Closing the ambition gap: Germany's energy transition in line with a 1.5ˆC carbon budget

To limit global warming to 1.5$^{\circ }$∘C, rapid and significant reductions in greenhouse gas emissions are essential. However, there is a lack of analyses considering transition pathways using sector-coupled energy system models that limit national emissions to a 1.5$^{\circ }$∘C per capita carbon budget. This paper uses the REMod energy system model to derive a possible transition pathway within this budget. The model results show that immediate action in all aspects of the energy system is required, together with fundamental changes in energy policy and society, in order to stay within the remaining carbon budget. A crisis response that induces substantial and immediate demand reduction through societal behaviour change is essential. Furthermore, annual capacity additions of renewable energy sources such as wind and solar need to increase at rates four to seven times higher than historical maxima and the direct electrification of all sectors should be accelerated by replacing technologies even before they reach the end of their life (e.g. gas boilers and internal combustion engine vehicles).To close the ambition gap and comply with a 1.5$^{\circ }$∘C carbon budget, a strong and immediate crisis reaction is needed.The reduction of energy demand by leveraging behavioural change is key to sharply cut emissions.Besides the unconventionally fast deployment of new technologies, the accelerated phase-out of existing fossil-based technologies in all sectors needs to be addressed.Delaying the transition or an intensifying urgency to reduce emissions due to increasing impacts of the climate crisis might lead to similar scenarios where a strong and immediate crisis reaction is needed to sufficiently cut emissions.