Global warming: A consequence of human activities rivaling earth's biogeochemical processes

The planet is growing warmer because of a massive disruption in global biogeochemical cycles. We are burning our reserves of fossil fuels, which formed over a period of 300 million years, in the blink of an eye in geologic time. One manifestation of our addiction to fossil fuels is a dramatic change in the composition of the atmosphere and its radiative properties. Evidence is discussed in this commentary that human-induced global warming has already occurred, that powerful inertia is in place to cause future warming, and that humans and ecosystems are currently being affected. Stabilizing the atmospheric concentration of carbon dioxide at 550 ppm within the next century will require a 70% cutback in emissions. Thus, a whole new system of powering our global economy is necessary.