Counting carbon. (IMAGE) University of Tokyo Caption Carbon emissions from burning fossil fuels contains very little carbon-14 (14C) because it has decayed so much over time. This makes carbon-14 very useful for tracing carbon emissions from natural compared to human sources. Credit 2023, Ippei Maruyama Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. License CC BY-NC 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.