Group: ca.environment · Group Profile
Author: Mike Vandeman Date: Dec 17, 2006 06:02
Date: Sun, 10 Dec 2006 20:45:12 -0700
To: greenspiration global list.web.net>
From: angela bischoff
Subject: Global Dimming
This is a truly mind-blowing BBC documentary on global dimming.
You can watch the documentary if you have high speed internet.
The transcript of the film is below...
SEE THE FILM AT:
12/05/06 - BBC
Runtime 49 Minutes
NARRATOR (JACK FORTUNE): This is a film that demands action. It
reveals that we may have grossly underestimated the speed at which our
changing. At its heart is a deadly new phenomenon. One that until very
recently scientists refused to believe even existed. But it may
led to the starvation of millions. Tonight Horizon examines for the
time the power of what scientists are calling Global Dimming.
NARRATOR: September 12th 2001, the aftermath of tragedy. While America
mourned, the weather all over the country was unusually fine. Eight
miles west of New York, in Madison, Wisconsin a climate scientist
David Travis was on his way to work.
DR DAVID TRAVIS (University of Wisconsin, Whitewater): Around the
later on in the day, when I was driving to work, and I noticed how
blue and clear the sky was. And at first I didn't think about it, then
realised the sky was unusually clear.
NARRATOR: For 15 years Travis had been researching an apparently
obscure topic, whether the vapour trails left by aircraft were having
a significant effect on the climate. In the aftermath of 9/11 the
entire US fleet was grounded, and Travis finally had a chance to find
DR DAVID TRAVIS: It was certainly, you know, one of the tiny positives
may have come out of this, an opportunity to do research that
never happen again.
NARRATOR: Travis suspected the grounding might make a small but
detectable change to the climate. But what he observed was both
immediate and dramatic..
DR DAVID TRAVIS: We found that the change in temperature range during
those three days was just over one degrees C. And you have to realise
that from a layman's perspective that doesn't sound like much, but
from a climate
perspective that is huge.
NARRATOR: One degree in just three days no one had ever seen such a
climatic change happen so fast. This was a new kind of climate change.
Scientists call it Global Dimming. Two years ago most of them had
heard of it, yet now they believe it may mean all their predictions
the future of our climate could be wrong. The trail that would lead to
discovery of Global Dimming began 40 years ago, in Israel with the
work of a
young English immigrant called Gerry Stanhill. A trained biologist,
got a job helping to design irrigation schemes. His task was to
strongly the sun shone over Israel.
DR GERALD STANHILL (Agricultural Research Organisation, Israel): It
important for this work to measure solar radiation, because that is
factor that basically determines how much water crops require.
NARRATOR: For a year Gerry collected data from a network of light
the results were much as expected, and were used to help design the
national irrigation system. But twenty years later, in the 1980s,
Gerry decided to repeat his measurements to check that they were still
valid. What he found,
DR GERALD STANHILL: Well I was amazed to find that there was a very
serious reduction in sunlight, the amount of sunlight in Israel. In
fact, if we
compare those very early measurements in the 1950s with the current
measurements, there was a staggering 22%% drop in the sunlight, and
really amazed me.
NARRATOR: A 22%% drop in solar energy was simply massive. If it was
surely Israelis should be freezing. There had to be something wrong.
So when Gerry published his results they were ignored. DR GERALD
STANHILL: I must say the publications had almost no effect whatsoever
on the scientific
NARRATOR: But in fact Gerry was not the only scientist who had noticed
fall in sunlight. In Germany a young graduate climatologist called
Liepert found that the same thing seemed to be happening over the
Alps too. DR BEATE LIEPERT (Lamont-Doherty Earth Observatory): I was
same, I was as sceptical as any other climatologist. But then, um, I,
the same results er in Germany, so um I believed him.
NARRATOR: Germany, Israel, what about the rest of the world? Working
independently of each other, Liepert and Stanhill began searching
publications, journals and meteorological records from around the
they both found the same extraordinary story. Between the 1950s and
early 1990s the level of solar energy reaching the earth's surface had
dropped 9%% in Antarctica, 10%% in the USA, by almost 30%% in Russia. And
16%% in parts of the British Isles. This was a truly global phenomenon,
Gerry gave it a suitable name - Global Dimming. But again, the
other scientists was one of sheer disbelief.
