Syllabus Edition

First teaching 2024

First exams 2026

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Greenhouse Gas Emissions Scenarios (HL) (DP IB Environmental Systems & Societies (ESS))

Revision Note

Alistair Marjot

Written by: Alistair Marjot

Reviewed by: Jacque Cartwright

Greenhouse Gas Emissions Scenarios

  • Purpose of scenarios:

    • Greenhouse gas (GHG) emissions scenarios help predict future climate outcomes

    • They help to define clear targets to reduce the risk of catastrophic climate change

    • Different scenarios are based on different levels of human actions and policies

  • Developed by IPCC:

    • The Intergovernmental Panel on Climate Change (IPCC) creates these scenarios

  • Uncertainty and variability:

    • Scenarios can vary greatly due to uncertainties about:

      • Future actions

      • Technological development (e.g. green energy technologies, carbon capture)

      • Policy changes

IPCC emissions scenarios (SSPs)

  • The IPCC has also developed five Shared Socioeconomic Pathways (SSPs) to model different future GHG emissions scenarios

  • These scenarios combine potential emissions changes with a range of socio-economic factors to give slightly different potential pathways

    • E,g. global cooperation

    • Economic policies

    • Population growth

    • Technological development

  • The SSPs reflect how choices in economic growth, energy use, and societal trends could shape GHG levels and climate change impacts by the end of the century

SSP1: Sustainability ('Taking the Green Road')

  • Description: A sustainable, environmentally-focused future

  • Features:

    • Strong global cooperation and reduced inequalities

    • Investments in green technologies and low-carbon energy sources

  • Climate Impact: Lower GHG emissions, likely to limit global warming to around 1.5–2°C

SSP2: 'Middle of the Road'

  • Description: A continuation of current global trends without significant changes (i.e. 'business-as-usual')

  • Features:

    • Moderate economic growth with limited inequality reduction

    • Balanced investments in both traditional and renewable energy

  • Climate Impact: Moderate GHG emissions, leading to moderate levels of warming

SSP3: Regional Rivalry ('A Rocky Road')

  • Description: A fragmented world with regional conflicts and minimal cooperation

  • Features:

    • Limited technology sharing, economic growth focused within regions

    • High reliance on fossil fuels, with few environmental protections

  • Climate Impact: High GHG emissions and a substantial risk of severe climate impacts

SSP4: Inequality ('A Road Divided')

  • Description: A world with significant social and economic inequality

  • Features:

    • High disparities between rich and poor countries and within societies

    • Wealthy nations adapt well, while poorer regions struggle with climate impacts

  • Climate Impact: Moderate to high GHG emissions with variable adaptation and mitigation success

SSP5: Fossil-fuelled Development ('Taking the Highway')

  • Description: high fossil fuel use and technological advancement are driving rapid economic growth

  • Features:

    • High energy consumption, widespread reliance on fossil fuels

    • Innovation and economic growth prioritised over environmental protection

  • Climate Impact: Very high GHG emissions, leading to significant warming

Graph showing CO2 concentration projections from 2000 to 2100 with six scenario lines (SSP5-8.5 to SSP1-1.9) and historical data ending in 2014.
Predicted atmospheric CO₂ concentrations for different Shared Socioeconomic Pathways (SSPs) across the 21st century (Wikimedia Commons, CC BY-SA 4.0)

IPCC Shared Socioeconomic Pathways (SSPs)

SSP

Scenario

Estimated warming
(2041–2060)

Estimated warming
(2081–2100)

Very likely range in °C
(2081–2100)

SSP1-1.9

very low GHG emissions:
CO2 emissions cut to net zero around 2050

1.6 °C

1.4 °C

1.0 – 1.8

SSP1-2.6

low GHG emissions:
CO2 emissions cut to net zero around 2075

1.7 °C

1.8 °C

1.3 – 2.4

SSP2-4.5

intermediate GHG emissions:
CO2 emissions around current levels until 2050, then falling but not reaching net zero by 2100

2.0 °C

2.7 °C

2.1 – 3.5

SSP3-7.0

high GHG emissions:
CO2 emissions double by 2100

2.1 °C

3.6 °C

2.8 – 4.6

SSP5-8.5

very high GHG emissions:
CO2 emissions triple by 2075

2.4 °C

4.4 °C

3.3 – 5.7

The names of these scenarios consist of the SSP on which they are based (SSP1-SSP5), combined with the expected level of radiative forcing in the year 2100 (1.9 to 8.5 W m-2). SSP4 has not been included.

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Alistair Marjot

Author: Alistair Marjot

Expertise: Biology & Environmental Systems and Societies

Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.

Jacque Cartwright

Author: Jacque Cartwright

Expertise: Geography Content Creator

Jacque graduated from the Open University with a BSc in Environmental Science and Geography before doing her PGCE with the University of St David’s, Swansea. Teaching is her passion and has taught across a wide range of specifications – GCSE/IGCSE and IB but particularly loves teaching the A-level Geography. For the past 5 years Jacque has been teaching online for international schools, and she knows what is needed to get the top scores on those pesky geography exams.