Ratcheting Ambition to Limit Warming to 1.5°C – Trade-Offs between Emission Reductions and Carbon Dioxide Removal

Environmental Research Letters, vol 13, no 6, doi: 10.1088/1748-9326/aac0c1

Posted: 3 Nov 2017 Last revised: 9 Oct 2018

See all articles by Christian Holz

Christian Holz

Carleton University - Department of Geography and Environmental Studies; Climate Equity Reference Project

Lori Siegel

Climate Interactive

Eleanor Johnston

Climate Interactive

Andrew Jones

Climate Interactive

John Sterman

Massachusetts Institute of Technology (MIT) - Sloan School of Management

Date Written: April 27, 2018

Abstract

Mitigation scenarios to limit global warming to 1.5°C or less in 2100 often rely on large amounts of carbon dioxide removal (CDR), with significant potential social, environmental, political and economic risks. A precautionary approach to scenario creation is therefore indicated. This letter presents the results of such a precautionary modelling exercise in which the models C-ROADS and En-ROADS were used to generate a series of 1.5°C mitigation scenarios that apply increasingly stringent constraints on the scale and type of CDR available. This allows us to explore the trade-offs between near-term stringency of emissions reductions and assumptions about future availability of CDR. In particular, we find that regardless of CDR assumptions, near-term ambition increase ("ratcheting") is required for any 1.5°C pathways, making this letter timely for the facilitative, or Talanoa, dialogue to be conducted by the UNFCCC in 2018. By highlighting the difference between net and gross reduction rates, often obscured in scenarios with large-scale CDR, we find that mid-term gross CO2 emissions reduction rates in scenarios with CDR constraints increase to levels without historical precedence. This in turn highlights, in addition to the need to substantially increase CO2 reduction rates, the need to improve emissions reductions for non-CO2 greenhouse gases. Further, scenarios in which all or part of the CDR is implemented as non-permanent storage exhibit storage loss emissions, which partly offset CDR, highlighting the importance of differentiating between net and gross CDR in scenarios. We find in some scenarios, storage loss trending to similar values as gross CDR, indicating that gross CDR would have to be maintained simply to offset the storage losses of CO2 sequestered earlier, without any additional net climate benefit.

Keywords: climate change mitigation, mitigation pathways, GHG emission pathways, carbon dioxide removal, Paris Agreement

Suggested Citation

Holz, Christian and Siegel, Lori and Johnston, Eleanor and Jones, Andrew and Sterman, John, Ratcheting Ambition to Limit Warming to 1.5°C – Trade-Offs between Emission Reductions and Carbon Dioxide Removal (April 27, 2018). Environmental Research Letters, vol 13, no 6, doi: 10.1088/1748-9326/aac0c1. Available at SSRN: https://ssrn.com/abstract=3063337 or http://dx.doi.org/10.2139/ssrn.3063337

Christian Holz (Contact Author)

Carleton University - Department of Geography and Environmental Studies ( email )

1125 colonel By Drive
Ottawa, Ontario K1S 5B6
Canada

Climate Equity Reference Project ( email )

United States

HOME PAGE: http://https://climateequityreference.org

Lori Siegel

Climate Interactive ( email )

Washington, DC
United States

Eleanor Johnston

Climate Interactive ( email )

Washington, DC
United States

Andrew Jones

Climate Interactive ( email )

Washington, DC
United States

John Sterman

Massachusetts Institute of Technology (MIT) - Sloan School of Management ( email )

E62-436
Cambridge, MA 02139
United States
617-253-1951 (Phone)

HOME PAGE: http://jsterman.scripts.mit.edu/

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