Outlook to 2100 using five greenhouse gas emission scenarios, derived from five socio-economic scenarios and five levels of radiative forcing.

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Contents

1. Summary for policymakers
   • Introduction
2. Sections
   • Introduction
   • Current status and trends
   • Long-term climate and development futures
   • Near-term responses in a changing climate

Greenhouse gas emissions scenarios

These have been formed from a combination of one of five ‘shared socio-economic pathways’ and one of five levels of ‘radiative forcing’ (see below).

1. Very low: SSP1-1.9*
2. Low: SSP1-2.6
3. Intermediate: SSP2-4.5
4. High: SSP3-7.0
5. Very high: SSP5-8.5

* SSP: shared socio-economic pathway. 1.9: level of radiative forcing.

SSP1 is used twice and SSP4 is not used.

Shared socio-economic pathways

A ‘shared socio-economic pathway’ is a scenario based on a set of socio-economic assumptions.

Key drivers: socio-economic challenges for adaptation versus mitigation.

• SSP1: Sustainability.
• SSP2: Middle of the Road.
• SSP3: Regional Rivalry.
• SSP4: Inequality.
• SSP5: Fossil-fueled Development.

Levels of radiative forcing

‘Radiative forcing’ is the difference between the earth’s incoming and outgoing energy, measured in watts per square metre in 2100.

• Very low: 1.9
• Low: 2.6
• Intermediate: 4.5
• High: 7.0
• Very high: 8.5