[cwes99_03]

Besides having an effect on runoff and what not. How much effect does the massive amounts of road surface have on global warming?
I've been watching the salt trucks and the natural melt of snow on all road surfaces when the sun warms up the black asphalt. This made me think about why snow on the grass doesnt melt away so quickly and of course it is because the white snow doens't absorb as much radiation from the sun as asphalt does. How much of the surface of the earth is covered by such dark substances as were covered say 40 years ago?

[Boerseun]

Originally Posted by cwes99_03

Besides having an effect on runoff and what not. How much effect does the massive amounts of road surface have on global warming?
I've been watching the salt trucks and the natural melt of snow on all road surfaces when the sun warms up the black asphalt. This made me think about why snot on the grass doesnt melt away so quickly and of course it is because the white snow doens't absorb as much radiation from the sun as asphalt does. How much of the surface of the earth is covered by such dark substances as were covered say 40 years ago?

The effective reflectivity (albedo) does indeed have a lot to do with global warming. And it also contributes greatly to thermal 'heat islands' around cities and built-up areas. In the desert, you can stick your hand about half a meter into the burning hot dunes, and find a suprisingly cool level - the light-coloured sand only heats on the surface, and reflects most of it away due to the high albedo. It doesn't transmit the gross of it downwards. That's why deserts like the Sahara and Kalahari is freezing cold at night and the early mornings. In the jungle, the albedo is much lower, most of the thermal input is absorbed. The evenings in the jungle is muggy, but very mild as far as temperature goes. Water vapour in the atmosphere also plays a large part in reflecting radiated heat back to the ground, also cooling the desert off at night due to the lack of it, but albedo certainly plays a large role here.
It is so influential regarding temperature, that one of the approaches considered in 'terraforming' Mars would be to powder the surface with a dark dust to decrease the albedo, thereby raising the temperature.
I've always wondered if it would help to pass a law that forces people to paint the roofs of houses with some sort of bright white reflective paint to counter some of the heat build-up caused by roads and pavements. Wonder if it'll work?

[cwes99_03]

Actually, let me clarify. I know these things, and have had some similar thoughts.
My question really should have been, has there ever been an analysis that connected global warming with something other than "greenhouse gas emission", such as increased paved roads and other objects that absorb more heat into the earth, or cause destruction toward things that normally reflect away some of that heat, such as snow.
But thanks B, for showing people how this thought shows a valid reason for being asked.

[TheBigDog]

I remember when I was in grade school in the 70's we had an assembly where Greenpeace (among others) was giving us a presentation. My child mind was filled with some of the following facts about what the world would be like when I grew up...

A candy bar will cost $3.00, weigh 1 oz and have 1 nut.

There will be no Blue Whales - they are already functionally extinct.

There will be no more paper for publishing most newspapers because paper will be so expensive that a newspaper will cost $5.00

Only the very rich will be able to drive cars because the global oil reserves will be gone in 30 years.

We will need to spread soot over the polar ice caps to melt them and prevent an ice age caused by pollution.

And to the point of this post (aside from the poor track record of predictions of global conditions)... While we do have an impact on global conditions, man's influence is so incredibly small that there is probably no way of understanding how any single action we are taking will impact the global weather. I live about 500 feet from Lake Erie, so I would rather have warming than cooling. It is already cold enough.

Bill

[cwes99_03]

Thanks Bill for you eloquent, "Global warming is good and environmentalists are wrong" speech.
Unfortuneately, that stance is not currently held to be scientifically accurate. While we do not know for sure what weather conditions will prevail in the next 20 years, one thing is certain and that is that the current global environmental markers suggest that the temperature will continue to increase for at least a decade, during which time more polar ice will melt and sea level will rise.
Whether this is reversible by human processes or not is equally uncertain as technology and science come up with new methods every day of every year.
But this is not the point of this thread. So please keep on topic.

Anyone with knowledge on the subject of albedo (you astrophysicists) want to comment on the increase in radiation absorbing surfaces and their effect on global warming.
Is there any data that might show a correlative effect between the two phenomena?

[Boerseun]

I suppose the biggest contributor to albedo is humans changing forest into grasslands. Grassland surface area is much more than built-up urban areas.

But this should be more reflective, and should add to cooling the Earth, not?

[TheBigDog]

cwes, the intention of my post was not what came across to you. I meant to come across as "Global warming is inevitable, and man's role is inconsequential". Here is data to support that assertion.

Typical asphalt albedo is 15% This of course varies with latitude and pigment of the surface.

By comparison farmland is also around 15%, depending upon the crop and the latitude.

Forests are not quite as good as roads at 10-15% typically.

Grasslands come in around 20%, so they are better than roads.

Cities range from 7-12% including the roads.

The best areas are wastelands such as sandy deserts that can range near 25%.

Because road surfaces take up such a low percentage of surface area in most non urban areas, the overall effect is probably negligable.

Bill

[Taraxanoid]

Don't worry, the Alien Observers will save us if the Earth ever gets too much altered by our impact. OR If there aren't any "Alien Observers" (what a silly idea..), we'll be able to figure something out in any dire situations brought on by us. And anyway, who said that WE are contributing in "the Greenhouse Effect" more than Mrs. Mother Nature herself? Mind you, she's probably got a title deed from the council in order to...
Ah, never mind.

[cwes99_03]

Originally Posted by webenton

cwes, the intention of my post was not what came across to you. I meant to come across as "Global warming is inevitable, and man's role is inconsequential". Here is data to support that assertion.

Typical asphalt albedo is 15% This of course varies with latitude and pigment of the surface.

By comparison farmland is also around 15%, depending upon the crop and the latitude.

Forests are not quite as good as roads at 10-15% typically.

Grasslands come in around 20%, so they are better than roads.

Cities range from 7-12% including the roads.

The best areas are wastelands such as sandy deserts that can range near 25%.

Because road surfaces take up such a low percentage of surface area in most non urban areas, the overall effect is probably negligable.

Bill

Ok, great post. Now, if we could get some square mileage of the above and see how things have changed on the earth, say since 1850, we'd be a step closer.
Anyone?

[questor]

Global warming now compared to what? what was the earth's temperature 150,000,000 years ago? how many ice ages in the last 150 million years?
is it man, or is it nature?