Figure 1 (image) Kobe University Share Print E-Mail Caption Figure 1: Graph showing the atmospheric levels of Δ14C values. The concentration was elevated by the nuclear bomb tests of the 1950s and 1960s. Credit Kobe University Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.