Contents taken from Glossary: Carbon Dioxide and Climate, 1990.
ORNL/CDIAC-39, Carbon Dioxide Information Analysis Center, Oak
Ridge National Laboratory, Oak Ridge, Tennessee. Edited by: Fred O'Hara Jr.
A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, U, V, W, Z
- ablation (glacial)
- All processes, which include melting, evaporation (sublimation), wind erosion,
and calving (breaking off of ice masses), that remove snow or ice from a glacier or
snowfield. The term also refers to the amount of snow or ice removed by these
- Shedding by a plant of its parts, such as leaves, flowers, fruits, or seeds. The
process is regulated by the plant hormone abscisic acid.
- absorption coefficient
- A measure of the amount of radiant energy, incident normal to a planar surface,
that is absorbed per unit distance or unit mass of a substance.
- acclimation (acclimatization)
- Change that occurs in an organism
to allow it to tolerate a new environment.
- accumulation (glacial)
- All processes, which include snowfall, condensation, avalanching, snow
transport by wind, and freezing of liquid water, that add snow or ice to a glacier,
floating ice, or snow cover. The term also includes the amount of snow or other solid
precipitation added to a glacier or snowfield by these processes.
- acidity profile
- The acid concentration in ice core layers as a function of depth as determined
from electrical measurements. The magnitudes of some volcanic eruptions in the
Northern Hemisphere have been estimated from the acidity of annual layers in ice
cores taken in Greenland. This methodology is sometimes referred to as acidity signal
or acidity record.
- The adjustment of an organism or population to a new or altered environment
through genetic changes brought about by natural selection.
- adiabatic process
- A thermodynamic change of state of a system such that no heat or mass is
transferred across the boundaries of the system. In an adiabatic process, expansion
always results in cooling, and compression in warming.
- adiabatic warming
- See adiabatic process.
- The predominately horizontal large-scale movement of air that causes changes
in temperature or other physical properties. In oceanography, advection is the
horizontal or vertical flow of sea water as a current.
- Particulate material, other than water or ice, in the atmosphere ranging in size
from approximately 10x-3 to larger than 10x2 īm in radius. Aerosols are important in
the atmosphere as nuclei for the condensation of water droplets and ice crystals, as
participants in various chemical cycles, and as absorbers and scatterers of solar
radiation, thereby influencing the radiation budget of the earth-atmosphere system,
which in turn influences the climate on the surface of the Earth.
- In meteorology, the process by which precipitation
particles grow larger by collision or contact with
cloud particles or other precipitation particles.
- Active volcano 10,380 ft (3,141 m) high in Bali, Indonesia. Last eruption was in
- airborne fraction
- The portion of CO2 released from all energy consumption and land use
activities that remains in the atmosphere as opposed to the amounts absorbed by
plants and oceans. How the world's total carbon is partitioned among the oceanic,
terrestrial, and atmospheric pools is determined by complex biogeochemical and
- airborne particulates
- Total suspended matter found in the atmosphere
as solid pieces or liquid droplets. Airborne particulates include windblown
dust, emissions from industrial processes, smoke from the burning of wood and coal,
and the exhaust of motor vehicles.
- A widespread body of in the atmosphere
that gains certain meteorological or polluted characteristics while set in
one location. The characteristics can change as it moves away.
- The fraction of the total solar radiation incident on a body that is reflected by
- An order of soils with a medium-to-high base supply, horizons of clay
accumulation, and gray-brown surface horizons.
- Simple rootless plants that grow in sunlit waters in relative proportion to the
amounts of nutrients available. They are
food for fish and small aquatic animals.
- algal blooms
- Sudden spurts of algal growth that can indicate potentially hazardous changes in
local water chemistry.
- A pressure- and temperature-independent property of seawater that determines
in part the carbon content of seawater. Carbonate alkalinity is the sum of the concen-
tration of bicarbonate plus two times the concentration of the carbonate ions. Total
alkalinity is the amount of acid required to bring seawater to a pH at which all dis-
solved inorganic carbon becomes freely exchangeable. The alkalinity of the oceans is
determined with potentiometric or normal titration techniques that detect and measure
the presence of bicarbonate, carbonate, and borate ions.
- altithermal period
- A period of high temperature, particularly the one from 8000 to 4000 B.P.
(before the present era), which was apparently warmer in summers, as compared with
the present, and with the precipitation zones shifted poleward. Also called the
- Fish that spend their adult lives in the sea but swim upriver to freshwater
spawning grounds to reproduce.
- analog (climate)
- A large-scale weather pattern of the
past that is similar to a current situation in its essential characteristics.
- Antarctic Ice Sheet
- See ice sheet.
- Man made. Usually used in the context of
emissions that are produced as the result of human activities.
- anticyclone (high-pressure area)
- An atmospheric high-pressure closed circulation with clockwise rotation in the
Northern Hemisphere, counterclockwise in the Southern Hemisphere, and undefined
at the Equator.
- A mineral species of calcium carbonate (CaCO3) with a crystal structure
different from that of vaterite and calcite, which are the other two forms of CaCO3. It
is precipitated from ocean surface waters mainly by organisms (e.g., coral) that use it
to make their shells and skeletons.
- Arctic haze
- A persistent winter diffuse layer in the Arctic atmosphere whose origin may be
related to long-range transport of midlatitude continental man-made pollutants.
- atmosphere (An)
- A standard unit of pressure representing the pressure exerted by a 29.92-in.
column of mercury at sea level at 45 degrees latitude and equal to 1000 g/cm2.
- atmosphere (The)
- The envelope of air surrounding the Earth and bound to it by the Earth's
gravitational attraction. Studies of the chemical properties, dynamic motions, and
physical processes of this system constitute the field of meteorology.
- atmospheric turbulence
- A state of the flow of air in which apparently random irregularities occur in the
air's instantaneous velocities, often producing major deformations of the flow.
- atmospheric window
- The spectral region between 8.5 and 11.0 microns where the atmosphere is
essentially transparent to longwave radiation.
- An organism that produces food from inorganic substances.
- baroclinic model
- A model of atmospheric circulation that, in contrast with barotropic models,
does not constrain constant-pressure surfaces to coincide with constant-density
- basal sliding (basal slip)
- The movement or speed of movement of a glacier on its bed.
- The science of measuring ocean depths to determine the topography of the sea
- benthic organism (benthos)
- A form of aquatic plant or animal life that is found on or near the bottom of a
stream, lake, or ocean.
- benthic region
- The bottom layer of a body of water.
- biogeochemical cycle
- The chemical interactions among the atmosphere, biosphere, hydrosphere, and
- biological productivity
- The amount of organic matter, carbon, or energy content that is accumulated
during a given time period.
- The total dry organic matter or stored energy content of living organisms that is
present at a specific time in a defined unit (community, ecosystem, crop, etc.) of the
- The portion of Earth and its atmosphere
that can support life. The part (reservoir) of the global carbon cycle that includes living
organisms (plants and animals) and life- derived organic matter (litter, detritus). The
terrestrial biosphere includes the living biota (plants and animals) and the litter and
soil organic matter on land, and the marine biosphere includes the biota and detritus
in the oceans.
- The animal and plant (fauna and flora) life of a given area.
- Dark, naturally occurring solid or semisolid substances composed mainly of a
mixture of hydrocarbons with little oxygen, nitrogen, or sulfur.
- buffer factor (Revelle factor)
- The ratio of the instantaneous fractional change in the partial pressure of CO2
(pCO2) exerted by seawater to the fractional change in total CO2 dissolved in the
ocean waters. The buffer factor relates the partial pressure of CO2 in the ocean to the
total ocean CO2 concentration at constant temperature, alkalinity and salinity. The
Revelle factor is a useful parameter for examining the distribution of CO2 between
the atmosphere and the ocean, and measures in part the amount of CO2 that can be
dissolved in the mixed surface layer.
- C3 plants
- Plants (e.g., soybean, wheat, and cotton) whose carbon- fixation products have
three carbon atoms per molecule. Compared with C4 plants, C3 plants show a greater
increase in photosynthesis with a doubling of CO2 concentration and less decrease in
stomatal conductance, which results in an increase in leaf-level water-use efficiency.
