Climate change mitigation in a regionalized world

This paper describes two mitigation scenarios leading to the stabilization of atmospheric CO2 concentrations at 550 and 750ppm. These mitigation scenarios are developed from the A2-ASF baseline scenario, which characterizes a regionalized world with continuous population growth (to about 15 billion in 2100), relatively slow technological progress, and high CO2 emissions reaching 28 Gt of carbon by 2100. It is argued here that large-scale GHG emission abatement measures needed to reach the agreed stabilization targets in such a world can be implemented only if negative impacts of global climate change become imminent and severe and opportunities for adaptation are limited. A single measure to reduce GHG emissions in the current analysis is a carbon tax on fossil fuels, the full amount of which is translated into an increase in corresponding fuel prices. This increase leads to an absolute reduction in fossil fuel use and a switch to non-fossil energy sources, such as nuclear energy and renewables. In order to reach the desired stabilization target, the 2100 total energy use has to be reduced to 50% of the baseline level for the 550ppm level and to 70% for the 750ppm level. At the regional level, the largest relative reductions are implemented in regions with relatively high per capita GDP growth and regions with a relatively low cost of renewable energy.