Carbon dioxide (CO2) emissions from industry and fossil fuels are projected to rise by 2 percent this year, researchers said Monday.
The increase comes after a period of almost no growth between 2014 and 2016, according to the Global Carbon Project's Global Carbon Budget 2017 report.
With its use of coal increasing, China's emissions were projected to rise by 3.5 percent. Emissions in the U.S. were projected to decline by 0.4 percent, although coal use is to rise slightly. Atmospheric CO2 concentration was expected to rise by 2.5 parts per million in 2017.
Lead researcher Corinne Le Quere, director of the Tyndall Centre for Climate Change Research at the University of East Anglia (UEA) in England, said: "Global CO2 emissions appear to be going up strongly once again after a three-year stable period. This is very disappointing."
Under the Paris climate agreement, reached at the end of 2015, world leaders committed to making sure global warming stays "well below" two degrees Celsius above pre-industrial levels, and to "pursue efforts" to limit the temperature rise to 1.5 degrees Celsius.
Le Quere said that with global CO2 emissions from human activities estimated at 41 billion tonnes for 2017, time was running out "on our ability to keep warming well below" the two degrees Celsius target, let alone 1.5 degrees.
"This year we have seen how climate change can amplify the impacts of hurricanes with more intense rainfall, higher sea levels and warmer ocean conditions favoring more powerful storms," she added.
"This is a window into the future. We need to reach a peak in global emissions in the next few years and drive emissions down rapidly afterwards to address climate change and limit its impacts."
The research was simultaneously published in the journals Nature Climate Change, Earth System Science Data Discussions and Environmental Research Letters.