Stable carbon isotope signatures in atmosphere and seawater as a basis for climate change studies

Carbon dioxide is the major anthropogenic greenhouse gas and its concentration in atmosphere has increased at a rate of (2.0 ± 0.1 ppm/yr) in the period 2002-2011. The ocean is a major sink of atmospheric CO2, absorbing about the 30 % of the emitted anthropogenic CO2 giving a contribution in the moderation of the climate change effects of these emissions. The accurate measurement of the stable carbon isotopes ratio ( 13 C/ 12 C), expressed as δ 13 C according to the convention of reporting stable isotope ratios in terms of a deviation from an international standard (δ-values), is a useful tracer of CO2 derived from fossil fuel and deforestation sources. In this paper, an overview of the importance of the measurement of δ 13 C both in atmosphere and in seawater, is given, with a particular focus on the use of these δ-values as isotopic signatures to support climate change studies. The importance of carrying out accurate and precise measurements and the need of reliable stable isotopes reference standards is also highlighted.