w: [cag] Global Dimming [RE-wrenches]

[Andrew Bortz]

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I forward this because #1-It seems way critical, & #2-I havn't seen it
Elsewhere

People,

Damn, the sky - IS - "falling", & creating problems for solar energy
production too!
So, it appears that now except for the places where there is too much sun
(the Ozone Holes), in much of the world, there is too little sun for climate
stability, etc.  It seems that we, the Solar/Renewable community, are more
important than ever to help turn things around!

Andrew B.
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----- Original Message ----- 
From: "MichaelP" <papadop at peak.org>
To: <unlikely suspects:>
Sent: Thursday, January 13, 2005 5:51 PM
Subject: [cag] global dimming

http://news.bbc.co.uk/2/hi/science/nature/4171591.stm BBC
Thursday, 13 January, 2005, 14:10 GMT By David Sington

WHY THE SUN SEEMS TO BE 'DIMMING'

Scientists have been studying solar measurements for decades

We are all seeing rather less of the Sun, according to scientists who have
been looking at five decades of sunlight measurements.

They have reached the disturbing conclusion that the amount of solar
energy reaching the Earth's surface has been gradually falling.

Paradoxically, the decline in sunlight may mean that global warming is a
far greater threat to society than previously thought.

The effect was first spotted by Gerry Stanhill, an English scientist
working in Israel.

CLOUD CHANGES

Comparing Israeli sunlight records from the 1950s with current ones, Dr
Stanhill was astonished to find a large fall in solar radiation.

"There was a staggering 22% drop in the sunlight, and that really amazed
me." Intrigued, he searched records from all around the world, and found
the same story almost everywhere he looked.

Sunlight was falling by 10% over the USA, nearly 30% in parts of the
former Soviet Union, and even by 16% in parts of the British Isles.

Although the effect varied greatly from place to place, overall the
decline amounted to one to two per cent globally every decade between the
1950s and the 1990s.

Dr Stanhill called it "global dimming", but his research, published in
2001, met a sceptical response from other scientists.

It was only recently, when his conclusions were confirmed by Australian
scientists using a completely different method to estimate solar
radiation, that climate scientists at last woke up to the reality of
global dimming.

My main concern is global dimming is also having a detrimental impact on
the Asian monsoon ... We are talking about billions of people



DIMMING APPEARS TO BE CAUSED BY AIR POLLUTION.

Burning coal, oil and wood, whether in cars, power stations or cooking
fires, produces not only invisible carbon dioxide - the principal
greenhouse gas responsible for global warming - but also tiny airborne
particles of soot, ash, sulphur compounds and other pollutants.

This visible air pollution reflects sunlight back into space, preventing
it reaching the surface. But the pollution also changes the optical
properties of clouds.

Because the particles seed the formation of water droplets, polluted
clouds contain a larger number of droplets than unpolluted clouds.

Recent research shows that this makes them more reflective than they would
otherwise be, again reflecting the Sun's rays back into space.

Scientists are now worried that dimming, by shielding the oceans from the
full power of the Sun, may be disrupting the pattern of the world's
rainfall.

There are suggestions that dimming was behind the droughts in sub-Saharan
Africa which claimed hundreds of thousands of lives in the 1970s and 80s.

There are disturbing hints the same thing may be happening today in Asia,
home to half the world's population.

"My main concern is global dimming is also having a detrimental impact on
the Asian monsoon," says Professor Veerhabhadran Ramanathan, professor of
climate and atmospheric sciences at the University of California, San
Diego. "We are talking about billions of people."

ALARMING ENERGY

But perhaps the most alarming aspect of global dimming is that it may have
led scientists to underestimate the true power of the greenhouse effect.

They know how much extra energy is being trapped in the Earth's atmosphere
by the extra carbon dioxide we have placed there.

What has been surprising is that this extra energy has so far resulted in
a temperature rise of just 0.6 degree Celsius.

This has led many scientists to conclude that the present-day climate is
less sensitive to the effects of carbon dioxide than it was, say, during
the ice age, when a similar rise in CO2 led to a temperature rise of six
degrees Celsius.

But it now appears the warming from greenhouse gases has been offset by a
strong cooling effect from dimming - in effect two of our pollutants have
been cancelling each other out.

This means that the climate may in fact be more sensitive to the
greenhouse effect than previously thought.

If so, then this is bad news, according to Dr Peter Cox, one of the
world's leading climate modellers.

As things stand, CO2 levels are projected to rise strongly over coming
decades, whereas there are encouraging signs that particle pollution is at
last being brought under control.

"We're going to be in a situation unless we act where the cooling
pollutant is dropping off while the warming pollutant is going up.

"That means we'll get reducing cooling and increased heating at the same
time and that's a problem for us," says Dr Cox.

Even the most pessimistic forecasts of global warming may now have to be
drastically revised upwards.

That means a temperature rise of 10 degrees Celsius by 2100 could be on
the cards, giving the UK a climate like that of North Africa, and
rendering many parts of the world uninhabitable.

That is unless we act urgently to curb our emissions of greenhouse gases.

======================


 http://www.mindfully.org/Air/2004/Global-Dimming8may04.htm

Knight Ridder News Service 8may04

AIR POLLUTION MAY BE CAUSING GLOBAL DIMMING
ROBERT S BOYD /

WASHINGTON - Scientists call it "global dimming," a little-known trend
that may be making the world darker than it used to be.

Because of thicker clouds and growing air pollution, much of the Earth's
surface gets about 15 percent less sunlight than it did 50 years ago,
according to Michael Roderick, a climate researcher at Australian National
University in Canberra.

"Global dimming means that the transmission of sunlight through the
atmosphere is decreasing," Roderick said.

"Just look out the window when you fly into New York or to California -- 
it's dimmer," said Beate Liepert, a climatologist at the Lamont-Doherty
Earth Observatory of Columbia University in New York.

Researchers say that global dimming, also known as solar dimming,
partially offsets the global warming that most scientists agree is
produced by greenhouse gases such as auto exhaust and emissions from
coal-burning power plants.

The solar dimming effect is "about half as large as the greenhouse gas
warming," said James Hansen, director of the National Aeronautics and
Space Administration's Goddard Institute for Space Studies in New York.

In global warming, gases in the atmosphere, such as carbon dioxide, trap
some of the sun's heat and keep it from radiating back out to space,
thereby raising the Earth's temperature. Clouds and air pollution, on the
other hand, block a portion of the heat energy that's coming from the sun,
just as it's cooler to sit under a beach umbrella than under a bright sky.

Although global warming has been widely accepted, global dimming remains
controversial. The theory has been advanced in recent years by a handful
of researchers who measure the decline of solar radiation at hundreds of
sites around the globe.

Liepert, Roderick and several other scientists will discuss their findings
at an international geophysical conference in Montreal this month.

"We still face a lot of controversy, but it's [solar dimming] getting
accepted," Liepert said in a telephone interview. "We've found it in the
United States, Europe, Israel and Asia. Already, major research
institutions are changing their point of view."

Support for the theory comes from two types of data collected in recent
decades:
  * Radiation meters -- black metal plates that absorb the sun's rays -- 
aren't heating up as rapidly as they previously did.
  * The rate at which water evaporates from special measuring pans placed
in sunlight has slowed over the years.



* National Oceanic and Atmospheric Administration's SURFRAD network,

source: http://www.dfw.com/mld/dfw/news/nation/8620703.htm 8may04





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