the ozone layer is a layer of o3 in the atmosphere which is pretty damn good at stopping lots of nasty stuff like radaitiona and uv rays. also creates heat loss which is jolly nice for a planet which is heating up.
the greenhouse is totally unrelated and is caused mostly by carbon oxides. same kind of stuff you breath out. normally the cycle went like so. air expired- plants take it in-make new-oxygen-breath in some more.
worked well when all that was expelling co2 was animals not cars and power stations in huge amounts. also helped when you weren't busy destroying the rain forests. so it builds up sitting happily in the atmosphere reflecting back heat which was gonna escape. so the planet heats up. this is global warming.
there is also something known as global dimming which is when heat was blocked out by air pollution and things like jet exhaust trails. (sept 12-14 2001 showed a great upsurge in average temperatures across the world) this for a time slowed down global warming. but we decided to cut down on air pollution so got rid of global dimming and so global wamring is now much faster than predicted.
the sequence would work like this for the global warming. world slowly heats up and ice caps slowly melt, gulf stream is cut off, heat deprived to europe and it freezes. southern hemisphere though would continue to heat. at the bottom of the sea there is a material who's name can't quite come to mind (it was on panorama or horison for anyone who saw it). this material is very sensitive to temperature and at the point where the temperature of the earth reaches a consistent 5 degrees higher for a length of a few years these deposist will be expelled from the sea as gas into the atmosphere. the gas released is 100 times more effective at the greenhouse effect than co2 and there are a few million tons of the stuff down there. which is a bugger. at this point there is no turning back. plant life will die due to intense heat or cold. this won't be another ice age. that was slow. animals evolved. animals don't eveolve in 50 years. so with the planet fast heating up. billions upon billions of animals and plants dead what then?
we are doomed to this fate until you put down that bloody gas can. stop burning all that bloody coal and gas and do something about it. america's view on this is sickening. a constant reactionist soceity. i have two hopes in this, that either america in the next few years turns around, agrees to kyoto and drops it's co2 levels dramtically. or come 50 years it suffers immensly for it's crimes against this planet and rues the day when it says it would never happen.
and i'm not sure as to the claim of cfc's being hugely a part of volcano's as far as i am aware and was taught that human releaseof the gas far out weighed volcano eruptions same is true with co2 and sulphur.
http://volcano.und.edu/vwdocs/Gases/man.html
goes other the various gases released by volcanos.