What a difference a thousand days can make. The effects of Hurricane Katrina gusted round trading rooms when it hit the US Gulf coast three years ago. But with Gustav, the most powerful Gulf storm since then, the market reaction has been a breeze. Even before Gustav was degraded to Category 2 with winds of 110 mph, oil prices had fallen while the dollar rose.

Such a reaction is a sign of how much the world economy has changed since 2005. Back then, oil prices were “just” $60 a barrel – and rising. Now, by contrast, oil prices are at about $115 a barrel – and they are falling. That a major storm in an area that accounts for 2 per cent of world production did not reverse that trend is a reminder of grim fundamentals. Global energy demand is slowing as the credit crunch bites – US petrol demand fell this summer by its furthest in 25 years. Opec supplies are also edging up, China is no longer stockpiling and speculative interest has wilted. Total assets under management by commodity index investors had slid by $87bn to $210bn by mid-August, according to Lehman estimates.