The DDC contains many terms about climate science that are well known to the climate science community and terms about socio-economic modelling that are well known to the Integrated Assessment Modelling community. However, many of these terms can mean different things depending on their context or may have specific meanings that are not clear to users beyond the original community. Further to this, both climate science and socio-economic modellers make extensive use of acronyms. This glossary contains definitions for acronyms and specialised terms that are found on the IPCC-DDC website.
SRES storyline and scenario families, see SRES scenarios
Initiatives and measures to reduce the vulnerability of natural and human systems against actual or expected climate change effects. Various types of adaptation exist, e.g. anticipatory and reactive, private and public, and autonomous and planned. Examples are raising river or coastal dikes, the substitution of more temperature-shock resistant plants for sensitive ones, etc.
The whole of capabilities, resources and institutions of a country or region to implement effective adaptation measures.
A collection of airborne solid or liquid particles, with a typical size between 0.01 and 10 �m that reside in the atmosphere for at least several hours. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in several ways: directly through scattering and absorbing radiation, and indirectly by acting as cloud condensation nuclei or modifying the optical properties and lifetime of clouds (see Indirect aerosol effect).
Atmospheric Model Intercomparison Project
Resulting from or produced by human beings.
Fourth IPCC Assessment Report link
American Standard Code for Information Interchange. ASCII is a character encoding scheme
SRES storyline and scenario families, see SRES scenarios
British Atmospheric Data Centre link
The baseline (or reference) is the state against which change is measured. It might be a �current baseline�, in which case it represents observable, present-day conditions. It might also be a �future baseline�, which is a projected future set of conditions excluding the driving factor of interest. Or it might be a 'non-intervention scenario', which is used as a reference in the analysis of intervention scenarios. Alternative interpretations of the reference conditions can give rise to multiple baselines.
Bundesminesterium f�r Bildung und Forschung / Federal Ministry of Education and Research link
In the context of climate change, capacity building is developing the technical skills and institutional capabilities in developing countries and economies in transition to enable their participation in all aspects of adaptation to, mitigation of, and research on climate change, and in the implementation of the Kyoto Mechanisms, etc.
Consultative Group of Experts
Centre for International Earth Science Information Network link
Computational Information Systems Laboratory link
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.
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, or to persistent anthropogenic changes in the composition of the atmosphere or in land use. Note that the Framework Convention on Climate Change (UNFCCC), in its Article 1, defines climate change as: �a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods�. The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmospheric composition, and climate variability attributable to natural causes.
Due to the thermal inertia of the ocean and slow processes in the biosphere, the cryosphere and land surfaces, the climate would continue to change even if the atmospheric composition were held fixed at today�s values. Past change in atmospheric composition leads to a committed climate change, which continues for as long as a radiative imbalance persists and until all components of the climate system have adjusted to a new state. The further change in temperature after the composition of the atmosphere is held constant is referred to as the constant composition temperature commitment or simply committed warming or warming commitment. Climate change commitment includes other future changes, for example in the hydrological cycle, in extreme weather and climate events, and in sea level change.
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 all or some of its known properties. The climate system can be represented by models of varying complexity (i.e., for any one component or combination of components a hierarchy of models can be identified, differing in such aspects as the number of spatial dimensions, the extent to which physical, chemical, or biological processes are explicitly represented, or the level at which empirical parameterisations are involved. Coupled atmosphere/ocean/sea-ice General Circulation Models (AOGCMs) provide a comprehensive representation of the climate system. More complex models include active chemistry and biology. Climate models are applied, as a research tool, to study and simulate the climate, but also for operational purposes, including monthly, seasonal, and interannual climate predictions.
A climate prediction or climate forecast is the result of an attempt to produce an estimate of the actual evolution of the climate in the future, for example, at seasonal, interannual or long-term time scales. Since the future evolution of the climate system may be highly sensitive to initial conditions, such predictions are usually probabilistic in nature.
A projection of the response of the climate system to emission or concentration scenarios of greenhouse gases and aerosols, or radiative forcing scenarios, often based upon simulations by climate models. Climate projections are distinguished from climate predictions in order to emphasize that climate projections depend upon the emission/concentration/radiative forcing scenario used, which are based on assumptions concerning, for example, future socioeconomic and technological developments that may or may not be realised and are therefore subject to substantial uncertainty.
