Global investments in renewable energy must double by 2020, according to the International Energy Agency (IEA). It said an investment of $23.9 trillion (£15 trillion) is needed to prevent global temperatures from rising beyond 2°C.

The IEA’s Energy Technology Perspectives 2012 book states the figure should rise to $140 trillion (£90 trillion) by 2050. It said the reduction in fossil fuels spending would outweigh the investment made by 2025, which would add up to at least $100 trillion (£64 trillion) in savings in the four decades.

The Agency said: “The window of opportunity is closing rapidly on achieving the 2°C target. The investments made today will determine the energy system that is in place in 2050, therefore, the lack of progress in clean energy is alarming.

“Continued heavy reliance on a narrow set of technologies and fossil fuels is a significant threat to energy security, stable economic growth and global welfare, as well as to the environment.”

The publication also said solar energy could provide a third of the world’s energy by 2060.