Climate change, air quality and energy security will change the way energy is used and supplied over the next century. Supplying increasing amounts of clean and secure energy will be a challenge that will require a great deal of innovation and investment. However, this paper shows that there are visible paths to clean and secure energy. There are plenty of resource and technology options that could lead to emissions reductions in the heat, transport and electricity sector, while improving energy security. The costs of supplying energy from different options vary widely. However, several clean energy options are viable today and several others are likely to be so in the future, as technologies improve, costs are reduced, and the competitive landscape for energy technologies evolves. Tackling climate change and energy security requires the simultaneous deployment of available commercial clean technologies, demonstration and commercialisation of technologies at the advanced research, development and demonstration stage, and research into new technologies. (c) 2006 Published by Elsevier B.V.