Editorial Board Co-Chairs:
John Agard (Trinidad and Tobago), E. Lisa F. Schipper (Sweden)
Editorial Board:
Joern Birkmann (Germany), Maximiliano Campos (Costa Rica), Carolina Dubeux (Brazil),
Yukihiro Nojiri (Japan), Lennart Olsson (Sweden), Balgis Osman-Elasha (Sudan), Mark Pelling
(UK), Michael J. Prather (USA), Marta G. Rivera-Ferre (Spain), Oliver C. Ruppel (Namibia),
Asbury Sallenger (USA), Kirk R. Smith (USA), Asuncion L. St. Clair (Norway)
TSU Facilitation:
Katharine J. Mach (USA), Michael D. Mastrandrea (USA), T. Eren Bilir (USA)
Annex II Glossary
brupt climate change
A large-scale change in the climate system that takes place over a few
decades or less, persists (or is anticipated to persist) for at least a few
decades, and causes substantial disruptions in human and natural systems.
Access to food
One of the three components underpinning food security, the other two
being availability and utilization. Access to food is dependent on (1) the
affordability of food (i.e., people have income or other resources to
exchange for food); (2) satisfactory allocation within the household or
society; and (3) preference (i.e., it is what people want to eat, influenced
by socio-cultural norms). See also Food security.
A change in functional or morphological traits occurring once or repeatedly
(e.g., seasonally) during the lifetime of an individual organism in its
natural environment. Through acclimatization the individual maintains
performance across a range of environmental conditions. For a clear
differentiation between findings in laboratory and field studies, the term
acclimation is used in ecophysiology for the respective phenomena
when observed in well-defined experimental settings. The term
(adaptive) plasticity characterizes the generally limited scope of changes
in phenotype that an individual can reach through the process of
See Adaptive capacity.
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.
Incremental adaptation Adaptation actions where the central
aim is to maintain the essence and integrity of a system or process
at a given scale.
Transformational adaptation Adaptation that changes the
fundamental attributes of a system in response to climate and its
See also Autonomous adaptation, Evolutionary adaptation, and
Adaptation assessment
The practice of identifying options to adapt to climate change and
evaluating them in terms of criteria such as availability, benefits, costs,
effectiveness, efficiency, and feasibility.
Adaptation constraint
Factors that make it harder to plan and implement adaptation actions
or that restrict options.
daptation deficit
The gap between the current state of a system and a state that
minimizes adverse impacts from existing climate conditions and
Adaptation limit
The point at which an actor’s objectives (or system needs) cannot be
secured from intolerable risks through adaptive actions.
Hard adaptation limit No adaptive actions are possible to avoid
intolerable risks.
Soft adaptation limit Options are currently not available to avoid
intolerable risks through adaptive action.
Adaptation needs
The circumstances requiring action to ensure safety of populations and
security of assets in response to climate impacts.
Adaptation opportunity
Factors that make it easier to plan and implement adaptation actions,
that expand adaptation options, or that provide ancillary co-benefits.
Adaptation options
The array of strategies and measures that are available and appropriate
for addressing adaptation needs. They include a wide range of actions
that can be categorized as structural, institutional, or social.
Adaptive capacity
The ability of systems, institutions, humans, and other organisms to
adjust to potential damage, to take advantage of opportunities, or to
respond to consequences.
Adaptive management
A process of iteratively planning, implementing, and modifying strategies
for managing resources in the face of uncertainty and change. Adaptive
management involves adjusting approaches in response to observations
of their effect and changes in the system brought on by resulting
feedback effects and other variables.
Aggregate impacts
Total impacts integrated across sectors and/or regions. The aggregation
of impacts requires knowledge of (or assumptions about) the relative
importance of different impacts. Measures of aggregate impacts include,
for example, the total number of people affected, or the total economic
costs, and are usually bound by time, place, and/or sector.
Ancillary benefits
See Co-benefits.
The deviation of a variable from its value averaged over a reference
Reflecting progress in science, this glossary entry differs in breadth and focus from the entry used in the Fourth Assessment Report and other IPCC reports.
This definition builds from the definition used in Park et al. (2012).
This glossary entry builds from definitions used in previous IPCC reports and the Millennium Ecosystem Assessment (MEA, 2005).
Glossary Annex II
Resulting from or produced by human activities.
Anthropogenic emissions
Emissions of greenhouse gases, greenhouse gas precursors, and
aerosols caused by human activities. These activities include the burning
of fossil fuels, deforestation, land use changes, livestock production,
fertilization, waste management, and industrial processes.
Arid zone
Areas where vegetation growth is severely constrained due to limited
water availability. For the most part, the native vegetation of arid zones
is sparse. There is high rainfall variability, with annual averages below
300 mm. Crop farming in arid zones requires irrigation.
Atlantic Multi-decadal Oscillation/Variability (AMO/AMV)
A multi-decadal (65- to 75-year) fluctuation in the North Atlantic, in
which sea surface temperatures showed warm phases during roughly
1860 to 1880 and 1930 to 1960 and cool phases during 1905 to 1925
and 1970 to 1990 with a range of approximately 0.4°C. See AMO Index
in WGI AR5 Box 2.5.
Atmosphere-Ocean General Circulation Model (AOGCM)
See Climate model.
See Detection and attribution.
Autonomous adaptation
Adaptation in response to experienced climate and its effects, without
planning explicitly or consciously focused on addressing climate change.
Also referred to as spontaneous adaptation.
The baseline (or reference) is the state against which change is measured.
A baseline period is the period relative to which anomalies are computed.
The baseline concentration of a trace gas is that measured at a location
not influenced by local anthropogenic emissions.
The variability among living organisms from terrestrial, marine, and
other ecosystems. Biodiversity includes variability at the genetic, species,
and ecosystem levels.
Energy derived from any form of biomass such as recently living organisms
or their metabolic by-products.
A fuel, generally in liquid form, developed from organic matter or
combustible oils produced by living or recently living plants. Examples
of biofuel include alcohol (bioethanol), black liquor from the paper-
manufacturing process, and soybean oil.
irst-generation manufactured biofuel
manufactured biofuel is derived from grains, oilseeds, animal fats,
and waste vegetable oils with mature conversion technologies.
Second-generation biofuel Second-generation biofuel uses non-
traditional biochemical and thermochemical conversion processes
and feedstock mostly derived from the lignocellulosic fractions of,
for example, agricultural and forestry residues, municipal solid
waste, etc.
Third-generation biofuel Third-generation biofuel would be
derived from feedstocks such as algae and energy crops by
advanced processes still under development.
These second- and third-generation biofuels produced through new
processes are also referred to as next-generation or advanced biofuels,
or advanced biofuel technologies.
The total mass of living organisms in a given area or volume; dead
plant material can be included as dead biomass. Biomass burning is the
burning of living and dead vegetation.
A biome is a major and distinct regional element of the biosphere,
typically consisting of several ecosystems (e.g., forests, rivers, ponds,
swamps within a region). Biomes are characterized by typical communities
of plants and animals.
The part of the Earth system comprising all ecosystems and living
organisms, in the atmosphere, on land (terrestrial biosphere), or in the
oceans (marine biosphere), including derived dead organic matter, such
as litter, soil organic matter, and oceanic detritus.
Boundary organization
A bridging institution, social arrangement, or network that acts as an
intermediary between science and policy.
Business As Usual (BAU)
Business as usual projections are based on the assumption that operating
practices and policies remain as they are at present. Although baseline
scenarios could incorporate some specific features of BAU scenarios
(e.g., a ban on a specific technology), BAU scenarios imply that no
practices or policies other than the current ones are in place. See also
Baseline/reference, Climate scenario, Emission scenario, Representative
Concentration Pathways, Scenario, Socioeconomic scenario, and SRES
Capacity building
The practice of enhancing the strengths and attributes of, and resources
available to, an individual, community, society, or organization to respond
to change.
This glossary entry builds from definitions used in the Global Biodiversity Assessment (Heywood, 1995) and the Millennium Ecosystem Assessment (MEA, 2005).
Annex II Glossary
arbon cycle
The term used to describe the flow of carbon (in various forms, e.g., as
carbon dioxide) through the atmosphere, ocean, terrestrial and marine
biosphere, and lithosphere. In this report, the reference unit for the
global carbon cycle is GtC or equivalently PgC (10
Carbon dioxide (CO
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, of
land use changes, and of industrial processes (e.g., cement production).
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.
Carbon dioxide (CO
) fertilization
The enhancement of the growth of plants as a result of increased
atmospheric carbon dioxide (CO
) concentration.
Carbon sequestration
See Uptake.
Clean Development Mechanism (CDM)
A mechanism defined under Article 12 of the Kyoto Protocol through
which investors (governments or companies) from developed (Annex
B) countries may finance greenhouse gas emission reduction or removal
projects in developing (Non-Annex B) countries, and receive Certified
Emission Reduction Units for doing so, which can be credited towards
the commitments of the respective developed countries. The CDM is
intended to facilitate the two objectives of promoting sustainable
development in developing countries and of helping industrialized
countries to reach their emissions commitments in a cost-effective way.
