By Sid Perkins
Scientists have developed a way to use corn plants to monitor and map the human-generated emissions of carbon dioxide.
Only a small fraction of Earth’s atmosphere is carbon dioxide. In summer 2004, that share averaged about 378 parts per million (ppm), says James T. Randerson, a biogeochemist at the University of California, Irvine. Within that component, about one in a trillion of the carbon atoms is carbon-14 (C-14), a radioactive isotope produced by cosmic rays at high altitudes.