Unless efforts are heightened, the United States will likely miss the goals it set under the 2015 Paris climate accord, a new study suggested.

Along with more than 190 nations, the U.S. vowed to dramatically reduce the country's emissions of greenhouse gases by 2025, with the goal of shrinking emissions up to 28 percent below 2005 levels.

However, researchers from the Department of Energy estimate that the country will only reach four-fifths of the 2025 goal, given the current efforts by local and state governments.

Jeffrey Greenblatt, lead author of the study, said the U.S. can't reach the goal with its current set of policies.

"We will likely fall short without additional policies," said Greenblatt.

Not Meant To Discourage

Greenblatt and his colleague Max Wei examined all types of greenhouse gas emissions including methane, nitrous oxide, carbon dioxide and other fluorocarbons in the country.

Current proposed policies require the U.S. to cut down 1,330 million tons of carbon emissions.

But Greenblatt and Wei suggest that in order to reach the 2025 goal, the U.S. will have to reduce around 1,660 million tons of yearly emissions.

The gap is at around 330 million tons of emissions, they calculated.

Still, Greenblatt says the study does not mean the U.S. can never reach the goal, but it does emphasize it has to do more. He says he is optimistic that with more action, the country can come close to 26 percent of the goal.

Reduction In Carbon Emissions

Greenblatt and Wei estimate that the biggest reduction in carbon emission would come from the Clean Power Plan, which was expected to decrease carbon pollution from power plants, particularly coal.

Unfortunately, the plan is on hold in courts. If it is not implemented immediately, it would become even harder for the U.S. to reach its 2025 carbon emission goal, said Greenblatt.

It is also a policy that Republicans, including presidential candidate Donald Trump, promise to repeal if they win.

John Sterman, a management professor at Massachusetts Institute of Technology, said the U.S. will have to take up more ambitious policies to fulfill the commitment under the Paris accord.

He said that in order to avoid the worst effects of climate change, the U.S. and other countries must reduce emissions sooner.

"There's simply no time to lose," added Sterman.

The report was published in the journal Nature Climate Change.

Photo: Dirk Duckhorn | Flickr