Ole Hansen, head of commodities at Saxo Bank, says that the falling dollar, along with global weather trends, is helping the rally in agricultural commodities - most notably sugar.

The Bloomberg agricultural index has risen by 25% since its March low, says Hansen. Hedge funds have taken long positions in sugar worth the equivalent of $5 billion.

Although there is a fundamentally strong outlook for sugar, Hansen says that bubbles can appear in agricultural commodities.