A plausible and often simplified representation of the future climate, based on an internally consistent set of climatological relationships that has been constructed for explicit use in investigating the potential consequences of anthropogenic climate change, often serving as input to impact models. Climate projections often serve as the raw material for constructing climate scenarios, but climate scenarios usually require additional information such as about the observed current climate. A climate change scenario is the difference between a climate scenario and the current climate.
Carbon Dioxide. CO2 is a naturally occurring gas, also a by-product of burning fossil fuels from fossil carbon deposits, such as oil, gas and coal, of burning biomass and of land use changes and other industrial processes. It is the principal anthropogenic greenhouse gas that affects the Earth�s radiative balance. It is the reference gas against which other greenhouse gases are measured and therefore has a Global Warming Potential of 1.
A model run carried out to provide a �baseline� for comparison with climate-change experiments. The control run uses constant values for the radiative forcing due to greenhouse gases and anthropogenic aerosols appropriate to pre-industrial conditions.
Coordinated Regional Climate Downscaling Experiment
Coupled Model Intercomparison Project
Fifth Coupled Model Intercomparison Project link
Climatic Research Unit link
Comma Separated Values. CSV files store tabular data in plain-text form
Department for Energy and Climate Change link
IPCC Data Distribution Centre link
Digital Object Identifier. The DOI system provides a technical and social infrastructure for the registration and use of persistent interoperable identifiers for use on digital networks. link
Digital Video Disk
Deutsches Klimarechensentrum / German Climate Computing Centre link
Data Reference Syntax. DRS is a commmon naming system used in the CMIP5 archive to identify datasets. link
A plausible representation of the future development of emissions of substances that are potentially radiatively active (e.g., greenhouse gases, aerosols), based on a coherent and internally consistent set of assumptions about driving forces (such as demographic and socioeconomic development, technological change) and their key relationships. Concentration scenarios, derived from emission scenarios, are used as input to a climate model to compute climate projections. In IPCC (1992) a set of emission scenarios was presented which were used as a basis for the climate projections in IPCC (1996). These emission scenarios are referred to as the IS92 scenarios. In the IPCC Special Report on Emission Scenarios (Nakicenovic and Swart, 2000) a new set of emission scenarios, the so-called SRES scenarios, were published. For the meaning of some terms related to these scenarios see SRES scenarios.
A group of parallel model simulations used for climate projections. Variation of the results across the ensemble members gives an estimate of uncertainty. Ensembles made with the same model but different initial conditions only characterise the uncertainty associated with internal climate variability, whereas multi-model ensembles including simulations by several models also include the impact of model differences. Perturbed-parameter ensembles, in which model parameters are varied in a systematic manner, aim to produce a more objective estimate of modelling uncertainty than is possible with traditional multi-model ensembles.
Earth System Model (See Climate Model)
An equilibrium climate experiment is an experiment in which a climate model is allowed to fully adjust to a change in radiative forcing. Such experiments provide information on the difference between the initial and final states of the model, but not on the time-dependent response. If the forcing is allowed to evolve gradually according to a prescribed emission scenario, the time-dependent response of a climate model may be analysed. Such an experiment is called a transient climate experiment.(See Climate Projection)
See Sea-Level Rise
See Vulnerability
Food and Agriculture Organisation (UN) link
First Assessment Report link
General Circulation Model. (See Climate Model)
Global Climate Model. (See Climate Model)
Gross Domestic Product
Geostationary Earth Orbit Tagged Image File Format link
Global Historical Climatology Network � Extended Reconstructed Sea Surface Temperature ERSST link, GHCN link
Greenhouse Gas
Geographical Information System. GIS is designed to capture, store, manipulate, analyze, manage and present geographical data.
The global surface temperature is an estimate of the global mean surface air temperature. However, for changes over time, only anomalies, as departures from a climatology, are used, most commonly based on the area-weighted global average of the sea surface temperature anomaly and land surface air temperature anomaly.
Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared radiation emitted by the Earth�s surface, the atmosphere itself, and by clouds. This property causes the greenhouse effect. Water vapour (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ozone (O3) are the primary greenhouse gases in the Earth�s atmosphere. Moreover, there are a number of entirely human-made greenhouse gases in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, dealt with under the Montreal Protocol. Beside CO2, N2O and CH4, the Kyoto Protocol deals with the greenhouse gases sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs).
GRIdded Binary. GRIB is a mathematically concise data format commonly used in meteorology to store historical and forecast weather data.
