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Exploring climate model data

Different socioeconomic scenarios of future world development

The SRES scenarios have so far been used widley in climate modelling. They are the basis for assumptions of future developement in the two latest publications by IPCC (TAR, 2001 and AR4, 2007). For the Fifth assesment report (AR5, due in 2014)  new types of scenarios have been developed, called the SSP and RCP scenarios, respectively.

SRES scenarios
The SRES scenarios are described in the IPCC Special Report on Emission Scenarios (2000). There are 40 different scenarios, each making different assumptions for future greenhouse gas pollution, land-use and other driving forces. Assumptions about future technological development as well as the future economic development are thus made for each scenario. These emissions scenarios are organized into families, A1, A2, B1, B2, which contain scenarios that are similar to each other in some respects.

The four main SRES categories. A2 and B2 were the main scenarios used in the IPCC Third Assesment Report (TAR, 2001) and later A1B has been the most common scenario. A1FI is the most extreme scenario regarding emission rate.

The A1 storyline and scenario family describes a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system. The three A1 groups are distinguished by their technological emphasis: fossil-intensive (A1FI), non-fossil energy sources (A1T) or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies).

The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is selfreliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines.

The B1 storyline and scenario family describes a convergent world with the same global population, that peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource-efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.

The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels. The SRES scenarios do not include additional climate initiatives, which means that no scenarios are included that explicitly assume implementation of the United Nations Framework Convention on Climate Change or the emissions targets of the Kyoto Protocol.

SSP and RCP scenarios
The RCP (Representative Concentration Pathways) scenarios are a new set of scenarios defined in terms of radiative forcing. They work both forwards towards climate modelling and backwards to analyse what future world development is needed to achieve a certain level of antrophogenic influence on the climate. They are associated with Shared Socioeconomic Pathways (SSPs) matrix wise, as explained on the starting page on scenarios.

The new SSPs are stretched again along two major development axes, as conceptualised in the graph below. For SSPs these axes correspond to the intensity of climate policies that will be neccessary in the future, either to prevent a certain level of climate change (mitigation on the verical axis), and/or to cope with a certain level of climate change (adaptation on the horizontal axis). These SSP in turn are driven or at least affected by Shared Policy Assumptions (SPAs). Climate policy scenarios are derived by combining an SSP and SPA (e.g. a set of climate policies designed to achieve a given RCP level), and, possibly, climate change projections. Because GDP and other variables would be affected by the climate policies and climate change impacts, model outputs would replace reference SSP assumptions when and where they were significantly different.

SSP1 'Sustainable Pathway' [to be completed....] SSP1 is most close to the old SRES B1 scenario.

SSP2 'Moderate Pathway' .... SSP2 is most close to the old SRES A1 scenario.

SSP3 'Rocky Road' .... SSP3 is most close to the old SRES A2 scenario.

SSP4 'Regional Pathways' .... SSP4 has no equivalent in the old SRES scenarios.

SSP5 'Taking the Fast Road' .... SSP5 has no equivalent in the old SRES scenarios.

Read more about the RCP and SSP scenarios: Towards new scenarios for analysis of emissions or Towards new scenarios for analysis of emissions (pdf, IPCC).

Related links

FAQ: Which SRES scenario to use?




The ENES3 project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 824084.