- C4 plants
- Plants (e.g., maize and sorghum) whose carbon fixation products have four
carbon atoms per molecule. Compared with C3 plants, C4 plants show little
photosynthetic response to increased CO2 concentrations above 340 ppm but show a
decrease in stomatal conductance, which results in an increase in photosynthetic
- A surficial gravel and sand conglomerate cemented by calcium carbonate.
- Also called hardpan; an opaque, reddish-brown-to-white calcareous material,
which occurs in layers near the surface of stony soils in arid and semiarid areas.
- Calvin cycle
- The incorporation of CO2 into glucose by enzymatic reactions.
- CAM plants (crassulacean acid metabolism)
- Plants (e.g, cactus and other succulents) that, unlike the C3 and C4 plants,
temporarily separate the processes of carbon dioxide uptake and fixation when grown
under arid conditions. They take up gaseous carbon dioxide at night when the stomata
are open and water loss is minimal. During the day when the stomata are closed, the
stored CO2 is released and chemically processed. When CAM plants are not under
water stress, they then follow C3 photosynthesis.
- The branches and leaves of woody plants that are formed some distance above
- carbon-based resources
- The recoverable fossil fuel (coal, gas, crude oils, oil shale, and tar sands) and
biomass that can be used in fuel production and consumption.
- carbon budget
- The balance of the exchanges (incomes and losses) of carbon between the
carbon reservoirs or between one specific loop (e.g., atmosphere - biosphere) of the
carbon cycle. An examination of the carbon budget of a pool or reservoir can provide
information about whether the pool or reservoir is functioning as a source or sink for
- carbon cycle
- All parts (reservoirs) and fluxes of carbon; usually thought of as a series of the
four main reservoirs of carbon interconnected by pathways of exchange. The four
reservoirs, regions of the Earth in which carbon behaves in a systematic manner, are
the atmosphere, terrestrial biosphere (usually includes fresh water systems), oceans,
and sediments (includes fossil fuels). Each of these global reservoirs may be
subdivided into smaller pools ranging in size from individual communities or
ecosystems to the total of all living organisms (biota). Carbon exchanges from
reservoir to reservoir by various chemical, physical, geological, and biological
- carbon density
- The amount of carbon per unit area for a given ecosystem or vegetation type,
based on climatic conditions, topography, vegetative-cover type and amount, soils,
and maturity of the vegetative stands.
- carbon dioxide fertilization
- Enhancement of plant growth or of the net primary production by CO2
enrichment that could occur in natural or agricultural systems as a result of an
increase in the atmospheric concentration of CO2.
- carbon dioxide reference gas
- A mixture of a known quantity of CO2-in air or CO2-in-N2 used to calibrate
carbon dioxide analyzers.
- carbon flux
- The rate of exchange of carbon between pools (reservoirs).
- carbon isotope ratio
- Ratio of carbon-12 to either of the other, less common, carbon isotopes, carbon-
13 or carbon-14.
- carbon pool
- The reservoir containing carbon as a principal element in the geochemical cycle.
- carbon sink
- A pool (reservoir) that absorbs or takes up released carbon from another part of
the carbon cycle. For example, if the net exchange between the biosphere and the
atmosphere is toward the atmosphere, the biosphere is the source, and the atmosphere
is the sink.
- carbon source
- A pool (reservoir) that releases carbon to another part of the carbon cycle.
- Fish that swim downstream to spawn.
- Chernozem (Tchernozem)
- A major group of dark-colored zonal soils with a rich and deep humus horizon
occurring in temperate-to-cool, subhumid climates.
- A family of inert nontoxic and easily liquified chemicals used in refrigeration,
air conditioning, packaging, and insulation or as solvents or aerosol propellants.
Because they are not destroyed in the lower atmosphere, they drift into the upper
atmosphere where their chlorine components destroy
- An organelle in the cells of green plants. It contains chlorophyll and functions in
photosynthesis and protein synthesis.
- clear cutting
- A forest-management technique that involves harvesting all the trees in one area
at one time.
- The statistical collection and representation of the weather conditions for a
specified area during a specified time interval, usually decades, together with a
description of the state of the external system or boundary conditions. The properties
that characterize the climate are thermal (temperatures of the surface air, water, land,
and ice), kinetic (wind and ocean currents, together with associated vertical motions
and the motions of air masses, aqueous
humidity, cloudiness and cloud water content,
groundwater, lake lands, and water content of snow on land and sea ice),
nd static (pressure and density of the atmosphere and ocean, composition of the dry
ir, salinity of the oceans, and the geometric boundaries and physical constants of the
system). These properties are interconnected by the various physical processes such
as precipitation, evaporation, infrared radiation, convection, advection, and
- climate change
- The long-term fluctuations in temperature, precipitation, wind, and all other
aspects of the Earth's climate. External processes, such as solar-irradiance variations,
variations of the Earth's orbital parameters (eccentricity, precession, and inclination),
lithosphere motions, and volcanic activity, are factors in climatic variation. Internal
variations of the climate system also produce fluctuations of sufficient magnitude and
variability to explain observed climate change through the feedback processes
interrelating the components of the climate system.
- climate sensitivity
- The magnitude of a climatic response to a perturbing influence. In mathematical
modeling of the climate, the difference between simulations as a function of change
in a given parameter.
- climate signal
- A statistically significant difference between the control and disturbed (see
climate sensitivity) simulations of a climate
- climate system
- The five physical components (atmosphere, hydrosphere, cryosphere,
lithosphere, and biosphere) that are responsible for the climate and its variations.
- climate variation
- The change in one or more climatic variables over a specified time.
- climatic analog
- A past climate situation in which changes similar to the present occurred. Used
in making climatic projections.
- climatic anomaly
- The deviation of a particular climatic variable from the mean or normal over a
- climatic optimum
- The period in history from about 5000 to about 2500 B.C. during which surface
air temperatures were warmer than at present in nearly all regions of the world. In the
Arctic region, the temperature rose many degrees, and in temperate regions, the
increase was 1.0 degrees - 1.7 degrees C. In this period, glaciers and ice sheets
receded greatly, and the melt-water raised sea level by about 3 meters.
- A visible mass of condensed water vapor particles or ice suspended above the
Earth's surface. Clouds may be classified on their visible appearance, height, or
- cloud albedo
- Reflectivity that varies from less than 10 to more than 90% of the insolation and
depends on drop sizes, liquid water content, water vapor content, thickness of the
cloud, and the sun's zenith angle. The smaller the drops and the greater the liquid
water content, the greater the cloud albedo, if all other factors are the same.
- cloud feedback
- The coupling between cloudiness and surface air temperature in which a change
in surface temperature could lead to a change in clouds, which could then amplify or
diminish the initial temperature perturbation. For example, an increase in surface air
temperature could increase the evaporation; this in turn might increase the extent of
cloud cover. Increased cloud cover would reduce the solar radiation reaching the
Earth's surface, thereby lowering the surface temperature. This is an example of
negative feedback and does not include the effects of
longwave radiation or the advection in the oceans and the atmosphere,
which must also be considered in the overall relationship of the climate system.
- coastal zone
- Lands and waters adjacent to the coast that exert an influence on the uses of the
sea and its ecology or whose uses and ecology are affected by the sea.
- The natural biological decomposition
of organic material in the presence of air to form a
- continental crust
- The layer of the Earth that lies under continents and the continental shelves. It ranges in thickness from 35 to
60 km. Its upper layer has a density of 2.7 g/cm3 and is composed of rocks that are rich
in silica and alumina.
- continental plate
- A thick continental crust.
- continental shelves
- Those parts of the continent that are covered by water. They are several to more
than 322 km wide and about 122 m deep. At the edges of the shelves, the continental slopes drop rapidly from 100 to 200 m to
3000 to 3700 m.
- continental slopes
- See continental shelves.
- Atmospheric or oceanic motions that are predominately vertical and that result
in vertical transport and mixing of atmospheric or oceanic properties. Because the
most striking meteorological features result if atmospheric convective motion occurs
in conjunction with the rising current of air (i.e., updrafts), convection is sometimes
used to imply only upward vertical motion.
- convective adjustment
- A numerical procedure applied in many atmospheric models to approximate the
vertical nonradiative heat transport. This procedure adjusts the lapse rate whenever
necessary so that some prescribed critical lapse rate is never exceeded.
- The quasi-horizontal flow of a fluid toward a common destination from
different directions. When waters of different origins come together at a point or
along a line (convergence line), the denser water from one side sinks under the lighter
water from other side. The ocean convergence lines are the polar, subtropical,
tropical, and equatorial. Also see divergence.
- Coriolis effect
- The tendency for an object moving above the Earth to turn to the right in the
Northern Hemisphere and to the left in the Southern Hemisphere relative to the
Earth's surface. The effect arises because the Earth rotates and is not, therefore, an
inertial reference frame.
- A leaf or leaves of the embryos of seed plants. They can function in food
storage and can become photosynthetic when the seed germinates.
- crop water-use efficiency
- A measure at the ecosystem level of how well plants use available water in
growth. The grams of dry weight gained by plants during the growing season per unit
land area are divided by the millimeters of water lost (including evaporation directly
from the soil).
- The portion of the climate system consisting of the world's ice masses and snow
deposits, which includes the continental ice sheets, mountain glaciers, sea ice, surface
snow cover, and lake and river ice. Changes in snow cover on the land surfaces are
by and large seasonal and closely tied to the mechanics of atmospheric circulation.
The glaciers and ice sheets are closely related to the global hydrologic cycle and to
variations of sea level and change in volume and extent over periods ranging from
hundreds to millions of years.
- Heterotrophic organisms that break down dead protoplasm and use some of the
products and release others for use by consumer organisms.
- The breakdown of matter by bacteria and fungi. It changes the chemical makeup
and physical appearance of materials.
- deep water
- That part of the ocean below the main thermocline.
- The removal of forest stands by cutting and burning to provide land for
agricultural purposes, residential or industrial building sites, roads, etc. or by
harvesting the trees for building materials or fuel. Oxidation of organic matter
releases CO2 to the atmosphere, and regional and global impacts may result.
- The dating of past events and variations in the environment and the climate by
studying the annual growth rings of trees. The approximate age of a temperate forest
tree can be determined by counting the annual growth rings in the lower part of the
trunk. The width of these annual rings is indicative of the climatic conditions during
the period of growth; wide annual rings signify favorable growing conditions,
absence of diseases and pests, and favorable climatic conditions, while narrow rings
indicate unfavorable growing conditions or climate.
- The use of tree growth rings as proxy climate indicators. Tree rings record
responses to a wider range of climatic variables over a larger part of the Earth than
any other type of annually dated proxy record.
- The progressive destruction or degradation of vegetative cover especially in arid
or semiarid regions bordering existing deserts. Overgrazing of rangelands, large-scale
cutting of forests and woodlands, drought, and burning of extensive areas all serve to
destroy or degrade the land cover. The climatic impacts of this destruction include
increased albedo leading to decreased precipitation, which in turn leads to less
vegetative cover; increased atmospheric dust loading could lead to decreased
monsoon rainfall and greater wind erosion and/or atmospheric pollution.
- The process by which single cells grow into particular forms of specialized
tissue (e.g., root, stem, or leaf).
- A horizontal flow of water, in different directions, from a common center or
zone; it is often associated with upwelling.
Also see convergence.
- The process of accumulation and sinking of warm surface waters along a
coastline. A change of air flow of the atmosphere can result in the sinking or
downwelling of warm surface water. The resulting reduced nutrient supply near the
surface affects the ocean productivity and meteorological conditions of the coastal
regions in the downwelling area.
- dust veil index
- A quantitative method developed by H. H. Lamb for comparing the magnitude
of volcanic eruptions. The formulae use observations either of the depletion of the
solar beam, temperature lowering in middle latitudes, or the quantity of solid matter
dispersed as dust. The reference dust veil index is 1000, assigned to the Krakatoa
1883 eruption, and the index is calculated using all three methods, where the
information is available, for statistical comparison purposes. Abbreviated D.V.I.
- The interacting system of a biological community and its nonliving
- A circular movement of water or air that is formed where currents pass
obstructions or between two adjacent currents that are flowing counter to each
- El Chicon
- Active volcano 7300 ft (2225 m) high in Mexico. The last eruption was in
- El Nino
- An irregular variation of ocean current that from January to March flows off the
west coast of South America, carrying warm, low-salinity, nutrient-poor water to the
south. It does not usually extend farther than a few degrees south of the equator, but
occasionally it does penetrate beyond 12 degrees S, displacing the relatively cold Peru
Current. The effects of this phenomenon are generally short-lived, and fishing is only
slightly disrupted. Occasionally (in 1891, 1925, 1941, 1957 - 58, 1965, 1972 - 73,
1976, and 1982 - 83), the effects are major and prolonged. Under these conditions,
sea surface temperatures rise along the coast of Peru and in the equatorial eastern
Pacific Ocean and may remain high for more than a year, having disastrous effects on
marine life and fishing. Excessive rainfall and flooding occur in the normally dry
coastal area of western tropical South America during these events. Some
oceanographers and meteorologists consider only the major, prolonged events as El
Nino phenomena rather than the annually occurring weaker and short-lived ones. The
name was originally applied to the latter events because of their occurrence at
- Materials (gases, particles, vapors, chemical compounds, etc.) that come out of
smokestacks, chimneys, and tailpipes.
- The ratio of the radiation emitted by a surface to that emitted by a black body at
the same temperature.
- energy balance models
- An analytical technique to study the solar radiation incident on the Earth in
which explicit calculations of atmospheric motions are omitted. In the zero-
dimensional models, only the incoming and outgoing radiation is considered. The
outgoing infrared radiation is a linear
function of global mean surface air temperature, and the reflected solar radiation is
dependent on the surface albedo. The albedo is a step function of the global meansurface
air temperatures, and equilibrium temperatures are computed for a range of values of
the solar constant. The one-dimensional models have surface air temperature as a
function of latitude. At each latitude, a balance between incoming and outgoing
radiation and horizontal transport of heat is computed. (Abbreviated as EBM.)
- The sum of all external conditions affecting the life, development, and survival
of an organism.
- The study of diseases as they affect populations, including the distribution of
disease or other health-related states and events in human populations, the factors
(e.g., age, sex, occupation, and economic status) that influence this distribution, and
the application of this study to control health problems.
- equilibrium line
- The level on a glacier where accumulation equals ablation and the net balance
- Regions of interaction between rivers and near-shore ocean waters, where tidal
action and river flow create a mixing of fresh and salt water.
- euphotic zone
- The layer of a body of water that receives sufficient sunlight for photosynthesis.
The depth of this layer, which is about 80 m, is determined by the water's extinction
coefficient, the cloudiness, and the sunlight's angle of incidence.
- Discharge of water from the Earth's surface to the atmosphere by evaporation
from bodies of water, or other surfaces, and by transpiration from plants.
- feedback mechanisms
- A sequence of interactions in which the final interaction influences the original
one. Also see positive feedback and
- A type of wetland that accumulates
peat deposits; they are less acidic than bogs, deriving most of their water from
groundwater rich in calcium and magnesium.
- Material that is transitional between snow and glacier ice. It is formed from
snow after passing through one summer melt season and becomes glacier ice after its
permeability to liquid water falls to zero.
- first detection
- Identification of a precursor signal, detectable above the noise of natural
climatic variability, of a significant change in a climate parameter and attribution of
this change to an increase in atmospheric carbon dioxide concentration. The signal
may be estimated by numeric modeling of the climate, and the noise can be estimated
using instrumental data. For any modeled signal that is estimated, the corresponding
noise can be estimated from observational data, and a signal-to-noise ratio can be
calculated to provide a quantitative measure of detectability.
- The burning of waste gases through a flare stack or other device before releasing
them to the air.
- flow law
- In glaciology, a constitutive relation for the analysis of three-dimensional
deformation states of ice subjected to stress.
- Liquid particles less than 40 microns in diameter that are formed by
condensation of vapor in air.
