A few years ago, Goldman Sachs analysts talked of a ‘Groundhog Day’ loop for oil. The market is far more volatile now. Photo: Bloomberg News Volatility is roiling the oil market, luring traders in search of quick profits but discouraging longer-term investors who had grown accustomed to more muted swings. Crude prices tumbled Thursday to their lowest levels in nearly a month after data released Wednesday showed inventories continuing to swell. Volatility has surged in recent months following a bruising selloff that cut global benchmark prices by 60% from June through January. That was followed by a jump of more than 30% in the first two weeks of this month. It is a sharp turnaround for a market that was relatively dull until a year ago, with Brent crude, the global oil benchmark, trading at more than $100 a barrel on average for three years in a row, […]