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-altering pollutants (CAPs)
Gases and particles released from human activities that affect the
climate either directly, through mechanisms such as radiative forcing
from changes in greenhouse gas concentrations, or indirectly, by, for
example, affecting cloud formation or the lifetime of greenhouse gases
in the atmosphere. CAPs include both those pollutants that have a
warming effect on the atmosphere, such as CO
, and those with cooling
effects, such as sulfates.
Climate change
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
he solar cycles, volcanic eruptions, and 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. See also Climate change
commitment and Detection and Attribution.
Climate change commitment
Due to the thermal inertia of the ocean and slow processes in 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
events, in extreme climate events, and in sea level change. The constant
emission commitment is the committed climate change that would
result from keeping anthropogenic emissions constant and the zero
emission commitment is the climate change commitment when emissions
are set to zero. See also Climate change.
Climate extreme (Extreme weather or climate event)
See Extreme weather event.
Climate feedback
An interaction in which a perturbation in one climate quantity causes
a change in a second, and the change in the second quantity ultimately
leads to an additional change in the first. A negative feedback is one in
which the initial perturbation is weakened by the changes it causes; a
positive feedback is one in which the initial perturbation is enhanced.
In this Assessment Report, a somewhat narrower definition is often
used in which the climate quantity that is perturbed is the global mean
surface temperature, which in turn causes changes in the global
radiation budget. In either case, the initial perturbation can either be
externally forced or arise as part of internal variability.
Climate governance
Purposeful mechanisms and measures aimed at steering social systems
towards preventing, mitigating, or adapting to the risks posed by climate
change (Jagers and Stripple, 2003).
Climate model (spectrum or hierarchy)
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.
The climate system can be represented by models of varying complexity;
that is, for any one component or combination of components, a
spectrum or hierarchy of models can be identified, differing in such
Glossary Annex II
spects as the number of spatial dimensions, the extent to which
physical, chemical, or biological processes are explicitly represented, or
the level at which empirical parameterizations are involved. Coupled
Atmosphere-Ocean General Circulation Models (AOGCMs) provide a
representation of the climate system that is near or at the most
comprehensive end of the spectrum currently available. There is an
evolution towards more complex models with interactive chemistry and
biology. Climate models are applied as a research tool to study and
simulate the climate, and for operational purposes, including monthly,
seasonal, and interannual climate predictions. See also Earth System
Climate prediction
A climate prediction or climate forecast is the result of an attempt to
produce (starting from a particular state of the climate system) an
estimate of the actual evolution of the climate in the future, for example,
at seasonal, interannual, or decadal time scales. Because the future
evolution of the climate system may be highly sensitive to initial
conditions, such predictions are usually probabilistic in nature. See also
Climate projection, Climate scenario, and Predictability.
Climate projection
A climate projection is the simulated response of the climate system to
a scenario of future emission or concentration of greenhouse gases and
aerosols, generally derived using climate models. Climate projections
are distinguished from climate predictions by their dependence on the
emission/concentration/radiative-forcing scenario used, which is in turn
based on assumptions concerning, for example, future socioeconomic
and technological developments that may or may not be realized. See
also Climate scenario.
Climate-resilient pathways
Iterative processes for managing change within complex systems in
order to reduce disruptions and enhance opportunities associated with
climate change.
Climate scenario
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 the observed current climate. See also
Emission scenario and Scenario.
Climate sensitivity
In IPCC reports, equilibrium climate sensitivity (units: °C) refers to the
equilibrium (steady state) change in the annual global mean surface
temperature following a doubling of the atmospheric equivalent carbon
dioxide concentration. Owing to computational constraints, the
equilibrium climate sensitivity in a climate model is sometimes estimated
by running an atmospheric general circulation model coupled to a
mixed-layer ocean model, because equilibrium climate sensitivity is
largely determined by atmospheric processes. Efficient models can be run
to equilibrium with a dynamic ocean. The climate sensitivity parameter
(units: °C (W m
) refers to the equilibrium change in the annual
lobal mean surface temperature following a unit change in radiative
The effective climate sensitivity (units: °C) is an estimate of the global
mean surface temperature response to doubled carbon dioxide
concentration that is evaluated from model output or observations for
evolving non-equilibrium conditions. It is a measure of the strengths of
the climate feedbacks at a particular time and may vary with forcing
history and climate state, and therefore may differ from equilibrium
climate sensitivity.
The transient climate response (units: °C) is the change in the global
mean surface temperature, averaged over a 20-year period, centered
at the time of atmospheric carbon dioxide doubling, in a climate model
simulation in which CO
increases at 1% yr
. It is a measure of the
strength and rapidity of the surface temperature response to greenhouse
gas forcing.
Climate system
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 among 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.
Climate variability
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). See
also Climate change.
The speed at which isolines of a specifiedclimatevariable travel across
landscapes or seascapes due to changing climate. For example, climate
velocityfor temperature is the speed at which isotherms move due to
changingclimate(km yr
) and is calculated as the temporal change
in temperature (°C yr
) divided by the current spatial gradient in
temperature (°C km
). It can be calculated using additionalclimate
variables such as precipitation or can be based on theclimaticniche of
Climatic driver (Climate driver)
A changing aspect of the climate system that influences a component
of a human or natural system.
Phases three and five of the Coupled Model Intercomparison Project
(CMIP3 and CMIP5), coordinating and archiving climate model
simulations based on shared model inputs by modeling groups from
around the world. The CMIP3 multi-model data set includes projections
using SRES scenarios. The CMIP5 data set includes projections using the
Representative Concentration Pathways.
Annex II Glossary
oastal squeeze
A narrowing of coastal ecosystems and amenities (e.g., beaches, salt
marshes, mangroves, and mud and sand flats) confined between
landward-retreating shorelines (from sea level rise and/or erosion) and
naturally or artificially fixed shorelines including engineering defenses
(e.g., seawalls), potentially making the ecosystems or amenities vanish.
The positive effects that a policy or measure aimed at one objective
might have on other objectives, irrespective of the net effect on overall
social welfare. Co-benefits are often subject to uncertainty and depend
on local circumstances and implementation practices, among other
factors. Co-benefits are also referred to as ancillary benefits.
Community-based adaptation
Local, community-driven adaptation. Community-based adaptation
focuses attention on empowering and promoting the adaptive capacity
of communities. It is an approach that takes context, culture, knowledge,
agency, and preferences of communities as strengths.
The validity of a finding based on the type, amount, quality, and
consistency of evidence (e.g., mechanistic understanding, theory, data,
models, expert judgment) and on the degree of agreement. Confidence
is expressed qualitatively (Mastrandrea et al., 2010). See Box 1-1. See
also Uncertainty.
Contextual vulnerability (Starting-point vulnerability)
A present inability to cope with external pressures or changes, such as
changing climate conditions. Contextual vulnerability is a characteristic
of social and ecological systems generated by multiple factors and
processes (O’Brien et al., 2007).
Vertical motion driven by buoyancy forces arising from static instability,
usually caused by near-surface cooling or increases in salinity in the
case of the ocean and near-surface warming or cloud-top radiative
cooling in the case of the atmosphere. In the atmosphere, convection
gives rise to cumulus clouds and precipitation and is effective at both
scavenging and vertically transporting chemical species. In the ocean,
convection can carry surface waters to deep within the ocean.
The use of available skills, resources, and opportunities to address,
manage, and overcome adverse conditions, with the aim of achieving
basic functioning of people, institutions, organizations, and systems in
the short to medium term.
Coping capacity
The ability of people, institutions, organizations, and systems, using
available skills, values, beliefs, resources, and opportunities, to address,
manage, and overcome adverse conditions in the short to medium
oral bleaching
Loss of coral pigmentation through the loss of intracellular symbiotic
algae (known as zooxanthellae) and/or loss of their pigments.
All regions on and beneath the surface of the Earth and ocean
where water is in solid form, including sea ice, lake ice, river ice, snow
cover, glaciers and ice sheets, and frozen ground (which includes
Cultural impacts
Impacts on material and ecological aspects of culture and the lived
experience of culture, including dimensions such as identity, community
cohesion and belonging, sense of place, worldview, values, perceptions,
and tradition. Cultural impacts are closely related to ecological impacts,
especially for iconic and representational dimensions of species and
landscapes. Culture and cultural practices frame the importance and
value of the impacts of change, shape the feasibility and acceptability
of adaptation options, and provide the skills and practices that enable
Dead zones
Extremely hypoxic (i.e., low-oxygen) areas in oceans and lakes, caused
by excessive nutrient input from human activities coupled with other
factors that deplete the oxygen required to support many marine
organisms in bottom and near-bottom water. See also Eutrophication
and Hypoxic events.
