Robbie Andrew

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It's getting harder and harder to limit ourselves to 2°C

First published: 2016. Updated 13 November 2017.

Note: Two new updates of this figure can be found here.

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Data Sources

Historical emissions to 2016 from CDIAC/Global Carbon Project, projection to 2017 from Global Carbon Project.


Global cumulative CO2 emissions quota of 1000GtC (66% chance of 2°C). Mitigation curves describe approximately exponential decay pathways such that the quota is never exceeded (see Raupach et al., 2014).

Mitigation curves are defined such that the sum of historical cumulative emissions and cumulative emissions following the mitigation curves exactly meets the global emissions quota.

This analysis assumes no net-negative emissions: that is, emissions are always globally positive. But the analysis is agnostic towards whether so-called 'gross-negative' emissions occur. Many IPCC scenarios allow global emissions to be negative before 2100.

The remaining carbon budget has been revisited several times since the IPCC's fifth Assessment Report, and there is now quite a range, including larger budgets than are used for the figure here. The point remains unchanged: all else equal, earlier mitigation would have been easier. With every year that global emissions don't go down, we make this significantly harder.

Selected media coverage

Dave Roberts, Vox, 15/5/2015: The awful truth about climate change no one wants to admit
Zeke Hausfather & Rosamund Pearce, CarbonBrief, 2/11/2017: Analysis: WRI data suggests emissions have already 'peaked' in 49 countries
This comment on uses a figure based on the figure above: 28/6/17: Three years to safeguard our climate
The Guardian, 17/9/2018: California plans to show the world how to meet the Paris climate target


Raupach MR, Davis SJ, Peters GP, Andrew RM, Canadell JG, Friedlingstein P, Jotzo F, Quéré CL 2014.
Sharing a quota on cumulative carbon emissions. Nature Climate Change 4(873-879).

Betting on Negative Emissions

Bioenergy with carbon capture and storage could be used to remove carbon dioxide from the atmosphere. However, its credibility as a climate change mitigation option is unproven and its widespread deployment in climate stabilization scenarios might become a dangerous distraction.Learn more »

Sharing a quota on cumulative carbon emissions

Any limit on future global warming is associated with a quota on cumulative global CO2 emissions. We translate this global carbon quota to regional and national scales, on a spectrum of sharing principles that extends from continuation of the present distribution of emissions to an equal per-capita distribution of cumulative emissions.Learn more »

Persistent growth of carbon emissions

Two thirds of the CO2 emission quota consistent with a 2°C temperature limit has already been used, and the total quota will likely be exhausted in a further 30 years at the 2014 emissions rates.Learn more »

Staying below 2°C

Global emissions are tracking the most pessimistic scenarios used by the IPCC. Glen Peters and colleagues present a comparison of emissions with all four sets of scenarios used by the IPCC since 1990, and argue that inertia in both human systems and the climate system make a 2°C goal harder with every day of inaction.Learn more »

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