[Off-topic] xaccers:
Lets look at the Wiki article, and what it says about 1913, and you'll see that the Ozone layer was discovered then, not the hole.

We've been using ozone depleting chemicals in commercial and domestic refigeration since the early 20th century, while the depletion was detected in the late 70s.

So even referring to Wiki you are unfortunately reading it incorrectly.

Mars has such a low gravity that the escape velocity is low enough for vast amounts of CO2 to escape into space on the solar wind, so during the summer this is what happens. Nothing is producing more CO2 in large enough quantities to replenish that which has been lost.

This has been going on for millions of years hence why Mars doesn't have much of an atmosphere.

It's also happening with gasses in our atmosphere too, but there's no need to start practicing holding your breath just yet :)

I'm very glad you've brought up Venus as it demonstrates my blanket analogy perfectly.

Let us look at Mercury, which is closer to the Sun and therefore one would expect to be the hottest planet in the solar system.

Except it isn't. Due to the additional blankets (CO2) on Venus, it is actually hotter than Mercury despite being a third of an AU further away from the Sun.

Also, due to the blanket effect of the CO2, Venus' temperature us rathe runiform and stable, demonstrating how CO2 traps heat, while Mercury ranges from -170C to 350C

So thank you for helping demonstrate how greenhouse gasses can raise the temperature of a planet.

In case you haven't understood, without the greenhouse gasses, being further away from the Sun, Venus would be colder than Mercury, but because it has greenhouse gasses trapping the heat it is actually hotter than it should be.

If you're wondering where the CO2 came from as there's no industry on Venus, then I'll have to explain about the super volcanoes on it's surface which make Mt Everest look like a mole hill (ok I exaggerate for dramatic effect, but not by much, they are seriously huge), and they spew out CO2.

Of course, who's to say there wasn't life on Venus once, the evidence does suggest it once had water oceans...

The CO2 produced from volcanoes on Earth is important, but cannot be blamed for the additional increase in CO2 levels we are experiencing.

There is a theory that during the Earth's history, back when the Sun was a lot less active and therefore cooler, it became nearly completely covered in ice, the so called snowball earth theory. With the temperature that low, precipitation all but stopped, so there was no "washing" of our atmosphere. This lead to a build up of CO2 spewed from volcanoes now long dormant, which raised the Earths temperature higher than it would have been before, thawing the planet and enabling life to continue.

Sakai is quite right in that if we manage to find cleaner ways of doing what we like then how is that a bad thing?

You only have to look at a city from a distance on a hot day to see the smog of pollution that us humans are producing.

We won't destroy the world, but we can quite easily make it inhospitable to humans, I'd rather we don't do that.

Without world governments taking it seriously rather than trying to make a quick buck at ultimately everyone's expense there isn't much direct effect one or two people can have, or for instance a small nation like the UK, but by making the change, following Sweden (I believe) and their plan to be oil free, can put pressure on other countries to follow suit.

As for your teacher telling you that global warming is a hoax, that shows a servere lack of professionalism. My Geography teacher couldn't seperate her own creationist beliefs when marking some of my course work (I did a 50 page essay on the geology and geography of the lands around where remains of our evolutionary ancesters had been found) and gave me 2 out of 20 as a grade. It was then that I realised what her problem was, as before I had found it stranged she denied oil was the remains of zooplankton and algae, instead stating it was "stored solar energy"

She was what we call in the industry a "very bad teacher" and looked like a Gummy bear.