Figure SI 4. Cumulative CO2 emissions over the period 2015-2100 in DICE-2016 R2, the recalibrated version for different stabilization targets compared to estimated cumulative emissions for different stabilization levels and probabilities as presented in IPCC SR 1.5.
In figure SI4 we present the cumulative emission budgets using DICE 2016 R2 for the 2.5°C target and compare that with the cumulative emission budget for the same temperature target using the recalibrated DICE model. We also use the recalibrated DICE model to estimate the carbon budget for the 2°C target and compare that with the IPCC SR 1.5 estimate (assuming a 50% probability of meeting the target). It shows that our recalibrated DICE model gives results that are in line with the IPCC estimate. In the same figure we also show the carbon budget from IPCC SR 1.5 for the 2°C target assuming a 67% probability of meeting the target and the 1.5°C (assuming a 50% probability of meeting the target). It may be noted that the DICE 2016 R2 carbon budget for meeting the 2.5°C is lower than the IPCC SR 1.5 estimate for the carbon budget for the 1.5°C target.
The CO2 emission budgets presented in figure SI4 for the IPCC cases are from table 2.2 in IPCC SR1.5 (Rogelj et al, 2018). These budgets refer to the period 2018 and onwards, while we present budgets for the period 2015-2100. Thus, we have added an estimated 120 GtCO2 to the IPCC budget in order to include the emissions that took place over the period 2015-2017.
Finally, we compare our estimated temperature to the average temperature during the period 1850-1900 when assessing the temperature stabilization targets. This is done in order to ensure comparability with the approach taken in DICE 2016 R2 where the surface temperature level is given in relation to the level in the year 1900. Further, the estimates of cumulative CO2 emissions compatible with different stabilization levels presented in IPCC SR 1.5 are based on temperature anomalies relative to the estimated global annual average surface temperature over the period 1850-1900 (Rogelj et al, 2018).