The corridors of power in the United States are ringing with the phrase 'cap and trade'. But when will carbon markets arrive in America — and what will they look like?

Energy efficiency is one of the least flashy but most promising ways to cut carbon dioxide emissions. In the first of two features, Declan Butler explores the energy-saving possibilities of an intelligent electrical grid. In the second, Zoë Corbyn looks at how labs can cut their energy use.