Hence, if competitive distortions can be avoided, we support airlines' inclusion in the EU Emissions Trading System as the first step towards a global cap-and-trade framework.

ECONOMIST: Letters

Critics of the EU's Emissions Trading System also argue that the European Union issued too many permits in the first place.

BBC: Chimneys at coal-fired power station

The EU's Emissions Trading System (ETS) created a market in CO2 emission allowances, meaning that heavy emitters of CO2 have to buy allowances from enterprises that have managed to cut their CO2 emissions.

BBC: EU court rebuffs Poland over CO2 emissions

That coincided with a sharp fall in the price of carbon allowances under the EU's flagship emissions trading system and rising European prices for natural gas.

CNN: Shale gas boom sparks EU coal revival