The process by which countries or other entities aim to achieve a low-
carbon economy, or by which individuals aim to reduce their consumption
of carbon.
Conversion of forest to non-forest. For a discussion of the term forest
and related terms such as afforestation, reforestation, and deforestation
see the IPCC Special Report on Land Use, Land-Use Change, and Forestry
(IPCC, 2000). See also the report on Definitions and Methodological
Options to Inventory Emissions from Direct Human-induced Degradation
of Forests and Devegetation of Other Vegetation Types (IPCC, 2003).
Land degradation in arid, semi-arid, and dry sub-humid areas resulting
from various factors, including climatic variations and human activities.
Land degradation in arid, semi-arid, and dry sub-humid areas is reduction
or loss of the biological or economic productivity and complexity of
rainfed cropland, irrigated cropland, or range, pasture, forest, and
woodlands resulting from land uses or from a process or combination
of processes, including processes arising from human activities and
habitation patterns, such as (1) soil erosion caused by wind and/or
water; (2) deterioration of the physical, chemical, biological, or economic
properties of soil; and (3) long-term loss of natural vegetation (UNCCD,
This glossary entry builds from the definition used in UNISDR (2009) and IPCC (2012a).
This glossary entry builds from the definition used in UNISDR (2009) and IPCC (2012a).
Glossary Annex II
etection and attribution
Detection of change is defined as the process of demonstrating that
climate or a system affected by climate has changed in some defined
statistical sense, without providing a reason for that change. An identified
change is detected in observations if its likelihood of occurrence by
chance due to internal variability alone is determined to be small, for
example, <10%. Attribution is defined as the process of evaluating the
relative contributions of multiple causal factors to a change or event
with an assignment of statistical confidence (Hegerl et al., 2010).
Detection of impacts of climate change
For a natural, human, or managed system, identification of a change
from a specified baseline. The baseline characterizes behavior in the
absence of climate change and may be stationary or non-stationary
(e.g., due to land use change).
Disadvantaged populations
Sectors of a society that are marginalized, often because of low
socioeconomic status, low income, lack of access to basic services such
as health or education, lack of power, race, gender, religion, or poor
access to communication technologies.
Severe alterations in the normal functioning of a community or a society
due to hazardous physical events interacting with vulnerable social
conditions, leading to widespread adverse human, material, economic,
or environmental effects that require immediate emergency response
to satisfy critical human needs and that may require external support
for recovery.
Disaster management
Social processes for designing, implementing, and evaluating strategies,
policies, and measures thatpromote and improve disaster preparedness,
response, and recovery practices at different organizationaland societal
Disaster risk
The likelihood within a specific time period of disaster. See Disaster.
Disaster Risk Management (DRM)
Processes for designing, implementing, and evaluating strategies,
policies, and measures to improve theunderstanding of disaster risk,
foster disaster risk reduction andtransfer, and promote continuous
improvement in disaster preparedness, response, and recovery practices,
with the explicit purpose of increasing human security, well-being,
quality of life,andsustainable development.
Disaster Risk Reduction (DRR)
Denotes both a policy goal or objective, and the strategic and instrumental
measures employed for anticipating future disaster risk; reducing existing
exposure, hazard, or vulnerability; and improving resilience.
A mathematical operation making monetary (or other) amounts received
or expended at different times (years) comparable across time. The
iscounter uses a fixed or possibly time-varying discount rate (>0) from
year to year that makes future value worth less today.
Disturbance regime
Frequency, intensity, and types of disturbances of ecological systems,
such as fires, insect or pest outbreaks, floods, and droughts.
Diurnal temperature range
The difference between the maximum and minimum temperature
during a 24-hour period.
Downscaling is a method that derives local- to regional-scale (10 to
100 km) information from larger-scale models or data analyses. Two
main methods exist: dynamical downscaling and empirical/statistical
downscaling. The dynamical method uses the output of regional climate
models, global models with variable spatial resolution, or high-resolution
global models. The empirical/statistical methods develop statistical
relationships that link the large-scale atmospheric variables with local/
regional climate variables. In all cases, the quality of the driving model
remains an important limitation on quality of the downscaled information.
A period of abnormally dry weather long enough to cause a serious
hydrological imbalance. Drought is a relative term; therefore any
discussion in terms of precipitation deficit must refer to the particular
precipitation-related activity that is under discussion. For example,
shortage of precipitation during the growing season impinges on crop
production or ecosystem function in general (due to soil moisture
drought, also termed agricultural drought), and during the runoff and
percolation season primarily affects water supplies (hydrological drought).
Storage changes in soil moisture and groundwater are also affected
by increases in actual evapotranspiration in addition to reductions in
precipitation. A period with an abnormal precipitation deficit is defined
as a meteorological drought. A megadrought is a very lengthy and
pervasive drought, lasting much longer than normal, usually a decade
or more. For the corresponding indices, see WGI AR5 Box 2.4.
Dynamic Global Vegetation Model (DGVM)
A model that simulates vegetation development and dynamics through
space and time, as driven by climate and other environmental changes.
Early warning system
The set of capacities needed to generate and disseminate timely and
meaningful warning information to enable individuals, communities,
and organizations threatened by a hazard to prepare to act promptly
and appropriately to reduce the possibility of harm or loss.
Earth System Model (ESM)
A coupled atmosphere-ocean general circulation model in which a
representation of the carbon cycle is included, allowing for interactive
calculation of atmospheric CO
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.
This glossary entry builds from the definition used in UNISDR (2009) and IPCC (2012a).
Annex II Glossary
cophysiological process
Processes in which individual organisms respond continuously to
environmental variability or change, such as climate change, generally
at a microscopic or sub-organ scale. Ecophysiological mechanisms
underpin individual organisms’ tolerance to environmental stress, and
comprise a broad range of responses defining the absolute tolerances
by individuals of environmental conditions. Ecophysiological responses
may scale up to control species’ geographic ranges.
A functional unit consisting of living organisms, their non-living
environment, and the interactions within and between them. The
components included in a given ecosystem and its spatial boundaries
depend on the purpose for which the ecosystem is defined: in some cases
they are relatively sharp, while in others they are diffuse. Ecosystem
boundaries can change over time. Ecosystems are nested within other
ecosystems, and their scale can range from very small to the entire
biosphere. In the current era, most ecosystems either contain people as
key organisms, or are influenced by the effects of human activities in
their environment.
Ecosystem approach
A strategy for the integrated management of land, water, and living
resources that promotes conservation and sustainable use in an equitable
way. An ecosystem approach is based on the application of scientific
methodologies focused on levels of biological organization, which
encompass the essential structure, processes, functions, and interactions
of organisms and their environment. It recognizes that humans, with
their cultural diversity, are an integral component of many ecosystems.
The ecosystem approach requires adaptive management to deal with
the complex and dynamic nature of ecosystems and the absence of
complete knowledge or understanding of their functioning. Priority
targets are conservation of biodiversity and of the ecosystem structure
and functioning, in order to maintain ecosystem services.
Ecosystem-based adaptation
The use of biodiversity and ecosystem services as part of an overall
adaptation strategy to help people to adapt to the adverse effects of
climate change. Ecosystem-based adaptation uses the range of
opportunities for the sustainable management, conservation, and
restoration of ecosystems to provide services that enable people to
adapt to the impacts of climate change. It aims to maintain and increase
the resilience and reduce the vulnerability of ecosystems and people in
the face of the adverse effects of climate change. Ecosystem-based
adaptation is most appropriately integrated into broader adaptation
and development strategies(CBD, 2009).
Ecosystem services
Ecological processes or functions having monetary or non-monetary
value to individuals or society at large. These are frequently classified as
(1) supporting services such as productivity or biodiversity maintenance,
(2) provisioning services such as food, fiber, or fish, (3) regulating services
such as climate regulation or carbon sequestration, and (4) cultural
services such as tourism or spiritual and aesthetic appreciation.
l Niño-Southern Oscillation (ENSO)
The term El Niño was initially used to describe a warm-water current
that periodically flows along the coast of Ecuador and Peru, disrupting
the local fishery. It has since become identified with a basin-wide
warming of the tropical Pacific Ocean east of the dateline. This oceanic
event is associated with a fluctuation of a global-scale tropical and
subtropical surface pressure pattern called the Southern Oscillation. This
coupled atmosphere-ocean phenomenon, with preferred time scales of
2 to about 7 years, is known as the El Niño-Southern Oscillation (ENSO).
It is often measured by the surface pressure anomaly difference between
Tahiti and Darwin or the sea surface temperatures in the central and
eastern equatorial Pacific. During an ENSO event, the prevailing trade
winds weaken, reducing upwelling and altering ocean currents such that
the sea surface temperatures warm, further weakening the trade winds.
