Modeling on this has been done by LBNL and others. You are correct in that the
heat island creates an environment for rising air. Unfortunately, this
sometimes results in thunderstorms that are essentially manufactured weather
(see, it can be done) that produce flooding rains that are of little use except
for the temporary cooling effect. Atlanta, GA is one example. As soon as the
clouds lift, however, it's back to cooking asphalt and bricks. So urban heat
islands don't offer much of an advantage as heat radiators. In the case of Los
Angeles, the terrain tends to trap air, allowing pollutants to build up.
The impact and effectiveness of the urban whitening effort can best be compared
to the Cash for Clunkers Program, which doesn't solve any one particular
problem, but helps to address several different ones all at once. Short term,
it benefits auto manufacturers and dealers and parts suppliers, longer term it
reduces the use of petroleum and by doing so, reduces air pollution and global
warming emissions. The whitening effort will not solve air pollution or global
warming, but will reduce some CO2 emissions and by cooling off some of the heat
islands, reduce the formation of ground level ozone.
----- Original Message -----
From: Andrew Lockley
To: agask...@nc.rr.com
Cc: geoengineering@googlegroups.com
Sent: Tuesday, August 04, 2009 6:23 AM
Subject: Re: [geo] No Wonder They Can't Find Any Aliens
I know that this cool roof thing is all very fashionable, but has anyone
actually modelled it properly? There are many atmospheric conditions where
heat islands could potentially drive air currents which transport large amounts
of air into higher levels of the atmosphere, where they can radiate more easily
into space. This may offset or overwhelm the initial net solar gain.
It would be embarrassing if the idea didn't work as well as expected due to
convective processes.
A
2009/8/4 Alvia Gaskill <agask...@nc.rr.com>
1% of the area of the U.S. is APX 38,000 square miles, about enough if
converted from black to white to offset about 1-2 years worth of GHG forcing in
2009. He also fails to understand that since that offset would be diluted
globally, it would have little impact on the melting of the Greenland Ice
Sheet. Before you start shoveling, better check to see what is in the shovel.
http://www.content.good.is/post/fighting-global-warming-with-pavement.html
Fighting Global Warming with Pavement
a.. Posted by: Seth Shostak
b.. on July 15, 2009 at 9:00 am
A new color scheme for our roads and highways could take some of the heat
off Earth's climate.
You may not have given it much thought, but your boistrous lifestyle runs
at about 10 kilowatts, day and night. Thirteen horsepower, if you prefer equine
units.
That's the average power consumed by each man, woman, and child in the
United States – the energy burden of everything you do and use – from heating
up dinner and cooling your apartment, to dashing out to the convenience store
in your candy red Bugatti. And while some of that energy is used for
illumination, the overwhelming majority degrades to heat.
Consider: At the end of an all-day drive, what happened to the chemical
energy in the tank of gas you bought before breakfast? It's gone into heating
up the engine, the tires, the brakes, and the air pushed out of the way by the
hood ornament. Virtually all of the calories in that refined natural resource
you bought for $3 a gallon end up warming the atmosphere.
Our energy burn is impressive. The residents of a burg the size of
Baltimore pump out 5 billion watts of heat just to enjoy life, or about 20
times the total sunlight beating down on the city. World-wide, our species is
toasting Earth's atmosphere at the rate of 10 trillion watts. That's a lot of
BTU pleasure.
OK, the heat's on. We know that, and we've all heard the standard
approaches to dealing with our profligate ways.
But here's my odd idea of something we could do that isn't so standard:
implement a pavement plan to mitigate atmospheric heating.
It goes like this: We've been busy for nearly a century covering the
civilized world with highways and byways. If you laid all the hard-surface
roads in the United States end to end, they'd stretch for 2.5 million miles.
That pavement covers a lot of ground, quite literally, and amounts to nearly
one percent of our country's total acreage (for comparison, the national parks
total four percent).
Now you may have noticed that many of those motorways are pretty dark.
Indeed, the reflectance of most roads is roughly 20 percent; that is, they
return only about one-fifth of the sunlight hitting them. But the stripes that
skip down their centerlines have a reflectance of about 50 percent, as measured
with my camera's light meter. That's why you can see these pavement markings:
they're twice as bright as the asphalt.
So here's my idea: we just invert this situation, and construct white
pavement with black stripes.
Not only will this improve your ability to follow the road at night (while
simultaneously lining the pockets of construction workers nationwide), it will
more than double the amount of sunlight reflected by roads – and thereby reduce
the amount of atmospheric heating.
How much? Well, my back-of-the-napkin calculation suggests inverting the
pavement color scheme would bounce an additional 5 trillion watts skyward.
Is that significant? You bet your Wellingtons. NASA has recently estimated
that the Greenland ice sheet is currently melting at the alarming rate of 50
cubic miles of ice per year. Invoke a bit of high school physics, and you can
figure that 2 trillion watts of continuous heating will melt that volume of
ice. But merely by changing the color of pavement, we can reduce the amount of
atmospheric heating by roughly three times that amount.
In other words, we could save the Greenland ice cap with road crews. Sounds
pretty cool to me, and this project is shovel-ready.
Now ... want to hear about my mirror roof tiles?
Guest blogger Seth Shostak is a Senior Astronomer at the SETI Institute. He
is the author of Confessions of an Alien Hunter: A Scientist’s Search for
Extraterrestrial Intelligence, and hosts SETI's radio show Are We Alone?
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