DR GERALD STANHILL: The scientific community was obviously not ready
to deal with the fact that there was a Global Dimming phenomena.
NARRATOR: Of course, there was a good reason for the scepticism. Less
energy from the Sun should be making the world cooler. Yet scientists
knew the Earth was getting hotter. As the carbon dioxide and other
greenhouse gases we emit trap ever more heat in the Earth's atmosphere
and cause Global Warming.
DR BEATE LIEPERT: My friends' reaction actually to Gerry's and to my
work at the same time too was, oh my God this is really extreme, you
contradicting global warming. Er do you know how many billions of
was spent on global warming research and you and this old guy er are
contradicting er us.
NARRATOR: So Liepert and Stanhill's work was widely dismissed. But
Dimming was not the only phenomenon that didn't seem to fit with
Warming. In Australia two more biologists, Michael Roderick and Graham
Farquhar were intrigued by another paradoxical result - the world-wide
decline in something called the pan evaporation rate.
PROF GRAHAM FARQUHAR (Australian National University): It's called pan
evaporation rate because it's evaporation rate from a pan. Every day
over the world people come out in the morning and see how much water
they've got to add to a pan to bring it back to the level it was the
same time the
morning before. It's that simple.
NARRATOR: In some places agricultural scientists have been performing
rather dull daily task for more than a hundred years.
PROF GRAHAM FARQUHAR: The long-term measurements of pan evaporation
are what gives it its real value.
DR MICHAEL RODERICK (Australian National University): And the fact
they're doing the same thing day in day out with the same instrument.
PROF GRAHAM FARQUHAR: Yeah, they deserve a medal. Each of them.
DR MICHAEL RODERICK: Yeah.
NARRATOR: For decades, nobody took much notice of the pan evaporation
measurements. But in the 1990s scientists spotted something very
the rate of evaporation was falling.
PROF GRAHAM FARQUHAR: There is a paradox here about the fact that the
pan evaporation rate's going down, an apparent paradox, but the global
temperature's going up.
NARRATOR: This was a puzzle. Most scientists reasoned that like a pan
on the stove, turning up the global temperature should increase the
rate at which
water evaporated. But Roderick and Farquhar did some calculations and
worked out that temperature was not the most important factor in pan
DR MICHAEL RODERICK: Well it turns out in fact that the key things for
evaporation are the sunlight, the humidity and the wind. But really
sunlight is a really dominant term there.
NARRATOR: They found that it was the energy of the photons hitting the
surface, the actual sunlight, that kicks the water molecules out of
and into the atmosphere. And so they too reached an extraordinary
DR MICHAEL RODERICK: You know, if the pan is going down then maybe
that's the sunlight going down. NARRATOR: Was the fall in pan
evaporation in fact evidence of Global Dimming? Somewhere in the
journals, they felt, must be the hard numbers that could tie the two
DR MICHAEL RODERICK: And then one day, just by accident, I had to go
to the library to get an article out Nature. As you do, I couldn't
find it. And I
just glanced at a, through the thing, and there was an article called
Evaporation Losing Its Strength. Which reported a decline in pan
over Russia, United States and Eastern Europe. And there in the, in
measurements, they said that the, the pans had on average, evaporated
about a hundred millimetres less of water in the last thirty years.
NARRATOR: Mike knew how much sunlight was needed to evaporate a
millimetre of water. So he put the two sets of figures together - the
evaporation with the drop in sunlight.
DR MICHAEL RODERICK: And so you just do the sum in your head. A
hundred millimetres of water, less a pan evaporation, two and a half
mega joules, so two and a half times a hundred is two hundred and
fifty mega joules. And that is in fact what the Russians have measured
with the decline in sunlight in the last thirty years. It was quite
NARRATOR: It was the same with Europe and the USA. The drop in
evaporation rate matched exactly the drop in sunlight reported by
Beate Liepert and Gerry Stanhill. Two completely independent sets of
observations had come to the same conclusion. Though it seemed
incredible, there was no doubting Global Dimming now.
