Page 30 - Alternative Energy Systems in Building Design

HUMAN INFLUENCES ON CLIMATE CHANGE 7

FOSSIL FUELS

Carbon dioxide variations over the last 400,000 years have shown a rise since the
industrial revolution. Beginning in the 1850s and accelerating ever since, the
human consumption of fossil fuels has elevated CO levels from a concentration
2
of 280 ppm to more than 380 ppm today. These increases have been projected to
reach more than 560 ppm before the end of the twenty-first century. It is known
that CO levels are substantially higher now than at any other time in the last
2
800,000 years. Along with rising levels of atmospheric pollutants, it is anticipated
that there will be an increase in global temperature by 1.4–5.6°F between 1990
and 2100 (Fig. 1.6).

MILLENNIAL PERSPECTIVE OF CARBON DIOXIDE
VARIATIONS
Organic materials such as plants (mainly formed from hydrocarbons and water molecules)
under certain conditions, such as natural disasters, fires, volcanic activity, tectonic plate
displacement, and extreme geoclimatic changes, lose significant amounts of their water
content and are left with solely carbon and mineral materials. It is because of the sun’s
energy that organic life, in accordance with certain chemical processes, is transformed
into various forms of hydrocarbon organic structures.

Figure 1.6 Projected changes in CO 2 and global temperature: summary of assumptions
in the IPCC 1992 alternative scenarios. Courtesy of United Nations Environmental Program/GRID-Arendal.