Climate science
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Here is a glossary of key vocabulary related to climate change.

 - A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z


                           - A -

  • Adaptation

The process of adjusting to current or expected climate change impacts. In human systems, the aim of adaptation is to reduce risks, increase resilience or seize on beneficial opportunities. In natural systems, human intervention may facilitate adjustments to expected climate change impacts.

  • Albedo

Meaning “whiteness”, albedo is the reflective power of an object or surface. For instance, ice and fresh snow have a high albedo, ranging from 40% to 80%. This means that they reflect 40% to 80% of the incoming sunlight. The ocean is darker, with an albedo of less than 10%.

  • Anthropogenic emissions

Greenhouse gases emitted by human activities.

                           - B -

  • Blue carbon

Carbon dioxide (CO2) removed from the atmosphere by world’s coastal ecosystems (such as mangroves, salt marshes, seagrasses and algae). Aquatic plants grow, accumulate CO2 that is then bury as organic matter (OM) in the soil. 

  • Biodiversity hotspot

Region of the world where the level of biodiversity is significantly highly threatened by human habitation. Biodiversity hotspots contain often local and specific (endemic) and high biodiversity. Biodiversity hotspots are commonly found in tropical regions. 

                           - C -

  • Calving

The breaking off or detachment of a glacier, ice sheet or an iceberg.

  • Carbon dioxide (CO2)

A gas produced by the combustion of carbon (for example: fossil fuels). It is also produced by living organisms through respiration. CO2contributes to the greenhouse effect and ocean acidification.

  • Carbonic acid (H2CO3)

This acid is formed when carbon dioxide dissolves in water, causing an increase in the acidity of the water.

  • Carbon sequestration

Long term storage of carbon dioxide (CO2) – or other forms of carbon – to mitigate climate change, by slowing down atmospheric and marine accumulation of greenhouse gases. 

  • Carbon sink

Natural reservoir that stores carbon-containing chemical compounds accumulated over time. Carbon sinks help reducing the amount of atmospheric CO2. The natural sinks are soil, that is the greatest carbon store ; and part of the biosphere via photosynthesis by terrestrial plants and marine phytoplankton and algaes a process that incorporates atmospheric CO2 into long carbon chain macromolecule using solar energy. 

  • Cascading effects

Inevitable and sometimes unforeseen chain of events due to an act affecting part of the climate system. These cascading effects are often negative.

  • Climate

An average pattern of weather conditions (over 30 years period) – defined by temperature, precipitation, humidity, wind, air pressure – over a given area, including their extremes.

  • Climate change

Climate change refers to changes in the global climate system that result from an enhanced greenhouse effect. These include changes in temperature, precipitation, extreme events, sea level rise and ocean acidification. The term is mostly used to describe the human-induced changes that have been occurring since the pre-industrial times due to an increase in global average temperature. The term “global warming” is also used.

  • Climate justice

A form of environmental and social justice that acknowledges responsibilities to address climate change and recognises differences in opportunities and resources to mitigate or adapt to its impacts.

  • Climate-resilient pathways

Climate-resilient pathways are trajectories of development that combine mitigation and adaptation to aim for sustainable human development and help avoiding dangerous interference with the climate system. 

  • Coastal ecosystems

Coastal ecosystems are created where land and ocean meet. The resulting mixture of freshwater and seawater creates unique environments and ecosystems with distinct structures and diversity. They include saltmarshes, mangroves, seagrass meadows, estuaries and bays. 

  • Coastal erosion

A phenomenon whereby material (sand and rock) is removed from the coast, leading to loss of land. This can be exacerbated by climate change (especially by sea level rise or an increase in precipitation).

  • CO2 uptake

All the processes that contribute to the removal of CO2 from the atmosphere. CO2 can be removed by biological processes such as ocean or land photosynthesis or by physical processes such as carbon absorption in seawater.

  • Complex system

A system (such as the climate system) regulated by many factors that interact with and influence each other: for example the atmosphere, the ocean, the cryosphere, land and the biosphere, in the case of the climate system.