DR BEATE LIEPERT: All of a sudden you see, oh my God the world is
dimming, and then you, all of a sudden you see oh my God this really
has a tremendous impact.
PROF GRAHAM FARQUHAR: There had to be dimming in Europe in America and
in Russia, this is on a global scale. And we thought, this is really
important because the amount of dimming was enormous. So this is BIG
on a global scale.
NARRATOR: But what was causing it? Scientists knew that there was
wrong with the sun itself. The culprit had to be here on Earth. And as
searched for clues, they would make another startling discovery.
dimming is a killer. It may have been behind the worst climatic
recent times, responsible for famine and death on a biblical scale.
Global Dimming is poised to strike again.
NARRATOR: The Maldives: a nation of a thousand tiny islands in the
middle of the Indian Ocean, so recently battered by the Asian tsunami.
It was here
that Veerabhadran Ramanathan, one of the world's leading climate
first began to unravel the mystery of what's causing Global Dimming.
first noticed declining sunlight over large areas of the Pacific Ocean
PROF VEERABHADRAN RAMANATHAN (University of California): But we didn't
know at that time it was part of a much larger global picture, but I
knew we had to find out what was causing that.
NARRATOR: Ramanathan was certain of one thing, the big drop in
reaching the ground had to be something to do with changes in the
atmosphere. There was one obvious suspect.
PROF VEERABHADRAN RAMANATHAN: Almost everything we do to create energy
NARRATOR: Burning fuel doesn't just produce the invisible greenhouse
gases which cause global warming. It also produces visible pollution,
airborne particles of soot and other pollutants. These produce the
which shrouds our cities. So Ramanathan wondered: Could this pollution
causing Global Dimming? The Maldives were the perfect place to find
out. The Maldives seem unpolluted, but in fact the northern islands
sit in a stream
of dirty air descending from India. Only the southern tip of the long
chain enjoys clean air coming all the way from Antarctica. So by
the northern islands with the southern ones, Ramanathan and his
would be able to see exactly what difference the pollution made to the
atmosphere and the sunlight. Project INDOEX, as it was called, was a
multinational effort. For four years every possible technique was used
sample and monitor the atmosphere over the Maldives. INDOEX cost
million dollars, but it produced results - and they surprised
PROF VEERABHADRAN RAMANATHAN: The stunning part of the experiment was
this pollutant layer which was three kilometre thick, cut down the
sunlight reaching the ocean by more than 10%%.
NARRATOR: A 10%% fall in sunlight meant that particle pollution was
far bigger effect than anyone had thought possible.
PROF VEERABHADRAN RAMANATHAN: Our models led us to believe the human
impact on the dimming was close to half to one per cent. So what we
discovered was tenfold.
NARRATOR: INDOEX showed that the pollution particles were blocking
sunlight themselves; but far more significant was what they were doing
the clouds. They were turning them into giant mirrors. Clouds are made
droplets of water. These only form when water vapour in the atmosphere
starts to condense on the surface of naturally occurring airborne
typically pollen or sea salt. As they grow, the water droplets
become so heavy they fall as rain. But Ramanathan found that polluted
contained far more particles than the unpolluted air, particles of
and sulphur dioxide.
PROF VEERABHADRAN RAMANATHAN: We saw ten times more particles in the
polluted air mass north of the Maldives compared with what we saw
south of the Maldives which was a pristine air mass.
NARRATOR: In the polluted air billions of man-made particles provided
times as many sites around which water droplets could form. So
clouds contained many more water droplets, each one far smaller than
would be naturally. Many small droplets reflect more light than fewer
ones. So the polluted clouds were reflecting more light back into
preventing the heat of the sun getting through. This was the cause of
PROF VEERABHADRAN RAMANATHAN: Basically the Global Dimming we saw in
the North Indian Ocean, it was contributed on the one hand by the
particles themselves shielding the ocean from the sunlight, on the
other hand making the clouds brighter. So this insidious soup,
consisting of soot, sulphates, nitrates, ash and what have you, was
having a double whammy on the Global Dimming.
