Solar Energy

The total solar energy incident on the surface of the earth averages about 86,000 terawatts (TW), which is more than 5,000 times the 15 TW of energy currently used by humans (of which roughly 12 TW now comes from fossil fuels) and more than 100 times larger than the energy potential of the next largest renewable source, wind energy (Hermann, 2006). Hence, the potential resource of solar energy is essentially limitless, which has led many to conclude that it is the best energy resource to rely...

Droughts and Floods Are Likely to Increase

Given the observed increases in heavy precipitation events and the expectation that this intensification will continue, the risk from floods is projected to increase in the future. Local water, land use, and flood risk-management decisions, however, can modify the actual flood vulnerability of communities. Drought is a complex environmental impact. It is strongly affected not only by the balance between precipitation and evapotranspiration (the sum of evaporation of water from the surface and...

Carbon Dioxide

The important role played by CO2 in the Earth's energy balance has been appreciated since the late 19th century, when Swedish scientist Svante Arrhenius first proposed a link between CO2 levels and temperature. At that time, humans were only beginning to burn fossil fuels which include coal, oil, and natural gas on a wide scale for energy. The combustion of these fuels, or any material of organic origin, yields mostly CO2 and water vapor, but also small amounts of other by-products, such as...