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Global warming due to asphalt?

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Posted by Steve on July 6, 2008, 10:29 pm
Has anyone done the calculation of the contribution that asphalt and
concrete surfaces make to global warming?

I visited relatives that live on the other side of a hill from the "city"
and it is about 10 degrees cooler there.  I frequently hear weather reports
that speak of temperatures being higher in cities.

Given the prevalence of pavement as a good thermal mass, I have to wonder if
it isn't a significant contributor to climate change.

If pavement is a significant contributor, there are many things we could do.
Planting trees along freeways to shade the pavement.  Covering buildings
with vines to reduce the absorbtion, etc.


Posted by Jeff on July 7, 2008, 12:59 pm
Steve wrote:

Look up Urban Heat Island.

I live in one (Atlanta).

There's a slight temperature rise over surrounding areas, but it is not
that much. What we do get this time of year is popup thunderstorms as
the island cools in the evening.


It's a complicated effect and is more tilted towards large urban areas
generating their own weather rather than any warming trend. The net
global warming effect is negligible.

   A larger problem in many places is that the hardened surfaces lead to
faster runoff. This is particularly true of concrete, but also true in
farmland areas where border woodsy/swampy areas have been cultivated...


Posted by PhattyMo on July 8, 2008, 11:50 pm
 Steve wrote:

No to mention the heat from all the human bodies,and appliances.
There are more heat sources in a city.

Posted by You on July 13, 2008, 8:39 pm

Temps are ALWAYS higher in a city, because that is where ALL that power
is dissipated. Duh......

Posted by Steve on July 13, 2008, 11:52 pm

On a clear sunny day about 1 KW/M^2 (kilowatt per square meter) reaches the
surface of the earth.  That's about 2.6 megawatts per square mile.

I know that if that energy falls on concreate or asphalt (a good thermal
mass) the heat is stored and re-released at night.  If it falls on foliage
it tends to get converted into chlorphyll.

It is certainly not obvious to me that this is a small effect.  Especially
when you consider how much of the earths surface we have covered with
concrete and asphalt.  Just bring up google earth and zoom in just about
anywhere in the US and you will find a lot of thermal mass.


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