Quite apart from what man does or doesn't do that may affect the weather to some extent, there is, according a Scientific American article I read, a cycle of ice ages, sometimes the ice age is small but sometimes it is a huge one, there were a couple that lasted for tens of thousands of years.
As far as I remember the beginnig of an ice age (northern hemisphere glaciation) depends on a couple of things, one is the Atlantic conveyor, and the other is precession.
Precession is a little complex, it involves the tilt of the earth's axis and it's wobble, and also the shape of the Earths orbit around the Sun plays a part, it being not a perfect circle but slightly egg shaped, not only that but the position of the egg gradually moves as well so the Earth isn't locked into the same path on every orbit.
The half period of Precession is roughly 11,500 years, (from memeory) from when the Earth's axis is pointed at maximum tilt in one direction to maximum tilt in the opposite direction (wobble) and another 11,500 years to return back the way it was, (Ice ages occurr, big or small, on average about every 25,000 years), the position in the egg shaped orbit where this occurrs is important; if the Earth is at the fat part of the orbital egg (further from the Sun and slightly cooler), with the tilt facing the Northern hemisphere towards the Sun more than the Southern hemispere and the Atlantic conveyor has slowed because of previous ice cap melt (more fresh cold water over the top of the salt water, like now) then the Southern oceans can cool, (much more water in the Southern hemisphere). If that happens then the Northern hemisphere can freeze over because the Northern hemisphere depends on the warm current from the Southern hemisphere and because the snow, ice and white clouds reflect the suns heat back out into space; then it could become another ice age, the only question is, how big and how long will it be?
So Barry get a ticket for Oz and keep it in reserve...just in case.
ps. Oh btw, on the news tonight, it SNOWED (heavily) in the middle of summer here in Oz, down south of course, but SNOW in Australia in the middle of summer????