This is a list of scientific terms which are frequently used throughout the website.

For further and more specific terms and definitions, please browse the International Panel for Climate Change’s (IPCC) glossaries on climate science, impacts and adaptation, and climate change mitigation.



Accuracy describes the ability of data, measurements or results to match the actual ‘true’ value. This differs from precision which is how close these data are to each other, working as a measure of the spread of data from the average.

A term coined by Paul Crutzen and Eugene Stoermer which refers to the present time interval, where human activities are having significant impacts on geological and environmental processes (including: global warming, erosion, and ocean acidification). The Anthropocene is not currently a formally defined geological unit, though it is under consideration by the International Commission on Stratigraphy for 2016. The beginning of the ‘Anthropocene’ has not been fully defined, though one suggestion places it at the time of the Industrial Revolution in Europe.

The layer of gas (dry gases and water vapour) and dust surrounding the Earth,which is subdivided into: Troposphere (closest to Earth’s surface); Stratosphere; Mesosphere; Thermosphere (furthest away from Earth’s surface). Dry gases comprise: 78.09% Nitrogen; 20.95% Oxygen; 0.93% Argon; 0.03% Carbon Dioxide; and trace gases (Neon; Krypton; Helium; Methane; Xenon; Hydrogen; Ozone). The composition of the atmosphere is finely balanced and is essential for sustaining life on Earth.


Refers to all life on Earth (plants, animals and micro-organisms).


Long-term (typically 30 years) average weather conditions at a particular location or world region. This incorporates parameters such as: precipitation; temperature; wind speed; atmospheric pressure; and humidity.

All snow, ice and permafrost in the world.


Techniques used to estimate when past (climate) 
events occurred. Past changes in the climate can be recorded in certain materials (e.g. rock, ice, organic matter) which are affected by natural processes. A time when natural events occurred can be estimated with the decay of radioactive isotopes (e.g. radiocarbon), counting of consistent markers (e.g. annual tree rings or snow layers), or the existence of specific biological species or sediment deposits within a sequence.

Also referred to as ‘tree ring dating’ – a technique used to determine the age of trees by counting their annual growth rings.

The process by which dry or arid land becomes increasingly dry and degraded. The loss of moisture and vegetation makes the land increasingly susceptible to erosion and further decline.


Ecological niche
The particular part of an environment to which a species is best suited.

A community of living (biotic) organisms (plants, animals and micro-organisms) existing and interacting alongside the non-living (abiotic) component of the environment (such as climate and geology) as a system.

The process through which rock and soil is removed from one location on the earth’s crust (due to the action of wind and water, for example), before being transported and deposited elsewhere. Transport distances can range from several millimetres to several hundred kilometres. Human activites are having an increasing impact on erosion processes, and in many instances are accelerating the natural erosion rate.

The degree to which an observation or measurement deviates from expectation (which in itself is defined by observation or theory).

The disappearance of a species in an ecosystem. This is due to: the evolution of a new species; environmental change; and the impact of human activity.


Fossil fuels
All fuels derived from the fossilisation of previously living organisms. Examples include: coal; oil; natural gas. Due to the long-time scales in their formation (thousands to billions of years) fossil fuels are effectively regarded as being non-renewable over human lifetimes.

Water that is less than 0.2% salinity (dissolved salt content).


A body of land-based (terrestrial) ice that moves downslope under the influence of gravity. In comparison to ice caps and ice sheets, glaciers are confined by topography.

Greenhouse gases
Gases within the atmosphere that absorb and emit thermal (infrared) radiation, helping retain Earth’s heat. The gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulphur dioxide (SO2), carbon monoxide (CO), ozone (O3) and water vapour (H2O2). They are responsible for the ‘Greenhouse effect’.

Water existing in the pores, cracks and cavities in crustal rocks. This water may have percolated from the surface, risen from chambers deep in the Earth’s crust, or been retained in rocks and sediments since their formation.


The environment in which an organism lives, and to which it has become adapted.

 Hadley Cell
A tropical atmospheric circulation cell involving upward movement of air at the equator, poleward motion, descending air in the subtropics, and then flow towards the equator at the surface. It is one of three cells (the others being Polar and Ferrell Cells), and is linked to the topical storms, Trade Winds and deserts.

The present warm period (interglacial) which began at the end of the Pleistocene (Ice Age) approximately 11,600 years ago.

This includes all liquid water on the Earth’s surface. The hydrosphere is inked to the atmosphere by the hydrological cycle.


