Implications of weak near-term climate policies on long-term climate mitigation pathways, Climatic Change

While the international community has agreed on the long-term target of limiting global warming to no more than 2 °C abov e pre-industrial lev els, only a f ew concrete climate policies and measures to reduce greenhouse gas (GHG) emissions hav e been implemented. We use a set of three global integrated assessment models to analy ze the implications of current climate policies on long-term mitigation targets. We def ine a weak-policy baseline scenario, which extrapolates the current policy env ironment by assuming that the global climate regime remains f ragmented and that emission reduction ef f orts remain unambitious in most of the world’s regions. These scenarios clearly f all short of limiting warming to 2 °C. We inv estigate the cost and achiev ability of the stabilization of atmospheric GHG concentrations at 450 ppm CO2e by 2100, when countries f ollow the weak policy pathway until 2020 or 2030 bef ore pursuing the long-term mitigation target with global cooperativ e action. We f ind that af ter a def erral of ambitious action the 450 ppm CO2e is only achiev able with a radical up-scaling of ef f orts af ter target adoption. This has sev ere ef f ects on transf ormation pathway s and exacerbates the challenges of climate stabilization, in particular f or a delay of cooperativ e action until 2030. Specif ically , reaching the target with weak near-term action implies (a) f aster and more aggressiv e transf ormations of energy sy stems in the medium term, (b) more stranded inv estments in f ossil-based capacities, (c) higher long-term mitigation costs and carbon prices and (d) stronger transitional economic impacts, rendering the political f easibility of such pathway s questionable.