That’s how fast the carbon clock is ticking

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.

As to the scientific basis of the carbon clock, we exclusively draw on data from the Intergovernmental Panel on Climate Change (IPCC), which represents the verified state of research. The IPCC last updated its estimate of the remaining carbon budget in autumn 2018, with the presentation of its Special Report on "Global Warming of 1.5°C". The next update of the carbon clock is likely to be in light of the IPCC's Sixth Assessment Report.
According to the Special Report (see here, table 2.2),on the 1.5 degree target, the atmosphere can absorb, calculated from end-2017, no more than 420 gigatonnes (Gt) of CO2 if we are to stay below the 1.5°C threshold. Annual emissions of CO2 – from burning fossil fuels, industrial processes and land-use change – are estimated to be around 42 Gt per year, the equivalent of 1,332 tonnes per second. With emissions at a constant level, the budget would be expected to be used up in less than seven years from now. The budget for staying below the 2°C threshold, for its part, of approximately 1,170 Gt, would be exhausted in about 25 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 MCC's carbon clock only reflects the remaining budget for CO2; the contribution of other greenhouse gases to global warming is subtracted before calculating this remaining budget.

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.

In an interview with the Zurich weekly WOZ (in German), MCC Secretary General Brigitte Knopf has explained in detail how the carbon clock illustrates climate change and indicates the urgency of political action.

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


Further information:

  • By using the following line of HTML code, you can embed the MCC carbon clock into your website:
    <iframe src="" style="width:600px; height:340px;"></iframe>
  • You can use the following link to drag the MCC carbon clock onto the entire screen of your device: