During
the past two centuries, human activities have undertaken a vast earth system
modification of the carbon (C) cycle. Early during this period, humans have
converted native vegetation to croplands. Such land use changes have mobilized
massive amounts of C. During the past century, increased use of fossil energy
sources, primarily coal and oil, have resulted in the rapid expansion of
industry and technology throughout the world.
The resulting impact has been to greatly increase the atmospheric
concentration of C dioxide (CO2) to where in 2004 it is estimated to
375ppm, nearly 100 pm greater than the pre-industrial levels. Fossil fuel
emissions and land use change have moved the global C cycle out of balance.
Author: P. Tschakert, M. Raupach, and D.S. Ojima (dennis at nrel dot colostate dot edu)
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