Actually, it's just one of a plethora of reasons, but the most relevant now. Warming increases the extremes. In fact, a paper I no longer have handy (I found it at Wikipedia, so the link's long since been edited away, and obviously I can't use the links to it I made on wotmania) concluded there was a 0.1% chance of the null hypothesis that the increasingly intense tropical cyclones in the six ocean basins they studied should ALL increase simultaneously as they did during that study. NO correlation has been found between tropical cyclone FREQUENCY and ocean temperatures, but the intensity of those that do develop is strongly correlated. Up until the last couple years (and I believe, though I may be mistaken, there's actually been a little cooling in that period) that's what we've seen for some time.

Warm oceans fuel intense weather, particularly (thought not exclusively) tropical cyclones. For that matter, so does warm land, just in different ways. Hot things rise, you see, or rather, cold things sink, and most of our weather comes from above rather than below us. Warm the ocean, more of it evaporates, more precipitation in the air, and heavier snowfalls in the mountains, as well as more humidity and heat inland to provide storms and tornadoes. And, of course, when you get a heavy snowfall followed by a hot spring and summer, you get floods from both heavier spring showers and heavier snowmelt.

And that's the simplistic presentation of a layman. I'll make ya a deal: You don't dismiss global warming on the grounds it should simply make the planet warmer and I won't assume I can hatch a chicken if I sit on an egg long enough. There's a BIT more to it than that, after all.

To a great extent I agree with your final point, but I do want to be very careful how we pursue that route. Greater efficiency, reduced consumption and clean renewable energy are all laudable economic goals. If we find out we were wrong about global warming they would still make efforts against it worthwhile--provided we're SINCERELY wrong (nothing wrong with that; the world would be a very empty place if we removed everyone sincerely wrong about something. ) If we do yet more research and find out man ISN'T largely responsible for global warming (which NO ONE disputes is happening anymore; now skeptics just seek ways to avoid doing anything about it) good science demands we admit that and continue pursuing greater efficiency, reduced consumption and clean renewable energy as ends in themselves.