GNU zip. GZIP is used for file compression and decompression
Hadley Centre/Climatic Research Unit gridded surface temperature data set version 3 link
Hyper Text Mark-up Language
Integrated Assessment Model
Integrated Assessment Modelling Consortium link
Impacts Adaptation and Vulnerability.
International Geosphere-Biosphere Programme link
International Human Dimensions Programme on Global Environmental Changelink
A period of rapid industrial growth with far-reaching social and economic consequences, beginning in England during the second half of the 18th century and spreading to Europe and later to other countries including the USA. The industrial revolution marks the beginning of a strong increase in combustion of fossil fuels and related emissions of
carbon dioxide. In the AR4, the term �pre-industrial� refers, somewhat arbitrarily, to the period before 1750.Intergovernmental Panel on Climate Change link
Intergovernmental Panel on Climate Change-Data Distribution Centre link
Illustrative Scenarios 1992, see SRES scenarios.
IPCC Scenarios 1992, see SRES scenarios.
See Post-Glacial Rebound.
Joint IAV IAM Committee link
The Kyoto Protocol was adopted at the Third Session of the Conference of the Parties (COP) to the UN Framework Convention on Climate Change (UNFCCC) in 1997 in Kyoto, Japan. It contains legally binding commitments, in addition to those included in the UNFCCC. Countries included in Annex B of the Protocol (most member countries of the Organisation for Economic Cooperation and Development (OECD) and those with economies in transition) agreed to reduce their anthropogenic greenhouse gas emissions (CO2, CH4, N2O, HFCs, PFCs, and SF6) by at least 5% below 1990 levels in the commitment period 2008 to 2012. The Kyoto Protocol entered into force on 16 February 2005.
Land Use and Land-Cover Change Programme link
See Scenario (Marker).
Model and Data Group link
Measures are technologies, processes, and practices that reduce GHG emissions or effects below anticipated future levels. Examples of measures are renewable energy technologies, waste minimization processes and public transport commuting practices, etc.
Information about meteorological and climatological data concerning how and when they were measured, their quality, known problems and other characteristics.
An anthropogenic intervention to reduce the anthropogenic forcing of the climate system; it includes strategies to reduce greenhouse gas sources and emissions and enhancing greenhouse gas sinks.
Max Planck Institute for Meteorology link
National Aeronautics and Space Administration link
National Centre for Atmospheric Research link
National Centre for Atmospheric Science link
National Communications Support Programme (UN) link
National Environment Research Council link
The triatomic form of oxygen (O3), a gaseous atmospheric constituent. In the troposphere, it is created both naturally and by photochemical reactions involving gases resulting from human activities (photochemical smog). In high concentrations, tropospheric ozone can be harmful to many living organisms. Tropospheric ozone acts as a greenhouse gas. In the stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O2). Depletion of stratospheric ozone, due to chemical reactions that may be enhanced by climate change, results in an increased ground-level flux of ultraviolet (UV) B radiation.
See Ozone Layer
The stratosphere contains a layer in which the concentration of ozone is greatest, the so-called ozone layer. The layer extends from about 12 to 40 km above the Earth�s surface. The ozone concentration reaches a maximum between about 20 and 25 km. This layer is being depleted by human emissions of chlorine and bromine compounds. Every year, during the Southern Hemisphere spring, a very strong depletion of the ozone layer takes place over the antarctic region, caused by anthropogenic chlorine and bromine compounds in combination with the specific meteorological conditions of that region. This phenomenon is called the ozone hole.
Very small solid exhaust particles emitted during the combustion of fossil and biomass fuels. Particulates may consist of a wide variety of substances. Of greatest concern for health are particulates of less than or equal to 10 nm in diameter, usually designated as PM10.
Program for Climate Model Diagnosis and Intercomparison link
Portable Document Format
pH is a dimensionless measure of the acidity of water (or any solution) given by its concentration of hydrogen ions (H+). pH is measured on a logarithmic scale where pH = �log10(H+). Thus, a pH decrease of 1 unit corresponds to a 10-fold increase in the concentration of H+, or acidity.
The study of natural phenomena that recur periodically (e.g., development stages, migration) and their relation to climate and seasonal changes.
In UNFCCC parlance, policies are taken and/or mandated by a government - often in conjunction with business and industry within its own country, or with other countries - to accelerate mitigation and adaptation measures. Examples of policies are carbon or other energy taxes, fuel efficiency standards for automobiles, etc. Common and co-ordinated or harmonised policies refer to those adopted jointly by parties.
