Kriegler E, Tavoni M, Aboumahboub T, Luderer G, Calvin K, Demaere G, Krey V, Riahi K, Rsler H, Schaeffer M and Van Vuuren DP (2013) What does the 2C target for a global climate agreement mean by 2020? The LIMITS study in The Durpan Platform Scenarios, Climate Change Ecoomics, 4, 4 aviation emissions are included and are based on data from Owen et al. (2010). For engagement trajectories, a small overall reduction in aviation data will be applied compared to current policy projections. Based on each CTU country analysis, global trajectories are generated for three scenarios: current policy projections, short-term commitments (by 2030) and long-term commitments (by 2050). For each of these three scenarios, we also assess a higher and lower trajectory, based on uncertainties in the underlying country analyses or on the commitment ranges. In 2010, the countries assessed by the Climate Action Tracker accounted for 81% of global emissions (excluding UTCATF). For countries that are not subject to individual assessment, we currently expect that emissions from these countries will follow a business as usual (BAU) path. The building paths used in this analysis come from the PRIMAP4 baseline, based on historical data EDGAR, CDIAC and CRF, and projected with WEO 2009 and POLES data. The basic structure is described in more detail on the PRIMAP website. To assess the climate impact of the targets presented by countries, we first build an overall emissions trajectory by 2100.

This global trajectory is then used as an input for a carbon cycle/climate model (MAGICC) that is executed several times to obtain a probability distribution of results such as global average temperature, CO2 concentration and total greenhouse gas concentration. The detailed methodology of the climate model is described in Meinshausen et al. 2009 -2011. In June 2020, we added international shipping and international aviation to the CTU. These new projections will be included in the next edition of our global trajectory assessment. A pathway for global deforestation is provided by the median of the limitS project`s baseline land-use emission scenarios (Kriegler et al., 2013). This track is virtually consistent with the median of the broad range of baseline scenarios assessed by Working Group III in the IPCC`s Fifth Assessment Report (AR5) and is slightly lower than that of RCP8.5 (Riahi et al. 2007), the high page of the range of new emission scenarios (see iiasa.ac.at). The entire analysis is done at the 5-region level, so the final step is to add up the regional trails of an overall trajectory, which is then used to calculate the global temperature after emissions from bunkers and deforestation have also been included. Several steps are needed to aggregate these scenarios into a global emission trajectory. First, we include emission trajectories for countries that are not individually assessed for CTU. Second, we will determine, if necessary, the impact of the accounting rules of the Kyoto Protocol.

Third, short-term pathways will be expanded to 2100 based on AR5 database scenarios. Fourth, emissions from international shipping and aviation emissions are added to national emission profiles to complement the overall emissions trajectory. Fifth, some greenhouse gas emission trajectories are derived from the resulting global greenhouse gas emission trajectories. Finally, CO2 emissions from land use changes will be added to national emission profiles to complement the overall emissions trajectory. Each of these steps is described below. To determine the relative effort of the CAT scenarios, we calculate the amounts of AR5DB path allocation corresponding to the CAT scenario for the last years of the scenario. We use a linear adjustment to determine the amount of the first year based on the end of the scenario, which we then keep constant until 2100 to maintain the level of effort. In the event of short-term commitments and political projection, the