- food chain
- A sequence of organisms, each of which uses the next lower member of the
sequence as a food source.
- fossil fuel
- Any hydrocarbon deposit that can be burned for heat or power, such as
petroleum, coal, and natural gas.
- Molds, mildews, yeasts, mushrooms, and puffballs, a group of organisms that
lack chlorophyll and therefore are not photosynthetic. They are usually nonmobile,
filamentous, and multicellular.
- general circulation models
- Hydrodynamic models of the atmosphere on a grid or spectral resolution that
determine the surface pressure and the vertical distributions of velocity, temperature,
density, and water vapor as functions of time from the mass conservation and
hydrostatic laws, the first law of thermodynamics, Newton's second law of motion,
the equation of state, and the conservation law for water vapor. Abbreviated as GCM.
Atmospheric general circulation models are abbreviated AGCM, while oceanic
general circulation models are abbreviated OGCM.
- The study of present-day landforms, including their classification, description,
nature, origin, development, and relationships to underlying structures. Also the his-
tory of geologic changes as recorded by these surface features. The term is sometimes
restricted to features produced only by erosion and deposition.
- The solid mass (lithosphere) of the Earth as distinct from the atmosphere and
hydrosphere or all three of these layers combined.
- geostrophic flow
- A type of movement where the Coriolis force balances exactly the horizontal
- glacial maximum
- The position or time of the greatest advance of a glacier (e.g., the greatest
equatorward advance of Pleistocene glaciation).
- glacial rebound
- The isostatic adjustment of previously glaciated areas after glacial retreat (e.g.,
the uplift of Scandinavia after the most recent glaciation).
- A mass of land ice that is formed by the cumulative recrystallization of firn. A
glacier flows slowly (at present or in the past) from an accumulation area to an
ablation area. Some well-known glaciers are: the Zermatt, Stechelberg, Grindelwald,
Trient, Les Diablerets, and Rhone in Switzerland; the Nigards, Gaupne, Fanarak,
Lom, and Bover in Norway; the Wright, Taylor, and Wilson Piedmont glaciers in
Antarctica; the Bossons Glacier in France; the Emmons and Nisqually glaciers on Mt.
Ranier, Washington; Grinnell glacier in Glacier National Park, Montana; the
Dinwoody glacier in the Wind River Mountains and the Teton glacier in Teton
National Park, both in Wyoming; and many glaciers in the Canadian Rockies.
- glacier flow (ice flow).
- The slow downward or outward movement of ice in a glacier caused by
- greenhouse effect
- A popular term used to describe the roles of water vapor, carbon dioxide, and
other trace gases in keeping the Earth's surface warmer than it would be otherwise.
These " radiatively active "
gases are relatively transparent to incoming
shortwave radiation, but are relatively opaque to outgoing longwave radiation. The latter radiation, which
would otherwise escape to space, is trapped by these gases within the lower levels
of the atmosphere. The subsequent reradiation of some of the energy back to the
surface maintains surface temperatures higher than they would be if the gases were
absent. There is concern that increasing concentrations of greenhouse gases,
including carbon dioxide, methane, and manmade chlorofluorocarbons, may
enhance the greenhouse effect and cause global warming.
- greenhouse gases
- Those gases, such as water vapor, carbon dioxide, tropospheric ozone, nitrous
oxide, and methane, that are transparent to solar radiation but opaque to longwave radiation. Their action is similar to that
of glass in a greenhouse. Also see greenhouse effect
and trace gas.
- Greenland Ice Sheet
- See ice sheet.
- A soil horizon, which is frequently marked by a bed of clay, that results from a
temporary halt in the accumulation of vegetal material.
- gross primary production
- The total amount or weight of organic matter created by photosynthesis over a
defined time period (total product of photosynthesis). Abbreviated GPP.
- ground cover
- Plants grown to keep soil from eroding.
- grounding line
- The boundary between the area where an ice shelf or a glacier is floating on
water and where it is in contact with the shore or underlying earth (grounded).
- The supply of fresh water found beneath the surface of the Earth (usually in
aquifers) that often supplies wells and springs.
- growth water-use efficiency
- A measure at the individual plant level of how well plants use available water in
growth. The units of dry matter synthesized are divided by the units of water lost.
- Gulf Stream meander
- A transient winding bend in the Gulf Stream. These bends intensify as the Gulf
Stream merges into the North Atlantic and can break up into detached eddies at about
40 degrees S.
- Major circular flow patterns in the oceans. The wind- driven eastward- and
westward-flowing equatorial currents are blocked by the continents and rotate slowly
in a clockwise direction in the North Atlantic and Pacific Oceans and in a counter-
clockwise direction in the South Atlantic, South Pacific, and Indian Oceans.
- Hadley cell
- A direct thermally-driven and zonally symmetric large- scale atmospheric
circulation first proposed by George Hadley in 1735 as an explanation for the trade
winds. It carries momentum, sensible heat, and potential heat from the tropics to the
mid-latitudes (30 degrees). The poleward transport aloft is complemented by
subsidence in the subtropical high pressure ridge and a surface return flow. The
variability of this cell and the Walker cell
is hypothesized to be a major factor in short-term climatic change.
- In the oceans, a well-defined vertical gradient of salinity.
- heat flux (thermal flux)
- The amount of heat that is transferred across a surface of unit area in a unit of
- heat island effect
- A dome of elevated temperatures over an urban area caused by the heat
absorbed by structures and pavement.
- An animal that feeds on plants.
- Organisms that break down and use organic matter.
- Wet organic soils, such as peats and mucks.
- Holdridge life zone
- A climate category defined by three weighted climatic indexes, namely, mean
annual heat, precipitation, and atmospheric moisture.
- The most recent epoch of the Quaternary period
, covering approximately the last 10,000 years.
- Decomposed organic material.
- hydrologic budget
- A quantitative accounting of all water volumes and their changes with time for a
basin or area.
- 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
- The science dealing with the properties, distribution, and circulation of
- The aqueous envelope of the Earth, including the oceans, freshwater lakes,
rivers, saline lakes and inland seas, soil moisture and vadose water, groundwaters,
and atmospheric vapor.
- hydrostatic equation
- In the vector equation of motion, the form assumed by the vertical component
when all Coriolis, earth-curvature, frictional, and vertical-acceleration terms are con-
sidered negligible compared with those involving the vertical pressure force and the
force of gravity. The error in applying the hydrostatic equation to the atmosphere for
cyclonic-scale motions is less than 0.01%. In extreme situations, the strong vertical
accelerations in thunderstorms and mountain waves can be 1% of gravity.
- hypsithermal period
- The period about 4000 to 8000 years ago when the Earth was apparently several
degrees warmer than it is now. More rainfall occurred in most of the subtropical
desert regions and less in the central midwest United States and Scandinavia. It is
also called the altithermal period and can serve as a past climate analog for predicting
the regional pattern of climate change should the mean Earth surface temperature
increase from an increase in atmospheric carbon dioxide concentration.
- ice age
- A glacial epoch or time of extensive glacial activity. Also, as Ice Age, which
refers to the latest glacial epoch, the Pleistocene
- ice and snow albedo
- The reflectivity of ice and snow-covered surfaces. The albedo of freshly fallen
snow may be as much as 90%, while older snow may have values of 75% or less. The
larger the areal extent of snow and ice cover, the higher the albedo value. The surface
albedo will also increase as a function of the depth of snow cover up to 13 cm and be
unaffected by increased snow cover after reaching that depth.
- ice and snow-albedo-temperature feedback
- Interactions that can be described as a theoretical concept of a feedback
mechanism in which the interacting elements are the areal extent of polar ice and
snow cover, the albedo of the polar region (dependent on areal extent of ice and
snow), absorption of solar radiation (dependent on the albedo), temperature
(dependent on the absorption of solar radiation) and the area of ice and snow cover
(dependent on temperature). Less snowfall would mean more absorption of solar
radiation, therefore a surface warming would occur. Climate modeling studies
indicate an amplification effect (i.e., positive
feedback) of the ice and snow-albedo feedback on increased surface air
temperatures caused by increases in the atmospheric concentration of carbon dioxide.
