Big Oil, investors face returns reckoning amid darkening economy

LONDON (Reuters) - Darkening clouds over the global economy have led two of the world's top oil firms to warn investors that promised growth in returns could be at risk for the first time since the 2014 oil downturn.Both BP and Royal Dutch Shell, which account for nearly 15% of the FTSE's total dividends, signalled this week that billions of dollars in shareholder returns could be delayed as oil prices failed to make their expected recovery.The stark warnings led to sharp drops in the shares of..