Scientists generally agree that the world could keep temperature rises below a dangerous level of two degrees Celsius (3.6 degrees F) if greenhouse gas emissions are halved by 2050.
However, according to the Telegraph, a new report from the WWF found that this will require a "green industrial revolution" by 2014, with heavy investment in moving from fossil fuels to 'low carbon alternatives' like wind, solar, nuclear and clean coal.
It will also mean switching to electric cars and other green technologies and improving energy efficiency by insulating our homes and wasting less electricity.
The stark warning comes as ministers and officials from around the world meet in London for the Major Economies Forum.
The WWF said that both rich and poor countries need to start investing in renewable energy and encouraging behaviour change among citizens in order to meet the targets.
The report used economic models to calculate how long it would take for a low carbon industry to grow to a point where it is big enough to cut emissions by 50 per cent.
According to Keith Allott, Head of Climate Change at WWF UK, any industry will only grow by 30 per cent every year; so the world has to invest in a low carbon industry now to allow the sector to grow to a point where it takes over from fossil fuels by 2050.
"Clean industry sectors can only expand so far, so quickly. If we wait until later than 2014 to begin aggressively tackling the problem, we will have left it too late to ensure that all the low-carbon solutions required are ready to roll out at the scale needed if we intend to keep within the world's remaining carbon budget," he said.
"This report is a compelling reminder of the scale of effort and the speed of action needed if we're going to make the global transition towards low and zero carbon economies before it's too late," he added.