Global carbon emissions have now stayed flat for the third year in a row, prompting environmental experts to say they’re “cautiously optimistic” about the future.Carbon dioxide, or CO2, is a major contributor to climate change. The amount emitted has tended to flatten or even fall when the global economy was suffering through recessions, but in 2016, even as the world’s economy grew, the rate of CO2 output didn’t, according to an International Energy Agency report released Friday. The United States played a huge role in keeping that rate flat, as the country’s CO2 emissions fell by 3 percent while the economy grew by 1.6 percent.That drop is thanks largely to the use of natural gas and renewable energy’s increasing affordability, said Jeff Deyette, who heads state policy and analysis for the nonprofit Union of Concerned Scientists’ climate and energy program.“In the U.S., it’s definitely due to market forces that are driving particularly coal generation here down,” he said, adding that both coal plants and mines are shuttering across the country as other energy sources become cheaper. “They just no longer can compete with newer, cleaner alternatives.”Obama-era standards for fuel economy and the related increase in the number of energy-efficient vehicles also likely contributed, Deyette said. (Trump recently announced he’ll re-evaluate one of Obama’s key standards.)“We’re hopeful to start to see this emissions trajectory not to be so flat and start actually inching downwards,” Dayette said, though he acknowledged that natural gas is a far from perfect substitute for coal because it’s composed mostly of methane and still a potent greenhouse gas.Michael Oppenheimer, director of the Program in Science, Technology and Environmental Policy at Princeton University, also urged caution. The International Energy Agency called the report “the first signs of an established trend of flat emissions,” but Oppenheimer said researchers need to wait for more data.“The change in the last three years is just the first inkling of a shift, and it’s not enough to put us on a trajectory that would actually get us to 2 degrees or less,” Oppenheimer said, referring to the Celsius temperature rise to which scientists have long said humanity needs to limit the Earth. Though this may seem very low, an increase of 2 degrees would still have serious consequences and leave the planet hotter than it’s been for 10,000 years.“Emissions are at a historically record high,” said Petier Tans, who studies the gases driving climate change for the National Oceanic and Atmospheric Administration. “The problem with CO2 is, it doesn’t disappear from the oceans and atmosphere for thousands of years. So the climate effect is not just due to this year’s emissions. No, it’s the sum total of all emissions since the Industrial Revolution started.”
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