IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Synthesis Report

Glossary J-P


Joint Implementation (JI)

A market-based implementation mechanism defined in Article 6 of the Kyoto Protocol, allowing Annex I countries or companies from these countries to implement projects jointly that limit or reduce emissions or enhance sinks, and to share the Emissions Reduction Units. JI activity is also permitted in Article 4.2(a) of the United Nations Framework Convention on Climate Change (UNFCCC). See also Kyoto Mechanisms; Activities Implemented Jointly.


Kyoto Mechanisms (also called Flexibility Mechanisms)

Economic mechanisms based on market principles that parties to the Kyoto Protocol can use in an attempt to lessen the potential economic impacts of greenhouse gas emission-reduction requirements. They include Joint Implementation (Article 6), Clean Development Mechanism (Article 12), and Emissions Trading (Article 17).

Kyoto Protocol

The Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) was adopted in 1997 in Kyoto, Japan, at the Third Session of the Conference of the Parties (COP) to the UNFCCC. It contains legally binding commitments, in addition to those included in the UNFCCC. Countries included in Annex B of the Protocol (most Organization for Economic Cooperation and Development countries and countries with economies in transition) agreed to reduce their anthropogenic greenhouse gas emissions (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulphur hexafluoride) by at least 5% below 1990 levels in the commitment period 2008 to 2012. The Kyoto Protocol entered into force on 16 February 2005.


Land use and Land-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 have a radiative forcing and/or other impacts on climate, locally or globally. See also: the IPCC Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000).

Last Interglacial (LIG)

See Interglacial

Learning by Doing

As researchers and firms gain familiarity with a new technological process, or acquire experience through expanded production they can discover ways to improve processes and reduce cost. Learning by Doing is a type of experience-based technological change.

Level of Scientific Understanding (LOSU)

This is an index on a 5-step scale (high, medium, medium-low, low  and very low) designed to characterise the degree of scientific understanding of the radiative forcing agents that affect climate change. For each agent, the index represents a subjective judgement about the evidence for the physical/chemical mechanisms determining  the forcing and the consensus surrounding the quantitative estimate and its uncertainty.


The likelihood of an occurrence, an outcome or a result, where this can be estimated probabilistically, is expressed in IPCC reports using a standard terminology defined as follows:

Terminology Likelihood of the occurrence / outcome
Virtually certain >99% probability of occurrence
Very likely >90% probability
Likely >66% probability
More likely than not >50% probability
About as likely as not 33 to 66% probability
Unlikely <33% probability
Very unlikely <10% probability
Exceptionally unlikely <1% probability

See also Confidence; Uncertainty


Macroeconomic costs

These costs are usually measured as changes in Gross Domestic Product or changes in the growth of Gross Domestic Product, or as loss of welfare or of consumption.


Endemic or epidemic parasitic disease caused by species of the genus Plasmodium (Protozoa) and transmitted to humans by mosquitoes of the genus Anopheles; produces bouts of high fever and systemic disorders, affects about 300 million and kills approximately 2 million people worldwide every year.

Market Exchange Rate (MER)

This is the rate at which foreign currencies are exchanged. Most economies post such rates daily and they vary little across all the exchanges. For some developing economies official rates and black-market rates may differ significantly and the MER is difficult to pin down.

Market impacts

Impacts that can be quantified in monetary terms, and directly affect Gross Domestic Product – e.g. changes in the price of agricultural inputs and/or goods. See also Non-market impacts.

Market potential

See Mitigation potential.

Mass balance (of glaciers, ice caps or ice sheets)

The balance between the mass input to an ice body (accumulation) and the mass loss (ablation, iceberg calving). Mass balance terms include the following:

Specific mass balance: net mass loss or gain over a hydrological cycle at a point on the surface of a glacier.

Total mass balance (of the glacier):  The specific mass balance spatially integrated over the entire glacier area; the total mass a glacier gains or loses over a hydrological cycle.

Mean specific mass balance:  The total mass balance per unit area of the glacier. If surface is specified (specific surface mass balance, etc.) then ice-flow contributions are not considered; otherwise, mass balance includes contributions from ice flow and iceberg calving. The specific surface mass balance is positive in the accumulation area and negative in the ablation area.

Mean Sea Level

Mean sea level is normally defined as the average relative sea level over a period, such as a month or a year, long enough to average out transients such as waves and tides. Relative sea level is sea level measured by a tide gauge with respect to the land upon which it is situated.

See Sea level change/sea level rise.


