When it comes to thinking about greenhouse gases, scientists and policymakers often focus on annual carbon emissions. They are missing a more important fundamental measure, however, a new study argues. Tracking how much energy infrastructure we’ve already built and tallying the emissions it is likely to produce—so-called committed emissions—is a better way to illuminate the global climate challenge, a research team writes today in Environmental Research Letters.
By their tally, committed emissions—the carbon emissions expected if existing energy infrastructure, such as coal-fired power plants, runs for its forecasted lifetime—have nearly tripled since 1980. In that year, the study says, carbon emissions from new and existing power infrastructure were 107 billion tons. In 2012, the total rose to 307 billion tons, assuming existing plants keep running for a 40-year lifetime. China has played a dominant role in the growth: That nation’s infrastructure accounted for a whopping 42% of global committed emissions as of 2012.
The paper's first author, energy scientist Steven Davis of the University of California, Irvine, co-authored an earlier paper in 2010 that quantified the committed emissions from infrastructure that existed in a single previous year, 2009. The new analysis, built off data from existing commercial and government databases, shows how committed emissions have shifted as nations have added new infrastructure and retired old facilities.
The traditional focus on annual emissions has masked the steady, and problematic, growth of committed emissions. Annual greenhouse gas emissions grew at a rate of 1.3% between 1970 and 2010 and have wavered around 3% growth since then. In contrast, the new research shows that the annual new commitment of emissions has grown at 4% per year. "Every year we are committed to more [future] emissions than we are making in that year," says Princeton University energy scientist Robert Socolow, a co-author. Furthermore, he says, “there hasn't been a single year where we have cut the amount of [global] fossil fuel infrastructure we have built more than we have expanded it."
If anything, the new forecast of 307 billion tons of committed emissions "probably understates the real carbon commitment,” says energy expert David Hawkins, director of climate programs at the Natural Resources Defense Council in Washington, D.C. That's because in their main scenario, Davis and Socolow assumed a 40-year lifetime for most power plants, but most plants are likely to run for at least 60 years, "absent policy intervention," Hawkins says. If current plants were to shutter after 20 years, the scientists found, they would emit 98 billion tons of carbon emissions over their lifetimes; if the plants run for 60 years, that number would rise to 578 billion tons. (Hawkins helped spur the research by urging the scientists to look into the issue, but he is not an author on the new paper.)
The scientists hope that the wide adoption of the new metric will enable “policymakers to confront the distant policymaking implications of the decisions they are making today,” Davis says in a video explanation of the paper. And that awareness should lead to action, adds Socolow, who says the research also highlights the importance of Western assistance to developing countries so that they build energy infrastructure of lower carbon intensity.