ABSTRACT
Detection and attribution studies make clear that the growth of energy use and food production during the twentieth century has vaulted human activities into the leading cause of recent changes in the global climate (IPCC 2007a). In addition, there is also suggestive evidence that changes in land cover and agricultural practices going back several thousand years altered the atmospheric concentrations of carbon dioxide (CO2) and methane (CH4), initiating continental to hemispheric-scale changes in climate well before the industrialization of society (Ruddiman 2001, 2007). The disturbing consequence of these findings is that continuing reliance on the present approaches for supplying energy and other commodities needed to sustain and enhance the standard of living and welfare of people around the world will cause even more significant changes in climate over coming centuries (IPCC 2007a). Indeed, substantial consequences are expected to result even if aggressive near-term efforts are made to limit emissions from combustion of coal, petroleum, and natural gas.
