Global average GDP might be reduced by 1–4% if we reduce the emissions of CO2 so that we stabilize the concentration in the atmosphere at 450 ppmv. In 2003 the concentration was 375 ppmv. If we stabilize at higher concentration levels, the GDP reduction will be less. The projected mitigation scenarios do not take into account potential benefits of avoided climate change. Cost-effectiveness studies with a century time scale estimate that the mitigation costs of stabilizing CO2 concentrations in the atmosphere increase as the concentration stabilization level declines. Different baselines can have a strong influence on absolute costs. While there is a moderate increase in the costs when passing from a 750 to a 550 ppmv concentration stabilization level, there is a larger increase in costs passing from 550 to 450 ppmv unless the emissions in the baseline scenario are very low.
From collection: Vital Climate Change Graphics Update
Philippe Rekacewicz, Emmanuelle Bournay, UNEP/GRID-Arendal