electricity for hundreds of thousands of people.
Oil and gas
Nicol also
fossil fuel.
When such fuels averting
the carbon re combines with oxygen
and is released back into the atmosphere
as carbon dioxide.
The carbon dioxide spreads evenly through the Earth's atmosphere.
Sickening.
The greenhouse blanket the
the world
and further warming the planet.
That blanket extends for miles above the earth's
as you climb up away from the Earth the.
Is become thinner.
The temperature.
As a result,
becomes colder.
It was while I was making the living planet in the mid 1980s
the tide began to appreciate the crucial role of the atmosphere
in shaping our climate.
We are
very close to the top
of
our environment
for all the
goes on
within the
5
brief Miles this
envelope
of atmosphere that wrapped
around the world,
it's here,
but the weather
is manufactured.
When I spoke those words
scientists were already detecting crucial changes in the
composition of the atmosphere.
In particular,
changes in the level
of carbon dioxide.
All over the planet
they were recording rising levels of that particular gas in there
. The first regular
measurements were started 48
years ago,
from the top of the extinct volcano of money on lower
in Hawaii.
And it is the rate at which the carbon dioxide blanket is
thickening
that is causing so much concern.
When I was a boy in the 1930s
. The carbon dioxide back it was still below 300
parts
per million.
This year
the thickness reached 382
the highest figure
for hundreds of thousands.
But how can we possibly know that carbon dioxide levels
are higher now
than they were thousands of years ago.
In Patagonia is ice fields
huge gaps open up in the summer months,
giving scientists a chance to investigate
far below the glasses.
Stephen Harrison
is taking the opportunity to descend deep into a pair of us in the
. It's risky.
You,
you know.
The glasses a melting so fast.
The potentially invaluable records of the past
artists.
Yes.
Ice cap in which his glasses flow from
is melting more quickly probably than any other comparable ice
mass on Earth.
You can see them out of water,
which is around us.
Stephen
has spent the last 20 years studying
Latinos and past climates,
he knows that ice can preserve valuable evidence.
Carbon dioxide is a as an important driver of climate change.
In other words,
is that important factor in in
in changing the global climate.
You have to see how come not citing changed with the pattern
periods and warm period throughout her history.
You can see the ice here is absolutely full
of of of bubbles
from the bubbles informed
when the ice
was formed.
And of course the bubbles contain
atmosphere oxygen and carbon dioxide
if we want to understand the the role of carbon dioxide
as a sort of as a thermal blanket over the earth.
We need to know about how come a dark side has changed the
concentrations of change in the atmosphere
over hundreds of thousands of years.
An analysis of bubbles such as these
in places like Antarctica and Greenland gives us that that that's
fantastic record.
That record is now also preserved thousands of miles away.
Not
in the ice fields as originally contained it
but in Denver,
Colorado.
In this store room of the United States national ice core
laboratory
hundreds of thousands of years' worth of ice core records
are maintained
at minus 36 degrees.
These ice cores have been extracted from as much as 3 kilometers
beneath the polar ice caps.
I mean for Professor marks a rare as
each one provides a valuable source of information
about a particular moment in the past.
Well,
this
particular
chunk of ice was about 16,000 years old
come from the Greenland ice sheet.
What we see here are layers of fossils
snow
every year on the top of Greenland,
there's an accumulation of snow
and
this is a good compacted
you're through years layer after layer of snow
eventually before these layers of ice
and it's within these layers of ice
that we can tell all kinds of things about deep that the Earth's
past
what we find today is at the carbonate
oxide concentrations in the atmosphere are higher than anything
we've seen in the past 600,000 years.
It's telling us that human activities are having a strong him.
Back on the claim it's,
it's.
It if we measure this in parts per million of carbon
oxides in the atmosphere,
what we call the pre-industrial output before he wins were
starting to have a team
with around 27280
Premier League.
What we've seen now.
The most recent record today are telling us that it's up to about
380
for the.
So you can see that today if levels are far beyond anything that
we.
If you talk to be 5 years ago
I would have been
kind of a fence sitter
on this whole idea
of
greenhouse gases involved in climate change
no war.
The changes that we've seen
seem to be much too strong much too radical to be just simply
explained by natural climate cycles.
What we're seeing now is the impact of humans
humans are starting to change the climate itself.
Those changes
could now be occurring.
Even in places
which are absorbing
huge amounts of cotton dioxide.
The Emerson
is often referred to as the lungs of the world
for here plants taken vast volumes of carbon dioxide and give out
oxygen
to appreciate the immensity of the greenery where this gaseous
exchange takes place.
You have to get up into the branches,
some 50m about the ground.
I'm
up in the canopy
of the jungle.
The tropical rainforest,
here
there is a greater bulk
of life both animal and plant and the greater diversity too
and can be found
anywhere else at all
and this huge proliferation
comes from 2 main courses
warmth
and witness
the wetness comes from the abundant Equatorial rains
for warmth
from the tropical sun
and between them.
Those 2 factors have created the jungle
which stretches in a broken
green band
Wright round.
20 years later
and in spite of intensive logging
vast areas of this phone is still survive.
