These data sources have been cited by market participants as useful in assessing emission allowance markets. Some of these publications offer free trial subscriptions. This is not necessarily a complete or exhaustive list.
SO2 Spot Market - Price and Regulatory Information
Chicago Climate Futures Exchange (CCFE) announced plans to wind down operations in August of 2011. Effective as of February 28, 2012 there is no remaining open interest in contracts at CCFE and all contracts have been delisted.