NEW YORK -- Global carbon markets expanded in 2011 behind an upward pitch in trading volume that offset bottom-of-the-barrel prices, according to two reports out today.

Separate analyses by Bloomberg New Energy Finance and Thomson Reuters Point Carbon found that worldwide trading of carbon inched up in 2011 compared with the previous year. BNEF said the value of the markets increased by 10 percent over 2010, while Point Carbon pinned the rise at 4 percent.

BNEF analysts said the value of the worldwide carbon market rose to €92 billion ($117 billion) in 2011, up from €84 billion ($106 billion) the previous year. In all, some 8.2 billion tons of CO2 equivalent was traded, compared with 6.7 billion tons the year prior, the firm said.

Point Carbon's lighter estimated gains were in part due to what the company called a smaller growth in carbon value than might have been expected given the volume. That dynamic was primarily due to low prices, with benchmark E.U. Emissions Trading System prices having dropped to a record low of €6.30 a ton in December.

That price point meant carbon was cut in half from a year before, according to the Point Carbon report.

Still, BNEF described the market as benefiting from "robust trading activity" that was driven in part by volatility in Europe. BNEF said traders throughout the year switched their attention from energy fundamentals to rumors about the future of the eurozone.

The firm added that the latter half of 2011 saw an increase in the trading of international carbon credits, including Certified Emission Reductions (CERs), Emission Reduction Units (ERUs) and Assigned Amount Units (AAUs) created under the Kyoto Protocol.

"The gradual decline in average prices in 2011 is in sharp contrast to the increase in traded volume, which rose steadily throughout the year from 1.8 billion tons in Q1 to 2.4 billion tons in Q4," the BNEF report says. "This jump in trading activity was seen across both the European and international carbon credit markets."

Click here to read the BNEF report.