ABSTRACT
The greatest challenge to sustainability is global climate change (GCC). Burning fossil fuels releases carbon dioxide (CO2), a known greenhouse gas, into the atmosphere. Business as usual models that assume no major changes in climate policies, and therefore continuing increases in atmospheric concentrations of greenhouse gases, project that global mean temperature will rise an additional 4°C. Since roughly the beginning of the Holocene epoch 10,000 years ago, Earth's climate has been hospitable and stable. The spread of agriculture initiated the Anthropocene period, defined as the time when humans have started to change the Earth on a global scale. Carbon dioxide in the atmosphere is only one part of the global carbon cycle. The carbon cycle is critical to understanding the greenhouse effect and global warming. The actual amounts of greenhouse gas emitted will depend on the future strength of the global economy and on the success of international climate mitigation agreements.
