INSTAAR graduate student Jocelyn Turnbull spent 8 weeks in Japan working on a carbon cycle research project with the greenhouse gas group at Tohoku University in Sendai (led by Dr. Takakiyo Nakazawa). She was chosen to participant in the National Science Foundation East Asia Pacific Summer Institutes (EAPSI) program for advanced graduate students. One goal of the program is for students to initiate personal relationships that will facilitate future international collaborations. Turnbull's summer project related to her PhD thesis on variations in 14C in carbon dioxide (14CO2) in the atmosphere. 14C is a nearly ideal tracer for fossil-fuel derived CO2 in the atmosphere because it has zero abundance due to radioactive decay. This is in strong contrast to high activity levels in the ambient atmosphere, biosphere, and upper ocean maintained by natural 14C production and (transiently) above-ground nuclear weapons testing. The stratosphere is a critical component of the global distribution of 14CO2 because it is the location where 14C is produced by interaction with cosmic rays. Turnbull's stratospheric measurements will help improve computer models that have been limited by sparse stratospheric data. The improved models will allow more accurate estimates of the human fossil fuel contribution.