The -qatsi trilogy's website has a discussion forum, and obviously one of the things that's come up - repeatedly - is the identity of the abortive launch at the end. The number of people asking whether it was Challenger - in spite of the facts that a) it's obviously not a shuttle launch because there's no bloody shuttle, and b) the film was released years too early - is quite astonishing. However, for future reference the question is answered plausibly here, with information allegedly taken from (a page which seems not to be available) :

The first Atlas Centaur, denoted "C-1", was erected on the new Launch Complex 36A at Cape Canaveral during the spring of 1961. It stood there for 15 months before finally lifting off on 1962 May 8. The vehicle rose cleanly and steered downrange, but 49 seconds after liftoff a portion of one of four Centaur LH2 tank "weather shield" insulating panels ripped away. The LH2 fuel tank quickly overheated, overpressurized, and failed. Centaur shredded, causing the vehicle to explode 55 seconds after liftoff.

Centaur's fiberglass foam core weather shield panels were designed to keep the LH2 fuel cool until Atlas fell away and Centaur's RL10 engines ignited. Then the panels were to be jettisoned to save weight. The shields were hinged at the bottom and held in place at the top by spring loaded tension straps and explosive bolts. The design turned out to be structurally inadequate, however. During the C-1 flight, a shock wave at the base of the nose cone impinged on the panels, causing negative pressure that dislodged the strap.

So there you have it. Apparently February is Spring in Florida.

I should probably watch the scene again after looking at loads of pictures of Atlas rockets, just to be sure, but it looks plausible from the ones I've just seen.
Yeah, I'd say February is Spring in Florida. It's not like Florida has much of a Winter.
It looked like a Titan engine falling to earth at the end to me, even though it was an Atlas taking off at the start.
Dunno. It seems to be a continuous shot, so presumably it's explicable by parts detaching, it being the upper stage, or different engines being used in different models of the launcher. Your idea, though, is at least as good as mine.
Spring is an odd concept in an climate where it's always growing season. I was in Boca Raton for a week starting the day after Xmas in 1999. It was 25C every day I was there, and people at the local synagogue were complaining about how cold it was at night (all the way down to 15C!). Oh, and most locals freely admit they only have three seasons: wet, dry, and baseball.
I lived in Jamaica for a couple of years when i was very young, and I only remember there being one season, the hurricane season, although given that it didn't cover the whole year I suppose there must have been a non-hurricane season too. I don't think I was old enough to make that logical leap at the time.