California Climate Change Glossary

Letter S

SBI. Subsidiary Body for Implementation. (IPCC)

Sea Level Alteration. A change in global average sea level brought about by volume changes in the world ocean. This may be caused by changes in water density or changes in the total mass of water. (Lenn)

Short Ton. Common measurement for a ton in the United States. A short ton is equal to 2,000 lbs or 0.907 metric tons. (EPA)

Sink. A reservoir that uptakes a pollutant from another part of its cycle. Soil and trees tend to act as natural sinks for carbon. (EPA)

Soil moisture. Water stored in or at the continental surface and available for evaporation. In IPCC 1990 a single store (or bucket) was commonly used in climate modes. Today's models which incorporate canopy and soil process view soil moisture as the amount held in excess of plant "wilting point." (IPCC)

Solar luminosity. A measure of the brightness of (i.e. the amount of solar radiation (q.v.) being emitted by the Sun. (IPCC)

Solar Radiation. Energy from the Sun. Also referred to as short-wave radiation. Of importance to the climate system, solar radiation includes ultra-violet radiation, visible radiation, and infra-red radiation. (EPA)

Source. Any process or activity which releases a greenhouse gas, an aerosol or a precursor of a greenhouse gas into the atmosphere. (Australia)

Spatial scales. Continental is 10 to 100 million square kilometers, Regional is 100,000 to 10 million square kilometers, and Local is less than 100,000 square kilometers. (IPCC)

Spin-up. A technique used to initialize an AOGCM. At present it is not possible to diagnose accurately the state of the coupled atmosphere-ocean system and therefore it is not possible to prescribe observed starting condit9ions for and experiment with an AOGCM. Instead, the atmosphere and ocean components of the model are run separately, forced with "observed" boundary conditions, followed perhaps by a further period of "spin-up" when the atmosphere and ocean are coupled together, until the AOGCM is near to a steady state. (IPCC) SBSTA Subsidiary Body on Scientific and Technological Advice established under the UNFCC. (IPCC)

Stabalization Triangle. Space in a graph depicting greenhouse gas emissions (tons per year) over the past century, between the trend line and the line representing stability at current levels. (Lenn)

Storyline. A qualitative description of a climate scenario based on extensive literature research and model results. This is often a quite simple description used to fill in policy makers on climate change developments. (Lenn)

Stratosphere. The part of the atmosphere directly above the troposphere. See Atmosphere.

Sulfate Aerosol. Particulate matter that consists of compounds of sulfur formed by the interaction of sulfur dioxide and sulfur trioxide with other compounds in the atmosphere. Sulfate aerosols are injected into the atmosphere from the combustion of fossil fuels and the eruption of volcanoes like Mt. Pinatubo. Recent theory suggests that sulfate aerosols maylower the earth's temperature by reflecting away solar radiation (negative radiative forcing). Global Climate Models which incorporate the effects of sulfate aerosols more accurately predict global temperature variations. (EPA)

Sulfur Dioxide (SO2). A compound composed of one sulfur and two oxygen molecules. Sulfur dioxide emitted into the atmosphere through natural and anthropogenic processes is changed in a complex series of chemical reactions in the atmosphere to sulfate aerosols. These aerosols result in negative radiative forcing (i.e., tending to cool the Earth's surface). (EPA)

Sulfur Hexafluoride (SF6). A very powerful greenhouse gas used primarily in electrical transmission and distribution systems. SF6 has a global warming potential of 24,900. (EPA)

Sustainable Development. Development that meets the needs of the present without compromising the ability of future generations to meet their own needs. (IPCC)

Sustainable Yield. In relation to wood products, the sustainable yield of a forest is the maximum level of harvest of commercial timber or project mix that can be maintained for a given area in perpetuity under a given management regime. The forested area must be sufficiently large to support a large number of stands at different stages in the projection cycle. The average yield over time must be equal to the average growth increment, in terms of product, of the area as a whole. (Australia)

System Vulnerability. The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. This is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity. (Lenn)