NARRATOR: And when he looked at satellite images, Ramanathan found the
same thing was happening all over the world. Over India. Over China,
extending into the Pacific. Over Western Europe... extending into
Over the British Isles. But it was when scientists started to
the effects of Global Dimming that they made the most disturbing
of all. Those more reflective clouds could alter the pattern of the
rainfall. With tragic consequences.
NEWS REPORT - MICHAEL BUERK VOICE OVER: Dawn, and as the sun breaks
through the piercing chill of night on the plain outside Korum it
lights up a biblical famine, now in the 20th Century. This place say
workers here is the closest thing to hell on earth.
NARRATOR: The 1984 Ethiopian famine shocked the world. It was partly
caused by a decade's long drought right across sub-Saharan Africa - a
region known as the Sahel. For year after year the summer rains
failed. At the time some scientists blamed overgrazing and poor land
management. But now there's evidence that the real culprit was Global
Dimming. The Sahel's lifeblood has
always been a seasonal monsoon. For most of the year it is completely
But every summer, the heat of the sun warms the oceans north of the
This draws the rain belt that forms over the equator northwards,
rain to the Sahel. But for twenty years in the 1970s and 80s the
rain belt consistently failed to shift northwards - and the African
failed. For climate scientists like Leon Rotstayn the disappearance of
rains had long been a puzzle. He could see that pollution from Europe
North America blew right across the Atlantic, but all the climate
suggested it should have little effect on the monsoon. But then
decided to find out what would happen if he took the Maldive findings
DR LEON ROTSTAYN (CSIRO Atmospheric Research): What we found in our
model was that when we allowed the pollution from Europe and North
America to affect the properties of the clouds in the northern
hemisphere the clouds
reflected more sunlight back to space and this cooled the oceans of
northern hemisphere. And to our surprise the result of this was that
tropical rain bands moved southwards tracking away from the more
northern hemisphere towards the southern hemisphere.
NARRATOR: Polluted clouds stopped the heat of the sun getting through.
That heat was needed to draw the tropical rains northwards. So the
rain belt never made it to the Sahel.
DR LEON ROTSTAYN: So what our model is suggesting is that these
droughts in the Sahel in the 1970s and the 1980s may have been caused
by pollution from Europe and North America affecting the properties of
the clouds and cooling the oceans of the northern hemisphere.
NARRATOR: Rotstayn has found a direct link between Global Dimming and
the Sahel drought. If his model is correct, what came out of our
and power stations contributed to the deaths of a million people in
and afflicted 50 million more. But this could be just of taste of what
Global Dimming has in store.
PROF VEERABHADRAN RAMANATHAN: The Sahel is just one example of the
monsoon system. Let me take you to anther part of the world. Asia,
where the same monsoon brings rainfall to three point six billion
people, roughly half the
world's population. My main concern is this air pollution and the
Dimming will also have a detrimental impact on this Asian monsoon. We
not talking about few millions of people we are talking about few
NARRATOR: For Ramanathan the implications are clear.
PROF VEERABHADRAN RAMANATHAN: There is no choice here we have to cut
down air pollution, if not eliminate it altogether.
NARRATOR: Fortunately, tackling air pollution needn't be too
wouldn't mean giving up on oil and coal altogether. We'd just have to
them more cleanly. And in Europe we've already made a start: scrubbers
power stations, catalytic converters in cars and low sulphur fuels,
they do nothing to reduce greenhouse gases, have already begun to cut
down visible air pollution. This should be good news for the Sahel,
and in recent
years the droughts have been nothing like as bad. But there's a
catch. Because while Global Dimming is itself a major threat to
now appears it has been protecting us from an even greater threat.
means that as we reduce the dimming, we may find ourselves faced by
something even worse.
NARRATOR: It was David Travis who first caught a glimpse of what the
could be like without Global Dimming. It happened in those chaotic
following the tragedy of 9/11. For fifteen years, Travis had been
the vapour trails, or contrails, left behind by high-flying aircraft.
each individual contrail seems small, when they all spread out, they
blanket the sky.
