One of the biggest risks to the world’s financial system is the $2.5 trillion of debt owed by oil and gas firms. After a year from hell, prices of commodities, and the shares and bonds of the firms that produce them, have bounced in the past month. But the evidence of financial pain is all around. Last week Energy XXI, an explorer with $4 billion of debt, filed for bankruptcy in Houston. And JPMorgan Chase, Wells Fargo and Bank of America complained of rising energy-sector bad debts in their first-quarter results. Only 5% of global energy debt sits on the balance-sheets of America’s biggest three banks. A further 34% of global energy debt comes in the form of US-listed bonds. The majority of global exposure is hidden in smaller banks or beyond America’s borders. With a Saudi-led attempt to curb oil output ending in failure yesterday, expect more yelps.