Glossary

The process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities. In some natural systems, human Intervention may facilitate adjustment to expected climate and its effects. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Aerosols are suspensions of fine particles in air. They exists in either liquid or solid form. Russ, sulphate and mineral dust count as aerosols. They influence climate by reflecting solar radiation (cooling effect) by supporting cloud and precipitation formation as condensation and ice nuclei.

The variability among living organisms from terrestrial, marine and other ecosystems. Biodiversity includes variability at the genetic, species and ecosystem levels. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging These variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an Extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Climate indicators such as summer days or frost days and many more help illustrating the climate and climate change of a station or region. They help users in practice to understand the climatic development. Climate indicators are computed from meteorological base variables such as temperature and precipitation.

A numerical representation of the climate system based on the physical, chemical and biological properties of its components, their interactions and feedback processes and accounting for some of its known properties. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

A climate projection is the simulated response of the climate System to a scenario of future emission or concentration of greenhouse gases (GHGs) and aerosols, generally derived using climate models. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

See also mitigation (of climate change).

Climate services are scientific data and information about climate, climate change and its impacts, that have been specifically user-tailored. They serve decision makers in politics, economy and society in order to reduce climate-related risks, detect opportunities and optimise costs.

The climate system is the highly complex system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the lithosphere and the biosphere and the interactions between them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations and anthropogenic forcings such as the changing composition of the atmosphere and land-use change. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Climate variability refers to variations in the mean state and other statistics (such as standard deviations, the occurrence of extremes, etc.) of the climate on all spatial and temporal scales beyond that of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability), or to variations in natural or anthropogenic external forcing (external variability). Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

This climate indicator provides the minimum temperature of the coldest night in a given year.

On a day with fresh snow, at least 1 mm of precipitation falls in the form of snow. The number of days with fresh snow as a climate indicator is relevant for different sectors, e.g. tourism, road construction, agriculture and others.

A coupled atmosphere–ocean general circulation model in which a representation of the carbon cycle is included, allowing for interactive calculation of atmospheric CO2 or compatible emissions. Additional components (e.g., atmospheric chemistry, ice sheets, dynamic vegetation, nitrogen cycle, but also urban or crop models) may be included. See also Climate model. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

A plausible representation of the future development of emissions of substances that are potentially radiatively active (e.g., greenhouse gases (GHGs), aerosols) based on a coherent and internally consistent set of assumptions about driving forces (such as demographic and socio-economic development, technological change, energy and land use) and their key relationships. Concentration scenarios, derived from emission scenarios, are used as input to a climate model to compute climate projections. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

A collection of model simulations characterizing a climate prediction or projection. Differences in initial conditions and model formulation result in different evolutions of the modeled system and may give information on uncertainty associated with model error and error in initial conditions in the case of climate forecasts and on uncertainty associated with model error and with internally generated climate variability in the case of climate projections. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Reaction of a system to a change: a positive feedback is a self-reinforcing process; a negative feedback means that a change is balanced by an opposite reaction.

On a frost day, the minimum temperature stays below 0°C. The number of frost days per year is a frequently used climate indicator.

See Climate model.

Global warming refers to the gradual increase, observed or projected, in global surface temperature, as one of the consequences of radiative forcing caused by anthropogenic emissions. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Hail area denotes the area affected by hail per hail event (POH ≥ 80%).

Hail days are defined as days with a high probability of hail (POH ≥ 80%). Here, the 24 hours between 8 a.m. and 8 a.m. of the following day (CEST) are considered.

Hail probability (i.e., Probability of Hail, or POH) refers to the probability with which hail can be expected on the ground per square kilometer.

Hailstone size (i.e., Maximum Expected Severe Hail Size, or MESHS) is defined as the maximum expected hailstone size per square kilometer. Conversely, this means that most of the hailstones in reference to this one square kilometer will be smaller.

Hailstone size on a reference area (i.e., Largest Expected Hail on a reference Area, or LEHA) describes the largest expected hailstone on a reference area smaller than the square kilometer considered by MESHS. LEHA is statistically derived from the hailstone size MESHS. The maximum hailstone size predicted by MESHS is expected on one or only a few LEHA reference areas within the MESHS square kilometer. However, the probability of such an occurrence is very small. On the majority of the smaller reference areas, LEHA sizes are expected.

The potential occurrence of a natural or human-induced physical Event or trend or physical impact that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, ecosystems and environmental resources. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

A period of abnormally and uncomfortably hot weather. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Heavy precipitation is precipitation which has high intensity relative to its duration. Heavy precipitation events can be either precipitation with short duration and high intensity or precipitation lasting for several hours or days with high rainfall amounts. In addition to duration and frequency, the size of the area affected by the heavy precipitation is also critical.

This climate indicator is described by the highest daily maximum temperature in a given year.

Impacts generally refer to effects on lives, livelihoods, health, ecosystems, economies, societies, cultures, services and infrastructure due to the interaction of climate changes or hazardous climate events occurring within a specific time period and the vulnerability of an exposed society or system. Impacts are also referred to as consequences and outcomes. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

See Climate variability.

A human intervention to reduce the sources or enhance the sinks of greenhouse gases (GHGs). Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

The annual minimum flow rate averaged over 7 days. Averaging over several days makes this low flow parameter less susceptible than others to measurement errors or short-term anthropogenic influences.

The term opportunity is often used to refer to the potential, when the outcome is uncertain, for positive consequences on lives, livelihoods, health, ecosystems and species, economic, social and cultural assets, services (including environmental services) and infrastructure. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

A projection is a potential future evolution of a quantity or set of quantities, often computed with the aid of a model. Unlike predictions, projections are conditional on assumptions concerning, for example, future socio-economic and technological developments that may or may not be realized. See also Climate projection. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Under Article 4 Waters Protection Act, the flow rate Q347 is the flow rate which, averaged over ten years, is reached or exceeded on an average of 347 days (95th percentile) per year and which is not substantially affected by damming, abstraction or inflow of water.

Radiative forcing is the change in energy flux caused by a driver and is calculated at the tropopause or at the top of the atmosphere. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

The potential for consequences where something of value is at stake and where the outcome is uncertain, recognizing the diversity of values. Risk is often represented as probability or likelihood of occurrence of hazardous events or trends multiplied by the impacts if these events or trends occur. The term risk is often used to refer to the potential, when the outcome is uncertain, for adverse consequences on lives, livelihoods, health, ecosystems and species, economic, social and cultural assets, services (including environmental services) and infrastructure. Source: IPCC, 2014: Annex II: Glossary. IPCC, Geneva, Switzerland, pp. 117-130.

Characteristic seasonal runoff variations in a watercourse, which is dependent on meteorological factors and the characteristics of the catchment. Glacial regimes are characterised by the glacier melt in summer, nival regimes by the snow melt in spring, pluvial regimes by the interplay of rain and evaporation.

This climate indicator is described by the maximum 1-day precipitation falling in a given year.

On a summer day, the maximum temperature is 25°C or higher. The number of summer days per year is a frequently used climate indicator.

Surface runoff is rainwater which does not percolate, particularly during heavy precipitation, but runs along the open ground and can cause damage.

In a tropical night the temperature does not sink below 20°C. The number of Tropical nights per year is a climate indicator for heat and heatstress.

Water management comprises all the human activities for use of the water, protection of the water and protection against hazards from the water.