This event has a great impact on the wind, sea surface temperature,
and precipitation patterns in the tropical Pacific. It has climatic effects
throughout the Pacific region and in many other parts of the world,
through global teleconnections. The cold phase of ENSO is called La
Niña. For the corresponding indices, see WGI AR5 Box 2.5.
Emergent risk
A risk that arises from the interaction of phenomena in a complex
system, for example, the risk caused when geographic shifts in human
populationin response to climate change lead to increased vulnerability
and exposure of populations in the receiving region.
Emission scenario
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 Emissions Scenarios (Nakićenović and Swart, 2000) emission
scenarios, the so-called SRES scenarios, were published, some of which
were used, among others, as a basis for the climate projections
presented in Chapters 9 to 11 of IPCC (2001) and Chapters 10 and 11
of IPCC (2007). New emission scenarios for climate change, the four
Representative Concentration Pathways, were developed for, but
independently of, the present IPCC assessment. See also Climate
scenario and Scenario.
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.
This glossary entry builds from definitions used in CBD (2000), MEA (2005), and the Fourth Assessment Report.
Glossary Annex II
nvironmental migration
Human migration involves movement over a significant distance and
duration. Environmental migration refers to human migration where
environmental risks or environmental change plays a significant role in
influencing the migration decision and destination. Migration may
involve distinct categories such as direct, involuntary, and temporary
displacement due to weather-related disasters; voluntary relocation as
settlements and economies become less viable; or planned resettlement
encouraged by government actions or incentives.All migration decisions
are multi-causal, and hence it is not meaningful to describe any migrant
flow as being solely for environmental reasons.
Environmental services
See Ecosystem services.
Over-enrichment of water by nutrients such as nitrogen and phosphorus.
It is one of the leading causes of water quality impairment. The two most
acute symptoms of eutrophication are hypoxia (or oxygen depletion)
and harmful algal blooms. See also Dead zones.
Evolutionary adaptation
For a population or species, change in functional characteristics as a result
of selection acting on heritable traits. The rate of evolutionary adaptation
depends on factors such as strength of selection, generation turnover time,
and degree of outcrossing (as opposed to inbreeding). See also Adaptation.
The presence of people, livelihoods, species or ecosystems, environmental
functions, services, and resources, infrastructure, or economic, social, or
cultural assets in places and settings that could be adversely affected.
External forcing
External forcing refers to a forcing agent outside the climate system
causing a change in the climate system. Volcanic eruptions, solar variations,
and anthropogenic changes in the composition of the atmosphere and
land use change are external forcings. Orbital forcing is also an external
forcing as the insolation changes with orbital parameters eccentricity,
tilt, and precession of the equinox.
Externalities/external costs/external benefits
Externalities arise from a human activity when agents responsible for
the activity do not take full account of the activity’s impacts on others’
production and consumption possibilities, and no compensation exists
for such impacts. When the impacts are negative, they are external costs.
When the impacts are positive, they are external benefits.
Extratropical cyclone
A large-scale (of order 1000 km) storm in the middle or high latitudes
having low central pressure and fronts with strong horizontal gradients
in temperature and humidity. A major cause of extreme wind speeds
and heavy precipitation especially in wintertime.
Extreme climate event
See Extreme weather event.
xtreme sea level
See Storm surge.
Extreme weather event
An extreme weather event is an event that is rare at a particular place
and time of year. Definitions of rare vary, but an extreme weather event
would normally be as rare as or rarer than the 10th or 90th percentile
of a probability density function estimated from observations. By
definition, the characteristics of what is called extreme weather may vary
from place to place in an absolute sense. When a pattern of extreme
weather persists for some time, such as a season, it may be classed as
an extreme climate event, especially if it yields an average or total that
is itself extreme (e.g., drought or heavy rainfall over a season).
Scarcity of food over an extended period and over a large geographical
area, such as a country, or lack of access to food for socioeconomic,
political, or cultural reasons. Famines may be caused by climate-related
extreme events such as droughts or floods and by disease, war, or other
See Climate feedback.
Fire weather
Weather conditions conducive to triggering and sustaining wild fires,
usually based on a set of indicators and combinations of indicators
including temperature, soil moisture, humidity, and wind. Fire weather
does not include the presence or absence of fuel load.
Fitness (Darwinian)
Fitness is the relative capacity of an individual or genotype to both
survive and reproduce, quantified as the average contribution of the
genotype to the gene pool of the next generations. During evolution,
natural selection favors functions providing greater fitness such that
the functions become more common over generations.
The overflowing of the normal confines of a stream or other body of
water, or the accumulation of water over areas not normally submerged.
Floods include river (fluvial) floods, flash floods, urban floods, pluvial
floods, sewer floods, coastal floods, and glacial lake outburst floods.
Food security
A state that prevails when people have secure access to sufficient
amounts of safe and nutritious food for normal growth, development,
and an active and healthy life.
See also Access to food.
Food system
A food system includes the suite of activities and actors in the food chain
(i.e., producing, processing and packaging, storing and transporting,
trading and retailing, and preparing and consuming food); and the
outcome of these activities relating to the three components underpinning
food security (i.e., access to food, utilization of food, and food availability),
all of which need to be stable over time. Food security is therefore
This glossary entry builds from definitions used in FAO (2000) and previous IPCC reports.
Annex II Glossary
nderpinned by food systems, and is an emergent property of the
behavior of the whole food system. Food insecurity arises when any
aspect of the food system is stressed.
See Climate prediction and Climate projection.
General Circulation Model (GCM)
See Climate model.
Geoengineering refers to a broad set of methods and technologies that
aim to deliberately alter the climate system in order to alleviate the
impacts of climate change. Most, but not all, methods seek to either
(1) reduce the amount of absorbed solar energy in the climate system
(Solar Radiation Management) or (2) increase net carbon sinks from
the atmosphere at a scale sufficiently large to alter climate (Carbon
Dioxide Removal). Scale and intent are of central importance. Two key
characteristics of geoengineering methods of particular concern are that
they use or affect the climate system (e.g., atmosphere, land, or ocean)
globally or regionally and/or could have substantive unintended effects
that cross national boundaries. Geoengineering is different from weather
modification and ecological engineering, but the boundary can be fuzzy
(IPCC, 2012b, p. 2).
Global change
A generic term to describe global scale changes in systems, including
the climate system, ecosystems, and social-ecological systems.
Global Climate Model (also referred to as General
Circulation Model, both abbreviated as GCM)
See Climate model.
Global mean surface temperature
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
Greenhouse effect
The infrared radiative effect of all infrared-absorbing constituents in the
atmosphere. Greenhouse gases, clouds, and (to a small extent) aerosols
absorb terrestrial radiation emitted by the Earth’s surface and elsewhere
in the atmosphere. These substances emit infrared radiation in all
directions, but, everything else being equal, the net amount emitted to
space is normally less than would have been emitted in the absence of
these absorbers because of the decline of temperature with altitude
in the troposphere and the consequent weakening of emission. An
increase in the concentration of greenhouse gases increases the
magnitude of this effect; the difference is sometimes called the enhanced
greenhouse effect. The change in a greenhouse gas concentration
because of anthropogenic emissions contributes to an instantaneous
radiative forcing. Surface temperature and troposphere warm in
response to this forcing, gradually restoring the radiative balance at
the top of the atmosphere.
reenhouse gas (GHG)
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 terrestrial radiation emitted
by the Earth’s surface, the atmosphere itself, and clouds. This property
causes the greenhouse effect. Water vapor (H
O), carbon dioxide (CO
nitrous oxide (N
O), methane (CH
), and ozone (O
) 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 CO
, N
and CH
, the Kyoto Protocol deals with the greenhouse gases sulfur
hexafluoride (SF
), hydrofluorocarbons (HFCs), and perfluorocarbons
(PFCs). For a list of well-mixed greenhouse gases, see WGI AR5 Table
Ground-level ozone
Atmospheric ozone formed naturally or from human-emitted precursors
near Earth’s surface, thus affecting human health, agriculture, and
ecosystems. Ozone is a greenhouse gas, but ground-level ozone, unlike
stratospheric ozone, also directly affects organisms at the surface.
Ground-level ozone is sometimes referred to as tropospheric ozone,
although much of the troposphere is well above the surface and thus
does not directly expose organisms at the surface. See also Ozone.
Groundwater recharge
The process by which external water is added to the zone of saturation
of an aquifer, either directly into a geologic formation that traps the
water or indirectly by way of another formation.
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.
In this report, the term hazard usually refers to climate-related physical
events or trends or their physical impacts.
Heat wave
A period of abnormally and uncomfortably hot weather.
A geographical area characterized by high vulnerability and exposure
to climate change.
Human security
A condition that is met when the vital core of human lives is protected,
and when people have the freedom and capacity to live with dignity.
In the context of climate change, the vital core of human lives includes
the universal and culturally specific, material and non-material elements
necessary for people to act on behalf of their interests and to live with
Human system
Any system in which human organizations and institutions play a major
role. Often, but not always, the term is synonymous with society or
Glossary Annex II
ocial system. Systems such as agricultural systems, political systems,
technological systems, and economic systems are all human systems in
the sense applied in this report.
