What are Shared Socioeconomic Pathways (SSPs)?

The Intergovernmental Panel on Climate Change (IPCC) references a set of narratives or standardized “scenarios” about the future called Shared Socioeconomic Pathways (SSPs).

The SSPs were first incorporated into the most recent Sixth Assessment Report (AR6). They offer a heuristic (exploratory) approach to evaluating mitigation and adaptation means for addressing climate change.

These pathways help us explore plausible future socio-economic possibilities, much like a “choose your own adventure” story. Scientists use them to foresee how different economic, policy, and societal changes might impact the amount of CO2 we emit into the atmosphere in the future.

A group of scientists known as the Integrated Assessment Modeling Consortium created this set of five SSPs. These are different potential pathways that represent a thorough variety of different likely future pathways of warming across the remainder of the century. Each has a different socioeconomic narrative linked to its assumptions about warming.

The key factors determining these assumptions are the amount of renewable energy deployed, and the level of economic growth expected. Global climate models can use this data to produce outputs for the likely level of greenhouse gas emissions we can expect.

The main takeaway from these scenarios is how devastating a “business as usual” or “no policy change” future could be. They help us envision the consequences of a future with slow or no coordinated action on climate change.

SSP1: The Sustainable Development Path

Key features:

  • Governments deploy large amounts of renewable energy resources, causing emissions to peak and decline, reaching negative emissions by 2075.

  • Global development aligns with scientific boundaries for natural resources and emissions.

  • Economic growth is de-emphasized, while human well-being is given more value.

  • Investments in health and education support demographic shifts supporting inequality reductions.

  • Society shifts towards lower consumption and lower resource and energy use.

CO2 emissions: Limited to 2C above pre-industrial times by 2100.

SSP2: Middle of the road

Key features:

  • No major change from current historical patterns occurs, but the world follows through with current policies and goals to implement renewable energy resources.

  • Global development is uneven with varying results around the world, and overall growth is similar to SSP1.

  • Governments make slow progress toward sustainable development goals.

  • Environmental systems continue to decline, but some improvements are made.

  • Overall energy and resource use declines.

  • Global population growth stagnates by the end of the century.

  • Inequality remains a challenge, and efforts to reduce vulnerability to environmental or economic changes are minimal.

CO2 emissions: Limited to 3C above pre-industrial times by 2100.

SSP3: Regional rivalry

  • Nationalism, regional rivalries, and competition for resources grows.

  • Policies prioritize national and regional security issues.

  • Countries focus on achieving their own energy and food security goals, without focussing on global development.

  • Fewer investments in education and technological development.

  • High material consumption, slow economic development, worsening inequality.

  • Low population growth in high-income countries.

  • Environmental protection is given low priority and countries remain dependent on fossil fuels.

CO2 emissions: Temperatures increase to 4.5C above pre-industrial times by 2100.

SSP4: High-inequality

Key features:

  • Noted disparities between those with political power and those without.

  • Further divisions between countries create major gaps.

  • Some countries have high-tech capital- and knowledge-intensive industries and others exhibit low education and a workforce primarily engaged in low-tech labor industries.

  • Social cohesion worsens, and conflict increases.

  • Investments in both high emissions and low emissions technologies persist, and low-carbon technologies are deployed rapidly.

  • Environmental policies are mostly domestic in scope within middle- or high-income regions.

CO2 emissions: Temperatures are limited to 3.5C above pre-industrial times by 2100.

Note: This scenario is not often cited or used in scientific literature.

SSP5: High-growth, fossil-fuel development

Key features:

  • Emphasis on high economic growth and integrated global markets.

  • Strong investments made in health, education, and institutions to advance human and social capital.

  • Energy- and material-intensive lifestyles become prominent world-wide.

  • Global population peaks around the end of the 21st century.

  • Technological management of environmental problems is prioritized (geo-engineering).

  • Other environmental problems are managed locally.

CO2 emissions: Temperatures increase to 5.5C above pre-industrial times by 2100.

Which pathway will we take?

The pathways are not meant to be prescriptive, but they do help us picture the range of possibilities our global society could take. They show that our future warming will likely fall somewhere between the range of 2C to 5.5C of global warming over the next century.

However, it is important to note that the climatic changes associated with 5.5C are very different from those of 2C.

We’ve already seen that issues like the global pandemic can greatly hinder economic growth. More disease, water insecurity, and sea-level rise, could threaten the economic value that exists worldwide.

Therefore, as we gain more information about the severity of impacts caused by climate change, we’ll have a stronger understanding of how the geophysical limitations of climate change correspond to societal development.

Are there other climate scenarios besides the SSPs?

While the SSPs are the most widely known scenarios, several other organizations have produced their own climate scenarios including the Network for Greening the Financial System (NGFS), and the International Energy Agency. These scenarios have different emphases, but generally show similar pathways to climate safe futures.

Sources:

Climate Change, Learning ResourcesErica EllerComment