President Nicolas Sarkozy says he will use France's presidency of the Group of 20 to tackle high global food prices. That is a laudable aim. Corn and wheat prices have nearly doubled in the last seven months, and sugar is up more than 150%.

Global food prices are now above their peak in June 2008, when they triggered riots in several countries. The recent unrest in Tunisia and Egypt partly reflects high food prices. But what can the Group of 20 industrial and developing nations do?