ultraviolet (UV) radiation

Short-wavelength electromagnetic energy emitted by the Sun. (Chapter 2)

unconventional reserves

Deposits of oil or natural gas that cannot be recovered with traditional oil/gas wells but may be recoverable using alternate techniques. (Chapter 19)

uniform distribution

A population distribution in which individuals are spaced evenly, perhaps due to territorial behavior or mechanisms for suppressing the growth of nearby individuals. (Chapter 9)

United Nations Framework Convention on Climate Change (UNFCCC)

A 1992 international treaty that formally recognized climate change as an emerging problem and that precautions should be taken to prevent dangerous anthropogenic interference with Earth’s climate system. (Chapter 24)

urban areas

Densely populated regions that include cities and the suburbs that surround them. (Chapter 25)

urban flight

The process of people leaving an inner-city area to live in surrounding areas. (Chapter 25)

urban heat island effect

The phenomenon in which urban areas are warmer than the surrounding countryside due to pavement, dark surfaces, closed-in spaces, and high energy use. (Chapter 25)

urbanization

The migration of people to large cities; sometimes also defined as the growth of urban areas. (Chapter 25)

U.S. Nuclear Waste Policy Act (1982)

The federal law which mandated that the federal government build and operate a long-term repository for the disposal of high level radioactive waste. (Chapter 22)