Why is global warming a bad thing?

[Gunner]

Global warming doesn't mean every place on earth suddenly gets warmer. A global shift of only a few degrees net can (and, historically, has) caused shifts in weather patterns. Rising sea levels are only a side effect. Generally, the temperate regions will get dryer - this means the central US grain belt will get a lot closer to Dust Bowl conditions on a permanent basis, while the shorter growing season of the Dakotas and central Canada will get longer and warmer. (Ditto for Ukraine, which is central Asia's breadbasket; the growing zone will move north into what is now forested areas.)

It also creates shifts in weather patterns, so that areas used to 20 inches of rain a year might now get 10, or 50. It's not any one 2012-style disaster; it's a gentle shaking of the whole snowglobe that changes the weather and conditions in nearly every spot on the globe.

Think of it as every plat in a city being shifted ten feet in a random direction. No big deal, except that now your bedroom is on a neighbor's land and he has to cross your front yard to get to his garage. The disaster is cumulative and almost universal instead of being localized like an earthquake or even a hurricane.

Whether it's caused by human activity or is a natural change in conditions such as has happened on an almost continuous basis for eons, it's going to change the rules of food production, energy distribution, water resources and the balance of arable land in our lifetimes. It would be nice if we could get our sh!t together and deal with it instead of turning it into another politicized clusterfork.