Glossary

atmosphere - The whole mass of gases surrounding the earth or other celestial bodies. Today's atmosphere is made up primarily of nitrogen (78%), free oxygen (21%) and greenhouse gases which can capture solar radiation: water vapor, which ranges from less than 1% in arid regions to over 3% in moist areas, carbon dioxide (0.035%) and methane (0.00018%). In the past the composition of the Earth's atmosphere has varied.


B
benthic Foraminifera - Single-celled animals that live near the sediment water interface and have calcium carbonate skeletons. The skeletons of benthic foraminifers are often preserved in ocean sediments, providing a rich fossil record of the environmental conditions of the water.

C
carbon dating - A dating method that uses the disintegration of the ¹⁴C atom to determine the age of sample containing carbon. ¹⁴C is produced in the atmosphere by cosmic ray bombardment, and has a half-life of 5570 years, making it useful for dating samples in the range of 0-40,000 years.

carbon dioxide - (CO₂) A gas whose molecules consist of one carbon and two carbon atoms. It is a greenhouse gas and a critical component in the global carbon cycle.

celestial equator - The great circle on the celestial sphere midway between the celestial poles (the projection of the north and south pole onto the celestial sphere).

celestial sphere - An imaginary sphere of infinite radius, on which the stars appear to be placed.

calcium carbonate (CaCO₃) - A molecule consisting of calcium, carbon and oxygen that is secreted by corals, forming their skeleton; it also secreted by mollusks (clams, oysters, etc.), forming their protective shells.

Calcium concentrations - Concentration (units mass/mass) of the calcium ion (Ca⁺), often found in layers of ice, and derived from atmospheric transport of dust.

calving - To separate or break so that a part becomes detached.

chronology - A general term for the age-depth relationship in ice, sediment, or another deposit. Ages are usually measured for discrete samples, and the ages of intermediate samples is interpolated between samples with measured ages.

climate - Long term characteristics of weather.

climatic feedback mechanisms - A feedback is an enhancement (positive feedback) or a damping (negative feedback) of an initial change, in this case in the climate system. For example, when less energy reaches the earth, temperature decreases and the area covered by snow increases. The albedo of the planet decreases, reflecting more energy towards the atmosphere. Consequently less energy is available at the surface, and temperature further decreases. The whole "cycle" from the initial cooling to the further cooling is a feedback. It is a positive feedback in this example.

continental processes - tectonic movements that relate to the continental land masses.

crossdating - The procedure of matching and synchronizing ring-width variations and other structural characteristics among trees that have grown in nearby areas, allowing the identification of the exact year in which the ring was formed.

cryosphere - The portion of the world's climate system which consists of snow and ice deposits

D
Dansgaard-Oeschger cycles - Climate oscillations averaging a few thousand years in duration that dominate Greenland ice-core records.

Deep Water - An ocean water mass with relatively uniform temperature, salinity, and density, found near the bottom of the ocean.

dendrochronology - A science based on the exact calendar dating of annual growth rings in wood.

dendroclimatology - A subfield of dendrochronology, which investigates the climatic effect on tree growth, and uses dated tree rings to reconstruct and study past and present climate.

density - The mass per unit volume of a substance under specified conditions of pressure and temperature.

diatom - Single celled phytoplankton that produce silica skeletons. Diatoms are one of the most abundant, widely distributed primary producers in the ocean. Different species of diatoms living in ocean and lakes have affinities for different environmental conditions such as alkalinity, available nutrients, salinity and acidity.

diurnal cycle - Mean solar day occurring as Earth rotates from east to west on its axis.

E
eccentricity - The amount that the earth's revolution deviates from a circular path; the variation of an ellipse from a circle, where a circle has an eccentricity of 0.

ecliptic - The apparent path of the sun on the celestial sphere, also used for the plane in which the motion of the earth around the sun takes place.

ecosystem - Relationships between and among living organisms and their non-living environment.

El Niño - The appearance of unusually warm waters in the eastern Pacific; termed the "Christ child," because of the time of year it effects the South American coastline.

ENSO - An acronym for El Niño Southern Oscillation

equinox - Either of two points on the celestial sphere where the celestial equator intersects the ecliptic; either of the two times each year when the sun crosses the equator, and day and night are of equal length (spring equinox, fall equinox).

erratics - Large boulders displaced from their natural geologic location by glaciers.

evolutionary change - Either phenotypic or genetic changes that occur in an organism from generation to generation through the exchange of genes.

F

forcing - a external force affecting climate, such as increased solar radiation, greenhouses gases, or variations in the Earth's orbit around the sun.

freshwater - water with little or no salt content, such as in most lakes and streams, as opposed to salty ocean water.

fossil air - A sample of air that preserves the composition of the environment at the time it was deposited. Bubbles found in ice cores are one example of fossil air that records the atmospheric composition of the atmosphere at the time the ice was formed.

flux - the flow, or rate of flow, of a fluid.

