Remaining carbon budget - Mercator Research Institute on Global Commons and Climate Change (MCC)

The MCC Carbon Clock shows how much CO2 can be released into the atmosphere to limit global warming to a maximum of 1.5°C and 2°C, respectively. With just a few clicks, you can compare the estimates for both temperature targets and see how much time is left in each scenario.

In line with the recent IPCC Special Report on Global Warming of 1.5°C, the Mercator Research Institute on Global Commons and Climate Change (MCC) has updated its Carbon Clock.
In 2015, with the Paris Climate Agreement, all nations around the world set themselves the goal of limiting global warming to well below 2°C (preferably 1.5°C) compared to pre-industrial levels. An ambitious goal.
 
The Special Report of October 2018 presents new figures: The atmosphere can absorb no more than 420 gigatonnes (Gt) of CO2 if we are to stay below the 1.5°C threshold. However, since around 42 Gt of CO2 is emitted globally every year—the equivalent of 1332 tonnes per second—this budget is expected to be used up in just over nine years. The budget for staying below the 2°C threshold, for its part, of approximately 1170 Gt, will be exhausted in about 26 years.

Thus, the clock keeps ticking and shows how little time is left for political decision-makers to  take action. Navigating the MCC website allows for an interactive understanding of the time frame of action required for a given political goal.

With just one click, the upper left-hand corner leads you to the scenario for the 2°C target, and the upper right-hand corner to the 1.5°C target. In both cases, the clock shows the remaining carbon budget—and the remaining time.

The concept of the carbon budget is based on a nearly linear relationship between the cumulative emissions and the temperature rise. Nevertheless, this does not mean that the earth would necessarily be 1.5⁰C warmer at the very point in time when the remaining carbon budget for staying below the 1.5⁰C threshold was used up. This is due to, among others, the fact that there is a time lag between the concentration of emissions in the atmosphere and the impact thereof on the temperature.
 
The update of MCC’s Carbon Clock based on the IPCC Special Report also involved a technical change: So far, the IPCC had illustrated the likelihood of a given outcome in terms of a lower (33 percent), a medium (50 percent) and a high (66 percent) probability. In light of the new findings, however, the scientists now say that the calculated budget of 420 Gt for reaching the 1.5⁰C threshold will be used up with 66 percent of the examined scenarios. This indicates a shift in uncertainties: away from the likelihood of staying below the temperature threshold, and towards the likelihood that the models will indeed translate into a 1.5°C rise in temperature.

While the Carbon Clock appears to be a precise measurement of the time left to ensure climate protection, many uncertainty factors remain, such as different definitions of the 1.5°C target as well as different assumptions about the climate sensitivity, the actually attained degree of global warming, and the future development of other greenhouse gases. Furthermore, the calculation assumes that the annual emissions of years to come will be close to those of the year 2017, while latest numbers show that emissions are still on the rise.
eit, dass die Modelle das Ziel einhalten.

Update December 2018: In agreement with the latest IPCC Special Report, the number for the 2°C budget was updated to 1170 Gt CO2 (see Table 2.2., IPCC SR15), while an earlier version referred to 1070 Gt CO2.

For questions about the Carbon Clock, please contact MCC Press and Public Relations.