Some scientists and analysts are touting carbon capture and storage as a necessary tool for avoiding catastrophic climate change. But critics of the technology regard it as simply another way of perpetuating a reliance on fossil fuels.

For more than 40 years, companies have been drilling for carbon dioxide in southwestern Colorado. Time and geology had conspired to trap an enormous bubble of CO2 that drillers tapped, and a pipeline was built to carry the greenhouse gas all the way to the oil fields of west Texas. When scoured with the CO2, these aged wells gush forth more oil, and much of the CO2 stays permanently trapped in its new home underneath Texas.