- ice cover
- During the present time, the extent, especially the thickness, of glacier ice on a
land surface. Also the same as ice concentration, which is the ratio of an area of sea
ice to the total area of sea surface within some large geographic area.
- ice flow
- See glacier flow.
- ice front
- The floating vertical cliff that forms the seaward face or edge of a glacier or an ice shelf
that enters water. It can vary from 2 to 50 m in height.
- ice sheet (continental glacier)
- A glacier of considerable thickness
and more than 50,000 sq km in area. It forms a continuous cover of ice and snow over
a land surface. An ice sheet is not confined by the underlying topography but spreads
outward in all directions. During the Pleistocene
Epoch, ice sheets covered large parts of North America and northern Europe but they
are now confined to polar regions (e.g., Greenland and Antarctica).
- ice shelf
- A sheet of very thick ice with a level or gently undulating surface. It is attached
to the land on one side, but most of it is floating. On the seaward side, it is bounded
by a steep cliff (ice front) 2 to 50 m or more
above sea level. Ice shelves have formed along polar coasts (e.g., Antarctica and
Greenland); they are very wide with some extending several hundreds of kilometers
toward the sea from the coastline. They increase in size from annual snow
accumulation and seaward extension of land glaciers.
They decrease in size from warming, melting, and calving.
- infiltration (soil)
- Movement of water from the ground surface into the soil.
- infrared radiation
- Electromagnetic radiation lying in the wavelength interval from 0.7 micrometers
to 1000 micrometersm. Its lower limit is bounded by visible radiation, and its upper limit
by microwave radiation. Most of the energy emitted by the Earth and its atmosphere is at
infrared wavelength. Infrared radiation is generated almost entirely by large-scale intra-
molecular processes. The tri-atomic gases, such as water vapor, carbon dioxide, and
ozone, absorb infrared radiation and play important roles in the propagation of infra-
red radiation in the atmosphere. Abbreviated IR; also called "longwave radiation".
- The solar radiation incident on a unit horizontal surface at the top of the
atmosphere. It is sometimes referred to as solar irradiance. The latitudinal variation
of insolation supplies the energy for the general circulation of the atmosphere.
Insolation depends on the angle of incidence of the solar beam and on the solar constant.
- instantaneous transpiration efficiency
- A measure at the physiologic level of how well plants use available water in
photosynthesis. The assimilation rate is
divided by the transpiration rate; the moles of CO2 taken up are divided by the moles
of water lost through transpiration in a
unit of time.
- An anomaly in the normal positive lapse rate;
usually refers to a thermal inversion, in which temperature increases rather
than decreases with height.
- The total radiant flux received on a unit area of a given real or imaginary
surface. Also called the radiant flux density.
- A line on a chart that connects all points of equal or constant density.
- isostatic adjustment (isostatic compensation)
- The process whereby lateral transport at the Earth's surface from erosion or
deposition is compensated for by movements in a subcrustal layer to maintain
equilibrium among units of varying masses and densities.
- A line on a chart that connects all points of equal or constant temperature.
- One of two or more atoms that have the same atomic number (i.e., the same
number of protons in their nuclei) but have different mass numbers.
- Krakatoa (Krakatau)
- Active volcano 2667 ft (813 m) high in West Indonesia. It forms an island
between Java and Sumatra. Its eruption in 1883, which was one of the most violent in
modern times, scattered debris and darkened skies over vast areas. Additional
eruptions occurred in late 1927 and in the l960s.
- lapse rate
- The rapidity with which temperature decreases with altitude. The normal lapse
rate is defined to be 3.6 degrees F per 1000 feet change in altitude. The dry adiabatic
lapse rate is about 5.5 degrees F per 1000 feet, and the wet adiabatic lapse rate varies
between 2 and 5 degrees F per 1000 feet.
- latent heat
- Energy transferred from the earth's surface to the atmosphere through the
evaporation and condensation processes.
- Le Chatelier's principle
- When an external force is applied to an equilibrium system, the system adjusts
to minimize the effect of the force.
- life zone
- A climatically-defined class that can be associated with regions of soil and biota
with a high uniformity in species composition and environmental adaptation. See
Holdridge life zone.
- The component of the Earth's surface comprising the rock, soil, and sediments.
It is a relatively passive component of the climate system, and its physical character-
istics are treated as fixed elements in the determination of climate.
- Undecomposed plant residues on the soil surface.
- Little Ice Age
- A cold period that lasted from about A.D. 1550 to about A.D. 1850 in Europe,
North America, and Asia. This period was marked by rapid expansion of mountain
glaciers, especially in the Alps, Norway, Ireland, and Alaska. There were three
maxima, beginning about 1650, about 1770, and 1850, each separated by slight
- A buff-colored, wind-blown deposit of fine silt, which is frequently exposed in
bluffs with steep faces. The thickness can range from 6 to 30 m. The loess of the
USA and Europe is thought to be the fine materials first transported and deposited by
the waters of melting ice sheets during the glacial period. It was later blown consider-
able distances with, in some cases, deposition in lakes. The origin of Asiatic loess,
however, is apparently wind-blown dust from central Asian deserts.
- longwave radiation
- The radiation emitted in the spectral wavelength greater than 4 micrometers
corresponding to the radiation emitted from the Earth and atmosphere. It is
sometimes referred to as terrestrial radiation or infrared radiation, although somewhat
- A type of wetland that does not
accumulate appreciable peat deposits and is dominated by herbacious vegetation.
Marshes may be fresh- or saltwater, tidal or nontidal.
- mass balance
- The application of the principle of the conservation of matter. For example, the
mass of a glacier is not destroyed or created;
the mass of a glacier and all its constitutive components remains the same despite
alterations in their physical states. The mass balance of a glacier is calculated with
the input/output relationships of ice, firn, and
snow, usually measured in water equivalent. Output includes all ablative processes of
surface melting, basal melting, evaporation, wind deflation, calving, and internal
melting. Input includes direct precipitation, avalanching, and the growth of
- Mauna Loa
- An intermittently active volcano 13,680 ft (4,170 m) high in Hawaii. Last
eruption was in 1984. Also see Mauna Loa record.
- Mauna Loa record
- The record of measurements of atmospheric carbon dioxide concentrations taken
at the Mauna Loa Observatory, Mauna Loa, Hawaii, since March 1958. The Mauna
Loa record is the longest reliable daily record of atmospheric carbon dioxide
measurements in the world.
- Maunder minimum
- The period from 1654 to 1714 when it was believed that there were no sunspots.
It is now thought that there were some sunspots during that time but less than the
numbers counted after 1800.
- mean sea level
- The average height of the sea surface, based upon hourly observation of the tide
height on the open coast or in adjacent waters that have free access to the sea. In the
United States, it is defined as the average height of the sea surface for all stages of the
tide over a nineteen year period. Mean sea level, commonly abbreviated as MSL and
referred to simply as sea level, serves as the reference surface for all altitudes in
upper atmospheric studies.
- mesic environment
- A habitat with a moderate amount of water.
- mesoscale eddies (mode eddies)
- In the ocean, dense and irregularly-oval high- and low- pressure centers about
400 km in diameter. The intensities of currents in these centers are about 10 times
greater than the local means.
- Milankovitch theory
- An astronomical theory formulated by the Yugoslav mathematician Milutin
Milankovitch that associates climate change with fluctuations in the seasonal and
geographic distribution of insolation determined by periodic variations of the Earth's
eccentricity and obliquity and the longitude of the perihelion.
- Liquid particles 40 to 500 microns in diameter that are formed by condensation
of vapor in air.
- An investigative technique that uses a mathematical or physical representation
of a system or theory that accounts for all or some of its known properties. Models
are often used to test the effects of changes of system components on the overall
performance of the system.
