BOSTON — Global warming could reach a tipping point in just 12 years if the world doesn’t take forceful steps to reduce the amount of man-made carbon dioxide released into the atmosphere.

That’s the conclusion of a United Nations report released Monday that put pressure on state governments to act in the light of the Trump administration’s inaction and skepticism about climate change.

The U.N.  panel of climate experts that issued the report warned carbon dioxide emissions need to be cut drastically around the globe by 2030 to stave off the worst effects of coastal erosion, natural disasters and other consequences.

Turning the tide, the report said, will require immediate, draconian reductions in emissions of heat-trapping gases and dramatic changes in the energy field.

President Trump, who has called climate change a hoax designed to help China make U. S. manufacturing non-competitive, cast doubt on the U.N. report. He cited unidentified other reports that determined the environment is “fabulous.”

The U.N. report is based on more than 6,000 scientific references from 91 authors across 40 countries.

“Time is running out,” said Jack Clarke, director of public policy at the Massachusetts Audubon Society. “There needs to be a radical approach by governments around the world.”

Massachusetts has pledged to reduce its carbon emissions by 25 percent below 1990 levels by 2020, and mandates an 80 percent reduction by 2050. Republican Gov. Charlie Baker is pursuing contracts for hydropower, solar, wind and other renewable energy sources to reduce greenhouse gases and meet those benchmarks.

But Clarke said the U.N. report shows the state needs to up its game by adopting even more aggressive goals to reduce emissions from power generators, homes and vehicles. “A decade ago those reduction goals seemed like a reasonable approach,” he said. “But things have gotten a lot worse since then, in terms of where the planet is headed.”

Clarke said the Atlantic coast faces a litany of serious problems from climate change — such as rising sea levels that threaten coastal towns, extreme heat and devastating storms.

Global average temperatures have already risen an average of 1 degree Celsius, or about 1.8 degrees Fahrenheit, above levels before the industrial age, according to the U.N. report.

If temperatures rise another half-degree, the report said, they could melt Antarctic ice sheets that could contribute to warmer, rising sea levels that intensify coastal storms and flooding, and endanger marine life. 

The U.N. panel said putting a price on carbon dioxide emissions  is key for getting global warming under control.

To date, more than 40 governments around the world now price carbon emissions, either through direct taxes on fossil fuels or through cap-and-trade programs.

Massachusetts is one of nine states participating in the Regional Greenhouse Gas Initiative, a market-based effort to reduce power plant emissions under their jurisdiction by another 30 percent from 2020 to 2030. Other participants are Connecticut, Delaware, Maine, Maryland, New Hampshire, New York, Rhode Island and Vermont.

Under the cap-and-trade program, power plants buy pollution permits at auctions held several times a year, which can be “traded” between companies based on how much carbon they release. That extra cost for generating electricity is meant to be incentive for fossil fuel-burning  plant owners to rely more on renewable energies.

Proceeds from auctions support energy efficiency programs. Since the initiative began in 2008, for example, Massachusetts has invested more than $440 million of its proceeds.

Most of the money has gone toward energy efficiency and clean technology programs which, in turn, further reduce the state’s carbon emissions.

“This initiative has proven cap-and-trade programs can and do work,” said Eric Wilkinson, general counsel and director of energy policy at the Environmental League of Massachusetts.

Wilkinson said the state needs to create a cap-and-trade program for transportation — vehicles and trucks — which account for about 45 percent of carbon emissions.

Environmentalists say the U.N. report — and the absence of leadership on climate change from Trump and the GOP-controlled Congress — puts the onus on states to act.

“Massachusetts has been a leader on climate change policy, but there’s some areas where we are lagging,” said Ben Hellerstein, state director for Environment Massachusetts, which is pushing an ambitious proposal for the state to get 100 percent of its energy from renewable sources by 2047. “This report shows that we really need a big vision on clean energy.”

Christian M. Wade is the CNHI state reporter in Massachusetts. Contact him at cwade@cnhi.com.