The course the Environmental Protection Agency will take in its regulation of greenhouse gases (GHG) is still being hashed out. There are important and subtle differences to weigh in regulatory approaches for mobile and stationary sources as well as existing and newly constructed facilities. Still, paths to regulation are interconnected and, as the EPA moves forward, watching the evolution of individual policies could shed some light on the greater picture.

This chart, created by RFF visiting scholar Nathan Richardson as part of a larger project involving other RFF researchers, provides a snapshot of the course to GHG control taking into consideration the tools the EPA has at its disposal and its likely course to implementing them.

As Nathan has explained in greater detail here and here, the EPA is working on rules for its regulation of GHGs from mobile sources. Details of its mobile sources regulation are expected later this month. Following that course of action through the chart, you can see that the EPA is likely on course to regulate emissions from new or modified sources (i.e. a newly constructed power plant). Regulation of existing, unmodified emissions sources would be the next step, but there is much less certainty about what this regulation would look like.

The agency's next steps and how the process may be legislated, regulated and litigated were the topic of discussion at an RFF First Wedesday seminar today. As is clearlly illustrated with the variety of regulatory options in the chart, there is plenty of room for debate on the road to regulation. Video, audio and an event transcript from the event will be posted here as they become available and you can expect further insight and  more discussion of the role of the Clean Air Act in future Weathervane posts.

Tiffany Clements is managing editor of Weathervane.