The world's existing power plants are on track to pour more than 300 billion tons of carbon dioxide into the atmosphere, and current monitoring standards often fail to take these long-term emissions into account, according to new research from scientists at UC Irvine and Princeton University.

The paper, published Tuesday in the scientific journal Environmental Research Letters, is the first to estimate the lifetime carbon emissions of power plants globally over multiple years.

The drive to meet the world's ever-growing energy demand means that global power sector commitments—the projected lifetime carbon emissions of currently working power plants—have not declined in a single year since 1950. These so-called committed emissions are growing at about 4 percent a year, according to the study, and in 2012 reached 307 billion tons of carbon dioxide.

The study comes as the United States is attempting for the first time to regulate emissions from existing power plants, a proposal the Environmental Protection Agency (EPA) announced several weeks ago and aims to finalize by next June. (See related: "Four Key Takeaways From EPA's New Rules for Power Plants.")

The researchers suggest that current United Nations accounting methods, which chart annual carbon dioxide discharge, should also tally the projected lifetime emissions of power plants to provide a more accurate picture of their impact on global warming. (See related interactive map: Global Greenhouse Gas Footprints)

"International efforts all center on what we emit every year, but that misses the point," said Steven Davis, an earth system scientist at the University of California, Irvine, and the study's co-author. "We have information about what is coming in the future." Davis wrote the paper with Robert Socolow of Princeton, known for his theory that a series of environmental steps that cut greenhouse gas, which he called wedges, could together flatline carbon emissions. (See related: "Climate Scientist Fears His 'Wedges' Made It Seem Too Easy")

More and More Fossil Fuel Power

The study reflects international trends in investment in coal-burning power plants, with construction of coal-fired power plants slowing in the West since the 1980s but increasing in China, India, and other areas of the developing world.

"There is a global effort to reduce carbon dioxide, but it is actually increasing at a shocking rate," Davis said. "When you build a power plant, it is going to stick around for 40 to 50 years and emit a lot of CO2."

In 2012, China's power sector represented 42 percent of worldwide committed emissions, 98 percent of which were tied to coal, the authors found. Plants in the United States and Europe together accounted for 20 percent. That share of lifetime carbon emissions has declined in the United States since the late 1980s, in part due to the shift from coal-burning power plants to plants fueled by natural gas, but also because the power infrastructure is not expanding. Levels remained steady in Europe.

The study found that lifetime emissions from China's power plants have experienced a less rapid increase since the country's 2006 peak. Although China continues to build power plants, they are not being built as rapidly as in the recent past, Davis said.

However, China is "passing the torch" to other industrializing countries—including Indonesia, Russia, Saudi Arabia, and Iran—which are ramping up their power sectors, often by building new coal plants. (See related interactive map: The Global Electricity Mix)

Faulty Emissions Accounting

The study presents a bleak look at international efforts to prevent global warming while it questions the accounting used to tally emissions to meet climate treaties.

The authors found that lifetime carbon emissions from currently operating power plants represent a substantial portion of what is allowed for in climate models to prevent global temperatures from warming more than 2 degrees Celsius from the preindustrial era—the current international target.

The emissions from existing power plants in China and the United States, for example, represent 53 and 21 percent, respectively, of each nation's carbon budget to meet its carbon target from all sources, according to the study.

Dave Hawkins, director of climate programs at the Natural Resources Defense Council, said the study illustrates a concept environmental advocates have talked about for years.

By focusing almost exclusively on annual emissions, the international community has disregarded the impact of investment in new power plants fired by fossil fuels, Hawkins said.

"It's like driving a car and looking out the driver's window at the ground passing by rather than looking out the windshield," Hawkins said.

The study did not factor in proposed EPA regulations to limit carbon emissions, and Davis said the regulations would likely have little impact on lifetime power plant emissions in the study. The average age of U.S. power plants is 36, Davis said. The study estimated a 40-year lifespan for power plants, so there is little time for new proposals to influence emissions considered in the study. (Vote and comment: "What Energy Solution Should We Develop Next?")

Although carbon commitments are growing at a rapid rate, Davis said projected emission rates are not set in stone. If the plants are retrofitted with carbon capture technology or retired early, emissions would fall, Davis said, although he thinks this is unlikely.

"Most people have the common-sense understanding that once you build a billion-dollar power plant, you don't just shut it off because the climate is getting too warm," he said.