The vertical movement of the land and sea floor following the reduction of the load of an ice mass, for example, since the Last Glacial Maximum (21 ka). The rebound is an isostatic land movement.
Programme of Research on Climate Change Vulnerability, Impacts and Adaptation link
Representative Concentration Pathway
(See Baseline)
Radiative forcing is the change in the net vertical irradiance (expressed in Watts per square metre; Wm�2) at the tropopause due to an internal or external change in the forcing of the climate system, such as a change in the concentration of CO2 or the output of the Sun.
Second Assessment Report link
A plausible and often simplified description of how the future may develop, based on a coherent and internally consistent set of assumptions about driving forces and key relationships. Scenarios may be derived from projections, but are often based on additional information from other sources, sometimes combined with a �narrative storyline�.
Scenarios that have a similar demographic, societal, economic and technical change storyline.
A scenario that is illustrative for each of the six scenario groups reflected in the Summary for Policymakers of Nakicenovic and Swart (2000). They include four revised scenario markers for the scenario groups A1B, A2, B1, B2, and two additional scenarios for the A1FI and A1T groups. All scenario groups are equally sound.
A scenario that was originally posted in draft form on the SRES website to represent a given scenario family. The choice of markers was based on which of the initial quantifications best reflected the storyline, and the features of specific models. Markers are no more likely than other scenarios, but are considered by the SRES writing team as illustrative of a particular storyline. They are included in revised form in Nakicenovic and Swart (2000). These scenarios received the closest scrutiny of the entire writing team and via the SRES open process. Scenarios were also selected to illustrate the other two scenario groups.
An increase in the mean level of the ocean. Eustatic sea-level rise is a change in global average sea level brought about by an increase in the volume of the world ocean. Relative sea-level rise occurs where there is a local increase in the level of the ocean relative to the land, which might be due to ocean rise and/or land level subsidence. In areas subject to rapid land-level uplift, relative sea level can fall.
Socio-Economic Data Applications Center link
Sensitivity is the degree to which a system is affected, either adversely or beneficially, by climate variability or change. The effect may be direct (e.g., a change in crop yield in response to a change in the mean, range or variability of temperature) or indirect (e.g., damages caused by an increase in the frequency of coastal flooding due to sea-level rise).
Scenarios concerning future conditions in terms of population, Gross Domestic Product and other socio-economic factors relevant to understanding the implications of climate change.
Special Report on Emission Scenarios link. The storylines and associated population, GDP and emissions scenarios associated with the Special Report on Emissions Scenarios (SRES) (Nakicenovic et al., 2000), and the resulting climate change and sea-level rise scenarios. Four families of socio-economic scenario (A1, A2, B1 and B2) represent different world futures in two distinct dimensions: a focus on economic versus environmental concerns, and global versus regional development patterns.
SRES scenarios are emission scenarios developed by Nakicenovic and Swart (2000) and used, among others, as a basis for some of the climate projections in IPCC AR4.
Shared Socio-Economic Pathway
A narrative description of a scenario (or family of scenarios), highlighting the main scenario characteristics, relationships between key driving forces and the dynamics of their evolution.
See Ozone
Third Assessment Report link
See Global Surface Temperature
See Biosphere
Task Group on data and scenario support for Impacts and Climate Analysis (IPCC) link
A device at a coastal location (and some deep-sea locations) that continuously measures the level of the sea with respect to the adjacent land. Time averaging of the sea level so recorded gives the observed secular changes of the relative sea level.
In the AR4 WGI report, the word trend designates a change, generally monotonic in time, in the value of a variable.
Technical Support Unit (IPCC) link
See Ozone
United Nations link
United Nations Environment Programme link
United Nations Framework Convention on Climate Change link. The Convention was adopted on 9 May 1992 in New York and signed at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries and the European Community. Its ultimate objective is the �stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system�. It contains commitments for all Parties. Under the Convention, Parties included in Annex I (all OECD countries and countries with economies in transition) aim to return greenhouse gas emissions not controlled by the Montreal Protocol to 1990 levels by the year 2000. The convention entered in force in March 1994.
Ultraviolet
Volatile Organic Compound
Vulnerability is the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity, and its adaptive capacity.
World Climate Research Programme link
World Data Centre for Climate link
Working Group on Coupled Modelling link
IPCC Working Group I: The Physical Science Basis link
IPCC Working Group II: Impacts, Adaptation and Vulnerability link
IPCC Working Group III: Mitigation of climate change link
World Meteorological Organisation link
World Wide Web