Abstract
In our original study we crafted trajectories for developed and developing countries that phased-out greenhouse gas emissions during 2015-2065 such that the maximum global warming does not exceed the 2℃ threshold adopted by the UN Framework Convention on Climate Change, and the cumulative emissions for developed and developing countries are identical. Here we examine the effects of increasing the start year from 2015 to 2030 in 5-year intervals, and the phase-out period from 50 to 100 years in 10-year intervals. We find that phase-out during 2020-2100 is optimal. This phase-out increases the year of peak emission from 2015 to 2030 for developed countries and from 2042 to 2053 for developing countries. It also increases the time from peak emissions to zero emissions from 50 to 70 years for developed countries and from 23 to 47 years for developing countries. Both outcomes should facilitate agreement of the Revised Fair Plan by the UNFCCC.
1. Introduction
“The ultimate objective of” the United Nations Framework Convention on Climate Change (UNFCCC) is “stabilization of greenhouse gases at a level that would prevent dangerous anthropogenic interference with the climate system” [1]. The European Council confirmed that, “with the view to achieving the ultimate objective of the UNFCCC, the global annual mean surface temperature increase should not exceed 2˚C above pre-industrial levels” [2]. At its sixteenth Conference of the Parties, the UNFCCC recognized “those deep cuts in global greenhouse gas emissions are required according to science” “to hold the increase in global average temperature below 2˚C above pre-industrial levels” [3]. In our original Fair Plan study (FP1) [4] we crafted trajectories for developed and developing countries that phased-out greenhouse gas emissions during 2015-2065 such that the maximum global warming did not exceed the 2˚C UNFCCC threshold and the cumulative emissions for developed (Annex B, AB) and developing (non-Annex B, nAB) countries were identical. The method for doing this is described in detail in FP1.
In FP1 we took the starting year and period for the phase-out of greenhouse gas (GHG) emissions to be 2015 and 50 years, respectively. Here we examine the effect of: 1) delaying the starting year until 2020, 2025 and 2030 (Section 2); and 2) increasing the phase-out period from 50 years to 100 years in 10-year increments (Section 3). In Section 4 we examine the optimum phaseout trajectory that begins in 2020 and completes in 2100. Our results are discussed in Section 5.
2. Start Year for the Phase-Out of Greenhouse Gas Emissions
Figure 1 presents the GHG emissions intensity for AB and nAB countries relative to the reference RCP-8.5 case (see FP1) for starting years of 2015—as in FP1, 2020, 2025 and 2030, and Figure 2 shows the corresponding