ABSTRACT
Paleontological records indicate that fluctuations in the
concentration of natural “greenhouse” gases such as carbon
dioxide (CO
), methane (CH
) and nitrous oxide (N
O) have
been closely correlated with the repeated cycling of the
Earth’s glacial and interglacial periods (Petit et al. 1999;
Monmin et al. 2001, and others). Recent increases in the
concentration of greenhouse gases have been largely the
result of human activities such as the burning of fossil fuels,
agriculture, and changes in land use. Since the last industrial
revolution, for example, CO
concentrations in the atmos-
phere have increased by 31% (Hoyer et al. 2001).
