Bringing new oil supplies to market could have an unexpectedly large impact on global emissions (see P. Erickson and M. Lazarus Nature Clim. Change 4, 778–781; 2014). New sources of oil increase carbon dioxide emissions in the short term, and make it harder and more expensive to scale down production in the long term. This 'carbon lock-in' entrenches our dependence on fossil fuels and commits economies to higher emissions (see

The scale of investment in oil supplies and the profits they bring over the long term already dwarf those associated with other fuels. And significant barriers still confront the adoption of competing low-carbon technologies, such as electric vehicles. Capital-intensive oil fields that have low operating costs relative to oil prices — as with most offshore oil deposits — make it even harder for us to switch. To wean us off oil, world leaders urgently need to curtail the billions of dollars that are currently earmarked for oil exploration and extraction.