  • Compound event

An event that has more than one possible outcomes. 

  • Continental ice

All ice masses on land comprising glaciers, ice sheets, ice shelves, ice caps etc. except snow, permafrost and sea ice. Continental ice is created by the accumulation and compaction of snow over a long period of time.

  • Cryosphere

The places on or beneath the Earth’s surface (including the ocean) that contain snow and ice (continental ice, sea ice and permafrost).

                           - D -

  • Displacement

Transfer of groups of people from one place of leaving to another. This movement can be temporary or permanent. People are moved away from a place that had became dangerous or that cannot sustain the concerned population due to climate change effects; to a safer place. 

                           - E -

  • Ecosystem services

An ecosystem is the totality of living beings in a given environment plus the environment itself. In an ecosystem, there is a functional interdependent relationship between the living beings and their environment. Humans can directly and indirectly benefit from ecosystems, providing them services. For example, ecosystems produce oxygen (through photosynthesis) and food, and they provide us with raw materials. Ecosystems also preserve soil fertility (through microorganisms and fungi in the soil), fertilise plants (through pollination) and protect coasts (through intact coral reefs or mangroves).

  • Emission pathways

Emission pathways refers to the modelled trahectories of global anthropogenic GHG emissions for the future following different scenarios possible (here for instance, we focus on the RCP2.6 and the RCP8.5).

  • Equity

Justice, fairness: when the same opportunities are given to all – education, health, rights etc. In a climate change context, equity is about fairness in sharing the burden and opportunities of climate change impacts.

  • Extreme events

Unusual events that can have a high negative impact on humans and nature, for example tornadoes, storm surges, landslides, droughts and heatwaves.

                           - F -

                           - G -

  • Glacier

A large mass of ice on land that slowly moves downhill.

  • Global warming

see definition of climate change

  • Greenhouse gas

Greenhouse gases cause the greenhouse effect. They include water vapour, carbon dioxide, methane, nitrous oxide and ozone.

  • Greenhouse effect

Solar radiation crosses the atmosphere, is absorbed by the Earth’s surface and warms it. The absorbed solar radiation is transformed into infrared radiation (heat). Some of this infrared radiation is trapped on its escape towards space by greenhouse gases in the atmosphere and is sent back towards the Earth’s surface – heating it up even more. This is called the greenhouse effect.

                           - H -

  • Heat sink

In the context of climate change, a heat sink is a body – for example a forest or the ocean – that absorbs heat from a warmer body – such as the atmosphere. This results in cooling of the warmer body. The most important heat sink in the climate system is the ocean which, so far, has absorbed over 90% of the heat that has resulted from global warming.

  • Heatwave

A period of abnormally hot weather with high daytime temperatures and no or little cooling down at night. A heatwave can last up to several weeks.

                           - I -

  • Ice sheet

A very large and thick layer of ice on a continent.

  • Industrial Revolution

Historical period between 1760 and the 1840s. It marks the transition from agricultural to industrial societies. The Industrial Revolution started in Europe and the United States and led to rapid development in productivity, technologies and science, and to population growth.

  • Infrared radiation

Infrared radiation is the invisible part of light we can feel as heat. It plays a key role in the greenhouse effect.

  • Invasive species

Species that is not native to a specific location and has the tendency to spread to a degree that ca cause damage to the environment, human economy or human health. A lot of factors can help the spreading of invasive species such as the increase of the intensity of global commercial fluxes. 

                           - J -

                           - K -

                           - L -

                           - M -

  • Marine currents

A flow of water through the ocean. Warm and cold currents redistribute heat around the globe.

  • Marine heatwave

Period of time of minimum 5 days when seawater temperatures exceed a seasonally based maximum temperature (minimum, an exceeding average 2°C).

  • Migration

See the definition of displacement. 

  • Mitigation

Human intervention to reduce global warming by reducing greenhouse gas emissions or enhancing greenhouse gas sinks.

