Meeting the EU 2 degrees C climate target: global and regional emission implications
What global and regional emission reductions are needed to meet the EU 2°C climate target? Meeting the EU climate policy target with more than 50% certainty implies that greenhouse gas concentrations need to stabilise at 450 (400) ppm CO2-equivalent. Global emissions need to peak around 2015, followed by substantial overall reductions by 30% (50%) compared to 1990 levels in 2050. Industrialized countries will need to reduce their emissions by 15-30% below 1990 levels in 2020. It also requires the USA to participate in significant reductions soon and major advanced developing countries within the next 10-15 years.
This report presents a set of multi-gas emission pathways for different CO2-equivalent concentration stabilization levels, i.e. 400, 450, 500 and 550 ppm CO2-equivalent, along with an analysis of their global and regional reduction implications and implied probability of achieving the EU climate target of 2 degrees C. The effect of different assumptions made for baselines, technological improvement rates, or delay of global action on the resulting emission pathways is also analysed.
For achieving the 2 degrees target with a probability of more than 60%, greenhouse gas concentrations need to be stabilized at 450 ppm CO2-equivalent or below, if the 90% uncertainty range for climate sensitivity is believed to be 1.5 to 4.5 degrees C. A stabilization at 450 (400) ppm CO2-equivalent requires global emissions to peak around 2015, followed by substantial overall reductions in the order of 30% (50%) compared to 1990 levels in 2050.
In 2020, Annex I emissions need to be approximately 15% (30%) below 1990 levels. Non-Annex I emissions may increase compared to the 1990 levels, but not compared to their baseline emissions (15-20% reduction). A further delay in peaking of global emissions by 10 years doubles maximum reduction rates to about 5% per year, and very likely leads to high costs. In order to keep the option open of stabilising at 400 and 450ppm CO2 equivalent, the USA and major advanced non-Annex I countries will have to participate in an agreement aimed at reductions within 10-15 years.
|Author(s)||Elzen MGJ den ; Meinshausen M|