Glossary

The Agriculture, Forestry and Other Land Use is a unique sector since the mitigation potential is derived from both an enhancement of removals of greenhouse gases (GHG), as well as reduction of emissions through management of land and livestock.

A naturally occurring gas, CO₂ is also a by-product of burning fossil fuels (such as oil, gas and coal), of burning biomass, of land-use changes (LUC) and of industrial processes (e.g., cement production). It is the principal anthropogenic greenhouse gas (GHG) that affects the Earth’s radiative balance. It is the reference gas against which other GHGs are measured and therefore has a global warming potential (GWP) of 1.

A process in which a relatively pure stream of carbon dioxide (CO₂) from industrial and energy-related sources is separated (captured), conditioned, compressed and transported to a storage location for long-term isolation from the atmosphere.

Anthropogenic activities removing CO₂ from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical sinks and direct air capture and storage but excludes natural CO₂ uptake not directly caused by human activities.

The price of avoided or released carbon dioxide (CO₂) or CO₂-equivalent emissions. This may refer to the rate of a carbon tax, or the price of emission permits. In many models that are used to assess the economic costs of mitigation, carbon prices are used as a proxy to represent the level of effort in mitigation policies.

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 used to provide a view of the implications of developments and actions.

The amount of work or heat delivered. Energy is classified in a variety of types and becomes useful to human ends when it flows from one place to another or is converted from one type into another. Primary energy (also referred to as energy sources) is the energy embodied in natural resources (e.g., coal, crude oil, natural gas, uranium) that has not undergone any anthropogenic conversion. It is transformed into secondary energy by cleaning (natural gas), refining (oil in oil products) or by conversion into electricity or heat. When the secondary energy is delivered at the end-use facilities it is called final energy (e.g., electricity at the wall outlet), where it becomes usable energy (e.g., light). Daily, the sun supplies large quantities of energy as rainfall, winds, radiation, etc. Some share is stored in biomass or rivers that can be harvested by men. Some share is directly usable such as daylight, ventilation or ambient heat. Renewable energy is obtained from the continuing or repetitive currents of energy occurring in the natural environment and includes non-carbon technologies such as solar energy, hydropower, wind, tide and waves and geothermal heat, as well as carbon-neutral technologies such as biomass.

GCAM is an Integrated Assessment Model (IAM) applied to the NGFS phase IV scenarios. It is a global market equilibrium model, that combines economic, energy, land -use, and climate systems to analyse the interactions between human activities and global environmental changes. It is designed to assess the impacts of various policy scenarios and technology options on energy use, land use change, greenhouse gas emissions and climate change.

A numerical representation of the climate system based on the physical, chemical and biological properties of its components, their interactions and feedback processes, and accounting for 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 aspects as the number of spatial dimensions, the extent to which physical, chemical or biological processes are explicitly represented, or the level at which empirical parametrisations are involved. 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.

The estimated global average of near-surface air temperatures over land and sea-ice, and sea surface temperatures over ice-free ocean regions, with changes normally expressed as departures from a value over a specified reference period. When estimating changes in GMST, near-surface air temperature over both land and oceans are also used. The temperatures in the NGFS climate scenarios are obtained from the reduced complexity climate model MAGICC 7.5.3.

Global warming (around 1.2°C to date) should be measured following the approach of the IPCC AR5 report in 2014. The Paris Agreement’s Temperature Goal is based on warming since pre-industrial times. Setting the guidelines for climate policy, the temperature goal is appropriately defined comprising the full scope of the problem at hand – in this case human-made warming – resulting from the greenhouse gas emissions since the industrial revolution.

Scientifically, however, this is a little more complicated, as temperature measurements even for the early 1900s are scarce, with increased uncertainties around their quality. Scientists generally choose more recent reference periods. In the case of the IPCC AR5 this was 1986-2005, from which they derived temperature differences both forwards and backwards in time.

The 2014 IPCC AR5, which serves as the scientific basis for the 2015 Paris Agreement, uses the 1850–1900 period as a proxy for the pre-industrial period. It assessed the global temperature increase between 1850–1900 and 1986–2005 to be 0.6°C – based on the HadCRUT4 dataset. This is the relevant reference for the Paris Agreement.

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 by clouds. This property causes the greenhouse effect. Water vapour (H2O), carbon dioxide (CO₂), nitrous oxide (N₂O), methane (CH₄) and ozone (O₃) are the primary GHGs in the Earth’s atmosphere. Moreover, there are a number of entirely human-made GHGs in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, dealt with under the Montreal Protocol. Besides CO₂, N₂O and CH₄, the Kyoto Protocol deals with the GHGs sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs).

