1 Impact of the Kyoto Protocol on Stabilization of Carbon Dioxide Concentration

Although the impact of the Kyoto Protocol on CO2 concentrations and temperature increase in 2012 is insignificant, its implementation has considerable impact on the pathways that are available in the future to reach certain climate stabilization levels. We demonstrate this using a set of global emission paths that are constrained to maximum 3 % change in emissions per year and a change in trend per year of maximum 0.5 percentage points. We translate these emission paths into CO2 concentration and temperature paths using the MAGICC model with an average carbon cycle and a climate sensitivity of 3°C. We find that while the implementing the Kyoto Protocol until 2012 has only an effect of 2 ppmv on CO2 concentration and several hundredth of degree Celsius in 2012, its implementation and reductions after 2012 enable reaching a maximum CO2 concentration level by 2050 that is by the order of 20 ppmv or two tenth of a degree Celsius lower than not implementing the Kyoto Protocol. If it is implemented excluding the USA, the maximum levels would be 10 ppmv or one tenth of a degree Celsius lower. Not implementing the Kyoto Protocol and reducing global emissions after 2012, the CO2 concentration level of 450 ppmv can only be reached, if global emission decline around 3 % per year over several decades. Implementing the Protocol would relax this condition to around 2 % per year. Delaying the start of global reductions until 2020 would increase the lowest reachable level further by around 40ppmv or 0.3°C.