The United States has long occupied the notorious position of the world's leading contributor to climate change, pumping into the atmosphere over the past decades more greenhouses gases than any other nation.
But later this year — or sometime next — China will ascend to the top of the heap, as it has done with so many other indicators, whether the size of its economy, its population, or its energy consumption.
And, analysts tell VICE News, China's overtaking of the US brings into sharp focus the changing dynamics of international climate change negotiations — as well as growing pressure inside China's borders to cut down on pollution.
The US Energy Information Administration projects that China's total carbon dioxide emissions between 1990 and the end of next year will reach 151 billion tons, compared to 147 billion tons produced by the United States.
For its part, the Center for International Climate and Environmental Research in Oslo, Norway, told Reuters that China will surpass the US even sooner, projecting that its total emissions from the year 1990 forward will surpass those of the US sometime this year.
China has been the world's top annual greenhouse gas emitter the past several years, David Waskow, director of the World Resources Institute's International Climate Initiative, told VICE News. But, he added, it has already begun taking substantial steps to slow down the rate of growth in its pollution.
"The country recognizes the health risks, and it has many reasons to act," Waskow told VICE News, adding that US per capita emissions remain about ten times higher than China's.
In November, President Xi Jinping pledged to cap China's emissions by 2030. Investment in renewable energy in China ballooned to $83 billion in 2014, more than double that of the second largest clean energy market — the United States.
Many experts and environmentalists see China's commitment to curbing emissions and boosting renewable energy development as a response to internal dynamics. Only seven of the country's 74 major cities met national air quality standards in 2014. Just prior to the release of those figures, Beijing's mayor, Wang Anshun, said that the capital was "not a livable city."
Barbara Finamore, Asia director for the Natural Resources Defense Council, echoed Waskow, urging focus on the improvements China is undertaking in cutting emissions and boosting clean energy investment. China's coal consumption dropped last year, as did its emissions, she said, and its coal imports have already plummeted a whopping 42 percent in the first quarter of 2015.
"China has declared a war on pollution and is moving very quickly," she said. "What China has already committed to do, and is doing, shows leadership — and this will lead the way for other developing countries."
But the Cato Institute's Chip Knappenberger remains skeptical of China's recent pledges.
"Fifty years from now maybe the developing countries can grow their economies without carbon dioxide emissions because of new technologies, but that definitely has not been true in the past, and China has been growing leaps and bounds," Knappenberger told VICE News. "They're going to continue into the future and India is right behind them."
A recent study from the International Energy Agency provides evidence for a possible rupture between the historic link between economic growth and greenhouse gas emissions. The agency found that in 2014, despite positive growth in the world economy, carbon dioxide emissions from the energy sector stalled, including a slight drop in China.
Follow Meredith Hoffman on Twitter: @merhoffman