There is unequivocal evidence that we are facing the greatest energy transition since the dawn of the industrial age. We need to urgently shift from a global fossil fuel and CO2-emitting energy system to 1) decrease our CO2 emissions and combat the effects of climate change and 2) face a future of depleting fossil fuel resources. Yet there is still a lack of collective action to start taking effective measures to meet these challenges. We argue that there is a need for narratives in general and for a special type of narrative in particular, allohistorical scenarios, that act as thought experiments whose main function is to defamiliarize us with what is taken for granted. Such scenarios invite us to explore plausible parallel paths, thereby making it possible to imagine futures that are essentially different from the path-dependence of an unyielding historical past. Such futures enable us to grapple with a present that is saturated by the inertia of past decisions and the sunken costs of existing infrastructure. We here present the design rationale for the Coalworld scenario: an alternative world where only half the oil ever existed. We also describe the methodology and the assumptions that underlie the Coalworld scenario.