Cap trade refers to a system that requires industries to cap the amount of carbon emissions that are released into the atmosphere over a specific time period. For businesses that cannot achieve this cap, they can trade with other companies that won’t reach their cap limits. Linking other national or regional cap-and-trade emissions trading systems to the EU ETS can create a bigger market, potentially lowering the aggregate cost of reducing greenhouse gas emissions. The increased liquidity and reduced price volatility that this would entail would improve the functioning of markets for emission allowances. Emissions trading, also known as ‘cap and trade’, is a cost-effective way of reducing greenhouse gas emissions. To incentivise firms to reduce their emissions, a government sets a cap on the maximum level of emissions and creates permits, or allowances, for each unit of emissions allowed under the cap.