Abstract Conventional energy security has been focused on the depletion of natural resources, particularly oil, natural gas and coal. More recently, the link between energy security and the military has been made, focused on the defence of international oil tanker chokepoints and the free flow of oil through these trade routes. This paper considers a possible future in which, the impacts of climate change have been realized far earlier than most experts have previously expected. This has promoted a transition to cleaner energy technologies long before the depletion of fossil fuel resources. In this scenario, the peak in demand for fossil fuels occurs before the peak in supply and some nations are strongly promoting the development and deployment of clean energy technologies. Some private companies developing and deploying these technologies benefit from sudden market expansion, fuelled largely by the world's richest nations struggling to reduce their carbon footprint. In this scenario the countries of the world would fall into one of the three categories: (1) the countries willing and readily able to adjust in response to rapid and serious climate change, (2) the countries willing to adjust, but facing significant economic hardship without external assistance and protection, (3) and those countries unwilling and, perhaps to their perception at least, unable to play a part in combating climate change. In this scenario, the Western Economies will likely fall under the first category while the BRIC countries (Brazil, Russia, India, China) might fall into the second category. These nations together are needed to achieve a viable, powerful, and effective formal or informal “Clean Energy Alliance”. Some countries however will probably fall into the third category. This paper considers how countries in the first two categories could respond by adjusting their foreign, trade and even military policies. If climate change is as severe and as pressing as some fear, leadership will be needed from those nations who are most capable of responding to the crisis. Within a generation, the great powers might find themselves shifting from keeping trade routes open to constraining the same trade. Severe climate change impacts could even approach the timescale of technological innovation needed to respond to this crisis. This paper proposes that our world may need new military and foreign policy options as well as new energy technology options in the years to come. Parallels are drawn between the challenge of decarbonising the global energy systems in the early twenty-first century and the ethical imperative of ending slavery in the early nineteenth century.