The global trade in greenhouse gas emissions was worth $64bn last year, according to the World Bank. The market is forecast to grow rapidly – to $3,000bn by 2020 if the US participates – according to market analysts Point Carbon.

The trade is meant to achieve a double benefit – encouraging companies to cut their emissions by penalising those that do not and rewarding those that do, and bringing investment and expertise in low-carbon technologies to poor countries. But although the trade has grown rapidly in value, the poorest areas of the world have yet to benefit.