What are emission scenarios?

Emission scenarios are plausible future development pathways of human greenhouse gas and aerosol emissions.

These emission scenarios for greenhouse gases and aerosols serve as the basis for working out the possible climate conditions of the future. The latest generation of emission scenarios, the so-called Representative Concentration Pathways (RCP), define trajectories representing greenhouse gas and aerosol concentrations for particular climate projections (namely, radiative forcing values in the year 2100). Each trajectory is, in turn, representative of a particular development scenario for anthropogenic emissions.

The scale of future anthropogenic emissions is heavily dependent on global political decisions as well as on population growth and technological advances. These uncertainties are depicted through various emission scenarios. One emission scenario thus works on the basis of the global community agreeing to drastically reduce emissions of greenhouse gases: RCP2.6. This scenario assumes an additional radiative forcing of 2.6 Watts per square metre by the end of the 21st century. Another scenario represents a situation in which humans continue in the same way as we have to date, emitting ever more greenhouse gases: RCP8.5 This represents a radiative forcing of 8.5 Watts per square metre by the end of the century. In between these two are other scenarios that entail greater or lesser degrees of technical advancement that would lead to slight reductions in greenhouse gases. The higher the radiative forcing value, the greater the change in climate conditions.

Climate models have been run on the basis of all of these scenarios so as to demonstrate the impact of political decision-making and other factors on the climate of the future. Emission scenarios therefore represent potential courses of action. They allow the climate-related consequences of courses of action to be quantified, without making any statements about which pathway is the most likely.

Scenario  RCP szenario  Characteristics
No mitigation RCP8.5  No climate mitigation measures are implemented. Greenhouse gas emissions continually increase. The radiative forcing in the year 2100 stands at 8.5 W/m2 in comparison to the year 1850.
Limited mitigation RCP4.5  Although greenhouse gas emissions are somewhat curbed, the content in the atmosphere continues to increase for another 50 years. The 2°C target is not achieved. The radiative forcing in the year 2100 stands at 4.5 W/m2 in comparison to the year 1850.
Concerted mitigation efforts RCP2.6  Climate mitigation measures are taken. With reductions in emissions being implemented straight away, the increase in greenhouse gases in the atmosphere is halted within around 20 years. This allows the targets of the Paris Climate Agreement of 2016 to be reached. The radiative forcing in the year 2100 stands at 2.6 W/m2 in comparison to the year 1850.
The set of emission scenarios that underpin the Swiss climate scenarios. Adapted from Proclim, "Brennpunkt Klima Schweiz" – a report on responding to climate change in Switzerland, published in 2016.


Last modification 12.10.2018

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