Nature: China’s premier Wen Jiabao announced on Saturday that China would aim to cut its energy intensity (carbon emission per unit of GDP) by 16% within five years. The target is ambitious. At the same venue, the annual Communist Party congress in Beijing, Wen also pledged that China would end poverty and continue to grow its economy at a rate of 7% per year. To reduce its use of fossil fuels, China must not only shift to low-carbon technologies, but also raise the efficiency with which it uses all forms of energy.