The International Energy Agency warned today at the launch of the agency’s annual flagship World Energy Outlook that the world’s use of fossil fuels will have to peak by 2020 if it is to escape a dangerous spike in global temperatures. Fatih Birol, the IEA’s chief economist, said: “This would be a revolution. This revolution could only take place if there is a financial signal to the energy industry.” He added: “We need a deal in Copenhagen. We need a signal for the energy industry. Without that, nothing will move.”