The world will need to invest $4.5 trillion (£3.7 trillion) a year from the start of the next decade if it is to reach net zero by 2050, the International Energy Agency (IEA) has said.The Paris-based organisation said that record growth in clean energy technology, including solar panels and electric vehicles, means it is still possible to limit rises in global temperatures to 1.5C.However, it would require a huge ramping up of spending. World governments and organisations are expected to spend $1.8 trillion (£1.5 trillion) on the transition to cleaner...