                           - N -

  • Natural variability

Variations in the climate system that are not related to human activities (for example, alternation of glacial and interglacial eras).

                           - O -

  • Ocean acidification

Increase in the acidity of seawater, caused by CO2 from the atmosphere dissolving in the ocean’s surface water. When CO2 reacts with water, the water becomes more acidic.

                           - P -

  • Permafrost

Soil, rock or sediment that is permanently frozen (for at least two consecutive years).

  • pH

pH is a measure of acidity and alkalinity of a solution on a scale in which 7 represents neutrality. A lower value indicates a more acidic solution whereas a higher value indicates a more alkaline solution.

  • Primary production

Primary production is the process by which primary producers, such as phytoplankton and kelp, produce organic matter from inorganic materials through photosynthesis.

                           - Q -

                           - R -

  • Relocation

See the definition of displacement. 

  • Resettlement 

See the definition of displacement. 

  • Runoff

The draining away of water or snow from the surface of an area of land, a building or a structure. 

                           - S -

  • Sea ice

Frozen seawater that floats on the ocean’s surface.

  • Sea level rise

Because of climate change, global mean sea level has risen by about 15 cm since 1900. 

  • Sea surface temperature

The average water temperature at a depth range from 1mm to 20 meters, according to the type of measurement.  

  • Shared socio-economic pathways (SSPs)

Scenarios of projected socioeconomic global changes up to 2100. They are used to derive greenhouse gas emissions scenarios with different climate policies. There are up to 5 SSPs:

  • SPP1: sustainability low mitigation and adaptation challenges 
  • SSP2: middle of the road intermediate challenges
  • SSP3: regional rivalry high mitigation and adaptation challenges
  • SSP4: inequality adaptation challenges dominate
  • SSP5: fossil-fueled development mitigation challenges dominate

SSPs will be used to help produce the IPCC 6th assessment report on global warming due in 2021. 

  • Storm surge

Local rising of the sea as a result of wind and atmospheric pressure changes due to a storm. 

  • Stratification

Layers of seawater masses with different properties: difference of salinity, oxygenation, density and/or temperature. Water of the ocean will then not mix leading to anoxia and lack of nutrients (the water is depleted in O2 and/or in nutrients, which has dramatic consequences on the marine wildlife).

  • Sustainable development

Development that meets the needs of the present generations without compromising the ability of future generations to meet their own needs.

  • Sustainable Development Goals (SDGs)

Universal calls to action to end global poverty, protect the planet and ensure that all people enjoy peace and prosperity by 2030. There are 17 different Sustainable development goals adopted by all United Nations Member States in 2015 : (1) no poverty, (2) zero hunger, (3) good health and well-being, (4) quality education, (5) gender quality, (6) clean water and sanitation, (7) affordable and clean energy, (8) decent work and economic growth, (9) industry, innovation and infrastructure, (10) reduced inequalities, (11) sustainable cities and communities, (12) responsible consumption and production, (13) climate action, (14) life below water, (15) life on land, (16) peace, justice and strong institutions and (17) partnerships for the goals. 

                           - T -

  • Thermal expansion

An increase in volume as a result of rising temperature. With regard to climate change: when the ocean gets warmer, it expands and occupies more space. 

  • Thermal inertia

A property of matter characterising the speed with which it approaches the temperature of its surrounding. The slower it does, the higher the thermal inertia.

  • Tipping point

The point at which a series of small changes or incidents becomes significant enough to cause a larger, more important change.  

  • Transformation

An adaptation that changes the fundamental attributes of a system in response to climate and its effects. 

                           - U -

                           - V -

  • Vulnerability

Sensitivity of a population, a building etc. when exposed to climate change hazards.

                           - W -

  • Weather

The state of the atmosphere at a particular time and place. To define it, many variables such as temperature, precipitation, cloudiness or wind are taken into account.

                           - X -

                           - Y -

                           - Z -

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