RCP vs SSP Scenarios: A Business Leader's Guide to IPCC Climate Pathways
TCFD, IFRS S2, and CSRD all expect companies to test their strategy against climate scenarios. Most disclosures cite RCP8.5 or SSP5-8.5 without explaining what separates them. The two frameworks come from different IPCC cycles and answer different questions. Boards, auditors, and investors now ask why a specific scenario was chosen.
This guide explains RCP vs SSP scenarios in plain terms. You will learn what each one is, the difference between RCP and SSP, the IPCC AR6 pathways, and which climate scenarios for business fit your disclosure obligations.
What are RCP and SSP scenarios?
Representative Concentration Pathways and Shared Socioeconomic Pathways scenarios are the two sets of climate pathways the Intergovernmental Panel on Climate Change (IPCC) uses to project warming. RCPs came first, in the Fifth Assessment Report. SSPs are the current set behind the IPCC AR6 scenarios.
Representative Concentration Pathways (RCPs)
An RCP describes a greenhouse gas concentration trajectory leading to a fixed radiative forcing level by 2100. The number is the forcing level in watts per square metre.
RCP2.6 reaches 2.6 W/m2; RCP8.5 reaches 8.5 W/m2. It sets the climate outcome without explaining how society reaches it.
Shared Socioeconomic Pathways (SSPs)
An SSP adds the missing story. It describes how population, economic growth, technology, and policy might develop. The IPCC introduced SSPs in AR6 to pair a societal narrative with each emissions outcome.
The shift from AR5 to AR6
The Fifth Assessment Report (AR5) used RCPs through CMIP5. AR6 uses SSPs through CMIP6. The change gave each pathway an economic rationale, not an emissions endpoint alone.
The difference between RCP and SSP, at a glance
The core difference between RCP and SSP is scope: an RCP fixes a climate outcome, while an SSP explains the socioeconomic path that produces it. How SSPs differ from RCPs comes down to that added narrative layer.
Dimension | RCP | SSP |
Introduced in | IPCC AR5 (2014) | IPCC AR6 (2021) |
Modelling cycle | CMIP5 | CMIP6 |
What the number means | Radiative forcing in W/m^2 by 2100 | Forcing level, after the SSP family number |
What it describes | An emissions and concentration outcome | A socioeconomic storyline plus an outcome |
Socioeconomic narrative | None | Five narratives (SSP1 to SSP5) |
Naming convention | RCP4.5 | SSP2-4.5 |
Best suited to | Physical climate projections | Combined physical and transition risk |
Each RCP has a close SSP equivalent. SSP1-2.6 broadly matches RCP2.6, and SSP5-8.5 broadly matches RCP8.5.
The SSP-RCP framework explained
The SSP-RCP framework arranges scenarios in a matrix: socioeconomic narratives form the columns, and forcing levels form the rows. Each cell is a specific pathway, written as SSPx-y.
The five SSP narratives
SSP1: Sustainability (with low challenges to mitigation and adaptation)
SSP2: Middle of the road (where current trends continue)
SSP3: Regional rivalry (with fragmented policy)
SSP4: Inequality (with uneven development)
SSP5: Fossil-fuelled development (with rapid growth)
Reading the labels
In SSP2-4.5, the "2" is the narrative and "4.5" is the forcing level. That forcing number aligns with the older RCP scale, keeping the two comparable.
The five IPCC AR6 pathways
AR6 highlights five illustrative scenarios. Median warming by 2100 runs from around 1.4°C under SSP1-1.9 to around 4.4°C under SSP5-8.5. SSP2-4.5 sits near 2.7°C and SSP3-7.0 near 3.6°C.
Climate scenarios for business: Which Pathways to Use
Climate scenarios for business should bracket a range of outcomes, not predict one. Frameworks expect at least one low-warming and one high-warming pathway.
What disclosure frameworks expect
TCFD-aligned climate scenario analysis sits in the strategy pillar and recommends at least two scenarios, including a 2°C-or-lower pathway. IFRS S2 inherits this language and asks how your analysis aligns with the latest climate agreement. CSRD reporting requirements under ESRS E1 ask you to disclose the scenarios used and whether they are Paris-aligned.
