Robert Socolow has led efforts to assess the challenges and benefits of mitigation strategies and to frame the carbon and climate problem in policy-relevant ways to spur action on carbon emissions.


“Committed” emissions

Work by Socolow with Steve Davis (UC Irvine) on “committed” emissions has led to a paper, “Commitment accounting of CO2 emissions,” that is currently under review. One argument of the paper is that the CO2 accounting reported by national governments should routinely include future emissions that are committed each year through capital investments that will run for many years. Databases on the world’s power plants reveal that annual increases in globally committed emissions in the power sector have exceeded actual annual emissions from that sector for many years (Figure 2).

Figure 2. Changes in remaining commitments. Total remaining committed emissions of power generators built worldwide since 1950 increased from near zero in 1950 to 307 Gt CO2 in 2012, driven by coal-fired generators (b) built in the US and Europe during the 1970s and 1980s, and in China, India and the rest of the world beginning about 1985 (a). Annual increases in remaining global commitments hovered around 6 Gt CO2 per year in the 1970s and 1980s, dipped to a minimum of 2.2 Gt CO2 per year in 1990, then rose sharply between 1994 and 2006, and declined again between 2006 and 2012 (c and d).

Removal of carbon from the atmosphere

Robert Socolow, with Massimo Tavoni, edited a ten-article special issue of Climatic Change on “negative emissions” which brings together technological considerations and integrated assessment models. Entitled “Carbon Dioxide Removal from the Atmosphere: Complementary Insights from Science and Modeling” the issue (Volume 113) is now publicly available online (see http://link. Socolow and Tavoni wrote the overview article at the front of the issue, “Modeling meets science and technology: an introduction to a special issue on negative emissions.” Socolow co-authored another of the articles, “Direct air capture of CO2 with chemicals: optimization of a two-loop hydroxide-carbonate system using a countercurrent airliquid contactor,” with Michael Desmond (bp) as well as Marco Mazzotti (ETH, Zurich) and Renato Baciocchi (University of Rome). This special issue culminates a five-year effort to provide context for the option of removing CO2 from the atmosphere via biology or chemistry. The overall messages are sobering:

  •  CO2 removal options can lower atmospheric concentrations only slowly, at a rate of 1-2 ppm per year.
  •  Biomass-based strategies create large land demands that are treated too casually today in models.
  •  Chemical-based removal presents formidable challenges related to cost reductions, but has much less land impact than biomass-based strategies. However, chemical options might better be applied to reduce costs for capture from concentrated sources.