G

glacial - A time interval characterized by widespread glacial ice - "Ice Age".

glacier - River of ice that under pressure can deform and flow plastically.

geologic time scale - Relative time scale based on stratigraphic position and correlation, and many different types of chronologic evidence. Geologic time is broken down into eons, eras, periods and epochs.

GISP2 - Greenland Ice Sheet Project 2, the second phase of an effort by a group of scientists to produce long records of climate by drilling into the Greenland Ice Sheet from the surface to bedrock.

global warming - an increase in temperature that occurs globally such as the interglacial warming period the earth experienced after the last Ice Age, or that predicted to result from human increases in greenhouse gases.

greenhouse gases - Any one of the gases found in the atmosphere (including CO₂, H₂O, CH₄) that act to allow short wave radiation from the sun to reach the earth, but which absorbs outgoing long wave radiation from the earth surface.

"Greenhouse effect" - The process by which the equilibrium temperature of the earth is increased due to presence of gases in the atmosphere that absorb outgoing longwave radiation.

GRIP - The joint European Greenland Ice Core Project (GRIP) a 3029m long ice core was drilled in Central Greenland from 1989 to 1992.

H
habitat - Location where a plant or animal species naturally lives and grows.

half-life - The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay.

haline - salty.

Heinrich Events - An interval of rapid flow of icebergs from the margin of ice sheets into the North Atlantic Ocean, resulting in deposition of sediment layers rich in debris eroded from land areas.

Holocene epoch - An epoch of the Quaternary period dating from the end of the Pleistocene approximately 11,000 years ago until the present.

I
Ice Age - Period during which polar ice extends to much lower latitudes than normal.

ice rafted detritus - Continental material transport within a matrix of ice and deposited in marine sediments when the ice matrix melts.

Ice sheet margin - Edge of the ice sheet where melting and calving of icebergs occurs.

Ice streams - Rapidly flowing ice generally in the bottom of an ice sheet and flowing from the middle to the ice sheet margin.

insolation - Amount of solar radiation received on a given body or in a given area.

instrumental record - data measured using instruments, such as thermometers and rain gauges.

interglacial - A time interval between glacial periods characterized by lack of glacial ice in mid-latitudes, such as modern Holocene climate.

Intertropical Convergence Zone - The region that circles the Earth, near the equator, where the trade winds of the Northern and Southern Hemispheres come together.

ion - Atoms that have either a positive or negative charge.

isotope - A form of a specific element that has the same number of protons, but differs in the number of neutrons; forms of the same element that have different mass numbers.

J-K-L
Jurassic period - The second period of the Mesozoic era, thought to have covered the span of time between 190 and 135 million years ago.

littoral zone - Area of shore between mean high water and mean low water.

lithic - Made of rock.

loess - A wind-deposited sediment consisting mostly of silt, the silt commonly derived from finely ground rock washed out of continental glaciers.

M
meltwater plume - Body of fresh water derived from the melting of glacial ice that floats in large bodies of salt water.

methane (CH₄) - An odorless, colorless, flammable gas, the major constituent of natural gas, and produced by a variety of natural sources.

Miocene epoch - An epoch of the early Tertiary period, found in-between the Oligocene and the Pliocene eras.

morphology - The scientific study of organic form, including both its development and its function.

N-O
natural climate record - A record of climatic events found by examining the natural environment (tree rings, coral growth bands, layers of ice in glaciers).

nepheloid layer - Layer of seawater containing a high concentration of suspended sediment that may reach heights of several hundred meters above the ocean floor.

obliquity - The angle between the planes of the celestial equator and the ecliptic, currently the earth has a 23.4 degree obliquity.

orbital cycles - time period of complete cycle in variation of the Earth's orbit around the sun. The major components of the Earth's orbital cycle vary at periods of approximately 23,000, 41,000, and 100,000 years.

Orbital forcing - Theory that proposes large scale climate changes are due in part to the variations in precession, eccentricity and obliquity that affects the amount of solar radiation received by the earth.

oxygen isotopes - Oxygen atoms having the same atomic number (protons) but different mass numbers (and different numbers of neutrons). The two stable isotopes of oxygen are ¹⁶O and ¹⁸O.

oxidation - Relative loss of electrons in a chemical reaction; usually associated with the liberation of energy.

Oxygen isotope ratio (d¹⁸O) - An expression for the ratio of the ¹⁸O to ¹⁶O atoms in a sample relative to a standard, defined as:D18O= (¹⁸O/¹⁶O_sample - ¹⁸O/¹⁶O_standard)/ ¹⁸O/¹⁶O_standard

P

paleoclimate - Past or ancient climates.

paleoclimatologist - One who studies ancient (paleo-) climate.

paleoenvironmental proxy - An environmental remnant of the past (pollen grains, tree rings, lake sediments, pack rat middens, ice cores, coral skeletons) that assist researchers in deciphering past climate conditions through the use of scientifically proven dating techniques.