A workable scenario set
Low: SSP1-2.6, to test transition resilience against a Paris-aligned path
Middle: SSP2-4.5, as a current-policy baseline
High: SSP3-7.0 or SSP5-8.5, to stress-test physical risk
Carbon-intensive businesses weigh the transition pathways. Companies with concentrated physical assets weigh the high-warming pathways. Either set should feed your decarbonisation strategy.
Key Takeaway
Scenario choice is becoming a point of audit and investor scrutiny, not a technical footnote. Documenting why you selected a given pathway will matter as much as the projection itself. Comparability across peers will push more companies toward the standard SSP set, and sound corporate climate governance depends on selecting scenarios you can defend.
Oren helps sustainability and finance teams select, document, and disclose climate scenarios across TCFD, IFRS S2, and CSRD. Schedule a demo to see how.
Frequently Asked Questions (FAQs)
Q1. What is the difference between RCP and SSP scenarios?
The difference between RCP and SSP scenarios is the socioeconomic narrative. An RCP defines a greenhouse gas concentration pathway and its radiative forcing by 2100, with no account of how emissions reach that level. An SSP adds that account through a storyline about population, economic growth, technology, and policy. RCPs drove the IPCC's Fifth Assessment Report; SSPs drive AR6. An SSP gives both the climate outcome and the economic conditions producing it, which suits combined physical and transition risk analysis.
Q2. How do SSPs differ from RCPs?
SSPs differ from RCPs by combining a societal pathway with an emissions outcome. An RCP specifies only the end-of-century forcing level. An SSP specifies the development path, such as sustainability or fossil-fuelled growth, then maps it to a forcing level. This is why SSP labels carry two numbers, as in SSP2-4.5, while RCP labels carry one. The added narrative lets analysts assess transition risk, not only physical climate change.
Q3. What are the IPCC AR6 scenarios?
The IPCC AR6 scenarios are five illustrative Shared Socioeconomic Pathways: SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. Each pair a societal storyline with a radiative forcing level. Median projected warming by 2100 runs from around 1.4°C under SSP1-1.9 to around 4.4°C under SSP5-8.5. SSP1-1.9 is the only pathway consistent with limiting warming to 1.5°C.
Q4. Which climate scenarios should a business use?
A business should use at least two scenarios that bracket a range of outcomes. A common set pairs a Paris-aligned low pathway, such as SSP1-2.6, with a high-warming pathway such as SSP3-7.0 or SSP5-8.5, often with SSP2-4.5 as a baseline. TCFD recommends a minimum of two, including a 2°C-or-lower scenario. Weighting depends on exposure: carbon-intensive firms emphasise transition pathways, asset-heavy firms emphasise physical-risk pathways.
Q5. Does the SSP number mean the same as the RCP number?
Partly. The forcing number is comparable, but the SSP label carries an extra number. In SSP2-4.5, the "4.5" matches the radiative forcing scale of RCP4.5, so the climate outcome aligns. The leading "2" identifies the socioeconomic narrative, which RCPs omit. Only the SSP version specifies the development path behind the outcome.
Q6. Are RCP scenarios still valid?
RCP scenarios remain valid and are still widely used, particularly in physical climate datasets built on the CMIP5 cycle. Many regional climate models and asset-level tools still reference RCPs. AR6 moved to SSPs as its primary framework, yet the two stay comparable through their shared forcing levels. For new disclosures, SSPs are the current standard.
Q7. Is RCP8.5 the same as SSP5-8.5?
RCP8.5 and SSP5-8.5 are not identical, though both share a radiative forcing level of 8.5 W/m2 by 2100. The climate outcome is broadly comparable. The difference is that SSP5-8.5 attaches a socioeconomic story of a fossil-fuelled, high-growth world. RCP8.5 specifies only the forcing trajectory. For physical risk, the two produce similar temperature ranges. For transition risk, SSP5-8.5 is more informative, since it describes the economy driving those emissions.
About the author
Kushagra
Senior ESG & Sustainability Advisor
Kushagra is a Senior ESG & Sustainability Advisor at Oren with 8+ years across CSR and sustainability consulting, specialising in GHG accounting, ESG strategy, and regulatory reporting across India, the UAE, and the Middle East.
