In short, the industrial revolution has created an engine of change that, while small and local in isolation, adds up to worldwide changes when many are working at the same time. It's called the machine.
Think of it: You got millions of power generators burning up fuel, heating up the area around them and throwing heat-trapping gasses into the air. Add in millions of factories and millions of cars which, while they don't produce 24/7, add in their share of heat and gasses when operating. Also include air conditioners (which move heat outside and blow "cool air" inside"), heaters, refrigerators, computers, incadescent lights and other small items which throw up small amounts of heat themselves, and one shouldn't wonder why we're warming up but instead why things aren't yet over the edge.
Compare this with your average volcano: It spews forth tonnes and tonnes of gasses and dust for great effect, but the effect stops. There's no constant spewing, as is the case with the millions of factories, cars and houses. And when the volcanos are quiet for years, their effects tend to fade out. It takes a Krakatoa to affect weather for hundreds of years, and you get that rarely.
So we're in agreement that humans can affect weather. The question, of course, is which way.
There's two theories (three, really) for how we could affect the environment:
- Heat up the world until it turns into Venus
- Overload the system, freeze the world into an icicle
- Speed up the cycle of freeze/warm
All three of these scenarios has made it into the public mind at one point or another. Right now, of course, the first alternative is considered the most obvious, although I've always found it interesting that books, radio and movies always seem to evoke the freeze-over scenario readily (The Day After Tomorrow comes to mind). Michael Crichton believes that, ha in the third theory, in which we speed up what's alread happening.
Of course, it's not just warming. Recently we've felt a cooling, thanks to China going whole-hog into coal plants and lack of pollution controls. Indeed, many places along the Pacific Coast have found themselves in violation of The Clean Air Act through nothing of their own actions. That has been affecting Thailand and Bangladesh, because the dust spreads out and blocks the surround areas. We may even see a drop of average temperatures over the next few years as China's industrialization matures.
And, fo course, there's the question of whether this is such a bad thing. One thin line of thought involves the possibility of a coming Ice Age and that only Man's industrial activity keeps the earth from becoming an icebox. Not really much out there, but this interesting essay goes into some intriguing points, based oddly enough from a Gaian viewpoint. I don't necessarily believe in it lock, stock and barrell, but I find it entertaining and intriguing for what it suggests.
Three down, at least one more to go...then I'll probably go into detail some of the point of my second crisis (the debt stuff)