1. Duke University, Nicholas School of the Environment
and Center on Global Change, Durham, North Carolina 27708 United States
2. Stanford University, School of Earth Sciences, Stanford, California 94305 United States
3. Boston University, Department of Earth and Environment, 675 Commonwealth Avenue, Boston Massachusetts 02215 United States
4. Gas Safety, Inc., Southborough, Massachusetts 01772 United States
5. Duke University, Pratt School of Engineering, Durham, North Carolina 27708 United States