What’s left in the world’s carbon budget?

February 9, 2017
January 2017, by Nika Knight on EcoWatch and Common Dreams

Our window of time to act on climate may be shrinking even faster than previously thought.  We may only have one year remaining before we lock in 1.5 C of warming—the ideal goal outlined in the Paris climate agreement—after which we’ll see catastrophic and irreversible climate shifts, many experts have warned.  That’s according to the ticking carbon budget clock created by the Mercator Research Institute on Global Commons and Climate Change (MCC). The clock’s countdown now shows that only one year is left in the world’s carbon budget before the planet heats up more than 1.5 C over pre-industrial temperatures.  That’s under the most pessimistic calculations. According to the most optimistic prediction, we have four years to kick our carbon habit and avert 1.5 C of warming.

And to limit warming to 2 C—the limit agreed upon in the Paris climate accord—we have nine years to act under the most pessimistic scenario, and 23 years to act under the most optimistic.

“So far, there is no track record for reducing emissions globally,” explained Fabian Löhe, spokesperson for MCC, in an email to Common Dreams. “Instead, greenhouse gas emissions have been rising at a faster pace during the last decade than previously—despite growing awareness and political action across the globe. Once we have exhausted the carbon budget, every ton of CO2 that is released by cars, buildings or industrial plants would need to be compensated for during the 21st century by removing the CO2 from the atmosphere again. Generating such ‘negative emissions’ is even more challenging and we do not know today at which scale we might be able to do that.”  (Climate activists and environmentalists have also long warned of the potential negative consequences of geoengineering and other carbon capture schemes, as Common Dreams has reported).  “Hence, the clock shows that time is running out: it is not enough to act sometime in the future, but it is necessary to implement more ambitious climate policies already in the very short-term,” Löhe added.

“Take all of the most difficult features of individual pathways to 2 C—like fast and ambitious climate action in all countries of the world, the full availability of all required emissions reduction and carbon removal technologies, as well as aggressive energy demand reductions across the globe—the feasibility of which were so heatedly debated prior to Paris,” Löhe said. “This gives you an idea of the challenge associated with the more ambitious 1.5 C goal.”

Directly from Mercator: That’s how fast the carbon clock is ticking

The MCC carbon clock demonstrates just how much carbon can be released into the atmosphere if global warming is to be capped at 1.5°C, or 2°C. By selecting a choice of temperature targets and estimates, you can see how much time remains in each scenario.

In the Paris Agreement, all countries worldwide decided to limit global warming to well below 2°C (ideally as much as 1.5°C) compared to pre-industrial levels. This is extremely ambitious and essentially means that we are tightening our carbon budget. In concrete terms, it means that reaching the 2°C target with a high probability would allow us to emit at maximum only about 980 gigatons of CO2 between 2016 and 2100 into the atmosphere.¹ However, at present the world is still emitting 40 gigatons of CO2 every year.⁴ This corresponds to 1268 tons per second. In that context, the remaining budget is shrinking rapidly.


 The clock is ticking. The carbon clock of the Mercator Research Institute on Global Commons and Climate Change (MCC) shows just how little time is left for political decision-makers. Visitors of the MCC website can set out to explore which policy objectives under which scientific assumptions would allow for how much time to implement effective action.

For example, on the top left of the clock you can select, for reaching the 2°C target, an optimistic upper estimate (about 940 Gt¹ remain in the budget), a medium estimate (about 760 Gt² remain), or a pessimistic lower scenario (about 390 Gt¹ remain). The right of the screen shows the scenarios that would correspond to the 1.5°C target.³ The carbon budget that corresponds to your selection is then displayed, alongside the remaining time left.

The calculation is based on the assumption that annual emissions remain at the level of 2014⁴; while between 2000 and 2010, an annual growth of greenhouse gas emissions of 2.2% has been observed¹. The MCC scientists Alexander Radebach and Tom Schulze are responsible for the concrete calculations based on the above-mentioned budgets and output rates as well as for the realization of the carbon clock.


¹ IPCC, Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA (Cambridge University Press, 2014); SPM Table 1.

² IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland; Table 2.2.

³ J. Rogelj et al., Energy system transformations for limiting end-of-century warming to below 1.5 [deg]C. Nature Clim. Change 5, 519 (2015). // The “medium estimate” for the 1.5°C target is the arithmetic mean of the upper and lower estimates from Rogelj et al.

⁴ C. Le Quéré et al., Global Carbon Budget 2015. Earth Syst. Sci. Data 7, 349 (2015).