Regensburg 2016 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

UP 5: AKE und UP: Energiewende und Klimawandel

UP 5.2: Hauptvortrag

Mittwoch, 9. März 2016, 10:00–10:30, H41

The 2°C climate policy goal: Chances & Challenges — •Hermann Held — University of Hamburg, Center for Earth System Research and Sustainability, Grindelberg 5, D-20144 Hamburg

The Conference of Parties held end of 2015 in Paris re-confirmed the so called 'two-degree target' (2°-target) as the global goal of climate policy. It encodes the consensus to limit an anthropogenically induced increase of global mean temperature to 2°C. The latest IPCC (Intergovernmental Panel on Climate Change) report (2014) summarizes cost estimates that can be interpreted as rather low, suggesting some political feasibility of the 2°-target. However in terms of an agreement on concrete cuts of greenhouse gas emissions, most likely there will be a gap, equivalent to about 1°C global warming. Furthermore, our work has shown that the 2° target requires a somewhat refined definition and interpretation once one acknowledged a probabilistic, long-tailed climate response to greenhouse gas forcing, in combination with anticipated future learning 'dynamic decision-making'). Here we present a generalization of the 2°-target that respects dynamic consistency under anticipated future learning. Consequences for climate policy are highlighted, including the possibility of a delayed 2° policy. We find that previous climate economic analyses of the 2°-target in terms of low cost for transforming the energy system are still valid, when being re-interpreted. Moreover, mitigation costs could be reduced by up to 1/3 if the climate response to greenhouse gas forcing were known with certainty, pointing to the expected economic value of geo-scientific information.