Glossary of climate science and adaptation terms

Submitted by Sukaina Bharwani | published 25th Mar 2011 | last updated 19th Mar 2014
  • Adaptation A system response to perturbations or stress that is sufficiently fundamental to alter the system itself, sometimes shifting the system to a new state. [Source: Kasperson, et al. (2002)]
  • Adaptive capacity The capacity of a system, region or community to adapt to the effects and impacts of climate change. It depends on a society's economic, social and human resources. Humans' ability to adapt depends on factors such as wealth, technology, education, information, skills, infrastructures, access to resources and management capacity.
  • Adjustment a system response to perturbations or stress that does not fundamentally alter the system itself. Adjustments are commonly (but not necessarily) short-term and involve relatively minor system modifications. [Source: Kasperson, et al. (2002)]
  • Average can refer either to the mean, median or mode but mean is most commonly meant when the word average is used. The mean is calculated by adding all numbers in a dataset together and dividing by how many numbers there are. The average temperature in July for the period 1960-1990 means that all the July temperatures from that period have been added up and divided by the number of years to find a value which is representative of July temperature over the period.
  • Anomalies An anomaly is the difference between the expected result and the actual result. The temperature anomaly in 2050 is the difference between the predicted temperature in 2050 and the average temperature in the present.
  • Boundary conditions Models cannot simulate all of reality, they must choose an area and model the processes within that area, so they have boundaries . Boundary conditions are how the model simulates the physical processes in this boundary region, and can have an impact on the way the rest of the simulation works. [1]
  • Boundary organisations Institutions that cross the gap between two different domains. They promote co-operation around a common interest instead of allowing the different domains to fight for control that leads to division. Boundary organisations are able to act beyond the boundary of each domain while remaining accountable to each side. They facilitate the flow of information across boundaries, permit dialog and exchange to take place, while maintaining authority in each domain. Since decision making under uncertainty requires an evaluation of all information available the boundary organisations goal is not to reach a decision but to encourage the interaction to ease decision making. If boundary organisations disappear then the objective has been reached. Example: ‘address relationship between public entities and users” ‘Boundary organisations serve as facilitators bridging separations between researchers and forecast users, often serving as primary contacts for each community and coordinators”
  • Climate is the combination of all the variations in weather at a given location over a period of time. It is the average conditions that are expected at a location. The period of time for measuring climate is defined by the WMO as 30 years, with the average conditions from 1960-1990 often used to define 'current' climate. IPCC WGII glossary
  • Climate Sensitivity is the change in the climate system that would occur in response to a given external forcing. It often refers to what change would occur (or how sensitive the climate is) under different concentrations of carbon dioxide. IPCC WGI glossary
  • 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 temporal and spatial 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). New risks, new geographical spread of risks, new population groups vulnerable and perhaps most importantly new combinations of risk, that impact beyond critical thresholds.
  • Dekad A ten day period
  • Diagnostic and Prognostic variables Prognostic variables are ones which are modelled using the internal physics of the model, such as temperature. Diagnostic models , such as rainfall, are ones which cannot be modelled dynamically, so are parameterized (see below). Projections of changes in prognostic variables are more reliable than those in diagnostic variables.
  • Exposure the contact between a system and a perturbation or stress. [Source: Kasperson, et al. (2002)]
  • Extreme events An extreme weather event is an event that is rare at a particular place and time of year. An extreme event would usually be rarer than the 10th or 90th percentile. Extreme events vary from place to plece; what is extreme in one area might be common in another. Single extreme events cannot be attributesd as being caused by climate change, as they may have occurred naturally, but climate change is expected to increase the occurence of extreme events. IPCC WGI glossary
  • Forecast A forecast is an expected outcome based on established patterns (physical, technological, economic, social etc) and is for the near-future - in climate terms forecasts can be made up to the level of seasons. IPCC WGIII glossary
  • GCM General Circulation Models (GCMs) are a class of computer-driven models for understanding climate and projecting climate change, where they are commonly called Global Climate Models. They are numerical representations of the real world which simulate actual processes, but do not capture all the complexity of the system. IPCC WGI glossary
  • GCM skill This is a measure of how good GCMs are at modelling particular processes.