Measures are technologies, processes, and practices that reduce greenhouse gas emissions or effects below anticipated future levels. Examples of measures are renewable energy technologies, waste minimisation processes, and public transport commuting practices, etc. See also Policies.

Meridional Overturning Circulation (MOC)

A zonally averaged, large scale meridional (north-south) overturning circulation in the oceans. In the Atlantic such a circulation transports relatively warm upper-ocean waters northward, and relatively cold deep waters southward. The Gulf Stream forms part of this Atlantic circulation.

Methane (CH4)

Methane is one of the six greenhouse gases to be mitigated under the Kyoto Protocol and is the major component of natural gas and associated with all hydrocarbon fuels, animal husbandry and agriculture. Coal-bed methane is the gas found in coal seams.

Methane recovery

Methane emissions, e.g. from oil or gas wells, coal beds, peat bogs, gas transmission pipelines, landfills, or anaerobic digesters, may be captured and used as a fuel or for some other economic purpose (e.g. chemical feedstock).


A consistent measurement of a characteristic of an object or activity that is otherwise difficult to quantify.

Millennium Development Goals (MDGs)

A set of time-bound and measurable goals for combating poverty, hunger, disease, illiteracy, discrimination against women and environmental degradation, agreed at the UN Millennium Summit in 2000.


Technological change and substitution that reduce resource inputs and emissions per unit of output. Although several social, economic and technological policies would produce an emission reduction, with respect to Climate Change, mitigation means implementing policies to reduce greenhouse gas emissions and enhance sinks.

Mitigative capacity

This is a country’s ability to reduce anthropogenic greenhouse gas emissions or to enhance natural sinks, where ability refers to skills, competencies, fitness and proficiencies that a country has attained and depends on technology, institutions, wealth, equity, infrastructure and information. Mitigative capacity is rooted in a country’s sustainable development path.

Mitigation Potential

In the context of climate change mitigation, the mitigation potential is the amount of mitigation that could be – but is not yet – realised over time.

Market potential is the mitigation potential based on private costs and private discount rates, which might be expected to occur under forecast market conditions, including policies and measures currently in place, noting that barriers limit actual uptake. Private costs and discount rates reflect the perspective of private consumers and companies.

Economic potential is the mitigation potential that takes into account social costs and benefits and social discount rates, assuming that market efficiency is improved by policies and measures and barriers are removed. Social costs and discount rates reflect the perspective of society. Social discount rates are lower than those used by private investors.

Studies of market potential can be used to inform policy makers about mitigation potential with existing policies and barriers, while studies of economic potential show what might be achieved if appropriate new and additional policies were put into place to remove barriers and include social costs and benefits. The economic potential is therefore generally greater than the market potential.

Technical potential is the amount by which it is possible to reduce greenhouse gas emissions or improve energy efficiency by implementing a technology or practice that has already been demonstrated. No explicit reference to costs is made but adopting ‘practical constraints’ may take implicit economic considerations into account.


See Climate model; Bottom-up model; Top-down model

Model hierarchy

See Climate model


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.


Rate of occurrence of disease or other health disorder within a population, taking account of the age-specific morbidity rates. Morbidity indicators include chronic disease incidence/ prevalence, rates of hospitalisation, primary care consultations, disability-days (i.e., days of absence from work), and prevalence of symptoms.


Rate of occurrence of death within a population; calculation of mortality takes account of age-specific death rates, and can thus yield measures of life expectancy and the extent of premature death.


Net market benefits

Climate change, especially moderate climate change, is expected to bring positive and negative impacts to market-based sectors, but with significant differences across different sectors and regions and depending on both the rate and magnitude of climate change. The sum of the positive and negative market-based benefits and costs summed across all sectors and all regions for a given period is called net market benefits. Net market benefits exclude any non-market impacts.

Nitrous oxide (N2O)

One of the six types of greenhouse gases to be curbed under the Kyoto Protocol. The main anthropogenic source of nitrous oxide is agriculture (soil and animal manure management), but important contributions also come from sewage treatment, combustion of fossil fuel, and chemical industrial processes. Nitrous oxide is also produced naturally from a wide variety of biological sources in soil and water, particularly microbial action in wet tropical forests.

Non-governmental Organisation (NGO)

A non-profit group or association organised outside of institutionalised political structures to realise particular social and/or environmental objectives or serve particular constituencies. Source: http://www.edu.gov.nf.ca/curriculum/teched/resources/glos-biodiversity.html

Non-market impacts

Impacts that affect ecosystems or human welfare, but that are not easily expressed in monetary terms, e.g., an increased risk of premature death, or increases in the number of people at risk of hunger. See also market impacts.


