In the fight to curb global carbon emissions, Europe has often taken a lead role: The European Union boasts the world's largest carbon market and has spent nearly twice as much as the United States this year on the promotion and adoption of renewable energy.

Yet the continent's efforts seem, at the moment at least, to swim against the current of market forces. A glut of coal exports from the United States, a mild winter and stubbornly high gas prices mean that power producers are turning increasingly to coal, the most carbon-heavy of the conventional fossil fuels.

As a result, Europe's emissions may edge higher this year, counteracting gains made by energy efficiency and the adoption of renewables. Coal consumption is up by between 6 and 7 percent, driving a 2.2 percent rise in E.U. carbon emissions, according to an analysis by Point Carbon, a Thomson Reuters company.

Then again, on a longer timeline, this reversal may be little more than a bump on the continent's downward-trending path to lower emissions.

After watching the price of carbon credits under the European Union's Emissions Trading System slide as oversupply from the developing world met underwhelming demand from an economically slow industrial sector, the European Union is girding itself to take action to raise the credits' value.

"The E.U. is delivering on its Kyoto commitment. While our economy grew 48 percent since 1990, emissions are down 18 percent," said E.U. Climate Action Commissioner Connie Hedegaard, at the release of the commission's latest report on its Kyoto Protocol goals. "These figures prove once again that emissions can be cut without sacrificing the economy. Now, it is important to keep the direction. Reaching the 20 percent target in 2020 does not come automatically. "

The stars align for cheap coal

Natural gas production has enjoyed a kind of revolution in the United States over the last half-decade, bringing domestic emissions down to a 20-year low and pushing coal overseas.

"The coal industry is focused on export now," said Edwin Feo, a managing director at consulting firm USRG Renewable Finance. "There's demand in Europe, while on the U.S. side you see stockpiling from the warm winter and competition with gas. The U.S. market is not a great one currently for coal."

Meanwhile, natural gas prices remain high in Europe, which is locked in an increasingly ugly legal dispute with Russian gas giant Gazprom. With coal prices dropping thanks to oversupply from the United States, prices have fallen even below those of coal-rich South Africa, according to Bloomberg.

"The question you have to ask is, is coal challenged outside of the U.S.?" Feo said. "The only thing you could point to would be if the U.S. increased its exports of natural gas. If you look at how many licenses have been granted to natural gas exporters, you can see that gas isn't about to flood world markets or cause a collapse of supply."

Other factors contribute to coal's attractiveness on European markets. Germany's decision, after Japan's Fukushima Daiichi nuclear disaster, to retire its nuclear fleet has left a gap in baseload supply, much of which has been filled by coal. And, like the United States, many European nations have been able to stockpile supplies during the warm winter, adding downward pressure to cost.

Burn coal now, fade away later

Part of coal's current success in Europe is predicated on the failure of the ETS. The price of carbon credits slid to €7 this week, far too low to offset coal's current competitive pricing. But a rally for credits could quickly put a crunch on power producers who have turned to the more carbon-intensive fuel.

Currently, the European Union is considering a number of proposals -- among them delaying or even reducing the number of credits to enter the market next year -- aimed at doing just that.

And beginning in 2013, the majority of credits will be auctioned rather than given out free of charge -- a change that will add substantially to their value.

Another set of E.U. regulations, aimed not at curbing greenhouse gases but at cutting down harmful toxins like sulfur dioxide and nitrogen, may also play a role.

European power stations producing 50 megawatts or more of thermal power must comply with the Large Combustion Plant Directive, a mandate placing strict limits on the emission of acidifying pollutants. A number of older power stations were able to opt out of those limits, however, electing instead to close after a set number of operational hours had been expended or by 2015, whichever came first.

Many of those older coal-fired power plants now appear to be capitalizing on the low coal prices by running full tilt, burning through their last allotted hours at a moment when coal prices are low.

Plants in England, Scotland and Germany are scheduled for closure in early spring, just as the price of carbon credits is likely to rise.