Ratcheting ambition to limit warming to 1.5 °C–trade-offs between emission reductions and carbon dioxide removal
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Holz_2018_Environ._Res._Lett._13_064028.pdf
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Author(s)
Holz, Christian
Siegel, Lori S
Johnston, Eleanor
Sterman, John
Jones, Andrew
Date Issued
June 2018
Journal
Environmental Research Letters
Publisher
IOP Publishing
Citation
Holz, Christian, Lori S Siegel, Eleanor Johnston, Andrew P Jones, and John Sterman. “Ratcheting Ambition to Limit Warming to 1.5 °C–trade-Offs Between Emission Reductions and Carbon Dioxide Removal.” Environmental Research Letters 13, no. 6 (June 1, 2018): 064028.
Version
Final published version
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), which carry 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 emission 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 pathway, 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, we find that mid-term gross CO2emission 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 CO2reduction rates, the need to improve emission reductions for non-CO2greenhouse 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 CO2sequestered earlier, without any additional net climate benefit.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
Massachusetts Institute of Technology. Institute for Data, Systems, and Society
Sloan School of Management
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DOI of Published Version
https://doi.org/10.1088/1748-9326/AAC0C1
