Dashing hopes and trashing projections, a new study shows global carbon dioxide emissions not only rose again last year, but are also on track to reach a new high this year, pushing the planet further toward irreversible climate change.

Global carbon dioxide emissions from burning fossil fuels and cement production last year climbed 2.3 percent to 36 billion metric tons, according to the study published Sunday in the science journal Nature. It forecasts emissions to rise past 40 billion metric tons – an increase of another 2.5 percent – this year.

The findings “requires urgent and widespread implementation of mitigation,” from a range of available options, the study said. They range from implementing technologies such as carbon capture-and-storage, which can sharply curtail carbon dioxide emissions at coal power plants, to broader use of renewable power sources like wind and solar, to driving less often and using more energy-efficient appliances.

“Breaking current emission trends in the short term is key to retain credible climate targets,” wrote the researchers, who hail from Europe and Australia.

They rank China, the U.S., the European Union countries and India as the world’s largest polluters, accounting for 58 percent of total global CO2 emissions.

The U.S. in particular saw a 2.9 percent increase in carbon dioxide production last year “due to a rebound in coal consumption,” the study found, “reversing the declining trend in emissions since 2008.”

The Obama administration has sought to rein in coal emissions, introducing controversial new regulations earlier this year aimed at new and existing coal-fired power plants. Coal, the world's largest source of man-made greenhouse gas emissions, makes up about 40 percent of the U.S. energy portfolio, up from 37 percent in 2012, the U.S. Energy Information Administration says. Consumption overall however has fallen since 2007.

Scientists widely agree that countries need to keep the global average temperature from rising by more than 2 degrees Celsius by 2100 to avoid runaway climate change. This study and another last week by the accounting and financial firm PricewaterhouseCoopers, however, found that two-thirds of that carbon “budget” – the amount of carbon countries can consume before reaching the 2-degree threshold ​– has already been exhausted.

PricewaterhouseCoopers' analysis, in fact, found temperatures could increase by as much as 4 degrees by 2100 unless developed economies reduce their total carbon output by 6 percent.

“Breaking current emission trends in the short term is key to retain credible climate targets within a rapidly diminishing emission quota,” the Nature study said.