Glossary of Terms Frequency of Natural Climate Change


Arctic Oscillation – An atmospheric circulation pattern in which the atmospheric pressure over the polar regions varies in opposition with that over middle latitudes (about 45 degrees North) on time scales ranging from weeks to decades. The oscillation extends through the depth of the troposphere. During the months of January through March it extends upward into the stratosphere where it modulates in the strength of the westerly vortex that encircles the Arctic polar cap region. (Taken from the National Snow and Ice Data Center)

Axial Precession – The change in the direction of the Earth’s axis of rotation relative to the fixed stars, meaning that the planet earth didn’t always point to the north star with it’s pole.  In a period of roughly 26,000 years this direction changes in relation to the earth’s location to the sun, and the effect of the moon’s gravity .  The motion, not unlike the spinning of a top when it starts to loose speed, is due to the tidal forces exerted by the sun and the moon on the solid Earth, associated with the fact that the Earth is an oblate spheroid shape and not a perfect sphere. The sun and moon contribute roughly equally to this effect.

Carbon Dating – A radiometric dating method that uses the naturally occurring radioisotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 58,000 to 62,000 years.

Chronostratigraphy – The branch of stratigraphy (see below) that studies the age of rock strata in relation to time.  The purpose of chronostratigraphy is to arrange the strata chronologically to catalog the history of a region and eventually, the entire geologic record of the Earth.

Climatology – The study of climate, which is scientifically defined as weather conditions averaged over a period of time.  This is a branch of atmospheric sciences.

Dendrochronology (Tree ring dating) – developed during the first half of the 20th century by A. E. Douglass, the founder of the Laboratory of Tree-Ring Research at the University of Arizona, sought to better understand cycles of sunspot activity and reasoned  that changes in solar activity would affect climate patterns on earth which would subsequently be recorded by tree-ring growth patterns.

El Niño-Southern Oscillation (ENSO) – A climate pattern that occurs in the tropical Pacific within a period of three to seven years, which is known as “quasi-periodic.” ENSO is characterized by warming or cooling of surface waters in the tropical eastern Pacific Ocean as well as the atmospheric component, the Southern Oscillation, which is characterized by changes in surface pressure in the tropical western Pacific.

Epoch – A division of the geologic timescale. Epochs are subdivisions of periods which are in turn divided into ages.

General Circulation Model (GCM) – A mathematical model of the general circulation of the planetary atmosphere or ocean and based on the Navier-Stokes equations of a rotating sphere with thermodynamic terms for various energy sources (radiation, latent heat). These equations are the basis for complex computer programs commonly used for trying to simulating the atmosphere or ocean of the Earth for the purpose of predicting weather and climates.

Glacioeustasy – Changes in sea level due to storage or release of water from glacial ice.

Holocene – A geological epoch which began approximately 12,000 years ago.  The Holocene period continues to the present day and is part of the Quaternary period.

Hydrology – The study of the movement, distribution, and quality of water throughout Earth, addressing both the hydrologic cycle and our planet’s water resources.

Ice Age – A geological period with a long-term reduction in the temperature of the Earth’s surface and atmosphere, which results in an expansion of continental ice sheets, polar ice sheets and alpine glaciers.

Interglacial – A geological interval of warmer global average temperatures that separate glacial periods within an ice age. The current Holocene interglacial period has persisted since the end of the Pleistocene era, about 11,400 years ago.

Milankovitch Climate Cycles – Milutin Milankovi? came up with a mathematical theory that suggested that the variations in the temperature on the surface of the earth could be linked to a variety of changes in the way that the earth moves around the sun. Factors include the path that the earth takes as it orbits the sun,  the tilt of the axis and axial precession.

Moraine – A glacially formed accumulation of  debris consisting of soil and rock which can occur in currently glaciated and formerly glaciated regions. This debris can be picked up off the valley floor by the ice as a glacier advanced or it could have fallen off the valley walls as a result of frost wedging.

Paleoclimatology – The study of climate change for the entire history of the earth using records from ice sheets, tree rings, sediment, corals, shells and rocks to determine the past state of the climate systems of the Earth.

Palynology (Pollen Records)- the study of contemporary and fossil pollen records. Palynology is used to infer the geographical distribution of plant species, which vary under different climate conditions. Different types of plants have pollen with their own unique shapes and textures.  Since the outer surface of pollen is very resilient, they resist decay over long periods of time. Changes in the type of pollen found in different sedimentation levels in lakes, bogs or river deltas indicate changes in the plant communities found their in the past, which is a factor of climate conditions.

Pleistocene – The epoch from 2.58 million to 12,000 years before the present day.  This epoch includes the world’s recent period of repeated glaciations.

Oscillation – The repetitive movement or change of some measure around a central value (often a point of equilibrium) between two or more different states. An example would be a pendulum swinging back and forth.

QBO (quasi-biennial oscillation) – A quasi-periodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with an average period between 28 and 29 months.

Quaternary Period – the second out of two periods of the Cenozoic era.  It follows after the Neogene period, spanning 2.58 million years ago to the present day. The Quaternary includes two geologic epochs: the Pleistocene and the Holocene epochs.

Solar Insolation – measure of solar radiation energy (sunlight) received on a given surface area in a given time.

Stadial – A period of colder temperatures during an interglacial period separating the glacial periods of an ice age.  These sections of time are not long enough to be considered glacial periods.

Stratigraphy – This is a branch of geology that studies rock layers and layering called stratification.  It’s main focus is used in the study of sedimentary and layered volcanic rocks.