I once took an inventory of the land mass at various latitudes, and IF(big if) the globe should warm enough to matter, agriculture can move north significantly before total acres available start to decline.  South is opposite, but is far outweighed by north.  Not saying anything about how much of that land has agricultural potential though.  The Canadian Shield takes a big chunk out. 

As for myself, All other things being equal, which is doubtful, I could produce much more with a warmer longer growing season.  

But the pessimist in me has trouble believing in the glorious scenarios of the forthcoming global warming, and all of the promise it holds.  I tend to believe the unbiased science that tells us that the warming cycles has long since ended, and the cooling phase has a long ways to run.   But I can always dream....