More than 350 cities across Europe have signed a "covenant of mayors" at the European Parliament in Brussels committing the municipalities to cuts of more than 20 percent in CO2 emissions by 2020. The EU as a whole aims to achieve a cut of 20% in greenhouse gas emissions by 2020. The CO2 Emissions Trading Scheme (ETS) will play a key role in that. But the EU's emissions allowances have hit a record low of EUR 9.5 a ton, undermining the carbon market, the BBC reports. There are fears that the low price weakens the incentive for enterprises to invest in green technologies, because it now costs less for them to pollute.