Hydrological cycle
The cycle in which water evaporates from the oceans and the land
surface, is carried over the Earth in atmospheric circulation as water
vapor, condenses to form clouds, precipitates over ocean and land as
rain or snow, which on land can be intercepted by trees and vegetation,
provides runoff on the land surface, infiltrates into soils, recharges
groundwater, discharges into streams, and ultimately, flows out into
the oceans, from which it will eventually evaporate again. The various
systems involved in the hydrological cycle are usually referred to as
hydrological systems.
Hypoxic events
Events that lead to deficiencies of oxygen in water bodies. See also Dead
zones and Eutrophication.
Ice cap
A dome-shaped ice mass that is considerably smaller in extent than an
ice sheet.
Ice sheet
A mass of land ice of continental size that is sufficiently thick to cover
most of the underlying bed, so that its shape is mainly determined by
its dynamics (the flow of the ice as it deforms internally and/or slides
at its base). An ice sheet flows outward from a high central ice plateau
with a small average surface slope. The margins usually slope more
steeply, and most ice is discharged through fast flowing ice streams or
outlet glaciers, in some cases into the sea or into ice shelves floating
on the sea. There are only two ice sheets in the modern world, one on
Greenland and one on Antarctica. During glacial periods there were
Ice shelf
A floating slab of ice of considerable thickness extending from the coast
(usually of great horizontal extent with a very gently sloping surface),
often filling embayments in the coastline of an ice sheet. Nearly all ice
shelves are in Antarctica, where most of the ice discharged into the
ocean flows via ice shelves.
(climate change) Impact assessment
The practice of identifying and evaluating, in monetary and/or non-
monetary terms, the effects of climate change on natural and human
Impacts (Consequences, Outcomes)
Effects on natural and human systems. In this report, the term impacts
is used primarily to refer to the effects on natural and human systems
of extreme weather and climate events and of climate change. Impacts
generally refer to effects on lives, livelihoods, health, ecosystems,
economies, societies, cultures, services, and infrastructure due to the
nteraction 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.
The impacts of climate change on geophysical systems, including floods,
droughts, and sea level rise, are a subset of impacts called physical
The maximum amount that a household, or other unit, can consume
without reducing its real net worth. Total income is the broadest measure
of income and refers to regular receipts such as wages and salaries,
income from self-employment, interest and dividends from invested
funds, pensions or other benefits from social insurance, and other current
transfers receivable.
Indian Ocean Dipole (IOD)
Large-scale mode of interannual variability of sea surface temperature
in the Indian Ocean. This pattern manifests through a zonal gradient of
tropical sea surface temperature, which in one extreme phase in boreal
autumn shows cooling off Sumatra and warming off Somalia in the
west, combined with anomalous easterlies along the equator.
Indigenous peoples
Indigenous peoples and nations are those that, having a historical
continuity with pre-invasion and pre-colonial societies that developed
on their territories, consider themselves distinct from other sectors of
the societies now prevailing on those territories, or parts of them. They
form at present principally non-dominant sectors of society and are
often determined to preserve, develop, and transmit to future generations
their ancestral territories, and their ethnic identity, as the basis of their
continued existence as peoples, in accordance with their own cultural
patterns, social institutions, and common law system.
Industrial Revolution
A period of rapid industrial growth with far-reaching social and
economic consequences, beginning in Britain during the second half of
the 18th century and spreading to Europe and later to other countries
including the United States. The invention of the steam engine was an
important trigger of this development. The industrial revolution marks
the beginning of a strong increase in the use of fossil fuels and emission
of, in particular, fossil carbon dioxide. In this report the terms preindustrial
and industrial refer, somewhat arbitrarily, to the periods before and after
1750, respectively.
Industrialized/developed/developing countries
There are a diversity of approaches for categorizing countries on the
basis of their level of development, and for defining terms such as
industrialized, developed, or developing. Several categorizations are
used in this report. In the United Nations system, there is no established
convention for the designation of developed and developing countries
or areas. The United Nations Statistics Division specifies developed and
developing regions based on common practice. In addition, specific
countries are designated as least developed countries, landlocked
Reflecting progress in science, this glossary entry differs in breadth and focus from the entry used in the Fourth Assessment Report and other IPCC reports.
This glossary entry builds from the definition used in OECD (2003).
This glossary entry builds from the definitions used in Cobo (1987) and previous IPCC reports.
Annex II Glossary
eveloping countries, small island developing states, and transition
economies. Many countries appear in more than one of these categories.
The World Bank uses income as the main criterion for classifying
countries as low, lower middle, upper middle, and high income. The
UNDP aggregates indicators for life expectancy, educational attainment,
and income into a single composite human development index (HDI) to
classify countries as low, medium, high, or very high human development.
See Box 1-2.
Informal sector
Commercial enterprises (mostly small) that are not registered or that
otherwise fall outside official rules and regulations. Among the
businesses that make up the informal sector, there is great diversity in
the value of the goods or services produced, the numbers employed,
the extent of illegality, and the connection to the formal sector.
Many informal enterprises have some characteristics of formal-sector
enterprises, and some people are in informal employment in the formal
sector as they lack legal protection or employment benefits.
Informal settlement
A term given to settlements or residential areas that by at least one
criterion fall outside official rules and regulations. Most informal
settlements have poor housing (with widespread use of temporary
materials) and are developed on land that is occupied illegally with
high levels of overcrowding. In most such settlements, provision for
safe water, sanitation, drainage, paved roads, and basic services is
inadequate or lacking. The term slum is often used for informal
settlements, although it is misleading as many informal settlements
develop into good quality residential areas, especially where governments
support such development.
Institutions are rules and norms held in common by social actors that
guide, constrain, and shape human interaction. Institutions can be
formal, such as laws and policies, or informal, such as norms and
conventions. Organizations—such as parliaments, regulatory agencies,
private firms, and community bodies—develop and act in response to
institutional frameworks and the incentives they frame. Institutions can
guide, constrain, and shape human interaction through direct control,
through incentives, and through processes of socialization.
A family of financial instruments for sharing and transferring risk among
a pool of at-risk households, businesses, and/or governments. See also
Risk transfer.
Integrated assessment
A method of analysis that combines results and models from the physical,
biological, economic, and social sciences, and the interactions among
these components, in a consistent framework to evaluate the status
and the consequences of environmental change and the policy responses
to it.
Integrated Coastal Zone Management (ICZM)
An integrated approach for sustainably managing coastal areas, taking
into account all coastal habitats and uses.
nvasive species/Invasive Alien Species (IAS)
A species introduced outside its natural past or present distribution (i.e.,
an alien species) that becomes established in natural or semi-natural
ecosystems or habitat, is an agent of change, and threatens native
biological diversity (IUCN, 2000; CBD, 2002).
Keyvulnerability, Key risk, Key impact
A vulnerability, risk, or impact relevant to the definition and elaboration
of “dangerous anthropogenic interference (DAI) with the climate
system,” in the terminology of United Nations Framework Convention
on Climate Change (UNFCCC) Article 2, meriting particular attention by
policy makers in that context.
Key risks are potentially severe adverse consequences for humans and
social-ecological systems resulting from the interaction of climate-
related hazards with vulnerabilities of societies and systems exposed.
Risks are considered “key” due to high hazard or high vulnerability of
societies and systems exposed, or both.
Vulnerabilities are considered “key” if they have the potential to combine
with hazardous events or trends to result in key risks. Vulnerabilities
that have little influence on climate-related risk, for instance, due to
lack of exposure to hazards, would not be considered key.
Key impacts are severe consequences for humans and social-ecological
Land grabbing
Large acquisitions of land or water rights for industrial agriculture,
mitigation projects, or biofuels that have negative consequences on
local and marginalized communities.
Land surface air temperature
The surface air temperature as measured in well-ventilated screens over
land at 1.5 m above the ground.
Land use and Land use change
Land use refers to the total of arrangements, activities, and inputs
undertaken in a certain land cover type (a set of human actions). The
term land use is also used in the sense of the social and economic
purposes for which land is managed (e.g., grazing, timber extraction,
and conservation). Land use change refers to a change in the use or
management of land by humans, which may lead to a change in land
cover. Land cover and land use change may have an impact on the
surface albedo, evapotranspiration, sources and sinks of greenhouse
gases, or other properties of the climate system and may thus give rise
to radiative forcing and/or other impacts on climate, locally or globally.
See also the IPCC Special Report on Land Use, Land-Use Change, and
Forestry (IPCC, 2000).
La Niña
See El Niño-Southern Oscillation.
Last Glacial Maximum (LGM)
The period during the last ice age when the glaciers and ice sheets
reached their maximum extent, approximately 21 ka ago. This period
Glossary Annex II
as been widely studied because the radiative forcings and boundary
conditions are relatively well known.
