2018 Benjamin Franklin Medal in Earth and Environmental Science presented to Susan Trumbore, Ph.D.

Susan Trumbore is a biogeochemist who has pioneered the use of radiocarbon (C-14) as a tracer of flow of carbon in the global carbon cycle. The carbon cycle is a complex and dynamic system that involves the oceans, atmosphere, and biosphere, and global climate through the regulation of atmospheric carbon dioxide. Trumbore has developed insights into the "turnover times" of carbon in various terrestrial systems (particularly soils and forests) by measuring levels of C-14 derived from atmospheric nuclear weapons testing in the late 1950s and early 1960s. This input of "bomb-C-14" serves as a transient tracer that now is present, at different levels, in different components of the global carbon system. Susan Trumbore not only provided many of the initial insights into the use of this tracer but also developed the technology capable of these measurements and trained many others in its use.