Sustainable Construction, 5th Edition

Chapter 12Built Environment Carbon Footprint

The major environmental challenge facing humanity today is climate change, a manifestation of an imbalance in the global biogeochemical carbon cycle caused by human activities. The main cause of climate change is the dramatically increasing emissions of carbon gases, mainly carbon dioxide (CO₂), into the atmosphere from fossil fuel combustion by power plants, transportation, building energy systems, cement production, and agriculture. At the same time, Earth is losing its ability to stabilize CO₂ concentrations because biomass, such as forests, which absorb CO₂, are being lost to land development, deforestation, and mining. The combination of rapidly increasing emissions and decreasing absorption capacity is accelerating the atmospheric concentrations of CO₂, methane (CH₄), and other climate change gases that trap solar energy. And as their atmospheric concentrations rise, average global average atmospheric temperatures also increase. Prior to the start of the Industrial Age (about 1780), the natural balance of CO₂ emissions and absorption resulted in a relatively stable global temperature regime, and the effect of human activities on climate was small. Increasing population and energy consumption have upset this balance and consequently Earth's climate is not as stable and is noticeably changing.

CO₂ released from combustion processes in both fossil fuel electric power plants and automobiles is the main source of increasing CO