Environmental Engineering Reference
In-Depth Information
Source: Boden, T.A., G. Marland, and R.J. Andres. 2010. Global, Regional, and National Fossil-Fuel CO
2
Emissions. Carbon Diox-
ide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/
CDIAC/00001_V2010
The natural concentration of carbon dioxide in the Earth's atmosphere is constantly changing due to seasonal
variations. Plants take in carbon dioxide for photosynthesis and then release it during cellular respiration and
decomposition. The world's oceans absorb slightly more than they release. This natural waxing and waning of
carbon dioxide concentrations is known as the
carbon cycle.
However, humans have altered the carbon cycle
by contributing excess carbon dioxide from the burning of fossil fuels in power plants and for transportation,
excessive deforestation and through other carbon-dioxide-producing activities. Plants and the world's oceans
can absorb some of this excess, but the imbalance between emissions and absorption leads to a net increase in
atmospheric CO
2
over time. The amount of carbon dioxide in the atmosphere has increased almost 39 percent
since 1750, shortly before the beginning of the Industrial Revolution (see the following table).
