The oil industry must step up exploration and investment in new supply; otherwise, the world risks a supply shortage, according to Amin Nasser, the chief executive of the Saudi state oil giant Aramco. “We had a decade . . . where people didn’t explore. It’s going to have an impact,” Nasser told the Financial Times. “If it doesn’t happen, there will be a supply crunch,” said the top executive of the world’s biggest oil firm by both production and market value. …