Carmen Bunzl - Universidad Pontificia Comillas

Chapter 3. Implications of future climate regime architectures 148
- Annex I regions
Substantial reductions are still needed in order to achieve a concentration
level of 550 ppmv CO2eq. 1 , Annex I countries need to reduce emissions below
1990 levels in the order of 15% to 30% in 2020 and 55% to 90% in 2050.
The impact of different approaches in a certain region wouldn’t change much
compared to the 450 ppmv CO2eq. scenario. The Multistage approach would be
the most demanding, followed by the CDC, C&C and the least demanding
would be the Triptych approach. Even though it is still not very large,
differences between approaches are more significant for a higher stabilization
level. This may be due to later participation of developing countries, under
staged approaches such as the Multistage and CDC.
One exception is USA in 2020, the Multistage approach would still be the most
demanding, but the CDC approach would even allow for an increase of
emissions compared to 1990 levels. A choice of a higher stabilization level,
regarding these results, would be much more beneficial for USA than for other
regions in 2020 – EU, for example, would have to reduce a 10% less; the USA
would have to reduce 20% less. This may be because of USA’s high emissions
per capita, under a higher stabilization level, these would not have to converge
such a low level; this beneficiates countries with high emissions per capita.
- Non-Annex I regions
On the other hand, a higher stabilization scenario requires less efforts from
developing countries. In 2020, none of them have to reduce their emissions
compared to 1990 levels. South Asia would even have more emission
allowances than their baseline scenario under C&C, so called “hot air”. Under
staged approaches such as CDC and Multistage, South Asia would not start to
participate until after 2020.
1 Using various probability distributions of the climate sensitivity, Hare and Meinshausen (2004;
Meinshausen 2005) conclude that it is “unlikely” that the 2°C will be met (70%-100% risk of stabilizing
above) with stabilisation at 550 ppmv CO2eq.
Escuela Técnica Superior de Ingeniería ICAI Carmen Bunzl Boulet Junio 2008