Some readers may question the value of a book on climate change by Bill Gates, who made his fortune in the computer software business. Yet Gates has a long history of philanthropic work and engagement in discussions about the environment, and he has the resources both to gather relevant data and to pick the brains of experts. His book is a highly readable summary of mainstream thinking on ways to prevent the worst. His essential conclusion is that in order to avert climate disaster we need to get to net-zero greenhouse gas emissions by 2050, deploy existing lower-emission forms of energy (like solar and wind power) ‘faster and smarter’, and ‘create and roll out breakthrough technologies that can take us the rest of the way’.

Emissions can be sorted into two baskets: electricity (which accounts for about a quarter of emissions) and everything else. The burning of fossil fuels accounts for two thirds of all electricity generated worldwide. Even though solar and wind power are getting cheaper by the year, they suffer from intermittency: dealing