The integrated assessment models used by the Intergovernmental Panel on Climate Change rely heavily on negative emissions technologies (NETs) for scenarios that keep global temperature rise to 2°C or lower. One favoured NET is bio-energy combined with carbon capture and storage (BECCS). Firstly, it is not established that BECCS is feasible at a scale sufficient to matter, nor that BECCS at sufficient scale is compatible with sustainable development. Secondly, substituting the prospect of BECCS later for ambitious mitigation of emissions now unjustifiably transfers risks from the present to the future. Thirdly, no NET can ‘buy time’ for unambitious mitigation because the later reduction of ‘over-shoots’ in emissions cannot reverse the passing of tipping points in the interim. The substitution of the dream of later negative emissions for immediate mitigations is therefore completely unjustified.