MarketWatch: The chief executive of oil firm Royal Dutch Shell PLC will tell a gathering of industry executives Tuesday that the world must find economic ways to reduce its dependence on the most polluting fossil fuels, calling on governments to institute an effective system for pricing carbon. According to excerpts of Ben van Beurden's speech to the Oil & Money conference in London seen by The Wall Street Journal, the boss of one of the world's biggest oil and gas companies is promoting a carbon-pricing plan...