Climate Change Glossary
Word Definitions Related to
Climate Change and Global Warming
Habitat
Ha·bi·tat ['ha-b&-"tat]. The place or environment where a plant or animal naturally or normally lives and grows.
Half-life
Also referred to as decay constant. The term is used to quantify a first-order exponential decay process.
Halocarbons
Compounds containing either chlorine, bromine or fluorine and carbon. Such compounds can act as powerful greenhouse gases in the atmosphere. The chlorine and bromine containing halocarbons are also involved in the depletion of the ozone layer.
Heat Stress
Heat Stress ['hEt 'stres]. A variety of problems associated with very warm temperatures and high humidity. Heat exhaustion is a condition marked by weakness, nausea, dizziness, and profuse sweating that results from physical exertion in a hot environment. Heat stroke is a condition marked especially by cessation of sweating, extremely high body temperature, and collapse that results from prolonged exposure to high temperature.
Heating degree days
The integral over a day of the temperature below 18°C (e.g. a day with an average temperature of 16°C counts as 2 heating degree days). See also: Cooling degree days.
Helium – (He)
A light inert gas and the second most abundant element in the universe.
Heterotrophic respiration
The conversion of organic matter to CO2 by organisms other than plants.
Hydrocarbons
Substances containing only hydrogen and carbon. Fossil fuels are made up of hydrocarbons.
Hydrochlorofluorocarbons (HCFCs)
Compounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons (CFCs). They have been introduced as temporary replacements for CFCs and are also greenhouse gases. See ozone depleting substance.
Hydrofluorocarbons (HFCs)
Compounds containing only hydrogen, fluorine, and carbon atoms. They were introduced as alternatives to ozone depleting substances in serving many industrial, commercial, and personal needs. HFCs are emitted as by-products of industrial processes and are also used in manufacturing. They do not significantly deplete the stratospheric ozone layer, but they are powerful greenhouse gases with global warming potentials ranging from 140 (HFC-152a) to 11,700 (HFC-23).
Hydrogen – (H)
At standard temperature and pressure it is a colorless, odorless, nonmetallic, univalent, tasteless, highly flammable diatomic gas. Having been used as an ingredient in some rocket fuels for several decades, hydrogen, or more specifically H2, is now widely discussed in the context of energy. Hydrogen is not an energy source, since it is not an abundant natural resource and more energy is used to produce it than can be ultimately extracted from it.
Hydrologic Cycle
The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30 percent of the mid-latitudes' heat transport from the equatorial to polar regions.
Hydrosphere
The component of the climate system comprising liquid surface and subterranean water, such as: oceans, seas, rivers, fresh water lakes, underground water etc.
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