The chance of a specific outcome occurring, where this might be
estimated probabilistically. Likelihood is expressed in this report using
a standard terminology (Mastrandrea et al., 2010), defined in Box 1-1.
See also Confidence and Uncertainty.
The resources used and the activities undertaken in order to live.
Livelihoods are usually determined by the entitlements and assets to
which people have access. Such assets can be categorized as human,
social, natural, physical, or financial.
Low regrets policy
A policy that would generate net social and/or economic benefits under
current climate and a range of future climate change scenarios.
Maladaptive actions (Maladaptation)
Actions that may lead to increased risk of adverse climate-related
outcomes, increased vulnerability to climate change, or diminished
welfare, now or in the future.
Mean sea level
The surface level of the ocean at a particular point averaged over an
extended period of time such as a month or year. Mean sea level is often
used as a national datum to which heights on land are referred.
Meridional Overturning Circulation (MOC)
Meridional (north-south) overturning circulation in the ocean quantified
by zonal (east-west) sums of mass transports in depth or density layers.
In the North Atlantic, away from the subpolar regions, the MOC (which
is in principle an observable quantity) is often identified with the
thermohaline circulation (THC), which is a conceptual and incomplete
interpretation. It must be borne in mind that the MOC is also driven by
wind, and can also include shallower overturning cells such as occur in the
upper ocean in the tropics and subtropics, in which warm (light) waters
moving poleward are transformed to slightly denser waters and subducted
equatorward at deeper levels. See also Thermohaline circulation.
Local climate at or near the Earth’s surface. See also Climate.
Mitigation (of climate change)
A human intervention to reduce the sources or enhance the sinks of
greenhouse gases.
Mitigation (of disaster risk and disaster)
The lessening of the potential adverse impacts of physical hazards
(including those that are human-induced) through actions that reduce
hazard, exposure, and vulnerability.
Mode of climate variability
Underlying space-time structure with preferred spatial pattern and
temporal variation that helps account for the gross features in variance
nd for teleconnections. A mode of variability is often considered to be
the product of a spatial climate pattern and an associated climate index
time series.
A monsoon is a tropical and subtropical seasonal reversal in both the
surface winds and associated precipitation, caused by differential
heating between a continental-scale land mass and the adjacent ocean.
Monsoon rains occur mainly over land in summer.
Non-climatic driver (Non-climate driver)
An agent or process outside the climate system that influences a human
or natural system.
A process is called nonlinear when there is no simple proportional
relation between cause and effect. The climate system contains many
such nonlinear processes, resulting in a system with potentially very
complex behavior. Such complexity may lead to abrupt climate change.
See also Predictability.
North Atlantic Oscillation (NAO)
The North Atlantic Oscillation consists of opposing variations of surface
pressure near Iceland and near the Azores. It therefore corresponds to
fluctuations in the strength of the main westerly winds across the Atlantic
into Europe, and thus to fluctuations in the embedded extratropical
cyclones with their associated frontal systems. See NAO Index in WGI
AR5 Box 2.5.
Ocean acidification
Ocean acidification refers to a reduction in the pH of the ocean over an
extended period, typically decades or longer, which is caused primarily
by uptake of carbon dioxide from the atmosphere, but can also be
caused by other chemical additions or subtractions from the ocean.
Anthropogenic ocean acidification refers to the component of pH
reduction that is caused by human activity (IPCC, 2011, p. 37).
Opportunity costs
The benefits of an activity forgone through the choice of another
Outcome vulnerability (End-point vulnerability)
Vulnerability as the end point of a sequence of analyses beginning with
projections of future emission trends, moving on to the development of
climate scenarios, and concluding with biophysical impact studies and
the identification of adaptive options. Any residual consequences that
remain after adaptation has taken place define the levels of vulnerability
(Kelly and Adger, 2000; O’Brien et al., 2007).
Oxygen Minimum Zone (OMZ)
The midwater layer (200 to 1000 m) in the open ocean in which oxygen
saturation is the lowest in the ocean. The degree of oxygen depletion
depends on the largely bacterial consumption of organic matter, and the
distribution of the OMZs is influenced by large-scale ocean circulation.
In coastal oceans, OMZs extend to the shelves and may also affect
benthic ecosystems.
Annex II Glossary
Ozone, the triatomic form of oxygen (O
), is a gaseous atmospheric
constituent. In the troposphere, it is created both naturally and by
photochemical reactions involving gases resulting from human activities
(smog). Tropospheric ozone acts as a greenhouse gas. In the stratosphere,
it is created by the interaction between solar ultraviolet radiation and
molecular oxygen (O
). Stratospheric ozone plays a dominant role in the
stratospheric radiative balance. Its concentration is highest in the ozone
Pacific Decadal Oscillation (PDO)
The pattern and time series of the first empirical orthogonal function
of sea surface temperature over the North Pacific north of 20°N. The
PDO broadened to cover the whole Pacific Basin is known as the Inter-
decadal Pacific Oscillation (IPO). The PDO and IPO exhibit similar
temporal evolution.
In climate models, this term refers to the technique of representing
processes that cannot be explicitly resolved at the spatial or temporal
resolution of the model (sub-grid scale processes) by relationships
between model-resolved larger-scale variables and the area- or time-
averaged effect of such sub-grid scale processes.
Very small solid 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 diameter less than or
equal to 10 nm, usually designated as PM
A livelihood strategy based on moving livestock to seasonal pastures
primarily in order to convert grasses, forbs, tree leaves, or crop residues
into human food. The search for feed is however not the only reason
for mobility; people and livestock may move to avoid various natural
and/or social hazards, to avoid competition with others, or to seek more
favorable conditions. Pastoralism can also be thought of as a strategy
that is shaped by both social and ecological factors concerning
uncertainty and variability of precipitation, and low and unpredictable
productivity of terrestrial ecosystems.
Path dependence
The generic situation where decisions, events, or outcomes at one point
in time constrain adaptation, mitigation, or other actions or options at
a later point in time.
Ground (soil or rock and included ice and organic material) that remains
at or below 0°C for at least 2 consecutive years.
Persistent Organic Pollutants (POPs)
Toxic organic chemical substances that persist in the environment for
long periods of time, are transported and deposited in locations distant
from their sources of release, bioaccumulate, and can have adverse
effects on human health and ecosystems.
The relationship between biological phenomena that recur periodically
(e.g., development stages, migration) and climate and seasonal changes.
Photochemical smog
A mix of oxidizing air pollutants produced by the reaction of sunlight
with primary air pollutants, especially hydrocarbons.
Poverty is a complex concept with several definitions stemming from
different schools of thought. It can refer to material circumstances (such
as need, pattern of deprivation, or limited resources), economic conditions
(such as standard of living, inequality, or economic position), and/or
social relationships (such as social class, dependency, exclusion, lack of
basic security, or lack of entitlement).
Poverty trap
Poverty trap is understood differently across disciplines. In the social
sciences, the concept, primarily employed at the individual, household,
or community level, describes a situation in which escaping poverty
becomes impossible due to unproductive or inflexible resources. A
poverty trap can also be seen as a critical minimum asset threshold,
below which families are unable to successfully educate their children,
build up their productive assets, and get out of poverty. Extreme poverty
is itself a poverty trap, since poor persons lack the means to participate
meaningfully in society. In economics, the term poverty trap is often
used at national scales, referring to a self-perpetuating condition
where an economy, caught in a vicious cycle, suffers from persistent
underdevelopment (Matsuyama, 2008). Many proposed models of
poverty traps are found in the literature.
The extent to which future states of a system may be predicted based on
knowledge of current and past states of the system. Because knowledge
of the climate system’s past and current states is generally imperfect,
as are the models that utilize this knowledge to produce a climate
prediction, and because the climate system is inherently nonlinear and
chaotic, predictability of the climate system is inherently limited. Even
with arbitrarily accurate models and observations, there may still be
limits to the predictability of such a nonlinear system (AMS, 2000).
See Industrial Revolution.
Probability Density Function (PDF)
A probability density function is a function that indicates the relative
chances of occurrence of different outcomes of a variable. The function
integrates to unity over the domain for which it is defined and has the
property that the integral over a sub-domain equals the probability that
the outcome of the variable lies within that sub-domain. For example,
the probability that a temperature anomaly defined in a particular way
is greater than zero is obtained from its PDF by integrating the PDF over
all possible temperature anomalies greater than zero. Probability density
functions that describe two or more variables simultaneously are
similarly defined.
This glossary entry builds from the definition in the Stockholm Convention on Persistent Organic Pollutants (Secretariat of the Stockholm Convention, 2001).
Glossary Annex II
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 socioeconomic and technological developments that may or may
not be realized. See also Climate prediction and Climate projection.
