Envisioning deep decarbonization futures

The Energy Program (ENE) is a world leader in shaping scientific understanding of low-carbon futures. In 2015, ENE continued this work by producing multiple studies that quantify the geophysical constraints for deep decarbonization pathways in terms of carbon budgets, and by leading the first comprehensive review of 1.5°C scenarios.

© Lucian Milasan | Dreamstime

© Lucian Milasan | Dreamstime

Understanding how society can transition to a low-carbon future and contain the threat of climate change is a fundamental question for our times. ENE looks at this deep decarbonization challenge from various angles.

A first activity is directed towards understanding and quantifying the geophysical constraints that the Earth system sets. Although it has been well-established that setting a limit on global warming implies accepting a cap on the total amount of carbon emissions that can ever be emitted [1], the precise size of this carbon budget is still uncertain. In order to better understand these uncertainties, ENE showed how carbon budgets can be interlinked with seemingly independent mitigation policy choices [2] and quantified the influence of non-CO2 mitigation on carbon budgets [3].

A second activity integrates this knowledge into policy-relevant pathways for achieving specific climate objectives. The existence of a limited carbon budget implies that global CO2 emissions must become zero at some point to halt global warming. In a dedicated effort to make these insights accessible to policymakers, a seminal study on global zero emissions targets was produced [4], which was highly topical given that such objectives were under discussion at the Paris climate summit. Furthermore, ENE also produced the first comprehensive review of scenarios that can limit warming to below 1.5°C [5], an aim now inscribed in the newly adopted Paris Agreement under the UN Framework Convention on Climate Change.


[1] Knutti R & Rogelj J (2015). The legacy of our CO2 emissions: a clash of scientific facts, politics and ethics. Climatic Change, 133(3): 361-373.
[2] Rogelj J, Reisinger A, McCollum DL, Knutti R, Riahi K & Meinshausen M (2015). Mitigation choices impact carbon budget size compatible with low temperature goals. Environmental Research Letters, 10(7): 075003.
[3] Rogelj J, Meinhausen M, Schaffer M, Knutti R & Riahi K, (2015). "Impact of short-lived non-CO2 mitigation on carbon budgets for stabilizing global warming." Environmental Research Letters 10(7): 075001.
[4] Rogelj J, Schaeffer M, Meinshausen M, Knutti R, Alcamo J, Riahi K, Hare W (2015). Zero emission targets as long-term global goals for climate protection. Environmental Research Letters, 10(10): 105007.
[5] Rogelj J, Luderer G, Pietzcker RC, Kriegler E, Schaeffer M, Krey V, Riahi K (2015). Energy system transformations for limiting end-of-century warming to below 1.5°C. Nature Climate Change, 5(6): 519-527.

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Last edited: 13 May 2016


Joeri Rogelj

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Keywan Riahi

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10 steps to removing carbon from the global economy

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