- A name for seasonal winds, first applied to the winds over the Arabian Sea that
blow for six months from the northeast and for six months from the southwest. The
term has been extended to similar winds in other parts of the world (i.e., the
prevailing west to northwest winds of summer in Europe have been called the
European monsoon). The primary cause for these seasonal winds is the much greater
annual variation of temperature over large land areas compared with neighboring
ocean surfaces, causing an excess of pressure over the continents in winter and a
deficit in summer, but other factors, such as topography of the land, also have an
effect. The monsoons are strongest in the southern and eastern sides of Asia, but also
occur along the coasts of tropical regions wherever the planetary circulation is not
strong enough to inhibit them. The monsoon climate can be described as a long
winter-spring dry season, which includes a cold season followed by a short hot season
just preceding the rains; a summer and early autumn rainy season, which is generally
very wet but may vary greatly from year to year; and a secondary warming
immediately after the rainy season.
- natural selection
- The process of survival of the fittest by which organisms that adapt to their
environment survive while those that do not adapt disappear.
- negative feedback
- An interaction that reduces or dampens the response of the system in which it is
- net primary production
- The part of the gross primary production that remains stored in the producer
organism (primarily green plants) after deducting the amount used during the process
of respiration. Abbreviated NPP.
- Any substance assimilated by living things that promotes growth.
- ocean mixing
- Processes that involve rates of advection, upwelling/ downwelling, and eddy
diffusion and that determine how rapidly excess atmospheric carbon dioxide can be
taken up by the oceans.
- The degree of obscuration of light; for example, a glass window has almost 0%
opacity, whereas a concrete wall has 100% opacity.
- optical thickness (optical depth)
- In calculating the transfer of radiant energy, the mass of an absorbing or
emitting material lying in a vertical column of unit cross-sectional area and extending
between two specified levels. Also, the degree to which a cloud prevents light from
passing through it; the optical thickness then depends on the physical constitution
(crystals, drops, and/or droplets), the form, the concentration, and the vertical extent
of the cloud.
- A molecule made up of three atoms of oxygen. In the
statosphere, it occurs naturally and it provides a protective layer shielding
the Earth from ultraviolet radiation and subsequent harmful health effects on humans
and the environment. In the troposphere, it is a chemical oxidant and major component
of photochemical smog.
- An ancient soil or soil horizon that formed on the surface during the geologic
- The expansion of a bog caused by the gradual rising of the water table as
accumulation of peat impedes water drainage.
- The science of reconstructing the past flora and past climate from pollen data
obtained from lake and bog sediments. The fossil pollen record is a function of the
regional flora and vegetation at a given time and location.
- particulate matter
- Very small pieces of solid or liquid matter, such as particles of soot, dust,
aerosols, fumes, or mists.
- past climate analogs
- The reconstructing of past climates at a given locality from modern climatic
conditions in a different elevation or latitudinal zone to infer past climatic
- The partial pressure of CO2 in the atmosphere and the ocean. In the atmosphere,
the partial pressure of CO2 is defined as the pressure the CO2 would exert if all other
gases were removed. The sum of the partial pressure of all the atmospheric gases will
equal the atmospheric pressure. The partial pressure of CO2 in the atmosphere is
determined by the atmospheric CO2 concentration and atmospheric temperature. In
the ocean, the pCO2 is determined by the amount of dissolved CO2 and H2CO3. It
varies with alkalinity, latitude, depth, and temperature. Biological processes in the
ocean also exert an influence on the pCO2 in the ocean.
- The movement of water downward and radially through the subsurface soil
layers, usually continuing downward to the groundwater.
- Perennially frozen ground that occurs wherever the temperature remains below
0 degrees C for several years.
- The study of periodic biological phenomena with relation to climate,
particularly seasonal changes. These phenomena can be used to interpret local
seasons and the climatic zones.
- photochemical smog
- Air pollution caused by chemical reactions among various substances and
pollutants in the atmosphere.
- Of or relating to the electrical effects of light, including the emission of
electrons, the generation of a voltage, or a change in resistance.
- The manufacture by plants of carbohydrates and oxygen from carbon dioxide
and water in the presence of chlorophyll with sunlight as the energy source. Oxygen
and water vapor are released in the process. Photosynthesis is dependent on favorable
temperature and moisture conditions as well as on the atmospheric carbon dioxide
concentration. Increased levels of carbon dioxide can increase net photosynthesis in
- That portion of the plankton
community comprised of tiny plants (e.g., algae
- planetary albedo
- The fraction (approximately 30%) of incident solar radiation that is reflected by
the earth-atmosphere system and returned to space, mostly by backscatter from
clouds in the atmosphere.
- planetary boundary layer
- The transition region between the turbulent surface layer and the normally
nonturbulent free atmosphere. This region
is about 1 km in thickness and is characterized by a well-developed mixing generated
by frictional drag as the air masses move over the Earth's surface. This layer contains
approximately 10% of the mass of the atmosphere. Also called the atmospheric
boundary layer or frictional layer.
- Passively floating or weakly motile aquatic plants (
phytoplankton) and animals (zooplankton
- The earlier of the two epochs of the Quaternary
period, starting 2 to 3 million years before the present and ending about
10,000 years ago. It was a time of glacial activity.
- positive feedback
- An interaction that amplifies the response of the system in which it is
- Any or all forms of liquid or solid water particles that fall from the atmosphere
and reach the Earth's surface. It includes drizzle, rain, snow, snow pellets, snow
grains, ice crystals, ice pellets, and hail. The ratio of precipitation to evaporation is
the most important factor in the distribution of vegetation zones. Precipitation is also
defined as a measure of the quantity, expressed in centimeters or milliliters of liquid
water depth, of the water substance that has fallen at a given location in a specified
amount of time.
- primary productivity
- See gross primary production and net primary production.
- primary succession
- The natural development of vegetation and soil on a site that had not previously
borne vegetation (e.g., a sand dune or lava flow), which vegetation will be replaced
by other, successive plant communities.
- primitive equations
- The Eulerian equations of fluid motion in which the primary dependent
variables are the velocity components of the fluid. In meteorology, they can be
specialized to apply directly to the cylonic-scale motions.
- proxy climate indicators
- Dateable evidence of a biological or geological phenomenon whose condition, at
least in part, is attributable to climatic conditions at the time of its formation. Proxy
data are any material that provides an indirect measure of climate and include
documentary evidence of crop yields, harvest dates, glacier movements, tree rings,
varves, glaciers and snow lines, insect remains, pollen remains, marine microfauna,
isotope measurements: 18O, in ice sheets, 18O, 2H, and 13C in tree rings; CaCO3 in
sediments; and speleothems. There are three main problems in using proxy data: (1)
dating, (2) lag and response time, and (3) meteorological interpretation. Tree rings,
pollen deposits from varved lakes, and ice cores are the most promising proxy data
sources for reconstructing the climate of the last five millennia because the dating are
precise on an annual basis while other proxy data sources may only be precise to +/-
- In the ocean, a region where the water density increases rapidly with depth.
- An instrument that measures radiation from the earth's surface into space.
- Quaternary period
- The latest period of geologic time, covering the most- recent 2,000,000 years of
the Earth's history. It is divided into two epochs: the
Pleistocene - 2 million years ago to approximately 10,000 years ago - and
the Holocene - the period from
approximately 10,000 years ago to the present. The Quaternary period is the artificial
division of time separating prehuman and human periods. It contains five ice ages and
four interglacial ages, and temperature indicators seem to show sharp and abrupt
changes by several degrees.
- radiant flux density
- The total flow of radiation received on a unit area of a given real or imaginary
surface. Also called the irradiance.
- radiation balance
- The difference between the absorbed solar radiation and the net infrared radiation. Experimental data show that radiation
from the earth's natural surfaces is rather close to the radiation from a black body at
the corresponding temperature; the ratio of the observed values of radiation to black
body radiation is generally 0.90 - 1.0.
- radiative-convective models
- Thermodynamic models that determine the equilibrium temperature distribution
for an atmospheric column and the underlying surface, subject to prescribed solar
radiation at the top of the atmosphere and prescribed atmospheric composition and
surface albedo. Submodels for the transfer of solar and terrestrial radiation, the heat
exchange between the earth's surface and atmosphere, the vertical redistribution of
heat within the atmosphere, the atmospheric water vapor content and clouds are
included in these one-dimensional models. Abbreviated as RCM.
- radiatively active gases
- Gases that absorb incoming solar radiation or outgoing
infrared radiation, thus affecting the vertical temperature profile of
the atmosphere. Most frequently being cited as being radiatively active gases are water
vapor, CO2, methane, nitrous oxide, chlorofluorocarbons, and ozone.
- A balloon-borne instrument for the simultaneous measurement and transmission
of meteorological data up to a height of approximately 30,000 meters (100,000 feet).
The height of each pressure level of the observation is computed from data received
via radio signals.
- The process by which water is added to a
reservoir or zone of saturation, often by
runoff or percolation from the soil
- The ratio of the energy carried by a wave that is reflected from a surface to the
energy of a wave incident on the surface.
- relative sea level
- The height of the boundary between sea and air as measured in relationship to a
fixed reference point on land.
- Any natural or artificial holding area used to store, regulate, or control a
- residence time
- The size of any specific reservoir or pool of mass (e.g., carbon) divided by the
total flux of mass into or out of that pool.
- A biochemical process by which living organisms take up oxygen from the
environment and consume organic matter, releasing both carbon dioxide and heat. In
plants, the organic matter in photosynthate produced during daylight hours.
- Revelle factor
- The ratio of the instantaneous fractional change in the partial pressure of CO2
(pCO2) exerted by seawater to the fractional change in total CO2 dissolved in the
ocean waters. The buffer factor relates the partial pressure of CO2 in the ocean to the
total ocean CO2 concentration at constant temperature, alkalinity and salinity. The
Revelle factor is a useful parameter for examining the distribution of CO2 between
the atmosphere and the ocean, and measures in part the amount of CO2 that can be
dissolved in the mixed surface layer.
- A rocket-borne instrument for measurement and transmission of upper-air
meteorological data in the lower 76,000 meters (250,000 feet) of the atmosphere,
especially that portion inaccessible to radiosonde techniques.
- That part of precipitation, snowmelt, or
irrigation water that flows from the land to streams or other
- The degree of salt in water.
- salt water intrusion
- The invasion of fresh, surface, or groundwater by salt water.
- seasonal variation
- The change in a set of meteorological parameters averaged over three months.
Seasonal variation is the largest climatic variation, and temperature is the most fre-
quently observed meteorological parameter. Often, monthly averaged data are
grouped into seasons, according to the prescribed definition.
- sea surface temperature
- The temperature of the layer of seawater (approximately 0.5 m deep) nearest the
- sea surface temperature anomalies
- Temperature of emitted energy from the sea surface. SST anomaly = (SST - SST
- secular carbon dioxide trend
- The fairly uniform and accelerating increase of carbon dioxide concentration in
the atmosphere, as illustrated by the Mauna Loa record.
The secular trend reflects the increase in global atmospheric carbon dioxide
concentrations produced by combustion of fossil fuels, kilning of limestone, and possibly
a net biospheric release of carbon dioxide resulting from deforestation.
- sensible heat
- The excess radiative energy that has passed from the Earth's surface to the atmosphere through advection, conduction, and
- shortwave radiation
- The radiation received from the sun and emitted in the spectral wavelengths less
than 4 īm. It is also called solar radiation.
- signal-to-noise ratio
- A quantitative measure of the statistical detectability of a signal, expressed as a
ratio of the magnitude of the signal relative to the variability. For first detection of a
CO2-induced climate change, the model signal is the mean change or anomaly in
some climatic variable, usually surface air temperature, attributed by a numerical
model to increased concentrations of carbon dioxide. Observed noise is the standard
deviation or natural variability computed from observations of that variable and
adjusted for sample size, autocorrelation, and time averaging.
- Management of forest land for timber.
- Air pollution associated with oxidants.
- Particles suspended in air after incomplete combustion of materials.
- soil carbon
- A major component of the terrestrial biosphere pool in the carbon cycle.
Organic soil carbon estimates, rather than total soil carbon, are generally quoted. The
amount of carbon in the soil is a function of historical vegetative cover and
productivity, which in turn is dependent upon climatic variables.
- solar constant
- The rate at which solar energy is received just outside the Earth's atmosphere on a surface that is normal to the incident
radiation and at the mean distance of the Earth from the sun. The current value is 0.140
- solar cycle
- The periodic change in sunspot
numbers. It is the interval between successive minima and is about 11.1 years.
- Southern Oscillation
- A large-scale atmospheric and hydrospheric fluctuation centered in the
equatorial Pacific Ocean. It exhibits a nearly annual pressure anomaly, alternatively
high over the Indian Ocean and high over the South Pacific. Its period is slightly
variable, averaging 2.33 years. The variation in pressure is accompanied by variations
in wind strengths, ocean currents, sea-surface temperatures, and precipitation in the
surrounding areas. El Nino occurrences are
associated with the phenomenon.
- Southern Oscillation Index
- An indicator based on the pressure gradient between the quasi-stationary low
pressure region and the center of a subtropical high pressure cell. A positive index
corresponds to an anomalously high pressure difference between the two centers of
- statistical-dynamical models
- Computer programs that calculate simplified climate models based on versions
of the conservation equations that have been averaged over longitude, with the effects
of the synoptic eddies parameterized statistically in the meridional plane.
- steric height
- The mean dynamic depth (or height) of the ocean for the month minus the
annual mean dynamic depth for the same isobaric reference level.
- stoma, plant stomata
- A minute pore in the epidermis of plant leaves or stems. Stoma, which are
bordered by guard cells that regulate the size of the opening, function in gas
exchange between the plant and the external environment. The stomatal apparatus or
stomate consists of the stoma plus guard cells.
- Separating into layers.
- The region of the upper atmosphere extending from the tropopause (8 to 15 km
altitude) to about 50 km. The thermal structure is determined by its radiation balance
and is generally very stable with low humidity.
- Suess effect
- The relative change in the 14C/C or 13C/C ratio of any carbon pool or reservoir
caused by the addition of fossil- fuel CO2 to the atmosphere. Fossil fuels are devoid
of 14C because of the radioactive decay of 14C to 14N during long underground
storage and are depleted in 13C because of isotopic fractionation eons ago during
photosynthesis by the plants that were the precursors of the fossil fuels. Carbon
dioxide produced by the combustion of fossil fuels is thus virtually free of 14C and
depleted in 13C. The term Suess effect originally referred to the dilution of the
14C/C ratio in atmospheric CO2 by the admixture of fossil-fuel produced CO2, but
the definition has been extended to both the 14C and 13C ratios in any pool or
reservoir of the carbon cycle resulting from human disturbances.
- A relatively dark, sharply defined region on the solar disk, marked by an umbra
approximately 2000K cooler than the effective photospheric temperature, surrounded
by a less dark but also sharply bounded penumbra. The average spot diameter is
about 3700 km, but can range up to 245,000 km. Most sunspots are found in groups
of two or more, but they can occur singly. Sunspots are cyclic, with a period of
approximately 11 years. The quantitative description of sunspot activity is called the
Wolf sunspot number, denoted R. The Wolf sunspot number is also referred to as
Wolfer sunspot number, Zurich relative sunspot number, or relative sunspot
- surface air temperature
- The temperature of the air near the surface of the Earth, usually determined by a
thermometer in an instrument shelter about 2 m above the ground. The true daily
mean, obtained from a thermograph, is approximated by the mean of 24 hourly
readings and may differ by 1.0 degrees C from the average based on minimum and
maximum readings. The global average surface air temperature is 15 degrees C.
- surface albedo
- The fraction of solar radiation incident on the Earth's surface that is reflected by
it. Reflectivity varies with ground cover, and during the winter months it varies
greatly with the amount of snow cover (depth and areal extent). Roughness of terrain,
moisture content, solar angle, and angular and spectral distribution of ground- level
irradiations are other factors affecting surface albedo.
- surface water
- All water naturally open to the atmosphere.
- A type of wetland that is dominated
by woody vegetation and does not accumulate appreciable peat deposits; it may be fresh-
or saltwater, and tidal or nontidal.
- Any rock material produced by a volcano.
- terrestrial radiation
- The total infrared radiation emitted by
the Earth and its atmosphere in the temperature range of approximately 200-300K.
