Help fight global warming, stop shoveling snow

It snowed last night. There was a lovely, six-inch blanket of white on the ground this morning. By 08:00, I had succumbed to spousal, and cultural, pressure, and was out working a shovel, trying to clear the lovely white stuff off the drive and sidewalks. Just like it was something undesirable that had to be got rid of.

I have one strong personal reason not to like cleanly shoveled sidewalks. I walk a lot, usually including an hour after dark in the wintertime, and I know that the really dangerous, slippery sections of sidewalk are those that have been shoveled clean. They may even be mostly dry, but just often enough, there are places where snow on the sides was melting during the day, and water was running across the sidewalk, and after dark this water turned into a sheet of black ice. Those are the slippery places that will surprise you, and put you down on your back.

This morning, however, I was thinking about the way the concrete warms up, once it has been shoveled and the sun gets to it. When the snow covers the ground, nearly all of the light from the sun that hits it is reflected. All that energy (about one kilowatt for every square meter of earth surface) gets turned around without warming anything up, and is headed back towards space, where it came from. The surface of the earth is cold beneath the snow, and it can't get warm because most of the energy that would warm it is being lost into space. That blanket of snow is causing a local episode of global cooling.

However, we have this strong cultural mandate to shovel that snow off the walk. If we don't, our walks sit out there for all the world to see, evidence of our shameful laziness. In many cities there are even laws that require people to shovel their walks. These laws have outlived their usefulness. They should be repealed, and people should be encouraged to leave that snow on their walks. As long as that snow is there, it's better than unplugging a standard electric space heater for every two square meters of concrete you have outside.

Greenhouse Effect Explained

It seems in spite of millions of people using the expression, "Greenhouse Effect", on a daily basis, very few people actually know how it works. Add to that, occasionally we find someone questioning whether, or not, they should "believe in" the Greenhouse Effect, which is just a little bit crazy. After all, we are talking about physical facts here. Does anyone talk about "believing in" the law of gravity?

So it seems there should be available on the web, an easily understood explanation, preferably with appended detail sections, so anyone that's interested can find out how the Greenhouse Effect works. A couple searches have turned up nothing that fits this description, so I want to write one. In doing so, I really want feedback from knowledgeable people, ultimately to come up with something that's easy to understand, simplifying perhaps, the underlying physics, but not twisting it.

So, starting with a bare sketch. All physical objects radiate energy in the form of electromagnetic waves, and the frequency of the radiation is dependent on the surface temperature of the object. Hotter objects radiate at higher frequencies.

Light is a form of electromagnetic waves, and it happens that objects that are as warm as the Earth radiate in the frequency range of infrared light. Objects that are as hot as the sun radiate in the range of blue, violet and ultra-violet. This is one of the important facts involved in the Greenhouse Effect.

Another important fact is different gases don't all allow all frequencies of light to pass equally well. This fact is a little hard to accept because we don't routinely see the effect (except for one effect, the blue sky). An important example is the fact that carbon dioxide is quite transparent to visible light, and ultra-violet light, but much less transparent to infrared light.

These two facts come together to explain the Greenhouse Effect as follows: Energy is radiated from the sun and passes rather easily through the Earth's atmosphere, and is absorbed by the Earth, which warms the Earth. The Earth, in it's turn, according to its surface temperature, radiates some of the energy back, but now the frequency of the radiation has been changed to infrared. This lower-frequency radiation runs into gases like carbon dioxide in our atmosphere, and it is scattered, or reflected back. It doesn't get away, so the surface of the Earth, and the atmosphere become slightly warmer.

This is the Greenhouse Effect. The more carbon dioxide, and other "greenhouse gases", there are in the atmosphere, the better insulated the Earth becomes. There have always been greenhouse gases in the atmosphere, and the Earth has always been insulated by them, but more greenhouse gases mean more insulation, and a warmer Earth.