To put it very broadly, the consensus is that climate change will hurt farmers in the tropics and help farmers in temperate countries. A famouspaper published in 2005 concluded that if we follow the most extreme trajectory for greenhouse gas production (the one we happen to be on at the moment), global warming would raise harvests in the rich nations by 3% by the 2080s, and reduce them in the poor nations by 7%. This gives an overall reduction in the world's food supply (by comparison to what would have happened without manmade climate change) of 5%.
It has become the norm and for many people, starvation is not waiting. - JO