MadSci Network: Environment

Re: Can the millions of miles of black roads be increasing global warming

Date: Mon Aug 21 10:51:50 2006
Posted By: Matthew McConeghy, Professor of Science
Area of science: Environment
ID: 1154150346.En

What a great question! It shows that you are really thinking about how the 
physical world works. The short answer would be 'Yes' the roads add heat. 
But the longer answer is more complicated. (You knew that it would be! 

OK, so the roads are black and we're thinking that the dark surface will 
absorb more sunlight energy, heating up the surface. This definitely 
happens and there is some research which directly relates ... you can 
start with an article from NASA:

which has shown that the heat absorbed by roads and other urban surfaces 
has a direct effect on the climate of the city area, including influencing 
the growth of plants for a fair distance around the city. 

On a world wide scale, the impact of roads, per se, would be pretty 
minimal, I think. Only because, although there are lots of roads and 
especially in cities they take a lot of space, they are not large compared 
to the whole surface of the earth. 

I'm thinking that this would actually make a terrific Science Fair 
project. You could calculate the area of roads vs the whole area of say, 
the state of Texas. Then, measure the heat of roads vs bare ground vs 
covered ground, and calculate how much extra heat that meant in the 
state?  You could even compare different kinds of road surfaces, say 
cement vs asphalt vs gravel or different kinds of asphalt surfaces, rough 
or smooth.... 

There's no telling when you might come up with a really important finding 
from this kind of simple research. Remember the Australian guys who found 
out about Global Dimming, like in the recent NOVA tv program:
by noticing a little change in the amount of water evaporated from some 

This is definitely worth some more investment of time to work out your own 
answer to your interesting question. 

Good luck

Dr. Matt McConeghy

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