Ocean acidification

A decrease in the pH of sea water due to the uptake of anthropogenic carbon dioxide.


Circumstances to decrease the gap between the market potential of any technology or practice and the economic potential, or technical potential.

Ozone (O3)

Ozone, the tri-atomic form of oxygen, is a gaseous atmospheric constituent. In the troposphere, ozone is created both naturally and by photochemical reactions involving gases resulting from human activities (smog). Troposphere ozone acts as a greenhouse gas. In the stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O2). Stratospheric ozone plays a dominant role in the stratospheric radiative balance. Its concentration is highest in the ozone layer.



Climate during periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available.

Patterns of climate variability

Natural variability of the climate system, in particular on seasonal and longer time scales, predominantly occurs with preferred spatial patterns and time scales, through the dynamical characteristics of the atmospheric circulation and through interactions with the land and ocean surfaces. Such patterns are often called regimes, modes or teleconnections. Examples are the North Atlantic Oscillation (NAO), the Pacific-North American pattern (PNA), the El Niño- Southern Oscillation (ENSO), the Northern Annular Mode (NAM; previously called Arctic Oscillation, AO) and the Southern Annular Mode (SAM; previously called the Antarctic Oscillation, AAO). Many of the prominent modes of climate variability are discussed in section 3.6 of the Working Group I Report.


A percentile is a value on a scale of zero to one hundred that indicates the percentage of the data set values that is equal to or below it. The percentile is often used to estimate the extremes of a distribution. For example, the 90th (10th) percentile may be used to refer to the threshold for the upper (lower) extremes.

Perfluorocarbons (PFCs)

Among the six greenhouse gases to be abated under the Kyoto Protocol. These are by-products of aluminium smelting and uranium enrichment. They also replace chlorofluorocarbons in manufacturing semiconductors.


Ground (soil or rock and included ice and organic material) that remains at or below 0°C for at least two consecutive years (Van Everdingen, 1998) . See also Frozen ground.


pH is a dimensionless measure of the acidity of water (or any solution). Pure water has a pH=7. Acid solutions have a pH smaller than 7 and basic solutions have a pH larger than 7. pH is measured on a logarithmic scale. Thus, a pH decrease of 1 unit corresponds to a 10-fold increase in the acidity.


The study of natural phenomena in biological systems that recur periodically (e.g., development stages, migration) and their relation to climate and seasonal changes.


The process by which green plants, algae and some bacteria take carbon dioxide from the air (or bicarbonate in water) to build carbohydrates. There are several pathways of photosynthesis with different responses to atmospheric carbon dioxide concentrations. See Carbon dioxide fertilisation.


Micro-organisms living in the upper layers of aquatic systems. A distinction is made between phytoplankton, which depend on photosynthesis for their energy supply, and zooplankton, which feed on phytoplankton.


In United Nations Framework Convention on Climate Change (UNFCCC) parlance, policies are taken and/or mandated by a government – often in conjunction with business and industry within its own country, or with other countries – to accelerate mitigation and adaptation measures. Examples of policies are carbon or other energy taxes, fuel efficiency standards for automobiles, etc. Common and co-ordinated or harmonised policies refer to those adopted jointly by parties. See also Measures.


A coherent set of a variety of measures and/or technologies that policy makers can use to achieve a postulated policy target. By widening the scope in measures and technologies more diverse events and uncertainties can be addressed.

Post-SRES (scenarios)

Baseline and mitigation emission scenarios published after completion of the IPCC Special Report on Emission Scenarios (SRES) (Nakic4enovic4 and Swart, 2000), i.e. after the year 2000.


See Industrial revolution.


A potential future evolution of a quantity or set of quantities, often computed with the aid of a model. Projections are distinguished from predictions in order to emphasise that projections involve assumptions concerning, for example, future socio-economic and technological developments that may or may not be realised, and are therefore subject to substantial uncertainty. See also Climate projection; Climate prediction.

Purchasing Power Parity (PPP)

The purchasing power of a currency is expressed using a basket of goods and services that can be bought with a given amount in the home country. International comparison of e.g. Gross Domestic Products (GDP) of countries can be based on the purchasing power of currencies rather than on current exchange rates. PPP estimates tend to lower per capita GDPs in industrialised countries and raise per capita GDPs in developing countries.