Integrated assessment models (IAMs) integrate knowledge from two or more domains into a single framework. They are one of the main tools for undertaking integrated assessments. One class of IAM used in respect of climate change mitigation may include representations of: multiple sectors of the economy, such as energy, land use and land-use change; interactions between sectors; the economy as a whole; associated GHG emissions and sinks; and reduced representations of the climate system. This class of model is used to assess linkages between economic, social and technological development and the evolution of the climate system. Another class of IAM additionally includes representations of the costs associated with climate change impacts but includes less detailed representations of economic systems. These can be used to assess impacts and mitigation in a cost-benefit framework and have been used to estimate the social cost of carbon. IAM models used for the NGFS scenarios are REMIND-MAgPIE, MESSAGEix-GLOBIOM and GCAM.

The International Institute for Applied Systems Analysis (IIASA) is an independent, international research institute that conducts policy-oriented research into issues that are too large or complex to be solved by a single country or academic discipline. This includes pressing concerns that affect the future of all of humanity, such as climate change, energy security, population ageing, and sustainable development.

The Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) offers a framework for consistently projecting the impacts of climate change across affected sectors and spatial scales. An international network of climate-impact modellers contributes to a comprehensive and consistent picture of the world under different climate-change scenarios.

MAGICC is a prime reduced-complexity model, often used by IPCC for scientific publications, and by a number of Integrated Assessment Models. The NGFS climate scenarios use MAGICC 7.5.3.

MESSAGE-GLOBIOM model, or MESSAGE in short, is an Integrated Assessment Model (IAM) applied to the NGFS phase IV scenarios. It is developed by the International Institute for Applied Systems Analysis (IIASA). It combines energy systems, environmental impacts, and economic analysis to evaluate the long-term implications of energy and climate policies.

MAgPIE is the landuse component of PIK‘s IAM framework REMIND-MAgPIE.

MAgPIE is a global land use allocation model, which is in turn connected to the grid-based dynamic vegetation model LPJmL (Lund-Potsdam-Jena managed Land) to simulate the interactions between the land surface and the atmosphere as well as the impact of human activities on the environment. As a partial equilibrium model, the objective function of MAgPIE is the fulfilment of agricultural demand for each region at minimum global costs under consideration of biophysical and socioeconomic constraints.

NiGEM is a peer-reviewed global econometric model provided by the National Institute of Economic & Social Research (NIESR). The model is part of the NGFS suite of models, providing the macro-economic impacts of climate implied by both the IAM transition risks as well as acute and chronic physical risks.

A term used under the United Nations Framework Convention on Climate Change (UNFCCC) whereby a country that has joined the Paris Agreement outlines its plans for reducing its emissions. Some countries’ NDCs also address how they will adapt to climate change impacts, and what support they need from, or will provide to, other countries to adopt low-carbon pathways and to build climate resilience.

A situation of net-zero CO₂ emissions is achieved when, as a result of human activities, the same amount of CO₂ is removed from the atmosphere than is emitted into it. Net CO₂ emissions become negative when more CO₂ is removed from the atmosphere than emitted into it (i.e. net negative CO₂ emissions).

When multiple greenhouse gases are involved, the quantification of negative emissions depends on the climate metric chosen to compare emissions of different gases (such as global warming potential, global temperature change potential, and others, as well as the chosen time horizon).

Physical risks relate to the effects of global warming on physical capital, human health and productivity and agriculture.

REMIND is the energy system component of PIK‘s Integrated Assessment Modeling framework REMIND-MAgPIE.

REMIND is a numerical model that generates projections for the future evolution of the world economies with a special focus on the development of the energy sector and the implications for our world climate. The goal of REMIND is to find the optimal mix of investments in the economy and the energy sectors of each of the 12 model regions given a set of population, technology, policy, and climate constraints. It also accounts for regional trade characteristics on goods, energy fuels, and emissions allowances. The most relevant greenhouse gas emissions due to human activities are represented in the model.

Scenarios that include time series of emissions and concentrations of the full suite of greenhouse gases (GHGs) and aerosols and chemically active gases, as well as land use/land cover (Moss et al., 2010). 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 emphasises 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.

These scenarios were developed to complement the RCPs by varying socio-economic challenges to adaptation and mitigation (Kriegler et al., 2012; O’Neill et al., 2014). Based on five narratives, the SSPs describe alternative socio-economic futures in the absence of climate policy intervention, comprising sustainable development (SSP1), regional rivalry (SSP3), inequality (SSP4), fossil-fueled development (SSP5) and middle-of-the-road development (SSP2) (O’Neill et al., 2017; Riahi, Vuuren, et al., 2017). The combination of SSP-based socio-economic scenarios and Representative Concentration Pathway (RCP)-based climate projections provide an integrative frame for climate impact and policy analysis. All NGFS scenarios are based on the SSP2 reference scenario. (References are listed in the Technical Documentation)

Transition risks relate to action taken to reduce emissions to reach net-zero greenhouse gas emissions.