Is there a God-ordained correlation between natural disasters and sin?
Whenever there’s a significant disaster in the world, especially if it's on a populated area that is characterized by ungodliness like New Orleans, it's easy for Christians to presume that God has authored that natural disaster as an act of judgment against those people. I think there is some peril in that. Certainly God has used judgment of that sort against peoples in the past, and we can see this in the Hebrew scriptures.
I just want you to notice, in virtually all of those cases, that judgment was proclaimed before the event itself happened. There may be some exceptions to this, but characteristically there is a declaration of some sort that God is judging because of iniquity. Even in Sodom and Gomorrah, the angels themselves told Lot God sent them to destroy the city because the outcry of their iniquity was so great. So, we have a record of the rationale in those cases of why God destroyed those cities.
What about nowadays? Certainly, God can do that, and he doesn't need to tell us. He’s not obliged to, but the biblical record is such that He generally does so that people don't miss the point. If a big disaster befalls some populated area that's particularly sinful, how are they going know that this is an act of God against them unless God tells them?
In the case of Katrina in New Orleans, I think it's kind of interesting that the most godless area of New Orleans, the French Quarter, being on high ground escaped virtually all of the impact of that storm. Which means, the worst place escaped it, and all of the poor people ended up drowning. It strikes me that that probably wasn't a judgment of God against that city.
Unless we have really good, concrete, objective reasons for claiming that God did this thing in judgment against a city, it's probably not the best thing for us to go out on a limb and make that claim. It ends up making us sound a little frivolous. If God wants to do that, He can do that. If He wants to let us know the reason why, He can do that too. Then, we can announce that to the world. But in the absence of that, I don't think we should make those conclusions. We should rather weep with those who weep and help the downtrodden and those who are the victims of these kinds of disasters rather than pointing the finger at them as victims of the judgment of God.