The greatest predicted temperature increases are in the northern taiga forests and tundra. That would make a lot of arable land.
If it's warmer, will it be usable farmland? Have there been any studies?
Usable farmland has to have halfway decent soil, not-too-awful soil chemistry, reasonable amounts of water, that sort of thing. Has somebody done a study on random taiga, to see if all it needs is to be warmed up?
There's no evidence that anyone has been inconvenienced by AGW.
All over the world, we've been having a large amount of weird weather, some of it destructive. Hurricane Sandy is a good example, and the flooding was exacerbated to some extent by rising sea levels, which are due to global warming. Now, we can't definitively point to any given incident and say it's because of global warming, but the theory predicts wonky weather, we get lots of wonky weather, and some of it has been pretty darn inconvenient. All together that amounts to evidence of inconvenience.
One problem with the climate change going on is that we don't know what specifically is caused by global warming and what's just flukes (until, of course, it's Too Late). That means that people who have some interest in denying its effects have no difficulty in doing so.