Ice cap
An ice cap covers less than 50,000 km2 but mainly submerges the underlying topography. They often form in relatively flat, high altitude areas – such as mountain plateaux.

Ice sheet
Ice masses of considerable thickness and extent (>50,000 km2) covering the underlying topography, at continental scales. Ice sheets currently exist over Green;and and Antarctica. During past Ice Ages (glacials), ice sheets also covered northern Europe (Eurasian Ice Sheet) and North America (Laurentide Ice Sheet).

Substances that are not associated with natural growth or living organisms (such as rock and minerals).

Variants of a chemical element. They have the same number of protons, but a different number of neutrons. isotope values are expressed as ‘delta values’ using the Greek symbol for ‘delta’ meaning ‘change in a value’ (for example: δ18O). As isotopes are measured in extremely small concentrations, we use the term ‘parts per mil’ or parts per thousand (‰). To ensure that all scientific studies of isotopes can be accurately compared, we refer to values relative to international standards. These are samples of known concentrations, and each standard for each element has a specific name depending on the type and/or location of the standard sample. For carbonate for example, we use a standard called Vienna Pee Dee Belemnite.


The Earth’s crust and upper mantle.


Literally means ‘large animal’ (usually weighing over 100 kg) and is commonly used to refer to the large Pleistocene mammals (such as Mammoths, Milodons, Woolly Rhinos and Mastodons).

The study of the atmosphere. This term usually specifically refers to processes in Troposphere and Stratosphere as it is in these layers that surface weather is generated. Processes in the Mesosphere and Ionosphere are usually studied via Geophysics rather than Meteorology.


Non-renewable resources
Resources that are not replenished at the same rate that they are consumed. Examples include oil and coal which form over thousands to millions of years. Such resources may also have a finite distribution across the Earth’s surface, meaning that continued use of these reserves will lead to their ultimate depletion.


Relating to a living organism (plant, animals and micro-organisms).


Palaeo (paleo – USA)
Pertaining to the past. This is commonly used as a prefix to other terms, such as: palaeoecology (the study of past ecology); palaeoclimate (past climates); palaeoceanography (the study of past ocean dynamics).

The layer at the Earth’s surface where soils and soil forming processes occur. The pedosphere can only develop where there is an interaction between the lithosphere, biosphere, hydrosphere and atmosphere.

Ground that remains frozen throughout the year (perennially).

The first epoch of the Quaternary, and often referred to as the last ice Age, the Pleistocene spans the period 2.6 million years ago to 11.6 thousand years ago.

The degree to which repeat measurements, using identical experiments, yield comparable results. The reproducibility of a set of results or experiment.

Records of past environments that are used by scientists as a replacement for direct measurements. Proxies can take the form of: biological records (fossils); chemical records (isotopes); geological (sediments and ice). For example, pollen grains from ancient sediments are used to indicate past vegetation.


Information based on measurement of qualities or features rather than quantities. Qualitative data is sometimes associated with human subjectivity.

Information based on empirical measurements of quantity. Quantitative data are often regarded as objective – not exposed to the subjectivity of human perception.

The most recent Geological time period spanning the last 2.6 million years.


 Refugium (plural Refugia)
An isolated location in which a species/or multiple species can persist when they become ecologically stressed elsewhere. This may be due to certain characteristics of the refiugium/refugia (climate; geology; ecology; or hydrology).

Renewable resources
Components of the Earth that maintain a sustained yield. Their replenishment is equal to or greater than the rate at which they are consumed. Examples include: wind and solar energy.


Most commonly refers to unconsolidated particles that are derived from rocks and have been transported and deposited elsewhere. Sediments cover a range of particle sizes from boulders to clay. Other materials, such as peat deposits, are also classed as sediments despite not originating from rocks.

Chemically precipitated deposits within caves. This term encompasses forms such as stalagmites and stalactites and are typically composed of calcite, aragonite or silica.


Taxon (plural Taxa)
The term used for a group or groups of populations of a particular organism.

Thermohaline circulation
Global ocean water circulation that is driven by changes in temperature (thermo) and salinity (haline). This is one of the dominant drivers of ocean currents.

Features of the Earth’s surface such as valleys and mountains.


 Water stress
The IPCC (Bates et al., 2008) define a watershed/river basin as being water stressed when either water availability per person, per year is below 1,000 m3 (100 m2) based on long-term average runoff; or the ratio of water withdrawals to long-term average annual runoff is above 0.4.

The average atmospheric conditions at a given time and location. This incorporates parameters such as: temperature, precipitation, atmospheric pressure and wind speed.