Paleozoic - An era of geological history which extends from the beginning of the Cambrian to the close of the Permian and is marked by the culmination of nearly all classes of invertebrates except the insects and in the later epochs of which seed-bearing plants, amphibians, and reptiles first appeared.

particulate - Material made up of small pieces.

photosynthesis - The process in green plants and certain other organisms by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Carbon dioxide (CO₂ ) and water (H₂ O) are combined in the presence of sunlight and the green pigment chlorophyll, to produce food (C₆ H₁₂ O₆ ) and oxygen (O₂ ).

plankton - Small or microscopic organisms, including algae and protozoan, that float or drift in great numbers in fresh or salt water, especially at or near the surface, and serve as food for fish and other larger organisms.

planktonic Foraminifera - Marine zooplankton that passively float or weakly swim, and have calcium carbonate skeletons that are present in large numbers on the surface of the ocean. The skeletons of planktonic foraminifers are preserved in large numbers in deep-sea sediments, providing a rich fossil record of the environmental conditions of the upper ocean. The size of the shells is typically from 50 to 100 microns.

Pleistocene epoch - An interval of the Quaternary period, from 1.8 million years before present to 10 thousand years before present.

pollen - Pollen grains that are made up of microspores containing a mature or immature male gametophyte.

precession (of the equinoxes) - A measure of the slow clockwise motion of the equinoxes along the ecliptic due to the motion of the earth's axis of rotation around the pole of the ecliptic; the angular movement of the spin axis of an object around an axis fixed in space.

proxy - Substitute. Paleoclimatologists use proxy evidence in place of direct measurements of climate parameters such as temperature, for times before instrumental measurements were made. Ocean sediments, glacial ice, and tree rings all contain proxies for climate conditions.

Proxy signals - A general term for paleoclimate evidence that can be used to indirectly infer or estimate some aspect of the environment such as precipitation or temperature.

Q-R
Quaternary period - The second period of the Cenozoic era containing the Pleistocene epoch and the Holocene epoch and dating from 1.8 million years to the present.

radiocarbon age - The age of plant or animal remains determined by measuring the remaining activity of the ¹⁴C atoms in the sample: A=A₀e^-ltwhere A is the measured activity, A₀ is the initial activity, l is the decay constant, and t is the sample age.

Radiocarbon time - The use of the regular known rates of radiocarbon decay to determine the exact ages of carbon-based life.

relative dating - Dating methods that determine time with respect to stratigraphic position, for example deeper layers being older, or with respect to some changing quantity or property, such as magnetic polarity.

S

Sahara - A large desert in northern Africa.

Sahel - A large savanna in northern Africa.

savanna - A semi-arid region of grasses and scattered trees.

sea surface temperatures - Temperature of the ocean's surface used in collaboration with other data to predict an El Niño occurrence.

solar variability - changes in the sun's radiation due to the sun's internal dynamics.

Southern Oscillation (ENSO) - Shifting of pressure zones in the Pacific during an El Niño event.

stable isotope - Different species of an element that have the same atomic number, but different atomic mass, that are not affected by radioactive decay.

Stable state - A steady state in a system, having no tendency to change absent an external force.

steppe - A semiarid treeless grassland region.

striations - Small-scale grooves cut into rock by the rasping action of rock-laden glaciers.

T

terrigenous - Derived from land areas. For example, wind-blown dust from desert areas can settle into oceans and form terrigenous sediment on the bottom.

teleconnection - Ripples of change that occur far away from the source; wildfires in the Australian Outback and flooding in the Peruvian Andes are teleconnections caused by El Niño.

thermohaline circulation (THC)- Density-driven circulation system for the world's oceans. Warm Atlantic water moves northward along the axis of the Gulf Stream, evaporation makes the water more and more dense while releasing heat to the colder atmosphere in the North Atlantic. Once dense enough, the water sinks into the deep ocean, forming a downward limb of a giant conveyor-like circulation that extends around the world's oceans.

tradewinds - A system of low-level winds occurring in the tropics; the tradewinds blow from the northeast to the equator in the Northern Hemisphere and from the southeast to the equator in the Southern Hemisphere.

U-V-W-X-Y-Z
upwelling - Rising of cold, nutrient-rich water towards the surface.

varves - Lake or ocean annual layers of finer and coarser silt/clay that represent the annual cycles of deposition in that lake or ocean.

vessel - Large, tube-like water-conducting element in the wood of angiosperms.

Vostok - The Vostok research station in Antarctica (78S, 106E), location of the world's oldest ice core record.

visual stratigraphy -The process of identifying different layers in ice, rock, sediment, or another paleo deposit, based on visually apparent distinctions such as color or other properties. The identified stratigraphic layers are usually assigned different ages or age intervals.

weather - Temperature, precipitation and wind speed and direction that occur on a daily basis.

Younger Dryas - An interval of abrupt cooling of the climate near the end of the last glacial period, approximately 12,700-11,500 years ago. The name is derived from the Dryas plant, a cold-loving plant that pollen records indicate was widespread in Europe during this period.


Also See: CDC's Climate Glossaries and Weather Tools