Lehman Brothers Inc said Tuesday it will start trading carbon credits in Japan, becoming the first global investment bank to link the Japanese and European carbon markets. Lehman Brothers has become the first foreign financial firm to open an account in Japan's national registry system for trading in Certified Emission Reductions, the company said. A CER is a carbon credit developed by carbon offset providers that is certified as being equivalent to one ton of carbon dioxide under the mechanism defined by the 1997 Kyoto Protocol to combat global warming. The carbon offset scheme allows emitters of greenhouse gases to pay another party to undertake to remove an equivalent amount of carbon dioxide from the atmosphere.