This global readership is evident by the diverging trends in volume and open interest relative to WTI and ongoing deepening dollar premium of Brent. You can also see the growing preference for ICE Brent options, which resulted in our volume quadrupling year-to-year in the second quarter.
Also in the second quarter, our Gasoil contract grew 7% year-to-year, and European emissions contract volume rose 11%.
The EU commission on climate change recently confirmed the U.K. government's up-tail option platform for Phase III, where ICE Futures Europe will provide that platform. We believe this will support our leading position for the third phase of the European Emissions Trading Scheme beginning in 2013.
While Brent, Gasoil and Emissions are our largest revenue contributors, our energy futures complex grew strongly, with U.K. natural gas, coal, heating oil, and oil and gasoline futures all posting more than 20% revenue growth over the prior second quarter.Moving to ICE Futures U.S. Rising open interest in our agricultural contract translated into 14% volume growth in the second quarter. Sugar volumes continued to improve, writing 7% year-on-year, while cotton volume increased 31%. Also, during the quarter, we successfully launched new contracts for corn, soybean and wheat. We're seeing encouraging levels of volume and participation, and we will continue to develop these markets based on customer feedback. Open interest across our Futures exchanges increased 30% year-to-year and reached 9 million contracts at the end of June. Tomorrow, we'll report July average daily volume for our Futures markets. Month-to-date volumes reflect continued momentum for 2Q and are up more than 17% year-to-year. Turning to Slide 8, our bureau OTC business for the second quarter. OTC energy average daily commissions grew 3% to $1.6 million. North American natural gas revenues were up modestly to $62 million despite tenure loads in natural gas prices.