Purpose
| The four SRES scenario families of the Fourth Assessment Report vs. projected global average surface warming until 2100 | ||
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| Globalisation |
A1 1.4 - 6.4 °C |
B1 1.1 - 2.9 °C |
| Regionalisation |
A2 2.0 - 5.4 °C |
B2 1.4 - 3.8 °C |
Because projections of climate change depend heavily upon future human activity, climate models are run against scenarios. 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. Most include an increase in the consumption of fossil fuels; some versions of B1 have lower levels of consumption by 2100 than in 1990 . Overall global GDP will grow by a factor of between 5-25 in the emissions scenarios.
These emissions scenarios are organized into families, which contain scenarios that are similar to each other in some respects. IPCC assessment report projections for the future are often made in the context of a specific scenario family.
According to the IPCC, all SRES scenarios are considered "neutral". None of the SRES scenarios project future disasters or catastrophes, e.g., wars and conflicts, and/or environmental collapse.
The scenarios are not described by the IPCC as representing good or bad pathways of future social and economic development.
Read more about this topic: Special Report On Emissions Scenarios
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