Crude oil prices have been back over $60 a barrel in the US due to concerns about supply disruptions as a tropical storm forced oil companies to evacuate rigs in the Gulf of Mexico. A combination of strong demand, limited production and refining capacity and market speculators looking to take advantage of the situation has pushed prices up. Brent crude has risen by $20 a barrel since the start of the year. Strong memories of last year’s Hurricane Ivan, which forced the closure of oil rigs across the Gulf of Mexico, are worrying the markets. Meanwhile, in Denmark, en-route to the G8 Summit, President Bush – the leader of the world’s largest energy user – addressed global warming and high oil prices. Offered a commitment to diversify the US’s energy supply, he said: Listen, the United States, for national security reasons and economic security, needs to diversify away from fossil fuels. And so we’ve put out a strategy to do just that. I can’t wait to share it with our G8 friends.. Bush is pushing his view that technology, such as hydrogen as a fuel source, can provide alternatives to the reliance on oil. But scientists say that is years away from widespread commercial use and the US and the other G8 countries remain divided on the need to cut back on greenhouse gas emissions.