How is the world going to get to net zero by 2050 and who is paying the bill? Former governor of the Bank of England, and UN Special Envoy on Climate Action and Finance, Mark Carney, recently put the figure we need to spend at 100 trillion dollars at least. Switching to renewable sources of energy, needs the global financial markets to pay for the necessary infrastructure. Costs will come down as the technology improves; take the example of solar panels where the last two decades have seen an astounding 96% drop, from 10 dollars a watt to 25 cents. Allan Little investigates innovate companies investing in green energy; direct air carbon capture technology and a plant producing the greenest aluminium in the world thanks to geothermal power. But the road to net zero is fragile, and vulnerable to geopolitical events. Every solution to global warming has an impact and unintended consequences. What is the real cost of getting to net zero? Presenter: Allan Little Producer: Anna Horsbrugh-Porter Editor: Susan Marling A Just Radio production for BBC World Service (Photo: Solar power plant, in Fujian Province, China. Credit: Getty Images)