The European Commission said on Monday a proposal to limit the use of some carbon credits from industrial gas projects in its emissions trading scheme might be unveiled during a United Nations climate summit in Mexico next week. The European Union Emissions Trading Scheme is the largest multi-national emissions trading scheme in the world. The trading Scheme currently covers more than 10,000 installations with a net heat excess of 20 MW in the energy and industrial sectors which are collectively responsible for close to half of the EU’s emissions of CO2 and 40% of its total greenhouse gas emissions. Under the Trading scheme, large emitters of carbon dioxide within the EU must monitor and annually report their CO2 emissions, and they are obliged every year to return an amount of emission allowances to the government that is equivalent to their CO2 emissions in that year. In order to neutralize annual irregularities in CO2-emission levels that may occur due to extreme weather events (such as harsh winters or very hot summers), emission credits for any plant operator subject to the Trading Scheme are given out for a sequence of several years at once. Each such sequence of years is called a Trading Period. The 1st Trading Scheme Trading Period expired in December 2007. Since January 2008, the 2nd Trading Period is under way which will last until December 2012.