Global Warming - Background and Definitions
Generically speaking, "Global Warming" means that the earth is getting
a little warmer each year ... and there is some evidence that this may be occurring.
However, the press and politicians define "Global Warming" as
"rich Americans destroying the planet by burning gasoline".
It is a fact that burning hydrocarbons (such as gasoline)
produces carbon dioxide gas (CO2).
It is also a fact that CO2 helps to hold heat
at the surface of the earth (known as the "Green House" effect).
The "Global Warming" theory (but they always say "the fact") is
that burning hydrocarbons produces so much CO2 that
we (rich Americans) are going to heat up the Earth (via the "Green House" effect)
to the point that life as we know it will not be possible.
(This is more correctly known as "anthropogenic Global Warming"
or "the anthropogenic greenhouse effect" - "anthropogenic" means human produced.)
One counter theory is that it is not possible to generate enough CO2
to ever see any effect.
Another counter theory is that the Earth is already over due for the next ice age
and that there is no way to produce enough CO2 to prevent it.
Currently, the available data can be used to support any of these theories ... and several more.
What is a "Green House"
| What are "Green House gasses"
What is a "Green House"
I am sure that you have noticed that
on a sunny day, when the windows are up and the AC is off,
the inside of a car is normally much hotter than the air outside.
This is because the glass allows the infrared radiation from
the sun to enter the car and heat the seats and other internal surfaces.
These surfaces then heat the air inside the car and the
windows keep the hot air from escaping.
This is exactly how a solar hot water heater works - a sheet of glass
is placed over a tube filled with water.
The water gets hot using free solar energy.
"Green Houses" are built out of glass (or some other IR transparent material)
so that plants can be grown when the outside temperature is too low.
Again, the intent is to harvest free energy.
What are "Green House gasses"
Normally, the Earth is colder at night than during the day
(but sometimes a warm front at night blows in hotter air).
Assuming no weather fronts, the amount of cooling at night
The reason that the Earth cools at night is because thermal energy is radiated
out into space as electromagnetic waves.
All warm bodies produce electromagnetic waves at many different frequencies.
When a body gets hot enough (like the filament in an incandescent light bulb),
we see some of the electromagnetic radiation as light,
we feel some of it as heat, and additional radiation is produced in other
frequency bands (including microwaves and radio waves).
- Whether or not there are clouds
- Winter nights are always colder when there are no clouds,
and frequently comfortable when there are.
- The amount of water vapor in the atmosphere
- Warm humid nights really are hotter than those
in areas with less humidity ... even when the daytime temperatures
are similar. This is particularly noticeable when comparing coastal
areas with deserts.
- Mountains are typically cooler than low lands anyway, but the temperature
drop at night is usually more. Part of this is due to lower
humidity and part is due to the thinner atmosphere.
The gasses that make up our atmosphere are transparent at some frequencies
(which is why you can see your hands) and opaque at others. For instance,
clouds block light but transmit radio waves.
Each gas in our atmosphere blocks some heat - acting like a "Green House" -
and some gasses block more heat than others.
Of the gasses in our atmosphere,
3 have important variable concentrations
These are the primary "Green House" gasses discussed in the "Global Warming"
debates. The primary atmospheric gases - Nitrogen, Oxygen, Argon (99.9% of the atmosphere) -
are never mentioned because nothing humans do can affect their concentrations.
- Carbon dioxide - more in the winter, less in summer
- Methane - more in summer, less in winter
- Water vapor / Water droplets (clouds) - highly variable, less in winter
By the way, the reason that the Earth warms up in the daytime is that
it is receiving more radiation than it is radiating ... but you should remember that
it is always radiating some energy.