U.S. investment bank Merrill Lynch and France's Societe Generale both global carbon indexes on Wednesday to track the international carbon markets, which were worth some $60 billion (30 billion pounds) last year.

The indexes will allow investors to access the world's carbon markets, including the European Union's emissions trading scheme and carbon trading markets under the United Nations' Kyoto Protocol.

"The (Merrill Lynch indexes) come in response to strong demand from our institutional, asset management, and wealth management clients who seek exposure to the rapidly growing global carbon market," Abyd Karmali, managing director and global head of emissions markets at Merrill Lynch, said in a statement.