Hi Quasar1011,
my apologies. No I did not contradict myself (nightmare of nightmares!), I simply did not explain myself clearly enough. So I'll try again.
disasters are disasters. It doesn't matter whether they are volcanos, floods, meteor impacts, black death, etc. The simplest way to model them into a game is as random events and I think that is what happened in civ[1]. A more sophisticated way is to make them more likely in certain game circumstances. In the common way of looking at this subject, if you go one step further and start to directly relate these events togame conditions you are talking about modeling a subsystem within the game.
The easiest illustration is disease. If disease just randomly happens some time, say to wipe out a city or reduce population in all your cities (or every city on the planet), then it is a disaster type event. If it only happens to cities above a certain size or when the, say, continental (or global) population density reaches a threshhold, but within thopse constraints it happens randomly then it is a disaster event. However if it is assigned an increasing likylyhood as population grows and/or communication/travel increases (roads etc.), it is becoming a subsystem of the game. If you then have medical advances, clean water technologies etc. that actually make it less likely to affect you, then it is clearly a fully integrated subsystem and is something to take into account as you play.
So if someone says they want weather modelled into the game, I'm not impressed with the idea if all they want is storm or flood damage to happen more or less randomly, but I am if they want major river valleys to flood according to some (behind the scenes) algorythm [oops can't spell that - let's just say algaerythm

] and crop failures to occur as a consequence of extended dry spells and so on. That would be weather in the game.
Now that said, I don;t believe the game scale lends itself to doing things like that in any detail. But it does lend itself to climate change affecting the conditions and terrain. The most obvious example is the way that mediterranean North Africa has changed over the last few thousand years ( I know that is not just climate because land usage methods affected it as well, but that canbe accomodated if you want). Average rainfall changes over time could be modelled in to affect different parts of the world and much more could be done. I'm not shouting from the rooftops for this but it is feasible.
Hope that clears up the misundersatanding. The only clue to this thinking in my original post was:
Weather or climate change would be a systematic attribute of the game.
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Thank you for listening
Algy