  • Gridded data the fundamental unit of gridded data is the cell, which represents a location in a continuous space set. The condition of a given cell is recorded as a numeric value for each cell. In spatial terms, gridded data are called rasters.
  • Hazard the threat of a stress or perturbation to a system and what it values. [Source: Kasperson, et al. (2002)]
  • Incremental adaptation (as distinct from transformational adaptation) involves gradual, minor extensions of actions and behaviors that are already undertaken to reduce the losses or enhance the benefits of natural variations in climate and extreme events (Kates et al., 2012).
  • Initial conditions are the state of the variables of the current climate which are used as the starting point for running GCMs. As we do not understand the whole of the climate system, these initial conditions are informed guesses and so can introduce uncertainty into GCM projections. To overcome this some groups run GCMs lots of different times, with slightly different initial conditions to give a range of outcomes.
  • Interpolation is a method of constructing new data points (and surfaces) within the range of a discrete set of known data points. Two broad categories of interpolation methods area available for spatial data, differing in the level of detail gained, the weighting approach used and their treatment of observed values. These categories are discussed in detail below, but include: Deterministic methods, which use polynomial functions to fit a surface onto a set of points. These include the methods of Inverse Distance Weighting and Splines, and Geostatistical - which determine a priori trends in the data and then applies these trends to the task of surface fitting. Kriging techniques are an example of this method.
  • ITCZ The Inter-Tropical Convergence Zone is a region of rising, unstable air near the equator which occurs when the NE and SE Trade Winds meet. The ITCZ migrates seasonally following the zone of greatest heating, and because it is an unstable mass of air causes significant rainfall. Changes in the way the ITCZ moves could have severe consequences on rainfall in many parts of Africa. [2]
  • Normal Often used to describe the average conditions of a site. 'Normal climate' is often used to mean 'Average climate'
  • Parameterization This refers to the technique in climate models of representing processes that can't be resolved by the dynamic physics of the model, or that are below the scale at which the model operates, by static relationships between the large-scale processes and the process being modelled. For example a model may not be able to create rainfall because it occurs at a scale which is too small, so it might create a relationship which says that when humidity is above 70% it will rain. IPCC glossary
  • Policy A policy is typically described as a deliberate plan of action to guide decisions and achieve rational outcome(s), a guide that establishes the parameters for decision making and action.
  • Prediction A prediction is an estimate of the way a system will react in the future, for example at a seasonal level. Predictions use the state of variables in the current system (for example sea-surface temperatures) to estimate the evolution of the system in the near-future. IPCC WGI glossary
  • Projection Looks at the response of the climate system to scenarios of changes in emissions, aerosols and radiative forcing. Projections depend on the assumptions underlying the scenario and model used, which may or may not occur, so are only possible futures as they are subject to uncertainty. IPCC glossary
  • Probability Density Function (PDF) This is a graphical representation of how often a certain outcome occurs, or is expected to occur. See Image
  • Probability is the likelihood, or chance that an event will occur. It is not yet possible to give climate projections probabilities because of the uncertainty present in the climate models.
  • Public policy Public policy can be generally defined as a system of laws, regulatory measures, courses of action, and funding priorities concerning a given topic promulgated by a governmental entity or its representatives. Public policy fluctuates with the changing economic needs, social customs, and moral aspirations of the people. Public policy enters into, and influences, the enactment, execution, and interpretation of legislation.
