Stable isotope ratio mass spectrometry in global climate change research

Stable isotope ratios of the life science elements carbon, hydrogen, oxygen and nitrogen vary slightly, but significantly in major compartments of the earth. Owing mainly to antropogenic activities including land use change and fossil fuel burning, the C-13/C-12 ratio of CO2 in the atmosphere has changed over the last 200 years by 1.5 parts per thousand (from about 0.0111073 to 0.0110906). In between interglacial warm periods and glacial maxima, the 180/160 ratio of precipitation in Greenland has changed by as much as 5 parts per thousand (0.001935-0.001925). While seeming small, such changes are detectable reliably with specialised mass spectrometric techniques. The small changes reflect natural fractionation processes that have left their signature in natural archives. These enable us to investigate the climate of past times in order to understand how the Earth's climatic system works and how it can react to external forcing. In addition, studying contemporary isotopic change of natural compartments can help to identify sources and sinks for atmospheric trace gases provided the respective isotopic signatures are large enough for measurement and have not been obscured by unknown processes. This information is vital within the framework of the Kyoto process for controlling CO2 emissions. (C) 2003 Elsevier B.V. All rights reserved.