An article by Brian Clark Howard, National Geographic.

Two days before the UN Climate Summit in New York, three new studies paint the clearest picture yet of rising greenhouse gas emissions and the dwindling opportunity for staving off the worst impacts—and also of at least one way that huge undertaking might be shared fairly among the nations of the world.

“The overall outlook is rather bleak,” says Steven J. Davis, a climate scientist at the University of California, Irvine, who co-authored a paper published Sunday in the journal Nature Climate Change on how nations might share in reducing their carbon emissions.

Davis points to the “Global Carbon Budget 2014,” which was published Sunday in the journal Earth System Science Data Discussions. Produced by dozens of scientists from around the world, it’s the latest in a series of annual reports showing that “we’re moving in the wrong direction,” says Davis.

“We’re talking a lot about putting the brakes on emissions, but we’re actually accelerating.”

According to the new carbon budget, global greenhouse gas emissions rose by 2.3 percent in 2013 over 2012. The authors estimate that emissions will riseanother 2.5 percent in 2014, to a level that is 65 percent above emissions in 1990—the benchmark year established in the Kyoto Protocol.

Meanwhile the concentration of carbon dioxide in the atmosphere exceeded 395 parts per million (ppm) in 2013. That’s an increase of more than 40 percent from the 277 ppm concentration in 1750, before the Industrial Revolution.

Country Breakdowns

According to a review paper published Sunday in Nature Geoscience by an international team led by Pierre Friedlingstein of the University of Exeter in the United Kingdom, three countries accounted for more than 90 percent of the growth in emissions from 2012 to 2013: China (57 percent), the United States (20 percent), and India (17 percent).

The fourth major emitter, the European Union, actually cut its emissions in 2013, such that the global rise was 11 percent less than it otherwise would have been.

What’s particularly striking, says University of Wisconsin climate scientist Galen A. McKinley, is that China is now emitting more on a per capita basis than the European Union, for the first time in history.

“In 2007 China overtook the U.S. in overall carbon emissions, but on a per capita basis we always thought of them as much smaller,” says McKinley, who was not involved in the research published Sunday. “But since then their emissions have been rising rapidly.”

According to the Nature Geoscience review, the world’s emissions in 2013 were 5 metric tons per person. China’s were 7.2 metric tons per person, the U.S. produced 16.4, the EU produced 6.8, and India produced 1.9. In 1990, China produced 2.2 metric tons per person, and the United States produced 19.1.

Cumulative emissions from 1870 to 2013 total 1,430 gigatons for the world, including 161 gigatons from China, 370 from the U.S., 328 from the European Union, and 44 from India.

Another important conclusion from the data is the role the state of the economy plays in emissions, notes Davis. “A lot of people thought the reason the U.S. emissions were down [in recent years] was because of the natural gas boom, in that we have substituted gas for coal,” he says. Natural gas emits about half as much CO2 as coal to produce the same amount of electricity.

Switching coal-fired power plants to gas has indeed helped slow emissions, Davis says, “but if you dig in deeper you see that a lot of the reason why our emissions were down was because of the recession, and with the economy improving they are on the rise again.” Relatively cold winters have also required the use of more fuel for heating.

Still, Davis says, the Environmental Protection Agency’s proposed rules curtailing emissions from power plants are likely to have a significant impact if they go into effect next year.

Filling the World’s Carbon Quota?

In Nature Geoscience, Friedlingstein and his colleagues write that the world has already used up two thirds of the CO2 emissions quota that scientists say will keep the planet from warming more than 2°C (3.6°F). Beyond that temperature threshold, serious consequences are expected from sea-level rise and widespread disruption of weather patterns.

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