Useful list of terms and definitions

afforestation The establishment of a forest or stand of trees (forestation) in an area where there was no previous tree cover

albedo The proportion of the incident light or radiation that is reflected by a surface, typically that of a planet or moon. Albedo is a measure of how much light that hits a surface is reflected without being absorbed. Something that appears white reflects most of the light that hits it and has a high albedo, while something that looks dark absorbs most of the light that hits it, indicating a low albedo.

Anthropocene Relating to or denoting the current geological age

atmosphere The envelope of gases surrounding the Earth or another planet

biosphere The relatively thin life-supporting stratum of Earth’s surface, extending from a few kilometres into the atmosphere to the deep-sea vents of the ocean. The biosphere is a global ecosystem composed of living organisms (biota) and the abiotic (nonliving) factors from which they derive energy and nutrients. It is comprised of the lithosphere, hydrosphere and atmosphere.

Blue Ocean Event A complete absence of Arctic sea ice (a common threshold is when the area is less than 1 million square km

carbon sink A carbon sink is anything that absorbs more carbon from the atmosphere than it releases, such as plants, the ocean and soil.

climate systems The global climate system includes processes on land, water, ice and air that interact to determine and change our climate. The Earth’s climate is influenced by numerous factors, such as solar radiation, wind and ocean currents.

cryosphere The frozen water part of the Earth system

deforestation Deforestation refers to the decrease in forest areas across the world that are lost for other uses such as agricultural croplands, urbanization, or mining activities.

dieback The process of death in tress or other vegetation due to drought, disease, deforestation and increases in the intensity and frequency of forest fires or other unfavourable environments.

feedback Refers to a change in a system that has consequences that ultimately add to or counteract the initial change.

hydrosphere All the waters on the Earth’s surface, such as lakes and seas, and sometimes including water over the Earth’s surface, such as clouds.

lithosphere The rigid outer part of the Earth, consisting of the crust and upper mantle.

mesophere The region of the Earth’s atmosphere above the stratosphere, between about 50 and 80 km (30 and 50 miles) in altitude.

permafrost Any ground that remains completely frozen

perturbation A nudge that moves a system away from its initial state

proforestation The practice of purposefully growing an existing forest intact towards its full ecological potential

reforestation The process of replanting an area with trees

stable state A state to which a system recovers under some range of perturbation

stratosphere The layer of the Earth’s atmosphere above the troposphere, extending to about 50 km (32 miles) above the Earth’s surface (the lower boundary of the mesosphere)

thermocline A dividing layer of the oceans that separate the deep and surface oceans. The thermocline is characterized by a rapid change in temperature with depth.

tipping point A point at which a small perturbation can cause a large change to a system, such as it entering a new stable state.

troposphere The lowest region of the atmosphere, extending from the Earth’s surface to a height of about 6 - 10 km (3.7 - 6.2 miles), which is the lower boundary of the stratosphere