California Climate Change Glossary

Letter R

Radiation. Energy emitted in the form of electromagnetic waves. Radiation has differing characteristics depending upon the wavelength. Because the radiation from the Sun is relatively energetic, it has a short wavelength (ultra-violet, visible, and near infra-red) while energy re-radiated from the Earth's surface and the atmosphere has a longer wavelength (infra-red radiation) because the Earth is cooler than the Sun. (EPA)

Radiative Damping. An imposed positive radiative forcing (q.v.) on the Earth-atmosphere system (e.g., through the addition of greenhouse gases) that represents an energy surplus. The temperature of the surface and lower atmosphere will then increase and in turn increase the amount of infrared radiation being emitted into space, thus establishing a new energy balance. The amount that emissions of infrared radiation to space increases for a given increase in temperature is known as the rediative damping.(IPCC)

Radiative Forcing. A change in the balance between incoming solar radiation and outgoing infra-red radiation. Without any radiative forcing, solar radiation coming to the Earth would continue to be approximately equal to the infra-red radiation emitted from the Earth. The addition of greenhouse gases traps and increased fraction of the infra-red radiation, reradiating it back toward the surface and creating a warming influence (i.e., positive radiative forcing because incoming solar radiation will exceed outgoing infra-red radiation). (EPA)

Reforestation. The Revised 1996 IPCC Inventory Guidelines defines reforestation as the planting of forests on land which has historically contained forest but which has been used for another purpose since last being covered by forest. (Australia)

Regeneration. Renewal of forest or tree crop by natural or artificial means. (Australia)

Relative Seal Level. Sea level measured by a tide gauge with respect to the land upon which it is situated. (Lenn)

Reservoir. Component of the climate system other than the atmosphere that can store certain quantities of substances, such as greenhouse gases and precursors. Examples are oceans, soils, and forests. (Lenn)

Residence Time. The average time spent in a reservoir by an individual atom or molecule. Also, the age of a molecule when it leaves the reservoir. With respect to greenhouse gases, residence time usually refers to how long a particular molecule remains in the atmosphere. (EPA) Reservoir. A component or components of the climate system where a greenhouse gas or precursor of greenhouse gas are stored. (Australia)

Respiration. The process by which animals use up stored foods (by combustion with oxygen) to produce energy. (EPA)

Response Time. The time needed for the climate system or its components to re-equilibrate to a new state. (Lenn)