PARIS -- Global carbon dioxide emissions may be dropping ever so slightly this year, spurred by a dramatic plunge in Chinese pollution, according to a surprising new study released Monday.
The unexpected dip could either be a temporary blip or true hope that the world is about to turn the corner on carbon pollution as climate talks continue in Paris, said the study's authors, a scientific team that regularly tracks heat-trapping pollution.
One skeptical scientist offered a $10,000 bet that world emissions will keep rising despite the findings, which were published on the same day that Beijing issued its first ever red alert for smog, urging schools to close and invoking restrictions on factories and traffic.
Still, some leaders cheered the study, published in the journal Nature Climate Change.
"That shouldn't tell us we don't need to do anything, but that shows there is action," Janos Pasztor, the United Nations assistant secretary general for climate change, told The Associated Press. "Things are going in the right direction. All we need is a strong agreement."
Using preliminary data through October 2015, the international team of emission trackers project that worldwide emissions of carbon dioxide this year will be down by 220 million tons. Last year, the world pumped an estimated 39.6 billion tons into the air by burning coal, oil and gas, along with making cement.
Still, the change is so small - 0.6 percent - that it may not be a decrease at all because of the margin of error. As a result, the change could range from a slight increase of 0.5 percent to a decrease of as much as 1.6 percent.
If it is indeed a decrease, however, study authors said this would be the first time global carbon dioxide emissions have dropped, even if only slightly, while the world economy grows. Global emissions fell during the last big recession.
While total emissions have been climbing, the rate of increase has slowed in recent years. Still, this year's figures could be a blip, with emissions going right back up, said study co-author Corinne Le Quere of the University of East Anglia.
"We have a mountain (of emissions) in front of us," Le Quere said. "Maybe the mountain is a bit less and steep than we thought. But it's still a mountain."
U.S. Environmental Protection Administrator Gina McCarthy said: "I will take the blip any day; it's much better than saying it's increasing. But I think it may just represent a strategy that will be more long term."
Greenpeace's international climate politics chief, Martin Kaiser, said this is not enough of a reason to celebrate or be complacent, as emissions have to come down fast in order to save the planet.
Stanford University's Ken Caldeira expressed even deeper caution: He offered to bet the authors $10,000 that emissions haven't peaked yet, a bet the authors weren't quite willing to take.
Le Quere said she also thinks world emissions, including China's, will go back up and 2014 will not end up being the peak year. She said emissions could go up or down a bit from now on.
The whole apparent drop is driven by China, said study co-author Glen Peters of the Center for International Climate and Environmental Research in Oslo. Their study shows a nearly 4 percent drop in emissions for the first eight months of the year when compared to the same time last year. China's plans don't have the country hitting carbon dioxide peak emissions until 2030, which is 15 years from now.
One factor may be issues concerning emissions reporting accuracy with China - and the monitoring and verification of emissions is a major hurdle in climate talks. Peters is confident that his figures based on industrial activity are good. But when asked if he trusts Chinese official emissions reporting figures, Peters paused for a long time and said, "You certainly have your doubts."
On the positive side, China has dramatically increased its renewable energy and is capping its coal burning, much of it driven by the effort to clean up traditional air pollution that is choking cities like Beijing, said study co-author Dabo Guan of the University of East Anglia.
Those efforts are aimed at coal because "coal is the criminal for that and they are reducing lots of coal consumption in the urban areas where most of the industry is based," he said.
Peters said in China, three-quarters of the carbon dioxide emissions come from the burning of coal. And the problem is so bad that even recent reductions haven't helped the smog and soot that on Monday choked the capital. The smog and soot are different pollutants than invisible heat-trapping carbon dioxide, but they usually come from the same source.
U.S. emissions in 2015 dropped by about 1.5 percent. Le Quere only had 2015 estimates for China and the U.S. But in 2014, Europe's emissions went down 6 percent or by 200 million metric tons - which was the same amount by which India's emissions rose, Peters said.
Princeton's Michael Oppenheimer, who wasn't part of the paper, said we need to wait a few years to see if this is a trend. But if it is, "we may be in the early stages of revolutionary change" mostly thanks to renewable energy.
He said it shows emissions can stop increasing even as the economy continues to grow.