A proxy climate indicator is a record that is interpreted, using physical
and biophysical principles, to represent some combination of climate-
related variations back in time. Climate-related data derived in this way
are referred to as proxy data. Examples of proxies include pollen analysis,
tree ring records, speleothems, characteristics of corals, and various data
derived from marine sediments and ice cores. Proxy data can be calibrated
to provide quantitative climate information.
Public good
A good that is both non-excludable and non-rivalrous in that individuals
cannot be effectively excluded from use and where use by one individual
does not reduce availability to others.
Radiative forcing
Radiative forcing is the change in the net, downward minus upward,
radiative flux (expressed in W m
) at the tropopause or top of atmosphere
due to a change in an external driver of climate change, such as a
change in the concentration of carbon dioxide or the output of the Sun.
Sometimes internal drivers are still treated as forcings even though they
result from the alteration in climate, for example aerosol or greenhouse
gas changes in paleoclimates. The traditional radiative forcing is computed
with all tropospheric properties held fixed at their unperturbed values,
and after allowing for stratospheric temperatures, if perturbed, to
readjust to radiative-dynamical equilibrium. Radiative forcing is called
instantaneous if no change in stratospheric temperature is accounted
for. The radiative forcing once rapid adjustments are accounted for is
termed the effective radiative forcing. For the purposes of this report,
radiative forcing is further defined as the change relative to the year
1750 and, unless otherwise noted, refers to a global and annual average
value. Radiative forcing is not to be confused with cloud radiative forcing,
which describes an unrelated measure of the impact of clouds on the
radiative flux at the top of the atmosphere.
Reanalyses are estimates of historical atmospheric temperature and
wind or oceanographic temperature and current, and other quantities,
created by processing past meteorological or oceanographic data using
fixed state-of-the-art weather forecasting or ocean circulation models
with data assimilation techniques. Using fixed data assimilation avoids
effects from the changing analysis system that occur in operational
analyses. Although continuity is improved, global reanalyses still suffer
from changing coverage and biases in the observing systems.
Reasons for concern
Elements of a classification framework, first developed in the IPCC Third
Assessment Report, which aims to facilitate judgments about what level
of climate change may be “dangerous” (in the language of Article 2 of
the UNFCCC) by aggregating impacts, risks, and vulnerabilities.
eference scenario
See Baseline/reference.
A system attribute where cause and effect form a feedback loop, in
which the effect changes the system itself. Self-adapting systems such
as societies are inherently reflexive, as are planned changes in complex
systems. Reflexive decision making in a social system has the potential
to change the underpinning values that led to those decisions. Reflexivity
is also an important aspect of adaptive management.
Planting of forests on lands that have previously contained forests but
that have been converted to some other use. For a discussion of the
term forest and related terms such as afforestation, reforestation, and
deforestation, see the IPCC Special Report on Land Use, Land-Use
Change, and Forestry (IPCC, 2000). See also the Report on Definitions
and Methodological Options to Inventory Emissions from Direct Human-
induced Degradation of Forests and Devegetation of Other Vegetation
Types (IPCC, 2003).
Relative sea level
Sea level measured by a tide gauge with respect to the land upon which
it is situated. See also Mean sea level and Sea level change.
Representative Concentration Pathways (RCPs)
Scenarios that include time series of emissions and concentrations of
the full suite of greenhouse gases and aerosols and chemically active
gases, as well as land use/land cover (Moss et al., 2008). The word
representative signifies that each RCP provides only one of many
possible scenarios that would lead to the specific radiative forcing
characteristics. The term pathway emphasizes that not only the long-
term concentration levels are of interest, but also the trajectory taken
over time to reach that outcome (Moss et al., 2010).
RCPs usually refer to the portion of the concentration pathway extending
up to 2100, for which Integrated Assessment Models produced
corresponding emission scenarios. Extended Concentration Pathways
(ECPs) describe extensions of the RCPs from 2100 to 2500 that were
calculated using simple rules generated by stakeholder consultations,
and do not represent fully consistent scenarios.
Four RCPs produced from Integrated Assessment Models were selected
from the published literature and are used in the present IPCC Assessment
as a basis for the climate predictions and projections in WGI AR5 Chapters
11 to 14:
RCP2.6 One pathway where radiative forcing peaks at approximately
3 W m
before 2100 and then declines (the corresponding ECP
assuming constant emissions after 2100).
RCP4.5 and RCP6.0 Two intermediate stabilization pathways in
which radiative forcing is stabilized at approximately 4.5 W m
6.0 W m
after 2100 (the corresponding ECPs assuming constant
concentrations after 2150).
Annex II Glossary
ne high pathway for which radiative forcing reaches
greater than 8.5 W m
by 2100 and continues to rise for some
amount of time (the corresponding ECP assuming constant emissions
after 2100 and constant concentrations after 2250).
For further description of future scenarios, see WGI AR5 Box 1.1.
The capacity of social, economic, and environmental systems to cope with
a hazardous event or trend or disturbance, responding or reorganizing
in ways that maintain their essential function, identity, and structure,
while also maintaining the capacity for adaptation, learning, and
Return period
An estimate of the average time interval between occurrences of an
event (e.g., flood or extreme rainfall) of (or below/above) a defined size
or intensity. See also Return value.
Return value
The highest (or, alternatively, lowest) value of a given variable, on
average occurring once in a given period of time (e.g., in 10 years). See
also Return period.
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 of occurrence of hazardous
events or trends multiplied by the impacts if these events or trends
occur. Risk results from the interaction of vulnerability, exposure, and
hazard. In this report, the term risk is used primarily to refer to the risks
of climate-change impacts.
Risk assessment
The qualitative and/or quantitative scientific estimation of risks.
Risk management
Plans, actions, or policies to reduce the likelihood and/or consequences
of risks or to respond to consequences.
Risk perception
The subjective judgment that people make about the characteristics and
severity of arisk.
Risk transfer
The practice of formally or informally shifting the risk of financial
consequences for particular negative events from one party to
That part of precipitation that does not evaporate and is not transpired,
but flows through the ground or over the ground surface and returns
to bodies of water. See also Hydrological cycle.
alt-water intrusion/encroachment
Displacement of fresh surface water or groundwater by the advance of
salt water due to its greater density. This usually occurs in coastal and
estuarine areas due to decreasing land-based influence (e.g., from
reduced runoff or groundwater recharge, or from excessive water
withdrawals from aquifers) or increasing marine influence (e.g., relative
sea level rise).
A plausible description of how the future may develop based on a
coherent and internally consistent set of assumptions about key driving
forces (e.g., rate of technological change, prices) and relationships. Note
that scenarios are neither predictions nor forecasts, but are useful to
provide a view of the implications of developments and actions. See
also Climate scenario, Emission scenario, Representative Concentration
Pathways, and SRES scenarios.
Sea level change
Sea level can change, both globally and locally due to (1) changes in
the shape of the ocean basins, (2) a change in ocean volume as a result
of a change in the mass of water in the ocean, and (3) changes in ocean
volume as a result of changes in ocean water density. Global mean sea
level change resulting from change in the mass of the ocean is called
barystatic. The amount of barystatic sea level change due to the addition
or removal of a mass of water is called its sea level equivalent (SLE).
Sea level changes, both globally and locally, resulting from changes in
water density are called steric. Density changes induced by temperature
changes only are called thermosteric, while density changes induced by
salinity changes are called halosteric. Barystatic and steric sea level
changes do not include the effect of changes in the shape of ocean
basins induced by the change in the ocean mass and its distribution.
See also Relative sea level and Thermal expansion.
Sea Surface Temperature (SST)
The sea surface temperature is the subsurface bulk temperature in the
top few meters of the ocean, measured by ships, buoys, and drifters.
From ships, measurements of water samples in buckets were mostly
switched in the 1940s to samples from engine intake water. Satellite
measurements of skin temperature (uppermost layer; a fraction of a
millimeter thick) in the infrared or the top centimeter or so in the
microwave are also used, but must be adjusted to be compatible with
the bulk temperature.
Semi-arid zone
Areas where vegetation growth is constrained by limited water availability,
often with short growing seasons and high interannual variation in
primary production. Annual precipitation ranges from 300 to 800 mm,
depending on the occurrence of summer and winter rains.
The degree to which a system or species 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,
This definition builds from the definition used in Arctic Council (2013).
This definition builds from the definitions used in Rosa (1998) and Rosa (2003).
Glossary Annex II
r variability of temperature) or indirect (e.g., damages caused by an
increase in the frequency of coastal flooding due to sea level rise).
Significant wave height
The average trough-to-crest height of the highest one-third of the wave
heights (sea and swell) occurring in a particular time period.
Any process, activity, or mechanism that removes a greenhouse gas,
an aerosol, or a precursor of a greenhouse gas or aerosol from the
Social Cost of Carbon (SCC)
The net present value of climate damages (with harmful damages
expressed as a positive number) from one more tonne of carbon in the
form of CO
, conditional on a global emissions trajectory over time.