DR DAVID TRAVIS: Here are some examples of what we call outbreaks of
contrails. These are large clusters of contrails. And here's a
er good one from Southern California. Here's the west coast of the
States.. And you can see here this lacing network of contrails er
at least fifty per cent, if not seventy five per cent or more of the
that area. It doesn't take an expert to er realise that if, if you
the satellite picture and see this kind of contrail coverage that
got to be having an effect on temperature at the surface.
NARRATOR: But the problem Travis faced was to establish exactly how
big an effect the contrails were actually having. The only way to do
that was to
find a period of time when, although conditions were right for
form, there were no flights. And, of course, that never happened.
September 2001. Then, for three days after the 11th virtually all
aircraft in the US were grounded. It was an opportunity Travis could
afford to miss. He set about gathering temperature records from all
DR DAVID TRAVIS: Initially data from over 5,000 weather stations
48 united states, the areas that was most dominantly affected by the
NARRATOR: Travis was not looking just at temperature - that varies a
from day to day anyway. Instead he focused on something that normally
changes quite slowly: the temperature range. The difference between
highest temperature during the day and the lowest at night. Had this
at all during the three days of the grounding?
DR DAVID TRAVIS: As we began to look at the climate data and the
began to grow I got more and more excited. The actual results were
larger than I expected. So here we see for the 3 days preceding
11th a slightly negative value of temperature range with lots of
as normal. Then we have this sudden spike right here of the 3 day
This reflects lack of clouds, lack of contrails, warmer days cooler
exactly what we expected but even larger than what we expected. So
indicates is that during this 3 day period we had a sudden drop in
Dimming contributed from airplanes.
NARRATOR: During the grounding the temperature range jumped by over a
degree Celsius. Travis had never seen anything like it before.
DR DAVID TRAVIS: This was the largest temperature swing of this
magnitude in the last thirty years.
NARRATOR: If so much could happen in such a short time, removing just
form of pollution, then it suggests that the overall effect of Global
Dimming on world temperatures could be huge.
DR DAVID TRAVIS: The nine eleven study showed that if you remove a
contributor to Global Dimming, jet contrails, just for a three day
we see an immediate response of the surface of temperature. Do the
thing globally we might see a large scale increase in global warming.
NARRATOR: This is the real sting in the tail. Solve the problem of
Dimming and the world could get considerably hotter. And this is not
theory, it may already be happening. In Western Europe the steps we
taken to cut air pollution have started to bear fruit in a noticeable
improvement in air quality and even a slight reduction in Global
over the last few years. Yet at the same time, after decades in which
held steady, European temperatures have started rapidly to rise
in the savage summer of 2003.
Forest fires devastated Portugal. Glaciers melted in the Alps. And in
people died by the thousand. Could this be the penalty of reducing
Dimming without tackling the root cause of global warming?
DR BEATE LIEPERT: We thought we live in a global warming world, um but
this is actually er not right. We lived in a global warming plus a
world, and now we are taking out Global Dimming. So we end up with the
global warming world, which will be much worse than we thought it will
NARRATOR: This is the crux of the problem. While the greenhouse effect
been warming the planet, it now seems Global Dimming has been cooling
down. So the warming caused by carbon dioxide has been hidden from us
by the cooling from air pollution. But that situation is now starting
DR PETER COX (Hadley Centre, Met Office): We're gonna be in a
unless we act where the cooling pollutant is dropping off while the
pollutant is going up, CO2 will be going up and particles will be
off and that means we'll get an accelerated warming. We'll get a
whammy, we'll get, we'll get reducing cooling and increased heating at
same time and that's, that's a problem for us.
NARRATOR: And that's not all. Climatologists like Peter Cox have begun
worry that Global Dimming has led them to underestimate the true power
global warming. They fear that the Earth could be far more vulnerable
greenhouse gases than they had previously thought.
