Global energy consumption is increasing rapidly, driven by rising living standards in developing countries. Energy provided by burning fossil fuels still accounts for over 80% of the total, and is also growing, albeit slowly. This is unsustainable. Decarbonisation is imperative – to moderate climate change, and reduce air pollution – but scenarios that meet the International Panel on Climate Change’s goal of net-zero emissions in the second half of the century all involve heroic technical, economic and political assumptions.

I will review the need to decarbonise and ways to reduce emissions, and identify and discuss ‘stubborn’ (especially hard to decarbonise) sectors. Increased electrification plays a key role in all low carbon scenarios. The rapid fall in the cost of wind and solar power provides grounds for optimism, but integrating them with other low-carbon sources will require large scale energy storage. I will present key findings of a major study that I am leading on how to assess the need for storage, storage technologies and what it may cost. Finally, I will discuss whether the world may be approaching a tipping point.