Social protection
In the context of development aid and climate policy, social protection
usually describes public and private initiatives that provide income or
consumption transfers to the poor, protect the vulnerable against livelihood
risks, and enhance the social status and rights of the marginalized, with
the overall objective of reducing the economic and social vulnerability of
poor, vulnerable, and marginalized groups (Devereux and Sabates-Wheeler,
2004). In other contexts, social protection may be used synonymously
with social policy and can be described as all public and private initiatives
that provide access to services, such as health, education, or housing,or
income and consumption transfers to people. Social protection policies
protect the poor and vulnerable against livelihood risks and enhance
the social status and rights of the marginalized, as well as prevent
vulnerable people from falling into poverty.
Socioeconomic scenario
A scenario that describes a possible future in terms of population,
gross domestic product, and other socioeconomic factors relevant to
understanding the implications of climate change.
Southern Annular Mode (SAM)
The leading mode of variability of Southern Hemisphere geopotential
height, which is associated with shifts in the latitude of the midlatitude
jet. See SAM Index in WGI AR5 Box 2.5.
Species distribution modeling
Simulation of ecological effects of climate change. Species distribution
modeling uses statistically or theoretically derived response surfaces to
relate observations of species occurrence or known tolerance limits to
environmental predictor variables, thereby predicting a species’ range
as the manifestation of habitat characteristics that limit or support its
presence at a particular location. Species distribution models are also
referred to as environmental niche models. Bioclimate envelope models
can be considered as a subset of species distribution models that predict
species occurrence or habitat suitability based on climatic variables only.
SRES scenarios
SRES scenarios are emission scenarios developed by Nakićenović and
Swart (2000) and used, among others, as a basis for some of the climate
projections shown in Chapters 9 to 11 of IPCC (2001) and Chapters 10
nd 11 of IPCC (2007). The following terms are relevant for a better
understanding of the structure and use of the set of SRES scenarios:
Scenario family Scenarios that have a similar demographic, societal,
economic, and technical change storyline. Four scenario families
comprise the SRES scenario set: A1, A2, B1, and B2.
Illustrative scenario A scenario that is illustrative for each of the
six scenario groups reflected in the Summary for Policymakers of
Nakićenović and Swart (2000). They include four revised marker
scenarios for the scenario groups A1B, A2, B1, and B2, and two
additional scenarios for the A1FI and A1T groups. All scenario
groups are equally sound.
Marker scenario A scenario that was originally posted in draft
form on the SRES web site 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 Nakićenović 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.
StorylineA 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.
Storm surge
The temporary increase, at a particular locality, in the height of the sea
due to extreme meteorological conditions (low atmospheric pressure
and/or strong winds). The storm surge is defined as being the excess
above the level expected from the tidal variation alone at that time and
Storm tracks
Originally, a term referring to the tracks of individual cyclonic weather
systems, but now often generalized to refer to the main regions where
the tracks of extratropical disturbances occur as sequences of low
(cyclonic) and high (anticyclonic) pressure systems.
The highly stratified region of the atmosphere above the troposphere
extending from about 10 km (ranging from 9 km at high latitudes to
16 km in the tropics on average) to about 50 km altitude.
Events and trends, often not climate-related, that have an important
effect on the system exposed and can increase vulnerability to climate-
related risk.
Subsistence agriculture
Farming and associated activities that together form a livelihood
strategy in which most output is consumed directly but some may be
sold at market. Subsistence agriculture can be one of several livelihood
Annex II Glossary
urface temperature
See Global mean surface temperature, Land surface air temperature,
and Sea Surface Temperature.
A dynamic process that guarantees the persistence of natural and
human systems in an equitable manner.
Sustainable development
Development that meets the needs of the present without compromising
the ability of future generations to meet their own needs (WCED, 1987).
Thermal expansion
In connection with sea level, this refers to the increase in volume (and
decrease in density) that results from warming water. A warming of the
ocean leads to an expansion of the ocean volume and hence an increase
in sea level. See also Sea level change.
The layer of maximum vertical temperature gradient in the ocean, lying
between the surface ocean and the abyssal ocean. In subtropical regions,
its source waters are typically surface waters at higher latitudes that have
subducted and moved equatorward. At high latitudes, it is sometimes
absent, replaced by a halocline, which is a layer of maximum vertical
salinity gradient.
Thermohaline circulation (THC)
Large-scale circulation in the ocean that transforms low-density upper
ocean waters to higher-density intermediate and deep waters and
returns those waters back to the upper ocean. The circulation is
asymmetric, with conversion to dense waters in restricted regions at
high latitudes and the return to the surface involving slow upwelling
and diffusive processes over much larger geographic regions. The
THC is driven by high densities at or near the surface, caused by cold
temperatures and/or high salinities, but despite its suggestive though
common name, is also driven by mechanical forces such as wind and
tides. Frequently, the name THC has been used synonymously with
Meridional Overturning Circulation. See also Meridional Overturning
Tipping point
A level of change in system properties beyond which a system reorganizes,
often abruptly, and does not return to the initial state even if the drivers
of the change are abated.
Traditional knowledge
The knowledge, innovations, and practices of both indigenous and local
communities around the world that are deeply grounded in history and
experience. Traditional knowledge is dynamic and adapts to cultural and
environmental change, and also incorporates other forms of knowledge
and viewpoints. Traditional knowledge is generally transmitted orally
from generation to generation. It is often used as a synonym for
indigenous knowledge, local knowledge, or traditional ecological
A change in the fundamental attributes of natural and human systems.
Tree line
The upper limit of tree growth in mountains or at high latitudes. It is
more elevated or more poleward than the forest line.
Tropical cyclone
A strong, cyclonic-scale disturbance that originates over tropical oceans.
Distinguished from weaker systems (often named tropical disturbances
or depressions) by exceeding a threshold wind speed. A tropical storm is
a tropical cyclone with 1-minute average surface winds between 18 and
32 m s
. Beyond 32 m s
, a tropical cyclone is called a hurricane,
typhoon, or cyclone, depending on geographic location.
The lowest part of the atmosphere, from the surface to about 10 km in
altitude at mid-latitudes (ranging from 9 km at high latitudes to 16 km
in the tropics on average), where clouds and weather phenomena occur.
In the troposphere, temperatures generally decrease with height. See
also Stratosphere.
A wave, or train of waves, produced by a disturbance such as a submarine
earthquake displacing the sea floor, a landslide, a volcanic eruption, or
an asteroid impact.
A treeless biome characteristic of polar and alpine regions.
A state of incomplete knowledge that can result from a lack of information
or from disagreement about what is known or even knowable. It may
have many types of sources, from imprecision in the data to ambiguously
defined concepts or terminology, or uncertain projections of human
behavior. Uncertainty can therefore be represented by quantitative
measures (e.g., a probability density function) or by qualitative statements
(e.g., reflecting the judgment of a team of experts) (see Moss and
Schneider, 2000; Manning et al., 2004; Mastrandrea et al., 2010). See
also Confidence and Likelihood.
United Nations Framework Convention
on Climate Change (UNFCCC)
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 “stabilization
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. In 1997, the UNFCCC
adopted the Kyoto Protocol.
The glossary for the Working Group I contribution to the Fifth Assessment Report defines tipping point in the context of climate: “In climate, a hypothesized critical threshold
when global or regional climate changes from one stable state to another stable state. The tipping point event may be irreversible.
Glossary Annex II
The addition of a substance of concern to a reservoir. The uptake of
carbon containing substances, in particular carbon dioxide, is often
called (carbon) sequestration.
Upwelling region
A region of an ocean where cold, typically nutrient-rich waters well up
from the deep ocean.
Urban heat island
The relative warmth of a city compared with surrounding rural areas,
associated with changes in runoff, effects on heat retention, and
changes in surface albedo.
Volatile Organic Compounds (VOCs)
Important class of organic chemical air pollutants that are volatile
at ambient air conditions. Other terms used to represent VOCs are
hydrocarbons (HCs), reactive organic gases (ROGs), and non-methane
volatile organic compounds (NMVOCs). NMVOCs are major contributors
(together with NO
and CO) to the formation of photochemical oxidants
such as ozone.
The propensity or predisposition to be adversely affected. Vulnerability
encompasses a variety of concepts and elements including sensitivity
or susceptibility to harm and lack of capacity to cope and adapt. See
also Contextual vulnerability and Outcome vulnerability.
Vulnerability index
A metric characterizing the vulnerability of a system. A climate
vulnerability index is typically derived by combining, with or without
weighting, several indicators assumed to represent vulnerability.
Water cycle
See Hydrological cycle.
Water-use efficiency
Carbon gain by photosynthesis per unit of water lost by evapotranspiration.
It can be expressed on a short-term basis as the ratio of photosynthetic
carbon gain per unit transpirational water loss, or on a seasonal basis
as the ratio of net primary production or agricultural yield to the amount
of water used.
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Annex II Glossary
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