DR PETER COX: We've got two competing effects really, that we've got
greenhouse effect, which has tended to warm up the climate. But then
got this other effect that's much stronger than we thought, which is a
cooling effect that comes from particles in the atmosphere. And
competing with one another. And we know the climate's moved to a
state by about point six of a degree over the last hundred years. So
whole thing's moved this way. If it turns out that the cooling is
than we thought then the warming also is a lot stronger than we
that means the climate's more sensitive to carbon dioxide than we
thought, and it means our models may be under sensitive to carbon
NARRATOR: The models that everyone has been using to forecast climate
change predict a maximum warming of 5 degrees by the end of the
century. But Cox and his colleagues now fear those models may be
wrong. Temperatures could rise twice as fast as they previously
thought with irreversible damage just twenty-five years away.
DR PETER COX: If we don't do anything by about twenty thirty we could
have a global warming of exceeding two degrees, and at that point it's
Greenland ice sheet would start to melt in a way that you wouldn't be
to stop it once it started it, it would melt. Take a long time to melt
ultimately it would lead to a sea level rise of seven or eight metres.
NARRATOR: Once the Greenland ice cap begins to melt, nothing will stop
Many of the world's major cities will be living on borrowed time.
decade, the risk of catastrophic flooding would increase inexorably.
unless action is taken it won't stop there. Because after Greenland,
world's tropical rainforests will start to wither in the heat.
DR PETER COX: 2040 it could be four degrees warmer, the climate change
could have led to big drying particularly in the Amazon Basin, that
would make the
forest unsustainable, we'd expect the forest to catch fire probably,
into savannah and maybe ultimately even desert if it gets really
as our model suggests.
NARRATOR: And as the rainforest burnt away, it would release vast
amounts of carbon dioxide into the atmosphere, driving global warming
Cox calculates that in just a century, the world could be 10 degrees
a warming more rapid than any in Earth history. If this were to
landscape of England would be utterly transformed.
DR PETER COX: We're talking about a change from er a lush, moist
environment like this, to a North African climate in just a few
decades or a
NARRATOR: Most British plant species could not survive a North African
climate. With vegetation dying everywhere, soil erosion would become a
severe problem. From a green and pleasant land, England would become a
country of extremes, with winter flooding giving way to summer dust
And it will be far worse elsewhere.
DR PETER COX: You can imagine ten degree warming in the UK in a
hundred years is catastrophic. Ten degree warming in a hot country
already makes it essentially uninhabitable.
NARRATOR: And just when one might think things could get no worse in
the far North a ten degree warming might be enough to release a vast
natural store of greenhouse gas bigger than all the oil and coal
reserves of the planet..
DR PETER COX: We will be in danger of destabilising these things
methane hydrates which store a lot of methane at the bottom of the
a kind of frozen form, ten thousand billions tons of this stuff, and
known to be destabilised by warming.
NARRATOR: At this point, whatever we did to curb our emissions, it
too late. Ten thousand billion tons of methane, a greenhouse gas eight
stronger than carbon dioxide, would be released into the atmosphere.
Earth's climate would be spinning out of control, heading towards
temperatures unseen in four billion years. But this is not a
prediction - it
is a warning. It is what will happen if we clean up pollution while
nothing about greenhouse gases. However, the easy solution - just keep
polluting and hope that Global Dimming will protect us - would be
DR PETER COX: If we carried on pumping out the particles it would have
terrible impact on human health, I mean particles are involved in all
of respiratory diseases, that's why they're being brought under
of course they effect climate anyway. If you, if you fiddle with the,
balance of the planet, the radiative balance of the planet, you affect
sorts of circulation patterns like monsoons, which would have horrible
effects on people. So it would be extremely difficult, in fact
to cancel out the greenhouse effect just by carrying on pumping out
particles, even if it wasn't for the fact that particles are damaging
NARRATOR: Instead we have to take urgent action to tackle the root
both global warming and Global Dimming - the burning of coal, oil and
We may have to make very difficult choices, about how we live and how
generate our electricity. We have been talking about such things for
years. But so far very little has been done in practical terms. The
discovery of Global Dimming makes it clear that we are rapidly running
DR PETER COX: One of the real driving forces is that you leave an
environment that is comfortable for your children. And we carry on
way we're going, we're not going to do that, we're going to leave an
environment that's much worse than the environment we lived in; and it
be down to what we did when we were using that environment, and that
would be, um, tragic really, if that happened.
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