In 2014, global greenhouse gas emissions rose by just 0.6 percent, as opposed to the average 2.4 percent annual growth seen over the past decade. And for 2015, emissions are projected to decrease by 0.6 percent, according to the research, also published this week in the journal Nature Climate Change.

Normally, declines in greenhouse gas emissions are linked with periods of economic downturn, such as the collapse of the Soviet Union in the 1990s or the global financial crisis in 2008. Less economic growth usually coincides with less need for power and industry, so not as much gas gets pumped into the atmosphere. But global GDP has grown stably since 2012 and is expected to grow even more robustly in 2015.

The study authors think that slow growth of petroleum use worldwide and a faster growth of renewable energies are responsible for the trends, but it's ultimately China's coal use that explains the numbers. Right now, the country is the world's biggest polluter, producing more than a quarter of the planet's industrial greenhouse gases. But recently, China has vowed to lower its reliance on coal-based energy, and from 2013 to 2014, more than half of the nation's power came from renewable forms of energy like hydropower and nuclear power.

Perhaps as a result, China's gas emissions grew by just 1.2 percent in 2014, much lower than the 6.7 percent annual growth the country has experienced over the past decade. And the country's emissions are expected to decline by 3.9 percent in 2015. Those changes, coupled with declines in greenhouse gas emissions from the United States, the European Union, and other nations, are likely responsible for the slow growth in emissions.

However, the emission reversal may not last for long. China's economic growth has slowed recently, so it's possible the country will use more coal when things pick back up. China has also been burning more coal than the country previously reported, meaning the country's coal consumption has been severely underestimated since 2000. Additionally, India is expected to double its greenhouse gas emissions by 2030, as it attempts to bring more than 300 million citizens onto the power grid. Right now, India produces as much greenhouse gas as China does, meaning the country is poised to surpass China as the leading polluter.