The Sensitivity of Methane Emissions from Northern Freshwater Wetlands to Global Warming


Human activities are changing the chemical composition of the Earth’s atmosphere. Emissions of pollutant gases from the burning of fossil fuels, production and use of synthetic chemicals, and the conversion of natural environments to agricultural systems have increased the atmospheric concentrations of carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons to the highest levels known for at least 160,000 years of Earth history. Trapped ancient gases in ice cores, and direct monitoring of more recent changes in air chemistry, have convincingly documented the links between the growth of the human population, the evolution of industrial societies, and increasing concentrations of these gases (e.g., Rowland and Isaksen, 1988; Chappellaz et al., 1990; Lorius et al., 1990). One likely consequence of the increasing concentrations of atmospheric gases like carbon dioxide and methane is a change in global climate. These gases have long lifetimes in the atmosphere, and as they accumulate they trap, in the lower atmosphere, increasing amounts of energy emitted from the earth’s surface (Ramanathan et al., 1987). The current consensus among climate experts is that the increasing burden of atmospheric gases projected for the next century will result in a global climate warming of some 2–6°C (Dickinson, 1986; Levine, Chapter 1, this volume). A warming of this magnitude would be unprecedentedly rapid and extreme in the history of industrial society.

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