1 Adaptation (to climate change) – The adjustments of an ecological and/or socio-cultural system to climate change for protection, enhanced resilience or transformation under the effects of the change. Adaptation is a central concept in the IPCC Fifth Assessment Report (AR5), where it conserves a very broad definition. This means in particular that it can remain consensual in international negotiations.

2 Albedo – The fraction of solar energy reflected directly into space and not absorbed by the terrestrial system. Pale surfaces reflect much more energy than dark ones.

3 Anomaly (climatic) – A climatic fluctuation whose amplitude (intensity and spatial extent) is outside the standard of the fluctuations observed, that is to say fairly remote from the climatic mean.

4 Anthropocene – A term proposed to indicate the present geological epoch during which anthropic activities have a determinant impact of the terrestrial ecosystem, making humans a major geological force at the scale of the planet. The Anthropocene thus follows the Holocene. The chronology of the Anthropocene has not been firmly decided as the date of the beginning of the new period is under discussion.

5 Attribution – The determination of the cause/s of a climatic anomaly and in particular the separation of the effect of a human forcing, a natural forcing or that of natural climate variability.

6Biomass (plant, soil or in a watercourse) – In ecology, this refers to the total mass of living organisms in a specific space at a given moment. It is estimated per unit of surface area or of volume for an aquatic environment. Plant biomass refers specifically to the total mass of vegetation.

7 Biotemporal signal – A signal detected in the natural environment and that receives a cultural interpretation by a given society as the precursor of a climatic variation. There are generally several signals that form a group of convergent signs that increase the reliability of the prediction and the resulting decision making.

8 Carbon cycle – The flow of carbon through the atmosphere, seas and continents. Carbon dioxide (CO₂) movements between the atmosphere and land ecosystems are numerous, involving photosynthesis, combustion, the decomposition of organic matter, etc. But oceans also play an important role by absorbing CO2 when the atmospheric level of this gas increases.

9 Citizen science – Research generally focused on the study of biodiversity in which amateur naturalists who have not had any particular training in research perform research tasks in observation, counting, census compilation or data entry on a volunteer basis.

10 Climate prediction – Simulation of the future evolution of the climate starting from a known initial state.

11 Climate projection – Simulation of the response of the climate system to various external forcing scenarios (greenhouse gas emission, aerosols, etc.).

12 Climate variability (natural or internal) – Intrinsic variations in the climate system as a result of pairings between systems (atmosphere, sea, etc.) with different physical, dynamic and chemical properties.

13 Climatic model – The use of a set of equations to represent the various components of the climatic system and their interactions. Computer processing is required to solve these equations.

14 CMIP (Coupled Model Intercomparison Project) – An international project with a common protocol for the performance of climate simulations and the placing of the results at the disposal of IPCC operations.

15 Compliance – The correct obeying of the instructions for the use of medicines. The term is used here in the broader good response of populations in the face of a threat or with regard to political recommendations concerning such a threat.

16 Convection (tropical) – Precipitation in the tropics is caused mainly by cloud systems consisting of strong vertical movements (storms, squall lines and cyclones). Such convection is also the main atmospheric transport vector of the surplus energy received by these zones to zones with energy deficits.

17Coupling – Transfer of information using certain variables between two parts of the terrestrial climate system, e.g. ocean-atmosphere coupling.

18 Ecotone – A transition zone between two very contrasted ecosystems. It can take very varied forms ranging from a clear-cut line to vast, widespread interpenetration to the extent that another ecosystem can form, with its own characteristics and dynamics.

19 Extreme climatic event – A climatic anomaly with very strong amplitude, for example one that is among the strongest 10 % observed.

20 Forcing – A disturbance from outside the climate system that disturbs the energy balance of the latter. Distinction is made between natural forcings (astronomic factors, volcanic activity), anthropic forcings (emission of greenhouse gases and aerosols, change in land use).

21 Global issues – Questions that go beyond the sphere of intervention by nation states and include climate warming and decreasing biodiversity. The notion refers to the complexity of taking these issues into account, with regard to both understanding them and providing responses.

