Paul Collier, writing in the current Foreign Affairs, argues thus about climate change and food prices:

In recent years, the increase in demand resulting from gradually increasing incomes in Asia has instead been matched with several supply shocks, such as the prolonged drought in Australia. These shocks will only become more common with the climatic volatility that accompanies climate change. Accordingly, against a backdrop of relentlessly rising demand, supply will fluctuate more sharply as well.

In other words, it’s increased variability that’s the real climate-food killer.

(It’s not the major point of his piece. His central thesis, which you should go read, is that ethanol subsidies, hostility to large commercial farming and opposition to genetically modified food are, together, making people starve.)