California Climate Change Glossary
Letter G
Gross Domestic Product (GDP). The value of all goods and services produced or consumed within a nation's borders. (IPCC)
General Circulation Model (GCM). A global, three-dimensional computer model of the climate system which can be used to simulate human-induced climate change. GCMs are highly complex and they represent the effects of such factors as reflective and absorptive properties of atmospheric water vapor, greenhouse gas concentrations, clouds, annual and daily solar heating, ocean temperatures and ice boundaries. The most recent GCMs include global representations of the atmosphere, oceans, and land surface. (EPA)
Geosphere. The soils, sediments, and rock layers of Earth's crust, both continental and beneath the ocean floors. (EPA)
Glacier. A huge mass of ice slowly flowing over a land mass, formed from compacted snow in an area where snow accumulation exceeds melting and sublimation. (Lenn)
Global Radiation Balance. A balance, which implies that globally the amount of incoming solar radiation must on average be equal to the sum of outgoing reflected solar radiation and outgoing infrared radiation emitted by the climate system. (Lenn)
Global Surface Temperature. The average of the sea temperature in the first few meters of the oceans and the temperature 1.5 m above ground on land surfaces. (Lenn)
Global Warming. An increase in the near surface temperature of the Earth. Global warming has occurred in the distant past as the result of natural influences, but the term is most often used to refer to the warming predicted to occur as a result of increased emissions of greenhouse gases. Scientists generally agree that the Earth's surface has warmed by about 1 degree Fahrenheit in the past 140 years. The Intergovernmental Panel on Climate Change (IPCC) recently concluded that increased concentrations of greenhouse gases are causing an increase in the Earth's surface temperature and that increased concentrations of sulfate aerosols have led to relative cooling in some regions, generally over and downwind of heavily industrialized areas. Also see Climate Change and Enhanced Greenhouse Effect. (EPA)
Global Warming Potential (GWP). The index used to translate the level of emissions of various gases into a common measure in order to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. GWPs are calculated as the ratio of the radiative forcing that would result from the emissions of one kilogram of a greenhouse gas to that from emission of one kilogram of carbon dioxide over a period of time (usually 100 years). Gases involved in complex atmospheric chemical processes have not been assigned GWPs due to complications that arise. Greenhouse gases are expressed in terms of Carbon Dioxide Equivalent. The International Panel on Climate Change (IPCC) has presented these GWPs and regularly updates them in new assessments.
Greenhouse Effect. The effect produced as greenhouse gases allow incoming solar radiation to pass through the Earth's atmosphere, but prevent most of the outgoing infra-red radiation from the surface and lower atmosphere from escaping into outer space. This process occurs naturally and has kept the Earth's temperature about 59 degrees F warmer than it would otherwise be. Current life on Earth could not be sustained without the natural greenhouse effect. (EPA)
Greenhouse Gas. Any gas that absorbs infra-red radiation in the atmosphere. Greenhouse gases include water vapor, carbon dioxide (CO
Gross Domestic Product (GDP). The value of all goods and services produced or consumed within a nation's borders. (Lenn)
Gross Promary Production (GPP). TThe amount of carbon fixed from the atmosphere through photosynthesis. (Lenn)