The unregulated voluntary market makes up a tiny percentage of carbon markets worldwide.
Most trading happens on regulated markets, such as the European Union Emissions Trading Scheme, the largest carbon market in the world.
The EU market launched in 2005 with the goal of combating climate change. Certain companies, such as power plants and airlines, are required to cap and trade their emissions.
Each "EU allowance" traded represents the permission to emit one tonne of carbon dioxide or the equivalent amount of another greenhouse gas.
While the voluntary market is characterised by one-off deals, markets such as the EU's have a standardised product that is traded on an exchange, said Konrad Hanschmidt, head of carbon markets analysis for Bloomberg New Energy Finance.
Market players can watch the price tick up or down by the second.
The EU market has suffered recently, however. The average price for EU allowances fell from double digits in 2011 to just €3.75 (Dh17.96) recently, according to data from Thomson Reuters Point Carbon.
Meanwhile, United Nations-backed carbon credits, called Certified Emissions Reductions, are trading for less than €0.50, having fallen 99 per cent since 2008.
* Vivian Nereim