How Much Carbon Reduction is Enough? New Metric Helps Gauge Policy Impacts

Note: Yale School of the Environment (YSE) was formerly known as the Yale School of Forestry & Environmental Studies (F&ES). News articles and events posted prior to July 1, 2020 refer to the School's name at that time.

Kroon hall yale
When Corey Johnson ’15 M.E.M. explains his masters project on university greenhouse gas accounting, he starts from an unexpected angle. “Pretend a university sets a goal to reduce water consumption by 50 percent in the next 20 years,” he says. “Now consider the validity of that target if its water supply runs dry within a decade.”
He quickly draws a parallel with climate change: “A university might set a goal to reduce greenhouse gas emissions, but is that goal aggressive enough to prevent us from crossing a potentially dangerous climate threshold?”
Johnson argues that the sustainability targets set by universities — and other large organizations, for that matter — tend to be fairly arbitrary. Often, they are based on reductions that are economically and logistically feasible, rather than using science to inform reductions that are necessary and meaningful.
Commitments to reduce greenhouse gas emissions on college and university campuses are ubiquitous. Yale University, for instance, has committed to a 43 percent reduction from 2005 levels by 2020. Harvard aims to reduce its emissions of these heat-trapping gasses by 30 percent by 2016, and Princeton plans to cut emissions to 1990 levels by 2020.
But the question remains, how much of a reduction is enough?
It’s a pretty innovative tool and provides an interesting way to look at sustainability initiatives on college campuses.
— Prof. Robert Bailis
To help answer that question, Johnson worked with several nonprofit organizations to develop a tool that helps universities calculate what he calls science-based emissions performance. The tool compares a university’s greenhouse gas emissions to a global emissions scenario — called a representative concentration pathway — that is most likely to keep global warming below two degrees centigrade. The output represents a new style of sustainability metric that benchmarks emissions against a university’s fair share of the global carbon budget.
Measuring sustainability performance relative to thresholds in natural systems is simple and intuitive, Johnson says, yet is seldom practiced. His research builds on work done in the corporate sector, where companies like Ford and Ben & Jerry’s are turning to science-based targets as the next phase of sustainability management.
“It's a pretty innovative tool and provides an interesting way to look at sustainability initiatives on college campuses," said Robert Bailis, an associate professor at F&ES and Johnson's project advisor. “You still want to consider certain circumstances, like the climate where they are located, the size, and whether students commute to school. But this provides a view of what universities are doing in a more balanced and systematic way. I think it will be valuable for universities to look at.”
Other members of the project team include Mike Bellamente from the Carbon Disclosure Project and Mark McElroy from the Center for Sustainable Organizations.
Johnson hopes the new tool will help universities start to think about their emissions and broader sustainability performance through a more scientific lens. “We’ve got the science,” Corey says. “Let’s use it.”