As the world began to work its way out of the Great Recession, power plants pumped more carbon dioxide into the air than ever in 2010, threatening international goals of bringing global warming under control.

According to the UN’s International Energy Agency (IEA), the emissions amounted to some 30.6 billion tons globally of the heat-trapping greenhouse gas, 5 percent more than the previous record, set in 2008. The emissions figure followed a global decline in 2009.

Electricity generation is the largest and fastest growing source of CO2, according to the emissions estimates, released May 30.

A build-up of carbon dioxide in the atmosphere since the beginning of the industrial revolution, along with changes in land use as populations have grown, is widely seen as the driver behind a general warming of Earth's climate, especially over the last 50 years.

The report was released as negotiators prepare to gather in Bonn from June 6 to June 17 for an interim round of talks ahead of the main global-climate negotiations set for Durban, South Africa, in late November.

In another bit of sobering news for the environment, a separate analysis is showing a plateau in the efficiency with which fossil fuels are used to drive industrial production.

As efficiency has increased, less fossil fuel has been necessary to drive economies. But the rate of reducing the amount of fossil fuels an economy needs for a given unit of production has been dropping since 1990, according to Roger Pielke Jr., a political scientist at the University of Colorado at Boulder who has written widely on the politics of climate.

Last year, he calculates, the growth rate in this declining rate of "decarbonization" hit zero.

The IEA figures represent "another wake-up call" to increase efforts to curb CO2 emissions, said Fatih Birol, the IEA's chief economist, in a prepared statement.

Essentially, emissions are rising faster than they should if the global community stands a chance of holding long-term global-average temperature increases to the stated goal of 2 degrees Celsius (3.6 degrees Fahrenheit) above preindustrial levels.

The goal is contained in the agreement coming our of last December's UN-sponsored global climate talks in Cancun, Mexico.

With the initial estimate for 2010's emissions figures in hand, Dr. Birol said, “the world has edged incredibly close” to a maximum level negotiators had hoped they'd have about 20 more years to reach – giving them two decades to implement policies that would put them on a path to emissions cuts of 85 to 90 percent over 1990 levels by 2050.

If the IEA's estimate holds up, the implication is that to keep to the 2-degree goal, economies will have to slam the brakes on emissions harder and faster than they otherwise would have.

“You've got a certain amount of running room in terms of what you can emit into the atmosphere by mid century,” explains Alden Myer, a veteran climate-policy specialist with the Union of Concerned Scientists in Washington. “If you use almost all of that up by 2020, technically you might be able to achieve the 2050 goal by crashing emissions to zero in the following couple of decades, but politically and economically, that's not going to happen.”

Indeed, as countries try to lay the groundwork for Durban, now is the time to begin the trajectory that bites into the growth in emissions, Mr. Myer says, “but the reality is there's no consensus on how to divide up” the emissions pie “and how to deal with the up-front economic costs” in ways that give developing countries and advanced economies a mutually agreeable strategy for meeting a 2-degree goal.

Figures from the IEA report highlight the challenge.

The 34 members of the Organization for Economic Cooperation and Development, made up largely of countries from North America and Europe, plus a small handful of Asian nations, accounted for 40 percent of emissions and 25 percent of emissions growth last year. Countries outside the OECD, with China in the lead, experienced “even stronger increases,” according to the report.

Still, on a per-capita basis, China emitted only 5.8 tons per person and India 1.5 tons per person, compared with 10 tons per person averaged over all OECD countries.