Exceeding the carbon budget

Rolling Stone has a somewhat pessimistic article, Global Warming's Terrifying New Math, about the political and economic difficulties in restricting global warming to 2°C. The reasoning, as put forward by the Carbon Tracker Initiative, is that entities such as oil companies which have proven reserves of fossil fuels have overwhelming incentives to extract those fuels. Their share prices, for example, are valued on their proven reserves. However, if those reserves are consumed then global warming will far exceed the maximum  temperature rise considered prudent by scientists. In addition, exploration for new reserves is not slowing down, and the extraction of fuel from reserves once thought uneconomical is hastening.