HEAT-TRAPPING CARBON emissions this year reached their highest level on record, dashing hopes by scientists, environmental groups and political leaders that countries had turned a corner on addressing climate change.

The results, released in a study published Wednesday as representatives gathered at a United Nations climate summit in Poland, marked the second straight year – after three years of declines – that emissions have risen rather than remaining flat or falling.

“We thought, perhaps hoped, emissions had peaked a few years ago,” Rob Jackson, a professor of Earth system science in Stanford University’s School of Earth, Energy and Environmental Sciences, said in a statement. “After two years of renewed growth, that was wishful thinking.”

Emissions are expected to rise by 2.7 percent in 2018, accelerating an increase in emissions of 1.6 percent last year. Much of the increase comes from the energy sector, a result of rising energy demand around the world, especially in developing economies, which have turned to coal to meet their power needs.

China, notably, after enduring an economic slowdown, has “now hit the accelerator” on emissions by greenlighting coal plants that had previously stalled. Emissions in China alone are expected to climb by 5 percent this year – up from an increase of 3.5 percent last year.

“China is jump-starting coal projects that were on hold,” Jackson said.

The U.S. has also reversed course on reining in emissions. After seeing carbon dioxide emissions decline for roughly a decade, such emissions are expected to increase 2.5 percent this year – a result not only of a deep cold snap in the East and unusually warm weather across the country through the spring and summer but also of renewed American appetites for oil and gas whet by low energy prices.

“We’re driving more miles in bigger cars, changes that are outpacing improvements in vehicle fuel efficiency,” Jackson said.

The report follows a drumbeat of alarming climate reports. Reports in the past two weeks by the U.N.’s Environment Programme and World Meteorological Organization as well as the latest U.S. National Climate Assessment warned that countries are heading in the wrong direction in addressing climate change and that the impacts of global warming – from wildfires to droughts to severe weather – are being felt now, with devastating consequences.

The reports, however, including the study released Wednesday published in the journal Environmental Research Letters, showed little sign of a turnabout.

“We need emissions to stabilize and quickly trend toward the zero line,” Jackson said.