ABSTRACT
This chapter provides some detailed explanations and examples to foster at least a partial appreciation for the role that proxies play in exploring the legacy of carbon dioxide. Economists use the consumer purchasing index as a proxy for inflation and the real value of wages. Proxies include such substances as dust, pollen, ash, soot, methane, and an extensive variety of chemicals as simple as elemental beryllium, or complex organic structures consisting of dozens of atoms. Sources of proxy materials include sea beds, lake sediments, tree rings, cave deposits, ice cores, and rock layers to cite some examples. Among the few difficulties encountered applying the borate proxy to expose atmospheric carbon dioxide information is the assumption that contributions to the isotope fractions from river runoffs have been constant. Calcite forms in soils, especially where evaporation of moisture exceeds the precipitation rate as is the situation in arid or less-than-humid regions.
