Multi-gas emission pathways for stabilising greenhouse gas concentrations

Abstract

This paper presents a set of multi-gas emission pathways compatible with different levels of ambition of avoiding long-term climate change, expressed in terms of different greenhouse gas concentration stabilization levels, i.e. 400, 450, 500 and 550 ppm CO₂-equivalent. Also the effect of different assumptions on the resulting emission pathways, such as different baselines and technological improvement rates is analyzed. The emission pathways are derived using a methodology to calculate the cost-optimal implementation of available reduction options over the greenhouse gases, sources and regions. The emission pathway is determined iteratively to match prescribed climate targets of any level.

Stabilizing greenhouse gas concentrations 450 CO₂ equivalent or lower requires global emissions to peak within the next two decades, followed by substantial overall reductions by as much as 30 to 50% in 2050 compared to 1990 levels. Further delay in peaking of the global emissions leads to delayed, but much steeper reductions. The total emission reductions strongly depend on the emissions growth in the baseline scenario and the further improvements of the abatement potential and reduction costs for all greenhouse gases in the future.