[Sender]

It would directly affect a large area, mainly whatever lies downwind of the area for hundreds of miles. The relatively heavy fallout would mostly enter the soil and groundwater after the next rain. Some lighter dust would undoubtedly make its way around the world, but I doubt that we would experience any significant contamination. The areas around and downwind of the explosions, however, would remain hazardous for a long, long time. These areas would not be like the desolation in sci-fi movies at all. They would have plenty of plant life and seem relatively normal. People would stay there or move back in. Cancer and birth defect rates would go up. In the end, we would get blamed for it all somehow and have to foot the bill for medical and cleanup. Most significantly though, if there is a nuclear exchange, the genie will be out of the bottle, so to speak. The first one is always the hardest. The next ones are easier. Or at least, no longer unthinkable.

[FReepaholic]

See post #10

[Dan Day]

Good analysis, including the political ramifications. That's my view as well.

[Mitchell]

Most significantly though, if there is a nuclear exchange, the genie will be out of the bottle, so to speak. The first one is always the hardest. The next ones are easier. Or at least, no longer unthinkable.

That's an important point -- this isn't just about India and Pakistan.