What are scenarios and why are they used?

Future greenhouse gas emissions are the product of very complex dynamic systems, determined by driving forces such as demographic development, socio-economic development, and technological change. Their future evolution is highly uncertain. Scenarios are not specific predictions or forecasts of future climate. Rather, scenarios are plausible alternative futures. Each scenario is an example of what can happen under particular assumptions about the use of fossil fuel and other human activities. Scenarios assist in climate modeling, help to examine potential climate change and explore vulnerabilities of humans and ecosystems under a changed climate. For more information, visit IPCC special report on Emissions scenarios.