Bridgestone Youzhny.
But scientists like
down
next had
in covering an even more sinister threat
to the health of the John.
Go
them deforestation
he has discovered
that many of the largest traders
are dying.
What I think
is for me the most scary part about the future of the Amazon
is drought
because when a drought comes often with very little warning
it affects not just
one or 2%
of the basin,
it's an effect 30%
for us
in ways that we are just now learning can be quite devastating to
the forest.
In 2005
the Amazon region suffered its worst drought in 60 years.
The lack of rain,
led to a catastrophic fall in river levels
decimating the fish popular.
6 months after the drought
Dan never stat is finding that the trees
have still not recovered.
Right now we're measuring how much
water stress the tree that
this leaf
growing on who was under when we cut it.
Last year's drought caught assault by surprise
they've had
devastating effects and the people who live in the Amazon.
We're just right now getting a handle on
how many hundreds of thousands of square kilometers of forest
were severely damaged by a drought killing
enormous trees,
which are the key organisms in these ecosystems
could be the 2006
is it your full of forest fire because of the drought of 2005.
The drought was linked to the abnormally warm seas in the Atlantic
, which disrupted the rainfall patterns in the forests.
It's particularly worrisome because.
It's the type of ocean heating and it seems to cause the drought
in the Amazon last year that is
exactly what is predicted,
and their scenario
hopeful who worry.
Yes.
But the Amazon
is not the only rich ecosystem
now at risk.
The world's coral reefs and other marine equivalent of the
rainforest teeming with countless different species.
That
you know.
Warming sea temperatures are already putting the oceans and the
life within them
under increasing strain.
The 2000 kilometer long Great Barrier Reef in Australia
is one of the wonders of the world.
Early in the life on Earth series
I examined it for myself.
The reason
may look like some fantastic
multicolored
jungle of plants and flowers.
But when you touch,
one,
it has a hard being incongruous
crunch
the stone.
Then 27 years ago
the reef
seemed won a huge unblemished and healthy world of its own.
I described the intimate relationship
between the tiny animal coral polyps
and the alchemy that shelter inside them.
Lately.
A relationship established hundreds of millions of years ago
that eventually produced Greece so immense that they're visible
from space.
So it may well be the river
passing astronaut came this way,
several hundred
million years ago,
you might have noticed.
But at the time I was making the series
I was unaware of a new and disturbing phenomenon.
Now,
in early 2006
the state of the car on the Barrier Reef
is worrying marine biologist Ove Hoegh Guldberg.
In recent years.
He and other scientists
have found that the reefs a far more sensitive to see temperatures
than they had previously.
This year
has seen temperatures are abnormally high.
Everywhere and up.
Well,
I can say it isn't blitz Carl's
Carlson
Adobe proudly
Anelka
existing
a brilliant bike.
This is the cost of the out,
you have a lot of that this is
all that's left of the
absolutely
reflect the skeletons
okay I'm here,
I just saved
and later after they don't
the time glitz golf
and silicone struggling,
but I think I said it really quite like this before.
If you cut off.
What is particularly unsettling
scientist
is that this reaching is becoming more frequent
is sea temperatures remain high for too long.
Then the out he won't return
and the call may die
Ove Hoegh
is using approved
to discover how stressed
this Congress.
I tells me that you know
most of the
Algeria,
who left in these corals
are severely damaged
and I've been terrorized by combination
of heat and likely.
Away.
When I come here and see this
said it really stressed out rescue
a former self getting really concerned
it's another reminder
that there are a huge changes on the way with climate change
in the,
this is the 3rd bleaching event
in the last 90 years of the Great Barrier anything and everything
they had
and
as predicted if
they getting more frequent
and
and more severe head
and I called customer funds that you rather frightening
movement
in the area.
Of
of.
Devastating thought
but if the warming continues.
Some of our richest environment.
Some species that live in them
will be under threat.
And it's not just the non-human.
We as a species will not be immune either.
How can we possibly know what the future holds.
Scientists don't pretend that they can predict specific changes to
the climate with absolute certainty.
But they can do
his calculate the likelihood
that they will occur.
It's here at the Met Office's Hadley Centre in Exeter
that we can't find the answer to some of the big questions.
This super computer can perform 10 billion
calculations per second
each one
contributing to a model that scientists like Peter Cox can use to
protect our future climber.
Climate
models that essentially
come out of weather forecasting models
they run for much longer periods around own for hundreds of years
rather than days
but they contain older complex they contain clouds they contain
rainfall patterns they contain winds
and Clark models have to contain slower components like how the
vegetation on the soil respond to changing how the oceans
change.
The model
is like a virtual world a sort of flight simulator.
Where everything from the melting ice in the Arctic to the
formation of clouds in the atmosphere
and the temperatures of the oceans
are represented by solemnly leap,
it can give us the probability
that future events may happen.
For instance,
one of the chances of are having another major heatwave
like the one of summer 2003
. And
as the planet warms up
can we expect
heatwaves more often.
It's impossible to put any particular climatic or weather event
down to climate change alone.
