The Intergovernmental Panel on Climate Change "Special Report on Emissions Scenarios" (SRES) explored pathways of future greenhouse gas emissions, derived from self-consistent sets of assumptions about energy use, population growth, economic development, and other factors. These considered a variety of possible "world-views", but explicitly exclude any global policy to reduce emissions to avoid climate change.
From SRES, six illustrative "marker" scenarios were selected for use in the climate projections of the IPCC Third Assessment Report. These are described below, followed by discussion of driving forces, climate impacts, and related topics.
| Global integration | Regionalism | |
| Economic emphasis | A1B Balanced energy |
A2 |
| A1FI Fossil-fuel Intensive |
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| A1T high-Tech renewables |
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| Environ-mental emphasis | B1 | B2 |
The A1 scenarios all describe a future world of very rapid economic growth and 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 difference between the A1FI, A1B, A1T and scenarios is mainly in the source of energy used to drive this expanding economy.
The A2 scenario describes a very heterogeneous world. The underlying theme is self-reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing global population. Economic development is primarily regionally oriented and per capita economic growth and technological change are more fragmented and slower than in other storylines.
For example, scenarios A1B, A1FI, A1T and B1 all have the same population, rising initially, but falling later this century, whilst for A2 and B2 the population, and consequent CO2 emissions, continue to rise in 2100. The implication is that global convergence of wealth in the A1/B1 group (look at the GDP data) helps to reduce population growth, and hence emissions.
The difference between A1B, A1T and A1FI emissions, is therefore mainly related to energy use. The energy data here refers to secondary energy, such as electricity, also including energy from traditional biomass sources (fuelwood) which is higher in developing countries. So the ratio energy/emissions tells you about the carbon "efficiency" of energy production, whilst GDP/energy might indicate more about the economic "efficiency" of its application.
See also:
The SRES also specifies other factors which influence climate change. For example, in scenarios A1FI, B1 and B2, CO2 emissions from land-use change drop below zero (implying net reforestation). (You can see this on the carbon cycle plot: drag the y-axis near the origin, to move it up)
Scenario A2 also has relatively higher sulphate emissions than A1FI (this causes local cooling). In scenario B1, the emissions of methane and HFCs are also much lower. See also:
You can check the correspondence of the predictions from this model, with data published in IPCC-TAR-WG1 SRES appendix, shown as small circles superimposed on the plots (expert level).
The 100-year time-frame of the SRES scenarios is too short to give a meaningful view of the effect on some slower climate processes, especially sea-level rise. In this model the scenarios are extended simply by assuming constant emissions after 2100. This is for transparency and is not intended as a prediction.
Also, the SRES projections for emissions other greenhouse gases may be combined with CO2 stabilisation scenarios (as in IPCC-TAR Synthesis report Q6).
Note, for this reason, the SRES menu remains available, even when the CO2 emissions are determined by other mitigation options.
The demo wizard cycles through the six SRES scenarios, showing in turn:
Click the button to stop the demo and explore for yourself.