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Zusammenfassung:
Scenarios from integrated assessment models play a central role in helping policymakers envisage pathways to limit global warming to well below 2 °C. We demonstrate that many models maintain a preference for inefficient combustion, in particular by relying on coal and bioenergy. In contrast to recent evidence from innovation studies, scenarios are optimistic on deployment of lumpy energy-systems technologies, such as carbon capture and storage, while insufficiently reflecting empirically observed innovation dynamics in more granular technologies such as solar photovoltaics. Our analysis shows that two key options for rapid decarbonization remain systematically undersampled in models that underpin IPCC scenarios: A) strong growth in intermittent renewables, in particular solar PV, together with electrification of sectors; and B) widespread adoption of efficient end use technologies enabling high service provision at low levels of energy demand. A combination of continued PV growth and sector coupling with low to medium energy demand (a corridor of 250 to 500 EJ of primary energy) would render carbon neutrality by 2050 feasible, thus enabling near-term cost-effective climate change mitigation and reducing the need for carbon dioxide removal in the 2nd half of the century. Models would benefit from updated cost assumptions, higher resolution on granular end-use technologies, higher resolution on sector coupling, and an overall consideration of demand-side solutions. Such updates – of which some are starting to be explored by modeling teams - are likely to demonstrate that some mitigation pathways are cost saving, rather than costly.
