This page provides definitions for words and terms used frequently in relation to climate change and global climate modelling

This page provides definitions for words and terms used frequently in relation to climate change and global climate modelling. 


The process of adapting to the physical impacts of climate change on the environment, the economy, infrastructure and society. Examples are raising river or coastal stopbanks and planting drought-resistant crops. There are various types of adaptation:

  • Planned adaptation is the result of a deliberate policy decision, based on an awareness that conditions have changed or are about to change, and that action is required to maintain, or achieve, a desired state.
  • Reactive adaptation is adaptation that takes place in response to the consequences of a particular event.
  • Anticipatory adaptation is that which takes place before impacts of climate change are observed.
  • Spontaneous (or autonomous) adaptation does not constitute a conscious response to climatic stimuli, but is triggered by ecological changes in natural systems, and by market or welfare changes in human systems.

 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 to climate change

Actions to reduce the vulnerability of a system to the negative impacts of anticipated human-induced climate change.

Adaptation to climate variability

Adaptation to climate variability involves taking action to reduce vulnerability to short-term climate shocks. Often, adaptation to climate variability will also result in adaptation to climate change. The objective of adaptation is to reduce vulnerability to climate change and variability, and to better enable us to capture any benefits of climate change.

Adaptation measures

Adaptation measures refer to actual adjustments, or changes in environments that affect decision-making, which might enhance resilience or reduce vulnerability to observed or expected changes in climate.

Adaptive capacity

Inherent capacity of a system or population to adjust to climate impacts or climate change, to moderate potential damages, exploit opportunities, and cope with the consequences.


Climate refers to the average weather experienced in a region over a long period, typically at least 30 years. This includes temperature, wind and rainfall patterns.

Climate change risk

Risk to investments (such as buildings and infrastructure) and current practices from potential climate change impacts.

Climate change impact

A specific change in a system caused by its exposure to climate change. Impacts may be harmful (impact) or beneficial (opportunity).

Climatic variability

The Earth’s climate is not static, but varies on time scales of decades to millennia in response to interactions between the ocean and the atmosphere, changes in the Earth's orbit, fluctuations in energy received from the sun and volcanic eruptions. A fluctuation in the Earth’s climate is known as climatic variability.

Cost-benefit analysis 

A method to appraise the advantages associated with various options by quantifying in monetary terms as many costs and benefits as possible, including items for which the market does not provide a satisfactory measure of value. Cost-benefit analysis is designed to help select the option which offers the greatest benefits for the lowest costs.

Critical threshold

The point in a system at which sudden or rapid change occurs.

Extreme event

An event that is rare at a particular place. Definitions of "rare" vary, but an extreme weather event would normally be an event that occurred less than once every 10 years. By definition, the characteristics of what is called extreme weather may vary from place to place. 

Extreme hot days

An extreme hot day in New Zealand is often defined as a day when the maximum temperature exceeds 30°C.

Global Climate Model (GCM)

A model of the global ocean-atmosphere system used to predict future climate scenarios.

Greenhouse gases

A greenhouse gas is a gas in the atmosphere that absorbs heat energy (known as infrared radiation). Greenhouse gases are important for the Earth's climate because they allow incoming energy from the sun through. However, that energy is transformed into heat at the Earth’s surface and radiates back into the atmosphere. Greenhouse gases absorb some of the outgoing energy and reflect it in all different directions including back to Earth, keeping the surface of the Earth (and the lower atmosphere) warmer than it would be otherwise.If there were no greenhouse gases in the atmosphere, the average temperature of the Earth would be far lower (around -18 degrees Celsius) and much of the Earth would be frozen. However, human activities have increased the concentration of certain greenhouse gases, such as carbon dioxide and methane, in the atmosphere, increasing global temperatures.

Intense rainfall days

An intense rainfall amount is the value reached that provides the uppermost 10% (or 90th quantile) of the total seasonal precipitation.

Inter-annual variability (IAV)

Climatic variations with periods of longer than 1 year (and normally less than 10 years).

Intergovernmental Panel on Climate Change (IPCC)

Established in 1988 by the World Meteorological Organisation and the UN Environment Programme (UNEP), the IPCC surveys world-wide scientific and technical literature and publishes assessment reports that are widely recognised as the most credible existing sources of information on climate change. The IPCC was established to provide the decision-makers and others interested in climate change with an objective source of information about climate change. The IPCC also works on methodologies and responds to specific requests from the Convention's subsidiary bodies. The IPCC is independent of the United Nations Framework Convention on Climate Change.


