The Three Salient Global Mitigation Pathways Assessed in Light of the IPCC Carbon Budgets

This briefing paper evaluates three global mitigation pathways—the 1.5°C marker, the 2°C marker, and the G8 marker—against the carbon budgets provided in the IPCC Fifth Assessment Report to determine their likelihood of limiting global surface temperature increases to 2°C by the end of the century.

• The 1.5°C marker pathway is characterized as the most challenging yet techno-economically achievable path, with emissions peaking in 2014 and declining by up to 7.1% annually. With cumulative emissions of 1,720 Gt CO2e for 2000–2100, it has a probability significantly greater than 66% of keeping warming below 2°C, though its likelihood of staying below 1.5°C cannot be estimated from IPCC carbon budgets.
• The 2°C marker pathway, which features emissions peaking in 2014 and declining by up to 3.4% per year with cumulative emissions of 2,380 Gt CO2e, is often presented as having a 'likely' chance of limiting warming to 2°C; however, analysis against IPCC budgets suggests it actually has less than a 50% chance of achieving this.
• The G8 pathway, based on a 2008 G8 declaration, involves emissions peaking in 2021 and declining by a maximum of 4.5% per year, with a cumulative budget of 2,860 Gt CO2e. This pathway has a chance of keeping warming below 2°C that is far less than 33%.

APA

Baer, P., Athanasiou, T., & Kartha, S. (2013). The Three Salient Global Mitigation Pathways Assessed in Light of the IPCC Carbon Budgets. Stockholm Environment Institute. https://www.sei.org/publications/the-three-salient-global-mitigation-pathways-assessed-in-light-of-the-ipcc-carbon-budgets/

Chicago

Baer, P., T. Athanasiou, and S. Kartha. The Three Salient Global Mitigation Pathways Assessed in Light of the IPCC Carbon Budgets. Stockholm Environment Institute, 2013. https://www.sei.org/publications/the-three-salient-global-mitigation-pathways-assessed-in-light-of-the-ipcc-carbon-budgets/.

Wikipedia

{{cite report |last1=Baer |first1=P. |last2=Athanasiou |first2=T. |last3=Kartha |first3=S. |title=The Three Salient Global Mitigation Pathways Assessed in Light of the IPCC Carbon Budgets |publisher=Stockholm Environment Institute |date=1 November 2013 |url=https://www.sei.org/publications/the-three-salient-global-mitigation-pathways-assessed-in-light-of-the-ipcc-carbon-budgets/ |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{baer2013three, author = {Baer, P. and Athanasiou, T. and Kartha, S.}, title = {{The Three Salient Global Mitigation Pathways Assessed in Light of the IPCC Carbon Budgets}}, institution = {Stockholm Environment Institute}, year = {2013}, month = nov, url = {https://www.sei.org/publications/the-three-salient-global-mitigation-pathways-assessed-in-light-of-the-ipcc-carbon-budgets/}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }