Is it possible to limit global warming to no more than 1.5°C?
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This study explores the feasibility of limiting increases in global temperature to 1.5°C above pre-industrial levels. A probabilistic simple climate model is used to identify emissions paths that offer at least a 50% chance of achieving this goal. We conclude that it is more likely than not that warming would exceed 1.5°C, at least temporarily, under plausible mitigation scenarios. We have identified three criteria of emissions paths that could meet the 1.5°C goal with a temporary overshoot of no more than 50 years: early and strong reductions in emissions, with global emissions peaking in 2015 and falling to at most 44–48 GtCO2e in 2020; rapid reductions in annual global emissions after 2020 (of at least 3–4% per year); very low annual global emissions by 2100 (less than 2–4 GtCO2e) and falling to zero (or below) in the 22nd century. The feasibility of these characteristics is uncertain. We conclude that the proposed date of review of the 1.5°C goal, set at 2015, may be too late to achieve the necessary scaling up of emissions cuts to achieve this goal.
KeywordsEmission Reduction Global Emission Global Average Temperature Emission Path Negative Emission
The authors wish to thank Brian Hoskins, Andrew Gouldson, Piers Forster, Nicholas Stern and the two anonymous reviewers for their comments. Nicola Ranger, Alex Bowen and Robert Ward were supported during this project by Grantham Foundation for the Protection of the Environment and the UK Economic and Social Research Council (ESRC). Laila Gohar and Jason Lowe were supported during this project by the AVOID programme funded by the UK Department of Energy and Climate Change (DECC) and Department for Environment, Food and Rural Affairs (Defra), under contract DECC/Defra GA0215. The Met Office Hadley Centre provided scientific input to this work but does not advocate particular policy choices.
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