Action or investment that increases vulnerability to climate change impacts rather than reducing them.


Any action that results, by design, in the reduction of greenhouse gas emissions by sources or enhances removals by sinks. Mitigation and abatement are often considered to be equivalent terms. Examples include using fossil fuels more efficiently for industrial processes or electricity generation, switching to solar energy or wind power, improving the insulation of buildings to reduce energy consumption and expanding forests to remove greater amounts of carbon dioxide from the atmosphere.

Paris Agreement

In 2015, all parties to the UNFCCC came together for the UN Climate Change Conference in Paris and adopted by consensus the Paris Agreement, aimed at limiting global warming to less than two degrees Celsius, and to pursue efforts to limit the rise to 1.5 degrees Celsius. The Paris Agreement entered into force on 4 November 2016, and for the first time brings together all member nations to undertake ambitious efforts to combat climate change and adapt to its effects, with enhanced support to assist developing countries to do so. As such, it charts a new course in the global climate effort.


The value below which falls a specified percentage (e.g. 90%) of a set of values. The 10th and 90th percentile values are commonly used to define the thresholds for extreme events. For example, the 90th percentile daily-average temperature is that which is exceeded on only one day in ten. 

Regional Climate Model (RCM)

An atmospheric model of higher resolution (finer scale) than a Global Climate Model (GCM) to provide more detailed simulations for a particular area.

Residual risk

Any risk above and beyond what is managed, such as a stopbank managing the risk of flooding up to a certain level, after which there is still the risk of flooding above that level, which is the residual risk. 


The ability of a social or natural system to absorb disturbances while retaining the same basic structure and ways of functioning and the capacity to adapt to stress and change.

Risk assessment

The structured analysis of hazards and impacts to provide information for decision-making. Risk assessment usually relates to a particular exposure unit for example, individual, population, infrastructure, building or environmental asset. The process usually involves identifying hazards that could have an impact, assessing the likelihoods and severities of impacts, and assessing the significance of the risk, which is usually related to the probability multiplied by the severity of the impact.

Risk management

A neutral risk approach would treat a risk with a low probability but a high potential benefit (e.g. winning the lottery) as similar to a risk with a high probability but lower benefits (e.g. regular maintenance). In contrast, a low-risk approach would try to avoid or manage a low probability event with high impacts, whereas a high-risk approach would be to have no plans in place for high impact events.


Plausible and often simplified descriptions of how the future may develop based on a coherent and internally consistent set of assumptions about driving forces and key relationships. Scenarios may be derived from projections but are often based on additional information from other sources and sometimes combined with a narrative storyline.

Thermal growing season

The growing season is the period of time each year during which plants can grow. The thermal definition of growing season length does not consider the impact of other climatic variables (e.g. wind, precipitation).


Thresholds help establish the acceptability of the risk posed to an exposure unit by future circumstances and decisions. Thresholds are determined by past records or experience of previous events that defined the edge of the coping range and the limit of a tolerable climate. Thresholds, or assessment endpoints, may be a fundamental property of a system (i.e. the water level at which a river bursts its banks, or the wind speed that leads to the felling of large areas of forest), or behavioural (i.e. a point at which individuals, or society at large, responds to an issue by a change in behaviour that has an economic or social outcome).


Uncertainty is an expression of the degree to which a value (e.g. the future state of the climate system) is unknown. Uncertainty can result from lack of information or from disagreement over what is known or even knowable. Uncertainty may arise from many sources, such as quantifiable errors in data, or uncertain projections of human behaviour. Uncertainty can be represented by quantitative measures or by qualitative statements.

United Nations Framework Convention on Climate Change (UNFCCC)

The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty adopted on 9 May 1992 and opened for signature at the 1992 Earth Summit in Rio de Janeiro. It then entered into force on 21 March 1994, after a sufficient number of countries had ratified it. The UNFCCC objective is to "stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system". The framework sets non-binding limits on greenhouse gas emissions for individual countries and outlines how specific international treaties may be negotiated to specify further action towards the objective of the UNFCCC. The UNFCCC has 197 parties as of December 2015.


Vulnerability to climate change is the degree to which something is susceptible to, and unable to cope with, adverse impacts.


Weather refers to the state of the atmosphere with regard to temperature, cloudiness, rainfall, wind, and other meteorological conditions.