Framing climate goals in terms of cumulative CO2-forcing-equivalent emissions

Journal article

The relationship between cumulative CO2 emissions and CO2-induced warming is determined by the Transient Climate Response to Emissions (TCRE), but total anthropogenic warming also depends on non-CO2 forcing, complicating the interpretation of emissions budgets based on CO2 alone. An alternative is to frame emissions budgets in terms of CO2-forcing-equivalent (CO2-fe) emissions – the CO2 emissions that would yield a given total anthropogenic radiative forcing pathway. Unlike conventional ‘CO2-equivalent’ emissions, these are directly related to warming by the TCRE and need to fall to zero to stabilise warming: hence CO2-fe emissions generalise the concept of a cumulative carbon budget to multi-gas scenarios. Cumulative CO2-fe emissions from 1870-2015 inclusive are found to be 2900 ± 600GtCO2-fe, increasing at a rate of 67 ± 9.5GtCO2-fe/year. A TCRE range of 0.8–2.5° Cper 1,000 GtC implies a total budget for 0.6° C of additional warming above the present decade of 880–2,750 GtCO2-fe, with 1,290 GtCO2-fe implied by the CMIP5 median response, corresponding to 19 years' CO2-fe emissions at the current rate.

Authors: Jenkins, S; Millar, R; Leach, N; Allen, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Geophysical Union
• Journal: Geophysical Research Letters
• Volume: 45
• Issue: 6
• Pages: 2795-2804
• Publication date: 2018-02-27
• Acceptance date: 2018-02-20
• DOI: 10.1002/2017gl076173
• EISSN: 1944-8007
• ISSN: 0094-8276
• Keywords: greenhouse gas metric; forcing equivalent index; climate stabilisation; cumulative carbon budget