22 Greenhouse gases – Gaseous constituents of the atmosphere that absorb infrared heat radiation emitted from the earth’s surface and re-emit it towards the surface. They thus contribute to the greenhouse effect by limiting energy loss into space. The main greenhouse gases of the earth are water vapour, carbon dioxide, methane, nitrous oxide and ozone. The increase in their concentration as a result of anthropic emissions is the cause of recent climate warming.

23 Greenwashing – A deceitful marketing method consisting of advertising using the ecological argument. The aim of greenwashing is to announce ecological responsibility that is far from the reality of the practices of the corporate structure concerned.

24 Human ecology – A research field addressing the full diversity of the relationship between humans and their environments. ‘Dynamics’ and ‘interactions’ are the keywords of this interdisciplinary scientific approach that examines the interfaces between society and nature and between biology and culture.

25 IPCC – The Intergovernmental Panel on Climate Change set up in 1988 by the United Nations. Its mission is the assessment of scientific knowledge on climate change of human origin and the consequences.

26 Isotopic composition (of water) – Water (H₂0) consists of stable isotopes of oxygen (¹⁶O, ¹⁷O,¹⁸O) and hydrogen (¹H and²H). Water isotope composition is used increasingly for studying the present water cycle (precipitation, water vapour, recycling) and its past variations, especially in the tropics.

27Mesh – Use of meshes in a climate model is based on discretisation aimed at drawing individual values from a continuous environment such as the atmosphere or the sea.

28 Mitigation – Reducing the exposure of a system by protecting it from strong disturbances in order to moderate the effects of climate change. A central theme in successive IPCC reports, mitigation is defined there as the human actions required to reduce greenhouse gas emissions and enhance sinks.

29 Modes of climatic variability – Atmospheric phenomena that can be linked to the sea, with a regional to supraregional spatial scale, with temporal recurrence of variable regularity and marked climatic impacts. The best known in the tropics is the El Niño Southern Oscillation (ENSO), a linked sea-atmosphere phenomenon that dominates climatic variability at interannual time scales.

30 Proxy data – Variables (water isotopes, etc.) that are climate-related and measurable in ‘archives’ (tree rings, corals, ice cores, etc.) that provide information about past climate conditions.

31 Radiative forcing – Expressed in energy units per second per surface area (W/m²). Positive forcing causes the warming of the climate system, as is the case with greenhouse gases, and negative forcing causes cooling, as is the case with aerosols.

32 Otolith – A mineral concretion in the inner ear of vertebrates. Otholiths are used frequently for measuring the age of fish.

33 Feedback – The result of an initial process that triggers changes in a second process that in turn affects the initial process. A positive feedback intensifies the initial process and a negative feedback reduces it.

34 Resilience – A polysemous concept that refers to the ability of a physical, biological, ecological or sociocultural system to absorb disturbance or withstand changes without modifying its functions, structure, identity and functioning.

35 Socio-ecological system – A coherent entity with a bio-geophysical component and a sociocultural component. The combination of the two sets the spatial, temporal, organisation and functional contours of the system to enhance study of its dynamics.

36 Uncertainty – Incomplete knowledge resulting from lack of information or disagreement concerning known features. It can be represented quantitively or by the opinion of experts.

37 Upwelling – The rise of deep water caused by winds that push the surface water out to sea. The phenomenon results in cold seawater charged with nutrient minerals along the coasts.

38Urban heat island – Local higher temperatures—especially maximum temperatures—recorded in an urban environment. Considerable temperature differences can be observed in the same city, depending on town planning features, albedo, relief and exposure.

39 Water cycle – The water cycle describes the movement of water in all its form. Solar energy causes the evaporation of seawater and continental water. Water vapour is redistributed by complex atmospheric currents and released as rainfall or snow. A proportion of the precipitation that falls on landmass evaporates again in contact with the ground. The rest takes the form of runoff or infiltrates and feeds reservoirs, lakes and rivers. Water from the land then returns to the sea, completing the global scale water cycle.