Stabilization Wedges and the Management

of Global Carbon for the Next 50 Years

Robert Socolow

Princeton University

More than 40 years after receiving a Ph.D. in physics, I am still working on problems where conservation laws matter. In particular, for the problems I work on now, the conservation of the carbon atom matters. I will tell the saga of an annual flow of 8 billion tons of carbon associated with the global extraction of fossil fuels from underground. Until recently, it was taken for granted that virtually all of this carbon will move within weeks through engines of various kinds and then into the atmosphere. For compelling environmental reasons, I and many others are challenging this complacent view, asking whether the carbon might wisely be directed elsewhere.

To frame this and similar discussions, Steve Pacala and I introduced the “stabilization wedge” in 2004 as a useful unit for discussing climate stabilization. Updating the definition, a wedge is the reduction of CO₂ emissions by one billion tons of carbon per year in 2057, achieved by any strategy generated as a result of deliberate attention to global carbon. Each strategy uses already commercialized technology, generally at much larger scale than today. Implementing seven wedges should enable the world to achieve the interim goal of emitting no more CO₂ globally in 2057 than today. This would place humanity, approximately, on a path to stabilizing CO₂ at less than double the pre-industrial concentration, and it would put those at the helm in the following 50 years in a position to drive CO₂ emissions to a net of zero in the following 50 years. Arguably, the tasks of the two half-centuries are comparably difficult.