But what you can do is say that climate change affects the chance
of an event occurring
and though it to the very extreme 2003 summer we've suffered in
Europe.
He killed many people in France for example
is a case in point.
That's something that is a,
a rare event now
is a one in 200 year type of event,
but that
is twice as likely as it was before we started to click change the
climate
and by 20-40 because of future climate change,
it will become a one in 2 year event
almost the norm by 20-80
will consider that call you.
One place where the Hadley model is predicting increasing
temperatures
is the next year
province in northern China.
Not good news for a land
where the desert is expanding.
Over the last 20 years,
there's been a marked decline in Maine.
Powerful winds have driven the thin soil into dues
smothering fields and villages.
In soup will drink
many villages have deserted their homes for the cities.
Those who are left behind like one lane
must endure a daily battle with the encroaching
dealings.
Yeah,
there wasn't so much sand here before.
Okay.
Now the wind is blowing.
More and more sensitive and.
So what do you know she also.
I remember when I was a child.
The
environment was really good.
And in 1973
went dry
the grass struck growing
but dust storms
the sand covered everything
and began to affect our lives in every way
Chi white.
If you go,
if you go you know and I get home if I don't brush I sand away
account gets into my house.
Then if you,
if there is takes a lot of time so it affects my work.
But they require
a lot of people have left the village already.
There was also sold
securities would you might they want to improve their lives.
So you know
moved to a better place with water and much better conditions
you
not
Georgia.
But the
group.
Those villages
that aren't swamped by sand
are suffering from severe drought
this village
ego
has not had a harvest for 3 years.
Professor Lin that
is working for the Chinese government
trying to discover how badly affected the local people are.
You know,
until that can you remember when you were
younger.
You know what.
At the same situation to do
and when I was a child who it was also sometimes very trying
IVF.
But it's become more serious.
In recent years.
So you know it's not on the radar
for troops being on recently
from the harvest was very bad
why was that
there's been a
rifle.
There's been no rain for 3 years
called White out
of work well by,
we can only depend on the food given by the government
and without crops.
We have no income
we can't buy anything
and we have no money to spend.
When the winds pick up
the dry soil
completely create a standstill.
Such storms are already afflicting cities like Beijing
if the dying
continues this will only get worse.
The bleak realities of climate change
are being felt all over the world.
And yet
despite so much evidence some people refused to believe that human
activity
is the cause of the changes we're seeing
the climate models
at the Hadley Centre,
believe that they have put.
They sat
both natural climate variations
and our carbon dioxide emissions into their model
to see which best explains the changes in temperature.
Over the last 120 years.
The key question of course
is how can we distinguish between variations due to natural causes
and those variations of the climate
that are induced by human activity.
And
the key thing
that
convinced me it anyway
was a graph like
this one that we marked out on the floor
that have been prepared from
climate scientists
like
Professor Peter Cox
now explain to us the significance
of this squad.
Okay.
What we're gonna do is to take a walk through time
and the first thing to note,
as we walk through its a bit the climate is naturally variable.
It's a spiky based
occasionally there's a downward trend that's associated a volcano
going off the coast of system down because of the dust,
it throws up
the general it just
isolates around
and then we get to a period
around about 1910
where you can start to see an upward trend
a warming of the climate and global warming,
if you like,
and the issue is
what caused that
was that
humans are was that natural.
So what we do to try and work that one hours to take a climate
model and to put in the various factors,
what we can say with its
blinkered here is a car model
that includes just these natural factors.
So this is when volcanoes go off
and the output from the sun
and you can see that the
curve can reproduce
recently well this mid-century warming so
up to this point,
you could reasonably argue
climate variation can be explained by natural factors,
but as we move on,
we can see that's no longer true.
If you get to the latter part of 20th century from about 1970
onwards.
Here
you can see the red curve.
He observed temperatures
in the green
really begin to diverge.
And the question again is what caused this recent woman.
So we run the model,
again we include human factors particularly include greenhouse
effect
from
mostly from carbon dioxide that comes to fossil
and then we get this yellow card and we can see
as well as reproducing.
The mid-century
warming
we get this recent
rather rapid warming reproduced
and that tells us 2 things,
one is that the model
looks realistic looks like the real world and the second thing,
the model tells us
but this recent morning is due to human beings.
So there you have it.
There seems little doubt
that this recent
rises
the steep rise in temperature
is due to human activity.
If you look at the green line of now.
True variability.
It's clear
that without the action of human beings,
they would have been far less temperature change
since the 19-7.
We are all involved in this,
our whole way of life is structured around the Burmese
of fossil fuels.
I find it sobering
to think
that while I've been traveling the world trying to record
the complexity and beauty of our planet.
The night to have been making my own contribution
to global warming
as I recognized when I presented life on Earth.
All those years ago.
We are a flexible and innovative species.
And we have the capacity to adapt and modify our behavior
now
we most certainly have to do so,
if we are to deal with climate change.
It's the biggest challenge
we have yet faced.
This
sea wall
was built
to keep out
what he
recognized it was a force of nature
something
beyond our.
We ourselves have become
a force of nature.