Because the Earth is nearly a perfect radiator, the radiation from its surface varies as
the fourth power of the surface's absolute temperature. Terrestrial radiation provides a
major part of the potential energy changes necessary to drive the atmospheric wind
system and is responsible for maintaining the surface air temperature within limits
- A transition layer of water in the ocean, with a steeper vertical temperature
gradient than that found in the layers of ocean above and below. The permanent ther-
mocline separates the warm mixed surface layer of the ocean from the cold deep
ocean water, and is found between 100- and 1000-m depths. The thermocline first
appears at the 55 - 60 degree N and S latitudes, where it forms a horizontal separation
between temperate and polar waters. The thermocline reaches its maximum depth at
mid-latitudes and is shallowest at the equator and at its northern and southern limits.
The thermocline is stably stratified, and transfer of water and carbon dioxide across
this zone occurs very slowly. Thus, the thermocline acts as a barrier to the downward
mixing of carbon dioxide.
- Refers to the combined effects of temperature and salinity that contribute to
density variations in the oceans.
- tidal marsh
- Low, flat marshlands traversed by channels and tidal hollows and subject to tidal
innundation; normally, the only vegetation present are salt-tolerant bushes and
- trace gas
- A minor constituent of the atmosphere. The most important trace gases
contributing to the greenhouse effect are water vapor, carbon dioxide, ozone,
methane, ammonia, nitric acid, nitrous oxide, ethylene, sulfur dioxide, nitric oxide,
dichlorofluoromethane or Freon 12, trichlorofluoromethane or Freon 11, methyl
chloride, carbon monoxide, and carbon tetrachloride.
- transient tracers
- Chemical elements (often radioactive) or compounds that have finite lifetimes.
Atmospheric testing of nuclear weapons from the mid-1950s to the early 1960s
released large quantities of radionuclides to the atmosphere. Atmosphere-ocean
exchange processes have transferred some of these elements to the oceans. Studying
the behavior and distribution of these specific isotopes and other chemical tracers in
the ocean will provide information on: residence times of the water and its dissolved
components in gyres, basins, etc.; the mode and rate of formation and the subsequent
spreading rates of specific water types, such as the polar water of the Norwegian and
Greenland Seas; deep-ocean circulation and ocean- mixing processes, such as
advection and upwelling; and the flux of anthropogenic carbon dioxide into the ocean
through its correlation with several different transient tracers.
- The process in plants by which water is taken up by the roots and released as
water vapor by the leaves. The term can also be applied to the quantity of water thus
- tree rings
- Annual growth increments of trees that indicate, among other factors, the
climatic conditions that enhance or limit growth. Tree ring widths and indexes have
been used to search for solar-terrestrial relationships and climatic cycles and to
reconstruct past climates. See also dendroclimatology
- trophic level
- A segment of the food chain in which all organisms obtain food and energy in,
basically, the same manner (e.g., photosynthesis,
herbivory, or carnivory) and in which all organisms are the same number of links
from the photosynthetic segment.
- The boundary between the troposphere and the stratosphere (about 8 km in polar
regions and about 15 km in tropical regions), usually characterized by an abrupt
change of lapse rate. The regions above the
troposphere have increased atmospheric stability than those below. The tropopause
marks the vertical limit of most clouds and storms.
- The inner layer of the atmosphere below about 15 km, within which there is
normally a steady decrease of temperature with increasing altitude. Nearly all clouds
form and weather conditions manifest themselves within this region, and its thermal
structure is caused primarily by the heating of the Earth's surface by solar radiation,
followed by heat transfer by turbulent mixing and convection.
- A type of ecosystem dominated by
lichens, mosses, grasses, and woody plants. It is found at high latitudes (arctic tundra)
and high altitudes (alpine tundra). Arctic tundra is underlain by permafrost and usually very wet.
- turnover rate
- The fraction of the total amount of mass (e.g., carbon) in a given pool or
reservoir that is released from or that enters the pool in a given length of time. The
turnover rate of carbon is often expressed as GtC/year.
- The vertical motion of water in the ocean by which subsurface water of lower
temperature and greater density moves toward the surface of the ocean. Upwelling
occurs most commonly among the western coastlines of continents, but may occur
anywhere in the ocean. Upwelling results when winds blowing nearly parallel to a
continental coastline transport the light surface water away from the coast.
Subsurface water of greater density and lower temperature replaces the surface water,
and exerts a considerable influence on the weather of coastal regions. Carbon dioxide
is transferred to the atmosphere in regions of upwelling. This is especially important
in the Pacific equatorial regions, where 1 - 2 GtC/year may be released to the
atmosphere. Upwelling also results in increased ocean productivity by transporting
nutrient-rich waters to the surface layer of the ocean.
- The gaseous phase of substances that are liquid or solid at atmospheric pressure
- A layer of sediment deposited in lakes during one year. Each layer consists of
two parts, which are deposited at different seasons and which differ in color and
texture; thus, the layers can be counted and measured. In a complete series, the
number of layers gives the date on which the ground was vacated by the retreating
- Walker cell
- A zonal circulation of the atmosphere confined to equatorial regions and driven
principally by the oceanic temperature gradient. In the Pacific, air flows westward
from the colder, eastern area to the warm, western ocean, where it acquires warmth
and moisture and subsequently rises. A return flow aloft and subsidence over the
eastern ocean complete the cell.
- water stress effect
- The closing of the stomata by a
plant in response to excessive water loss through
transpiration or in response to drought conditions. The stomatal closing
reduces CO2 uptake as well as water loss, thus decreasing the photosynthetic rate.
However, under conditions of elevated CO2 concentration, the CO2 gradient between
the atmosphere and the leaf is higher than
under ambient conditions, and CO2 can pass through partially closed stomates at a
rate similar to that under conditions of lower CO2 and open stomates. The humidity
gradient remains the same at higher CO2, and
transpiration is impeded. The net result is improved water-use efficiency
by some plants.
- water table
- The level of groundwater.
- water-use efficiency
- A measure of the amount of water used by plants per unit of plant material
produced. The term can be applied at the leaf, whole-plant, and ecosystem levels. At
the leaf level, it is more precisely referred to as the
instantaneous transpiration efficiency, the CO2 assimilation rate (photosynthesis) divided by the transpiration rate (the moles
of CO2 taken up divided by the moles of water lost through transpiration in a unit of
time per unit leaf area). At the whole-plant level, it is more precisely referred to as the
growth water-use efficiency, the units of
dry matter synthesized divided by the units of water lost. At the ecosystem level, it is
more precisely referred to as the crop water-use
efficiency, the grams of dry weight gained by plants during the growing
season per unit land area divided by the millimeters of water lost (including evaporation
directly from the soil).
- water vapor
- Water present in the atmosphere in
gaseous form; the source of all forms of condensation and precipitation. Water vapor,
clouds, and carbon dioxide are the main atmospheric components in the exchange of
terrestrial radiation in the troposphere,
serving as a regulator of planetary temperatures via the
greenhouse effect. Approximately 50 percent of the atmosphere's
moisture lies within about 1.84 km of the earth's surface, and only a minute fraction
of the total occurs above the tropopause.
- water vapor feedback
- A process in which an increase in the amount of water vapor increases the atmosphere's absorption of longwave radiation,
thereby contributing to a warming of the atmosphere. Warming, in turn, may
result in increased evaporation and an increase in the initial water vapor anomaly.
This feedback, along with carbon dioxide, is responsible for the greenhouse effect and operates virtually continuously
in the atmosphere.
- The instantaneous state of the global atmosphere-ocean- cryosphere system.
- West Antarctic Ice Sheet
- See ice sheet.
- An area that is regularly saturated by surface
water or groundwater and
subsequently is characterized by a prevalence of vegetation that is adapted for life in
- zonally-averaged models
- Statistical-dynamical or energy-balance models in which only the latitudinally
averaged quantities are determined and the effects of the longitudinally varying
transports are determined parametrically. Abbreviated as ZAM.
- That portion of the plankton
community comprised of tiny aquatic animals eaten by fish.
Contents taken from Glossary: Carbon Dioxide and Climates, 1990.
ORNL/CDIAC-39, Carbon Dioxide Information Analysis Center, Oak
Ridge National Laboratory, Oak Ridge, Tennessee.
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