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Framing Climate Goals in Terms of Cumulative CO 2 ‐Forcing‐Equivalent Emissions
Author(s) -
Jenkins S.,
Millar R. J.,
Leach N.,
Allen M. R.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl076173
Subject(s) - radiative forcing , environmental science , greenhouse gas , atmospheric sciences , global warming , carbon dioxide equivalent , forcing (mathematics) , climate change , global warming potential , climatology , climate model , physics , geology , oceanography
The relationship between cumulative CO 2 emissions and CO 2 ‐induced warming is determined by the Transient Climate Response to Emissions (TCRE), but total anthropogenic warming also depends on non‐CO 2 forcing, complicating the interpretation of emissions budgets based on CO 2 alone. An alternative is to frame emissions budgets in terms of CO 2 ‐forcing‐equivalent (CO 2 ‐fe) emissions—the CO 2 emissions that would yield a given total anthropogenic radiative forcing pathway. Unlike conventional “CO 2 ‐equivalent” emissions, these are directly related to warming by the TCRE and need to fall to zero to stabilize warming: hence, CO 2 ‐fe emissions generalize the concept of a cumulative carbon budget to multigas scenarios. Cumulative CO 2 ‐fe emissions from 1870 to 2015 inclusive are found to be 2,900 ± 600 GtCO 2 ‐fe, increasing at a rate of 67 ± 9.5 GtCO 2 ‐fe/yr. A TCRE range of 0.8–2.5°C per 1,000 GtC implies a total budget for 0.6°C of additional warming above the present decade of 880–2,750 GtCO 2 ‐fe, with 1,290 GtCO 2 ‐fe implied by the Coupled Model Intercomparison Project Phase 5 median response, corresponding to 19 years' CO 2 ‐fe emissions at the current rate.