  • Perturbation a disturbance to a system resulting from a sudden shock with a magnitude outside the normal vulnerability. [Source: Kasperson, et al. (2002)]
  • Radiative Forcing is the change in the net irradiance (in watts) at the tropopause due to an external driver such as an increase in greenhouse gasses. IPCC WGI glossary
  • Resilience the ability of a system to absorb perturbations or stresses without changes in its fundamental structure or function that would drive the system into a different state (or extinction). [Source: Kasperson, et al. (2002)]
  • Risk the conditional probability and magnitude of harm attendant on exposure to a perturbation or stress. [Source: Kasperson, et al. (2002)]
  • Robustness The property of statistical procedures that are insensitive to small departures from the assumptions on which they depend, such as the assumption that certain distributions are normal. [3]
  • Scenarios A scenario is a plausible description of how the future may develop, it is not a prediction of the what the future will be. They are based on a coherent set of assumptions about the driving forces and key relationships that determine what the future will look like. IPCC WGI glossary
  • Sensitivity the extent to which a system or its components is likely to experience harm, and the magnitude of that harm, due to exposure to perturbations or stresses. [Source: Kasperson, et al. (2002)]
  • Spatially Smoothed- a set of statistical methods used to fit spatial surfaces, such as those of a GCM to a set of observations (such as station data).
  • Stationarity is an issue in empirical downscaling and refers to the assumption that relationships which exist between variables at present will stay the same into the future.
  • Stochastic A stochastic event is based on random behavior. The occurrence of individual events cannot be predicted, although measuring the distribution of all observations usually follows a predictable pattern. These patterns can be described by statistical means. Stochastic threats to a natural system, generally fall within the categories of environmental, demographic and genetic threats. An example is the decay of radio active material, where a clump of matter has a measurable and thus predictable half-life time. It is impossible, however, to mark an individual atom and predict when it will decay and emit radiation. The latter process is a stochastic event. [4] Stochastic events can occur in relation to deterministic factors such as exogenous threats (habitat loss, habitat degradation and habitat isolation) and endogenous threats (changes in biology, behaviour and species interactions). There are also several exogenous stochastic and endogenous stochastic threats. [Fischer, J. and Lindenmayer, D. B. (2007) Landscape modification and habitat fragmentation: a synthesis. Global Ecology and Biogeography, 16: 265-280]
  • Stress cumulating pressure on a system resulting from processes within the normal range of variability, but which over time may result in disturbances causing the system to adjust, adapt, or be harmed. [Source: Kasperson, et al. (2002)]
  • Surprise Strictly speaking, a surprise is an outcome cannot be anticipated; by definition it is an unexpected event. However, what gets labeled as `surprise' depends on the extent to which what happens departs from community expectations and on the salience of the problem [5]
  • Synoptic circulation is the large-scale circulation such as fronts and cyclones which drive the climate system.
  • Teleconnections A connection between climate variations over widely separated parts of the world, so that climate variations in one part of the world will cause the climate system in a different part of the world to respond in a certain way.
  • Thresholds A threshold is a point in a system at which external forcing of system (for example due to increasing greenhouse gasses) causes a reorganisation of the system into a significantly different state from which it is impossible, or takes a very long time, to return to the original state. For example warming may switch ocean circulation in the N. Atlantic into a different state in which the thermohaline circulation does not transport as much heat to N. Europe, and it would take several hundred years to switch back. IPCC WGII glossary
  • Transformational adaptation (as distinct from incremental adaptation) entails actions and behaviors much larger in scale or intensity than those already undertaken to reduce the losses or enhance the benefits of natural variations in climate and extreme events, actions and behaviors totally new to a region or resource system, and/or actions and behaviors that transform places and shift locations (Kates et al., 2012).
  • Uncertainty This is the unpredictability of a system or model. Uncertainty in models can come from many sources; a lack of information, lack of technical ability to model complex processes, a lack of knowledge about a system or uncertainty over human behaviour.
  • Vulnerability the degree to which a person, system or unit is likely to experience harm due to exposure to perturbations or stresses. [Source: Kasperson, et al. (2002)] More Vulnerability definitions
  • Weather is the actual state of the atmosphere at a given time in a given place. It is what people experience on a day to day basis.
  • Weather Generator Based on the statistical characteristics of observed weather at a site, a weather generator can produce long-term forecasts of weather at that site. [6]