Isotopes infer past climatic

For more than 80 years, tree-ring data have been used to make inferences about past climatic variation. In general, the characteristic most often used has been the variations in widths of the annual growth rings. However, during the past decade other properties, such as cell density (measured by x-ray densiometric techniques), relative widths of early and late wood, and isotopic composition of the cellulose have been used to infer past environmental conditions. It is the isotopic composition that is of interest here. 

Buhay, W. M., 1997. Inferring precipitation isotopic compositions from lake sediment organics and pore water Workshop on water and climate studies in Canada using isotope tracers Past, present, future. University of Waterloo, Waterloo. 

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