DEEP DECARBONISATION TOWARDS 1.5 °C - 2 °C STABILISATION

Kurzfassung

Limiting global mean warming to well below 2°C or even 1.5°C relative to pre-industrial levels requires a major transformation of the energy system. The ADVANCE project has analysed this mitigation challenge in detail, from the implications of the Intended Nationally Determined Contributions INDCs) to decarbonisation bottlenecks in energy end-use sectors, taking into account both technological as well as behavioural emission reduction measures. Our key fndings are: The implementation of the Paris Agreement initiates a low-carbon transition for major emitting countries but an intensifcation of global effort is still required in order to limit global warming well below 2°C. In 2030, the implementation of the INDCs is expected to reduce GHG emissions by 10% of pre-Paris Reference emission levels. However, the global emissions gap relative to cost-optimal reduction pathways remains at 14 [4-25]1 GtCO2eq for the 2°C target and 25 [13-30] GtCO2eq for the 1.5°C target. The decarbonisation of the power sector accounts for more than half the CO2 reductions achieved by the INDCs in 2030. It also holds the greatest potential for further near-term eductions which would put the world on track for 1.5-2°C stabilisation. In 2030, the INDCs are expected to generate an increase in the share of zero carbon power supply by 5% [1-12%] relative to pre-existing trends, achieving a total share of 48% [40-66%]. Optimal 2°C and 1.5°C scenarios feature 57% [50-90%] and 73% [57-93%] zero carbon power supply respectively. In contrast, the INDCs have little effect on near-term emissions from non-electric end-use, even though progress in abating emissions, particularly from industry and transportation, is important for 1.5-2°C-consistent climate stabilisation. The 1.5°C temperature target requires reductions in emissions from energy supply and demand as well as removal of CO2 from the atmosphere. A warming limit of 1.5°C requires adherence to a stringent carbon budget of around 400 Gt CO2 or lower over the 2011-2100 period. As the supply-side sector already needs to eliminate nearly all of its emissions by 2050 for 2°C stabilisation, most of the additional emission reductions need to occur on the demand side. Effciency improvements, as well as an accelerated electrifcation, will play a key role in achieving the 1.5C° target. However our analysis also shows that energy supply and demand will still combine to generate at least 1000 Gt of residual CO2 emissions over the 2011-2100 period. Accordingly, a 1.5°C-consistent budget will require cumulative carbon dioxide removal of at least 500 Gt CO2 over the course of the century. Renewable energy from wind and solar power has great potential to produce environmentally friendly and economical electricity supply. Reaping the benefts of high and low-cost emission reduction of the power sector at an early stage is essential for climate change mitigation. We fnd that the sector could be almost fully decarbonised through wind and solar power alone, without the use of nuclear and carbon capture and storage (CCS). This would require, however, considerable additional investments into grid infrastructure and storage systems. Most previous modelling studies have underestimated the role of wind and solar because of overly conservative assumptions on technology costs and the challenges related to coping with a variable renewable electricity supply. We also fnd that the low-carbon transformation yields substantial environmental co-benefts, which outweigh adverse environmental side-effects. Among the alternative decarbonisation pathways available, strategies relying heavily on wind and solar are superior to those with substantial CCS and nuclear deployment, in terms of minimising environmental impacts. Technological developments promoting effciency, electrifcation and use of low-carbon fuels are the key to demand-side emission reductions. Technology options that promote energy effciency, electrifcation and a switch to low-carbon fuels in primary energy demand sectors (transport, industry and buildings), become increasingly important if a climate target of below 2°C is to be achieved. This is despite the continuously increasing demand for energy services. In the long-term, conventional fuels will have to be almost completely phased out from transportation energy use. This will largely depend on the development and adoption of new technologies, but also on life-style changes towards low-carbon transport modes. Policies influencing consumers’ attitudes will need to support the energy transformation. Policies targeting consumers’ behaviour and preferences can encourage the adoption of advanced technologies and use of cleaner fuels. These will ultimately speed-up the transition to a low-carbon energy system. For instance, in the transport sector we find that consumers have different attitudes towards vehicle choice, apart from pure fnancial concerns. This is why a rise in the market in alternative fuel vehicles will critically depend on non-fnancial measures, such as vehicle effciency standards and mandates, refuelling infrastructure investments and exclusive access to parking spaces and roadways. Also, with regard to energy access in developing countries, we fnd that household cooking decisions largely depend on income. Therefore subsidies for cleaner fuels and stoves can speed up the transition to universal clean cooking and even offset the negative effects of rising fuel costs spurred by climate policy.